Patent Application
20240190733
The present invention relates to sequestering a carbon dioxide gas from the atmosphere, and in particular to methods and system for alkalizing a body of water that is in contact with the atmosphere, measuring the carbon dioxide uptake and storage, and a dosing station therefor, thereby sequestering the carbon dioxide from the atmosphere.
It is of interest to reduce or stabilize atmospheric CO2 concentrations in order to avoid deleterious climate and ocean chemistry impacts. Various thermo-chemical and electrochemical processes have been developed to reduce CO2 emissions as well as to remove CO2 from air.
Among these processes, CO2 capture through the reaction with certain CO2-reactive, alkaline chemicals has been explored in capturing and sequestering CO2 coming from a variety of concentrated and dilute sources. These alkaline chemicals include but are not limited to metal oxides, hydroxides, carbonates and silicates that may be in dissolved, solid or mixed form that ultimately completely or partially dissolve to produce alkalinity in solution.
For example, the addition of CO2-reactive alkalinity to surface ocean waters can remove and store atmospheric CO2 through the transformation of some of the CO2 naturally dissolved in seawater, into dissolved bicarbonate and carbonate ions. This can force a CO2 undersaturation relative to air in the seawater such that when equilibrated with air, CO2 diffuses from air to the seawater via air-sea gas equilibration processes. Thus, an atmospheric CO2 sink is created.
On the other hand, the addition of CO2-reactive alkalinity to solutions that are supersaturated in CO2, where the CO2 partial pressure in the solution is naturally greater than that of the atmosphere, consumes some or all of the excess CO2 such that the otherwise natural flux of CO2 from the solution to the air is reduced or eliminated. In this way the natural addition of such CO2 to the existing atmospheric CO2 burden is beneficially reduced or avoided. Examples include the addition of CO2-reactive alkalinity to areas of the surface ocean or other water bodies that are naturally supersaturated in CO2 relative to air, and that is a natural source of atmospheric CO2. Ocean areas where subsurface ocean water supersaturated in CO2 is forced to the ocean surface due to wind-driven upwelling or other mixing mechanisms. In the extreme, if enough alkalinity is added to such an area of natural CO2 emissions to the atmosphere, seawater CO2 can become undersaturated relative to air, thus converting what was once an atmospheric CO2 source into a CO2 sink.
There is a significant global potential for such approaches to contribute to atmospheric CO2 management. However, actual measurement and verification of such CO2 removal and/or sequestration is challenging. Therefore there is a need in the industry for developing a system and methods for accurate determining of carbon dioxide removal, and a dosing station therefor.
Methods and system are described for adding CO2-reactive chemical compounds in particular certain chemical bases or alkalinity, for example magnesium hydroxide or another metal hydroxide, to a body of water that is in contact with the atmosphere so as to effect CO2 removal from the atmosphere or to prevent CO2 from entering the atmosphere.
More specifically, methods and system are described that allow maximum CO2 removal or emissions reduction while staying within desired environmental limits and to allow increased precision and accuracy of the measurement of the CO2 removal or emissions reduction effected. This includes a dosing and monitoring apparatus that automatically adjusts the dosing rate based on pH, total suspended solids or other parameter thresholds which are undesirable to exceed.
The embodiments of the present inventions also include methods of quantifying gross CO2 removal. In particular methods are described for measuring the loss of alkalinity from a surface mixed layer of the body of water relative to the air/water CO2 exchange rate, so as to quantify the efficiency of the CO2 removal/storage relative to the quantity of the added alkalinity. Methods of calculating net CO2 removal and accounting for uncertainty in the preceding measurements are also described.
There is an object of the present invention to provide a system, method, dosing station and controller for determining and dispensing a required amount of alkalinity to the body of water that is in contact with the atmosphere to achieve a permissible target carbon dioxide removal from the atmosphere.
According to one aspect of the invention, there is provided a computer implemented method for Carbon Dioxide Removal (CDR) from the atmosphere using a body of water that is in contact with the atmosphere, the method comprising:
(1) setting an amount of CO2-reactive alkalinity to be added to the body of water, and a rate of dispensing of the amount to the body of water, the amount of CO2-reactive alkalinity being less than a target amount;
(2) dispensing the amount of the CO2-reactive alkalinity in the body of water at the rate of dispensing;
(3) during said dispensing, monitoring the body of water by one or more sensors, and adjusting the rate of dispensing so as to ensure measurements of said one or more sensors are within respective predetermined limits; (4) estimating a CDR achieved by said dispensing, according to a chemical mass stoichiometry of carbon dioxide reaction with the CO2-reactive alkalinity;
(5) adjusting the estimated CDR from the step (4) by taking into account a Fequil factor, indicating a fraction of alkalized, CO2-depleted water equilibrated with air, thus determining an adjusted CDR; (6) determining a cumulative amount of the CO2-reactive alkalinity that has been dispensed over time to the body of water; and
(7) if the cumulative amount of alkalinity is less than a predetermined target amount of alkalinity to be dispensed to the body of water, repeating the steps (1) to (6) until the predetermined target amount of alkalinity has been dispensed; thereby removing carbon dioxide from the atmosphere.
before the step (1), setting a target CDR;
after the step (5), determining a cumulative adjusted CDR; and
in the step (7), further verifying if the cumulative adjusted CDR is less than the target CDR, and repeating the steps (1) to (6) until the earlier of: the predetermined target amount of alkalinity has been dispensed or the target CDR has been achieved.
The method further comprises: (5a) further adjusting the adjusted CDR by taking into account a Fhback factor indicating a degree of uncertainty of the adjusted target CDR, thereby determining a further adjusted CDR, the step (5a) being performed after the step (5).
In the method described above, the CDR of the step (5a) is determined as follows: CDR=(t alkalinity added×t CO2 removed/t alkalinity)×(Fequil−Fhback), wherein “t” is amount measured in tonnes (metric tons).
The method further comprises: (5b) further adjusting the further adjusted CDR of the step (5a) by taking into account a CDRww achieved within a wastewater pipe prior to discharge to said body of water, wherein CDRww is determined under assumption that unalkalized wastewater is supersaturated in CO2 relative to air, the step (5b) being performed after the step (5a).
In the method described above, the CDR of the step (5b) is determined as follows: CDR=[(t alkalinity added×t CO2 removed/t alkalinity)−CDRww)×(Fequil−Fhback)]+CDRww wherein “t” is amount measured in tonnes, and Fhback is a factor, indicating a degree uncertainty of the adjusted target CDR of the step (5).
The method further comprises: (5c) further adjusting the CDR of the step (5b) by taking into account carbon dioxide emissions that occurred during production, transportation and distribution of the CO2-reactive alkalinity.
In the method described above, the CDR of the step (5c) is determined as follows: CDRnet=[((t alkalinity added×t CO2 removed/t alkalinity)−CDRww)×(Fequil−Fhback)]+CDRww−LCAemiss, wherein “t” is amount measured in tonnes.
dispensing the amount of CO2-reactive alkalinity to the body of water in doses, at predetermined time intervals;
measuring respective water properties by said one or more sensors, at the predetermined time intervals; and
for a next dose, regulating a magnitude of the next dose as a function of two successive measurements of said one or more sensors, respective pre-defined lower bounds and pre-defined upper bounds of said one or more sensors.
In the method described above, the CO2-reactive alkalinity is a metal hydroxide, for example a monovalent metal hydroxide, or a polyvalent metal hydroxide, for example magnesium hydroxide.
In the method described above, the step (5) further comprises determining the Fequil factor by adding a chemical tracer mixed with the CO2-reactive alkalinity, and monitoring a downstream concentration of the chemical tracer at specified locations in the body of water.
In the method described above, the step (5) further comprises determining the Fequil factor using a partial carbon dioxide pressure pCO2air in the air above the alkalized body of water, and a partial pressure of carbon dioxide pCO2ocean of the alkalized body of water.
In the method described above, the step (5) comprises determining the Fequil factor as follows: Fequil=(Gasex−CDRloss)/Gasex, where Gasex is a rate of air-water gas exchange, CDRloss is a rate of removal of CO2 undersaturated water to depths out of contact with the atmosphere, and where GASex>CDRloss.
In the method described above, the one or more sensors are capable of measuring one or more of the following characteristics of the body of water:
In the method described above, the body of water is one or more of the following: seawater; the ocean; a body of water that discharges into the ocean; a wastewater discharge; a discharge of cooling water from an industrial facility; a natural or artificial reservoir of water.
According to another aspect of the invention, there is provided a system for Carbon Dioxide Removal (CDR) from the atmosphere using a body of water that is in contact with the atmosphere, the system comprising:
a reservoir containing dissolved, partially dissolved or undissolved, CO2-reactive alkalinity;
a dispenser for dispensing the CO2-reactive alkalinity in the body of water;
a controller comprising: a processor; a memory device; computer executable instructions stored in the memory device, for execution by the processor, causing the processor to:
(1) set an amount of CO2-reactive alkalinity to be added to the body of water, and a rate of dispensing of the amount of CO2-reactive alkalinity to the body of water, the amount of CO2-reactive alkalinity being less than a target amount;
(2) dispense the amount of the CO2-reactive alkalinity in the body of water at the rate of dispensing;
(3) during dispensing, monitor the body of water by one or more sensors, and adjust the rate of dispensing so as to ensure measurements of said one or more sensors are within respective predetermined limits;
(4) estimate a CDR achieved by the dispensing, according to a chemical mass stoichiometry of carbon dioxide reaction with the CO2-reactive alkalinity;
(5) adjust the estimated CDR from (4) by taking into account a Fequil factor, indicating a fraction of alkalized, CO2-depleted water equilibrated with air, thus determining an adjusted CDR;
(6) determine a cumulative amount of the CO2-reactive alkalinity that has been dispensed over time to the body of water; and
(7) if the cumulative amount of alkalinity is less than a predetermined target amount of alkalinity to be dispensed to the body of water, repeat the steps (1) to (6) until the predetermined target amount of alkalinity has been dispensed; thereby removing carbon dioxide from the atmosphere.
In the system described above, computer executable instructions further cause the processor to: before (1), set a target CDR; after (5), determine a cumulative adjusted CDR; and in (7), further verify if the cumulative adjusted CDR is less than the target CDR, and repeat the steps (1) to (6) until the earlier of: the predetermined target amount of alkalinity has been dispensed or the target CDR has been achieved.
The system described above further comprises a floating platform having a hull for holding the CO2-reactive alkalinity, for delivering and disposing the dispensed required amount of the CO2-reactive alkalinity in the body of water.
According to yet another aspect of the invention, there is provided a system for Carbon Dioxide Removal (CDR) from the atmosphere using a body of water that is in contact with the atmosphere, the system comprising:
setting a target CDR;
(i) estimating an amount of the CO2-reactive alkalinity to be added to the body of water for achieving the target CDR as determined by chemical mass stoichiometry of carbon dioxide reaction with the CO2-reactive alkalinity;
(ii-1) adjusting the target CDR by taking into account a Fequil factor, indicating a fraction of alkalized water equilibrated with air, thus determining an adjusted target CDR and a corresponding adjusted amount of CO2-reactive alkalinity;
(iii) monitoring the body of water by one or more sensors, and further limiting the adjusted amount of the CO2-reactive alkalinity and the adjusted target CDR so as to ensure measurements of said one or more sensors are within respective predetermined limits when the further adjusted amount of the CO2-alkalinity is dispensed in the body of water over the given time interval, thus determining a further adjusted amount of the CO2-reactive and a corresponding further adjusted target CDR;
(iv) setting the further adjusted amount of CO2-reactive alkalinity as the required amount, and the further adjusted target CDR as the permissible target CDR, and determining the required rate of dispensing over the given time interval based on the permissible target CDR and the respective predetermined limits of measurements of said one or more sensors; and
(v) dispensing the required amount of the CO2-reactive alkalinity in the body of water at the required rate, thereby achieving the permissible target CDR from the atmosphere in the given time interval.
In the system described above, the computer executable instructions further cause the processor to: (ii-2) further adjust, before (iii), the amount of the CO2-reactive alkalinity of (ii-1) by taking into account a Fhback factor, indicating uncertainty of the adjusted target CDR.
In the system described above, the CDR of (ii-2) is determined as follows:
CDR=(t alkalinity added×t CO2 removed/t alkalinity)×(Fequil−Fhback), wherein “t” is amount measured in metric tonnes.
In the system described above, the system comprises a waste water pipe discharging waste water in the body of water, and wherein the computer executable instructions further cause the processor to: (ii-3) yet further adjust, before (iii), the adjusted amount of the CO2-reactive alkalinity and the adjusted target CDR of (ii-1) by taking into account the CDRww achieved within the waste water pipe prior to discharge to said body of water, wherein CDRww is determined under assumption of CO2 supersaturation, relative to air, in the alkalinity discharge waste water.
In the system described above, the CDR of (ii-3) is determined as follows, taking into account CO2 supersaturation in the waste water, relative to air, and the CDRww that occurs within the wastewater pipe prior to discharge to said body of water:
CDR=[(t alkalinity added×t CO2 removed/t alkalinity)−CDRww)×(Fequil−Fhback)]+CDRww, wherein “t” is amount measured in metric tonnes, Fhback is a factor, indicating uncertainty of the adjusted target CDR.
In the system described above, the computer executable instructions further cause the processor to: (ii-4) yet further adjust the adjusted amount of the CO2-reactive alkalinity and the adjusted target CDR of (ii-1) by taking into account carbon dioxide emissions occurred during production, transportation and distribution of the CO2-reactive alkalinity.
In the system described above, the CDR of (ii-4) is determined as follows:
CDRnet=[((t alkalinity added×t CO2 removed/t alkalinity)−CDRww)×(Fequil−Fhback)]+CDRww−LCAemiss, wherein “t” is amount measured in metric tonnes, Fhback is a factor, indicating uncertainty of the adjusted target CDR, CDRww achieved within the waste water pipe prior to discharge to said body of water, wherein CDRww is determined under assumption of CO2 supersaturation in the alkalinity discharge waste water, and LCAemiss indicates carbon dioxide emissions during the production, transportation and distribution of said CO2-reactive alkalinity.
In the system described above, the CO2-reactive alkalinity is a metal hydroxide, for example a monovalent metal hydroxide, or a polyvalent metal hydroxide.
In the system described above, the CO2-reactive alkalinity is magnesium hydroxide.
In the system described above, the Fequil factor is determined by adding a chemical tracer mixed with the CO2-reactive alkalinity, and monitoring a downstream concentration of the chemical tracer at specified locations in the body of water.
In the system described above, the Fequil factor is further determined using a partial carbon dioxide pressure pCO2air in the air above the alkalized body of water, and a partial pressure of carbon dioxide pCO2ocean of the alkalized body of water.
In the system described above, the Fequil factor is determined as follows: Fequil=(Gasex−CDRloss)/Gasex, where Gasex is a rate of air-water gas exchange, CDRloss is a rate of removal of CO2 undersaturated water to depths out of contact with the atmosphere, and where Gasex>CDRloss.
In the system described above, the one or more sensors are capable of measuring one or more of the following characteristics of the body of water: Temperature (T); Salinity (S); Pressure (depth); pH, a measure of H+ concentration; pCO2, partial pressure of CO2; TSS, total suspended solids; NH3, ammonia concentration; DIC, total dissolved inorganic carbon; TA, total alkalinity concentration, or any other chemical, physical or biological parameter to control the rate of said CO2-reactive alkalinity addition to the body of water.
In the system described above, the body of water is one or more of the following: seawater; the ocean; a body of water that discharges into the ocean; a wastewater discharge; a discharge of cooling water from an industrial facility.
The system further comprises a floating platform having a hull for holding the CO2-reactive alkalinity, for delivering and disposing the dispensed required amount of the CO2-reactive alkalinity in the body of water.
According to one more aspect of the invention, there is provided a method for Carbon Dioxide Removal (CDR) from the atmosphere using a body of water that is in contact with the atmosphere, the method comprising:
setting a target CDR;
(i) estimating an amount of the CO2-reactive alkalinity to be added to the body of water for achieving the target CDR as determined by chemical mass stoichiometry of carbon dioxide reaction with the CO2-reactive alkalinity;
(ii-1) adjusting the target CDR by taking into account a Fequil factor, indicating a fraction of alkalized water equilibrated with air, thus determining an adjusted target CDR and a corresponding adjusted amount of CO2-reactive alkalinity;
(iii) monitoring the body of water by one or more sensors, and further limiting the adjusted amount of the CO2-reactive alkalinity and the adjusted target CDR so as to ensure measurements of said one or more sensors are within respective predetermined limits when the further adjusted amount of the CO2-alkalinity is dispensed in the body of water over the given time interval, thus determining a further adjusted amount of the CO2-reactive and a corresponding further adjusted target CDR;
(iv) setting the further adjusted amount of CO2-reactive alkalinity as the required amount, and the further adjusted target CDR as the permissible target CDR, and determining the required rate of dispensing over the given time interval based on the permissible target CDR and the respective predetermined limits of measurements of said one or more sensors; and
(v) dispensing the required amount of the CO2-reactive alkalinity in the body of water at the required rate, thereby achieving the permissible target CDR from the atmosphere in the given time interval.
The method further comprises: (ii-2) further adjusting, before (iii), the amount of the CO2-reactive alkalinity of (ii-1) by taking into account a Fhback factor, indicating uncertainty of the adjusted target CDR.
The method further comprises determining the CDR of (ii-2) as follows:
CDR=(t alkalinity added×t CO2 removed/t alkalinity)×(Fequil−Fhback), wherein “t” is amount measured in metric tonnes.
The method further comprises: (ii-3) yet further adjusting, before (iii), the adjusted amount of the CO2-reactive alkalinity and the adjusted target CDR of (ii-1) by taking into account the CDRww achieved within the waste water pipe prior to discharge to said body of water, wherein CDRww is determined under assumption of CO2 supersaturation in the alkalinity discharge waste water.
The method further comprises determining the CDR of (ii-3) as follows, taking into account CO2 supersaturation in the waste water and the CDRww that occurs within the wastewater pipe prior to discharge to said body of water:
The method further comprises: (ii-4) further adjusting the adjusted amount of the CO2-reactive alkalinity and the adjusted target CDR of (ii-1) by taking into account carbon dioxide emissions occurred during production, transportation and distribution of the CO2-reactive alkalinity.
The method further comprises determining the CDR of (ii-4) as follows: CDRnet=[((t alkalinity added×t CO2 removed/t alkalinity)−CDRww)×(Fequil−Fhback)]+CDRww−LCAemiss, wherein “t” is amount measured in metric tonnes, Fhback is a factor, indicating uncertainty of the adjusted target CDR, CDRww achieved within the waste water pipe prior to discharge to said body of water, wherein CDRww is determined under assumption of CO2 supersaturation in the alkalinity discharge waste water, and LCAemiss indicates carbon dioxide emissions during the production, transportation and distribution of said CO2-reactive alkalinity.
In the method described above, the adjusting the rate of dispensing further comprises:
dispensing the amount of CO2-reactive alkalinity to the body of water in doses, at predetermined time intervals;
measuring respective water properties by said one or more sensors, at the predetermined time intervals; and
for a next dose, regulating a magnitude of the next dose as a function of two successive measurements of said one or more sensors, respective pre-defined lower bounds and pre-defined upper bounds of said one or more sensors.
In the method described above, the CO2-reactive alkalinity is a metal hydroxide, for example a monovalent metal hydroxide, or alternatively a polyvalent metal hydroxide.
In the method described above, the CO2-reactive alkalinity is magnesium hydroxide.
The method further comprises determining the Fequil factor by adding a chemical tracer mixed with the CO2-reactive alkalinity, and monitoring a downstream concentration of the chemical tracer at specified locations in the body of water.
The method further comprises determining the Fequil factor using a partial carbon dioxide pressure pCO2air in the air above the alkalized body of water, and a partial pressure of carbon dioxide pCO2ocean of the alkalized body of water.
The method further comprises determining the Fequil factor as follows: Fequil=(Gasex−CDRloss)/Gasex, where Gasex is a rate of air-water gas exchange, CDRloss is a rate of removal of CO2 undersaturated water to depths out of contact with the atmosphere, and where Gasex>CDRloss.
In the methods described above, the one or more sensors are capable of measuring one or more of the following characteristics of the body of water: Temperature (T); Salinity (S), Pressure (depth); pH, a measure of H+ concentration; pCO2, partial pressure of CO2; TSS, total suspended solids; NH3, ammonia concentration in a gas; DIC, total dissolved inorganic carbon; and TA, total alkalinity concentration.
In the methods described above, the body of water is one or more of the following:
seawater; the ocean; a body of water that discharges into the ocean; a wastewater discharge; a discharge of cooling water from an industrial facility.
According to one more aspect of the invention, there is provided a dosing station, comprising:
(1) set an amount of CO2-reactive alkalinity to be added to the body of water, and a rate of dispensing of the amount of CO2-reactive alkalinity to the body of water, the amount of CO2-reactive alkalinity being less than a target amount;
(2) dispense the amount of the CO2-reactive alkalinity in the body of water at the rate of dispensing;
(3) during dispensing, monitor the body of water by one or more sensors, and adjust the rate of dispensing so as to ensure measurements of said one or more sensors are within respective predetermined limits;
(4) estimate a CDR achieved by the dispensing, according to a chemical mass stoichiometry of carbon dioxide reaction with the CO2-reactive alkalinity;
(5) adjust the estimated CDR from (4) by taking into account a Fequil factor, indicating a fraction of alkalized, CO2-depleted water equilibrated with air, thus determining an adjusted CDR;
(6) determine a cumulative amount of the CO2-reactive alkalinity that has been dispensed over time to the body of water; and
(7) if the cumulative amount of alkalinity is less than a predetermined target amount of alkalinity to be dispensed to the body of water, repeat the steps (1) to (6) until the predetermined target amount of alkalinity has been dispensed;
thereby removing carbon dioxide from the atmosphere.
In the dosing station described above, computer executable instructions further cause the processor to: before (1), set a target CDR; after (5), determine a cumulative adjusted CDR; and in (7), further verify if the cumulative adjusted CDR is less than the target CDR, and repeat the steps (1) to (6) until the earlier of: the predetermined target amount of alkalinity has been dispensed or the target CDR has been achieved.
According to yet one more aspect of the invention, there is provided a controller for a dosing station, for determining a required amount of alkalinity for dispensing in a body of water in contact with the atmosphere, for Carbon Dioxide Removal (CDR) from the atmosphere, the controller comprising: a processor; a memory device; computer executable instructions stored in the memory device, for execution by the processor, causing the processor to:
(1) set an amount of CO2-reactive alkalinity to be added to the body of water, and a rate of dispensing of the amount of CO2-reactive alkalinity to the body of water, the amount of CO2-reactive alkalinity being less than a target amount;
(2) dispense the amount of the CO2-reactive alkalinity in the body of water at the rate of dispensing;
(3) during dispensing, monitor the body of water by one or more sensors, and adjust the rate of dispensing so as to ensure measurements of said one or more sensors are within respective predetermined limits;
(4) estimate a CDR achieved by the dispensing, according to a chemical mass stoichiometry of carbon dioxide reaction with the CO2-reactive alkalinity;
(5) adjust the estimated CDR from (4) by taking into account a Fequil factor, indicating a fraction of alkalized, CO2-depleted water equilibrated with air, thus determining an adjusted CDR;
(6) determine a cumulative amount of the CO2-reactive alkalinity that has been dispensed over time to the body of water; and
(7) if the cumulative amount of alkalinity is less than a predetermined target amount of alkalinity to be dispensed to the body of water, repeat the steps (1) to (6) until the predetermined target amount of alkalinity has been dispensed;
Thus, the improved methods, system, a dosing station and a controller for removing carbon dioxide from the atmosphere using a body of water that is in contact with the atmosphere have been provided.
The accompanying drawings, which constitute a part of the specification, illustrate specific embodiments of the invention which, together with the detailed description of the specific embodiments, serve to explain the principles of the invention.
The general objective of the invention is to improve methods and apparatus to conduct carbon dioxide removal (CDR) from the atmosphere or other sources of excess CO2 through the addition of a CO2-reactive chemical base or alkalinity to a large body of water such as the ocean. It is known that various chemical bases such as metal oxides, hydroxides, carbonates and silicates can react with and consume CO2, forming solid or dissolved metal carbonates and/or bicarbonates. Indeed, as a result of such natural geochemical reactions, dissolved metal bicarbonates in seawater form the largest carbon reservoir on the Earth's surface. It is therefore of interest to promote or increase such reactions so as to reduce the CO2 burden in the atmosphere.
In one embodiment of the invention CO2-reactive metal hydroxide, for example Mg(OH)2, is added to the surface ocean so as to consume some of the surface ocean's dissolved CO2 and induce CO2 undersaturation relative to air. Exposure to air of this undersaturated water then forces, via air-to-sea CO2 diffusion, removal of CO2 from air.
In another embodiment example Mg(OH)2 is first added to an existing, permitted, outfall of industrial or municipal wastewater that is ultimately discharged to the ocean. Note that other types of alkalinity other than or in addition to Mg(OH)2 can be used including other metal hydroxides or oxides such as Ca(OH)2, CaO, KOH, MgO and NaOH as well as soluble metal carbonates such as MgCO3 and Na2CO3. Metal here refers to elements contained in the alkali metals or alkaline earth metals, groups IA and IIA, of the periodic table. Also, other discharges to the ocean can be considered for alkalinity addition including cooling water discharges from power plants, natural discharges such as rivers and streams as well as artificial discharge points from land or from floating or submerged platforms. Discharging onto water bodies other than the ocean for the purpose of performing CDR can also be considered, including to lakes, rivers, and natural or unnatural reservoirs or ponds.
When CO2-reactive alkalinity is added to water, some or all of the dissolved CO2 contained in the water is consumed and transformed to bicarbonate and carbonate ions.
This consumption of dissolved CO2 and hence the reduction in its concentration results in either i) an undersaturation in dissolved CO2 relative to air or ii) a reduction in dissolved CO2 supersaturation relative to air. Thus, if or when such alkalized water contacts the atmosphere either i) a negative air-water CO2 concentration gradient is created, or ii) a reduction in a positive air-water CO2 concentration gradient is produced. Because of the gradient in CO2 concentration so created either i) air CO2 is drawn in and removed for air or ii) the natural diffusion of CO2 from the water to air is reduced. In either case the burden of atmospheric CO2 is desirably reduced through i) CO2 uptake and storage by the water or ii) a reduction in CO2 emissions from the water to air.
It is desirable to measure the quantity of CO2 removed from or emissions avoided to the atmosphere. This is determined by either i) measuring the increase in dissolved carbon concentration in the water following the alkalized water's CO2 uptake from air or ii) the maintenance of a dissolved carbon concentration above what it would otherwise be in the absence alkalization and thus without the loss of CO2 from the water. However, such measurements are difficult if not impossible to do due to a rapid horizontal and vertical spread and dilution of the alkalinity added to and CO2 depletion effected in the surface ocean relative the slow air-water CO2 gas exchange (months). Such measurements would require extensive geographic and temporal coverage as the alkalized, CO2-depleted water spread out over time and because of the extensive dilution of that water with ambient seawater, the measurement would have to be conducted with a precision that is higher than current direct analysis methods can achieve. Therefore, the present invention offers new methods and procedures for measuring or estimating the CDR achieved, and a dosing station therefor.
A pump 530 is mechanically coupled to the container 520 (reference 531), through a direct pipe 526, for example, to extract doses of the content of the container to be released in the waterbody through a discharge pipe 538.
A dosing controller 540 is configured to receive signals from a plurality of sensors and process contents of the signal to adaptively regulate the release of the alkaline substance in the water.
The pump 530 may be electrically coupled to the controller 540 (reference 532) to receive control signals. The pump 530 may also be only communicatively coupled to the controller 540. Controller 540 communicates with the sensors, and possibly with computing facilities, through communication channels 560.
A pump 530 is mechanically coupled to the container 520 (reference 531), through a direct pipe 526 to extract doses of the content of the container to be released in the body of water through a discharge pipe 538.
An outlet sensor detects specified properties of treated water, which is the raw water mixed with the alkaline substance 522 in container 522 and transferred through discharge pipe 538. Outlet sensor 882 is communicatively coupled to electronic circuitry 884 for partial processing of signals from the outlet sensor. A pipe 890 transfers the treated water to the body of water. Controller 540 has communication channels 860, wireless or otherwise, to sensors and to other devices.
A first pump 530A draws raw water from the waterbody 902. Pump 530A is mechanically coupled (reference 531A) to a pipe 935 and a pipe 910. Pump 530A is electrically coupled (reference 532A) to controller 540. A second pump 530B is mechanically coupled to the container 520 (reference 531B), through a direct pipe 526 to extract doses of the content of the container to be released in the waterbody through a discharge pipe 538. Pump 530B is electrically coupled (reference 532B) to controller 540.
An inlet sensor 912 (which may include multiple specialized sensor units) detects designated properties of the raw water. Inlet sensor 912 is communicatively coupled to electronic circuitry 814 (as in the mechanism of
A first pump 530A draws raw water from the waterbody 902. Pump 530A is mechanically coupled (reference 531A) to a pipe 935 and a pipe 910. Pump 530A is electrically coupled (reference 532A) to controller 540. A second pump 530B is mechanically coupled to compartment 712 (reference 531B), through a direct pipe 1026 to extract doses of the content of compartment 1026 to be released in the waterbody through a discharge pipe 538.
An inlet sensor 1012 (which may include multiple specialized sensor units) detects designated properties of the raw water extracted from the waterbody 902. Inlet sensor 1012 is communicatively coupled to electronic circuitry (not illustrated) for electronic processing of signals from inlet sensor 1012. An outlet sensor 1082 (which may include multiple specialized sensor units) detects designated properties of the partially treated water. Outlet sensor 1082 is communicatively coupled to electronic circuitry (not illustrated) for electronic processing of signals from outlet sensor 1082.
Controller 540 is communicatively coupled to a servomechanism which regulates releasing the content of container 710, holding supplied alkaline substance 720, to dispensing compartment 712. Thus, controller 540 is communicatively coupled to sensors 1012, 1082, pump 530A, pump 530B, and said servomechanism. Additionally, controller 540 may be communicatively coupled to external computing devices.
For each of a number, Σ, Σ>1, of sensors, the table indicates a sensor identifier 1210 (may be a vector of quantified properties), location coordinates 1220, and respective properties 1230 to be detected (a subset of properties P1 to P9 in the illustrated example.
A sensor identifier 1210 may comprise a serial number and an indication of a respective sensor type determined from a list of available sensor types. Location Coordinates 1220 of an installed sensor at a given site may be planer polar coordinates (ρ, ϕ), ρ being a radial distance from a point of dosing and ϕ being an angular displacement from a predefine direction. A depth dimension with respect to a (calm) water surface may be considered. Sensors placed at equal radial distances, but different angular displacements, from a dosing point may report significantly different readings due to varying water currents. Specified water-characterizing parameters 1230 of interest may vary according to coordinates of installed sensors.
At a selected sensor, processes 1360 concurrently perform two processes 1362 and 1364.
Process 1362 detects (significant) water-quality changes that are attributed to the selected alkalinity source. Process 1364 reports the start and end of a detection interval (if any) to the controller. The sequence of processes 1320, 1340, and 1360 are repeated a predetermined number of times (based on known rules of statistical significance) to enable calculating a reliable estimate of the advection latency of the water-flow medium (action 1380).
Network interface is configured to communicate with external controllers. Sensors' interface 1430 is configured to communicate with sensors associated with a dosing station. Pump interface 1440 is configured to generate electrical signals that controls specific operations of a dosing pump. The operational data stored in the memory device 1470 comprise pre-computed, or experimental, data needed for executing software modules stored in memory devices 1450 and 1460.
The addition of Mg(OH)2 to seawater and hence the calculated CDR can be limited by the desire to stay within specified seawater chemical parameters. In the illustrated case, the rate at which Mg(OH)2 can be uniformly added over a month to 3×108 L (107 L/day) of well-mixed seawater in equilibrium with air is approximately 500 tonnes/month (17 tonnes/day) if a pH of 9 is not to be exceeded.
An initial estimate of the potential gross CDR effect by a given mass of alkalinity added to a water body such as the ocean is determined by the chemical mass stoichiometry of the CO2 reaction with that alkalinity. For example, in molar units at pH<6 the approximate reaction is Mg(OH)2+2CO2-->Mg+++2HCO3−. By applying the mol weights of the respective compounds, 1.51 tonnes (metric tons) of CO2 is then calculated to be removed per tonne of Mg(OH)2. Thus, an initial calculation of CDR for a given addition of a given mass of Mg(OH)2 to the water body is:
CDR=t alkalinity added×1.51 t CO2 removed/t alkalinity (1)
However, the pH of many water bodies is significantly higher than in the preceding example, and this significantly modifies the preceding reaction in that carbonate ion is also produced in this case. Because carbonate ions are divalent they require twice the Mg2+ to charge balance as does HCO3−. For example, the mean pH of the surface ocean is approximately 8.1 and therefore the molar reaction is:
Mg2++2OH−+A(CO2aq)--->Mg2++B(HCO3−)+C(CO32−+H2O)+D(OH−) (2)
This molar ratio can be converted to a mass ratio. For example, at pH=8.1, 1.65 mols CO2/mol Mg(OH)2)×44(wt./mol CO2)/58.3(wt./mol Mg(OH)2)=1.25 t CO2 removed/t Mg(OH)2. Thus, the CDR calculation in typical seawater becomes:
CDR=t alkalinity added×1.25 t CO2 removed/t Mg(OH)2 (3)
An example of the use of this equation in calculating CDR as a function of mass of Mg(OH)2 added to the ocean in shown as “Calc1” 1710 in
Calc1 1710 graph uses equation 3 above;
Calc2 1720 graph modifies Calc 1 by incorporating Fequil=0.90 (equation 9 below);
Calc3 1730 graph includes an Fhback factor=0.15 in this example (equation 10 below);
Calc4 1740 graph include a CDRww factor, in this example=30% of the CDR in Calc 1 (equation 11 below); and
Calc5 1750 graph includes an LCAemiss factor, in this example=0.35 tonnes CO2 emitted/tonne Mg(OH)2 added to the ocean (equation 14 below).
Further refinement/limitation of the amount of magnesium hydroxide permitted to the added to the body of water, and a corresponding reduced CDR has been determined by also considering measurement from sensors, for example pH, temperature, salinity and pressure in the body of water. Namely, a vertical line 1780 in
In this application, we'll refer to the maximum permitted amount of magnesium hydroxide as “required amount of CO2-reactive alkalinity” or “target amount of CO2-reactive alkalinity”, and to corresponding permissible CDRs as “permissible target CDRs” or “target CDR”.
The above graphs Calc1, Calc2, Calc3, Calc4 and Calc5 (1710, 1720, 1730, 1740 and 1750) determine the amount of magnesium hydroxide to be added to the body of water, under different progressively improved calculation models 1710, 1720, 1730, 1740 and 1750, to achieve respective Carbon Dioxide Removal (CDR) from the atmosphere corresponding to the above models.
The tonnes/tonne ratio will also vary among different sources of alkalinity used depending on the valence and mol weight of the alkalinity. For example, the equivalent to the above 1.25 ratio for Mg(OH)2 is 1.82 tonnes CDR/tonne NaOH, and 0.98 tonne CDR/tonne Ca(OH)2 in typical seawater.
Under circumstances where the source alkalinity is chemically impure or unknown, the ratio can be empirically determined by adding a given mass of alkalinity to a known volume of air-equilibrated, stirred water or seawater. After full dissolution of the alkalinity and with re-equilibration with air, the increase in the solution's DIC concentration times the volume of solution divided by the mass of alkalinity added can provide a direct measure of mass CDR/mass alkalinity at the pH, salinity, temperature and pressure of the test solution. Indeed, experimental 2 L scale seawater testing showed that under rapid stirring of 1 mM Mg(OH)2 in seawater, approximately 50% of the theoretical carbon uptake per mass alkalinity added is achieved the first day following alkalization, and 99% of the theoretical yield, 1.25 t CO2 removed/t Mg(OH)2, was achieved after about 20 days. Thus, by knowing the tonnes CDR per tonne of alkalinity, the potential CDR achieved by a given mass alkalinity addition to a water body can be determine by multiplying the tonnes alkalinity added by the preceding tonnes CDR/tonne alkalinity.
However, using Calc1 1710 of
In the case of magnesium hydroxide, the dissolution of solid Mg(OH)2 occurs on timescales of hours-to-days, the reaction of dissolved Mg(OH)2 with dissolved CO2 occurs nearly instantaneously, air-sea CO2, equilibration (CDR) occurs on timescales of weeks to months, while advection of surface seawater to depth out of contact with the atmosphere can occur in minutes to months. For example, global model output for CO2 equilibration timescales indicates a global mean value of about 4 months, a standard deviation of about 3.5 months, and only a small fraction of areas in offshore waters where the value exceeded about 12 months.
Methods of measuring the fraction of alkalized water that has equilibrated with air, Fequil, include differencing the rate of air-sea gas exchange (Gasex, mols CO2 m−2 day−1) and the rate of removal of CO2 undersaturated water to depths out of contact with the atmosphere (CDRloss, mols CO2 m−2 day−1), divided by the Gasex:
F
equil=(Gasex−CDRloss)/Gasex (4)
Gasex can be determined by this equation:
Gasex=K×(pCO2air−pCO2ocean,t) (5)
Thus, when pCO2ocean is initially equal to or less than pCO2air, the difference between air and ocean pCO2 will increase with increasing presence of Mg(OH)2 and thus Gasex will proportionally increase. K can be estimated from wind speed, or other methods known in the art.
Gasex can also be measured by eddy covariance in the air above the alkalized ocean wherein high-frequency wind and scalar atmospheric data (CO2, energy, and momentum) can yield values of vertical CO2 flux across the air/sea boundary.
CDRloss may be measured via the downstream monitoring of the concentration of a chemical tracer that is either naturally present in wastewater or other discharge water or that is artificially added, for example Rhodamine or Fluorescein or other tracers known in the art and homogeneously mixed with the alkalinity prior to addition to the ocean. After addition to the ocean, the concentration of the tracer will decline over time and distance from the ocean discharge point due to dilution with unamended seawater. Its presence at whatever concentration at a point and time in the ocean following release denotes that some fraction of the wastewater+alkalinity has penetrated to a given location at a given time.
Thus, by measuring any increase above background in concentrations of the tracer over time in waters within and below the ocean surface mixed layer (water in contact with the atmosphere) and integrating over the volume of the respective volume affected, the fraction of tracer lost from the mixed layer, ft can be determined:
f
t=Rhodsubsurf,t/(Rhodsurf,t+Rhodsubsurf,t) (6)
CDRloss,t,=f×tonnes Mg(OH)2 added×(tonnes CDR/tonne Mg(OH)2 added) (7)
Another option for Fequil estimation is based solely on the CDRloss,t term above. That is, over a time length sufficient to equilibrate the majority of the surface seawater with the air following alkalinization, e.g., 3 months, Fequilis simply the mean fraction of the alkalized CO2-undersaturated seawater in the surface layer during t:
F
equil=1−(0.5×ft) (8)
Gasex, CDRloss and thus Fequil can also be estimated or predicted via computer models of ocean chemistry and physics (known in the art). Models reliant on a suite of regional ocean observations (e.g., turbulence rates and density gradients) can utilize certain assumptions to estimate Gasex and CDRloss and thus Fequil in the ocean region alkalized.
It is also possible to predict the fraction of air equilibration using computer models of ocean physics and air-sea gas exchange as affected by measured or prescribed wind, thermal, salinity and geostrophic forcings. Such models can be used to predict the distribution and surface ocean residence time of a mass of alkalinity add at a given point in the ocean over a set time period.
Finally, the accuracy and precision of the preceding models can be validated or adjusted and improved, and uncertainties of prediction reduced by comparison to the measurements described above. Use of models whose accuracy and precision are thus improved can reduce uncertainty in Fequil estimation and thus uncertainty in the CDR calculation.
By whatever method Fequil is measured or estimated, it can be inserted into equation (3) to provide a more accurate estimate of CDR:
CDR=(t alkalinity added×t CO2 removed/t alkalinity)×Fequil (9)
where in this case, t=tonnes.
An example of the effect of calculation on CDR according to the equation (9) is shown as the Calc2 1720 graph in
The embodiments of the invention provide an additional refinement to the CDR calculation by considering the uncertainty of the preceding CDR estimate and then reducing the CDR value accordingly to provide a more conservative and more certain estimate:
CDR=(t alkalinity added×t CO2 removed/t alkalinity)×(Fequil−Fhback). (10)
For example, if the 95% confidence level of the preceding CDR estimate is +/−15%, a reduction factor of 0.15 can be introduced into the calculation to provide great certainty of the resulting estimate. The Fhback calculated for a given alkalinity discharge may be reduced or increased following the discharge if the uncertainty in the initial calculation reduced or increased by the use of more direct measurement or more accurate modeling of the alkalinity release following its discharge to a water body (Calc3, 1730 of
Embodiments with Waste Water Pipe
A further refinement offered by the invention is consideration of any CDR effected prior to the addition alkalinity to a water body. For example, in the case of the use municipal wastewater discharge as a vehicle for alkalinity addition to the surface ocean, the high biomass loading and biological metabolism characteristic of these waste streams means that they are very highly supersaturated in CO2 relative to air. Thus, by adding alkalinity to these streams there is significant potential for CO2 removal to occur in the delivery pipe before the alkalized wastewater is delivered to the ocean. Because this respired CO2 represents CO2 that was recently removed from the atmosphere by biological activity (e.g., plant photosynthesis), any removal and storage of this carbon can be considered CDR.
CDRww denotes the tonnes of CDR that occurs in the wastewater or other pipeline carrying supersaturated CO2 (relative to air) prior to discharge to the ocean.
Thus, when and where CO2 supersaturation is present in the alkalinity discharge water, the CDR calculation can be refined by adding the CDRww term:
CDR=[(t alkalinity added×t CO2 removed/t alkalinity)−CDRww)×(Fequil−Fhback)]+CDRww where t=tonnes. (11)
That is, the quantity of CDR achieved prior to discharge (CDRww) to the water body or ocean can be added to the CDR calculated in eq. (9), but where the quantity of CDR effected in the water body is proportionately reduced to reflect that some CO2-reactive alkalinity has been consumed prior to discharge. This calculation assumes that all the CO2 consumed prior to discharge to the ocean or water body would otherwise have been emitted to the atmosphere and therefore CDRww in this example is not subject to corrections involving Fequil and Fhback in the case of CO2-reactive alkalinity discharge to the ocean or water body. An example of this effect of the inclusion of CDRww on the CDR calculation is shown in Calc4 1740 in
CDRww can be directly measured by differencing: i) the wastewater CO2 partial pressure (pCO2) prior to or upstream of the addition of alkalinity to the wastewater stream, and ii) the pCO2 following alkalinity addition to the wastewater measured at or near the point of discharge to the ocean. This pCO2 decline together with its measured duration and affected wastewater discharge rate can be used to calculate tonnes of CO2 removed from the waste stream. Specifically:
CDRww(tonnes)=(WW pCO2pre−WW pCO2post)×Sol. Constant×WW rate×time (12)
Using conventional methods, WW pCO2pre and WW pCO2post are either measured directly in the wastewater stream or by lowering a sampling tube into the flowing pipe and directly pumping effluent (using, for example, a peristaltic pump) into an above-ground reservoir containing the pCO2 probe. In this way the wastewater is contacted by the probe before being pumped back into the wastewater pipe, as illustrates in
Both WW pCO2pre and pCO2post are measured continuously or at least on an hourly basis. To account for any temporal change in upstream, unalkalized WW pCO2pre before and during the course of alkalization, pCO2 of the wastewater upstream of the alkalinity addition point before and during alkalization is also monitored. Differencing upstream and end-pipe pCO2 prior to commencing alkalization measures changes in pCO2 between upstream and the discharge point due to non-alkalization processes, such as CO2 leakage from the pipe to the atmosphere or dilution of the wastewater stream from, for example, storm drain runoff.
Other options for measuring WW pCO2post are as follows.
Option 1, where no second access point is available, a piece of tubing connected to the above-ground Sensor Box is deployed into the pipe from the single access point and directed downstream. The tubing length determines the distance relative to the Mg(OH)2 addition point.
Option 2, a sensor package attached to a wire is sent down the pipe to the end of the system. This sensor (our “artificial fish”) internally logs pCO2 measurements (and other ancillary data channels that are feasible) as it travels down the pipe, propelled by the flow of effluent. The length of wire tether released determines where the effluent is being sensed.
Option 3, a piece of tubing (as in option 1) or sensor package (as in option 2) are inserted into the wastewater stream from the pipe's endpoint (i.e. where the effluent exits into the ocean).
At sites where direct in-pipe measurement of WW pCO2post at or near the final discharge point to the ocean is not feasible, this value can be estimated using marine measurement surveys near the point of discharge. Because wastewater typically has a much lower salinity than seawater, a ‘mixing line and extrapolation’ method for calculating WW pCO2post at wastewater salinity is illustrated in
Measurement of seawater pCO2 and salinity throughout and outside the effluent plume may yield co-variability along a ‘mixing line(s)’ 2030, 2040 illustrating change of salinity versus distance in the vicinity of the discharge point from the waste water pipe to the body of water. Mixing lines 2030 and 2040 correspond to the pre-alkalinity addition (2030) and post-alkalinity addition (2040), and extrapolating the mixing lines 2030 and 2040 to the y-axis (i.e. zero-salinity), yields the respective WW pCO2post, 2010 and 2020, to be referred to as pCO2before (2010) and pCO2after (2020). Additionally, at the salinity of wastewater, here zero, the difference between the “before MH (Mg(OH)2) addition” pCO2 2010 and the pCO2 “after MH (Mg(OH)2) addition” 2020 can be used to calculate CDRww:
CDRww=(pCO2before−pCO2after)×C×total alkalized WW discharge volume (m3) (13)
A further refinement offered in the CDR calculation in eq. (11) is the subtraction of the CO2 emissions emitted in the production, transportation and distribution of the alkalinity mass used in the CDR, thus allowing the calculation of the net CDR achieved, CDRnet. We designate the quantity of CO2 emitted as life cycle analysis CO2 emissions, LCAemissin units of tonnes of CO2. This term is then inserted into the calculation of CDR as follows:
CDRnet=[(alk mass added×CO2 removed/alk mass−CDRww)×(Fequil−Fhback)]+CDRww−LCAemiss (14)
For example, if the use of 1,000 t of Mg(OH)2 for CDR results in 200t CO2 emitted in its production, 100 t CO2 emitted in its transportation and 50 t CO2 emitted in its distribution, then 350 t CO2 must be subtracted from the previously calculated CDR yield a CDRnet value. An example of the effect of the LCAemiss on the CDR calculation is shown in Calc5 1750 in
While the preceding describes the calculation of CDRnet that can be achieved for a given addition of alkalinity, for example Mg(OH)2, to a water body, the rate at which the alkalinity can be added to a volume of water can be limited by the chemical or physical effects of such addition such that the effects do not exceed desired or permitted limits. For example, if the alkalinity is to be added to 107 L of well-mixed, air-equilibrated seawater per day, a maximum of about 17 tonnes of Mg(OH)2 per day can be added to that volume so as to keep pH at or below a desired pH of 9. This limit is shown by the vertical line 1780 in
The effect of dosing rate on pH and vice versa in the above noted example is shown in
Similarly, other physical or chemical limits such as total suspended solids (TSS) may further limit the dosing rate below that allowed by pH. Increasing the volume of water per day into which alkalinity is added provides further dilution of the alkalinity added, decreasing the effects on chemical or physical parameters, thus allowing greater alkalinity addition rates than in the case of the treatment of smaller volumes of water.
The dosing station 340 has been exploited in two modes of operation. In the first mode of operation of the dosing station 340, to be referred to as “inverse” mode of operation, we set a target CDR (for example, set by governmental or environmental authorities), and then determine a corresponding amount of alkalinity to be added to the body of water to achieve the target CDR, according to the models 1720, 1730, 1740 and 1750 of
The target CDR may be further limited to a permissible target CDR under limitations imposed by water sensor measurements 1110, 1120, 1130, as shown by the vertical line 1780 in
Thus, in the first mode of operation, we solve a so called “inverse” problem of how much alkalinity needs to be added (which is not known upfront) to achieve the target CDR.
The first mode of operation of the dosing station 340 is illustrated in more detail in the flow-chart 5000 of
Upon Start, a target CDR is set (box 5150), followed by estimating an amount of alkalinity to be dispensed to the body of water for achieving the target CDR, according to chemical stoichiometry of carbon dioxide reaction with CO2-reactive alkalinity (box 5200). Then the procedure 5000 adjusts the target CDR by taking into account a Fequil factor, indicating a fraction of alkalized water that has equilibrated with air, thus determining an adjusted target CDR and an adjusted amount of CO2-reactive alkalinity (step 5300). Further, the procedure 5000 further adjusts the adjusted CDR and the adjusted amount of CO2-reactive alkalinity by taking into account a holdback Fhback factor, indicating uncertainty of the adjusted target CDR (box 5400). Then, the procedure 5000 yet further adjusts the CDR and the amount of alkalinity from the step 5400 by taking into account CDRww achieved within the waste water pipe prior to discharge to said body of water, wherein CDRww is determined under assumption of CO2 supersaturation in the alkalinity discharge waste water (box 5500). The procedure keeps monitoring the body of water by sensors (box 5600), and limit the rate at which the alkalinity is added to the water body and hence the rate at which the adjusted target CDR is achieve so as to ensure sensor measurements are within predetermined limits (box 5800), thereby determining a permissible target CDR that can be achieved in a given time span (box 5900). The procedure 5000 sends instructions to the processor 1410 to cause the dispenser 700 to dispense the amount of alkalinity determined in the step 5800 in the body of water at a required rate that is determined by sensor measurements (box 5950).
In the second mode of operation of the dosing station 340, to be referred to as a “direct” mode of operation, we keep dispensing alkalinity to the body of water, and calculate corresponding CDR achieved during each dispensing cycle according to the models 1720, 1730, 1740 and 1750 of
The second mode of operation of the dosing station 340 is illustrated in more detail in flow-chart 6000 of
Upon start, the procedure 6000 sets an amount of CO2-reactive alkalinity to be added to the body of water, and a rate of dispensing of the amount to the body of water, the amount of CO2-reactive alkalinity being less than the target amount (box 6100). Then the procedure 6000 causes the processor 1410 to dispense the amount of the CO2-reactive alkalinity in the body of water at the rate of dispensing, and during the dispensing, monitoring the body of water by one or more sensors, and adjusting the rate of dispensing so as to ensure measurements of said one or more sensors are within respective predetermined limits (box 6150). Further, the procedure 6000 causes the processor 1410 to estimate the CDR achieved by the dispensed amount of CO2-reactive alkalinity, according to a chemical stoichiometry of carbon dioxide reaction with the CO2-reactive alkalinity (box 6200), further followed by adjusting the estimated CDR by taking into account a Fequil factor, indicating a fraction of alkalized, CO2-depleted water that has equilibrated with air, thus determining an adjusted CDR (box 6250). Also the procedure 6000 keeps track of a cumulative amount of the CO2-reactive alkalinity that has been added to the body of water (box 6300), and if the cumulative amount of alkalinity is less than a predetermined target amount of alkalinity to be dispensed to the body of water (exit No from box 6350), the procedure 6000 returns back to the step 6100, thereby repeating the procedure for the next amount of added alkalinity, until the target amount of alkalinity has been dispensed (exit Yes from box 6350), followed by termination of the procedure (box 6400).
For a given alkalinity discharge site it is necessary to identify and characterize one or more sources of alkalinity that are safe and cost-effective to use. Specifically, it is necessary to determine the potential CDR performance of a given source, the economic and environmental desirability of that use and the size or capacity of source. This evaluation begins by obtaining representative samples of various alkalinity sources and characterizing the particle size distribution, moisture content and elemental and chemical constituents present in the material. Those materials thus identified as having sufficient alkalinity are further tests by submerging each in a volume of water or seawater (e.g. 30 mg/L) where increases in solution pH, total dissolved inorganic carbon (DIC) and/or dissolved alkalinity over time are measured. This then provides a measure of expected potential CDR once released into a body of water like the ocean. Especially, this measures the ratio of potential CDR/t (dry or wet weight) alkaline material added (the OAE Ratio). Together with the increase in pH, DIC and/or alkalinity measured, the releases of other dissolved elements or compounds accompanying dissolved alkalinity (such as trace metals, chlorine, sulfur or organic compounds, etc.) release are also measured so as to predict any undesirable chemical effects to the body of water into which the alkalinity is to be released and to thus determine the rate at which the alkaline material can be desirably and safely added to the body of water. Where discharges a body of water are regulated by a maximum allowable concentration of one or more elements or compounds, the preceding concentrations experimentally released per mass of alkalinity added to a given volume of freshwater or seawater can be used to determine the maximum alkalinity dosing rate allowed to a body of water so as not to exceed permitted element or compound concentrations in the receiving water body.
Process 2110 accesses information relevant to designated sources of alkalinity. Process 2120 selects a candidate source. Process 2130 determines chemical and physical characteristics of the candidate source and of variations of the candidate source, if any. Process 2140 performs laboratory testing of potential Ocean Alkaline enhancement (OAE). Process 210 normalizes OAE measurements. Process 2160 determines realizable CDR (CDRnet) of the candidate alkalinity source. Process 2170 determines whether CDRnet meets an acceptable level. If CDRnet is acceptable, an identifier of the candidate alkalinity source is entered in a list of site-specific qualified sources. If CDRnet is not acceptable, an attempt is made to adapt the candidate source to meet the acceptable level. If adaptation is feasible, an identifier of the candidate alkalinity source together with a description of an adaptation action are entered in the list of site-specific qualified sources. If adaptation is not feasible, an identifier of the candidate alkalinity source is archived for further follow-up if needed.
If further alkalinity resources may be considered, process 2185 revisits process 2120 resulting in activating processes 2130 to 2185. Otherwise, the site-specific evaluation is considered to be complete.
For the present embodiment, the process of adding or dosing alkalinity at a specific rate to the wastewater stream or any discharge to the ocean is done using a Dosing Station 340 of
The dosing station 340 has a controller 540 (shown in more detail in
Such chemical measurements include, but are not limited to:
Using the preceding measurements alone to control dosing rate requires that any other elemental or chemical concentration released by the alkaline material used stays within its permitted level at the dosing rate allowed by those chemical parameters being monitored. Whether or not the concentration maxima of these unmonitored chemical constituents are violated can be determined from elemental or chemical releases per unit mass of alkaline material determined during the Alkalinity Selection activity (above). For example, if a total aluminum concentration is not to exceed 3 mg/L and Alkalinity Selection testing shows that an alkaline material releases 300 mg L−1 g−1 hr−1, then the dosing rate of the material must not exceed 0.01 g L−1 hr−1 regardless of if higher rates of dosing are allowed by the chemical parameters being monitored during dosing.
In
Furthermore, by also positioning one or more chemical sensors upstream of the alkalinity dosing point, the difference in downstream minus upstream chemistry provides direct measurement and quantification of the absolute chemistry change effected by the dosing at the point in the pipe where downstream chemical sensors are present. These differences can then be used to measure the quantity of an element or compound that has been added to that downstream measurement point in the pipe.
For example, a wastewater discharge with an upstream alkalinity of 8 mM, a pCO2 of 38,000 uatms, a pH of 6.8 and a TSS of 50 mg/L, the downstream response of pH, TSS and CO2 removal to the addition of dissolved or particulate Mg(OH)2 is shown in
Thus, in the example of
Assuming a constant wastewater flow rate of 1.8×108 L/day, the quantity of CO2 removed from the wastewater as a function of dissolved Mg(OH)2 added to the above wastewater stream is shown in
According to the present invention, two embodiments regarding disciplines for controlling the rate of dosing are applicable to the aforementioned dosing station. According to a first embodiment, the amount of dosing is based on continuous sensing of the effect of dosing. According to the second embodiment, controlling the dosing rate is based on characterizing the raw water, which may vary over time, and continuously tracking dosing amounts over a moving time window. The dosing rate is then based on verified characterization of chemical reactions for each pair of {alkalinity-source type, raw water type}. The verified characterization may necessitate off-site experimentation which would rely on sensors. However, sensors would not be needed in actual field operations apart from further assurance of consistency of operation of the dosing station.
To start, a dosing pump and appropriate sensors are installed (process 2810). Process 2820 selects an alkalinity source to be supplied to a container. Process 2824 determines whether a sufficient amount of the alkalinity source is currently available. If a supply of the alkalinity source is needed, process 2820 is revisited. If the container has a sufficient amount, process 2830 actuates the pump and tracks the cumulative amount of released alkalinity substance. Process 2832 detects signals from relevant sensors and process 2834 determines values of relevant water parameters. Process 2850 determines whether all of the relevant parameters are within the reference interval 2730. If so, the current amount of the periodic dose need not be changed (reference 2852) and process 2824 is revisited. Otherwise, process 2860 determines whether any of the relevant parameters is above the reference interval 2730. If so, process 2862 is activated to reduce the dose according to the algorithm of
(i) an indication 2940 of type of change (with “+” indicating an increment and “−” indicating a decrement of a respective dose;
(ii) magnitude 2941, β, of an increment or a decrement (β=200 in the example of
(iii) dose magnitude 2942 (same arbitrary units) after an increment or a decrement.
The doses are applied periodically, every D time units, and signals from a designated sensor are also acquired every D time units. As indicated in
The value of the tracked parameter prior to applying the alkaline substance is denoted Ω0. A first dose of β units is applied at time t0. With the parameter equal to Ω0. At time t1, t1=t0+D, a signal from the sensor is acquired and used to compute a corresponding value Ω1 of the parameter. Since, in the illustrated case, Ω1<Ω*, the dose applied at t1 is increased to (D0+β), which is 400 units, according to process 2870. Likewise, the dose is increased at instants t2, t3, and t4, leading to a dose of 1000 units at t4. At time t5, the signal from the sensor is processed and a corresponding value of the parameter, Ω5, is determined to be larger than Ω*. Thus, at instant t5, the dose is decreased from its value of 1000 at t4 to (1000−β)=800, according to process 2862. At instant t6, the value Ω6 of the parameter is determined to be less than Ω*.
Hence, the dose applied at t6 is increased from its value at t5 to (800+β)=1000, according to process 2870. The dose values continue to fluctuate and the corresponding values of the parameter continue to fluctuate around Ω* until any of relevant conditions, such as changes in the composition of the raw water, causes the parameter values to drift before returning to fluctuate around Ω*.
As in the case of
As in the case of
At time t5, the signal from the sensor is processed and a corresponding value of the parameter, Ω5, is determined to be larger than Ω*. Thus, at instant t5, the dose is decreased from its value of 1000 at t4 to (1000−0.5×β)=900, according to process 2862 and process 3384
(
As in the case of
At time instant t5, the signal from the sensor is processed and a corresponding value of the parameter, Ω5, is determined to be larger than ΩH. Thus, at instant t5, the dose value is decreased from its value of 1000 at t4 to (1000−0.5×β)=900, according to process 2862, 3456, and 3458. At instant t6, the value Ω6 of the parameter is determined to be within the reference interval 2730. Hence, the dose applied at t6 remains unchanged from its value of 900 at t5, according to process 2852. Likewise, at instants t7, t8, and t9 the dose value remains constant at 900 units. At instant t10, the value Ω10 of the parameter is determined to be below ΩL while the value of Ω9 is within the reference interval 2730, hence the dose value is increase from 900 to (900+0.5×β), which is 1000, according to processes 2870, 3444, and 3448.
The algorithms of
Process 3320 determines a current value of η1, which starts with Ωj, j=1, based on a sensor's signal. Process 3340 branches to process 3380 if η1 is greater than single reference value Ω* or branches to process 3360 otherwise.
Process 3360 branches to process 3364 which increases the dose value according to a current value of Δ subject to a determination that η0 is less than Ω* or branches to process 3362 if η0≥Ω* where Δ is reduced half its current value before performing process 3364.
Process 3380 branches to process 3384 which decreases the dose value according to a current value of Δ subject to a determination that η0≥Ω* or branches to process 3382 if η0 is less than Ω* where Δ is reduced half its current value before performing process 3384.
Process 3390 then applies the calculated value of the dose. Process 3395 sets η0 to equal η1 then revisits process 3320 to continue the process of determining dose values.
Process 3420 determines a current value of η1, which starts with Ωj, j=1, based on a sensor's signal. Process 3430 branches to process 3450 if current value of η1 is greater than the upper bound value ΩH or branches to process 3435 otherwise.
Process 3435 branches to process 3460 if the current value of η1 is within the reference interval 2730. Otherwise, process 3435 branches to process 3440 which guides determination of a value of a dose increment. Process 3440 branches to process 3448 if the previous value η0 of the parameter is less than ΩL. Process 3448 increases the dose value according to current value of Δ from Φ to (Φ+Δ).
Process 3440 branches to process 3442 if the previous value η0 of the parameter is equal to or greater than ΩL. If value η0 is greater than ΩH, process 3442 branches to process 3446 which reduces the current value of Δ to 0.5×Δ then proceed to process 3448 to determine a new dose value. If value η0 is within the reference interval 2730, process 3442 leads to process 3444 when resets the value of Δ to be half the preset value β then proceed to process 3448 to determine a new dose value.
If η0 is greater than ΩH. process 3450 branches to process 3458 which decreases the dose value from its current value Φ to (Φ−Δ). Otherwise, process 3450 leads to process 3452. If η0 is less than ΩH process 3452 branches to process 3456 to reduce the value of Δ to 0.5×Δ before determining a new value of the dose in process 3458. If η0 is within the reference interval 2730, process 3452 branches to process 3454 which resets Δ to equal half the preset value β then leads to process 3458 to determine a new dose value.
which increases the dose value according to a current value of Δ subject to a determination that η0 is less than Ω* or branches to process 3362 if η0≥Ω* where Δ is reduced half its current value before performing process 3364.
Process 3460 then applies the calculated value of the dose. Process 3490 sets η0 to equal η1 then revisits process 3320 to continue the process of determining dose values.
Site selection or conducting the CDR can be used to identify places that maximize the CDR performed while minimizing the cost of the CDR. This will be dictated by the cost, availability and CO2 reactivity of alkalinity sources available (determined in the Alkalinity Selection and Supply activity) at a given site, the discharge rate and chemistry of a candidate alkalinity discharge stream (determined in a pre-alkalinity discharge MRV activity), the discharge permitting requirements of a given site, the chemistry and physics of the body of water into which the alkaline discharge is to be made and the CO2 emissions associated with conducting the CDR. These features can be measured or modeled prior to alkalinity release to estimate the rate at which alkalinity could be discharged, the gross and net CDR achievable with that release per unit time, and the cost of the preceding activity at a given site. A model can be constructed that takes available information on alkalinity sources, discharge points, permitting requirements, water body (e.g., ocean) chemistry and circulation/mixing, and LCA emissions and generates an estimate of net CDR attainable per unit time, the cost of that net CDR, and the uncertainty of those estimates. The uncertainty can be determined by the sum of the statistical variances in each of the subcomponents of the contributing variables. In this way specific regions or locations can be evaluated for their potential CDR performance and cost prior to actual alkalinity release and thus potential sites prioritized for CDR activity. If data bases exist on potential sites, alkalinity sources, existing discharge characteristics, permitting and ocean conditions, then some or all of the selection process can be computer automated.
Thus, methods and system for alkalizing a body of water that is in contact with the atmosphere, measuring the carbon dioxide uptake and storage, and a dosing station therefor have been described.
Although specific embodiments of the invention have been described in detail, it should be understood that the described embodiments are intended to be illustrative and not restrictive. Various changes and modifications of the embodiments shown in the drawings and described in the specification may be made within the scope of the following claims without departing from the scope of the invention in its broader aspect.
| Number | Date | Country | |
|---|---|---|---|
| 63432320 | Dec 2022 | US |
