Patent Application
20230390699
The present invention relates to a method and a plant for producing decarbonized oxide or hydroxide using carbonate and electric power.
The effects of so-called “greenhouse gases” on the climate have long been known, especially the correlation between the concentration in the atmosphere of CO2 (carbon dioxide) and global warming.
The efforts of the scientific community and world politics in recent years have been concentrated on trying to counteract the increase in greenhouse gas emissions into the atmosphere, in order to avoid the phenomenon of global warming, i.e. the rise in the average temperature at a global level.
In a per se known way, many initiatives aimed at containing CO2 emissions into the atmosphere have been promoted at an international level: the Kyoto Protocol in 1997 and the Paris Agreement in 2015, among others, are worth mentioning.
The forms identified by the scientific community to avoid global warming are many and substantially concern the decrease in the use of fossil fuels such as coal, oil and natural gas favouring the development of renewable energies such as hydraulic, wind, solar, biomass energy and of zero-emission fuels such as hydrogen or ammonia.
Furthermore, many efforts of the international community are focused on improving the efficiency of energy use, like in the case of lighting with low consumption lamps, on the transport with new generations of high-efficiency engines and, in the field of power generation, on replacing old, inefficient coal- or oil-fired power stations with new combined-cycle plants with gas turbine and vapour turbine having energy yields approaching 60%.
Despite the technological efforts being made in the most advanced nations, the forecasts of well-known international institutions on the energy needs at global level over the next few years indicate a sharp increase in the demand of electric power, thermal energy for industry and of fuels for transportation.
Consequently, these forecasts indicate a steady increase in the use of fossil sources such as oil, coal and natural gas, especially by emerging, newly industrialised and developing countries. This consumption is in fact favoured by the huge availability of these resources and by the discovery of new deposits and techniques for the extraction thereof, factors which altogether make these energy sources economically favourable.
Using the data envisaged by these authoritative studies, a decrease in CO2 emissions is just globally not expected in order to combat global warming, but a substantial increase in the emissions is instead expected over the next 50 years, mainly due to the increase in world population and the new industrialisation of entire countries.
The catastrophic effects of such a situation on the climate are easy to see and difficult to avoid especially because developing nations believe that the renewable energy option is too sophisticated and costly, and are more oriented towards short-term economic development programmes than towards CO2 emission containment and environmental issues.
One of the industries that will be targeted by the future decarbonization of the economy is represented by the lime industry.
The calcination process that transforms the carbonates (limestones and dolomites) into oxides produces large quantities of CO2 mainly coming from the decomposition of the ore at high temperature and secondarily from the fuels used.
It is therefore impossible to decarbonize the lime industry if no permanent CO2 storage is available, even if the fuels used in the calcination process were completely renewable.
Different technologies have been proposed in order to be able to produce oxides with CO2 capture, but with all the proposed technologies there remains the problem of the permanent storage of the CO2 emissions produced in the process.
In a per se known way, CO2 capture and storage technologies are commonly referred to as CCS (Carbon Capture and Storage or also Carbon Capture and Sequestration).
The main CCS technologies proposed and known are:
Although various technological alternatives are available, one of the most important issues still to be solved is the prohibitive cost of CO2 capture and the limited availability of permanent storages of the CO2 produced to offer decarbonized lime-based products on the market.
As can be immediately understood, there is a need to identify a technology that allows the production of oxides through the carbonate calcination process to be carried out with simple technologies and to solve the problem of storing CO2 in a distributed form throughout the territory at an acceptable cost.
The task of the present invention is to make available a method and a plant that can enable the efficient generation of oxides by calcination of carbonates with permanent storage of CO2 at lower costs than known technologies.
This object and these tasks are achieved by means of a plant according to claim 1 and by means of a method according to claim 9.
In order to better understand the invention and appreciate its advantages, some exemplary and non-limiting embodiments thereof are described below, with reference to the attached drawings, in which:
In the description, reference will also be made to “carbonic gas”, meaning thereby a gas mixture containing mainly CO2, and possibly other substances including N2, O2, H2O, Ar, whereas when reference is intended to be made to the chemical element CO2 (carbon dioxide) alone, CO2 will be used in the description.
In the description, reference will also be made to “non-soluble” gases, meaning thereby all gases that are not very soluble in water, including H2, CO, CH4, N2, Ar.
In the description reference will also be made to “water”, meaning thereby water in the liquid phase with the chemical and temperature characteristics necessary for use in the process according to the invention, whereas when reference is intended to be made to the chemical element H2O alone, H2O will be used in the description.
In the description, reference will also be made to the “vapour”, meaning thereby water in vapour form with the temperature and pressure characteristics necessary for use in the process according to the invention.
In the description, reference will also be made to the “sea”, meaning thereby the sea itself but also the ocean, a lake, a river or any salt or fresh water body.
The description will also refer to “carbonate” meaning any calcareous or dolomitic sedimentary rock such as calcite, aragonite, dolomite, siderite, magnesite, marble, but also any other carbonate material such as shells or corals.
In the description reference will also be made to the “electric calciner” (or electric furnace) meaning any electrical apparatus under controlled atmosphere, per se known, capable of calcining the carbonate according to the reactions:
CaCO3→CaO+CO2(+183 kJ/mol) or
MgCO3→MgO+CO2(+118 kJ/mol).
The calcination process, per se known, takes place at temperatures preferably comprised between 600° C. and 1200° C. and is an endothermic process. The controlled-atmosphere electric calciner does not allow direct contact of the calcining zone with the ambient air, while it does allow flushing the calcining zone possibly with water vapour.
In the description, reference will also be made to the “oxide”, meaning thereby the product of the calcination formed mainly by calcium oxide CaO or magnesium oxide MgO and to a lesser extent by other materials present in the carbonate rock with which the calciner is fed.
In the description, reference will also be made to the “hydroxide”, meaning thereby the product of the hydration of calcium oxide Ca(OH)2 or of magnesium oxide Mg(OH)2 with the following chemical reactions:
CaO+H2O→Ca(OH)2(−64.8 kJ/mol)
MgO+H2O→Mg(OH)2(−37.0 kJ/mol)
In the description reference will be made to the “bicarbonates” meaning thereby the chemical compounds Ca(HCO3)2(aq) and/or Mg(HCO3)2(aq)
In the description, reference will be made to the “impurities”, meaning thereby foreign substances present in the carbonate which do not take part in the chemical reactions in the reactor according to the invention.
In the description, reference will be made to the “contactor”, meaning thereby a reactor in which CO2, water and possibly carbonate are reacted according to the following reactions
CO2(aq)+H2O(l)H2CO3(aq)
H(aq)++HCO3(aq)− and
CaCO3+CO2+H2O→Ca(HCO3)2(aq)
where Ca can be substituted with Mg if it were present in the carbonate rock. This reactor is known as “limestone contactor” or “calcite contactor” and is normally used for remineralising drinking water from reverse osmosis plants and can be with fixed bed (updraft or downdraft), fluidised bed, either pressurised or atmospheric.
In the description, reference will be made to the “ionic mixture”, meaning thereby a mixture where the carbonate, if any, has dissolved and Ca2+ or Mg2+ are in ionic form. “Ionic mixture” also refers to the mixture of water and CO2 alone.
In the description, reference will be made to the “buffered ionic mixture”, meaning thereby an ionic mixture in which the pH has been corrected to the desired value by the addition of an oxide or a hydroxide.
In the description, reference will be made to “Ωcal”, meaning thereby the calcite saturation state in seawater.
In the description, reference will be made to “pH”, meaning thereby the measurement scale indicating the acidity or the basicity of a liquid which is defined by the following formula:
pH=−log10[H3O+]
In the description, reference will be made to the “alkalinity”, meaning thereby the quantity of hydroxides OH−, carbonates CO32− and bicarbonates HCO32− present in seawater.
In the description reference will be made to the “hardness”, meaning thereby a value expressing the total content of Ca2+ and Mg2+ ions present in seawater.
In the description, reference will also be made to the “buffering substance”, meaning thereby both the oxide and the hydroxide.
In the description, reference will also be made to the “atmosphere”, meaning thereby any place in contact with atmospheric air.
In the description, reference will be made to “bara”, meaning thereby the unit of absolute pressure in the CGS system (centimetre-gram-second). 1 bara corresponds to 105 Pa in the International System.
In the description, reference will also be made to “high temperature” meaning thereby a temperature greater than 600° C.
In the description, reference will also be made to “ambient temperature”, meaning thereby a temperature lower than 50° C.
In the description, reference will also be made to the “preheating temperature”, meaning thereby a temperature comprised between 50° C. and 600° C.
In the description, reference will also be made to the “average pressure of the contactor”, meaning thereby the weighted average pressure to which the carbonate is subjected during the dwell time in the contactor.
In the description, reference will also be made to the concept of “decarbonized”, meaning thereby a product or service that does not entail CO2 emissions into the atmosphere, i.e. where the CO2 produced by the production process has been stored permanently.
In the attached figures, the reference 100 indicates as a whole the plant according to the invention.
A first aspect of the invention concerns a plant 100 for producing decarbonized oxide or hydroxide. With reference to
CO2(aq)+H2O(l)H2CO3(aq)
H(aq)++HCO3(aq)− and
CaCO3+CO2+H2O→Ca(HCO3)2(aq)
CaC+H2O+2CO2→Ca(HCO3)2(aq) or
Ca(OH)2(aq)+2CO2→Ca(HCO3)2(aq)
In some embodiments of the plant 100 according to the invention (see, for example,
CaO+H2O+2CO2→Ca(HCO3)2(aq)
(where Ca can be substituted with Mg if present in the carbonate).
In some embodiments of the invention (see, for example,
CaO+H2O→Ca(OH)2
(where Ca can be substituted with Mg if present in the carbonate) and to release at the outlet a flow of hydroxide 630; 640 and possibly, a flow of vapour 620.
The hydroxide production unit 60 may be installed between the electric calciner 10 and the dosing device 40 (see
In such embodiments of the plant 100, the buffering substance fed to the pH correction apparatus 30 may be the hydroxide 630; 640 produced by the hydroxide production unit 60.
In accordance with an embodiment of the plant 100 according to the invention and with reference to
In accordance with some embodiments of the plant 100 (see, for example,
In accordance with some embodiments of the plant 100 (see, for example,
In a per se known form, the carbonate preheating unit 15 is a heat exchanger which may be a direct-contact unit in which the flow of carbonic gas comes into direct contact with the carbonate, or it may be an indirect-contact unit in which the carbonate and the carbonic gas always remain separate while exchanging heat.
A skilled person will certainly be able to understand that the size of the contactor 20 depends on the flow rates of carbonic gas 140 or 151, of water 210 and possibly of carbonate 220 and on the kinetics of the chemical reactions that take place. The ratios between the flow rates of carbonic gas 140 or 151, water 210 and carbonate 220 are established with physico-chemical criteria that allow the reactions to be completed
CO2(aq)+H2O(l)H2CO3(aq)
H(aq)++HCO3(aq)− and
CaCO3+CO2+H2O→Ca(HCO3)2(aq)
(where Ca can be substituted with Mg if present in the carbonate) avoiding the precipitation of carbonates in the pH correction apparatus 30 during the insertion of the buffering substance 440 or 640 due to too high Ωcal.
A skilled person will therefore agree that the required contact time between the water 210, the carbonic gas 140 or 151 and possibly the carbonate 220 is the main parameter that allows sizing the contactor 20: if for a contact time of 10 s, a flow rate of carbonic gas 140 or 151 of 1 kg/s, it were required 1 m3/s of water 210, this means that the size of the contactor 20 must be about 10 m3, whereas if the flow rate of carbonic gas 140 or 151 were 10 kg/s, it would be required 10 m3/s of water and the size of the contactor would be about 100 m3.
In accordance with an embodiment of the plant 100, the contactor 20 has a volume which allows a contact time of the water 210 with the carbonate 220 and the carbonic gas 140 or 151 of at least 1000 s and an average pressure of the contactor greater than 1.0 bara.
In accordance with an embodiment of the plant 100 (see for example
In a per se known form and in accordance with experimental results and the scientific literature, the time it takes for CO2 to completely hydrate in water to form carbonic acid H2CO3 according to the reaction:
CO2(aq)+H2O(l)H2CO3(aq)
H(aq)++HCO3(aq)−
has a characteristic time ranging from a few seconds to a few minutes.
It should be noted here that the carbonic gas fed to the contactor 20 can be either the carbonic gas (indicated with 140) coming directly from the electric calciner 10 or it can be the carbonic gas (indicated with 151) coming from the carbonate preheating unit 15.
It should be noted here that the carbonate fed to the electric calciner 10 can be both carbonate at room temperature (indicated with 110 in
It should be noted here that the buffering substance fed to the pH correction unit 30 may be the oxide (indicated with 440;
It should be noted here that the buffering substance fed to the dosing device 40 can be either the oxide (indicated with 130;
A second aspect of the invention concerns a method for decarbonized calcination. The method according to the invention comprises the steps of:
CaCO3→CaO+CO2
CO2(aq)+H2O(l)H2CO3(aq)
H(aq)++HCO3(aq)−
Cao+H2O+2CO2→Ca(HCO3)2(aq), or
Ca(OH)2(aq)+2CO2→Ca(HCO3)2(aq);
In accordance with some embodiments of the invention, the method further comprises the step of feeding to the contactor 20 a predetermined flow of carbonate 220 so that the reaction can take place
CaCO3+CO2+H2O→Ca(HCO3)2(aq)
(where Ca can be substituted with Mg if present in the carbonate).
In accordance with some embodiments of the invention, the flow of buffering substance fed to the pH correction apparatus 30 is a flow of oxide 440.
In accordance with some embodiments of the invention, the method further comprises the steps of:
CaO+H2O→Ca(OH)2
In accordance with such embodiments of the method, the flow of buffering substance fed to the pH correction apparatus 30 may be a flow of hydroxide 640.
In accordance with such embodiments, the method may further comprise the steps of:
In accordance with some embodiments of the invention, the method further comprises the steps of:
In accordance with some embodiments, the method may further comprise the steps of:
Referring to
In a per se known form, the calcination of the carbonate 110 takes place according to the reaction
CaCO3→CaO+CO2
where Ca can be substituted with Mg if present in the carbonate 110, at temperatures comprised between about 600° (MgCO3) and 1200° C. (CaCO3) and at intermediate values depending on the chemical composition of the carbonate, which can also be a dolomite CaMg(CO3)2, and of the chemical composition of the atmosphere in the calciner.
In a per se known form, the calcination reaction is an endothermic reaction requiring 118 kJ/mol of heat in the case of MgCO3 calcination and 183 kJ/mol in the case of CaCO3.
A skilled person can understand that the CO2 produced by an electric calcination under controlled atmosphere generates a carbonic gas 140 formed by CO2 and traces of non-soluble gases that may have entered with the carbonate 110 or 111 inside the electric calciner 10 or gases intentionally fed to the electric calciner 10 to improve the process conditions, such as in the case of water vapour (
Referring to the embodiment of
In a per se known form, the contactor 20 uses water 210 and carbonate 220 as a means for absorbing CO2 from the flow of carbonic gas 140 and forming the ionic mixture 230 according to the reaction:
CO2(g)+CaCO3(s)+H2O=>Ca2+(aq)+2HCO3-(aq) [1]
where Ca can be substituted with Mg if present in the carbonate 220.
In a per se known form, there exist different types of contactors (limestone contactors or calcite contactors), generally used for the remineralisation of drinking water downstream of desalination treatments.
In a per se known form, the permanent storage of CO2 in the form of bicarbonates in the sea using contactors has been proposed in several scientific articles and patents, among which it is worth mentioning the U.S. Pat. No. 6,890,497 B2 entitled “Method for extracting and sequestering carbon dioxide” and the Italian patent application 102020000000037 entitled “Plant and method for sequestering CO2 with a growing pressure reactor conduit”.
In a per se known form, the contactors used for the remineralisation of water or whose use has been proposed for the permanent storage of CO2 in the form of bicarbonates must keep the water that is in contact with the carbonate sufficiently undersaturated, with an Ωcal preferably comprised between 0.01 and 0.6, to allow a dissolution kinetics of the carbonate that is sufficiently rapid and acceptable for an industrial plant. For this reason, the commercial contactors use an excess of CO2 in the water, a pH generally comprised between 5 and 6, and a final degassing of the CO2 to bring the pH of the water back to values above 7.
In a per se known form, the CO2 storage technologies by means of bicarbonates in the sea include, as mentioned above, the discharge of an acid effluent (pH comprised between 6 and 7), with still a significant quantity of CO2 not reacted with the carbonate according to the reaction [1]. This fact turns out to be environmentally harmful if the effluent discharge takes place in the depths of the sea where there is no possibility of degassing CO2 or it is very inefficient (CO2 storage efficiencies of about 50%) where the discharge takes place on the surface with degassing of the residual CO2.
A skilled person will understand that by neutralizing this acidity present in the acid mixture 230 with a buffering substance 440 or 640, an effluent with the same natural pH as seawater could be discharged into the sea and all the residual CO2 could be stored in the form of bicarbonates according to the reaction
Ca(OH)2+2CO2+H2O→Ca2++(HCO3)2
where the Ca2+ ion can be substituted with the Mg2+ ion, eliminating the environmental issues due to the discharge of acid effluents and achieving a CO2 storage efficiency of about 100%.
In a per se known form, the reaction of Ca(OH)2 (where Ca can be substituted with Mg if present in the carbonate) with seawater is a complex reaction due to the presence of other chemical elements and therefore it results that for each mole of Ca(OH)2 it is possible to neutralise less than the 2 moles of CO2 envisaged by the stoichiometry of the equation
Ca(OH)2+2CO2+H2O→Ca(HCO3)2(aq).
Referring to the embodiment of
A skilled person can easily understand that the composition of the ionic mixture 230 released by the contactor 20 may contain impurities which should conveniently be filtered from the mixture 230 by means of special filters (not shown in the figure) placed between the mixer 20 and the pH correction apparatus 30 or downstream of the pH correction apparatus 30.
Referring to the embodiment of
In a per se known form, the dissolution of the carbonate 220 in the contactor 20 depends on the quantity of water and on the pH according to the equilibrium curve presented in
A skilled person will certainly be able to calculate, with the information available in the literature, the dissolution rate of the carbonate as a function of the quantity of water and the pH and the sizes of the contactor 20.
In a per se known form and as already mentioned above, the dissolution rate of the carbonate decreases asymptotically to zero as the equilibrium conditions are approached and therefore, in order to keep the sizes of the contactor 20 within commercially acceptable limits, it is necessary to maintain process conditions away from the equilibrium by using in the contactor 20 a water pH preferably comprised between 5 and 6.5 with water quantities from 1000 m3/tonCO2 to 4000 m3/tonCO2.
A skilled person can certainly understand that the ionic mixture 230 released by the contactor 20, if not subjected to CO2 degassing with a loss of storage efficiency, generally has a pH comprised between 6 and 6.5, lower than the pH of the sea which is about pH 8.
A skilled person will certainly be able to understand that, in order to avoid acidifying the sea by releasing an acid ionic mixture 230, it is necessary to buffer the pH with a basic substance such as the oxide 440 or the hydroxide 640.
A skilled person will certainly be able to understand that it would also be possible to use other substances to buffer the ionic solution 230, such as NaOH or KOH, but that their cost would make them not economically convenient.
A skilled person will certainly be able to verify that the contact times between the water 210 and the carbonate 220 inside the contactor 20 required for a complete dissolution of the carbonate depend on the sizes of the carbonate 220 itself and on the ratio between the quantities of CO2 present in the carbonic gas 140 and the quantity of water 210.
A skilled person will certainly be able to verify that by using a ratio of mass flow of water 210 to CO2 present in the carbonic gas 140 of less than 2000:1, and a carbonate particle 220 greater than 6 microns, the minimum contact time between water 210 and carbonate 220 inside the contactor 20 that are necessary to have a residual quantity of CO2 in the mixture 230 lower than 80% are higher than 50000 s.
A skilled person will easily be able to verify that with the same mass ratio between the water 210 and the CO2 present in the carbonic gas 140 and by decreasing the quantity of carbonate 220 used in the contactor 20 according to the invention, the necessary contact time between the water 210, the CO2 and the carbonate 220, progressively decreases until reaching a few seconds that are necessary only for the hydration of the CO2 in the particular case in which the carbonate 220 used is zero.
A skilled person will certainly be able to understand that the choice of the contact time between the water 210, the CO2 present in the carbonic gas 140 or 151 with the carbonate 220 or the choice of not using the carbonate 220 to buffer the CO2 present in the carbonic gas but only the buffering substance 440 or 640 are economic choices: in fact, by decreasing the quantity of carbonate 220 used with the same quantity of CO2 present in the carbonic gas 140 or 151 and of water 210, the sizes and the plant cost of the contactor 20 are reduced at the expense of a greater consumption of electric power necessary to produce greater quantities of oxide 130 necessary to buffer the CO2 present in the ionic mixture 230 or of smaller quantities of hydroxide 650 available for sale.
In a per se known form, the dissolution of the carbonate in water is favoured and directly proportional to pressure. A skilled person will certainly be able to understand that it is advisable that the average pressure of the contactor 20 be higher than the pressure of 1 bara.
Referring to
Ca(OH)2(aq)+2CO2→Ca(HCO3)2(aq)
As a skilled person can well understand from the above example, the hydroxide 650 available for other uses is a fully decarbonized hydroxide in case the electric power 120 powering the calciner and the electric power (not shown in the example) powering the extraction, the transport and the crushing of the carbonate and the pumping of the water were renewable; otherwise, the hydroxide 650 would be decarbonized except for the share of the emissions due to the energy contribution mentioned above.
As a skilled person can understand, the hydroxide 650, or the oxide 450, can be conveniently used to capture CO2 coming from industrial processes or power plants by means of the reactions
Ca(OH)2(aq)+2CO2→Ca(HCO3)2(aq)
or, in a less efficient form,
Ca(OH)2+CO2→CaCO3+H2O
(where Ca can be substituted with Mg if it were present in the carbonate).
A skilled person will certainly be able to understand that the hydroxide 650 or the oxide 450 produced in a plant according to the invention could be conveniently used for capturing CO2 directly from the atmospheric air once dispersed over large areas both in dry and in liquid or slurry form.
Referring to
Ca(OH)2(aq)+2CO2→Ca(HCO3)2(aq)
As the skilled person can well calculate using market values, the cost of a ton of decarbonized oxide or hydroxide depends mainly on the cost of the carbonate and electric power, while the plant and labour costs have a marginal impact on the final result. In particular, about 2000 kWh of electric power and 2000 kg of carbonate are needed to produce 1 ton of decarbonized calcium hydroxide Ca(OH)2. If the cost of carbonate were 7.5 €/ton and the cost of renewable electric power were 30 €/MWh (this is the LCOE—Levelized Cost Of Energy of wind power), the variable cost of hydroxide would be 75 €/ton.
A skilled person could therefore calculate that the installation costs of the electric calciner, the contactor, the dosing device, the limestone mill, the civil works and the services account for about 5 €/ton of Ca(OH)2 while the personnel costs are negligible.
A skilled person will therefore be able to calculate that the final cost of a ton of Ca(OH)2 is 80€. Considering that with one ton of Ca(OH)2 used in a CO2 storage plant using a contactor as illustrated in
As a skilled person may certainly know, if a ton of hydroxide Ca(OH)2 were spread on the sea surface in a process known as “ocean liming”, 0.9 tons of negative CO2 emissions would be generated: in that case, 1 ton of negative CO2 emissions would cost about €90.
As a skilled person may certainly know, if a ton of hydroxide Ca(OH)2 were spread on a solid surface such as on a wall or on the ground in contact with atmospheric air, this would absorb the atmospheric CO2 transforming into calcium carbonate CaCO3, generating 0.59 tons of negative emissions: in such a case, 1 ton of negative CO2 emissions would cost about 135 €.
In a per se known form, about 10 km2 of surface exposed to the air are required to capture 1000000 tons/year of CO2 from the atmosphere. This surface can be conveniently obtained in flat and desert areas where the hydroxide can be spread in the form of slurry in special tanks built in a similar way to salt pans or rice fields and allowed to dry forming a solid mainly formed by CaCO3 and possibly salts if the water used to form the slurry is seawater.
In the latter case, the desert surfaces covered with carbonate generated by carbonation of the hydroxide would be white and would generate an albedo effect reflecting part of the solar radiation and further contributing to contain the increase in the average temperature on earth.
As a skilled person can certainly understand, the process for producing decarbonized oxide or hydroxide according to the invention makes it possible to permanently store CO2 in the sea in the form of bicarbonates and on land in the form of carbonates at a cost that is competitive with the cost of geological CCS, and above all to be able to generate negative CO2 emissions at a much lower cost than any technology currently available on the market, such as DAC+CCS (Direct Air Capture and CCS) or BECCS (Bio Energy and CCS).
As a skilled person will certainly be able to understand, in some cases it may be advantageous to opt for a simplified plant 100 in which, at the expense of a higher energy cost for the calcination process, it is possible to eliminate the investment in an expensive large-sized contactor 20 by eliminating the step of dissolution of the carbonate 220 and by buffering all the CO2 present in the carbonic gas 140 or 151 by means of the oxide 440 or the hydroxide 640.
Referring to
Ca(OH)2(aq)+2CO2→Ca(HCO3)2(aq)
As a skilled person will certainly be able to deduce from the above data, not using carbonate 220 in the contactor 20 leads to a reduction of hydroxide 650 available for market or for negative emissions and an increase in specific energy consumption that goes from about 2 MWh/ton to 4 MWh/ton of Ca(OH)2 but with the elimination of a large-sized contactor 20.
As a skilled person will certainly be able to understand, in places where the LCOE of renewable energy power is low, such as in particularly windy areas of Norway or Patagonia, it may be more convenient to use a less energy efficient system 100 but with a lower investment (CAPEX) in the contactor 20.
As a skilled person can well understand from the above example, the hydroxide 650 available for other uses is a fully decarbonized hydroxide in case the electric power 120 powering the calciner and the electric power (not shown in the example) powering the extraction, the transport and the crushing of the carbonate and the pumping of the water were renewable; otherwise, the hydroxide 650 would be decarbonized except for the share of the emissions due to the energy contribution mentioned above.
As a person will certainly be able to understand, the availability of carbonate, water and renewable electric power are not limiting factors to produce enough decarbonized oxide or hydroxide according to the invention to permanently store all the anthropogenic CO2 and to generate the negative CO2 emissions needed to comply with the 2015 Paris Agreements.
As the skilled person can well conclude, the method and the plant according to the invention make it possible to produce decarbonized oxide or hydroxide: it is thus possible to overcome one of the most important technical/economic obstacles to the spread of the plants for the permanent storage of the CO2 and for the generation of negative emissions worldwide and with competitive costs.
It is clear that the specific characteristics are described in relation to different embodiments of the plant and of the method with an illustrative and non-limiting intent. Obviously, further modifications and variations may be made to the plant and the method according to the present invention by a person skilled in the art, in order to meet contingent and specific requirements, all of which are however within the scope of protection of the invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102020000031562 | Dec 2020 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/061832 | 12/16/2021 | WO |
