Patent Application
20160053182
The present disclosure provides a system and method for producing biochar from biomass. In particular, the present disclosure provides pyrolytic systems and methods of producing biochar.
There is an increasing interest in fuel derived from biomass such as forestry, agricultural products or waste. There are various technologies for converting biomass to fuel such as direct burning, co-firing, gasification, fermentation, pyrolysis, and the like. Depending on the feedstock and the process used the resultant product will have different utilities and properties. In many cases, it is desired to produce a product to replace a fossil fuel leading to sustainability and environmental benefits.
Pyrolysis is a type of thermal decomposition in which a substance is heated in the absence of oxygen, or under limited oxygen conditions. Pyrolysis may be termed ‘fast’ or ‘slow’ depending on the heating rate and residence time of the biomass. In the case of dried biomass, the pyrolysis can result in decomposition into three major products: bio-char (also known as biochar or biocoal), bio-oil, and syn-gas. The development of efficacious technology that enables the pyrolytic conversion of lower-value biomass into higher energy bio-fuels and products (bio-char/bio-coal and bio-oil) is desirable. In particular, it is of interest to provide technology for the production, optimization, and delivery of bio-fuels, particularly biochar, to be used in various agricultural, forestry, and industrial applications that can benefit from using renewable fuel sources
Pyrolysis for the conversion of biomass into fuel products are described, for example, in CA 2,242,279 which discloses an apparatus for continuous charcoal production; which CA 2,539,012 discloses a closed retort charcoal reactor system; CA 2,629,417 which discloses systems and methods for the continuous production of charcoal by pyrolysis of organic feed.
Although pyrolysis systems are known, to date they have met with limited commercial success. Several factors can affect the utility of such systems including the availability, moisture content and cost to transport the feedstock. As well as the efficiency, robustness and flexibility of the system.
It would be advantageous to have a relatively inexpensive, transportable and/or modular pyrolysis system for producing biochar. The system may be simple, robust and/or flexible enough to handle a variety of locations, feedstocks and conditions.
The disclosure provides, at least in part, a system for producing biochar from biomass. The present systems may be modular comprising, for example, a reactor module and a syn-gas management module.
As used herein, the term ‘biomass’ refers to material derived from non-fossilized organic material, including plant matter such as lignocellulosic material and animal material such as wastes, suitable for conversion into biofuels.
As used herein, the term ‘pyrolysis’ refers to thermal decomposition in which a substance is heated in the absence of substantial amounts of oxygen.
As used herein, the term ‘biochar’ or ‘biocoal’ refers to pyrolyzed biomass. Generally bio-char will have a calorific value of about 15 MJ/Kg or greater, such as about 17 MJ/Kg or greater, or about 19 MJ/Kg or greater, about 21 MJ/Kg or greater, about 23 MJ/Kg or greater, about 25 MJ/Kg or greater, about 27 MJ/Kg or greater, about 29 MJ/Kg or greater.
As used herein, “a” or “an” means “one or more”.
This summary does not necessarily describe all features of the invention. Other aspects, features and advantages of the invention will be apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention.
In the accompanying drawings, which illustrate one or more exemplary non-limiting embodiments:
The present disclosure provides, at least in part, a system for pyrolysis of biomass, the system comprising:
The present disclosure provides, at least in part, a system for pyrolysis of biomass, the system comprising:
The present thermosensor may be capable of generating a signal when the temperature is above and below optimal levels. The temperature value at above or below which the thermosensor generates a signal may be predetermined. Such value may be altered depending on a variety of factors such as the needs of a particular production run, the feedstock, the output desired, or the like.
The bio-char produced via the present process may have a calorific value of about 18 MJ/Kg or greater, about 22 MJ/Kg or greater, about 24 MJ/Kg or greater, about 26 MJ/Kg or greater, about 28 MJ/Kg or greater, about 30 MJ/Kg or greater. The present bio-char may have an energy density of about 4 MEL or greater, about 6 MEL or greater, about 8 MEL or greater, about 10 MEL or greater.
The present bio-char may be hydrophobic. For example, if processed at temperatures under about 400° C. the bio-char may be hydrophobic. The present bio-char may be hydrophilic. For example, if processed at temperatures above about 400° C. the bio-char may be hydrophilic. For example, the present bio-char may have a water contact angle ranging from about 102° to about 20° depending on process temperature.
The present biochar preferably is grindable. The coal industry uses the Hardgrove Grindability Index (“HGI”) as a standard test to measure grindability where samples are compared to a standard reference sample (“SRS”). For example, if the grindability of a sample was equal to the SRS coal, it would score 50. A score of less than 50 would indicate a sample is harder to grind and a score of greater than 50 would indicate is easier. The present biochar preferably has a HGI of about 50 or greater, about 52 or greater, about 54 or greater, about 56 or greater, about 58 or greater, about 60 or greater.
The present disclosure provides a reactor for converting biomass into biochar. The reactor has at least one retort extending through it. For example, the reactor may have two, three, four, or more retorts. It is preferred that the reactor have at least four retorts. The retort may comprise a suitable conveyor such as, for example, an auger or paddle conveyor, an inlet and an outlet. The inlet receives biomass which passes through the reactor on the auger to the outlet.
The reactor further comprises a heating system which heats the biomass as it passes through the reactor. The heating system can heat the biomass to a temperature suitable to cause pyrolysis of biomass. The heating system may be any suitable design such as, for example, a plurality of heating elements, heat exchangers, or burners throughout the length of the reactor.
The reactor comprises one or more thermosensors. The thermosensors may be used to monitor the temperature of within the reactor enabling the temperature to be kept at the appropriate level to achieve the desired result. Multiple sensors may allow for more accurate assessment of the temperature at different points in the reactor. For example, based on the temperature reading the heating may be increased or decreased.
Certain exemplary embodiments of the present disclosure comprise one or more additional sensors such as, for example, a sensor for sensing the speed of the auger. This sensor enables the controller to assess the speed with which the biomass is moving through the retort. If this speed is too slow the controller may cause the speed to increase or if the speed is too fast the controller may cause the speed to decrease.
In certain exemplary embodiments of the present disclosure, the reactor produces a biochar stream and a gaseous stream. Biochar can have utility as a fuel source, soil additive, or the like. The gaseous stream may comprise condensable and non-condensable components. The condensable components may, for example, be condensed to form pyrolysis oil (bio-oil). Bio-oil may be used as a petroleum substitute. The non-condensable gases (syn-gas) may be combustible and used, for example, to fuel the reactor heating system. The biochar stream may exit the reactor via a biochar delivery system such as described further herein. The gaseous stream may exit the reactor via a gas collection system such as described further herein.
The present system may comprise a biochar delivery system for receiving the biochar exiting the reactor. The delivery system receives the biochar stream from the retort via the outlet. The system may include a char cooling means. Any suitable cooling means may be used such as direct contact with a cooling medium, indirect contact with a cooling medium, direct contact fluid quenching, or the like. For example, the means may be an auger which moves the hot biochar through a cooling zone to compaction and/or bagging area. An airlock such as a rotary valve airlock may be positioned between the cooling zone and the compaction/bagging area. The cooling of the biochar may be aided by the application of a liquid such as water.
It is possible enrich the biochar with additives such as nutrients or minerals. The resultant biochar could derive advantageous properties from such enrichment. For example, when used as a soil additive the addition of nutrients and minerals markedly improves the performance of the product. Examples of minerals include, but are not limited to, nitrogen, sulphur, magnesium, calcium, phosphorous, potassium, iron, manganese, copper, zinc, boron, chlorine, molybdenum, nickel, cobalt, aluminum, silicon, selenium, or sodium. Examples of nutrients include compost tea, humic and fulvic acids, plant hormones, and other solutions of benefit to plant growth and soil health such as buffers, pH conditioners, and the like.
The addition of the additives to the bio-char may be achieved in any suitable manner. For example, additives may be applied at the biochar delivery system. Additives can be introduced to the cooling liquid and applied to the biochar at the cooling zone. As the cooling liquid boils off the additives can be left behind on the char. Additives may be introduced as a solid and, for example, incorporated through mixing in the cooling zone.
Gases may exit the retort(s) via a gas collection system. The system may be in any suitable form but can advantageously be a series of pipes dispersed throughout the reactor such that gas developed in the retort(s) during the pyrolysis process enters the pipes and is carried out of the reactor. Where the reactor comprises more than one retort it is preferred that each retort have a separate gas collection pipe. Each retort may have more than one gas collection pipe. The separate pipes may feed into a gas collection module but it has been found that having separate pipes running from a section of the retort that has been shown to correspond with a particular biomass temperature and thermochemical stage of decomposition (see
The reactor comprising one or more retorts, one or more thermosensors, and a heating system may be in the form of a module. This can aid in the transportation of the pyrolysis system to various locations. The reactor module may also comprise a gas collection system.
The present system comprises a syn-gas management system. The system is adapted to receive the gaseous stream from the reactor, for example via the gas collection system. The gaseous stream may comprise condensable components. The syn-gas management system may comprise a condenser to remove at least some of the condensable components to form bio-oil. The resultant oil may be stored in one or more bio-oil storage tanks. The system may comprise a pump such as, for example, a pump capable of creating at least a partial vacuum. The pump may be positioned downstream of the reactor, but upstream of the syn-gas and bio-oil collection tanks to facilitate gas movement from retort to collection tanks and combustion burners. The pump may take various forms, but will preferably be capable of conveying a corrosive, and high temperature gas stream. The pump may be a liquid-ring pump, a positive displacement pump, or any other suitable pump or combination of pumps. Preferred are pumps able to tolerate a temperature greater than about 0° C., a temperature greater than about 50° C., a temperature greater than about 100° C. Suitable pumps may be able to tolerate a temperature of less than about 600° C. The pump preferably delivers a pressure greater than about zero (0), but less than about two (2) pounds per square inch when measured at the tank or at the burner.
The syn-gas may be stored in a syn-gas tank. The storage tank may have an inlet for receiving the flow of syn-gas from the reactor and an outlet in fluid communication with the heating system and a flare pipe or other means for discharging the syn-gas. The communication may be controlled via a valve, such as a three-way valve, configurable between a first position where flow is directed to the heating system and a second position where flow is directed to the flare pipe or other discharge means. Alternatively the second position may direct the flow of gas to a storage tank for later use.
The syn-gas management system comprising the syn-gas storage tank, optionally the condenser and bio-oil storage tank may be in the form of a module. This aids in the transportation of the pyrolysis system to different locations and improves the ease of implementation.
The present system may comprise a controller, such as for example a programmable logic controller. The controller may be in communication with the thermosensor and the valve. The controller switches the valve from the first position to the second position upon receiving a signal from the thermosensor that, for example, the temperature in the reactor is above optimal levels. The controller may also switch the valve from the second to the first position upon receiving a signal from the thermosensor that, for example, the temperature in the reactor is below optimal levels. The controller will frequently be a microprocessor. The controller may be a separate module or may be a part of one of the other modules. As a separate module the controller can be located remote from the pyrolysis system. The controller may control more than just the valve. Depending on the particular embodiment the controller may control a variety of factors such as, for example, the delivery of biomass feedstock from the dryer to reactor, the residence time of biomass in each retort, the speed and/or pressure of vacuum pump(s), the residence time of biochar or bio-coal in any cooling portion of the system, the amount of additive added to biochar or biocoal, the speed of the retort, the speed of the conveyor, or the like, or any combination thereof.
The present system may include a biomass dryer module. The drying can receive biomass feedstock and may comprise a moisture sensor. The dryer receives biomass and dries it to reduce the moisture content. Preferably, the moisture content is about 20% or less, about 18% or less, about 15% or less. The dryer may be, for example, a flash dryer, a belt dryer, or a drum dryer. Once the desired moisture content is reached the biomass can be fed into the retort via the inlet means. A rotary valve airlock may be used between the dryer and the reactor in order to control the delivery of the biomass. In an embodiment of the present disclosure hot air from the reactor can be used in the dryer thus reducing the need for external heat sources in the dryer and improving the overall efficiency of the system.
Any suitable biomass feedstock may be used herein such as, for example, those comprising wood fibre, agricultural fibre, by-products or waste (from plant or animal sources), municipal waste, or the like. The selection of biomass may vary depending on availability, the desired output and the particular application. Softwood-fibre typically comprises three major components: hemicellulose (25-35% dry mass), cellulose (40-50% dry mass), and lignin (25-35% dry mass). The energy content of wood fibre is typically 17-21 GJ/tonne on a dry basis.
The feedstock may be in particulate form and may have an average particle size of from about 1 mm to about 50 mm, such as from about 5 mm to about 25 mm. It is preferred that the feedstock have a moisture content of about 15% or less, such as about 10% or less, before commencement of pyrolysis.
Depending on the nature of the biomass it may be necessary to prepare the feedstock prior to pyrolysis. For example, the certain feedstocks may require grinding to produce particles of an appropriate particle size and/or shape. The present method may comprise a moisture removal step where the feedstock is heated to such a temperature that moisture is driven off.
The present disclose provides a method of producing bio-char.
The present method may comprise a cellulose decomposition step. The cellulose decomposition step may be at a temperature of from about 240° C. to about 400° C., such as about 300° C. to about 380° C. The temperature may vary throughout the step or may stay constant. For example, the temperature may be increased at a rate of about 100° C./min or less, about 50° C./min or less, about 35° C./min or less, about 20° C./min or less, about 15° C./min or less, about 10° C./min or less. The step may continue for any suitable length of time such as, about 1 minute or more, about 2 minutes or more, about 3 minutes or more, about 4 minutes or more, about 5 minutes or more, about 10 minutes or more. It is preferred that by the end of the pyrolysis at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, of the mass of cellulose in the feedstock has been decomposed.
The present method may comprise a lignin decomposition step. The cellulose decomposition step may be at a temperature of from about 280° C. to about 500° C., such as about 400° C. to about 500° C. The temperature may vary throughout the step or may stay constant. For example, the temperature may be increased at a rate of about 100° C./min or less, about 50° C./min or less, about 35° C./min or less, about 20° C./min or less, about 15° C./min or less, about 10° C./min or less. The step may continue for any suitable length of time such as, about 1 minute or more, about 2 minutes or more, about 3 minutes or more, about 4 minutes or more, about 5 minutes or more, about 10 minutes or more. It is preferred that by the end of the pyrolysis at least about 5%, at least about 10%, at least about 15%, at least about 20%, of the mass of lignin in the feedstock has been decomposed.
Yields of bio-char, bio-oil, and syn-gas can be altered by varying the process temperatures and/or heat transfer rates. While not wishing to be bound by theory, it is believed that higher temperatures tend to favour the production of bio-oil and/or syn-gas by driving off more of the condensable volatiles produced from decomposition of cellulose. Conversely, slow pyrolysis may favour the production of bio-char by limiting the decomposition of cellulose and reducing the amount of bio-oil produced. Bio-coal production can generally be maximized at temperatures of approximately 285° C. It is believed that at these temperatures hemicellulose still decomposes into syn-gas while much of the cellulose remains as a solid within the lignin matrix. By limiting the decomposition of the cellulose fraction, yields of bio-coal can be increased to around 70%. This type of pyrolysis is known as torrefaction and the resulting bio-char is referred to torrefied bio-char or bio-coal. Producing torrefied bio-char leads to a reduced amount of bio-oil thus reducing the issues associated with storing and handling such oil. In addition, many industrial scale kilns are already equipped to handle solid fuels such as bio-coal rather than liquid bio-oil.
Certain embodiments according to the present disclosure may provide bio-char yields in the range of from about 20% to about 80%, such as about 25% to about 70%. In general, higher yields are seen with torrefaction than with other types of pyrolysis. Certain embodiments according to the present disclosure may provide bio-oil yields in the range of from about 10% to about 40%, such as about 20% to about 50%.
According to a further aspect of the invention, a method for converting biomass to biochar is provided. The method comprises the steps of:
Referring to
The reactor produces a gaseous stream which passes to a condenser 11 which can condense condensable components such as bio-oil. The condensed bio-oil is collected in a bio-oil collection tank 12. A vacuum pump 13 moves the remain gaseous stream to a oil tank 14, a syn-gas collection tank 15. The gaseous stream is fed to a three-way valve 16. A controller 18 receives a signal from a thermosensor (not shown) in the reactor 4. Depending on the needs of the reactor the controller 18 can direct the valve via a control signal 19 to direct the syn-gas to a flare 17 or to the reactor 4 where the syn-gas can be burnt by a furnace (not shown).
Referring to
At least a portion of the gaseous stream is collected by the gas collection system 8 which comprises pipes leading to a gas collection manifold. The gases are then fed into a condenser 10 which can condense condensable components such as bio-oil. The condensed bio-oil is collected in a bio-oil collection tank 17 which the gaseous stream is fed to a three-way valve 19. Depending on the needs of the furnace 6 the valve can direct the gas to a flare 18 or to syn-gas burners 9 via syn-gas pipe 20.
Biochar at the downstream end of retorts 7 is collected and delivered to a cooling retort with a water jacket and auger 13. The assembly comprises a coolant (water) tank 11 and an additive tank 12. The water and/or additive are applied to the biochar via spray nozzles 14. Cooled and improved biochar is the delivered to a collection bin 16 controlled via a rotary valve airlock 15.
It is contemplated that the different parts of the present description may be combined in any suitable manner. For instance, the present examples, methods, aspects, embodiments or the like may be suitably implemented or combined with any other embodiment, method, example or aspect of the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this invention belongs. Unless otherwise specified, all patents, applications, published applications and other publications referred to herein are incorporated by reference in their entirety. If a definition set forth in this section is contrary to or otherwise inconsistent with a definition set forth in the patents, applications, published applications and other publications that are herein incorporated by reference, the definition set forth in this section prevails over the definition that is incorporated herein by reference. Citation of references herein is not to be construed nor considered as an admission that such references are prior art to the present invention.
Use of examples in the specification, including examples of terms, is for illustrative purposes only and is not intended to limit the scope and meaning of the embodiments of the invention herein. Numeric ranges are inclusive of the numbers defining the range. In the specification, the word “comprising” is used as an open-ended term, substantially equivalent to the phrase “including, but not limited to,” and the word “comprises” has a corresponding meaning.
The invention includes all embodiments, modifications and variations substantially as hereinbefore described and with reference to the examples and figures. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims. Examples of such modifications include the substitution of known equivalents for any aspect of the invention in order to achieve the same result in substantially the same way.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2014/050298 | 3/20/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61803739 | Mar 2013 | US |
