JP7043130B2 - Treatment method of biomass material under pressure environment - Google Patents

Description

The present invention relates to a method for treating a biomass material in a pressurized environment, and more specifically, to reduce the amount of biomass material such as food waste, livestock excrement, agricultural waste, marine waste, and forest waste, and to semi-carbonize the biomass material. The present invention relates to a method for treating a biomass material in a pressurized environment, which can be carried out with a low energy consumption.

With the growing awareness of the recycling of biological resources, in recent years, most of the waste biomass materials have been composted and returned to the soil as resources. Among them, food waste such as livestock manure and swill (hereinafter, collectively referred to as "livestock manure"), which are the livestock excrement most expected to be composted and recycled, are at the time of occurrence. In many cases, it is highly moist and has a so-called muddy shape. Since such livestock manure is muddy, it is difficult to take in air (oxygen) inside, and it is difficult for biochemical reactions due to normal microbial decomposition to occur and it is difficult to compost. Therefore, conventionally, a method of lowering the water content and facilitating the uptake of oxygen into the inside has been adopted.

As one means of lowering the water content, there is a method of giving heat energy, ventilation, etc. to the biomass material to reduce the water content, but there is a problem in terms of cost and it is not realistic. Also, as another means, as in the case of livestock manure, which is livestock excrement, agricultural by-products such as ogakuzu, rice straw, and rice husks are mixed with biomass materials to reduce the water content, and as a result, make it easier for air to pass through. There are ways to promote biochemical reactions by microbial degradation. However, in this case, there are areas where it is difficult to procure the agricultural by-products, and even if they can be procured, the cost increases due to the processing work of the agricultural by-products, and the mixing of such agricultural by-products is rather total treatment. There is a drawback that the amount increases and the cost increases.

It is conceivable to reduce the amount of waste biomass and return it to the natural world without composting or recycling it, but even in that case, the water content of the muddy biomass must be reduced, and the same problem as above occurs. .. In addition, simply lowering the water content of the muddy biomass and drying it does not cause a composting reaction due to microbial decomposition, and when the dried biomass is returned to the natural world, it returns to the original muddy biomass. Moreover, it is not costly enough to treat sewage like human excrement.

Carbonization is one of the methods for recycling and energizing waste biomass, and charcoal made from biomass is called biochar. In general, carbonization thermally decomposes biomass in an oxygen-free or oxygen-poor environment at a temperature range of 500 ° C or higher, removes hydrogen and oxygen contained in the biomass, and removes solid matter (biochar) having a relatively high carbon content. It is a thermochemical process to obtain. However, an external heat source is indispensable for biochar production. In response to this situation, a semi-carbonization technique for carbonizing in a lower temperature range has been proposed with the aim of improving energy and solid yield.

Patent Document 1 proposes a waste treatment method for carbonizing and reducing the amount of waste by pressurizing and heating (150 to 200 ° C.) the waste containing swill in a steam kettle. Further, in Patent Document 2, the concentration of carbon monoxide contained in the atmospheric gas in contact with the object to be dried inside the drying apparatus is measured, and the concentration of the carbon monoxide is maintained at a predetermined value of 10 ppm or more and 100 ppm or less. A method for drying organic substances and the like is described. Further, in Patent Document 3, the kitchen is crushed and mixed with sewage to make slurry raw water, which is pressurized by a high-pressure pump, and high-pressure gas containing oxygen or high-pressure air is press-fitted to heat it to a wet oxidation temperature. A mixed treatment method for kitchen waste to be wet-oxidized has been proposed. Further, in Patent Document 4, wastes such as livestock products are subjected to a reaction temperature of 130 to 374 ° C. and saturation of the reaction temperature by using a sub-critical water decomposition apparatus provided with a reaction vessel, a heating means and a pressurizing means. A method of sub-critical water decomposition treatment at a reaction pressure higher than the water vapor pressure has been proposed.

However, in any of the above-mentioned Patent Documents 1 to 4, there is a problem that the processing temperature needs to be raised to a high temperature by a heat source from the outside, and the processing cost is high. Specifically, Patent Document 1 needs to have a high temperature of 150 to 200 ° C., Patent Document 2 also needs to have a high temperature of 350 to 600 ° C., and Patent Document 3 also needs to have a high temperature of 100 to 300 ° C. It is necessary to have a high temperature, and Patent Document 4 also needs to have a high temperature of 130 to 374 ° C.

Under such circumstances, the present inventor can first obtain a biochemical reaction by microbial decomposition if oxygen is effectively shared inside the muddy organic waste having a high water content. And, surprisingly, we found that the temperature rises to 100 ° C and 200 ° C beyond the temperature at which self-heating due to microbial decomposition ends (around 70 ° C). , The organic waste was placed in a closed container that can be pressurized, and oxygen was forcibly supplied to the inside of the organic waste under a pressurized environment exceeding atmospheric pressure and 15 atm or less, and oxygen was supplied. The first reaction step in which the internal temperature of the organic waste is raised to at least 55 ° C. by the organic matter decomposition reaction of the microorganisms present in the organic waste, and the organicity in which the temperature is at least 55 ° C. or higher by the first reaction step. In the container in which the waste is sealed, the temperature rises to 100 ° C. or higher while being maintained in the presence of oxygen and 100 ppm or more of carbon monoxide originating from the organic waste after the first reaction stage. The organic waste is characterized by having a second reaction step, or the organic waste is placed in a hermetically sealed container with pipes and valves, and oxygen is introduced into the organic waste using a tube. The first reaction step, in which the internal temperature of the organic waste directly injected and supplied and supplied with oxygen is raised to at least 55 ° C. by the organic decomposition reaction of the microorganisms present in the organic waste, and the first reaction stage. In the container in which the organic waste whose temperature has reached at least 55 ° C. in the reaction step is sealed, in the presence of oxygen and 100 ppm or more of carbon monoxide originating from the organic waste after the first reaction step. We have proposed a method for treating organic waste, which comprises a second reaction step in which the waste is maintained at 100 ° C. or higher and raised to a temperature of 100 ° C. or higher (Patent Document 5).

Furthermore, the present inventor has proceeded with the study, and the same temperature rise as described above naturally causes a temperature rise even in other biomass materials having a low water content when placed under specific conditions at the initial stage. It was found that the biomass material can be reduced in weight or carbonized without high-temperature heating as in the above, and after the biomass material is placed in a container, the inside of the container is (a) an oxygen-containing atmosphere, (b) 55. The biomass material is raised to a temperature exceeding 80 ° C. by creating an initial environment that satisfies all of (c) over atmospheric pressure to 15 atmospheric pressure, and (d) carbon monoxide concentration of 100 ppm or more. After the temperature exceeds 80 ° C., the inside of the container is in a continuous environment that satisfies all of (a) oxygen-containing atmosphere, (b) above-atmospheric pressure to 15 atm, and (c) carbon monoxide concentration of 100 ppm or more. (Patent Document 6) has proposed a method for treating a biomass material, which comprises naturally raising the biomass material to a temperature exceeding at least 150 ° C. to reduce or carbonize the biomass material (Patent Document 6).

According to the treatment methods of Patent Documents 5 and 6, oxygen is forced into the muddy organic waste even if it is a muddy organic waste in which oxygen does not easily permeate into the inside and a biochemical reaction by microorganisms does not easily occur in a stationary state. By supplying oxygen in a positive manner, it was possible to promote and continue the self-heating reaction due to the oxidation of biomass, and it was possible to realize composting and recycling of organic waste.

However, even with such treatment methods of Patent Documents 5 and 6, although a reduction in energy consumption can be expected as compared with the conventional method, in addition to the fact that drying is difficult to proceed due to the method, drying is to proceed by a decompression operation or the like. There is concern that the self-heating reaction of biomass will be hindered, and it has been desired to develop an energy-saving treatment method that simultaneously dries and carbonizes biomass.

Japanese Unexamined Patent Publication No. 2001-137806 Japanese Unexamined Patent Publication No. 2000-46472 Japanese Unexamined Patent Publication No. 1-310799 WO2005 / 077514 (International Pamphlet) Japanese Unexamined Patent Publication No. 2009-249240 Japanese Unexamined Patent Publication No. 2011-98330

The present invention has been made to solve the above problems, and an object thereof is to produce biomass materials such as food waste, livestock waste, agricultural waste, marine waste, and forest waste at extremely low cost. It is an object of the present invention to provide a method for treating a biomass material which can be reduced in weight and carbonized.

In order to solve the above problems, the present inventor has investigated a new semi-carbonization system using a self-heating reaction of biomass. The self-heating reaction of biomass is promoted by the oxidation reaction, and the temperature is raised to an arbitrary temperature to dry and decompose the biomass. In this system, it was expected that the lower the temperature range where the self-heating reaction of biomass started, the less energy was required for carbonization.

For this reason, we focused on the low temperature oxidation reaction (LTO) in order to cause a self-heating reaction of biomass. The low-temperature oxidation reaction proceeds below 100 ° C. and is known to be the main heat source for self-heating and spontaneous combustion of coal (Wang H, Drugogorski BZ, Kennedy EM. Oxidations, reaction mechanism andkinetic modeling. Prog Energy Combust Sci 2003; 29: 487-513. Doi: 10.016 / S0360-1285 (03) 00042-X.). The oxidation reaction at low temperature is relatively slow and is greatly affected by the amount of water. If the amount of water is appropriate, the water itself plays a role as a catalyst or a reaction field to promote the reaction between biomass and oxygen, whereas an excessive amount of water inhibits the reaction (Petit JC. A comprehensive). study of the water catalyst / coal system: application to the role of water in the weathering of catalyst 1991; 70: 1053-8. Doi: 10.1016 / -2. al., 2003; Yu J, Tahmasebi A, Han Y, Yin F, Li X. A review on water on low rank coals: The examination, catalyst reaction. -20. Doi: 10.016 / j.fuproc. 2012.09.051.).

This suggests that even with high-moisture biomass, a low-temperature oxidation reaction and a self-heating reaction of biomass can be achieved if a stable oxygen supply is performed. The amount of dissolved oxygen is considered to increase as the atmospheric pressure rises. From this, it was expected that the low-temperature oxidation reaction and the subsequent self-heating reaction of the biomass would be promoted by placing the biomass in a high-pressure environment and realizing a stable oxygen environment.

Therefore, under a gauge pressure of 0.9 MPa and a relatively high constant oxygen supply, we proceeded with the research in the temperature range where the low-temperature oxidation reaction and self-heating reaction of biomass are induced. As a result, it was confirmed that the self-heating of the biomass started in the temperature range of 85 ° C. or higher in this atmosphere. Biomass was converted to biochar by undergoing oxidative decomposition, heating to 300 ° C. and drying process only by its own heat generation. From the above, the feasibility of oxidative semi-carbonization using the self-heating reaction of biomass under a high pressure environment was shown, and the present invention was reached.

That is, in the method for treating a biomass material of the present invention, which solves the above-mentioned problems, after the biomass material is placed in a container, (a) an oxygen-containing gas is placed in the container in terms of oxygen supply amount of 3.4 to 33. While supplying with 6 g-O ₂ h ^-1 kg-AFS- ¹ , (b) keep the inside of the container at 0.5 to 1.5 MPa with a gauge pressure, and (c) set the initial temperature to 85 to 160 ° C. Then, when the processing of the biomass material is started by heating from the outside and the temperature of the biomass material exceeds the initial temperature due to the self-heating of the biomass, the supply of the oxygen-containing gas and the gauge pressure in the container are maintained. The heating conditions are controlled so that (i) the heating from the outside is stopped, or (ii) the heating is controlled so that the temperature difference between the temperature of the biomass material and the temperature of the surrounding space of the container is within 1.5 ° C. It is characterized in that, by continuing the reaction, the biomass material is naturally raised to a temperature exceeding at least 160 ° C., and the biomass material is reduced in weight and carbonized.

In the method for treating a biomass material according to the present invention, when the biomass material naturally rises to a temperature exceeding at least 160 ° C. and then reaches an appropriate temperature, the supply of oxygen-containing gas is stopped halfway and the combustion reaction is stopped. End the process.

In the method for treating a biomass material according to the present invention, (a) oxygen-containing gas is supplied by 13.9 to 30.4 g-O ₂ h ^-1 kg-AFS ^-1 in terms of oxygen supply amount, and (b). It is preferable to keep the inside of the container at 0.9 to 1.0 MPa with a gauge pressure and (c) set the initial temperature to 85 to 130 ° C.

In the method for treating a biomass material according to the present invention, the biomass material is naturally raised to a temperature of at least 160 to 300 ° C., then depressurized and cooled to an environmental temperature (25 ° C. ± 10 ° C.) while supplying nitrogen gas. Is preferable.

In the method for treating a biomass material according to the present invention, it is preferable to use livestock manure having a water content of 40 to 80% as the biomass material.

According to the method for treating a biomass material according to the present invention, after the biomass material is placed in a container, the inside of the container is heated to a predetermined temperature under high pressure conditions and high oxygen supply conditions to obtain a biomass material. It is possible to induce a low temperature oxidation reaction and a self-heating reaction. Further, after the temperature rise starts, the biomass material can be naturally raised to a high temperature to reduce the amount and carbonize the biomass material by maintaining the above-mentioned pressurizing condition and oxygen supply condition. As a result, it is not necessary to perform high-temperature heating as in the conventional case, and it is possible to realize weight reduction and carbonization of the biomass material at an extremely low cost. Further, since the gas supplied to the reaction system may be only an oxygen-containing gas typified by air, it is a particularly advantageous method in terms of control and cost.

It is a block diagram which shows an example of the apparatus used to carry out the process of treating the biomass material which concerns on this invention. It is a graph which shows the time-dependent change of the temperature by the self-heating reaction of the biomass when the initial temperature of the biomass is set to 80 degreeC to 100 degreeC under the pressure of the gauge pressure of 0.9MPa. The relationship between (a) oxygen supply rate and oxygen consumption temperature, and (b) CO and CO ₂ generation rates in the biomass treatment in one embodiment of the biomass material treatment method according to the present invention is shown. It is a graph.

The method for treating a biomass material according to the present invention will be described in detail based on the embodiment. It should be noted that the following embodiments are preferable examples of the present invention and are not limited to the embodiments thereof.

[Processing method of biomass material under pressurized environment]
The method for treating a biomass material according to the present invention is to supply a relatively high oxygen gas under relatively high pressure conditions to heat the biomass material to a predetermined initial temperature, thereby performing a low temperature oxidation reaction of the biomass material and subsequent reaction. It promotes a self-heating reaction, thereby drying and carbonizing only by the heat generated by the biomass itself.

The characteristics are that after the biomass material is placed in a container, (a) oxygen-containing gas is placed in the container in terms of oxygen supply amount of 3.4 to 33.6 g-O ₂ h ^-1 kg ^- AFS-. While supplying in ¹ , (b) keep the inside of the container at 0.5 to 1.5 MPa with a gauge pressure, (c) set the initial temperature to 80 to 160 ° C, and heat from the outside to process the biomass material. When the temperature of the biomass material exceeds the initial temperature due to the self-heating of the biomass, the heating from the outside is stopped or the heating is performed while maintaining the supply of the oxygen-containing gas and the pressure inside the container. By controlling the temperature difference between the temperature of the material and the temperature of the surrounding space of the container body to be within 1.5 ° C. and continuing the reaction, the temperature of the biomass material exceeds at least 160 ° C. It is a method for treating a biomass material, which is characterized in that the biomass material is naturally increased to reduce the amount and carbonize the biomass material.

Hereinafter, the configuration of the present invention will be described in detail. In the following, "%" is "% by weight (mass%)" unless otherwise specified.

(Biomass material)
Biomass material is one or more kinds of waste selected from food waste, livestock excrement, agricultural waste, marine waste and forest waste. Specifically, food waste such as garbage (food residue), livestock excrement such as cows, pigs, and horses (manure), surplus products, sorting-excluded products, and agricultural waste such as processed by-products (rice bran, etc.). , Excessive landed products, marine waste such as processed waste, wood waste, wood chips, forest waste such as processed waste, and the like. These may be individual or a mixture of a plurality of types.

The biomass material may be muddy or dry, and may or may not be already composted, regardless of its water content. As an example, a biomass material having a high water content, which makes it difficult for oxygen to permeate into the inside and a biochemical reaction by microorganisms to occur in a stationary state; a biomass material that becomes muddy as a whole or locally and has poor air permeability; Dry biomass materials having carbon as a substrate, such as dairy cow manure, wood chips, brown rice, etc.; already composted biomass materials; etc. can be applied.

The composted biomass material is one that has risen to at least 55 ° C. and composted by the organic matter decomposition reaction of microorganisms that occurs in contact with oxygen. Since this biomass material is composted (composted) and then applied to the treatment method of the present invention to reduce or carbonize the biomass material, it can be returned to the natural world by landfill or the like thereafter.

If the water content of the biomass material is 80% or more as a whole, such as livestock excrement (manure) and agricultural waste, or if it is not large as a whole but locally 80% or more, it becomes muddy. However, in the treatment method of the present invention, even a muddy biomass material can be used without any problem.

When the biomass material is food waste such as swill, the water content of the biomass material as a whole is 40% or more, or 40% or more locally, although it is not large as a whole. In the case of those containing a large amount of fiber such as the above-mentioned livestock excrement (manure) and agricultural waste, the total or local water content becomes muddy when the water content is 80% or more. On the other hand, swill that does not contain so much fiber tends to become muddy even if it is less than 80%, and usually becomes muddy even if it is 40% or more. Similar to the above, such food waste can be used without any problem by the treatment method of the present invention. The water content "as a whole" refers to the ratio when the biomass material contains water evenly or relatively evenly. On the other hand, the water content "locally" means that the biomass material as a whole is less than 80% (for example, in the case of livestock excrement) or less than 40% (for example, in the case of food waste such as swill). , It refers to the case where there is a muddy part of 80% or more or 40% or more when viewed partially.

The water content of the entire biomass material can be measured by collecting a certain amount of biomass material as a sample and measuring the mass of the sample before and after drying. On the other hand, the local moisture content of the biomass material can be evaluated by locally collecting a small amount of sample and measuring the mass before and after drying. Although not particularly limited, livestock manure having a water content of 40 to 80% is desirable as the object to be treated in the method for treating a biomass material of the present invention.

Other wastes may be mixed with such biomass materials. Other wastes include, for example, plastic materials (baluns, human brims, bottle caps, straws, rubber bands, packaging materials, etc.), paper products, wood products (disposable chopsticks, toothpicks, etc.) that are easily disposed of together with household garbage. Can be mentioned. Since the heat resistance of the plastic material differs depending on the type, here, a plastic material having a glass transition temperature of 200 ° C. or less, particularly a plastic material having a glass transition temperature of 150 ° C. or less, for example, polyethylene naphthalate (glass transition temperature: 120 ° C.), polybutylene. Examples thereof include terephthalate (75 ° C.), polyethylene terephthalate (75 ° C.), polyphenylene sulfide (90 ° C.), polyetheretherketone (143 ° C.), and polycarbonate (145 ° C.). By mixing these wastes with the biomass material, it can be reduced or carbonized with the biomass material that rises to a temperature above at least 150 ° C.

(Processing container)
FIG. 1 is a block diagram showing an example of an apparatus that can be used in the method for treating a biomass material according to the present invention. The reaction vessel 100 that stores the biomass material 90 and provides a reaction field under heating and pressurizing conditions can withstand such predetermined heating and pressurizing conditions to form a substantially sealed space. If so, the shape and the like are not particularly limited.

The material of the container 100 is not particularly limited, but may be any material as long as it is corrosion-resistant to the biomass material 90 and has heat resistance, and examples thereof include stainless steel. Further, it is desirable that the biomass material 90 stored inside has a heat insulating structure for maintaining the heat insulating property. For example, the wall surface of the container 100 has a double structure separated by air or is provided with a heat insulating material. It is preferable to use a thing or the like.

The method of pressurizing the inside of the container 100 is not particularly limited as long as the inside of the container 100 can be maintained under the above-mentioned predetermined pressurizing conditions. Usually, compressed oxygen or compressed air, or a pressure applying means such as a compression pump or a compressor is applied to bear a predetermined pressure value. On the other hand, the oxygen-containing gas is supplied into the container 100 in the above-mentioned predetermined supply amount.

Although it is possible to use pure oxygen or high-concentration oxygen as the oxygen-containing gas, it is desirable to use air (oxygen content of about 21%) from the viewpoint of cost. Of course, if necessary, air and two or more kinds such as pure oxygen or high-concentration oxygen can be used in combination.

The pressurization in the container 100 and the supply of the oxygen-containing gas into the container 100 can be independent mechanisms, but the efficiency and mechanism can be one system. It is simple and preferable. For example, as in the example shown in FIG. 1, compressed air (air cylinder 10) and a mass flow controller 30 are used to supply a predetermined amount of oxygen from the bottom of the container 100, and the back pressure regulator 120 on the exhaust line from the top of the container. The pressure inside the container is adjusted to a predetermined value. As shown in FIG. 1, the container 100 is provided with a pressure gauge 110 capable of measuring a pressure of about atmospheric pressure to 2.0 MPa. As the pressure gauge, a commercially available one can be applied and is not particularly limited.

The heating means of the container 100 is also not particularly limited, and for example, an electric heater wound around the outer wall surface of the container, or a hot air oven 130 provided with a heater 60 and a fan 50 as shown in FIG. In addition, heating by infrared rays, high frequency induction, etc. can be used, but in order to maintain the predetermined initial temperature of 80 ° C. to 160 ° C. described above with good controllability, an oven 130 as shown in FIG. 1 is used. It is preferable to adopt a structure in which the reaction vessel 100 is housed inside. It is desirable that the walls of the oven 130 are also covered with insulation.

The container 100 is provided with a thermometer 80 such as a thermoelectric pair coated with heat resistance. The thermometer 80 is preferably provided in a container, preferably at a portion where the biomass material 90 is filled, and can accurately measure the temperature of the biomass material 90 in the container.

A thermometer 70 such as a thermoelectric pair coated with heat resistance is also provided in the oven 130. The thermometer 70 is provided in the oven 130 so that the temperature in the oven 130, that is, the surrounding space for heating the container 100 from the outside can be accurately measured.

In the example shown in FIG. 1, the temperature data of the biomass material measured by the thermometers 80 and 90 and the temperature data inside the oven are sent to an automatic arithmetic processing device 40 such as a microcomputer, where both data are sent. From the difference between the two, the calorific value of the heater 60 of the oven 130 and the rotation speed of the fan 50 are controlled by a program so that the temperature can be maintained at a predetermined temperature.

In FIG. 1, a liquid collecting device 140, a gas sampling port 150, an ammonia collecting device 160, a deodorizing device (silica gel) 170, and an oxygen sensor 180 are provided in order on the exhaust line from the container behind the back pressure regulator 120. ing. The back pressure regulator is for adjusting the pressure inside the container, and is not limited to this as long as it is a device or device configuration having a similar function. All of the other devices are provided for the purpose of treating and analyzing the reacted exhaust gas, and none of them is essential for the implementation of the method of the present invention, and the arrangement order thereof is also particularly limited. It's not something.

(Initial environment)
In the treatment method according to the present invention, after the biomass material 90 is placed in the container 100, (a) the oxygen-containing gas is placed in the container 100 in terms of oxygen supply amount of 3.4 to 33.6 g-O ₂ h ^-1 . It is supplied in kg-AFS ^-1 , more preferably 13.9 to 30.4 g-O ₂ h ^-1 kg-AFS ^-1 , and (b) the inside of the container is charged with a gauge pressure of 0.5 to 1.5 MPa. More preferably, it is kept at 0.9 to 1.0 MPa, and (c) the initial temperature is set to 80 to 160 ° C., more preferably 85 to 130 ° C., and the mixture is heated from the outside.

In the present invention, as described above, it is considered that the low-temperature oxidation reaction and the self-heating reaction of the biomass can be achieved if a stable oxygen supply is performed even if the biomass is high in water content, and the dissolved oxygen amount is an atmosphere. Since the biomass is expected to increase as the pressure rises, the biomass is placed in a relatively high-pressure environment to provide a relatively high oxygen supply.

Although it is affected to some extent by the water content of the biomass material to be treated and the set pressure in the container, the oxygen-containing gas is 3.4 to 33.6 g in terms of oxygen supply amount-O ₂ h ^-1 kg-AFS ^-1 . It is possible to induce a low-temperature oxidation reaction and a self-heating reaction of biomass at the above-mentioned predetermined initial temperature. When air is used as the oxygen-containing gas, the air aeration amount should be about 0.2 to 2.0 Lmin ^-1 kg-AFS ^-1 in a roughly converted value in order to obtain the above oxygen supply amount. good. The oxygen supplied in this way is contained in the container as an essential atmospheric gas and reacts with the carbon of the biomass material 90 to contribute to the exothermic reaction.

It is necessary to set the gauge pressure in the container to 0.5 to 1.5 MPa in order to increase the amount of dissolved oxygen in the container. It is highly possible that the high-pressure environment assists the reaction between biomass and oxygen even in high moisture conditions, and also causes a low-temperature oxidation reaction and self-heating of biomass. It also has the effect of suppressing heat loss due to water evaporation that occurs at around 100 ° C when the boiling point rises due to high pressure. When the gauge pressure in the container is less than 0.5 MPa, even if a high oxygen supply amount is given and the initial temperature is set to a predetermined temperature, the self-heating reaction of biomass cannot be induced. Since the heat generation rate at around 100 ° C. is small, for example, in an atmospheric pressure environment, the heat loss rate due to water evaporation is high, which does not lead to self-heating. On the other hand, a pressure exceeding 1.5 MPa in gauge pressure is not very desirable from the economical point of view and from the viewpoint of work safety because the equipment configuration for withstand voltage becomes large. The pressure in the container may be controlled so as to be constant at all times, or may be arbitrarily fluctuated as long as it is within the above-mentioned predetermined pressure range.

The temperature inside the container is set to 80 to 160 ° C. By setting the temperature in this range, the biomass material 90 can undergo a low-temperature oxidation reaction and a self-heating reaction, and can be raised to a temperature of up to about 300 ° C. If the temperature is less than 85 ° C., the heat generation rate due to the reaction becomes smaller than the heat loss rate due to aeration, and there is a possibility that a remarkable temperature change does not occur. On the other hand, setting the temperature to exceed 160 ° C. is not preferable because it deviates from the original purpose of reducing energy consumption. Since this temperature is within the range of the initial environment, after the temperature of the biomass material 90 in the container exceeds the initial temperature due to the self-heating reaction of the biomass material and shifts to the "heating environment" described later. , The heating from the outside may be stopped, or the heating may be suppressed only by controlling the temperature difference between the temperature of the biomass material and the temperature of the surrounding space of the container body within 1.5 ° C.

As described above, by setting a specific initial environment, it is possible to induce a low temperature oxidation reaction and a self-exothermic reaction of the biomass material to raise the temperature of the biomass material to a temperature exceeding the initial temperature.

(High temperature environment)
In the treatment method according to the present invention, when the temperature of the biomass material exceeds the initial temperature due to the self-heating of the biomass, the external heating is stopped or the heating from the outside is stopped while maintaining the supply of the oxygen-containing gas and the pressure inside the container. By limiting the heating so that the temperature difference between the temperature of the biomass material and the temperature of the surrounding space of the container is within 1.5 ° C. and continuing the reaction, the biomass material is heated to at least 160. The biomass material can be reduced and carbonized by spontaneously raising it to a temperature above ° C. The temperature rise environment is almost the same as the above-mentioned initial environment except for the temperature requirement and the heating requirement for that purpose.

Supplying the oxygen-containing gas in terms of oxygen supply amount of 3.4 to 33.6 g-O ₂ h ^-1 kg-AFS ^-1 will continue even if the temperature rise environment is changed.

The pressure inside the container is also maintained at a gauge pressure of 0.5 to 1.5 MPa in the same manner as in the initial environment described above. By setting the pressure in this range, the above-mentioned oxygen can be easily injected into the biomass material and carbonization of the biomass material can proceed.

In the treatment method according to the present invention, if the temperature rising environment is continued, the biomass temperature can be raised to a temperature higher than 300 ° C. However, from the viewpoint of semi-carbonization of the biomass material 90, heat treatment above 300 ° C. is a harsh condition for the biomass material. Therefore, it is desirable to terminate the reaction at 170 ° C. or higher and 300 ° C. or lower, more preferably 230 ° C. or higher and 280 ° C. or lower to obtain carbides of the biomass material.

The reaction can be easily stopped by stopping the oxygen supply (ventilation) and stopping the reaction at an appropriate combustion temperature. Further, in order to prevent further decomposition of the carbides of the obtained biomass material, it is preferable to reduce the pressure after the reaction is stopped and cool the obtained biomass material to the environmental temperature (25 ° C ± 10 ° C) while supplying nitrogen gas.

Next, a specific experimental example will be shown and the method for treating the biomass material according to the present invention will be described in more detail.

[Experiment 1]
Milk cow manure was used as an experimental sample. Prior to the experiment, the moist sample was dried at 105 ° C. for 24 hours and then incinerated at 600 ° C. for 3 hours to measure the water content and ash content. The total amount of organic matter (volatile components and fixed carbon) was expressed as ash-free solids (AFS), which was determined by subtracting ash from the dry solids. Samples (200 ± 1 g, moisture content 63 ± 2% wet bases (wb)) were placed in reaction vessels in each experiment.

A schematic diagram of the experimental system is shown in FIG. As the reaction vessel 100, a stainless steel pressure-resistant vessel having a volume of about 1 L was used. In order to maintain the heat insulating property of the experimental sample 90, the wall surface of the container has a double structure separated by air. The reaction vessel 100 was placed in the oven 130 and ventilated from the bottom of the vessel 100 using an air cylinder 10 and a mass flow controller 30 (F-201CV Series, manufactured by Bronkhorst). The air volume was set to 0.83 ± 0.02 L min ^-1 kg-AFS ^-1 (corresponding to oxygen supply amount: 13.9 ± 0.4 g-O ₂ h ^-1 kg-AFS ^-1 ). The pressure in the container 100 was adjusted to 1.0 MPa (= gauge pressure: 0.9 MPa) with a back pressure regulator 120 (BP-3 Series, manufactured by Go Regulator). The concentrations of gas species (O ₂ , CO, CO ₂ ) contained in the exhaust gas were measured by an oxygen sensor 180 and a gas chromatograph (GC-4000, GL Science, Inc.), respectively. Various gas concentrations were converted to consumption rate or generation rate according to the method of Sarudes et al. (Saludes RB, Iwabuchi K, Kayanuma A, Shiga T. Composting of dairy cattle manure using a thermophilic-mesophilic sequence. Biosyst. Eng 2007; 98: 198-205. Doi: 10.1016 / j.biosystemseng.2007.07.003.).

The initial temperature was set to 4 levels (80, 85, 90, 100 ° C.) in order to investigate the temperature range in which the low temperature oxidation reaction of biomass and self-heating started. After the material temperature exceeded the initial temperature due to the self-heating of the biomass, the temperature in the oven and the temperature of the sample were controlled to be within 1.5 ° C. The experiment was terminated after the temperature of the biomass reached 300 ° C. In order to prevent biomass decomposition after the end of the experiment, the pressure was reduced and then cooled to the environmental temperature (25 ° C ± 10 ° C) while supplying nitrogen gas. It took about 20 minutes for the sample temperature to drop from 300 ° C to 200 ° C. For comparison, the experiment was conducted under atmospheric pressure (0.1 MPa) at a starting temperature of 100 ° C.

For elemental analysis of the sample, the CHN content was measured using an elemental analyzer (CE-440, Exeter Analytical, Inc.). The amount of oxygen was determined by the difference (O = 100-CHN-Ash). The weight loss rate of each element was calculated according to the method of Chen et al. (Chen WH, Kuo PC. Torrefaction and co-torrefaction characterization of hemicellulose, cellulose and lignin as well as torrefaction of some basic biomass in biomass. Energy 2011; 36: 803-11. doi: 10.1016 / j.energy.2010.12.036.). The high calorific value (HHV) was measured with a cylinder type calorimeter (OSK200, manufactured by Ogawa Sampling Co., Ltd.). The energy yield determined by the measured HHV and solid yield was determined according to the formula of Lu et al. (Lu KM, Lee WJ, Chen WH, Liu SH, Lin TC. Torrefaction and low). temperature carbonization of oil palm fiber and eucalyptus in nitrogen and air atmospheres. Bioresour Technol 2012; 123: 98-105. Doi: 10.1016 / j.biortech.2012.07.096.).

[result]
The sample temperature during the reaction is shown in FIG. When the initial temperature of the oven was set to 85 ° C. or higher, the self-heating reaction of the biomass proceeded, and it was confirmed that the temperature was raised to 300 ° C. During the temperature rise, a temperature stagnation of about 24 hours was observed around 160 to 170 ° C. due to the drying process (the boiling point of water is about 180 ° C. at a gauge pressure of 0.9 MPa). On the other hand, although a slight increase in temperature occurred at the initial temperature of 80 ° C., the self-heating reaction of biomass did not occur.

The oxygen consumption and the generation rates of CO and CO ₂ are shown in FIG. Oxygen consumption rate increased with increasing temperature. In the temperature range of 140 ° C. or higher, the consumption rate was constant (13.6 g-O ₂ h ^-1 kg-AFS ^-1 ), which was approximately the same as the supply rate. The CO ₂ generation rate showed the same tendency as the oxygen consumption rate. The CO ₂ generation rate increased sharply between 100 ° C and 140 ° C, and above 140 ° C, it was approximately 15.0 g-CO ₂ h ^-1 kg-AFS- ¹ . On the other hand, the CO generation rate increased exponentially, and was 0.8 g-COh ^-1 kg-AFS ^-1 at 300 ° C.

Table 1 shows the properties of the raw material and the produced biochar. The water content of the biochar was 1.0% or less, and the biochar was sufficiently dried. Through the process, the amount of carbon, hydrogen and oxygen in biochar was reduced. The weight loss rate of each element was 62.5% for carbon, 88.5% for hydrogen, and 80.3% for oxygen. The HHV of biochar was lower than the raw material due to its high ash content. The solid and energy yields were 47.1% and 34.9% on a dry matter basis, respectively.

It was confirmed that the low-temperature oxidation reaction and self-heating of biomass occurred at an initial temperature of 85 ° C. or higher in an atmosphere with a gauge pressure of 0.9 MPa, and the temperature was raised to 300 ° C.

It was found that the initial temperature affects the reaction rate, especially in the lower temperature range and the duration of the whole process. When starting at the initial temperatures of 85 ° C. and 90 ° C., there was a difference of 20 hours or more until reaching 300 ° C. as compared with 100 ° C. Therefore, in order to complete the process in a shorter period of time, it can be said that it is suitable to carry out the process at an initial temperature of 100 ° C. or higher. In this experiment, the initial temperature of 80 ° C. seemed to induce a low temperature oxidation reaction, but no significant temperature change was observed because the heat generation rate due to the reaction was smaller than the heat loss rate due to aeration.

The high pressure environment contributes significantly to the promotion of the reaction process. Under atmospheric pressure, the maximum reaction rate of the low temperature oxidation reaction is the critical moisture content of 7 to 17% (drying standard (db)) (Chen XD, Stott JB. The effect of moisture content on the oxidation rate of coal). during near-equilibrium drying and wetting at 50 ℃. Fuel 1993; 72: 787－92. Doi: 10.1016 / 0016-2361 (93) 90081-C.), It is expected that the reaction will be inhibited in higher water conditions. Will be done. On the other hand, in a high-pressure environment as in this experiment, even when dairy cow manure with a water content of 63% wb (≈170% db) was used, a low-temperature oxidation reaction and subsequent self-heating of biomass were observed. rice field. That is, it was shown that it is highly possible that the high-pressure environment assists the reaction between biomass and oxygen even in a high water state, and further causes a low-temperature oxidation reaction and self-heating of biomass. It also has the effect of suppressing heat loss due to water evaporation that occurs at around 100 ° C when the boiling point rises due to high pressure. As already mentioned, since the heat generation rate near 100 ° C is small, the heat loss rate due to water evaporation is high in an atmospheric pressure (0.1 MPa = gauge pressure (0.0 MPa)) environment, so self-heating is possible. It doesn't connect. Thus, the high pressure environment certainly promotes the low temperature oxidation reaction and the self-heating reaction of the biomass.

Generally, in the carbonization process, the amount of oxygen in the biomass decreases, but the carbon content increases relatively. However, as a result of elemental analysis, it was confirmed that the oxidation reaction during the reaction led to a decrease in hydrogen and oxygen and an increase in carbon loss. On the other hand, looking at the weight reduction rate of each element, the reduction rate of hydrogen and oxygen was larger than the carbon reduction rate. From this, it was shown that cow dung was converted to charcoal.

From the analysis results of the elements and the calorific value, it can be said that the temperature rise reaction up to 300 ° C. was a harsh condition from the viewpoint of producing a bio-solid fuel. Semi-carbonization is classified into three stages according to the temperature range (230 ° C, 260 ° C, 300 ° C) (Chen WH, Kuo PC. Torrefaction and co-torrefaction characterization of hemicellulose, cellulose and lignin as well as torrefaction of some basic constituents in biomass. Energy 2011; 36: 803-11. doi: 10.1016 / j.energy.2010.12.036.). In this experiment, the reaction was terminated when the temperature reached 300 ° C, and it can be said that the bovine manure underwent intense semi-carbonization. In addition, oxidative semi-carbonization has been reported to lower the thermal decomposition temperature of biomass and increase the rate of decomposition (Calvo LF, Otero M, Jenkins BM, Moran A, Garcia AI. Heating process characteristics and kinetics of rice. straw in different atmospheres. Fuel Process Technol 2004; 85: 279－91. doi: 10.1016 / S0378-3820 (03) 00202-9;

Chiang WF, Fang HY, Wu CH, Chang CY, Chang YM, Shie JL. Pyrolysis Kinetics of Rice Husk in Different Oxygen Concentrations. J Environ Eng 2008; 134: 316-25. 2008) 134: 4 (316);

Fang MX, Shen DK, Li YX, Yu CJ, Luo ZY, Cen KF. Kinetic study on pyrolysis and combustion of wood under different oxygen concentrations by using TG-FTIR analysis. J Anal Appl Pyrolysis 2006; 77: 22-7. Doi 10.1016 / j.jaap.2005.12.010;

Wang C, Peng J, Li H, Bi XT, Legros R, Lim CJ, et al. Oxidative torrefaction of biomass residues and densification of torrefied sawdust to pellets. Bioresour Technol 2013; 127: 318-25. doi: 10.1016 / j. biortech.2012.09.092.). From these facts, it was suggested that the optimum condition for carbonization in the present invention is a temperature range lower than 300 ° C.

As described above, as a result of the investigation in the temperature range where the low temperature oxidation reaction and the self-heating reaction of the biomass start in the atmosphere of the gauge pressure of 0.9 MPa, the self-heating of the biomass starts in the temperature range of 85 ° C. or higher. It was confirmed that. During the process, although oxygen deficiency occurred, the temperature was confirmed to rise to 300 ° C, and the biomass was converted to biochar by undergoing oxidative decomposition and drying processes. From the above, the feasibility of oxidative semi-carbonization using the self-heating reaction of biomass in a high pressure environment was shown.

Claims (5)

After putting the biomass material in the container, (a) oxygen-containing gas is supplied in the container with 3.4 to 33.6 g-O ₂ h ^-1 kg-AFS ^-1 in terms of oxygen supply amount. , (B) Keep the inside of the container at 0.5 to 1.5 MPa with a gauge pressure , (c) Set the initial temperature inside the container to 85 to 160 ° C, and heat from the outside to start processing the biomass material. Then, when the temperature of the biomass material exceeds the initial temperature due to the self-heating of the biomass, the heating conditions are changed (i) from the outside while maintaining the supply of the oxygen-containing gas and the gauge pressure in the container . Either stop or (ii) limit heating to only control the temperature difference between the temperature of the biomass material and the temperature of the surrounding space of the container to be within 1.5 ° C. A method for treating a biomass material, which comprises spontaneously raising the biomass material to a temperature exceeding at least 160 ° C. by continuing the reaction to reduce and carbonize the biomass material. The first aspect of the present invention, wherein when the biomass material naturally rises to a temperature exceeding at least 160 ° C. and then reaches an appropriate temperature, the supply of the oxygen-containing gas is stopped halfway and the combustion reaction is stopped to terminate the treatment. Biomass material processing method. (A) Oxygen-containing gas is supplied at 13.9 to 30.4 g-O ₂ h ^-1 kg-AFS ^-1 in terms of oxygen supply amount, and (b) the inside of the container is 0.9 to 1.0 MPa. The method for treating a biomass material according to claim 1, wherein the method is maintained and (c) the initial temperature is set to 85 to 130 ° C. The treatment of the biomass material according to claim 1, wherein the biomass material is naturally raised to a temperature of at least 160 to 300 ° C., then depressurized and cooled to an environmental temperature (25 ° C. ± 10 ° C.) while supplying nitrogen gas. Method. The method for treating a biomass material according to claim 1, wherein livestock manure having a water content of 40 to 80% is used as the biomass material.

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