Circulation type combustion treatment method, power generation method and carbon dioxide absorbent obtained therefrom

Abstract

To provide a circulation type combustion method that enables effective use of incineration ash generated by burning biomass fuel and reduction of emissions of carbon dioxide, and an inorganic fertilizer and a carbon dioxide absorbent that are obtained therefrom.SOLUTION: A circulation type combustion treatment method includes: a combustion process of burning biomass fuel for heat recovery and obtaining incineration ash mainly composed of an inorganic component; a carbon dioxide adsorption process of causing the incineration ash to react with carbon dioxide to obtain a carbonate-containing material; and a process of converting the carbonate-containing material to a fertilizer. Since the fertilizer is used for biomass fuel or for growing a plant serving as a material of the biomass fuel, the carbon dioxide emissions are reduced.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a circulatory combustion treatment method for biomass fuel with reduced carbon dioxide emissions, a power generation method, and a carbon dioxide absorbent using incineration ash obtained by combustion. [Background technology]

[0002] Biomass fuels are attracting attention as a fuel that can reduce carbon dioxide emissions. As biomass fuels, wood biomass fuels such as wood and unused parts of vegetables, fruits, grains, etc. are expected to be biomass fuels. For example, vegetable waste, residues discharged from food processing facilities and alcohol and juice factories, as well as grain stalks, leaves, and roots are also attracting attention as renewable energy resources. By using these plant biomasses as fuel for power generation, etc., carbon dioxide emissions can be reduced.

[0003] The incineration ash generated by the combustion of biomass fuel cannot be incorporated into a recycling-oriented society unless it is reused, and will be disposed of as waste. It is widely known that grass and wood ash is reused as fertilizer, focusing on the fact that it contains a lot of potassium. Plant-based biomass fuel contains a lot of potassium, as well as other inorganic components such as phosphorus and magnesium that are necessary for plant growth, so it would be advantageous if it could be used as inorganic fertilizer.

[0004] When incineration ash is generated from the combustion of biomass fuel, it is believed that metals exist as oxides such as potassium oxide when the fuel is burned at high temperatures. It is assumed that such oxides will react with carbon dioxide and become carbonates if left in the air. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-150958 A [Patent Document 2] JP 2020-168740 A [Patent Document 3] JP 2018-145338 A

[0006] Patent Document 1 discloses that, among the incineration ash from a biomass fuel combustion device, fine powder with a relatively high potassium concentration is reused as a raw material for fertilizer, while coarse powder with a low potassium concentration is discarded without being reused. In order to solve this problem, fertilizer components are mixed into the entire combustion ash and the entire ash is used as fertilizer.

[0007] Patent Document 2 discloses blending a calcium-containing substance with biomass fuel in order to solve problems such as clogging of combustion equipment that occur when phosphorus-rich biomass fuel such as sludge is burned.

[0008] Patent Document 3 discloses that potassium is dissolved in the ash by adding zeolite and water to cellulosic incineration ash, and the potassium is adsorbed onto the zeolite to produce artificial sand containing fertilizer for use as a gardening material or greening material. Summary of the Invention [Problem to be solved by the invention]

[0009] However, these documents only disclose the use of incineration ash as fertilizer, and do not teach the use of incineration ash as a carbon dioxide adsorbent. If carbon dioxide emissions can be reduced, it is expected to have a great effect on maintaining and improving the global environment. The present invention has been made in consideration of the above problems, and aims to provide a circulatory combustion method that effectively utilizes incineration ash produced by the combustion of biomass fuel and reduces carbon dioxide emissions, as well as inorganic fertilizer and carbon dioxide absorbent obtained therefrom. [Means for solving the problem]

[0010] The present invention is a circulatory combustion treatment method characterized by comprising a combustion step in which biomass fuel is burned to recover heat and incineration ash containing inorganic components as a main component is obtained, a carbon dioxide adsorption step in which the incineration ash is reacted with carbon dioxide to form a carbonate-containing material, and a step in which the carbonate-containing material is used as fertilizer, and the fertilizer is used to grow biomass fuel or plants that are the raw material for the biomass fuel.

[0011] The present invention also provides a circulatory power generation method that burns biomass fuel to generate power and includes a combustion step of obtaining incineration ash mainly composed of inorganic components, a carbon dioxide adsorption step of reacting the incineration ash with carbon dioxide to obtain a carbonate-containing material, and a step of using the carbonate-containing material as fertilizer.

[0012] The fertilizer can be used as a fertilizer with carbon dioxide emission rights, and the incineration ash can be used as a carbon dioxide absorbent.

[0013] The present invention also relates to a carbon dioxide gas absorbent produced from the incineration ash obtained in the above combustion process. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram showing an example of the carbon dioxide gas recovery processing method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described below. The biomass fuel to be burned in the present invention is a biological fuel extracted from organic resources in nature, such as plants and agricultural products other than fossil fuels. Examples of biomass fuels include waste wood, thinned wood, driftwood, agricultural crops, grasses, vegetable waste, food processing residues, fruits, unused parts of grains and wood, pulp residues, etc. Other examples include waste food, household waste, sludge, livestock manure, etc., but from the viewpoint of heat recovery and mass processing, wood-based or food processing residues or those mainly containing these are suitable. In addition, chicken manure and other materials containing a relatively large amount of potassium are also suitable. Biomass fuel may be mixed with auxiliary materials containing alkaline earth metal oxides, such as materials that promote or increase combustion and heat generation, materials that adjust the properties of incineration ash, and materials that mold the fuel into a specific shape such as granules. As such auxiliary materials, those containing one or more alkaline earth metal oxides selected from calcium oxide, light-burned dolomite, and light-burned magnesia are preferable.

[0016] There are no limitations on the equipment that burns biomass fuel, but a combustion equipment for power generation or boilers is suitable in terms of heat recovery efficiency and large-scale processing. Equipment may be either dedicated to biomass fuel or equipment that can be used in combination with fossil fuel, but a combustion equipment dedicated to biomass fuel or one that uses biomass fuel as the main component is preferable. The higher the combustion temperature, the higher the proportion of inorganic components such as potassium present in the incineration ash as oxides, so it is preferable to burn at 800°C or higher, preferably 950°C or higher.

[0017] The combustion method may be either a method of completely burning the material by supplying sufficient air or a method of partially burning the material by supplying less than the theoretical amount of air. The former method has the advantage of maximizing the calorific value and improving the heat recovery efficiency. The latter method has the advantage that the amount of generated heat is small, but the amount of carbon dioxide contained in the combustion exhaust gas can be significantly reduced. In this case, unburned carbon or carbide will be present in the incineration ash, but even if this is contained in the fertilizer, it can be expected to function as a soil conditioner. In the latter case, it is preferable to increase the calorific value by adjusting the amount of air so that at least a part of the carbon content, preferably 50 to 80 wt%, is burned.

[0018] When biomass fuel is burned, heat is generated, and combustion exhaust gas and incineration ash are also produced. The heat is used for generating electricity and heating boilers. Incineration ash contains metal oxides such as potassium, so it is useful as a carbon dioxide adsorbent. The potassium content in the incineration ash should be 5 wt% or more, preferably 10 wt% or more, as potassium oxide.

[0019] The carbon dioxide gas adsorbent may be made of only incineration ash, but it is preferable to provide a mixing step in which auxiliary materials containing an oxide of an alkaline earth metal are mixed with the incineration ash, and the mixture is mixed and granulated as necessary to obtain a carbon dioxide gas adsorbent with adjusted components and shape. As the oxide of an alkaline earth metal, magnesia or burnt dolomite, which is useful as a fertilizer component, is preferable, but quicklime or slaked lime, etc., or a mixture of these may also be used. When granulating, a method in which the incineration ash and auxiliary materials are kneaded and mixed in the presence of moisture is suitable.

[0020] In the combustion treatment method or power generation method of the present invention, in the carbon dioxide adsorption step, the incineration ash is brought into contact with a carbon dioxide-containing gas to adsorb carbon dioxide, and metal oxides in the incineration ash are converted into carbonates.

[0021] There is no limitation on the equipment used in the carbon dioxide gas adsorption step, but an equipment capable of efficiently contacting the incineration ash or the carbon dioxide gas adsorbent with the carbon dioxide gas-containing gas is suitable. When making an inorganic fertilizer, it is preferable that this equipment has a granulation function, and examples of such equipment include a fluidized granulation reaction tank and a fluidized drying equipment, and commercially available equipment can be used. In the carbon dioxide gas adsorption step, auxiliary materials such as water and magnesia can be mixed in order to granulate, increase the adsorption of carbon dioxide gas, or adjust the fertilizer components. The temperature in the carbon dioxide gas adsorption step must be hot, and is preferably 250 to 900°C, and preferably 400 to 700°C. If the temperature is high, carbonates will decompose, and if the temperature is low, the reaction rate will decrease.

[0022] There are no restrictions on the carbon dioxide-containing gas used in the carbon dioxide adsorption process, but if it is combustion exhaust gas generated when burning biomass fuel, the equipment and operation will be simple and it will be possible to significantly reduce the amount of carbon dioxide emitted as exhaust gas.

[0023] In the carbon dioxide gas adsorption process, the incineration ash adsorbs carbon dioxide gas and becomes a carbonate-containing material. It is preferable to carry out the process so that all or most of the metal oxide in the carbonate-containing material becomes carbonate. Specifically, it is preferable to carry out the process so that 90 wt% or more of potassium oxide becomes carbonate.

[0024] The carbonate-containing material obtained in the carbon dioxide gas adsorption step contains inorganic fertilizer components including potassium carbonate, and is therefore used as a fertilizer. The fertilizer may be the carbonate-containing material alone, but may also be mixed with other components for ease of use as a fertilizer or to adjust the fertilizer components, and may be molded or otherwise processed. Advantageously, the carbonate-containing material recovered in the recovery step is sent to a fertilizer production step to produce an inorganic fertilizer of a predetermined quality. In the fertilizer production step, various fertilizer components, moldability improvers, water-soluble regulators, water, etc. can be added to the carbonated incineration ash as necessary, and the mixture can be mixed or granulated.

[0025] The fertilizer of the present invention is not limited to those used as fertilizers, but also includes those used as soil improvement materials containing fertilizer components.

[0026] If this inorganic fertilizer is used to fertilize plants that are the source of biomass fuel, a circular system will be completed.

[0027] Next, the circulation type system which the present invention aims at will be described with reference to a block diagram showing an example of the carbon dioxide gas recovery processing method of the present invention.

[0028] Biomass fuel is burned in the combustion process, and thermal energy is recovered and used for power generation, etc., resulting in incineration ash and combustion exhaust gas. The incineration ash is mixed with auxiliary materials as necessary to become a carbon dioxide adsorbent. This carbon dioxide adsorbent is sent to the carbon dioxide adsorption process, where it comes into contact with combustion exhaust gas with a specified carbon dioxide concentration and temperature, converting the oxides of alkaline (earth) metals into carbonates, creating a carbonate-containing material. This is sent to the fertilizer manufacturing process to become fertilizer. This fertilizer is spread on farmland to help the growth of plants that will become food ingredients. The grown plants are sent to food factories, and the waste discharged here is used again as biomass fuel. EXAMPLES

[0029] Examples of the present invention will be described below.

[0030] Example 1 1 kg of sun-dried grape prunings was heated and incinerated in air in a large iron crucible to obtain 129 g of incineration ash.

[0031] Example 2 1 kg of sun-dried, harvested tomato branches and leaves was used and heated and combusted in the same manner as in Example 1 to obtain 70 g of incineration ash.

[0032] Example 3 1 kg of sun-dried asparagus branches and leaves was heated and combusted in the same manner as in Example 1 to obtain 82 g of incineration ash.

[0033] Example 4 1 kg of dried coffee beans was used and burned in the same manner as in Example 1 to obtain 33 g of incineration ash.

[0034] Example 5 1 kg of dried tea leaves was used and burned in the same manner as in Example 1 to obtain 70 g of incineration ash.

[0035] Example 6 1 kg of commercially available roasted chicken manure was used and heated and combusted in the same manner as in Example 1 to obtain 375 g of incineration ash.

[0036] Example 7 We used 1 kg of thinning wood chip incineration ash discharged from a biomass power plant.

[0037] The chemical composition (wt%) of the incineration ash in each example by X-ray fluorescence (XRF) analysis is shown in Table 1. In addition, the volatile matter in the incineration ash was taken as unburned matter, and the content (g / 100 g) was measured, and the results are shown in Table 1.

[0038] [Table 1]

[0039] Example 8 The incineration ash obtained in Examples 1 to 7 was used as carbon dioxide gas adsorbents (1 to 7), which were filled into a ceramic tube and reacted with carbon dioxide gas by heating for 1 hour at the temperatures shown in Table 2 in a carbon dioxide gas stream with the air blocked off. The incineration ash obtained in Example 1 was designated as adsorbent 1, and the same applies below. The reaction product was cooled to room temperature in a carbon dioxide gas stream, and then heated at 1100°C for 1 hour in a muffle furnace to pyrolyze the reaction product and release carbon dioxide gas. The amount of carbon dioxide gas absorbed (g) per 100 g of the adsorbent was calculated from the weight loss. The results are shown in Table 2. It can be seen that a high carbon dioxide absorption rate is observed within the temperature range of approximately 400°C to 700°C.

[0040] [Table 2]

[0041] Example 9 For the carbon dioxide gas adsorbents (1 to 7), the content (wt%) of fertilizer components in the reaction products contained after carbon dioxide gas adsorption at 400° C. in Example 8 was determined by X-ray fluorescence (XRF) analysis. The results are shown in Table 3. [Table 3]

Claims

1. A circulatory combustion treatment method with reduced carbon dioxide emissions, comprising: a combustion step in which biomass fuel is burned to recover heat and to obtain incineration ash mainly composed of inorganic components; a carbon dioxide adsorption step in which the incineration ash is reacted with carbon dioxide to form a carbonate-containing material; and a step in which the carbonate-containing material is used as fertilizer, the fertilizer being used to grow biomass fuel or plants that are the raw material for the biomass fuel.

2. 2. The circulatory combustion treatment method according to claim 1, wherein the fertilizer is used as a fertilizer with carbon dioxide emission rights attached.

3. 3. The circulating combustion treatment method according to claim 1 or 2, characterized in that the incineration ash obtained in the combustion step is used as a carbon dioxide absorbent.

4. A carbon dioxide gas absorbent characterized by being produced from incineration ash obtained in a combustion process.

5. A circular power generation method with reduced carbon dioxide emissions, comprising: a combustion step of burning biomass fuel to generate electricity and obtaining incineration ash mainly composed of inorganic components; a carbon dioxide adsorption step of reacting the incineration ash with carbon dioxide to form a carbonate-containing material; and a step of using the carbonate-containing material as fertilizer.

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