Method and device for producing gas through combined biomass gasification of desulfurized gypsum and forestry and agricultural residues

Abstract

The invention discloses a method and a device for producing gas through combined biomass gasification of desulfurized gypsum and forestry and agricultural residues. Industrial tail gas desulfurization gypsum (the main component is CaSO4) and agricultural waste straw are crushed and screened, and are subjected to thermal decomposition and gasification at 700-950 DEG C to obtain a synthesis gas product with hydrogen and carbon monoxide as main components, and the total content of hydrogen and carbon monoxide in a gas phase product is greater than 80 vol%. Compared with other biomass gasification processes, the method provided by the invention has the advantages that the consumption is lower, and the purity of the prepared synthesis gas product is higher. Compared with other biomass gasification processes, the method provided by the invention has the advantages that the consumption is lower, and the purity of the prepared synthesis gas product is higher. And resource utilization of agricultural and forestry waste biomass is achieved while low-energy-consumption treatment and resource utilization of industrial tail gas desulfurized gypsum are achieved, so that development of biomass new energy is achieved.

Description

Technical Field

[0001] The invention relates to the field of biomass gasification, and in particular to a method and device for producing gas by combining desulfurized gypsum with agricultural and forestry waste biomass gasification. Background Art

[0002] Industrial flue gas desulfurization gypsum is mainly composed of calcium sulfate (CaSO4), which is a solid waste and a sulfur, calcium and gypsum resource with multiple potential uses. In order to reduce the impact of the stacking of desulfurization gypsum on the ecological environment, researchers at home and abroad have conducted relevant research on its resource utilization. The comprehensive application of flue gas desulfurization gypsum is mainly concentrated in the following aspects: in agriculture, phosphogypsum is mainly used as a soil conditioner or as sulfur, calcium, and silicon fertilizers; in the building materials industry, it is mainly used to produce gypsum cementitious materials, including α-type and β-type hemihydrate gypsum and phosphogypsum decomposition to produce sulfuric acid and cement. Phosphogypsum is processed through a series of chemical processes and becomes a chemical raw material that can be used in downstream production, such as for the preparation of ammonium sulfate, potassium sulfate and calcium sulfate whiskers. However, the high-value utilization of phosphogypsum has not been further promoted industrially. The main reason is that the composition of phosphogypsum is complex and contains a large amount of non-major components other than calcium sulfate dihydrate, which affects the performance of phosphogypsum, making it difficult to ensure the quality of the products obtained by the phosphogypsum resource utilization process technology; at the same time, most of the phosphogypsum processing process conditions are demanding, energy-intensive and have high operating costs, which greatly increases the cost of phosphogypsum processing.

[0003] On the other hand, in order to convert the energy stored in agricultural and forestry waste biomass into clean energy, various biomass energy conversion technologies must be used. At present, the main biomass energy conversion technologies are shaped fuel technology, direct combustion technology, biomass gasification technology, pyrolysis liquefaction technology, biogas technology, fuel ethanol technology and biodiesel technology. Compared with other existing technologies, biomass gasification technology is considered to be a sustainable energy conversion technology with broad application prospects. It not only has high resource utilization efficiency, but also can use a variety of agricultural and forestry waste biomass as raw materials and further convert it into clean energy products. Biomass gasification technology helps to reduce dependence on fossil energy, reduce greenhouse gas emissions and realize the rational and effective utilization of agricultural and forestry waste resources.

[0004] CN114437833A discloses a biomass hydrogen production method and system, which includes the following contents: (1) biomass raw materials enter a carbonization reactor for reaction, and obtain biochar and volatile gas after the reaction; (2) the biochar obtained in step (1) is mixed evenly with a gasification catalyst and then enters a gasification reactor, where it is contacted with water vapor for reaction, and the gasified gas obtained by the reaction is further subjected to a water vapor shift reaction and pressure swing adsorption treatment to obtain a hydrogen product. Since water vapor is used as a gasifying agent in the process, and the preparation process of water vapor consumes a lot of energy, the process is complicated and the operating cost is high. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a method and device for preparing synthesis gas by gasifying agricultural and forestry waste biomass using industrial flue gas desulfurization gypsum as a solid-phase gasifier. The present invention realizes the preparation of synthesis gas products by catalytic gasification of agricultural and forestry waste biomass through experimental results. In this process, after the biomass raw materials and solid waste phosphogypsum are pretreated, the phosphogypsum solid-phase gasifier releases lattice oxygen to partially oxidize the biomass at 700-950°C, and gasifies to generate synthesis gas. The present invention establishes a theoretical basis for further engineering design and amplification, so as to achieve the purpose of "treating waste with waste", resource utilization of solid industrial flue gas desulfurization gypsum, and development of new energy sources of biomass.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention pre-treats agricultural and forestry waste biomass raw materials and solid waste phosphogypsum, and then releases lattice oxygen to partially oxidize the biomass under the condition of 700-950°C, and gasifies to generate a synthesis gas product. The solid phase product can be added to the filtration and precipitation process after hydrolysis to remove insoluble and insoluble impurities in the liquid phase, and a light calcium carbonate product with higher purity can be obtained.

[0008] Specifically, a method for producing gas by combining desulfurized gypsum with agricultural and forestry waste and biomass gasification is carried out according to the following steps:

[0009] (1) Thermal decomposition process of agricultural straw biomass

[0010] The flue gas desulfurization gypsum (whose main component is CaSO4) and agricultural straw biomass are crushed and sieved at 100-110°C for pretreatment to remove more than 97wt% of free water for standby use. The pretreated desulfurization gypsum and agricultural straw biomass are mixed in a ratio of 1:3-6 and mixed evenly. The mixed material is subjected to a reduction thermal decomposition reaction at 200-800°C under the condition of nitrogen as a protective gas, and the reaction time is greater than the reduction reaction as follows:

[0011] C m H n Oy → Biochar + tar + gas products (CO2, CO, CH4, H2, etc.)

[0012] The products of reduction decomposition, biochar and impurities, participate in the subsequent gasification reduction process. The starting temperature of CH4 in the process exceeds 200°C, and the demethylation reaction process required for methane production requires a higher temperature than other gas products. H2 is mainly generated by polycondensation during pyrolysis. The generation of CO2 during pyrolysis is mainly attributed to the cracking and rearrangement of carbonyl and carboxyl groups. Carbon monoxide is the main gas produced by the pyrolysis of lignin in biomass, which is mainly released due to the breakage of COC and CO bonds.

[0013] (2) Flue gas desulfurization gypsum as gasifier agricultural straw biomass gasification process

[0014] The solid product biochar generated in (1) participates in the gasification process, and a large amount of CO2, CO and H2 are produced during the biochar gasification stage. These gaseous products are produced by the oxidation of lattice oxygen [O] in the flue gas desulfurization gypsum. The main mechanisms involved in this stage are as follows.

[0015] C+[O]=CO

[0016] CO + [O] = CO2

[0017] H2+[O]=H2O

[0018] CH4+[O]=2H2+CO

[0019] At the same time, a small amount of CO and H2 will also be produced through the intermediate process described by the following formula.

[0020] C+CO2=2CO

[0021] C+H2O=CO+2H2

[0022] CH4+H2O=CO+3H2

[0023] In this process, industrial flue gas desulfurization gypsum removes lattice oxygen to form a solid phase product calcium sulfide (purity greater than 90%). The slightly soluble calcium sulfide solid product is hydrolyzed to form soluble calcium hydrosulfide and slightly soluble calcium hydroxide, which can be used to capture carbon dioxide in exhaust gas to generate calcium carbonate products.

[0024] In the above process, the gas phase product can be subjected to heat exchange and separation and purification to obtain a synthesis gas product with hydrogen and carbon monoxide as main components. The total content of hydrogen and carbon monoxide in the gas phase product is greater than 80 vol%.

[0025] The device used in the present invention to implement the above method includes: a pressurized blower, a bubbling bed reactor, a first cyclone gas-solid separator, a second cyclone gas-solid separator, and a heat exchanger agent gas phase product purification device; the pressurized blower is connected to the air inlet of the bubbling bed reactor, the first cyclone gas-solid separator and the second cyclone gas-solid separator are connected to the heat exchanger via the series gas phase outlet, and then the gas phase product is cooled by the heat exchanger, and the temperature is lower than 100°C before entering the gas phase product purification device.

[0026] Compared with the prior art, the technical effects and advantages of the present invention include:

[0027] ① For the biomass gasification process, air, oxygen, water vapor and other gaseous substances are generally used as gasifying agents for pyrolysis, and thermochemical reactions occur under certain conditions to generate a conversion process of synthesis gas with carbon monoxide and hydrogen as the main components. Among them, the gasification process using oxygen and water vapor as gasifying agents has a complex process and high operating cost; and in the synthesis gas product obtained by using air as the gasifying agent, a large amount of nitrogen and other gas components are mixed, which makes the purity of the synthesis gas product low. In order to meet the requirements of the downstream production process for the purity of the synthesis gas, the synthesis gas purification process has to be added, thereby increasing the operating cost and energy consumption. In the present invention, industrial flue gas desulfurization gypsum is used as a solid-phase gasifying agent, which avoids the high cost and complex pure oxygen production process using air, oxygen, water vapor and other gaseous substances as gasifying agents;

[0028] ② The main component of industrial flue gas desulfurization gypsum is CaSO4, which is also a sulfur, calcium and gypsum resource with multiple potential uses. However, its general processing energy consumption is high, and the presence of impurities makes its processing process complicated. In order to reduce the impact of its stacking on the ecological environment, the present invention proposes that industrial flue gas desulfurization gypsum is used as a solid-phase gasification agent in the agricultural straw biomass gasification process, thereby reducing the processing energy consumption of industrial flue gas desulfurization gypsum, recycling the calcium and sulfur resources therein, and processing and resource utilization in large quantities;

[0029] ③ The present invention realizes the green and environmentally friendly treatment of desulfurized gypsum by combining the gasification process of industrial solid waste desulfurized gypsum with agricultural and forestry waste, and at the same time promotes the development and comprehensive utilization of biomass energy, thereby realizing the efficient utilization of resources and energy;

[0030] ④ This method not only has low energy consumption, but also the process of the gas production device is simple and feasible. The reactor technology is relatively mature and the process is easier to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of the method of the present invention.

[0032] Figure 2 It is a schematic diagram of the composition of the gas production device of the present invention.

[0033] In the figure: 1-pressure blower, 2-bubble bed reactor, 3-first cyclone gas-solid separator, 4-second cyclone gas-solid separator, 5-heat exchanger device, 6-gas phase product purification device. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below by way of examples, but the protection scope of the present invention is not limited to the contents described above.

[0037] Example 1

[0038] Industrial exhaust flue gas desulfurization gypsum and agricultural waste straw are crushed and sieved, dried at 100°C for 1 hour, free water of more than 97wt% is removed, and gypsum powder with a particle size of ≤150μm is obtained through a standard sieve. 20g of the above gypsum powder is mixed with carbon according to a ratio, and each component is calculated by weight, and the ratio is desulfurization gypsum powder: biomass = 1:4. The experimental test is to place the prepared materials in a tubular resistance furnace, and quickly heat them to 700-900°C under nitrogen protection for reaction. During the process, the temperature in the furnace is controlled between 700-900°C, and the reaction lasts for 1 hour. At the same time, the reaction solid phase is analyzed, and the CaS content in the solid phase product can be calculated to be 93%. At the same time, the gas phase product is separated, cooled, heat exchanged and purified to obtain a synthesis gas product, and the purity (total content) of the main components of hydrogen and carbon monoxide in the synthesis gas product is greater than 80vol%.

[0039] Example 2

[0040] The industrial exhaust flue gas desulfurization gypsum is crushed and sieved, naturally air-dried, dried at 100°C for 20 minutes, and more than 97wt% of free water is removed. The gypsum powder with a particle size of ≤150μm is obtained by standard sieve. The above gypsum powder is mixed evenly with agricultural waste straw according to the ratio. Each component is calculated by weight. The ratio is desulfurization gypsum powder: biomass = 1:3-6, and 3kg of the mixed material is taken for standby. In the experiment, the prepared material is placed in a small bubbling bed reactor, and the temperature is quickly raised to 750-950°C for reaction. During the process, the temperature in the furnace is controlled between 750-950°C, and the reaction is carried out for 2 hours. After that, it passes through a cyclone separator for gas-solid separation. At the same time, the solid phase product of the reaction is analyzed. By calculation, the CaS content in the solid phase product is 90%. At the same time, the gas phase product is separated, cooled, heat exchanged and purified to obtain a synthesis gas product. The purity (total content) of the main components of hydrogen and carbon monoxide in the synthesis gas product is greater than 80vol%.

[0041] Example 3

[0042] A desulfurized gypsum and agricultural and forestry waste combined biomass gasification gas production device, comprising: a pressurized blower 1, a bubbling bed reactor 2, a first cyclone gas-solid separator 3, a second cyclone gas-solid separator 4, a heat exchanger 5 and a gas phase product purification device 6; the pressurized blower 1 is connected to the air inlet of the bubbling bed reactor 2, the first cyclone gas-solid separator 3 and the second cyclone gas-solid separator 4 are connected to the heat exchanger 5 via a series gas phase outlet, and then the gas phase product is cooled by the heat exchanger 5, and the temperature is lower than 100°C before entering the gas phase product purification device 6.

Claims

1. A method for producing gas by combining desulfurized gypsum with agricultural and forestry waste and biomass gasification, characterized in that: The following steps are involved: Step 1, crushing and screening the industrial exhaust flue gas desulfurization gypsum and agricultural and forestry waste, mixing them according to a weight ratio of 1:3-6 and evenly mixing them; Step 2, pre-treating the mixed material by drying to remove free water; Step 3, adding the mixture into a bubbling bed reactor to carry out thermal decomposition and gasification reaction to obtain a gas-solid phase mixed product; Step 4, subjecting the gas-solid mixed product to multi-stage cyclone gas-solid separation to obtain a gas phase product and a solid phase product respectively; Step 5, separating and purifying gaseous impurities in the gaseous product through a heat exchange device to obtain a synthesis gas product containing hydrogen and carbon monoxide, wherein the total content of hydrogen and carbon monoxide in the gaseous product is greater than 80 vol%.

2. The method according to claim 1, characterized in that The weight percentage of CaSO4 in the industrial flue gas desulfurization gypsum in step 1 is not less than 80%.

3. The method according to claim 1, characterized in that The thermal decomposition and gasification reaction temperature in step 3 is 700°C to 900°C.

4. The method according to claim 1, characterized in that: The gas-solid mixed product obtained by the thermal decomposition and gasification reaction in step 3 includes CaS, and the purity of the CaS is greater than 90%.

5. The method according to claim 1, characterized in that The addition of the bubbling bed reactor in step 3 and the multi-stage cyclone gas-solid separation in step 4 are both carried out in a sealed state.

6. The method according to claim 1, characterized in that The temperature of the gas phase product after the heat exchange device in step (5) is lower than 100°C.

7. The method according to claim 1, characterized in that The waste heat generated by the heat exchanger in step (5) is used for the drying pretreatment in step 2.

8. The method according to claim 1, characterized in that The drying pretreatment in step 2 is performed at 100-110° C. for 1 hour to remove more than 97 wt % of free water.

9. The method according to any one of claims 1 to 8, characterized in that: The thermal decomposition and gasification reaction in step 3 is carried out under nitrogen protection.

10. A device for realizing the method of combining desulfurized gypsum with agricultural and forestry wastes to produce biomass gas according to any one of claims 1 to 9, characterized in that: The device comprises: a pressure blower (1), a bubbling bed reactor (2), a first cyclone gas-solid separator (3), a second cyclone gas-solid separator (4), a heat exchanger (5) and a gas phase product purification device (6); The pressurized blower (1) is connected to the air inlet of the bubbling bed reactor (2), and the cyclone gas-solid separator 1 (3) and the cyclone gas-solid separator 2 (4) are connected to the heat exchanger (5) via the gas phase outlets in series. The gas phase product is cooled by the heat exchanger (5) and then enters the gas phase product purification device (6).

Images