System and method for preparing synthesis gas through combination of biomass washing-baking pretreatment and chemical looping gasification

Abstract

The invention discloses a system for preparing synthesis gas by combining biomass washing-baking pretreatment with chemical looping gasification, which comprises a washing-baking pretreatment unit, a chemical looping gasification unit and an oxygen carrier regeneration unit, which are connected in sequence; the washing-baking pretreatment unit comprises a crusher, a washing stirrer, a solid-liquid separator, a baking reactor and a gas-liquid separator; the crusher, the washing stirrer, the solid-liquid separator, the baking reactor and the gas-liquid separator are connected in sequence; a liquid phase outlet of the gas-liquid separator is connected with a feeding hole of the washing stirrer, and a solid phase product outlet of the baking reactor is connected with a lower feeding hole of the chemical chain gasification unit. The invention also discloses a method for preparing synthesis gas by combining biomass washing-baking pretreatment with chemical looping gasification. By adopting the system and the method provided by the invention to convert and utilize the biomass, the quality of the synthesis gas is remarkably improved.

Description

[0001] The present invention relates to the technical field of biomass pretreatment and chemical-looping gasification for syngas production, and particularly to a system and method for preparing syngas by combining biomass washing-baking pretreatment with chemical-looping gasification. Background Art

[0002] As the fourth-largest energy source in the world after coal, oil, and natural gas, biomass is also the only renewable carbon-based resource, with characteristics such as a wide variety of types, extensive distribution, and carbon neutrality. Biomass resources in China are abundant and diverse, with great development potential and utilization value. Currently, various types of biomass can be converted into high-quality fuels and chemicals through various engineering means, which is of great significance for improving practical problems such as China's energy consumption structure and supply-demand contradictions.

[0003] Biomass chemical-looping gasification technology is a promising thermochemical conversion technology, with significant advantages in improving reaction efficiency and reducing pollutant emissions. This technology uses metal oxides as oxygen carriers and heat carriers between the fuel reactor and the air reactor, avoiding the direct contact between the biomass raw material and air. This not only prevents the syngas product from having its calorific value reduced due to dilution by nitrogen in the air but also reduces the difficulty of separating and capturing carbon dioxide.

[0004] However, biomass raw materials have disadvantages such as high moisture content, high O / C ratio, low energy density, and poor grindability, resulting in a relatively high content of CO in the gas products obtained by chemical-looping gasification. 2 Moreover, at high temperatures, alkali and alkaline earth metal elements (AAEMs) in the ash are prone to causing the oxygen carrier to sinter and deactivate, as well as corroding the reactor equipment, affecting safe and stable operation. Therefore, it is very important to perform appropriate pretreatment on biomass to remove moisture, oxygen elements, and low-melting-point ash in the raw material, which helps to increase the energy density of the raw material and obtain friendly physical and chemical properties, laying a foundation for subsequent chemical-looping gasification conversion and utilization. By combining biomass washing, baking, and other pretreatment processes with chemical-looping gasification, not only is the reaction performance of biomass chemical-looping gasification significantly improved, but also high-quality syngas products can be obtained. Summary of the Invention

[0005] Aiming at the problems that biomass raw materials have high moisture content, high O / C ratio, low energy density, poor grindability, and ash rich in low-melting-point metal elements, resulting in poor chemical-looping gasification reaction performance and easy sintering and deactivation of the oxygen carrier, the present invention proposes a system and method for preparing syngas by combining biomass washing-baking pretreatment with chemical-looping gasification.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A system for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification, characterized in that it comprises: a washing-torrefaction pretreatment unit, a chemical chain gasification unit and an oxygen carrier regeneration unit; The washing-baking pretreatment unit, the chemical chaining gasification unit and the oxygen carrier regeneration unit are connected in sequence; The washing-baking pretreatment unit includes a pulverizer, a washing agitator, a solid-liquid separator, a baking reactor and a gas-liquid separator; The discharging port of the pulverizer is connected to the feeding port of the washing and stirring device; The discharge port of the washing and stirring device is connected to the feed port of the solid-liquid separator; The solid outlet of the solid-liquid separator is connected to the feed inlet of the baking reactor; The gas-liquid product outlet of the roasting reactor is connected to the feed inlet of the gas-liquid separator; The liquid phase outlet of the gas-liquid separator is connected to the feed inlet of the washing stirrer; The solid product outlet of the roasting reactor is connected to the lower feed inlet of the chemical looping gasification unit; The chemical chaining gasification unit is a fuel reactor; The oxygen carrier regeneration unit is an air reactor; The upper feed port of the air reactor is connected to the upper discharge port of the fuel reactor; The lower discharge port of the air reactor is connected to the lower feed port of the fuel reactor.

[0007] Furthermore, the baking reactor is a screw-propelled moving bed reactor with an operating temperature of 200-300° C. and a residence time of 30-80 min.

[0008] Furthermore, the baking reactor adopts a jacket heating method, and the heat source is selected from at least one of high-temperature flue gas or water vapor.

[0009] Furthermore, the washing agitator is provided with a washing medium supply port for adding washing medium and adjusting the pH value.

[0010] Furthermore, the pulverizer pulverizes the biomass raw material to a size below 80 meshes.

[0011] A method for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification comprises the following steps: S1. The biomass raw material is transported to a pulverizer and pulverized into biomass fine powder below 80 mesh; S2, conveying the biomass fine powder to a washing and stirring device, fully contacting with the biomass roasting liquid phase product, and washing and removing ash; S3. Transport the washed mixture to a solid-liquid separator for solid-liquid separation to obtain wash liquor and washed biomass fine powder; S4. Transport the washed biomass fine powder through the solid outlet of the solid-liquid separator to a baking reactor for baking treatment; S5. Transport the solid-phase product generated by the baking reactor through the solid-phase product outlet to the lower feed port of the chemical looping gasification unit as fuel for the chemical looping gasification reaction; S6. Transport the gas-liquid phase product generated by the baking reactor to a gas-liquid separator for separation. The obtained baked liquid-phase product is transported through the liquid-phase outlet to a washing agitator for recycling as a washing medium; S7. Transport the pretreated biomass and the oxidized oxygen carrier generated by the oxygen carrier regeneration unit to a fuel reactor together for chemical looping gasification reaction to generate syngas and reduced oxygen carrier; S8. Transport the reduced oxygen carrier through the upper discharge port of the fuel reactor to the upper feed port of the air reactor to react with air to generate oxidized oxygen carrier; S9. Transport the regenerated oxidized oxygen carrier through the lower discharge port of the air reactor to the lower feed port of the fuel reactor to realize the recycling of the oxygen carrier.

[0012] Furthermore, the biomass raw material can be one or a mixture of more of domestic waste, agricultural straws, garden waste branches and leaves, and forestry residues.

[0013] Furthermore, the oxygen carrier includes at least one of the following: iron ore oxygen carrier, iron-based spinel oxygen carrier, and iron-containing solid waste oxygen carrier.

[0014] The present invention has the following advantages compared with the prior art: (1) By washing the biomass, the ash content in the raw material is reduced, and the sintering inactivation of the oxygen carrier in the subsequent chemical looping gasification process is slowed down; (2) The biomass washing utilizes the baked liquid-phase product formed by the baking pretreatment, realizing the efficient utilization of the baked liquid by-product; (3) By performing baking pretreatment on the biomass, the oxygen element content in the raw material is significantly reduced, the generation of tar in the subsequent chemical looping gasification process is reduced, and the CO 2 content in the syngas is reduced, improving the product quality. Description of the Drawings

[0015] Figure 1 is a schematic diagram of a system for preparing syngas by combining biomass washing-baking pretreatment and chemical looping gasification of the present invention; Figure 2 is an experimental device diagram for carrying out the baking reaction of washed biomass in Example 3 of the present invention Figure 3 It is the experimental device diagram of chemical looping gasification of biomass after washing-baking pretreatment in Embodiment 4 of the present invention Figure 4 It is the analysis diagram of the influence of different biomass samples on the composition of syngas in chemical looping gasification after washing-baking pretreatment in Embodiment 4 of the present invention Figure 5 It is the analysis diagram of the influence of reaction temperature on the composition of syngas in chemical looping gasification in Embodiment 4 of the present invention Among them, 1. Washing-baking pretreatment unit; 2. Chemical looping gasification unit; 3. Oxygen carrier regeneration unit; 4. Crusher; 5. Washing stirrer; 6. Solid-liquid separator; 7. Baking reactor; 8. Gas-liquid separator; 9. Fuel reactor; 10. Air reactor; 11. Upper discharge port of fuel reactor; 12. Upper feed port of air reactor; 13. Lower feed port of fuel reactor; 14. Lower discharge port of air reactor; 15. Washing medium supply port.

Claims

1. A system for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification, characterized in that: include: Washing-baking pretreatment unit (1), chemical chain gasification unit (2) and oxygen carrier regeneration unit (3) The washing-baking pretreatment unit (1), the chemical chain gasification unit (2) and the oxygen carrier regeneration unit (3) are connected in sequence; The washing-baking pretreatment unit (1) comprises a pulverizer (4), a washing agitator (5), a solid-liquid separator (6), a baking reactor (7) and a gas-liquid separator (8); The discharge port of the pulverizer (4) is connected to the feed port of the washing and stirring device (5); The discharge port of the washing and stirring device (5) is connected to the feed port of the solid-liquid separator (6); The solid outlet of the solid-liquid separator (6) is connected to the feed inlet of the baking reactor (7); The gas-liquid product outlet of the roasting reactor (7) is connected to the feed inlet of the gas-liquid separator (8); The liquid phase outlet of the gas-liquid separator (8) is connected to the feed inlet of the washing stirrer (5); The solid product outlet of the roasting reactor (7) is connected to the lower feed inlet (13) of the chemical looping gasification unit (2); The chemical chaining gasification unit (2) is a fuel reactor (9); The oxygen carrier regeneration unit (3) is an air reactor (10); The upper feed port (12) of the air reactor (10) is connected to the upper discharge port (11) of the fuel reactor (9); The lower discharge port (14) of the air reactor (10) is connected to the lower feed port (13) of the fuel reactor (9).

2. A system for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification according to claim 1, characterized in that: The baking reactor (7) is a screw-propelled moving bed reactor with an operating temperature of 200-300° C. and a residence time of 30-80 min.

3. A system for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification according to claim 2, characterized in that: The baking reactor (7) adopts a jacket heating method, and the heat source is selected from at least one of high-temperature flue gas and water vapor.

4. The system for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification according to claim 1, characterized in that: The washing agitator (5) is provided with a washing medium supply port (15).

5. The system for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification according to claim 1, characterized in that: The pulverizer (4) pulverizes the biomass raw material to a size below 80 meshes.

6. A method for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification, characterized in that: The system implementation according to any one of claims 1 to 5 comprises the following steps: S1, conveying the biomass raw material to the pulverizer (4), and pulverizing it into biomass fine powder below 80 mesh; S2, conveying the biomass fine powder to the washing and stirring device (5), where it is fully contacted with the biomass roasting liquid phase product, and washed to remove ash; S3, conveying the washed mixture to a solid-liquid separator (6) for solid-liquid separation to obtain a washing liquid and washed biomass fine powder; S4, transporting the washed biomass fine powder to a torrefaction reactor (7) through the solid outlet of the solid-liquid separator (6) for torrefaction treatment; S5, transporting the solid phase product generated by the roasting reactor (7) to the lower feed port (13) of the chemical chain gasification unit (2) through the solid phase product outlet to serve as fuel for the chemical chain gasification reaction; S6, transporting the gas-liquid phase products generated by the roasting reactor (7) to the gas-liquid separator (8) for separation, and transporting the obtained roasting liquid phase product to the washing stirrer (5) through the liquid phase outlet for recycling as a washing medium; S7, transporting the pretreated biomass together with the oxidized oxygen carrier generated by the oxygen carrier regeneration unit (3) to the fuel reactor (9), performing a chemical chain gasification reaction to generate synthesis gas and reduced oxygen carrier; S8, transporting the reduced oxygen carrier through the upper outlet (11) of the fuel reactor (9) to the upper feed inlet (12) of the air reactor (10), and reacting with air to generate an oxidized oxygen carrier; S9, transporting the regenerated oxidized oxygen carrier to the lower feed port (13) of the fuel reactor (9) through the lower discharge port (14) of the air reactor (10), thereby realizing the recycling of the oxygen carrier.

7. The method for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification according to claim 6, characterized in that: The biomass raw material may be a mixture of one or more of domestic garbage, agricultural straw, garden waste branches and leaves, and forestry residues.

8. The method for preparing synthesis gas by combining biomass washing-torrefaction pretreatment with chemical chain gasification according to claim 6, characterized in that: The oxygen carrier comprises at least one of the following: an iron ore oxygen carrier, an iron-based spinel oxygen carrier and an iron-containing solid waste oxygen carrier.

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