A down-draft type biomass gasifier using water vapor to increase the calorific value of gas

Abstract

The utility model discloses a kind of to increase the lower suction type biomass gasifier of gas heat value with water vapor, the gasification furnace includes furnace body, the upper end of furnace body is equipped with feed inlet, and lower part is equipped with gas outlet and slag outlet respectively;Furnace body inner cavity is from top to bottom in turn drying zone and pyrolysis zone, oxidation zone and reduction zone;Annular air duct is equipped along the inner wall of furnace body oxidation zone, the outer side of this annular air duct is communicated with the water vapor inlet for passing in water vapor;Annular air duct is constituted by upper baffle and lower baffle, and its vertical section is triangle structure;Upper baffle middle is funnel shape, and it is communicated with reduction zone;Lower baffle is equipped with air hole, and annular air duct is communicated with oxidation zone through the air hole.The utility model is simple in structure, reasonable in design, can reduce the energy consumed by lower suction type biomass gasification furnace in-furnace temperature excessively high, increase gas production and save fuel, make low quality biomass gas into high calorific value, low emission combustible gas.

Description

Technical Field

[0001] This utility model belongs to the technical field of biomass gasification furnaces, and relates to a downdraft biomass gasification furnace that utilizes water vapor to increase the calorific value of the fuel gas. Background Technology

[0002] Existing biomass gasifiers are divided into updraft and downdraft types. Updraft gasifiers are rarely used now due to problems such as high tar emissions, the need for a sealed furnace opening, and the inability to continuously feed fuel. The more advanced downdraft biomass gasifier is now widely used. In the gas production process of downdraft biomass gasifiers, combustible gases such as carbon monoxide, hydrogen, and methane are produced through oxidation-reduction reactions. Insufficient oxygen and hydrogen during the reaction reduces the calorific value of the combustible gas. Researchers have been trying to increase the calorific value by adding oxygen or hydrogen to the reaction, but this significantly increases costs in practical applications. How to control the carbon, hydrogen, and oxygen to complete the reaction completely without increasing costs or with minimal cost increase is a pressing issue for researchers of downdraft biomass gasifiers. Utility Model Content

[0003] The purpose of this invention is to provide a downdraft biomass gasifier that uses water vapor to increase the calorific value of the gas. This gasifier can reduce the energy consumed by excessively high temperatures inside the downdraft biomass gasifier, increase gas production and save fuel, and transform low-quality biomass gas into high-calorific-value, low-emission combustible gas.

[0004] The technical solution adopted in this utility model is as follows: The gasifier includes a furnace body 1, with a feed inlet 2 at the upper end and a gas outlet 7 and a slag outlet 6 respectively at the lower part; the inner cavity of the furnace body 1 consists of a drying zone and a pyrolysis zone 13, an oxidation zone 12, and a reduction zone 10 from top to bottom; its characteristic is:

[0005] An annular gas passage 3 is provided along the inner wall of the oxidation zone 12 of the furnace body 1. The outer side of the annular gas passage 3 is connected to the steam inlet 8 for introducing steam.

[0006] The annular airway 3 is composed of an upper baffle 4 and a lower baffle 5, and its vertical cross-section is a triangular structure.

[0007] The upper partition 4 is funnel-shaped in the middle and leads to the reduction zone 10; the lower partition 5 is provided with a vent hole, and the annular air passage 3 communicates with the oxidation zone 12 through the vent hole.

[0008] With the above structure, during operation, steam is injected into the oxidation zone of the gasifier through the steam inlet, annular gas duct, and vents on the lower baffle. This steam undergoes a reduction reaction with CO2, absorbing heat and producing mostly CO, CH4, and H2. C reacts with H2O, absorbing heat and reacting as water gas to produce CO and H2. The normal oxidation zone temperature is 1000-1200 degrees Celsius. Injecting steam lowers the surrounding temperature of the oxidation zone, except for the funnel opening which maintains a high temperature (facilitating chemical decomposition). The steam undergoes a displacement reaction with the carbon and carbon dioxide gases in the furnace after high-temperature decomposition in the oxidation zone. Because the upper baffle is funnel-shaped: 1. When the furnace body is suctioned and discharged from the bottom, the vacuum zone below the funnel opening lacks air for reaction. The steam's entry replaces the air, introducing a large amount of nitrogen and increasing the mass of combustible gases such as CO, CH4, and H2; 2. It facilitates the falling of carbonized material from the pyrolysis zone into the reduction zone. The high-temperature exothermic reaction in the reduction zone produces CO2, and the conical shape of the carbonized material, combined with the angle of the lower baffle and the angle at which the carbonized material falls, creates a certain space.

[0009] The working principle of this invention is as follows: The inner cavity of the downdraft gasifier consists of a drying zone, a pyrolysis zone, an oxidation zone, and a reduction zone. Biomass is dried in the drying zone at 200-300 degrees Celsius and then enters the pyrolysis zone. At 300-500 degrees Celsius, some of the biomass is carbonized, producing some combustible gas and a small amount of oxygen, which then burns. The resulting high temperature of 900-1200 degrees Celsius produces CO2 through the reaction C + 2O = CO2. A small amount of water in the wood is heated in the pyrolysis zone and turned into water vapor. After passing through the reduction zone at a high temperature of 600-800 degrees Celsius, an oxidation-reduction reaction (CO2 + H2O) occurs, reacting with carbon to produce gases such as H, CO, CH4, and CO2. At this point, the content of combustible gases H, CO, and CH4 is relatively low, while the proportion of non-combustible gas CO2 is relatively high. Moisture in the biomass cannot be carbonized in the pyrolysis zone due to the lower temperature, affecting combustion in the oxidation zone and reducing gas production. Only after carbonization and at the high temperature in the oxidation zone, adding water vapor (H2O) to the biomass produces CO2 allows the carbon, CO2, and water vapor (as a gasifying agent) to react and generate gas. Controlling the amount of water vapor lowers the temperature of the oxidation zone, reducing the consumption of effective substances during combustion. Simultaneously, effectively and uniformly adding water vapor to the oxidation zone is a problem that needs to be solved. This is achieved by monitoring the discharge of various combustible gases and adjusting the amount of water vapor; insufficient or excessive amounts will affect the production of combustible gases. Practice has shown that increasing water vapor causes the O in a large number of water molecules to combine with carbon to form CO, and the hydrogen in water molecules to combine with carbon to form CH4. Adding water vapor reduces non-combustible CO2 and increases CO and CH4. 4， This increases the unit content of combustible gas, making biomass combustible gas a high-quality combustible gas.

[0010] This utility model has a simple structure and reasonable design, which can reduce the energy consumed by excessively high temperature inside the downdraft biomass gasifier, increase gas production and save fuel, and turn low-quality biomass gas into high-calorific-value, low-emission combustible gas. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of this utility model.

[0012] In the diagram: 1-furnace body; 2-feed inlet; 3-annular gas duct; 4-upper baffle; 5-lower baffle; 6-slag outlet; 7-gas outlet; 8-steam inlet; 9-plasma atomizer; 10-reduction zone; 11-thermometer; 12-oxidation zone; 13-drying zone and pyrolysis zone. Detailed Implementation

[0013] As shown in the figure, the steam inlet 8 is connected to the plasma atomizer 9 via a pipe. The plasma atomizer 9 atomizes water to produce atomized steam, which supplies steam to the steam inlet 8. Using the plasma atomizer 9 can effectively control the amount of steam injected, thereby effectively controlling the temperature of the oxidation zone.

[0014] A thermometer 11 is installed on the inner wall of the reduction zone 10 of the furnace body 1 to measure the temperature of the reduction zone, thereby controlling the temperature of the reduction zone and keeping the reduction reaction in the optimal gas production state.

[0015] The included angle between the upper partition 4 and the lower partition 5 is 30°-60°.

[0016] The working process of this utility model is as follows:

[0017] Biomass fuel is fed into the inner cavity of the furnace body 1 through the feed inlet 2 and ignited. The biomass fuel burns in the upper part of the biomass furnace through a middle oxidation reaction to provide heat, thus drying the upper biomass. The dried biomass enters the oxidation reaction zone, where C and O2 burn and release heat to produce CO2 in an oxygen-deficient environment, with the temperature reaching as high as 900-1100 degrees Celsius. In an oxygen-deficient environment, the temperature drops to 700-800 degrees Celsius. During the heat absorption process, C and CO2 undergo a reduction reaction to produce CO and H2. At this time, water vapor enters the oxidation zone 12 through the water vapor inlet 8, the annular gas channel 3, and the vent on the lower baffle 5. In the oxidation zone 12, C absorbs heat to produce water gas and reacts to produce CO and H2. The addition of water vapor improves the quality and calorific value of the fuel gas, saving biomass fuel.

Claims

1. A downdraft biomass gasifier that utilizes steam to increase the calorific value of fuel gas, the gasifier comprising a furnace body (1), a feed inlet (2) at the upper end of the furnace body (1), and a fuel gas outlet (7) and a slag outlet (6) at the lower end; the inner cavity of the furnace body (1) consists, from top to bottom, a drying zone and a pyrolysis zone (13), an oxidation zone (12), and a reduction zone (10); characterized in that: An annular gas passage (3) is provided along the inner wall of the oxidation zone (12) of the furnace body (1), and the outer side of the annular gas passage (3) is connected to the steam inlet (8) for introducing steam. The annular airway (3) is composed of an upper partition (4) and a lower partition (5), and its vertical cross-section is a triangular structure; The upper partition (4) is funnel-shaped in the middle and leads to the reduction zone (10); the lower partition (5) is provided with a vent hole, and the annular air passage (3) is connected to the oxidation zone (12) through the vent hole.

2. The downdraft biomass gasifier that utilizes steam to increase the calorific value of fuel gas according to claim 1, characterized in that: The steam inlet (8) is connected to the plasma atomizer (9) through a pipe. The plasma atomizer (9) atomizes water to generate steam, which supplies steam to the steam inlet (8).

3. A downdraft biomass gasifier that utilizes steam to increase the calorific value of fuel gas according to claim 1 or 2, characterized in that: A thermometer (11) is installed on the inner wall of the reduction zone (10) of the furnace body (1).

4. A downdraft biomass gasifier that utilizes steam to increase the calorific value of fuel gas according to claim 1 or 2, characterized in that: The included angle between the upper partition (4) and the lower partition (5) is 30°-60°.

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