Downdraft biomass gasifier

The downward suction fixed bed biomass gasifier is a new and efficient biomass gasifier independently developed and designed by the company based on years of coal gasification production experience and combined with domestic and foreign manufacturer technology. It can gasify various biomass materials such as wood chips, wood blocks, particles, herbs, straw, etc. The flow direction of the combustible gas in this furnace type is the same as the feed direction of biomass. A high-temperature oxidation zone is set up inside the furnace, and the combustible gas is sucked out from the lower part of the grate. The structure of the down draft gasifier requires combustible gases to pass through the high-temperature oxidation zone, which is conducive to further cracking of tar. The tar content in the gas is between 50-100mg/M3, which is relatively low compared to the up draft gasifier. During the reaction process, the amount of air supplied by the gasifier increases, causing more intense combustion in the throat or oxidation zone of the gasifier, resulting in a rapid increase in temperature in the oxidation zone in a short period of time. This drives the temperature of the drying zone, pyrolysis zone, and reduction zone to rise through mass and heat transfer;

Gasification principle:

The downward suction fixed bed gasification process is mainly divided into four reaction zones from top to bottom: drying zone, pyrolysis zone, oxidation zone, and reduction zone.

(1) Dry zone: The free water and bound water in biomass evaporate, and the moisture content decreases from less than 20% to below 5%. The temperature in the dry zone is 30-200 ℃.

(2) Pyrolysis zone: Biomass is cracked under anaerobic conditions to produce a large amount of non condensable combustible gas (CO, H2, CH4, etc.) and condensable tar, with a temperature range of 200-600 ℃.

(3) Oxidation zone: The gasifying agent is sent into the gasifier at this location, where biomass charcoal burns with the supplied oxygen to produce CO2. The H2 produced from partial cracking also reacts with oxygen to produce water. These two oxidation reactions generate a large amount of heat. If the oxygen supply is not sufficient to completely convert the charcoal into CO2, the charcoal will also produce CO due to partial production, with a temperature of 800-1200 ℃. Due to the downward movement of tar with combustible gas, it must pass through a high-temperature oxidation zone, resulting in secondary cracking of tar.

(4) Reduction zone: Multiple endothermic reduction reactions occur in an environment of 800-1000 ℃ and oxygen deficiency, increasing the content of CO, H2, and CH4 in combustible gas and increasing the heat value of gas production.

Advantages of Downdraft Fixed Bed Gasifier:

The pyrolysis gasification furnace uses insufficient air (anaerobic) to decompose organic matter into combustible gases, transforming the incomplete combustion process into a complete gas combustion process, and reducing the emissions of solid particles to below the emission standards. The gasification system is fully enclosed, the site is clean and beautiful, and harmless to operators. Fully automatic control process, simple and convenient operation. All feeding, slag discharge, and maintenance doors are soft sealed, and the top of the pyrolysis furnace is equipped with a sealing cover to avoid gas leakage. The furnace body is well sealed, ensuring the effectiveness of oxygen controlled pyrolysis. When pyrolysis gas self ignites, it enters the self ignition process, and the combustion aid device will automatically stop. The entire self ignition process reaches more than 90%, greatly reducing operating costs. To achieve the resource utilization of thermal energy, not only does it harmless the emission of smoke, but it also reduces the total amount of CO2 emissions.

The main components of biomass gas:

Category CO H2 CH4 CO2

For more detailed information on our biomass gasifier please do not hesitate to contact us! Welcome your inquiries,and look forward to working with you.