Process and apparatus thereof for low-temperature cracking and high-temperature gasification of biomass

Abstract

The invention discloses a process and an apparatus thereof for low-temperature cracking and high-temperature gasification of biomass. By adopting superheated vapor steam as oxidizing agent and an energy carrier, the process comprises the following steps of: firstly, carrying out the low-temperature cracking on the biomass fuel in the temperature region of 500-800 DEG C and obtaining the crude synthetic gas and the coke without containing alkali metal oxides; secondly, carrying out the high-temperature gasification on the crude synthetic gas and the coke in the temperature region of 1200-1600 DEG C to obtain the initial synthetic gas without containing tar component; finally, cooling, dust-removing, deacidifying and drying the generated initial synthetic gas, i.e., acquiring the pure synthetic gas of high quality. The apparatus mainly consists of a cracking furnace, a gasifying furnace, a low-temperature plasma torch heater, a high-temperature plasma torch heater, a water storage tank,a water delivery pump and a heat exchanger and the like. The process of the invention has the advantages of easy control, low energy consumption and investment cost and high efficiency of cooled coalgas; the generated synthetic gas has high calorific value and does not contain tar and alkali metal compounds. The invention is suitable for not only biomass gasification combined cyclic power generation, but also preparation of biomass liquid fuel.

Description

technical field [0001] The invention relates to a technology for converting combustible materials into clean and high-efficiency synthesis gas, in particular to a biomass low-temperature cracking high-temperature gasification process and its equipment. Background technique [0002] The gasification technology of combustible materials has developed rapidly at the end of the 20th century, especially the technology for gasification of coal has been quite mature. Researchers have successfully developed a gasification technology with wide applicability to coal types, high gasification efficiency, and pollution-free gasification. Less coal gasification process. The gasification technology of biomass such as branches, straw, rice straw or other agricultural and forestry wastes is a new technology for comprehensive energy utilization that has emerged in this century. The existing biomass gasification technology mainly includes fixed bed gasification technology. , fluidized bed gasi...

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Problems solved by technology

[0003] 1. The composition and calorific value of biomass fuel are extremely unstable, the ignition point is low, the ignition reaction is fast, and deflagration is prone to occur, and over-temperature coking and scaling are formed in the local area of ​​the gasifier, and the operating temperature of the gasifier is extremely difficult to control

[0004] 2. When air is used as the oxidant, due to the presence of a large amount of unreacted N in the air, 2 components, will lead to N in the syngas 2 High content, effective gas (CO+H 2 ) content is low, H 2 The / CO ratio decreases, and the calorific value of the synthesis gas is low and unstable, generally only maintained at 5000KJ / Nm 3 Below, it is difficult to meet the subsequent industrial utilization

[0005] 3. When oxygen-enriched air is used as the oxidant, although the N in the syngas can be reduced 2 content, but it is necessary to install an air separation device with a large volume and high energy consumption, which will greatly increase the cost of the entire gasification process

[0006] 4. When the combination of oxygen-enriched air and water vapor is used as the oxidant, although the N in the syngas can be reduced 2 content, increasing H in syngas 2 content, but water vapor still needs to consume a lot of heat energy as a reaction medium, and the accumulation of energy consumption for separating air will also greatly increase the investment of the entire gasification process

Moreover, the high-temperature syngas and the air mixed in it will take away a large amount of sensible heat, so that the ratio of heat energy converted into chemical energy will be greatly reduced, resulting in low cold gas efficiency of the entire gasification process, generally below 70%. In the best case, it will not exceed 80%

[0008] 6. The operating temperature of the gasifier is mostly designed to be 800-1200°C, and the biomass fuel that undergoes gasification reaction in this temperature range will produce a large amount of tar that is difficult to remove, and too much tar will accumulate and stick in equipment and pipelines , can cause pipeline blockage and equipment contamination

[0010] In view of several fatal flaws in the above-mentioned biomass direct gasification process, it is still difficult to apply it in actual production

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