Method for two-stage coal gasification on composite external heat fixed bed and gas furnace

Abstract

The invention discloses a method for two-stage coal gasification on a composite externally heated fixed bed and a gas furnace. In the method, by using more than two kinds of external heat for the dry distillation of raw material coal in a dry distillation stage of a two-stage gas furnace, the coal gas in a gasification stage and the coal gas in the dry distillation stage can be utilized efficiently by adopting different simple purification measures respectively, gas generation is performed by a continuous gas generation method and a circulating gas generation method, chemical synthetic raw material gases meeting different component requirements can be produced by using different oxidizers and gasifying agents, and at the same time, tar with high economic value is extract from a raw material soft coal. The method and the gas furnace have the advantages of small investment, simple operation, environmental friendliness, high comprehensive coal gasification efficiency and low gas generation cost, and are suitable for constructing or reconstructing fixed bed gas generation furnaces which operates widely at present.

Description

technical field [0001] The invention belongs to the field of coal gasification to produce chemical synthesis raw material gas, and in particular relates to a two-stage coal gasification method with a composite external heat fixed bed and a gas furnace. Background technique [0002] At present, in the production of synthetic ammonia and methanol in my country, the fixed-bed batch gas furnace with coke, anthracite or anthracite coal as raw materials occupies a considerable proportion. Since this furnace is a one-stage furnace, it cannot directly use bituminous coal with high volatile content as raw material. Otherwise, there will be problems such as high raw material gas methane and relatively serious tar phenol water pollution. As the price of anthracite is getting higher and higher, this also brings great cost pressure to manufacturers of synthetic ammonia and methanol produced by fixed-bed batch gas furnaces. It is urgent to adopt suitable non-anthracite gasification technol...

AI Technical Summary

Problems solved by technology

Due to the high operating temperature of the entrained bed coal gasification method, the raw material gas produced by it has a high effective gas composition, but this method has a long construction period, a large investment and high financial costs for operation, high-temperature ablation and wear of the nozzle, high start-up, shutdown and maintenance costs , and this method cannot extract tar light oil with high economic value in raw coal

[0006] The fluidized bed coal gasification method and the entrained bed coal gasification method also have a common deficiency: the temperature of the gas produced is above 1000°C, so the sensible heat of the high temperature gas can only be recovered in the form of steam, which reduces the production cost. Air-cooled gas efficiency

Due to the high temperature operation, the steam decomposition rate is high, the steam consumption is greatly reduced, the gasification intensity is 3 to 4 times higher than that of the dry ash Lurgi furnace, and the calorific value of the gas is increased by about a quarter, but there is still a considerable amount of methane and others in the gas Hydrocarbons, suitable as fuel gas, not suitable as raw material gas for chemical synthesis

[0010] The common disadvantages of the Lurgi furnace and the BGL furnace are: 1. Dry distillation and gasification are carried out in the first-stage furnace. Although the raw coal in the dry distillation section can recover the sensible heat of the gasification section gas produced in the gasification section, due to the direct gas-solid Heat transfer and recovery, so the mixture of the undecomposed steam in the gasification section and the tar-rich dry distillation gas from the dry distillation section will produce more phenol water, which is difficult to handle, so that it brings serious environmental problems

2. The coal gas produced by Lurgi furnace and BGL furnace is a mixture of retort gas and gasification section gas. Since retort gas contains a high amount of methane, such gas has a high calorific value and is only suitable for use as fuel gas. If it is used as a manufacturing The use of raw material gases such as synthetic ammonia and methanol requires the separation of methane, but the separation of methane is relatively difficult and consumes a lot of energy.

[0015] 1. In the down blowing stage, the carbonization heat cannot be provided for the raw coal in the carbonization section, which is intermittent carbonization, resulting in low carbonization efficiency and incomplete carbonization of the raw coal, which in turn leads to high methane content in the gasification section gas, which is not suitable for use as synthetic raw material gas

[0016] 2. The generated city gas and power gas have low calorific value and complex composition, so they can only be used as low-grade fuels with very limited uses, and cannot be further purified and used as synthetic raw material gas

[0017] 3. When the water gas in the lower stage is used as the heat carrier to directly heat and retort the raw coal in the upper stage (internal heat retort), a large amount of undecomposed steam in the water gas in the lower stage (the decomposition rate of fixed bed gasification steam is about 40-60%) and the retort generated in the upper stage Gas mixing will produce a large amount of phenol water, which is difficult to handle and will easily lead to serious environmental problems

[0018] In view of the above reasons, the two fixed-bed circulating gas production two-stage furnace process methods have not been widely used in industry

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