Method for preparing liquefied natural gas by converting raw materials of coke oven gas and blast furnace gas

Abstract

The invention discloses a method for preparing liquefied natural gas by converting raw materials of coke oven gas and blast furnace gas. In the technology, the coke oven gas and the blast furnace gas are taken as the raw materials, the raw materials are subjected to normal-temperature normal-pressure dry desulfurization, gas compression, gas adsorption purification, gas isothermal-adiabatic serial methanation, gas adsorption drying and demetalization, freezing liquefication separation and other technical processes, and high-quality liquefied natural gas with the purity of over 99 percent is produced. By the technology, harmful impurities such as sulfur, naphthalene, tar, benzene, mercury and the like in the gas can be efficiently and easily removed fully at low cost, and components with low value, such as H2, CO, CO2 and the like are completely converted into required CH4 component with high value, so the method has the characteristics of low requirement on quality of feed gas, high yield of liquefied natural gas product, high product purity, low production energy consumption, no environmental pollution, reliable flow, low investment, simple operation and good economic benefit.

Description

【Technical field】 [0001] The invention relates to a process flow method for comprehensively utilizing coke oven gas and blast furnace gas to produce a large amount of liquefied natural gas. 【Background technique】 [0002] my country is the largest coke producer in the world. During the coke production process, a large amount of coke oven gas (over 80 billion cubic meters per year) will be produced by-product. Except for about half of the coke oven gas being returned to the furnace as fuel, the remaining half needs to be used separately. , Such as gas, power generation, production of synthetic ammonia, methanol, dimethyl ether, etc. However, due to the common problem of large investment or low benefit in these utilization methods, many coke production enterprises still directly burn and discharge coke oven gas in large quantities, resulting in a large waste of resources and environmental pollution. At the same time, my country is the largest steel producing country in the wor...

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Problems solved by technology

[0004] So far, some people have tried the direct liquefaction of coke oven gas to produce LNG, which is involved in the patent 200820132075.5, but because coke oven gas contains a lot of H 2 S, naphthalene, tar, CO 2 、H 2 O, metal mercury and other components, so direct liquefaction is actually impossible, and it will block the LNG cold box, and the quality of natural gas cannot meet the national standard, and the output of liquefied natural gas is small and the benefit is low

In the patent 200810055168.7, a method for producing liquefied natural gas with coke oven gas as raw material is also mentioned, but the method has the following problems: 1) coke oven gas needs to be boosted and pretreated with a blower before compression, so This prolongs the process and increases investment and operating costs; 2) After the coke oven gas is compressed, a hydrolysis process needs to be set up. The hydrolysis process uses a chemical reaction method to convert organic sulfur into inorganic sulfur and then remove it. The investment is large and the energy consumption is high. , the service life of the hydrolytic desulfurizer is also short, and the process is complicated and there are many equipments; 3) After the hydrolysis process, it is necessary to set up a rough desulfurization section and a fine desulfurization section. The MDEA process is also a process with large investment and high energy consumption; ZnO desulfurization is used for fine desulfurization, and the price of desulfurizer is high, the sulfur capacity is small, and the operating cost is high; 4) the technology adopted in its patent desulfurizes CO 2 is also removed at the same time, instead of converting it to CH 4 , so the technical CH 4 Small output and poor economy; 5) The methanation process adopted is the three-stage reaction technology of Topsoe in Denmark or Lurgi in Germany, the reaction temperature is as high as 500-600°C, the process is complicated, the investment is high, the operating load adjustment range is narrow, and it is more difficult to adapt to coke. Furnace gas mixed with blast furnace gas contains a large amount of CO, CO 2 (more than 20%) components; 6) This patent does not set a demetallization reactor before cryogenic cooling, which will cause the cold box heat exchange equipment to corrode rapidly due to the mercury present in the gas, and the equipment has a short operating life

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