Liquefaction process method and device capable of adjusting carbon dioxide concentration and separating carbon dioxide from critical biogas

Abstract

The invention discloses a liquefaction process method and a device capable of adjusting carbon dioxide concentration and used for separating carbon dioxide from biogas, wherein the biogas is subjected to dehydration and desulfurization pretreatment and then is subjected to multi-stage compression until the partial pressure of carbon dioxide in the biogas reaches 6.5 MPa and a critical state at the temperature of less than or equal to 25 DEG C is reached, and then the biogas is cooled to the temperature of less than 25 DEG C through a condenser; and carbon dioxide gas in the biogas is liquefied, separated and recycled. Moreover, the concentration of the carbon dioxide is increased by arranging bypass adjustment, and the partial pressure of the carbon dioxide is ensured to be 6.5 MPa or above, so that the carbon dioxide is liquefied at the normal temperature of 25 DEG C and is convenient to store. After the liquid carbon dioxide is separated, the remaining gas is pressurized and purified to obtain high-concentration methane. According to the method and the device, the content of methane separated from the biogas can reach 98% or above, the purity of carbon dioxide gas liquefied at normal temperature through pressurization can reach 98% or above through purification and enrichment, the method and the device are suitable for large-scale continuous production, the system is simple in structure, continuous and convenient to operate, energy consumption is reduced, and the method and the device have wide technical application prospects.

Description

technical field [0001] The invention belongs to the technical field of biogas comprehensive utilization, and in particular relates to a liquefaction process method and device for separating carbon dioxide from critical biogas with adjustable carbon dioxide concentration. Background technique [0002] Energy is a strategic resource for the economic development of countries all over the world, and is the core and power source of social productivity. Biogas is a clean fuel with excellent performance. It not only has rich sources of raw materials and is cheap, but also has the advantages of high combustion thermal efficiency, low cost, green, low emission, renewable, and better anti-knock performance than other gases. It is a high-quality renewable Biomass energy. [0003] Biogas usually contains about 60% methane, about 40% carbon dioxide, hydrogen sulfide and water vapor and a small amount of impurity gases. Therefore, it is necessary to purify the biogas and increase the pu...

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Problems solved by technology

[0008] 4) Membrane method is that when the compressed biogas without liquid water and oil flows along the inner cavity of the hollow fiber tube, the partial pressure of various gases is determined by the high pressure side (raw material side) and the low pressure side (permeation side) of the hollow fiber tube. The driving force of formation - under the action of partial pressure difference, the gas with large solubility coefficient and diffusion coefficient (such as CO 2 、H 2 S) preferentially permeates through the tube wall, and the rest of the gas (CH 4 ) is relatively difficult to achieve the purpose of separation, but the price is expensive, the investment is not proportional to the recovery, and it is difficult to promote

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