Full-temperature range pressure swing adsorption purification method for simultaneously removing water and hydrocarbon from natural gas

Abstract

The invention discloses a full-temperature range pressure swing adsorption purification method for simultaneously removing water and hydrocarbon from natural gas. The full-temperature range pressure swing adsorption purification method comprises a light hydrocarbon and water vapor concentration process and a temperature swing adsorption rectification process, wherein in the light hydrocarbon and water vapor concentration process, the adsorption pressure is 0.5-7.0MPa, the operating temperature is 50-150 DEG C and normal-atmosphere evacuation desorption is performed; unabsorbed natural gas, containing methane and the like, is discharged from the top of an adsorption tower, is used as intermediate gas for removing most of water and light hydrocarbon, and then enters the temperature swing adsorption rectification process; a natural gas product with dew point drops of water and the hydrocarbon being lower than the minimum ambient temperature of 30-50 DEG C escapes from the top of the tower; one part is used as regenerating gas for regenerating the temperature swing adsorption rectification process and then the regenerating gas and raw gas are mixed and return to the light hydrocarbon and water vapor concentration process for further recycling the natural gas, or one part is used as purging gas of the light hydrocarbon and water vapor concentration process and the purging gas and desorption gas are pressurized for processing and recycling C2+ or sent out of a boundary for processing. By the full-temperature range pressure swing adsorption purification method, the yield of methane is 90-95% or above and the yield of C2+ is higher than 90%.

Description

technical field [0001] The invention relates to the purification field of natural gas dehydration and dehydrocarbonation, and more specifically relates to a full temperature-range pressure swing adsorption purification method for simultaneous dehydration and dehydrocarbonation of natural gas. Background technique [0002] Natural gas is a high-quality, economical and clean energy and chemical raw material. It is mainly composed of methane, as well as alkanes such as ethane, propane and butane, and a small amount of non-hydrocarbons such as nitrogen, carbon dioxide and water vapor. gas components. Natural gas must be processed or purified before it can be transported or used. Among them, natural gas dehydration and dehydrocarbonation are the two most important processes in natural gas purification, namely controlling the dew point and / or recovering alkanes. [0003] Natural gas dehydration and dehydrocarbonation are two very important independent units in natural gas purific...

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Problems solved by technology

However, the easier the adsorption, the more difficult the general desorption is, and, under the working condition of the low content of strong adsorbate in the separation or purification system, the desorption is more difficult or the regeneration is not good due to the instantaneous adsorption or co-adsorption in the traditional PSA cycle. Completely, for example, although C2+ light hydrocarbons in natural gas can be well adsorbed at normal temperature or low temperature, it is difficult to desorb, and even destroy the bed layer; and in the FTrPSA process, the inventor proposed for the first time that natural gas can be desorbed in the medium and high temperature range. PSA and its coupling with various other separation technologies have completely solved the technical bottleneck or low efficiency of natural gas at room temperature and low temperature. The adsorption and desorption mechanisms of boiling point components (methane and a small amount of hydrogen, nitrogen) and high boiling point components (water and C2+) on different adsorbents at a temperature of 60~150°C and a pressure of 0.5~6.0MPa are different. Process design, including the combination of multi-tower adsorption and multi-tower regeneration in series, composite beds composed of different adsorbents, and coupling with other separation methods (temperature swing adsorption, condensation, etc.) to reduce the cost of desorption and regeneration during the PSA cycle load or difficulty and make it easy to match with the adsorption steps, overcome the contradiction that adsorption is easy and desorption is difficult, and achieve energy saving and consumption reduction, and prolong the life of the adsorption bed; Generally, the different physical properties of various components under temperature and pressure, such as the different adsorption and desorption mechanisms on different adsorbents, first adopt the water and C2+ concentration process mainly in the medium and high temperature PSA step, and divide the raw material gas into methane The intermediate gas, hydrocarbon-rich gas and water gas (referred to as "light hydrocarbon-rich water gas") composed of nitrogen and other components can absorb most of the easily adsorbed water and C2+ at medium and high temperatures, while methane at medium and high temperatures There is basically no adsorption, so it is easy to realize the separation of most water, C2+ components and intermediate gases composed of methane, a small amount of nitrogen and hydrogen, etc.

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