Method and device for carrying out liquefaction and heavy hydrocarbon treatment on natural gas

Abstract

The invention relates to a process for carrying out liquefaction and heavy hydrocarbon treatment on natural gas, which comprises a low temperature liquefaction process and a heavy hydrocarbon treatment process. The low temperature liquefaction process comprises the following step that mixed refrigerant provides refrigerating capacity for the natural gas which is subjected to partial heavy hydrocarbon removal in the heavy hydrocarbon treatment process so as to implement cooling, complete heavy hydrocarbon removal and liquefaction on the natural gas in a cold box to obtain LNG (Liquefied Natural Gas); the heavy hydrocarbon treatment process comprises the following steps that the natural gas rich in heavy hydrocarbon is subjected to partial heavy hydrocarbon in a heavy hydrocarbon washing tower and the removed heavy hydrocarbon sequentially enters a deethanizing column and a rectifying column to be subjected to removal of light components and be separated into LPG (Liquefied Petroleum Gas) and light oil. According to the process disclosed by the invention, by-products, i.e. the LPG and the light oil, are also produced when the LNG is produced, the process route is advanced and the process is economical and reliable; the process can be suitable for the condition that raw material gas comprises aromatic hydrocarbon such as benzene and the like, the aromatic hydrocarbon such as the benzene and the like are removed along with the heavy hydrocarbon component and the cold box is prevented from being frozen and blocked; the process has large operation elasticity and can be suitable for natural gas heavy hydrocarbon content in a large range; the mixed refrigerant is adopted to circulate the flow and provide refrigerating capacity and gas-phase and liquid-phase refrigerants respectively enter the cold box to carry out heat exchange, so that heat exchange curves of cold and hot fluids are further matched; and the adopted refrigerating flow can effectively avoid liquid accumulation at the bottom of the cold box.

Description

technical field [0001] The invention provides a brand-new process and device for natural gas liquefaction and heavy hydrocarbon treatment, which removes heavy hydrocarbons from natural gas rich in heavy hydrocarbons, and produces liquefied petroleum as a by-product while liquefied to obtain liquefied natural gas (LNG) Gas and light oil products. Background technique [0002] As a primary energy source, the proportion of natural gas in various fields of society is gradually increasing, and its application fields have gradually expanded to power generation, automobile gas, industrial gas, urban residential gas, etc., and the market demand is increasing rapidly. However, due to the limitation of raw material conditions and user distribution, a considerable part of resources cannot be transported long-distance by pipeline using the traditional natural gas pipeline supply method, and a more convenient and reasonable method is to use liquefaction to convert methane into liquid and...

AI Technical Summary

Problems solved by technology

The purified raw natural gas first enters the plate-fin heat exchanger group for pre-cooling, and after being cooled to -30℃~-60℃, it enters the heavy hydrocarbon separator for gas-liquid separation. The gas phase flow separated from the top of the heavy hydrocarbon separator The stock continues to enter the heat exchangers of the remaining stages of the heat exchanger group, where it is cooled to -130°C ~ -166°C, and the obtained liquefied natural gas is sent to the liquefied natural gas (LNG) storage tank for storage, and the bottom of the heavy hydrocarbon separator Separation of some heavy hydrocarbons; however, this method is not effective in removing aromatics such as benzene, and the removal effect is even worse as the content of aromatics increases. For example, the raw material gas contains a large amount of aromatics (the melting point of benzene is only 5.51 degrees) , will lead to freezing blockage of the refrigerator; and the heavy component removal effect of this process is also difficult to control

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