Method and equipment for recovery of oilfield associated gas hydrocarbon mixture

Abstract

The invention relates to a method for recovery of oilfield associated gas hydrocarbon mixture, which includes steps: firstly, delivering associated gas into a compressor for compression to form compressed gas with a pressure P1; secondly, subjecting the compressed gas to primary condensation at a temperature T1 to form condensed gas and liquid; thirdly, delivering the condensed gas to a molecular sieve for dewatering; fourthly, subjecting the dewatered condensed gas to dew point detection; fifthly, exhausting the dewatered condensed gas as recovered gas if the dew point temperature of the dewatered condensed water is higher than a temperature T2, and performing following steps if the dew point temperature of the dewatered condensed water is lower than the temperature T2; sixthly, subjecting the dewatered condensed gas to secondary precooling at a certain temperature T3; seventhly, subjecting the gas subjected to secondary precooling to secondary condensation at a certain temperature T4; and eighthly, separating and storing a product of secondary condensation to generate recovered hydrocarbon mixture.

Description

technical field [0001] The invention relates to the field of petrochemical industry, in particular to a recovery device and a recovery method for oilfield associated gas mixed hydrocarbons. Background technique [0002] Associated gas, also called oilfield gas, is a flammable gas mixture that accompanies crude oil spillage during oil extraction, and its components are usually methane, ethane, propane, butane, etc. Since these combustible gas mixtures cannot be discharged directly, and the recovery and reuse process is complicated, many oil fields directly burn them and discharge them. This combustion emission not only causes serious pollution to the environment, but also wastes a large amount of combustible gas energy. [0003] The traditional recovery method of oilfield associated gas is to build a light hydrocarbon processing plant. This method is complicated in installation, slow in plant construction, and inconvenient to relocate. For the associated gas produced by scat...

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Problems solved by technology

Both propane and ammonia refrigerants are flammable, difficult to realize automatic operation, and improper handling or operation can easily cause safety hazards

[0008] Whether it is expansion machine refrigeration or ammonia or propane refrigeration, the structure is relatively large, only suitable for on-site installation, and it is not easy to realize automatic operation

Moreover, the traditional process does not pay enough attention to the dehydration of molecular sieves. For the molecular sieve installed between the raw gas compressor and the refrigeration device, the temperature of the raw gas entering the molecular sieve is greatly affected by the ambient temperature, and the drying effect is very unstable. Due to the relationship between structure, it is easy to cause freeze blockage, and the production of mixed hydrocarbons often stagnates due to this

In order to solve the problem that the heat exchanger is easy to freeze and block, some manufacturers have adopted shell-and-tube heat exchangers with large gaps and low heat transfer efficiency. It is often used for low-temperature heat exchange, and the shell-and-tube heat exchanger needs to use stainless steel that can withstand low-temperature impact, so the investment in the heat exchanger is very large

In order to save costs, unscrupulous manufacturers use ordinary carbon steel shell-and-tube heat exchangers that are not resistant to low-temperature shocks, causing serious safety hazards

[0009] When the system operates when the dehydration depth of the molecular sieve does not exceed the secondary condensation temperature, the entire shell-and-tube heat exchanger needs to be heated and defrosted every one or two days. Due to the large mass of the shell-and-tube heat exchanger, the heat capacity Large, slow temperature rise, serious delay in production, difficult continuous operation of mixed hydrocarbon production, low output of mixed hydrocarbons

[0010] Since molecular sieve equipment needs to consume regeneration gas when regenerating molecular sieve equipment, the traditional process is to purge and regenerate the dry raw material gas at the outlet of the molecular sieve itself, which will consume about 10% of the raw material gas. Under the same displacement of the raw gas compressor, the mixed hydrocarbon production will decrease

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