METHOD FOR OPTIMIZING THE PROCESS OF WASHING THE INHIBITOR FROM UNSTABLE GAS CONDENSATE AT LOW-TEMPERATURE GAS SEPARATION PLANTS OF OIL AND GAS CONDENSATE FIELDS OF THE NORTH OF RUSSIA Russian patent published in 2021 - IPC F17D3/16 

FIELD: technological processes.

SUBSTANCE: invention relates to preparation of natural gas and gas condensate to long-distance transport, in particular to automatic control of washing inhibitor - methanol - from unstable gas condensate (UGC) at low-temperature gas separation plants located in regions of the North of Russia. Method includes separation of water-methanol solution (MWS) from UGC in gas separators and liquid separators (LS) of the first and second stages of gas separation. LS of the last step involves washing methanol from the condensate with low concentration MWS. Obtained MWS at the LS output of the second gas separation stage is supplied for regeneration of methanol with its return to the process of gas and gas condensate preparation for long-distance transportation at the plant, controlled by automated process control system (PAS). PAS with specified periodicity searches for optimal flow rate of low-concentration MWS, which must be supplied to gas-liquid mixture coming from intermediate and low-temperature separators for washing from LTC methanol. At that, inertia of technological processes is taken into account. Detected PAS value is recorded in its database (DB) as the low-concentration optimum flow rate MWS setting. After that, automatically, in PID-control mode PAS maintains supply of found optimum flow rate MWS of low concentration for injection into combined flow of gas-liquid mixture, supplied to LS from intermediate and low-temperature gas separators. PAS with specified periodicity controls actual concentration of methanol in low-concentration MWS flow fed to injection injector inlet. PAS also controls temperature and concentration of methanol in MWS at output LS of last stage of gas separation. And when searching for the low-concentration optimum flow rate MWS setpoint supplied to the methanol washing injector input, prior to each next step of increasing its flow PAS calculates expected concentration C_i^ex of methanol in MWS at output LS of last stage of gas separation using formula. PAS after calculating C_i^ex, using the actual MWS actual temperature measurement data at LS output of the last gas separation stage, according to the special table loaded into its database, evaluates the possibility of MWS freezing at the next, i-th step. And, if for the next step of the setpoint search the difference between the actual MWS temperature and the MWS freezing point evaluation is less than 5°C, PAS stops the search for the setpoint and assigns the low-concentration MWS flow rate obtained at the (i-1)-th step.

EFFECT: method provides higher reliability of the plant and prevents occurrence of emergencies at production associated with potential freezing of MWS at output LS of the last stage.

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