DMC-1 process

Is used for treating light oils and gas condensates for hydrogen sulfide (from 100 to 5 ppm) and low molecular weight С1-С2 mercaptans (from 600 tо 20 ppm).

Stabilized oil at 40-60oC is mixed in mixer M-1 with 0.5-1 % aqueous solution of sodium hydroxide and fed to pre-alkalization device V-1. Selective removal of hydrogen sulfide and naphthenic acids from oil takes place in M-1 and V-1.

The oil, treated for hydrogen sulfide and naphthenic acids, enters the bottom of demercaptanization reactor R-1, after being premixed in mixer M-2 with a catalyst complex (CC) and air, supplied by a compressor. The catalyst complex presents a 10-20 % aqueous solution of sodium hydroxide and IVKAZ catalyst. The mixture of oil, CC and dissolved air is supplied via distributing collector to reactor R-1, where at a temperature 50─600С and a pressure 0.6─1.5 МPа oxidation of mercaptans to disulfides takes place following reaction:

dmc-1

The reactor presents a column with sieve perforated trays. Intensive mixing of the oil and CC is provided in the inter-tray space of the column due to a high velocity of flow through perforations of the trays.

From the top of the column the reaction mixture passes to separator V-2, where the oil is settled from the CC. From the bottom of V-2 the CC is returned to reactor R-1 via mixer M-1.

Depending on mercaptan content the pressure in the reactor is maintained equal to 0.6-1.5 MPa in order to provide complete air dissolution in a liquid phase. A mixture of the crude, CC and dissolved air is fed through a distributing collector to the reactor, where oxidation of mercaptans to disulfides at 50-60oC proceeds according to reaction (1).

A reactor presents a column with sieve perforated trays. Intensive mixing of the oil and CC is provided in the intertray space of the column due to a high velocity of flow through perforations of trays. From the top of the column the reaction mixture passes to separator V-2, where the oil is settled from the CC. From the bottom of V-2 the CC is returned to reactor R-1 via mixer M-1. The demercaptanized oil from the top of V-2 flows to separator V-3 for separation from entrained drops of the CC. From V-3 the oil is loaded to storage tanks.

Alkaline solutions and catalyst complex solution are prepared in vessels V-2 and V-3. A direct supply of spent CC supply directly to V-1 from a pump P-1 is also provided. In 1995, a commercial oil demercaptanization plant for 4 MM t/yr capacity was built and put into operation on Tengiz GPZ. Catalyst consumption is 0.05 g/t, alkaline consumption is 50 g/t. The process provides removal of methyl- and ethyl mercaptans to residual content below 5 ppm.

DMC-1 process flow diagram

dmc3 dmc4