Is used for treating sulfur-alkaline waste waters and technological water condensates for sulfur compounds
The process consists in liquid-phase oxidation of toxic sulfur compounds (hydrogen sulfide, sodium sulfide, hydrosulfide, sulfite and mercaptides) with air oxygen to neutral products (dialkyl disulfides, sodium sulfate and thiosulfate) over homogeneous IVKAZ-W catalyst.
Waste waters, separated from oil products and mechanical impurities, are supplied from vessel V-1 with pump P-1 via heat exchangers H-1 and H-2 to reactor R-1. Before the reactor IVKAZ catalyst solution is pumped with a dosing pump to the waste water flow. Oxidation of sulfide and mercaptide sulfur takes place in the reactor at a temperature of 40–65 oC and a pressure of 0.4–0.5 MPa over the catalyst with air oxygen, supplied to the bottom of the reactor, following the reactions:
2 Na2S + 2 O2 + H2O Na2S2O3 + 2 NaOH
Na2SО3 + O2 Na2SO4
2 RSNa + 0,5 O2 +H2O RSSR + 2 NaOH
From the top of R-1 the treated waste waters with air are passed to air separator V-2. From the top of V-2 the spent air is directed to the nearest incinerator and treated waste waters after cooling in a cooler C-1 to 40–50oC to biological treatment plants. The process provides the degree of sulfide and mercaptide sulfur oxidation up to 99.9 %.
Serox-W process is being used since 1990 at Ryazan refinery and since 1995-96 on Yaroslavl and Kuibyshev refineries for treatment of sulfur-alkaline waste waters and technological condensate from catalytic cracking units and also for treatment of sulfur-alkaline waste waters of pyrolysis plant of J.S. «LUKOIL-Neftokhim» (Burgas, Bulgaria).
The capacity of the plants is 30 m3/hr, the residual sodium sulfide content does not exceed 20 mg/l, that of sodium mercaptides does not exceed 5 ppm. At present all Serox plants are designed with utilization of special homogeneous IVKAZ-W catalyst.
FLOW DIAGRAM OF THE SEROX-W PROCESS