Shaybah


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The treatment system has been installed on a turnkey basis to upgrade raw water by stripping it with air and completely disposing of the contaminated off-gases by oxidation. Water, containing up to 200 mg/l of Hydrogen Sulphide and 3 mg/l of oil, is pumped from boreholes into a flash tank positioned above the feed tank where dissolved gases "flash off" and are discharged to the top of the tank. From here they are ducted to the Thermal Oxidiser for incineration.

Stripping

Following pH adjustment, water is pumped to eight Hydrogen Sulphide Stripping Columns (two for each of four streams) with up to 200 ppm of Hydrogen Sulphide and flowrates of up to 54 m³/hour. Water is discharged through a distributor at the top of each packed stripping column; flowing downwards over the whole area of random packings which form multiple surfaces for the displacement of Hydrogen Sulphide. A centrifugal fan blows air into the base of each stripper to absorb Hydrogen Sulphide as it passes upwards through the packings and discharges at the top of each column. Each stripping column is designed to accept variations in the flow of liquid without affecting the optimum performance of the process.

The stripping columns have a 99.5% removal efficiency and are operated with a liquid inlet temperature of 55°C at atmospheric pressure. Hydrogen Sulphide vented from the stripping columns passes to the thermal oxidiser for incineration.

Thermal Oxidiser

To meet stringent air quality emission standards, the stripping air, contaminated with Hydrogen Sulphide and hydrocarbons, passes to the thermal oxidiser which destroys the contaminants by incineration. The Thermal Oxidiser is a horizontal cylindrical unit internally lined with a suitable refractory and ceramic fibre to protect the shell against thermal stresses during warm-up.

The diesel-fired burner, mounted at the end of the unit, fires horizontally and provides the support fuel necessary for oxidation of the waste stream. Contaminated air enters the ignition tube via the plenum chamber and is rapidly heated to 800°C as it enters the thermal oxidation zone, where Hydrogen Sulphide and VOC's are incinerated. The treated gases are then vented to atmosphere through a 30 m high exhaust stack.

The plant's electrical control panel incorporates all the motor starters and inverters, together with a PLC system which enables the plant to be automatically controlled and to transmit required information to the site SCADA system.

Project Details

Client: Shaybah, Saudi Arabia

Industry: Petrochemical construction

Application: Four Hydrogen Sulphide stripping systems treating sour water prior to being treated in the reverse osmosis unit, also supplied by ACWa Services Ltd. Thermal Oxidiser to treat 10 000 m3/h of vent air containing Hydrogen Sulphide and a natural gas vent stream.

Technologies

Wet Scrubbing Systems
Packed Towers