Albright & Wilson Ltd

Due to the combined efforts of high temperature exhaust gas, corrosive process chemicals and abrasive particulate matter produced, the scrubbing system had to be built of specially selected materials, designed to withstand the combined effects of adverse operating conditions.

The complete packaged system comprises a high efficiency venturi scrubber followed by a target plate scrubbing tower mounted directly over a rubber lined, mild steel liquor recycle tank. Other materials of construction include corrosion resistant Derakane 470 resin for the body of the scrubber and Hastalloy C276 for the high efficiency venturi, to provide chemical resistance and withstand the relatively high operating temperature of 260°C. Polypropylene is used for the manufacture and coating of internal components such as sprays, demisters, pipework and valves.

Operation
The contaminated process exhaust gases enter the converging section of the high efficiency venturi and are accelerated before passing to the venturi throat. To prevent a build up of solids at this point, scrubbing liquor, using caustic soda, is released around the top of the converging section to flush the walls, whilst liquor sprays completely fill the throat with droplets.

The high velocity exhaust gases atomise the liquid droplets which trap solid particles and cool the gas to its adiabatic saturation temperature. Scrubbed gases and liquid droplets then pass from the venturi throat through a diverging section and enter the top of the recycle tank where they impinge onto the surface of the liquor.

The gas then flows across the surface of the liquor and enters the base of the target plate scrubber.

To maintain high scrubbing efficiencies with varying gas flows, the throat section of the ACWA AIR high efficiency venturi has adjustable blades. These can be easily modulated to ensure the necessary pressure drop required by the scrubber, even with reduced throughputs.

In the base of the scrubber, humidification sprays ensure that the waste gas is saturated with liquor before it moves upward through three individual target plates. As it passes throughperforations in the target plates, the gas gathers momentum and remaining particles of dust impinge on baffles positioned directly above each perforation. Liquor flowing across the target plates collects the solid particles and absorbs quantities of hydrogen fluoride before gravitating via downcomers back into the recycle tank.

Cleaned gas passes through a chevron mist eliminator before discharging to atmosphere at the top of the scrubber, whilst waste solids are removed from the system through a purge stream discharged from the recycle line.

Project Details

Client: Albright & Wilson Ltd, Whitehaven, England

Industry: Chemical

Application: A Venturi scrubber and Plate scrubbing system to remove particulates and HF from 80 000 m3/h of kiln gases from the production of Sodium Tripolyphosphate - the base material for a variety of household detergents

Technologies

Wet Scrubbing Systems
Plate Scrubbers
Venturi Scrubbers