Industrial acid plant tail gas treatment methods

4 Industrial acid plant tail gas treatment methods 

Further SO2 removal is carried out by contacting the S02-bearing tail gas with a basic solution that removes SO2 forming a liquid or solid by-product or waste (Fig. 28.2). The basic solution is often caustic NaOH(aq) (caustic) or Ca(OH)2(aq) (lime). 

The gas and liquid are often placed in contact in a large vertical cylindrical tower. Several tower designs are shown in Fig. 28.3. Packed towers, spray towers, tray towers, and reverse jet-type scrubbers have aU been used to treat acid plant tail gas. They are usually constructed of fiber reinforced plastic with a suitable corrosion-resistant liner. Unlined stainless steel and rubber-lined carbon steel are also used. 

The amount of SO2 removed by the tail gas scmbber is controlled by controlling the pH of the solution in contact with the gas. The pH is specified and controlled to maximize SO2 solubility while preventing scale buildup. 

The ratio of the feed liquid flow rate (m /h) to the actual saturated gas outlet flow rate (m /h) is the liquid-to-gas ratio or L/G ratio. A minimum L/G ratio is required to ensure the target SO2 absorption is achieved for a given SO2 solubility in the solution (Yosemite, 2012). 

---