Acid Towers

Extraction.—(1) From Pyrites.—In the oxidation of the pyrites (or other sulphur mineral) for the formation of sulphur dioxide in the manufacture of sulphuric acid, foreign elements like arsenic and selenium also undergo oxidation and pass ofC as vapours with the sulphur dioxide. The selenium dioxide produced in this manner their suffers more or less complete reduction by the sulphur dioxide, when finely divided selenium separates, mainly in the lead chambers, as a red, amorphous powder, accompanied possibly by some of the greyish-black form a portion of the dioxide is also found in the Glover tower acid. The amount of selenium in the chamber mud depends, of course, on the nature of the pyrites relatively large quantities of compounds of arsenic, zinc, tin, lead, iron, copper or mercury are always present, arising almost entirely from impurities in the pyrites. 

The presence of much selenium in the Glover tower acid imparts a red colour to the liquid. The element can be separated by dilution followed by treatment with sulphur dioxide.5... 

Modifications of the process include towers to recover excess nitrogen oxides and to increase the final acid concentration from 65% (chamber acid) to 78% (tower acid). 

Synonyms Battery acid, Chamber acid, Contact acid, Dipping acid, Fortifying acid, Hydrogen sulfate, Oil of Vitriol, Tower acid, Vitriolic acid. 

Industrial applications of corrosion inhibitors are too numerous to cover in the present context. The inhibitor industry amounts to several billion dollars annually. Applications of inhibitors in petroleum production, oil and gas wells and pipelines, potable water, water cooling towers, acid systems, automobile antifreeze systems, paints, boiler waters,... 

Fig. 23.1. Simplified single contact sulfuric acid production flowsheet. Its inputs are moist feed gas and water. Its outputs are 98 mass% H2S04, 2 mass% H20 sulfuric acid and dilute S02, 02, N2 gas. The acid output combines gas dehydration tower acid, H2S04 making tower acid and liquid water. The equivalent sulfur burning acid plant sends moist air (rather than moist feed gas) to dehydration. Appendix V gives an example sulfur burning calculation.

Chapter 23 examines the input of moist metallurgical and spent acid regeneration gases into Fig. 23.1 s dehydration tower. It quantifies the amount of H20(g) that enters dehydration tower acid ... 

This section duplicates Section 23.4.1 s calculation of kg-mole H20(g) into dehydration tower acid per kg-mole of dry 1st catalyst bed feed gas. 

Tanks, tower, acid distribut- Storage (steel). 6... 

Wash tower acid (scrubber discharge from the roaster acid plant). Typically this flow is about 25 m /h and it contains 10 g/L H2SO4, 0.5 g/L HF, 1 g/L HCl and 0.5 g/L Zn. 

These two streams cannot be treated in the SRB plant because their sulfate content is too high, and in case of the wash tower acid, the fluoride content is also high. Between 1995 and 1999 various processes were studied to treat these streams. The objective was to develop a process that allowed a direct purge of these streams or to have the capability of bleeding them, after a final treatment, to the SRB plant. Extensive testwork was done at the laboratory and pilot plant scale. Based on these results, the biological process route was chosen. 

Neutralization of the wash tower acid, WTA, with calcine... 

Separate acid circulation circuit for final absorption tower to avoid stripping of dissolved SO2 from the inter-pass absorption tower acid circuit which can occur if a common acid circulation tank is used. 

Water washing drilling mud from a plugged tower Acidize/degrease trays Reestablished liquid seal Foaming of degraded glycol... 

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