Acid plants with stainless steel

To prompt remedial action when stainless-steel agitators in a phosphoric-acid-plant reactor show a potential shift towards a value associated with active corrosion due to an increase in corrosive impurities in the phosphate rock. 

Monel, the classic nickel-copper alloy with the metals in the ratio 2 1, is probably, after the stainless steels, the most commonly used alloy for chemical plant. It is easily worked and has good mechanical properties up to 500°C. It is more expensive than stainless steel but is not susceptible to stress-corrosion cracking in chloride solutions. Monel has good resistance to dilute mineral acids and can be used in reducing conditions, where the stainless steels would be unsuitable. It may be used for equipment handling, alkalies, organic acids and salts, and sea water. 

Univ of Illinois, Urbana, 111, April 1,1951 Alloys Suitable for Use in Ordnance Plants should be acid resistant, heat resistant and nonreactive with explosives. The most useful alloys in die manuf of acids and expls are various kinds of stainless steels. Among the non-ferrous alloys may be cited Chlorimet 2 and Chlorimet 3- During WWII the Germans used some high temp alloys such as Bohler, Chromadur, Remanit, Sicromal, Therm an it, Thetmat, etc... 

Dilevalol DBTA Salt to Dilevalol Hydrochloride. Very little improvement in the RR composition results from the transformation of dilevalol DBTA salt to dilevalol hydrochloride. Ethyl acetate was used as the solvent vehicle in early work. In a search for a more stable solvent methyl isobutyl ketone (MIBK) was selected as the best alternative. DBTA was removed by extraction into water with sodium hydroxide (DBTA of excellent quality was recovered from the aqueous phase in high yield >90%). The MIBK solution of dilevalol was then treated with hydrochloride acid to precipitate dilevalol hydrochloride (Scheme 9). The pH needed for maximum efficiency in the crystallization of dilevalol hydrochloride was 0.5 (this is in sharp contrast to the pH required for maximum efficiency in the crystallization of labetalol hydrochloride—pH 3.0). It should also be noted that dilevalol hydrochloride could not be handled in stainless steel equipment. Hastelloy, plastic or ceramic equipment was employed to eliminate the risk of coloration of dilevalol hydrochloride by traces of iron compounds. The plant equipment layout for this step is shown in Figure 5. 

Steeps are large tanks that may be constructed of any material resistant to the corrosive action of solutions of sulfur dioxide and lactic acid at pH 3 1, but stainless steel construction is now the most common. Steep tanks will vary in size and number depending on the capacity of the facility. It is common in newer US facilities for tanks to hold 250-600 metric tons (10000-25000 bushels), but tanks as small as 60 metric tons (2500 bushels) of com are still in use in some plants, with even smaller tanks being used in some other countries. The number of tanks in each separate steep battery varies, ranging from 6 to over 50. 

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