Acid Regeneration Tanks

The bulk storage tank, which contained a 93% sulfuric acid solution, was connected to two tanks, the day tank and an acid regeneration tank (also caUed the dUute tank), by 2.5-cm carbon steel Unes. The valve in the line connecting the bulk storage tank and the dUute tank was located near the dilute tank. The acid spray was caused by a failure in the line where it was connected to the valve. The procedure for transferring acid from the bulk tank to the day tank required that the valve at the dilute tank be closed and a transfer pump be used to facilitate the transfer of acid from the bulk tank to the day tank. When the accident occurred, the valve at the dilute tank was closed and the transfer pump had been started. The pump built up pressure in the pipe, causing the acid to spray out. 

Correction of pH level via caustic soda (after the degasser and before the BX) is standard practice. Because both acid regeneration and caustic pH correction are practiced, it is usual to isolate the plant from the mains by providing a break tank. The full plant therefore tends to be break tank, RW booster pump, acid measuring tank, WAC, degasser, degassed water booster pump, pH correction, and BX. A schematic layout of this type of plant is shown in Figure 9.3a. 

Acid regeneration plants have storage tanks for spent and regenerated acid and these tanks are potential sources of HC1 emissions. Emission estimates for uncontrolled and controlled storage tanks at acid regeneration facilities are 0.0126 and 0.008 tpy per 1000 gallons of storage capacity, respectively. 

The 163-N facility contains demineralization equipment, including ion exchange units, regeneration tanks, treatment tanks (for pH adjustment) that are part of the elementary neutralization unit (ENU), acid and caustic-materials storage tanks, a heater, and a degasifier (DOE-RL 1990). 

A sulfuric acid solution was used to regenerate cation resins a sodium hydroxide solution was used to regenerate anion resins. The solutions were pumped through the resins in the regeneration tanks and drained to the 1324-N Surface Impoundment until 1988, when a spent regenerant surge tank and ENU were installed (DOE-RL 1990). 

N chemical unloading facility 120-N-7 unloading station french drain 120-N-6 sulfuric acid tank french drains 108-N neutralization pit UN-lOO-N-15 unplanned release UN-lOO-N-33 unplanned release December 26, 1987 unplanned release 120-N-5 acid/caustic trench and neutralization unit UN-lOO-N-34 unplanned release August 7, 1987 unplanned release September 2, 1987 unplanned release November 9, 1987 unplanned release 120-N-3 neutralization pit and french drain 120-N-8 sulfuric acid day tank french drain Regeneration waste transport system June 14, 1986 unplanned release June 30, 1986 unplanned release 124-N-l septic tank. 

But then I realized that I had seen all this before. Six years before, in 1974, 1 had been the operating superintendent of a sulfuric acid regeneration plant in Texas City. Acid was lifted out of our mix tank by injecting nitrogen into the bottom of a 2-inch riser pipe. The shift operators called it an "air lift pump."... 

The resultant yellow sodium cellulose xanthate is dispersed in an aqueous caustic soda solution, where some hydrolysis occurs. This process is referred to as ripening and the solution as viscose . When the hydrolysis has proceeded sufficiently the solution it transferred to a hopper from which it emerges through a small slit on to a roller immersed in a tank of 10-15% sulphuric acid and 10-20% sodium sulphate at 35-40°C. The viscose is coagulated and by completion of the hydrolysis the cellulose is regenerated. The foil is subsequently washed, bleached, plasticised with ethylene glycol or glycerol and then dried. 

After the cotton has been removed from the nitration tank (Fig. 135) the composition of the acid in the tank is adjusted so that in quantity and strength of it remains unchanged throughout. The waste acid from the centrifuge is low in nitric acid. The regeneration of this spent acid by addition of oleum and fresh nitric acid is uneconomic. Spent acid is denitrated. 

Tanks for manufacturing, storing and regeneration of hydrochloric acid. 

This requires a second zeolite tank that has a zeolite resin in the hydrogen form in addition to the usual tank with the resin in the sodium form. The two tanks are operated in parallel. In one tank, calcium and magnesium ions are replaced by hydrogen ions. The effluent from this tank with the resin in hydrogen form is on the acid side and has a lower total-solids content. The total flow can be proportioned between the two tanks to produce an effluent with any desired alkalinity as well as excellent hardness removal. When the hydrogen resin is exhausted, it is regenerated with acid. 

The two types of resins can be located in separate tanks. In this system, the two tanks are operated in series in a cation-anion sequence. The anion resin is regenerated after exhaustion with a solution of sodium hydroxide. The cation resin is regenerated with an acid, either hydrochloric or sulfuric. Some leakage of cations always occurs in a cation exchanger, resulting in leakage of alkalinity from the anion exchanger. 

The nitrating mixture is prepared from fresh concentrated nitric acid, 55% regenerated nitric acid (from the denitration of spent acid), and 96% sulphuric acid recovered by distillation. The mixture of acids is fed into the nitrator from a metering tank through a vacuum started siphon. Toluene is conveyed to the nitrator from another metering tank by means of compressed nitrogen. Air is considered as too dangerous to use, because the explosibility of mixtures of toluene vapour with air. 

The giant molecules in tank A may be regenerated after use by passing moderately concentrated sulfuric acid through the tank ... 

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