Pulp Storage Vessels

Tile construction is not used to any great extent for very aggressive liquid corrosives because the tile and the mortar joints are relatively thin approximately V2 in. deep) and are somewhat porous. These structures, therefore, have a tendency to weep or leak. Other factors which contribute to this tendency are the lack of a membrane and the susceptibility of the Portland cement core to attack by acidic media. Also, because the tiles are essentially the forms for the concrete and are not removed after the concrete cures, controlling the quality of the concrete wall by visually identifying stone pockets, pour lines, etc., is impossible. Structural tile vessels are, therefore, used in stock tanks, pulp storage tanks, washers, etc., where some leakage can be tolerated or the solids in the contained media will plug leaks. 

The feed-preparation screen between crusher and separately vessel may be of either the revolving or the vibrating type. Wash water is apphed only to the feed end ofthe screen so that the process feed will enter the separator moist but without any free water, which would lower pulp density. In a few instances it has been found advantageous to provide for surge storage between screen and separator to drain off further excess water. 

Chemicals, Chlor alkali. Paper and pulp, Fertilizers, Oil drilling and Pharmaceu ticals Chemical resistant linings for storage tanks, road and ship tankers, process vessels, pipelines, valves, pumps, filters, agitators, centrifuges, impellers, etc. Soft natural rubber or ebonite, neoprene, butyl and hypalon depending on operating temperature, and application. 

The important property of high mechanical strength of duplex stainless steels has been profitably used in the fabrication of pressure vessels, and storage tanks. The digesters in the pulp and paper industry are made of duplex stainless steels of wall thickness of 19-21 mm compared with 31 mm thickness of carbon steel. Some typical wall thickness values of steels calculated for pressure vessels are noted below ... 

In the kraft mill the wood is debarked and chipped, and the chips are pre-heated in a steaming vessel to remove air and assure good liquor permeation. The steamed chips are loaded into the top of the digester along with white liquor, which consists of sodium hydroxide plus sodium sulfide in water. After heating the chips to 170°C for 1 to 2 hours, the pulp is discharged into the blow tank. The pulp is washed free of black liquor and cleaned, then unbleached pulp is either sent to storage or to the bleach plant. 

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