Dissolver-tank explosions

Research studies conducted in both areas are reviewed in this section. C. Dissolver Tank Explosions... 

Sallack (1955) was the first to publish a study of dissolver-tank explosions. He was motivated by incidents which occurred in a soda pulp operation with a dissolver tank 4.3 m in diameter and 3.7 m tall. Molten smelt entered the tank at the top and was to be broken up with a jet of recirculating green liquor. Agitation of the bulk liquid was also accomplished by air jets. Operation was normally smooth, but if a boiler upset led to a sharp increase in smelt flow, then the smelt-green liquor breakup operation was inefficient and unbroken slugs of smelt could enter the bulk green liquor in the tank. Explosions could then occur. 

Nelson, H. W., and Kennedy, E. H. (1956b). What causes Kraft dissolving tank explosions. Pap. Trade J. 140(30), 30. 

Dissolving Tank Explosions — Practical Step Towards Eliminating. A device is described for controlling dissolving tank expins in a sulfate mill by shattering the smelt stream with a mech fan-like device above the liquor level in the tank... 

Dissolving tank explosives-practical step towards eliminating 5 D1508... 

Molten salt (smelt) tapped from black liquor boilers is quenched and dissolved to form green liquor in tanks near the boiler. On occasion, explosions have resulted which severely damaged the dissolver tank. (These events are different from the smelt-water boiler explosions described later.)... 

Whereas these early experiments provided interesting data, no mechanism was developed to explain the explosion phenomenon. In fact, since the 1950s there has been little interest in conducting further studies in dissolver tanks because the addition of efficient steam-shatter jets at the smelt entrance has effectively eliminated explosions in this section of the process. Further studies were directed to the explosions which took place within the recovery boiler as a result of water contacting the smelt on the furnace floor. 

A similar incident occurred in a tank truck used to cany waste liquids. While it was being filled with a nonflammable liquid and the driver was standing on the top, smoking, an explosion occurred, and the manhole cover was thrown 60 m. On its previous Journey the tank truck had carried a waste liquid containing dissolved flammable gas. Some of the gas was left in the tank and was pushed out when it was filled with the next load. For other examples see Reference lO. 

Hydrocarbon layers frequently form above used acids in storage tanks. This layer is with high probability partly, if not mainly, a pseudoalkylate produced when isoalkyl acid sulfates dissolved in the used acid decompose. In at least two storage tanks, serious explosions of hydrocarbon-air mixtures have occurred. ... 

After recovery, the VCM is held in a holding tank under pressure or refngeration. A chemical inhibitor, such as a hindered phenol, is sometimes added to prevent polyperoxide formation. Normally any polyperoxide formed is kept dissolved in the VCM, where it will react slowly and safely to form PVC. However, if liquid VCM containing polyperoxides is evaporated, polyperoxides may precipitate. Such precipitated polyperoxides can decompose exothermically with the risk of explosion. 

The only method of distributing acetylene other than pipeline, is by means of portable steel tanks containing a porous solid filler saturated with acetone or other suitable solvent, in which the acetylene is dissolved under pressure. Acetylene alone is not handled at pressures higher than two atmospheres because of its tendency to decompose explosively dissolved in acetone it may be stored at pressures of 10 to 15 atmospheres. 

---