Dry Chemical Covers

Dry chemical systems are well known for being an effective means of fire extinguishment of flammable and combustible liquid fires however, certain types also have application as neutralizing and solidifying agents for liquid spills. Products are available for treating both acids and caustics. 

Acids such as sulfuric, hydrochloric, nitric, phosphoric, perchloric, formic, acetic, chlorosulfonic, 50% hydrofluoric, and adipic can be treated by a mix of magnesium oxide and other chemical additives. It must be expected that when the dry chemical agent is applied to an acid spill, there will be a momentary increase in the volume of vapor coming off the spill. This puff is caused by the heat generated from the neutralization of the acid. To protect the personnel applying the dry chemical cover from this puff, suitable personnel protective equipment should be worn. 

Such treatment results in a residue that is salt-based, e.g., magnesium sulfate from sulfuric acid. Thus, dry chemical agents should be readily available in areas where such materials are stored and handled, for example, tank track transfer sites. The application systems or equipment for application of dry chemical agents should have their locations marked. These areas should be kept clear, marked, and inspected periodically in the same manner as fire extinguishers. 

Releases of caustics, such as sodium hydroxide, aniline, diethylamine, potassium hydroxide, and hydrazine, can be treated by a mix of citric and fumaric acid blended with other chemical additives. The treatment results 

As with the acid treatment, application can be made by shovel, hand-portable device, or larger wheeled or stationary units. A typical application measure might be a 10-lb pail of agent to a 10-ft2 spill, which is a typical 3-gallon spill. Treatment time is usually 10 to 20 minutes, during which period only a moderate amount of heat is produced. The resulting residue will also be pastelike and harden over time (ANSUL, 1991b). 

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Adsorbents. The use of dry chemicals as adsorbents has been discussed above. However, there are other adsorbent materials, such as activated charcoal, hay, com cobs, sawdust, and such, that can be utilized as well. Most of them would work on many organic compounds as long as the spill was confined to a small area by either dikes or curbs, or as long as the spill was small and covered only a minimal area. The major problem in this application technique is that the personnel who apply the materials must wear adequate protective gear. An alternate technique would be to blow the absorbent material over the spill from a distance, using suitable machinery, such as a snow blower or forage blower unit (Greer, 1976). 

Recent pelagic sediments containing over 30% calcium carbonate, by dry weight, cover a quarter of the surface of the earth (see Figure 1). These sediments make up a vast and chemically reactive carbonate reservoir which has a major influence on the chemistry of the oceans and atmosphere. In order to have a predictive understanding of the natural carbon dioxide system and the influence of man on it, the chemical dynamics of calcium carbonate deposition in the deep ocean basins must be known in detail. 

Iodine tends to be concentrated in Earth s crust in only a few places. These places were once covered by oceans. Over millions of years, the oceans evaporated. They left behind the chemical compounds that had been dissolved in them. The dry chemicals left behind were later buried by earth movements. Today, they exist underground as salt mines. 

Mallinckrodt Chemical Works supplies a kit of eight dry indicators covering the pH range 3-10, each with the color change and pH marked on the label. Each bottle... 

Accidents In the event of skin contact, immediately remove contaminated clothing and any metal partieles and wash with soap and water. In case of eye contact, promptly wash with copious amounts of water for 15 min (lifting upper and lower lids occasionally) and obtain medical attention. If sodium is ingested, obtain medieal attention immediately. In the event of a spUl, remove all ignition sources, cover the sodium with a dry chemical extinguishing agent, sweep up, place in an appropriate container under an inert atmosphere, and dispose of properly. Respiratory protection may be necessary in the event of a spiU or release in a confined area. 

All dip tanks exceeding 150 gallons of flammable liquid capacity or having a liquid surface area exceeding 4 square feet must be protected with at least one of the following automatic extinguishing facilities water spray system, foam system, carbon dioxide system, dry chemical system, or automatic dip tank cover. 

Practical separation techniques for hquid particles in gases are discussed. Since gas-borne particulates include both hquid and sohd particles, many devices used for dry-dust collection (discussed in Sec. 17 under Gas-Sohds Separation ) can be adapted to liquid-particle separation. Also, the basic subject of particle mechanics is covered in Sec. 6. Separation of liquid particulates is frequently desirable in chemical processes such as in countercurrent-stage contacting because hquid entrainment with the gas partially reduces true countercurrency. Separation before entering another process step may be needed to prevent corrosion, to prevent yield loss, or to prevent equipment damage or malfunc tion. Separation before the atmospheric release of gases may be necessaiy to prevent environmental problems and for regula-toiy compliance. 

The dry helical lobe rotary compressors nonlubricated cylinder types of compressors are used for injecting of the fuel in gas turbines at the high pressure needed. The gas turbine application requires that the compressor be dry. This standard is primarily intended for compressors that are in special purpose application and covers the minimum requirements for dry helical lobe rotary compressors used for vacuum, pressure, or both in petroleum, chemical, and gas industry services. This edition also includes a new inspector s checklist and new schematics for general purpose and typical oil systems. 

Resistance to penetration by micro-organisms is covered by EN 374-2 and protection from low temperatures in EN 511. Careful handling and regular inspection are essential since chemicals and abrasion will eventually cause deterioration of gloves. Rinsing in clean water and drying naturally will prolong their life. 

The removal of solid particles from gas/vapor or liquid streams can be accomplished by several techniques, some handling the flow dry, others wetting the stream to settle/agglomerate the solids (or even dissolve) and remove the liquid phase from the system with the solid particles. Some techniques are more adaptable to certain industries than others. Figure 4-54 illustrates typical ranges of particle size removal of various types of common equipment or technique. All of these will not be covered in this chapter. Attention will be directed to the usual equipment associated with the chemical/petrochemical industries. 

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