Proper control

Unlike catfish, tilapia, trout and salmon, that produce several hundred to several thousand eggs per female, many marine species produce large numbers of very small eggs. Hundreds of thousands to millions of eggs are produced by such species as haUbut, flounders, red dmm, striped bass, and shrimp. Catfish, salmon, and trout spawn once a year, while tilapia and some marine species spawn repeatedly if the proper environmental conditions are maintained (1). Red dmm, for example, spawn every few days for periods of several months when light and temperature and properly controlled (10). 

Chlorine and bromine add vigorously, giving, with proper control, high yields of 1,2-dihaloethyl ethers (224). In the presence of an alcohol, halogens add as hypohaUtes, which give 2-haloacetals (225,226). With methanol and iodine this is used as a method of quantitative analysis, titrating unconsumed iodine with standard thiosulfate solution (227). 

The stoichiometric and the catalytic reactions occur simultaneously, but the catalytic reaction predominates. The process is started with stoichiometric amounts, but afterward, carbon monoxide, acetylene, and excess alcohol give most of the acrylate ester by the catalytic reaction. The nickel chloride is recovered and recycled to the nickel carbonyl synthesis step. The main by-product is ethyl propionate, which is difficult to separate from ethyl acrylate. However, by proper control of the feeds and reaction conditions, it is possible to keep the ethyl propionate content below 1%. Even so, this is significantly higher than the propionate content of the esters from the propylene oxidation route. 

Without proper control of hazards, a sequence of events (scenario) occurs which results ia an accident. A hazard is defined as anything which could result ia an accident, ie, an unplaimed sequence of events which results ia iajury or loss of life, damage to the environment, loss of capital equipment, or loss of production or inventory. 

Because this reaction is highly exothermic, the equiUbrium flame temperature for the adiabatic reaction with stoichiometric proportions of hydrogen and chlorine can reach temperatures up to 2490°C where the equiUbrium mixture contains 4.2% free chlorine by volume. This free hydrogen and chlorine is completely converted by rapidly cooling the reaction mixture to 200°C. Thus, by properly controlling the feed gas mixture, a burner gas containing over 99% HCl can be produced. The gas formed in the combustion chamber then flows through an absorber/cooler to produce 30—32% acid. The HCl produced by this process is known as burner acid. 

Acid mixtures are used to oxidize and remove the dark materials. Proper control gives a series of bleached waxes. A white wax requires double refining and reduces the yield to about 30% of the cmde wax input. A series of synthetic waxes is prepared by separating the acids and alcohols produced during saponification of the wax and reesterifying them with acids or alcohols selected to give desired properties of hardness, solubiHty, emulsification, and gloss. 

Air Pollution. Particulates and sulfur dioxide emissions from commercial oil shale operations would require proper control technology. Compliance monitoring carried out at the Unocal Parachute Creek Project for respirable particulates, oxides of nitrogen, and sulfur dioxide from 1986 to 1990 indicate a +99% reduction in sulfur emissions at the retort and shale oil upgrading faciUties. No violations for unauthorized air emissions were issued by the U.S. Environmental Protection Agency during this time (62). 

Some of the important parameters in the Bnchamp process are the physical state of the iron, the amount of water used, the amount and type of acid used, agitation efficiency, reaction temperature, and the use of various catalysts or additives. When these variables are properly controlled, the amine can be obtained in high yields while controlling the color and physical characteristics of the iron oxide pigment which is produced. 

Trichlorosilane. The primary production process for trichlorosilane is the direct reaction of hydrogen chloride gas and sihcon metal in a fluid-bed reactor. Although this process produces both trichlorosilane and sihcon tetrachloride, production of the latter can be minimi2ed by proper control of the reaction temperature (22). A significant amount of trichlorosilane is also produced by thermal rearrangement of sihcon tetrachloride in the presence of hydrogen gas and sihcon. 

Toluenesulfonic Acid. Toluene reacts readily with fuming sulfuric acid to yield toluene—sulfonic acid. By proper control of conditions, /)i7n7-toluenesulfonic acid is obtained. The primary use is for conversion, by fusion with NaOH, to i ra-cresol. The resulting high purity i7n -cresol is then alkylated with isobutylene to produce 2 (i-dii-tert-huty -para-cmso (BHT), which is used as an antioxidant in foods, gasoline, and mbber. Mixed cresols can be obtained by alkylation of phenol and by isolation from certain petroleum and coal-tar process streams. 

Electronic Vacuum Tube. In special electronic vacuum diode tubes, with spacing between the cathode and anode of 10 )J.m, high gas concentrations of some types are beneficial to the operation of the tube under proper control. 

Oxygen Control. To meet industrial standards for both oxygen content and the allowable metal oxide levels in feed water, nearly complete oxygen removal is required. This can be accompHshed only by efficient mechanical deaeration supplemented by an effective and properly controlled chemical oxygen scavenger. 

Improper operation of a process may result in the vessel s exceeding design temperature. Proper control is the only solution to this problem. Maintenance procedures can also cause excessive temperatures. Sometimes the contents of a vessel may be burned out with torches. If the flame impinges on the vessel sheh, overheating and damage may occur. 

Product removal mechanisms from apparatuses that are explosion resistant can be protected with a. double-slide system. Here, the shdes must be at least as resistant as the apparatuses. By means of proper control, it must be assured that a shde is always closed. 

Elimination. Porosity in general can be minimized by using clean, dry materials and by properly controlling weld current and arc length. 

DCS sampling frequency too low or the response time for some analog instruments may be too slow for proper control of transient nature of batch processes and may lead to a process upset. 

Success will largely depend upon the proper control of... 

The most widely used pulping process is the kraft process, as shown in Fig. 6-11, which results in recovery and regeneration of the chemicals. This occurs in the recovery furnace, which operates with both oxidizing and reducing zones. Emissions from such recovery furnaces include particulate matter, very odorous reduced sulfur compounds, and oxides of sulfur. If extensive and expensive control is not exercised over the kraft pulp process, the odors and aerosol emissions will affect a wide area. Odor complaints have been reported over 100 km away from these plants. A properly controlled and operated kraft plant will handle huge amounts of material and produce millions of kilograms of finished products per day, with little or no complaint regarding odor or particulate emissions. 

Heavy metals on or in vegetation and water have been and continue to be toxic to animals and fish. Arsenic and lead from smelters, molybdenum from steel plants, and mercury from chlorine-caustic plants are major offenders. Poisoning of aquatic life by mercury is relatively new, whereas the toxic effects of the other metals have been largely eliminated by proper control of industrial emissions. Gaseous (and particulate) fluorides have caused injury and damage to a wide variety of animals—domestic and wild—as well as to fish. Accidental effects resulting from insecticides and nerve gas have been reported. 

Pressure can also be controlled by variable heat transfer coefficient in the condenser. In this type of control, the condenser must have excess surface. This excess surface becomes part of the control system. One example of this is a total condenser with the accumulator running full and the level up in the condenser. If the pressure is too high, the level is lowered to provide additional cooling, and vice versa. This works on the principle of a slow moving liquid film having poorer heat transfer than a condensing vapor film. Sometimes it is necessary to put a partially flooded condenser at a steep angle rather than horizontal for proper control response. 

The control valve allows the Jets to pull noncondensibles out of the condenser as needed for system pressure control. In addition to requiring extra surface area for control, the vacuum condenser also needs enough surface area for subcooling to ensure that the Jets do not pull valuable hydrocarbons or other materials out with the noncondensibles. To allow proper control and subcooling, some designers add approximately 50% to the calculated length. 

Disposal Discharge of wastes to air, water or land in properly controlled, or safe, ways such that compliance is achieved. Secure land disposal may involve volume reduction, encapsulation, leachate containment and monitoring techniques a c j 5 j ... 

Combustion air blower located at the base of the flare stack, complete with the electric motor drive and proper control system. 

In order to make sound decisions based on test and measurement data, the equipment used to provide that information must be properly controlled. This section of the standard addresses various control elements, corrective actions, and outside testing. 

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