Recovery efficiency

MPa (15—20 atm), 300—400 kg benzene per kg catalyst per h, and a benzene ethylene feed ratio of about 30. ZSM-5 inhibits formation of polyalkjlated benzenes produced with nonshape-selective catalysts. With both ethylene sources, raw material efficiency exceeds 99%, and heat recovery efficiency is high (see Xylenes and ethylbenzene). 

Mill Tailings. Recovery efficiency in ore processing is not 100%. Accumulated mill tailings contain tens of thousands of metric tons of uranium. Whereas improved techniques have been employed to recover some of this uranium, the recovery rate is still generally low, approximately 35—50%, owing to metallurgical problems and economic considerations (33). 

The effect of temperature, pressure, and oil composition on oil recovery efficiency have all been the subjects of intensive study (241). Surfactant propagation is a critical factor in determining the EOR process economics (242). Surfactant retention owing to partitioning into residual cmde oil can be significant compared to adsorption and reduce surfactant propagation rate appreciably (243). 

AH three parameters, the cut size, sharpness index, and apparent bypass, are used to evaluate a size separation device because these are assumed to be independent of the feed size distribution. Other measures, usually termed efficiencies, are also used to evaluate the separation achieved by a size separation device. Because these measures are dependent on the feed size distribution, they are only usefiil when making comparisons for similar feeds. AH measures reduce to either recovery efficiency, classification efficiency, or quantitative efficiency. Recovery efficiency is the ratio of the amount of material less than the cut size in the fine stream to the amount of material less than the cut size in the feed stream. Classification efficiency is defined as a corrected recovery efficiency, ie, the recovery efficiency minus the ratio of the amount of material greater than the cut size in the fine stream to the amount of material greater than the cut size in the feed stream. Quantitative efficiency is the ratio of the sum of the amount of material less than the cut size in the fine stream plus the amount of material greater than the cut size in the coarse stream, to the sum of the amount of material less than the cut size in the feed stream plus the amount of material greater than the cut size in the feed stream. Thus, if the feed stream analyzes 50% less than the cut size and the fine stream analyzes 95% less than the cut size and the fine stream flow rate is one-half the feed stream flow rate, then the recovery efficiency is 95%, the classification efficiency is 90%, and the quantitative efficiency is 95%. 

There are relationships between the independent size separation device parameters and the dependent size separation efficiencies. For example, the apparent bypass value does not affect the size distribution of the fine stream but does affect the circulation ratio, ie, the ratio of the coarse stream flow rate to the fine stream flow rate. The circulation ratio increases as the apparent bypass increases and the sharpness index decreases. Consequendy, the yield, the inverse of the circulating load (the ratio of the feed stream flow rate to the fine stream flow rate or the circulation ratio plus one), decreases hence the efficiencies decrease. For a device having a sharpness index of 1, the recovery efficiency is equal to (1 — a). 

Raw material usages per ton of carbon disulfide are approximately 310 m of methane, or equivalent volume of other hydrocarbon gas, and 0.86—0.92 ton of sulfur (87,88), which includes typical Claus sulfur recovery efficiency. Fuel usage, as natural gas, is about 180 m /ton carbon disulfide excluding the fuel gas assist for the incinerator or flare. The process is a net generator of steam the amount depends on process design considerations. 

Reclamation, Disposal, and Toxicity. Removal of poisons and inorganic deposits from used catalysts is typically difficult and usually uneconomical. Thus some catalysts are used without regeneration, although they may be processed to reclaim expensive metal components. Used precious metal catalysts, including automobile exhaust conversion catalysts, are treated (often by the suppHers) to extract the metals, and recovery efficiencies are high. Some spent hydroprocessing catalysts may be used as sources of molybdenum and other valuable metals. 

The volatile solvents recoverable by the activated carbon system or any other system are nearly all organic, and many of them form flammable or explosive mixtures with air. Such mixtures may lie between upper and lower explosive limits. The activated carbon system can avoid the explosive range by staying well below the lowest percentage of vapor which is still explosive it functions well at very low concentrations. The system also recovers solvents efficiently even in the presence of water the recovery efficiency is high (98 percent and 99 percent are not unusual) it may be fully automatic. The annual maintenance charge rarely exceeds 5 percent of the cost of equipment. The recovery expense may be as low as 0.2 cent per pound in some installations it rarely exceeds 1 cent per pound. 

Example A ventilation system (Fig. 9.64) handling 20 mVs of air needs to heat the supply air from 10 °C to 20 C. Doubling the number of heat exchangers from one to two increases the heat-recovery efficiency from 50% to 75% and introduces an extra pressure drop of 300 Pa. As we can see from Table 9.19, this is probably a cost-efficient measure. 

The chiller is usually a kettle type exchanger. Freon (which is cooled in a refrigeration cycle to -20 F) is able to cool the gas to approximately - 15°F. Propane, which can be cooled to -40°F, is sometimes used if lower gas temperatures and greater recovery efficiences are desired. 

Gas-Fired water heaters are also made more efficient by a variety of designs that increase the recov-ei y efficiency. These can be better flue baffles multiple, smaller-diameter flues submerged combustion chambers and improved combustion chamber geometry. All of these methods increase the heat transfer from the flame and flue gases to the water in the tank. Because natural draft systems rely on the buoyancy of combustion products, there is a limit to the recovery efficiency. If too much heat is removed from the flue gases, the water heater won t vent properly. Another problem, if the flue gases are too cool, is that the water vapor in the combustion products will condense in the venting system. This will lead to corrosion in the chimney and possible safety problems. 

For special applications the design of a mist eliminator unit may actually be an assembly in one casing of wire mesh and fiber packs/pads or in combination with Chevron style mist elements (see Figure 4-17A and 17B and — 17C.) This can result in greater recovery efficiencies for small particles and for higher flow rates through the combined unit. Refer to the manufacturers for application of these designs. 

Spacing of the plates and their angles is a part of the design using the manufacturers data. Muldple pass designs can result in higher recovery efficiencies. The units can be designed/installed for vertical or horizontal flow. 

A process for depolymerizing nylon-6 and polyester-nylon-6 mixed scrap was patented by Allied Chemical Corporation in 19656 and 1967.7 Ground scrap was dissolved with high-pressure steam at 125-130 psig (963-997 kPa) pressure and 175-180°C for 0.5 h in a batch process and then continuously hydrolyzed with superheated steam at 350°C and 100 psig (790 kPa) to form -caprolactam at an overall recovery efficiency of 98%. The recovered monomer could be repolymerized without additional purification. 

Figure 4. Recovery efficiency of Arochlor 1242 from sediment reference material.

Key mechanisms important for improved oil mobilization by microbial formulations have been identified, including wettability alteration, emulsification, oil solubilization, alteration in interfacial forces, lowering of mobility ratio, and permeability modification. Aggregation of the bacteria at the oil-water-rock interface may produce localized high concentrations of metabolic chemical products that result in oil mobilization. A decrease in relative permeability to water and an increase in relative permeability to oil was usually observed in microbial-flooded cores, causing an apparent curve shift toward a more water-wet condition. Cores preflushed with sodium bicarbonate showed increased oil-recovery efficiency [355]. 

The extraction method for prohexadione-calcium in soil was developed using alluvial soil and volcanic ash soil. Extraction by shaking the soil with a mixture of 1N sulfuric acid-acetonitrile (1 3, v/v) and/or of 1N sulfuric acid-acetone (1 3, v/v) showed an acceptable extraction recovery efficiency. 

Once method validation has been completed, the treated samples may be analyzed. The method should be under control so that no additional changes will be necessary. Analysis of laboratory-fortified samples and control samples will be used to monitor the quality of the study. The purpose of laboratory-fortified samples is confirmation of the recovery efficiency of residues from the sample matrix. A minimum of two laboratory recovery samples need to run with each set. Recoveries should average 70-120%. 

The purge and the higher boiling mixture are processed away from the plant, and the recovered aniline returned to the crude aniline storage tank. The aniline recovery efficiency in the purge unit is 87.5 per cent, and a continuous stream of high-purity aniline may be assumed. 

The in situ combustion method of enhanced oil recovery through air injection (397,503,504) is an exceeding complex process chemically. However, because little work has been done on the effect of chemical additives to oil recovery efficiency, this process will not be discussed herein. 

Effect of pH. Interfacial tensions between heavy crude oils and alkaline solutions were measured at temperatures up to 180°C by Mehdizadeh and Handy T341. They observed that tensions increased with an increase in temperature. However, recovery efficiencies obtained at high temperatures were comparable to those obtained at lower temperatures, apparently because the ease of emulsification at high temperatures counteracted the increase in tens i on. 

Process efficiency, in this study, is defined as the tertiary oil recovery per unit volume of the slug injected. This refers to the efficiency of an oil-rich slug. Economic recovery efficiency varies from slug to slug due to variations in the surfactant content. it should be noted that the micellar slugs were formulated with an effort to keep the cost a minimum. 

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