Other Recovery Systems

Dialkylphenols are also produced in specialized plants. These plants combine complex batch reactors with vacuum distillation trains or other recovery systems. Alkenes with carbon numbers between 4 and 9 react with phenol to make an unrefined alkylphenol mixture, which is fed into the recovery section where very high purity product is isolated. The product is stored, handled, and shipped just as are the monoalkylphenols. 

Within a relatively short period after their commercialization, membranes for gas separation have been utilized in a wide variety of applications. Among these applications are recovery of hydrogen from purge streams such as encountered in ammonia plants, retrofit chemical plants and from hydroprocessors in refineries. Membrane systems have been introduced into oil fields for C02 recovery from well-head gas in enhanced oil recovery, and they have been used to separate oxygen from nitrogen in air. Also, they have been utilized in combination with other recovery systems, such as cryogenic and adsorption, to both reduce cost and increase efficiency. 

The policy for waste heat recovery from the flue gas varies between incinerator operators. Incinerators located on the waste producer s site tend to be fitted with waste heat recovery systems, usually steam generation, which is fed into the site steam mains. Merchant incinerator operators, who incinerate other people s waste and... 

Asahi Chemical Industries (ACl, Japan) are now the leading producers of cuprammonium rayon. In 1990 they made 28,000 t/yr of filament and spunbond nonwoven from cotton ceUulose (65). Their continuing success with a process which has suffered intense competition from the cheaper viscose and synthetic fibers owes much to their developments of high speed spinning technology and of efficient copper recovery systems. Bemberg SpA in Italy, the only other producer of cuprammonium textile fibers, was making about 2000 t of filament yam in 1990. 

Uranium ores are leached with dilute sulfuric acid or an alkaline carbonate [3812-32-6] solution. Hexavalent uranium forms anionic complexes, such as uranyl sulfate [56959-61-6], U02(S0 3, which are more selectively adsorbed by strong base anion exchangers than are other anions in the leach Hquors. Sulfate complexes are eluted with an acidified NaCl or ammonium nitrate [6484-52-2], NH NO, solution. Carbonate complexes are eluted with a neutral brine solution. Uranium is precipitated from the eluent and shipped to other locations for enrichment. Columnar recovery systems were popular in South Africa and Canada. Continuous resin-in-pulp (RIP) systems gained popularity in the United States since they eliminated a difficult and cosdy ore particle/leach hquor separation step. 

Other Specialty Chemicals. In fuel-ceU technology, nickel oxide cathodes have been demonstrated for the conversion of synthesis gas and the generation of electricity (199) (see Fuel cells). Nickel salts have been proposed as additions to water-flood tertiary cmde-oil recovery systems (see Petroleum, ENHANCED oil recovery). The salt forms nickel sulfide, which is an oxidation catalyst for H2S, and provides corrosion protection for downweU equipment. Sulfur-containing nickel complexes have been used to limit the oxidative deterioration of solvent-refined mineral oils (200). 

Heterogeneous hydrogenation catalysts can be used in either a supported or an unsupported form. The most common supports are based on alurnina, carbon, and siUca. Supports are usually used with the more expensive metals and serve several purposes. Most importandy, they increase the efficiency of the catalyst based on the weight of metal used and they aid in the recovery of the catalyst, both of which help to keep costs low. When supported catalysts are employed, they can be used as a fixed bed or as a slurry (Uquid phase) or a fluidized bed (vapor phase). In a fixed-bed process, the amine or amine solution flows over the immobile catalyst. This eliminates the need for an elaborate catalyst recovery system and minimizes catalyst loss. When a slurry or fluidized bed is used, the catalyst must be separated from the amine by gravity (settling), filtration, or other means. 

Much of the equipment used in the recovery system is identical with or closely related to equipment used in other chemical industries. This includes multiple-effect evaporators, and forced-circulation concentrators, causticizing equipment, and lime kiln. The function and nature of equipment essentially unique to the kraft recovery system are discussed herein. 

The steam balance in the plant shown in Figure 2 enables all pumps and blowers to be turbine-driven by high pressure steam from the boiler. The low pressure exhaust system is used in the reboiler of the recovery system and the condensate returns to the boiler. Although there is generally some excess power capacity in the high pressure steam for driving other equipment, eg, compressors in the carbon dioxide Hquefaction plant, all the steam produced by the boiler is condensed in the recovery system. This provides a weU-balanced plant ia which few external utiUties are required and combustion conditions can be controlled to maintain efficient operation. 

Dichloroethane is produced commercially from hydrogen chloride and vinyl chloride at 20—55°C ia the presence of an aluminum, ferric, or 2iac chloride catalyst (8,9). Selectivity is nearly stoichiometric to 1,1-dichloroethane. Small amounts of 1,1,3-tfichlorobutane may be produced. Unreacted vinyl chloride and HCl exit the top of the reactor, and can be recycled or sent to vent recovery systems. The reactor product contains the Lewis acid catalyst and must be separated before distillation. Spent catalyst may be removed from the reaction mixture by contacting with a hydrocarbon or paraffin oil, which precipitates the metal chloride catalyst iato the oil (10). Other iaert Hquids such as sdoxanes and perfluorohydrocarbons have also been used (11). 

Butyl slurry at 25—35 wt % mbber continuously overflows from the reactor through a transferline to an agitated flash dmm operating at 140—160 kPa (1.4—1.6 atm) and 55—70°C. Steam and hot water are mixed with the slurry in a nozzle as it enters the dmm to vaporize methyl chloride and unreacted monomers that pass overhead to a recovery system. The vapor stream is compressed, dried over alumina, and fractionated to yield a recycle stream of methyl chloride and isobutylene. Pure methyl chloride is recovered for the coinitiator (AlCl ) preparation. In the flash dmm, the polymer agglomerates as a coarse cmmb in water. Metal stearate, eg, aluminum, calcium, or zinc stearate, is added to control the cmmb size. Other additives, such as antioxidants, can also be introduced at this point. The polymer cmmb at 8—12 wt % in water flows from the flash dmm to a stripping vessel operated under high vacuum to... 

Control of ga.s movement by recovery. The movement of gases in landfills can also be controlled by instadhng gas-recovery wells in completed landfills (see Fig. 25-74b). This is considered an active venting system. Clay and other hners are used when landfill gas is to be recovered. In some gas-recovery systems, leachate is collected and recycled to the top of the landfill and reinjected through perforated lines located in drainage trenches. Typically, the rate of gas production is greater in leachate-recirculation systems. 

The equipment for the pollutant removal system includes all hoods, ducting, controls, fans, and disposal or recovery systems that might be necessary. The entire system should be engineered as a unit for maximum efficiency and economy. Many systems operate at less than maximum efficiency because a portion of the system was designed or adapted without consideration of the other portions (4). 

The code provides for the testing of gas turbines supplied with gaseous or liquid fuels (or solid fuels converted to liquid or gas prior to entrance to the gas turbine). Test of gas turbines with water or steam injection for emission control and/or power augmentation are included. The tests can be applied to gas turbines in combined-cycle power plants or with other heat recovery systems. 

Depreciation. This is a noncash cost that accumulates money to rebuild the facilities after the project life is over. There are usually two depreciation rates. One is the corporation s book depreciation, which reflects the expected operating life of the project. The other is the tax depreciation, which is usually the maximum rate allowed by tax laws. To be correct, the tax depreciation should now be called Accelerated Capital Cost Recovery System (ACRS). 

In recent years, the use of solvent-borne adhesives has been seriously restricted. Solvents are, in general, volatile, flammable and toxic. Further, solvent may react with other airborne contaminants contributing to smog formation and workplace exposure. These arguments have limited the use of solvent-bome adhesives by different national and European regulations. Although solvent recovery systems and afterburners can be effectively attached to ventilation equipment, many factories are switching to the use of water-borne rubber adhesives, hot melts or 100% solids reactive systems, often at the expense of product performance or labour efficiency. 

Condensation is normally used for the recovery of organic compounds from process or tank vent gases or from releases during loading. Condensation is used to recover valuable compounds prior to incineration, or to reduce the organic load entering other control systems, such as adsorbers or absorbers. Adsorption and absorption processes benefit from low condenser outlet temperatures. 

Having now established the space requirement for the boilers, we must consider the other items of plant to be housed in the same structure. These may include water-treatment plant, heat-recovery system, tanks and pump, instrument and controls. With oil- and gas-fired installations, there is little additional plant to consider within the boiler house. With solid fuel then the handling, distribution and perhaps storage could also form part of the building with provision for ash handling and removal. 

Sodium hydrosulfite is produced through the Formate process where sodium formate solution, sodium hydroxide, and liquid sulfur dioxide reacted in the presence of a recycled stream of methanol solvent. Other products are sodium sulfite, sodium bicarbonate, and carbon monoxide. In the reactor, sodium hydrosulfite is precipitated to form a slurry of sodium hydrosulfite in the solution of methanol, methyl formate, and other coproducts. The mixture is sent to a pressurized filter system to recover sodium hydrosulfite crystals that are dried in a steam-heated rotary drier before being packaged. Heat supply in this process is highly monitored in order not to decompose sodium hydrosulfite to sulfite. Purging is periodically carried out on the recycle stream, particularly those involving methanol, to avoid excessive buildup of impurities. Also, vaporized methanol from the drying process and liquors from the filtration process are recycled to the solvent recovery system to improve the efficiency of the plant. 

---