Commercial operation

In 1939 there were 14 commercial Fischer-Tropsch plants operating throughout the world. Nine of these were in Germany, one in France, and the others in Japan and Manchukuo. About three-fourths of the total annual output of about a million tons of synthetic fuels came from Germany. 

Plants have recently been constructed at Brownsville, Tex., and Sasol, South Africa, that have incorporated, the newest operating techniques. 

A simplified flow sheet of the original plant is shown in Fig. 11-8. About 64 million cu ft per day of natural gas is required, including that used as fuel for processing the products. An oxygen plant supplies about 1,800 tons per day to the gas generator where the partial combustion of natural gas occurs at a pressure of about 400-450 psi in accordance with the following equation v 

Approximately 180 million cu ft per day of s mthe8is gas is produced. High-pressure steam is generated by heat recovery from the hot synthesis gas. This steam is utilized in the oiorgen plant. Carbon dioxide is scrubbed from the s mthesis gas at elevated pressure. 

The distribution of liquid products from this plant was expected to be about 26 per cent oxygenated compounds and 75 per cent hydrocarbons. Of the hydrocarbon liquids, about 85 per cent is gasoline, 10 per cent distillate fuel, and 5 per cent heavier fuel oil. The finished gasoline is highly olefinic, with a research octane number of about 85 unleaded. The scheduled annual production of water-soluble chemicals is shown in Table 11-5. 

Rhodium catalysts with phosphine ligands are used only for propylene hydroformylation, to produce butyrddehyde and then 2-ethyl hexan, but are not used for the production of higher aldehydes. The available processes are complementary and do not compete. The main factor in choosing a process is the product required. 

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In 1997, UOP announced the PX-Plus process which also uses a selectivated catalyst to convert toluene to para-rich xylenes. Pina commercialized a TDP process known as the (T2PX) process in 1984 (70). It uses a proprietary catalyst to react toluene at 42—48% conversion with selectivities to benzene of 42 wt % and to xylenes of 46 wt %. The xylenes produced are at equiUbrium. Typical commercial operating conditions of 390—495°C, H2 partial pressure of 4.1 Mpa, H2/hydrocarbon molar ratio of 4 1, and LHSV of 1—2/h. Pina s first commercial implementation occurred in 1985 at their Port Arthur refinery. 

In contrast to trace impurity removal, the use of adsorption for bulk separation in the liquid phase on a commercial scale is a relatively recent development. The first commercial operation occurred in 1964 with the advent of the UOP Molex process for recovery of high purity / -paraffins (6—8). Since that time, bulk adsorptive separation of liquids has been used to solve a broad range of problems, including individual isomer separations and class separations. The commercial availability of synthetic molecular sieves and ion-exchange resins and the development of novel process concepts have been the two significant factors in the success of these processes. This article is devoted mainly to the theory and operation of these Hquid-phase bulk adsorptive separation processes. 

Table 4. Commercial Operation of Linear Olefin Extraction...

The olefin product contains 1.1% of residual / -paraffins. Essentially similar results have been obtained in commercial operations on Cg—C q and C g feedstocks. The desorbents used are generally hydrocarbon mixtures of lower boiling range than the feed components. The concentrated olefin stream may then be used for production of detergent alcohols. 

Although bulk polymerization of acrylonitrile seems adaptable, it is rarely used commercially because the autocatalytic nature of the reaction makes it difficult to control. This, combined with the fact that the rate of heat generated per unit volume is very high, makes large-scale commercial operations difficult to engineer. Lastiy, the viscosity of the medium becomes very high at conversion levels above 40 to 50%. Therefore commercial operation at low conversion requires an extensive monomer recovery operation. 

Almost all battery scrap and paste is converted to impure lead or lead alloys by pyrometaHurgical processes employing blast, reverberatory, rotary, Isasmelt, or electric furnaces. In many plants, a furnace combination is used. PIectrowinning technologies have also been developed but as of this writing none is yet in fliU commercial operation. 

Space Velocity. The space velocity is the ratio of the volumetric rate of gas at standard conditions to the volume of the catalyst. Generally, the percentage of ammonia in the existing gas decreases as space velocity increases however, the same volume of catalyst at the increased space velocities is capable of producing more ammonia (Fig. 4) (27). Normally space velocities for commercial operations are between 8,000 and 60, 000 h . ... 

Most commercial processes produce polypropylene by a Hquid-phase slurry process. Hexane or heptane are the most commonly used diluents. However, there are a few examples in which Hquid propylene is used as the diluent. The leading companies involved in propylene processes are Amoco Chemicals (Standard OH, Indiana), El Paso (formerly Dart Industries), Exxon Chemical, Hercules, Hoechst, ICl, Mitsubishi Chemical Industries, Mitsubishi Petrochemical, Mitsui Petrochemical, Mitsui Toatsu, Montedison, Phillips Petroleum, SheU, Solvay, and Sumimoto Chemical. Eastman Kodak has developed and commercialized a Hquid-phase solution process. BASE has developed and commercialized a gas-phase process, and Amoco has developed a vapor-phase polymerization process that has been in commercial operation since early 1980. 

Catalysts. In industrial practice the composition of catalysts are usuaUy very complex. Tellurium is used in catalysts as a promoter or stmctural component (84). The catalysts are used to promote such diverse reactions as oxidation, ammoxidation, hydrogenation, dehydrogenation, halogenation, dehalogenation, and phenol condensation (85—87). Tellurium is added as a passivation promoter to nickel, iron, and vanadium catalysts. A cerium teUurium molybdate catalyst has successfliUy been used in a commercial operation for the ammoxidation of propylene to acrylonitrile (88). 

Pure zirconium tetrachloride is obtained by the fractional distillation of the anhydrous tetrachlorides in a high pressure system (58). Commercial operation of the fractional distillation process in a batch mode was proposed by Ishizuka Research Institute (59). The mixed tetrachlorides are heated above 437°C, the triple point of zirconium tetrachloride. AH of the hafnium tetrachloride and some of the zirconium tetrachloride are distiUed, leaving pure zirconium tetrachloride. The innovative aspect of this operation is the use of a double-sheU reactor. The autogenous pressure of 3—4.5 MPa (30—45 atm) inside the heated reactor is balanced by the nitrogen pressure contained in the cold outer reactor (60). However, previous evaluation in the former USSR of the binary distiUation process (61) has cast doubt on the feasibHity of also producing zirconium-free hafnium tetrachloride by this method because of the limited range of operating temperature imposed by the smaH difference in temperature between the triple point, 433°C, and critical temperature, 453°C, a hafnium tetrachloride. 

A completely new approach for BTX production has emerged in recent years. It converts to paraffins into aromatics using a modified ZSM-5 zeoHte catalyst which contains gallium (19). An example of this approach, the Cyclar process, has been in commercial operation by British Petroleum at Grangemouth, Scotiand since August 1990 (20). It uses C —feed and employs UOP s CCR technology to compensate for rapid catalyst coking. 

The overall benefits of this high efficiency combustor over a conventional bubbling- or turbulent-bed regenerator are enhanced and controlled carbon-bum kinetics (carbon on regenerated catalyst at less than 0.05 wt %) ease of start-up and routiae operabiUty uniform radial carbon and temperature profiles limited afterbum ia the upper regenerator section and uniform cyclone temperatures and reduced catalyst iaventory and air-blower horsepower. By 1990, this design was well estabUshed. More than 30 units are ia commercial operation. 

The first commercial operation of the Lurgi process was in Germany in 1936 using brown coal. The reactor was modified to stir the coal bed to permit utilization of bituminous coal. One plant was built at the Dorsten Works of Steinkohlengas AG, and the Sasol plants were built in South Africa to provide synthesis gas for Hquid fuels. 

Wet-Throwaway Processes. By 1978, three wet-throwaway systems were in commercial operation lime scmbbing, limestone slurry scmbbing, and dual alkah (1). Time/limestone wet scmbbing (Fig. 11) remains the most common post-combustion control technique appHed to utiHty boilers (67). The waste product from the scmbbers can either be sent to a landfill or be upgraded by oxidation to become saleable gypsum. 

Additions of new flocculants after conventional thickening produce further dewatering of mineral slimes. A clay flocculated with polyacrylamides and rotated in a dmm can produce a growth of compact kaolin pellets (84), which can easily be wet-screened and dewatered. A device called a Dehydmm, which flocculates and pelletizes thickened sludges into round, 3-mm pellets, was developed for this purpose. Several units reported in commercial operation in Japan thicken fine refuse from coal-preparation plants. The product contains 50% moisture, compared with 3% soflds fed into the Dehydmm from the thickener underflow (85). In Poland, commercial use of the process to treat coal fines has been reported (86), and is said to compare favorably both economically and technically to thickening and vacuum filtration. 

In the United States the most extensive commercial deposits are located in California, Nevada, Oregon, and Washington. The U.S. Bureau of Mines also reports the commercial operation of diatomite deposits in Arizona (7). 

Most distillations conducted commercially operate continuously, with a more volatile fraction recovered as distillate and a less volatile fraction recovered as bottoms or residue. If a portion of the distillate is condensed and returned to the process to enrich the vapors, the Hquid is called reflux. The apparatus in which the enrichment occurs is usually a vertical, cylindrical vessel called a stiU or distillation column. This apparatus normally contains internal devices for effecting vapor—Hquid contact the devices may be categorized as plates or packings. 

Instead of gas turbine exhaust, air preheat has been used in some plants to reduce fuel consumption. Flue gas leaving the furnace stack passes through an air preheater, and the preheated air is suppHed to the burners. By using mostly hearth burners, the duct work and the investment cost can be minimised with air preheat and gas turbine exhaust. It is also possible with 100% waH-fired furnaces, and has been proven in commercial operation (34). 

Silver-containing catalysts are used exclusively in all commercial ethylene oxide units, although the catalyst composition may vary considerably (129). Nonsdver-based catalysts such as platinum, palladium, chromium, nickel, cobalt, copper ketenide, gold, thorium, and antimony have been investigated, but are only of academic interest (98,130—135). Catalysts using any of the above metals either have very poor selectivities for ethylene oxide production at the conversion levels required for commercial operation, or combust ethylene completely at useful operating temperatures. 

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