Capacity purification

Jain, R, Sun, L., Dai, ]., Baker, G. L., Bruening, M. L., High-Capacity Purification of His-Tagged Proteins by Affinity Membranes Containing Functionalized Polymer Brushes, BzoffwcroffioZecj 2007,8, 3102-3107. 

The estimated world production of wet-process phosphoric acid was 24,001,000 metric tons of P20 in 1993. Capacity was 34,710,000 metric tons. Over 90% of phosphoric acid production is wet-process (agricultural-grade) acid the remainder is industrial-grades (technical, food, pharmaceutical, etc) made by the thermal route or by the purification of wet-process acid. Table 11 fists U.S. production of wet-process and industrial-grade acids. 

Steam-Reforming Natural Gas. Natural gas is the single most common raw material for the manufacture of ammonia. A typical flow sheet for a high capacity single-train ammonia plant is iadicated ia Figure 12. The important process steps are feedstock purification, primary and secondary reforming, shift conversion, carbon dioxide removal, synthesis gas purification, ammonia synthesis, and recovery. 

Sasol Fischer-Tropsch Process. 1-Propanol is one of the products from Sasol s Fischer-Tropsch process (7). Coal (qv) is gasified ia Lurgi reactors to produce synthesis gas (H2/CO). After separation from gas Hquids and purification, the synthesis gas is fed iato the Sasol Synthol plant where it is entrained with a powdered iron-based catalyst within the fluid-bed reactors. The exothermic Fischer-Tropsch reaction produces a mixture of hydrocarbons (qv) and oxygenates. The condensation products from the process consist of hydrocarbon Hquids and an aqueous stream that contains a mixture of ketones (qv) and alcohols. The ketones and alcohols are recovered and most of the alcohols are used for the blending of high octane gasoline. Some of the alcohol streams are further purified by distillation to yield pure 1-propanol and ethanol ia a multiunit plant, which has a total capacity of 25,000-30,000 t/yr (see Coal conversion processes, gasification). 

Oxygen-enriched air is sometimes used in spent acid decomposition furnaces to increase furnace capacity. Use of oxygen-enriched air reduces the amount of inerts in the gas stream in the furnace and gas purification equipment. This permits higher SO2 throughput and helps both the heat and water... 

Alternatives to oxychlorination have also been proposed as part of a balanced VCM plant. In the past, many vinyl chloride manufacturers used a balanced ethylene—acetylene process for a brief period prior to the commercialization of oxychlorination technology. Addition of HCl to acetylene was used instead of ethylene oxychlorination to consume the HCl made in EDC pyrolysis. Since the 1950s, the relative costs of ethylene and acetylene have made this route economically unattractive. Another alternative is HCl oxidation to chlorine, which can subsequently be used in dkect chlorination (131). The SheU-Deacon (132), Kel-Chlor (133), and MT-Chlor (134) processes, as well as a process recently developed at the University of Southern California (135) are among the available commercial HCl oxidation technologies. Each has had very limited industrial appHcation, perhaps because the equiHbrium reaction is incomplete and the mixture of HCl, O2, CI2, and water presents very challenging separation, purification, and handling requkements. HCl oxidation does not compare favorably with oxychlorination because it also requkes twice the dkect chlorination capacity for a balanced vinyl chloride plant. Consequently, it is doubtful that it will ever displace oxychlorination in the production of vinyl chloride by the balanced ethylene process. 

Terminal Stream Compositions and Quantities These are basically linked to an arbitrary given the produc tion capacity of the leaching plant (rate of extrac t production or rate of raw-material purification by extrac tion). When options are permitted, the degree of solute remov and the concentration of the extrac t stream chosen are those that maximize process economy while sustaining conformance to regulatory standards. 

High or ultrahigh product purity is obtained with many of the melt-purification processes. Table 22-1 compares the product quality and product form that are produced from several of these operations. Zone refining can produce very pure material when operated in a batch mode however, other melt ciystallization techniques also provide high purity and become attractive if continuous high-capacity processing is desired. Comparison of the features of melt crystalhza-tion and distillation are shown on Table 22-2. 

Performance information for the purification of p-xylene indicates that nearly 100 percent of the ciystals in the feed stream are removed as produc t. This suggests that the liquid which is refluxed from the melting section is effectively refrozen oy the countercurrent stream of subcooled crystals. A high-meltingproduct of 99.0 to 99.8 weight percent p-xylene has been obtained from a 65 weight percent p-xyfene feed. The major impurity was m-xylene. Figure 22-12 illustrates the column-cross-section-area-capacity relationship for various product purities. 

Adsorption for gas purification comes under the category of dynamic adsorption. Where a high separation efficiency is required, the adsorption would be stopped when the breakthrough point is reached. The relationship between adsorbate concentration in the gas stream and the solid may be determined experimentally and plotted in the form of isotherms. These are usually determined under static equilibrium conditions but dynamic adsorption conditions operating in gas purification bear little relationship to these results. Isotherms indicate the affinity of the adsorbent for the adsorbate but do not relate the contact time or the amount of adsorbent required to reduce the adsorbate from one concentration to another. Factors which influence the service time of an adsorbent bed include the grain size of the adsorbent depth of adsorbent bed gas velocity temperature of gas and adsorbent pressure of the gas stream concentration of the adsorbates concentration of other gas constituents which may be adsorbed at the same time moisture content of the gas and adsorbent concentration of substances which may polymerize or react with the adsorbent adsorptive capacity of the adsorbent for the adsorbate over the concentration range applicable over the filter or carbon bed efficiency of adsorbate removal required. 

Blowing air through the hot, crude, liquid metal oxidizes traces of metals such as Fe, Cu, Zn and Pb which form an easily removable scum. Further purification is by distillation under reduced pressure. About 4000 tonnes of mercury are used annually but only half is from primary, mine production the other half being secondary production and sales from stockpiles. The main primary producer is now Spain, but several other countries, including the former Soviet Union, China and Algeria, have capacity for production. 

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