Plant chemicals

Reverse osmosis is used for desalination of seawater, treatment of recycle water in chemical plants and separation of industrial wastes. More recently the technique has been applied to concentration and dehydrogenation of food products such as milk and fruit juices. See ultrafiltralion. 

B. F. Warner, joint symposium. The Scaling-Up of Chemical Plant and Processes, London, 1957, p. 44. 

The gasification plant is equipped with two Texaco gasifiers, each capable of producing all of the synthesis gas required for operation of the complex. Eastman chose an entrained-bed gasification process for the Chemicals from Coal project because of three attractive features. The product gas composition using locally available coal is particularly suitable for production of the desired chemicals. Also, the process has excellent environmental performance and generates no Hquids or tars. EinaHy, the process can be operated at the elevated pressure required for the downstream chemical plants. 

In general, the geometric properties of the natural fibers are highly variable from fiber to fiber, both within a given lot and among lots of the same fiber type. In the synthetic fibers, the geometric properties are extremely uniform in view of the production control possible in a chemical plant but not in an agricultural product. 

Fig. 1. Fine chemicals plant design showing successive additions of processing equipment, where A represents the reaction vessel with agitator B, centrifuge C, dryer D, crystaUi2ation vessel E, raw material feed tanks F, centrifuge which may have an automatic discharge G, mother Hquor tank H,...

In the design of a fine chemicals plant equally important to the choice and positioning of the equipment is the selection of its size, especially the volume of the reaction vessels. Volumes of reactors vary quite widely, namely between 1,000 and 10,000 L, or ia rare cases 16,000 L. The cost of a production train ready for operation iacreases as a function of the 0.7 power. The personnel requirement iacreases at an even lower rate. Thus a large plant usiag large equipment would be expected to be more economical to mn than a small one. 

Fig. 2. Schematic of a multipurpose fine chemicals plant. Computer-assisted process control is utilized.

The production building is only one part of a full-fledged fine chemicals plant. Apart from the multipurpose plant building there is usually an office and R D building, the warehouse, the maintenance shop, tank farms, the iaciaerator, and wastewater treatment faciUties. 

Eig. 15. Eurfural, phenols, and ethanol production from wood in a multiproduct process biomass chemical plant (52). Wood (qv) is ca 50% cellulose (qv),... 

Fluorozirconate Crystallization. Repeated dissolution and fractional crystallization of potassium hexafluorozirconate was the method first used to separate hafnium and zirconium (15), potassium fluorohafnate solubility being higher. This process is used in the Prinieprovsky Chemical Plant in Dnieprodzerzhinsk, Ukraine, to produce hafnium-free zirconium. Hafnium-enriched (about 6%) zirconium hydrous oxide is precipitated from the first-stage mother Hquors, and redissolved in acid to feed ion-exchange columns to obtain pure hafnium (10). 

Total hafnium available worldwide from nuclear zirconium production is estimated to be 130 metric tons annually. The annual usage, in all forms, is about 85 t. The balance is held in inventory in stable intermediate form such as oxide by the producers Teledyne Wah. Chang (Albany, Oregon) and Western Zirconium in the United States Ce2us in France Prinieprovsky Chemical Plant in Ukraine and Chepetsky Mechanical Plant in Russia (crystal bar). 

H. Tongue, The Design and Construction of High Pressure Chemical Plant, 2nd ed.. Chapman Had Ltd., London, 1959. 

The dominant role of petroleum in the chemical industry worldwide is reflected in the landscapes of, for example, the Ruhr Valley in Germany and the U.S. Texas/Louisiana Gulf Coast, where petrochemical plants coimected by extensive and complex pipeline systems dot the countryside. Any movement to a different feedstock would require replacement not only of the chemical plants themselves, but of the expensive infrastmcture which has been built over the last half of the twentieth century. Moreover, because petroleum is a Hquid which can easily be pumped, change to any of the soHd potential feedstocks (like coal and biomass) would require drastic changes in feedstock handling systems. 

Industrial Wastewater Treatment. Industrial wastewaters require different treatments depending on their sources. Plating waste contains toxic metals that are precipitated and insolubiHzed with lime (see Electroplating). Iron and other heavy metals are also precipitated from waste-pidde Hquor, which requires acid neutralization. Akin to pickle Hquor is the concentrated sulfuric acid waste, high in iron, that accumulates in smokeless powder ordinance and chemical plants. Lime is also useful in clarifying wastes from textile dyeworks and paper pulp mills and a wide variety of other wastes. Effluents from active and abandoned coal mines also have a high sulfuric acid and iron oxide content because of the presence of pyrite in coal. 

The four process control parameters are temperature, pressure, flow, and level. Modem process level detection systems are varied and ubiquitous in modem chemical plants there are thousands of processes requiring Hquid level indication and Hquid level control. From accumulators to wet wells, the need for level devices is based on the need for plant efficiency, safety, quaUty control, and data logging. Unfortunately, no single level measurement technology works rehably on all chemical plant appHcations. This fact has spawned a broad selection of level indication and control device technologies, each of which operates successfully on specific appHcations. 

Applications Research. Specialty chemical producers devote a larger share of their time and costs to appHcations research than do producers of most commodity chemicals. As noted earHer, the most successful specialty chemical producers have been those companies that ate able to respond quickly to customer needs and problems under the conditions found in the customer s plant. This entails having, at the specialty chemical plant, equipment and procedural knowledge which closely approximate those found among customers. Tests can then be mn and a solution to the problem or need may result. If successful, even in part, it can be brought to the customers and tried there. In practice, of course, each customer s plant has some variables which make a single answer or product quite unlikely. Fortunately, slight modifications by the suppHer will often solve the next customer s problem. 

For pipelines in service in chemical plants, it is not usually convenient to place a radiation source inside the pipe and position it to irradiate each welded joint. The radioisotope source container maybe placed on the outer surface of the pipe. The radiation beams then pass through two pipe wall thicknesses to expose films placed diametrically opposite the radiation source, also on the outside of the pipe wall. Other methods, such as magnetic particle inspection of welds in steel pipe, or ultrasonic inspection of welds in pipes of all materials, supplement x-rays in many critical appHcations. The ultrasonic tests can often detect the thin, laminar discontinuities parallel to the pipe surface or the incomplete fusion discontinuities along the weld... 

Most aroma chemicals are relatively high boiling (80—160°C at 0.4 kPa = 3 mm Hg) Hquids and therefore are subject to purification by vacuum distillation. Because small amounts of decomposition may lead to unacceptable odor contamination, thermal stabiUty of products and by-products is an issue. Important advances have been made in distillation techniques and equipment to allow routine production of 5000 kg or larger batches of various products. In order to make optimal use of equipment and to standardize conditions for distillations and reactions, computer control has been instituted. This is particulady well suited to the multipurpose batch operations encountered in most aroma chemical plants. In some instances, on-line analytical capabihty is being developed to work in conjunction with computer controls. 

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