Industrial Operation

The preparation of crystallizable polypropylene, as practiced in the earlier days of polypropylene, involved the preparation of catalyst, polymerization, purification, solvent recovery, and, finally, compounding. Typically, yields were 500 1000 lb of polymer per pound of catalyst [6]. Each manufacturer practiced one s own version of these process steps in an effort to produce a uniform product with regard to molecular weight and molecular weight distribution, ash content, color and color stability, and atactic, noncrystallizable polymer content. As discussed earlier, some systems used solvents that kept the atactic polymer in solution. 

Others, which used propylene under pressure as the solvent, required washing after the unreacted monomer was removed and recycled. The particular process was unique to each of the polymer manufacturers. 

As discussed above, there have been major improvements in catalyst efficiency and selectivity. The amount of atactic polymer has been reduced, and the number of pounds of polymer produced per pound of catalyst has been increased from five- to tenfold and more. Polymerization in the gas phase has been improved [73] in order that resin with low atactic content can be produced without solvent removal or polymer washing. The new processes [74] have reduced and, in some cases, eliminated the purification and solvent recovery steps, thereby simplifying the polymerization process and reducing the cost of a polymer plant. In addition, the new processes yield polymers with reduced catalyst residues and fewer gels, resulting in better filterability and improved pack life during fiber melt spinning. 

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X 10 J/kg(10.4 X 10 Btu/lb) in 1990. The shift in coal production toward western coal deposits also reflects the shift in coal utilization patterns (Table 7). Electric utiUties are increasing coal consumption on both absolute and percentage bases, whereas coke plants, other industrial operations, and residential and commercial coal users are decreasing use of this soHd fossil fuel. 

Ca.rhona.tlon, GalHum can be extracted by fractional carbonation which consists of treating the aluminate solution with carbon dioxide in several controlled stages. This process is no longer under industrial operation (6). 

The exact status of the development of the AVLIS process is subject to security classification. It is beHeved that the process is ready for transition to an industrial operator for commercial development. 

Fluid mixing is a unit operation carried out to homogenize fluids in terms of concentration of components, physical properties, and temperature, and create dispersions of mutually insoluble phases. It is frequently encountered in the process industry using various physical operations and mass-transfer/reaction systems (Table 1). These industries include petroleum (qv), chemical, food, pharmaceutical, paper (qv), and mining. The fundamental mechanism of this most common industrial operation involves physical movement of material between various parts of the whole mass (see Supplement). This is achieved by transmitting mechanical energy to force the fluid motion. 

As for the selectivity of DBO, the higher the reaction pressure and the lower the reaction temperature, the higher the selectivity. As for the reaction rate, the higher the reaction temperature, the larger the rate. Therefore, the industrial operation of the process is conducted at 10—11 MPa (1450—1595 psi) and 90—100°C. In addition, gas circulation is carried out in order to keep the oxygen concentration below the explosion limit during the reaction, and to improve the CO utili2ation rate and the gas—Hquid contact rate. 

The ratio of cycHc to linear oligomers, as well as the chain length of the linear sdoxanes, is controlled by the conditions of hydrolysis, such as the ratio of chlorosilane to water, temperature, contact time, and solvents (60,61). Commercially, hydrolysis of dim ethyl dichi oro sil a n e is performed by either batch or a continuous process (62). In the typical industrial operation, the dimethyl dichi orosilane is mixed with 22% a2eotropic aqueous hydrochloric acid in a continuous reactor. The mixture of hydrolysate and 32% concentrated acid is separated in a decanter. After separation, the anhydrous hydrogen chloride is converted to methyl chloride, which is then reused in the direct process. The hydrolysate is washed for removal of residual acid, neutralized, dried, and filtered (63). The typical yield of cycHc oligomers is between 35 and 50%. The mixture of cycHc oligomers consists mainly of tetramer and pentamer. Only a small amount of cycHc trimer is formed. 

The industry operates by using standardized procedures for testing and characterizing materials. These procedures are pubHshed and updated by the American Society for Testing Materials in consultation with interested parties in the industry. 

Occasional brief contacts of Hquid carbon tetrachloride with unbroken skin do not produce irritation, though the skin may feel dry because of removal of natural oils. Prolonged and repeated contacts may cause dermatitis, cracking of the skin, and danger of secondary infection. Carbon tetrachloride is apparenfly absorbed through the skin but at such a slow rate that there is no significant hazard of systemic poisoning in normal industrial operations. 

The ease with which nuclei can be produced by contact nucleation is a clear indication that this mechanism is dominant in many industrial operations. Research on contact nucleation is continuing with the objective of building an understanding of the phenomenon that will allow its successful inclusion in models describing commercial systems. 

Industrial ethyl alcohol can be produced synthetically from ethylene [74-85-17, as a by-product of certain industrial operations, or by the fermentation of sugar, starch, or cellulose. The synthetic route suppHes most of the industrial market in the United States. The first synthesis of ethanol from ethylene occurred in 1828 in Michael Faraday s lab in Cambridge (40). 

AU industrial operations produce some wastewaters which must be returned to the environment. Wastewaters can be classified as (1) domestic wastewaters, (2) process wastewaters, and (3) coohng waste-waters. Domestic wastewaters are produced by plant workers, shower facihties, and cafeterias. Process wastewaters result from spills, leaks, and product washing. Coohng wastewaters are the result of various cooling processes and can be once-pass systems or multiple-recycle cooling systems. Once-pass coohng systems employ large volumes... 

Large industrial operations with on-site needs for electricity and heat in the form of process steam, direct heat, and/or space heat. 

For further details of industrial operating costs see Annual Oil and Gas Kngine Fower Costs, published hy the American Society of Mechanical Engineers. Engine manufacturers will supply recommended schedules for preventive maintenance. 

Many industries operated throughout the world do not fall into the previous categories. Some of these are universal, such as asphalt batching plants, whereas others are regional, such as bagasse-fired boilers. Each has its own emission and control problems and requires knowledgeable analysis and engineering. Some of the more widely used processes are examined in this section. 

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