Tubing production processes

Michael C. Kasprzyk, Large Silicon Carbide Radiant Tube Production Process, in Silicon Carbide 87, ed. D. Cawley, The American Ceramic Society, Columbus, OH, 1989, pp. 387-394. 

Monitoring and control of the production process will be performed by a combination of instrumentation and control equipment plus manual involvement. The level of sophistication of the systems can vary considerably. For example, monitoring well performance can be done in a simple fashion by sending a man to write down and report the tubing head pressures of producing wells on a daily basis, or at the other extreme by using computer assisted operations (CAO) which uses a remote computer-based system to control production on a well by well basis with no physical presence at the wellhead. 

The above example is a simple one, and it can be seen that the individual items form part of the chain in the production system, in which the items are dependent on each other. For example, the operating pressure and temperature of the separators will determine the inlet conditions for the export pump. System modelling may be performed to determine the impact of a change of conditions in one part of the process to the overall system performance. This involves linking together the mathematical simulation of the components, e.g. the reservoir simulation, tubing performance, process simulation, and pipeline behaviour programmes. In this way the dependencies can be modelled, and sensitivities can be performed as calculations prior to implementation. 

Reaction and Heat-Transfer Solvents. Many industrial production processes use solvents as reaction media. Ethylene and propylene are polymerized in hydrocarbon solvents, which dissolves the gaseous reactant and also removes the heat of reaction. Because the polymer is not soluble in the hydrocarbon solvent, polymer recovery is a simple physical operation. Ethylene oxide production is exothermic and the catalyst-filled reaction tubes are surrounded by hydrocarbon heat-transfer duid. 

Selectivity may also come from reducing the contribution of a side reaction, e.g. the reaction of a labile moiety on a molecule which itself undergoes a reaction. Here, control over the temperature, i.e. the avoidance of hot spots, is the key to increasing selectivity. In this respect, the oxidative dehydrogenation of an undisclosed methanol derivative to the corresponding aldehyde was investigated in the framework of the development of a large-scale chemical production process. A selectivity of 96% at 55% conversion was found for the micro reactor (390 °C), which exceeds the performance of laboratory pan-like (40% 50% 550 °C) and short shell-and-tube (85% 50% 450 °C) reactors [73,110,112,153,154]. 

The extent of formation of these NOC depends upon the presence of nitrogen oxides present in the atmosphere during the manufacturing cycle. The major contaminants are NDMA, A-nitrosodiethylamine (NDEA), A-nitrosopyrrolidine (NPYR), NMOR, A-nitrosodiphenylamine (NDPhA), A-nitrosopiperidine (NPIP) and A-nitrosodibutylamine (NDBA)68. NMOR was found in the hot process areas NDMA occurred in tube production areas in which NDPhA was being used as retarder and tetramethylthiuram disulphide as an accelerator. Figure 12 shows a proposed reaction scheme of formation of NOC in the rubber industry and subsequent exposure67. 

The use of nitrocellulose with a nitrogen content below 12% also increases the smoothness of the surface of the tubes. The addition of higher nitrated cellulose is not detrimental in this respect if the production process is well managed. 

Powder for rockets is usually in the form of perforated grains with a large diameter, considerably larger than that of the tubes used for cannon charges. This makes the production process for extruding the powder mass very complicated. 

In bulk polymerization, no solvents are employed and the monomer acts as the solvent and continuous phase in which the process is carried out. Commercial bulk processes for acrylic polymers are used mainly m the production of sheets, rods and tubes. Rulk processes are also used on a much smaller scale in the preparation of dentures and novelty items and in the preservation of biological specimens. Acrylic castings are produced by pouring monomers or partially polymerized sirups into suitably designed molds and completing the polymerization. Acrylic bulk... 

The production processes used are (i) dip-coating for plates and tubes, (and ii) spin-coating, mainly for plates. 

Litharge and the other lead oxides that are used in the production of glasses and ceramics are obtained primarily through the oxidation of refined (purified) metallic lead. Because metallic lead does not occur naturally in large quantities, it must be extracted from either primary sources (mineral ores) or secondary sources (recycled materials such as lead-acid batteries and cathode ray tubes). The processing required to refine metallic lead can be broken down into three major steps, as seen in Fig. 3 ... 

The EMIT protocol was followed through the production of NADH. The 50 fxl of the NADH-containing reaction mixture was diluted 11 1 with 0.1 M phosphate pH 7.4, vortexed, and sampled by HPLC. Under the conditions used the NADH residence time on the Knauer column was 2 min 47 sec. Tubes were processed every 12 min in this manner. 

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