Carbon coking process

Approximately 50—55% of the product from a coal-tar refinery is pitch and another 30% is creosote. The remaining 15—20% is the chemical oil, about half of which is naphthalene. Creosote is used as a feedstock for production of carbon black and as a wood preservative. Because of modifications to modem coking processes, tar acids such as phenol and cresyUc acids are contained in coal tar in lower quantity than in the past. To achieve economies of scale, these tar acids are removed from cmde coal tar with a caustic wash and sent to a central processing plant where materials from a number of refiners are combined for recovery. 

Residues may also be processed by removing carbon. These processes include deasphalting and coking, which produce usable liquid fuel components while rejecting a carbon-rich phase (asphalt or coke). 

Figure 12-8A. Piston rings. The piston rod is manufactured from heat-treated stainless steel and is coated with wear-resistant overlays, such as ceramic, chromium oxide, and tungsten carbide applied by plasma techniques. Piston rod cross-head attachment has mechanical preloading system for the threads. Rider rings and seal rings are manufactured from PTFE filled resins fillers are matched to the gas, piston speed, and liner specifications. Typical fillers are glass, carbon, coke, or ceramic. (Used by permission Bui. BCNA-3P100. Howden Process Compressors Incorporated. All rights reserved.)...

Hojanas Also called Siurin. An iron extraction process. Magnetite, mixed with carbon-coke breeze and limestone, is heated in a ceramic retort by passage through a tunnel kiln at 1,200°C. Used commercially in Sweden since 1911. See also DR. 

Present coking processes generally are of two types (I) highiempcriiliire (900- I200=C) carbonization lor producing melallurgical coke and (2) low-temperature (500-750°Cl carbonization, still practiced in some countries where there is a market for "semi-coke" as a smokeless home fuel and tars as feedstock for synthetic liquid fuels. 

The traditional synthesis route involves the direct reaction of silicon with nitrogen at temperatures above 1,300 °C, or by heating silica with carbon (coke) in a stream of nitrogen and hydrogen at 1,500 °C.41 However, as in the case of silicon carbide, the high processing and fabrication temperatures focused attention on the need for alternative access routes based on preceramic polymers. 

The fixed-carbon value is one of the values used in determining the efficiency of coal-burning equipment. It is a measure of the solid combustible material that remains after the volatile matter in coal has been removed. For this reason, it is also used as an indication of the yield of coke in a coking process. Fixed carbon plus ash essentially represents the yield of coke. Fixed-carbon values, corrected to a dry, mineral-matter-free basis, are used as parameters in the coal classification system (ASTM D-388). 

Coking processes have the virtue of eliminating the residue fraction of the feed, at the cost of forming a solid carbonaceous product. The yield of coke in a given coking process tends to be proportional to the carbon residue content of the feed (measured as the Conradson carbon residue see Chapter 2). The data (Table 7-11) illustrate how the yield of coke from delayed and fluid coking varies with Conradson carbon residue of the feed. 

The bed temperature in the burner is of the order of 590 to 650°C (1095 to 1200°F), and any excess coke that is not removed as part of the burning is periodically removed from the burner. The coke yield from the process may be as little as 1.2 or as high as 1.7 times the carbon residue of the feedstock. As with delayed coking, the fluid coking process is capable of producing liquid products with substantially lower sulfur contents than the feedstock (Table 7-14), but part of the sulfur in the feedstock is concentrated in the coke. There is elimination of sulfur into the gaseous products but uses for the coke depend very much upon the amount of feedstock sulfur. 

Carbon rejection processes, visbreaking, steam cracking, fluid catalytic cracking, and coking. 

Technologies for upgrading heavy crude oils such as heavy oil, bitumen, and residua can be broadly divided into carbon rejection and hydrogen addition processes (Chapter 8). Briefly, carbon rejection processes are those processes in which a carbonaceous by-product (coke) is produced along with distillable liquid products. On the other hand, hydrogen addition processes involve reaction of the feedstock with an external source of hydrogen and result in an overall increase in H/C ratio of the products as well as a decrease in the amount of coke produced. 

Carbon rejection processes upgrading processes in which coke is produced, e.g., coking (q.v.). 

British Carbonization Research Assoc iatioriTBCRA), "An Infrared Spectroscopic Study of the Influence of Oxygen in Coal on the Plastic Stage of the Coking Process", Carbonization Research Report 64, 1979, 22 pp. 

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