Semicoke

Semibulk containers Semicarb azones Semichemical pulps Semichemicals Semicoke... 

The fluidity of coal increases and then decreases at a given temperature. This has been interpreted in terms of reaction sequence of coal — fluid coal — semicoke. In the initial step, a part of the coal is decomposed to add to that which normally becomes fluid. In the second step, the fluid phase decomposes to volatile matter and a soHd semicoke. The semicoke later fuses accompanied by evolution of additional volatile matter to form a high temperature coke. 

A coherent plastic layer from a few mm to 2—3 cm thick separates the semicoke and coke from the unfused coal in the coke oven. Coking properties are assessed in Russia and some other countries by a measurement of the thickness of this plastic layer. A standardized test widely used in eastern Europe is the best known of this type (6) and involves a penetrometer used to measure the thickness of the plastic layer in a column of coal heated from the bottom. The various standard tests give results that are similar but do not give close correlations with each other. 

Fig. 3. Development of plastic layer movement during coking (a), about midway in coking cycle (b), convergence of plastic envelope and (c), end of coking cycle. The thick, dark, soHd line represents the plastic envelope, defining the boundary between coal and semicoke and M represents the plasticized...

Halb-kochen, n. partial boiling, parboiUng. -koks, m. semicoke. -kokung,/. semieoking, partial carbonization. -koUoid, n. semi-colloid. 

Ur alk, m. primitive limestone, -koks, m. low-temperature coke, semicoke. 

The process is conducted at 700 °C. It yields semicoke, which is popular as a smokeless domestic fuel. It can at times be used in boiler also to avoid smoke. Yield of coke oven gas is less, of tar high, and of ammonia less. Calorific value of coke oven gas generated is more. The process produces aliphatic natured tar. Following carbonization the coke discharging process is difficult as it swells extensively but does not shrink much upon carbonization. Free carbon in tar (produced from the cracking of hydrocarbons) is less Coke produced is weaker. Volatile matter in the coke produced is more. Hydrogen content in the coke oven gas is less. 

Materials used in the activation with KOH include high volatile bituminous coal C, coal semi-coke CS, pitch mesophase PM, pitch semicoke PS and commercial activated carbon AC. The semi-cokes CS and PS were produced by the heat treatment of corresponding parent materials at 520°C with a heating rate of 5°C/min and 2 hours soaking time. The preparation of mesophase PM comprised the soaking of coal-tar pitch at 450°C for 7 h with a continuous stirring. All the treatments were performed under argon in a vertical Pyrex retort of 45 mm diameter. 

The circular black region is a resin filled devolatilization pore surrounded by bitumen semicoke. Fused vitrinite is the bright region with very little texture. The photomicrograph suggests that neither the bitumen or the plastic coal are mutually soluble and the presence of bitumen does not interfere strongly with the fusion of vitrinite macerals. 

Figure 6. Semicoke texture a) flow domain anisotropy in a LVB semicoke b) fine grain mosaic anisotropy in a HVB semicoke c) vacuum bottoms and carboniferous MVB coal at 554 " C (coal 30% by weight).

Influence of additives (inorganic salts) or mineral matter on coal softening, fusion and semicoke texture Coal-binder interaction during carbonization... 

Softening, fusion and semicoke texture for different coals and coal blends... 

As discussed earlier, the Plastofrost estimate of the resolidification temperature (semicoke formation) is incorrect for MVB and LVB coals. Thus, that technique does not give the "real plastic range. The best estimate seems to come from using the Plastofrost measurement of the initial fusion temperature and the dilatometer reading of the temperature of maximum dilatation. 

Figure 1. Optical micrograph of semicoke from carbonization of oxidized Pha-len Seam coal at 550° C, showing isotropic coke structure...

Figure 3. Optical micrograph of the semicoke from carbonization of the hydrogenated Phalen Seam coal at 550°C OV, oxidized vitrinite...

Figure 5. Semicoke of oxidized Phalen Seam coal hydrogenated at 450°C and 1,5 MPa for 3 hr, showing a very fine grain, mosaic coke structure...

The environmental risk leachates from the retort residue represent on the ecosystem is not only related to the absolute content of various potentially toxic trace elements in the semicoke, which in most cases may not be significantly higher than the content of the natural oil shales. It also depends on the leachability of these elements when the residue comes in contact with water, and on the elemental speciation. Important factors to consider in this context are ... 

James Bayer. Would the authors define what they mean by ordered arrangement of micelles or degree of anistropy in semicokes, as related to rank and fluidity ... 

Drs. Pregermain and Deduit. It was not the object of our work to study the degree of anisotropy of semicokes as related to the rank and fluidity of coal. The change of anisotropy and the size of the orientated areas as a function of the rank were studied in CERCHAR by B. Alpem (4). 

It is also almost certain that the methyl groups are completely eliminated during pyrolysis at 600°C. Infrared (7) and chemical studies (24) on semicoke indicate that semicoke is about 1009 aromatic in character and hence contains no methyl carbon. 

Semicoke Middle temperature High temperature coke coke... 

Figure 1. Naphthaeene carbon-mosaic structure in semicoke. X 189...

Figure 8. Boundaries of mosaic units in semicoke as re vealed by quinoline-insoluble material X 189...

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