Application of Fluidization Technique to Coal Carbonization

Fluidized and allied carbonization processes developed abroad are reviewed. The processes developed by Pittsburgh Consolidation Coal Co., Institute of Gas Technology, Bureau of Mines and United Engineers and Constructors Inc., are described. The first two processes propose to treat both non-caking as well as caking coals with the object of producing semi-coked char for blanding and power generation. The Bureau of Mines process which has been developed commercially is limited to coals with oxygen content above 12%, heating value less than 14250 B.t.u./lb. on pure coal basis. The process developed by United Engineers & Constructors Inc., operates continuously with any coal but it has not been tried on any large plant. The two processes developed by Imperial Chemical Industries and national Coal Board, in U.K., are described. The former could be operated continuously with caking coal and the latter has the object of using high volatile non-caking coals for producing smokeless domestic fuel for open grates. The fluidized carbonization process operating on a commercial scale in Germany is discussed

Bulk Density of Coal

The influence of various factors such as moisture, grain size, and addition of oil on the bulk density of coal is described. There is a progressive reduction in the bulk density as the moisture content of coal increases, followed by an increase in bulk density which however never reaches the values for the dry coals. This optimum moisture content for a minimum bulk density is different for different coals. The higher the percentage of ash in the coal, the higher is the bulk density at any moisture content

Utilization of Coal Carbonization By-products in India

The present position of the coal tar and by-product industry in India is reviewed in relation to the industrial development programme under the five year plans. The need for developing an integrated industry is emphasized and also the need for developing new methods of coal tar utilization is stressed. The work carried out at the Central Fuel Research Institute in the development of processes for the catalytic oxidation of tar oils into phthalic anhydride, production of water-soluble resins from tar for making laminated and moulded products, conversion of tar oil to diesel oils, use of creosote oil for benzole recovery and production of carbon black from anthracene oil residues are described here

Upgrading of Difficult-cleaning Coals of Jharia Coalfield to Supplement the Future Coking Coal Reserves of India

The paper describes the results of experiments on the washing of some lower seam of Jharia in a 6” diameter cyclone and a 2,000 g.m. sub-aeration type Denver cell. The need for a survey of the cleaning possibilities of the difficult coals of Jharia and Bokaro is stressed. Industrial processes that can be tried are listed. The problems of screening and drying of coals, treatment of slurry, effluent etc., recovery and utilization of the middlings and rejects are considered in some detail. The authors then draw attention to the importance of evolving an integrated plan for the washing of difficult coals in India

Assessment of the Yield of Products from Coal Carbonization

Correlation factors have been developed for the yield of different products, e.g., coke, tar, liquor, ammonia, and gas obtained from laboratory Gray-King Assay, pilot oven tests and from commercial coke Plants. The yield of gas from commercial oven is higher and the yield of coke lower, evidently due to higher carbonizing temperature which results in cracking. The correlation between assay and experimental oven yield is found to be poor and indicates the need of carrying out larger number of tests on the same types of coals. Addition of 4-5% of coke breeze to coking coals or their blends gives increased yield of coke, tar and gas per ton of coal charged. Blends of high volatile weakly coking coals from Raniganj with 15-20% of low volatile coking coals from Jharia filed or L.T.C. char give metallurgical coke ; the yield of coke is lower but the tar yield is more than double that normally obtained from Jharia coking coals

Influence of Carbonizing Conditions on coke Properties

The influence of various factors like stamping, bulk density, rate of heating, grain size etc., of the coal charge on the properties of coke was studied. On stamping the 10 mm micum index tended to decrease while changes in the other physical properties were erratic. Some blends of high volatile weakly coking and low volatile good coking coals gave better coke on stamping. Small addition of oil produced some improvement in the physical properties of the coke due to increases in the bulk density of the charge. And increase in the bulk density caused by the addition of water gave anomalous results

Mechanism of Coke Formation

The mechanism of coke formation is discussed in relation to recent knowledge on the nature of reactive groups present in coal. The non-coking coals are characterized by a preponderant number of oxygenated groups such as OH, CO and COOH. The coking coals, on the other hand, have a negligible proportion of reactive groups. Further the OH groups are chelated with CO group and exist mostly as quinhydrone in the non-coking coals and as semi-quinone in the coking coals. It is postulated by the authors here that the mobility of the coal units in the non-coking coals at 300-500ºC is hampered due to condensation reactions involving the reactive groups, whereas in the case of coking coal there are no condensation reactions and the coal units are more free to exhibit fusion and plastic flow

Fluidized Carbonization Assay of Indian Coals in a 2" Diameter Laboratory Unit

This paper reports the work done on fluidized carbonization of non-caking coals from Raniganj field, caking and weakly caking coals from Assam and lignites from South Arcot and Palana. During the course of work, three different, 2” dia. Electrically heated units (2 to 3 lb. capacity) were installed and operated batchwise. The time of carbonization varied between 15-40 minutes and 30-60 minutes for carbonization at 500ºC and 600ºC temperature respectively, depending upon the rate of heat input