CONTENTS Channeling of fuel beds and blowing over of fuel. Attempts to overcome fuel channeling__. Conditions revealed by heat balance Incomplete absorption of heat from gases_- Heat of combustion of unburned stack gas. III TABLES Table 1. Conditions and results during heat-balance test period__ 2. Analyses of gas oil and tar___ 3. Analyses of coals, blown-over fuel, and generator refuse_ 4. Average analyses of gases--- 5. Heat input per 1,000 cubic feet of finished gas during test. 6. Heat output per 1,000 cubic feet of finished gas during test____ PLATE I. A, Water-gas fuel bunker, with car loading and weighing plat- form level with operating floor; B, Water-gas plant of Coal Products Manufacturing Co., Joliet, Ill., before installation II. A, Critchlow valve nest, gauge board, and automatic control for one set; B, Turbine-blower unit for supplying air blast to one set__. 7 V. A, Thomas recording gas calorimeter; B, Recorder of Thomas 66 VI. A, Worthington displacement water meter; B, Homemade FIGURE 1. Arrangement of dust collector on generator offtake.... 3. Charging car and hand chute__ 4. Chart for determining costs of coal and of coke giving same gas- USE OF BITUMINOUS COAL AS GENERATOR FUEL FOR LARGE WATER-GAS SETS WITH WASTE-HEAT BOILERS By Wм. A. DUNKLEY INTRODUCTION Under certain conditions in the fuel market the prices of coke or anthracite-the commonly used water-gas fuels differ considerably from those of bituminous coal. Such differences were marked during the World War especially in the Middle West, and stimulated the study of methods of using bituminous coal for making water gas. Trouble was experienced during early attempts to use bituminous coal for this purpose. Mechanical difficulties caused some annoyance, but low production capacities and poor fuel efficiencies were even more discouraging. After extensive experiments, operating methods were gradually improved, difficulties were almost entirely overcome, and fuel consumption per unit of gas production was so reduced, especially in the smaller water-gas sets, as to place bituminous coal almost on a par with low-volatile fuels, even at the same price per ton. Results have not been so promising for the larger sizes of water-gas sets—that is, those having generators 8 feet 6 inches or more in diameter-in which the tendencies hindering good efficiencies seem to be emphasized. In the water-gas sets of 11.0-foot generator diameter—the largest size commonly installed these unfavorable tendencies are especially marked. Much study has been given to the use of bituminous coal in a battery of sets of this size in the plant of the Coal Products Manufacturing Co. at Joliet, Ill. The water-gas installation at this plant is new and is equipped with refinements found in a few other plants. It has been possible therefore to study the use of bituminous generator fuel under especially favorable conditions for about two years. Although it can not be said that the difficulties of operation peculiar to the use of bituminous fuel in large sets have been entirely overcome at Joliet, the experiences have been instructive. This paper summarizes the tests up to January 1, 1923, shows the practical efficiencies obtained, and discusses economic phases of the 1 process, in order that operators who contemplate using bituminous generator fuel may have some data upon which to base calculations when they try to estimate whether the use of such fuel would be economically feasible. When this paper was written, fuel-market conditions were not as favorable to bituminous fuel as formerly. Nevertheless bituminous coal is still used in several plants, and since under certain conditions it can be used with noticeable saving in operating costs the subject is important to gas manufacturers. The use of this fuel also gives a water-gas plant increased flexibility under varying conditions of fuel supply. A fact worthy of note is that the low-sulphur coals of Illinois and Indiana, which are not regarded as first-grade coals for coal-gas and coke manufacture, give results in the water-gas machine nearly as good as those obtained from eastern high-volatile coals. Hence, the more these Middle Western coals can take the place of coke from eastern coals, the more coke is saved for use in industries where bituminous coal can not be employed to advantage; moreover, transportation of coal from eastern fields is avoided. ACKNOWLEDGMENTS Most of the work for this paper was done in the plant of the Coal Products Manufacturing Co. at Joliet, Ill. Thanks are due Messrs. W. M. Willett, C. C. Boardman, W. J. Murdock, E. E. Lundgren, and W. R. Bigelow, officials of the company, for their hearty cooperation at all times. Other company employees assisted efficiently and helpfully in the various tests and operations whose results are reported here. PREVIOUS STUDIES OF BITUMINOUS COAL AS GENERATOR FUEL Developing the use of bituminous coals as generator fuel in water-gas production has been the work of many individuals. Doubtless many unreported experiments have been made with results not encouraging enough to warrant continued operation. Among the most successful attempts are those that have been made in the Middle West. Some of the pioneer plants that use the process are those at East St. Louis, Ill., and Beloit, Wis. Some of the plants of the Illinois Traction System also used coal intermittently for several years, even before the fuel stringency of 1917 and 1918. Fuel Administration measures at that time greatly accelerated the development of the process. Gas companies in the Middle West found it difficult or impossible to obtain enough coke to operate their water-gas plants and anthracite was unobtainable; many of them faced the alternatives of using raw coal or of shutting down. They recognized that intensive study of the use of coal was needed by men who could devote time to the technical aspects of the process without being obliged to direct their attention almost exclusively to the problems of obtaining fuel and labor and maintaining equipment, as most operating engineers and superintendents of plants were obliged to do. TESTS AT STREATOR, ILL. Early in 1918 the agencies of the cooperative mining agreement at the University of Illinois undertook the study with the cooperation of the gas industry. The Public Service Co. of Northern Illinois offered the use of the small water-gas plant at Streator, Ill., for test purposes. During an investigation which lasted several months, W. W. Odell, of the Bureau of Mines, and the writer of this paper, who was then with the Illinois State Geological Survey, studied a number of Illinois coals as water-gas fuel in the Streator plant under service conditions. The results of this investigation were reported in Cooperative Mining Investigations Bulletin 24 of the Illinois State Geological Survey. The work at Streator demonstrated that in small water-gas sets not over 6 feet in external diameter, running only a few hours a day, the coals of southern Illinois can be used with success. By use of the right operating cycle and charging interval and proper weight of coal charged, and by adoption of the so-called "blow-run " cycle, in which a part of the richest blast gas is saved, it was possible to avoid almost entirely excessive production of smoke, caking of the generator fire, sticking of gas valves through pitch formation, and overheating of the oil-fixing chambers-all of which had characterized former operation with bituminous coals. A production capacity approximately 75 to 80 per cent of the nominal rated capacity of the apparatus could also be obtained even with the low blast pressure available—the rated capacity being based upon the use of good coke and a high blast pressure. In fact the production rate with coal was higher than could be obtained in the same sets with the coke and the blast pressure available under the usual operating conditions. TESTS AT BELOIT, WIS. While the Streator tests were going on, other operators were trying coal as generator fuel. Many of these experiments, although quite successful, were not reported in the technical press. R. G. Krumrey has discussed the results obtained in the 6-foot watergas sets he was operating at Beloit, Wis. His results were much like 1 1 Krumrey, R. G., Experiments with bituminous coal in the manufacture of water gas: Am. Gas Eng. Jour., vol. 110, Apr. 5, 1919, p. 291 |