Robert A. Graff

Flash hydrogenation of coal. 1. Experimental methods and preliminary results

Abstract A laboratory reactor system has been developed for the determination of products obtainable from the flash heating of raw coal in flowing hydrogen at pressures up to 100 atm. The system provides for control of heating rate, solids-contact time and vapour-product residence time. A comparison of results in which each of these time parameters was varied in turn illustrates their importance in determining the yields of alkanes and single-ring aromatics.

Flash hydrogenation of coal 2. Yield structure for Illinois No. 6 coal at 100 atm

Abstract Hydrocarbon yields are mapped for a mine-mouth sample of Illinois No. 6 coal in 100 atm of flowing hydrogen, brought to reaction temperature at 650 °C/s. The influence of reac tion temperature was explored from 620 to 980 °C with a vapour-product residence time of 0.6 s. The effect of increasing residence time was explored at 700 °C. The only light products observed in more than trace amounts (above 1%) were methane, ethane, propane, and BTX (benzene, toluene, and xylene). Carbon balances show little if any heavier material in the product at temperatures beyond 850 °C at 0.6 s vapour-residence time or beyond a residence time of 3 s at 700 °C.

Agglomeration of Ash in Fluidized Beds Gasifying Coal: The Godel Phenomenon

In a bed of anthracite or bituminous coke fluidized by air at 10 to 15 meters per second at 1200� to 1400�C, molten ash forms beads on the surface of a coke particle, some exuding from its interior. The beads merge and detach them-selves to grow further as loose fluidized ash agglomerates of low carbon content.

A thermobalance for high pressure process studies

Abstract A DuPont 950 TG has been modified to permit operation at up to 30 atm, 1100°C, with corrosive atmospheres, and steam partial pressures up to 20 atm. The major areas of instrument development included: weight and temperature measurement at high pressures in a dynamic flow system; modification of a TG to accept corrosive gas atmospheres containing high partial pressures of steam; design of a pressure balanced flow system for safe introduction of corrosive gas atmospheres; design of a working steam generation system for low flows. Process studies illustrating the utility of the high presure thermobalance include the cyclic CO 2 -acceptor reaction for half-calcined dolomite and the cyclic H 2 S absorption and regeneration reaction for half-calcined dolomite

Flash hydrogenation of coal. 3. A sample of US coals

Abstract The susceptibility of a group of US coals to the production of light gaseous and liquid hydrocarbons during flash hydrogenation is examined. Eight coals ranging from lignite to high-volatile A bituminous and representing five provinces, have been flash heated in 101.3 MPa of flowing hydrogen using a bench scale reactor. A 0.6 s gas phase residence time was provided to hydrocrack the vapour products. Temperatures ranged from 750 to 850°C, where maximum yields of ethane and BTX (benzene+toluene + xylene) are found. The carbon conversion decreased with increasing rank at fixed reaction conditions. Methane yields are highest for lignite. Peak ethane yields range from 6.4 to 9% carbon conversion. BTX yields have a shallow maximum at intermediate ranks, decreasing towards high and low rank coals. Total liquid yields range from 14 to 43%. Although a definite variation of yield with rank is evident, the trends, especially total liquid yields, are attended by considerable scatter. Rank is not the only, and indeed may not be the most significant variable in determining the yield of individual species in flash hydrogenation. To establish the significant variables a stepwise regression procedure was applied to the experimental data using information from the elemental, proximate and petrographic compositions of the coals as independent variables. Two variables are adequate in all cases to correlate species yield and coal properties. Exinite appears to be capable of increasing the amount of liquid obtained from other macerals.

Flash hydrogenation of a bituminous coal.

Flash heating of Illinois coal (to 700�C in 1 second) in flowing hydrogen at 100 atmospheres, limiting the vapor residence time at 700�C to 3 seconds, converts 14 percent of the coals carbon to methane, 7 percent to ethane, and 10 percent to benzene, toluene, and xylenes. The remainder is coke; the carbon balance shows that heavy tar, if any exists, is less than 3 percent.

Design of high-velocity fluid beds for flash hydrogenation

Abstract Successful commercial development of flash hydrogenation for the production of light liquids and gases from coal is largely dependent on the design of the coal-hydrogen reactor. Reactors which operate in the high velocity regimes of fluidization (turbulent and fast fluid beds) offer potential advantages over dilute phase reactor systems. Lower hydrogen circulation rates, lower hydrogen preheat temperatures and reactor temperatures are the most significant of these, resulting in lower capital costs, increased energy efficiency and reduced product cost. Pilot plant experience with high velocity beds fed with caking coal is promising for the development of flash hydrogenation reactors. These trials suggest criteria for design of the coal injection zone and show how growth of char agglomerates can be controlled. Two design examples are developed to explore the applicability of high velocity beds to flash hydrogenation in concrete terms. The first deals with processing of lignite in a fast fluidized bed, the second with processing a bituminous coal in a turbulent bed. The designs in both cases show the advantage of this approach, as well as its uncertainties and limitations. They suggest that further development would be rewarding.