Desulfurization Of Hot Fuel Gas Produced From High Chlorine Illinois Coals Technical Report March 1 1992 May 31 1992

New coal gasification processes are now being developed which can generate electricity with high thermal efficiency either in an integrated gasification combined cycle (IGCC) or in a fuel cell (MCFC). Both of these new coal-to-electricity pathways require that the coal-derived fuel gas be at a high temperature and be free of potential pollutants, such as sulfur compounds. Unfortunately, some high-sulfur Illinois coals also contain significant chlorine which converts into hydrogen chloride (HCl) in the coal-gas. This project investigates the effect of HCl, in concentrations typical of a gasifier fed by high-chlorine Illinois coals, on zinc-titanate sorbents that are currently being developed for H2S and COS removal from hot coal gas. This study is designed to identify any deleterious changes in the sorbent caused by the HCI, both in absorptive operation and in the regeneration cycle, and will pave the way to modify the sorbent formulation or the process operating procedure to remove HCl along with the H2S and COS from hot coal gas. This will negate any harmful consequences of utilizing high-chlorine Illinois coal in these processes. The work activity during the third quarter of this project involved the performance of the second block-set of experiments in the bench-scale fluidized-bed reactor. These experiments were designed to study the effect of HCl in the desulfurization of a low-Btu fuel gas. Nine single-cycle experiments were performed, at operating temperature of 538, 650, and 750°C, with HCl concentrations of 0, 200, and 800 ppMv. The presence of HCl in the coal gas significantly enhanced the desulfurization efficacy of the sorbent. A 10-cycle sulfidation-regeneration sequence is currently being performed at 650°C with 800 ppMv HCl in the simulated fuel gas to determine any adverse effects on the sorbent structure or its desulfurization capability.

In this project, simulated gasifier-product streams were contacted with the zinc titanate desulfurization sorbent in a bench-scale atmospheric fluidized-bed reactor at temperatures ranging from 538 to 750 [degree]C (1000 to 1382 [degree]F). The first set of experiments involved treating a medium-Btu fuel gas (simulating that of a ''Texaco'' oxygen-blown, entrained-bed gasifier) containing 1.4 percent H[sub 2]S and HCl concentrations of 0, 200, and 1500 ppmv. The second experimental set evaluated hot-gas desulfurization of a low-Btu fuel gas (simulating the product of the ''U-Gas'' air-blown gasifier), with HCl concentrations of 0, 200, and 800 ppmv. These operating conditions were typical of the gas-treatment requirements of gasifiers fueled by Illinois basin coals containing up to 0.6 percent chlorine. The results of the experiments at 538 and 650 [degree]C at all the HCl concentrations revealed no deleterious effects on the capability of the sorbent to remove H[sub 2]S from the fuel gas mixtures. In most cases, the presence of the HCl significantly enhanced the desulfurization reaction rate. Some zinc loss, however, was encountered in certain situations at 750 [degree]C when low-steam operating conditions were present. Also of interest, a portion of the incoming HCl was removed from the gas stream and was retained permanently by the sorbent. This behavior was examined in more detail in a limited set of experiments aimed at identifying ways to modify the sorbents composition so that the sorbent could act as a simultaneous desulfurization and dechlorination agent in the hot-gas cleanup process.

Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.

There is a primary need to increase the utilization of Illinois coal resources by developing new methods of converting the coal into electricity by highly efficient and environmentally acceptable systems. New coal gasification processes are now being developed that can generate electricity with high thermal efficiency in either an integrated gasification combined cycle (IGCC) system or a molten carbonate fuel cell (MCFC). Both of-these new coal-to-electricity pathways require that the coal-derived fuel gas be at a high temperature and be free of potential pollutants, such as-sulfur compounds. Unfortunately, some high-sulfur Illinois coals also contain significant chlorine which converts into hydrogen chloride (HCI) in the coal gas. This project investigates the effect of HCI, in concentrations typical of a gasifier fed by high-chlorine Illinois coals, on zinc-titanate sorbents that are currently being developed for H2S and COS removal from hot coal gas. This study is designed to identify any deleterious changes in the sorbent caused by HCI, both in adsorptive operation and in the regeneration cycle, and will pave the way to modify the sorbent formulation or the process operating procedure to remove HCl along with the H2S and COS from hot coal gas. This will negate any harmful consequences Of utilizing high-chlorine Illinois coal in these processes.

New coal gasification processes are now being developed which can generate electricity with high thermal efficiency either in a combined gas-turbine, steam-turbine cycle or in a fuel cell. Both of these coal-to-electricity pathways require that the coal-derived fuel gas be at a high temperature and be free of potential pollutants, such as sulfur compounds. Unfortunately, some high-sulfur Illinois coals also contain significant chlorine which converts into hydrogen chloride (HC1) in the coal-gas. This project investigates the effect of HC1, in concentrations typical of a gasifier fed by high-chlorine Illinois coals, on zinc-titanate sorbents that are currently being developed for H2S and COS removal from hot coal-gas. This study is designed to identify any deleterious changes in the sorbent caused by the HC1, both in adsorptive operation and in the regeneration cycle, and will pave the way to modify the sorbent formulation or the process operating procedure to remove HC1 along with the H2S and COS from the coal-gas. This will negate any harmful consequences of utilizing high-chlorine Illinois in these processes. The bench- scale fluidized bed has been modified to prevent potential HC1 corrosion and startup experiments have proven the reactor system operable and capable of yielding reliable experimental results. The first of the planned experiments in the project are now being performed. 1 fig.

Proceedings of the NATO Advanced Study Institute on Desulfurization of Hot Coal with Regenerable Metal Oxide Sorbents: New Developments, held in Kusadasi, Turkey, July 1996

At present, the focus of work being performed on Hot Coal Gas Desulfurization is primarily in the use of zinc ferrite and zinc titanate sorbents; however studies at the US Steel Fundamental Research Laboratories in Monroeville, PA, by E.T. Turkdogan indicate that an alternate sorbent, manganese dioxide-containing ore in mixture with alumina (75 wt % ore + 25 wt % Al2O3) may be a preferable alternative to zinc-based sorbents. A significant domestic source of manganese in Minnesota is being explored for an in situ leach process which has potential for producing large tonnages of solutions which may be ideal for precipitation and recovery of pure manganese as a carbonate in a reactive form. In the current program the following studies will be addressed: Preparation of manganese sorbent pellets and characterization tests on pellets for strength and surface area; analysis of the thermodynamics and kinetics of sulfur removal from hot fuel gases by individual sorbent pellets (loading tests) by thermogravimetric testing; regeneration tests via TGA on individual sorbent pellets by oxidation; and bench-scale testing on sorbent beds in a two-inch diameter reactor. The developed information will be of value to METC in its determination of whether or not a manganese-based regenerable sorbent holds real promise for sulfur cleanup of hot fuel gases. This information is necessary prior to pilot-scale testing leading to commercial development is undertaken.

The Midwest Ore Processing Co. (MWOPC) has reported a precombustion coal desulfurization process using perchloroethylene (PCE) at 120 C to remove up to 70% of the organic sulfur. The purposes of this research were to independently confirm and possibly to improve the organic sulfur removal from Illinois coals with the PCE desulfurization and to verify the ASTM forms-of-sulfur determination for evaluation of the process. An additional goal was to develop a dechlorination procedure to remove excess PCE from the PCE-treated coal. A laboratory scale operation of the MWOPC PCE desulfurization process was demonstrated, and a dechlorination procedure to remove excess PCE from the PCE-treated coal was developed. The authors have determined that PCE desulfurization removed mainly elemental sulfur from coal. The higher the level of coal oxidization, the larger the amount of elemental sulfur that is removed by PCE extraction. The increased elemental sulfur during short-term preoxidation is found to be pH dependent and is attributed to coal pyrite oxidation under acidic (pH