(93b) Development of Arnold M. Leas Fluidized Catalytic Gasification Process

The advanced Fluidized Catalytic Gasification (FCG) process developed by Arnold M. Leas is designed to produce medium-Btu syngas, which consists mainly of carbon monoxide and hydrogen, from coal and other types of carbonaceous feedstocks. It is based upon proven petroleum refining operations. The process uses a circulating, fluidized bed gasifier with low-temperature, non-slagging conditions. The technology is suitable for use in integrated gasification combined cycle (IGCC) plants for power generation, chemical production, and industrial applications.

The most recent and comprehensive US patents of the gasification technology were issued in 1999, 1998, and 1997 as follows: 5,855,631 ? Catalytic Gasification Process and System; 5,776,212 ? Catalytic Gasification System; 5,641,327 ? Catalytic Gasification Process and System for Producing Medium-grade Btu Gas. Since 1970, development activities completed include laboratory, bench scale, and pilot plant operations. Several hundred engineering heat & material balances, economic studies, and process flow drawings have also been completed for addressing different types of feedstocks, product orientations and clients. This work has resulted in more than 30 patents to support the process development and approximately 50 man-years of effort.

Technology features include: (1) catalytic gasification operating temperatures in the range of 1300 to 1600 F, (2) production of medium BTU syngas (225 Btu/scf) without an air separation unit, (3) projected cold gas conversion efficiency greater than 80%, (4) near-instantaneous gasification, and (5) preparation and purification of the catalyst. The process also provides a hot gas treating system for removal of hydrogen sulfide, particulates, and chlorine from the syngas. Heavy metals from the ash are removed in a concentrated stream. Expected benefits for a commercial plant would be higher operating efficiency, lower capital costs, and lower operating costs as compared to other state-of-the-art gasification systems.

In September of 2001, Arnold passed away at the age of 86. The patents represent his efforts and desire to develop a gasification process that was efficient, economical, and had high environmental standards. They represent many years of dedication, development work, financial resources, and cover a lifetime of experience including 32 years in petroleum & chemical refining operations.

PROCESS DESCRIPTION

The FCG unit consists of a single cylindrical gasification reactor with four processing zones and an external regenerator vessel as shown in Figure 1. Operations include reactor and regenerator sections with circulation of powdered catalyst and other features. Primary gasification takes place in the lower part of the reactor where a stainless steel sleeve defines an inner zone as the beta-leg and an outer annular zone as the gamma-leg. Other zones are located higher up in the reactor and consist of an endothermic gasification zone and a hot gas treating zone.

Pulverized coal and recycle catalyst are charged from a lock-bin into the beta-leg. Here the mixture is contacted with a concurrent upward flow of hot catalyst/syncoal and air. Complex molecular structures of raw carbonaceous feedstocks are cracked and gasified into their most basic fuel form consisting of dry gas (carbon monoxide and hydrogen) and dry carbon. A very minute liquid tar stage is just sufficient to attach dry carbon to the catalytic reagent and syncoal. Additional details are listed.

? The sodium promoted alumina silica catalyst (Al₂O₃-SiO₂-Na₂O) as developed for this process is a stable compound that enhances dry gas production much better than the base catalyst. The high contact ratio of solids to coal avoids the formation of tars, oils, phenols, and hydrocarbon liquids. Other reactions include the fuel decomposition of sulfur, halogens, oxygen, and metals that occurs in the gasifier's hot reducing environment. Also, the deposited carbon on the catalyst overflows to the gamma-leg and further reacts with percolating steam.

? Silican and aluminum oxide complex compounds of the coal ash are coated with carbon to become syncoal. Its properties are very similar to the basic catalytic reagent (sillimanite: Al₂O₃-SiO₂). The reducing environment of the beta-leg allows powdered heavy metals such as iron, nickel, and vanadium to gravitate to the base of the reactor for removal or be partially adsorbed on the catalyst. Most virgin coal feeds contain alkali metals that may be adsorbed on the catalyst/syncoal as a catalytic agent.

The endothermic gasification zone consists of a deep fluidized bed of syncoal, which floats on top of the catalyst due to specific gravity differences. Syncoal is a purified carbonated ash product with very free flowing and non-magnetic properties. Within the zone, carbon is further gasified with carbon dioxide and steam. This reduces the bed temperature. A stream of syncoal is withdrawn and reheated via external carbon combustion in the regenerator. It then circulates to the beta-leg and provides a supplemental source of heat for endothermic gasification reactions. For some applications, the syncoal may be recycled directly to the reactor.

Generated syngas flows upward to the hot-gas treating zone where it passes through a conical perforated tray into a fluidized bed of lime for removing hydrogen sulfide. Calcium sulfide floats on top of the lime and is withdrawn as a separated by-product. Other powdered reagents classified as high temperature precipitates (HTP) are used to remove contaminates including hydrogen chloride and particulates. Since the catalyst in the reactor may partially adsorb some coal metals, the Leas process includes an on-site catalyst purification and preparation unit.

Most gasification systems do not use hot gas treating system and rely on downstream clean-up to remove contaminates from syngas. It is generally accepted that conventional systems are available for removing mercury, COS, and other contaminates from the syngas.

TECHNOLOGY DEVELOPMENT

Arnold M. Leas was a 1937 chemical engineer graduate from Tri-State University, Angola, Indiana who received many patents relating to energy developments involving petroleum refining and coal gasification. He received the Governor Nunn Outstanding Citizen Award in 1968 from Kentucky and the Distinguished Citizen Award from Tri-State College in 1971. His professional experience at Ashland Oil & Refining Company from 1937 until 1970 was unique and provided an understanding of proven petroleum processing methods. After taking early retirement from Ashland at the age of 55, Arnold invested his personal funding and devoted his efforts towards developing the fluidized catalytic gasification technology. He believed that the development of clean and efficient energy from coal would be absolutely essential to the future of the United States.

In 1971, Arnold founded Leas Brothers Development (LBD) with Lawrence Leas and Robert Leas PE, both of whom also received engineering degrees from Tri-State. Carl Clark was the company attorney and also part of the founding group. The company had an administrative office in Columbus, Ohio. The engineering office, laboratory, and pilot plant facilities were located in Columbia City, Indiana until 1979 at which time Arnold then moved his office to Richmond, Indiana. The company operated until 1989. Afterwards, Arnold continued to pursue the technology development as Leas Industrial Associates.

Specifically, the reapplication of fluidized catalytic cracking technology to gasification allowed almost 85% of the processing hardware to be commercially proven for many decades. The remaining R&D involved adapting the process to use solid fuels. A timeline of activities is listed below.

1971-1974: Laboratory and bench scale tests were conducted.

1974-1978: Pilot plant operations (10 TPD) were successful in gasifying coal without tar production, caking, and hardware plugging problems. It demonstrated the use of a sodium promoted alumina silica catalyst, production of syncoal, circulation of the catalyst/syncoal with external carbon combustion and other results.

1979-1989: Design studies were completed to optimize the process. Other activities were also conducted.

1989-2001: Proposals were prepared under the name Leas Industrial Associates for construction of a demonstration scale plant. Funding agencies contacted included USDOE Clean Coal Technology Program, US Department of Commerce's Advanced Technology Program, and other programs.

2005: A report was prepared by Tom Leas PE. It provided a technical review of the process and documented the development activities.

SUMMARY

The technology is a patented process with pilot plant operations completed. Future plans may include the construction and operation of another pilot plant/demonstration unit (>25 TPD) to update and confirm key operating variables.

Figure 1 ? Fluidized Catalytic Gasification Unit