Operational Experience at the 150 t/d EAGLE Gasification Pilot Plant. Gasification Technologies 2003 San Francisco, California October 12-15, 2003

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1 Operational Experience at the 150 t/d EAGLE Gasification Pilot Plant Gasification Technologies 2003 San Francisco, California October 12-15, 2003 Sadao WASAKA Energy and Environment Technology Development Dept. New Energy and Industrial Technology Development Organization JAPAN Eiki SUZUKI EAGLE Technology Development Group Wakamatsu Research Institute Technology Development Center

2 J-POWER/Electric Power Development Co., Ltd. JAPAN

3 ABSTRACT IGFC realizes the dream of a triple generating system: a combination of fuel cell, gas turbine, and steam turbine capable of dramatically extending the 42% electrical efficiency of today's most advanced coal fired thermal power generating plants in Japan to 60%. Because of its high efficiency, this generating system will decrease the emission of carbon dioxide by 70% compared with a conventional thermal plant. It is hoped that this technology will be put into practical use in the future. To this end, the "EAGLE" Project aims to develop a gasifier producing medium calorific value syngas and to establish a gas clean-up process for removing impurities such as sulfide compounds, halogenated compounds, ammonia and particulate matter to a level acceptable for fuel cells, specifically molten carbonate fuel cells (MCFCs) and solid oxide fuel cells (SOFCs), the so-called high-temperature fuel cells. The EAGLE pilot plant has been intermittently operated since March 2002 after its unit test, and accumulated coal gasification operation time reaches over 840 hrs for about 14 months. This paper describes the operational experience of the EAGLE pilot plant as of May, 2003 and our rough future plan on this project. INTRODUCTION The New Energy and Industrial Technology Development Organization (NEDO) was established in October 1980, immediately after the second oil crisis, as a semi-governmental organization under the Ministry of International Trade and Industry, which is now the Ministry of Economy, Trade and Industry (METI). NEDO embraces an active commitment to the development of clean coal technologies such as coal gasification and to their introduction and dissemination. s extensive experience as a power producer encompasses the development and operation of 66 power plants in Japan, with a combined generating capacity of more than 16 gigawatts and a transmission network exceeding 2,400 kilometers of power lines. The company has responded to various situations by drawing on its unique strengths in the areas of energy and the environment, and has developed new technologies to improve the efficiency and reliability of thermal power, hydroelectric power and transmission lines. has conducted the EAGLE project, achieving new technology for both energy and the environment. The EAGLE gasification technology is based on a previous Japanese national project, HYCOL, which aimed to produce hydrogen from coal. We realize that gasification technology is a core technology for multiple purposes, such as the production of methanol as an alternative fuel and ammonia as a raw material as well as power generation. This is reflected in the project's name, EAGLE, which stands for coal Energy

4 Application for Gas, Liquid & Electricity. In keeping with that, the EAGLE project s specific focus is now on application for IGFC. Fuel cells, which are high efficiency direct power generation technologies, are expected to be the next-generation power generating technologies. When coal is used in fuel cells, the coal must be supplied to fuel cells after converting it into an impurities-free fuel gas. The 150 t/d EAGLE pilot plant employs a pressurized dry feed oxygen blown 2-stage spiral flow type entrained bed gasifier that inherits the 50 t/d HYCOL gasifier and the gas clean-up unit composed of water scrubbers, a rough desulfurizer based on MDEA and a fine desulfurizer to meet the tolerance limits of fuel cells. Figure 1 shows the development schedule. A feasibility study of integrated coal gasification fuel cell combined cycle (IGFC) systems was conducted in fiscal Basic and detail designs of the EAGLE pilot plant with a coal feed rate of 150 tons per day were drawn up in fiscal The construction work, including the manufacturing of a gasifier and other main facilities of the pilot plant was started in The EAGLE pilot plant has been intermittently operated since March 2002 after its unit test, and accumulated coal gasification operation time reaches over 840 hrs for about 14 months. Fiscal Year Feasibility Study & Preliminary Tests Design Construction Operation Evaluation Figure 1 EAGLE Gasification Project Schedule PILOT PLANT DESCRIPTION The EAGLE pilot plant was built at s test site, the Wakamatsu Research Institute located in Kitakyusyu, Fukuoka, which is about 50km northeast of Fukuoka City. Figure 2 shows an aerial view photograph, which was taken on completion of the EAGLE pilot plant in June Figure 3 shows the block diagram of the plant. The pilot plant mainly consists of gasifier unit, char recycle unit, gas clean-up unit including fine desulfurizer, sulfur recovery unit, water treatment unit, Figure 2 Aerial View of EAGLE Pilot Plant

5 air separation unit and power section. Table 1 shows the specifications of the plant. Coal Steam as Utility Condensate Feedstock Preparation pulverized Coal Gasifie Raw Syugas Heat Recovery Boiler Stack GT Char Removal (Cyclone,Filter) HRSG Water Scrubber Incine rator COS Hydrorysis Fine Desulfurizer Water Scrubber Clean Syugas Sulfur Removal Acid Gas Stack Tale Gas Sulfur Recovery Unit Air GT Nitrogen oxygen air Separation Unit Slag / waste water Recycle Water Char Recycle Waste Water Pretreatment Waste Water Recycle Water Reclaimer Gypsum Slag Handling Brine system disposal slag Figure 3 Solids to disposal Process Block Diagram of EAGLE Pilot Plant Table 1 Specifications of EAGLE Pilot Plant Coal Gasifier Oxygen-blown entrained flow gasifier (2-stage spiral flow type) Coal Feed Rate 150 tons per day Gasification Pressure 2.5 MPa Gas Clean-up Cold gas clean-up with MDEA Syngas Volume 14,600 m 3 N/h (MDEA absorber outlet) Sulfur Recovery Limestone-gypsum wet scrubbing Air Separation Pressurized cryogenic separation Amount of Oxygen 4,600 m 3 N/h Oxygen Concentration 95 vol% Air Feed 27,500 m 3 N/h GT Output 8,000 kw GASIFICATION UNIT The gasifier is a pressurized dry feed oxygen blown 2-stage spiral flow type entrained bed gasifier. Raw coal is pulverized to about 45 microns in average diameter with the bowl mill warmed with hot air at 65 degrees C in advance, and stocked in the storage hopper. The gasifier is composed of three sections: the heat recovery section, the gasification section

6 and the quench section as shown in Figure 4. The pulverized coal is transported into the gasification section of the gasifier from the upper coal burners and the lower coal burners with pure nitrogen from the air separation unit through the lock hopper system. Meanwhile, oxygen is also fed into the gasification section from the burners of two stages as gasifying agent. Coal is blown into the gasifier to form a spiral flow in the gasification section to prolong the residence time of the particulate including char. In addition, by optimizing the distribution of the oxygen ratio of each stage, it is possible to obtain both high gasification efficiency and stable operation. Although the inner surface of the gasification section is lined with alumina-based refractory, the refractory gradually changes into slag self-coating during gasification operation. This is expected to prolong the life of the gasifier. Heat Recovery Section Gasification Section Quench Section Figure 4 EAGLE Gasifier There are a lot of nozzles that spout syngas, or so-called quench gas, from the water scrubber to form a cold gas layer on the wall at the outlet of the gasification section. Vitreous slag, which is melted coal ash, adheres to the wall of the gasification section due to the centrifugal force of the spiral flow and forms slag self-coating. Almost all slag is discharged from the slag tap into the water-laden quench section. Slag is crushed with the rotary crusher in the quench section and discharged with water to a slag conveyer. Although slag is disposed of in an ash pond, the water used to carry the slag is fed into the quench section again. The heat recovery section serves as a radiant cooler. In this section raw syngas is cooled down to about 1,000 degrees C. Raw syngas exits the gasifier unit after its heat is recovered with a convection syngas cooler (SGC) at 450 C, and is forwarded to the char recycle unit. The gasifier also has steam nozzles at the lower stage of the gasifier to gasify high temperature melting point ash coal. CHAR RECYCLE UNIT The char recycle unit has a cyclone and a char filter device. Char in raw syngas is recovered with a cyclone and a char filter at a rate of fifty-fifty, and then recycled to the lower stage of

7 the gasifier through a lock hopper system with nitrogen. The char filter device is composed of a lot of sintered metallic filter elements made of iron aluminide. Char on the char filter elements is back washed with pressurized dust-free raw syngas from the first water scrubber. GAS CLEAN UP UNIT, SULFUR RECOVERY UNIT AND WASTEWATER TREATMENT UNIT Cold gas clean up is applied in the EAGLE pilot plant to meet the strict tolerance limits of fuel cells, because it is difficult at present for hot gas clean up to remove ammonia and halogenated compounds to a level acceptable for fuel cells. Water scrubbers remove fine grain, which cannot be recovered with the char filter device, water-soluble halogenated compounds and ammonia. Carbonyl sulfide (COS) in syngas is converted into hydrogen sulfide by the hydrolysis reaction of a COS converter catalyst made of titanium oxide. Highly concentrated hydrogen sulfide is absorbed with methyl di-ethanol amine (MDEA) as the rough desulfurizer, and acid gas discharged from the MDEA is burned and changed into gypsum by gypsum-limestone wet-scrubbing in the sulfur recovery unit. Part of the rough-desulfurized coal syngas is finely desulfurized with adsorbent made of iron oxide (Fe2O3). Clean syngas is fed to an incinerator and a gas turbine (GT) respectively. The wastewater treatment unit consists of slag handling device, wastewater pretreatment device and brine system. Although the slag handling device includes a filter to remove slag particles, the filter has not been used because it clogs up immediately. Stripper in the wastewater pretreatment device can strip ammonia and cyanide simultaneously. Part of the wastewater from water scrubbers is dried with a brine system to separate Salt. Salt is treated as industrial waste. AIR SEPARATION UNIT The air separation unit (ASU) is a pressurized cryogenic air separation unit that operates at a pressure of 1.09 MPa. It can generate 99.5% pure nitrogen and 95% pure oxygen. Raw air is provided with a standalone 4-stage compressor. And there is also a raw air feed line that connects a gas turbine compressor to the ASU to test the integration between ASU and gas turbine compressor. There are three compressors for nitrogen and a compressor for oxygen. Most of the nitrogen is used for coal and char transportation, and NOx reduction at the gas turbine combustor. Oxygen is used as gasifying agent. POWER SECTION Although IGFC consists of steam turbine, gas turbine and fuel cell, the pilot plant only employs a gas turbine. The gas turbine is the H-14 turbine made by Hitachi Ltd., and its combustor is a modified H-15 turbine for middle calorific value clean syngas. The power generated with the gas turbine is consumed as the auxiliary power of the pilot plant. The gas turbine compressor is designed so that air extracted from it is supplied to the air separation

8 unit. An incinerator is installed instead of a flare stack, and the waste heat of its exhaust is recovered with an HRSG. Generated steam is used as auxiliary steam. OPERATIONAL EXPERIENCE The first operation of the gasifier was in mid March 2002 and the first raw syngas was produced in that month. Continuous gasification operation hours are shown in Figure 5. The longest continuous gasification time was about 291 hrs in October, Although the operational characteristics of various equipment of the plant have been solved and grasped steadily, many tests were interrupted on account of setbacks and clogging at the slag tap hole of the gasifier. We readjusted the equipment and made a change of an operation procedure, etc., in order to conquer the foregoing operation troubles. Accumulated Operation Time The Number of Test Run Figure 5 Accumulated Gasification Operation Time STATISTICS ON PILOT PLANT OPERATION Figure 6 shows statistics on causes of plant shut-down. The number of scheduled shut-downs was 2 times in 14 months. The principal causes of plant shut-down were for slag handling and char recycling. The causes and numbers of times that plant operation was stopped due to reasons concerning slag handling were 3 times because of clogging at the slag tap hole and 3 times in total for reasons such as leakage at the main valve and overloading of the recycle water pump. There were 3 occurrences of shut-down of the char recycle unit because of the clogging of its line with foreign matter. Other causes were a syngas leak at the wastewater treatment unit, and clogging of the strainer for feed water because of imperfect blowing of the pipe scale.

9 The oxygen / coal feed ratio has been adjusted to control slag viscosity and to prevent tap hole plugging through many gasification operations. We figured out that the upper side of gasification temperature should be limited in order to control slag viscosity. Furthermore, we revised our start-up manual to stabilize gasification conditions. The failure of the char recycle unit has never occurred during a recent 6-month period due to rigorous control of foreign matter. Scheduled (2 times) 13% Others (4 times) 27% Slag Handling (6 times) 40% Char Recycling (3 times) 20% Figure 6 The Causes of Plant Shut-Down SUMMARY OF TARGETS Table 2 shows numerical results for targets of the EAGLE project. We use a kind of bituminous coal from the USA at present. Two targets on carbon conversion and sulfide compounds have been cleared as of this May. Carbon conversion fulfills an excellent result of 99%, but cold gas efficiency has not achieved its target, which is more than 78%. The calorific value of syngas also has not achieved its target, 10,000 kj/m3n (HHV). We will optimize the oxygen / coal feed ratio to achieve a balance between stable slag discharge and high gasification efficiency. The slag self-coating is favorably formed on the inner surface in the gasification section of the gasifier. We continue to confirm the coal burner tip with or without erosion. It is necessary that sulfide compounds in syngas be less than 1 ppm for SOFC and MCFC. According our test result, sulfide compounds are completely removed to a level of less than 0.1 ppm with MDEA absorbent and Fe2O3 adsorbent. The performance of the COS converter maintains high conversion at a rate of more than 95% without degradation of its catalyst. Halogenated compounds are removed to 4 ppm through two water scrubbers and an MDEA absorber. We have investigated the formation of halogenated compounds so as not to remove halogenated as the design. Ammonia and particulate matter are almost completely removed as the design. In particular, the tendency of differential pressure on the char filter maintains its stability. We continue to raise the precision of analyses of ammonia and particulate matter.

10 Table 2 Summary of Results Item Targets Results Carbon Conversion Cold Gas Efficiency Calorific Value (HHV) Continuous Operation Time Kinds of coal >98% >78% 10,000 kj/m 3 N (*3) 1,000 hrs 5 99% 76% 9,540 kj/m 3 N (*3) 291 hrs 1 Sulfide compounds Halogenated compounds Ammonia Particulate Matter 1 ppm (*1) 1 ppm (*1) 1 ppm (*1) 1 mg/m 3 N (*1) N.D.(<0.1 ppm) (*1) 4 ppm (*1) 2 ppm (*2) 1 mg/ m 3 N (*3) *1 : at Outlet of Fine Desulfurizer *2 : at Outlet of MDEA Desulfurizer *3 : at Outlet of First Water Scrubber FUTURE PLAN The EAGLE project will continue until June Future plans include implementation of longer continuous gasification operation, testing for many kinds of coal and connecting the fuel cell as well as optimizing the oxygen / coal feed ratio for high gasification efficiency. Although the target for continuous gasification time is 1,000 hrs, we will try to test longer continuous gasification operation as long as we can afford to do so, because it is important to raise the reliability of equipment. Regarding the testing of many kinds of coals with ash melting point and volatile matter widely chosen as parameters, it is required to obtain operation data for the design of the next plant. We are considering testing lignite and anthracite as well as bituminous and sub-bituminous. We will connect the EAGLE pilot plant to the elements of an SOFC or an MCFC next year to investigate the fuel cell s degradation. SUMMARY A pilot plant with a capacity of 150 t/d has been equipped with a coal gasification unit, a gas clean-up unit, an air separation unit, a gas turbine unit, etc., to develop technology for gasification and gas clean up for fuel cells. It is now possible to implement experiments on a total coal gasification system for fuel cells. A pilot plant test has been continuing since March Obtaining results in which coal gasification technology for fuel cells is put into practical use is very much anticipated.

11 ACKNOWLEDGEMENT We would like to express our deep appreciation for the support and guidance we have received from all concerned parties, including the Agency of Natural Resources and Energy of METI.