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Literature Cited Anderson, H. C., Green, W. J., Steele, D. R., Id.Eng. Chem.. 53, 199 (1961). Bauerie, G.L., Wu, S.C., Nobe, K., Ind. Eng. Chem. Prod. Res. D e v . , 14, 268 (1975). Hirota, K., Kera, Y., Teratani, S.,J . Phys. Chem., 72, 3133 (1968). Kakioka, H., Ducarme, V., Teichner, S.J., J . Chim. Phys., 66, 1715 (1971). Kasaoka, S.,Sasaoka, E., Senda, K., Nenryo Kyokaishi. 56, 818 (1977a). Kasaoka, S.,Yamanaka, T., Sasaoka, E., Nenryo Kyokaishi. 56, 834 (1977b). Kasaoka, S.,Sasaoka, E.. Yamamka, T., Ono, M., Nippon Kagaku Kaishi, 874 (1978). Klimisch, R. L., Larson, J. G.,Ed., “The Catawic Chemistry of Nitrogen Oxides”, Plenum Press, New York. 1975. Kugler, E. L., Kadet, A. B., Gryder, J. W., J. Catal., 41, 72, (1976). Markvart, M., Pour, V., J. Catal., 7, 279 (1967). Miyamoto, A,, Yamazaki. Y., Murakami, Y.. N/ppon Kagaku Kaishi, 619 (1977). Otto,K., Shelef, M., J . Phys. Chem., 76, 37 (1972). Shannon, R. D., Calvo. C., Can. J . Chem., 50, 3944 (1972). Strupler, N., Ann. Chim., 10, 345 (1965).
V.
Takagi. M., Kawai, T., Soma, M., Ohnishi, T., Tamaru, K., J. Catal., 50, 441 (1977). Tarama, K., Teranishi, S., Yoshida, S.,Hirakawa, K., Abstracts of 18th Annual Meeting of Japanese Chemical Society, 35 (1965). Todo. N., Kurlta, M., Hagiwara, H., Ueno, H., Sato, T., Preprints of Papers for the Japan-U.S.A. Seminar on Catalytic NO, Reaction, 3-1, 1975.
Received f o r review May 11, 1979 Accepted July 3, 1979
This work was partially supported by a “grant-in-aidfor scientific research” from the Ministry of Education. Presented at the Symposium on Surface Science of Catalysis: Surface Intermediates, Division of Colloid Chemistry,ACS/CSJ Congress, Honolulu, Hawaii, April 1979.
Tenth Biennial Lignite Symposium W. R. Kube Grand Forks, North Dakota, May 1979
Methanol Derivation from North Dakota Lignite and Use as a Fuel‘ E. C. Glass,” Andrew L. Freeman, and T. 0. Wentworth Northern States Power Company, Minneapolis, Minnesota 5540 1
Methanol has the potential for a significant replacement of oil in the US. Its utilization by electric and gas utilities and by industry appears favorable. Methanol has an advantage over oil where a very clean flame is required. I t can also be converted to gasoline at a modest cost. A process design firm has performed an engineering evaluation and a study of economic feasibility of a plant producing 2.5 billion gallons of methanol annually from North Dakota lignite. The study was underwritten by 16 electric and natural gas utilities, an industrial user, an equipment manufacturer, a coal company, and the Electric Power Research Institute (EPRI). A range of costs for methanol from $18 to $28/bbl (1978 $) of oil equivalent is indicated depending mainly on type of financing.
Introduction Most alcohols are too expensive for consideration as a common fuel. The one alcohol, however, which has the simplest molecule and is the cheapest to make has the potential for significant replacement of oil in the U S . Thirteen plants of the size described here could replace a million barrels a day of imported oil. Wood alcohol, methyl alcohol, and methanol are various names for this alcohol which originally was manufactured by heating hardwood in the absence of air through destructive distillation. Methanol has been around a long time. The first record of its manufacture indicates an origin of about 1630. By 1923, synthesis of this alcohol from carbon monoxide and hydrogen was developed and the first commercial plants installed making possible its production from natural gas. Methanol is versatile. It can be produced from not only wood and natural gas, but forest and agricultural products, municipal solid waste, manure, peat, and coal. The over one billion gallons produced in the U S . each year are used as the chemical feedstock for formaldehyde, solvents, plastics, fibres, fungicides, and insecticides. Methanol is Presented at the Tenth Biennial Lignite Symposium, Grand Forks, N.D., May 1979, cosponsored by the Grand Forks Energy Technology Center (DOE) and the University of North Dakota. 0019-7890/79/1218-0288$01.00/0
also used for antifreeze, for the purification of hormones and vitamins, and for fuels for cooking equipment because of its low-soot flame. It is the source of energy for the high compression-ratio Indianapolis 500 type of racing cars. Methanol has been referred to as again the leading candidate to serve as an alternative fuel to distillate and gasoline (Barr and Parker, 1976). This paper describes the potential use of methanol as a utility fuel and as an industrial boiler fuel, with its production from lignite. Methanol Characteristics Methanol is related to methane gas through the substitution of an OH radical for a hydrogen atom. CHI thereby becomes CH,OH. Its heat content is about half of that of gasoline or fuel oil, being about 65000 Btu/gal. The lowered heat content results from oxygen comprising about half of the molecular mass. In contrast to chemical grade methanol-which must consist of 99.85% or more pure methanol-fuel-grade methanol consists of 97-98’70 methanol and varying amounts of higher alcohols and water. Not having to attain the higher percentage of pure methanol required in the chemical grade means that the process is simpler and the cost significantly less. One impurity which is virtually nonexistent is sulfur-a necessity because the manufacturing process utilizes catalysts which must not be exposed to sulfur-requiring a complete clean-up of the gases prior
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to the methanol synthesis process. This fuel is compatible with the existing liquid fossil fuel delivery system. It has a Reid vapor pressure of just under 5 psi, allowing it to be economically stored and transported in conventional API oil field tankage, pipelines, and barges. Unlike LNG, it does not have to be transported in refrigerated ships, nor monitored for volatile boil-off. Because its molecular masses are less, its vapors disperse more readily rather than accumulating in low-lying regions and greater concentration of vapor is required for flammability with air. It is completely soluble in water and biodegradable-an alcohol spill would have no serious consequences-an alcohol fire can be extinguished with water. It has excellent flow characteristics at low temperatures. All of these attributes make for ease of transport in super tankers. One significant characteristic in the balancing direction is its lower Btu content which essentially doubles storage and transportation requirements when compared to oil.
Proposed Feasibility Study A number of utilities and industries were approached in 1977 by Wentworth Brothers, Inc., a process design firm located in Cincinnati, Ohio. The firm proposed that a group of potential methanol users sponsor an engineering evaluation and a study of the economic feasibility of producing methanol from North Dakota lignite. The proposal contemplated a 25 OOO ton per day plant located in western North Dakota, for study purposes, which would produce 2.5 billion gallons of methanol annually. Because pipeline transportation would be the least costly overland transportation, the proposal included the construction of a pipeline from the plant in North Dakota to the Great Lakes and then to the Minneapolis/St. Paul area. The necessary funding was subsequently underwritten by a group of 20. This group was comprised of 16 electric and natural gas utilities, an industrial user, an equipment manufacturer, a coal company, and the Electric Power Research Institute (EPRI). The specifics of the interest which each participant has in this product is as follows. Use by Electric Utilities. Until the oil embargo of 1973, electric utilities installed combustion turbines as a routine part of the expansion of their generating capacity. Both the jet engine type and the industrial type combustion turbine were installed burning distillate fuel. The planned ratio of such peaking capacity to base load generating capacity was that which balanced out the higher cost of operation against the lower capital cost. This capital cost presently runs at about one-third the cost of base-load coal burning equipment with scrubbers. Now, even though such equipment may be ideal for carrying the utilities’ peak loads and has a lead time for installation of about one-third of base load equipment, the utilities have virtually given up on this type of generation. The reason, of course, is the big uncertainty with oil. Will there be oil available to run new equipment-or even the existing combustion turbines? Twenty percent of Northern States Power Company’s generating equipment is of this type of peaking capacity. The utilization of methanol to fuel combustion turbines promises to be quite favorable from the results of several performance tests designed to determine such feasibility. (See Jarvis, 1974; Klapatch, 1976.) Both the power output and efficiency increased somewhat compared to no. 2 distillate fuels. Because temperature levels generally are lower, NO, emissions are significantly decreased, about 60% ; carbon monoxide was considerably increased but still well below E.P.A. proposed standards. This lower tem-
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perature also indicates an increase in turbine component life. Certain modifications will be required for methanol fuel: starts must be on oil fuel with subsequent transfer to methanol and a switch back for shutdown. The low flash point means that care must be exercised to prevent vapor buildups and eliminate possible sources of ignition-the turbine will need explosion proof motors, cable, switches, etc. The low lubricity and lowered heat content mean that the fuel system components must be redesigned and the fuel storage system increased as well as modified to protect against the greater tendency for corrosion of metal. However, none of these modifications represents substantial expenditures. If an assured source of methanol fuel were to be available, a utility would have the ability to rely on long-term operation of its combustion turbine equipment. It would be possible to install base load and peaking capacity in optimum proportions with the potential for delivering electric energy at a lower cost. Of further interest would be the combining of combustion turbines with waste heat boilers, referred to as combined cycle. This concept produces overall efficiencies of near 45% compared to 30% for simple cycle combustion turbines. An evaluation of the performance of a combined cycle plant using today’s technology, operating on methanol compared to no. 2 distillate, indicates an increase in power of 8% but a decrease in efficiency of 5% (Seglem, 1979). Technology advancements are projected to regain the efficiency loss. With advanced combustion systems, a methanol fueled combined cycle plant could have zero emission of particulates, SOz and NO,. The improved ability to site such a plant would have a considerable value. If a utility has existing oil-fired boilers, these can be retrofitted rather easily to burn methanol. The major changes are the modification of the burners and modifications of the storage facilities. Existing coal-fired boilers can be retrofitted with methanol burners where the plant is not in compliance and installing a flue gas clean-up system is not economically justified. Burners can also be added to coal burning units to recover capacity de-rates brought about by the burning of western coals in boilers designed for higher Btu coal. Finally, there is the potential for operating diesel engines on methanol. Several firms are testing this possibility. Use by Gas Utilities. Methanol could serve a reserve duty for gas utilities. It can be converted to methane by passing over a catalyst at the appropriate temperature and pressure conditions. The methane then can be introduced directly into a natural gas pipeline. The overall process efficiency is approximately 92% although, because it is exothermic, some of the energy loss could be used a t the conversion site. This process is similar to, but less complicated than, conventional conversion of naphtha into SNG. The advantage of using a liquid fuel feedstock for the gas is that the liquid fuel can be easily stored and gasified as needed. The concept also permits gasification for use by electric utilities for fueling combustion turbines. Assuming the ability to make use of existing gas pipelines, this approach provides a means of transport to those utilities not lying on the methanol pipeline nor on convenient waterways. The combining of the electric utility requirements and those of the gas utilities is looked to as providing a smoothing effect in the production of methanol, the primary storage system and in the potential gasifying stage. Industrial Uses. The utilization of methanol in industrial boilers, kilns, and similar facilities permits the
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PREPARAIION
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GENERAIION
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b PURIIICAllON
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Figure 1. Plant flow system.
same performance as in electric utility applications. Like fuel oil, methanol can be delivered by truck to plants that are short of natural gas or oil. It has an advantage over oil where a very clean flame is required such as in bakeries, food processing plants, and glass annealing plants. The use of methanol for industrial and agricultural drying operations is a possibility. Here, the industrial user may alternatively prefer to continue being supplied through the regular gas distribution network and, in effect, switching to methanol-derived SNG when the gas utility does. S t u d y Commenced In July 1977, Wentworth began work. Technical input to the study also included contributions from: Foster Wheeler Energy Corp., Green Construction Co., Hahn & Clay, Latepro Corp., the North American Coal Corp., the Ralph M. Parsons Co., Earl Ruble and Associates, Inc., and the Texaco Development Corp. Here were the bases for the study: (1)The study was to determine the feasibility of an integrated process plant to produce methanol, utilizing North Dakota lignite and applying technology which was known and proven; (2) 25000 ton/day output of methanol (base case); 10000 ton/day output of methanol (alternate case); (3) delivered cost of lignite at plant, $7. 50/ton; (4) export electric energy, 2.5&/kWh;(5) financing: (a) debit-equity ratio, 80/20; (b) interest, 9%; (c) equity return, 12%; (d) plant life, 20 years. S t u d y Results Engineering Design. Illustrated in Figure 1 is the designed plant flow system for a single train designed to output 5000 tons per day of methanol fuel. The base case considered five such trains; the alternate case considered two such trains. Starting with the lignite preparation area, which would be common to all trains, a water slurry feed of 55% lignite is pumped to high pressure gasifiers operating at 1550 psig. Oxygen is also fed into the gasifier obtained by air separation with the distillation of air at low temperature. (In this process, nitrogen is also obtained for stripping in the C 0 2and sulfur removal.) The three gasifiers are of a type developed by Texaco at Montebello, Calif., and employ noncatalytic partial oxidation of the feedstock utilizing oxygen and steam from the slurry. The raw synthesis gas generated is a mixture of hydrogen, carbon monoxide, carbon dioxide, methane, nitrogen, and argon, and small amounts of hydrogen sulfide and other sulfur compounds. Prior to being synthesized to methanol, the synthesis gas must be cleaned of most of the carbon dioxide and cleaned of sulfur to avoid poisoning the methanol synthesis catalyst. Additionally, a shift conversion must take place because the production of methanol requires a hydrogen to carbon monoxide ratio of a little more than 2:1, but the synthesis gas has a lower ratio. This shift conversion is the reaction of carbon monoxide with steam to make hydrogen and carbon dioxide in the presence of a catalyst. All of this takes place in the gas adjustment and purification stage. Finally, the purified synthesis gas is compressed and sent to the methanol synthesis loop where two hydro-
gen molecules and a carbon monoxide molecule are combined in the presence of a catalyst to form CH,OH. This overall process produces all the heat required for the process and the steam required to generate the electric energy requirements with surplus electric energy available for sale. The process thermal efficiency is 52-54% depending on the Btu credit given for surplus electric energy. Except for start-up, the 35% moisture content of the lignite furnishes the water requirements for the process. The work force required to manage and operate a five train plant is about 840 employees. Approximately 25 million tons of lignite would be used annually. Operation of the first train is projected to be possible 5.5 years following project commitment. Environmental Impact. The environmental impact of such a plant appears to be low. No outside water is required for the process except for start-up. Air-cooled condensers are used for the electric generation eliminating the need for cooling water. The only discharge to the atmosphere is from a small separately fired steam superheater for the electric energy production in which are burned various purge gas streams. The major constituents of the superheater flue gas are carbon dioxide, nitrogen, water vapor, and oxygen. Because of a low flue gas flame temperature, NO, is minimal. The flue gas contains approximately 9 ppm by volume of sulfur in the form of sulfur dioxide. About 4800 tons per day of slag will be produced. The ash is granular, generally less than 2 in. in size, and extremely hard. The ash is returned to the mine as back fill. S t u d y Review. The participation of EPRI was premised on the understanding that a qualified firm would be retained, by EPRI, to review the study. C. F. Braun, a major process plant design and construction company, was engaged for this work. This review was completed recently. C. F. Braun concluded that while the design is based on known process technology, demonstration of certain facilities is required of a size which can be safely scaled up to justify proceeding with such a complex. The major items of concern were the lignite pretreatment to permit slurrying lignite at a 55% concentration, the gasifier operation at 1550 psig, and the radiant and convective heat recovery exchangers. The lignite pretreatment is a concern because the North Dakota lignite 35% moisture content is bound inside the lignite pores and does not contribute to slurrying of the lignite. Conventional drying can be used to remove some of the moisture but the solids concentration of a pumpable slurry is not substantially changed because the moisture tends to be reabsorbed into the lignite pores. The purpose of the lignite pretreatment is to irreversibly reduce the moisture content so that a pumpable slurry at a significantly higher solids concentration can be obtained. With respect to the gasifier, Texaco operated their Montebello demonstration gasifier on eastern and western coals at 1200 psig and their pilot plant on oil at 2500 psig. Additional to these concerns a spare gasifier was recommended and continuous operation of the start-up boiler to cover the event of two gasifiers tripping out at the same time. Costs. Not surprisingly, the dual engineering activity produced certain differences of opinion and a range of costs. The estimated plant investment can best be described in round numbers as about $2 billion in first quarter 1978. When interest during construction and working capital are included, the total capital requirement would round off to 2.5 billion. Assuming that a 55% lignite slurry mixture will be obtained, a range of methanol costs from $3.65 to $4.80 per million Btu has been developed.
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The lower figure reflects Wentworth's base design and 80% debt financing. The higher figure reflects the design as adjusted by C. F. Braun with 50% debt utility financing. The study additionally offered leveraged lease financing as an alternative financing method. Assuming the adjusted design and leveraged lease financing, the cost appears to be lowered to about $3.00 per million Btu. For the alternate case of a two train, 100oO TPD plant, penalty of about 5% results. A further impact on this cost will be the DOE'S rule adopted last year giving synthetic fuels a $2 per barrel subsidy similar to the $2 per barrel crude oil entitlement. This amounts to about 354: per million Btu. These costs referred to are all FOB plant. The capital cost of a 22-in. pipeline to transport the methanol from a site in western North Dakota to Superior, Wis., with an extension to Pine Bend, Minn., was also estimated. Including 90 days storage equally divided between the two receiving terminals, this cost was estimated to be $260 million, or 344: per million Btu if the entire production were so transported. From these terminals the fuel can be moved via lake tanker or barge. To St. Louis would be an additional 324:, Chicago 55t, and Omaha 804:. All these costs are referenced to first quarter 1978. In order to better assess these figures, consider $3 per million Btu to be equivalent to 424: per gallon distillate, $4 equivalent to 564: per gallon, and $5 equivalent to 704: per gallon.
(2) Although methanol can be used to directly fuel automobiles, as well as other transportation, it can also be converted to gasoline. Mobile Oil Corp. demonstrated this catalytic conversion last year. The estimated cost ranges from 54: to 104: per gallon of gasoline produced. (3) The sulfur byproduct, which is pure sulfur and inert, is presently planned to be returned to the mine. However, sulfur has many uses and may be saleable. (4) With simple over-the-fence add-on facilities, ammonia and urea can be produced a t relatively low cost for agricultural use. (5) The carbon dioxide gas will be available for tertiary recovery of oil. Conclusion
Circumstances strongly suggest that synthetic fuel projects are timely. For this project, the initial needs are to address the technical concerns expressed in the study review and initiate resolution, determine feasible size and the most favorable financing, establish the likely cost of delivered methanol fuel, and then to make a decision on a realistic course of action. Literature Cited Barr, W. J., Parker, F. A,, "The Introduction of Methanol as a New Fuel into the United States Economy", Foundation for Ocean Research, 1976. Jarvis, P. M., "Methanol as Gas Turbine Fuel", presented at Engineering Foundation Conferences, 1974. Klapatch, R. D., "Gas Turbine Emissions and Performance on Methanol Fuel", United Technologies Corp., 1976. Seglem, C. E., "Performance of Combined Cycle Power Plants Fueled by Methanol", presented at Middle Atlantic Regional Meeting, American Chem ical Society, 1979.
Additional Benefits
(1) Because the capital cost component of the cost of methanol is substantial, escalation of methanol cost is anticipated to be significantly less than for conventional fuels.
Received for review July 19, 1979 Accepted August 27, 1979
Synthetic Natural Gas from Peat' Arnold M. Rader Minnesota Gas Company, Minneapolis, Minnesota 55426
Peat has long been overlooked in listings of US. energy resources, but it is our second largest fuel resource. US. peat resources are estimated at 1443 quadrillion Btu's, second only to coal, and it is equivalent to about 240 million barrels of oil. Peat is a geologically young coal that has been used as a fuel for centuries in Europe. The US. has not considered it as a commercial source of energy in the past due to the low cost of other available fuels, but peat has been a significant fuel for electric generation for several decades in Ireland and Russia. Minnesota Gas Company (Minnegasco) began evaluating peat as a new material for production of synthetic natural gas in September 1974. Peat gasification research has been conducted by the Institute of Gas Technology and has been co-funded by Minnegasco and the US. Department of Energy since July 1976. Research and tests have indicated that peak can be converted to synthetic natural gas more easily, and at a lower cost, than either lignite or bituminous coal. Present plans indicate that pilot plant hydrogasification tests on peat will be started July 1979 with co-funding by Gas Research Institute and U S . Department of Energy. This would allow engineering design and economic evaluation for a demonstration plant during 1981, so that Minnegasco could have an 80 million cubic foot per day synthetic natural gas plant operating in northern Minnesota by 1985.
Introduction
Peat, a geologically young coal, has been used as a fuel for centuries, and in the past few decades has become an important industrial fuel in a number of European coun*Presented at the Tenth Biennial Lignite Symposium, Grand Forks, N.D., May 1979, cosponsored by the Grand Forks Energy Technology Center (DOE) and the University of North Dakota. 0019-7890/79/1218-0291$01 .OO/O
tries. The Soviet Union, with the largest peat resources in the world, fuels 76 electric generating plants with peat. Peat presently accounts for about 25% of Ireland's energy supply and for about 2% of the total energy supply of the Soviet Union. The United States, with the second largest peat resources in the world, has not used peat commercially as a source of energy in the past, due to the low cost of other available fuels. Recent increases in energy costs make peat 0 1979 American Chemical Society
