SPECIFICATION

Field of the Invention

This invention relates to electric power plants; and particularly to combined cycle power plants.

Backcrround of the Invention

It now seems obvious that dependence on imported crude oils or residual or distilled fuel oils for electric power generation in the remaining free nations of the world is no longer reasonable, since most of the world's remaining economically recoverable crude oil reserves are in a small area of the Persian Gulf and in the Soviet Union. The Soviet Union and a few small nations can essentially control both availability and price of crude oil and petroleum products, world-wide, beyond some point in the near future. This will be a matter of critical importance so long as the world remains heavily dependent on such fuels for primary energy supplies. Control by these nations seems destined to become more dominant as the remaining reserves of economically recoverable crude oil in other areas of the world are rapidly depleted. It is primarily this situation which makes the development of new, alternative means for electric power generation, which are not dependent on petroleum, so critically

important. Sources of economically recoverable natural gas which can be delivered by pipeline are also declining rapidly in the United States. Most of the world's known reserves of natural gas are in areas where production and delivery by pipelines to conventional markets is not economically feasible, and virtually not even possible.

The maximum use of coal for power generation is now widely advocated, because the resources are so very great. However, there are serious problems involved in greatly increasing the use of coal. If the necessary technologies for economical, long distance coal transportation; for utilization of the lower quality coals; and for adequate environmental controls are developed; the known, mineable coal reserves are sufficient to provide most of the world's energy needs for centuries. By comparison, the known reserves of natural gas which is economically recoverable and deliverable by present means may last only a few decades, and serious shortages may evolve in just a few years. The coal resources are widely distributed throughout much of the world, and many nations which have little or no crude oil or natural gas resources, have coals or lignites available, and could become relatively self-sufficient from the standpoint of their energy needs. Broadening the energy base for all nations would surely serve to stabilize the economies of nations throughout the world, and stimulate the development of many of the emerging nations.

The present state-of-the-art provides various means for utilizing coal or natural gas as alternative to fuel oils for generating electric power. Some of these are well known, or conventional, and in wide commercial use, others are in various stages of development. Conventional methods include the pulverized coal-fired steam turbine power plants, and

gas-fired steam turbine power plants, (the Rankine cycle power plants) . Others are the natural gas-fired, open cycle, gas turbine power plants (Brayton cycle plants) , and the more efficient natural gas-fired, combined cycle power plants (Brayton/Rankine cycle plants) . Many U.S. Utility companies have adopted and promoted the use of gas-fired combined cycle plants, because of their low capital cost and high efficiencies, but many are now expressing concern about becoming committed to deliverable natural gas, which surely will once again become limited in supply and high in cost in the near future. The proven, economically recoverable natural gas reserves were recently estimated at seventeen years supply for the United States, at current rates of use. The prospects for significant new discoveries are not good, and the rate of use is growing.

There are some emerging technologies which may prove useful and beneficial to the utility industry. Two types of coal-fired, fluid-bed combustion boilers are under development, and may be useful, at least in relatively small Rankine cycle power plants. They are quite expensive to build, operate and maintain, and produce large amounts of solid waste which must be disposed of, about comparable in this respect to conventional coal-fired plants with limestone scrubbers. They are capable of substantially reducing sulphur oxides and nitrogen oxides emissions, and can use relatively high sulphur coals.

In recent years, the integrated gasification combined cycle (IGCC) power plants have been developed to burn low-Btu gases produced by coal gasification. These plants are very expensive, but have the advantage that they can burn high-sulphur coals and also meet rather strict air pollution standards for sulphur oxides, nitrogen oxides and particulate emissions. The

IGCC power plants require first gasifying the coal, then thoroughly cleaning the gas, then burning it in gas-fired combined cycle power plants (Brayton/Rankine cycle plants) . In both of the above cases for the gas- fired combined cycle (Brayton cycle/Rankine cycle) power plants, some additional fuel may be burned in the heat recovery steam generators of the Rankine cycle portion of the plant. This is called "supplementary firing", and can provide some additional capacity, but with reduced efficiency. It is generally not recommended, because with the high cost of the fuels required for such plants, the drop in efficiency makes it uneconomical.

Fully-fired combined cycle plants have been designed and are now in use in West Germany, and perhaps in other areas. (See Gas and Coal-Fired Combined Cycle Plants, a booklet for presentation at the American Power Conference, Chicago, Illinois, April 14-16, 1986, Utility Power Corporation) . These plants burn natural gas in the gas turbine generators and use the gas turbine exhaust gases for combustion air for burning coal in conventional pulverized coal-fired steam generators for Rankine cycle power plants. Similar plants designed to burn natural gas and oil have been proposed in the United States, and a conceptual design was done for Electric Power Research Institute by Westinghouse Electric Company a few years ago. However, these types of plants do not solve the problems of oil and gas availability and the future escalating costs expected for these fuels. Consequently, they would be high risk investments which might result in very high costs for producing power in the relatively near future. It has been proposed that they could be converted to IGCC plants by adding coal gasification plants, when the cost of natural gas and/or oil becomes too high for their practical use as

power plant fuels. These would be a very costly conversions, and dependent on conventional coal delivery and handling methods.

Other technologies have been proposed as improved means for utilizing coal to produce electric power, but appear to have only little potential for commercial use. These include the stabilized coal-oil slurry fuels and coal-water slurry fuels, simulating the fluid characteristics of the stable Methacoal fuels, and proposed to replace heavy or residual fuel oils for oil-fired power plants. It is very questionable whether either of these have any real-world potential for commercial development. Residual fuel oil prices in the range of forty dollars or more per barrel are considered necessary by most proponents to justify their commercial development. Both of these slurry fuels have reportedly increased the ash-fusion problems in the boilers, which may be very difficult to overcome, and which imposes costly and wasteful limits on the quality of coal which can be used. Both may compound the problem of the formation of carcinogenic, ultra-fine, one-tenth micron, particulate emissions of vaporized and re-condensed heavy-metal compounds, already plaguing both coal-fired and residual oil-fired power plants. Ultra-clean and ultra-fine coal is considered a prerequisite for firing of coal-water slurries, and this prices these fuels at levels too high to provide significant profit potentials or incentive for their development.

New developments in these fields which may lead to commercial utilization, include the improved coal-oil slurry fuels, (see U.S. Patent No. 4,089,657, May 16, 1978, Stabilized Suspension of Carbon in Hydrocarbon Fuel and Method of Preparation) . This process uses methanol to improve both rheological characteristics and combustion characteristics of the coal-oil slurry

fuels. New developments in coal-water slurry fuels, also using methanol for improving the rheological and combustion characteristics of the slurry fuels, are pending, (see U.S. Patent Application Serial No. 185391, Feb. 22, 1988, Stabilized Suspensions of Carbonaceous Fuel Particles in Water) , now allowed for issuance.

Magnetohydrodynamics has been under development for several decades with little chance for success. Coal-chemical batteries for direct conversion of coal to electric power have been proposed also, but seem to have limited if any potential.

Conventional coal-fired steam power plants have almost reached the practical limits of expansion, in the United States because of the limitations of siting with respect to coal supply, length of power lines required for the transmission of power from mine-mouth plants, transportation difficulties in delivering coal to plants located near the load centers, problems in meeting clean air requirements for exhaust gases, and limits on coal quality which are required for operating the standard types (state-of-the-art) boiler plants now available. The necessary coal quality limits, imposed by design limitations of the power plants, render most of the U.S. coal resources unusable, with today's boiler and combustion designs and exhaust cleaning capabilities. Users must set rigid standards to insure reliable operations, and valuable coal resources must be left unused and are often degraded or wasted by selective mining requirements to meet the imposed standards, or to gain bonuses for high quality. This presents very serious, but generally unrecognized, conservation problems, which are greatly in need of technical and scientific solutions. The present invention contributes greatly to those solutions.

New, patented technologies for providing superior- quality boiler fuels from coal, or from coal and remote natural gas, for use in converted oil-fired type boilers could allow circumventing many of the problems associated with other coal slurry fuels, but Industry has been slow to adopt their use. These are the unique coal-methanol slurry fuels and the coal-methanol-water slurry fuels hereinafter referred to as Methacoal or Methacoal fuels. These fuels actually burn better and provide better performance than residual oils or heavy fuel oils in boilers designed for oil firing. Methacoal fuels (slurries or suspensoids) were developed by one of the present inventors and patent applications were filed before the more recently popularized development of stabilized coal-oil slurry fuels and ^" coal-water slurry fuels. The development of these later slurry fuels evolved from the development of the Methacoal fuels (coal-alcohol slurry fuels and coal-alcohol-water slurry fuels) , from the new rheological and combustion technologies originated and revealed by the developing company, and from the patents cited hereinafter. The potentials for Methacoal boiler fuels development, as replacements for residual and heavy fuel oils is very great. More than one hundred thousand megawatts of power plant capacity in the United States alone could be converted at savings of tens of billions of dollars to the Utility Industry.

However, even more advantageous means for utilizing coal or lignite and natural gas resources together, or coal or lignite resources alone, delivered as anhydrous or low moisture content Methacoal fuels, are urgently needed. The proposed means should be capable of accelerating the development and utilization of these resources, of reducing the exhaust gas pollution levels, of reducing fuel consumption (or heat rates) , and of making the remote natural gas resources

and the low-quality, high moisture content coal resources, (which are usually also low-sulphur coals or lignites) , profitably useful as high-quality power plant fuels. This necessitates the use of the unique, Methacoal-derived liquid and particulate fuels, delivered as Methacoal slurry fuels, then separated at the power plant; and the development of a new type of high efficiency power plant to make optimum use of the unique fuels provided. This makes both the remote natural gas (natural gas which cannot be economically delivered to conventional markets) and distant or remote coals or lignites easily and economically transportable for great distances to the power plant facilities located near the load centers. The present invention provides these means. "^

The use of natural gas as boiler fuel for gas- fired steam generation plants has been greatly expanded in the United States during the past several years, even though there are estimates indicating only seventeen years of remaining proven reserves and not very good possibilities of finding significant new reserves which are economically recoverable and transportable by pipeline. Also, gas turbine peaking units and cogeneration plants based on natural gas firing have become popular and widely developed, because they are low-cost and economically attractive for the very short, near-term future, while natural gas prices are depressed by low oil prices and temporary surpluses of production capacity.

The United States should be seeking means for effecting conservation of the precious, and non- replenishable, natural gas resources, and for limiting their use to only the most efficient means available. There are now about ten fewer years of natural gas reserves remaining than there was at the time the United States Congress first passed legislation to

curtail the wasteful inefficient use of natural gas as fuel for power plant boilers. The very wasteful use of any pipeline deliverable natural gas as boiler fuels should probably again be curtailed, and will have to be at some point in time. The temporary excess of production and delivery capability has apparently misled many into believing that the natural gas resources are virtually undiminishable.

The use of remote and otherwise valueless natural gas for the production of fuel grade methanol, which could then be transported economically to user locations and burned as fuel for combined cycle power plants, gas turbine generators or even as boiler fuel for Rankine cycle power plants, has been proposed many times in the past, and is now again being proposed by some. The economics, however, were never sufficiently attractive for this to be done commercially, even though it would accomplish significant environmental improvements, even compared to burning natural gas.

However, the use of such methanol to process and transport coals or lignites, thereby reducing the costs of transportation for energy derived from the natural gas and also from the solid fuels, and also improving the quality of the coal-derived fuels, provides efficient resource utilization and reasonably low fuel costs. The production, transportation and use of Methacoal fuels can make the use of the remote natural gas resources technically, economically and environmentally feasible for providing fuels to replace residual and heavy fuel oils even at the present "cheap" oil prices.

Even though the potentials for Methacoal fuels development for replacing fuel oils is great indeed,, commercial development has been delayed by the large investments required for facilities, and by complacency, fear of change, and fear of the power of

either OPEC or Saudi Arabia to lower world oil prices to levels at which no alternative fuels could compete. As an example, when crude oil prices were dropped to under ten dollars per barrel, recently, Methacoal fuels were not sufficiently competitive to encourage would-be investors to fund their development. This is no longer the case.

Conversion of remote natural gas to liquid natural gas (I_NG) for transport and then for use as fuel for power generation is too costly, wasteful and dangerous to be practically or economically viable. Obviously, improved new means for more efficient and profitable use of remote natural gas, which is so abundantly and widely distributed throughout much of the world, are also urgently needed. This can have a really beneficial, stabilizing effect on world economics and encourage free trade in ways not susceptible to monopolization.

The present invention, as will be shown, provides practical solutions to many of the existing problems of coal and remote natural gas utilization. It can also provide expanded use of the relatively low sulphur content coals and lignites to gain substantial environmental improvements, while the development of coal cleaning technologies materialize and become technically and economically feasible. It can also provide substantial reductions in carbon dioxide emissions per unit of power generated compared to most other means of fuel-fired power generation. When the high sulphur content coals can be cleaned sufficiently and economically, to allow their economical use, it may be preferable in many cases to use the cleaned coals as Methacoal fuels in the improved power generation facilities provided by the present invention, instead of relying on current state-of-the-art power generation technologies.

It is desirable that the invention provide the following features:

1. The invention should provide a new type of coal-based, combined cycle power plant which can be provided by the retrofitting of existing steam-turbine power plants or gas-turbine power plants, or by constructing new, low-capital-cost, fuel-integrated combined cycle power plants, which do not require coal gasifiers, fuel gas cleaning systems, or air reduction oxygen plants for preparation of gaseous fuels, as do the integrated gasification combined cycle power plants.

2. The invention should provide cost effective and energy efficient means for utilizing the unique characteristics and potentials of the cdal-methanol slurry fuels, called Methacoal fuels, (see U.S. Patent No. 4,045,092, August 30, 1977, Fuel Composition and Method of Manufacture) ; to facilitate the low-cost production and transportation of fluid fuels derived from coals or lignites alone, or derived from coals or lignites and remote or other low-cost natural gas; and should also provide means for utilizing the unique liquid fuels and particulate solid fuels which can be separated from Methacoal fuels, (see U.S. Patent No. 4,192,651, March 11, 1980, Method of Producing Pulverulent Carbonaceous Fuels) .

3. The invention should provide a new type of fuel-integrated, coal-based, combined cycle power plant with heat rates, in the same range of, or less than, those of the natural gas-fired or oil-fired, combined cycle power plants with heat recovery power generation systems, and less than those of the proposed fully- fired natural gas and coal-fired combined cycle power plants.

4. The invention should provide a new type of coal-based combined cycle power plant which can make

possible the efficient and economical use of many low- rank, low-sulphur, high-moisture-content coals and lignites, which either cannot be burned, or can only be burned with great difficulty and low e ficiencies, in the state-of-the-art, conventional power plants because of the low ash fusion temperatures, the ash buildup characteristics, the very high ash content, or the very high moisture content of such fuels.

5. The invention should provide effective and profitable means for developing and utilizing remote natural gas (which has little if any value for other uses) , and oil-associated natural gas resources; which may otherwise be wasted by flaring or left undeveloped because of the very high costs of long-distance pipeline transportation of natural gas or the high costs and safety problems associated with liquid natural gas production, transportation and storage.

6.. The invention should provide a new type of power plant which can achieve significant reductions in sulphur oxides emissions by economically using low or medium sulphur content coals or lignites from distant sources, and by also effecting approximately fifty percent additional reduction in sulphur oxides emissions compared to burning the same low-sulphur coals or lignites in conventional power plants without chemical scrubbers, while simultaneously achieving significant reductions in carbon dioxide emissions compared to other fossil fuel-fired power plants.

7. The invention should provide a new type of power plant for which sites can be selected as optimum with respect to the power load center and the existing power distribution system and the fuel can be delivered to the plant site from distant coal and lignite resources and remote natural gas resources and no rail, ship or barge transportation of bulk coal or stockpiling of bulk coal is required.

8. The invention should provide a new type of coal-based power plant which can operate with very low nitrogen oxides levels in the exhaust gases, but without prohibitively expensive chemical scrubbers for nitrogen oxides removal, while incorporating the new technologies for nitrogen oxides reduction, (see U.S. Patent No. 4,742,784, May, 10, 1988, Methods for Reducing Nitrogen Oxides Emissions from Power Plants Fired by Various Fuels) , in addition to the other pollutant reductions described herein.

9. The invention should provide for combustion of the Methacoal-derived pulverized solid fuels with minimum production of the ultrafine, minus one-tenth micron particle-size, (and probably carcinogenic) , condensates of heavy metals and heavy metal compounds which are typically found in great quantity in the exhaust gases from most coal-fired and residual oil- fired power plants. See article by EPRI/DOE researchers, "Size Distribution of Fine Particles from Coal Combustion", Science (AAAS) , 1 January 1982, Volume 215, Number 4582.

10. The invention should make possible the use of low-cost, low-pressure, suspensoid pipelines, (Methacoal pipelines) ; of all sizes, (using low-cost centrifugal pumps) , and tanker ships and barges to replace railroad transportation of coal and long¬ distance, high-voltage power transmission lines.

11. The invention should provide coal-based power plants of any size at lower capital cost than alternative power generation means, provide for low- cost retrofitting of existing power plants, and provide more economical means for generating and delivering electric power to the consumers, thus benefitting the economies of the geographic areas and the nations where the technologies are utilized.

Summary of the Invention

It is an object of this invention to provide one or more of the features delineated as desirable hereinbefore and not heretofore provided by the prior art.

It is a specific object of this invention to provide substantially all of the features delineated hereinbefore as desirable and not heretofore provided by the prior art, and specifically those features listed in the preceding section and numbered 1 through 11.

These and further objectives will be apparent from the descriptive matter hereinafter; particularly when taken in consideration with the appended drawings.

In accordance with this invention there is provided a means of utilizing anhydrous or low moisture content Methacoal (coal-methanol slurry) fuels, employing the use of remote, low-value natural gas resources and/or distant, low-sulphur coal or lignite resources to provide fuels for electric power generation at the point of need with respect to the power load center and the power distribution system, and also provided a new type of power plant called the Methacoal Integrated Combined Cycle (MICC) Power Plant, specifically designed to utilize Methacoal-derived fuels and to provide low capital cost, new or retrofit, electric power generation facilities and low-cost, low- pollution, high-efficiency electric power generation.

Brief Description of the Drawings

Fig. 1 is a block-flow diagram showing unique means for utilizing remote, low-value resource materials to provide low-cost electric power at the point of need on the power distribution system. The diagram shows resources and facilities, their inter¬ relationship, means of transportation, flow of

materials, generation of electrical power in the new highly efficient MICC power plants, and delivery of electricity to the power distribution system.

Fig. 2 is a schematic representation of a preferred embodiment of an MICC power plant design.

Fig. 3 is a horizontal cross-section, or plan view, showing a preferred embodiment of a uniquely small firebox, a square design, with corner firing, and also showing the approximate relative dimensions of the new type of fireboxes compared to conventional fireboxes used for pulverized coal firing.

Fig. 4 is a vertical cross-section of the firebox of Fig. 3, taken along line "A-A" of Fig. 3, and also showing the relative dimensions of this new type of firebox and a conventional firebox for pulverized coal firing.

Fig. 5 is a horizontal cross-section, or plan view, of a retrofitted firebox of a previously conventional coal-fired or lignite-fired power plant, showing the means for reducing the volume of the firebox.

Fig. 6 is a vertical cross-section of the firebox of Fig. 5, taken along line "B-B" of Fig. 5, and showing further details of the means for firebox volume reduction for retrofitting to provide MICC power plants.

Detailed Description of the Invention

Referring to Figs. 1 and Fig 2, the present invention, in the form of the Methacoal Integrated Combined Cycle (MICC) Power Plant 1 provides low- capital-cost, fuel-integrated, fully-fired combined cycle electric power ^' plants, uniquely designed with the capability to utilize both the clean condensate liquid fuels (CLF) 2 and the highly reactive pulverulent carbonaceous fuels (PCF) 3 produced from Methacoal

fuels 4 (coal-methanol slurries, or more accurately, suspensoids) , in the proportions provided by separation of the Methacoal fuels 4. Methacoal fuels 4 are produced in a Methacoal fuels plant 5, from coal or lignite 6 and fuel methanol 7 which is produced from natural gas 8 or from coal or lignite 6. Fuel methanol transportation 9 may be by pipeline, ship or barge 10 to the Methacoal fuels plant 5. Methacoal fuels 4 transportation may be by Methacoal pipeline, ship or barge 11 to Methacoal storage at MICC power plants 12.

Methacoal fuels 4 are delivered to the thermal separation plant 13 at the MICC power plant 1 site as slurries, or suspensoids, of coal or lignite-derived particulate material and methanol, or crude methanol, or crude alcohols which are predominantly methanol, see Methacoal Fuel System 14. Methacoal fuels 4 are stored as feedstock for the thermal separation plant 13, and CLF 2 and PCF 3 are stored to provide fuels inventory for operation of the MICC power plant 1.

The clean CLF 2 is used as fuel for the gas turbine generator plant 15 portion of the MICC power plant 1. The PCF 3 is used as fuel for the boiler plant 16 of the steam turbine generator plant 17 portion of the MICC power plant 1. The hot gas turbine exhaust gases 18 become gas turbine exhaust gases as preheated combustion air 19, for burning of the highly reactive PCF 3 in the uniquely small fireboxes 20 of the specially designed boiler plant 16, of the steam turbine generator plant 17 portion of the MICC power plant 1. Fly ash collection 21 and disposal of fly ash 67 are provided for the cleaning of the boiler plant 16 exhaust gases 22 to minimize the environmental effects of operating the facilities. The information of U.S. Patent No. 4,742,784; "Methods for Reducing Nitrogen Oxides Emissions from Power Plants Fired by Various

Coals", is incorporated herein by reference for any details omitted herefrom.

The gas turbine generator plant 15 and the steam turbine generator plant 17 are sized in relation to one another so that during normal modes of operation essentially all of the CLF can be burned in the gas turbine generator plant 15, essentially all of the PCF 3 can be burned in the firebox 20 of the steam turbine generator plant 17, and all of the gas turbine exhaust gases as combustion air 19 can be used for burning the PCF 3 to provide optimum efficiency, with some supplementary ambient air 23 or preheated ambient air 24 from the combustion air heater 70, used as necessary. The MICC power plants 1 are designed so that any one or more of the power generation units can be operated independently, if desired or necessary, for limited periods of time from stored fuels.

Power generation rates of the gas turbine generator plants 15 and the steam turbine generator plant 17 are cycled up and down together at the optimum fuel use ratio for load following, to the extent this is practical. When greater turndown is required than can be accomplished at the optimum fuel use ratio, optimum use can be made of heat from the hot gas turbine exhaust gases 18, as long as both types of units are operating. This can be done by passing the excess of gas turbine exhaust gases as combustion air 19, through the lower-temperature sections of the steam boiler plant 16, bypassing the firebox 20 and the initial nucleate-boiling section 41 of the boiler plant 16, in order to recover some of the excess heat energy from the gas turbine generator plant 15.

Uniquely small fireboxes 20 must be employed in designing the MICC power plants 1, because heat from the lower-temperature combustion gases 57 of the boiler plant 16 cannot be used to preheat large amounts of

combustion air, as is done in conventional power plants. Consequently, that heat must be used in feedwater heater 54, to provide preheated feedwater, 68, recovered from steam turbine exhaust steam 71 by the exhaust steam condensers 72, and delivered to the firebox 20 of the boiler plant 16 by feedwater pumps 64. Therefore, less heat can be recovered from the watertube-lined walls 29 of the fireboxes 20 by heating boiler feedwater 25. The volume of the fireboxes 20 must be smaller than for conventional power plants in order to gain optimum advantages from the rapid combustion of the highly reactive fuels, PCF 3, and to accommodate the higher temperatures of the preheated feedwater 68.

Fig. 3 is a horizontal cross-sectional view, or plan view, looking downward into the uniquely small firebox 20, showing a preferred embodiment thereof as a square design, with corner firing of PCF 3 using gas turbine exhaust gases as combustion air 19, and using burners 26, similar to burners 27 used for burning pulverized coal with preheated combustion air in conventional fireboxes 28. A conventional firebox 28 and burners 27 are shown with dashed lines illustrating, approximately, the relative sizes and dimensions of the fireboxes 20 and 28, and showing the watertube-lined walls 29 and 30, and the bottom-ash hoppers 31 and 32 at the bottom of the fireboxes 20 and 28. The outer metal shells 33 and 34 are lined with refractories 35 and 36, for mechanical support, protection from high-temperatures, and reduction of heat losses from the fireboxes 20 and 28.

Fig. 4 is a cross-sectional view of the same fireboxes 20 and 28, taken vertically through the center of the fireboxes, on section "A-A" of Fig. 3, and showing the burners, 26, on two different levels, 37 and 38, in firebox 20, and showing the burners 27,

at two different levels 39 and 40, in firebox, 28. Additional burners may also be placed on other levels or in different locations in some designs. Nucleate- boiling section 41 tubing must be placed to first receive the firebox exit gases 42, from the new,type of fireboxes 20, before these high-temperature firebox exit gases 42 reach the superheater 43 tubing of the boiler plant 16. This is required in order to reduce the temperatures of the firebox exit gases 42 to acceptable levels before they come in contact with the superheater 43 tubing. Superheater 43 tubing cannot tolerate firebox exit gas 42 temperatures as high as can the watertube-lined walls 29 of the firebox 20, or the nucleate-boiling section 41 tubing.

Fig. 5 is a horizontal cross-sectioial view looking downward into the firebox 44 of a retrofitted conventional pulverized coal-fired power plant, with burners.45, watertube lining 46, outer shell 47, refractory lining 48, and bottom-ash hoppers 49, all shown in dashed lines, and the water-cooled or air- cooled refractory-covered plug 73 used for reducing the effective volume of the firebox 44. This reduction in volume is required when retrofitting previously coal- fired or lignite-fired power plant boilers to provide the steam generation portion of Methacoal Integrated Combine Cycle Power Plants 1, and to minimize nitrogen oxide levels in the boiler plant exhaust gases 22.

Fig. 6 is a cross sectional view of the firebox 44, shown in Fig. 5, taken vertically, on section "B-B" of Fig. 5, at the center of the firebox 44 and showing the burners 45, on two different levels 50 and 51, in the firebox 44, and showing the refractory-covered plug 73, added in retrofitting. The now smaller bottom-ash hoppers 49 are sufficient for the bottom-ash which will accumulate under the new combustion conditions and the higher upward combustion gas velocities provided. The

watertube-lining 46 heat exchange surface areas may be reduced, when retrofitting, if desired or necessary, by covering over some of the tubing at the bottom of the firebox 44 with filler refractories 52.

Additional nucleate-boiling section 41 tubing, not shown, must be placed in the firebox exit gas 53 stream from the retrofitted fireboxes 44, before the superheater 43 tubing of the retrofitted boiler plant, not shown. This is required in order to reduce the temperatures of the firebox exit gases 53 to acceptable levels before they come in contact with the superheater 43 tubing. Superheater 43 tubing cannot tolerate combustion gas temperatures as high as can the watertube-lined firebox walls 46 or the nucleate- boiling section 41. tubing. Various tubing arrangements may be used to satisfy this requirement.

Referring again to Fig. 1 and Fig. 2, sufficient heat is removed from the hot gas turbine exhaust gases 18, prior to using those gas turbine exhaust gases as combustion air 19 for burning of the PCF 3, to reduce the temperatures of the products of combustion sufficiently to thereby minimize or eliminate ash fusion and slagging problems in the fireboxes 20 of the steam boiler plant 16. This provides fuel flexibility for the MICC power plants 1, and allows the use of coals or lignites 6, for Methacoal fuels 4 production, which either cannot be burned, or can only be burned with difficulty, in conventional coal-fired or lignite- fired power plants. This is very important from the standpoint of conservation. When excess heat is removed from hot gas turbine exhaust gases 18, in exhaust gas heat recovery heat exchangers 59, it may be used for preheating of boiler feedwater 25, preferably in series with and after the steam turbine generator plant 17 feedwater heaters 54. Such heat can also be used for providing reheated steam 55, allowing this

heat to be used primarily for heating high-pressure turbine exhaust steam 69 to provide reheated steam 55, either in series or in parallel with the steam reheat section 56 of the boiler plant 16. This provides good plant operating flexibility and control. The combination of these two uses, and varying of the amounts of each, may be employed to optimize specific MICC power plant 1 designs.

Feedwater heaters 54 are provided for the initial heating of boiler feedwater 25, utilizing heat from the lower-temperature combustion gases 57, which is the lower temperature exhaust heat typically used to preheat most or all of the combustion air for conventional coal-fired or lignite-fired plants. The initial boiler feedwater 25 heating may be done at an intermediate pressure, much lower than the boiler feedwater 68 pressure, to reduce the pressure requirements of the initial heat exchangers, and consequently their cost. This will also allow the use of more expensive corrosion-resistant materials for construction of the feedwater heaters 54, since much less material will be required for the lower pressures. A minimal amount of ambient air 23 may also be heated to provide preheated ambient air 24 for the burners 26 to accelerate the initial combustion for PCF 3.

Some boiler plant exhaust gases 22 from the steam turbine generator plant 17, taken after the fly ash collectors 21, may be recirculated to the firebox 20, or to parts of the boiler plant 16 after the firebox 20 for reducing temperatures of the products of combustion for minimizing nitrogen oxides formation, for controlling ash fusion or slagging problems, or for facilitating control of the temperature profile throughout the steam turbine generator plant 17. The feedwater heater 54, and nucleate boiling 41, superheating 43 and steam reheat 56 sections of the

boiler plant 16 are all designed for near-optimum performance with the smaller fireboxes 20 required, with the unique combustion characteristics and unusual heat release properties provided by the highly reactive PCF 3, and with the lower oxygen content of the gas turbine exhaust gases as combustion air 19, and the consequently higher combustion gas volumes and velocities through the steam boiler plant or steam generator 16.

Fuels and energy may be conserved as a result of the very high efficiencies which can be achieved by these MICC power plants 1. Heat rates, (Btu per kilowatt hour) , are expected to be equal to or lower than those of conventional natural gas-fired combined cycle power plants with exhaust gas heat ^" "recovery steam generators and steam power generation systems. This will surely be the case for the MICC power plants which are designed to operate at the higher steam temperatures and pressures, or in the supercritical range, or with multiple reheat cycles. Draft control fans or blowers, if used between the gas turbine 58 exhaust gas heat recovery heat exchangers 59 and the burners 26 for the PCF 3, will reduce gas turbine exhaust gas 18 pressures and facilitate gaining highest gas turbine 58 efficiencies. They will also provide good control of firebox and boiler housing 74 pressures, operating in controlled relationship with the exhaust gas fans or blowers 75 after the fly ash collectors 21, and before the boiler plant exhaust stack 60. The condensate liquid fuels 2, which are primarily fuel methanol 7, will provide about ten percent higher gas turbine efficiencies than would natural gas firing, and even higher relative efficiencies compared to burning fuel oils in gas turbines. This contributes greatly to the high overall MICC power plant 1 efficiencies achievable.

The increased availability of convection heat from the lower-temperature combustion gases 57, for feedwater heater 54, is compatible with the reduced need for firebox 20 volume for the very reactive PCF 3 burned, since the firebox 20 watertube-lined walls 29 are generally used primarily for bringing boiler feedwater 25 up to boiling temperatures or near to boiling temperatures. More combined radiant/convection tubing can be used in these boiler plants 16 than is generally used in conventional coal-fired or lignite- fired plants. This should reduce the cost of the boiler plants and provide better control of load- following operation of the boiler plant 16 and steam turbine generator plants 17. The smaller firebox 20 volume and shorter retention time of the products of combustion, at the maximum temperatures, will reduce nitrogen oxides formation in the fireboxes 20 and the steam boiler plants 16, and also reduce the production of ultra-fine particulates of vaporized and recondensed heavy-metal laden materials, (probably carcinogenic) , which are typical of most conventional coal, lignite and residual fuel oil-fired power plants, (see Science, Vol. 215, 1 January 1982).

The sulphur oxides emissions per unit of power produced will be reduced by about fifty to sixty percent, compared to burning the same coal or lignite used in producing the Methacoal fuels 4, in conventional coal-fired or lignite-fired power plants without chemical scrubbers and at the same power capacity. The nitrogen oxides emissions per unit of power generated are expected to be reduced by fifty to eighty percent compared to conventional coal-fired or lignite-fired or residual fuel oil-fired power plants without nitrogen oxides removal from the exhaust gases. The emissions of ultra-fine, one-tenth micron particle size range, heavy-metal laden, particulate materials

per unit of power generated is expected to be reduced to insignificance.

An intermediate-pressure steam turbine exhaust 61 extraction system (not shown) may be used to provide low-pressure, saturated or slightly superheated process steam 62 to supply the heat energy for effecting separation of the Methacoal fuels 4 in the thermal separation plant 13 to produce CLF 2 and PCF 3 and returning condensate 63 to the feedwater pump 64. This allows high-efficiency reuse of the process steam 62, as in cogeneration of electric power and process steam. Energy may also be conserved by taking the vaporized CLF 2 from the thermal separation plant 13 directly to the gas turbine generator plant 15, and burning it as high pressure vapor in the gas turbines 58. To supplement this system, stored liquid CLF 2 may also be pressurized, vaporized and superheated, then burned in these same gas turbines 58 as needed, thus it is not necessary to store CLF 2 as vapor, which would be costly and perhaps also dangerous. Vaporizing and superheating the CLF 2 (methanol) before burning it in the gas turbine 58 adds about 2 percentage points to the gas turbine efficiency.

Improved coal-water slurry fuels, stabilized and activated by fuel methanol, may be produced from the Methacoal fuels 4 by evaporating off most of the methanol 7 therein and replacing it with water. This is easily accomplished by admitting low-pressure steam to the Methacoal fuels 4 to provide the heat for vaporization and also the water for slurrying. The saturated steam can be generated very economically from untreated water by use of process steam 62 in saturated steam generating heat exchangers. The activated coal- water slurry fuels can then be burned in fireboxes 20 instead of burning PCF 3. This allows handling, storing and burning a fluid, or slurry, type

fuel instead of the dry, powdered PCF 3. The slurry fuel combustion characteristics may be better suited to some boiler plants, especially for the previously oil- fired retrofitted plants, than are those of PCF 3.

Technologies will soon be available for economically removing both organic and inorganic sulphur from coals, and may be incorporated as an integral part of the process for separating the Methacoal fuels 4 to produce CLF 2 and low-sulfur PCF 3. The method requires Methacoal fuels 4 as feedstock for removal of organic sulphur from the coal or lignite, and heat energy requirements can be provided economically from process steam 62 from steam turbine generator plant 17.

The capital cost for new MICC power-plants 1 is expected to be in the range of fifty to sixty percent of the cost for new, conventional coal or lignite-fired power plants with chemical scrubbers. The capital costs for retrofitting of existing power plants such as oil-fired, coal-fired or lignite-fired plants, will be very minimal, probably about fifteen to twenty-five percent of the cost of new, conventional coal-fired or lignite-fired power plants with the same capacity as the retrofitted facility. The uncontaminated components of abandoned nuclear power plants, and much of the basic facilities, could be effectively used for providing retrofitted MICC power plants 1 in order to reduce the capital expenditures required.

The present invention also provides the means for effecting profitable, efficient, and beneficial development and utilization of resource materials which are otherwise of very limited value or of no value whatever. These resources are the low-sulphur coal and lignite resources which are located too far from the point of need to be economically useable by conventional means, and the remote natural gas and oil-

associated natural gas resources from which natural gas cannot economically be delivered and marketed by pipeline systems. These two categories of resources represent a major percentage of the world's proven, probable and possible fossil energy reserves.

Fuel methanol 7 plants may be used at the natural gas 8 source or at the coal or lignite 6 source to convert these resources to economically transportable fuel methanol 7. The methanol 7 can be economically delivered to the coal or lignite 6 source, where it is used with comminuted coal or lignite to produce Methacoal fuels 4. The Methacoal fuels 4 are then transported to the thermal separation plant 13 located at a new or retrofitted MICC power plant- 1, where they are converted to clean condensate liquid'"fuels, CLF 2, and highly reactive pulverulent carbonaceous fuels, PCF 3. The CLF 2 is burned in the gas turbine generator plant 15 which produces electric power 65. The PCF 3 is burned in the fireboxes 20 of the steam boiler plants 16, to provide steam for a steam turbine generator 66, for the steam turbine generator plants 17, which also produce electric power 65. The gas turbine exhaust gases as combustion air 19, are used during normal operating conditions and load range requirements, as the principal source of combustion air for the burners 26 of the fireboxes 20 for the steam boiler plant 16, supplemented as needed by ambient air 23 or preheated ambient air 24. Excess heat is removed from the hot gas turbine exhaust gases 18, prior to their use as combustion air 19, to reduce ash fusion, slagging and ash buildup problems in the firebox 20 and other parts of the boiler plant 16. The excess heat from hot gas turbine exhaust gases 18 is used in exhaust gas heat recovery heat exchangers 59 for providing reheated steam 55, and could also be used for preheating boiler feedwater 25. The gas turbine

generator plants 15 and the steam turbine generator plants 17 are sized with respect to one another so that they can provide the total electric power 65 capacity required, and can also, during ordinary operating conditions and load range requirements, consume the CLF 2 and PCF 3 in essentially the same proportions as they are produced from the Methacoal fuels 4.

On the basis of projected low fuel and operating costs plus estimated capital burden, nuclear power plants once seemed like a good investment. Environmental concerns; avarice of contractors, utilities and bureaucrats; cost over-runs; unreliable safety systems; human shortcomings of operators etc. ; have reversed the situation, bankrupting utilities and multiplying consumer power rates. More ^" recently the costs and difficulties of disposing of nuclear wastes have been revealed and publicized. The facts are appalling. The price of electricity may well triple. It is possible that most of the remaining nuclear power plants in the United States may be shut down and scrapped. If the contaminated reactors and steam generators are removed most of the remaining equipment in these plants is usable as components for building retrofitted Methacoal Integrated Combined Cycle Power Plants 1, thereby converting liabilities into assets.

Although this invention has been described with a certain degree of particularity, it is understood that the present disclosure is made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention, reference being had for the latter purpose to the appended claims.