WO2009046522A1

WO2009046522A1 - Method of retrofitting a coal based power plant with steam gasification

Info

Publication number: WO2009046522A1
Application number: PCT/CA2008/001782
Authority: WO
Inventors: Adalbert W. Goraczko
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-10-10
Filing date: 2008-10-06
Publication date: 2009-04-16
Anticipated expiration: 2010-04-10

Abstract

A traditional small to medium sized coal power plant can expect to generate 10-15% less electricity when implementing modern emissions/greenhouse gas controls Disclosed is a method of retrofitting an existing coal power plant with steam based gasification where the gasifier (320) operates in a substantial absence of gases such as air or oxygen and uses steam to activate the coal to produce a synthesis gas The incorporation of the coal gasifier (320) into an existing power plant increases the power output of the existing power plant, while reducing harmful emissions and greenhouse gases.

Description

METHOD OF RETROFITTING A COAL BASED POWER PLANT WITH STEAM GASIFICATION

BACKGROUND OF THE INVENTION

TECHNICAL FIELD

The invention relates to a method of retrofitting of an existing coal burning power plant to include a steam based coal gasifier. The method produces more electricity per tonne of coal than the existing coal burning power plant thereby also reducing greenhouse gases and harmful emissions per tonne of coal burned.

DESCRIPTION OF THE PRIOR ART

There is a growing demand for electricity, the rate at which demand for electricity is increasing in the United States is estimated at 1% per year, or an increase of 25% more electricity by 2025 than present levels. This requirement for "more electricity" is further coupled with the requirement to reduce harmful emissions and greenhouse gases .

Existing small (50 MW) and medium (250-300 MW) sized power plants "cannot" afford to invest the capital to install various types of scrubbers (end of the pipe solutions) to address harmful emissions, because they tend not to be very profitable. The small/medium sized power plants which are typically investor or state owned, usually cannot afford to invest the capital to implement the newest CO₂ sequestration solutions. These new solutions are just now coming to market and they carry with them a hefty price tag, as well as a parasitic effect on the amount of electricity being produced. Power plants implementing these environmental solutions can expect to generate 10-15% less electricity with these types of harmful emissions/greenhouse gas controls.

Further, due to the high and variable cost for energy sources such as natural gas and oil, there is a continued need to generate electrical energy using coal based fuels, and to do this in an economically and environmentally responsible manner. Furthermore, due to the variation of electrical demand during the day and the necessity to meet peak power requirements, utility companies operate in a broad range of 30 to 100% load, where low load operation are less efficient both economically and environmentally. There is also a need to operate equipment at higher load% for greater efficiency.

Over 50% of all electricity produced in the US comes from coal and most estimates conclude that this percentage will not change significantly over the next 20 years. Almost all coal-fired power plants in the United States use steam turbines to produce electricity.

U.S. Patent 3,849,662 relates to a combined cycle power generating plant in which both a steam turbine and a gas turbine burn gasified coal as a fuel. The gasifier is an entrainment-type gasifier in which pulverized coal, air and steam are reacted in suspension at high temperature to form a fuel gas containing primarily carbon monoxide and hydrogen. The power plant includes a steam and gas turbine and a gas holder. The gas turbine is used at high peak requirement using stored gas . Various electricity generating methods have been developed to improve efficiency and may include a gasifier, some of these improved methods will be discussed below. U.S. Patent 4,441,028 teaches a power generating apparatus and method of operation for meeting a variable demand which includes a compressor for supplying gas to a heat engine which generates power and a reservoir positioned intermediate of the compressor and the heat engine. A portion of the power produced by a heat engine which may be operated at an average rate of the demand is utilized to compress gas which is directed to the reservoir. The compressed reservoir of gas is selectively directed to the heat engine to increase the generation of power to satisfy the increased rates of demands .

U.S. Patent 4,212,160 relates to a combined cycle electric power generating plant having a steam generator and a gas turbine. The gasifier uses pre-heated air and water to produce a fuel gas. The gas turbine drives the compressors for both the air and a low BTU gas used to generate the hot combustion gases therein, while oxygen- containing exhaust gases from the gas turbine are used to support combustion for a fuel in the steam generator.

U.S. Patent 4,852,996 is directed to a synthesis gas produced by coal gasification in an allothermically heated fluidized bed reactor. The coal is gasified allothermically by means of a steam/flue gas mixture produced in a combustion chamber. The synthesis gas leaving the reactor is freed of dust and is typically between 800 and 900⁰C. The quantity of free oxygen is limited in the gasifier. The greater quantity of oxygen brought into the process the greater the quantity of nitrogen in the synthesis gas and hence the greater the design capacities for the cyclone separator, the waste boiler, the condenser and the sulfur scrubber. This system further includes a steam turbine and an expansion turbine each linked to an electrical generator. U.S. Patent 6,966,190 is directed at a combined cycle process that includes gas turbines, a steam turbine train, a heat recovery unit and a gasification unit that produces low or mid BTU fuels from coal and other suitable hydrocarbon containing materials. The fuel gas is further burned in a heat recovery unit to increase the steam rate of the turbine train. The gasification reactor is a refractory- lined fluidized bed that operates at between 20 to 60 psig and between 1800 and 2200⁰F (982°C and 1204⁰C) both air and steam are fed into the bottom of the reactor. The gas turbine combustion exhaust gas streams are combined and conveyed to a gas inlet of the heat recovery unit. In this recovery unit the combined turbine exhaust gas stream gives up sensible heat to boil the condensate stream and reheat an extracted steam stream. Due to temperatures below 2500⁰F (1371°C) mechanical damage is reduced and NO_x air pollutants are not generated.

U.S. Patent Application 2001/0039760 is directed at a zero pollution waste disposal and clean energy generation system including a system of gasification that includes a catalyst to lower the temperature for gasification and to prolong the life of the gasification reactor. The system further includes simultaneous direct and indirect heat transfer that supplies heat required for the carbon steam reaction. These improvements increase efficiency and economy of the system and promote smooth operation. The catalysts employed are various combinations of alkaline metal salts and salts of iron and chromium.

Although many power plants have improved coal utilization, there is still a further need to optimize and retrofit existing plants for greater electrical production with a reduction of harmful and greenhouse gas emissions. SUMMARY OF THE INVENTION

It is therefore an aim of the present invention to provide a method of retrofitting an existing coal power plant with a gasifier converting coal in a steam atmosphere producing a synthesis gas having a high energy value, the synthesis gas can be converted to: electricity, in a quantity that is greater than that produced formerly in the existing coal power plant; and /or a marketable chemical product .

It is also an aim of the present invention to provide retrofitted equipment in such a manner to produce electricity in an economical manner, by using most of the steam produced in a furnace/boiler (or other steam generator) , that previously was left unused or lost in known processes and at the same time producing less harmful gas emissions and less greenhouse gas emissions per unit of electricity produced.

It is yet a further aim of the present invention to provide a fixed bed gasifier for reacting a coal product with steam in a steam atmosphere to produce a raw synthesis gas .

It is yet another aim of the present invention to provide a method of producing at least one of electricity or a marketable chemical product comprising a gasifier converting in a coal product and steam an efficient manner into a synthesis gas and such that harmful gas and greenhouse gas emissions are reduced, where the synthesis gas may then be further converted to at least one of electricity and the marketable chemical product. It is yet a further aim of the present invention to provide a coal power plant comprising a fixed bed gasifier for reacting a coal product with steam in a steam atmosphere to produce a raw synthesis gas.

In one aspect of the present invention there is provided a method of retrofitting an existing coal power plant, the power plant producing a specific amount of electricity and having at least a coal treatment unit; a furnace/boiler and a steam turbine/electric generator, the method comprising the steps of: adding a steam based gasifier downstream of the coal treatment unit and the furnace/boiler; adding a coal product splitter in a coal product flow stream between the coal treatment unit and the furnace/boiler; dividing the coal product flow stream at the coal product splitter into at least a first and a second coal product stream, wherein the first coal product stream is combusted in the furnace/boiler to produce a superheated steam flow stream and the second coal product stream is sent to the steam based gasifier; adding a steam splitter in the superheated steam flow stream between the furnace/boiler and the steam turbine/electric generator; dividing the superheated steam flow stream at the steam splitter into at least a first and a second superheated steam flow stream, wherein the steam turbine/electric generator produces a first portion of electricity from the first superheated steam flow stream and the second superheated steam flow stream is sent to the steam based gasifier; and operating the steam based gasifier in a steam atmosphere and with additional heating to produce a raw gas through a reaction of the second coal product stream and the second superheated steam flow stream. In another aspect of the present invention there is provided a fixed bed steam based gasifier for reacting a coal product and a superheated steam at a temperature range from 700⁰C to 1000⁰C into synthesis gas, the gasifier operating in a steam atmosphere and comprising: a reactor vessel comprising a base section comprising a steam inlet having adjacent to or within the steam inlet a catalyst for activating the steam to react with the coal product, and an ash outlet; an upper section comprising: a coal product inlet; and a synthesis gas outlet; and an intermediate section contiguous with and between the base section and the upper section whereby a fixed bed level for the coal product is established at a point in the intermediate section; and a heat exchanger associated with the reactor for indirectly heating the coal product.

In a further aspect of the present invention there is provided a method for producing at least one of electricity and a marketable chemical product from a coal product comprising the steps of: preparing a coal product having a uniform and homogeneous particle size distribution; dividing the coal product into at least a first and a second coal product stream; feeding the first coal product stream to a furnace/boiler,- producing a superheated steam from a water stream indirectly heated by combustion of the first coal product stream in the furnace/boiler; dividing the superheated steam into at least a first and a second superheated steam flow stream; feeding the first superheated steam stream to a steam turbine system to produce a first portion of the electricity; feeding the second superheated steam flow stream and the second coal product stream to a steam-based gasifier; operating the steam-based gasifier in a steam atmosphere and reacting the second superheated steam flow stream and the second coal product stream to produce a raw gas,- treating the raw gas to remove impurities to produce a synthesis gas; and feeding the synthesis gas to at least one of a gas turbine system to produce a second portion of electricity, wherein the second portion of electricity is greater than a total existing amount of electricity, wherein the total existing amount of electricity is an amount of electricity produced if all the coal product flow stream of the coal treatment unit had been combusted in the furnace/boiler and converted to electricity in the steam turbine/electric generator, and a hydrocarbon conversion system converting the synthesis gas to marketable chemical product .

In yet another aspect of the invention there is provided a coal power plant comprising: a coal treatment system for producing a coal product, the coal product transferred into at least two streams comprising a first and a second coal product stream; a furnace/boiler downstream of the coal treatment system for combusting the first coal product stream and indirectly heating water to produce a superheated steam; a steam splitter downstream of the furnace/boiler for dividing the superheated steam into at least a first and a second superheated stream; a steam turbine/electric generator downstream of the steam splitter producing first portion of electricity from the first superheated steam stream; a fixed bed steam based gasifier for conversion of the second coal product stream and the second superheated steam stream in a temperature range from 700⁰C to 1000⁰C into a raw gas, the gasifier operating in a steam atmosphere and comprising a reactor vessel comprising a base section comprising a steam inlet having adjacent to or within the steam inlet, a catalyst for activating the steam to react with the coal product, and an ash outlet; an upper section comprising: an coal product inlet; and an synthesis gas outlet; and an intermediate section contiguous with and between the base section and the upper section whereby a fixed bed level for the coal product is established at a point in the intermediate section; and a heat exchanger associated with the reactor for indirectly heating the coal product whereby the second superheated steam stream produces a steam atmosphere within the gasifier and reacts with the second coal stream to produce the raw gas .

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

Fig. 1 is a flowsheet of a power plant of the prior art producing electric power with a steam turbine (PRIOR ART) ;

Fig. 2 is a flowsheet of a combined cycle power plant of the prior art which includes a steam and a gas turbine (PRIOR ART) ;

Fig. 3 is a flowsheet of a power plant according to one embodiment of the present invention including a steam gasifier;

Fig. 4 is a detailed flowsheet of synthesis gas to turbine systems and electrical, and/or to the production of a marketable chemical product according to one embodiment of the present invention, and

Fig. 5 is a flowsheet of auxiliary processes for the production of various products with surplus electricity during low power demand periods . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Fig. 1 illustrates an existing coal power generating system known in the prior art that includes the following unit operations: a coal treatment system 101, a steam generator or furnace/boiler 103 producing steam for a steam turbine 109 which produces electric power via a generator 110. The system further includes: auxiliary equipment such as a condenser 111 to condense steam leaving the turbine and reduce the temperature of the steam leaving the steam turbine 109.

Coal 100 is fed to coal treatment 101 which can include crushing, drying and pelletizing to a uniform particle size of a produced coal product. The coal 100 can be any one of a variety of well known types of coal including but not limited to lignite, sub-bituminous, bituminous and anthracite coals. In fact various other biomasses may also be employed, including a coal transformation method disclosed in US Patent 6,942,707 B2 by A. Goraczko, which is hereby incorporated by reference.

The steam generator, in a preferred embodiment is a furnace/boiler 103, producing steam, which may be superheated, by indirectly heating the water in a heat exchanger 106 within the boiler, through the combustion of coal in a combustion zone or chamber 105 with air 104 although higher temperatures may be achieved by using oxygen gas. The gases generated from the coal product combustion, (i.e. combustion or flue gases) leave the steam generator, via a stack and/or gas cleaning process 113. These flue gases 114 may be treated by various processes known to the skilled practitioner including: cooling, dust and particulate removal and acid neutralization. These gas cleaning processes typically occur before entering the stack 113 but may also be performed upon leaving the stack.

The steam from the steam generator drives the steam turbine 109, to produce electricity in the generator 110. The partially condensed steam from the turbine 109 is further condensed in a condenser 111 with cooling water or other cooling means and returned to the steam generator. This type of system can effectively produce electricity, but includes limitation that the turndown ratio is limited by the turbine which is typically designed to produce power at a specific maximum output and has limited variation. At lower than maximum output the steam turbine 109 is not operating at a optimum level with respect to optimized coal product use. In this type of system, the furnace/boiler 103 produces a large amount of unused steam 115 that cannot be utilized in the turbine 109, in Fig. 1 unused steam has been illustrated as stream 115 leaving Fig. 1.

Therefore, the process illustrated in Fig. 1 includes at least three conversions of energy: A) the combustion of coal in combustion unit 105; B) the production of steam from a water feed 108 in the furnace/boiler 103 from the combustion energy produced by the coal in heat exchanger 106 and C) the use of the steam from the boiler to drive the steam turbine 109 to produce electricity in the generator 110. This amount of electricity is defined a specific amount of electricity produced by the existing power plant. Importantly, the thermal efficiency of conversion of the energy for the listed process A) ; B) , and C) above are in the range of: 90 to 95%; 75 to 80% and 30 to 40% respectively. These thermal efficiency conversion values clearly indicate that, of the steam produced in the furnace/boiler 103, less than half is in fact used to turn the turbine 109 and produce electricity 110, and is therefore lost.

It will be seen that one advantage of the present invention is its efficient and more complete use of steam produced in the furnace/boiler 103. Particularly, the formerly un-used steam 115 will also be used in the process (by incorporation into the synthesis gas) and therefore will increase the total thermal value of synthesis gas produced, and that of the process as a whole.

As will be further described, the furnace/boiler -steam turbine generating systems of the prior art may be retrofitted to integrate the features of the present invention and generate a greater capacity of MWh per tonne of input coal .

Fig. 2 illustrates a combined cycle electric power generation system which has greater flexibility in producing electricity and is described in US Patent 4 ,212,160. The introductory numbering of the unit operations of Fig. 2 include reference numeral with two numbers. The first is a three digit number analogous to that of the present application with the last two digits identifying similar process units to those found in Fig. 1 and Fig. 3 but having a numerical prefix of 2. The second number in parentheses is the reference numeral used in the US 4,212,160.

Coal 200 is fed to coal treatment 210 (N/A) and on to coal gasification 220 (10) . Gasification is conducted in air to produce a raw synthesis gas.

The gas treatment (gas desulfurization treatment) 230

(12) cleans the raw synthesis gas produced by the gasifier

220 and produces a clean synthesis gas which can be used to produce electricity. A portion of the synthesis gas 231 is delivered to the gas turbine system 244 which may include various elements comprising: a gas compressor 243 (26), an air compressor 245 (30) , combustion chamber 246 (32) , a gas turbine 247 (28) and an electrical generator 248 (36) producing electricity. The compressors 243 and 245, the turbine 247 and the electrical generator 248 may be mounted on the same shaft for greater efficiency.

Steam produced in the gasifier 220 is converted to electricity in a steam turbine 206 (22) and steam electrical generator 210 (24) combination.

The system of US Patent 4,212,160 further includes, auxiliary features of an air preheater 250 and a steam generator 249 burning a second portion of the synthesis gas 232 with off-gases from the gas turbine 247 are fed to the steam generator 249 (18) where the steam produced is used to pre-heat air in the preheater 250 (50) , and then to feed the steam turbine 209. The additional gas turbine and recycling of waste heat improves the efficiency and operability this combined cycle over the system in Fig. 1, however the efficiency increase due to this heat recovery is limited because the system of Fig. 2 does not use a boiler or heat recovery steam generator to produce steam used in gasification. The combined cycle of Fig. 2 is furthermore not amenable to retrofitting of existing plants that already comprise a boiler and steam turbine because the process of Fig.2 only partially takes advantage of the additional heat available in unused steam in the steam generator, and cannot incorporate the unused steam into the synthesis gas.

Fig. 3 and 4 represents possible embodiments of a power plant for the present invention that can be obtained by the method of retrofitting the existing coal power plant according to the method of the present invention. The central process units of the process of Fig. 3 and 4 include: i) a heat recovery steam generator, which in a preferred embodiment may be an existing furnace/boiler 303; ii) a coal gasifier 320 which produces synthesis gas from coal in a substantial absence of oxygen; iii) a steam turbine 309, which in a preferred embodiment is an existing steam turbine system,- iv) a steam splitter and v) a gas pressure equalizer 340 which is illustrated in Fig. 3 and the new gas turbines systems 364 and 384. Each of these listed process units will be discussed in turn.

i) The Heat Recovery Steam Generator, furnace/boiler 303

Fig. 3 illustrates one embodiment of the process of the present invention. As seen in Fig. 1, a furnace/boiler of a conventional power plant produces heat and superheated steam in typically a large excess from the combustion of a coal product. The superheated steam produced in the furnace/boiler 103 drives a steam turbine 109 coupled to an electrical generator 110 to produce a first portion of electricity, thus the furnace/boiler 103 can be used as the heat recovery steam generator. An important feature of the present invention is the optimized use of the heat and the steam produced by the heat recovery steam generator 303.

It should be noted that the reference numbers of Fig. 1, Fig. 2 and Fig. 3 share the same two-digit suffix for equivalent process units and streams but are distinguished from one another by their single digit prefix. Where reference numerals, IXX, 2XX and 3XX indicate same process unit or stream in Fig.l, Fig. 2 and Fig. 3 respectively. Coal 300 and in a preferred embodiment dolomite 300A are combined into a homogeneous coal product with a uniform size distribution in a coal treatment unit 301. The coal product is combusted with air 304, in a combustion zone 305 within the boiler 303, to convert an incoming water stream 308 to a superheated steam stream. Furthermore, exhaust gases 390 from the gas turbine systems 364 and 384 may also be used in the boiler 303, possibly to heat the incoming coal product or preheat incoming air 304. Ash 307 is expelled from the bottom of the boiler 303.

Steam and heat from the downstream furnace/boiler 303 is contacted with coal product produced in coal treatment 301 where the steam and heat activate coal product to produce raw (synthesis) gas in a steam gasifier 320. However, steam from the boiler is divided at splitter 316 downstream of the furnace/boiler 303 to actuate the existing steam turbine system (309,310) and obtain some or all of the power available from steam turbine 309 if required. The steam leaving the steam turbine 309 is condensed in a condenser 311 and combined with the incoming water steam 308.

ii) The Coal Gasifier, 320

The steam coal gasifier 320 of the present invention is a specialized reactor which operates at high pressure and at a relatively mild temperature range (700-1000⁰C) . This unit operation and the reaction that it uses, i.e. the conversion of coal and steam, in absence of air to produce a raw

(synthesis) gas, is key to the invention. The excess steam formerly left unused in the prior art is utilized more fully to increase the amount of electricity produced by the power plant of the present invention. The terms "raw gas" and

"raw synthesis gas" are synonym and are used to described the raw synthesis gas typically at the outlet of the gasifier that includes impurities that are preferably removed before use. While the term "synthesis gas" is used to described a cleaned or treated synthesis gas after treatment where impurities have been removed for the most part.

In a preferred embodiment, the gasifier is a fixed bed reactor, that can with operated with a superheated steam atmosphere, and at a temperature range of 700 to 1000⁰C. The superheated steam atmosphere is such that there is a substantial absence of other gases particularly oxygen and/or air. The gasifier in a preferred embodiment is a cylindrical reactor vessel with the axis of the center of the cylinder oriented in a substantially vertical plane. The gasifier 320 is typically a steel vessel, which includes: a upper section 320A having a coal product inlet 320B, and a raw gas outlet 324, and intermediate section 320C below the upper section 320B and wall of sufficient height such that a fixed bed level of the coal product is established at a point in the intermediate section 320C; and a base section 320D below the intermediate section 320C having a steam inlet 320E where a catalyst is within or adjacent to the steam inlet 320E, and the catalyst activates the steam. The base section 320D further includes an ash outlet 322 from where the non-combustible or non-reacted coal product is expelled from the gasifier 320. Due to the pressure that the reactor must withstand in a preferred embodiment the upper and base sections are arcuate or dish shaped .

The gasifier 320 has a heat exchanger 321 associated therewith. The heat exchanger 321 can take the form of an indirect heater using steam, combustion gases or an induction type electric heater. The use of combustion gases due to their availability in the process is a preferred embodiment illustrated in Fig. 3, this embodiment will be described further on in greater detail. The heat exchanger 321 may also used at the inlet of the coal product, and be within the gasifier. In a preferred embodiment the heat exchanger 321 takes the form of a jacketed portion incorporated into the intermediate portion of the vessel, through which the heat required for the gasification process to proceed is added. The heat exchanger may also have heating coils that are within the gasifier 320 that allow the coal and the steam to react while allowing the ash to leave the gasifier 320. The heat exchanger includes a combustion gas outlet 323 which depending on the location of the heat exchanger 321 may also leave the gasifier 320. Exhaust or flue gas stream 323 may be combined with- stream 390 from the gas turbines and returned to the heat recovery steam generator 303, to preheat the incoming water stream 308 in a water heat exchanger (not shown) or incoming air 304 in an air heat exchanger (also not shown) .

Although the fixed bed in the gasifier is in a state of flux, at equilibrium the level of coal product within the gasifier remains at a substantially fixed level or at a point within the gasifier, generally in the intermediate section of the vessel. This fixed bed level is achieved by the simultaneous replenishment of the coal product fed from the top of the reactor, which is matched to the rate at which the coal product is consumed in the bottom of the gasifier. The coal product, is typically in the form of lumps greater then 2 cm in size flow and is fed from a top inlet while superheated steam is fed into the bottom of the reactor through an series of nozzles, and flows upward and thus countercurrent to the flow of the coal product. The superheated steam is used in the reaction and percolates through the coal product bed and converts the coal product into a raw synthesis gas. Under reaction the coal product, the steam and the additional heat produce a intermediate often described as a char. This char is in fact the material produced from the coal product starting materials which is likely to make up at least part of the material establishing the level of the fixed bed within the gasifier. However when the contents of the gasifier are in a state of equilibrium there are likely the two raw materials (coal product and superheated steam) as well as char at the level of the fixed bed within the gasifier.

The superheated steam is conditioned by passage through or contact with a catalyst. The catalyst is typically a molecular sieve, such as an aluminum silicate mineral, and in a preferred embodiment is specifically a zeolite. In an preferred embodiment the catalyst molecular sieve is located in or adjacent to the inlet for steam within the gasifier. The catalyst must be able to withstand the high temperature and pressure conditions required by the process. For a gasifier having a flowrate of 28 tonnes coal product/hour some 0.2 tonnes of molecular sieve are required within the gasifier. Typically, the catalyst is replaced once a year for optimum efficiency.

The steam fed to the gasifier also serves to evacuate the oxygen and pressurize the gasifier, as well as serving as an activator in a general reaction such as:

C + H₂O ==> CO + H₂ -4H₂₉₈ = +119KJ/mole

The positive value of ΔH₂9β in the reaction above indicates that the reaction is endothermic and requires additional heat to proceed. This additional heat is added via the heat exchanger 321. The heat exchanger 321 is also adapted to control and optimize the reaction at a specific temperature. In a preferred embodiment the temperature within the gasifier is maintained between 700⁰C and 1000⁰C, where in a particularly- preferred embodiment the temperature range is between 800⁰C and 950⁰C, with 900⁰C being a particularly preferred embodiment. The reaction within the gasifier 320 occurs at a pressure in a range of 20 to 30 bars, more preferably between 25 and 28 bars, in a particularly preferred embodiment the pressure is set at 26 bars. In the case of a gasifier having a coal product input of 28 t/h (where "t/h" is 1000 kg/hour) and a superheated steam input of 26.6 t/h

(approximately 1200⁰C, 22 bar) , the gasifier will have an internal diameter of 3.8 m, and an internal height of 7.6 m

(as measured in vertical straight wall height) .

The coal product feed produced in the coal treatment unit 301 and delivered to the gasifier 320 particle distribution may vary slightly but in a preferred embodiment has a homogeneous and uniform particle size distribution, and is preferably spheroid, and more preferably spherical. The particle size of the coal product varies depending on the cross sectional area of the gasifier 320, and is typically in the range of 0.05 cm. to 5.0 cm, with a preferred range being between 2.0 and 3.0 cm., in a particularly preferred embodiment the coal product has a particle size of 2 cm.

The particle size of the coal product also relates to the residence time of the particle within the gasifier 320. The larger the cross-sectional area of the gasifier the longer the residence time and the larger the particle size distribution. For a smaller gasifier receiving 28 tonnes/hour of coal and 22.5 tonnes of steam the gasifier diameter would be in the order of 1.5 m,and would require a coal product particle of approximately 2 cm. For the reaction to proceed 226.5 MMBtu(56,950 Meal) would have to be added to the coal product. In the preferred range of coal product particle size between 2.0 and 3.0 cm. the residence time will vary from 10 seconds to 2 minutes, with a residence time between 30 and 40 seconds being preferred.

The coal product may be made up entirely of carbonaceous material or may include a reactive additive that neutralize various impurities in the coal. These additives include: dolomite (CaCO₃/MgCO₃), lime (CaO), limestone (CaCO₃) and magnesite (MgCO₃) , with limestone and/or dolomite being preferred embodiments.

The raw synthesis gas produced in the gasifier 320 includes mainly the following components: CO; H₂; CH₄; and CO₂. The expected ratios of these components are approximately: (in moles %) 40-46% / 46-58% /0.1-0.5%/l-2% respectively.

Returning to the method of retrofitting an existing coal power plant and the power plant of the present invention illustrated of Fig. 3, the method according to the present process includes a coal treatment system 301, for sizing and mixing the components of the coal product together. As previously discussed coal is typically mixed with an acid neutralizing or reactive additive such as dolomite, lime, limestone, or magnesite.

From coal treatment 301, the coal product is divided in a coal splitter 302, into at least two coal product streams 302A and 302B. The first coal product stream 302A is burned in a heat recovery/steam generator downstream of coal treatment 301. The heat recovery/steam generator is typically a furnace/boiler 303 in which the first carbon product stream is ignited in air 304 and indirectly heats water 308 to produce steam in excess. The combustion flue gas from the heat recovery/steam generator 303 are transferred to and enter a stack 313 where they may be treated to remove particulates and possible further cleaned to neutralize sulfur products before being expelled as flue gas, after which the cleaned flue gases are sent to atmosphere 314. One obvious advantage of including a dolomite, or other reactive additive in the coal product is the minimization of sulfur emissions to the atmosphere and reducing the need for liquid scrubbing of acidic gas emissions .

Furthermore, due to the absence of air, (and nitrogen gas in particular) in the gasification process, the process has the further advantage that there is no formation of NO_x compounds which are formed in synthesis gas production using air. Thus, the emission levels of NO_x produced by the present process are also very low.

The superheated steam produced in the boiler 303 is typically high pressure steam and is split into at least two streams at a stream splitter 316 downstream of the heat recovery/steam generator 303. A first superheated steam stream 315 from the splitter 316 may be used in steam turbine 309 to generate electricity.

iii) The Steam Turbine, 309

The steam turbine 309 commonly requires a large surplus of steam to ensure their electrical production rates . It is not uncommon that for 2 t of steam/ hour, steam inefficiencies (lost and unrecoverable steam) within the turbine amount to 1 t/h or more. It is this unrecoverable steam (see Fig. 1, ref number 115) that the present invention exploits by capturing and recycling the unused steam redirecting it to the coal/steam gasification system to produce a synthesis gas, and subsequently more electricity than would else be possible.

The steam turbine 309 is coupled with and electric generator 310 producing the electricity. The steam leaving the turbine 309 is condensed (liquefied) in condenser 311 and contacted directly with the incoming water stream 308 and returned to the heat recovery/steam generator 303. The steam turbine 309 and steam electric generator 310 are also understood to be part of the steam turbine system. An existing amount of electricity may be generated with the steam turbine, and this existing amount of electricity is defined at the amount of electricity produced if all the coal product flow stream of the coal treatment unit 301 has been combusted in the furnace/boiler 303 and converted to electricity in the steam turbine 309/electric generator 310.

iv) The Steam Splitter, 316

The use of second superheated steam stream 317 from the splitter 316 and is an important feature of the present process. The steam splitter 316 is located downstream from the boiler 303, and upstream of the gasifier 320 and the steam turbine 309. The steam splitter divides the total superheated stream leaving the furnace/boiler into at least a first and a second superheated steam stream 315 and 317 respectively. As was mentioned previously, the first superheated steam stream 315 is sent to the steam turbine 309. The second superheated steam stream 317, is the excess steam produced in the furnace/boiler 303 is sent towards the downstream gasifier 320 where it is consumed to produce a raw gas 324, and after cleaning and treatment, a clean synthesis gas 332. The excess steam 317, may in a preferred embodiment be sent to a downstream superheater 318, which uses combustion of a portion of the clean synthesis gas 352 from the synthesis gas splitter 350 to superheat the second superheated steam stream 317 further before entering the gasifier 320. The superheater 318 comprises a heat exchanger 319, typically within the superheater 318, that uses the combustion gases from synthesis gas combustion to further heat the steam 317. In a preferred embodiment the ratio of streams 317 to 315 is from 65-80 to 35-20 parts of the total superheated steam stream entering the steam splitter 316. In a preferred embodiment ratio of streams 317 to 315 is 75 to 25 parts of the total superheated steam stream exiting the steam splitter 316.

The superheated steam stream 317 combines with the second coal product stream 302B from splitter 302, and is eventually fed to the gasifier 320. The process of the gasifier 320 was previously discussed above, and produces a very hot raw gas, (or untreated synthesis gas) which is cooled and treated in a raw gas treatment system 330.

The raw gas treatment system 330 is located downstream from the gasifier 320 and cools the raw synthesis gas while recovering the heat which is sent back to various points of the process. The raw gas treatment system 330 further includes: the removal of dust and other particulates; tar removal; sulfur removal and mercury removal. These synthesis gas treatment systems are sub-systems well known to the skilled person. The raw synthesis gas after treatment is a clean synthesis gas 332 that is suitable for various application which shall now be described. In a preferred embodiment there is a further recovery of heat from the raw gas treatment system, which may be used to preheat incoming water stream 308 and/or incoming air stream 304 to the furnace/boiler.

v) Gas Pressure Equalizer, 340

Downstream of the raw gas treatment 330 is pressure equalizer 340 and synthesis gas splitter 350 that regulate the efficient and balanced use of the synthesis gas produced and used in the downstream gas turbine systems 364 and 384 (Fig. 4), to take advantage of the cyclical nature of electrical power needs. For instance, electric power consumption peaks in the early evening hours of the day, while minimum electric power needs occur during the early morning hours of the day. The synthesis gas produced in raw gas treatment 330, enters a pressure equalizer 340 which regulates the pressure of the synthesis gas throughout the gas turbine systems 364 and 384 downstream of the gas splitter 350. The equalizer 340 may be located at various points in the system but is typically found downstream the raw gas treatment 330 and upstream of a synthesis gas splitter 350. However, the position of the equalizer 340 and the splitter 350 may quite easily be inverted, however this would likely require individual equalizers 340 on each of the split synthesis gas streams and more complicated process control requirements .

The synthesis gas splitter 350 splits the synthesis gas into at least a first and a second synthesis gas stream 360 and 380. It should be noted that in Fig. 3, three synthesis gas streams are presented. A third synthesis gas stream 352 is recycled back upstream to the superheater 318, where the third of synthesis gas 352 is burned to heat the steam sent to the gasifier further while the exhaust gases 323 are used to heat the gasifier 320 contents. The following two synthesis gas streams 360 and 380 are represented in Fig. 4. The third synthesis gas stream need not be treated to remove impurities. A raw gas stream before treatment may be obtained and combusted directly after the gasifier 303.

Synthesis gas streams 360 and 380 are respectively a first and a second synthesis gas streams and are sent to gas storage tank (or tanks) 362, and upgrader 382 respectively. Downstream for the storage tanks 362 and the synthesis gas upgrader are respectively found two gas turbines systems 364 and 384 which in a preferred embodiment each include: the following unit operations: an air compressor 365, 385 and a combustion chamber 366, 386, gas turbine 367, 387 and an electrical generator 368, 388 respectively. It is understood that each of the gas turbines systems may be made up of multiple trains of equipment that may work in parallel. The total amount of electricity produced by both of the two gas turbines systems 364 and 384 is defined as a second portion of electricity. It will be shown that the second portion of electricity is greater that the specific amount of electricity produced in the existing plant before any retrofit.

Associated with the storage of the synthesis gas 360 there may also be auxiliary systems which include methane production 370. The methane 374 produced may be either used to produce electricity or sold. Methane is understood as one of a number of marketable chemical products that may be produced or in the alternative all the sythesis gas produced may go to the production of methane or other marketable chemical product .

A marketable chemical product is understood to be a any type of hydrocarbon or substituted hydrocarbon. In a preferred embodiment the hydrocarbon or substituted hydrocarbon is selected from the group consisting of saturated groups of 1 to 8 carbon atoms and unsaturated groups of 2 to 8 carbon atoms, each of which can be substituted with -OH, -OR, -COR, -COOR where R is an Ci_-4 alkyl, C₂-₄ alkenyl , or C₂-₄ alkynyl . Particularly preferred marketable chemical products are: methane, ethane, ethylene, propane, propylene, butane and butylene, with methane being most preferred. Alternative marketable chemical products are alcohols, esters and ethers having from 1 to 4 carbon atoms .

The method and the power plant of the present invention may be conceived to produce at least one of electricity or chemical marketable product .

Furthermore, the electric power typically generated from generator 368 associated with the synthesis gas storage is defined as a third portion of electricity. This third portion of electricity may be used to produce various auxiliary products illustrated and produced by auxiliary process 400 illustrated in Fig. 5. The auxiliary process 400 include: water demineralization 410 (or evaporation) used in electrolysis 420 of the demineralised water to hydrogen 425; air may also be separated 430 into nitrogen 433, and oxygen 435, for example a pressure swing membrane or cryogenic distillation column. The production of these various products is typically with generator 368 during low power demand periods .

The operational philosophy of the gas turbines is such that system 384 will operate almost constantly at or near its optimum capacity. The electricity produced in generator 388 is understood to be a fourth portion of electricity. During low power demand, synthesis gas will be stored in tanks 362 which have roughly a 12 hour capacity. During peak requirements gas turbine system 364 will be activated to meet the demand. The electricity produced in generator 368 is understood to be the third portion of electricity. During low electrical requirements generator 368 may also produce the auxiliary products of hydrogen; nitrogen and oxygen, which may serve at start-up and/shutdown of the power plant, heat recovery steam generator and gasifier. Therefore the second portion of electricity is the sum (or combined total) of the third and the fourth portion of electricity.

A synthesis gas stream 360 from splitter 350 is used primarily as an energy storage buffer, so that the capacity of the power plant may be increased during periods of high energy consumption. The synthesis gas is stored in one or more synthesis storage tanks 362. The tanks 362 may take any one of many forms and in a preferred embodiment the one or more tanks include a floating roof, and other sealing means that ensure safe storage of carbon monoxide gas .

Air streams 363 and 383 at the* outlet of air compressors 365, 385 are combusted respectively with synthesis gas streams 360, and 380 (where 380 has possibly been upgraded, by CO₂ removal or other means) in the combustion chambers 366, 386. The combustion gases respectively drive gas turbines 367, 387 coupled to electric generators 368 and 388. In a preferred embodiment, the air compressor 365, 385 and the gas turbines 365, 385 are actuated by the same rotating shaft respectively. Combustion gases 369, 389 from the turbines 365, 385 are returned to the heat recovery/steam generator 303. The skilled person will understand that the although the turbines 365 and 385 are described at a single unit they may in fact include multiple trains of turbines, air compressors and combustion chambers. The turbine system 384 is designed to operate on a relatively continuous basis at their optimal capacity, and will typically have a capacity greater than that of the turbine system 364 which is more likely to operate intermittently when electric demand is high, or when there is a requirement to refill auxiliary products (hydrogen, oxygen, or nitrogen) or when methane or other marketable chemical product is to be sold to a client.

Due to the efficiency of the present process, turbine systems 364 and 384 will produce more electrical power from the superheated steam produced in the furnace/boiler 303 and the other heat sources recovered from the retrofitted process than the steam turbine 309 would have otherwise produced if 100% of the coal have been burned in the furnace/boiler 303 to produce steam to drive the steam turbine/electric generator 309/310. The increase in electricity produced will be more than 50%, in a preferred embodiment more than 75% than that produced by the steam turbine. This further allows the steam turbine 309 to operate at roughly 30 to 45% of its production at full capacity on an annual basis using between 5 and 10% less coal product.

The gasification system is also designed so that it can be integrated into an existing electric power generating plant as illustrated in Fig. 1, and so as to take advantage of this increased process efficiency of steam utilization. Comparing Fig.l with Fig. 3, the following unit operations must be included to fully integrate the gasifier 320 into the existing plant particularly: a coal preparation device to produce a 2 cm. diameter coal product; a coal product splitter 302; a superheated steam splitter 316; a gasifier 320; a raw gas treatment 330 and a gas turbine systems 364 and 384. The coal product stream between the coal treatment unit 101 (301 in Fig.3) and the furnace/boiler 103 (303 in Fig.3) must be split with a coal product splitter 302. The stream must be divided to feed a second coal product stream 302B to the gasifier 320. The coal splitter is adapted to operate at the same split ratios as the steam splitter 316 particularly in a preferred embodiment the ratio of streams 302B to 302A is from 65-80 to 35-20 parts of the total coal product stream entering the coal splitter 302. In a preferred embodiment ratio of streams 302B to 302A is 75 to 25 parts of the total coal product stream entering the coal splitter 302.

As previously mentioned, the superheated stream from the heat recovery/steam generator 103 (303 in Fig.3) must have a steam splitter added and the steam line must be tapped and extended such that a second superheated steam stream 317 is sent to the gasifier 320.

With a complete retrofit, the gasifier 320 will be integrated into an existing power plant and will produce a quantity of synthesis gas which when combusted in air and linked to a gas turbine system (s) 364, 384, will produce more electricity than if the same amount of superheated steam produced from the furnace/boiler 303 actuated the steam turbine 309 alone.

Further integration of unit operations such as the raw gas treatment 330, and the gas turbine system (s) 364 and /or 384 must be added and connected to complete this requirement and connected as per the preceding description. Upon completion of the integration of the gasifier 320 into the existing power plant the electric power output of the plant will increase at least 70%, and likely between 70 and 80%, while consuming from 5 to 10% less coal product feed to the existing plant before being retrofitted.

Greenhouse gases produced by the retrofitted power plant of .the present invention will produce less CO₂ per unit of electricity than if all the coal product where burned in the furnace/boiler 303 and the electricity produced was all generated by steam turbine 309 /steam generator 310 alone ("existing amount of electricity") or produced by the existing plant before being retrofitted ("specified amount of electricity").

The retrofitted power plant of the present invention will operate at a ratio of: tonnes of CO₂ produced in both the furnace/boiler and the synthesis gas turbine systems,- to the sum of first portion of electricity and the second portion of electricity together, that is less than, and specifically 30 to 60% less than a ratio of: tonnes of CO₂ produced in the existing coal power plant; to the specific amount of electricity produced in the existing power plant before retrofitting.

Furthermore the power plant of the present invention will operate at a ratio of: tonnes of CO₂ produced in both the furnace/boiler and the synthesis gas turbine system; to the sum of the first portion of electricity and the second portion of electricity together that is less than, and specifically 30 to 60% less than the ratio of: tonnes of CO₂ produced in the furnace/boiler to the total existing amount of electricity produced if all the coal product of the coal treatment system 301 had been combusted in the furnace/boiler 303 and converted to electricity in the steam turbine/electric generator 309/310. EXAMPLE 1 - The process of Fig. 1

To illustrate the overall thermal efficiency of the process described in Fig. 1, a coal having a heating value of 6700 kcal/kg at a rate 1000 kg/hr of coal is fed to the boiler 103. The properties of a typical coal are presented in Table 1.

Typical Coal Properties

Table 1

Proximate Analysis Chemical Analysis (wt% dry basis) (wt% dry basis)

Moisture 8. 5% Ash 14.0 (as received)

Fixed Carbon 52 .1% C 70.22

Volatile Matter 33 .95 H 4.77%

Ash 14 .0% N 1.38%

LHV (MJ/kg) 27 .95 Cl 100 ppm

S 1.09%

O 8.535

The coal is combusted with air 104 in a 20% excess in a boiler. The efficiency of combustion is 95% in the boiler therefore some 6365 Mcal/hr are transferred by the combustion. The combustion gases produced in the boiler superheat 5250 kg/hr of water (5090 Mcal/hr) which is converted to steam (at a pressure of 11 bars) in an indirect heat exchanger 106 having an efficiency of 80%. Although the boiler 103 produces 5250 kg/hr of steam, only 40% are used (2100 kg/hr and 2036 Mcal/hr) to move the steam turbine 109. Furthermore, the turbine efficiency is 38% thus only 800 Mcal/hr or 0.930 MW of electricity is produced. As much as 60% or more of the boiler output of steam (3150 kg/hr or 3054 Mcal/hr) is not used or is under utilized.

EXAMPLE 2 - Integration of Oxygen-Free synthesis gas generation into an existing power plant

A power plant similar to that described in Fig. 1 comprising an existing boiler (26.6 t/hr with 0.4 t/h of dolomite) which will be used as a heat recovery steam generator 301. The existing plant also includes a 60 MW steam turbine 309 is intergrated into a system present in Fig. 3.

For the integrated plant, 34.6 t/hour of coal as defined in Table 1 above and including 0.6 t/h of dolomite are prepared in a coal preparation unit to feed the whole power plant .

The coal stream is prepared and split into a first portion of a 6.1 t/h coal/dolomite (coal product) mixture sent to an existing boiler 301 where it is combusted to produce heat and steam. The boiler 301 has the required overcapacity which is under utilized. The heat output together with recuperated heat must be at least 226.5 MMBtu/h. A second portion 28.5 t/h of the coal/dolomite mixture is fed to the gasifier along with 26.6 t/h of superheated steam at 1200⁰C. In order to maintain the reactor equilibrium, at least the 33.5 MMBtu/h additional heat must be added to the gasifier, for an equilibrium reaction temperature of 900⁰C. The gasification reaction converts the coal to into a synthesis gas of CO/H₂/CH₄/CO₂ of a weight composition of 86%/8.5%/0.1%/5,4, and a molar percentage of 41.1%/57. l%/0.1%/1.7% respectively. Therefore, the amount of synthesis gas produced by this process is at a conversion rate of approximately 95% is 52.35 t/h with a composition in t/h of 45/4.5/0.05/2.8 CO/H₂/CH₄/CO₂ respectively.

Example 3 - Model of an operating plant

A model of a current plant uses 165,000 tons of bituminous coal per year to produce 367,920 MW hours of electricity via a 57MW steam turbine.

A retrofitted power plant according to the present invention will use 154,115 tons of bituminous coal per year to produce 656,916 MW hours of electricity via 70 MW' s of new gas turbine capacity and the existing 57MW steam turbine .

This equates to 78% more electricity using 7% less coal .

The retrofitted power plant would use a coal splitter to direct 75% of the coal to the gasifier and 25% of the coal to the existing furnace/boiler.

The existing furnace/boiler in conjunction with the recapture/reuse of waste heat throughout the retrofitted process, will produce enough steam while comsuming only 25% of the total coal product to convert the coal product in the gasifier to a raw synthesis gas. The end products of the gasification process of the present invention that will be integrated into the existing coal-fired power plant are: (i) electricity from the existing steam turbine: (ii) electricity from the bank of new gas turbines being fed syngas directly from the gasifier process, working in a combined cycle approach with the steam turbine; and (iii) electricity generated at demand from the bank of new gas turbines being fed syngas from a syngas storage tank.

The synthesis gas generated from one ton of coal has a heat value of 33,500 MMBTU' s and using the standard gas turbine heat rate in the combined cycle at regular load, we achieve the production of 656,916 MW hours of electricity from the combination of the gasification system and the existing steam turbine generator set.

Reducing harmful emissions and greenhouse gases:

Sulfur:

The retrofitted plant will only send 25% of the total coal to be consumed to the furnace/boiler for burning, thus immediately reducing the amount of sulfur emitted.

Additionally, the temperature used in the gasifier is relatively "mild" which contributes to the sulfur staying in a non-offensive form and eventually being collected in the bottom ash.

Moreover, dolomite is added to the coal before it arrives in the gasifier or the boiler to facilitate this overall reduction of SOx emissions. Nitrogen Oxides :

The retrofitted plant will only send 25% of the total coal to be consumed to the furnace/boiler for burning, thus immediately reducing the amount of nitrogen emitted.

In the gasifier, the conversion of coal is made in the absence of air, which plays a major role in further reducing the amount of NOx produced. The final amount of NOx reduced in the retrofitted plant will depend on the varying specifications of the new equipment installed (gasifiers, gas cleaning systems, gas turbines) .

The embodiment ( s) of the invention described above is (are) intended to be exemplary only. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

Claims

CLAIMS :

1. A method of retrofitting an existing coal power plant, the power plant producing a specific amount of electricity and having at least a coal treatment unit; a furnace/boiler and a steam turbine/electric generator, the method comprising the steps of:

adding a steam based gasifier downstream of the coal treatment unit and the furnace/boiler;

adding a coal product splitter in a coal product flow stream between the coal treatment unit and the furnace/boiler ;

dividing the coal product flow stream at the coal product splitter into at least a first and a second coal product stream, wherein the first coal product stream is combusted in the furnace/boiler to produce a superheated steam flow stream and the second coal product stream is sent to the steam based gasifier;

adding a steam splitter in the superheated steam flow stream between the furnace/boiler and the steam turbine/electric generator;

dividing the superheated steam flow stream at the steam splitter into at least a first and a second superheated steam flow stream, wherein the steam turbine/electric generator produces a first portion of electricity from the first superheated steam flow stream and the second superheated steam flow stream is sent to the steam based gasifier; and operating the steam based gasifier in a steam atmosphere and with additional heating to produce a raw gas through a reaction of the second coal product stream and the second superheated steam flow stream.

2. The method according to claim 1, further comprising:

adding a raw gas treatment system downstream of the steam based gasifier for removing impurities from the raw gas and producing a synthesis gas; and

adding at least one of a synthesis gas turbine system producing a second portion of electricity from combustion of the synthesis gas,

wherein the first portion of electricity plus the second portion of electricity together are more than the specific amount of electricity; and

a hydrocarbon conversion system converting the synthesis gas to a marketable chemical product .

3. The method according to claim 2, wherein a ratio of: tonnes of CO₂ produced in both the furnace/boiler and the synthesis gas turbine system; to the sum of the first portion of electricity and the second portion of electricity together, is less than a ratio of tonnes of CO₂ produced in the existing coal power plant to the specific amount of electricity produced.

4. The method according to claim 3, wherein a ratio of: tonnes of CO₂ produced in both the furnace/boiler and the synthesis gas turbine system; to the sum of the first portion of electricity and the second portion of electricity together is less than 30 to 60 % less than the ratio of tonnes of CO₂ produced in the existing coal power plant to the specific amount of electricity produced.

5. The method according to claim 2, comprising equalizing the pressure of the synthesis gas downstream of the raw gas treatment system, splitting the synthesis gas downstream of equalizing the pressure into at least a first and a second synthesis gas stream, wherein the second portion of electricity comprises a third portion of electricity derived from combustion of the first synthesis gas stream, wherein the first synthesis gas stream is stored before combustion.

6. The method according to claim 5, wherein the second portion further comprises a fourth portion of electricity derived from combustion of the second synthesis gas stream derived directly from raw gas treatment without storage.

7. The method according to claim 5, comprising further splitting the synthesis gas downstream of equalizing the pressure into a third synthesis gas stream, and combusting the third synthesis gas stream in a superheater that indirectly heats the second superheated steam flow stream upstream of and before entering the steam based gasifier, and produces a combustion gas stream leaving the superheater.

8. The method according to claim 7, wherein the combustion gas stream is used for the additional heating of the steam based gasifier.

9. The method according to claim 8, wherein further heat is recovered from the raw gas treatment to preheat a water stream to the furnace/boiler that will be converted to the superheated steam flow stream.

10. A fixed bed steam based gasifier for reacting a coal product and a superheated steam at a temperature range from 700⁰C to 1000⁰C into synthesis gas, the gasifier operating in a steam atmosphere and comprising:

a reactor vessel comprising,

a base section comprising,

a steam inlet having adjacent to or within the steam inlet a catalyst for activating the steam to react with the coal product, and

an ash outlet;

an upper section comprising:

a coal product inlet; and

a synthesis gas outlet; and

an intermediate section contiguous with and between the base section and the upper section whereby a fixed bed level for the coal product is established at a point in the intermediate section; and

a heat exchanger associated with the reactor for indirectly heating the coal product.

11. The gasifier according to claim 10, wherein the catalyst is a zeolite.

12. The gasifier according to claim 11, wherein the heat exchanger is an electric induction type, or an indirect heat exchanger using combustion gases to heat the coal product.

13. The gasifier according to claim 12, wherein the indirect heat exchanger is a jacketed type heat exchanger mounted on the wall of the steam based gasifier.

14. A method for producing at least one of electricity and a marketable chemical product from a coal product comprising the steps of:

preparing a coal product having a uniform and homogeneous particle size distribution;

dividing the coal product into at least a first and a second coal product stream;

feeding the first coal product stream to a furnace/boiler,-

producing a superheated steam from a water stream indirectly heated by combustion of the first coal product stream in the furnace/boiler;

dividing the superheated steam into at least a first and a second superheated steam flow stream;

feeding the first superheated steam stream to a steam turbine system to produce a first portion of the electricity;

feeding the second superheated steam flow stream and the second coal product stream to a steam-based gasifier; operating the steam-based gasifier in a steam atmosphere and reacting the second superheated steam flow stream and the second coal product stream to produce a raw gas;

treating the raw gas to remove impurities to produce a synthesis gas; and

feeding the synthesis gas to at least one of a gas turbine system to produce a second portion of electricity,

wherein the second portion of electricity is greater than a total existing amount of electricity, wherein the total existing amount of electricity is an amount of electricity produced if all the coal product flow stream of the coal treatment unit had been combusted in the furnace/boiler and converted to electricity in the steam turbine/electric generator, and

a hydrocarbon conversion system converting the synthesis gas to marketable chemical product.

15. The method according to claim 16, comprising:

equalizing the pressure of the synthesis gas downstream of the treating the raw gas,

splitting the synthesis gas downstream of equalizing the pressure into at least a first and a second synthesis gas stream,

directing the first synthesis gas stream to a synthesis gas storage system, and at least one of a first gas turbine system downstream of the synthesis gas storage system,

wherein the second portion of electricity comprises a third portion of electricity produced by combustion of the first synthesis gas in the first turbine system, and

the hydrocarbon conversion system downstream of the synthesis gas storage system.

16. The method according to claim 15, wherein the second portion further comprises a fourth portion of electricity derived from combustion of the second synthesis gas stream in a second gas turbine system, wherein the second synthesis gas stream is derived directly from raw gas treatment without storage.

17. The method according to claim 15, wherein the first synthesis gas stream is stored in the synthesis gas storage system or converted in the hydrocarbon conversion system to the marketable chemical product when demand for electricity is low and converted to the third portion of electricity when demand for electricity is high.

18. A coal power plant comprising:

a coal treatment system for producing a coal product, the coal product transferred into at least two streams comprising a first and a second coal product stream; a furnace/boiler downstream of the coal treatment system for combusting the first coal product stream and indirectly heating water to produce a superheated steam;

a steam splitter downstream of the furnace/boiler for dividing the superheated steam into at least a first and a second superheated stream;

a steam turbine/electric generator downstream of the steam splitter producing first portion of electricity from the first superheated steam stream;

a fixed bed steam based gasifier for conversion of the second coal product stream and the second superheated steam stream in a temperature range from 700⁰C to 1000⁰C into a raw gas, the gasifier operating in a steam atmosphere and comprising

a reactor vessel comprising,

a base section comprising,

a steam inlet having adjacent to or within the steam inlet, a catalyst for activating the steam to react with the coal product, and

an ash outlet;

an upper section comprising:

an coal product inlet; and

an synthesis gas outlet; and an intermediate section contiguous with and between the base section and the upper section whereby a fixed bed level for the coal product is established at a point in the intermediate section; and

a heat exchanger associated with the reactor for indirectly heating the coal product whereby the second superheated steam stream produces a steam atmosphere within the gasifier and reacts with the second coal stream to produce the raw gas .

19. The power plant according to claim 18, comprising

a raw gas treatment system downstream of the gasifier removing impurities from the raw gas and producing a synthesis gas; and at least one of

a gas turbine system downstream of the raw gas treatment system producing second portion of electricity from combustion of the synthesis gas,

wherein the second portion of electricity is greater than a total existing amount of electricity, wherein the total existing amount of electricity is an amount of electricity produced if all the coal product of the coal treatment system had been combusted in the furnace/boiler and converted to electricity in the steam turbine/electric generator, and

hydrocarbon conversion system downstream of the raw gas treatment system converting the synthesis gas to a marketable chemical product.

20. The power plant according to claim 19, wherein the gas turbine system comprises at least a first and a second gas turbine system operating independently, the power plant further comprising:

a synthesis gas equalizer, and

a synthesis gas splitter,

wherein the equalizer and the gas splitter are located between the raw gas treatment system and the first and the second gas turbine systems and the hydrocarbon conversion system, the equalizer regulating the pressure of the synthesis gas upstream of the first and the second gas turbine systems, and the gas splitter splitting the synthesis gas into at least a first synthesis gas portion and a second synthesis gas portion, respectively the first and the second gas turbine system, the division of synthesis gas based on a pressure signal from the equalizer and consumption requirements of the synthesis gas at the first and the second gas turbine system and the hydrocarbon conversion system.

21. The power plant according to claim 20, comprising a synthesis gas storage system downstream of the synthesis gas splitter and upstream of at least one of the hydrocarbon conversion system and the first gas turbine system.

22. The power plant according to claim 21, wherein the a ratio of tonnes of CO₂ produced in both the furnace/boiler and the synthesis gas turbine system to the sum of the first portion of electricity plus the second portion of electricity together is less than a ratio of tonnes of CO₂ produced if all the coal product of the coal treatment system had been combusted in the furnace/boiler and converted to electricity in the steam turbine/electric generator to the total existing amount of electricity produced.

23. The method according to claim 21, wherein the ratio of tonnes of CO₂ produced in both the furnace/boiler and the synthesis gas turbine system to the sum of the first portion of electricity plus the second portion of electricity together is 30 to 60 % less than the ratio of tonnes of CO₂ produced if all the coal product of the coal treatment system had been combusted in the furnace/boiler and converted to electricity in the steam turbine/electric generator to the total existing amount of electricity produced.

24. The power plant according to claim 20, further comprising a superheater, downstream of the steam splitter and upstream of the steam based gasifier, wherein the second superheated steam stream is further superheated in the superheater through the combustion of a third synthesis gas portion.

25. The method according to claim 21, wherein the catalyst is a zeolite.