Title of Invention

SOLID FUEL FIRED STEAM GENERATOR

Abstract

There is proposed to be an invention of an improved solid fuel fired steam generator comprising a solid fuel combustor (1), an intermediate heat exchanger (2), the said intermediate heat exchanger being disposed in the flow path of the flue gases from the solid fuel combustor, the outlet of the said intermediate heat exchanger being connected to another heat exchanger (3) in a closed circuit to exchange heat with the hot water leaving the combustor, a feed water pump (4) for supplying water to the heat exchanger (3) and a feed line (6) for supplying the heat depleted water from the heat exchanger (3) to the intermediate heat exchanger (2).

Full Text

THE PATENT ACT, 1970 COMPLETE SPECIFICATION (SECTION 10) TITLE SOLID FUEL FIRED STEAM GENERATOR APPLICANT M/S. THERMAX LIMITED, D-13, MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE-411 019, MAHARASHTRA, INDIA, AN INDIAN ORGANIZATION. The following Specification particularly describes and ascertains the nature of this invention and the manner in which the same is to be performed. Introduction to the field of invention. This invention relates to a new solid fuel fired steam generator. This invention more particularly relates to the development of a solid fuel fired steam generator in which the water holdup does not exceed 22.75 litres. Prior art and drawbacks. It is already known in the prior art to generate stem using solid fuels. And in these conventional solid fuel fired stem generators, it is known to generate stem by exchange of heat from hot flue gases to the water/steam. In this process, the heat transfer coefficient ranges from 15 to 50 kcal/h. m ^C. Hence the water holdup invariably exceeds 22.75 litres. The main limitation of the prior art is that the water hold up of the pressure part exceeds 22.75 litres bringing this unit under purview of Indian Boiler Regulations (IBR). Discussion of further prior art. The applicant is aware of Japanese Patent 10196316 and 3000931. These prior art patents have been analyzed and it is observed as follows. Japanese Patent 10196316 - This Patent relates to a combined power generating plant and closed air cooling gas turbine system. Straight away this Patent does not have anything in common with our invention where the question of gas turbines and power generation do not come into picture. The construction in the Japanese Patent has a closed air cooling gas turbine, a gas steam mixture is obtained which is passed to a heat exchanger for heat utilization and for obtaining water steam required. Japanese Patent 3000931 - This Patent relates to a gas turbine cooling generation system with solid fuel. This is entirely different from the applicant's invention because a hot gas obtained in a combustor using solid fuel are particularly in contact with the thermal heat exchanger within the combustor which is enclosed loop arrangement with the secondary heat exchanger having feed water. Compared to this, the Japanese Patent has a generator driven by a gas turbine and has a compressor 4 which is driven through a shaft connected to the gas turbine. The compressed air is introduced to a high temperature heat exchanger, which is heated by composition gas of solid fuels. The gas is exchanged from the high temperature heat exchanger is introduced to a waste heat boiler for steam generation and the steam is reused in the high temperature heat exchanger through gas turbine. The intend and purpose of this Japanese Patent and the construction are 2 entirely different from the applicant's invention, which has no such gas turbine and creation of compressed air and high pressure heat exchanger. None of the two Japanese Patent either alone or in any combination thereof can destroy the novelty and inventive character of the applicant's invention. Objects of the invention It is the principal object of this invention to propose a new design or improvement in the existing solid fuel fired steam generators. It is another object of this invention to propose the use of an intermediate fluid which primarily absorbs/exchange heat with the hot products of combustion of the solid fuel (flue gases). It is also an object of this invention to propose that the heat absorbed/exchanged by the intermediate fluid is to be rejected to the water/steam in the new heat exchanger/steam generator to generate steam. It is yet another object of this invention to propose a new heat exchanger/steam generator design in which the heat transfer coefficient is in the range of 400 to 3000 kcal/m 20C and hence maintaining the water holdup below 22.75 litres. 3 These and other objects of the invention will be clear from the following paragraphs. Brief Statement of the invention. According to this invention, there is provided, an improved solid fuel fired steam generator comprising a solid -— fuel - combustor — (1), an , intermediate heat exchanger (2), the said intermediate heat exchanger being disposed in the flow path of the flue gases from the solid fuel combustor, the outlet of the said intermediate heat exchanger being connected to another heat exchanger (3) in a closed circuit to exchange heat with the hot water leaving the combustor, a feed water pump (4) for supplying water to the heat exchanger (3) and a feed line (6) for supplying the heat depleted water from the heat exchanger (3) to the intermediate heat exchanger (2). The intermediate heat exchanger is disposed within an enclosure through which the hot flue gases pass and the said enclosure is inside the solid fuel combustor. In a preferred embodiment, the intermediate heat exchanger is preferably integral with the solid fuel combustor. In another embodiment, the intermediate heat exchanger is provided in an enclosure external to the solid fuel combustor which enclosure is meant for passing the hot fule gases from the solid fuel combustor. The heat exchanger in the water boiler/steam generator and the intermediate heat exchanger are in a closed loop. It is also possible to have a steam generating system comprising a plurality of said steam generators, intermediate heat exchangers and solid fuel combustors as stated earlier. There is also proposed a method for the generation of steam from using solid fuel comprising the steps of combusting the solid fuel to generate hot flue gases, a passing a cold intermediate fluid in indirect heat exchange relationship with the flue gases to generate hot intermediate fluid passing the hot intermediate fluid in indirect heat exchange relationship with water in a steam generator, recycling the heat depleted intermediate fluid for further intermediate heat exchange with the flue gases in a closed loop and generating steam in the steam generator. 4 BRIEF DESCRIPTION OF THE DRAWINGS. In the accompanying drawings, the only Figure 1 schematically represents the novel heat exchanger of this invention. DETAILED DESCRIPTION OF THE DRAWINGS. In the drawings, numeral 1 schematically represents a conventional solid fuel combustor. The combustor can use any conventional agro based solid fuel. The fuel combustor is provided with usual accessories like fuel feed means, air blower or air inducer as required. There is provided an intermediate heat exchanger (2), in the flow path of the flue gases for indirect heat exchange. Cold fluid flowing through the intermediate heat exchanger (2), picks up almost all the recoverable heat from the hot flue gases and the heat depleted flue gas is admitted to the stack. Though we have shown the intermediate heat exchanger (2) and the fuel combustor (1) in the same enclosure, it is also possible to have the heat exchanger externally as an independent unit. We have tried a number of such cold fluids and it is found workable with air, water, organic fluids or inorganic fluids used in heat exchange operations. There is also provided another heat exchanger (3) preferably in closed circuit with the intermediate heat exchanger (2). Theat exchanger (3) uses water and is provided with the usual accessories for control of water/steam and pressure of steam generated. The closed circuit exchanger is designed to exchanger substantially all the heat of the intermediate fluid to the feed water supplied by the pump (4). The steam generated exists the boiler through outlet (5) of the heat exchanger (3) while the heat depleted intermediate fluid is recycled through circuit (60 to the intermediate heat exchanger. 5 While we have shown counter current heat transfer system, it is also possible to have suitable co-current heat transfer system. If desired, a chilling or cooling unit can be interposed to cool the intermediate fluid while recycling the same. We have further found that it is possible to have a series of such heat exchangers as a plurality of modular units instead of a single unit. Advantages: 1. The whole system is compact and can be easily maintained. 2. Because of low water hold up, the unit does not fall under Indian Boiler Regulations Act (IBRA) and hence is cheap to manufacture. 3. It is easy to install and operate. 4. Water side cleaning is very simple and effective. 6 We claim. 1. An improved solid fuel fired steam generator in which the water hold up does not exceed 22.75 litres comprising a solid fuel combustor (1), an intermediate heat exchanger (2), the said intermediate heat exchanger being disposed in the flow path of the flue gases from the solid fuel combustor, the outlet of the said intermediate heat exchanger being connected to another heat exchanger (3) in a closed circuit to exchange heat with the hot water leaving the combustor, a feed water pump (4) for supplying water to the heat exchanger (3) and a feed line (6) for supplying the heat depleted water from the heat exchanger (3) to the intermediate heat exchanger (2). 2. An improved solid fuel fired steam generator as claimed in Claim 1 wherein the intermediate heat exchanger is disposed within an enclosure through which the hot flue gases pass. 3. An improved solid fuel firted steam generator as claimed in claims 1 and 2 wherein, the intermediate heat exchanger is preferably integral with the solid fuel combustor. 4. An improved solid fuel fired steam generator as claimed in Claim 1, wherein, the intermediate heat exchanger is provided in an enclosure external to the solid fuel combustor which enclosure is meant for passing the hot flue gases from the solid fuel combustor. 5. An improved solid fuel fired steam generator substantially as herein described with reference to the accompanying drawings. Dated this the 7th day of September 2001. DILIP WAMAN BAPAT For THERMAX LIMITED

Documents:

875-mum-2001-abstract(3-3-2005).doc

875-mum-2001-abstract(3-3-2005).pdf

875-mum-2001-cancelled pages(3-3-2005).pdf

875-mum-2001-claims(granted)-(3-3-2005).doc

875-mum-2001-claims(granted)-(3-3-2005).pdf

875-mum-2001-correspondence(9-5-2005).pdf

875-mum-2001-correspondence(ipo)-(20-11-2005).pdf

875-mum-2001-drawing(3-3-2005).pdf

875-mum-2001-form 1(12-9-2001).pdf

875-mum-2001-form 19(12-3-2004).pdf

875-mum-2001-form 2(granted)-(3-3-2005).doc

875-mum-2001-form 2(granted)-(3-3-2005).pdf

875-mum-2001-form 3(12-9-2001).pdf

875-mum-2001-form 3(3-3-2005).pdf

875-mum-2001-form 5(3-3-2005).pdf

875-mum-2001-petition under rule 137(3-3-2005).pdf

875-mum-2001-petition under rule 138(3-3-2005).pdf

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