RU2143084C1 - Method for combined-cycle combustion of natural gas, pulverized coal, and gas products of thermochemical treatment of coal - Google Patents

Abstract

FIELD: power engineering; thermal power stations. SUBSTANCE: fuel is admitted to vertical tetrahedral prismatic furnace together with primary air portions in amount insufficient for complete fuel combustion through burners installed on one of furnace walls and secondary air portions, through nozzles arranged along its walls. Method involves supply of gas and pulverized fuel mixed up with primary air portions in separate cocurrent flows; gases produced in thermochemical treatment of coal and respective primary air portion are introduced in furnace in separate flows concurrently with streams of gas-air and fuel-air mixtures; separate primary air portion is introduced under and above fuel flows. Gas products are generated, prior to introducing them in furnace, in coal reactors operating as gasifiers of steam-gas-air mixture in swirling flow formed by jets of suspended fuel-air, steam, and stack gases. EFFECT: improved fuel burnout with minimal emission of nitrogen oxides; increased gas output of reactor. 10 dwg

Description

 The invention relates to energy and can be used in boilers of thermal power plants that burn natural gas, coal dust and gaseous products of thermochemical processing of coal.

 A known method of the combined combustion of natural gas and coal dust by feeding into a vertical tetrahedral furnace through fuel streams with air installed on one of the burner walls (see A.S. USSR N 1163088, IPC (6) F 23 C 1/12 dated 04.04. 1983; B.I. N 23, 1985). The method provides economical combustion of fuel and increases the reliability of the burners. However, when gaseous products of thermochemical processing of coal produced in coal reactors near the combustion chambers are fed into the furnace, the conditions ensuring the efficiency and reliability of the burners are violated, which manifests itself in a high degree of fuel underburning.

 A known method of combined burning in a furnace of natural, coke oven, blast furnace gas and pulverized fuel (see A. p. N 1755006, IPC (6) F 23 C 1/12 dated 03/07/1990; IPC (6) F 23 1 / 12; B.I. N 30, 1992). The method ensures the operation of the combustion chamber of an energy boiler in economical and environmentally friendly multi-fuel modes. However, when fuel flows are introduced in combination with gaseous products of thermochemical processing of coal into the furnace, the conditions for its reliable and economical operation are violated also due to a significant underburning of fuel.

 A known method of operation of a vertical tetrahedral combustion chamber for the joint combustion of natural gas and coal gasification products (see RF patent N 2026512 from 06/09/1992, B.I. N1, 1995). In accordance with the patent, gasification products are introduced through a nozzle in the hearth of the combustion chamber along its vertical axis, and natural gas and afterburning air through nozzles mounted on the walls, which minimizes the release of harmful substances into the atmosphere. The disadvantage of this method is associated with the inability to supply coal dust through the burners installed on the walls. In the absence of a system that ensures slag removal from under the combustion chamber, ash and slag particles accumulate to the level of air nozzles and burners on the walls with a violation of the aerodynamics and temperature conditions of the furnace until the flame goes out and the boiler stops.

 There is a method of preliminary thermochemical processing of coal in the mode of gas-vapor gasification in fluidized bed apparatus and the subsequent introduction of gaseous products for afterburning into the furnace (see RF patent N 2078283 from 03/03/95; B.I. N 12, 1997). The disadvantage of this method is the low activity of the process, which causes the need for large-sized fluidized bed apparatus, poorly fitting into the dimensions and technology of modern thermal power plants.

 Closest to the claimed is a method of burning coal dust in a vertical prismatic tetrahedral combustion chamber by supplying fuel and primary air portions through burners mounted on one of the walls, and secondary afterburning air flows along the walls through nozzles (see a.s. USSR No. 964337; IPC (6) F 23 C 7/02 of 12/11/1980 B.I. N 37 of 1982). Combustion occurs in non-slag and economical modes with a minimum yield of harmful nitrogen oxides. However, when gaseous products of thermochemical processing of coal (products of gasification of solid fuel) are fed through burners, the degree of underburning of fuel is high.

 The objective of the present invention is to increase the degree of burnout of gas, coal dust and gaseous products of thermochemical processing of coal with a minimum yield of nitrogen oxides, as well as increasing the production of chemically active gaseous products in a coal reactor.

 To achieve this goal, in a method for the combined combustion of natural gas, coal dust and gaseous products of thermochemical processing of coal, implemented by supplying a vertical tetrahedral prismatic furnace of fuel and primary air portions with a quantitative deficiency for complete combustion through burners and secondary afterburning portions installed on one of the walls air through nozzles along the walls of the furnace, gas and dust are supplied in separate satellite flows in a mixture with their own primary portions of air, and gas braznye produce products before entering the furnace in the coal-steam mode reactors gasification; according to the invention, gasification is carried out in a swirling vortex stream formed by jets of carbohydrate suspension of steam and flue gases, and the gases of thermochemical processing of coal from reactors and the corresponding primary portion of air are introduced into the furnace by separate streams in a stream of gas-air and dust-air mixtures, with the primary portion of air being supplied under and over the fuel flows.

 Separate supply of primary portions of air and gaseous products of the thermochemical processing of coal, followed by afterburning of fuel by secondary portions near the shielded walls of the combustion chamber, ensures a minimal exit of nitrogen oxides with products of complete combustion from the furnace, and the inlet of gas-air and dust-air mixtures minimizes the degree of underburning of fuel; gasification in a swirling vortex stream leads to an increase in the gas productivity of the reactor; introducing primary portions of air under and above the streams of gaseous products of thermochemical processing of coal reduces the yield of nitrogen oxides.

 The essence of the proposed method is illustrated by drawings, where in FIG. 1 is a diagram of a vertical tetrahedral prismatic furnace with burners placed on one of the walls, and fuel preparation and supply units; in FIG. 2 is a section along AA in FIG. 1; figure 3 - diagram of a burner with dispersed symmetrical nodes of the fuel input; figure 4 is a view of B in figure 3; figure 5 is a diagram of a burner with concentrated symmetric nodes of the fuel input; figure 6 is a view In figure 3; 7 is a diagram of a burner with asymmetric nodes of the input of fuel and primary portions of air; in FIG. 8 is a view G of FIG. 7; Figures 9 and 10 are diagrams of vortex reactors with systems for introducing carbon-air suspension, flue gases, removal of gaseous products, afterburning and ash removal, variants with a cylindrical and prismatic chambers, respectively.

 The method is implemented in a furnace 1 with screens 2 of pipes with a steam-water mixture placed on all walls, nozzles 3 for introducing afterburning air, also installed on the walls and oriented along the walls. Burners 5 are installed on the wall 4. The burners have channels 6 with nozzles 7 for introducing a gas-air mixture, channels 8 for introducing a dust-air mixture or products of thermochemical processing of coal (in particular, gasification products, generator gas), as well as air channels 9, 10 placed above and below the channels 8, for air inlet. A gas supply system 11 is connected to the nozzles 7, a dust preparation system with mills 12 and coal reactors 13 are connected to the channel 8, in which thermochemical processing of solid fuel is carried out with the release of gaseous chemically active products that produce heat when interacting with atmospheric oxygen; nozzles 3, channels 6, 9, dust preparation systems 12 and coal reactors 13 are connected to the boiler air supply system 14. Coal reactors 13 are connected with nozzles for introducing carbon-air suspension, flue gases, steam, fuel supply system 15, removal of gaseous products with burners 5, afterburning and ash output 16. For the production of gas from coal, vertical coal reactors 13 can be used (Fig. 1) or horizontal type (Fig. 9, 10) with reaction chambers of a cylindrical (Fig. 1, 9) or prismatic (Fig. 10) form, in which the vortex movement of particles of coal, air, flue gases and steam is organized, and for dissimilar fuel combustion fire chambers - burners according to figures 3, 4; FIGS. 5, 6; 7, 8.

 The method is implemented by feeding natural gas, coal dust or gaseous products of thermochemical processing of coal, primary and afterburning air portions into the furnace 1, which, when interacted, form a high-temperature torch with the release of a certain amount of heat. This heat heats the water circulating in the screens 2, which, evaporating, turns into steam. The latter is sent to a turbogenerator to generate electricity. Natural gas used as one of the fuels comes from the gas supply system of the boiler house and boiler to nozzles 7 located in the channels 6 of the burners 5. From the air supply system, a primary portion of air is fed to channel 6, which is not enough to completely burn the gas. The gas-air mixture introduced into the furnace 1 through the channels 6 of the burners 5 forms a gas flame, the lack of an oxidizing agent in which is compensated by the oxygen of the air introduced through the nozzles 3 along the walls. Coal dust is obtained in dust preparation systems with mills 12, which also serves a primary portion of air. A mixture of dust with air (aerosol) with a deficiency for complete combustion through the channels 8 of the burners 5 is sent to the furnace 1, where the ignition and the formation of a pulverized coal flame occur; for afterburning, air is introduced through the same nozzles 3. When coal reactors are turned on, the feed channels of the dust preparation system 12 are cut off and the channels of the burner 5 are fed into the furnace 1 by streams of gaseous chemically active products of thermochemical processing of coal (generator gases, gasification products). The gasification activity in reactors is determined by the intensity (speed) of rotation of the medium; the temperature is maintained by the consumption of flue gases and steam. The ash discharged from the reactors is burned with air in system 16, then discharged into the ash removal channels or to the processing of building materials enterprises. Gases are led off to burners 5 at high temperature, they are very active against oxidizing agents, in particular, oxygen, in connection with which the primary portions of the latter are separated and introduced by satellite flows above and below the hot gas flows through channels 9, 10. In quantitative terms, oxygen primary air flows are not sufficient for complete combustion of gases from reactors 13, and therefore, compensating air flows are provided through nozzles 3 to ensure complete combustion of fuel. During operation of the furnace 1, the supply of natural gas, coal dust, and gaseous products of the processing of solid fuel is combined. It is allowed to feed simultaneously in one burner natural gas and dust, or natural gas and gaseous products of coal processing. If necessary, three types of fuel supplied through various burners, or one of three, can be burned at once in the furnace. In this case, a prerequisite for the combustion of natural gas and dust is their supply to the furnace 1 in a mixture with primary portions of air, and the gaseous products of the thermochemical processing of coal - a separate supply with the necessary primary portion of air above and under the fuel flows.

 Such a separation of fuel flows from reactors and primary portions of air in the burners 5, a satellite feed into the furnace 1 together with gas-air and dust-air mixtures, and subsequent combustion with air streams from nozzles 3 supplied along the walls, maximize the output of gaseous products from the reactor and the degree of fuel burnout in the furnace with a minimum output of harmful nitrogen oxides from the boiler. The experiments on the boiler BKZ-210-140F of the Chelyabinsk CHPP-2 with a gas supply system, mills and coal reactors showed that this set of operations determines the effectiveness of the developed method, any deviation in the technology for introducing fuel and air flows leads to a violation of the aerothermodynamic characteristics of the flame with deterioration of combustion and increased yield of nitrogen oxides. The stability and uniformity of the operating parameters of the furnace and torch are supported by the redistribution of fuel and air flow rates in burners and nozzles, which is carried out in manual or automatic modes.

Claims (1)

 A method of combined combustion of natural gas, coal dust and gaseous products of thermochemical processing of coal by feeding fuel and primary air portions into a vertical tetrahedral prismatic furnace with a quantitative disadvantage for complete combustion through burners and secondary air afterburning portions of air through nozzles along the furnace walls, moreover, gas and dust are supplied in separate satellite streams mixed with their own primary portions of air, and gaseous products are produced before water into the furnace in coal reactors in the mode of gas-vapor gasification, characterized in that gasification is carried out in a swirling vortex stream formed by jets of carbon-air suspension, steam and flue gases, and the gases of thermochemical processing of coal from the reactors and the corresponding primary portion of air are introduced into the furnace in separate streams in a stream of gas-air and dust-air mixtures, moreover, a primary portion of air is fed under and above the fuel flows.

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