RU2777164C1 - Method for reduction in nitrogen oxide emission and conversion of burner into low-toxic one, device for its implementation - Google Patents

Abstract

FIELD: heat power engineering.

SUBSTANCE: method for the reduction in nitrogen oxide emission, using in-stream recirculation of flue gases, consists in that, in a burner containing an air box, outer and inner shells, a central pipe for supplying fuel gas with a conical nozzle at an output with holes, in which a trunk with a fuel oil nozzle is located, in an air channel between outer and inner shells, peripheral gas-distributing pipes are additionally installed, coming out of a gas collector and equipped with nozzles at an output, nozzles of gas-distributing pipes are moved in a furnace outside of an airflow, and portholes are placed along a perimeter, flue gases are ejected with jets of fuel gas flowing out of nozzles, fuel gas is diluted with flue gases before its mixing with an airflow coming out of the burner and ignition.

EFFECT: invention allows for the reduction in nitrogen oxide emission.

3 cl, 2 dwg

Description

The invention relates to fuel combustion plants and can be used to supplement burners with a device that reduces emissions of nitrogen oxides (NOx).

Single-flow fuel gas burners are known, such as GMU, GMPV, etc., which, while ensuring the quality of fuel combustion, do not provide low NOx emissions. The most common in Russia unified oil-gas burner of the GMU type (OST 108.836.05-82 “Oil-gas burners and loopholes for stationary steam boilers”) consists of a nozzle assembly, a gas part and an air guide. The nozzle assembly includes a steam-mechanical nozzle with a flap. The gas part of the burner consists of an annular gas collector, a gas-distributing nozzle in the form of a cone with holes and a gas supply pipe. The inner pipe of the gas collector is the guide pipe of the steam injector. The air guide device of the GMU type burner consists of an air box and two bladed swirlers: axial and tangential. Inside the box there is a partition that divides the air flow into two streams.

The disadvantage of the GMU-type burner is the low environmental efficiency of fuel combustion, due to the design flaws of the burner in the method of organizing the combustion process, in which all the fuel gas is supplied to the air.

Known direct-flow-vortex burner type GMPV (RU 2 137 043 C1, IPC F23D 17/00, published 09/10/1999) which consists of an air channel, an axial swirler installed in the air channel, gas-distributing tubes located around the swirler, and having at the outlet nozzles with outlets. The burner provides lower NOx emissions than the GMU burner by reducing the mixing rate of fuel and air at the border of the direct-flow and swirling air flow, but due to the supply of all gas into the air flow, NOx emissions remain high.

One of the effective ways to reduce NOx emissions is the use of forced flue gas recirculation, which reduces the flame temperature and reduces the concentration of reactants that determine the formation of NOx. In this case, the most effective method is the supply of flue gases to the burner channels (SU 1 101 622 A1, IPC F23D 17/00, published on 07/07/1984). This method is implemented in the burner of the TGMP-204 boiler, which consists of two air supply channels (central and peripheral), equipped with tangential registers, a recirculation flue gas inlet channel is located along the periphery, and an oil burner is installed in the center of the heater. The gas part of the burner consists of an annular gas collector, a gas-distributing nozzle in the form of a cone with holes and a gas supply pipe. The inner pipe of the gas collector is the guide pipe of the steam-mechanical nozzle (Y.P. Storozhuk. Testing the TGMP-204 boiler of the 800 MW unit after the reconstruction of the recirculation flue gas inlet into the furnace / Ya.P. Storozhuk, D.R. Nosulko // Thermal power engineering. - 1984. - No. 5 - S. 13-15.). This burner failed to achieve a good result in reducing NOx emissions due to design flaws in the way the combustion process is organized.

Successful NOx suppression requires that recirculation flue gases do not ballast in the root area of the burner, but reach the combustion core, where the main formation of NOx occurs. The main disadvantage of this method of organizing combustion remains the need for a system of forced recirculation of flue gases with a recirculation smoke exhauster.

Close to the invention is a method for reducing NOx emissions, described in the inventions: RU 2689654C2 published on 2019-05-28, SU 1588987A1 published on 1990-08-03, SU 1695040A1 published on 1991-11-30, KR 101254928B1 published on 2013-04-19, EP 0893651A1 published 1999-01-27; US 2012/0186265A1 published 2012-07-26; WO 01|07833A1 published 2001-02-01; US 2005/0239005A1 published 2005-10-27; EP 2479491A1 Published 2012-07-25, KR 2012-06-29, KR 20120074868A published 2012-07-06, KR 2012-07-24, KR 20130061167A published 2013-06-10, US 5350293 Published 1994- 09-27. In some cases, these inventions were developed in order to stabilize the combustion regime by sucking incandescent combustion products from the furnace. In these inventions, flue gas recirculation is organized by the burners themselves without additional flue gas supply systems, including a chimney system and a recirculation smoke exhauster. The flue gases are ejected into the combustion zone, which burns the diluted fuel and reduces the formation of NOx. The disadvantage of the method used in these inventions is: the complexity and high cost of the design of the burners, a small amount of sucked flue gases from the furnace. The flue gases are ejected by the fuel or air flow at the burner mouth inside the main air flow, combustion takes place in the air environment, which in general reduces the efficiency of NOx suppression. The considered inventions cannot be applied to the existing burners installed in the combustion plant.

Closer to the invention is a group of inventions in which the principle of in-furnace recirculation is used due to the injection of fuel gas not into the air stream, but outside the burner mouth: US 5542840A published 1996-08-06, US 6773256B2 published 2004-08-10, RU 2426030C2 published 2011 -08-10, US 5275552A published 1994-01-04, US 20080096146A1 published 2008-04-24, US 6007325A published 1999-12-28, US 7670135B1 published 2010-03-02, US 9593847B1-published 2014. US 9593848A1 published 2015-12-10, US 20150285491A1 published 2015-10-08, US 6875008 B1 published 2005-04-05, KR 101213883B1 published 2012-12-18. In these inventions, technical solutions are patented in which fuel gas and/or air are diluted with flue gases before they are mixed and reacted. The main condition for reliable combustion of fuel gas when using this technology is to maintain the temperature in the furnace of a fuel combustion plant above the ignition temperature of the fuel and use a stable flame stabilizer, while ignition and combustion stabilization is provided by special loopholes or the overall temperature of the furnace. The disadvantages of these inventions are the complexity of the design, the need to use a special loophole made of heat-resistant concrete and the impossibility of their use for existing burners installed in a fuel combustion plant.

The closest to the proposed invention is a group of inventions in which the entire burner head (gas-distributing device with an air channel) protrudes into the furnace: KR 101569455B1 published 2015-11-16, EP 1980788A1 published 2008-10-15, US 6071115A published 2000-06- 06, KR 1020170138042 published 2017-12-14, KR 101822997B1 published 2018-02-01, JP 6595089B2 published 2019-10-23, KR 102115576B1 published 2020-05-27, KR 10211430 published In this group of inventions, flue gas ejection is organized by gas nozzles with cylindrical nozzles located in the furnace along the outer perimeter of the burner air channel. The disadvantages of these inventions are the complexity of the design, the need to use special heat-resistant alloys of the burner part protruding into the furnace, and the impossibility of using them to reduce NOx emissions on existing burners installed in the combustion plant.

The main goal of the patented invention is to reduce NOx emissions from fuel gas combustion due to low-cost modernization of burners without changing the elements of the combustion plant furnace. The invention can be applied to the modernization of installed, operating burners in a fuel combustion plant. The solution of the problem is achieved by the fact that an additional peripheral channel of fuel gas is built into the burner, which removes the fuel gas to the area outside the air flow along the periphery of the loophole, while the gas-distributing tubes are installed without changing the elements of the furnace of the fuel-burning plant: the mouth of the burner, the loophole and the screen pipes of the furnace. Mixers can be installed on the gas nozzles to organize a controlled ejection quality. Due to the organization of intra-furnace recirculation of flue gases, by ejecting flue gases directly from the furnace with fuel gas jets flowing from nozzles located in the furnace outside the air flow, NOx is effectively suppressed as a result of a decrease in the temperature of the flame and the concentration of reacting substances.

In FIG. 1 shows a longitudinal section of a GMU-type burner with an integrated additional peripheral fuel gas channel (highlighted in red). Figure 2 shows a view from the furnace to the burners of the GMU type with a patented device (option) for reducing NOx emissions due to the organization of intra-furnace flue gas recirculation.

In a burner installed on a combustion plant or in a new burner, consisting of an air box 1, an outer air shell 2 and an inner air shell 3, a central fuel gas supply pipe 4 with a cone nozzle 5 with holes, inside the central fuel gas pipe there is a barrel for fuel oil fuel oil nozzle 6, an additional peripheral channel of fuel gas is built into the annular gap of the air channel between the outer air shell and the inner air shell. An additional peripheral fuel gas channel consists of a gas manifold 7, gas-distributing tubes 8 leading nozzles 9 into the furnace along the perimeter of the burner embrasure beyond the air flow 10. Around the embrasure there can be screen pipes of the fuel combustion plant 11.

A similar upgrade, with the installation of an additional peripheral channel of fuel gas, can be made with GMPV burners and with burners of another type.

As a result of the introduction of such a device, the fuel gas 12 flowing from the nozzles 9 ejects the flue gases 13, diluted with them, the new prepared fuel 14 reaches the air flow 10 and the combustion process occurs with lower temperatures and concentrations of reactants, which reduces the formation of NOx. A mixer 15 can be installed on the nozzles of the additional peripheral channel of the fuel gas, which ensures the mixing of the ejected flue gases and fuel gas and the formation of a diluted fuel jet.

The central gas channel 4 ensures the stability of fuel combustion. The diameter 16, on which the nozzles of the additional peripheral fuel gas channel are installed, is determined by the aerodynamic characteristics of the air flow and the pressure of the fuel gas.

The proposed way to reduce NOx emissions is as follows:

the burner is ignited in the central gas channel, gas is not supplied to the peripheral channel, after the power of the fuel-burning installation is increased above 20% and the furnace is heated to sufficient temperatures for stable ignition, fuel gas is supplied to the peripheral channel, then the burner power is increased by increasing the fuel consumption. gas through the peripheral channel with a constant or gradually decreasing fuel gas flow through the central channel. At maximum burner power, the fuel gas flow through the center channel may be 10% or less to ensure ignition stabilization. At intermediate loads, the ratio of fuel gas consumption between the peripheral and central channels depends on the design features of a particular furnace and is determined during the performance and commissioning tests.

The use of the proposed method for reducing NOx emissions provides a reduction in the NOx content in flue gases by 40-70% without reducing the technical and economic characteristics of the combustion plant and building an external flue gas recirculation system.

Claims (3)

1. A method for reducing emissions of nitrogen oxides using intra-furnace flue gas recirculation, which consists in the fact that in a burner containing an air box, outer and inner shells, a central pipe for supplying fuel gas with a cone nozzle at the outlet with holes, in which a barrel with oil nozzle, in the air channel between the outer and inner shells, peripheral gas-distributing tubes are additionally installed, coming out of the gas collector, and equipped with nozzles at the outlet, the nozzles of the gas-distributing tubes are brought into the furnace outside the air flow and placed along the perimeter of the embrasure, with jets of fuel gas flowing from nozzles, eject flue gases, the fuel gas is diluted with flue gases before mixing it with the air flow leaving the burner and igniting it. 2. A burner for reducing emissions of nitrogen oxides, containing an air box, outer and inner shells, a central pipe for supplying fuel gas with a cone nozzle at the outlet with holes, in which a barrel with an oil burner is placed, additionally installed in the air channel between the outer and inner shells peripheral gas-distributing tubes coming out of the gas manifold, and equipped with nozzles at the outlet; 3. The burner according to claim 2, in which mixers are installed on the gas nozzles.

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