RU2213907C1 - Method for stepwise burning of fuel in boiler with cooled combustion chambers and fire tubes - Google Patents

Abstract

FIELD: furnace equipment, applicable in heating, heat cumulative and steam power systems. SUBSTANCE: the method of stepwise burning of fuel in a boiler with cooled combustion chambers and fire tubes is perfected by its exothermic interaction with oxygen of the primary portion of air in the combustion chamber, final oxidation of the formed products of incomplete combustion by the jets of the secondary portion of air in the exhaust port of the combustion chamber and cooling of flue gases in the system of water-cooled fire tubes. The process of the exothermic reacting is accomplished in the fire tubes, and the air jets with oxygen for the process of the secondary thermal reactions are introduced tangentially to the circumference in the center of the inlet section of the system of fire tubes. EFFECT: enhanced efficiency of water heating and steam generation at a low exhaust of nitrogen oxides into the atmosphere. 5 dwg

Description

 The invention relates to a furnace technique and can be used in boilers with smoke tubes for highly efficient heating of water and steam production with a low exit to the atmosphere of nitrogen oxides.

 A known method of burning fuel in a boiler with a combustion chamber and cooling flue gases in smoke tubes (see book. K.F. Roddatis, E.I. Romm, N.A. Semenenko, etc. Boiler installations. T. 2. - M .-L.: Gosenergoizdat, 1946, p. 9-19, Fig. 5, 9). The heat of the fuel burned is transferred to the water in the chimneys to heat it. The disadvantage of this method is a large degree of underburning, heat loss and a significant release of nitrogen oxides into the atmosphere.

 There is a method of staged combustion of fuel in a boiler with a cooled combustion chamber by exothermic interaction with oxygen of a primary portion of air in a combustion chamber with cooled wall screens and subsequent oxidation of the resulting products of incomplete combustion with secondary air flows (journal "Electric stations", 11, 1991, Osintsev V.V., Dzhundubaev A.K., Gigin V.Ya., et al. Transfer of the BKZ-220 boiler to the technology of stepwise combustion of fuel. P. 17-22). The method provides a higher degree of fuel burnout and a reduction in heat loss and the concentration of nitrogen oxides in the exhaust products of combustion. However, it does not give effect on boilers with smoke tubes.

 There is a method of stepwise combustion of fuel in a boiler with a cooled combustion chamber by exothermic interaction with oxygen of a primary portion of air in the combustion chamber and subsequent reoxidation of the resulting combustion products with secondary air introduced by parallel jets in the form of an air curtain to the combustion products leaving the furnace through the exit window (see author USSR certificate 1627781, IPC R 23 C 11/01; published in BI 6, 1991). The air curtain when implementing the known method in the absence of a smoke section increases the efficiency of the combustion process. The disadvantage of this method is the high unevenness of the occurrence of secondary exothermic reactions in the cross section of the exit window, which leads to overheating and ruptures of smoke tubes, as well as high heat losses, underburning of fuel and the output of nitrogen oxides - is manifested when the smoke section is connected to the exit window of the combustion chamber.

 The objective of the present invention is to reduce the underburning, heat loss and the release of nitrogen oxides into the atmosphere with combustion products leaving the boiler with a cooled combustion chamber and smoke tubes.

 For this, during step-by-step burning of fuel in a boiler with a cooled combustion chamber and smoke pipes by exothermic interaction with oxygen of a primary portion of air in the combustion chamber, additional oxidation of the products of incomplete combustion with jets of a secondary portion of air in the exit window of the combustion chamber and cooling of flue gases in a water-cooled exhaust smoke system pipes, according to the invention, the secondary exothermic reaction is carried out in the exhaust smoke pipes, and air jets with oxygen for secondary reactions to occur, they are introduced tangentially to a circle in the center of the inlet section of the smoke pipe system.

 The tangential injection of secondary air jets ensures uniformity of the concentration field of the reacting system, uniformity of oxidation of incomplete combustion products and reduction of fuel underburning, and secondary reaction directly in cooled smoke tubes increases the efficiency of water heating, reduces heat loss and the concentration of nitrogen oxides in the exhaust products of combustion.

 Figure 1-5 presents the installation that implements the developed method of stepwise combustion of fuel. Figure 1 - diagram of a boiler with lateral exhaust gas through smoke tubes; figure 2 is a section aa in figure 1; figure 3 is a diagram of a boiler with a vertical exhaust gas through smoke tubes; figure 4 is a section bB in figure 3; figure 5 - section bb in figure 3.

 The installation in figures 1, 2 implements the proposed method when working on solid fuel: wood and coal, contains a combustion chamber 1 with water-cooled screens 2, a primary air supply system with nozzles 3 installed in the hearth of the chamber 1, a fuel input system 4, a system of tangential introduction of secondary air with nozzles 5, a water-cooled section 6 with smoke tubes 7. The outlet of gases cooled after section 6 into the atmosphere (or into the chimney) - through pipe 8.

 The method is implemented by introducing fuel (coal, firewood) through the device 4 to the blast grill with primary air nozzles 3 and supplying a primary portion of air under the same grill 3, which is sufficient only for partial oxidation with the formation of products of incomplete combustion. Based on the exothermic effects of the reagents, these products heat up and give part of their heat to the screens 2 through which water is supplied. Water heated in the combustion chamber is diverted to heat supply and heating systems for other needs. Ash through the grate 3 enters the ash pan, from where it is periodically removed during the operation of the boiler. The products of incomplete combustion, cooled in chamber 1, are directed to the entrance to the smoke tubes 7 (to the exit window 9 of chamber 1, where section 6 is connected), a secondary portion of air is introduced there through tangential nozzles 5. Air jets through nozzles 5 are introduced tangentially to circle 11 in the center of the inlet section 12 of the system 6 of the smoke pipes 7, which coincides with the exit window 9 of the chamber 1. In the smoke pipes 7, the combustion and heat transfer from gases to water continue. Flue gases from the pipes 7 fall into the collection pipe 8, from where to the chimney (not shown) or directly to the atmosphere through the after-treatment system (not shown). The water heated in section 6 is directed to production or heating needs. The tangential introduction of air jets through nozzles 5 provides a high degree of mixing of products of incomplete combustion and an oxidizing agent, the most complete and deep course of secondary exothermic reactions, and the simultaneous cooling of the reagents allows to reduce heat loss with the exhaust products of combustion. The stepwise combustion of the fuel and cooling of the combustion products achieves a low-temperature course of the combustion process and slows down the oxidation of nitrogen and air with a reduced output of the concentration of nitrogen oxides into the atmosphere.

 Figure 3, 4, 5 shows a diagram of an installation for implementing the method for the combustion of natural gas and the vertical exhaust of flue gases. The same notation is introduced here as in FIG. 1, 2. Gas through the fuel supply system 4 (perforated manifolds) is introduced into the chamber 1, and primary air is supplied there through the supply system with nozzles 3. Section 6 with pipes 7 is installed vertically, its inlet section 12 is aligned with the exit window of the chamber 1.

 The implementation of the method in the installation of figure 3, 4, 5 is similar to the above description for the installation of figure 1, 2.

 The ratio of primary and secondary air flow rates, circumference 11, inclination angles, sizes and installation location in nozzle window 9 of nozzle 5 can be further optimized by the parameters of the ongoing processes and the final result (heat loss, concentration of nitrogen oxides, degree of fuel burnout) during commissioning.

 The shape of the chamber 1 and section 6 with pipes 7 may be round (not shown in the explanatory drawings). As the fuel system 4, nozzles for introducing liquid atomized fuel, plates for droplet evaporation, and other devices can be used.

 The method can be used in boilers of energy companies, metallurgy energy systems, construction enterprises.

Claims (1)

 A method of stepwise combustion of fuel in a boiler with a cooled combustion chamber and smoke tubes by exothermally interacting with oxygen of a primary portion of air in a combustion chamber, further oxidizing the resulting products of incomplete combustion with jets of a secondary portion of air in the exit window of a combustion chamber and cooling flue gases in an air-cooled exhaust pipe system characterized in that the process of secondary exothermic reaction is carried out in smoke tubes, and air jets with oxygen m for the secondary reactions to be introduced tangentially to a circle in the center of the inlet section of the smoke pipe system.

Images