RU2548706C1 - Method for preparation and combustion of coal fuel at lighting-up of pulverised-coal fired boiler (versions) - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: coal crushing and mechanical activation is performed inside a disintegrator chamber so that fine coal is obtained, which is then conveyed to a vortex start-up burner, where it is intensely mixed with secondary air so that a PC/air mixture is obtained, further ignition of which and its further combustion together with regular grind coal at lighting-up of a pulverised-coal fired boiler is performed directly in furnace volume of the PC fired boiler, and after the lighting-up stage is completed, fine coal supply to the start-up burner is stopped.

EFFECT: use of a simpler, more reliable and cost-effective technological process of lighting-up of a PC fired boiler and stabilisation of coal combustion in it.

3 cl, 1 dwg

Description

The group of inventions relates to a power system and relates to a technology for producing, transporting, separately and co-burning mechanically activated coal microprites (hereinafter, coal micropomol) and coal from a regular dust preparation system (hereinafter, conventional grinding coal) in a vortex kindling burner (hereinafter, kindling burner) during kindling boiler and stabilization of combustion in order to replace expensive fuel oil or natural gas.

The unfavorable conditions for burning coal fuel during the kindling of a pulverized coal boiler and the functioning of the kindling devices, including the low level of air and furnace temperatures, increased oxidizer excesses, and a significant range of fuel consumption changes determined the use of highly reactive fuel, for example, heavy fuel oil or natural gas, as a kind of kindling fuel. However, due to rising prices for liquid and gaseous fuels and, consequently, increasing costs for kindling a coal-fired boiler, the task of replacing this fuel with coal dust is becoming increasingly important. This task is determined by the way to increase the reaction properties of coal fuel to acceptable values, allowing it to be used in adverse conditions of kindling.

At present, coal-fired thermal power plants in Russia have technologies for kindling coal-fired boilers without using liquid fuel. They imply the use of special burner devices in which high-temperature conditions are created in local heat-insulated chambers for igniting coal of the usual grinding of the existing standard dust preparation system. This process of increasing the reaction properties of coal fuel is provided by its thermal activation, which requires the presence of a high-enthalpy energy source inside the burner device, for example, a plasma torch.

There is a known (RF patent No. 2460941, F23D 1/02, published 02/11/2011) method for co-burning micro-grinding coal (average dust fraction of 50 μm) and conventional coal in a pulverized-coal burner, including the intensification of the combustion process by using a local heat-insulated chamber in the burner.

The disadvantages of this method include the use of a complex two-stage scheme for burning coal fuel, in which the tangential input of coal fuel is used as a micronizing mill, conventional grinding, secondary and tertiary air into four coaxial channels. This determines the bulkiness of the coal burner, which complicates its operation and maintenance. In addition, the process of burning coal fuel inside a thermally insulated chamber of a coal-dust burner is uncontrolled due to the inability to install a flame control sensor in the known construction.

There is a known (patent RU No. 2419033, published 01/20/2011, F23K 1/00) method of mechanical activation (hereinafter mechanical activation) of coal microfine before burning. The specified method includes micromilling, mechanical activation (a decrease in the activation energy of a substance under the action of mechanical forces during grinding) and the combustion of micropromic coal. Moreover, micromilling operations and mechanical activation are carried out simultaneously inside the disintegrator chamber, and the resulting solid coal solution is subjected to thermal shock for ignition purposes.

The reasons that impede the achievement of the following technical result when using the known method include:

a) partial burnout of the heat-insulated chamber of the kindling burner during ignition and combustion of fuel inside it;

b) the use of expensive alloys in the structural elements of the mill - disintegrator, the fragility of which (elements) entails high operating costs;

c) the use of special additional equipment: a high-enthalpy source (plasmatron or gas burner), necessary to ignite the fuel and maintain the necessary temperature in the heat-insulated chamber of the burner device.

The objective of this group of inventions is to improve the technology of kindling coal-fired boilers by burning solid fuel with its preliminary activation.

A single technical result achieved by carrying out the invention for each of the claimed options is to use a simpler, more reliable and cost-effective technological process for kindling a pulverized coal boiler and stabilizing the combustion of coal fuel in it.

The specified single technical result for the first of the claimed variants of the invention is achieved due to the fact that in the method of preparing and burning coal fuel during the kindling of a pulverized coal boiler, the grinding and mechanical activation of coal is carried out inside the chamber of the disintegrator to produce coal micron grinding, which is then transported to a vortex kindling burner, where its intensive mixing with secondary air to obtain a dusty air mixture, the ignition and subsequent combustion of which upon kindling of pulverized coal the boiler is carried out directly in the furnace volume of the pulverized coal boiler.

The specified single technical result for the second of the claimed variants of the invention is achieved due to the fact that in the method of preparing and burning coal fuel during the kindling of a pulverized coal boiler, the grinding and mechanical activation of coal is carried out inside the chamber of the disintegrator to produce coal micron grinding, which is then transported to a vortex kindling burner, where its intensive mixing with secondary air to obtain a dusty air mixture, the further ignition of which and its subsequent combustion together with the usual grinding mantle during the kindling of the pulverized coal boiler is carried out directly in the furnace volume of the pulverized coal boiler, and after the completion of the stage of kindling, the supply of micronomic coal to the kindling burner is stopped.

In the inventive method, coal micromilling with increased reactivity and a reduced level of activation energy is obtained from pre-dried raw materials, which usually passes through the grinding and mechanical activation stages inside the disintegrator chamber.

Ignition of a dusty-air mixture of coal micronomics is carried out using a standard ignition device installed in the furnace chamber of the pulverized coal boiler, which is usually used as a fuel oil nozzle. After stable ignition of the dust-air mixture of coal, the micro-grinding ignition device is turned off. Subsequently, the kindling of the pulverized-coal boiler continues at the angle of the micron grinder (the first embodiment of the invention) with the gradual addition (the second embodiment of the invention) of conventional grinding coal to it. Upon reaching the nominal operating mode of the pulverized coal boiler (completion of the kindling stage) according to the second of the claimed embodiments of the invention, the supply of micro-grinding coal to the ignition burner is stopped, and thus only conventional grinding coal is burned in the pulverized-coal boiler.

Ignition and combustion of a dusty air mixture of coal micron grinding (during kindling and in nominal mode according to the first embodiment) or a dusty-air mixture of coal micronizing with coal of ordinary grinding (during kindling and in nominal mode according to the second embodiment) occurs directly in the furnace volume of a coal-dust boiler. The process of ignition and combustion of coal fuel is monitored using a torch control sensor directed to the torch root of a kindling burner.

To clarify the essence of the claimed invention, a drawing is shown, which shows a specific, but not the only possible design of a vortex kindling burner, with which the claimed method can be carried out according to any of the claimed options to achieve the above single technical result.

The kindling burner consists of a central cylindrical 1 and two annular channels 2 and 3, the axes of which coincide with the axis of the burner.

The Central cylindrical channel 1 is designed to enter the dusty air mixture of coal micron grinding coming from the mixer mill-disintegrator.

A dust pipe 4, coaxial with the channel, is built into the central channel 1, through which a dusty air mixture of coal of ordinary grinding is supplied, which is, as a rule, the main fuel for a coal-fired boiler.

Through the annular channels 2 and 3, secondary air is supplied, to regulate the flow of which at the inputs of the annular channels 2 and 3, the sliders 5 are installed.

Inside the annular channel 2 in order to form a closed zone for recirculation of high-temperature combustion products, twisting devices 6 are installed in its axial region.

The implementation of the inventive method according to the second of the claimed options using this design of the burner is as follows.

At the beginning of the process, secondary air is supplied through the annular channels 2 and 3. Conventional coal is not supplied from the existing pulverization system. The micromolt coal coming through the central cylindrical channel 1, after mixing with secondary air, is ignited using a kindling fuel oil nozzle. After ignition, the supply of fuel oil is stopped and the feed of coal microfinish increases to the nominal capacity of the mill-disintegrator and the kindling burner. In the future, they continue to kindle a coal-fired boiler based on a micron grinding coal with the gradual addition of conventional grinding coal through a dust pipe 4.

When the pulverized coal boiler enters the nominal mode, the supply of coal micro-grinding through the central channel 1 is stopped and the combustion of conventional grinding coal continues.

The stability of ignition and stabilization of combustion of coal fuel during operation of the kindling burner of the proposed design is based on the formation of a fixed front, which is formed at the interface between counter-directed media: the primary mixture (dusty air mixture of a micromolder) from the central cylindrical channel of the kindling burner and high-temperature combustion products of this mixture in the return zone flow (mixing zone) formed in the axial region of the kindling burner near its edge at the boundary with the top a coal-fired boiler. In the front, due to intensive mixing of the primary pulverized coal mixture with secondary air, an increase in the temperature of the pulverized coal mixture, heating of the coal dust particles, exit and combustion of the volatile components of the fuel, as well as the ignition of small coke particles. The intensity of this process depends on the characteristics of coal (kinetic constants, grain characteristics of dust), the temperature level of the recirculation gases and the amount of secondary air entering the mixing zone. A further combustion process takes place in the boundary layer of the mixing zone, formed from the medium coming from the combustion front, secondary air, and ejected combustion products. The intensity of this process, as well as the location of the reversal of the recycle stream of high-temperature combustion products, in turn, determine the temperature level of the gases supplied to the combustion front, and hence the ignition stability of the dusty air mixture.

The stabilization of combustion also depends on a number of the following factors: the return flow zone, the fuel / air ratio, the ratio of the velocities of the dusty air-coal mixture and air, the specific surface area of the coal dust, micron grinding, and the activation energy of coal dust.

Claims (3)

1. The method of preparation and combustion of coal fuel during kindling of a coal-fired boiler, characterized in that the grinding and mechanical activation of the coal is carried out inside the chamber of the disintegrator to produce coal micropolite, which is then transported to a vortex kindling burner, where it is intensively mixed with secondary air to obtain a dust-air mixture the ignition and subsequent combustion of which during the kindling of a pulverized coal boiler is carried out directly in the furnace volume of the pulverized coal boiler. 2. A method of preparing and burning coal fuel during the kindling of a pulverized coal boiler, characterized in that the grinding and mechanical activation of the coal is carried out inside the chamber of the disintegrator to produce coal microfinish, which is then transported to a vortex kindling burner, where it is intensively mixed with secondary air to obtain a dusty air mixture further ignition of which and its subsequent combustion together with conventional coal during the kindling of a pulverized coal boiler is carried out directly in the furnace SG screen pulverized coal boiler, and after completion of the step feeding microgrinding kindling coal in the ignition burner is stopped. 3. The method according to claim 2, characterized in that in order to stabilize the combustion of coal fuel in the furnace volume of the pulverized coal boiler, microfine coal is fed to the kindling burner.