WO2015108448A1

WO2015108448A1 - Method for preparing and combusting coal fuel

Info

Publication number: WO2015108448A1
Application number: PCT/RU2015/000008
Authority: WO
Inventors: Александр Юрьевич БУЙДОВ
Original assignee: Общество с ограниченной ответственностью "ТОХИЛ"
Priority date: 2014-01-20
Filing date: 2015-01-15
Publication date: 2015-07-23
Also published as: RU2548706C1

Abstract

The group of inventions relates to thermal power engineering and pertains to technology for the transport of, and the separate and combined combustion of mechanically activated micro-ground coal and standard dust-preparation system coal in a vortex ignition burner while igniting a coal-dust boiler and stabilizing combustion, with the aim of replacing expensive mazut or natural gas. The technical result consists in using a simpler, more reliable and economically-viable technological process for igniting a coal-dust boiler and stabilizing the combustion therein of coal fuel, and is achieved in that, in a method for preparing and combusting coal fuel, when igniting the coal-dust boiler, the grinding and mechanical activation of the coal is carried out inside a disintegrator chamber, producing micro-ground coal, which is then transported into the vortex ignition burner and undergoes intensive mixing with secondary air, producing a dust-air mixture, the ignition and subsequent combustion of which is carried out, during the ignition of the coal-dust boiler, directly in the combustion space of the coal-dust boiler.

Description

METHOD FOR PREPARING AND BURNING COAL FUEL

The group of inventions relates to a power system and relates to a technology for the production, transportation, separate and combined burning of mechanically activated coal micropolines (hereinafter, coal microfinels) and coal from a regular pulverization 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, the increased excess of oxidizing agents and the significant range of fuel consumption changes predetermined the use of highly reactive fuel, for example, heavy fuel oil or natural gas, as kindling fuel. However, due to rising prices for liquid and gaseous fuels and, consequently, increased costs for kindling a pulverized coal 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 N ° 2460941, F23D1 / 02, published 02/11/2011) method for co-firing of micropomol coal (average dust fraction of 50 μm) and conventional coal in a pulverized coal burner, including the intensification of the combustion process due to the use of a local heat-insulated chamber in the burner.

The disadvantages of the known method include the use of a complex two-stage scheme for coal fuel compression, in which the tangential input of coal fuel is 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 Ns 2419033, published 01/20/2011, F23K 1/00) method for the mechanical activation (hereinafter mechanical activation) of micropomol coal 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, micromoling operations and mechanical activation carried out simultaneously inside the chamber of the disintegrator, and the obtained 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 reliable and cost-effective technological process of 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 intensive mixing with secondary air to obtain a dust-forming mixture, the ignition and subsequent combustion of which during the pulverized-coal kindling 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 micromilling is carried out using a standard ignition device installed in the furnace volume 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 for

coal micromilling (first embodiment of the invention) with the gradual addition (second embodiment of the invention) to it conventionally ground coal. 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 option) occurs directly in the furnace volume of a coal-fired 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. Secondary air is supplied through the annular ducts 2 and 3, to regulate the flow rate of which the sliders 5 are installed at the inlets of the annular ducts 2 and 3. Inside the annular duct 2, twisting devices 6 are installed in its axial region to form a closed zone for recirculation of high-temperature combustion products.

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, coal supply the micron grinding in the central channel 1 stops and the burning of coal of ordinary grinding 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 of the 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 stability of ignition 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

F O R M U L A

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 the volume of the pulverized coal boiler, and after the completion of the stage of kindling, the supply of coal microfiner to the kindling burner is stopped.

3. The method according to p. 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.