RU2174649C2 - Pulverized-coal lighting-up burner and method of its operation - Google Patents

Abstract

FIELD: boilers and furnaces. SUBSTANCE: invention is designed for lighting-up and stabilization of flame at combustion of solid fuels in boilers and furnaces. Proposed lighting-up pulverized-coal burner body with radiating setting, coaxial pulverized coal-air mixture feed branch pipe whose mouth is made slotted, two auxiliary liquid-fuel or gas burners installed symmetrically relative to longitudinal axis of slotted mouth of pulverized coal-air mixture feed branch pipe. EFFECT: reduced consumption of expansive lighting-up gaseous or liquid fuel, speeding up lighting, simplified design of burner. 3 cl, 2 dwg

Description

 The invention relates to a power system and can be used in thermal power plants, in boiler houses and in the furnace industry of enterprises when burning pulverized solid fuel.

 Currently, liquid fuel (fuel oil) or gas is mainly used for kindling solid fuel boilers.

 In Russia and abroad, several designs and methods for the operation of kindling pulverized coal burners have been developed in order to completely or partially replace scarce liquid fuel during kindling.

 They are based on the principle of partial gasification of coal dust, which allows to obtain a flammable gas-air mixture. For gasification, a preliminary heating of the dusty air flow is necessary. Different designs of kindle pulverized-coal burners differ in the way of preliminary heating.

 A kindling pulverized coal burner with the supply of dust-air mixture along the axis of the burner, equipped with an electric heater for igniting the fuel mixture, is shown in patent N 12743 (USSR). In the housing of this kindling pulverized coal burner along its axis, three shells are additionally installed with radial clearances, in which solid fuel is burned in stages.

 In the application of the United Kingdom N 1585943 the ignition system of pulverized coal with electric arc heating. Part of the air is heated in a separate device by an electric arc discharge and fed into the combustion chamber in the form of a high-temperature jet for ignition of pulverized coal transported by an air stream. The position of the arc is controlled by the magnetic field generated by the coil. The coal entering the combustion chamber is distributed axially by a movable device, additional air is supplied through control blades.

 In the kindling pulverized coal burners developed in the GDR (patent 156544 and the patent 238176), coal dust is transported to the kindling burners by a vapor-air mixture. During transportation, coal dust, mixed with a vapor-air mixture having a higher temperature, is preheated, which contributes to the stable ignition of the fuel mixture in the kindling burner. To ensure stable ignition and combustion of coal dust in the burner, a fuel oil nozzle or gas ignition burner is used. Part of the air necessary for the complete combustion of coal dust (secondary air) is supplied directly to the burner tunnel (muffle). When using steam for transportation and heating of coal dust, and also when secondary air is supplied to the burner, reliable stable ignition and combustion of the fuel mixture are possible under conditions of using very dry and fine grinding of dust with a sufficiently powerful ignition nozzle.

 Known pulverized coal burner (application N 2165633, UK), designed for the combined combustion of liquid or gaseous fuels and coal dust. In this burner, the consumption of liquid (or gaseous) fuel is up to half of the total fuel consumption. This burner is designed primarily for continuous operation on combination fuel.

 In another known kindling pulverized coal burner (patent No. 4614492, USA), coal dust is supplied tangentially to the inner surface of the cylindrical part of the burner body. The liquid fuel nozzle is located along the axis of the burner in the center of its rear wall. Secondary air is supplied to the combustion zone of the primary dust-air mixture. The design of the burner is such that the bulk of the fuel burns out in the burner itself, and hot flue gases and a small portion of unburned coal dust enter the firebox. In such kindling burners, the temperature of the medium may exceed the melting temperature of the ash, which will lead to slagging of the inner surface of the burner. And this reduces the reliability of the burner.

 The above constructions and methods of operation of the kindling burners are rather cumbersome and complex, require increased attention during kindling and operation, additional types of energy (electricity, steam of increased parameters), and a significant consumption of liquid or gaseous fuel.

 The closest in design and method of operation to the proposed kindling pulverized coal burner according to patent N 4466363 (USA). Ignition of coal dust is carried out by a pilot with gaseous or liquid fuel in an auxiliary burner, which is the internal pipe of the burner. After the coal dust steadily ignites in the auxiliary burner, the coal dust begins to be fed into the main ring torch burner external to the inner one. Secondary air is supplied along the periphery of the burner at its outlet neck.

 The disadvantage of this method and design of the burner is the difficulty of regulating the flow rates of primary and secondary air, the relative time lag of the burner kindling process due to the sequential ignition of the internal auxiliary burner first and then the external main one, which increases the fuel consumption for kindling, the complexity and bulky design slagging and burning of a large number of steel cylindrical shells, as well as significant erosive wear of the burner elements. In the event of a torch break for any reason, it is necessary to repeat all operations for igniting the burner, starting from the supply of liquid or gaseous fuel. And this will increase the cost of expensive fuel.

 The proposed kindling pulverized coal burner allows you to speed up the start of the process of gasification of solid fuel, speed up the kindling process in this regard, and get a steady kindling torch. At the same time, the design of the kindling burner is much simplified, and the reliability and safety of the burner are increased.

 This problem is solved by accelerated intensive partial preliminary gasification of coal dust in a kindling pulverized coal burner, followed by the main combustion of the fuel mixture at the outlet of the burner. The preliminary partial gasification of coal dust compensates for the decrease in the reactivity of the fuel during the transition from kindling with liquid fuel (fuel oil) or gas to the kindling of the boiler with coal.

 The proposed design of a kindling pulverized coal burner is shown in the drawing. A kindling pulverized coal burner consists of the following elements: housing 1 with a refractory radiating lining 2 (tunnel, muffle); coaxial wiring of the supply pipe of the dust-air mixture 3 with a slotted mouth 4; two identical auxiliary liquid fuel or gas burners 5 placed symmetrically with respect to the longitudinal axis of the slotted mouth of the nozzle; supplying part of the secondary air 6; supply of the main part of the secondary air 7; radiating lining of the furnace 8.

The kindling is carried out as follows. Two auxiliary liquid-fuel or gas burners are ignited 5. Then through the nozzle 3 a dusty air mixture (coal dust with primary air) is supplied, which, leaving the slotted mouth 4, takes the form of a flat jet, elongated vertically. The jet has a developed lateral surface and at the initial moment (before heating the lining) it senses the heat of the flames (torch temperature of at least 1400 ^o C) of auxiliary liquid or gas burners simultaneously from both planes by radiation, which allows for the rapid heating of pulverized fuel.

 Heated coal dust begins to gasify intensively (there is a process of steady pyrolysis); the gas resulting from pyrolysis burns, additionally heating coal dust, which contributes to further gasification. Due to the intense heating and gasification, the pulverized fuel is ignited by torches from auxiliary liquid fuel or gas burners inside the housing.

 For faster heating of dust and its subsequent gasification, the dust concentration during operation of a kindling pulverized coal burner should be taken increased (by reducing the amount of primary air), and within 20-50 kg of fuel per kg of air. At the same time, large concentrations refer to poorly flammable coals with a low yield of volatile substances. This will reduce the heat consumption from the flames of auxiliary liquid fuel or gas burners for heating the air transporting coal dust (spurious, in terms of heat consumption for the gasification of coal particles), but will increase the amount of heat used to heat the coal particles.

 After warming up the lining 2, auxiliary oil or gas burners are switched off: further gasification, heating and ignition of the pulverized fuel will occur due to the radiation of the walls of the lining, the heating of which, in turn, will be supported by the partial combustion of coal dust inside the tunnel.

 With a stable pulverized-coal jet plume, a small part of the secondary air is supplied through a pipe 6, and the rest - through a supply 7.

 The afterburning of all coal dust occurs at the outlet of the stream from the burner to the furnace when it is mixed with secondary air and the air available in the furnace chamber.

 If there is a source of hot air near the source (for example, from other boilers), the tunnel can be warmed up by supplying this air through inlet 6 before ignition of the ignition burners.

 In the case of a short-term extinction of the torch for any reason, for example, a short-term interruption in the supply of coal dust, the subsequent ignition of the pulverized-coal jet will occur due to radiation from the walls of the lining, which has a significant reserve of thermal energy.

 The proposed kindling coal-dust burner can be used both for ignition and stabilization of combustion (torch support) of the main burners in boiler furnaces when burning any solid fuels, including low-reaction and ballasted coal in thermal power plants, in industrial and domestic boiler houses, in furnace industry enterprises.

Claims (3)

 1. A kindling pulverized coal burner containing a housing with a lining, a coaxial nozzle for supplying a dusty air mixture, an auxiliary oil or gas burner, characterized in that another auxiliary oil or gas burner is installed, the mouth of the nozzle for supplying a dusty air mixture is slotted, while the auxiliary liquid fuel or gas the burners are placed symmetrically with respect to the longitudinal axis of the slotted mouth of the dust-air mixture supply pipe, and the lining is made emitting.  2. The method of operation of a kindling pulverized coal burner by pre-heating the flow of pulverized fuel with its subsequent gasification, ignition from the torch of an auxiliary liquid fuel or gas burner inside the housing with lining and burning, characterized in that the pulverized fuel is supplied in the form of a flat jet, elongated vertically, and heated from both planes with torches of auxiliary liquid fuel or gas burners at the initial moment (before heating of the lining), after heating of the lining of auxiliary liquid fuels Some gas or gas burners are switched off and the jet of pulverized fuel is heated from the radiating lining.  3. The method according to claim 2, characterized in that the pulverized fuel is supplied with a high concentration (within 20-50 kg of fuel per 1 kg of air).