RU2200278C2 - Method and system for pre-combustion fuel pulverizing - Google Patents

Abstract

FIELD: solid-fuel burning boiler units of power stations; heating steam and hot-water boilers. SUBSTANCE: method includes pre-crushing of solid fuel to particle size of below 5 mm followed by its pulverizing and conveying pulverized fuel in a gas flow to burners. Pulverization is made in oxidizing medium by dry mechanical destruction in the field of centrifugal forces to particle size of 6-15 mcm due to interaction with blades disposed on concentrically mounted disks rotating in opposite directions; prior to fuel combustion steam is injected in dust-gas flow in the amount of 1.0-3.0 mass percent. Fuel pulverizing system has bin, mill, fan whose inlet pipe is joined with air inlet and/or furnace-gas outlet pipeline, and burners communicating through dust line with mill. In addition system has jet-type rotary mill incorporating several concentrically mounted rotors made in the form of disks with blades forming nozzle channels and rotating in opposite directions. Burners are also connected to steam pipeline. Proposed system provides for pulverizing solid fuel to fractional composition optimal for combustion process at minimal cost. EFFECT: simplified design, enhanced efficiency of pulverized-fuel combustion and reliability of system. 3 cl, 1 dwg

Description

 The invention relates to the field of energy and can be used both in boiler plants of power plants running on solid fuel, and in heating steam and hot water boilers.

 The prior art method for the preparation of pulverized fuel for combustion by grinding crushed pieces of solid fuel-coal to particles smaller than 300 microns, separating particles larger than 50 microns and transporting the resulting dust with a gas stream to the burners (SU 150 100 A, F 23 K 1/02 , 1962; M. A. Styrikovich, K.Ya. Katkovskaya, E.P. Serov, Steam generators of power plants, M-L., "Energy", 1966, pp. 54-57, 67-68).

 The main disadvantage of the fuel prepared in this way is the significant heat loss during combustion due to incomplete combustion due to the uneven fractional composition of dust and the relatively large particle size.

 There is also known a method of preparing pulverized fuel for combustion, which includes the preliminary grinding of solid fuel to particles smaller than 6 mm, followed by fine grinding to a size less than 20 microns (RU 1796663 C1, C 10 L 1/32, 1989; SU 1530099 A1, C 10 L 1/32, 1984). In this case, fine grinding is carried out in the presence of water in a hydraulic dispersant, which leads to the formation of water-coal fuel, the combustion of which produces exhaust gases with high humidity, which have increased aggressiveness, which sharply reduces the reliability of the tail surfaces of the heating, increases the metal corrosion of various structural elements of the boiler plant generally.

 A known system for the preparation of pulverized fuel containing a hopper, mill, fan, the inlet of which is connected to the air supply pipe and / or flue gas selection, and a burner connected by a dust pipe to the mill (SU 1250782 A1, F 23 K 1/00, 1986; M .A. Styrikovich, K.Ya. Katkovskaya, EP Serov, Steam generators of power plants, M-L., "Energy", 1966, p. 66).

 In such a fairly simple scheme with direct dust injection, the mill productivity determines the boiler load, and the efficiency of the latter, especially in variable modes, largely depends on the fineness of coal dust grinding and the uniformity of the fractional composition.

 However, with a single-stage grinding using well-known designs of mid-stroke mills and grinding fans, it is difficult to obtain the parameters of solid particles of fuel that are optimal for the combustion process, which makes this dust preparation system economically impractical.

 The invention is aimed at increasing the efficiency of combustion of pulverized fuel and the creation of a simple and reliable in operation system for the preparation of pulverized fuel, which provides optimal fractional composition of solid fuel particles for the combustion process with minimal cost.

 The solution to this problem is ensured by the fact that in the method of preparing pulverized fuel for combustion, comprising pre-grinding solid fuel to particles less than 3 ÷ 5 mm in size, followed by fine grinding and transporting dust by gas flow to the burners, according to the invention, fine grinding is carried out in an oxidizing medium by dry mechanical destruction in the field of centrifugal forces to particles with a size of 6 ÷ 15 microns due to interaction with the blades located on concentrically mounted disks, to which rotate in opposite directions, while in the dust and gas stream before burning water vapor is introduced in an amount of 1.0 ÷ 3.0 wt.%.

 Moreover, the pulverized fuel preparation system comprising a hopper, a mill, a fan, the inlet of which is connected to the air supply and / or flue gas extraction pipe, and the burners connected by the dust pipe to the mill, according to the invention further comprises a jet rotary mill included in the dust pipe in front of the burners , consisting of several concentrically mounted rotors, made in the form of disks with blades forming nozzle channels that rotate in opposite directions.

 In addition, the burners are additionally connected to the water vapor pipeline.

 The presence of a jet-rotor mill provides a mechanically activated finely dispersed fraction (phase) with a particle size of 6 to 15 μm, saturated with chemically bound oxygen, which is transported directly to the burners in the gas stream, which, when introduced, 1.0 ÷ 3.0 wt.% water vapor allows to obtain a pulverized fuel with high energy properties, which, with the optimal organization of the combustion process in the furnace, can provide the most economically high heat generation with maximum heat utilization combustion with a minimum level of harmful emissions into the environment.

 The drawing shows a diagram of a system for the preparation of pulverized fuel.

 The pulverized fuel preparation system comprises a hopper 1, a coal feeder 2, a mill 3 with a separator 4, a jet rotor mill 5, which is connected by a dust pipe 6 to a burner 7, and a fan 8, to the inlet of which is connected an air supply pipe 9 and a flue gas extraction pipe 10 from the boiler 11. The jet-rotor mill 5 consists of a set of concentrically mounted rotors 12, 13, 14, made in the form of disks with blades 15, forming nozzle channels 16 that rotate in opposite directions.

 Burners 7 for burning pulverized fuel are provided with a pipe 17 for supplying water vapor and a pipe 18 for secondary air.

 The claimed method for the preparation of pulverized fuel can be used for individual maintenance of the boiler 11 with direct injection and is implemented as follows.

 Lump fuel from the hopper 1 is fed to a coal feeder 2, by means of which the amount of coal supplied to the mill 3 is regulated, where drying occurs, which is provided by a mixture of hot air and flue gases pumped by fan 8, and the solid fuel is milled. Dust particles less than 5 mm in size, separated in the separator 4, are transported by gas flow to the jet-rotor mill 5, where in the field of centrifugal forces as a result of the acceleration of the gas suspension jets formed in the nozzle channels 14 of the rotors 12, 13, 14, rotating in different directions, and multiple collisions with blades 15 — targets of the rotor next in the direction of gas suspension, which have opposite directions of rotation (vectors of peripheral velocities), dry mechanical destruction processes occur in the oxidizing medium created by the incoming d into the grinding chamber of the jet-rotor mill 5 with a mixture of air and flue gases, providing fine grinding of dust particles to a size of 6-15 microns, which are accompanied by processes of mechanical activation with oxygen binding (oxidation).

 From a jet-rotor mill 5, pulverized fuel having an almost uniform fractional composition of solid particles with a high content of chemically bound oxygen is transported in the form of a gas suspension directly to the burners 7 of boiler 11, where 1.0 ÷ 3.0 wt.% Water is introduced into the dust and gas stream steam, which significantly intensifies the ignition process, ensures the completeness of combustion of solid particles of fuel in the furnace 19, reduces the amount of harmful emissions from combustion products into the environment.

Claims (3)

 1. A method of preparing pulverized fuel for combustion, comprising pre-grinding solid fuel to particles less than 5 mm in size, followed by fine grinding and transporting dust by gas flow to the burners, characterized in that fine grinding is carried out in an oxidizing medium by dry mechanical destruction in a centrifugal force field to particles of size 6.. . 15 μm due to the interaction with the blades located on concentric mounted discs that rotate in opposite directions, while in the dust and gas stream before burning water vapor is introduced in an amount of 1.0. . . 3.0 wt. %  2. A pulverized fuel preparation system comprising a hopper, a mill, a fan, the inlet of which is connected to an air supply and / or flue gas extraction pipe, and a burner connected by a dust pipe to a mill, characterized in that it further comprises a jet stream included in the dust pipe in front of the burners a rotary mill, consisting of several concentrically mounted rotors made in the form of disks with blades forming nozzle channels that rotate in opposite directions.  3. The system according to claim 2, characterized in that the burners are additionally connected to the water vapor pipeline.