RU2217658C1 - Method of combustion in boiling bed - Google Patents

Abstract

FIELD: industrial boilers, particularly for combustion of particulate solid fuel and combustible waste. SUBSTANCE: method involves feeding of primary blast air and following introducing of secondary blast air into over-bead volume from blowing-up zones towards stagnation zones in tangential direction to simulated body of rotation. Blowing-up zones and stagnation zones located under blowing-up zones in over-bead volume profile are formed by lining and/or furnace shields. Part of secondary blast air is supplied separately and/or together with fuel and entrained matter, entrapped beyond furnace. EFFECT: increased effectiveness of fuel combustion process and blast air usage. 2 cl, 1 dwg

Description

The invention relates to a power system and can be used in industrial and energy boilers burning solid fuel and combustible waste.

A known method of combustion in a fluidized bed [1, Ch. 5.5] with the filing of the primary blast and the subsequent introduction of the secondary blast, trapping and afterburning of the entrained particles of the fluidized bed in a cyclone and their return to the fluidized bed. Today it is the most efficient and environmentally friendly, the so-called method of burning in a circulating fluidized bed, has several modifications [1], for example, according to the Alstrem scheme [1, Fig. 5.36, p. 240]. The disadvantages of this method are the expensive design of the high-temperature cyclone, poor mixing and low efficiency of using secondary blast in the superlayer volume of the furnace. Combustion processes are completed only in the cyclone.

Of the known technical solutions, the closest in technical essence to the claimed method, selected as a prototype, is a method of burning in a fluidized bed [2], with the primary blast being fed under the layer and the second blast being introduced from opposite sides tangentially to the conditional body of revolution in the superlayer volume fireboxes. The vortex flow in the form of a conditional body of revolution creates mixing and increases the efficiency of using secondary blast in the superlayer volume of the furnace.

The disadvantages of the prototype is the need to supply in the form of a secondary blast of most of the air, since to change the nature of the flow, heavily loaded with the carried particles of the stream from the fluidized bed, a much larger pulse of the secondary blast is required than with conventional layered or pulverized coal combustion. The supply of most of the blast in the form of a secondary one will cause a violation of the air balance and, accordingly, reduce the efficiency of the combustion process, including due to large losses with flue gases. On the other hand, maintaining air balance (for furnaces with a circulating layer, the proportion of primary blast is usually [1] about 50% or more, and for a bubbling fluidized bed more than 70%) due to an increase in the density of the upward flow due to entrained particles by 2– 10 times [1] will not allow you to organize a vortex motion and effective mixing in the superlayer volume. In addition, for a symmetric expanding channel according to the scheme proposed in the prototype [2], it is typical [3, p. 602, Fig. 22.4. ] the flow that flows from one wall to another. Accordingly, the operation of such a furnace will be characterized by the presence of ripples and reduced efficiency.

The aim of the present invention is to increase the efficiency of fuel combustion and increase the efficiency of using secondary blast.

This goal is achieved by the fact that according to the proposed method of combustion in a fluidized bed, which consists in feeding the primary blast and then introducing the secondary into the superlayer volume, the secondary blast is fed tangentially to the conditional body of rotation from the sections of the flow in the direction of the stagnant zones, and the sections of the flow in and of the stagnant the zones located beneath them in the profile of the superlayer volume are formed by lining and / or furnace screens.

Additionally, it is proposed that a part of the secondary blast be introduced also tangentially to the conditional body of rotation separately and / or together with the fuel and entrainment trapped behind the furnace.

The drawing shows a vertical section of the profile of the combustion device. At the bottom of the air distribution grill 1 there is a fluidized bed 2 with primary blow through the path 3 from the fan 4. In the super-layer volume 5, nozzles 7 of the secondary blast are installed in the overrun sections 6 (the section is indicated by the arrow) of the flow. The secondary blast nozzles 7 are oriented tangentially to the conditional body of revolution 8 (marked with a dashed line and filled) and are directed towards the stagnant zones 9 (marked by hatching).

The profile of the superlayer volume is formed by lining 10 and / or furnace screens 11. In this case, in the flow, the required run-in sections 6 and stagnant zones 9 are formed naturally according to the known laws of aerodynamics [3] in accordance with the furnace geometry (on the ledges - run-in areas, behind indents - stagnant zones).

The chimney chimneys have ash settling bins 12 with ejection return fans 13, which, like the pneumatic fuel inlet system 14, are connected to the fan 4 by the secondary blowing paths 15 and there are other elements necessary for the operation and maintenance of the fluidized bed firebox.

The proposed method of combustion in a fluidized bed is as follows.

A fluidized bed 2 is located on the air distribution grill 1. Particles of ash and burning coal, heated to 800-1000 ° C, are maintained in a state of fluidization and intensive mixing due to the supply through the primary blast layer from fan 4 through path 3. The flow of burning gaseous products of combustion and small carry-out particles of ash and coke are carried out in the superlayer volume 5 and then sucked out by the exhaust fan from the installation.

The profile and geometry of the superlayer volume 5 is formed by lining 10 and / or furnace screens 11 with the formation of at least one section 6 of the flow and one stagnant zone 9 below it. This shape of the superlayer volume 5 in accordance with the geometry provides a turn and movement of the dusty stream along the run-in section 6 over the stagnant zone 9.

In this case, firstly, according to the well-known laws of aerodynamics [3], the upward flow is concentrated under the run-in area 6, and in the stagnant zone 9 a detachable reverse vortex flow is formed. Such aerodynamics contributes to good mixing of the flow, convective heat exchange with the furnace screens 11, separation and retention of particles removed from the fluidized bed in the furnace. Accordingly, the proposed supply of secondary blast from the run-up areas 6 through nozzles 7 tangentially to the conditional body of revolution 8 toward the stagnant zones 9 only enhances the vortex flow, mixing, convective heat transfer, separation and retention of 5 particles removed from the fluidized bed in the superlayer volume. In this case, the jets of the secondary blast easily penetrate the upward stream, which is concentrated under the run-in area 6. Thus, the fraction of the secondary blast can be small and is determined independently, primarily, from the conditions for organizing a highly efficient furnace process. Secondly, oxygen-rich jets of the secondary blast easily penetrate into the volume of the conditional body of revolution 8, the stagnant zone 9 and into the root of the stream ascending from the fluidized bed 2. Combustion and combustion processes are evenly distributed throughout the entire volume of the furnace.

The supply of additional secondary blast along the tracts 15 together with the entrainment from the ash collecting bins 12 through the ejection return ejectors 13 and together with the fuel through the fuel air inlet system 14 not only enhances the vortex flow, but also saturates the superlayer volume 5 with combustibles.

As a result, the proposed method provides:

highly efficient convective cooling and, accordingly, low-temperature mode of the combustion process;

separation, retention and filling of the superlayer volume with particles;

a two-stage combustion scheme with uniform filling of the superlayer volume and minimal emission of harmful emissions;

improving fuel combustion;

increasing the efficiency of using secondary blast and, accordingly, the minimums of excess air in the furnace and heat loss with flue gases.

Thus, the application of the proposed method of combustion in a fluidized bed in comparison with the prototype [2] can improve the efficiency of combustion of fuel and increase the efficiency of the use of secondary blasting.

EXAMPLE. According to the proposed method, SIC PA “Biyskenergomash” reconstructed for burning Berezovsky coal of grade B2 in the furnace of the fluidized bed of a layer boiler No. 1 of type KV-TS-20-150 PV. The boiler is installed in the peak boiler room of Municipal Unitary Enterprise “OSP Housing and Public Utilities” in Lesosibirsk. With the help of the screen installed inside the furnace, a leakage section and a stagnant zone located under it are formed. The table shows a comparison of the performance of boiler No. 1, made by the proposed method, and a typical layered boiler No. 2.

The data presented show that the reconstructed boiler No. 1 has the best, compared with a standard boiler No. 2, indicators: high efficiency, reduced emissions of harmful substances CO and NO _x and minimal excess air. The heat output of the reconstructed boiler is almost three times higher than that of a typical layered boiler

Literature

1. Baskakov A.P., Matsnev V.V., Raspopov I.V. Fluidized-bed boilers and furnaces. M .: Energoatomizdat, 1996.

2. Copyright certificate SU No. 1453118, F 23 C 6/04, publ. 01/23/89, bull. No. 3.

3. Schlichting G. Theory of the boundary layer. M .: Nauka, 1974.

Claims (2)

1. The method of combustion in a fluidized bed, with the supply of primary blast and the subsequent introduction of the secondary blast into the superlayer volume from the sections of the flow in the direction of the stagnant zones, tangentially to the conditional body of rotation, and the sections of the flow and the stagnant zones located under them in the superlayer volume profile lining and / or furnace screens. 2. The method according to claim 1, characterized in that part of the secondary blast is introduced separately and / or together with the fuel and entrainment trapped behind the furnace.

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