RU2236641C1 - Solid fuel combustion method - Google Patents

Abstract

FIELD: railway transport.

SUBSTANCE: invention can be used for combustion of solid fuels, for instance, in heating boilers of railway cars at self-contained operation. Proposed method comes to delivery of fuel into burning zone, its ignition and combustion, removal of fine fractions of slag through grate bar slot which is periodically expanded for removal of larger fractions out of burning zone. Burning zone is divided into upper and lower parts, combustion is carried out in two steps, respectively, in said parts for which purpose fuel is displaced from one part into the other, ignition of fresh portion of fuel is provided in process of second step from combustion products and radiant heat of previous portion. Fresh portion of fuel is fed into upper part of burning zone after displacing of previous portion into lower zone. Slot of grate bars in lower part is expanded during second step. Displacement of fuel from upper part into lower part is carried out after complete removal of slag from lower part. Incomplete combustion products are afterburnt in burning zones. Delivery of fuel is done by striking of fuel against wall of combustion chamber and its jumping back to grate bars. Slot of grate bars is gradually increased in process of second step. Fuel elements in process of their combustion are grouped in lower part of burning zone. Burning zones are arranged one over the other.

EFFECT: provision of complete burning of fuel, increased efficiency of furnace, reduced formation of nitrogen oxides.

10 cl, 5 dwg

Description

The invention relates to the field of energy and can be used for burning solid fuels, for example, in a heating boiler of railway cars to operate in an autonomous automatic mode.

A known method of burning solid fuel by feeding it with a screw through a retort into the burning layer of the combustion chamber, followed by afterburning on slowly rotating drums and removing slag [1].

The disadvantages of this method are:

- incomplete combustion of fuel, due to the fact that large pieces of fuel that have already partially burnt onto the drum and do not have time to completely burn out before falling into the slag collector. If you try to rotate the drum more slowly, these pieces will be filled with slag from the small-sized fuel that has passed through the retort and has already burned. Moreover, since the pieces of fuel falling on the drum are scattered and are removed from the high-temperature combustion zone during its rotation, the burning intensity decreases, which does not allow them to burn completely. If to intensify the burning of pieces on the drum, place the latter closer to the high-temperature zone, then the slag removed subsequently will have a high temperature, which will lead to an increase in heat loss and ultimately to a decrease in the efficiency of the furnace;

- a device that implements this method requires significant energy costs for driving augers and drums, which also reduces the overall efficiency of the installation.

The prototype is a method of burning solid fuels, including the supply of fuel to the combustion zone, its ignition and combustion while crushing large pieces, removing small fractions of slag through the grate slit, which is periodically expanded to remove larger fractions from the combustion zone [2].

The disadvantages of this method are:

- incomplete combustion of fuel, due to the fact that its pieces, commensurate with the size of the slit of the grate, fall together with the slag into the dump. If the gap is made very small, the resulting slag will be poorly removed from the combustion zone and prevent the latter;

- crushing pieces of fuel involves additional energy costs, which reduces the efficiency of the installation;

- instability of the combustion process over time (especially when small amounts of fuel are burned) due to a partial or complete cessation of combustion when the remaining portion of the previous portion is filled with fresh fuel.

The aim of the invention is to increase the completeness of combustion of fuel, increase the efficiency of the furnace and reduce the formation of nitrogen oxides.

This goal is achieved by the fact that in the method of burning solid fuel, which includes supplying fuel to the combustion zone, igniting and burning it, removing small fractions of slag through the grate slit, which is periodically expanded to remove larger fractions from the combustion zone, the combustion zone is divided into the upper and the lower part, the combustion is carried out in two stages, respectively, in the indicated parts, for which the fuel is transferred from one part to another, and the ignition of a fresh portion of the fuel is carried out during the course of the second stage from the combustion products and radiant heat of the previous portion.

In addition, a fresh portion of the fuel is served in the upper part of the combustion zone. A fresh portion of the fuel is fed to the upper part of the combustion zone after moving the previous portion to the lower part. The grate slit is expanded in the lower part during the course of the second stage. The movement of fuel from the upper to the lower part is carried out after complete removal from the last slag. Products of incomplete combustion are burned out in combustion zones. Fuel is supplied by first striking it against the wall of the combustion chamber and subsequent bouncing on the grate. The grate slit is expanded gradually during the course of the second stage. In the lower part of the combustion zone, fuel elements are grouped during their combustion, and the combustion zones are placed one below the other.

The prior art does not reveal solutions that have signs that match the distinctive features of the claimed invention and have the same effect as they, on the technical result.

The invention is reflected in the operations:

- the combustion zone is divided into upper and lower parts and placed one below the other;

- combustion is carried out in two stages: respectively, in the upper and lower parts of the combustion zone, for which partially burnt fuel is moved from one (upper) part to another;

- ignition of a fresh portion of the fuel is carried out during the course of the second stage from the combustion products and radiant heat of the previous portion;

- a fresh portion of the fuel is fed to the upper part of the combustion zone after moving the previous portion to the lower part;

- the movement of fuel from the upper to the lower part is carried out after complete removal from the last slag;

- the grate slit is gradually expanded in the lower part during the course of the second stage;

- products of incomplete combustion are burned up in combustion zones;

- in the lower part of the combustion zone grouping of fuel cells in the process of burning them.

These operations allow you to achieve the following advantages compared with the prototype.

Dividing the combustion zone into the upper and lower parts and placing them one under the other makes it possible to efficiently and reliably ignite a portion of fresh fuel (lower ignition) from the combustion products and radiant heat of the previous portion, which at this time is in the burning stage under a fresh portion. At the same time, particles of solid fresh fuel are washed well by the hot products of combustion and radiant heat, as a result of which they quickly heat up and ignite. In addition, for fuel in the upper part, conditions are created under which the oxidizing agent (air) is mixed with the combustion products produced by the fuel combustion process in the lower part. Such mixing is equivalent to recirculation of flue gases into the blast air path, which, as you know, is an effective way to reduce the formation of nitrogen oxides in the combustion chamber.

Burning fuel in two stages (in the upper and lower combustion zones) improves the stability of the combustion process over time even in small furnaces that burn small amounts of fuel. In the prototype, an accidental rash of a large portion of the fuel (which in addition may partially be mixed with snow) can lead to the extinction of the flame and the cessation of the combustion process in the remains of the previous portion of the fuel intended for ignition. In the claimed solution, due to the heat emitted from the normally burning in the lower part of the fuel zone and the grate located in the upper part, a quick drying of a fresh portion of fuel and its subsequent ignition will occur. Note that with a sufficiently close location of the combustion zones, the ignition of the fuel can also be carried out with a flame (sparks) from the fuel burning in the lower part.

The supply of a fresh portion of fuel to the upper part of the combustion zone after moving the previous portion to the lower part excludes its mixing with slag formed during combustion of the previous portion (in the upper part) and subsequently removed with it to the lower part. This contributes to good mixing of fuel with air (oxidizing agent) and its more complete combustion.

The movement of fuel from the upper to the lower part after complete removal from the last slag promotes good mixing of the fuel with air (oxidizing agent) in the lower part of the combustion zone and its more complete combustion in the second stage.

The gradual expansion of the grate slit in the lower part during the course of the second stage contributes to a more complete combustion of the fuel, since larger pieces of fuel do not fail when slag is removed and continue to burn until their shape becomes smaller than the gap. At the same time, we note that lumps of fuel that failed in the ash pan but did not burn out due to a lack of oxygen in the ash pan will emit carbon monoxide (a product of incomplete combustion), which, rising upward, will be burned in the lower and upper combustion zones. This achieves a more complete combustion of fuel.

Grouping of fuel elements (fuel particles) in the process of burning them in the lower part makes it possible to intensify the combustion process and prevent it from stopping on separate (disparate) elements.

These advantages allow for more complete combustion of fuel, increase the efficiency of the furnace and make it possible to automate the operation of the boiler due to the stability of the combustion process over time.

The invention is illustrated by drawings.

Figure 1 shows a diagram of the operation of a furnace for burning solid fuels: a) at the time of loading a fresh portion of fuel; b) at the time of fuel combustion in the upper and lower parts of the combustion zone; c) at the time of burning of fuel in the lower part of the combustion zone; d) at the time of movement of the fuel from the upper to the lower part of the combustion zone.

Figure 2 shows a section aa of the furnace.

The furnace contains a housing 1 of the combustion chamber, grates 2 with a slot 3, an ash pan 4 for receiving slag 5, channels 6 for supplying air (oxidizing agent) 7, a hatch 8 for loading fuel 9, combined with a pallet 10, above which a hopper 11 with fuel is placed. The grate and the pan are equipped with blades 12 mounted for moving fuel relative to them. Between the furnace body and the upper grate, a groove 13 is made for transferring fuel from the upper to the lower part of the combustion zone. The fuel combustion process is accompanied by a flame 14.

The method is implemented as follows.

From the hopper 11 through the hatch 8 serves a fresh portion of fuel 9 to the upper part of the combustion zone using blades 12 placed on a pallet 10 and working, for example, according to the principle of the blades of a snow blower (Fig. 1, a). While the pieces of fuel hit the wall of the housing 1 of the combustion chamber and bounce to the grate 2. Due to the curvature of the surface of the wall and different masses, the pieces bounce at different angles and at different distances, laying a relatively even layer on the grate 2, which allows you to refuse the leveling operation layer .

Heating and lower ignition of the resulting layer of fresh fuel is carried out from the combustion products and radiant heat of the previous portion of the fuel, which is burned at this time in the lower part of the combustion zone (on the lower grate 2). After ignition, the combustion process, accompanied by a flame 14, extends to the entire portion of fresh fuel (Fig. 1, b). The combustion of the indicated portion (at the first stage in the upper part of the combustion zone) occurs under conditions of mixing the air 6 entering through the channels 7 with the combustion products produced by the combustion process of the previous portion of fuel on the lower grate 2. Such mixing is equivalent to recirculation of the flue gases into the path of blast air and helps to reduce the formation of nitrogen oxides. Moreover, the specified mixing is free from the disadvantages inherent in recirculation and associated with the presence of a recirculation fan, gas ducts and increase the resistance of the air path.

Slag 5 is removed from the lower part of the combustion zone (from the lower grate) through the slit 3 of the grate, which is periodically expanded to output larger fractions of slag into ash pan 4 as the fuel burns (Fig. 1, c). Since the mass of fuel on the grate decreases and the distance between the individual pieces increases, then to intensify the combustion process, it is necessary to group the remaining fuel, for example, by moving the blades 12 to the center of the lower grate (figure 2). Note that these blades can also be used for lining fuel. After removing all the slag from the lower grate, the gap 3 is narrowed in it. 4 pieces of fuel that have not been burned up to this point and got into the ash pan due to a lack of oxygen begin to emit combustible gas (carbon monoxide), which, rising upwards, burns in the upper and lower parts of the combustion zone .

Move the fuel through the groove 13 from the upper to the lower part of the combustion zone (Fig. 1, d), in which it continues to burn (the second stage). Upon receipt of the next portion of fresh fuel, the described process is repeated.

The implementation of the invention will automate the operation of boilers for solid fuels, such as heating boilers of railway cars, to increase the completeness of combustion and fuel efficiency of the furnace, as well as reduce the formation of nitrogen oxides.

Sources of information

1. A.S. No. 1281814, F 23 V 1/32, 1987 - analogue.

2. A.S. No. 1165849, F 23 H 9/00, 1980 - prototype.

Claims (10)

1. A method of burning solid fuel, including the supply of fuel to the combustion zone, its ignition and combustion, removal of small slag fractions through the grate slit, which is periodically expanded to remove larger fractions from the combustion zone, characterized in that the combustion zone is divided into upper and lower parts, the combustion is carried out in two stages, respectively, in the indicated parts, for which the fuel is transferred from one part to another, and the ignition of a fresh portion of the fuel is carried out during the course of the second stage from the combustion products and the radiant heat of the previous portion. 2. The method according to claim 1, characterized in that a fresh portion of the fuel is served in the upper part of the combustion zone. 3. The method according to one of claims 1 and 2, characterized in that a fresh portion of the fuel is fed to the upper part of the combustion zone after moving the previous portion to the lower part. 4. The method according to one of claims 1 to 3, characterized in that the grate of the grate is expanded in the lower part during the course of the second stage. 5. The method according to one of claims 1 to 4, characterized in that the movement of fuel from the upper to the lower part is carried out after complete removal from the last slag. 6. The method according to one of claims 1 to 5, characterized in that the products of incomplete combustion are burned in the combustion zones. 7. The method according to one of claims 1 to 6, characterized in that the fuel is supplied by first striking it against the wall of the combustion chamber and subsequent rebound to the grate. 8. The method according to one of claims 1 to 3 , 5-7 and 4, characterized in that the grate gap during the course of the second stage is expanded gradually. 9. The method according to one of claims 1 to 8, characterized in that in the lower part of the combustion zone a grouping of fuel cells is performed during their combustion. 10. The method according to one of claims 1 to 9, characterized in that the combustion zone is placed one below the other.

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