SU1368568A1 - Method of operation of fluidized bed furnace - Google Patents

Abstract

Invention m. used in fluidized bed devices. The purpose of the invention is to expand the range of load control. To this end, a reduction in fuel consumption is carried out by shutting off the fuel supply to the lower discharge zone. In this case, the bottom ash dispenser 21 is closed and the resulting surplus zone is drained along the chute 18 of the top ash ash. For a deeper decrease in the heat gap in the layer, the supply of coal to the lower zone of layer 1 is stopped by a pneumatic conveyor 16 with the adjustment of the supply of coal to the spreader 9. 1 Il. (ABOUT

Description

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The invention relates to energy and can be used in fluidized bed devices. The purpose of the invention is to expand the range of load control. I The drawing shows schematically the fluidized bed heater in which the proposed method of operation is implemented.

The fluidized bed furnace 1 contains a gas distribution grid 2 with an air duct 3, heating surfaces 4, a fuel supply system consisting of a coal bin 5, feeders 6 and 7, feeding coal to the ejector 8 and thrower 9, and then to layer 1 and Layer 1. In addition, the firebox contains a system for recycling of entrainment to afterburning, consisting of gas duct 10, cyclone 11, line 12 of a clean flue gas, flashers 13, ejector 13 of returning entrainment, as well as systems 15-17, respectively, supplying air under the grill 2 pneumatic coal transport under layer 1, ash for afterburning. The furnace also contains heat 18 and 19 of the upper and lower ash discharge with dispensers 20 and 21.

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In the implementation of the method, part of the head from the bunker 5 is fed by the feeder 7 to the bunker-spreader 9, which feeds the coal into the furnace on the surface of the fluidized bed 1. The other part is fed by the charcoal 6 to the ejector 8, to which air is fed to the pneumatic transport 16. The mixture of coal and air is blown under layer 1. At the same time, the bottom ash dispenser 21 is closed and the resulting ash is discharged by the PO; the top 18 of the bottom ash is discharged. The unburned coal particles removed from layer 1 go through the gas duct 10 to the cyclone 11, where solid fraction comes out of the gas stream and through the flasher 13 is fed to the ejector 14 of the return of ash, where it mixes with the transport air and is blown into the underlayer of the firebox. Air for liquefaction is supplied to the air duct 3 via system 15. In the fluidized bed 1, heating surfaces 4 are located. By reducing the load of the boiler unit to 70-75%, the air supply to the liquefaction and the consumption of coal to the spreader are reduced. To reduce the heat loss in the layer more deeply, the supply of coal to the lower zone of the layer 1 is stopped by pneumatic transport

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16 with the adjustment of coal supply to the spreader 9.

Stopping the feeds under the layer 1 when the gas velocity decreases (due to a decrease in fuel and air consumption) leads to deterioration of coal particles from the surface of the layer 1 to the bottom, resulting in a burning in the lower part of the layer 1, which leads to a decrease in gas velocity in this parts of layer 1 to grid 2, i.e. a fixed sublayer is formed. In this case, a part of the heating surfaces 4 occurs in the volume of the fixed bed 1 and the cooled filter 1 with air of the layer 1, where there is no heat exchange between this layer 1 and the heating surfaces 4. As a result, in the hot fluidized bed 1, the surface area of the 4th surface is reduced, which naturally reduces the heat removal from bed 1. In order to ensure slagless operation, the fuel consumption is reduced.

Stopping the supply of coal under layer 1 and putting the whole coal on feed by layer 9 on the surface of layer 1 reduces the concentration of coal in the lower part of layer 1. Poor mixing of the solid phase of the fluidized bed 1 vertically when burning relatively large particles of coal (up to 10 mm and above) leads to the fact that the gas temperature in the lower part decreases, which causes a decrease in the gas filtration rate at the same air flow rate. At the same time large particles of ash fall out of the layer and settle on. grid 3 and the fluidization process for them is stopped, this part of layer 1 is fixed. The fixed (non-liquefied) layer 1 is, as it were, an extension of the gas distribution grid 2. As a result, the heat removal from the heating surfaces 4 remaining in this dense layer 1 decreases sharply. It is also possible that the heat exchanger transfers heat to the filter through the dense layer 1 to air (if the temperature of the fluidizing air is less than the temperature of the medium circulating in the heat exchanger).

The load is set as follows.

Reduce the height of the upper level of the fluidized bed 1 to the nominal opening of the lower estrus 19 while at the same time gradually increasing the fuel consumption by the spreader 9 to maintain the operating temperature of the layer 1. Then the carbon feeder 6 is turned on under the layer 1, and the coal starts to burn in the lower part of layer 1, the gas velocity increases and the lower portion of layer 1 is liquefied. By adjusting the fuel consumption on the spreader, the working temperature of the bed is maintained

Example 1. Changing the temperature profile along the layer height when changing the way coal is fed to the furnace.

At the bench installation (with the grating dimensions of 1400x840 mm) of the fluidized bed at the height of the fluidized bed, switching off the lower fuel supply leads to a decrease in the layer temperature at a height of 300 mm from the grate to the temperature of the liquefying air.

Temperature distribution over the heights of the fluidized bed with the supplied coal size mm - one curve - feed under the layer (ss 0 mm), another curve - feed by the spreader on the layer (. 700 mm). Slagging of the layer in this case does not occur. To further reduce the load, it is necessary to stop the discharge of the formed ash by closing the upper ash shutter 20, as a result of which the upper level of the fluidized bed rises, which leads to an increase in the height of the dense layer and a decrease in the heating surface in the volume of the fluidized bed. At the same time there is a reduction in fuel consumption. An extreme case is possible when the entire heating surface is in a dense layer.

PRI mme R 2. In a laboratory setting, 5 kg / h of Ekibastuz coal is fed under a pneumatic conveyor under a layer, and 13 kg is applied to the surface of the layer. Total air consumption 83 nm / h. The particle size of coal is 0–10 The temperature of the layer is 875 ° C. When the supply of coal under the layer is stopped and the air consumption drops to 70 nm / s, the temperature of the layer drops to 770 ° C, after 5 minutes

tour of the layer begins to grow through 13o

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15 min becomes equal to 875 C and continued to grow. When fuel consumption drops to 11 KG / H, the bed temperature stabilizes at 860-865 C. When the ash hole closes, the bed temperature begins to rise slowly. The supply of ash to a layer of 2–8 mm in an amount of 2 kg for 10 min leads first to a slight decrease in the temperature of the bed, then the temperature increases further and to stabilize the temperature of the bed within 860–870 ° G the fuel consumption is reduced to 9 kg / h . The supply of ash in the amount of 1 kg per layer leads to a decrease in fuel consumption to 7.3 kg / h, at the same time the temperature of the layer stabilizes at a level of 860-875 ° G. When coal consumption decreases to 6 kg / h, the bed temperature decreases to 82 ° C.

When a part of the material of the layer is drained from its lower part and at the same time increases the fuel consumption to 10 kg / h, the temperature of the layer is set at 850-860 ° C. Upon further discharge of ash from the layer without increasing the consumption of coal, the temperature of the layer decreases to 780 ° C. An increase in fuel consumption to 15 kg leads to an increase in temperature to.

In the presence of one fluidized bed section in the boiler, the load change range is 33-tOO%.

Claims (1)

Invention Formula The method of operation of the fluidized bed furnace by supplying fuel to the upper and lower zones of the layer and filtering air through the latter while simultaneously draining the layer to maintain its predetermined height and reducing the load on the fuel and air consumption, characterized in that, in order to extend the load control range , a reduction in fuel consumption is accomplished by turning off its supply to the lower zone of the bed.