JPS6364688B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention enables easy incineration in a fluidized bed furnace of collected ash that collects soot dust in exhaust gas discharged from several boilers in power plants, etc., and whose calorific value fluctuates. This article relates to a method of burning collected ash.

FIG. 1 shows a case where the combustion apparatus is used as a boiler and the ash collected by three boilers is burned in an incinerator (the illustrated example is a fluidized bed furnace). The exhaust gases from the boilers 1A, 1B, and 1C, which are operated independently, collect the soot and dust contained in the dust collectors 2A, 2B, and 2C, and are sent to the unit storage tanks 3A, 3B, and 3C, respectively. The collected soot dust (collected ash) is passed from this unit storage tank to cushion tanks 3A', 3B', and 3C' and is sent to low-pressure air (approx.
2.0Kg/cm ² g) and is further sent to the collection tank 10 via pipes 5A, 5B, 5C, valves 6A, 6B, 6C, switching box 7, main pipe 8, and valve 9. The pressurized air is sent from the pipe 11 to the incinerator 14 and is used as part of the combustion air. The collected ash in the collective storage tank 10 is sent to the incinerator 14 via a valve 10a and, if necessary, a supply device (not shown) via a pipe 10b for combustion treatment. The auxiliary combustion fuel is supplied from the pipe 12 to the incinerator 14, and the fluidizing and combustion air and the combustion air are supplied from the blower 13 to the incinerator 14.
5 to the incinerator 14.

Figure 2 shows six units (symbol a) in one power plant.
This shows the change in the calorific value of the collected ash collected at a certain time over 11 days when the boiler of ~f) is installed. As can be seen from this figure, the number of
It shows a change between 100Kcal/Kg and about 6000Kcal/Kg. Also, even with the same boiler, approximately
Range of 6000-2500Kcal/Kg and about 40% of the highest value
This indicates that fluctuations may decrease up to a point close to the current level.

The ash stored in the collective storage tank is sent to an incinerator (fluidized bed furnace)
However, as mentioned above, the amount of heat generated fluctuates greatly.

Furthermore, when we investigated the relationship between the content of ammonium sulfate (NH ₄ ) ₂ SO ₄ in this collected ash and the calorific value, we found that there was a relationship as shown in Figure 3, and that there was considerable variation.

On the other hand, the collected ash is the V (vanadium) in the fuel.
Difficulty due to content rate, S content (sulfur) content,
It is easily flammable and variable.

During operation, if the combustion in the fluidized bed is active, the amount of combustion in the cavity decreases, and if the combustion in the fluidized bed decreases, the combustion in the cavity must be increased. In any case, the temperature of the cavity is 600℃.
In the following cases, NOx generated in the layer is discharged as is. Figure 4 shows the NOx amount distribution and temperature pattern inside the furnace. This incinerator is equipped with a cylinder burner to promote gas phase reduction, and controls the cylinder temperature to reduce NOx to 250ppm.
( _O2 12% conversion) or less.

The calorific value of the collected ash that is thrown in is 5400 ~
In the case of low calorie sand, such as 5500Kcal/Kg or less, increasing the amount of combustion in the bed will increase the amount of molten coating that will adhere to the fluidized sand, leading to deterioration of fluidization. If the amount of coating increases, difficulties such as the formation of clinker (small lumps) and adhesion of sand to the furnace wall are likely to occur. Therefore, when incinerating medium-low calorie ash, the temperature in the bed is set in the range of 645 to 675°C, and the combustion rate in the bed is made low (to make it difficult to burn). In the event that the fluidized sand enlarges, (a) reduce the amount of incineration, (b) further lower the temperature in the bed, (c) increase the amount of fluidizing air to make the fluid more active (d) for a long time. If this occurs, it is necessary to take operational measures such as stopping the burning of dry ash and mixing it with humidified ash.

On the other hand, when high-calorie ash of 6000 cal/Kg class is input, the temperature in the bed is raised and the combustion rate in the bed is increased. High-calorie ash is generally flame-retardant, so unless the temperature in the bed is raised to increase the ignition and combustion rate, the amount of heat generated in the hollow cylinder will increase when the collected ash particles pass through the hollow cylinder in an unburned or burnt state. This makes it difficult to control the temperature of the hollow cylinder.

It is not very difficult to determine during operation whether the collected collected ash is high-calorie ash or medium-low-calorie ash. 50% of rated load when burning dry ash only
But it goes into self-combustion mode. (When the auxiliary oil amount adjustment valve becomes 0 and the oil amount becomes 0/hr), it means that medium and low calorie ash has started to be introduced, so lower the temperature setting in the bed and start combustion in the bed. This will reduce the proportion (not the amount of incineration).
In the case of high-calorie ash, the combustion rate in the bed decreases even during operation at rated load (if the temperature in the bed is constant, the combustion rate in the bed is low for flame-retardant ash)
Therefore, the amount of auxiliary fuel oil increases, and conversely, since it starts to burn in the cavity, the amount of cavity burner oil starts to be reduced, which can be easily determined by the operator. When incinerating high-calorie ash, the temperature in the layer may be set at 660 to 680°C. The temperature in the bed is automatically controlled by the cascade method (step system) to automatically control the amount of auxiliary oil, and as a preventive measure when medium and low calorie ash is suddenly added, a warning is issued at the minimum amount of auxiliary oil and the amount of oil is added at 0/h. The control is to reduce the amount of ash to the minimum amount.

In short, this invention provides a method for burning ash collected from exhaust gas from a boiler or the like in a fluidized bed furnace, in which the ash is collected with a low calorie content based on the signals of the amount of oil supplied to the auxiliary burner and the amount of oil in the cylinder burner. By determining whether it is ash or high caloric collected ash and controlling the amount of supplied ash, oil, air and exhaust gas, the temperature in the bed of the fluidized bed is controlled. It is characterized by being a combustion method.

FIG. 5 is a diagram showing a control system of a collected ash incinerator according to the present invention. To take out the collected ash from the collection tank 10, rotary feeder 16a, 1 is used.
6b are placed in series and a deaeration box 17 is provided in between and connected to the incinerator cavity through a pipe line 17a, the collected ash in the deaeration box 17 is degassed because the cavity is under negative pressure. Quantitative feeding using a rotary feeder is possible. The collected ash sent out from the rotary feeder 16b is supplied to the fluidized bed section of the incinerator 14 through a pipe line 18. This conduit 18 may be provided with an air flow transport device if necessary.

The temperature in the fluidized bed is sent from a temperature transmitter 19, and the temperature in the cavity is sent from a temperature transmitter 20 to a control box 21 which compares the measured value with the stored value and outputs a control signal.

The auxiliary fuel is supplied through a pipe 12, a control valve 22, and a flow meter 23.
The fuel is supplied to the auxiliary combustion burner 24 via. The cylinder burner 25 has a pipe line 26, a control valve 27, and a flow meter 28.
Fuel is supplied via. Flowmeter 23, 28
A signal indicating the amount of fuel to be supplied is sent to the control box 21.

Pressure air for both combustion and flow is supplied from the blower 29 via the pipe 15 to the air chamber via the damper 30 and flow meter 31, and for jet flow via the damper 32, flow meter 23, and pipe 15a. Ru. Air flow signals from the flowmeters 31 and 33 are sent to the control box 21.

The control box 21 determines whether high-calorie ash or low-calorie ash is being supplied based on the temperature, fuel, and air supply values based on these signals, and then controls the rotary feeders 16a, 16b.
, the amount of oil supplied by the control valves 22 and 27, the amount of air supplied by the dampers 30 and 32, and the amount of exhaust gas by the damper 34 provided in the exhaust gas pipe, and the temperature in the fluidized bed is adjusted when medium and low calorie ash is used. Approximately 645-675
℃, high calorie ash is controlled at about 645-670℃, and the cavity temperature is controlled at about 700-900℃. With this control
Emissions of NOx are low, and operation can be performed without causing combustion defects in the fluidized bed.

By carrying out this invention, even if the calorific value of the collected ash changes over time, an appropriate bed temperature is ensured, and the collected ash, whose calorific value fluctuates, is efficiently incinerated by continuous operation. This has various effects such as being able to reduce NOx emissions.

[Brief explanation of drawings]

Figure 1 is a pipe system diagram of a processing device for collected ash in a power generation plant, etc., Figure 2 is a diagram of the daily record of fluctuations in the calorific value of collected ash over 11 days, and Figure 3 is a diagram of the collected ash. Figure 4 is a diagram showing the relationship between ammonium sulfate content and calorific value of collected heavy crude oil ash, Figure 4 is a diagram showing the relationship between temperature in the furnace height direction and NOx amount in exhaust gas, and Figure 5 is a diagram showing the relationship between the temperature in the furnace height direction and the amount of NOx in the exhaust gas. 1 is a drawing of a control system showing an embodiment of the invention. 1A, 1B, 1C... Boiler, 10... Collective storage tank, 14... Incinerator, 16a, 16b... Rotary feeder, 19, 20... Temperature transmitter, 21...
...Control box, 22, 27...Control valve, 23, 28...
...Flowmeter (oil), 29...Blower, 31, 33...
...Flowmeter (air).

Claims (1)

[Scope of Claims] 1. A combustion process in which when ash collected from exhaust gas from a boiler, etc. is burned in a fluidized bed furnace, the amount of oil supplied to an auxiliary burner and a cylinder burner is controlled to maintain a constant temperature in the bed. In the method, it is determined whether the ash is low-calorie collected ash or high-calorie collected ash based on signals of the amount of oil supplied to the auxiliary combustion burner and the amount of oil supplied to the cylinder burner, and the amount of ash to be supplied and the amount of supplied ash are determined. A method for burning collected ash with varying calorific value, characterized by controlling the temperature in a fluidized bed by controlling the amount of oil, the amount of supplied air, and the amount of exhaust gas. 2. A patent characterized in that when high calorie collected ash is burned, the temperature in the fluidized bed is maintained at about 660 to 680 degrees Celsius with a cavity temperature of about 700 to 900 degrees Celsius and an auxiliary fuel supply amount of zero to allow natural combustion. A method for burning collected ash having a varying calorific value as set forth in claim 1. 3. A patent claim characterized in that when low-calorie collected ash is burned, the temperature in the fluidized bed is maintained at about 645-675°C with a cavity temperature of about 700-900°C and an amount of auxiliary combustion fuel of 0 to allow natural combustion. A method of burning collected ash having a varying calorific value as described in item 1. 4 Compare the measured values with the stored values using the fluidized bed temperature signal, the cavity temperature signal, the oil amount supplied to the cavity burner, and the oil amount supplied to the auxiliary burner, and issue a control signal. Claim 1, characterized in that it is sent to a control box and controls the supply amount of collected ash, the amount of auxiliary fuel, the amount of cylinder burner oil, the supply amount of air that serves both combustion and flow, and an exhaust gas damper. Item to third
A method of burning collected ash whose calorific value fluctuates according to any one of paragraphs. 5. When the operation of the fluidized bed furnace that burns collected ash becomes malfunctioning, the supplied amount of collected ash should be reduced to approximately 50% of the rated load.
When the temperature is lowered to 645 to 670 degrees Celsius and normal natural operation is started even without the supply of auxiliary fuel, it is assumed that the ash is medium-low calorie collected and the temperature in the bed is maintained at approximately 645 to 670 degrees Celsius. When the amount of oil starts to decrease, it is assumed that the collected ash has a high calorie content, and the temperature in the layer is increased to about 660~660℃.
5. A method for burning collected ash having a variable calorific value as claimed in any one of claims 1 to 4, characterized in that the collected ash is combusted while being controlled to maintain the temperature at 680°C.