JPS6257888B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention uses heavy crude oil ash (hereinafter referred to as This paper relates to a method of operating a fluidized bed combustion furnace for incinerating EP ash.

<Conventional technology and its problems> Recently, in the boilers of power plants, etc., two-stage combustion methods and other low O ₂ combustion methods are used to reduce nitrogen oxides (hereinafter referred to as NOx) in the exhaust gas. The problem of increasing the amount of carbon and also increasing the amount of ammonium sulfate [(NH ₄ ) ₂ SO ₄ ] due to the spray supply of reducing agents such as ammonia (NH ₃ ) to remove NOx and sulfur oxides (SOx). is occurring. Therefore, it is necessary to incinerate low-melting-point molten materials containing ammonia components (EP ash is an example of this), but at that time, ammonium sulfate melts during the decomposition process, and in the case of a fluidized bed furnace, it becomes fluid. It adheres to the media and the furnace walls, causing various difficult problems in the operation of the furnace. Furthermore, depending on the operating conditions of the furnace, there is a problem in that NOx is generated due to oxidation of NH ₃ and must be disposed of. In addition to this, if the sulfur dioxide gas in the exhaust gas at the system outlet falls below its dew point (for example, below 120°C), there is a problem of corrosion of the duct material due to condensation, so the furnace exhaust gas temperature is operated at approximately 500°C or higher. Ta. However, at this temperature, a problem arose in that the unburned carbon contained in the exhaust gas was in a red-hot state in the exhaust gas duct or dust collector, so-called ``open combustion'' (``burnt combustion''), resulting in a burnout accident.

<Object of the invention> This invention solves the first problem of adhesion of low melting point melts.
In addition to solving the NOx generation caused by _NH3 decomposition,
The purpose of this project is to propose an operating method that solves the problem of "open combustion."

<Summary of the Means> In short, the present invention provides a method for operating a fluidized bed incinerator in which the temperature of the empty column is made higher than that of the fluidized bed and cooling water is sprayed near the furnace outlet in a method of burning low-melting-point containing materials in a fluidized bed incinerator. It is characterized by

<Example> First, a method of operating a fluidized bed incinerator that solves the first problem will be described. In Fig. 1, a fluidized bed incinerator 1 has an air chamber 2 at the bottom that supplies combustion and fluidizing air, and a fluidized medium 4 such as sand is stored on a perforated plate 3, and the fluidized bed is heated by the fluidizing air. form 5. This fluidized bed is heated by a starting burner (not shown), and when it reaches a certain temperature, the EP ash is passed from a hopper 6 that accommodates the EP ash via a feeder (rotary feeder, etc.) 7, a chute 8, and a nozzle 8a.
Ash is fed into the fluidized bed. In addition, a plurality of auxiliary combustion burners 9 and a plurality of empty column burners 10 are provided, and the temperature inside the fluidized bed is maintained at approximately 580 to 600°C, and the temperature of the upper surface of the fluidized bed in the empty column is maintained higher than the temperature inside the bed. Even if NH ₃ is oxidized by ammonium sulfate decomposition and NOx (nitrogen oxides) is generated, this is reduced in the gas phase and converted into harmless N ₂
Make it.

When incinerating EP ash in such a fluidized bed incinerator, in order to appropriately control the temperature described above, there is a temperature transmitter 11 that detects the temperature of the fluidized bed and outputs a signal, and a temperature transmitter 11 that measures the temperature of the empty column and outputs a signal. A transmitter 12 is provided on the wall of the fluidized bed incinerator, and these signals are sent to a control box 13. The control box 13 receives the temperature signal and controls the opening degree of each control valve and the supply amount of EP ash using a storage device. Control commands are issued to the drive motor of the feeder 7 in the case of the EP ash supply device consisting of the hopper 6, feeder 7, chute 8, and nozzle 8a. For fuel supply, empty tower burner 1
0 control valve 15, control valve 1 for the auxiliary burner
6, a control command is issued to the control valve 17 regarding the circulating jet air, and a control command is issued to the damper 18 regarding the main supply air amount.

Further, when inert gas is supplied to the mixer 21 through the conduit 19 and the control valve 20, a control command is issued to the control valve 20 from the control box 13.

This invention proposes an operating method for the apparatus shown in FIG. 1 which solves the first problem, in which cooling water is further sprayed to cool the exhaust gas at the furnace outlet. Experiments have confirmed that the exhaust gas temperature required to prevent "burning" is approximately 350-450°C. FIG. 2 shows the structure of an apparatus according to the present invention. In addition to the conventional device shown in FIG.
sent to. In addition to the exhaust gas temperature itself, this signal
It includes the rate of rise and rate of fall (dT/dt), and is sent to the control box 13 as a display that can be displayed separately on the meter. This is because the fluidized bed furnace has a slow temperature change, so the control box 13 predicts the supply amount of each fuel, air, and EP ash using the dT/dt signal (T = temperature t = time) and uses it as a command signal. Each control valve 15,
16, 17a, 20, the damper 18, and the rotary feeder 7 to control them. At the same time, the flow rate control valve 24 that supplies cooling spray water to the water injection nozzle 23 is controlled. The temperature transmitter 22 may measure the gas temperature in the wake duct of the exhaust gas outlet and at the inlet of the first dust collector, for example, a single cyclone. This is based on the idea that the measured temperature (exhaust gas) in the downstream stream has less fluctuation and is more reliable than the temperature at the exhaust gas outlet, which is measured when the cooling water and exhaust gas are not sufficiently mixed.

The temperature conditions considered when defining the temperature of each part of the fluidized bed incinerator are schematically shown in FIG. In other words, in order to combine the fluidized medium in the fluidized bed and eliminate the cause of inhibiting the flow, and to eliminate the formation of acidic ammonium sulfate, the temperature in the fluidized bed indicated by the symbol A in Fig. 3 is lower than the formation temperature of 270 to 380°C. The temperature was increased to instantly decompose ammonium sulfate and generate NH ₃ and SO ₃ .

To briefly describe the production of acidic ammonium sulfate (NH ₄ HSO ₄ ), ammonium sulfate undergoes the following decomposition within the temperature range of 270 to 380°C.

(NH ₄ ) ₂ SO ₄ →NH ₄ HSO ₄ +H ₂ O...(1) This acidic ammonium sulfate has strong adhesiveness and sticks to the fluid medium, turning it into small agglomerates and inhibiting flow.

Therefore, the fluidized bed section indicated by symbol A is heated to a high temperature higher than 380°C, and NH ₃ is decomposed and generated as shown in the following formula.
This is to instantly reduce the NOx generated in the gas phase.

The decomposition of NH ₃ production is shown by the equation below.

NH ₄ HSO ₄ →NH ₃ +SO ₃ +H ₂ O...(2) In addition, the generated NH ₃ is combined with NOx in the highly active state during the generation stage by the overhead burner 10 near the top of the fluidized bed by so-called gas phase reduction. I tried to disassemble it. For reference, ammonia (NH ₃ ) is 500
The decomposition reaction in the range of ~680°C is shown by the following formula.

4NH ₃ +5O ₂ =4NO+6H ₂ O …(3) 2NH ₃ +3O ₂ =2HNO ₂ +2H ₂ O …(4) NH ₃ +2O ₂ =HNO ₃ +H ₂ O …(5) Empty tower shown by symbol B in Figure 3 In this section, the part near the top of the fluidized bed is heated by the empty column burner 10 to make it higher than the inside of the fluidized bed, and the NO released from the fluidized bed in the nascent state and the NO generated by the decomposition of equation (2) are heated. Ta
It has a great gas phase reduction effect by reacting with NH ₃ in the gas phase.

In addition, in the section B shown in Fig. 3, the empty column is formed to be relatively tall in order to maintain a high temperature and reaction time suitable for combustion of the unburned components. ing.

In addition, in the part indicated by C in FIG. 3, the combustion gas is cooled to 350 to 450° C. with water spray to prevent the high-temperature combustion gas from flowing and causing "burning" in the wake dust collector. This temperature is approximately the temperature at which sulfuric acid is produced.
The temperature is much higher than 120℃, so there will be no corrosion of the components that make up the duct.

<Effects of the Invention> Through the above-described control according to the implementation of the present invention, ammonium sulfate as a nitrogen component-containing material is sufficiently decomposed in the fluidized bed, and the formation of lumps due to the bonding of the fluidized medium due to the generation of sticky components is prevented. Stable fluidized bed combustion is possible, and the space section where the space tower burner is located has a high temperature that is suitable for the reaction of NH ₃ and NO as a gas phase reduction reaction, and there is no NOx emission, and the residence time of the high temperature gas is ensured. The unburnt component gas is sufficiently combusted, and the exhaust gas is further cooled by water spray near the top of the furnace to prevent "burning". This is because the specific gravity of water as a fluid is much greater than the specific gravity of high-temperature gas, so the spray water enters the high-temperature gas flow at the center of the exhaust gas flow and vaporizes.

In other words, by implementing this invention, it is possible to stably incinerate EP ash in the fluidized bed section and reduce NOx, and also to prevent various burnout accidents caused by "open combustion" in the wake of the exhaust gas outlet, and to ensure stable continuous operation of the equipment. This has various effects such as making it possible to

[Brief explanation of the drawing]

Figure 1 is a diagram showing the control system and equipment arrangement of a fluidized bed incinerator that solves the first problem mentioned above;
The figure is a drawing showing the arrangement and control system of an apparatus according to an embodiment of the present invention, and FIG. 3 is a schematic sectional view of the apparatus for explaining reactions in the parts of the apparatus indicated by symbols A, B, and C. 1... Fluidized bed incinerator, 2... Air chamber, 3... Perforated plate, 4... Fluidized medium, 5... Fluidized bed, 6... Hopper, 7... Feeder, 8... Chute, 8a...
... Nozzle, 9 ... Assist burner, 10 ... Sky tower burner, 11, 12 ... Temperature transmitter, 13 ... Control box, 18 ... Damper, 15, 16, 17, 20 ...
...Control valve, 19...Inert gas pipe, 21...
Mixer, 22...Temperature transmitter, 23...Water injection nozzle, 24...Flow rate control valve.

Claims (1)

[Claims] 1. In a method for burning a substance containing an ammonia component-containing low melting point molten material in a fluidized bed combustion furnace having a fluidized bed section and a hollow column section located above the fluidized bed section, The furnace is operated by performing combustion using a partial burner and maintaining the temperature of the empty column higher than the temperature of the fluidized bed, and by spraying cooling fluid near the top of the furnace at the furnace outlet to raise the temperature of the exhaust gas at the furnace outlet and maintain it below the combustion temperature. A method of operating a fluidized bed incinerator, characterized by: