JP2001242154A - Method and apparatus for estimating dioxin concentration in flue gas and waste combustion furnace control device using the same - Google Patents

Abstract

(57) [Problem] To provide a highly accurate estimation method of dioxin concentration in order to control dioxin generation. A method for estimating the concentration of dioxin in flue gas of a combustion furnace, based on the concentration of chlorophenols and the concentration of hydrocarbons in the flue gas, formula (1)
p is the concentration of chlorophenols, Hc is the concentration of hydrocarbons, a and b are correction coefficients (-), and n and m are multipliers. (Equation 5)

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for continuously estimating the concentration of dioxins in flue gas on-line, and more particularly to a method for estimating dioxin concentration with higher accuracy than before.

[0002]

2. Description of the Related Art FIG. 5 schematically shows the structure of a conventional general waste combustion furnace. The combustion device is a waste pit 43, a waste input hopper 45, an incinerator 54, an air flow controller 92 for waste combustion, an air flow control valve 95 for secondary combustion, a steam flow controller 63 for temperature control, and waste. It is composed of a supply amount adjusting dust supply device 96, a gas cooling boiler 46, an electric dust collector (or dust filter) 48, a flue line 1, a suction blower 49 and a chimney 51.

[0003] This apparatus uses a suction blower 49 to operate the combustion furnace 5.
After suctioning the whole 4 to make it negative pressure, the auxiliary burner 87 is ignited. Thereafter, the wastes 44 are continuously introduced into the incinerator 54 while adjusting the supply amount using the dust supply device 96, and are burned by the air 88 supplied from the lower part of the incinerator 54.

The amount of air is adjusted by an air flow controller 92 so that the furnace temperature becomes 850 ° C. This air is heated in an air preheater 86 to 250-300 ° C.

When the furnace temperature rises to near 900 ° C., steam is supplied from the upper part of the furnace by a steam flow control valve 93 to lower the temperature. Cinder (or ash)
53 is continuously extracted from the lower part of the incinerator 54.

On the other hand, since the combustion gas has a high temperature of 850 ° C.,
Gas cooling boiler 4 to reduce the effect on downstream equipment
At 6, the gas temperature is reduced from 850 ° C. to around 300 ° C. Since the combustion gas contains ash, HCl, and the like, the HCl removes the HCl remover 94 from before the dust collector 48 to reduce the HCl concentration.

The ash is removed using an electric dust collector or a bag filter 48, and the flue gas is released into the atmosphere from a chimney 51 (the main components in the combustion gas are nitrogen, water vapor,
It is carbon dioxide and its trace components are hydrogen chloride, sulfur oxide,
Nitrogen oxides, carbon monoxide, etc.). In the flue, NOX, CO, and O were used to monitor the components in the combustion gas.
₂ , an analyzer 84 for analyzing HCl and the like is provided.

It is said that such combustion gas discharged from the combustion furnace 54 contains a trace amount of dioxins, and improvement of control, treatment and measurement techniques is one of the problems of waste incineration. One of them.

What is generally referred to as dioxins is polychlorinated dibenzoparadioxins (abbreviated as PCDDs). Two benzene nuclei are connected in parallel by two oxygens, and part of the hydrogen attached to the benzene nuclei is replaced by chlorine. There are 75 isomers depending on the number and position of the chlorine substitution.

The polychlorinated dibenzofuran produced together with PCDDs also has 135 isomers, and these two are collectively called dioxins (hereinafter referred to as DXN).

Although the process of producing DXN in the process of burning waste is not clear, many research results have shown that unburned components remaining without being completely burned in the secondary combustion chamber, or precursors, are contained in the boiler or dust collector. In the process of passing through the vessel, if the conditions such as temperature, atmosphere, catalyst and the like are properly adjusted, DXN is generated by reacting with hydrogen chloride generated by combustion.

That is, (1) 300 to 500
(2) Decomposition of precursor substances such as chlorophenol and chlorobenzene by catalytic reaction with heavy metals and unburned carbon in ash in an atmosphere of
There is a reaction route synthesized by a synthesis reaction.

Therefore, it can be understood that DXN in the combustion gas can be estimated by focusing on unburned hydrocarbons and precursor substances such as chlorophenol and chlorobenzene.

It is important that the analyzer for controlling the amount of DXN generated as described above can accurately and accurately predict the concentration of DXN in the combustion gas in real time.

FIG. 6 is a schematic diagram of a conventional apparatus for ingesting DXN in exhaust gas. The intake device 80 includes the exhaust gas intake pipe 3, the dust collection unit 55, the liquid collection units 58 and 59, and the resin adsorption unit 6.
1. Consisting of liquid collecting sections 64 and 65, a suction pump 66, a gas measuring section 68, and respective connecting pipes 57 and 67.

This device adsorbs and absorbs and collects at each collecting part while sucking at a constant flow rate by the suction pump 66, and then analyzes by a specified analysis method to calculate the DXN concentration.

The structure of the exhaust gas intake pipe 3 is defined by the gas temperature in the flue 1. When the temperature is higher than 500 ° C., the outside is cooled by water, and the intake pipe 3 is made of transparent quartz glass. I do. Further, when the temperature is lower than 500 ° C., a material made of hard glass is used.

The dust collecting unit 55 is provided with a container containing a cylindrical filter paper at the outlet of the intake pipe 3 to remove dust in the exhaust gas. Thereafter, the liquid collection units 58 and 59 (empty) filled with 100 to 300 ml of hexane washing water in a 1-liter glass container 58 are circulated to absorb and collect the XAD.
-2, flows through the resin adsorption section 61 filled with 40 to 70 g of resin 62 to be adsorbed and collected, and then flows into containers 64, 65 (empty) filled with 100 ml of diethylene glycol,
Absorb and collect.

The space between the liquid collecting units 58 and 59 and the liquid collecting units 64 and 65 is placed in an ice bath in a container 63 in order to maintain the temperature of the intake gas at 5 to 6 ° C. or less. I do. Further, the length of the connecting pipe 56 from the exhaust gas intake pipe 3 to the liquid collecting sections 58 and 59 is made as short as possible, and a glass pipe or a fluororesin pipe is used. Since DXN is taken into dust, moisture and liquid, the liquid, column, dust and the like are collected, and DXN adsorbed and absorbed therein is analyzed.

The above-mentioned method has a problem that it takes about one month to obtain a DXN analysis value after ingesting gas from the plant and starting a take-out analysis operation. Therefore,
This method cannot be applied to operation control of a combustion furnace based on the concentration of DXN itself.

As a control method for suppressing the DXN concentration, it is said that there is a correlation between the DXN concentration and the CO concentration. Therefore, based on the CO concentration in the combustion exhaust gas, the air amount of the combustion furnace and the damper The furnace temperature is controlled by the opening and the amount of water vapor, and the concentration of hydrogen chloride is controlled by introducing slaked lime to control the operation. However, in a region where the DXN concentration is low, the correlation with the CO concentration is low, and the development of an alternative index having a higher correlation is being promoted.

As such an alternative index, there is the following method.

(1) A method of measuring the concentration of chlorobenzenes, the concentration of chlorophenols, and the concentration of dust in exhaust gas, and estimating and calculating the DXN concentration from these measurement results and the residence time of the exhaust gas (Japanese Patent Application Laid-Open No. 9-15229) Gazette).

(2) Exhaust gas generated from the furnace is reduced by 50 to 20
A method of removing dust at 0 ° C. to adsorb, concentrate, desorb, and analyze chlorobenzenes and chlorophenols (JP-A-8-26663).

(3) From the correlation with the concentration of chlorobenzenes, which has a correlation with DXN in the low concentration region, DX
A method for estimating the N concentration (Japanese Patent Application Laid-Open No. 5-313796).

(4) There is a method of quickly and accurately estimating the DXN concentration by using chlorophenols as an indicator substance of DXN (JP-A-10-153591).

[0027]

SUMMARY OF THE INVENTION These precursor concentrations and D
As a typical example of the correlation with the XN concentration, FIG. 4 shows the relationship between the chlorophenol concentration and the DXN concentration.

In the figure, the results measured at a plurality of incineration plants are plotted. The horizontal axis represents the concentration of chlorophenols (μg / Nm ³ ), and the vertical axis represents the concentration of DXN (ng-T
EQ / Nm ³ ).

As can be seen from this figure, the correlation between the DXN concentration and the DXN precursor (chlorophenols or chlorobenzenes) concentration has a wide range.

An object of the present invention is to provide a method for estimating the concentration of DXN in combustion exhaust gas, which accurately estimates the concentration of DXN in exhaust gas in real time.

Another object of the present invention is to provide an apparatus for estimating the DXN concentration.

Another object of the present invention is to provide a waste combustion furnace control apparatus using the above-described DXN concentration estimation method.

[0033]

The gist of the present invention to achieve the above object is as follows.

[1] A method for estimating the concentration of DXN in the flue gas of a combustion furnace, comprising the following formula (1) based on the concentration of a DXN precursor (chlorophenols) and the concentration of hydrocarbons in the flue gas.

[0035]

(Equation 4)

The combustion is characterized in that the DXN concentration is estimated by [where Cp is the concentration of chlorophenols, Hc is the concentration of hydrocarbons, a and b are correction coefficients (-), and n and m are multipliers]. In the method for estimating the concentration of DXN in exhaust gas.

The hydrocarbons are benzene, phenol,
Toluene, cresol, xylene and hydroquinone.

[2] A DXN concentration estimating apparatus for estimating the DXN concentration by the formula (1) based on the DXN precursor (chlorophenols) concentration and the hydrocarbons concentration.

[3] A waste supply unit, a combustion furnace for burning the waste, and a DXN concentration estimator for estimating the DXN concentration in the combustion exhaust gas of the combustion furnace are provided. A waste combustion furnace control device for controlling combustion of the combustion furnace based on the DXN precursor (chlorophenols) concentration and the hydrocarbons concentration based on the DXN precursor (chlorophenols) concentration and the hydrocarbons concentration according to the formula (1). In the waste combustion furnace control device to estimate the concentration.

In the present invention, the concentration of chlorophenols is n
By estimating the concentration of DXN from the sum of the power and the m-th concentration of hydrocarbons, the DXN concentration can be calculated in real time. Here, the values of n and m vary depending on the performance of the combustion furnace, but the range is 0.5 to 2.

Further, based on the indication value of the DXN prediction device in which the above equation (1) is stored, an air flow control valve, a temperature controller, a combustion air amount, a damper, a secondary combustion air amount, etc. of the waste combustion furnace. By laying a waste combustion furnace control device that operates and controls the concentration of DXN in the combustion furnace, the amount of DXN generated can be controlled.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] Exhaust gas is continuously supplied for estimating the DXN concentration based on the DXN precursor (chlorophenols) concentration and the hydrocarbon concentration in the flue gas of the present invention. An embodiment in combination with a pretreatment device connected to a DXN precursor analyzer will be described with reference to FIGS.

A pretreatment apparatus connected to a DXN precursor analyzer for continuously measuring the emission concentrations of the DXN precursor and hydrocarbons of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention. The configuration of the entire pretreatment device is the exhaust gas intake pipe 3,
Dust collector 7, Inhibitor absorption pipe 14, Exhaust gas supply line 25, Exhaust gas suction pump 27, Temperature controller for heating the connecting pipe of each device, Standard substance supply system 29 for calibration of chlorophenols concentration, Dust collection Opening / closing valves 4, 6, 9, 13, 1 for the collector backwash gas system 23 and the exhaust gas supply line
6 and so on.

The exhaust gas suction pump 27 may be installed either before or after the introduction of the analyzer 28. In the pretreatment device, the DX
Care was taken so that the concentration of N precursor and the like would be equal to the concentration in the flue.

Next, the operation procedure of the present apparatus will be described. Closing open / close valves 4, 9 and 16 and open / close valve 13
And 6 are opened, and the air pump 31 and the suction pump 27 are simultaneously operated to allow air to flow through the chlorophenols concentration calibration reference material supply system 29 and to be supplied from the inlet line of the dust collector 7 to the exhaust gas line. Then, it is supplied to the DXN front section analyzer 28 through the dust collector 7, the absorption pipe 14, and the exhaust gas supply line 25.

Thereafter, the calibration standard sample is loaded into the calibration standard sample loading section 30, and the detection status of the signal intensity of the calibration standard sample is confirmed. After confirming that the calibration standard sample is stably detected in the air at the position of the specified mass number in air,
Is opened, and the combustion gas 2 is sucked through the exhaust gas intake pipe 3.

After the suction, the air amount and the combustion gas suction amount are set to predetermined flow rates, and the concentrations of the chlorophenols and hydrocarbons in the combustion gas are determined from the detected intensity signals to DX.
N is calculated by the prediction device (or data processing device) 70, and D
XN concentration was estimated. The DXN precursor analyzer 28
Is an analysis method for ionizing a sample of a trace component by an ion / molecule reaction in an ion source under atmospheric pressure.

FIG. 2 shows the relationship between the concentration of chlorophenols and the concentration of DXN with respect to the concentration of hydrocarbons. On the horizontal axis,
Chlorophenol concentration (μg / Nm ³ )
The XN concentration (ng-TEQ / Nm ³ ) is shown.

FIG. 2 shows that the concentration of hydrocarbons is 1 to 1000.
Although the DXN concentration at μg / Nm ³ is shown, it can be seen that the DXN concentration can be estimated more accurately than before by the hydrocarbon concentration.

That is, the concentrations of chlorophenols and hydrocarbons are measured, and the DXN concentration is estimated from the sum of the nth power of the chlorophenols concentration and the mth power of the hydrocarbons concentration, thereby real-time calculation. It is possible to calculate accurately. That is, it can be obtained from the relationship of the above equation (1).

The DXN concentration can be estimated from the signal intensity of benzene, phenol, toluene, cresol, xylene, hydroquinone and the like in hydrocarbons.

The values of n and m in the above formula (1) differ depending on the performance of hydrocarbons and chlorophenols produced from each incinerator, and the range is 0.5 to 2.

Next, each device installed in the exhaust gas supply line 25 will be described. Using the suction pump 27,
While sucking the combustion gas 2 in the flue line 1 of the combustion furnace from the exhaust gas intake pipe 3 at a constant flow rate at a constant flow rate, the dust collector 7 and the absorption pipe 14 inhibit the inhibitory components (ash, hydrogen chloride, etc.) in the exhaust gas 2. After removing the waste gas, the waste gas is supplied through the exhaust gas supply line 25 and supplied to the detection unit of the DXN precursor analyzer 28 via the suction pump 27 (with the inhibitor removed).

Each device is heated and kept at a certain temperature so that the DXN precursor does not adsorb or decompose. As a heating means, a sheathed heater is wound around each device and the outer wall of the connecting pipe, insulated with a heat insulating material, and thermocouples 12 and 1 are provided at main points.
5, 18, 26, 39, 11 are installed, and the temperature controller 72
The temperature was controlled by

The dust collector 7 employs an element system, has a filter 8 incorporated in an outer cylindrical container, and continuously collects ash. This dust collector has a dust collector backwashing gas supply system 23 that separates ash from the filter 8. This operation is performed by installing the pressure gauge 17 at the outlet line (pipe) 89 of the dust collector 7 and opening and closing the open / close valve 90 and closing the open / close valve 6 when the indicated value reaches a preset indicated value. I do.

The pressure regulator of the air cylinder 24 is opened in advance. Then, the solenoid valve 22 is opened at the same time as the closing valve 13 is closed, and air is stored in the air tank 20.
The solenoid valve 19 and the opening / closing valve 16 are simultaneously opened, and the air in the air tank 20 is instantaneously removed from the filter 8 in the dust collector 7.
To remove ash adhering to the surface of the filter 8. After repeating this operation two or three times, the normal operation starts.

The suction pump 27 used was a diaphragm type having a withstand temperature of 240.degree. C. and a suction capacity of 18 liter / min, depending on the length of the connecting pipe.

The absorption tube 14 is composed of a catalyst layer for removing inhibitors such as hydrogen chloride, sulfuric acid and nitric acid. The absorption tube 14 reacts in contact with a pre-filled catalyst and removes trace amounts of hydrogen chloride and the like contained in the combustion gas 2. After removal, the combustion gas is discharged into an exhaust gas supply line 2
Distribute 5

In addition, a metal filter 74 was provided in the inlet pipe of the DXN precursor analyzer 28 to protect the ion part of the analyzer 28. Since the filtration accuracy of the filter 8 in the dust collector 7 is 5 to 10 μm, dust of 10 μm or less is removed by the metal filter 74. This filtration accuracy is 0.
4 μm.

The material of the connecting pipe connecting each device is made of stainless steel, and the size of the pipe is 1/4 inch to 1/2.
An inch tube was used.

[Embodiment 2] FIG.
The schematic diagram of the DXN suppression method by the waste combustion furnace control device 75 in which the N prediction device 70 is laid is shown.

A waste combustion furnace control device 75 in which the DXN prediction device 70 is laid is installed at the flue or at the outlet of the combustion furnace 54, and the flow rate and the opening of each operation valve are determined based on the values indicated by the DXN prediction device 70. By adjusting the waste, the waste combustion furnace 5
No. 4 DXN generation amount is suppressed.

That is, a DXN reference density is set in the DXN prediction device 70 in advance, and the reference value is compared with the indicated value obtained by the DXN prediction device 70 based on the reference value. When the indicated value is equal to or larger than the reference value, the waste combustion furnace control device 75 transmits operation signals 80, 81, 82, 97, 98 to the respective operation devices, and the air dampers 76, 77, 78 for air adjustment. The operation of adjusting the opening degree of the secondary combustion air flow control valve 95, the dust supply device 96 for controlling the supply amount of waste, and the like according to the situation is executed. By these operations, the desired D
The amount of XN generated can be suppressed, and the waste combustion furnace can be operated stably for a long period of time.

Although the embodiment in which the combustion control method of the present invention is applied to the above-described waste combustion furnace is shown, the present invention is not limited to this, and can be applied to various types of furnaces.

[0066]

According to the present invention, the concentration of DXN precursor (chlorophenols) in exhaust gas and the concentration of hydrocarbons contained in combustion exhaust gas can be estimated with high accuracy from the concentration of DXN. This makes it possible to continuously calculate the DXN concentration in real time.

Further, the DXN of a waste combustion furnace or the like is
The amount of generation can be suppressed, and a stable and clean operation for a long period of time is possible.

[Brief description of the drawings]

FIG. 1 shows a DXN in which a DXN concentration prediction device of the present invention is laid.
It is the schematic of a structure including the pre-processing apparatus of the precursor analysis apparatus.

FIG. 2 is a graph showing the relationship between the concentration of chlorophenols and the concentration of DXN with respect to the concentration of hydrocarbons of the present invention.

FIG. 3 is a schematic diagram showing a configuration of an example of a waste combustion furnace in which the waste combustion furnace control device of the present invention is laid.

FIG. 4 is a graph showing a conventional relationship between DXN concentration and chlorophenol concentration.

FIG. 5 is a schematic diagram showing a configuration of a typical waste combustion furnace.

FIG. 6 is a schematic diagram of a configuration of a conventional DXN analysis method.

[Explanation of symbols]

1 flue line, 2 combustion gas, 3 exhaust gas intake pipe,
4, 13, 16: open / close valve, 5: thermometer (or thermocouple), 6, 9, 90: open / close valve, 7: dust collector,
8 ... Filter, 10 ... Ash collection container, 11, 12, 15,
18, 26, 36, 39 ... thermometer (or thermocouple), 1
4 ... Absorption pipe, 17,21 ... Pressure gauge, 19,22 ... Solenoid valve, 20 ... Air tank, 21 ... Pressure gauge, 23 ... Dust collector Backwash gas supply system, 24,31 ... Air cylinder, 25
... Exhaust gas supply line, 27 ... Suction pump, 28 ... Dioxin precursor analyzer, 29 ... Chlorophenol concentration calibration standard material supply system, 30 ... Calibration standard sample loading section, 3
2 ... Each component operation operating mechanism device, 33 ... Open / close valve 4 operation signal, 34 ... Open / close valve 6 operation signal, 35 ... Open / close valve 13 operation signal, 36 ... Open / close valve 9 operation signal,
37: operation signal of solenoid valve 19, 38: operation signal of solenoid valve 22, 40: water heater, 41: steam header, 42: gas cooling boiler, 43: waste pit, 44: waste, 45
... Waste input hopper, 46 ... Heat transfer tube, 47 ... Air, 48
... Electric dust collector (or bag filter), 49 ... Suction blower, 50 ... Flue, 51 ... Chimney, 52 ... Pretreatment system, 53 ...
Ash, 54: Combustion furnace, 55: Dust collection unit, 56, 57,
67 ... connecting pipe, 58 ... liquid collecting part 1, 59 ... liquid collecting part 2, 60 ... ice bath, 61 ... resin adsorption part, 62 ... XAD-2
Resin, 63: ice bath container, 64: container, 65: empty container, 6
6 suction pump, 68 gas flow meter, 70 dioxin prediction device (or data processing device), 71 signal, 7
2: Temperature controller, 73: Exhaust gas introduction line, 74: Metal filter, 75: Waste combustion furnace control device, 76, 77,
78: air damper, 84: NOX, CO, O ₂ , HCl
Isoanalyzer, 85 ... electric signal, 86 ... air preheater, 87 ...
Combustion burner, 88 ... air, 89 ... dust collector outlet line, 90 ... open / close valve, 92 ... air flow control valve, 93 ...
A steam flow control valve, 94: HCl remover, 95: air flow control valve for secondary combustion, 96: dust supply device.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Morihara 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Electric Power & Electric Research Laboratory, Hitachi, Ltd. (72) Inventor Minoru Sakairi Higashi Koigakubo, Kokubunji-shi, Tokyo 280-chome, Hitachi, Ltd.Central Research Laboratories, Ltd. Hitachi, Ltd.Measurement Instruments Group (72) Inventor Shozo Sakamoto 882, Oji-shi, Ota, Hitachinaka-shi, Ibaraki Co., Ltd. Address F-term in Hitachi Measuring Instruments Group, Ltd. (reference) 3K06 2 AA02 AB01 AC01 BA02 CA02 CA05 CB08 DA01 DA22 DA23 DA25 DB01 DB07 DB08 4D004 AA46 CA28 DA16 DA17

Claims (4)

[Claims] 1. A method for estimating dioxin concentration in flue gas of a combustion furnace, comprising the following formula (1) based on a dioxin precursor (chlorophenols) concentration and a hydrocarbons concentration in the flue gas. Equation 1 [However, Cp is the concentration of chlorophenols, Hc is the concentration of hydrocarbons, a and b are correction coefficients (-), and n and m are multipliers]
A method for estimating the concentration of dioxin in combustion exhaust gas, comprising estimating the concentration of dioxin by using the method. 2. The method according to claim 1, wherein said hydrocarbons are benzene, phenol, toluene, cresol, xylene and hydroquinone. 3. Based on the concentration of dioxin precursor (chlorophenols) and the concentration of hydrocarbons, the following formula (1): [However, Cp is the concentration of chlorophenols, Hc is the concentration of hydrocarbons, a and b are correction coefficients (-), and n and m are multipliers]
A dioxin concentration estimating device for estimating a dioxin concentration by means of: 4. A waste supply unit, a combustion furnace for burning the waste, and a dioxin concentration estimating device for estimating a dioxin concentration in flue gas from the combustion furnace, based on calculation processing data of the concentration estimating device. A waste combustion furnace control device for controlling combustion in the combustion furnace, wherein the dioxin concentration estimating device is based on a dioxin precursor (chlorophenols) concentration and a hydrocarbons concentration, and the following formula (1): ] [However, Cp is the concentration of chlorophenols, Hc is the concentration of hydrocarbons, a and b are correction coefficients (-), and n and m are multipliers]
A waste combustion furnace control device characterized by estimating dioxin concentration by means of: