JP4899259B2 - SO3, NH3 simultaneous continuous concentration meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a SO ₃ and NH ₃ simultaneous continuous concentration meter contained in exhaust gas in a flue of a combustion facility such as a boiler or a waste incinerator.
[0002]
[Prior art]
Gases emitted from combustion facilities such as boilers and garbage incinerators contain harmful components such as sulfur oxides and nitrogen oxides, so they must be removed with a flue gas treatment device or the like.
[0003]
This flue gas treatment equipment removes nitrogen oxide (NOx) from the exhaust gas discharged from the boiler, recovers heat through a gas-air heater, removes it with an electric dust collector, and then introduces it into a wet desulfurization equipment. Absorbs and removes sulfur oxide (SOx) in exhaust gas and releases it to the atmosphere.
[0004]
Sulfur oxides include SO ₂ and SO ₃ , and nitrogen oxides include NO and NO ₂ .
[0005]
In a normal boiler, NO is reduced by passing NO through a denitration catalyst in a denitration apparatus for removing NO. At that time, ammonia (NH ₃ ) is injected, and NO is expressed as in the following formula. Reduce.
[0006]
4NH ₃ + 4NO + O ₂ = 4N ₂ + 6H ₂ O
However, not all of the injected NH ₃ is used in the above formula, and partly leaks and passes through a denitration device (a normal device is around 400 ° C.). This amount increases as the catalyst in the denitration device deteriorates.
[0007]
In addition, SO ₃ is also generated by combustion in the boiler, but as the denitration catalyst progresses, the conversion rate of SO ₂ to SO ₃ by the catalyst increases as shown in the following formula, so the SO ₃ concentration increases. .
[0008]
2SO ₂ + O ₂ = 2SO ₃
Thus, NH ₃ and SO ₃ are present simultaneously in the boiler flue (temperature of 350 ° C. or higher), and it is necessary to measure the gas concentrations of both at the same time.
[0009]
When the gas temperature is lowered, SO ₂ and SO ₃ change into acidic ammonium sulfate or ammonium sulfate as shown in the following formula, which is liquid or solid and adheres to the flue wall surface or the equipment in the flue.
[0010]
NH ₃ + SO ₃ + H ₂ O = NH ₄ HSO ₄
2NH ₃ + SO ₃ + H 2 O = (NH ₄ ) ₂ HSO ₄
Acidic ammonium sulfate causes clogging due to adhesion of air heaters to elements. Acidic ammonium sulfate is a corrosive substance, and if it adheres, the walls and equipment will corrode.
[0011]
Ammonia is also used for neutralization of SO ₃ and is injected into the flue before the electric dust collector. Therefore, in order to control the amount of ammonia, it is necessary to grasp the amount of ammonia and the amount of SO ₃ .
[0012]
Thus, NH ₃ and SO ₃ need to be measured simultaneously.
[0013]
However, a manual analysis method such as a condensation method is generally used for SO ₃ concentration measurement, and there is no reliable continuous measurement meter. In addition, the NH ₃ concentration meter includes an ultraviolet absorption method, an infrared absorption method, a solution conductivity analyzer, and the like, but there is no reliable continuous measurement meter, and there is no measurement device capable of simultaneously measuring SO ₃ and NH ₃ .
[0014]
In general, the detection of the concentration in a gas by UV absorption analysis is performed by taking a UV absorption spectrum of a known concentration, creating a calibration curve in which the absorbance is plotted for each concentration, and comparing it with the absorbance at an unknown concentration. Seeking the concentration.
[0015]
The measurement of the concentration by the calibration curve is based on the principle that the calibration curve created by Lambert Beer's law becomes a straight line, and if the equation of the straight line is obtained, the concentration can be obtained by substituting the absorbance.
[0016]
When measuring the SO ₂ and SO ₃ gas concentrations in the boiler flue gas based on this calibration curve by ultraviolet absorption analysis, the exhaust gas in the flue is introduced into the gas cell by the suction force of the pump, and ultraviolet rays are transmitted through the gas cell. Then, an absorption spectrum is obtained and measured.
[0017]
At this time, since the absorption spectrum bands of SO ₂ and SO ₃ were the same, it was difficult to measure them individually, but Japanese Patent Application No. 11-374106 (name of the invention) filed earlier by the present applicant. : SO ₂ and SO ₃ concentrations can be detected by the method of calculating the concentration of SO ₃ gas in the flue). The concentration calculating method, a gas obtained by mixing SO ₂ as the interference gas in detecting the concentration of SO _3, taking the absorbance spectrum while changing the composition ratio of SO _3, based on the absorbance spectrum data, PLS ( The SO ₂ and SO ₃ calibration curves were created by multivariate analysis such as (Partial Least Squares), and based on the calibration curves, the flue gas in the flue was subjected to ultraviolet absorption analysis, and SO ₂ and SO of unknown concentrations in the exhaust gas. ₃ is obtained by allowing measure, similarly NH ₃ also taking the absorbance spectrum while changing the the composition ratio at multivariate analysis can measure the sO ₃ and NH ₃ simultaneously.
[0018]
[Problems to be solved by the invention]
By the way, in the boiler as described above, ammonia is injected at the inlet of the denitration device to reduce NO, and at the inlet side of the electrostatic precipitator, ammonia is injected to recover SO ₃ as ammonium sulfate. Therefore, it is necessary to grasp the amounts of ammonia and SO ₃ .
[0019]
However, although the flue gas temperature at the outlet side of the denitration apparatus is 400 ° C., ammonia and SO ₃ exist at the same time. Therefore, when the exhaust gas is sampled and measured in this state, it reaches the gas cell. Since the piping temperature is not controlled, there is a problem that ammonia and SO ₃ are combined to be changed into acidic ammonium sulfate or ammonium sulfate, so that accurate ammonia concentration and SO ₃ concentration cannot be measured.
[0020]
Accordingly, an object of the present invention is to solve the above-mentioned problems and provide an SO ₃ and NH ₃ simultaneous continuous concentration meter that can reliably and continuously measure ammonia and SO ₃ in exhaust gas by an ultraviolet absorption analysis method.
[0021]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, exhaust gas in a flue is introduced into a gas cell, and SO ₃ and NH ₃ in the exhaust gas introduced into the gas cell are simultaneously and continuously measured by ultraviolet absorption analysis. In the densitometer, a pipe for introducing exhaust gas from the flue into the gas cell is connected, and a pipe for introducing a calibration gas for zero measurement and a standard gas for reference is connected to the gas cell, and the temperature of these pipes is set to 350 to 450. This is a SO ₃ and NH ₃ simultaneous and continuous densitometer in which the concentration is measured while being kept at ° C.
[0022]
The invention according to claim 2 is the SO ₃ and NH ₃ simultaneous continuous concentration meter according to claim 1, wherein the concentration is measured while maintaining the temperature of the pipe and the gas cell at 350 to 450 ° C.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
[0024]
With reference to FIG. 1, the SO ₃ and NH ₃ simultaneous continuous concentration meter in the present invention will be described.
[0025]
In FIG. 1, reference numeral 10 denotes a flue through which exhaust gas from a boiler flows, and enters the inlet probe 12, the outlet probe 13, and the flue 10 through flanges 11, 11 along the flue gas flow direction of the flue 10, respectively. The inlet / outlet probes 12 and 13 are connected by a bypass pipe 14 and a filter 15 and a blower 16 are connected to the bypass pipe 14.
[0026]
The filter 15 is connected to an introduction pipe 18 for introducing exhaust gas after dust removal into the gas cell 17, and an exhaust pipe 19 as exhaust means is connected to the outlet side of the gas cell 17. A trap 20, a pressure is connected to the exhaust pipe 19. The monitor 21, the control valve 22, the pump 23, and the flow meter 24 are sequentially connected to constitute an exhaust means.
[0027]
A gas supply pipe 25 for supplying a calibration gas and a reference standard gas is connected to the introduction pipe 18, and a nitrogen gas supply cylinder 27 for zero measurement is connected to the gas supply pipe 25 via an on-off valve 26. At the same time, a standard gas supply cylinder 29 for reference is connected via the on-off valve 28. The cylinders 27 and 29 are provided with regulators 30 and 31 for adjusting the supply gas pressure.
[0028]
Switching valves 32 and 33 are connected to the introduction pipe 18 and the gas supply pipe 25, respectively. An exhaust valve 34 is connected to the introduction pipe 18.
[0029]
The nitrogen gas supply cylinder 27 may be air other than nitrogen gas. The standard gas may be SO ₃ , ammonia, or other stable SO ₂ gas.
[0030]
The bypass pipe 14, the introduction pipe 18, and the gas supply pipe 25 are provided with heaters 35, 36, and 37 for keeping the gas introduced into the gas cell 17 at 350 to 450 ° C. A heater 38 is also provided in the gas cell 17.
[0031]
One of the gas cells 17 is provided with a light source 40 for irradiating ultraviolet rays, such as an Xe lamp, a deuterium lamp, and an Xe flash lamp, and a light receiving unit 41, and total reflection mirrors 42, 43, 44 are provided on both sides of the gas cell 17. Provided.
[0032]
As shown in the figure, the total reflection mirrors 42, 43, 44 are located at the light source 40 and the light receiving part 41 of the gas cell 17, and the two total reflection mirrors 42, 43 are provided, and the one total reflection mirror 44 is provided on the other side. UV light from the light source 40 is reflected by the total reflection mirror 42 and transmitted through the gas cell 17, and is reflected by the total reflection mirror 44 disposed on the other gas cell 17 side and transmitted through the gas cell 17. The light is incident on the light receiving unit 41 from the total reflection mirror 43.
[0033]
Thus, by forming a multi-pass in the gas cell 17, the ultraviolet absorption path length can be increased, and the measurement accuracy can be improved.
[0034]
The ultraviolet UV incident on the light receiving unit 41 is split by the spectroscope 46 through the optical fiber 45 and the light intensity is detected.
[0035]
The spectroscope 46 divides the wavelength in the range of 200 to 350 nm in the ultraviolet rays (range 0 to 400 nm), detects it with the light detection element, and the absorbance data is input to the calculation device 47 and calculated.
[0036]
Next, the operation of the present invention will be described.
[0037]
First, exhaust gas in the flue 10 is introduced from the inlet probe 12 into the bypass pipe 14 by the blower 16, and the exhaust gas is returned by the outlet probe 13. At this time, the inlet probe 12 is provided so as to protrude in the flue 10 so as to be orthogonal to the exhaust gas, thereby minimizing dust intrusion into the bypass pipe 14.
[0038]
Next, a part of the exhaust gas that bypasses the inside of the bypass pipe 14 is introduced into the gas cell 17 through the filter 15 and the introduction pipe 18 by the pump 23 on the downstream side of the gas cell 17.
[0039]
When introducing the exhaust gas into the gas cell 17, the bypass pipe 14 is kept at the same temperature as the temperature of the flue 10 (about 400 ° C.) by the heater 35, and from the fly ash in the exhaust gas and the compounds adhering to the dust , So that SO ₃ and ammonia are not regenerated.
[0040]
Further, the amount of exhaust gas introduced into the gas cell 17 through the filter 15 may be small. However, when exhaust gas is introduced directly from the flue 10, the amount of exhaust gas is small, so that the exhaust gas temperature control is difficult and adheres to the filter 15. The amount of dust to be increased. Therefore, exhaust gas is introduced from the flue 10 through the bypass pipe 14 and flows downstream of the flue 10, and a part of the exhaust gas in the bypass pipe 14 is sucked through the filter 15 connected to the bypass pipe 14. Thus, the amount of dust adhering to the filter 15 is small, and the exhaust gas temperature can be easily controlled by introducing the necessary amount of the exhaust gas from which dust has been removed to the gas cell 17 through the introduction pipe 18.
[0041]
At this time, the piping from the flue 10 to the gas cell 17, that is, the bypass piping 14 and the introduction piping 18 are maintained at the exhaust gas temperature at 350 to 450 ° C. by the heaters 35 and 36, and the inside of the gas cell 17 is heated by the heater 38. , And keep at 350-450 ° C.
[0042]
That is, when the exhaust gas temperature is 350 ° C. or lower, ammonia in the exhaust gas reacts with SOx to become acidic ammonium sulfate or ammonium sulfate, and when the exhaust gas temperature is 450 ° C. or higher, SO ₂ is converted to SO ₃ and accurate ammonia and Although SO ₃ cannot be measured, the exhaust gas components in the flue 10 can be accurately measured while maintaining the temperature range as described above.
[0043]
After the measurement, the exhaust gas is cooled by the trap 20 from the exhaust pipe 19 to remove the corrosive gas components such as SO ₃ in the exhaust gas, the measured pressure is monitored by the pressure monitor 21, and then the flow meter from the pump 23. Exhaust out of the system through 24.
[0044]
At this time, corrosive gas such as SO ₃ is removed by cooling the exhaust gas after measurement to 100 ° C. or less with the trap 20 from the exhaust pipe 19. Therefore, the pressure monitor 21 is protected from a corrosive environment, and a normal semiconductor pressure gauge or the like can be used.
[0045]
Further, when preparing a calibration curve for SO ₃ , NH _3, etc., nitrogen gas is supplied from the nitrogen gas supply cylinder 27 into the gas cell 17 through the calibration gas supply pipe 25 and zero transmittance is measured in the cell. And a reference standard gas such as SO ₃ , NH ₃ , SO _2, etc. is supplied into the gas cell 17 from the standard gas supply cylinder 29, and these gases are heated to a temperature of 350 to 450 ° C. by the heater 37. In this case, when the pressure in the gas cell 17 changes, the absorbance also changes. Therefore, the pressure monitor 21 controls the control valve 22 of the exhaust means so that the measured pressure becomes constant.
[0046]
Further, since the pressure and the absorbance are in a fixed proportional relationship, the absorbance data may be corrected according to the pressure at the time of measurement detected by the pressure monitor 21.
[0047]
Next, an outline of the measurement method will be described.
[0048]
The concentrations of NH ₃ and SO ₃ are simultaneously obtained by the ultraviolet absorption method, but the exhaust gas in the flue 10 contains not only NH ₃ and SO ₃ but also gases such as SO ₂ and NO.
[0049]
In the range from 200 nm to 260 nm where SO ₃ is absorbed, NH ₃ is absorbed, and SO ₂ and NO are absorbed.
[0050]
Therefore, sample gases with various composition ratios of NH ₃ and SO ₃ are flowed into the gas cell 17 through the standard gas supply cylinder 29 and the calibration gas supply pipe 25, and their absorbance spectra are taken. A calibration curve of NH ₃ and SO ₃ is prepared by analysis, and this is used as data. Based on this, the absorbance spectrum of the exhaust gas introduced into the gas cell 17 is measured. From this absorbance spectrum, NH ₃ and SO ₃ are analyzed by multivariate analysis. Measure the concentration of ₃ .
[0051]
The calibration curve data is stored in the arithmetic unit 47 in advance, and SO ₂ from the standard gas supply cylinder 29 and nitrogen gas from the nitrogen gas supply cylinder 27 are supplied to the gas cell via the calibration gas supply pipe 25 as sample gases. In this case, the change in absorbance due to dirt or the like may be corrected.
[0052]
【Effect of the invention】
In short, according to the present invention, since the concentrations of SO ₃ and NH ₃ are determined at the same time, the temperature at which acidic ammonium sulfate and ammonium sulfate are generated can be predicted, the temperature control of the flue can be performed, and the acidic ammonium sulfate that is generated, The amount of ammonium sulfate can be predicted. Further, in the management of the denitration apparatus, it is possible to simultaneously monitor the amount of leaked ammonia that increases due to catalyst deterioration and the amount of SO ₃ . Furthermore, a calibration curve can be created by introducing a calibration gas and a standard gas into the gas cell via a pipe, and a change in absorbance due to contamination of the gas cell can be corrected.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of the present invention.
[Explanation of symbols]
10 Chimney 14 Bypass piping (piping)
17 Cell 18 Introduction piping (piping)
40 Light source (Xe lamp)
46 Spectrometer 47 Computing Device

Claims (2)

In the concentration meter that introduces flue gas in the flue into the gas cell and continuously measures SO ₃ and NH ₃ in the flue gas introduced into the gas cell by UV absorption analysis, a pipe for introducing the flue gas from the flue into the gas cell SO ₃ , characterized in that a pipe for introducing a calibration gas for zero measurement and a standard gas for reference is connected to the gas cell, and the concentration is measured while maintaining the temperature of these pipes at 350 to 450 ° C. , NH ₃ simultaneous continuous concentration meter.   The SO concentration according to claim 1, wherein the concentration is measured while maintaining the temperature of the pipe and the gas cell at 350 to 450 ° C. _Three , NH _Three Simultaneous continuous densitometer.

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