JPH0445311A - Device for treating combustion exhaust gas - Google Patents

Abstract

PURPOSE:To prevent generation of clinker and efficiently effect dust collection, removal of SO2, HCl, etc., and heat recovery by making a nozzle of a cooling water spray device a two-fluid nozzle, providing a combined feed mechanism of cooling water and NaOH raw liquid equipped with a device able to independently control the feed rates of liquids for the two-liquid nozzle and making other fluid feed mechanism an air feed one. CONSTITUTION:Raw liquid of NaOH is introduced into a cooling water feed pipe and the solution of NaOH is supplied into a two-fluid nozzle 14, as one fluid, and hence cooling and desulfurization treatment of combustion exhaust gas can be simultaneously and satisfactorily carried out. Sufficient amount of NaOH required for producing sodium sulfite (Na2SO3) which is produced by the reaction between NaOH and SO2 of combustion exhaust gas is contained in the aqueous solution sprayed from a cooling water spray device 13. Water is evaporated and sodium sulfite is turned into powder which is collected at a dry dust collector 4. In this manner, the sprayed aqueous solution acts so as to simultaneously effect cooling the temperature of the combustion exhaust gas to a specifeed temperature and reducing the concentration of SO2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a combustion engine equipped with a gas cooler equipped with a cooling water spray device, a dry dust collector, and a chimney that processes combustion exhaust gas generated from an incinerator, etc. by removing dust, desulfurization, etc. This relates to exhaust gas treatment equipment.

[Conventional technology] Generally, combustion exhaust gas generated from incinerators, boilers, etc.
It is a high-temperature gas with a temperature of 00 to 800°C and contains soot, SO2, etc., so it is necessary to remove them and release them into the atmosphere. Therefore, various types of equipment for treating these combustion exhaust gases have been proposed and used for a long time. Exhaust gas desulfurization treatment equipment can be roughly divided into equipment suitable for dry absorption methods and wet absorption methods. Equipment adapted to the wet absorption method treats S02, etc. with an alkaline solution or slurry as an absorbent, so the desulfurization rate is high and excellent, but there are problems such as corrosion, which increases VLll costs and maintenance costs. .

Therefore, many facilities adapted to dry absorption methods are being considered. - For example, there is a facility in which limestone powder or slaked lime is blown into the inside of a boiler, thermally decomposed into oxides, and while this is transported by combustion exhaust gas, S02 is fixed and air is supplemented with a dust collector. In this equipment, the boiler itself becomes the desulfurization device.

As another example, when using a dry dust collector (electrostatic precipitator, etc.), it is necessary to cool the high-temperature gas of 600 to 800 °C and maintain the temperature of the combustion exhaust gas at the inlet of the dust collector at about 200 to 400 °C. Therefore, a flue gas treatment facility is used that is connected to the flue gas generating furnace and includes a gas cooler with a cooling water spray device, a dry dust collector, and a chimney.

In addition, Japanese Patent Application Laid-open No. 63-236513 discloses that, as a treatment for combustion exhaust gas containing organic chlorine compounds, a cooling tower such as a water sprinkler type (gas cooler) is installed between the outlet of a garbage incinerator and an electrostatic precipitator. (same) describes rapid cooling to 250°C or lower. The combustion exhaust gas introduced into the gas cooler having these cooling water spray devices is rapidly cooled along the adiabatic cooling line by water evaporation. In this case, a liquid fluid nozzle is generally used as the nozzle of the cooling water spray device.

[Problems to be Solved by the Invention] However, the above-mentioned flue gas desulfurization treatment equipment that uses the boiler itself as a desulfurization device is effective in saving on auxiliary equipment for desulfurization, but there is a problem in terms of the desulfurization effect. .

In addition, a gas cooler dry type seating machine with a cooling water spray device,
Combustion exhaust gas treatment equipment equipped with a chimney has the following problems.

In a gas cooler equipped with a cooling water spray device, water from the cooling water spray does not completely evaporate and adheres to the inner wall as droplets, resulting in the generation of clinker such as Na2SO3.

FIG. 5 is a diagram showing the state of clinker generation in the gas cooler. In FIG.
A caustic soda (hereinafter referred to as NaOH) solution as a -fluid is sprayed in the direction shown by the arrow from the retan nozzle 3 provided on the shoulder 1b to the combustion exhaust gas introduced in the direction shown by the thick arrow from the combustion exhaust gas. cooling and S02, HCI
Such removal processing is performed. In this case, the sprayed water may not completely evaporate and may adhere to the inner wall as droplets. This is because - as a fluid, the droplet diameter of the NaOH solution is large at about 250 μm, so it takes time and force to completely evaporate, and it does not completely evaporate inside the gas cooler 1, but collides with the inner wall and adheres to it. Then, clinker 2 is generated. When the clinker 2 is generated, it gradually grows and finally blocks the combustion exhaust gas passage, making it impossible to smoothly process the combustion exhaust gas.Here, 1c is a manhole.

Further, in the dry type dust collector as described above, it is necessary to maintain the temperature of the combustion exhaust gas immediately before the inlet at 200 to 400°C. If the combustion exhaust gas temperature is less than 200°C, it will be below the acid dew point and corrosion of the dust collection chamber, dust hopper, etc. will occur. Furthermore, the heat recovery efficiency in the heat recovery device that is normally installed subsequently is reduced. If the combustion exhaust gas temperature exceeds 400° C., the strength of the device becomes a problem and the dust removal rate decreases.

On the other hand, the SO□ of the flue gas must be lowered by the NaOH solution to the set value using the NaOH solution as a fluid, so the cooling of the flue gas and the adjustment of the flue gas to the set S02 concentration are necessary. However, it becomes a conflicting control and it is difficult to satisfy 0 at the same time.
The present invention aims to solve the above-mentioned problems, and aims to provide a method for preventing the generation of clinker, collecting dust, removing SO2, HCI, etc., and recovering heat efficiently. do.

[Means for Solving Problem i1] In order to achieve the above object, the present invention provides a combustion exhaust gas treatment facility equipped with a gas cooler equipped with a cooling water spray device, a dry dust collector, and a chimney. The nozzle is a two-fluid nozzle, one fluid supply mechanism that supplies the two-fluid nozzle is a combination supply mechanism for cooling water and Na'o H stock solution that has a mechanism that can each be independently controlled, and the other fluid supply mechanism is a two-fluid nozzle. This is a combustion exhaust gas processing equipment characterized by an air supply mechanism.

[Operation] Since the present invention involves purification as described above, when two fluids are sprayed into high-temperature combustion exhaust gas, the droplet diameter of the NaOH solution is approximately 150% compared to the diameter of the sprayed particles from the liquid nozzle.
Since the size can be appropriately reduced to less than μm, the time required for complete evaporation of the droplets in the combustion exhaust gas can be shortened, as will be described later, and the adhesion of the droplets to the inner wall of the gas cooler can be prevented. I can do it.

In the present invention, one fluid supply mechanism is a combination supply mechanism for cooling water and NaOH stock solution, and has a mechanism that can independently control each of them. Therefore, a combustion exhaust gas measuring device installed in front of the gas cooler measures the gas temperature, SO2 concentration, etc. of the combustion exhaust gas, and the cooling water supply pump is operated to supply the necessary cooling water to the gas cooler. Cooling of the combustion exhaust gas is measured by a temperature measuring device in front of the inlet of the dry dust collector, and controlled to maintain it at a predetermined temperature.

On the other hand, the concentration of S02 is measured by an S02 meter installed just before the chimney, and in response to the difference between that value and the set value, the NaOH stock solution injection pump is activated to measure the concentration of S02 in the combustion exhaust gas. The required absolute amount of NaOH is supplied as a NaOH stock solution in order to approach the set value. N
The a01-1 stock solution is introduced into the cooling water supply pipe, and NaOH
As a solution, it is supplied as one fluid to a two-fluid nozzle. Therefore, it is possible to carry out an operation that satisfies both the cooling of the combustion exhaust gas and the desulfurization treatment at the same time.

The aqueous solution sprayed from the cooling water spray device is made to contain the absolute amount of NaOH required to react with SO2 of the combustion exhaust gas to produce sodium sulfite (NaaSOx). The water evaporates and the sodium sulfite turns into powder, which is collected in a dry dust collector. The aqueous solution sprayed in this manner can act to simultaneously satisfy a predetermined cooling of the temperature of the combustion exhaust gas and a reduction in the S02 concentration.

In the present invention, combustion exhaust gas is collected by a gas cooler, a dry dust collector,
After processing such as dust removal and desulfurization, the retained heat is recovered by a heat recovery device and released into the atmosphere from the chimney.

In particular, a dry electric collector can be used as the dry collector I1. This is because dry electrostatic precipitators can easily collect fine particles and are less affected by the properties of gas and dust. Examples of heat recovery devices include waste heat boilers.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 0, 4 is a dry electrostatic precipitator, 5 is a chimney, 6 is a combination supply mechanism, 7 is a cooling water tank, 8 is a NaOH stock solution tank, and 10 is SO2 11 is a temperature measuring device, and 13 is a cooling water spray device.

A rotary kiln 17 is used as an incinerator, and a gas cooler 1 is provided through a discharge pipe from the rotary kiln 17 to treat soot, S02, etc. of combustion exhaust gas generated from the rotary kiln 17. The gas cooler 1 is usually provided with a plurality of cooling water spray devices 13 on its upper part. The nozzle of the cooling water spray device 13 is a two-fluid nozzle, and one fluid supply mechanism that supplies the two-fluid nozzle is a combination supply mechanism 6 for cooling water and caustic soda stock solution having a mechanism that can independently control each fluid supply mechanism, and the other fluid The supply mechanism is an air supply mechanism 9.

A connecting pipe 19 is provided at the lower part of the gas cooler 1 for introducing combustion exhaust gas, which has been cooled to a predetermined temperature and treated to a predetermined S02 concentration, into the dry electrostatic precipitator 4. The coarse soot and dust treated by the gas cooler 1 are sent to a discharge tank 18 through a discharge port provided at the bottom of the gas cooler 1, and are removed therefrom. Similarly, in the dry electric inverter 4, soot and dust are collected and sent to the discharge tank 18 from the discharge port provided at the bottom, where they are removed. On the other hand, the clean combustion exhaust gas from which dust has been removed undergoes heat exchange in the waste heat boiler 24, and the retained heat is recovered. The heat-recovered combustion exhaust gas is discharged into the atmosphere through the chimney 5 by the induced draft l1115.

FIG. 2 is a diagram showing an example of a two-fluid nozzle used in the present invention.

Here, the two-fluid nozzle 14 has a main body composed of an inner pipe 16 for liquid and an outer pipe 15 for air, and a cap 19 is attached to the tip thereof. The liquid inner tube 16 contains NaOH.
A fluid supply pipe for the solution is connected to an air supply pipe, and an air supply pipe is connected to the outer pipe 15 for air.

Further, in FIG. 1, a cooling water tank 7 is connected via a cooling water supply pipe 2o. On the other hand, in the middle of the cooling water supply pipe 20, there is a NaO tube connected to the NaOH stock solution tank 8 at one end.
An H stock solution supply pipe 21 is connected so that the gas cooler 1 can be supplied with the absolute amount of NaOH required to react with the combustion exhaust gas S02 to produce sodium sulfite (Na2SOs). The concentration of S02 in the combustion exhaust gas is at chimney 5.
The NaOH solution injection pump 22 is operated in response to the difference between the SO2 meter 10 attached immediately before the SO2 meter 10 and the set value, and the NaOH solution injection pump 22 operates as necessary to bring the concentration of 802 in the combustion exhaust gas closer to the set value. The absolute amount of NaOH is NaOH
Supplied as a solution. Regarding the temperature of combustion exhaust gas,
The temperature of the combustion exhaust gas just before the inlet of the dry electrostatic precipitator 4 is set to 20
In order to maintain the temperature at 0 to 400° C., the cooling water supply pump 23 is operated according to the temperature of the combustion exhaust gas measured by the temperature measuring device 11, and the necessary cooling water is supplied to the gas cooler 1. In this case, for the amount of cooling water supplied, N a
Since the amount of OH solution is about 1/100, NaO
The influence of the amount of H solution on cooling can be ignored.

12 is a combustion exhaust gas measuring device in front of the gas cooler;
This measures the gas temperature, So concentration, etc. of the combustion exhaust gas.

FIG. 3 is a diagram showing the relationship between droplet diameter and complete evaporation time of a two-fluid nozzle. Here, a logarithmic scale is used, and 50μ
m, 100℃, 150℃ for 70μm, 100μm
, 200°C, 250°C, and 300°C. It can be seen from the thick arrow that the complete evaporation time at 300° C. in the case of 100 μm is 0.34 seconds. For comparison, in the case of a single-fluid nozzle, the droplet diameter is about 250μ, so it is 1 minute from the dotted arrow.
．． It turns out that it takes 6 seconds.

As for the two-fluid nozzle, a commercially available one can be used, and a suitable droplet diameter can be selected by selecting dimensions, liquid pressure (kg/c2), etc.

Figure 4 shows N when using the two-fluid nozzle of the present invention.
FIG. 3 is a diagram showing the relationship between the aOH injection equivalent ratio (N a OH/S O2) and the desulfurization rate. The solid line A is an example of the present invention, and the dotted line B is a comparative example, in which a first-flow nozzle is used instead of a two-fluid nozzle.
As is clear from Figure 0 under the same conditions except that a two-fluid nozzle was used, a high desulfurization rate was obtained when a two-fluid nozzle was used.

This is considered to be because when a two-fluid nozzle is used, the adhesion of droplets can be prevented, so desulfurization is performed in accordance with the NaOH injection equivalence ratio.

(Example) Using the equipment of the present invention, 4100 O
Nnf/H was processed by the method of the present invention.

Five two-fluid nozzles of a cooling water spray device were arranged in the upper part of the gas cooler. A two-fluid nozzle capable of obtaining a droplet diameter of 100 μm was used.

The temperature of the combustion exhaust gas just before the entrance of the dry electrostatic precipitator is set to 300℃.
℃, and the concentration of S02 in the combustion exhaust gas was set to 30 ppm just before the chimney.

Table 1 shows the average experimental results when the equipment of the present invention was operated for 16 hours.

As is clear from Table 1, it was possible to obtain predetermined values for the desulfurization rate and the HCI removal rate. No clinker was generated in the gas cooler during operation, and exhaust gas treatment was performed smoothly.

[Effects of the Invention] According to the equipment of the present invention, the gas cooler is arranged in front of the dry dust collector, and the nozzle of the cooling water spray device of the gas cooler is a two-fluid nozzle. By making it possible to independently control the cooling water to be purified and the NaOH stock solution, it is possible to prevent clinker from forming on the inner wall of the gas cooler, and to simultaneously cool the combustion exhaust gas temperature appropriately and adjust the S02 concentration. As a result, dust collection of combustion exhaust gas, removal of SO2, HCI, etc., and heat recovery can be efficiently processed.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing an embodiment of a two-fluid nozzle used in the present invention, and Fig. 3 is a diagram showing the droplet diameter and completeness of the two-fluid nozzle used in the present invention. Figure 4 is a diagram showing the relationship between evaporation time, Figure 4 is a diagram showing the relationship between NaOH injection equivalent ratio (NaOH/SO2) and desulfurization rate in the case of the two-fluid nozzle used in the present invention, and Figure 5 is a diagram showing the relationship between desulfurization rate and clinker in a gas cooler. It is a figure showing the occurrence state of. 1... Gas cooler, 4... Dry electrostatic precipitator, 5...
...Chimney, 6...Combination supply mechanism, 7...Cooling water tank, 8...NaOH stock solution tank, 10...SO2
11... Temperature measuring device, 13... Cooling water spray device, 14... Two-fluid nozzle.

Claims (1)

[Claims] In a combustion exhaust gas treatment facility equipped with a gas cooler having a cooling water spray device, a dry dust collector, and a chimney, the nozzle of the cooling water spray device is a two-fluid nozzle, and one fluid supply mechanism for supplying to the two-fluid nozzle is provided in each case. A combustion exhaust gas processing equipment characterized by having a combined supply mechanism for cooling water and a caustic soda stock solution that can be independently controlled, and an air supply mechanism as the other fluid supply mechanism.