JPH0122012B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves spraying an alkaline solution or the like into a reaction tower to cause a neutralization reaction with sulfur oxides in the gas, and then capturing reaction products and unreacted materials in a bag filter installed afterward. Regarding semi-dry desulfurization equipment.

In semi-dry desulfurization equipment, the lower the reaction tower outlet temperature, the higher the desulfurization rate, but in order to collect the reaction products as dry powder, it is necessary to maintain the temperature 15 to 20°C higher than the saturation temperature.
The temperature of 5 to 10°C in this part greatly affects the desulfurization rate.

Therefore, the reaction tower outlet temperature is 5 to 10% lower than the saturation temperature.
It is characterized by controlling the temperature to a temperature higher than 100°C and guiding it to around 100°C using a heating device through a heating bag filter. Previously, part of the exhaust gas was bypassed and used for heating.

Figure 1 shows the flow. That is, the slurry is sprayed from the upper part of the reaction tower 2 in which the alkali slurry or solution is spray-dried using a nozzle 3, and then a bag filter 4 is installed to collect and clean dust, reaction products, and excess alkali powder. The generated gas is released into the atmosphere from the chimney 5 in the reaction tower and the dust collected in the bag filter, and the reaction products are collected in the hopper 6.
is discharged outside the machine.

Conventional semi-dry desulfurization equipment consisting of a reaction tower and a bag filter cannot lower the reaction tower outlet temperature below approximately 70°C (saturation temperature + approximately 20°C). However, the lower the outlet temperature, the higher the desulfurization rate becomes. Also, when comparing the construction and operating costs, the semi-dry method is about half the cost of the wet method. Therefore, when the required desulfurization rate becomes high, it is necessary to adopt a wet method, and depending on the outside air conditions, water vapor in the gas condenses at the reaction tower outlet temperature of 70°C, resulting in the generation of white smoke. To prevent this, a method is adopted in which a part of the exhaust gas is bypassed through the reaction tower and mixed. However, this method lowers the desulfurization rate. There is also a method of installing an afterburner just before the chimney, but this is not preferred as it increases fuel costs.
Furthermore, if the outlet temperature is 70°C, not only will there be a problem with white smoke, but the diffusion of exhaust gas will be poor, so reheating will be necessary as described above.

Therefore, in conventional semi-dry desulfurization equipment, the exit gas temperature cannot be lowered, so the desulfurization rate is low, white smoke is generated, and diffusion is poor, so heating is required, and bypass heating reduces the desulfurization rate. However, afterburner heating had drawbacks such as high fuel costs.

The present invention solves the drawbacks of the conventional semi-dry desulfurization equipment, and uses a rotary heater that does not require fuel costs to heat the outlet gas to around 100℃ using the thermal energy of the inlet flue gas. The present invention provides a desulfurization device that controls the gas temperature at the outlet of the reaction tower to 5 to 10°C above the saturation temperature.

Hereinafter, embodiments of the present invention will be explained based on the drawings. In the conventional semi-dry method shown in Fig. 1, the inlet temperature of the reaction tower 2 is 150°C, and the outlet gas temperature
However, in the apparatus of the present invention shown in Fig. 2, a rotary heater 7 is installed at the outlet of the reaction tower, and after heating the gas temperature of 20°C above the saturation temperature to about 100°C, it is introduced into the bag filter 4. , dust removal and secondary desulfurization are performed and clean gas is discharged from the chimney. On the other hand, the inlet gas is heated to about 100 to 130℃ from 150℃ using a rotary heater.
After reducing the temperature to ℃, it is led to the inlet of the reaction tower.

In the device of the present invention, the gas that was released into the atmosphere at the saturation temperature +20°C in the conventional semi-dry method has been reduced to approximately 100%.
Since it is heated to ℃, generation of white smoke is prevented and the diffusion effect is improved. On the other hand, since the operating temperature of the bag filter is approximately 50°C higher than the saturation temperature, the fear of clogging of the cloth due to mist can be reduced, and
The properties of the dust collected by the bugs also improve, making transportation easier.

On the other hand, when it becomes necessary to increase the required desulfurization rate, a high desulfurization rate can be obtained by lowering the reaction tower outlet gas temperature from the saturation temperature +20°C to +10°C. On the other hand, rotary heaters have a gas leak of several percent.

Currently, rotary heaters are often installed on the downstream side of wet gas absorption equipment, but the clean gas is re-contaminated by leak gas, but in the case of this equipment, dust, reaction products, and excess alkali (unreacted alkali) powder are removed. 5% of this is collected in the reaction tower and the remaining 95% is collected in a bag filter. Therefore, the unreacted alkali powder on the surface of the cloth reacts with the sulfur oxide in the leaked exhaust gas, so there is no decrease in the desulfurization rate, and the dust in the leaked gas is completely collected by this bag. Re-contamination of clean gas by leak gas does not occur.
In other words, by effectively utilizing the thermal energy of exhaust gas,
Increase in desulfurization rate, prevention of white smoke and increase in diffusion efficiency can be obtained. Moreover, safe operation of the bag filter becomes easier.

[Brief explanation of drawings]

Figure 1 is a process flow diagram of a conventional semi-dry desulfurization equipment.
FIG. 2 is a process flow diagram of the semi-dry desulfurization apparatus of the present invention. Incidentally, the symbols of the main parts in the figure are as follows. 1
... Flue, 2 ... Reaction tower, 3 ... Nozzle, 4 ...
Bug filter, 5...Chimney, 6...Hotsupa, 7
...Rotary heater.

Claims (1)

[Claims] 1. Spray an alkaline solution or slurry into the reaction tower to cause a neutralization reaction with sulfur oxides in the exhaust gas, and completely evaporate the liquid using the heat retained in the exhaust gas. Dust, reaction products, and In a semi-dry desulfurization device that collects unreacted dry alkali powder, a rotary heater is installed between the reaction tower and the bag filter, and the gas at the outlet of the reaction tower is heat exchanged with the exhaust gas by the rotary heater. A semi-dry type desulfurization equipment characterized in that after raising the temperature, it is introduced into a bag filter to perform dust removal and desulfurization.