JPS62140623A - Method for preventing corrosion of filter of dust collector in dry flue gas desulfurizer - Google Patents

Abstract

PURPOSE:To prevent the corrosion of the filter of a dust collector by providing a heat exchanger between an SO2 reducing furnace and the dust collector, and heating and cooling the SO2 reducing furnace outlet gas with the heat exchanger to control the temp. of the gas entering the dust collector. CONSTITUTION:The SO2-enriched gas discharged from an activated carbon regeneration tower is introduced into the SO2 reducing furnace 2 from a line 1 and reduced by contact with a carbonaceous catalyst. A gas contg. vaporized sulfur is taken out, then supplied to the shell side of the heat exchanger 4, heat-exchanged with the gas supplied to the tube side from a line 5, and sent to the dust collector 7 through a line 6. Since the filter of the dust collector 7 exhibits corrosion resistance only in the temp. range 240-280 deg.C, the gas temp. of the line 6 is detected, a control valve 11 or 13 is regulated by a controller 8, hence the combustion waste gas or air is sent into the line 5, and the gas temp. of the line 6 is kept at 240-280 deg.C.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a dust collector installed downstream of an SO2 reduction furnace of a dry flue gas desulfurization equipment and used to remove dust contained in the reduction furnace outlet gas. This invention relates to a method for protecting a filter from corrosion.

[Prior Art] As one of the dry flue gas desulfurization methods, a method is known in which SO2-containing flue gas is brought into contact with an activated carbon adsorbent to adsorb and remove SO2. In this method, activated carbon that has adsorbed SC2 is regenerated with high-temperature inert gas, and SC2 is recovered from the activated carbon as S02 rich gas.

Then, this S○2 rich gas is supplied to the S02 reduction furnace,
S02 is reduced to vaporous sulfur by contacting it with a carbonaceous catalyst such as coke in cross flow. The reducing furnace outlet gas contains vaporous sulfur.

This is passed through a dust collector to remove dust, and then sent to a sulfur recovery device to condense and separate vaporized sulfur.Then, the remaining gas is supplied to the Claus reactor to generate new sulfur, and the reactor exits. It is common to condense and separate this sulfur from the gas.

[Problems to be solved by the invention] When implementing the dry flue gas desulfurization method, the preheating of the reduction furnace required at startup of the SO2 reduction furnace is performed using combustion exhaust gas, but this exhaust gas contains a considerable amount of For example, heavy oil combustion exhaust gas contains approximately 11,000 SC2.
Usually, about pp SC2 is included. Therefore, until the temperature of the reduction furnace rises to the reduction reaction temperature of S02, the exhaust gas S02 used for preheating is sent as is to the dust collector.

Incidentally, stainless steel fibers are used in the filters of dust collectors in flue gas desulfurization facilities. This filter can maintain corrosion resistance only in the temperature range of 240 to 280 degrees Celsius, so if gases containing water vapor, SO, SOI, etc. come into contact with the filter at temperatures below the dew point, the filter will be corroded. . Therefore, in the conventional method in which it is customary to preheat the S02 reduction furnace with S02-containing exhaust gas as described above, it is almost impossible to avoid corrosion of the dust collector filter at startup.

Regarding the steady operation of the S02 reduction furnace, the H2S/SO2 in the reduction furnace outlet gas or (H2S+C03)/So2
Since the temperature inside the reduction furnace is controlled so that the molar ratio of SO and SO is maintained at about 2, the temperature of the gas at the exit of the reduction furnace changes accordingly. Therefore, the temperature of the reducing furnace outlet gas is 240
Exceeding the temperature range of ~280'C will also corrode the precipitator filter.

[Means for Solving the Problems] The present invention provides a heat exchanger between the S02 reduction furnace of the dry flue gas desulfurization equipment and the dust collector installed downstream thereof, and the heat exchanger By heating or cooling the outlet gas of the reduction furnace to adjust the temperature of the gas entering the precipitator,
Prevent corrosion of the dust collector filter mentioned above.

[Function] Hereinafter, the filter corrosion prevention method of the present invention will be explained in more detail with reference to the accompanying drawings. When each device of the dry flue gas desulfurization equipment is in steady operation, the So2-rich gas brought from the activated carbon regeneration tower (not shown) is sent from line 1 to SO2 reduction furnace 2 together with oxygen-containing gas (typically air). is introduced and comes into contact with a carbonaceous catalyst such as coke forming a moving bed within the furnace. The temperature inside the reduction furnace is such that S02 is reduced to vaporized sulfur, and H2S/S of the reduction furnace outlet gas is
The molar ratio o□ or (I-I, S+C03)/So is constantly adjusted so that the molar ratio is maintained at approximately 2. Therefore, the molar ratio is maintained at approximately 2 from the reduction furnace 2, and gas containing vaporous sulfur is taken out. This reducing furnace outlet gas is then supplied to, for example, the shell side of the heat exchanger 4,
After exchanging heat with the gas supplied from line 5 to the tube side, it is sent to dust collector 7 via line 6.

As mentioned earlier, the filter of dust collector 7 is 240~2
It exhibits corrosion resistance only in a temperature range of 80°C. Therefore,
In the present invention, the temperature of the gas flowing through the line 6 is detected by the control device TIC indicated by the reference numeral 8, and the temperature is 240°C.
If the temperature is below 'C, the combustion exhaust gas sent to the line 10 from the tail gas incinerator 9, which will be described later, is supplied to the line 5 via the control valve 11 to heat the reducing furnace outlet gas.

On the other hand, when the temperature of the gas flowing through the line 6 is 280° C. or higher, air from the air blower 12 is supplied to the line 5 via the control valve 13 to cool the reducing furnace outlet gas. Therefore, the filter of the precipitator 7 will not be corroded by the gas from the line 6.

The gas from which dust has been removed in the precipitator 7 is supplied to a sulfur recovery device 14, which usually comprises a sulfur condenser, a knockout drum, and a sulfur scrubber, where vaporized sulfur in the gas is recovered. The gas from which the vaporous sulfur has been separated is then sent to the Claus reactor 15 and subjected to the Claus reaction, and the Claus reactor outlet gas containing vaporous sulfur produced here is a sulfur reactor having the same structure as described above. After being supplied to the recovery device 16 and condensing and separating the vaporous sulfur, it is sent to the tail gas incinerator 9 and incinerated.

Then, the combustion exhaust gas obtained at this time is sent from the line 10 to the line 5 as necessary, and is supplied to the heat exchanger 4.

Next, the present invention will be described in detail at the time of startup of the SO2 reduction furnace 2. Generally, the reduction furnace is preheated by introducing heavy oil combustion exhaust gas supplied from the line 3 into the reduction furnace 2.

As mentioned above, this preheating exhaust gas contains water vapor, SO2,
The gas contains SO1, etc., and after passing through the reduction furnace is sent to the dust collector 7 via the heat exchanger 4, so if the gas temperature is below the dew point, the filter of the dust collector will corrode. However, in the present invention, in the heat exchanger 4, the preheating exhaust gas leaving the reduction furnace is heated to a temperature above the dew point using an appropriate heating medium, for example, heavy oil combustion exhaust gas. Therefore, the dust collector filter will not be corroded even during startup.

[Effects of the invention] If a heat exchanger is installed between the SO2 reduction furnace of the dry flue gas desulfurization equipment and the dust collector, the temperature of the gas entering the dust collector can be adjusted as desired. Corrosion of the dust collector filter, which exhibits corrosion resistance only in the temperature range of ~280°C, can be prevented.

[Brief explanation of drawings]

The accompanying drawings are flow sheets for carrying out the method of the present invention. 1... SO2 rich gas line 2... SO2 reduction furnace 3... Gas line for preheating the reduction furnace 4... Heat exchanger 5... Gas line for heating/cooling 6... Dust collector inlet gas Line 7... Dust collector 8.
...Control equipment 9...Tail gas incinerator 10...Combustion exhaust gas line 11.13.
...Control valve 12...Air blower

Claims (1)

[Claims] 1. A heat exchanger is installed between the SO_2 reduction furnace of the dry flue gas desulfurization equipment and the dust collector, and the outlet gas of the SO_2 reduction furnace is heated or cooled by this heat exchanger and sent to the dust collector. A method for preventing corrosion of a filter of a precipitator, characterized in that the temperature of the entering gas is adjusted.