JPS6060908A - Method for recovering liquefied gaseous sulfurous acid from apparatus for dry-desulfurizing stack gas - Google Patents

Abstract

PURPOSE:To recover efficiently liquefied gaseous SO2 by removing dust from exhaust gas contg. gaseous SO2 at high concn. after regenerating a desulfurizing agent, cooling the gas to a temp. close to room temp., drying it, and cooling the dried gas to the liquefaction temp. of gaseous SO2. CONSTITUTION:Stack gas contg. SOx is introduced into an absorption tower 1, where it is desulfurized. A desulfurizing agent contg. absorbed SOx is fed to a regeneration tower 2, where it is heated to convert the SOx into SO2, and gas contg. SO2 as starting material is introduced into a dust collector 3 to remove dust. The gas is then introduced into coolers 4, 5, where it is cooled to a temp. close to room temp., and condensed water is sprayed into stack gas from a spray nozzle 8 through a receiving tank 6. The cooled gas is pressurized with a blower 10 and introduced into a drier 11a or 11b, where it is dried to such a dew point that moisture in the gas is not condensed in a gaseous SO2 condenser 23. The dried gas is compressed with a compressor 21 and introduced into the condenser 23 through an after-cooler 22. In the condenser 23, the gas is cooled to the liquefaction temp. of gaseous SO2 to recover the gaseous SO2 in the gas as liquefied gaseous SO2.

Description

Detailed Description of the Invention The present invention is a dry flue gas desulfurization device that removes SOx from flue gas from boilers, heating furnaces, etc. This invention relates to a method for recovering liquefied sulfur dioxide gas from.

Normally, when exhaust gas containing about 11,000 pp of SOx is desulfurized using a dry flue gas desulfurization device using activated carbon or the like, the SO2 concentration in the recycled exhaust gas is concentrated to 15 to 25%. Conventionally, to recover the sulfur content in this recycled exhaust gas, coal or coke was partially combusted at temperatures of 700 to 900°C.
Regenerated exhaust gas is supplied to a carbon reactor maintained at a high temperature of The exhaust gas is led to the Claus reactor, and unreacted So2 in the exhaust gas and H2S generated by side reactions in the carbon reactor are converted into 2H2S +
A common method is to recover elemental sulfur through the reaction So2→'/2S2+2H20.

In this conventional method, the amount of sulfur removed by the desulfurization equipment is equivalent to 1 day's worth of elemental sulfur! If the equipment size is 1 liter or less than 15 tons, the rate of heat radiation loss in each reactor will be large, which will be economically disadvantageous, and the carbon reactor will generate partial combustion gas of coal or coke in addition to the recycled exhaust gas. Therefore, as the amount of gas to be treated increases, the SO2 concentration in the gas to be treated decreases, resulting in a slight decrease in desulfurization efficiency, and carbon materials such as coal or coke are required to recover elemental sulfur. There are drawbacks such as:

The present invention has been made in view of the above points, and uses desulfurization agent regeneration exhaust gas containing a high concentration of sulfur dioxide gas, which is emitted from a desulfurization agent regeneration tower of a dry flue gas desulfurization equipment, as a raw material gas, and removes dust contained in this raw material gas. After removing the raw material gas, the raw material gas is cooled to around room temperature, and then dried to a dew point at which the moisture in the raw material gas does not condense in the sulfur dioxide gas condenser, the raw material gas is compressed, and the raw material gas is further condensed into sulfur dioxide gas. By cooling the sulfur dioxide gas in the raw material gas to a temperature that liquefies it in the reactor and recovering the SO2 in the regenerated exhaust gas as liquefied sulfur dioxide gas, it is easy to operate, and even small-scale desulfurization equipment can liquefy the sulfur dioxide gas in the regenerated exhaust gas. SO2 can be recovered efficiently and economically,
The object of the present invention is to provide a method for recovering liquefied sulfur dioxide gas from a dry flue gas desulfurization device, which is easy to handle because the recovered material is a liquid.

Hereinafter, the configuration of the present invention will be explained based on the drawings.

Exhaust smoke containing SOx from boilers, heating furnaces, etc.
It is introduced into the absorption tower 1 at a temperature of 0 to 160°C, is desulfurized by a desulfurizing agent such as activated carbon filled in the absorption tower 1, and then exits the absorption tower 1. The desulfurizing agent that has absorbed SOx in the flue gas is extracted from the lower part of the absorption tower 1 and enters the regeneration tower 2.

The regeneration tower 2 has a built-in heating pipe, and high-temperature gas such as hot air generated by a hot air stove or high-temperature exhaust gas from a boiler is passed through the heating pipe, and the desulfurization agent in the regeneration tower 2 is heated to 350 to 400%
Heat to 0°C. The heated desulfurization agent is released as SOx f SO2 adsorbed in the absorption tower 1, and N20. CO2, N2, etc. are generated, and the SO2 concentration in the regenerated exhaust gas is usually 15 to 25 VO1%. The present invention recovers liquefied sulfur dioxide gas using the regenerated exhaust gas released from the desulfurization agent in the regeneration tower 2 as a raw material gas.

The liquefied raw material gas (hereinafter referred to as raw material gas) containing a high concentration of S02 from the regeneration tower 2 enters the dust collector 3, and after removing dust from the raw material gas, enters the raw material gas cooler 4.5. The raw material gas cooler 4.5 is cooled with cooling water and cooling gas, respectively, and the raw material gas is kept at around room temperature, that is, 20 to 40 degrees.
It is cooled to C. In the process of cooling the raw material gas, water vapor is condensed in the raw material gas, and condensed water is extracted from the raw material gas cooler 4.5. This condensed water contains 2-3% S.
Since O2 is dissolved, this condensed water is sent to the condensed water receiving tank 6,
It is sprayed from a spray nozzle lv8 to the flue gas line that enters the absorption tower 1 of the desulfurization equipment via the pump 7, and is evaporated into the flue gas.

The raw material gas exiting the raw material gas cooler 4.5 is externally pressured by the blower 10 to a pressure slightly higher than normal pressure, and then transferred to the dryer 11a.
to go into. The dryer is filled with dehumidifiers such as activated alumina, zeolite, molecular sieves, and silica gel, and is dried to the extent that the moisture in the raw gas is condensed in the SO2 liquefaction process. In this tank, it is necessary that the dew point of the moisture in the raw material gas at the dryer intake is usually -40°C or less. The dryer is used to continuously dry the raw material gas.
Usually, two or more units are provided. The drawing shows an example in which two dryers are provided. One of the dryers 11a is in a state where the raw material gas is vented and dried. The other dryer 11b passes through a blower 12 and an air heater 13, and
Air heated to 0 to 300°C is ventilated, and the dryer 11
This shows the condition in which the desiccant filled in b is being regenerated. To switch the dryer between drying operation and regeneration operation, for example, if the raw material gas drying time is 4 hours and the dehumidifier regeneration time using heated air is 3 hours, each time is set on a timer and the regeneration using heated air is performed. When the time has passed, the shutoff valve 14 closes, the shutoff valve 15 opens, and cold air flows into the blower 1.
Step 2 enters the dryer 11b and starts cooling the regenerated desiccant with heated air. Next, when the drying time of 4 hours has elapsed, the cutoff valves 15 and 16 are closed and the cutoff valves 17 and 14 are opened, and the raw material enters the dryer 11b where the regeneration has been completed, and the raw material gas is dried. . On the other hand, heated air enters the dryer 11a through the blower 12 and air heater 13, and the desiccant is regenerated.゛The settings for the dehumidification time of the raw gas, the regeneration time of the dehumidifier, and the cooling time of the dehumidifier are just examples to explain the operation of the dryer, and each operation of dehumidification, regeneration, and cooling is If three or more dryers are used, drying can be carried out individually and in parallel. In addition to removing moisture from the raw material gas, the drying process also removes impurity gases such as ammonia gas and hydrochloric acid that may be present in trace amounts in the raw material gas, and has the effect of increasing the purity of the liquefied sulfur dioxide gas. On the other hand, some S02 in the regenerated exhaust gas is also adsorbed by the dehumidifier, so the regenerated exhaust gas from the dehumidifier is circulated through the flue gas line that enters the absorption tower 1 of the desulfurization equipment to remove SO2 in the regenerated exhaust gas. .

High-temperature exhaust gas from a hot air generator, boiler, etc. is used to heat the air in the air heater 13, and the exhaust gas after being used for heating the air is made to join the flue gas line by the blower 18.
After removing SOx from the exhaust gas, it is released into the chimney. If the high-temperature exhaust gas for heating the air is clean gas that does not contain SOx, it is released directly into the chimney. 2o is a blower for discharge.

The raw material gas dehumidified in the dryer is reduced to 4 to 6% in the compressor 21.
Compressed to G. The compressed raw material gas enters the aftercooler 22 and is cooled down to around room temperature using cooling water, and then introduced into the sulfur dioxide gas condenser 23. In the sulfur dioxide gas condenser 23, the raw material gas is cooled to a temperature at which S02 in the raw material gas is liquefied in the condenser 23, using a prine or the like cooled to below -30° C. by the refrigerator 24 as a refrigerant. Usually, the raw material gas is cooled to -20 to -35°C, and about 90% of the S02 in the raw material gas is recovered as liquefied sulfur dioxide gas.

The processing raw material gas (hereinafter referred to as processing gas) after recovering S02 in the sulfur dioxide gas condenser 23 is depressurized by the expansion valve 25 to a pressure slightly higher than normal pressure.

When the processing gas is rapidly expanded by the expansion valve 25, the processing gas is lowered to below the outlet temperature of the sulfur dioxide gas condenser 23 due to the Joule-Thomson effect. This low-temperature processing gas enters the raw material gas cooler 5, exchanges heat with the raw material gas, and is then circulated to the flue gas line that enters the absorption tower 1 of the desulfurization equipment in order to remove residual SO2 in the treated gas.

As explained above, the method of the present invention provides the following effects compared to conventional methods.

(1) Since the S O2 concentration at the outlet of the regeneration tower is high and the amount of gas to be treated is small, the equipment is small and the amount of utility effacement is small.

(2) Since it does not involve complicated reactions, it is easy to operate and automate. Additionally, since no wastewater is generated from the process, wastewater treatment equipment is not required.

(3) Since it is recovered as So, auxiliary raw materials are not required.
In addition, compared to the case of recovering as gypsum or sulfuric acid, the recovered by-products are lighter in weight and easier to handle because they are in liquid form.

(4) Since the amount of heat dissipated is small even with a small-scale device, it is more economical than conventional sulfur recovery methods.

(5) The recovered liquefied SO2 has a wide range of uses, including as a raw material for sulfuric acid, pesticides, pharmaceuticals, bleach, and non-aqueous solvents.

Next, embodiments of the present invention will be described.

Example 100,00 ONnf/H of exhaust gas containing SOx IoooI)II)m was desulfurized using a dry desulfurization device. In this case, the S○2 concentration in the raw material gas at the outlet of the regeneration tower is
Approximately 20 VO engineering%, moisture in raw gas is approximately 60 VO1%
The raw material gas amount was 60ONyd/H. This raw material gas was processed according to the flow shown in the drawing. That is,
So2 in the raw material gas after cooling and drying this raw material gas
'A degree is 45VO%, and this raw material gas is 5%l.
G and cooled to -25°C in a condenser. As a result, 88% of the So2 in the raw material gas could be recovered as liquefied sulfur dioxide gas. The power required to liquefy SO2 in the raw material gas includes a blower, compressor, and refrigerator, and the amount of cooling water for 13QKWH1 was 30 T/H, making it possible to recover liquefied sulfur dioxide gas with very little utility.

[Brief explanation of the drawing]

The drawing is a flow sheet showing an example of an apparatus for carrying out the method of the present invention. 1... Absorption tower, 2... Regeneration tower, 3... Dust collector,
4.5...Cooler, 6...Condensed water receiver, 7...Pump, 8...Spray nozzle, lO...Blower, ll
a,llb...Dryer, 12...Blower, 13...
・Air heater, 14.15.16.17...Shutoff valve,
18.20...Blower, 21...Compressor, 22...
・Aftercooler, 23...Sulfur dioxide gas condenser, 24
... Refrigerator, 25 ... Expansion valve amount Applicant: Kawasaki Heavy Industries Co., Ltd. agent Patent attorney Makoto Shiide - 2...□ (Par...

Claims (1)

[Scope of Claims] ■ Desulfurization agent regeneration exhaust gas containing high concentration of sulfur dioxide gas discharged from a desulfurization agent regeneration tower of a dry flue gas desulfurization device is used as a raw material gas,
After removing the dust contained in this raw material gas, the raw material gas is cooled to around room temperature, and then dried to a dew point at which the moisture in the raw material gas will not condense in the sulfur dioxide gas condenser, and then the raw material gas is compressed. A method for recovering liquefied sulfur dioxide gas from a dry flue gas desulfurization device, which further comprises cooling the raw material gas in a sulfur dioxide gas condenser to a temperature at which the sulfur dioxide gas in the raw material gas liquefies to recover liquefied sulfur dioxide gas. 2 The desulfurization agent regeneration exhaust gas containing a high concentration of sulfur dioxide gas emitted from the desulfurization agent regeneration tower of the dry flue gas removal 1IIFJ equipment is used as the raw material gas, and after removing the dust contained in this raw material gas, the raw material gas is heated to around room temperature. After cooling and then drying to a dew point at which the moisture in the raw material gas does not condense in the sulfur dioxide gas condenser, the raw material gas is compressed, and the raw material gas is further heated in the sulfur dioxide gas condenser until the sulfite gas in the raw material gas is removed. The liquefied sulfur dioxide gas is recovered by cooling it to the temperature at which it liquefies.Meanwhile, when the raw material gas is cooled to around room temperature, the condensate that condenses from the raw material gas enters the absorption tower of the dry flue gas desulfurization equipment. A method for recovering liquefied sulfur dioxide gas from a dry flue gas desulfurization device, which comprises spraying it into a flue gas line. 3. The desulfurization agent regeneration exhaust gas containing high concentration of sulfite from the desulfurization agent regeneration tower of the dry flue gas desulfurization equipment is used as the raw material gas,
After removing the dust contained in this raw material gas, the raw material gas is cooled to around room temperature, and then dried to a dew point at which the moisture in the raw material gas does not condense in the sulfur dioxide gas condenser, and then the raw material gas is compressed. Then, the raw material gas is further cooled in a sulfite force condenser to a temperature at which the sulfur dioxide gas in the raw material gas liquefies to recover liquefied sulfur dioxide gas.Meanwhile, in the raw material gas drying (DA process), activated alumina , zeolite,
Multiple dryers filled with dehumidifiers such as molecular sieves and silica gel are used to alternately dry the raw material gas and regenerate the dehumidifier in the dryer, reducing the amount of gas released from the dehumidifier during the regeneration period. A method for recovering liquefied sulfur dioxide gas from a dry flue gas desulfurization device, characterized in that it is circulated through a flue gas line that enters an absorption tower of the dry flue gas desulfurization device. 4. The desulfurization agent regeneration exhaust gas containing high concentration of sulfur dioxide gas, which is emitted from the desulfurization agent regeneration tower of the dry flue gas desulfurization equipment, is used as the raw material gas,
After removing the dust contained in this raw material gas, the raw material gas is cooled to around room temperature, and then dried to a dew point at which the moisture in the raw material gas will not condense in the sulfur dioxide gas condenser, and then the raw material gas is compressed. Further, the raw material gas is cooled in a sulfur dioxide gas condenser to a temperature at which the sulfur dioxide gas in the raw material gas liquefies, the liquefied sulfur dioxide gas is recovered, and the treated gas is separated, and the treated gas is depressurized to around normal pressure. Method 2 for recovering liquefied sulfur dioxide gas from a dry flue gas desulfurization device, characterized by circulating it into the flue gas line that enters the absorption tower of the dry flue gas desulfurization device.