JP3823203B2 - Semi-dry exhaust gas desulfurization / desalination method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is, for example, a semi-dry exhaust gas desulfurization / desulfurization technology among technologies for removing sulfurous acid gas contained in the exhaust gas of coal fired boilers and hydrogen chloride contained in the exhaust gas of municipal waste incinerators, that is, desulfurization / desalination technology of exhaust gas. The present invention relates to a desalting method .
[0002]
[Prior art]
Conventionally, a semi-dry type exhaust gas desulfurization / desalination method is already known. This technology belongs to a simple desulfurization / desalination method , and the structure of the apparatus is simple, so the initial investment is small, and the desulfurization / desalination rate. Has the advantages of good operation and low operating costs.
[0003]
The conventional semi-dry type exhaust gas desulfurization / desalination method allows exhaust gas containing a harmful gas component made of sulfurous acid gas or hydrogen chloride gas to pass upwardly from the lower part of the reaction tower to the fluidized bed at the lower part of the reaction tower. While circulating ash is introduced, the lime slurry and the exhaust gas humidity conditioning water are sprayed onto the fluidized bed below the reaction tower using compressed air. Then, the lime slurry is attached to the circulating ash of the fluidized bed, and while the exhaust gas rises in the reaction tower, calcium sulfite / calcium sulfate or calcium chloride is brought into contact with the sulfite gas / hydrogen chloride gas and lime in the exhaust gas. Generate. In this way, the harmful gas component in the exhaust gas is transferred to the solid matter side, and the discharge from the reaction tower is guided to the dust collector to be separated into gas and solid matter. The cleaned exhaust gas is discharged to the atmosphere, and a part of the collected matter consisting of a mixture of dust, reaction products and unreacted lime collected in the dust collector is discharged out of the system, and the remainder of the collected matter is removed. Recirculated as ash to the fluidized bed at the bottom of the reaction tower.
[0004]
Such a semi-dry type exhaust gas desulfurization / desalination method is rarely applied to the exhaust gas of large boilers for power plants and the like, and mainly has an exhaust gas flow rate of 10,000 to 100,000 (Nm ³ / h). To some extent, it was applied to the exhaust gas treatment of small industrial boilers and municipal waste incinerators.
[0005]
[Problems to be solved by the invention]
However, in the small industrial boilers and municipal waste incinerators as described above, there are many cases where the fluctuation of the exhaust gas flow rate is large. On the other hand, according to the conventional exhaust gas desulfurization / desalination method , a large amount of circulating ash is suspended in the exhaust gas, lime slurry is coated on the surface of the circulating ash, and the contact surface area with the gas is increased. Because it reacts acidic components with lime, the amount of gas fluctuates, especially when the gas flow rate drops below a certain value, there is a problem that circulating ash falls in the reaction tower and accumulates at the bottom of the reaction tower. There was a problem that it was vulnerable to fluctuations in gas flow rate.
[0006]
Here, FIG. 2 is a curve diagram illustrating an example of an exhaust gas flow rate measurement chart measured by the present inventors in a semi-dry exhaust gas desulfurization apparatus attached to a small industrial boiler. Since the automatic operation is performed according to the demand for steam, when the demand for steam is small, the operation is temporarily stopped and the exhaust gas flow rate may be reduced to zero (see the arrow portion in FIG. 2).
[0007]
In such a state, in the conventional exhaust gas desulfurization apparatus, the circulating ash falls and accumulates on the bottom of the reaction tower, and the sprayed lime slurry and the water for humidity control are scattered in the lower part of the reaction tower. Since it adheres to the inner wall and becomes a huge lump, there is a problem that the operation of the desulfurization apparatus cannot be resumed even if the gas flow rate is recovered.
[0008]
The present inventors have made intensive studies in view of the above points, the so-called Ru circulation type exhaust gas desulfurization / desalting method, the flow rate of the exhaust gas supplied to the fluidized bed reaction tower bottom below a certain value When the supply of circulating ash, lime slurry, and exhaust gas humidity control water to the fluidized bed below the reaction tower is stopped at the same time, and the exhaust gas flow rate recovers to a certain value or more, the fluidized bed below the reaction tower It was found that all the problems of the above prior art can be solved by restarting the supply of the circulating ash, the exhaust gas humidity conditioning water, and the lime slurry to this in this order, and the present invention has been completed.
[0009]
An object of the present invention, falls FGD / desalting methods smell of circular fashion Te, when applied to a small industrial boilers and municipal waste incinerators large variation of the exhaust gas flow rate, lime slurry and circulating ash in the reaction tower Thus, when the gas flow rate is recovered without forming a huge lump, the operation of the apparatus can be reliably restarted and continued, and it is resistant to fluctuations in the gas flow rate. Is to provide a way .
[0010]
[Means for Solving the Problems]
To achieve the above object, semidry FGD / desalting how by the present invention is a so-called circular fashion, the exhaust gas for removing harmful gas components composed of sulfur dioxide / hydrogen chloride gas contained in the exhaust gas This is a desulfurization / desalting method , in which exhaust gas containing harmful gas components is passed upwardly from the lower part of the reaction tower to introduce circulating ash into the fluidized bed at the lower part of the reaction tower, and the flow at the lower part of the reaction tower The lime slurry and water for conditioning the exhaust gas are sprayed on the bed, the lime slurry is adhered to the circulating ash of the fluidized bed, and while the exhaust gas rises in the reaction tower, the sulfurous acid gas / hydrogen chloride gas and lime in the exhaust gas To produce calcium sulfite / calcium sulfate or calcium chloride, the harmful gas components in the exhaust gas move to the solids side, the exhaust from the reaction tower is led to the dust collector, and separated into gas and solids The exhaust gas that has been cleaned is released to the atmosphere, and a part of the collected matter consisting of the collected dust, reaction product and unreacted lime is discharged out of the system, and the remainder of the collected matter is removed. In the semi-dry type exhaust gas desulfurization / desalination method that recirculates as circulating ash to the fluidized bed at the bottom of the reaction tower, when the flow rate of exhaust gas supplied to the fluidized bed at the bottom of the reaction tower drops below a certain value, circulating ashes to the layer, the supply of lime slurry and the exhaust gas humidity water, simultaneously stopped, when the exhaust gas flow rate is restored above a certain value, the circulation ash into the reaction tower bottom of the fluidized bed, gas humidity water and The supply of the lime slurry is resumed in this order.
[0011]
In addition, when the flow rate of exhaust gas supplied to the fluidized bed at the bottom of the reaction tower is reduced to 20% or more and 50% or less of the design value, circulating ash, lime slurry, and exhaust gas humidity control water to the fluidized bed at the bottom of the reaction tower Is preferably stopped.
[0012]
Furthermore, it is preferable to stop the supply of circulating ash, lime slurry and exhaust gas conditioning water to the fluidized bed at the bottom of the reaction tower when the time during which the exhaust gas flow rate decreases to a certain value or less is continued for 10 seconds or more.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0014]
Referring to Figure 1 showing an apparatus for implementing the method of the present invention, in the method of the present invention, an exhaust gas containing hydrogen chloride from the exhaust gas and municipal waste incinerators, including sulfur dioxide from coal-fired boiler, the exhaust gas inlet tube It is introduced from (1) into the fluidized bed at the bottom of the reaction tower (2). The exhaust gas passes through the reaction tower (2) as an upward flow flowing upward.
[0015]
On the other hand, quick lime or slaked lime (hereinafter referred to as lime) is supplied from the lime supply pipe (3) to the hopper (4), and the necessary amount is introduced from the lime transport conveyor (5) into the emulsifier (6). Water is supplied to the emulsifier (6) through a water supply pipe (7), and lime is dissolved in water to prepare a lime slurry having a predetermined concentration. This lime slurry is supplied to the slurry spray nozzle (10) provided at the lower part of the tower (2) from the lime slurry flow pipe (8) by the operation of the pump (9), and rises in the reaction tower (2). Inject into the exhaust gas.
[0016]
In this embodiment, compressed air is used as the spray medium for the lime slurry. That is, a flow rate adjusting valve (23) is provided near the tip of the lime slurry flow pipe (8), and a flow rate adjusting valve (24) near the tip of the compressed air supply pipe (11) from the compressor (30). The flow rate of lime slurry and compressed air is adjusted by these valves (23) and (24), and blown into the exhaust gas rising from the slurry spray nozzle (10) into the reaction tower (2). is there.
[0017]
Further, the exhaust gas humidity control water is blown into the fluidized bed below the reaction tower (2) from the introduction pipe (12) provided with a nozzle dedicated to the humidity control water.
[0018]
In addition, although illustration is abbreviate | omitted, depending on the case, you may make it blow off exhaust gas humidity-control water from a spray nozzle (10) with a lime slurry and compressed air.
[0019]
In the exhaust gas rising in the reaction tower (2), a part of circulating ash (described later) in the fluidized bed is further supplied and mixed from the supply pipe (13) at the lower part of the tower (2).
[0020]
The lime slurry sprayed with the compressed air from the slurry spray nozzle (10) is naturally sprayed on the circulating ash of the fluidized bed, and the lime slurry adheres to the circulating ash of the fluidized bed. While the exhaust gas rises in the reaction tower (2), the sulfurous acid gas or hydrogen chloride gas in the exhaust gas contacts the lime in the slurry on the surface of the circulating ash in the fluidized bed, that is, with the reaction surface area increased. Calcium sulfite / calcium sulfate or calcium chloride is generated, and harmful gas components in the exhaust gas shift to the solid side, so that the exhaust gas can be purified.
[0021]
Next, the gas component of the exhaust gas flowing out from the top of the reaction tower (2), the dust in the exhaust gas, the calcium compound after the reaction, and the effluent consisting of unreacted lime are put into a dust collector (14) made of a cyclone. Introduced and separated into gas components and solids. The gas components from which most of the harmful gases and dusts have been removed are further sent to the bag filter (15) for dust removal, and then discharged from the chimney to the atmosphere as clean gas through the exhaust pipe (17) by the induction fan (16). .
[0022]
Circulating ash consisting of a mixture of the dust collected by the cyclone (14) and the above-mentioned calcium compound after reaction and unreacted lime is introduced into the circulation box (18) from the lower part of the cyclone (14), and a part of the circulating ash is introduced. Re-introduced from the circulation pipe (13) to the fluidized bed at the bottom of the reaction tower (2), and the remainder of the circulating ash is taken out by the conveyor (19) to collect the collected ash from the bag filter collection ash removal pipe (20). After mixing, it is stored in the byproduct yard (22) from the outside discharge conveyor (21) and used as a byproduct.
[0023]
In the above embodiment, when the so-called circulation-type exhaust gas desulfurization / desalination method according to the present invention is applied to a small industrial boiler or municipal waste incinerator having a large fluctuation in exhaust gas flow rate, the fluidized bed below the reaction tower (2) If the flow rate of the exhaust gas supplied falls below a predetermined value, the reaction column (2) circulating ash to the lower fluidized bed, the supply of lime slurry and the exhaust gas humidity water, it resumed in the order of this.
Further, when the flow rate of the exhaust gas supplied to the fluidized bed below the reaction tower (2) is reduced to 20% or more and 50% or less of the designed value, preferably 25% or more and 40% or less, the reaction tower (2 It is preferable to stop the supply of circulating ash, lime slurry, and exhaust gas humidity conditioning water to the lower fluidized bed.
[0024]
Furthermore, when the time during which the exhaust gas flow rate falls below a certain value continues for 10 seconds or longer, the supply of circulating ash, lime slurry, and exhaust gas conditioning water to the fluidized bed below the reaction tower (2) may be stopped. ,preferable.
[0025]
According to the circulation type exhaust gas desulfurization / desalination method of the above embodiment of the present invention, when applied to a small industrial boiler or municipal waste incinerator having a large fluctuation in exhaust gas flow rate, lime slurry or lime slurry and circulating ash react. When the gas flow rate is recovered without falling into the tower (2) and forming a huge lump, the operation of the apparatus can be reliably resumed and continued. Therefore, the exhaust gas desulfurization / desalination method is resistant to fluctuations in the gas flow rate.
[0026]
【The invention's effect】
The present invention, as described above, the so-called Te FGD / desalting methods smell of a circular fashion, the exhaust gas containing toxic gas components from the bottom of the reaction column is passed upflow upward, the reaction tower bottom of In addition to introducing circulating ash into the fluidized bed, spraying lime slurry and exhaust gas humidity conditioning water onto the fluidized bed at the bottom of the reaction tower to attach the lime slurry to the circulating ash in the fluidized bed, and the exhaust gas rises in the reaction tower. In the meantime, contact between sulfite gas / hydrogen chloride gas and lime in the exhaust gas produces calcium sulfite / calcium sulfate or calcium chloride, and harmful gas components in the exhaust gas move to the solids side, from the reaction tower. The waste is guided to a dust collector, separated into gas and solids, the cleaned exhaust gas is released to the atmosphere, and the collected matter consisting of a mixture of dust, reaction products and unreacted lime collected. Some out of the system As well as out, a semidry FGD / desalting process for recycling into the fluidized bed reaction tower bottom of the remainder of the collected matter as circulating ash, flow rate of the exhaust gas supplied to the fluidized bed reaction tower bottom fixed value When the flow rate drops below, the supply of circulating ash, lime slurry, and exhaust gas humidity conditioning water to the fluidized bed at the bottom of the reaction tower is stopped at the same time. circulating ashes to the layer, the supply of the exhaust gas humidity water and lime slurry, is intended to resume in that order, according to the present invention, with the FGD / desalting method circular fashion, a large fluctuation of the exhaust gas flow rate when applied to a small industrial boilers and municipal waste incinerators, lime slurry over contact and circulating ash may fall within the reaction column, without forming a huge mass in the gas flow is restored, operation of the apparatus Surely resume and continue It and be an effect that strong fluctuations of gas flow rate.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing an embodiment of an apparatus for carrying out the method of the present invention.
FIG. 2 is a curve diagram showing an example of an exhaust gas flow rate measurement chart measured in a semi-dry exhaust gas desulfurization apparatus attached to an industrial boiler.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exhaust gas introduction pipe 2 Reaction tower 3 Lime supply pipe 4 Hopper 5 Lime conveyance conveyor 6 Emulsifier 7 Water supply pipe 8 Lime slurry flow pipe 9 Pump 10 Slurry spray nozzle 11 Compressed air supply pipe 12 Exhaust gas conditioning water supply pipe 13 Circulation Ash supply pipe 14 Dust collector (Cyclone)
15 Bag filter 16 Attraction fan 17 Clean gas discharge pipe 18 Circulation box 19 Discharge conveyor 20 Bag filter collection ash take-out pipe 21 Out-of-system discharge conveyor 22 By-product yard 23 Valve 24 Valve 25 Valve 30 Compressor

Claims (1)

An exhaust gas desulfurization / desalination method for removing harmful gas components composed of sulfurous acid gas / hydrogen chloride gas contained in exhaust gas, and passing exhaust gas containing harmful gas components upward from the bottom of the reaction tower. And circulating ash into the fluidized bed at the bottom of the reaction tower, spraying lime slurry and exhaust gas humidity control water onto the fluidized bed at the bottom of the reaction tower to adhere the lime slurry to the circulating ash in the fluidized bed. While rising in the reaction tower, sulfite gas / hydrogen chloride gas in the exhaust gas comes into contact with lime to produce calcium sulfite / calcium sulfate or calcium chloride, and harmful gas components in the exhaust gas move to the solid side The exhaust from the reaction tower is guided to a dust collector, separated into gas and solids, the exhaust gas cleaned is released to the atmosphere, and the collected dust, reaction products, and unreacted lime are mixed. While discharging a part of the collected matter consisting of objects out of the system, in a semi-dry flue gas desulfurization / desalting process for recycling into the fluidized bed reaction tower bottom of the remainder of the collected matter as circulating ash reactor bottom of When the flow rate of exhaust gas supplied to the fluidized bed drops below a certain value, the supply of circulating ash, lime slurry, and exhaust gas conditioning water to the fluidized bed at the bottom of the reaction tower is stopped simultaneously, and the exhaust gas flow rate exceeds a certain value. A semi-dry type exhaust gas desulfurization / desalination method characterized by restarting the supply of circulating ash, exhaust gas humidity conditioning water and lime slurry to the fluidized bed at the lower part of the reaction tower in this order .

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