JP5534126B2 - Exhaust gas treatment method and exhaust gas treatment apparatus - Google Patents

Description

  The present invention relates to an exhaust gas treatment method and an exhaust gas treatment device used to purify exhaust gas discharged from a boiler when fossil fuel such as coal is burned by a boiler, for example.

  As the above-described exhaust gas treatment method for purifying exhaust gas, for example, there is an exhaust gas treatment method for purifying coal combustion exhaust gas discharged from a coal fired boiler. In this exhaust gas treatment method, smoke from a coal fired boiler to a chimney In the electrostatic precipitator placed on the road, after removing most of the dust in the exhaust gas by static electricity, in the desulfurization tower placed on the chimney side of this precipitator, the lime aqueous solution is circulated and brought into gas-liquid contact Thus, SOx in the exhaust gas is absorbed.

In this exhaust gas treatment method, gypsum as a reaction product generated in the desulfurization tower is recovered by solid-liquid separation of the slurry-like solution. At this time, the organic COD contained in the separated waste water is collected. (Organic COD contained in lime or organic COD such as “algae” contained in water of aqueous solution) is treated using an activated carbon adsorption method (see, for example, Patent Document 1). ).
Japanese Patent Laid-Open No. 11-137958

  However, in the exhaust gas treatment method described above, organic COD contained in the wastewater after recovering gypsum as a reactant from the slurry solution is treated by the activated carbon adsorption method. Since COD has extremely low adsorptivity to activated carbon, it is necessary to enlarge the adsorption equipment in order to adsorb and remove organic COD in an amount sufficient to satisfy the requirements, resulting in an increase in exhaust gas treatment costs. There has been a problem of inviting, and it has been a conventional problem to solve this problem.

  The present invention has been made to solve the above-described problems, and an exhaust gas treatment method and exhaust gas that can reduce COD in wastewater generated when treating exhaust gas without increasing the exhaust gas treatment cost. An object is to provide a processing apparatus.

In conducting research and development of an exhaust gas treatment device that removes dust and SOx from exhaust gas generated by burning fossil fuels such as coal, the present inventors have conducted exhaust gas treatment with a desulfurization function based on the lime-gypsum method so far. When various data of the apparatus was collected and detailed examination was attempted, the data shown in FIG. 3 was focused.
The data shown in FIG. 3 is data obtained when the desulfurization tower for removing SOx contained in the exhaust gas is remodeled from the soot separation type to the soot mixing type, and the soot separation type shown on the left side of the graph of FIG. In the case of the desulfurization tower, the organic COD value in the desulfurization tower was 18 mg / l, but in the case of the dust mixing type desulfurization tower shown on the right side of the graph of FIG. The present inventors have found from this data that the dust has the ability to adsorb organic COD.

Here, the organic COD is contained in an absorbent such as lime used for desulfurization and the water content of the aqueous solution of the absorbent, and the organic COD flowing into the desulfurization tower is decomposed in the desulfurization system, It is mixed with reactants such as gypsum and discharged outside the desulfurization system, or it is included in the wastewater generated in the desulfurization tower and discharged outside the desulfurization system.
Therefore, the present inventors utilize the fact that soot and dust have the ability to adsorb organic COD in order to prevent the organic COD from being contained in the waste water and discharged outside the desulfurization system, It came to make this invention.

The invention according to claim 1 of the present invention removes SOx contained a dust removal step and an alkaline aqueous solution removes dust contained in the exhaust gas generated by burning fossil fuels in the exhaust gas by spraying into the exhaust gas An exhaust gas treatment method having a desulfurization step, wherein the amount of organic COD in waste water generated in the desulfurization step is monitored, and the monitoring result of the amount of organic COD is reflected in the dust removal step, and the dust removal step In the desulfurization step, the alkaline aqueous solution is sprayed on the exhaust gas containing the dust at the concentration , and the organic COD in the alkaline aqueous solution is adsorbed and removed by the dust. The configuration of this exhaust gas treatment method is characterized by the above-mentioned means for solving the above-mentioned conventional problems. To have.

Also, an exhaust gas processing method according to claim 2 of the present invention, when a predetermined purity of the reactants that are generated contain the dust in the desulfurization step is not obtained, a configuration of classifying the dust from the reactant Yes.

On the other hand , the invention according to claim 3 of the present invention includes a dust collecting means for removing dust contained in the exhaust gas generated by burning fossil fuel, and SOx contained in the exhaust gas by spraying an alkaline aqueous solution onto the exhaust gas. In the exhaust gas treatment apparatus equipped with a desulfurization tower for removing water, a COD amount measuring means for measuring the amount of organic COD in the wastewater generated in the desulfurization tower is provided, and a control unit for controlling the dust collection amount by the dust collection means is provided. in the control unit, said actuates the measurement result the dust collection unit on the basis of from COD amount measuring means, to control the dust concentration in the exhaust gas passing through said dust collection means, the concentration of the desulfurization tower It is characterized in that the organic COD in the alkaline aqueous solution is adsorbed and removed by spraying the alkaline aqueous solution to the exhaust gas containing soot and dust. , And a means for solving the conventional problems described above the configuration of the exhaust gas treatment apparatus.

Also, a gas processing device according to claim 4 of the present invention, in order maintain the purity of the reactants that are generated contain the dust in the desulfurization tower to a predetermined value, the classification means for classifying the dust from the reactant The configuration is provided.

In the exhaust gas treatment apparatus according to the exhaust gas processing method and claim 3 according to claim 1 of the present invention, since the exhaust gas which has flowed into the desulfurization system contains a predetermined amount of dust, by spraying an alkaline aqueous solution with respect to the exhaust gas For example, the organic COD in the alkaline aqueous solution is adsorbed and removed by the organic COD adsorption capacity of the dust, and therefore, it is not necessary to increase the size of the adsorption facility as compared with the conventional method using activated carbon. In addition, it is possible to achieve a very excellent effect that it is possible to reduce the exhaust gas treatment cost.

Further, in the air pollution control apparatus according to the exhaust gas processing method and claim 3 according to claim 1 of the present invention can perform efficient exhaust gas treatment while removing the organic COD in A alkaline aqueous solution, of the present invention in the exhaust gas treatment apparatus according to the exhaust gas processing method and claim 4 according to claim 2 can maintain the purity of the reactants that are generated contain dust in the de vulcanization system to a predetermined value.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an exhaust gas treatment apparatus according to an embodiment of the present invention. In this embodiment, the exhaust gas treatment method and the exhaust gas treatment apparatus of the present invention are applied to the treatment of exhaust gas discharged from a coal-fired boiler. An example will be described.
As shown in FIG. 1, the exhaust gas treatment apparatus 1 includes a heat exchanger 3, an electric dust collector 4, an induction ventilator 5, and a desulfurization tower 6 that are sequentially arranged in a flue R from a coal burning boiler B to a chimney 2. The electrostatic precipitator 4 removes most of the dust in the exhaust gas by static electricity, while the desulfurization tower 6 absorbs SOx in the exhaust gas by circulating and spraying an aqueous solution of lime and bringing it into gas-liquid contact. It is supposed to be.

In this case, gypsum S as a reaction product generated in the desulfurization tower 6 is recovered by subjecting the slurry-like solution to solid-liquid separation through a gypsum dehydrator 7, and the separated waste water is filtrated at this time. It is sent to the waste water treatment device 9 side through the pit 8.
Further, the exhaust gas treatment apparatus 1 has a control unit 10 that controls the amount of dust collected by the electric dust collector 4, and in this control unit 10, a predetermined amount of dust is left in the exhaust gas that passes through the electric dust collector 4. Thus, the amount of dust collected by the electric dust collector 4 is controlled.

That is, exhaust gas containing a predetermined amount of soot and dust controlled by the control unit 10 is intentionally flowed into the desulfurization tower 6, and an aqueous solution of lime (alkaline aqueous solution) is sprayed on the exhaust gas containing a predetermined amount of soot and dust in the desulfurization tower 6. Thus, the organic COD contained in the alkaline aqueous solution is adsorbed and removed by the organic COD adsorption capability of the dust.
Furthermore, in this embodiment, the COD amount measuring means 11 for measuring the amount of organic COD contained in the waste water is provided in the filtrate pit 8, and the control unit 10 is based on the measurement result from the COD amount measuring means 11. When the amount of organic COD contained in the wastewater is large, the electrostatic precipitator 4 is operated to increase the soot concentration in the exhaust gas, and when the amount of organic COD contained in the wastewater is small, In order to lower the soot concentration, the electrostatic precipitator 4 is operated to control the soot concentration in the exhaust gas.

  In the exhaust gas treatment apparatus 1 having such a configuration, the exhaust gas flowing into the desulfurization tower 6 is controlled so as to contain a predetermined amount of soot. By spraying an alkaline aqueous solution on the exhaust gas, Organic COD in the alkaline aqueous solution can be adsorbed and removed. As a result, compared with the conventional method using activated carbon, the cost of exhaust gas treatment can be reduced by the amount not required to enlarge the adsorption equipment. Become.

Further, in the exhaust gas treatment apparatus 1 described above, since the COD amount measuring means 11 for measuring the amount of organic COD contained in the waste water is provided in the filtrate pit 8, it is efficient while removing the organic COD in the alkaline aqueous solution. A good exhaust gas treatment can be performed.
FIG. 2 shows an exhaust gas treatment apparatus according to another embodiment of the present invention. In this embodiment as well, the exhaust gas treatment method and the exhaust gas treatment apparatus of the present invention are applied to the treatment of exhaust gas discharged from a coal fired boiler. A case will be described as an example.

  As shown in FIG. 2, this exhaust gas treatment device 21 is different from the exhaust gas treatment device 1 according to the previous embodiment in that the purity of gypsum S produced by containing debris in the desulfurization tower 6 is kept at a predetermined value. Therefore, a classifying means 22 for classifying the dust from the gypsum S is provided between the desulfurization tower 6 and the gypsum dewatering machine 7, and the other configuration is the same as that of the exhaust gas treatment apparatus 1 according to the previous embodiment. It is.

In the exhaust gas treatment device 21 according to this embodiment, since the classification means 22 for classifying the dust from the gypsum S is provided, the purity of the gypsum S generated in the desulfurization tower 6 can be maintained at a predetermined value.
In each of the above-described embodiments, the exhaust gas treatment method and the exhaust gas treatment apparatus of the present invention are applied to the treatment of exhaust gas discharged from a coal fired boiler. However, the present invention is not limited to this.

BRIEF DESCRIPTION OF THE DRAWINGS It is schematic structure explanatory drawing which shows the waste gas processing apparatus by one Embodiment of this invention. It is schematic structure explanatory drawing which shows the exhaust gas processing apparatus by other embodiment of this invention. It is a graph which shows the data obtained when the desulfurization tower which removes SOx contained in exhaust gas was remodeled from the dust separation type to the dust mixing type.

Explanation of symbols

1,21 Exhaust gas treatment equipment 4 Electric dust collector (dust collecting means)
6 Desulfurization tower (washing tower)
10 Control Unit 11 COD Measurement Unit 22 Classification Unit S Gypsum (Reactant)

Claims (4)

An exhaust gas treatment method comprising: a dust removal step for removing dust contained in exhaust gas generated by burning fossil fuel; and a desulfurization step for removing SOx contained in the exhaust gas by spraying an alkaline aqueous solution on the exhaust gas,
The amount of organic COD in the wastewater generated in the desulfurization process is monitored, the result of monitoring the amount of organic COD is reflected in the dust removal process, and the concentration of dust in the exhaust gas passing through the dust removal process is controlled. Then, in the desulfurization step, an alkaline aqueous solution is sprayed on the exhaust gas containing the concentration of dust, and organic COD in the alkaline solution is adsorbed and removed by the dust. Wherein when a predetermined purity of the reactants that are generated contain the dust in the desulfurization step is not obtained, an exhaust gas treatment method according to claim 1 for classifying the dust from the reactant. Dust collecting means for removing dust contained in exhaust gas generated by burning fossil fuel ;
In the exhaust gas treatment apparatus provided with a desulfurization tower for spraying an alkaline aqueous solution onto the exhaust gas to remove SOx contained in the exhaust gas,
Provided with a COD amount measuring means for measuring the amount of organic COD of the wastewater generated in the desulfurization tower, and provided with a control unit for controlling the amount of dust collected by the dust collecting means,
Wherein the control unit, said on the basis of the measurement results from COD amount measuring means actuates said dust collection means controls the dust concentration in the exhaust gas passing through said dust collection means of the concentration in the desulfurization tower An exhaust gas treatment apparatus characterized in that organic COD in an alkaline aqueous solution is adsorbed and removed by spraying the alkaline aqueous solution on exhaust gas containing dust. The exhaust gas treatment apparatus according to claim 3 , further comprising a classifying means for classifying the dust from the reactant so as to keep the purity of the reactant generated including the dust in the desulfurization tower at a predetermined value.

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