TWI414342B - Flue gas desulphurization system - Google Patents

Abstract

A system for flue gas desulphurization is disclosed. The system includes a steel mill, a water-treatment plant, a first pipe a flue gas desulphurization apparatus, and a second pipe. a first pipe has one end connected to the steel mill and the other end connected thereto. The first pipe transports wastewater produced in a steel fabrication process from the steel mill to the water-treatment plant to generate industrial wastewater. A second pipe has one end connected to the water-treatment plant and the other end connecting thereto. The second pipe transports the industrial wastewater from the water-treatment plant to the flue gas desulphurization apparatus as a water supply source. The industrial wastewater has sulphate of 100 mg/L to 250 mg/L.

Description

Flue gas desulfurization system

The present invention relates to a flue gas desulfurization system, and more particularly to a flue gas desulfurization system for industrial wastewater produced from self-smelting steel wastewater.

Generally, when a combustion process is performed using a burner such as a coal-fired boiler, a sintering machine, a heating furnace, or an incinerator, the fuel used in the burner, such as fossil fuel, industrial waste, or municipal waste, has a sulfur-containing component. . Therefore, these fuels contain gaseous sulfur oxides (such as sulfur dioxide, sulfur trioxide, etc.) in the exhaust gas produced after combustion, and these components cause air pollution. In order to avoid the air from continuing to be polluted and to achieve the purpose of environmental protection, the exhaust gas generated by the burner must pass through a row of flue gas desulfurization devices to separate and absorb the above gaseous sulfur oxides until the gaseous sulfur oxides in the exhaust gas reach a dischargeable level. Standard, exhaust gas can be discharged.

The flue gas desulfurization device mainly comprises an absorption tower and a water supply unit, and the absorption tower comprises an intake cooling section, an absorption section and a water gas removal section. After the exhaust gas enters the absorption tower, it passes through the three sections in sequence. The intake cooling section is used to cool the exhaust gas, the absorption section is used to dissolve the sulfur oxides in the exhaust gas in the water, and the moisture removal section can remove the moisture of the gas for recycling. The water supply unit is used to supply the water used for the three sections, and the water of the water supply unit is usually derived from industrial water. This water will eventually flow to the bottom of the unit, and the water pump will continue to circulate the water in the absorption section. However, since water evaporates in the cooling section, additional replenishment water is required in order to maintain the efficiency of desulfurization. In the case of long-term operation, a large amount of supplementary water is required, which causes a great waste of water resources.

In view of this, there is an urgent need for a flue gas desulfurization system that can reduce the waste of water resources and reduce the cost of water supply.

Accordingly, an aspect of the present invention is to provide a flue gas desulfurization system to effectively solve the aforementioned problems.

In accordance with the above objects of the present invention, a flue gas desulfurization system comprising a steel mill, a water treatment plant, a first line, a flue gas desulfurization unit, and a second line is provided. One of the first lines is connected to the steel plant and the other end is connected to the water treatment plant. The first pipeline is used to transport the steelmaking wastewater used by the steel mill to a water treatment plant to produce industrial wastewater. One end of the second line is connected to the water treatment plant and the other end is connected to the flue gas desulfurization unit. The second pipeline is used to transport the industrial wastewater generated by the water treatment plant to the flue gas desulfurization device as a water supply source for the flue gas desulfurization device. The industrial wastewater contains sulfate, and the range of sulfate ranges from 100 mg/liter to 250 mg/liter.

According to an embodiment of the invention, the industrial wastewater comprises a chloride salt between 100 mg/liter and 250 mg/liter.

According to another embodiment of the invention, the industrial wastewater has a Chemical Oxygen Demand (COD) ranging from 20 mg/liter to 100 mg/liter.

In the above embodiment, the above industrial wastewater has a BioOxygen Demand (BOD) ranging from 5 mg/liter to 20 mg/liter.

According to still another embodiment of the present invention, the industrial wastewater has a solid suspension concentration (Suspended Solid; SS) ranging from 2 mg/liter to 30 mg/liter.

According to still another embodiment of the present invention, the above-described flue gas desulfurization apparatus includes an absorption tower and a water supply unit. The absorption tower includes an intake cooling section, an absorption section, and a moisture removal section.

According to still another embodiment of the present invention, the absorption tower is a plate layer absorption tower or a spray absorption tower.

By using the embodiment of the invention, the waste of water resources can be effectively reduced, thereby greatly reducing the cost of water supply.

As stated above, the present invention provides a flue gas desulfurization system that utilizes industrial wastewater for steelmaking to replace industrial water.

The term "industrial wastewater for steelmaking" as used herein refers to industrial wastewater from a steelmaking plant produced by a steelmaking plant that has been treated by a water treatment plant to meet dischargeable standards. Steelmaking wastewater can be divided into sanitary wastewater, coking wastewater, cold rolling wastewater, dust washing wastewater and miscellaneous wastewater. The coking wastewater comes from the ammonia solution and its drainage during the recovery of by-products during coking, most of which comes from the condensed water cooled by gas, and a small part comes from the light oil separator. Since the gas condensate contains a large amount of phenol, pretreatment is required, and an extractive phenol removal device can be used to remove most of the phenol compound. However, there is no economic benefit in recovering the phenol removal unit, and the phenol content in the separation liquid still exceeds the water quality standard of the discharged water, and cannot be directly discharged, but this treatment process can greatly reduce the load of the secondary treatment equipment, thus Reduce the capacity and construction costs of subsequent processing facilities. In the conventional ammonia distillation system, the coking wastewater is first removed from the free ammonia distillation tower by free ammonia and acid gas, and then the alkali value is raised to about 11 by adding alkali, and then removed by a fixed ammonia distiller. The fixed acid is then discharged into a water treatment plant to meet dischargeable standards before industrial wastewater is discharged.

Please refer to FIG. 1 , which is a schematic diagram of a flue gas desulfurization system according to an embodiment of the present invention. In the present embodiment, the flue gas desulfurization system 100 includes a steel refinery 110, a water treatment plant 120, a flue gas desulfurization device 130, a first conduit 140, and a second conduit 150. One end of the first line 140 is connected to the steelworks 110 and the other end is connected to the water treatment plant 120. The first line 140 is used to transport the steelmaking wastewater used by the steelmaking plant 110 to the water treatment plant 120 to produce industrial wastewater. One end of the second line 150 is connected to the water treatment plant 120 and the other end is connected to the flue gas desulfurization unit 130. The second line 150 is used to transport the industrial wastewater generated by the water treatment plant 120 to the flue gas desulfurization unit 130 to serve as a water supply source for the flue gas desulfurization unit. The industrial wastewater produced by the above steelmaking comprises a sulfate of between 100 mg/liter and 250 mg/liter per liter.

The steelmaking wastewater is sent to the water treatment plant 120 by the first line 140 to purify the steelmaking wastewater into industrial wastewater that can be discharged. In one embodiment, the water treatment plant can be divided into a wastewater treatment plant (not shown) and an industrial wastewater discharge plant (not shown). The sanitary wastewater and coking wastewater will be discharged into the wastewater treatment plant (not shown). After physical treatment, it will enter the sedimentation tank (not shown) after coagulation, aeration gasification and gelation, and finally through the sand. After filtration and activated carbon adsorption treatment, it enters a purification tank (not shown) of an industrial wastewater discharge plant (not shown). As for the remaining waste water, such as cold rolling, dust washing, cooling and miscellaneous waste water, each of them is discharged into an industrial wastewater discharge plant (not shown) after being pretreated, and then transported to the exhaust pipe by the second pipe 150. Sulfur device 130.

Please refer to FIG. 2, which is a schematic diagram of a flue gas desulfurization apparatus according to an embodiment of the present invention. The flue gas desulfurization device 130 includes an absorption tower 131 and a water supply unit 132. The absorption tower 131 includes an intake cooling section 2, an absorption section 9, and a moisture removal section 4. The second line 150 described above delivers industrial wastewater to the water supply unit 132 of the flue gas desulfurization unit 130 as a source of water supply. In the present embodiment, the absorption tower 131 is, for example, a plate type absorption tower or a spray type absorption tower. After the exhaust gas 10 enters the absorption tower 131, it passes through the three sections in sequence. The exhaust gas 10 first enters the absorption tower 131 from the intake cooling section 2, and the intake cooling section 2 serves to cool the exhaust gas 10. Then, after the exhaust gas 10 enters the absorption tower, it enters the absorption section 9 upwards. In the present embodiment, the absorption section 9 is provided with at least one layer of orifices 3 and utilizes a spray water curtain 9 to provide an opportunity for the exhaust gas 10 to contact with water for use. The sulfur oxides in the exhaust gas 10 are dissolved in water. The water-gas removal section 4 is supplied from the water-gas removal section inlet pipe 12 to the water-gas removal section cleaning pipe 6, and the moisture of the gas is removed for recycling. Finally, the desulfurized exhaust gas 10 is discharged from the exhaust port 11. The water supply unit 132 is used to supply water for use in the three sections, including the water removal section inlet pipe 12 and the supply source of the supplementary water inlet pipe 13. This water finally flows to the circulating water portion 8 at the bottom of the device, and the water pump 7 is used to transport the water into the circulating water distribution pipe 5 for continuous recycling. The drain pipe 15 is used to discharge part of the circulating water, and part of the hydration can be performed to maintain the quality of the circulating water.

The following examples will use a flue gas desulfurization unit having different absorption towers (a laminar absorption tower and a spray absorption tower). Among them, the inside of the plate-type absorption tower can be equipped with 3 or 4 layers (holes), and the plate layer is covered with many round holes of the same diameter, which can be according to different opening ratios (the total area of the round hole relative to the area of the circular steel plate) ) The design (10~40%), while planning the number of different round holes. When the exhaust gas passes through the slab round hole from the bottom to the top, the mass transfer reaction occurs when it contacts the circulating water flowing through the circular hole by gravity. Compared with the laminar absorption tower, the inside of the spray absorption tower is not loaded with anything, and only two nozzle layers of circulating water generate a mass transfer reaction purely by the conical water curtain which is sprayed upward through the nozzle.

In addition, in the case where a sulfur-containing exhaust gas is introduced and no additional agent (such as a desulfurization agent) is added, the following exemplary embodiment and comparative examples respectively use industrial wastewater produced by steelmaking and industrial water to compare sulfur oxide removal. difference. The limiting conditions for the industrial wastewater produced by steelmaking are as described above, and the sulphate per liter of industrial water contains less than 100 mg. Since sulphate does not pollute the environment, it is an environmentally friendly substance, so it is not necessary to specifically remove sulphate from wastewater. The industrial wastewater produced by steelmaking contains sulfates ranging from 100 mg/liter to 250 mg/liter. Alternatively, the industrial wastewater produced by steelmaking may comprise a chloride salt ranging from 100 mg/liter to 250 mg/liter. In yet another embodiment, the industrial wastewater produced by steelmaking has a chemical oxygen demand ranging from 20 mg/liter to 100 mg/liter. In still another embodiment, the industrial wastewater produced by steelmaking has a biological oxygen demand ranging from 5 mg/liter to 20 mg/liter. In still another embodiment, the industrial wastewater produced by steelmaking has a solids suspension concentration ranging from 2 mg/liter to 30 mg/liter.

Example 1

Water source: Industrial wastewater from a water treatment plant, the circulating water volume is set to 204 L/min, and the ratio to the exhaust gas intake amount is 4 L/m ³ .

In this embodiment, a plate-type absorption tower is used, and sulfur-containing exhaust gas is introduced for desulfurization. The gas flow rate into the absorption tower was quantitatively controlled by a variable frequency windmill to be 51 m ³ /min. At the same time, the exhaust gas analyzer is used to monitor the concentration of sulfur oxides in the exhaust gas outlet, and also to monitor the pH value and conductivity (EC) of the water. The measured changes in sulfur oxide concentration, pH value, and conductivity and time are shown in Figures 3A and 3B.

Example 2

Water source: Industrial wastewater from a water treatment plant, the circulating water volume is set to 204 L/min, and the ratio to the exhaust gas intake amount is 4 L/m ³ .

This embodiment is substantially the same as Embodiment 1, except that the absorption tower used in the present embodiment is a spray type absorption tower. At the same time, the exhaust gas analyzer is used to monitor the concentration of sulfur oxides in the exhaust gas exhaust outlet, and also to monitor the pH value and conductivity of the water. The measured changes in sulfur oxide concentration, pH value, and conductivity and time are shown in Figures 3C and 3D.

Comparative example 1

Water source: Industrial water from the water supply system, the circulating water volume is set to 204 L/min, and the ratio to the exhaust gas intake amount is 4 L/m ³ .

This comparative example is substantially the same as that of Example 1, except that the water source used in the comparative example is industrial water. At the same time, the exhaust gas analyzer is used to monitor the concentration of sulfur oxides in the exhaust gas exhaust outlet, and also to monitor the pH value and conductivity of the water. The measured sulfur and oxygen concentrations, pH values, and changes in conductivity and time are shown in Figures 4A and 4B.

Comparative example 2

Water source: Industrial water from the water supply system, the circulating water volume is set to 204 L/min, and the ratio to the exhaust gas intake amount is 4 L/m ³ .

This comparative example is substantially the same as that of Example 1, except that the absorption tower used in the comparative example is a shower type absorption tower, and the water source is industrial water. At the same time, the exhaust gas analyzer is used to monitor the concentration of sulfur oxides in the exhaust gas exhaust outlet, and also to monitor the pH value and conductivity of the water. The measured changes in sulfur oxide concentration, pH value, and conductivity and time are shown in Figures 4C and 4D.

Both of Examples 1 and 2 used industrial wastewater discharged from a water treatment plant, and only the absorption tower type was different. The monitoring results showed that there was a slight difference in the rate of decline in exhaust sulfur oxide concentration between the two. Because the water sources used by the two are the same, there is little change in the water quality. The pH of the pH decreased from the initial value of 7 to 8 to 4.0, and the conductivity increased by about 70% in the next 950 seconds.

Comparative Examples 1 and 2 correspond to Examples 1 and 2, respectively, but the water was changed to industrial water supplied to the water supply system. The monitoring results are slightly different from the rate of decline of sulfur oxide concentration in the exhaust gas of Comparative Example 1 and 2, and the pH value of the exhaust gas from the initial value of 7-8 to 4.0 takes nearly 400 seconds, while at nearly 650 seconds, both of them The conductivity is increased to 1.5 micromhos/cm. It can be seen that under the same water source, the trend of cyclic water quality changes is similar, and does not vary depending on the type of absorption tower.

Comparing Example 1 with Comparative Example 1, it can be observed that in the same absorption tower type, different water sources are used, and the exhaust sulfur oxide concentration trends are consistent (refer to Figures 3A and 4A), and can be reduced. Below 20 ppm.

Similarly, referring to FIG. 3C and FIG. 4C, in the comparison between Example 2 and Comparative Example 2, the sulfur oxide concentration of Example 2 using water discharged from a water treatment plant can be reduced to 30 ppm, and the feed water system is supplied. The sulfur oxide concentration of Comparative Example 2 for industrial water was reduced to 50 ppm. Although there is a small gap between the exhaust sulfur oxide concentrations of the two, this change is still acceptable.

From the above comparison, the use of steelmaking wastewater generated by steelworks, industrial wastewater treated by the water treatment plant, the sulfur oxide removal in the laminar and spray absorber exhaust gas performance is not inferior to the use of the water supply system The performance of industrial water. Therefore, since industrial wastewater generated by steelmaking is used, not only the industrial waste water can be reused, but also the use of industrial water can be greatly reduced, thereby reducing the cost of water supply using industrial water.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

100. . . Flue gas desulfurization system

110. . . Steel mill

120. . . Water treatment plant

130. . . Flue gas desulfurization device

131. . . Absorption tower

132. . . Water supply unit

140. . . First line

150. . . Second pipeline

2. . . Intake cooling section

3. . . Orifice plate

4. . . Water gas removal section

5. . . Circulating water distribution tube

6. . . Water gas removal section cleaning tube

7. . . Water pump

8. . . Circulating water department

9. . . Absorption section

10. . . Exhaust gas

11. . . exhaust vent

12. . . Water gas removal section inlet pipe

13. . . Supplementary water inlet pipe

The above and other objects, features, advantages and embodiments of the present invention will become more apparent and understood.

1 is a schematic view showing a flue gas desulfurization system according to an embodiment of the present invention.

2 is a schematic view showing a smoke exhausting desulfurization apparatus according to an embodiment of the present invention.

Fig. 3A is a graph showing the comparison of sulfur oxide concentration and time according to Example 1 of the present invention.

Fig. 3B is a graph showing the comparison of the pH value and the conductivity with time in accordance with Example 1 of the present invention.

Fig. 3C is a graph showing a comparison of sulfur oxide concentration and time according to Example 2 of the present invention.

Fig. 3D is a graph showing the comparison of the pH value and the conductivity with time in accordance with Example 2 of the present invention.

Fig. 4A is a graph showing the comparison of sulfur oxide concentration and time in Comparative Example 1 according to the present invention.

Fig. 4B is a graph showing the comparison of the pH value and the conductivity with time in Comparative Example 1 according to the present invention.

Fig. 4C is a graph showing the comparison of sulfur oxide concentration and time in Comparative Example 2 according to the present invention.

Fig. 4D is a graph showing the comparison of the pH value and the conductivity with time in Comparative Example 2 according to the present invention.

100. . . Flue gas desulfurization system

110. . . Steel mill

120. . . Water treatment plant

130. . . Flue gas desulfurization device

140. . . First line

150. . . Second pipeline

Claims (7)

A flue gas desulfurization system comprising at least: a steelmaking plant; a water treatment plant; a first pipeline, one end of the first pipeline is connected to the steelmaking plant, and the other end of the first pipeline is connected To the water treatment plant, the first pipeline is used to transport one of the steelmaking wastewater generated by the steelmaking plant to the water treatment plant to generate an industrial wastewater; the exhaust gas desulfurization device comprises: an absorption tower, the absorption The tower comprises an intake cooling section, an absorption section and a water removal section, wherein the water removal section is supplied from a water removal section inlet pipe to a water removal section cleaning pipe, and the gas moisture is removed to circulate Using a second line, one end of the second line is connected to the water treatment plant, the other end of the second line is connected to the flue gas desulfurization device, and the second line is used for treating the water The industrial wastewater generated by the plant is sent to the flue gas desulfurization device as a water supply source of the flue gas desulfurization device; and a water supply unit connected to the water gas removal section inlet pipe and the second pipeline To provide the water required for the flue gas desulfurization device, wherein the industry Water comprises a sulfate, this sulfate range between 100 mg / liters to 250 mg / liter. The flue gas desulfurization system of claim 1, wherein the industrial wastewater comprises a monochlorinated salt ranging from 100 mg/liter to 250 mg/liter. The flue gas desulfurization system of claim 1, wherein the industrial wastewater has a chemical oxygen demand (COD) ranging from 20 mg/liter to 100 mg/ Between the liters. The flue gas desulfurization system according to claim 1, wherein the industrial wastewater has a Bio-Oxygen Demand (BOD), and the biological oxygen demand ranges from 5 mg/L to 20 mg/ Between the liters. The flue gas desulfurization system of claim 1, wherein the industrial wastewater has a Suspended Solid (SS) concentration ranging from 2 mg/L to 30 mg/L. between. The flue gas desulfurization system of claim 1, wherein the absorption tower is a laminar absorption tower. The flue gas desulfurization system of claim 1, wherein the absorption tower is a spray absorption tower.