JPS6352953B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a treatment device for wastewater from a wet flue gas desulfurization device that produces gypsum as a by-product.

[Prior art]

As a result of technological development over the past 10 years, wet flue gas desulfurization equipment has been widely used as a device with excellent desulfurization performance and capable of meeting Japan's strict air pollution control regulations.

Furthermore, its economic efficiency has improved significantly compared to its initial stage, and it is now being evaluated as having maintained a reasonable balance between environmental conservation and economic efficiency.

However, although thorough consideration is naturally given to the treatment of SO ₂ , which is a source of pollution in flue gas, in various wet flue gas desulfurization processes, other trace components in flue gas, In particular, chlorine (including its compounds), fluorine (including its compounds),
Almost no countermeasures have been taken for ammonia (including its compounds), and since these trace components are water-soluble, the trace components captured are not discharged into the system as wastewater from flue gas desulfurization equipment. It had been thrown outside.

This wastewater is generally discharged outside the system after undergoing simple treatments such as neutralization, air oxidation, and precipitation separation.

The composition of the treated wastewater other than water is mainly alkali and alkaline earth metal sulfates, chlorides,
The substance was ammonia salt, etc., and did not have any particular negative impact on the environment, and was allowed to be disposed of in public rivers.

However, this wastewater increases the water consumption of the wet flue gas desulfurization equipment, and some installers are wondering if even the evaporated water in the flue gas will be enough.
This has forced an extra burden on them, and as a reaction,
This created an opportunity for the dry method to be reconsidered.

Additionally, due to this drainage, location was sometimes restricted, especially in narrow areas.

In particular, sodium salts and calcium chloride, which are water-soluble even after treatment, and sulfates, which remain at equilibrium solubility even after precipitation, are difficult to remove from water, and especially large amounts of Cl ^- Attempts have been made to separate them by electrolysis, but the problem is that they are technically and economically expensive and cannot be carried out industrially. .

[Purpose of the invention]

The present invention was made in view of the current situation, and its purpose is to bring a small amount of wastewater after separating gypsum into contact with high-temperature exhaust gas,
The object of the present invention is to provide a wastewater treatment device for removing impurities in the wastewater as solids by evaporating the wastewater.

[Structure of the invention]

That is, the wastewater treatment device from the wet flue gas desulfurization device that produces gypsum as a by-product of the present invention has a cylindrical spray space in which the sulfur oxides in the flue gas are separated as gypsum in the wet flue gas desulfurization device. A wastewater spraying means is installed, and a flue gas introducing means for introducing flue gas at 130 to 190°C is attached tangentially to the cylindrical spray space, and a cone-shaped air/solid is installed at the bottom of the cylindrical spray space. A separation section is provided, an internal gas riser that rises in the gas/solid separation section and has an internal rotation zone around it is provided in the gas/solid separation section, and the internal gas riser is connected to a gas discharge pipe in the middle of the spray space. The present invention is characterized in that a solid discharge means is provided at the lowest part of the gas/solid separation section.

The present invention will be described below based on embodiments shown in the drawings.

Embodiment 1 of the wastewater treatment device 4 of the present invention is shown in FIG.
This shows a gas-liquid direct contactor 4 as
The tray-shaped gas introduction part 21 that introduces the flue gas G as a sidestream fluid communicates with the exhaust channel 2 that introduces the flue gas G,
As shown in FIG. 2, the exhaust gas G is preferably given a rotational motion by a guide vane (not shown) and comes into intense contact with the waste water W which is spouted out in a mist form from the spraying means 22 for the waste water W. do.

In the present invention, wastewater refers to a part of the circulating water that is used in wet flue gas desulfurization equipment by recirculating the filtered water after separating by-product gypsum to the desulfurization equipment and removing impurities such as Cl ^- . This means a small amount of liquid that is extracted from the system depending on the amount of accumulated liquid.

As for this spraying means 22, a pressurized type is effective when the wastewater W does not contain solids (other than those dissolved), and when the wastewater W is in the form of a slurry, even though the gaps between the constituent parts are large. First, a rotary spray type that can be atomized is preferable.

Furthermore, when atomization is required (such as when trying to obtain a solidified product in a more completely dry state), a two-fluid nozzle type that introduces pressurized air into these means is also suitable.

In the cylindrical spray space 23, the water in the waste water W evaporates and transfers into the flue gas G.

The impurities 6 that were dissolved at the same time solidify as the water disappears, become fine particles and fall while rotating, and pass from the cone-shaped gas/solid separation section 24 to the internal rotation zone 28 via the internal guide zone 25, and then the gas and The solid particles flow in while being rotated.

Here, the internal rotating belt 28 is a tube provided around the internal gas riser 26 in the form of a double pipe, and its upper end is sealed and supported by the internal gas riser 26, and its lower end is open. In this internal rotating zone 28, the gas and solid particles flowing in while rotating are separated into gas and solid particles, and the separated solid particles fall by gravity within the internal rotating zone and further by the centrifugal force of the flue gas G. It moves to the outside of the internal rotating zone 28, finally reaches its wall 27, slides down the cone-shaped wall 27 due to gravity, and is discharged to the outside by the rotary valve 5, which is the solid rotating discharge means at the bottom. .

On the other hand, in the internal rotation zone 28, the gas/solid separation is performed as described above, and some of the unevaporated waste water is brought into intense contact with the flue gas again, promoting vaporization of the waste water due to gas-liquid contact. .

From the internal gas riser 26, the gas g from which solid particles have been removed rises and flows out from the gas exhaust pipe 20, which is a gas exhaust port, to the wet flue gas desulfurization device 9 via the conduits 7 and 13.

As shown in FIG. 1, one spraying means 22 is preferable because it has a simple structure, but if the amount of wastewater to be treated is large, there is no problem in installing a plurality of spraying means 22, and from the perspective of the purpose of the present invention. This is one of the modifications that a person skilled in the art who is familiar with the prior art can naturally make.

Further, a cylindrical spray space 2 having the above configuration is also provided.
3. Cone-shaped gas/solid separation section 24, internal guide band 25
At the bottom of the internal gas riser 26, the wall 2
7. It is also effective as a similar modification to devise a structure in which a plurality of internal rotary zones 28, rotary valves 5, etc. are increased depending on the throughput.

The direct contactor 4 having the above configuration is not limited to the first embodiment shown in FIG.
It may be configured as in the second embodiment shown in the figure, or the third
In the figure, the same parts as in FIG. 1 are indicated by the same part numbers, and the same functions as in the first embodiment of FIG. 1 can be provided.

Next, the functions of the wastewater treatment apparatus of the present invention will be described.

FIG. 4 shows the steps of a wastewater treatment method using the wastewater treatment device of the present invention, preferably at a temperature of 130 to 190°C.
Exhaust smoke G from boilers, etc. is sent to flue 2 by a fan.
After that, it is introduced into the approximately cylindrical and hollow wastewater treatment apparatus of the present invention, here a direct contactor 4 .

A small amount of waste water W discharged from the wet flue gas desulfurization device 9 is sprayed by the spray means 22 from the top of the direct contactor 4 through the conduit 3 by the pump 10, contacts the high temperature flue gas G, and evaporates. Only the gas g is discharged from the conduit 7 while leaving the dissolved impurities as a solid.

The gas g from the conduit 7 is further cooled by water l, which is regulated and sent from the conduit 8 as necessary, to a temperature of 40° C., which is suitable for the wet flue gas desulfurization device 9.
It is introduced into the wet flue gas desulfurization device 9 through the conduit 13 at 80°C.

In the wet flue gas desulfurization unit 9, a suitable neutralizing agent such as caustic soda, ammonia, lime, limestone, etc., or (and) an oxidizing agent such as oxygen, air, hypochlorous acid, etc. is added and treated to produce _SO2. The removed gas g passes through the conduit 11 and is released into the atmosphere from the chimney 12.

The impurities in the waste water W solidified in the direct contactor 4 fall to the lower part thereof and are discharged from the system through the rotary valve 5, which is a solid rotary discharge means.

The solidified impurity 6 is conveyed to an appropriate place,
Or it is transported by truck.

The advantage of the present invention is that the flue gas G, which is relatively high in temperature (130 to 190°C), comes into contact with a relatively small amount of waste water W, so dust and fly ash in the flue gas G are also removed from the waste water W.
It is much easier to handle because it is discharged together with the impurities 6 in a dry state, rather than the wet state obtained in a general wet flue gas desulfurization device.

Furthermore, even if a small amount of solidified impurities 6 such as fly ash and dust flow out from the conduit 7, they will eventually be captured by the wet flue gas desulfurization device 9.

For greater safety, a normal electrostatic precipitator may be used after the direct contactor 4.

The wet flue gas desulfurization method to which the exhaust treatment device of the present invention is applied includes the caustic soda washing method (including the Wellman method), the lime or limestone washing method (oxidizing the neutralized product with air in series or parallel) Lime plaster method (including the Chiyoda Thoroughbred 121 method), water washing method (including the Chiyoda Thoroughbred 101 method, in which the generated sulfurous acid is oxidized to sulfuric acid, and then the lime water is neutralized), This includes the double alkali method, which involves cleaning with an absorbent solution and later treating it with lime or limestone.

Here, the waste water from the wet flue gas desulfurization equipment using the limestone cleaning method invented by Japanese Patent Publication No. 55-37295 to treat asphalt combustion gas of 3020 Nm ² /H is separated from Cl ^- caused by salt in the asphalt. Equipment material SUS316L (Cr18%, Ni12%, Mo2.5%,
52/H was necessary to protect the wastewater (the remainder of which is made of stainless steel), but previously this was treated along with other wastewater, but other equipment was stopped for rationalization. Therefore, we were forced to use only this flue gas desulfurization equipment.

Therefore, the shape of Figure 1 has an outer diameter of 1080 mm and a total height of 2800 mm.
As a result of installing a direct contactor 4 of 1.0 mm in diameter as shown in Fig. 4 and feeding the entire amount of the above-mentioned wastewater into it, there were no problems with the treatment of the wastewater W from the wet flue gas desulfurization equipment 9 even after 12 days of operation. I was bored.

The solid material discharged at this time was black in color, but it was solid and dry enough to be easily handled with a scoop or the like.

〔Effect of the invention〕

As described above, according to the present invention, the following effects are achieved.

(a) The internal rotating zone 28 not only promotes the gas-liquid contact between the waste water and the exhaust gas as described above, but also promotes gas-solid separation between the waste gas and impurities already precipitated by evaporation of the waste water. can.

(b) A cone-shaped air/solid separation section 24 is provided below the cylindrical spray space 23 (Fig. 1), and this air/solid separation section 24 is provided below.
Since the internal riser 26 having an internal rotation zone 28 around the solid separation section 24 stands up, the sprayed waste water W comes into contact with the rotating flow of exhaust gas, and impurities in the waste water precipitated by evaporation of the waste water are removed. teeth,
It moves outward due to centrifugal force, forming a cone of air.
While falling through the solid separator 24, it is discharged from the solid discharge means 5 at the bottom.

On the other hand, in the internal rotating zone 28 as well, the waste water and the flue gas come into contact again, and the precipitation of impurities due to evaporation of the waste water is repeated.

That is, two-stage contact between the waste water and the exhaust gas can be performed, and evaporation of the waste water is promoted.

Therefore, by applying the treatment device of the present invention, the color tone of the gypsum from the flue gas desulfurization device was improved, becoming slightly grayer than black-gray, but the dust in the flue gas was not collected by the treatment device. It became clear that this was due to a significant reduction in the dust load on the flue gas desulfurization equipment.

In addition, it was confirmed that the cooling water to the flue gas desulfurization equipment was reduced from the conventional 188/H to 131/H due to the application of this treatment equipment.

It goes without saying that evaporating waste water using the heat of flue gas satisfies the energy savings currently required, and the present invention is extremely advantageous in that it can be implemented with a relatively simple device. The treatment equipment of the present invention, which can remove impurities from flue gas in dry form, regardless of whether they are water-soluble or water-insoluble, can solve the shortcomings of the conventional wet flue gas desulfurization method, and can only be used to prevent pollution. However, since it can reduce the consumption of water and heat, its utility value is extremely large in terms of resource and energy conservation.

Furthermore, although the treatment equipment of the present invention is mainly suitable for treating wastewater from flue gas desulfurization equipment, it is almost impossible to apply it to these similar wastewaters, especially wastewater from denitrification equipment that uses NH ₃ . Those skilled in the art will readily understand that this method has the advantage of avoiding the release of wastewater and extracting solid matter containing _NH3 , which can also be used as fertilizer. be.

[Brief explanation of drawings]

FIG. 1 is an enlarged side sectional view showing a first embodiment of a wastewater treatment device from a wet flue gas desulfurization device that produces gypsum as a by-product of the present invention, FIG. 2 is a schematic plan view of FIG. 1, and FIG. A schematic side sectional view showing a second embodiment of the present invention, a fourth embodiment.
The figure is a process diagram of a wet flue gas desulfurization method using the wastewater treatment device of the present invention. 20...Gas exhaust pipe, 21...Gas introduction pipe, 2
2... Spraying means, 23... Cylindrical spray space, 24
... Cone-shaped gas/solid separation section, 26 ... Internal gas riser.

Claims (1)

[Claims] 1. At the top of the cylindrical spray space, a means for spraying the waste water after sulfur oxides in the flue gas are separated as gypsum in the wet flue gas desulfurization equipment is installed, and flue gas introduction that introduces flue gas at a temperature of 130 to 190 °C A means is attached tangentially to the cylindrical spray space, a cone-shaped gas/solid separation section is provided at the bottom of the cylindrical spray space, and the gas/solid separation section is installed at the bottom of the cylindrical spray space.
An internal gas riser that rises in the solid separation section and has an internal rotation zone around it is provided in the gas/solid separation section,
A wet flue gas desulfurization device that produces gypsum as a by-product, characterized in that the internal gas riser is connected to a gas discharge pipe in the middle of the spray space, and a solid discharge means is provided at the lowest part of the gas/solid separation section. Treatment equipment for wastewater from.