JPS62121687A - Apparatus for treating waste water from wet wast gas desulfurizing method for forming gypsum as byproduct - Google Patents

Abstract

PURPOSE:To take out impurities in waste water as a solid, by providing a waste water spray means to the upper part of a cylindrical spray space and providing a waste gas intoruding part to the spray space from the tangential line direction thereof and providing a coneshaped gas-solid separation part to the lower part of the spray space. CONSTITUTION:A small amount of waste water W discharged from a wet waste gas desulfurizing apparatus 9 is passed through a conduit 3 by a pump 10 to be sprayed from the top part of a contact part 4 by a spray means 22 and contacted with high temp. waste gas G and only gas (g) is exhausted from a conduit 7 while dissolved impurities are allowed to remain as a solid. The gas (g) is cooled by water (l) from a conduit 8 and introduced into the desulfurizing tower 9 at 40-80 deg.C and treated with a neutralizing agent such as caustic soda or ammonia or an oxidizing agent such as air in said apparatus 9 to remove SO2. The impurities in waste water W directly solidified in the contact device 4 fall to the lower part thereof and discharged out of the system from a rotary valve 5.

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 process that produces gypsum as a by-product.

[Prior art]

Wet flue gas desulfurization equipment is a result of technological development over the past 10 years.
It has been widely used because it has excellent desulfurization performance and can meet Japan's strict air pollution control regulations.

In addition, 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 S02, which is a source of pollution in flue gas, in various wet flue gas desulfurization processes, other trace components in flue gas, especially chlorine, Almost no measures have been taken for fluorine (including its compounds), fluorine (including its compounds), and ammonia (including its compounds), and these trace components may be water-soluble. The captured trace components were disposed of as wastewater from the flue gas desulfurization equipment.

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 outside the water plate is mainly alkali and alkaline earth metal sulfates, chlorides, ammonia salts, etc., and does not have any particular negative impact on the environment, and should not be disposed of in public rivers. It was recognized.

However, this wastewater increases the amount of water consumed by the wet flue gas desulfurization equipment, placing an extra burden on installers who may think that even the evaporated water in the flue gas is not enough. 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 CFI is discharged in particularly large amounts. Attempts have been made to separate - by electrolysis, but the problem is that it is 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, and to evaporate the wastewater to remove impurities in the wastewater into solid form. The purpose of the present invention is to provide a wastewater treatment device for extracting wastewater.

[Structure of the invention]

That is, the wastewater treatment device from the wet flue gas desulfurization method that produces gypsum as a by-product of the present invention has a wastewater spraying means installed in the upper part of a cylindrical spray space, and a flue gas introduction system that introduces flue gas from around the spraying means. A section is provided in the tangential direction to the spray space, and a cone-shaped gas/solid separation section is provided below the cylindrical spray space. A gas riser is provided in the electrical/solid separation section, the internal gas riser is connected to a gas discharge pipe in the middle of the spray space, and a solid discharge means is further provided at the lowest part of the gas/solid separation section. That is.

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

FIG. 1 shows a gas-liquid direct contactor 4 as Embodiment 1 of the wastewater treatment device 4 of the present invention, and a basin-shaped gas introduction section 21 that introduces flue gas G as a sidestream fluid is as follows: It communicates with a flue 2 that introduces the exhaust gas G, where the exhaust gas G is preferably given a rotational motion by a guide vane (not shown) and is ejected in the form of a mist from the spraying means 22 for the exhaust gas W. Violent contact with W.

Here, in the present invention, wastewater refers to a part of the circulating water that is used in wet flue gas desulfurization equipment after separating the by-product gypsum and recirculating it to the desulfurization equipment. This refers to a small amount of liquid that is drawn out of the system depending on the amount accumulated.

As for this spraying means 22, a pressurized type is effective when the wastewater W does not contain solids (other than dissolved ones), and when the wastewater W is in the form of 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,
Shifts to smoke exhaust G.

At the same time, the dissolved impurities 6 solidify as the water disappears, become fine particles, fall while rotating, and move from the cone electric/solid separation section 24 to the internal rotation zone 28 into the internal guide zone 25.
The gas and solid particles flow in while being rotated as shown in FIG.

The solid particles fall downward due to gravity within the internal rotating zone 28, and are further pushed down into the internal rotating zone 2 by the centrifugal force of the flue gas G.
8, finally reaches its wall 27, slides down the cone-shaped wall 27 due to gravity, and is discharged to the outside by the rotary pulp 5, which is the solid rotary discharge means at the bottom.

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

One spraying means 22 as shown in FIG. 1 is simple in structure and is desirable, 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.

In addition, the internal gas riser 26, wall 27, internal rotation zone 28, rotary valve 5, etc. are processed in the lower part of the cylindrical spray space 23, the cone electric/solid separation section 24, and the internal guide band 25 having the above configuration. It is also effective as a similar modification to devise a structure in which a plurality of numbers are increased depending on the amount.

The direct contactor 4 having the above configuration is not limited to the first embodiment shown in FIG. 1, but may have a structure such as the second embodiment shown in FIG. The same parts are indicated by the same part numbers, and can have the same functions as those in the first embodiment shown in FIG.

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 apparatus of the present invention. Desirably, exhaust gas G from a boiler or the like at a temperature of 130 to 190°C is passed through a flue 2 by a fan and formed into a substantially cylindrical shape. The hollow wastewater treatment device of the present invention is introduced into the direct contactor 4 here.

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, and comes into contact with the high temperature flue gas G.
The gas is evaporated from conduit 7 leaving dissolved impurities as a solid; 2. Only g is discharged.

The gas g from the conduit 7 is further cooled by water β that is regulated and sent from the conduit 8 as necessary, and is then transferred to the conduit 1 at a temperature of 40°C to 80°C suitable for the wet flue gas desulfurization device 9.
3 to the wet flue gas desulfurization device 9.

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 remove S02. The gas g is discharged from the chimney 12 into the atmosphere through the conduit 11.

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 impurities 6 are transported to an appropriate location by a conveyor, trunk, or the like.

The advantage of the present invention is that the flue gas G, which has a relatively high temperature of 130 to 190°C, comes into contact with a relatively small amount of waste water W, so the flue gas G
The dust and fly ash inside, along with the impurities 6 in the wastewater W, are discharged in a dry state, and not in a wet state, which is obtained with general wet flue gas desulfurization equipment, making it much easier to handle. It is.

Further, 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 wastewater 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, etc.), water washing method (oxidizing the generated sulfite to form sulfuric acid, and then neutralizing the limestone)
Examples include the Chiyoda Thoroughbred 101 method), and the double alkali method, which involves cleaning with a clear absorbing liquid 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 3.02 ONm"/H is as follows:
Equipment material S from Cp- caused by salt in asphalt
52j2/H was necessary to protect OS 316L, but previously this was treated along with other wastewater, but other equipment had stopped operating for rationalization, so this flue gas desulfurization We had no choice but to process using equipment only.

Therefore, the shape of Figure 1, outer diameter 1.081hm, total height 2.
, an 800 m1 direct contactor 4 was installed as shown in Fig. 4, and as a result of feeding the entire amount of the above-mentioned wastewater into it, the wastewater W from the wet flue gas desulfurization equipment 9 was treated even after 12 days of operation. There were no problems.

The solid matter discharged at this time was black in color,
It was solid and dry enough to be easily handled with a shovel.

〔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 wastewater and the exhaust gas as described above, but also promotes the gas-solid separation between the impurities already precipitated by the evaporation of the wastewater and the exhaust gas. .

(b) A cone-shaped air separation section 24 is provided below the cylindrical spray space 23 (FIG. 1), and this air separation section 2
4, an internal riser 26 having an internal rotation zone 28 around it stands up, so that the sprayed waste water W comes into contact with the rotating flow of exhaust gas, and the impurities in the waste water precipitated by the evaporation of the waste water are removed to the outside by centrifugal force. Moving, cone-shaped Qi・
While falling through the separating section 24, it is discharged from the solid discharge means 5 at the bottom.

On the other hand, in the internal rotating zone 28, the waste water comes into contact with the flue gas 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 and became slightly grayer than black-gray, but this is because the dust in the flue gas was collected by the treatment device. It has become clear that this is 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 188β/H to 13111/H due to the application of this treatment equipment.

Evaporating waste water using the heat of flue gas not only meets the current need for energy conservation, but the present invention, which can realize this method with a relatively simple device, is very convenient. The treatment equipment of the present invention, which can remove impurities in dry form, regardless of whether they are water-soluble or water-insoluble, has solved the drawbacks of the conventional wet flue gas desulfurization method, and is effective not only for preventing pollution but also for preventing pollution. Since it reduces the consumption of water and heat, its utility value is extremely large in terms of resource and energy conservation.

Further, although the treatment device of the present invention is mainly suitable for treating wastewater from flue gas desulfurization equipment, even if it is applied to similar wastewater, especially wastewater from denitrification equipment that uses NH3, it will hardly work. Those skilled in the art will readily appreciate 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.

[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;
The figure is a schematic plan view of Fig. 1, Fig. 3 is a schematic side sectional view showing a second embodiment of the present invention, and Fig. 4 is a process diagram of a wet flue gas desulfurization method using the wastewater treatment device of the present invention. be. 20... Gas discharge pipe, 21... Gas introduction pipe, 22.
... Spraying means, 23... Cylindrical spray space, 24...
Cone electrical separation section, 26...internal gas riser.

Claims (1)

[Claims] A wastewater spraying means is installed in the upper part of the cylindrical spraying space, and a flue gas introduction part for introducing exhaust gas from around the spraying means is provided in the tangential direction to the spraying space, and in the lower part of the cylindrical spraying space. A cone-shaped air/solid separation section is provided, and an internal gas riser that has an internal rotation zone around it and rises within the air/solid separation section is provided in the air/solid separation section, and the internal gas riser is connected to the spray space. An apparatus for treating waste water from a wet flue gas desulfurization method that produces gypsum as a by-product, characterized in that the device is connected to a gas exhaust pipe in the middle of the gas-solid separation section, and further includes a solid discharge means provided at the lowest part of the gas/solid separation section.