JPS6043198B2 - Neutralization and solidification treatment method for waste sulfuric acid - Google Patents

Description

[Detailed description of the invention]
-f! More specifically, in a lime-burning thermal power plant that uses a desulfurization device that generates sulfuric acid during the desulfurization process, such as the activated carbon method, the generated sulfuric acid is used as waste sulfuric acid and is used for intermediate treatment using fly ash. This relates to a method of summing and processing.

The most commonly used method is to recover waste sulfuric acid, which is a desulfurization product in flue gas desulfurization equipment, as gypsum.In the case of the activated carbon method, which generates sulfuric acid during the desulfurization process, the recovered sulfuric acid can be used to neutralize alkaline wastewater from factories or as fertilizer. Although it is used for various purposes, the demand for it cannot be expected to be very large, and dilute sulfuric acid has problems in transportation and storage, so it is neutralized using limestone slurry, etc. and turned into gypsum. It is being collected by

In this case, since the neutralization reaction is carried out in a solution, a large-capacity reaction tank and a separator for solid-liquid separation are required, and furthermore, the separated waste liquid needs to be detoxified, so such equipment is also required. This method has the disadvantage of requiring large equipment.
On the other hand, although some fly ash is effectively used as an admixture for cement, the current situation is that the disposal of fly ash is outsourced to specialized companies at the expense of processing fees, which poses economic problems. It is something that

7 The present invention has been made in order to solve the drawbacks and problems in coal combustion furnaces as described above.

According to the present invention, when these waste sulfuric acid and fly ash are mixed and treated to undergo a neutralization reaction, by adjusting the water content in the mixture before the neutralization reaction, the product after the neutralization reaction is substantially reduced. It can be made into a solidified product.

Therefore, waste sulfuric acid and fly ash can be treated at the same time extremely easily, without producing any complicated waste liquid, and this is highly effective. The basis of the present invention is as follows.

According to the study by the present inventors, fly ash contains C.
a,. Na. ．． M? Contains alkaline components of Tei,
Depending on the type of coal, the content of these substances is quite high, and they exist as hydration hardening minerals, so when neutralizing this with sulfuric acid, the sulfuric acid concentration must be selected appropriately, or By adjusting the amount of water added, etc., the amount of water in the mixture before neutralization reaction is adjusted to the total amount of water that evaporates during the neutralization reaction, water of crystallization in the reaction product, and water on the surface of the solidified reaction product. When the entire reaction product is solidified, waste sulfuric acid can be treated at the same time as fly ash, and no waste liquid is produced, which is extremely effective. In the above, when adjusting the concentration of sulfuric acid,
It was confirmed that the concentration of the flue gas recovered sulfuric acid should be set at 20 to 60%, although this differs depending on the components of the fly ash. In addition, in such a neutralization reaction, since the sulfuric acid concentration is relatively high as mentioned above, the reaction time is short, and during this period, the phase changes follow the states of mixing, fluidization, and solidification ζ, so the neutralization It has been confirmed that it is effective to carry out the reaction in a reactor equipped with a stirring blade.

The present invention will be described below with reference to embodiments and system diagrams.

c Example 1 The main chemical components of the fly ash used in this example are as shown in Table 1.

4 In this embodiment, as shown in the system diagram of FIG. 1, exhaust gas discharged from a boiler 1 passes through a dust collector 2 and a sulfuric acid concentrator 3, enters an exhaust gas desulfurization device 4, and is further led to a chimney 5.

The sulfuric acid concentrator 3 condenses dilute sulfuric acid produced by the flue gas desulfurizer 4 using the sensible heat of the exhaust gas, and the concentrated sulfuric acid is stored in a concentrated sulfuric acid tank 6.

In this case, the degree of concentration in the sulfuric acid concentrator 3 is determined by the sulfuric acid concentration under the neutralization reaction conditions in Table 2, which will be explained later. Concentrated sulfuric acid in tank 6 is supplied into neutralization reactor 11 by sulfuric acid supply pump 7 . As for its supply amount, the amount of sulfuric acid under the neutralization reaction conditions in Table 2, which will be explained later, is applied. Fly ash is collected by a dust collector 2, and sent to a fly ash hopper 8, a quantitative feeder 9, and a transfer feeder 1.
0 into the neutralization reactor 11.

In this way, sulfuric acid and fly ash are supplied into the neutralization reactor 11, and a neutralization reaction process is performed.The reaction conditions for this neutralization reaction are shown in Table 2. There are things that ensure that the conditions are met.

That is, the above-described adjustment of the sulfuric acid concentration and the amount of sulfuric acid supplied into the neutralization reactor 11 are made to conform to the reaction conditions shown in Table 2. The neutralization reactor 11 has a structure equipped with stirring blades for effectively carrying out the reaction in the treatment of the present invention. The mixture of sulfuric acid and fly ash supplied into the neutralization reactor 11 is stirred by a stirring blade and subjected to a neutralization reaction treatment, and the product discharged from the bottom of the reactor 11 is substantially solidified. It was hot. This solidified material is transported to a storage area by a conveyor 12 and stored as a solidified material 13. As described above, according to the present invention, waste sulfuric acid can be solidified and processed by fly ash without generating waste liquid, so waste sulfuric acid and fly ash can be processed at the same time. becomes.

Example 2 This example is as shown in the system diagram in FIG. 2, and is different from Example 1 described above in that the fly ash supplied into the neutralization reactor 11 contains limestone, The point is that alkali is added as an additive.

For additives, additive hopper 8″, additive quantitative feeder 9″
The fly ash is added to the fly ash and supplied into the neutralization reactor 11 by the transfer feeder 10. Other operations are completely the same as in Example 1.

This embodiment is effective when the alkali content in fly ash is low.

As explained above with the embodiments, according to the present invention,
It is said that the effect is extremely significant, as it enables a desulfurization system that simultaneously detoxifies fly ash from coal-fired power plants and sulfuric acid, a byproduct of flue gas desulfurization equipment, and does not generate any waste liquid. be able to.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing one embodiment of the present invention, and FIG. 2 is a system diagram showing another embodiment of the invention. 1... Boiler, 2... Dust collector, 3.
... Sulfuric acid concentrator, 4 ... Flue gas desulfurization device, 5 ... Chimney, 6 ... Concentrated sulfuric acid tank, 7 ... Sulfuric acid supply Pump, 8...Fly ash hopper, 8''...Additive hopper, 9
, 9''...quantitative feeder, 10...transfer feeder, 11...neutralization reactor.

Claims (1)

[Claims] 1. When waste sulfuric acid is mixed with coal combustion fly ash and treated by a neutralization reaction, the amount of water contained in the mixture before the neutralization reaction is reduced so that the product after the neutralization reaction is substantially reduced. A method for neutralizing and solidifying waste sulfuric acid, which is characterized by adjusting the waste sulfuric acid so that it is solidified. 2 The amount of water contained in the mixture before the reaction is adjusted to be the total amount of evaporated water during the neutralization reaction, crystallized water of the reaction product, and water on the solid surface of the reaction product. 1
Neutralization and solidification treatment method for waste sulfuric acid described in Section 1. 3. The concentration of the waste sulfuric acid is adjusted such that the amount of water contained in the mixture before the reaction substantially becomes a solidified product after the neutralization reaction. The method for neutralizing and solidifying waste sulfuric acid described above. 4. Neutralization and solidification of waste sulfuric acid according to any one of claims 1 to 3, wherein the mixture before the neutralization reaction is further added with an alkaline additive such as lime or limestone. Processing method. 5. A method for neutralizing and solidifying waste sulfuric acid according to any one of claims 1 to 4, wherein the neutralization reaction is carried out in a neutralization reactor equipped with a stirring blade. .