JPS6327076B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a method for treating dust, acidic or alkaline waste discharged from a coal-fired power plant in a non-polluting state, and in particular, it relates to a method for treating dust, acidic or alkaline waste discharged from a coal-fired power plant, and in particular, to treat neutralized waste generated within the system. It relates to a method for effectively utilizing treated water within a plant.

BACKGROUND OF THE INVENTION In thermal power plants, especially coal-fired power plants, large amounts of clinker and fly ash are generated from the combustion of pulverized coal and fine grain coal, and their disposal has become a problem. A water jet is preferred for discharging and transporting clinker accumulated in the slag tank at the bottom of the furnace, and water for water sealing is required to airtight the slag tank and the bottom of the furnace. On the other hand, the particle size of the debris collected by a dust collector such as an electrostatic precipitator is micron-level, as is called fly debris, and it is easily blown up, requiring careful handling, and the amount of discharge is large.

As an example, if these amounts are shown for one boiler for a 700 MW class coal-fired power plant, the clinker is
10T/h, fly ash 80T/h, clinker transport water 300T/h, fly ash humidification water 15-20T/h. In addition, the waste water discharged from the cooling tower of the desulfurization equipment is a strong acid with a pH of 1 to 2, and the amount discharged is
18T/h, and the wastewater from Shitukuna, which concentrates CaSO ₄ (gypsum) produced when SO ₂ and SO ₃ in exhaust gas are treated with CaO, is an alkaline liquid with a pH of 9.0 to 9.5.

As mentioned above, large amounts of fly ash and clinker are discharged from coal-fired power plants, and from the desulfurization process, a sulfuric acid solution containing highly concentrated hydrochloric acid and hydrofluoric acid is produced by the spray water used to cool the exhaust gas, and CaSO is produced by the reaction with CaO. _Four
Due to the treatment and transportation of
It requires a water flow of 350T/h.

Although some of these wastes are used as valuable materials, the wastewater, flyash, and clinker all need to be neutralized before being discharged to prevent secondary pollution. The treatment process described above requires a large amount of water, but it is uneconomical to supply this from outside.
It is preferable to reuse the water used within the system as much as possible.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a method of reusing the water produced within the system as much as possible to reduce the amount of supplementary water supplied from outside.

In short, this invention is a method characterized in that the neutral liquid produced in the system by neutralizing wastewater is used for desulfurization and as water for sealing the slag tank and boiler.

Embodiments of the present invention will be described below with reference to the drawings.

Exhaust gas from the coal-fired boiler 1 passes through an electric precipitator 2, pipes 3 and 4, a desulfurization fan 5, a heat exchanger 6, enters a cooling tower 7a of a desulfurization device 7, passes through a mist eliminator 7b, and flows into an absorption tower 7c. do. In this absorption tower, the exhaust gas is sprayed with water containing limestone powder from a device consisting of a circulation pump 7d, a pipe 7g, and a spray nozzle 7e, and the SO ₂ and SO ₃ gases it contains react with it and become CaSO ₄ . It is stored at the bottom of the absorption tower 7c. The gas containing water droplets is removed by a demister 7f, heated by a heater 8, further heated by a heat exchanger 6, and discharged into the atmosphere via a pipe 9 and a chimney 0. The dampers 11a, 11b, and 11c are used to switch the exhaust gas flow when stopping or inspecting the desulfurization equipment. On the other hand, the fly ash collected by the electrostatic precipitator 2 is pneumatically transported through a pipe line 13 using pressurized air from a blower 12, and is supplied to a silo 14. An appropriate amount of the mixture is sent to the mixer 15 via the pipe 50, humidified and kneaded with water sprayed from the spray nozzle pipe 15a, and then transported to a predetermined location by the truck 16, where it is dumped or put to effective use (for example, added to cement). In addition to being discharged through this pipe 50, the fly ash flows into a pipe 47 and is mixed with the supernatant liquid extracted from the wastewater treatment tank 29 via pipes 30, 31, and 31a in a mixer 47a. After that, it is supplied to the wastewater treatment tank 29 as an alkaline liquid. The exhaust gas cooling water that circulates between the cooling tower 7a, the cooling tower circulation tank 20, the circulation pump 21, and the pipe line 22 becomes a strongly acidic liquid with a pH of about 1 to 2 during the cooling process, and a part of it is extracted through the pipe line 23. The wastewater is supplied to the wastewater treatment tank 29. Here, it is mixed with the alkaline liquid and neutralized. The neutralized treatment liquid (water) is supplied to the cooling water circulation path through the pipe 30a to dilute this strong acidic liquid. Also, the pipe line 44
The processing liquid flowing into the pipe passes through this pipe and joins with the make-up water W in the pipe . The make-up water (hereinafter simply referred to as "make-up water") W that has merged with the processing liquid is first used for sealing the slag tank 1a and the boiler 1 and as water supply to the slag tank 1a. FIG. 2 shows the details of the slag tank, and the make-up water W is supplied to the groove 6, which has a substantially U-shaped cross section, formed in the slag tank 1a.
Flows into 0. A partition plate 1c suspended from the header 1b is disposed approximately at the center of the groove 60, and the partition plate 1c and makeup water W flowing into the groove 60 keep the slag tank 1a airtight. The make-up water overflowing from the groove 60 flows into the pipe 46.
b and is used for the next time. On the other hand, conduit 46c
The make-up water W flowing into the slag tank 1a flows into the slag tank 1a and is stored therein. The molten incombustibles flow down the boiler 1 and are rapidly cooled by this stored water, disintegrating into relatively small particles and flowing into the slag tank 1.
It is deposited as clinker at the bottom of a. Note that the space above the slag tank 1a is at a very high temperature, so that the stored water evaporates rapidly, so make-up water W is supplied through the pipe 46c and the water flow is controlled so that the water surface is always maintained at a constant height. Next, the make-up water overflowing from the groove 60 is supplied as make-up water by the pump 45 through the pipe 46b to the pipe 7g which circulates desulfurization liquid containing limestone from the bottom of the absorption tower 7c to the spray nozzle 7e. Limestone slurry used as a desulfurization agent is stored in limestone silo 17 containing limestone powder.
Limestone powder sent from limestone slurry tank 1
The mixed water is mixed with feed water in the tank 8 and supplied to the absorption tower 7c via a pump 19 and a pipe 19a.

Next, the sludge in the wastewater treatment tank 29 reaches a water jet conveyor 37 via a pipe 52, and a pump 33
The water flowing into the pipe line 35 is transported by water flow and flows into the dehydrator 38 . Further, the clinker in the slag tank 1a reaches a water jet conveyor 36, and is supplied to a dehydrator 38 by the water flow in a pipe 34 in the same way as the sludge. The clinker and sludge supplied to the dehydrator 38 are dehydrated and then discharged and transported to a predetermined location by the truck 16a. On the other hand, the water used for transportation is sent to a settling tank 39, where the suspended matter is settled. The purified water after the removal of suspended matter is completed reaches a circulation tank 40 and a pump 41, a part of which is used for diluting exhaust gas cooling water through a pipe 24, and the rest is used for sludge and clinker through a pipe 42. Used for replenishing water for water transport.

By implementing this invention, the neutralized treated water can be used for sealing the connection between the boiler furnace and the slag tank, replenishing water for the desulfurization process, replenishing the stored water in the slag tank, etc. Treated water can be used without waste.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an effluent treatment plant for carrying out the method according to the invention, and FIG. 2 is a detailed diagram of the connection between the boiler and the slag tank. 1...Coal-fired boiler, 1a...Slag tank, 7...Desulfurizer, 7a...Cooling tower, 7g...
Desulfurizing agent-containing liquid circulation pipe, 29... wastewater treatment tank, 4
4... Pipe line for supplying neutralized liquid, 46, 46b... Pipe line for supplying makeup water.

Claims (1)

[Scope of Claims] 1. In a device that collects fly ash in exhaust gas discharged from a coal-fired boiler and desulfurizes the exhaust gas itself, the strongly acidic liquid used for cooling the exhaust gas in the desulfurization process contains fly ash. The water is neutralized with an alkaline liquid, and the neutralized water is used for sealing the boiler and slag tank, and the overflow water from this seal is supplied as make-up water to the circulation process of desulfurizing agent-containing water. A distinctive method for reusing neutralized water. 2. The method for reusing neutralized water according to claim 1, characterized in that a part of the water supplied to the seal portion of the slag tank is supplied to the slag tank as slag tank stored water through a branching pipe.