CN105481143A - Coal-fired boiler tail flue gas dust removal sewage circulation treatment system - Google Patents

Abstract

The invention discloses a flue gas dedusting sewage circulation treatment system at the tail of a coal-fired boiler. A sewage self-wetting electrostatic precipitator is installed at the tail of the coal-fired boiler. After acid-base neutralization in the neutralization tank, it is sent to the flocculation sedimentation tank. After the sewage passes through the flocculation sedimentation tank, the suspended fine dust particles quickly flocculate into larger particle groups, and some of them settle. The lower sewage is discharged into the sewage treatment center, and the upper sewage After being filtered by the filter, the sewage after the particulate matter is intercepted enters the sewage treatment center for treatment, and the filtered sewage becomes relatively clean flushing water, which is sent to the nozzle at the front of the dust collector for continued use, and the nozzle at the rear of the dust collector The flushing water is clean make-up water provided by the make-up water tank. The invention can economically and efficiently solve the problems existing in the sewage circulation treatment of the wet electrostatic precipitator.

Description

Coal-fired boiler tail flue gas dust removal sewage circulation treatment system

technical field

The invention relates to a sewage circulation treatment system, in particular to a sewage circulation treatment system after wet electrostatic dust removal of flue gas at the tail of a coal-fired boiler.

Background technique

With the emergence of "smog" and the improvement of people's environmental requirements, air pollution emissions are becoming more and more strict. For large coal-fired boilers in thermal power plants and other industrial coal-fired boilers, the pollutant emission value of tail flue gas has received more and more attention. The "Coal Power Energy Conservation and Emission Reduction Upgrading and Transformation Action Plan" stipulates the emission limit of coal-fired boiler tail gas in key areas and the central and western regions. Provisions were made. Taking Guangdong Province as an example, it is required that the flue gas dust emission of large coal-fired units shall not exceed 10mg/m3. Under such a large environment, the coal-fired boiler units that have been built have been upgraded and transformed, and a wet electrostatic precipitator is installed at the tail of the boiler to finely remove dust from the flue gas. Almost all new units have wet electrostatic precipitators.

The dust removal particle size of the wet electrostatic precipitator at the tail of the coal-fired boiler is generally about a few microns, the dust content drops from about 50mg/m3 at the inlet of the dust collector to less than 10mg/m3 at the outlet, and the dust removal efficiency is generally about 80%. The water consumption is generally about 1t/(Wanfang flue gas·h), and it is recycled. At present, the wet electrostatic precipitator sewage circulation treatment process on the market is either equipped with multi-stage filtration, which increases the cost of power equipment and virtually increases the operating cost; or sets up multiple settling tanks, but due to the small particle size of the dust, it is difficult to suspend in water Settling requires a larger settling tank, which virtually increases equipment investment costs.

Contents of the invention

Aiming at the technical problems existing in the above-mentioned prior art, the present invention provides a coal-fired boiler tail flue gas dedusting sewage circulation treatment system, which can economically and efficiently solve the problems existing in the wet electrostatic precipitator sewage circulation treatment.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A coal-fired boiler tail flue gas dedusting sewage circulation treatment system, a sewage self-wetting electrostatic precipitator is installed at the tail of the coal-fired boiler, a sewage neutralization tank is arranged at the rear of the water collection tank at the lower part of the dust collector, and the sewage passes through the neutralization tank After acid-base neutralization, it is sent to the flocculation sedimentation tank. After the sewage passes through the flocculation sedimentation tank, the suspended fine dust particles quickly flocculate into larger particle groups, and part of the sedimentation, the lower sewage is discharged into the sewage treatment center, and the upper sewage is sent to the filter. In the filter, after being filtered by the filter, the sewage after the particulate matter is intercepted enters the sewage treatment center for treatment, and the filtered sewage becomes relatively clean flushing water, which is sent to the front nozzle of the dust collector for continued use, and the flushing water of the rear nozzle of the dust collector is Clean make-up water, provided by the make-up tank.

The neutralization tank is equipped with a pH value measuring device and an automatic metering and dropping device for lye.

The flocculation sedimentation tank is equipped with an automatic dripping device for flocculant.

The flocculant is a solution composed of polyaluminum chloride with a mass percentage concentration of 1% and a polyacrylamide solution with a mass percentage concentration of 0.1%.

The filter is a quartz sand filter.

There are two filters, one of which is used as a backup.

The quantity of supplementary water in the supplementary water tank is equal to the sum of the sewage discharge volume of the flocculation settling tank and the discharge volume of filtered sewage.

The purpose of the present invention is achieved like this: after the sewage flows out by gravity from the lower sump of the wet electrostatic precipitator, it enters the sewage neutralization pool. The neutralization tank is equipped with a pH measuring device and an automatic metering and dropping device for lye. The sewage is pumped into the flocculation sedimentation tank after acid-base neutralization in the neutralization tank. The flocculation and sedimentation tank is equipped with a flocculant automatic dripping device. After the sewage passes through the flocculation sedimentation tank, the suspended fine dust particles quickly flocculate into larger particle groups, and part of them settles. The lower sewage is discharged into the sewage treatment center of the whole plant, and the upper sewage is pumped into the filter. After being filtered by the filter, the sewage after the particles are trapped enters the sewage treatment center of the whole plant for treatment, and the filtered sewage becomes cleaner flushing water pumped into the front nozzle of the dust collector for further use. The flushing water of the nozzle at the rear of the dust collector is clean make-up water provided by the make-up water tank.

The sewage neutralization tank is equipped with a PH online measuring instrument and an automatic metering and dropping device for lye. Since the wet electrostatic precipitator is located after the flue gas desulfurization at the tail of the coal-fired boiler, some SO2 remains after the flue gas passes through the desulfurization tower. Has a strong corrosive effect. Therefore, the neutralization tank is equipped with a PH online monitoring device to monitor the pH value of the sewage in real time, and forms a loop with the lye (NaOH) automatic metering and dropping device to control the amount of lye dripping, so that the PH value of the sewage outlet reaches 7. ~8.

The flocculation sedimentation tank is mainly to reduce the settling time of the dust particles suspended in the sewage. The flocculant is a solution composed of polyaluminum chloride with a mass percentage concentration of 1% and a polyacrylamide solution with a mass percentage concentration of 0.1%. The flocculant can be added dropwise automatically, and the suspended particles are flocculated by the flocculant to form large particle groups and then settle.

The filter is a quartz sand filter, one for backup and one for backwash after running for a period of time. The particulate matter concentration in the filtered rinse water is less than 50 mg/l.

The supplementary water tank provides clean flushing water for the nozzles at the rear of the dust collector to ensure the flushing efficiency of the rear of the dust collector and the dust removal effect of the dust collector. The amount of supplementary water is equal to the sum of the amount of sewage discharged from the flocculation settling tank and the amount of filtered sewage discharged.

The beneficial effects of this patent are as follows:

1. The process is simple, the investment in equipment is small, and the most economical and efficient way is to treat the flue gas dust removal sewage at the tail of the coal-fired boiler, and the energy saving effect is obvious.

2. After the sewage comes out of the dust collector, it will be neutralized with acid and alkali to avoid corrosion of equipment and pipelines behind and save operating costs.

3. Set up flocculation and sedimentation, reduce the sedimentation time of particles, and reduce the volume of the sedimentation tank, reducing the cost of equipment investment.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is a block diagram of a coal-fired boiler tail flue gas dedusting sewage treatment system provided by the present invention.

1- supplementary water tank; 2- neutralization tank; 3- flocculation sedimentation tank; 4- filter; 5- flocculant dropping device; 6- lye automatic metering dropping device;

detailed description

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Shown in accompanying drawing 1, the embodiment of this patent is described as follows: the dedusting sewage of wet electrostatic precipitator 7 flows in the neutralization pool 2, carries out pH monitoring and lye (NaOH) automatic metering and dropping device 6 carries out lye dripping After the sewage is neutralized, it is pumped into the flocculation sedimentation tank 3 . The flocculant dripping device 5 adds the flocculant into the flocculation sedimentation tank 3, the particles suspended in the sewage are agglomerated and settled, the lower sewage is pumped out by the sewage pump, and the upper sewage is pumped into the filter 4. The filtered sewage becomes cleaner flushing water, which is pumped into the nozzle at the front of the dust collector. The filtered waste water (with high pollution content) is pumped out by the sewage pump. The flushing water of the nozzle at the rear of the dust collector comes from the clean water in the supplementary water tank 1 to ensure the dust removal effect of the dust collector. Supplementing the water tank 1 provides clean water for backwashing to the filter 4 at the same time to ensure the filtering effect of the filter.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (7)

1. A coal-fired boiler tail flue gas dedusting sewage circulation treatment system, a sewage self-wetting electrostatic precipitator is installed at the coal-fired boiler tail, it is characterized in that a sewage neutralization pool is set at the rear of the water collection tank at the bottom of the dust collector , the sewage is neutralized by acid and alkali in the neutralization tank and then sent to the flocculation sedimentation tank. After the sewage passes through the flocculation sedimentation tank, the suspended fine dust particles quickly flocculate into larger particle groups, part of which settles, and the lower sewage is discharged into the sewage treatment center. The upper layer of sewage is sent to the filter, and after being filtered by the filter, the sewage after the particulate matter is intercepted enters the sewage treatment center for treatment, and the filtered sewage becomes relatively clean flushing water, which is sent to the front nozzle of the dust collector for continued use, and the rear of the dust collector The rinse water for the nozzles is clean make-up water provided by the make-up water tank. 2. The coal-fired boiler tail flue gas dedusting sewage circulation treatment system according to claim 1, characterized in that the neutralization tank is equipped with a pH value measuring device and an automatic lye metering and dropping device. 3. The coal-fired boiler tail flue gas dedusting sewage circulation treatment system according to claim 1, characterized in that the flocculation sedimentation tank is provided with a flocculant automatic dripping device. 4. The coal-fired boiler tail flue gas dedusting sewage circulation treatment system according to claim 1, characterized in that the flocculant is polyaluminum chloride with a mass percentage concentration of 1% and a mass percentage concentration of 0.1% A solution consisting of polyacrylamide solution. 5. The coal-fired boiler tail flue gas dedusting sewage circulation treatment system according to claim 1, characterized in that the filter is a quartz sand filter. 6. The coal-fired boiler tail flue gas dedusting sewage circulation treatment system according to claim 6, characterized in that there are two filters, one of which is used as a backup. 7. The coal-fired boiler tail flue gas dedusting sewage circulation treatment system according to claim 1, characterized in that the amount of supplementary water in the supplementary water tank is equal to the sum of the sewage discharge volume of the flocculation settling tank and the discharge volume of filtered sewage.