Wastewater treatment technology for flue gas desulfurization in thermal power plants

In the production of flue gas desulfurization in thermal power plants, affected by the desulfurization process and flue gas, the wastewater contains a large amount of insoluble substances, such as calcium chloride, fluoride, and heavy metal elements such as mercury ions and magnesium ions, resulting in wastewater. Water quality decreased.

The types of coal and limestone used in thermal power plants can cause serious pollution of wastewater quality.

At present, in the process of using flue gas desulfurization technology in some thermal power plants in my country, the wastewater generated contains a lot of suspended solids and a wide variety of heavy metal elements.

People need to take heavy metal elements as the primary management object, master their specific concentration characteristics, understand the self-purification and degradation characteristics of the water environment, clarify the situation of the biological chain, and take reasonable measures to treat the wastewater.

Process analysis of wastewater treatment technology

In the treatment of flue gas desulfurization wastewater, thermal power plants need to clarify specific technical processes and rationally use neutralization methods and sedimentation methods for treatment.

Ensure the continuity and application effect of each program, realize the automatic management technology mode, and enhance the anti-corrosion performance of processing machinery and equipment, rationally use advanced materials, and ensure the good implementation of wastewater treatment work.

Specifically, people can take the following actions.

Carry out treatment according to the characteristics of water quality

  • In actual work, it is necessary to stack the desulfurization wastewater mixed with by-product gypsum, etc., to clarify the specific water quality characteristics, and to build a wet desulfurization system to form a desulfurization wastewater treatment mode.
  • Electric precipitators and air preheaters can be used to implement the work to clarify the evaporation of flue wastewater, and to reasonably collect solid substances and fly ash and other components.
  • However, due to the limitations of mechanical equipment and process conditions, my country cannot reasonably use such processes.
  • A professional wastewater treatment system can be set up to ensure that it meets the relevant national wastewater discharge standards and requirements after treatment.

Neutralization work measures

In actual use, there are mainly two ways to neutralize.

One is to use the neutralization reaction of acid and alkali to promote the pH value of wastewater to be close to the neutral range. The second is to use the precipitation method to promote the precipitation of zinc and copper elements during the neutralization reaction.

During the neutralization process, the commonly used additives are lime, limestone, calcium carbonate and other substances. Among them, limestone comes from a wide range of sources, the use cost is very low, and the treatment process is simple. when using limestone.

It can be fused with water, and the concentration of the ratio is 21%, and it is transported to the preparation box by means of a feeding tube, and then the density of the circulating tube of the slurry is tested according to the result.

Strictly manage the pH value of wastewater, reasonably carry out the addition of limestone slurry, and promote the pH value of desulfurization wastewater to be within a reasonable range, so that heavy metal elements are precipitated.

Analysis of settlement measures

After the neutralization method is used, sedimentation treatment measures should be used reasonably to transport the wastewater to the sedimentation tank. The main reason is that not all metal elements can react and precipitate with the limestone slurry.

For example, elemental mercury does not interact with limestone slurries and precipitation is difficult.

Therefore, during the sedimentation treatment, it is necessary to appropriately add organic sulfur substances and polyiron substances to the sedimentation box to settle the remaining heavy metal elements in the wastewater.

For organic sulfur, during the actual addition, the amount can be controlled according to the test results and specific measurement conditions.

Analysis of flocculation treatment measures

After the neutralization and settling process is completed, flocculation treatment is required.

The main reason is that wastewater also contains a lot of colloidal substances and suspended solids, during which appropriate coagulants and coagulants can be added to promote particle settling and form flocculation.

For desulfurization wastewater, in the process of using this kind of treatment method, ferric chloride, aluminum sulfate, etc. should be used reasonably for treatment, and limestone can also be used as a coagulant aid to promote the good implementation of the flocculation process.

Enterprises can set up stirring devices in equipment such as neutralization and settling, and add chemical substances to ensure uniformity and effectiveness, so that it will not affect the flocculation particles and improve the management level.

Analysis of Clarification Actions

In the overall wastewater treatment process, clarification is the final process. After clarification, purified water can flow into the tank. In order to better detect the purified water after treatment, during the clarification treatment.

According to the national wastewater discharge standards and requirements, a pH value detection technology device can be set up in the box, and the turbidity detection system can be combined to analyze it.

If the pH value of the purified water in the box is between 6 and 9, it meets the national standard; if the pH value is greater than 9, it is necessary to appropriately add concentrated hydrochloric acid to the wastewater for reasonable adjustment.

If the pH of the wastewater is less than 6, it should be re-treated and then properly tested. During the turbidity test, it is necessary to ensure that the turbidity of the wastewater is around 190 mg/L.

If this range is exceeded, the discharge work should be terminated and the neutralization and sedimentation treatment should be carried out again to ensure that the purified water can meet the regulations.

Analysis of key points of flue gas desulfurization wastewater treatment technology

Strictly manage the residence time of wastewater

In the wastewater treatment work, it is necessary to clarify the residence time of wastewater in the neutralization box, sedimentation and flocculation box, and comprehensively improve the treatment effect of sedimentation and flocculation.

For the reaction tank, it is necessary to fix the solvent in the box within a reasonable range, and conduct strict analysis according to the flow rate and the residence time of wastewater, and carry out reasonable adjustment experiments.

Under normal circumstances, the residence time of wastewater needs to be controlled at about 60 minutes to promote the good treatment of heavy metal elements and achieve the expected work purpose.

Management measures for the use of additive drugs

Usually, the additive drugs are limestone slurry, organic sulfur slurry and coagulant slurry, etc., which are required to be stored separately during storage, and the ventilation performance and fireproof performance of the storage location are ensured. After the problem is found, automatic alarm work is realized .

limestone slurry

The limestone slurry is mainly made by adding appropriate water to the limestone. After the production is completed, it is transported to the storage box by a tanker, and then analyzed by a metering pump and a dose box.

Drugs are added to the tank through the management and control of the metering pump. For limestone slurry, the concentration usually needs to be controlled at about 21%. If the concentration is too high, it is easy to cause blockage of the metering pump.

Therefore, the concentration of limestone slurry should be adjusted reasonably during the use period to promote the good implementation of all aspects of work.

Organic sulfur slurry

The organic sulfur slurry is a solution containing organic sulfur compounds. It is set in the drug dissolving box during processing, and then the drug is regulated by a diaphragm pump, so that the drug enters the sedimentation box to form a good adjustment effect.

In the process of using the organic sulfur slurry, the concentration should be determined according to the content of mercury in the wastewater. Through the analysis of the experimental results, if the content of mercury is very small.

The organic sulfur slurry with a concentration of 16% can be added with a dosage of 41mL/m3 wastewater, in order to improve the treatment effect and optimize all aspects of the work mode.

coagulant slurry

When using the flocculant, the slurry can be added by the diaphragm dosage method, and the turbidity of the flocculation box can be reasonably analyzed to clarify the actual amount of slurry added to ensure strict control of wastewater treatment.

In the meantime, it is necessary to carry out reasonable analysis and research work. Usually, 41% concentration of ferrous sulfate can be added to it, and the dosage is 26mL/m3 wastewater.

Enhance the use effect of the flocculation link, and use scientific and reasonable methods to solve the current problems and improve the specific treatment level.

Control points for other treatment measures

Fluoride treatment measures

In desulfurization wastewater, fluorides are mainly wastewater pollutants produced after coal combustion. Usually, it can be treated with lime substances, etc., and the problem can be solved by adjusting the pH value.

Lime is used as the main chemical reagent for fluoride treatment.

At the same time, the wastewater contains a lot of magnesium and iron elements, which can form precipitates under the action of alkalinity. Therefore, during the actual treatment period, the lime material should be used reasonably to promote the precipitation and removal of various substances in the wastewater.

At the same time, it is necessary to carry out the precipitation management work reasonably, to ensure that the concentration of lime is controlled at about 890mg/L, and to improve the level of wastewater treatment in combination with the current work characteristics and requirements.

COD (chemical oxygen demand) treatment

In the process of flue gas desulfurization wastewater treatment, people can use COD treatment to solve the problem. The main reason is that the chemical oxygen demand factor in wastewater does not contain organic components, which are inorganic ions in a reduced state, and the main component is disulfate.

In the meantime, the oxidant can be set to air, and during the actual treatment of the waste water tank, the system aeration treatment can be carried out, the time is controlled at about 7h, and the ratio of air to water is controlled at about 2:1.2.

For the aeration device, the main pipe branch pipe method can usually be used. After relevant practical research, it can be known that after aeration treatment of wastewater, it is necessary to ensure that the COD removal rate reaches 9%. At the same time, in the COD treatment of wastewater, inorganic acid substances can also be added, and wastewater can be added in an acidic environment to promote the decomposition of COD.

In actual work, thermal power plants should clarify the purpose and requirements of flue gas desulfurization wastewater treatment, rationally use advanced technology, and formulate a sound management plan to comprehensively improve the effect of management and control.

And intensify management efforts to improve the effect of scientific and technological research and application.

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