What are the basic principles of industrial wastewater treatment?

Principle of chemistry: SO2 in flue gas is essentially acidic and can be removed from flue gas by reaction with appropriate alkaline substances. The most common basic substances used in flue gas degasification are limestone (calcium carbonate), quicklime (calcium oxide, Cao), and hydrated lime (calcium hydroxide). Limestone is relatively cheap because it is abundant, and both quicklime and hydrated lime are made from limestone by heating. Other alkaline substances such as sodium carbonate (soda ash), magnesium carbonate and ammonia are sometimes used. The basic substance used reacts with SO2 in the flue gas to produce a mixture of sulfites and sulfates (which may be calcium, sodium, magnesium, or ammonium depending on the basic substance used). The ratio of sulfites to sulfates depends on the process conditions, and in some processes, all sulfites are converted to sulfates. Reactions between SO2 and alkaline substances occur either in alkaline solutions (wet flue gas desulfurization technology) or on wet surfaces of solid alkaline substances (dry or semi-dry flue gas desulfurization technology).

What are the seven basic principles of industrial wastewater treatment

1, give priority to the selection of non-toxic production process to replace or reform the backward production process, as far as possible in the production process to eliminate or reduce the production of toxic and harmful wastewater.

2. In the process of using toxic raw materials and producing toxic intermediates and products, strict operation and supervision shall be conducted to eliminate dripping and reduce loss, and reasonable processes and equipment shall be adopted.

3. Waste water containing highly toxic substances, such as some heavy metals, radioactive substances, high concentration of phenol and cyanide, should be separated from other waste water for treatment and recovery of useful substances.

4. Waste water with large flow and light pollution shall be properly treated and recycled, and shall not be discharged into sewers. Waste gas treatment equipment manufacturers of paper mills shall not increase the load of urban sewage and municipal sewage treatment.

5. Organic wastewater similar to urban sewage, such as food processing wastewater, sugar wastewater and papermaking wastewater, can be discharged into the urban sewage system for treatment.

6. Some biodegradable toxic waste water, such as phenol and cyanide waste water, should be treated first, discharged into the city sewer according to the permitted discharge standards, and then further biochemical treatment.

7. Toxic waste water that is difficult to biodegrade should be treated separately and not discharged into urban sewers. The development trend of industrial wastewater treatment is to recycle waste water and pollutants as useful resources or to implement closed circulation.

The most widely used commercial technology in the world is calcium method, accounting for more than 90%. The desulfurization technology can be divided into wet method, dry method and semi-dry (semi-wet) method according to the dry and wet state of absorbent and desulfurization product in the desulfurization process. Wet FGD technology is to use solution or slurry containing absorbent to desulphurize and treat desulphurization products in wet state. This method has the advantages of fast desulphurization reaction speed, simple equipment and high desulphurization efficiency. Dry process desulphurization absorption of the FGD technology and product processing are conducted in the dry state, the law has no sewage waste acid discharge, equipment corrosion, to a lesser degree, no significant cooling in the process of purification, purifying flue gas after high temperature smoke, conducive to the chimney exhaust diffusion, less secondary pollution, but the desulfurization efficiency is low, reaction speed is slow, huge equipment, etc. Semi-dry FGD technology refers to flue gas desulfurization technology in which desulfurizer is desulfurized in the dry state and regenerated in the wet state (such as the regeneration process of water-washed activated carbon), or desulfurized in the wet state and desulfurized in the dry state (such as spray drying method). In particular, the semi-dry method of desulfurization under wet state and desulfurization under dry state has attracted wide attention because of its advantages of fast reaction speed and high desulfurization efficiency, as well as the advantages of dry method of no waste sewage acid discharge and easy disposal of desulfurization products. According to the use of desulphurization products, it can be divided into two methods: discard method and recovery method.