China will take the construction of ecological civilization as an important part of the 13th Five-Year Plan, implement the development concepts of innovation, coordination, green, open and sharing, and implement a series of policy measures such as optimizing industrial structure, building a low-carbon energy system, developing green buildings and low-carbon transportation, and establishing a national carbon emission trading market through scientific and technological innovation and institutional mechanism innovation, so as to form human beings and nature. New pattern of harmonious development and modernization. Shenzhen Pure Water No. 1 Water Treatment Technology has always been concerned about and is at the forefront of scientific and technological innovation. This paper mainly introduces the basic principles, process flow and application scope of four core processes commonly used in zero-discharge technology of wastewater treatment. Details are as follows:

I. RCC Technology

The core technologies of RCC are "mechanical steam recirculation evaporation technology", "seed crystallization technology" and "mixed salt crystallization technology".

1 Mechanical Steam Recompression Cyclic Evaporation Technology

1.1 Basic Principles

The so-called mechanical vapor recirculation evaporation technology is based on the principle of physics, equal amount of material, from liquid to gaseous process, need to absorb quantitative heat energy. When a substance is changed from a gaseous state to a liquid state, it emits an equal amount of heat energy. According to this principle, the heat energy needed to evaporate wastewater is provided by the evaporator when it is used to treat wastewater, and the heat energy released by steam condensation and condensate cooling is provided by the evaporator. There is no loss of latent heat during operation. The energy consumed in the operation is only the power consumed by the pumps, steam pumps and control systems that drive the circulation and flow of wastewater, steam and condensate in the evaporator.

In order to resist the corrosion of wastewater to the evaporator and ensure the service life of the equipment, the main body of the evaporator and the internal heat exchanger tubes are usually made of high-grade titanium alloy. Its service life is 30 years or more.

The single unit wastewater treatment capacity of evaporator starts from 27 tons/day to 3800 tons/day. If the amount of wastewater needed to be treated is larger than the maximum amount of single machine, it can be treated by installing multiple evaporators. Evaporator is also called Brine Concentrator when it runs with seed technology.

1.2 Brine Concentrator Structure and Process Flow

(1) The brine to be treated enters the storage tank, in which the PH value of the brine is adjusted to 5.5-6.0 to prepare for degassing and decarbonization. The brine enters the heat exchanger and raises the temperature to the boiling point.

(2) The heated brine passes through the degasser to remove the insoluble substances in the water, such as oxygen and carbon dioxide.

(3) The new brine enters the bottom trough of the condenser, mixes with the brine circulating inside the concentrator, and then is pumped to the top water tank of the heat exchanger tube bundle.

(4) Through the device, the brine distributor at the top of the heat exchanger tube flows into the tube and distributes evenly on the inner wall of the tube, which is in the shape of a thin film and falls to the bottom trough by gravity. When some brine drops along the pipe wall, the heat released by the steam outside the absorption tube evaporates, and the steam and the non-evaporated brine drop together to the bottom trough.

(5) The steam in the bottom trough enters the compressor through the mist eliminator, and the compressed steam enters the concentrator.

(6) The latent heat of compressed steam passes through the wall of the heat exchange tube, heating the brine film with a lower temperature falling along the inner wall of the tube, evaporating part of the brine and condensing distilled water on the outer wall of the heat exchange tube when the latent heat of compressed steam is released.

(7) Distilled water drops along the tube wall, accumulates at the bottom of the concentrator, is pumped through the heat exchanger and put into the storage tank for use. When distilled water passes through the heat exchanger, the new brine is heated.

(8) Some brine in the bottom trough is discharged to control the concentration of brine in the concentrator.

2. Seed Crystallization Technology

Seed Crystallization Technology: It can solve the scaling problem of evaporator heat exchanger tubes. The concentrated wastewater discharged after treatment is usually sent to the crystallizer or dryer to crystallize or dry into solid and transport to landfill. The above-mentioned cyclic process has been going on from one cycle to another.

If the wastewater contains a large amount of salt or TDS, when the wastewater evaporates in the evaporator, TDS in the water is easy to adhere to the surface of the heat exchanger tube and scale, which will affect the efficiency of the heat exchanger slightly, and plug the heat exchanger tube strictly. To solve the scaling problem of heat exchanger tubes in evaporator is the key to whether the evaporator can be used to treat industrial wastewater. RCC has successfully developed an exclusive "seed method" technology to solve the scaling problem of heat exchanger tubes of evaporators, so that the evaporators designed and manufactured by RCC can be successfully applied to the treatment of salt-containing industrial wastewater and are widely used. The evaporator using "seed method" technology is also called "brine concentrator". The TDS content of concentrated wastewater discharged after brine concentrator treatment can reach 300,000 pp, which is usually sent to crystallizer or dryer to crystallize or dry into solid and transport to landfill.

The seed method is based on calcium sulfate. There must be calcium and sulfide in the wastewater. Before the concentrator starts to operate, if the natural content of calcium and sulfide ions in the wastewater is insufficient, it can be manually supplemented by adding calcium sulfate seeds to the wastewater, so that the content of calcium and sulfide ions in the wastewater reaches an appropriate level. When the wastewater begins to evaporate, the calcium and calcium sulfate ions that begin to crystallize in the water reach an appropriate level. When the wastewater begins to evaporate, the calcium and calcium sulfate ions that begin to crystallize in the water adhere to these seeds and remain suspended in the water, and do not adhere to the surface of the transfer tube scaling. This phenomenon is called "selective crystallization". Brine concentrator can normally operate continuously for up to one year or more before regular cleaning and maintenance is required. In general, in addition to the possibility of adding "crystal seeds" when the concentrator is started, it is not necessary to add crystal seeds when the concentrator is in normal operation.

3, mix