Faced with the increasingly serious pollution of industrial wastewater, improper disposal of industrial waste produces harmful water when it comes into contact with water. In fact, over the past 30 years of reform and opening up, the total amount of industrial production has skyrocketed, and similarly, the amount of industrial wastewater will also increase significantly. The mainstream of industrial wastewater is pyridine wastewater treatment, and the types and chemical properties vary greatly depending on the production process.
Current processing technology
1. Biochemistry of salt tolerant bacteria
The salt substances contained in high salt wastewater are mostly Cl -, SO42-, Na+, Ca2+and other salt substances. Although these ions are essential nutrients for microbial growth, they play an important role in promoting enzyme reactions, maintaining membrane balance and regulating osmotic pressure during microbial growth. But if the concentration of these ions is too high, it will have inhibitory and toxic effects on microorganisms. Therefore, microorganisms that have been domesticated for a long time and can gradually adapt to growing and reproducing in high concentration saline water require a relatively high level of salt concentration in the biochemical influent, and cannot fluctuate rapidly, otherwise a large number of microorganisms will die.
The biochemical treatment of salt tolerant bacteria has strict requirements for water quality and is greatly affected by organic matter in wastewater.
2. Membrane technology desalination
The combined application of various membrane separation technologies such as microfiltration, ultrafiltration, reverse osmosis (RO), and electrodeionization (EDI) in industrial water treatment achieves the goal of removing pollutants and desalination. However, it is only suitable for the treatment of small amounts of high salt wastewater, and the equipment is delicate, prone to clogging and pollution.
3. Electrolytic desalination
The electrolysis of wastewater containing sodium chloride, whether by ion membrane method or membrane method, cannot meet the electrolysis requirements due to the presence of organic matter. Taking a step back, even if feasible, electrolysis of wastewater containing other salts cannot solve the problems of electrode plates, safety, and subsequent treatment. Its disadvantage is that it can only treat the salts in the wastewater.
4. MVR evaporator
At present, a wastewater treatment technology introduced from abroad can solve the problem of zero discharge of enterprise wastewater. It utilizes advanced MVR evaporators to recover salts from wastewater through evaporation concentration, and uses its own secondary steam as a heat source during the process, saving energy and reducing operating costs. And this technology will be more suitable for domestic enterprises after localization.
MVR evaporator, also known as secondary steam mechanical compression evaporator, uses a compressor to compress the evaporated secondary steam to increase its temperature, and then sends it to an evaporation heater for repeated use. When the original liquid that needs to be evaporated enters the evaporator at the evaporation point, the MVR evaporator theoretically does not need to consume steam, only electricity. The consumption of its electrical energy mainly depends on the temperature rise required for secondary steam and the efficiency of the compressor. Its advantages are:
Consumes a small amount of fresh steam and has low operating costs;
There are few supporting facilities for public utilities, and the land occupation is small;
Easy to start, simple to operate, and stable to run;
Simple construction, low operating cost, mild evaporation
Principle of MVR evaporator:
The working process of MVR is to compress low-temperature steam through a compressor, increase temperature and pressure, increase enthalpy, and then enter a heat exchanger for condensation to fully utilize the latent heat of steam. Except for starting the vehicle, there is no need to generate steam during the entire evaporation process. The secondary steam that comes out of the evaporator is compressed by the compressor, increases in pressure and temperature, and increases in enthalpy. It is then sent to the heating chamber of the evaporator as heating steam to maintain the boiling state of the feed liquid, while the heating steam itself condenses into water. In this way, the steam that was originally intended to be discarded can be fully utilized, latent heat can be recovered, thermal efficiency can be improved, and the economy of steam production is equivalent to 30 effects of multi effect evaporation.
MVR evaporator is different from ordinary single effect falling film or multi effect falling film evaporator. MVR is a single evaporator that integrates multiple effect falling film evaporators. It adopts segmented evaporation according to the required material concentration. That is, when the material cannot reach the required concentration after passing through the evaporator for the first time, it is pumped to the upper part of the evaporator by the vacuum pump at the lower part of the evaporator after leaving the evaporator, and then enters the evaporator again. Through repeated evaporation, the required concentration is achieved.
The inside of the evaporator is arranged with thin tubes, which contain steam. The material is sprayed from top to bottom outside the tubes, increasing the heating area and allowing for rapid evaporation and concentration. After heating, the residual steam and materials are heated and evaporated in the evaporator to produce steam and some condensed water, which enter the separator for separation. The condensed water flows out from the lower part of the separator and enters the plate heat exchanger in the waste heat module to preheat the materials before entering the evaporator. The steam is compressed by the compressor and then enters the evaporator again through the pipeline.
Adding a portion of fresh steam for preheating during equipment startup can reduce the startup time of the equipment. After normal operation, the required fresh steam will be significantly reduced, and generally no more fresh steam is needed when the concentration ratio reaches 6 times or more. The compressor compresses the secondary steam and converts electrical energy into thermal energy of steam.
In summary, wastewater evaporators not only significantly reduce pollution in the field of environmental protection, but also achieve the effect of resource recycling while reducing pollution. It can be said to be a win-win situation. Therefore, in the future, with the development of technology, wastewater evaporators may become more perfect, providing greater benefits for enterprises and the country.
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