FAQ about VNOR and MVR Evaporators

Boiling point rise refers to the temperature of different salt solutions at boiling, sodium chloride saturated boiling point rise 107 ℃, ammonium chloride is 115 ℃; scaling solution is difficult, it is best to do to prevent, one to control Ca2+, Mg2+, two to control silicon; if scaling occurs, water washing and acid washing.

The temperature rise of a domestic compressor is 22°C, and the temperature rise of an imported compressor is 8-9°C.

It is best not to raise the boiling point above 10-12℃; The total temperature rise of the compressor is 22℃. If the boiling point rises above 15℃, the evaporation effect will be very bad if considering the loss of 2℃ and the temperature difference of 5℃. We hope that the effective evaporation temperature difference will be as large as possible, and 7-8℃ will be better.

The heat transfer coefficient of the falling film is generally 1200-1500, and the forced circulation is 600-800. Try to choose a more conservative heat exchange coefficient, a larger heat exchange area, and a sufficient temperature rise for the compressor to ensure the final evaporation, which can make the system more reliable.

All steam compressors need to be filled with water, because there will be an overheating process during the compression of secondary steam, which needs to be turned into saturation.Generally speaking, one ton of steam will replenish about 50 kilograms of water, but domestic compressors and imported compressors have different opportunities.

The most important thing about economy is to consider the investment cost of electricity consumption and steam. If the price of steam exceeds 150 yuan and the price of electricity is about 1 yuan, the MVR system is more cost-effective.

There are several situations. One is that the system design only considers concentration and does not make a crystallizer. The other is that the design does not achieve enough evaporation. For example, the concentration of sodium chloride in the feed is 8%, and it is 20% when it comes out. If it does not reach saturation, it will not crystallize (because the sodium chloride will crystallize when it reaches 27-28%).
Surge occurs due to the mismatch between the rotating speed and the air flow (designed amount). At this time, it is necessary to quickly adjust the evaporation to balance the rotating speed, the air flow and the feed volume. This also needs to be judged based on the on-site situation of the project.

It needs steam. The premise of synthesis is to use the condensed water of the system as much as possible, because the condensed water comes out at 90-100°C, and the temperature of the condensed water is consumed as much as possible to reduce to 40-45°C.And the second is that the condensed water is not enough to raise all the feed materials to 90-95°C, raw steam is needed to supplement the heat, so that the feed temperature is guaranteed to be 90-95°C. So the steam generator ratio is calculated, based on the feed volume and temperature increase, to calculate the tonnage of condensate water and the demand for raw steam.

Generally speaking, it is better to produce salt within a COD of 10,000 mg/L, and the salt may turn yellow and black when produced with a COD of 30,000-50,000 mg/L. The specifics need to be determined by testing water samples in the laboratory.

Both MVR and multi-effect evaporation are just a way of evaporation. It is difficult to guarantee water quality, but it is necessary to judge and prevent as much as possible. For example, feed COD is 1000mg/L, to ensure that the COD of condensed water is as low as possible, how to do it: first, use a demister, and second, the evaporation temperature should be relatively low, so that all the light components in the water will not be evaporated.