Multi-effect evaporation is a series evaporation device that uses pre-effect secondary steam as the next-effect heating steam. In multi-effect evaporation, the operating pressure of each effect, the corresponding heating steam temperature and the boiling point of the solution are sequentially decreased. At present, multi-effect evaporators have a wide range of applications in the pharmaceutical and other industries. This article mainly introduces the selection techniques of multi-effect evaporators and the causes of abnormal vacuum.
How to choose a multi-effect evaporator?
How to choose a multi-effect evaporator in the face of a variety of equipment on the market? The industry believes that the main considerations are the effectiveness, steam consumption, process and heating area.
Among them, the effect mainly considers the size of the treatment amount, the boiling point rise value of the evaporated material, and the number of equipment.
Spent steam means that steam that releases heat potential is discharged from the exhaust port. The industry said that when the spent steam must be recycled, it is recommended to use indirect condensers, such as tube-type, spiral plate heat exchangers; when the steam does not need to be recycled, you can use direct condensers, such as direct atmospheric condensers, water jet pumps Condensation, etc.
Users should pay attention to the process when selecting a multi-effect evaporator. In the downstream process, the pressure of the after-effect evaporation chamber is lower than that of the pre-effect, and the pump required for the delivery of the solution between the effects is small. In addition, since the after-effect evaporation temperature is low, after the pre-effect solution enters the after-effect, a part of the steam is flashed off, so the raw steam consumption is relatively small. In the downstream process, the after-effect concentration is high, the temperature is low, the viscosity is increased, and the heat transfer rate is small.
Some enterprise technicians said, "The reverse operation is the opposite of the downstream operation. The pre-effect temperature is high, the concentration is high, the after-effect temperature is low, and the concentration is low, so that the heat transfer rate of each effect is close, but the required effect is over-material. The pump power is large, the steam consumption is too large, it is not suitable for processing heat sensitive materials, and it is not suitable for materials with enhanced corrosion and temperature with increasing temperature and concentration. In addition, it can adopt the advection and mixed flow process according to the specific conditions of the materials.
Determining the heating area of the evaporator is determined by comprehensive consideration of factors such as material balance, heat balance, heat transfer calculation, and the type of process used. Depending on the application, the multi-effect evaporator can be divided into a common multi-effect evaporation system and a forced circulation multi-effect evaporator. The forced circulation evaporator is based on the use of multiple external circulation evaporators to increase the external circulation pump. The evaporator produced by the forced circulation wastewater evaporator company can be applied to the case where there is crystallization during the evaporation process and it is a non-heat sensitive material.
The reason why the vacuum is too high or too low
During the operation of the multi-effect evaporator, the vacuum is too high or too low, which affects the production capacity of the equipment. In this regard, the industry has made a brief analysis of the reasons.
There are generally four reasons why the degree of vacuum is too low. First, the equipment of each part is concentrated into the air, the air increases the additional burden of the vacuum equipment; second, the cooling water is insufficient, the secondary steam cannot be condensed in time, seriously affecting the operation of the vacuum equipment; third, the cooling water temperature If the temperature is too high, a large amount of secondary steam generated by concentrated heating cannot be condensed in time, and the concentration of the vacuum will be lowered. Fourth, the steam pressure is too high, and a large amount of secondary steam production increases the load of the cooling equipment, and the vacuum is gradually reduced. Increased evaporation temperature of materials, while affecting product quality and equipment production capacity.
When the vacuum is too high, there are generally four cases. First, the temperature of the cooling water inlet of the concentrating equipment is too low, and the vacuum of the equipment is too high, because the latent heat of vaporization of the secondary steam increases with the increase of the degree of vacuum, correspondingly increases the steam consumption; second, the evaporation due to the low pressure or steam flow rate The rate is greatly reduced; thirdly, the condensate discharge is not good due to the blockage of the water separator, and the heater water is severe; fourthly, if the quality of the heated steam is poor, or the insulation of the cold steam pipe is poor, and the water of the heater is severe It makes the heat transfer difficult and makes the vacuum too high. Fifth, the severe coking of the heater surface reduces the heat transfer coefficient of the heating surface, the evaporation speed is slow, and the vacuum degree of the pot exceeds the standard.
Article link: Food Machinery Equipment Network http://www.foodjx.com/news/detail/133319.html