There are various reasons for the low evaporation capacity of a three effect evaporator, and the following are some of the main factors:
1. Complex composition of the original solution: The original solution has an excessively complex composition with high organic content, containing easily scaling ions such as calcium, magnesium, and silicon. These ions adhere to the inner side of the tube wall, affecting heat transfer and efficiency, thereby reducing evaporation.
2. Design issues:
Insufficient area: If the design and calculation area of the three effect evaporator is too small, the evaporation capacity will be affected. When calculating the area, it is usually necessary to multiply it by a margin of 1.1~1.2 to ensure the evaporation capacity of the evaporator.
Improper selection of temperature difference: In the process of designing an evaporator, it is crucial to choose the appropriate heat transfer temperature difference for each effect evaporator. If the temperature difference is too small or too large, it will affect the evaporation effect. Generally, setting the effective temperature difference between 10 and 20 ℃ is more stable.
Improper selection: Key data such as effective temperature difference, evaporation intensity, and boiling point rise are helpful for calculating the heat exchange area, while separator volume data affects design and selection. Improper selection may result in insufficient evaporation.
3. Operational issues:
Improper temperature control: The three effect evaporator needs to operate within a certain temperature range to ensure its normal operation. Excessive or insufficient temperature can have a negative impact on the evaporation efficiency.
Improper negative pressure control: If it is a falling film evaporator, it is necessary to consider whether the design of the fabric tray can evenly distribute the fabric, and whether the material can form a film on the tube after distribution. If the film formed by the tube is not good, it will affect the evaporation rate.
Delayed emission of non condensable steam: The accumulation and emission of non condensable steam in a timely manner can lead to the accumulation of non condensable steam in the heating chamber heat exchanger, resulting in a decrease in heat transfer coefficient and thus affecting the evaporation rate.
The problem of condensate discharge: Whether the condensate can be discharged in a timely and stable manner, and whether the overflow of secondary steam is well controlled during the process of discharging the condensate, will also affect the evaporation rate.
4. Equipment issues:
Blockage: The three effect evaporator generates a lot of waste and sediment during operation. If not removed in time, it can cause equipment blockage, affecting the normal operation and evaporation capacity of the evaporator.
Aging or damage: Equipment aging or damage can lead to energy loss and decreased efficiency. If the sealing of the equipment is not good, it will lead to energy loss, thereby reducing evaporation.
Unreasonable preheater: If the feed temperature is too low and new materials need to be added during the evaporation process, the entire evaporation system will cool down, affecting the evaporation effect. Therefore, the setting of the preheater needs to be reasonable.
5. High COD in wastewater: When the COD (chemical oxygen demand) in wastewater is too high, the evaporation capacity of the three effect evaporator will decrease. If the COD content is too high and not pretreated, it will seriously affect the desalination effect and evaporation capacity of the evaporator.
To improve the evaporation capacity of the three effect evaporator, it is necessary to comprehensively consider and optimize multiple aspects such as the composition of the original liquid, design, operation, equipment, and wastewater treatment.
