The technical advantages of the multi-effect evaporator are evident in the following aspects: The lower operating temperature helps prevent or slow down equipment corrosion and scaling. Additionally, the low-temperature waste heat from power plants and chemical factories can be fully utilized due to the lower operating temperature. For the multi-effect evaporator technology, low-grade steam at 50℃-70℃ can serve as an ideal heat source, significantly reducing the impact of backpressure steam extraction on power plant generation.

The pretreatment of raw brine is quite simple; another advantage of the multi-effect evaporator operating at low temperatures is that it significantly simplifies the pretreatment process. Before the brine enters the low-temperature multi-effect unit, it only needs to be filtered through a screen and added with a small amount of scale inhibitor, without the need for multi-stage flash vaporization or acidic degassing treatment.

The multi-effect evaporator system offers great operational flexibility. During peak periods, the desalination system can provide 110% of the designed product water value; during off-peak periods, it can consistently supply 40% of the rated product water.The system consumes low power. The low-temperature multi-effect liquid transportation system has a very low power consumption, only 0.9-1.2 kwh/m3. This can significantly reduce the cost of producing desalinated water, which is particularly important in areas with high electricity prices.

The multi-effect evaporator system boasts high thermal efficiency. The heat transfer efficiency is above 12, with a temperature difference of over 30 degrees, and an output rate of around 10.

The system operates safely and reliably. In the multi-effect low-temperature system, steam condenses inside the pipes and liquid film evaporates outside. Even if the heat transfer pipes leak due to corrosion and perforation, the concentrated saltwater will not enter the product water, as the pressure on the steam side is greater than that on the liquid film side. At most, only a small amount of steam leakage may occur, affecting the water production.

Refining enterprises have a vast abundance of low-temperature waste heat available for utilization. The fresh water processed by multi-effect evaporator technology can be reused in multiple process stages such as circulating water补给, thereby achieving the resourceful use of wastewater and low-temperature waste heat.

Introducing the multi-effect evaporator technology to the water treatment industry in refining enterprises can achieve an organic combination of low-temperature waste heat utilization and deep treatment of refining and chemical wastewater, thereby solving the difficulties of desalination and high energy consumption in high-salinity wastewater from oil refining and chemical industries.

The comparison table of low-temperature heat utilization technology reveals that compared to conventional heat pump technology and multi-stage flash evaporation technology, multi-effect evaporators demonstrate significant advantages in heat utilization rates and process integration with wastewater treatment. They represent the development trend in the relevant technical field and are a key direction for the development of coupled waste heat utilization and wastewater treatment technologies.

The multi-effect evaporator process features the following modes of operation:

The flow direction of the solution and steam is the same, from one effect to the next. The feed liquid is pumped into an effect and automatically flows into the next effect for processing based on the pressure difference between the effects, thereby completing the liquid pumping of the end-effect pump.

The pressure is lower in the latter effect, resulting in a relatively lower boiling point of the solution. Consequently, as the solution transitions from the first effect to the latter effect in a multiple-effect evaporator, it evaporates spontaneously due to superheating, a process known as flash vaporization. Therefore, the latter effect may produce more secondary steam than the former effect. However, since the concentration of the latter effect is higher than that of the former effect and the working temperature is lower, the heat transfer coefficient of the latter effect is lower than that of the former effect. Typically, the heat transfer coefficient of one effect is much higher than that of the other.