The process flow has four forms: cocurrent (parallel flow), countercurrent, mixed flow (cross flow), and advection:
Downstream
Solution and steam flow in the same direction, and both flow sequentially from the first effect to the last effect. The raw material liquid is pumped into the first effect, depending on the pressure difference between the effects, it automatically flows into the next effect, and the finished liquid is pumped out of the last effect (usually operating under negative pressure). Because the pressure of the latter effect is low, the boiling point of the solution is also low. When the solution enters the latter effect from the former effect, it will flash part of the water and produce more secondary steam. Because the concentration of the latter effect is higher than that of the former effect and the operating temperature is lower , Often the heat transfer coefficient of the first effect is much higher than that of the final effect. The downstream process is generally suitable for processing materials that are heat sensitive in high concentrations.
countercurrent
The raw materials are sent from the last effect to the front effect by the pump, the finished liquid is discharged by the first effect, and the material liquid and steam flow in the opposite direction. It is generally suitable to handle solutions whose viscosity changes greatly with temperature and concentration, and it is not easy to handle heat-sensitive materials.
Mixed flow
The combination of forward and reverse flow processes has the advantages of both forward and reverse flow to avoid its shortcomings, but the operation is complicated and requires a high degree of self-control.
advection
Each effect is filled with materials to produce a complete liquid, and each effect has crystals, which can separate the crystals in time, and is generally used for the evaporation of saturated solutions.