Falling film enrichment facilities

Falling film evaporation is to add the material liquid from the upper tube box of the heating chamber of falling film evaporator, distribute it evenly to each heat exchange tube through the liquid distribution and film forming device, and flow from top to bottom in a uniform film shape under the effect of gravity, vacuum induction and air flow. In the process of flow, the steam generated is heated and vaporized by the shell side heating medium, and enters the separation chamber of the evaporator together with the liquid phase. After full separation, the steam enters the condenser for condensation (single effect operation) or enters the next effect evaporator as the heating medium, so as to realize multi effect operation. The liquid phase is discharged from the separation chamber.

Working principle

The main body of the equipment is composed of I, II and III effect heaters, separators, hot pressure pumps, condensers, sterilizers, heat preservation pipes, feed pumps, water pumps and instrument cabinets. This equipment is made of high quality stainless steel in contact with materials.

Scope of application

Widely used in medicine, food, chemical industry, light industry and other industries of water or organic solvent solution evaporation concentration, and can be widely used in the above industries of waste liquid treatment. Especially suitable for heat sensitive materials, the equipment can operate continuously under vacuum and low temperature conditions, with high evaporation capacity, energy saving and consumption reduction, low operating cost, and can ensure the invariability of materials in the evaporation process.

Technological process

There are four types of process flow: forward flow (parallel flow), reverse flow, mixed flow (staggered flow) and horizontal flow

Downstream:

The flow direction of solution and steam is the same, from the first effect sequence to the last effect. The feed liquid is pumped into the first effect, and automatically flows into the next effect depending on the pressure difference between each effect. The liquid is pumped out from the final effect (generally operated under negative pressure). Because of the low pressure of the first effect and the low boiling point of the solution, when the solution enters the first effect from the front effect, it will flash some water and generate more secondary steam. Because the concentration of the second effect is higher than that of the first effect and the operating temperature is lower, the heat transfer coefficient of the first effect is much higher than that of the last effect. The downstream process is generally suitable for the treatment of heat sensitive materials in the case of high concentration.

Against the Current:

The raw material is pumped from the end effect to the front effect in turn, and the finished liquid is discharged from the first effect, and the feed liquid and steam flow in reverse. Generally, it is suitable to deal with the solution whose viscosity changes greatly with the temperature and concentration, and it is not easy to deal with the heat sensitive materials.

Mixed flow:

It is a combination of the upstream and downstream flow processes, and has the advantages of the upstream and downstream flow to avoid its disadvantages, but the operation is complex and requires a high degree of self-control.

Advection:

Each effect is fed out of the finished solution, and each effect has crystallization, which can separate crystallization in time, generally used for evaporation of saturated solution.

Characteristic

(1) l / D = 100-250; (2) heat transfer coefficient k = 1000-3000 kcal / (M2 * c *);

(3) it can handle materials with high concentration and poor liquidity;

(4) the temperature difference of heat transfer is small and there is no influence of hydrostatic pressure.

Falling film principle

The principle of falling film evaporation process is shown in the figure below. The materials to be evaporated enter from the top of falling film evaporator through feed pump and go through the evaporation tube (tube side). The materials are distributed in the heat exchange tube in the form of film through the film distributor. When the materials flow down the tube cavity by virtue of gravity, they are heated by the steam outside the tube and evaporate when they reach the evaporation temperature. The materials and the secondary steam flow down the tube and evaporate in the form of film. After the secondary steam is compressed by the steam compressor, it is sent to the shell side of the falling film heating chamber as the heating steam. There are plates on the shell side of the falling film heating chamber to guide the secondary steam, condense and discharge the non condensable gas In the process, the heat energy is transferred from the outside to the evaporation material in the tube through the tube wall, and the secondary steam is condensed into water after heat exchange and discharged out of the falling film evaporator.

Features of falling film evaporation system:

1) the feed liquid of the falling film evaporator is added from the top of the evaporator, falling down the tube wall in a film shape under the action of gravity, and in the process of evaporation and concentration, the concentrated liquid is obtained at the bottom. Falling film evaporator can evaporate materials with high concentration and viscosity (for example, in the range of 0.05 ~ 0.45ns / m2).

2) the heat transfer coefficient of the solution is high because of the film flow in the one-way evaporator.

3) short residence time, not easy to cause material deterioration, suitable for handling heat sensitive materials.

4) the liquid retention is small, and the falling film evaporator can operate rapidly according to the change of energy supply, vacuum degree, feed quantity, concentration, etc. Near constant

5) as the process fluid flows only under the action of gravity, rather than driven by high temperature difference, low temperature difference evaporation can be used.

6) falling film evaporator is suitable for evaporating and concentrating foaming materials. As the material liquid evaporates in the heating tube, vapor liquid separation is formed, and at the bottom of the effective body, most of the liquid material is removed. Only a small amount of liquid and all two steam enters the separator to strengthen separation. The process of material and liquid has not formed too great impact, thus avoiding the formation of foam.

The complete unit of the project is to recycle sulfuric acid of future materials through single effect or multi effect forced circulation evaporator

The dilute ammonium solution is evaporated and concentrated to a certain solid content, then crystallized in the crystallizer to the centrifuge for solid-liquid separation, and the mother liquor after centrifugation returns to the evaporation system.

Process characteristics:

1. The evaporator adopts forced circulation evaporator, which is suitable for evaporation crystallization of ammonium sulfate.

2. It can realize switching operation of single effect or multi effect evaporator.

3. The evaporation crystallization process is simple, the production can be automatic, continuous and stable, and the production efficiency is high.

4. Detailed design can be carried out according to customer requirements