Structure and principle of falling film evaporator

Evaporation (or concentration) refers to the process of evaporating and concentrating a solution containing a non-volatile solute and a volatile solvent. The double-effect falling film evaporator is designed by the process of evaporation principle, mainly by heating to make the solution A part of the solvent is obtained by vaporization.

The two-effect falling film evaporator process is widely used in the production of pharmaceutical, food, biological, etc. For example, in the production of traditional Chinese medicine, the extract is concentrated by evaporation to obtain a concentrate or a flow extract, and as in the antibiotic production, the evaporation operation is used. The fermentation filtrate, the resin eluate, and the various extracts were concentrated. Falling film evaporation equipment is generally called an evaporator, and its structure and variety are numerous, and its development history is long.

From the operation mode, it can be divided into single-effect evaporation, multi-effect evaporation and direct contact evaporation; according to the fluid circulation mode, it can be divided into non-circulating evaporation, natural circulation evaporation, forced circulation evaporation, wiped film evaporation and centrifugal thin film evaporation. Different evaporators are used for different materials during design. The correct application can not only improve the quality of the products, but also save energy, reduce production costs and improve economic efficiency. Among them, falling film evaporator is a common unit operation in modern evaporation technology.

The falling film evaporator outlines the working principle: the material is added by the heating chamber and flows downward through the liquid distributor. The tube is heated and vaporized, and the vaporized vapor is taken out from the lower end of the heating tube together with the liquid, and the concentrated liquid is obtained by gas-liquid separation. In the operation of the falling film evaporator, due to the short residence time of the material (about 5 ~ 10s) and high heat transfer coefficient, it is widely used in heat sensitive materials, and can also be used for evaporation viscosity. Material, but not suitable for handling solutions that are easily crystallized. Double-effect falling film evaporator structure The double-effect falling film evaporator is composed of evaporator, separator, preheater, condenser, condensate tank, circulation pump and other components, and its structure is shown in the figure.

1. The evaporator evaporator is a tubular heat exchanger, the tube passes through the liquid material, the shell passes through the heated steam, the liquid material enters from the top of the evaporator, passes through the distributor into the heating tube, and the liquid material flows down the heating tube. It is heated and evaporated until the bottom of the heater. The concentrated liquid and the secondary steam generated by evaporation enter the separator for separation. The bottom of the heater is equipped with a liquid level switch for controlling the water distribution. Function: Heating and evaporating liquid materials.

2, the separator separator is a single-layer tank, the upper secondary steam interface is connected to the condenser, and the lower interface is connected to the evaporator. Function: The secondary steam generated after heating is separated from the concentrated liquid vapor.

3. The preheater preheater is a horizontal tube-and-tube heat exchanger, the tube passes through the liquid material, and the secondary steam generated by the shell process is evaporated. Function: (1) Preheating the liquid material entering the evaporator: (2) Cooling the secondary steam for recycling.

4. The condenser condenser is a horizontal tube-and-tube heat exchanger. The tube passes through the cooling water, and the shell side is connected to the shell side of the preheater. Function: The secondary steam is condensed for recycling.

5, the condensate tank condensate tank is a single-layer tank, the tank is equipped with a liquid level switch to control the liquid level. Function: The condensate in the automatic drain can be realized by connecting to the pump at the outlet.