Commonly used evaporator mainly by the heating chamber and separation chamber composed of two parts. There are a variety of heating chamber type, the initial use of jacketed or snake tube heating device, e liquid vaporizer then there are horizontal short tube heating chamber and vertical short tube heating room. And then invented the vertical long tube liquid film evaporator, and scraper film evaporator and so on. e liquid vaporizer Depending on the flow of the solution in the evaporator, the indirect heating evaporator commonly used in industry can be divided into two types: recirculating and one-way.
Cyclic evaporator This type of evaporator is characterized by the solution flowing in the evaporator for circulation. According to the principle of causing liquid circulation, e liquid vaporizer it can be divided into two types: natural circulation and forced circulation. The former is by means of different degrees in the heating chamber at different degrees of heating, e liquid vaporizer so that the solution produced by the density difference caused by the natural cycle; the latter is to rely on external power to force the cycle of forced circulation.
In the middle of the tube bundle, e liquid vaporizer there is a larger diameter pipe, called the central circulation pipe, e liquid vaporizer the cross-sectional area is 40 to 100% of the total cross-sectional area of the heating tube bundle.
When the heating medium is heated between the tubes, e liquid vaporizer the relative density of the liquid in the heating tube is small because the heating area per unit volume of the liquid in the heating tube is larger than the heating area of the liquid in the central circulation pipe, resulting in a difference in density between the heating pipe and the liquid in the central circulation pipe , This density difference makes the solution from the central circulation pipe down, and then by the heating tube rose natural circulation. e liquid vaporizer The cycle speed of the solution depends on the density difference produced by the solution and the length of the tube. The larger the density difference, the longer the tube and the greater the circulation rate of the solution. e liquid vaporizer However, this type of evaporator due to the total height limit, heating tube length is short, generally 1 ~ 2m, diameter 25 ~ 75mm, aspect ratio of 20 ~ 40.
Central circulation tube evaporator has the advantages of compact structure, convenient manufacturing, reliable operation, so it is widely used in industry, so called "standard evaporator". But in fact, due to structural constraints, the cycle speed is low (usually below 0.5m / s); e liquid vaporizer and because the solution in the heating tube continuous circulation, so that the concentration is always close to the completion of the liquid concentration, The effective temperature difference decreases. In addition, the equipment cleaning and maintenance is not convenient enough.
Suspension type evaporator is the central circulation tube evaporator improvement. The heating chamber is like a hanging basket, suspended in the lower part of the evaporator shell, e liquid vaporizer can be removed from the top, easy to clean and replace. The heating medium enters the heating chamber from the central steam pipe and has an interstitial passage between the outer wall of the heating chamber and the inner wall of the evaporator housing, which acts similarly to the central circulation pipe. In operation, e liquid vaporizer the solution descends along the annulus and rises along the heating tube to form a natural circulation. The general annular cross-sectional area is about 100 to 150% of the total area of the heating tube, e liquid vaporizer and thus the solution circulation rate is high (about 1 to 1.5 m / s). As the evaporator shell is in contact with the lower temperature of the boiling liquid, so the heat loss is small.
Suspension-type evaporator is suitable for evaporation of fouling or crystal precipitation solution. e liquid vaporizer Its shortcomings are the complexity of the structure, the unit heat transfer surface needs a larger amount of equipment.