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Single and Multi-Effect Evaporators: Technology for Efficient Liquid Concentration
Single and Multi-Effect Evaporators: Technology for Efficient Liquid Concentration

Introduction: What is an Evaporator?


An evaporator is a machine used to convert liquids into vapor by applying heat, commonly to concentrate solutions by removing water. Evaporators are widely used in:


  • Food processing
  • Dairy industry
  • Pharmaceutical production
  • Effluent treatment plants


In food manufacturing, evaporation helps concentrate products like fruit juice, milk, tomato puree, and herbal extracts while preserving flavor and nutrition.


How Does Evaporation Work?


  • Liquid is fed into tubes or vessels where it is heated.
  • Steam transfers heat, evaporating the water component.
  • Vapors and remaining liquid move into a separator chamber.
  • Vapors exit; concentrated liquid is collected.


Food consultants often work with evaporator manufacturers to ensure system designs align with product sensitivity, energy use, and hygienic processing.


Key Factors Affecting Evaporation


  1. Heat transfer rate to the liquid
  2. Latent heat of vaporization required
  3. Maximum allowable temperature for the product
  4. Evaporation pressure
  5. Product changes during heating (foaming, browning, viscosity)


Single-Effect Evaporator (SEE)


Working Principle

  • Liquid is heated in a single vessel
  • Steam enters from one side
  • Vapor and concentrated liquid are separated in a chamber
  • Only one heat exchange cycle occurs


Functions

  • Heat exchange
  • Vapor-liquid separation


Limitations

  • High steam consumption
  • Not energy-efficient for large-scale or continuous processes
  • Product may experience overheating


Multi-Effect Evaporator (MEE)


What Is It?


A system of multiple evaporator vessels connected in series, where vapor from one effect heats the next.


  • Only the first effect uses external steam
  • Subsequent effects use vapor from the previous vessel
  • Each vessel operates at lower pressure and boiling point


Construction Highlights


  • Multiple tubular heat exchangers (horizontal or vertical)
  • Vapor-liquid separators in each effect
  • Piping for vapor, condensate, and feed transfer


Features

  • Extremely energy-efficient
  • Suitable for large-scale continuous operations
  • Reduces steam cost by up to 50–70%
  • Used in dairy, sugar, juice, pharmaceutical, and chemical industries


A food manufacturing consultant may recommend MEEs to improve productivity, reduce energy costs, and prevent overheating in heat-sensitive foods.


Single vs Multi-Effect Evaporators: A Comparison


🧪 Applications in the Food Industry


  • Milk concentration in dairy processing
  • Juice evaporation for nectar and pulp standardization
  • Tomato paste concentration
  • Coffee and tea extract production
  • Starch, glucose, and syrup concentration


Conclusion: Choose the Right Evaporator for the Right Process


Evaporators are essential for liquid concentration, waste minimization, and energy recovery. While single-effect evaporators are simple and cost-effective for small volumes, multi-effect systems are ideal for high-capacity plants where efficiency and thermal control are critical.


A qualified food consultant or process engineer can:


  • Recommend the ideal evaporator setup
  • Optimize steam usage
  • Ensure hygienic, GMP-compliant construction
  • Improve process yield and energy savings


PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering SINGLE AND MULTI-EFFECT EVAPORATORS Competent People. Smarter Work Systems. Exceptional Customer Interactions. PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering Table of content 1. Introduction to evaporators 2. Types of evaporators 3. Single Effect evaporators 4. Multi Effect evaporators 5. Difference between Single and Multi-effect evaporator 6. Conclusion 7. Reference Competent People. Smarter Work Systems. Exceptional Customer Interactions. 2 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 1. Introduction to evaporators • An evaporator is a machine that is used to convert liquids into a gaseous state through the transfer of heat. • The raw material which has been fed into the evaporators passes through heated tubes and the heat gets evaporates the water within the raw material. • Widely used in processing industries, work best in low-temp applications in food, pharma industries, and in effluent treatment. 3 Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 2. Types of evaporators 1. Single-effect evaporator 2. Multi-effect evaporator 3. Horizontal-type natural evaporator 4. Vertical-type natural evaporator 5. Long tube vertical type 6. Falling film type 7. Forced circulation type 8. Agitated Film Evaporator 9. Open pan solar Evaporator 10. Open cattle or pan Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 4 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 2.1 Factors affecting evaporation process The rate of evaporation in evaporators depends upon the following factors:- 1. Rate of heat transfer to the liquid. 2. Quality of heat which is required to evaporate each kg of water. 3. Max allowable temp. of the liquid. 4. Pressure of evaporation. 5. Changes that may occur in the food during evaporation. 5 Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 3. Single effect evaporator • • • The Liquid enters the bottom of the tubes and rises. • Steam enters from the side and it goes down in tubes and makes indirect contact with the liquid to give up its heat. Steam condenses and leaves as condensate. Liquid heats rising to the top, vapors form, and both the heated liquid and vapors, enter a chamber on the side called the separator. • The liquid leaves from the top and again enter the bottom of the evaporator section and after it condenses it is be removed from the section from the side as a concentrated liquid. Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 6 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 7 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 3.1 Functions of single effect evaporator To exchange heat and To separate the vapor that has formed from the liquid. The single effect evaporator has two functions - - Further practical considerations in evaporators are:- • maximum allowable temperature, which may be substantially below 100°C. • Promotion of circulation of the liquid across the heat transfer heat transfer coefficients and to surfaces, to attain reasonably high prevent any local overheating. • Viscosity of the fluid which will often increase substantially as the concentration of the dissolved material increases. • Tendency to foam which makes separation of liquid and vapor difficult Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 8 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 4. Multi-effect evaporator Steam enters the first effect and condensate leaves at the bottom. • • The liquid enters and rises in tubes as it heats to the top. • Some of the liquid turns into vapor and the rest is concentrated liquid which moves down the vapors where they leave. • Rather than discharging them into the atmosphere, vapor will enter the second effect. Steam enters only in the first effect, the rest of the heating in the second, third effect, and so on is done by the vapors that are been discharged from the previous effect. Steam is the focus point as it needs to procure vapor in every effect. • • Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 9 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 10 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 4.1 Construction of MEE • Consists of a sequence of heat exchangers (vapor-liquid separators), which are used widely in industries to achieve evaporation and obtain desired concentration by using an efficient amount of steam or hot water for evaporation. • Mostly, evaporators have tubular heating surfaces. The tubes may be horizontal or vertical, long or short and the liquid may be inside or outside the tubes • Evaporation is normally stopped before the solute starts to precipitate in the operation of an evaporator. 11 Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 4.2 Features of MEE Some salient features are as follows:- • An apparatus that efficiently uses the heat from steam to evaporate water. • Water is boiled in a sequence of vessels, each of which is at a lower pressure than the last. • As the boiling point of the water decreases with pressure, the vapor produced in one vessel can be used to heat the next vessel. • Only the first vessel requires a source of external heat. • Evaporators with more than four to five effects are rarely practical. Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 12 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 5. Single vs Multi-effect evaporation Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 13 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 6. Conclusion • Water and any other liquid evaporation processes can take place at any temperature, but the process becomes faster with increases in temperature. • At elevated temperatures, the molecules of a liquid or water vibrate with increasing intensity as elicited by the prevalent temperature. • Using a multiple-effect evaporator make the evaporation process more economical. The same as Parallel feed systems, they help in increasing the overall production rate of low viscous products. • Condensate of the vapor chest can be used to pre-heat the incoming feed. Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 14 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering 7. Reference 1. https://www.shachiengineering.com/evaporators-types-and-uses/ 2. https://www.sciencedirect.com/topics/engineering/evaporators 3. https://www.slideshare.net/SumerPankaj1/single-and-multiple- effective-evaporator-mee 4. https://www.slideshare.net/PavelRout/multiple-effect-evaporator- 242774077 5. https://nzifst.org.nz/resources/unitoperations/evaporation1.htm Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 15 PMG Engineering Private Limited The End-to-End Engineering Company in Food Industry info@pmg.engineering | www.pmg.engineering About PMG Engineering Competent People. Smarter Work Systems. Exceptional Customer Interactions. Competent People. Smarter Work Systems. Exceptional Customer Interactions. 16 We deliver End-to-End Engineering Design and Construction Management Projects in Food and Beverage Industry. Meeting Global Benchmarks In ENGINEERING DESIGN and PROJECT MANAGEMENT for FOOD and BEVERAGE Industry with SINGLE POINT ACCOUNTABILITY Process Engineering | Project Management | Mechanical | Electrical | Automation | Food Safety Key Clients We deliver End-to-End Engineering Design and Construction Management Projects in Food and Beverage Industry. Meeting Global Benchmarks In ENGINEERING DESIGN and PROJECT MANAGEMENT for FOOD and BEVERAGE Industry with SINGLE POINT ACCOUNTABILITY Process Engineering | Project Management | Mechanical | Electrical | Automation | Food Safety Key Clients We deliver End-to-End Engineering Design and Construction Management Projects in Food and Beverage Industry. Meeting Global Benchmarks In ENGINEERING DESIGN and PROJECT MANAGEMENT for FOOD and BEVERAGE Industry with SINGLE POINT ACCOUNTABILITY Process Engineering | Project Management | Mechanical | Electrical | Automation | Food Safety Key Clients
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