Evaporador Handbook

Evaporator Handbook

CONTENTS Introduction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Evaporators.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Evaporator Type Selection.. . . . . . . . . . . . . . . . . . . . . 20 Configurations For Energy Conservation.. . . 24 Residence Time In Film Evaporation.. . . . . . . . .28 Designing For Energy Efficiency.. . . . . . . . . . . . . . 32 Physical Properties.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Mechanical Vapor Recompression Evaporators.. . . . . . . . . . . . . . . . . . 36 Evaporators For Industrial And Chemical Applications. . . . . . . . . . . . . . . . . . . . . . . . . . 42 Waste Water Evaporators.. . . . . . . . . . . . . . . . . . . .. 47 Evaporator Control.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Preassembled Evaporators.. . . . . . . . . . . . . . . . . . . . 52 The Production Of High Quality Juice Concentrates.. . . . . . . . . . . . . 53 Engineering Conversion.... . . . . . . . . . . . . . . . . . . . . . 58 Properties Of Saturated Steam Temperature Tables... . . . . . . . . . . . . . . . . . . . 592

Introduction
As one of the most energy intensive processes used in the dairy, food and chemical industries, it is essential that evaporation be approached from the viewpoint of economical energy utilization as well as process effectiveness. This can be done only if the equipment manufacturer is able to offer a full selection of evaporation technology and systems developed to accommodatevarious product characteristics, the percent of concentration required, and regional energy costs. This handbook describes the many types of evaporators and operating options available through the experience and manufacturing capabilities of APV.

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Evaporators
Types and Design In the evaporation process, concentration of a product is accomplished by boiling out a solvent, generally water.The recovered end product should have an optimum solids content consistent with desired product quality and operating economics. It is a unit operation that is used extensively in processing foods, chemicals, pharmaceuticals, fruit juices, dairy products, paper and pulp, and both malt and grain beverages. Also it is a unit operation which, with the possible exception of distillation, is the mostenergy intensive. While the design criteria for evaporators are the same regardless of the industry involved, two questions always exist: is this equipment best suited for the duty, and is the equipment arranged for the most efficient and economical use? As a result, many types of evaporators and many variations in processing techniques have been developed to take into account different productcharacteristics and operating parameters. Types of Evaporators The more common types of evaporators include: • • • • • • • • Batch pan Forced circulation Natural circulation Wiped film Rising film tubular Plate equivalents of tubular evaporators Falling film tubular Rising/falling film tubular

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Batch Pan Next to natural solar evaporation, the batch pan (Figure 1) is one of the oldestmethods of concentration. It is somewhat outdated in today’s technology, but is still used in a few limited applications, such as the concentration of jams and jellies where whole fruit is present and in processing some pharmaceutical products. Up until the early 1960’s, batch pan also enjoyed wide use in the concentration of corn syrups. With a batch pan evaporator, product residence timenormally is many hours. Therefore, it is essential to boil at low temperatures and high vacuum when a heat sensitive or thermodegradable product is involved. The batch pan is either jacketed or has internal coils or heaters. Heat transfer areas normally are quite small due to vessel shapes, and heat transfer coefficients (HTC’s) tend to be low under natural convection conditions. Low surface areas...