Vacuum evaporator - drawing

Contents

CONTENTS

Task

Introduction

1. Description and basis of the process for the equipment under development. Justification of the selection of the apparatus. Literary review

2. Requirements for the equipment under development

3. Description of the apparatus design, selection of materials for its manufacture

4. Calculation of the set

5. Labour protection measures

6. Technical and economic assessment

Literature

Introduction

Currently, the hardware design of food production has achieved significant technical excellence on the basis of recent scientific research, general technological progress and automation of production processes, especially began to be widely used in food technology to achieve physics.

The technique of high pressures, vacuum, deep cooling, ultrasound, membrane separation took place in the food industry. These problems are successfully solved on the basis of these sciences processes and devices of food production.

Processes of food technology represent a combination of hydrodynamic, thermal, mass exchange, biochemical and mechanical processes.

In this work, the calculation of the vacuum evaporator for evaporating the broth is carried out.

Suitably built apparatus must meet operational, structural, aesthetic and safety requirements.

Currently, when designing devices to achieve optimal indicators, work is underway to reduce energy intensity and increase the intensity of processes taking place in devices, to reduce material capacity during the production of devices, as well as reduce overall dimensions.

Description and theoretical basis of evaporation process. justification of apparatus selection. literary review

Evaporation is the concentration of solutions of substantially non-volatile or minor substances in liquid volatile solvents.

Evaporation typically removes the solvent partially from the entire solution at its boiling point. Therefore, evaporation is fundamentally different from evaporation, which is known to occur from the surface of the solution at any temperatures below the boiling point. In some cases, the evaporated solution is subjected to subsequent crystallization in evaporators specially adapted for this purpose.

Production of highly concentrated solutions, practically dry and crystalline products makes their transportation and storage easier and cheaper.

Heat for evaporation can be supplied by any heat transfer agents used in heating. However, in the vast majority of cases, water vapor, which is called heating or primary, is used as the heating agent during evaporation.

The primary steam is either steam obtained from the steam generator or spent steam, or steam from the intermediate extraction of steam turbines.

The steam generated by evaporation of the boiling solution is called secondary.

The heat necessary to evaporate the solution is usually supplied through the wall separating the coolant from the solution. In some industries, concentration of solutions is carried out with direct contact of the evaporated solution with flue gases or other gaseous heat carriers.

Evaporation processes are carried out under vacuum, at elevated and atmospheric pressures. The choice of pressure is related to the properties of the evaporated solution and the possibility of using heat of secondary steam.

Evaporation under vacuum has certain advantages over evaporation at atmospheric pressure, despite the fact that the heat of evaporation of the solution increases slightly with a decrease: the pressure and, accordingly, the steam consumption for evaporation of 1 kg of solvent (water) increases.

By vacuum evaporation, it becomes possible to carry out the process at lower temperatures, which is important in the case of concentrating solutions of substances prone to decomposition at elevated temperatures. In addition, under vacuum, the useful temperature difference between the heating agent and the solution increases, which allows to reduce the heating surface of the apparatus (all other things being equal). In case of the same useful temperature difference during vacuum evaporation, a heating agent of lower operating parameters (temperature and pressure can be used. As a result, vacuum evaporation is widely used to concentrate high-boiling solutions, for example alkali solutions, as well as to concentrate solutions using heat carrier (steam) for products with low thermophysical properties.

The use of vacuum makes it possible to use the secondary steam of the evaporator itself as a heating agent, except for primary steam, which reduces the consumption of the primary heating steam. However, the vacuum application increases the cost of the evaporator because additional costs are required for vacuum devices (condensers, traps, vacuum pumps) as well as increased operating costs.

By evaporating at a pressure above atmospheric pressure, secondary steam can also be used, both for evaporation and for other needs not related to the evaporation process.

Secondary steam taken from the apparatus is called extrapar. Extraction of the extrapar by evaporation under excess pressure allows better use of heat than by evaporation under vacuum. However, evaporation under excessive pressure is associated with an increase in the boiling point of the solution. Therefore, this method is used only for evaporation of thermally stable substances. In addition, higher temperature heating agents are required for evaporation under pressure.

In atmospheric evaporation, secondary steam is not used and is usually removed to the atmosphere. This evaporation process is the simplest but least economical.

Evaporation under atmospheric pressure, and sometimes evaporation, under vacuum is carried out in single evaporators (single-body evaporators). However, the most common are multi-body evaporators, consisting of several evaporators, or housings in which the secondary steam of each previous housing is sent as heating to the subsequent housing. At the same time, the pressure in the bodies connected in series (in the course of the evaporated solution) is reduced so as to provide a temperature difference between the secondary steam from the previous body and the solution boiling in this body, i.e., to create the necessary driving force of the evaporation process. In these installations, only the first housing is heated with primary steam. Consequently, in multi-hull evaporators, significant primary steam savings are achieved compared to single-hull evaporators of the same capacity.

Primary steam (and accordingly fuel) savings can also be achieved in single-hull evaporators with a heat pump. In such installations, the secondary steam at the outlet of the apparatus is compressed by a heat pump (for example, a thermal compressor) to a pressure corresponding to the temperature of the primary steam, after which it is again returned to the solution evaporation apparatus.

The concentration of solution in the batch evaporator only approaches the final one at the end of the process period. Therefore, the average heat transfer coefficient here can be slightly higher than in a continuously operating apparatus, where the concentration of the solution is closer to the final one during the entire evaporation process.

Modern evaporators have very large heating surfaces (sometimes exceeding 2000 m2 in each case) and are large heat consumers.

In industry, vertical evaporators are most often used. Their advantages: compactness, natural circulation (due to the presence of a circulation pipe), significant circulation multiplicity, small occupied area, large steam space,

Requirements for evaporators

Suitably built apparatus must meet operational, structural, aesthetic, economic and safety requirements.

2.1Operational requirements

The set corresponds to the target purpose. The purpose of the device is to create conditions that are optimal for the process.

2.2High intensity of the apparatus operation.

Intensification can be achieved, for example, by replacing periodic processes with continuous ones: this eliminates the time spent on auxiliary operations, and makes it possible to automate management. It is also possible to increase the heat exchange area by increasing the tubes, etc.

2.3Stability of apparatus material against corrosion. The material from which the apparatus is built must be stable when exposed to treated media. In turn, the interaction products of the medium and material should not have harmful properties if the product is used for food.

2.4Mole energy consumption. Power consumption of the apparatus is characterized by energy consumption per unit of processed raw materials or output .

2.5Reachable for inspection, cleaning and repair. For proper operation of the device, it is subjected to systematic inspections, cleaning and ongoing repair. The design of the apparatus should allow these operations to be carried out without long stops.

2.6The reliability of the device is determined by its reliability, repairability, durability. Reliability and durability - indicators that are of great importance and determine the feasibility of the device.

2.7Safety requirements. Ergonomics

A staircase is provided for ease of maintenance and monitoring of the process.

For ease of maintenance, the device shall be controlled from one point where the control panel is installed.

Also, high sanitary and hygienic conditions must be provided that prevent the product from being infected or contaminated with products from the environment and material from which the device is built.

2.8Constructive and aesthetic requirements

This group includes the standardization and replaceability of the parts of the apparatus; least labor input during assembly; easy transportation, disassembly and repair; minimum mass of both the entire apparatus and its individual parts.

Consider the mass requirements of the machine. When designing cylindrical machines, this height-to-diameter ratio should be selected. Metal consumption can also be reduced when replacing flat covers with convex ones, riveted structures are replaced with welded ones.

The device should have a pleasant shape and color to look at.

2.9Economic requirements

When designing the apparatus, it is necessary to ensure that the process taking place in it is carried out optimally. The task of optimization is to choose such an option in which the value characterizing the operation of the apparatus (optimality criterion) was the optimal value. The cost of production is chosen as the criterion of optimality.