Digester

Contents

MAINTAINING

1. ANALYSIS OF MODERN CONDITION OF DIGESTERS

1.1 Theoretical foundations of cooking products

1.2 Purpose and classification of digesters

1.3 Modern digester designs

1.4 Patent study of digester

1.5 Project Feasibility Study

1.6 Purpose and objectives of the course work

2. DIGESTER DESCRIPTION

2.1. Brief description

2.2. Design and operation

2.3 Description of the developed units

2.3.1 Double safety valve 19 2.3.2 Valve - turbine

2.4. Description of the part. Teng

3. ENGINEERING CALCULATIONS

3.1. Design Calculations

3.2. Heat Engineering Calculations

3.3. Energy calculations

4. INSTALLATION, OPERATION AND ADJUSTMENT

5. SAFETY PRECAUTIONS

CONCLUSION

Literature

APPLICATION

Introduction

Cooking is one of the main types of heat treatment of food products. This is a hydrothermal treatment process comprising heating the substance in a liquid medium .

The main technological machine for production is a cooking boiler.

In the first chapter, an analysis of the modern state of cooking boilers was carried out, on the basis of which the purpose and tasks of the course work were formulated.

The second chapter contains a description of the digester: its brief characteristic, structure and device, as well as a description of the unit in question and its main parts.

In the third chapter, the structural and thermal calculation of the machine was carried out, as well as the energy one with a choice of tens.

The fourth chapter considered the installation and dismantling of structures.

In the fifth chapter, they got acquainted with the safety of production and, in particular, a digester.

Digester State of the Art Analysis

1.1 Theoretical foundations of cooking products

Cooking equipment is widely used not only in the hot shops of catering enterprises, but also in the enterprises of the meat, dairy and canning industries. Cooking is one of the main types of heat treatment of food products. This is a hydrothermal treatment process comprising heating the substance in a liquid medium. Such medium can be water, broth, milk, sauce, juice, syrup and wet saturated steam.

The heat-technical feature of the cooking process is characterized by limiting the temperature of the heating medium, and therefore the temperature of the surface layer of the product, the boiling point of the liquid, uniquely determined by the pressure in the working volume of the apparatus.

Since the product is heated by a moist medium during cooking, even with as much heat flow as desired, overheating of the product surface is avoided, and therefore moisture evaporation. This creates optimal conditions for surface heating of the food product, since the wet inner layer is characterized by a maximum coefficient of thermal conductivity.

Since the temperatures of the surface of the product and the heating media are close to the boiling point, the temperature difference between them is small. This causes the "soft" heating of the food project, which, unlike the "hard" (with a large temperature difference), provides minimal thermal destruction of the raw materials and high nutritional value of the finished product.

The quality of the cooked article often depends on the intensity of the power supply that determines the boiling activity of the heating medium. As a rule, active boiling, characterized by intensive vaporization, impairs the organoleptic properties.

Depending on whether the food product is heated in the liquid medium or in wet steam, a cooked product with various organoleptic properties is obtained.

Cooking in a large volume of water is characterized by a higher concentration difference than cooking in steam, since in the latter case, when it is condensed, a thin condensate film is formed on the surface of the product, which is quickly saturated with released substances.

For this reason, steaming presumes less weight loss of the product and higher nutritional value of the culinary products.

It is practically possible to increase the cooking speed only by increasing the boiling point, and therefore the pressure in the working volume of the apparatus (autoclaving principle). However, the temperature increase further accelerates the thermal failure of the product and generally degrades the quality of the product.

In order to avoid this negative result, when cooking, it is necessary to limit the temperature difference between the heating and heated media during the boiling period to 10... 12 ° C and thereby limit the specific heat flow through the heating surface. In jacket heaters, this is achieved by maintaining the pressure in the jacket at a level.

1.4 Patent study of digester

Digester relates to cooking devices and can be used at catering and canning plants. This simplified digester design improves its reliability. The cooking boiler contains a body, a cooking vessel with a steam jacket, heaters. Heaters are made in the form of current-conducting plates with self-regulating semiconductor positioners decentralized on them and fixed on external side of bottom of digester housing. Posistors are pressed to the bottom of the housing by plates using spring fasteners. Description of the invention "Digester" is given in Annex 1.

1.5 Project Feasibility Study

Cooking boilers with direct heating are very simple to install and operate, but have significant disadvantages: low efficiency, it is very difficult to control the thermal regime, since the heat exchange between the heat carrier and the thermally treated medium occurs through the separation wall, the surface of which is the active heating surface, and since the temperature of the flame and flue gases is high, it is possible to burn products to the bottom of the cooking vessel. The most progressive method of heating digesters is indirect heating. It eliminates the possibility of local burning of products.

Solid-fuel digesters are simple in design and work, as a rule, on local fuel. But they have a number of drawbacks:

• Due to high heat losses with exhaust gases, they have low efficiency;

• during its operation, it is difficult to control the thermal regime, so the high temperature of the boiler walls leads to burning of products ;

• When using solid fuels, especially coal, it is very difficult to maintain adequate sanitary and hygienic conditions;

• Special personnel are required to service such equipment;

• Vehicles for transport are required;

• fuel storage warehouses are required;

• increased fire risk compared to other equipment.

Gas digesters have a higher efficiency than solid fuels, in addition to heat at catering enterprises, it allows you to automatically control the degree of heating of devices during cooking, quickly turn on and off heat devices, makes it possible to decentralize the cooking process, widely introduce automation in production processes and sufficiently accurately take into account the consumption of gaseous fuel using gas meters.

However, gas as fuel has negative properties. The main one is the ability of combustible gases to form an explosive mixture with air. In addition, some components of artificial gases, as well as products of incomplete combustion of gases, are toxic. Incorrect operation of gas-heated digesters can lead to fires and poisonings.

Compared to other boilers, the lowest specific metal consumption in steam boilers (when comparing gas, electric, solid fuel and steam digestive boilers of the same capacity). But steam-heated equipment is advisable to use in industrial enterprises with boiler plants.

Digesters with electric heating are widely used in enterprises, since this type of energy has a number of advantages compared to other types of energy. Among the advantages are: relatively easy conversion of electric energy into thermal energy, fast and economical transmission of energy over long distances, the ability to accurately account for its consumption, the simplicity and reliability of control of electric thermal devices, good sanitary and hygienic conditions in production, relatively high efficiency of equipment.

Thus, the efficiency of solid fuel heaters is 1827%, gas equipment is about 4070%, and electrical equipment is about 50%. Digesters with electric heating have a number of significant advantages, the main of which are:

• fast start-up and output to rated power;

• possibility of high thermal power extraction in small volume and high temperature level achievement;

• easy control of temperature conditions at high degree of uniformity of heating;

• the possibility of sealing the working volume, and therefore of creating an excessive pressure, vacuum or protective atmosphere in it;

• compactness of electric heaters;

• Ease of mechanization and automation;

• improvement of working conditions;

• high ecological cleanliness.

1.6 Purpose and objectives of the course work

The purpose of this course work is to calculate and design a cooking boiler of the Vulcan type.

To achieve the objective, the following objectives were set:

- analysis of design and technological features of the digester;

- assembly process

- performance of engineering calculations: boiler characteristics, selection of tens and energy calculation, selection of heat-insulating material, calculation of heat balance of the boiler for stationary and non-stationary modes, calculation of boiler heating surface, calculation of specific metal consumption and specific heat consumption;

- graphically represent the general view of the digester, the two main units, as well as the details of the digester.

2.2 Design and Principle of Operation

2.2.1 Digester Design

The boiler under development has a cooking vessel capacity of 600 liters. The shape of the housing is cylindrical

The boiler is a welded structure consisting of a cylindrical cooking vessel with a concave bottom, an external boiler covered with heat insulation and lining.

The closed space between the cooking vessel and the external boiler serves as the steam-water jacket of the boiler.

A rectangular steel box is welded to the bottom of the outer body - a steam generator, inside of which there are six tens, a water level crane and a "dry stroke" protection electrode.

On top, the digester digester is closed by a hinged cover having a spring counterweight that facilitates lifting and holding it in the open position. Tight abutment of the cover to the cooking vessel is provided by a rubber heat-resistant gasket laid along an annular slot.

To drain liquid from the cooking vessel, a drain valve with a mesh is installed. Control and safety valves are installed on the boiler, which serves for monitoring and controls the value of steam pressure in the steam-water jacket.

The boiler has: an electric contact pressure gauge, a level valve, a double safety valve and a filling funnel with a shut-off valve.

Pressure gauge is installed to measure pressure in steam-water jacket of boiler. An electromagnetic pressure gauge is installed on the boilers, using which it is possible to automatically set the pressure level in the steam-water jacket and control the thermal mode.

Three arrows are installed in such a pressure gauge. One movable and two fixed, which are moved by means of a special key.

The movable arrow constantly shows the pressure in the steam-water jacket of the boiler. The fixed arrows are set to the upper and lower limit of the steam pressure in the jacket before the start of operation.

When the steam generator is put into operation, the steam pressure in the steam-water jacket begins to increase, and when the upper set pressure level is reached, the movable arrow coincides with the stationary one, their contacts are closed, and the boiler automatically switches to 1/6 of its power.

The pressure in the steam-water jacket begins to decrease and when the movable arrow coincides with the lower stationary one, the boiler again switches to maximum power. Thus, the operation of the boiler is automatically maintained in the desired operating mode.

The double safety valve consists of two valves - steam and vacuum - which serve for emergency discharge of steam from the steam-water jacket, when the pressure increases above 0.05 MPA (0.5 kgf/cm), and to eliminate the vacuum in it after the boiler is finished.

2.2.2 Digester operation principle

The working chamber is heated by steam formed in the steam generator: when heat is supplied, the water in the steam generator is heated to a boil and turns into steam. Steam enters the steam-water jacket and condenses on the walls of the cooking vessel, giving heat to steam generation and heating them, and flows back to the steam generator in the form of condensate .

When the pressure in the steam-water jacket of the boiler exceeds the permissible value, steam through the steam cap begins to escape to the atmosphere. The vacuum valve is opened under ambient air pressure when a vacuum is formed in the jacket. The vacuum in the boiler jacket is formed by cooling the boiler as a result of steam condensation, since the specific volume of steam is greater than the specific volume of water (condensate).

The level valve is installed in the boiler steam generator and controls the upper water level, and the lower level controls the "dry run" electrode.

Filling funnel with shutoff valve is intended for steam generator filling with distilled or boiled water. It is installed in the upper part of the boiler and has a filter mesh with a cover.

Hot and cold water supply pipeline is supplied to the boiler, which are connected into one rotary pipe ending with a valve and a branch pipe.

Next to the boiler, a control station is installed on the wall, which is a metal box, inside of which there is a terminal board, two magnetic starters, Start and Stop buttons, signal lamps, relays, fuses, boiler mode switch, toggle switches with the inscription "Automatic operation" and "Heating."

The terminal board is used to connect all devices of the control station to the electrical network. Magnetic starters and buttons turn on and off the boiler tens, and fuses protect electrical circuits from short circuit. The signal lamps are used to monitor the connection of the boiler to the electrical network and the mode of its operation. With the help of toggle switches the required operation mode of the boiler is switched on.

The boiler operates in two modes. In the first mode, the boiler operates first at full power, and then, after increasing the pressure in the jacket da of the rear upper limit, it switches to low heating (1/9 of the power). After lowering the pressure to the lower set limit, the boiler is again turned on at full power. In the second mode, the boiler operates at full power until the pressure in the jacket reaches the upper predetermined limit. The heating elements are then completely disconnected. The product is brought to readiness due to accumulated heat.