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Pasteurizing and cooling plants
Plate-type pasteurization-cooling units are designed for heat treatment of milk in the production of pasteurized milk and milk used for the production of fermented milk products, as well as for pasteurization of cream and ice cream mixture.
The composition of the pasteurization and cooling unit of the plate type includes a plate heat exchanger, an equalizing tank with a float-type regulator of the milk level in the tank, a centrifugal pump, a milk cleaner separator, a holder, a heat carrier preparation unit, a control panel with process control and regulation devices.
The plate heat exchanger has sections in which the following processes are carried out: pasteurization (heating the product to the pasteurization temperature), cooling (with water, cooling with brine or ice water), heat recovery between hot and cold products.
On two racks (front and rear) of the apparatus, two rods are fixed, which are the supports of the heat exchange plates, the corner holes of the plates are surrounded by gaskets. A gasket is laid along the periphery of the Plate.
When assembling the apparatus and compressing the plates, two isolated systems of sealed channels are formed. A hot medium flows in one channel, and a cold medium moves in the other. The assembled plates are combined into sections. Inside the sections, the plates are grouped into packages, in the channels of which the product moves in parallel. The surge tank is a container with nozzles for the inlet and outlet of the product. A float control valve is installed inside the tank, which maintains a constant level of product in the tank.
The centrifugal pump is designed to take milk from the tank and supply it to the plate heat exchanger.
In the separator - milk purifier, the milk heated in the apparatus is purified from mechanical impurities.
Drinking milk, fermented milk products, drinking cream and ice cream are pasteurized in various pasteurization and cooling units.
In a pasteurizing and cooling plant for drinking milk, raw milk enters an equalizing tank, in which a constant level of the product is maintained by means of a float regulator. The centrifugal pump takes the product from the tank and delivers it to the first recovery section of the heat exchanger, where the milk is heated to 40-45 °C. The flow regulator installed behind the centrifugal pump ensures a constant flow of milk entering the heat exchanger. Heated milk enters the separator - milk cleaner, where it is cleaned of mechanical impurities, and then fed to the second recovery section 11, where it is heated to 65-70 °C. Further, the milk passes through the internal channel into the pasteurization section 111, where it is heated with water up to 76-78 ° C: The milk is kept at the pasteurization temperature and is sent for cooling, first in the recovery sections 11 and 1, then in the water 1 V and brine cooling sections. Cooled to 4-6 °C, milk passes through a return valve, which directs the flow of milk either to storage tanks (subject to processing modes), or to re-pasteurization in an equalizing tank (if pasteurization modes are violated).
Figure 4 - Scheme of pasteurization - cooling plant for milk;
1 - surge tank; 2 - float level regulator; 3 - pump for milk; 4 - rotametric regulator; 5 - plate heat exchanger; 6 - separator-milk cleaner; 7 - holder; 8, 12 - temperature sensors; 9, 10, 13, 14.20, 22, 23 - pressure gauges; 11 - valve for adjusting the brine supply; 15 - return valve; 16 - hot water pump; 17 - storage tank; 18, 19 - valves that regulate the supply of steam; 21 - pump for pasteurized milk
course project
Plate pasteurization and cooling plant for milk with a capacity of 10,000 l/h
Introduction
In order to significantly increase food production, measures are planned to increase the volume of milk processing, improve the assortment and improve the quality of dairy products. The implementation of these measures is connected with the implementation of the tasks of the agro-industrial complex and the technical re-equipment of the food industry, including the dairy industry.
The technical re-equipment of the dairy industry provides for the use of high-performance technological equipment, the manufacture of sets of machines, apparatuses and flow technological lines that increase labor productivity, the development of new technological equipment and automated lines for bottling milk and equipment for packaging dairy products.
One of the main tasks set by the Food Program is to complete, by 1990, the re-equipment of the dairy industry on a new technical basis, ensuring an increase in the technical level, quality and reliability of the machines and apparatus used.
At present, batch-operated machines and apparatuses are increasingly being replaced by continuous-operated equipment, which makes it possible to increase the volume of production and significantly increase the efficiency of the use of equipment.
Scientific and technological progress in the dairy industry contributes to the introduction of new methods of processing and processing milk based on the use of progressive, most high-performance equipment. When using such equipment, it is very important to preserve the original properties of milk and its components as much as possible. Therefore, a prerequisite for the rational technical equipment of the enterprise is the observance of technological requirements for the product being developed.
Modern technology is based on extensive experience in the development of milk processing technology. The role and importance of world science, to which Soviet scientists have made a significant contribution, is growing.
Machines and apparatus for the production of dairy products, as well as for carrying out operations preceding processing or processing and preparing products for sale, must meet the following conditions:
high productivity and technologically optimal impact on the processed product;
minimum costs per unit of product produced on technological lines with the inclusion of appropriate machines and apparatus;
process sealing;
automated control and regulation of work processes;
cleaning in place and the use of standard detergents.
Technological equipment is diverse. Its classification can be based on various features: the structure of the work cycle, the degree of mechanization and automation, the principle of combining machine elements in the production flow, and a functional feature.
The functional attribute is the basis for the classification of technological equipment in the course program "Technological equipment of dairy industry enterprises" and the structure of this textbook. Equipment is divided into equipment for storage and transportation, for mechanical and thermal processing of milk, production of dairy products, preparation of products for sale and general factory purposes.
Storage and transportation equipment includes transport tanks and milk storage tanks, process and inter-operational tanks and pipelines, pumps and pneumatic transport systems. As a rule, no changes in the product structure should occur in this equipment. The only exceptions are tanks for technological purposes, in which such changes are specified.
The equipment for mechanical and heat treatment of milk includes filters, filter presses and membrane filtration apparatuses, homogenizers and homogenizers-plasticizers, separators and centrifuges, as well as installations for thermal vacuum treatment, heaters and coolers. This equipment achieves a certain technological effect. However, the constituents remain unchanged, i.e., by concentrating the individual constituents after mixing, the original product can be obtained.
Equipment for the production of dairy products includes pasteurization and sterilization-cooling units, freezers and freezers, butter makers and a system of machines for making cheese, for thickening and drying dairy products; to equipment for preparing products for sale - machines for filling and packaging dairy products, equipment for preparing containers for filling (bottle washing machines, etc.), devices for measuring the quantity and assessing the quality of products in production lines.
Description of the technological process
Reception and preparation of raw materials
Heating, cleaning
t \u003d (35 40) C
Cooling and intermediate storage
Normalization
Heating
t \u003d (40 5) C
Homogenization
t = (60 65) C
P = (10 15) MPa
Pasteurization
t = (76 C, τ = 20 sec
heating
t = (95 99) C
Cooling and
intermediate storage
Packing and packaging
Storage and implementation
Acceptance of milk and other raw materials is carried out according to the mass and quality established by the laboratory of the enterprise. The quality of milk is assessed in accordance with GOST 52054 for raw cow's milk.
Immediately after acceptance, milk is heated to a temperature of (35-40) C and cleaned on centrifugal milk cleaners or other equipment without heating. To purify raw milk, it is also recommended to use a bacteriophage with a specially built hermetic separator to remove bacteria from the milk. After that, the milk is sent for processing or cooled to a temperature of C and stored in intermediate storage tanks. Storage of milk cooled to a temperature of 4 C before processing should not exceed 12 hours, cooled to a temperature of 6 C - 6 hours.
Normalization of milk raw materials is carried out in order to standardize the composition of the finished product in terms of the mass fraction of fat and / or dry skimmed milk residue (SOMO). Normalization of milk according to the mass fraction of fat can be carried out in two ways: a periodic method and a continuous method.
After normalization, the milk is heated to a temperature of (40 5) C and cleaned on separators-milk cleaners. Heating takes place in the recovery section of the plate pasteurizer. Then the milk is again heated to a temperature of (60-65) C and fed to a homogenizer, where it is homogenized at a pressure of (10-15) MPa. Homogenization is recommended, including low-fat and classic types of milk to improve the taste.
After homogenization, the milk enters the plate installation for pasteurization and pasteurization at a temperature of (76 C with a holding time of 20 seconds. In the production of baked milk, pasteurization is carried out at temperatures of (9599) C. Then the milk is heated.
After pasteurization or heating, milk is cooled to a temperature of C. Cooling takes place in a plastic pasteurization-cooling unit. After that, the milk is sent to an intermediate storage tank or directly to bottling. It is allowed to store chilled pasteurized milk before bottling for no more than 6 hours. And at this temperature, milk can be stored from 36 hours to 10 days.
Description of the installation
In the dairy industry, pasteurization and sterilization units, as well as sterilizers, are used to pasteurize and sterilize milk and dairy products.
Pasteurization plants are of lamellar and tubular types. Plate-type pasteurization units, or pasteurization-cooling units, are designed for pasteurization and cooling in the flow of drinking milk, milk in the production of fermented milk products, cream and ice cream mixtures, tubular-type pasteurization units - for pasteurization in the flow of milk and cream.
Pasteurizing and cooling plants for drinking milk are distinguished by their performance. They produce pasteurization and cooling units with a capacity of 3000, 5000, 10000, 15,000 and 25,000 l/h.
Pasteurization-cooling units with a capacity of 3000 and 5000 l/h have a number of components and parts of the same design. In these devices, the placement of sections in relation to the main rack is one-sided. In the first apparatus, heat transfer plates P-2 are used, and in the second, mesh-flow AG-2. In pasteurizing and cooling plants with a capacity of 10,000, 15,000 and 25,000 l/h, plate-type apparatuses with two-sided arrangement of sections in relation to the main rack are used. In the first two devices, tape-in-line plates P-2 are used, in the third - mesh-in-line PR - 0.5M.
The most common is the pasteurization-cooling unit with a capacity of 10,000 l/h.
From the milk storage compartment, milk is fed into the surge tank 1 which has a float level control 2. During operation of the unit, a constant level in the surge tank is maintained by the regulator, which contributes to the stable operation of the centrifugal pump and prevents overflow of milk from the tank. Further milk by centrifugal pump 3 is injected into the first recovery section I lamellar apparatus 5. A rotametric regulator is installed between the centrifugal pump and the vane apparatus 4, which ensures the constant performance of the installation. In the first recovery section, milk is heated to a temperature of (40 - 45) ° C and enters the separator-milk cleaner 6, where it is cleaned. The plant can have one milk separator with centrifugal sludge discharge or two milk separators without centrifugal discharge operating alternately. After cleaning, milk, heated to a temperature of (65 - 70) ° C in the second recovery section II, through the internal channel goes to the pasteurization section III, where it is heated to a pasteurization temperature (76 - 80) ° С. After the pasteurization section, the milk is aged in a holding 7 and returns to the apparatus, where it is pre-cooled in the recovery sections I And II and finally to the final temperature - in the water cooling sections IV and brine cooling V.
A non-return valve is installed at the outlet of the apparatus. 15. It regulates the direction of the flow of pasteurized chilled milk to filling machines or to the surge tank for in-line pasteurization in case of violation of the pasteurization regime.
Hot water for heating milk is supplied to the pasteurization section by a pump 16. From this section, the chilled water, after it gives off heat to the milk, returns to the storage tank. 17. Water is heated to a temperature of (78 - 82) ° C by steam in a steam contact heater 21.
Steam is supplied to the steam contact heater by supply control valves. 18 And 19.
A temperature sensor is installed at the outlet of pasteurized milk from the pasteurization section 8, which is connected to the automatic pasteurization temperature control system by means of a valve 19 and returning milk for re-pasteurization through a valve 15. temperature sensor 12 designed to control the temperature of chilled pasteurized milk.
The unit is equipped with indicating pressure gauges to control the pressure of milk after the separator-milk cleaner 9, for cold water pressure control 10, for brine pressure control 13, to control the pressure of the heating steam 20, 22 And 23.
Payment
Initial data for calculation :
Performance…………………………… G 1 = 2.77kg/s (10000 kg/h)
Initial milk temperature………………………………... t 1 = 4 °С
Pasteurization temperature………………….………………….. t 3 = 75 °С
End temperature of milk…………………………….…….. t 6 .= 4°C
Heat recovery coefficient………………………………..ɛ = 0.76
Initial hot water temperature………………….…….. t’ r = 79 °C
Hot water ratio……………………………………..….. n r = 4
Initial cold water temperature……………….……….. t’ c = 8 °С
Multiplicity of cold water……………………………………..... n c = 3
Initial temperature of ice water………………………….. t’ l= +1 °С
Multiplicity of ice water………………………………………... n l = 4
Milk temperature after water cooling section…….. t 5 = 10 °С
Total allowable hydraulic resistance……….. Δ P\u003d 500 kPa (5 kgf / cm 2)
Average specific heat capacity of milk…………………. c M = 3880 J / (kg. ° С)
Density of milk………………………………………….. ρ M. = 1033 kg / m 3
Specific heat capacity of cold and hot water……… from in = from r = from l \u003d 4186 J / (kg. ° С)
The device is planned to be manufactured on the basis of plates of the P-2 type with horizontal corrugations of a tape-flow type
Basic plate data:
working surface F 1 = 0.21 m 2
working width b = 0.315 m
reduced height L n= 0.800 m
cross-sectional area of one channel f 1 \u003d 0.00075 m 2
equivalent flow diameter d ϶ = 0.006 m
plate thickness δ = 0.00125 m
thermal conductivity coefficient of the plate material λ CT= 16 W/(m.°С)
For a plate of this type, the heat transfer and energy loss equations are valid:
Eu \u003d 760 Re -0.25; ξ = 11.2 Re -0.25
Solution
1. Determination of initial and final temperatures, calculation of temperature differences and parameters S:
but. Heat recovery section:
Raw milk temperature at the end of the heat recovery section (when entering the pasteurization section):
t 2 = t 1 + ( t 3 - t 1 ) ɛ \u003d 4 + (75 - 4) 0.76 \u003d 57.96 ° С ≈ 58 ° С
Temperature of pasteurized milk after the recovery section (at the entrance to the water cooling section):
t 4 = t 1 + ( t 3 – t 2 ) \u003d 4 + (75 - 58) \u003d 21 ° С
The average temperature difference in the recuperation section with a constant temperature difference characteristic of it:
=
t 3
–
t 2 \u003d 75 - 58 \u003d 17 ° C
Then the simplex:
S rivers = 
°C
b. Pasteurization section:
Hot water temperature at the exit from the milk pasteurization section from heat balance conditions:
t’’
r = t’
G - 
(
t 3
–
t 2
) = 79 –
(75 - 58) \u003d 75.06 ° С
Average temperature difference at:
Δ t b = t’’ G – t 2 \u003d 75.06 - 58 \u003d 17.06 ° С
Δ t m = t’ G – t 3 \u003d 79 - 75 \u003d 4 ° C
define by the formula:
S n = 
in. Water cooling section:
Temperature of cold water leaving the water section:
t’’
in = t’
in + 
(
t 4
–
t 5
) = 8 +
(21 - 10) \u003d 11.4 ° С
Average temperature difference at:
Δ t b = t 4 – t’’ c \u003d 21 - 11.4 \u003d 9.6 ° C
Δ t m = t 5 – t’ c \u003d 10 - 8 \u003d 2 ° С
find from the equation:
Then the simplex:
S n = 
d. Ice water cooling section:
The temperature of the ice water at the outlet of the apparatus:
t’’
l = t’
l + 
(
t 5
–
t 6
) = 1 +
(10 - 4) \u003d 2.4 ° С
Average temperature difference for the ice water cooling section at:
Δ t b = t 5 – t’’ l \u003d 10 - 2.4 \u003d 7.6 ° C
Δ t M = t 6 – t’ l \u003d 4 - 1 \u003d 3 ° С
define by the formula:
Then the simplex:
S l \u003d 
2. The ratio of working surfaces and permissible hydraulic resistance by sections:
We select approximately the following values of heat transfer coefficients for sections (in W / (m 2 .°С):
recovery section k rivers = 2900
pasteurization section k P = 2900
water cooling section k in = 2320
ice water cooling section k l = 2100
The ratio of the working surfaces of the section is
Taking the smaller of these ratios as unity, we can write
F rivers: F P : F in : F l \u003d 1.92: 1.15: 1.71: 1
Assuming the distribution of permissible hydraulic resistances corresponding to the distribution of working surfaces and allowing for slight rounding, we obtain Δ P rivers: Δ P P: Δ P in: Δ P l \u003d 1.92: 1.15: 1.71: 1
Since the total allowable hydraulic resistance according to the task Δ P\u003d 5.10 5 Pa, then we can write:
Δ P rivers + Δ P n+ Δ P in + Δ P l = 5.10 5 Pa
Since the ratio of resistances is already known, in accordance with it, we will distribute the resistances among the sections as follows:
Δ P rivers = 166,000 Pa
Δ P n = 99 500 Pa
Δ P c = 148,000 Pa
Δ P l = 86 500 Pa
3. Determination of the maximum allowable product speeds in the interlamellar channels by sections:
For the operating conditions of this apparatus, it is advisable to determine only the maximum allowable speeds in the sections for the movement of the product. Hydraulic resistance on the side of movement of the working media is small, since the length of the corresponding paths is short.
This allows you to choose the speed of the working media from the conditions of maintaining an acceptable multiplicity in relation to milk, and in the presence of conditions, circulation and reuse, you can choose large values.
We preliminarily set auxiliary values: the expected heat transfer coefficient of milk is approximately - α m = 5000 W / (m 2 .°С).
Average wall temperature:
in the recovery section
in the pasteurization section
in the water cooling section
in the ice water cooling section
General hydraulic resistance coefficient:
in the recovery section ξ p = 1.6
in the pasteurization section ξ p = 1.4
in the water cooling section ξ in = 1.95
in the ice water cooling section ξ l = 2.2
Using these data, we determine the maximum allowable speeds of milk movement:
a) in the recovery section
b) in the pasteurization section
c) in the water cooling section
G) in the ice water cooling section
The obtained speed values for the sections almost coincide with each other. The presence of a significant difference would indicate an error in the calculation or incorrect distribution of permissible hydraulic resistances.
Volumetric productivity of the device:
We determine the number of channels in the package by accepting ω m = 0.57 m/s:
Since the number of channels in the package cannot be fractional, we round up to T= 6
In this regard, we specify the value of the milk flow rate:
The speed of cold water is taken equal to the speed of milk:
ω in = ω m = 0.59 m/s
We accept the speed of circulating hot water and ice water:
ω G = ω l = 2ω m = 1.18 m/s
4. Average temperature, Rg number, viscosity and thermal conductivity of the product and working fluids:
Rg number, kinematic viscosity v and the thermal conductivity of the product and working fluids are determined at average temperatures of liquids, using reference data.
but. Heat recovery section:
Raw milk average temperature (heating side) :
For milk at this temperature
Pr = 9.6; λ m \u003d 0.524 W / (m. ° С)
ν \u003d 1.27.10 -6 m 2 / s
Average temperature of pasteurized milk (cooling side) :
This milk temperature corresponds to
Pr = 5.7; λ m \u003d 0.575 W / (m. ° С)
ν \u003d 0.87.10 -6 m 2 / s
b. Pasteurization section:
Average hot water temperature (cooling side) :
Pr = 2.30; λ m \u003d 0.671 W / (m. ° С)
ν \u003d 0.38.10 -6 m 2 / s
Average milk temperature (heating side)
Pr = 4.0; λ m \u003d 0.611 W / (m. ° С)
ν \u003d 0.63.10 -6 m 2 / s
in. Milk water cooling section:
Average cold water temperature (heating side)
Pr = 9.7; λ m \u003d 0.572 W / (m. ° С)
ν \u003d 1.32.10 -6 m 2 / s
This milk temperature corresponds to
Pr = 17.4; λ m \u003d 0.476 W / (m. ° С)
ν \u003d 2.07.10 -6 m 2 / s
Average temperature of ice water (heating side)
This water temperature corresponds to
Pr = 12.9; λ m \u003d 0.557 W / (m. ° С)
ν \u003d 1.8.10 -6 m 2 / s
Average milk temperature (cooling side)
This milk temperature corresponds to
Pr = 24.0; λ m \u003d 0.455 W / (m. ° С)
ν \u003d 2.6.10 -6 m 2 / s
5. Reynolds number calculation:
The Reynolds number is calculated from the viscosity at average temperatures of liquids in each section
but. Heat recovery section:
For cold milk:
For hot milk;
b. Pasteurization section:
For milk:
For hot water:
For milk:
For water:
d. Ice water milk cooling section:
For milk:
For ice water:
6. Determination of heat transfer coefficient:
To determine the heat transfer coefficients α 1 and α 2, we use the formula for plates of type P-2:
Nu = 0.1 Re 0.7 Pg 0.43 (Pg / Pg st) 0.25
or 
The ratio (Rg/Rg C t) 0.25 can be taken as an average for all sections:
heating side 1.05
cooling side 0.95
but. Heat recovery section:
For raw milk heating side:
For cooling side of pasteurized milk:
Heat transfer coefficient taking into account the thermal resistance of a wall 1.25 mm thick:
b. Pasteurization section:
For the milk heating side:
For the hot water cooling side:
Heat transfer coefficient:
Taking into account the gradual deposition of burn, we reduce this value when calculating to k P = 2800 W/(m 2 .°C) to ensure stable operation of the pasteurizer.
in. Milk water cooling section:
For the hot water side:
Heat transfer coefficient:
d. Ice water milk cooling section:
For the hot water side:
For the milk cooling side:
Heat transfer coefficient:
7. Calculation of the working surfaces of the section of the number of plates and the number of packages:
but. Heat recovery section:
Working surface of the section:
Number of plates per section:
Number of packages X determine, knowing the number of channels in packets m = 8 received above):
Accept X rivers = 6 packs
b. Milk pasteurization section:
The working surface of the section is equal to:
Number of plates per section:
Number of bags per section on the milk side:
Accept X n = 3 packets.
in. Milk water cooling section:
Working surface of the section:
Number of plates per section:
Number of packages in a section:
If the number of packets as a result of the calculation turns out to be fractional, then it is necessary to decide whether to increase the number of packets to the next larger number, or to reduce the number of channels in the packets of this section.
With a decrease in the number of channels, the flow rate will increase, which should be taken into account when determining the required pressure. The decrease in the number of channels will affect the heat transfer slightly upwards and can be ignored.
In our case, we will keep the package layout and round the resulting value to X in = 5 packages.
The small headroom resulting from rounding the number of packs to the next higher number compensates for the reduction in average temperature difference in mixed flow.
d. Ice water milk cooling section:
Working surface of the section:
Deviations can only be due to the fact that some parameters were averaged in the calculation and the number of channels and the number of packets were rounded in one direction or another.
To check this deviation and the compliance of the actual hydraulic resistance with the allowable one, in conclusion, a control calculation of the total hydraulic resistance along the product flow path should be made. In addition, it is necessary to calculate the hydraulic resistance for working fluids.
Hydraulic resistance for each section is determined by the formula
We will make such a calculation for all sections, taking into account that for the accepted type of plates, the resistance coefficient of a unit relative length of the channel is determined by:
ξ = 11.2 Re -0.25
but. Heat recovery section: (X = 6)
For a flow of cold heated milk at 
= 2551:
The section resistance will be:
d. Ice water milk cooling section: (X = 2)
For the flow of milk at Re l = 1246 we get:
The section resistance will be different:
The total hydraulic resistance of the apparatus along the line of movement of the young. ka will be:
The calculation shows that the distribution of resistances in sections is somewhat different from that obtained previously in the first approximation, however, the total resistance is close to the initial allowable hydraulic resistance of 0.5 MPa.
Safety
The pasteurizer-cooler is installed on the floor of the dairy plant workshop without a foundation strictly according to the level, using the adjusting devices of the apparatus legs. After inspecting all the elements of the apparatus, making sure that they are in good condition and clean, as well as that the heat exchange plates are correctly positioned in accordance with their numbering, it is assembled.
Plates and intermediate plates are manually moved along the rods to the workplaces. To reduce the effort during the shift of plates and plates, it is necessary to lightly lubricate the working surfaces of the rods and threads of the clamping devices. The heat exchange plates and plates are finally pressed with a screw clamp using a special key.
The degree of compression of the thermal sections required for tightness is determined by the arrow marked on the upper and lower struts, which must coincide with the center of the vertical strut of both rods. At the same time, taking into account the presence of a two-screw clamp, it is necessary to tighten each screw device evenly in order to avoid distortion.
Before the installation is put into operation, it must be cleaned, washed and sterilized with hot water, and in case of CIP cleaning - with detergents using special installations for this purpose. Cleaning in place, in which cleaning solutions circulate in a closed system with the milk cleaner turned off, is only permissible if there are no parts made of bronze and aluminum.
To stop the operation of the installation, the milk supply is turned off and water is supplied instead. After displacing milk from the apparatus, turn off steam, hot water and brine, turn off the milk cleaners, de-energize the control panel and release all the brine. After that, the entire installation is subjected to sanitization. During cleaning and washing, do not use metal brushes and other abrasive materials.
At high-temperature pasteurization it is necessary to supply the device with a protective casing.
During non-working hours, do not leave the brine in the apparatus; it must be completely drained and the sections flushed, otherwise the service life of the plates will be reduced due to their corrosion.
Racks and other cast iron parts should be wiped frequently with a lightly greased cloth to keep the unit looking good and protect painted parts.
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The safety of perishable and dairy products has always been and remains relevant at all times. The presented equipment for milk meets the most modern requirements for its collection, storage and further processing.
All components of the units are made of high-quality and high-strength food-grade materials that meet the conditions of sanitary standards, as well as the technical parameters applicable to this equipment. The body of the milk plant, regardless of shape and volume, is made of heat-insulating materials to reduce energy consumption and reduce heat loss to the environment.
All milk equipment has a control system with metering devices and control of production processes.
It is also mandatory to have washing and mixing plants to maintain a homogeneous mass of the dairy product, uniform distribution of any auxiliary components, whipping, etc.
When choosing, you can also specify additional equipment for the convenience of servicing the dairy unit, calculate the required consumption and determine the size of the required containers.
Pasteurization and cooling plants for milk
In addition to the function of preservation and processing in the form of pasteurization, it also has regenerating and cooling properties.
Only natural resources are used as a refrigerant and heat carrier in the equipment - ordinary water purified by hard filters, which is heated, or vice versa, cooled to the desired temperature and passed through plate pipes through a tank with milk.
The installation itself consists of a tank that receives milk and water with the help of a pump, the supply and output pumps themselves, a plate-type water circulation unit, temperature modules for heating and cooling water for production needs, an automatic production control panel, liquid volume control sensors and warning systems for the case of a decrease or increase in the minimum allowable level, as well as deviations from the specified technical processes.
The equipment requires sufficient overall space for placement. When starting a pasteurization plant and a pasteurization and cooling plant for milk, it is necessary to have steam outlet pipelines, as well as mechanically filtered cold water supply, power supply of at least 230V with the possibility of grounding, floor drain and drainage systems, and sewerage.
Pasteurization plant and pasteurization and cooling plant for milk designed for heat treatment of dairy products without losing its main properties.
Using gentle processing methods, protein, sugar and fat molecules remain unchanged in milk. The principle of their operation is that milk sequentially flows from one tank to another, gradually mixing with already heated milk and, finally, its entire volume is heated to the temperature necessary for regeneration and maintained for the required time (milk - 30 seconds, fermented milk mixtures - 300 sec.) at pasteurization temperature.
After heat treatment, the product is cooled and can be filled and packaged.
All parameters of the production process are automatically registered and controlled by special sensors. If there are any deviations from the specified modes, the dairy product is sent for secondary pasteurization. At the same time, the warning system is triggered, the backflow valve opens and the regeneration process starts again.
Plants for the production of powdered milk
It is somewhat different from the equipment used for drying other food products. In the dairy industry, an indicator of the quality of milk powder is its solubility, that is, when interacting with a liquid, the product must quickly break down into molecules and mix with it. And this is exactly what it becomes thanks to the phased technological process of its drainage.
When installing and starting up the milk powder production unit, the room where the unit is supposed to be installed must comply with sanitary and building standards. It is obligatory to have sewerage, water supply, electricity from 220V, ventilation hood, walls and floors must be tiled or plastic.
The production technology of powdered milk consists of several stages: milk supply, filtration, measurement and determination of fat content, pasteurization and cooling. After that, it enters the sublimation chamber, where it first thickens, then it is brought to a homogeneous consistency and after that it is dried.
Pasteurization in the manufacture of milk powder is necessary to destroy various kinds of microbes, dissolve somatic cells in it to achieve a homogeneous liquid. In addition, milk, before becoming a powder, goes through several degrees of purification. The more and better filters, the better.
As a raw material, you can use the lowest fat milk with a high content of somatic cells. It's no secret that our cows often get sick with mastitis and organic matter gets into the milk. After a series of filtering and processing, this problem is solvable.
What else is beneficial installation of the production of powdered milk?
In addition to dairy products, this equipment can produce egg powder, make cheeses, soup bases, etc.
In the market of goods and services, dairy products are in special demand. And the questions of their suitability for consumption, shelf life and quality are always of concern to the consumer.
Freeze-dried milk is widely used in the production of cosmetics, in cooking, various baby food is made from it by mixing and adding certain fillers, animal feed, it is restored, canned, and even some fermented milk products are made on its basis.
Under certain storage conditions, it has an extended shelf life, it retains all the beneficial properties of real cow's milk, which is extremely important, for example, for the regions of the Far North.
Examples of modern milk installations are demonstrated at the annual Agroprodmash exhibition!
Plate pasteurization-cooling units are designed for cleaning from mechanical impurities, pasteurization with a given exposure and milk cooling. They are used in livestock farms, in mini-plants of agricultural enterprises and in large processing plants. For pasteurization of milk in farm conditions, the B6-OP2-F-1 installation, which does not require steam from the boiler room during operation, is widely used. Its technical data, as well as brief characteristics of other plate installations are given in Table. 3.11.
The B6-OP2-F-1 installation (Fig. 3.34) consists of a plate heat exchanger 4, a centrifugal milk cleaner 6, a tubular holder 11, a milk receiving tank 8, a milk pump 7, a hot water pump 1, an electric water heater 2, water and milk pipelines, a bypass valve 10, control panel 9.
The plate heat exchanger has five sections: I - pasteurization; II and III - regeneration; IV - cooling with artesian water; V - cooling with ice water. The sections are separated from each other by dividing plates with fittings for supplying and discharging the corresponding liquid.
The installation workflow is fully automated. Milk from the surge tank 8 is supplied by pump 7 to the regeneration section of the first stage III, in which it is heated by the heat of the oncoming milk flow to a temperature of 37...40 °C. From section III, the heated milk enters the separator-cleaner 6. The purified milk is sent for further heating to a temperature of 55 ... .95°C (depending on the set mode) and through the bypass valve 10 is fed into the holder 11, where it stays for 20 or 300 s. From the retainer, milk sequentially enters sections II and III of regeneration, gives off heat to the oncoming milk flow, then to sections IV and V, where it is cooled with cold, then ice water to a temperature of 2 ... 8 ° C and sent to the thermos tank. The milk is heated to the preset pasteurization temperature in section I with hot water pumped by pump 1 in a closed circuit: electric water heater 2 - pump 1 - heat exchanger section I - electric water heater.
A holder with an electric water heater provides heating of water for milk pasteurization and holding at the pasteurization temperature for a specified time.
The holding coil is made of stainless steel. Its upper section serves to hold milk from a healthy herd at the pasteurization temperature for 20 seconds. If it is necessary to process milk from sick animals (brucellosis, foot-and-mouth disease, etc.), the upper and lower sections are connected in series with a jumper, and the milk is held for 300 s.
An electric water heater housing is installed on the holder, in which heating elements (heating elements) are placed. Water is supplied to the heater from a surge tank with a float level control. A drain pipe is located in the center of the body from its top, and a discharge pipe with a flange is welded concentrically to it in the lower part, from which the water pump is supplied.
I ... V - sections of a plate heat exchanger; 1 - hot water pump; 2 - electric water heater; 3 - hot water return pipeline; 4 - plate heat exchanger;
5 - milk pipeline; 6 - milk cleaner; 7 - milk pump; 8 - milk tank; 9 - control panel; 10 - bypass valve; 11 - holder
Figure 3.34 - Scheme of the pasteurization-cooling unit
Water heating is carried out by three groups of heating elements: starting, main and adjusting. Starting heating elements are switched on by an electronic bridge. The primary signal about a change in the temperature of milk is supplied from a thermal converter installed on the path of hot milk from the pasteurization section.
To control the temperature of the chilled milk, a manometric thermometer is installed at the outlet of the ice water cooling section. The preset milk pasteurization temperature is maintained automatically by means of an electro-hydraulic bypass valve 10, which serves to switch the milk flow to reheating in case of pasteurization temperature decrease.
Figure 3.35 - Scheme of the flow of milk, hot, cold and ice water
When calculating pasteurization plants (Fig. 3.35), the following parameters should be taken:
the specified temperature regime for pasteurization and cooling of milk;
the temperature of raw milk at the inlet to the regeneration section of the 1st stage can be in the range from 10 to 35 °C;
The separator-milk cleaner of the plant provides high-quality cleaning of milk leaving the regeneration section of the 1st stage at temperatures of 37...45°C;
the hot water temperature at the inlet to the pasteurization section is set to 2...18°C higher than the milk pasteurization temperature, taking into account the boiling point;
milk is cooled to a temperature of 4 ... 10 ° C, taking into account the season and local conditions;
when calculating the installation, depending on the mode of pasteurization, milk cooling and climatic conditions, the temperature of the cooling liquids can be: artesian water - 4 ... 10 ° C; tap water - 5...16°С; ice water -1...4°С; brine - 0...-5°С.
The pasteurizing and cooling plant is used to pasteurize and cool fermented milk products. In other words, this installation is necessary for all enterprises that work with this category of goods. In addition, this unit is equipped with an automatic temperature control and regulation system, which makes its use even more convenient.
Installation Description
To date, there are tubular and plate installations. Next, the device of the second type of such devices will be described. So, a plate pasteurization and cooling unit consists of such basic elements as:
- plate heat exchanger;
- a system designed for the preparation of hot water (it includes a pump, an injector and a convection type tank).
The main purpose of this system is that it heats the products to the fermentation temperature. There is also a pump for the products themselves. Naturally, since there is an automatic system for monitoring and regulating parameters, there is also a control panel for this system. It is important to note that the pasteurization-cooling unit is quite compact and made in a modular style. The only thing is the holder, which is a separate structural element. Regarding installation, it can be mounted in any available location. The result is a convenient system that has everything you need for automatic operation, which at the same time takes up little space.
Purpose of installation
The pasteurization-cooling unit is designed to perform such actions as:
- Heating of the dairy product to a temperature of 55-60 degrees Celsius (separation temperature).
- Heating to a temperature of 75-80 degrees (milk homogenization).
- Heating up to the pasteurization temperature of the dairy product - 90-95 degrees.
- The equipment also holds the product at its pasteurization temperature for 300 seconds.
- The last operation is cooling the product to the fermentation temperature, that is, up to 20-50 degrees.
Purpose of elements
The plate milk pasteurization and cooling unit is also capable of handling liquid products such as beer, juice, wine, beverages, alkalis, and others. A plate heat exchanger is responsible for heating and cooling these products. All operations are carried out with a closed stream. It should also be noted that due to the high thermal efficiency of such heat exchangers, they have a compact size. As for the efficiency, for all installations made on the basis of this model, it is more than 90%. All parts of the pasteurization-cooling plant that come into contact with food during operation are made of steel approved for use in the food industry.
The coolant in such systems is either water or brine. The heat carrier can also be water or steam. The device has which consists of plates, a bed and a pressure plate. All these parts are tied together with fixing pins.
Technical characteristics of the installation
The pasteurization and cooling plant for milk has a certain number of technical parameters, which vary depending on the model. Next, the parameters of the PBK-1 product will be described.
The first and most important parameter is, of course, performance. For this equipment, it is in the range from 1000 to 10,000 l / h. The next parameter is the temperature of both the coolant and the coolant in the system. The difference between the outgoing products and these carriers is from 2 to 4 degrees Celsius at a factor of 1/3. All models also differ in their dimensions, but not too much, and the parameter itself is not very important. The material used to make the plate is steel grade 12X18H10T. The thickness of the plates is 0.6 mm. The maximum temperature for PBK-1 is 150 degrees.
The principle of operation of the pasteurization-cooling plant
In an automatic plate-type system, the workflow is as follows.
At the factory, there is a milk collector, which is connected to the surge tank of the device. From the collector to this module, the products come either by means of a pump or by gravity. Here it is important to ensure that the milk level does not fall below 300 ml, otherwise air will begin to leak into the milk pump. The pump then pumps the product to the first section of the heat exchanger. Here, the dairy product is heated, as there is a heat exchange with hot milk following from the pasteurization section, through the holder. Here the temperature of the object rises to about 47-50 degrees Celsius, after which the milk is pumped through the purifier into the second section. Here the product is reheated. The heat exchange takes place with the same pasteurized milk that has undergone preliminary type heat exchange in section number 1. After this procedure is completed, the milk enters the pasteurization section, which is considered the third. Here, the heat carrier is already ordinary water. The heat exchange lasts until the dairy product is heated to 76 degrees Celsius.
Further, as described above, pasteurized milk returns through sections 1 and 2, where it gives off heat, thereby cooling to 20-25 degrees. After that, the products are pumped into the cooler, where the temperature drops to 5-8 degrees. The fully chilled milk is then fed into the storage tanks. This completes the work of the pasteurization and cooling plant for milk.
Tube type installation
The description above concerned a plate-type device, but there is also a second one - a tubular one. Such devices consist of a tubular apparatus, two centrifugal pumps, a non-return valve, condensate removal units, as well as a control panel designed to control automatic control and monitoring devices.
Description of the unit elements
The tubular pasteurizing and cooling plant includes in its composition It consists of two cylinders, upper and lower, which are interconnected by means of a pipe system. Tube sheets are welded into the ends of these cylinders, each of which contains 24 pipes with a diameter of 30 mm. The gratings are made of stainless steel and have short channels. These channels connect all 24 pipes. The result is a continuous coil with a total length of about 30 m. The cylinders, in turn, are closed with covers, which are equipped with rubber seals. This is done not only to create a completely sealed structure, but also to separate the short channels from each other.
In the operation of the device, there is steam, which, upon admission, enters the space between the cylinders. After it has worked, it is removed from the device in the form of condensate using thermodynamic type steam traps.
The essence of the unit
The milk to be heated moves in turn through the upper and then the lower cylinder. It moves along the intratubal space. The unit also has a valve that regulates the steam supply. It is located immediately at the entrance of this substance. At the outlet of the device there is another valve, but of a return type. It works in automatic mode, and its main purpose is the return of under-pasteurized milk for a second operation. To perform this function, the mechanism is connected to a temperature sensor through a device such as a temperature controller, which is also located at the milk outlet. Since the device has steam and milk pressure, the unit also has several pressure gauges.
It is worth noting that the processing starts from the lower cylinder, where there is steam, which heats the milk to a temperature of 50-60 degrees. The milk enters the lower part under the influence of the first centrifugal pump. For pumping to the upper one, a second pump is used. In the upper part, pasteurization of the substance is carried out to a temperature of 80-90 degrees Celsius.
The main advantages of the installation
This equipment has become widespread, as it stands out for a number of significant advantages that are important for this industry. Firstly, the device fully complies with thermal conditions both during pasteurization and cooling. At the same time, the specified performance is maintained. Secondly, the design of the modular type minimizes the size of the device, which makes it compact and, therefore, convenient for placement and use.
