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Preliminary analytical of pasteurizing tunnel

Views:86     Author:Robin     Publish Time: 2021-12-31      Origin:Site

Tunnel pasteurization machine is a continuous spraying, heat preservation, cooling sterilization equipment developed and promoted in the 1990s.  Mainly used for all kinds of bottled, canned dairy drinks, fruit and vegetable juice, canned products of atmospheric sterilization; Can also be used for PET polyester bottle package of tea drink, fruit juice drinks after hot filling of the cooling and sparkling beverages, beer bottles.  It is composed of modules with different functions. It adopts multi-stage treatment such as circulating warm water pre-cooling, circulating hot water spraying sterilization, circulating cold water cooling, etc. It adopts atomization spraying technology, with excellent water-saving and heat-saving performance.  With smooth, wear resistant, high temperature resistant polyethylene mesh belt conveying products, can automatically into the bottle and out of the bottle, to achieve production automation.  

Tunnel pasteurization machine is frame structure and modular design.  With chain network transmission, driven by motor, reducer and frequency converter, stable operation, simple structure, convenient maintenance.  Through the field bus technology, it can also realize the remote monitoring of the sterilizer.  Humanized operating system, sterilization temperature all controlled by program, high automation, accurate control.  

Pasteurization machine consists of frame, heating system, water tank, pipeline system, sprinkler system, main transmission system and network chain support system.  ① Frame.  It is a frame-type design. The frame is welded from square pipes. A conveyor belt bracket is installed in the frame, and each frame has a water tank at the bottom.  ② Heating system.  It is composed of steam pipe, steam flow film control valve and other valve parts. The water in the water tank is conveyed to the plate heat exchanger by circulating pump, and then enters the spray pipe after being heated to the set temperature.  ③Water tank.  The water tank of the pasteurization machine is located at the lower part of each frame to collect spray water.  ④ Pipeline system.  The piping system enables the spray water to sterilize and recycle.  The piping system is arranged in 3 temperature zones, with 8 water pumps for spraying, including 1 for heating, 4 for insulation, and 3 for cooling.  ⑤ Sprinkler system.  It is composed of spray pipe and stainless nozzle.  The nozzle is installed under the top cover of the machine, and the stainless nozzle is installed below the spray tube, and the water is sprayed to the product through the nozzle when working.  ⑥ Conveying system.  It is composed of two high temperature polyethylene mesh belts with smooth surface and wear resistance driven by two reducer respectively.  The delivery system transfers the product from one end of the tunnel pasteurizer to the other to complete the sterilization process.

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Performance analysis of pasteurizing tunnel

1. Spray method

Spray heating is the use of hot water to transfer heat to the heated items, and gradually from the outside to the inside, so that the center temperature of the items to the specified value.  The heating process is affected by both external and internal factors. If the external heating is insufficient, the heating time will be affected.  The optimization of spraying mode is an important part of improving the utilization rate of heat energy.  The experiment proves that the spray water flow is increased.

It is a simple and effective method to increase the heating intensity.  The widely used water curtain large area spray plate system is a better spray way.  The spray plate system is composed of spray plate and pipe. In order to prevent impurities from blocking, the spray hole on the spray plate is made into a convex shape.

Compared with the traditional nozzle spray system, the flow of water in this spray method is large and uniform.  This system structure is simple, practical, the use of high pressure water can be cleaned, even if the individual spray hole blocked, the whole system has little impact.  And the use of spray plate system, the adjustment of different temperature areas will be more convenient.

2. Water and energy saving

Tunnel pasteurization machine with each frame at the bottom of a water tank, water tank volume and irregular shape, the radiating surface area is larger, in order to achieve energy saving, water saving and water tank can be divided into two parts, one part is small capacity water tank, with small capacity of the water tank is connected to the large capacity of the buffer tank, the heater arrangement on a tank capacity, so that heating and cooling rapidly, water saving and energy saving.

According to the different running curve and temperature, the large capacity buffer tank is divided into three buffer tanks: hot buffer tank, cold buffer tank and pre-buffer tank.  The water in the heat buffer tank is sent to the heat exchanger through the pump and heated to the specified temperature. Part of the water is sent to the temperature zone as the spray water. Due to the load change, the water that can not be used will return to the heat buffer tank.  The cold buffer tank and the pre-buffer tank are communicated by a balance pipe.  In the cold buffer tank, the water output from the cold buffer tank is used by a pump to regulate the temperature.

Overflow device is installed in each temperature zone. When the water tank is full, it automatically overflow into the buffer tank for storage. In order to save energy and save water, each buffer tank is isolated from each other, and the overflow water will automatically flow to the buffer tank with similar temperature for recycling.

In order to reduce the heat loss in the cooling section, the heat recovery is realized through the balance pipe between the pre-buffer tank and the cold buffer tank.  In the preheating section, collect the cooling spray water and send it to the cooling section to cool the container with higher temperature.

After the water temperature rises, it is transported back to the preheating section, so that the preheating area and the cooling area are connected with each other, and the appropriate temperature adjustment is made, and the heat has been rationally utilized.  The pasteurization machine adopts the design of heat recovery and utilization, and the energy consumption is greatly reduced.  This design scheme can also realize automatic recycling and reuse of water, saving water consumption.  The only loss of water is natural evaporation and overflow of the container out of the machine.

3. Intelligent Control

The sterilization process has two important control factors: sterilization time and sterilization temperature.  These two controls can be defined using PU values (pasteurization units).  PU value is: pasteurization effect obtained by sterilization for one minute at a temperature of 60℃.  Good sterilization process requires precise control of pasteurization units. The best sterilization process should be the smallest pasteurization unit to maintain maximum product quality and freshness.  This process is the result of adjustment using advanced control system.

Advanced control systems are based on the pasteurization unit of the product, not the temperature of the product.  The control system can record the historical data of the production process, as a reference for further improvement and control scheme.  The control system collects the process parameters in real time, adjusts the parameters according to the requirements of the pasteurization process, and realizes the automatic intelligent control of the sterilization process.

PU value automatic control system of sterilization machine: the system will be PU value and spraying water temperature, running time and other parameters associated, the operator only need to input the required PU value, the control system will automatically set the spraying water temperature in each temperature area and display sterilization machine in each detection point reached PU value.

The temperature and pressure in each temperature zone are converted into signals of 4 ~ 20 mA by the platinum resistance temperature transmitter and pressure transmitter, which are sent to the programmable controller for sequential acquisition.  On the one hand, the programmable controller performs input and output data processing and PID operation.  On the other hand, all kinds of signals will be transmitted to the aircraft.

On flight reservation as man-machine interface, real-time monitoring of operation condition of the sterilization process and various parameters, has alarm function, historical trend chart and report data files, and can set PU value by an operator, the computer on the basis of calculated temperature range of the spray water temperature set point, after the PID operation by programmable controller output standard electric signal (o ~ 24 V dc) to the solenoid valve.

Solenoid valve electric control signal (O ~ 24 V) into the gas control signal (20 ~ 100 kPa), and finally by the pneumatic film valve to perform adjustment, control cooling water or steam through the heat exchanger, control the temperature of each temperature zone.

Sterilization machine working process temperature is controlled by the program, high degree of automation, accurate control.  Variable heating intensity, transmission speed and temperature zone can be adjusted, can adapt to the sterilization requirements of different series of products.  Realize the sterilization process of one key operation of intelligent control.

The tunnel pasteurization machine has compact structure, simple, flexible and convenient operation. By adding PU value automatic control system, the sterilizing machine can have good PU value control precision and expand the scope of application for different series of products.


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