Energy Saving and Automatic Control of Ammonia Refrigerant Refrigeration (Freezing) Cold Storage

The issue of energy conservation is one of the issues that the world must urgently solve today, and it is the long-term strategic principle of national economic construction. At the same time, the product quality and refrigeration cost of the cold (freezing) cold storage will determine the survival of an enterprise. Through high-tech transformation and automated management of cold storage, reasonable use of equipment can be achieved, equipment utilization and service life can be improved, and automation management measures for the operation and operation of refrigeration systems can be improved, which can improve the reliability of safe operation, save energy, and reduce production costs of cold storage enterprises. The product quality of refrigerated (freezer) cold storage has important economic and practical significance.
First, the main features of the cold storage energy-saving control system Cold storage energy often needs to be achieved through advanced refrigeration equipment, suitable system matching, flexible contingency measures and strict operation management. Based on the optimization of the refrigeration process design, our company is familiar with energy-saving needs, combines the characteristics of the project, and uses its expertise to design a complete and optimized cold storage energy-saving automatic control program. Through a series of measures including PC+PLC control, variable frequency control, electric valve adjustment, and control point reconstruction, the energy-saving and intelligent control of cold storage can be realized, and the loss of storage quality caused by abnormal reasons can be reduced, and the operating cost can be reduced by 15%. More than 30%, general large and medium-sized cold storage energy-saving reform, according to the calculation of comprehensive benefits, one to two years to recover the investment costs, with high energy-saving investment cost-effective. The system has various functions such as temperature control of the warehouse, variable evaporation temperature control, variable flow control, additional overrun control, automatic defrosting, closed loop temperature control of the circulating water temperature, and operation requirements of the cold storage process.
Second, the current problems in the general cold storage equipment work
1. The level of automatic control of cold storage equipment is low, and it completely depends on manual operation. The human subjective initiative and technical level, etc., vary greatly due to people's time, and it is difficult to achieve optimal control. Even the equipment accident may be caused by improper booting, or the storage may be damaged or the storage period may be reduced, resulting in significant economic losses. The on-duty staff needs to wait around the clock and bring the cost of manual operation.
2. Compressor star--Triangular start impact on compressor equipment and power grid, affecting the service life of the equipment; Moreover, the equipment can only run at full speed after the start of the equipment, and the refrigeration capacity can be controlled by adjusting the return valve (evaporation pressure) opening degree. The power consumption is wasted, the equipment failure rate is high, and the economical operation is poor.
3. Each branch library can not automatically adjust the cooling capacity according to its own requirements according to the change of storage or the change of storage conditions and the difference in thermal insulation performance, and causes excessive cooling of the original library that does not require cooling. Evaporator defrosting and cooling water pump operation are difficult to achieve the best results.
Third, the purpose of automatic control transformation With the development of electronic technology, programmable logic controller (PLC), the maturity of the development of AC frequency control technology, the use of a variety of sensing sensors for a variety of applications, making automatic control More and more powerful functions, system optimization and energy-saving management and control capabilities are also becoming stronger. For the cold storage automated transformation provides a good prerequisite.
The purpose of the transformation is to achieve automation and intelligent control through transformation, improve the quality of cold storage, reduce power consumption, increase equipment life, reduce equipment failure rate, and reduce the cost of on-duty personnel. Comprehensively improve the efficiency of cold storage, ensuring that investment costs are recovered within 2 years.
Fourth, the main work of equipment reform:
1. Cold storage automatic control system uses S7 PLC control and programming; through MPI communication to achieve data communication with the host computer; for large cold storage, using Profibus-dp communication, with all branch cold storage, cooling control equipment to achieve full data exchange ;
2. The refrigerating compressor is driven by the AC variable frequency speed control device; it realizes full data exchange and control through modbus communication and PLC;
3, using the upper computer + industrial touch display (or touch screen) +wincc configuration software to make the host computer management screen of the cold storage system. Real-time dynamic display of the operating status of all equipment in the cold storage, recording equipment operating parameters and operating curves to provide energy-saving data analysis data, real-time alarm for various abnormal phenomena.
4. The air intake valve of the regulating station is changed to an electric mechanism, and various types of sensors are added to realize PLC automatic control.
5. Realize the automatic operation and commissioning of the refrigeration system of the aquatic cold storage.
Fifth, after the equipment transformation has the function:
1, on the whole cold storage system on the host computer management and control, in the host computer, with the screen real-time display of the cold room cooling room temperature, the compressor operating conditions, equipment at various points of the working status, such as equipment start and stop, operation, fault, valve control status , each set temperature and actual control value of the cold, etc., use the curve to record the temperature of each cold room, and the compressor runs the load current. Real-time monitoring and alarming of parameters such as temperature and pressure, displaying parameters such as return valve pressure and operation of operating equipment. It has a process temperature for storing different storages in different refrigeration rooms, and sets a database of process parameters such as storage temperature and optimal refrigerating capacity (return pressure) for the user to call.
2. The system shall be considered according to an unattended scheme, and the temperature of each cold storage shall be separately detected and controlled to realize the closed-loop control of the valve opening and closing degree and the actual measured temperature of the warehouse at the time of starting. Temperature detection and control using PLC, temperature control range of high precision; measured and set temperature of the cold storage are displayed on the touch screen, and has an upper and lower limit alarm function
3, the system has automatic and manual control of the two-bit operation function, and has a variety of automatic protection device, when a fault occurs, automatically give an alarm signal (can be remotely transmitted alarm signal) to alert the user to deal with, in case of serious accidents, automatic parking And alarm. If necessary, the user can notify the user by sending a short message notification. The system has the advantages of accurate temperature control, simple operation and high reliability.
4, the compressor has a soft start, soft stop, continuous smooth speed control function, can extend the life of equipment, to achieve energy-saving regulation. Intelligent fuzzy start-stop control is performed according to the measured temperature of each cold room, reducing the number of start-stops.
5. According to the process requirements, different working modes such as storage, delivery, storage, etc. are set; for the actual conditions of different warehouses, separate automatic control is performed; through PLC programming, different storage temperatures are set for the storage requirements of the warehouse, and the temperature is adjusted automatically. The speed of the liquid supply valve or the chiller not only satisfies the requirements for freezing (refrigeration) in different freezer rooms, but also avoids the waste phenomenon of excessive freezing in individual stores. Such warm storage adjustment can meet the requirements of energy saving, and can also meet the need of high-precision temperature adjustment in some warehouses. The temperature control can meet the accuracy requirement of 0.250C.
6. Utilize the peak-valley electricity price to make cooling energy-saving reserve at night and reduce the electricity price consumption;
7. It has the closed-loop regulation function of return air pressure and achieves the best energy-saving operation control mode; the control valve of the regulation station is based on the difference between the actual temperature and the set temperature of the corresponding freezing (refrigeration), and the temperature difference of each refrigerator compartment. The size is adjusted automatically. When there is no difference, the valve is closed. When the difference is large, the opening degree of the valve is automatically increased. When the difference is small, the opening degree of the valve is automatically reduced;
8, automatic detection of condenser frosting status, timely defrosting, to ensure the play of refrigeration efficiency;
9, for the circulating water cooling system, according to the ambient temperature, the actual operating temperature, in the cooling effect of the working state, to achieve automatic closed-loop control function.
10, all the fan operation monitoring function, which fan stops running, immediately give alarm information;
11, ammonia liquid level detection, automatic adjustment;
12, timing reminder of oil collection and discharge. Refrigerator refrigerator door opening several times and time recording and monitoring.
Sixth, cold storage transformation steps
1. Project negotiation, Party A provides basic information such as on-site process equipment and floor plans, Party B makes energy-saving plans and quotations according to the information provided by Party A. After the two parties reach a consensus, they sign the contract.
2, equipment production, on-site reconstruction materials preparation; (site support production provided by Party A)
3, on-site equipment installation, debugging;
On-site installation includes: installation of new equipment, manual valve change to electric valve, warehouse temperature sensor installation, wire (wire provided by Party A) to connect, old equipment fan and compressor power line to be connected to new equipment. On-site commissioning, commissioning, and delivery to Party A for use.