Ammonia Cold Storage

Ammonia Refrigerant Cold Storage
Ammonia refrigerant synthesis process is mature, easy to manufacture, low prices. Ammonia refrigerant in the condenser and evaporator pressure is moderate (condensing pressure is generally 0.981MPa, evaporation pressure is generally 0.098-0.49MPa); unit volume refrigeration capacity than CFC-12, HCFC-22 large; high cooling coefficient, put When the thermal coefficient is large, the same temperature and the same cooling capacity, the minimum size of ammonia compressor. Ammonia refrigerant in a large cold storage, supermarket food display cabinets are widely used.

Chinese name: Ammonia refrigerant Chemical characteristics: flammable, toxic Use characteristics: mature technology, easy to prepare, low prices

Applicable areas: large cold storage, supermarket food display cabinet use requirements: safety, corrosion resistance
Advantages: Capacity per unit volume is greater than CFC-12
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Features: Ammonia refrigerant flammable, toxic, after the water on the zinc, copper, bronze alloy (except phosphor bronze) have a corrosive effect, a pungent odor.
The use of ammonia as a refrigerant refrigeration system needs to have two characteristics: security, to have a sound system and leak detection system and improve the alarm system. Corrosion resistance
Sex, in the ammonia refrigeration device, its pipes, meters, valves, etc. can not use copper and copper alloy material.
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Safety devices and safety precautions

Safe operation of the refrigeration system In addition to relying on excellent installation quality, the necessary safety devices are also essential. In the refrigeration system to be installed enough ammonia pressure gauge, safety valve, level meter, thermometer, etc., effective and adequate safety device can accurately monitor the system operating conditions (such as pressure, temperature, etc.), in order to detect the presence of refrigeration system Abnormal, and can appear in the system overpressure and other abnormal circumstances in a timely manner to avoid accidents. It should be noted that the above table must be regularly verified to ensure that it is within the validity period.
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Comparison of ammonia refrigeration system and green environmental protection fluorine refrigeration system
In China, the industrial refrigeration industry has long been the choice of the use of artificial control of the ammonia system as a refrigeration system. Over the past five years, Freon refrigeration units (including stand-alone and parallel operation) in the country began to use in large and medium-sized logistics system. In Europe and the United States from the late fifties of last century has been the Freon parallel unit refrigeration system used in the slaughtering industry and large industrial cold storage. After nearly half a century of development, has become a very mature and efficient technical system. Is widely used in large-scale industrial refrigeration industry. And a large number of screw parallel unit. The system is also a centralized cooling, rather than some small domestic piston fluorine refrigeration system as a machine-like decentralized cooling. Automatic control of the fluorine parallel unit refrigeration system and artificial control of the ammonia machine refrigeration system comparison, mainly the following major advantages:
1) Fluorine parallel unit refrigeration efficiency, can maintain constant efficient operation, greatly saving system power consumption, in line with national energy development strategy. Because in the long run to see the energy shortage is a long-term irreversible problem, the price of electricity is certainly a step by step increase;
2) Fluorine parallel unit can achieve automatic control, so that the system running high reliability, more reasonable science, while reducing system operation and maintenance of labor costs;
3) Fluorine parallel system due to the use of R404A as a refrigerant, the safety is much better than toxic, explosive ammonia refrigerant, which can effectively ensure the safety of employees within the system and the surrounding residents to avoid vicious accidents;
(2) the following on the use of the two cooling systems to compare the use of some more detailed description:
Fluorine parallel unit system why than the current domestic use of artificial control of the ammonia system in the operation of power?
According to the actual detection of cold storage at home and abroad and the operation of frozen storage data, cold storage in the operation of the process most of the time is part of the load operation. There are two main reasons, first from the local said that the single-term freezer, the raw material meat (general storage temperature at +15 degrees) just full of design storage, due to the high surface temperature of the meat, thermal conductivity, will give cold storage But with the freezing process, the surface temperature of the meat is reduced to ice, forming the ice, the thermal conductivity of the meat is decreasing rapidly, the heat efficiency of the inside of the meat is reduced, and the temperature of the meat is reduced, The cold load of the whole cold storage also will be reduced rapidly, the formation of part of the load, ammonia machine cooling efficiency can not be adjusted with the cold load is also rapidly reduced, resulting in large horse car phenomenon. The fluorine parallel unit due to cold storage with the cold load changes and adjust the number of compressor boot, so that the compressor will always maintain efficient operation, to avoid the phenomenon of large horse car. Second, the entire frozen store, because of different cold storage time, the number will not be the same, resulting in the entire cold storage for most of the time part of the load. According to the statistics provided by several German cold storage, the full-load operation time of the quick-freezing reservoir is only about 2% of the whole running time, and the running time of 50% load accounts for about 60%. It is because most of the cold storage is part of the load operation, and the fluorine parallel unit can be adjusted with the load to adjust the number of compressor starts, so as to maintain the efficient operation of the compressor; and ammonia system can not do this. This determines that the fluorine-parallel unit system has a greater potential in terms of efficiency.
(3) Fluorine parallel unit system and ammonia system actual power consumption data comparison
Domestic ammonia system quick-frozen library, according to our data measured in Shuanghui and gong two companies, frozen a ton of meat, according to the purchase center temperature at +15 degrees, 20 hours the center temperature dropped to -15 degrees. Universal power consumption between 150 degrees to 200 degrees. And the actual operation we measured the power consumption at 120 degrees or slightly lower, but most of the central temperature is only about -7 degrees, or quick freezing is much larger than the design, so that the compressor is always in a small horse-drawn cart , Resulting in rapid freezing time greatly extended.
(4) the two systems on the safety of contrast and add refrigerant problems
From the safety of the refrigerant is self-evident. Here to talk about the main leak. Ammonia system due to the use of open connection, a coupling shaft, the use of mechanical seals, the leakage is normal, ammonia system for the use of ammonia valve packing or PTFE ring seal, the switch will occur after the sealing material from the stem Leakage, and ammonia system to discharge the system several times a year non-condensable gas, this operation led to a direct discharge of a large number of ammonia. So the system needs a lot of liquid ammonia every year. At present, we use the fluorine parallel unit is a semi-sealed unit, all the pipes are welded into.
(5) other
Full liquid fluorine parallel unit refrigeration system, the use of fluorine pump for the liquid, the efficiency of dry system 20% higher, to 100% efficiency. In this way, the ammonia system has the advantage that the fluorine system also has the same. Defrosting with independent hot gas defrost. Automatic frost monitoring can do each library, each fan individual defrost. And do not like water as a defrost system like water to help defrost. Fluorine parallel unit system, normally only 2 part-time staff responsible for operation and maintenance. Do not need to be on duty. The ammonia system because of manual control, need to be 24 hours duty, consider the four classes of three operations, at least 6 people. Normal should be more than 10 people. Fluorine system room costs only 30% of the ammonia system, can also reduce investment. Fluorine parallel unit system reliability is also higher than the domestic ammonia system, the compressor used in Germany Bitzer, the solenoid valve with Denmark Danfoss, many parts of the fluorine machine are well-known international brands, technical conditions are ripe. Normal operation for ten years to fifteen years without overhaul. The ammonia system is generally overhaul once every two or three years. Affecting the normal production, increased maintenance costs related to investment and operating costs.

Comparison of Comprehensive Benefit of Fluorine / Ammonia Refrigeration
10,000 tons of cold storage as an example
Fluorine refrigeration large screw parallel system
Domestic ammonia refrigeration system
System operating costs
Refrigerated per ton / day power consumption: 0.2 to 0.3 degrees
Refrigeration per ton / day Power consumption: 0.4 degrees or more
According to the cold storage of 10,000 tons, 300 working days throughout the year
60-90 million electricity throughout the year
1.2 million kWh throughout the year
Year saving
Annual savings of electricity: about 30-60 million degrees
Manual maintenance costs
Only 2 people shift time observation 2000 / person 24000 people / year a total of 48000 yuan a year wages
Need at least 6 technicians 24 hours operation and maintenance, according to staff monthly cost of 2,000 yuan, 24,000 per person per year a total of 144,000 yuan
Daily maintenance costs
Annual maintenance costs about 10,000 yuan
Annual maintenance costs 90,000 yuan
Overhaul cost / time
Ten years without overhaul
Once every three times, each time 150,000 yuan
Add about 300Kg each year, the cost: 6600 yuan R404
10 tons of ammonia per year to be added, the cost: 40,000 yuan NH3
Refrigeration oil
Basically no need to fill the oil
Need to add 5 tons of oil per year, the cost: 30,000 yuan
Room construction costs
Need about 60m2 500 yuan / m2 30,000 yuan
At least need 400m2 500 yuan / m2 20 million
Difficulty in construction
Construction is simple, equipment molding site assembly is easy, short duration, high safety factor
Parts of the pipeline more, on-site installation, all pipeline welds have to go through the technical supervision of the film detection, error-free, long construction period
degree of automation
Automatic control, mobile phone remote monitoring a high degree of automation, no duty, just regular inspection and weekly inspection
Can not fully control the manual control For security reasons, must be 24 hours on duty
Energy saving performance
Strong: 1) When the heat load is small, shut down part of the compressor. Unit cooling capacity energy consumption unchanged. 2) expansion valve can maintain heat transfer temperature difference is basically unchanged
Weak: 1) The thermal load is reduced by 50%, and the motor power after unloading the screw compressor is 65% of the full load, which means that the unit cooling capacity will increase by 30%. 2) variable operating conditions when the heat transfer temperature difference, the temperature difference increased by 1%, energy consumption increased by 3%
Colorless, tasteless, do not burn, do not explode
When the refrigerant leaks, the air concentration exceeds 15% immediately fire and explodes
Equipment reliability
1) semi-sealed or fully enclosed compressor, multi-head screw parallel unit, equipment, high reliability.
2) SRS system, even if the maintenance, but also to provide cooling
1) prone to failure, there are moving parts and static components of the sealing problem
2) ammonia system is complex, many parts, equipment failure probability
3) Maintenance can not provide cooling
Material dry consumption
Smaller, fluorine machine with expansion valve, heat transfer temperature difference is basically the same, so dry consumption is small
Large: the evaporation temperature of the ammonia machine does not change with the performance of the library temperature, so when the import and export frequently, the heat transfer temperature difference, dry consumption increases.
System scalability
Strong expansion can be temporary or single cooling
After installation, the unit is not extensible

From the system operating costs, labor costs, daily maintenance costs, overhaul costs, each year to add refrigerant and refrigeration oil six
Fluorine (referring to the traditional freon refrigerant and alternative green refrigerant refrigeration system) and ammonia machine refrigeration system can be from the energy saving, system operation safety and other aspects of comparison, the specific comparison is as follows.
Energy saving
A) Ammonia machine full liquid system to provide a single, stable evaporation pressure, but the adjustment is to adapt to the temperature changes in the poor ability, for the temperature is often in the occasion of fluctuations, such as regular storage pull temperature, the heat transfer temperature difference in temperature The case will be very large, which means that the decline in efficiency, usually increase the heat transfer temperature of 1 degree Celsius will cause nearly 3% of the increase in energy consumption; for direct liquid supply of fluorine system, because of its good adjustment through the expansion valve function, Its efficiency under the same conditions is higher than the ammonia machine full liquid system. Another increase in heat transfer temperature also means that the increase in dry consumption, will lead to the decline in product quality and weight loss of goods.
B) For large stand-alone systems, the actual operation process, most of the time is running under a partial load, for energy-adjustable compressors, especially screw compressors, the partial load energy efficiency ratio is lower than At full load, the energy efficiency ratio is significantly higher when the load falls below 70%, so the actual operating cost of the stand-alone system will be much higher than the evaluation value calculated with the full load energy efficiency ratio. For the parallel system and SRS (distributed refrigeration system) because it is through the control of the compressor to start and stop the energy adjustment, it can ensure that the unit in the part of the load operation of each head to maintain its highest energy efficiency ratio, the actual operating costs will be greatly reduce.
2. security
A) green environmental protection refrigerant R404A for the use of the project refrigerant, colorless, tasteless, non-burning, non-explosive safe working fluid; and ammonia colorless, toxic (secondary toxicity), contains a strong irritating odor, Eye, nose, throat, lung and skin are strongly stimulated and toxic risk, the air concentration of more than 15% immediately cause the risk of fire and explosion. Based on these shortcomings, people-intensive public places and people-intensive workplace will be banned. Ammonia refrigeration system is therefore also subject to the national safety management department of the approval management and operation supervision.
B) In addition, the parallel technology of the fluorine system has been developed very well, the parallel system in operation will not be due to individual compressor failure or maintenance needs and affect the normal operation of the entire system. And the same cooling capacity is generated relative to the stand-alone system. The average running time of each press of the parallel unit is much smaller than that of the stand-alone cooling system. The compressor has a longer service life.
3. The degree of automation
SRS control system, according to the heat load to control the unit in the compressor start and stop, in order to achieve the control of the library temperature. We can set the upper and lower limits on the centralized control screen, the temperature difference can be set very small, the quality of the store during the storage of food is very favorable. The domestic ammonia system control of the library temperature is generally full manual control, according to the staff of the observation of the library to determine the opening or stop the number of compressor starts. Because all the manual operation of the staff, which need to rely on the technical level of the operator and responsibility. So this work on the quality requirements of personnel is very high According to the survey of industry operators, to train a qualified ammonia machine operators, generally 5 - 10 years. Moreover, even qualified operators, the operation of the machine and the system there are many uncertainties, such as the operator's sense of responsibility, fatigue, etc. will affect the normal use of equipment, or even safe. The ammonia system requires 24 hours of duty and adjustment.
4. System complexity comparison
Fluorine system is compact, less accessories, most of the unit can be


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