A recovery/reclamation system can be used to recover and store refrigerant in cylinders and decontaminate it on-site.

Table 1. Solubility of Ammonia in Water Curve. Water in the refrigerant side reduces compressor capacity and increases power consumption.
Because chlorofluorocarbons (CFCs) are becoming increasingly regulated and CFCs and hydrochlorofluorocarbons (HCFCs) are being phased out, using ammonia as an alternative refrigerant is gaining popularity. While ammonia systems are a successful substitute in many manufacturing environments, contamination problems exist that reduce efficiency, increase energy use and can lead to catastrophic damage, resulting in line shutdown. Recent technological developments can predict contamination problems such as moisture, oil and particulate.

Because ammonia and water have a great affinity for each other, water in the refrigerant side of an ammonia chiller can create serious problems. It mixes with lubricating oil and forms organic acids that can damage the cooling system. By changing the ammonia from an anhydrous to an aqueous ammonia solution, water degrades chiller efficiency as power use ramps up.

Moisture can enter an ammonia chiller in several ways. The most common include tube ruptures; joint, seal, packing and valve leakage; and condensation during installation. When water enters the ammonia side of a chiller, it:

  • Increases refrigerant temperature.
  • Decreases pump performance, piping pressure and evaporator efficiency.
  • Increases energy costs.
  • Mineral- and paraffin-based oils in an ammonia system can:

    • Leech into the ammoniaside from the discharge side of the compressor.
    • Travel through the condenser and receiver to settle in the evaporator.
    • Oil log the evaporator, thereby significantly reducing system efficiency.

    When particulate such as rust, metal particles or dirt contaminate a chiller, they cause serious damage, including premature wear; clogged restrictions, metering devices, oil lines and filters; and reduced efficiency.

    To address these problems, processors can use a refrigerant-side decontamination system. It recovers refrigerant at high speeds and simultaneously decontaminates it.

    The system works by recovering ammonia when a system is down for repairs. The system recovers and stores refrigerant in the proper cylinders, then decontaminates it on-site so it can be used to recharge the system. This can be particularly important to a plant's toxicity reduction inventory.

    Table 2. Effects of Water Dilution As water content increases, the saturated temperature of the aqueous ammonia solution increases. The system must operate at lower suction pressure to maintain desired temperatures.
    Two examples can show how this recovery/reclamation system works.

    Example. A vitamin manufacturer had a process chiller that was scheduled for repairs, but it was having trouble finding a company willing to perform the refrigerant recovery. This two-tiered system used simple refrigerant-grade ammonia on one side and special process ammonia, which contained acetylene, hexane and potassium hydroxide, on the other. Because ammonia reacts negatively with many chemicals and attacks anything made of copper, the refrigerant was difficult to recover, making the process mixture even more volatile.

    Using its recovery system, special hoses and safety gear, recovery system peronnel connected to the process chiller. A day and a half later, 20,000 lb of ammonia had been recovered and stored to await reinstallation. "That was impressive to watch," said the vitamin plant manager. "The ammonia was recovered faster than we expected. Days were cut off the repair time, and a small fortune was saved in lost production."

    Recovery/reclamation technology also provides increased uptime. Ammonia-side services use the system to remove water, oil and particulate from a refrigeration system while it continues to operate.

    While the ammonia replacement cost is low, the downtime needed to recover the old ammonia and replace it with new can be prohibitive. The recovery/reclamation system can be used to decontaminate old ammonia that is warehoused for disposal, allowing it to be used again. This significantly reduces the net weight of materials to be disposed.

    Another Example. An 8,000 gal liquid overfeed system used to manufacture latex rubber was performing significantly below capacity. The service contractor discovered a large amount of water in the refrigerant. The standard method for returning the system to peak efficiency would have been to shut down the line, recover the contaminated refrigerant and replace it with new. If the leak was slow, it could be identified and repaired during the scheduled maintenance shutdown. But, the downtime could cost the plant hundreds of thousands of dollars a day in lost production.

    Instead, the decontamination system, primed with ammonia, was connected to the chiller and provided high volume distillation. As the refrigerant passed through the system, moisture was removed as well as particulate and excess lubricating oil. In a matter of 10 days, more than 1,000 gal of water had been removed and the chiller returned to peak efficiency.