Absorption refrigeration: An alternative for lubricant dewaxing – A case study

• Mechanical vapour compression and two absorption system options were compared.
• Industrial application: lubricating oil dewaxing.
• Absorption systems are found to be thermally more efficient using lower pressure and lower cost steam.
• Ammonia/lithium nitrate is the most efficient system, but there is little or no industrial experience.
• Ammonia/lithium nitrate has significant disadvantages for heat and mass transfer.

Three refrigeration systems applied to a lubricant dewaxing process were analysed and compared: existing mechanical vapour compression and proposed ammonia/water and ammonia/lithium nitrate absorption refrigeration. The absorption systems offer higher thermal efficiencies using cheaper, lower pressure steam. The ammonia/lithium nitrate system has the capacity to provide the highest efficiency option at the cost of a higher investment due to its adverse transport properties: high viscosities. The ammonia/water system is a tried and tested technology whereas the ammonia/lithium nitrate has been demonstrated, but to the authors' knowledge, not used in an industrial scale system.