Disadvantages of ammonia absorption refrigeration

Ammonia absorption refrigeration is widely used across the country; for example, the Haolianghe Fertilizer Plant in Heilongjiang and the Harbin Gasification Plant have been in operation for over a decade with excellent performance – there are no issues during operation throughout that time. It is also used by companies such as Shanxi Tianji, Xinjiang Guanghui, and Xinjiang Qinghua. No special machinery is required for this system; sufficient waste heat is all that’s needed. The main equipment includes distillation towers, absorbers, storage tanks for concentrated ammonia solution, storage tanks for liquid ammonia, ammonia water pumps, condensers, heat exchangers for ammonia water solutions, underground tanks for ammonia water, vacuum pumps, and systems for removing inert gases.

Thank you for your advice. I would also like to ask if there are any standard equipment available for this type of unit? Or should it be the various design institutes to handle the design of the process equipment? Why don’t several of the major domestic refrigeration companies offer this service?

The ammonia water pump used in operating the equipment is a single-stage centrifugal pump, and many manufacturers are capable of producing it. Another type is the water ring vacuum pump, which is something you’re familiar with; design institutes can handle its design – institutions like Tianchen and Saiding can do this. I’m referring to ammonia absorption refrigeration, not mixed refrigeration. In the case of mixed refrigeration, an additional ammonia compressor is needed, and this is not something that domestic refrigeration companies handle. This system utilizes the phase change of liquid ammonia to absorb large amounts of heat and cool the liquid; the gaseous ammonia resulting from this phase change then enters the absorber, where it is absorbed by dilute ammonia water in the distillation tower to form concentrated ammonia water. This concentrated ammonia water is then pumped into the distillation tower using an ammonia water pump. At the bottom of the distillation tower, there is a reboiler (which heats the ammonia water using steam or process gas). The heated gaseous ammonia experiences increasing pressure at the top of the tower, and its temperature further drops due to the action of the condenser at the tower’s top. Before leaving the tower, its temperature drops even more, resulting in liquid ammonia that is stored in a liquid ammonia tank, thus enabling recycling.

Ammonia absorption refrigeration – I really haven’t heard of it; generally, it’s ammonia compression refrigeration systems that are used. We installed one such system last year

The purpose of using ammonia absorption refrigeration is to minimize energy consumption and make full use of the waste heat generated by the system. If the amount of waste heat available is insufficient, ammonia compression refrigeration can be considered. Energy balance must be carefully taken into account from the initial stage of a project; otherwise, the waste heat from the system will be wasted needlessly. For example, in the Datang Keqi coal-to-gas project, there is an excess of low-pressure steam, with around 100 tons being emitted per hour. Compression refrigeration is used for cooling in this process, resulting in significant waste of thermal energy.

Those companies are involved in mechanical compression refrigeration, that is, they use compressors. They are basically laypeople when it comes to absorption refrigeration

Mechanical compression refrigeration and absorption refrigeration are basically two different approaches; companies like Dual Good, which specialize in absorption refrigeration, can develop ammonia-based absorption refrigeration systems

I just called Shuangliang to ask, and they don’t handle ammonia absorption refrigeration either; they only work with lithium bromide

Thank you for your generous guidance. I would also like to ask you: regarding ammonia absorption refrigeration technology, are there any methods available to improve the coefficient of performance COP or the thermal efficiency?

I can’t give you an answer to this; firstly, I’m not aware of the operating conditions, and secondly, some things need to be calculated. What’s the purpose of having a design institute then? Let them do it for you.