Applications for Ammonia Absorption Machines

Heat Pump

Ammonia absorption machines can also work as heat pumps (AHP). By means of a high level heat input (e.g. 180°C, or direct firing), heat is extracted from a low temperature heat source (e.g. 0°C) and used to increase the water temperature of e.g. a central heating system from 45°C to 55°C. Colibri b.v. has delivered several heat pumps for domestic heating with capacities in the range of 500 kW. (Look at the picture on our page Engineering, Service)

scheme ammonia absorption heat pump cycle
Scheme absorption heat pump cycle, click to expand.

Heat Transformer

Heat transformers (AHT) are another type of ammonia absorption machines. They use medium level waste heat (e.g. 80°C) to provide high level heat (e.g. > 100°C). At lower temperatures, heat rejection to cooling water or ambient air is required. The components used for such machines are the same as those used in heat pumps.

scheme absorption heat transformer working principle
Scheme absorption heat transformer cycle, click to expand.

Kalina Cycle

In a Kalina Cycle a low temperature heat source can be used to produce electricity. The main difference to a Rankine cycle is working fluid, which is an ammonia-water mixture. Except from the turbine all other components are similar to what is used in an ARP and can be delivered from colibri b.v..

Ammonia Absorption Machines in Combination with other Systems

Trigeneration

The combination of a combined heat and power plant (CHP) with an absorption refrigeration plant (ARP) is called trigeneration, because it produces electricity, heat and cooling. Industries with mainly cooling demand (food production and storage) can use the heat coming from the exhaust gasses from an engine or a gas turbine as driving heat source for an ARP.

Indirect use of exhaust gasses:

The exhaust gases of the Cogen unit are used to produce steam, hot water or thermal oil in a standard exhaust gas heat exchanger. The ARP is driven with the steam or the hot fluid coming from this heat exchanger. The advantage of this system is that the steam or the hot water can not only be used to drive the ARP, but also additionally or alternatively for other purposes. In production processes with fluctuations in steam consumption the ARP can form a buffer which consumes the excess steam coming from the Cogen unit.

scheme indirect use of exhaust gasses for heat input of ARP
Scheme indirect use of exhaust gasses for heat input of ARP, click to expand.
Direct use of exhaust gasses:

The exhaust gases are used directly to drive the ARP. Coming out of the Cogen they enter straight into the desorber of the ARP. To avoid pressure drops and save costs for piping of the exhaust gases, the ARP should be located near the Cogen unit. The desorber will be similar to a conventional steam boiler for exhaust gasses and can be designed according to the specifications of the engine or turbine. In comparison to the indirect linkage, this system saves an extra steam or hot water system (boiler, pump, piping).

scheme direct use of exhaust gasses for heat input of ARP
Scheme direct use of exhaust gasses for heat input of ARP, click to expand.
Use of Heat from Cooling of the Engine:

The outlet temperature of the cooling water (glycol-water) for the jacket cooling of an engine is usually approx. 90°C The return temperature should be usually 70°C. For ambient temperatures below 20°C an ARP can use this heat providing a return temperature of approx. 80°C. (Lower is possible at lower ambient temperatures). The fluid to be chilled can be cooled to temperature of approx. -8°C.

scheme use of jacket water cooling for heat input of ARP
Scheme use of jacket water cooling for heat input of ARP, click to expand.

Turbine Inlet Air Cooling (TIAC)

Turbine compressor efficiency and power output of a gas turbine is proportional to the inlet air mass flow. By cooling the inlet air the mass flow can be increased due to the increasing density at lower temperatures. To provide the cooling of the turbine inlet air an absorption refrigeration plant can be used. The heat of the exhaust gas outlet will be the main energy input for the ARP.

scheme turbine air inlet cooling
Scheme turbine air inlet cooling, click to expand.

Load Balancing

An ARP can be used in different ways for balancing of heat or refrigeration load of a process or in a factory.

Balancing of heat load:

In a process where excess heat is available and a certain cooling demand is required an ARP can be installed to use the excess heat always when it is available. The main task for the ARP is to avoid dissipating of excess heat which can’t be used for other purposes.

Balancing of refrigeration load:

In a process with a strong fluctuating refrigeration demand an ARP can be designed with internal storage capacities, so that the heat input can be lower than what would be normally required to fulfill the peak load of refrigeration.