In the towers, absorption and heat exchange take place simultaneously The design was based on a shell-and-tube type heat exchanger, with a vertical tube arrangement. The absorption-condensation of NH3 occurs inside the tubes by a descending film process.

The absorption-condensation heat is removed by cooling water circulating in the shell. Each tower has an extraction capacity of 12500 kW.

The units consist of three different parts each with a different operating requeriment: Lower Retention Container, Heat Exchanger and Premixer-Distributor.

The Heat Exchanger is the active component of the equipment. Here the absorption-condensation of ammonia takes place. The ammonia and water solution descends inside the tubes forming a turbulent film of high heat transfer capacity. The gaseous ammonia flowing in the same downward direction, is rapidly absorbed, releasing the dissolution heat.

Heat is transferred to the cooling water that flows in a cross current in the shell side. The heat is then sent to the cooling towers of the Plant.

The main design parameters of the equipment are as follows:

• Diluted ammonia - water solution flow: 170000 kg/h
• Anhydrous ammonia flow: 25000 kg/h
• Cooling water flow: 1100 m3/h
• Design pressure: 19 bar
• Design temperature: -30 to +90 °C

The main dimensions of the towers are as follows:

• Diameter: 1.6 m
• Height: 20 m
• Weight: 20 metric tons

The towers are of carbon steel, according to ASME Code, Section VIII, Division 1, and the TEMA Standard.