In a self-cleaning heat exchanger the tubes remain clean and therefore the heat transfer can kept constant which improves the energy performance:
A shell and tube heat exchanger to cool quench water had a decrease in heat transfer coefficient of 50% within 20 days of operation. With a self-cleaning heat exchanger, the heat transfer coefficient remained constant.
Because of the lower fluid velocities and shorter tube lengths in most applications, the pumping power required is reduced. In the application mentioned above the reduction was more than 50%.
Applying the self-cleaning fluidized bed technology for an evaporator that concentrates waste water allows to reach higher solid concentrations in the recirculation flow without incurring in fouling problems as compared to falling film evaporators. This results in a higher water recovery and a drastic reduction of the blow down. When adding a spray dryer to come to Zero Liquid Discharge the overall energy consumption of the self-cleaning unit combined with the spray dryer is only 60% of the energy consumption of the falling film unit combined with the spray dryer. Main reason for this is that with the technology of Klaren International the waste water can be further concentrated meaning a smaller volume flow as blow down requiring less energy for spray drying.
A shell and tube heat exchanger uses water to recover heat from an exothermic reaction. The heat is used elsewhere in the process. Fouling on the chemical component side of the heat exchanger causes a decrease on heat transfer coefficient which results in a decreasing heat recovery capacity. As the fouling layer develops an increasing amount of make-up steam has to be used to further heat the process elsewhere. With a self-cleaning heat exchanger the heat recovery from the exothermic reaction remains constant and no steam has to be used.
