![[principle_fig2K] Select for larger version.](/images/principle_fig2.gif)
The operating principle of the self-cleaning exchangers is shown in figure 1.
The fouling liquid is fed upward through a vertical shell and tube exchanger that incorporates specially designed inlet and outlet channels. Solid particles are also fed at the inlet, where a flow distribution system uniformly provides the liquid and suspended particles throughout the internal surface of the bundle. The particles are transported by the upward flow of liquid through the tubes, where they create a mild scraping effect on the wall of the heat exchange tubes, thereby removing any deposit at an early stage of fouling formation. These particles consist of cut metal wire, glass or ceramic balls with diameters varying from 1 – 4 mm. At the top, inside the separator connected to the outlet channel, the particles disengage from the liquid and are returned to the inlet channel through an external downcomer, and the cycle is repeated.
Figure 2 shows a configuration with a new type of KLAREN separator, which reduces the pressure drop required for separation.
For both configurations, the process liquid fed to the exchanger is divided into a main flow and a control flow that transport the particles into the exchanger. By varying the control flow, it is possible to control the amount of particles in the tubes. This controls the efficiency of the cleaning mechanism, allowing the particle circulation to be either continuous or intermittent.
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| Figure 1: Principle of self-cleaning heat exchanger with cyclone. | Figure 2: Principle of self-cleaning heat exchanger with KLAREN separator. |
