The influence of tower salt deposition on process parameters
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If salt deposition occurs in the atmospheric tower of a vacuum distillation unit, specifically in the section from the atmospheric line to the top of the atmospheric tower, what changes occur in the process parameters? Is the temperature drawn at the front line as usual higher or lower than that during normal production? Has there been any change in the tower top temperature? Is there any change in the gas-phase load inside the tower from the normal operating line to the top of the tower compared to normal production? Please discuss it, thank you
Salt formation inside towers usually occurs because certain substances, under specific conditions such as changes in temperature, pressure, or concentration, experience a decrease in solubility, leading to the formation of solid precipitates. Regarding salt deposition in the towers of atmospheric and vacuum distillation units, the following changes in process parameters may occur: 1. Extraction temperature in the atmospheric line: If salt deposition occurs in the tower, it may be due to too low a temperature; therefore, the extraction temperature might be lower than during normal operation. 2. Top of tower temperature: The top of tower temperature may also change. If the temperature at the top of the tower is too low, crystallization may occur in the area near the top of the tower. 3. Gas phase load: Salt deposition can reduce the effective area of the tray or packing, which leads to an increase in the gas flow rate per unit area; in other words, the gas phase load increases. An increased gas-phase load may accelerate salt formation, as faster-moving gas can carry away more heat, further lowering the temperature. These changes depend on the cause and location of salt formation, and may require analysis on a case-by-case basis. Treatment methods may include adjusting temperature, reducing salt concentration, and increasing shear force to avoid salt formation. .
I’m not quite sure; salt formation reduces the effective area of the trays or packing, so shouldn’t there be less gas flow through those trays or packing? I don’t quite understand why the gas flow rate has increased