In water purification, degasifiers are used to remove CO2 that is present in acidic waters that leave the cation exchange beds (Meltzer, 1993). More specifically, the use of hydrogen-cation exchange resin substitutes hydrogen ions for the calcium and magnesium ions removed from the solution. The enrichment of the treated water with hydrogen ions (its acidification) converts the bicarbonate and carbonate ions to carbonic acid. The acid decomposes readily to release carbon dioxide.
Degasifiers are packed towers, similar to strippers and absorbers. The removal of the generated CO2 is accomplished by blowing air (or some other gas into the column) or by applying vacuum. The latter approach is followed in the semiconductor and pharmaceutical industries where general and microbiological contamination of the water (by the stripping gas) is a concern. Vacuum degasifiers substitute vacuum for the sweeping airstream to remove carbon dioxide from the thin films of water permeating the packing of the deaeration towers. This removes the threat of microbiological contamination but substitutes other disadvantages, among them the high capital and energy costs of vacuum pumps, the need for ASME-code vessels to withstand the vacuum, and requirements for the stainless steel construction and piping necessary to avoid contamination by iron, etc.
This is a very simple model. The material balances are based on the removal percentage of the gaseous components that is specified by the user. To account for utilities (steam for vacuum generation, electricity for pumps, and cooling water for vacuum pumps) the user can specify specific (based on flowrate or amount of water treated) or absolute values.
In Design Mode of calculation, the program divides the volumetric throughput by the rated flux of the equipment to estimate its cross sectional area and diameter. If the calculated diameter exceeds its maximum possible value (part of the equipment description), multiple units are assumed that operate in parallel. The ‘Height to Diameter’ ratio is used to estimate the column height.
Dividing the operating flux by the rated flux yields the equipment capacity utilization.
1. Meltzer, T.H. (1993). “High Purity Water Preparation for the Semiconductor, Pharmaceutical, and Power Industries”, Tall Oaks Publishing, Littleton, Colorado.
The interface of this operation has the following tabs:
● Oper. Cond’s, see Degasification: Oper. Conds Tab
● Utility Data, see Degasification: Utility Data Tab
● Labor, etc, see Operations Dialog: Labor etc. Tab
● Description, see Operations Dialog: Description Tab
● Batch Sheet, see Operations Dialog: Batch Sheet Tab
● Scheduling, see Operations Dialog: Scheduling Tab