APPLICATIONS
Sugar Mill (C-743) SAMPLE ION EXCHANGE
A sugar mill has determined the need to install a water treatment plant to soften hardness in order to be able to serve different production processes. Basic specifications indicate a capacity requirement of treating approximately 1635 m3 / day (300 U.S. gpm) reducing hardness from ca. 200 ppm to about 10 ppm. It is desired to estimate the volume of resin involved as well as the required area and inputs, indicating a preliminary configuration.
According to the information provided, the system to be installed must soften the following daily load:
1635000 L * 200 mg / L = 327 * 10 ^ 6 mg = 327 * 10 ^ 3 g = 327 * 10 ^ 3 * 15,432 grains = 327 * 15,432 kilograins = 5046 kilograins
Using a generic exchange resin for calculations, and a ballpark value of 10 lb NaCl per cu.ft. of resin, which allows the softening of approximately 27.1 kilograins per cu.ft. of resin, we can figure out required resin volume as follows:
volume of resin required = 5046 kilograins / 27.1 kilograins / cu.ft. = ca. 186.2 cu.ft. = approx. 5.3 m3 of resin
Since softener systems are typically organized in service and regeneration cycles, in many cases accompanying or contingent on the organization/scheduling of production / industrial activity / personnel shifts, the operation is frequently interleaved or divided into shorter cycles.
Suppose the installed system had only 132 cu.ft. of resin, maintaining the regeneration of 10 lb NaCl / cu.ft. The capacity of the system would then be:
132 cu.ft. * 27.1 kilograins / cu.ft. = 3577.2 kilograins
After approximately 17 hours (= 3577.2 * 24/5046) we would have used the possible softening capacity, then forcing the activation of a similar unit in order not to interrupt the supply of softened water to the industrial process in question.
If originally 8-hour service cycles had been specified, thus implying three daily regenerations, the volume of resin associated with each tank would then be calculated in an analogous way:
kilograins per softener tank = 8 * 5046/24 = 1682 kilograins
volume of resin per softener tank = 1682 kilograins / 27.1 kilograins / cu.ft. = 62 cu.ft. = 1.75 m3 of resin
Then a semiautomatic system could consist of two of these tanks in order to fulfill the required service.
Similarly, it can be seen that by structuring the load in 12-hour cycles, to simply require only two daily regenerations, the amount of resin is approximately 93 cu.ft. resin per softener tank
Starting at the specified flow rate and a hydraulic rate of 6 US gpm / sq.ft. An estimate of the dimensions will then result:
required area = flow / hydraulic rate = 300 US GPM / 6 = 50 sq.ft.
Using two units then it results
softener tank diameter = 2 * (25 / 3.1415) ^ 0.5 = ca. 5.6 '= ca. 1.72m
The use of multi-tank systems allows the provision of the requested service without interruptions. Dimensions as well as operating conditions and capacities are often standardized.
Beverage Industry: Operating Regime and Unit Sizing Considerations (applicable to most sectors) - Sample Preliminary Feedback
Prospect industry is unsure as to how best balance budget with plant schedule. There's also concern as regards temperature, hardness.
There are several ways of dealing with this application. The least expensive would be to use a machine that would need to operate 24 hours/day in order to produce enough water that the factory would use in 8 hours. This option is best for the overall operation of the machine as well as being the least expensive. The downside is that the factory needs to have space for product water storage.
The water temperature is important for the machines needed to be derated with decreasing water temperatures with the standard rating temperature being 25 degrees C. With a feed water temperature of 20 degrees C the machines put out only 90% of the rated output and when the temperature is reduced to 15 Degrees C they only put out 77% of the rated output.
Hardness will cause definite problems if left untreated. One can relate hardness solubility to CaSO4 which has a solubility of about 500 ppm at a pH of 7. Since the concentrate stream of the machine concentrates the hardness by a factor of 3 or 4X depending on how the machine is operated something needs to be done to keep the hardness in solution. One way is reduce the pH be adding acid to the feed stream but since there is so much hardness this is not a good solution. A second way is to add an anti-scalant to the feed. This chemical can be obtained from local suppliers who should be consulted as to the appropriate chemical and dosing rate. The third option is use soften the water prior to the feeding it to the machine.
To reach the required water quality probably the least expensive option will be to first soften the water to remove the hardness followed by reverse osmosis although it is tough to say for certain without seeing a complete water analysis, knowing how many hours per day they need quality water and if they other requirements such as the minimum and maximum pH.
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