This master thesis project was carried out as a part of the chlorate research conducted at the Process RD&I department for bleaching chemicals at AkzoNobel Pulp and Performance Chemicals AB in Bohus. During the project already implemented filter cloths as well as new types of filters were studied and compared by experimental trials. The results were then examined in an attempt to evaluate existing filtration systems as well as investigate if there are other, better alternatives. The impurities found in a chlorate plant account for an efficiency loss in the process and a reduction of impurities would hence result in an energy reduction and a cleaner product. The trials were conducted at one of AkzoNobel’s chlorate plants. Six filters were studied and evaluated by measuring turbidity of the electrolyte and pressure over the filter during the experiments. Samples of the electrolyte were analyzed to obtain the metal content, and thereby the impurity content, of the electrolyte. The structures of the filters were studied by optical microscopy. The results from the trials show that all filter types except one, a needle felt filter, seem to be suitable for chlorate electrolyte filtration (including the filter types already used in the plants). The other filters all reach turbidity values below 0.1 FNU immediately or within 90 minutes of filtration, which is considered good enough. The results from the metal content analysis show a similar trend where the metal concentrations decrease to levels below the detection limits immediately or within 90 minutes of filtration. Apart from the lab trials performed some measurements were made on the existing filtration equipment in the chlorate plant. The measurements show varying results, partly similar to those achieved during the lab filter trials but also results showing a higher turbidity value and metal content, indicating that full scale operation are more complicated than lab scale operation. The lab trial results obtained with the filter types already used in the plants show that lower impurity content is possible to achieve. However, this would require closer monitoring of the filtration systems in the plants. Apart from the filtration trials, an attempt to determine the sizes of the particles present in the electrolyte using laser diffraction was performed. However, too little was known of the chlorate electrolyte’s optical data for the measurements to be reliable. Further work is needed before a method for size determination of the particles in a chlorate electrolyte can be achieved. Also, an Optical Filtration Test was tried on the electrolyte but was not sensitive enough for utilization on electrolyte with low (below 1 FNU) turbidity values. The project concluded that a switch to another filtration system is unmotivated, unless a change in the product requirements would occur. Since the impurities have proven to affect the efficiency of the process, it is recommended to make an effort into utilizing the filtration system to its full extent.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:ltu-59489 |
| Date | January 2016 |
| Creators | Jakobsson, Elsa |
| Publisher | Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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