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Remediation of former In-Situ uranium mining region.
Kříž, Jakub ; Kalous, Jaroslav (referee) ; Jícha, Jaroslav (advisor)
Remediation process of region, formally exploited for chemical leaching of uranium, is based on pumping water contaminated mostly by residuals of sulfuric acid from the relevant geological horizons. The contaminated water is then treated in a chemical plant. In the treatment process evaporators play the key role. Presently operating evaporators – three units – are of falling film type. Heating service is provided by compressed vapor that is generated by evaporators. For driving the compressors and associated circulating pumps of each unit electric power of 3,4 MW is required. In the evaporators treated solution is distributed into individual tubes by nozzles of cyclone type that are mounted at the top end of tubes. In the evaporators feed solution contains calcium sulfide of low concentration. Once the calcium sulfide concentration in the evaporating process reaches the state of saturation, even locally, fouling is initiated. Thus the solids start to grow on the inner surface of the tube wall and the nozzle’s openings become restricted. The evaporator performance – evaporating rate – gradually declines and when it reaches the bottom limit the evaporator has to be shut down. This is followed by carrying out the cleaning procedure. At the time when the evaporators started operating (1996) the period between shut downs lasted around a half a year. However, gradually, this period has become substantially shorter – presently it may even last one week only. The thesis proposes two ways of approaching the present hardly acceptable state. First, replacement of distributing nozzles by a set of properly perforated sieve trays secures the uniform distribution of solution into each individual tube. Second, evaporators’ duty will be taken over by newly build multi-flash concentrator that will substitute the presently operating evaporators. Configuration of this new equipment is derived from widely used multi-flash distillation of sea water. Heat required by the concentrator’s end heaters is drawn from a gas turbine exhaust gas. Steam provided by Heat Recovery Steam Generator is supplied to the condensing heat exchangers installed on the evaporator’s feed stream. Generator coupled to the gas turbine, fueled by natural gas, provides the electric power of 30 MW for export.
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Remediation of former In-Situ uranium mining region.
Kříž, Jakub ; Kalous, Jaroslav (referee) ; Jícha, Jaroslav (advisor)
Remediation process of region, formally exploited for chemical leaching of uranium, is based on pumping water contaminated mostly by residuals of sulfuric acid from the relevant geological horizons. The contaminated water is then treated in a chemical plant. In the treatment process evaporators play the key role. Presently operating evaporators – three units – are of falling film type. Heating service is provided by compressed vapor that is generated by evaporators. For driving the compressors and associated circulating pumps of each unit electric power of 3,4 MW is required. In the evaporators treated solution is distributed into individual tubes by nozzles of cyclone type that are mounted at the top end of tubes. In the evaporators feed solution contains calcium sulfide of low concentration. Once the calcium sulfide concentration in the evaporating process reaches the state of saturation, even locally, fouling is initiated. Thus the solids start to grow on the inner surface of the tube wall and the nozzle’s openings become restricted. The evaporator performance – evaporating rate – gradually declines and when it reaches the bottom limit the evaporator has to be shut down. This is followed by carrying out the cleaning procedure. At the time when the evaporators started operating (1996) the period between shut downs lasted around a half a year. However, gradually, this period has become substantially shorter – presently it may even last one week only. The thesis proposes two ways of approaching the present hardly acceptable state. First, replacement of distributing nozzles by a set of properly perforated sieve trays secures the uniform distribution of solution into each individual tube. Second, evaporators’ duty will be taken over by newly build multi-flash concentrator that will substitute the presently operating evaporators. Configuration of this new equipment is derived from widely used multi-flash distillation of sea water. Heat required by the concentrator’s end heaters is drawn from a gas turbine exhaust gas. Steam provided by Heat Recovery Steam Generator is supplied to the condensing heat exchangers installed on the evaporator’s feed stream. Generator coupled to the gas turbine, fueled by natural gas, provides the electric power of 30 MW for export.
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