The objectives of this study are to investigate characteristics of electrochemical oxidation of wastewater depending on electrode materials and to analyze the influence of the chloride ion as an electrolyte on electrochemical oxidation of pigment wastewater using a Ti/IrO 2 tube-type electrode. The Ti/IrO 2 electrode was adopted as the most proper material in the comparative analysis under COD removal efficiency and current efficiency. The current efficiency for each electrode material was decreased in the order of Ti/IrO 2 16.5%, Ti/Pt 14.0%, and graphite 3.4%. Two kinds of electrolytes of NaCl and Na 2 SO 4 revealed different levels of electrochemical oxidation under the same conductivity conditions. Specific energy consumption was reduced by adding a chloride ion in the electrochemical oxidation treatment. The chlorite ion (ClO 2-) and free chlorine were produced in the Ti/IrO 2 tube-type electrochemical oxidation systems. The production amount of chlorite ion was larger than double that of free chlorine production. The indirect oxidation process by the intermediate product was concluded to be the major principle for COD removal.
A study of a variable diffuser vane capacity control method was done for the delivery of air into degasser of a SRU (Sulfur Recovery Unit) in a refinery process which requires a wide operating range and high head rise. Rig tests were made with diffuser vanes with various diffuser turning angles to evaluate performance of the compressor with variable diffuser vane. The compressor running on the test rig consisted of inlet bell mouth venturi, unshrouded impeller and vaned diffuser with tip clearance and scroll. To evaluate performance of the impeller and diffuser, static pressure was measured on the shroud side through 30 pressure tabs. The performance characteristics of the compressor stage, such as head coefficient, work coefficient, impeller exit flow condition and diffuser pressure recovery, are evaluated for 3 diffuser vanes and speeds. All performance characteristics are expressed as dimensionless form for each diffuser turning angle and speed. For the stage performance, compressor capacity is reduced as diffuser turning angle increase. For the impeller and diffuser performance, impeller exit flow coefficient is used for impeller exit flow condition and its performance. Based on the rig test, 6 customized single stage compressors with the variable diffuser vane capacity control system for the degasser of SRU were made and shop test were performed on each compressor. It was found that surge of the compressors can be controlled by variable diffuser vane and largely depends on the diffuser geometry.
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