Dimethyl phthalate (DMP) was treated via wet oxygen oxidation process (WOP). The decomposition efficiency η
DMP of DMP and mineralization efficiency η
TOC of total organic carbons were measured to evaluate the effects of operation parameters on the performance of WOP. The results revealed that reaction temperature T is the most affecting factor, with a higher T offering higher η
DMP and η
TOC as expected. The η
DMP increases as rotating speed increases from 300 to 500 rpm with stirring enhancement of gas liquid mass transfer. However, it exhibits reduction effect at 700 rpm due to purging of dissolved oxygen by overstirring. Regarding the effects of pressure P
T, a higher P
T provides more oxygen for the forward reaction with DMP, while overhigh P
T increases the absorption of gaseous products such as CO2 and decomposes short-chain hydrocarbon fragments back into the solution thus hindering the forward reaction. For the tested P
T of 2.41 to 3.45 MPa, the results indicated that 2.41 MPa is appropriate. A longer reaction time of course gives better performance. At 500 rpm, 483 K, 2.41 MPa, and 180 min, the η
DMP and η
TOC are 93 and 36%, respectively.
Abstract:The mechanical heat treatment (MHT) is one of the pre-treatment alternatives for conditioning the municipal solid waste (MSW) before its further separation, recovery and reuse. The MHT would result in the change of properties of constituents of MSW, making it suitable for separation. For example, the plastics may be softened and shrunken. Therefore, the MSW via the pre-MHT can be more easily separated into various fractions of resources such as metals, plastics, compost-like and primary refuse derived fuel (RDF) or bio-char for further re-utilization.The objective of this study was to examine the efficiency and effective of energy recovery and volume downsize of plastics via MHT process. The commonly used plastic, high-density polyethylene (HDPE) was tested. The changes of weight, triple components, true density and calorific value of target plastic before and after the MHT with saturated steam at 100, 150 and 180 o C were examined. The effects of temperature on the performance of MHT were assessed. The results indicated that an increase of MHT temperature induces more significant shrinkage and higher volume density, enhancing its feasibility for the separation from non-plastic materials. The information obtained in this study is useful for the rational design and proper operation of MHT system for treating the used plastics in the MSW and separating it for the re-utilization as energy resource.
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