The objectives of this study are to evaluate char component from pyrolysis of MSW as an applicable solid fuel and to research the mechanism of dechlorination during the pyrolysis not only by establishing the material balance but also by understanding the Cl behavior into pyrolysis products. The pyrolysis experiments have been performed with a RDF (Refuse Derived Fuel) obtained from actual MSW as a model sample. The RDF is pyrolyzed by an externally indirect heat source for an hour under nitrogen gas stream (7×10-2cm/s) at 250-800°C. The results show that; (1) The pyrolysis temperature of 500-600°C may be optimal to pyrolyze the RDF.(2) The char obtained by the pyrolysis can be used as a substitute for bituminous-class coals, meeting the following process targets: (1) Calorific value (d.a.f.), 32000-34000kJ/kg; Fuel ratio (ratio of fixed carbon to volatile matter), about 2 (-); (3) Degree of carbonization (H/C atomic ratio), 0.5 (-).(3) Provided the char formed by the pyrolysis below 600°C is subjected to be washed with water, the chlorine content in it could be reduced to the target (0.3-0.5wt%).
For the purpose of establishing recycle technology to reduce environmental load, technical and practical development of supercritical water (SCW) is required. That is non-catalytic hydrolysis expected to develop.SCW has some advantages in chemical processes. SCW can form a homogeneous phase with oil and gas and in addition, changing the conditions of SCW can be used to control equilibrium and reaction without catalyst. Dithionic acid, which is difficulty to decompose, is a Chemical Oxygen Demand waste generated during desulfurization. Experiments were conducted to hydrolyze ditionic acid in SCW. In the experiments, it was found that decomposition rate of dithionic acid was the same regardless of whether hydrogen peroxide was added or not. Dithionic acid occurred at 100% conversion at 350°C. The sulfuric acid ion/sulfurous acid ion concentration ratio increased with increasing the amount of hydrogen peroxide. Activation energy for decomposition of ditionic acid in SCW under non-catalytic conditions was determined to be 39kcal/mol and was slightly higher than activation energy of the catalytic reaction.
The authors investigated life cycle carbon dioxide and methane inventories for the exploration, exploitation and transportation (incl. their capital) of natural gas produced in Minami Nagaoka Natural Gas Field in Japan. Around 22% of total domestic natural gas production was exploited from the field in 2001. According to the results obtained through the investigation, 5.18g-CO2-eq. of carbon dioxide and methane is released by the exploration, exploitation and transportation of 1 MJ of the natural gas. The amount is almost 10% of the carbon dioxide emission by the combustion of the natural gas. Hence, the emission data by its production should be counted for precise implementation of LCA. The largest carbon dioxide emission source is the release of carbon dioxide which is extracted from underground with natural gas and separated from the target gas (CH4). The next largest emission is released natural gas during its transportation by pipe lines. Because of re-construction of roads or development of the route area, the pipe lines are required to detour. For the diversion process, certain amount of natural gas inside the pipes is released to the environment. These releases are more than 70% of the total GHG emission obtained by this investigation.