Although the methane fermentation process requires less energy and the collected gas may be used as a fuel, the reaction speed is slow. It leads to the large size reactor and high cost. Therefore, to investigate the practicability and efficiency of the Methane Fermentation as the waste disposal system from the perspective of energy production, advancement of load and reduction of discharge, the thermophilic methane fermentation tests were carried out at the temperature of 55°C changing the loading rate from 2.28 kg-VS/m3/d to 9.90 kg-VS/m3/d continuously. The fermentation could be stable under the following condition, HRT: over 10 days, loading rate: under 9.29 kg-VS/m3/d, moisture percentage: over 90%, Nitrogen content: under 0.0020 kg-N/kg. In case of that the nitrogen concentration in the treated waste is higher, the dilution water is necessary to control the concentration of nitrogen. In the thermophilic methane fermentation, two times more additional water is necessary compared with the mesophilic methane fermentation. The obtained net energy was two times greater by the thermophilic methane fermentation than by the mesophilic methane fermentation in the condition that the additional water for the waste was unnecessary. On the other side, there was no great difference between thermophilic and mesophilic methane fermentation in the condition that the additional water was necessary.
The research is proceeding on the process development to manufacture calcium acetate which is an environmentally adaptable deicer by means of wet oxidation of organic wastes. In the current research, separation and concentration of calcium acetate in an aqueous solution obtained by the process were investigated, using reverse osmosis membrane and ion-permeable membrane independently and in combination. Calcium acetate was highly concentrated with each methods. Moreover, separation of acetic acid and formic acid, which was a product produced by a wet oxidation reaction of organic matter as well as acetic acid, was possible by performing multi-stage separation and concentration using a reverse osmosis membrane.
It is important to establish the efficient removal method of the tramp elements such as copper and tin in recycling ferrous scraps, because the elements cause adverse effects on the mechanical properties of steel products. In the present study, the activity coefficient of copper in molten iron is increased by adding silicon and/or carbon, which have a strong affinity with iron, and the effects of silicon and carbon on the evaporation rate of copper in molten iron have been investigated at 1923 K under the chamber pressure of 133 Pa. In the case of the Fe-Si-Cu alloy, the apparent evaporation rate constant of copper has a maximum value at about 3mass%Si. The appearance of the optimum silicon content at which the copper evaporation rate is maximized can be thermodynamically explained. The enhancement effect of copper evaporation by the carbon addition is larger than that by the silicon addition. Moreover, the addition of both silicon and carbon introduced twice higher removal rate of copper. The optimum composition of Fe-Si-C alloy at which the copper evaporation rate is enhanced is around the composition of Fe-1.5mass%Si-3mass%C.
This study was carried out to manufacture portland cement clinker using low grade limestone and waste paper sludge. Waste paper sludges were added to supply CaO component in low grade limestone, because low grade limestone contains relatively poor CaO. The cement raw materials such as limestone, clay and iron-ore were obtained in Ssangyong cement in Donghae, waste paper sludge in Samil paper. Composition and texture of raw materials and cement mineral phases were investigated by XRF, XRD and DTA etc.. Portland clinker was made as follows. Modulus of mixture of raw materials was fixed in LSF = 94.0, SM = 2.4 and IM = 1.7. Raw materials are crushed, mixed and ground to fine powder, then put into furnace where it is heated to burning temperature. In here, CaF2 as a fluxing agent was used to facilitate burning. From the experimental results it appears CaF2 promotes that produces C2S at relatively low temperature of 1, 100°C. Cement minerals were produced as C2S at 1, 100°C and C3S at 1, 200°C. Also it was found that when water is added to cement minerals, there follows formation of cement hydrates such as C-S-H and ettringite.