Azhar Uddin

Thermal and catalytic degradation of structurally different types of polyethylene into fuel oil

The degradation of four different types of polyethylene (PE) namely high density PE (HDPE), low density PE (LDPE), linear low density PE (LLDPE), and cross-linked PE (XLPE) was carried out at 430 °C by batch operation using silica-alumina as a solid acid catalyst and thermally without any catalyst. For thermal degradation, both HDPE and XLPE produced a significant amount of wax-like compounds and the yields of liquid products (58–63 wt%) were lower than that of LDPE and LLDPE (76–77 wt%). LDPE and LLDPE produced a very small amount of wax-like compounds. Thus the structure of the degrading polymers influenced the product yields. The liquid products from thermal degradation were broadly distributed in the carbon fraction of n-C5 to n-C25 (boiling point range, 36–405 °C). With silica-alumina, all of the polyethylenes were converted to liquid products with high yields (77–83 wt%) and without any wax production. The liquid products were distributed in the range of n-C5 to n-C20 (mostly C5–C12). A solid acid catalyst indiscriminately degraded the various types of polyethylene into light fuel oil with an improved rate.

Role of SO2 for elemental mercury removal from coal combustion flue gas by activated carbon

In order to clarify the role of SO 2 in the removal of mercury from coal combustion flue gas by activated carbon, the removal of Hg° vapor from simulated coal combustion flue gas containing SO 2 by a commercial activated carbon (AC) was studied. The Hg° removal experiments were carried out in a conventional flow type packed bed reactor system with simulated flue gases having a composition of Hg° (4.9 ppb), SO 2 (0 or 500 ppm), CO 2 (10%), H 2 O (0 or 15%), O 2 (0 or 5%), and N 2 (balance gas) at a space velocity (SV) of 6.0 × 10 4 h -1 in a temperature rang 60-100 °C. It was found that, for SO 2 containing flue gas, the presence of both O 2 and H 2 O was necessary for the removal of Hg° and the Hg° removal was favored by lowering the reaction temperature in the order of 60 > 80 > 100 °C. The presence of SO 2 in the flue was essential for the removal of Hg° by untreated activated carbon. The activated carbons pretreated with SO 2 or H 2 SO 4 prior to the Hg° removal also showed Hg° removal activities even in the absence of SO 2 ; however, the presence of SO 2 also suppressed the Hg° removal of the SO 2 -pretreated AC or H 2 SO 4 preadded AC.

Recycling of waste lubricant oil into chemical feedstock or fuel oil over supported iron oxide catalysts

The recycling of waste lubricant oil from automobile industry was found to be best alternative to incineration. Silica (SiO2), alumina (Al2O3), silica–alumina (SiO2–Al2O3) supported iron oxide (10 wt% Fe) catalysts were prepared by wet impregnation method and used for the desulphurisation of waste lubricant oil into fuel oil. The extent of sulphur removal increases in the sequence of Fe/SiO2–Al2O3<Fe/Al2O3<Fe/SiO2 and this might be due to the presence of smaller crystalline size (7.4 nm) of Fe2O3 in Fe/SiO2 catalyst. X-ray diffraction results suggest the presence of iron sulphide in the used catalyst. Gas chromatography with thermal conductivity detector analysis confirms the presence of H2S in gaseous products. In addition, Fe/SiO2 catalyst facilitated the formation of lower hydrocarbons by cracking higher hydrocarbons (≈C40) present in waste lubricant oil.

Pyrolysis of Polypropylene/Polyethylene/Polystyrene and Polyvinylchloride Mixed Plastics using CaCO3

The recycling of halogenated waste plastics poses serious problems. The pyrolysis of PP/PE/PS/PVC was performed by using CaCO3 sorbent to remove the chlorine content during the process. The presence of water (10 wt%) in the plastic mixture did not effect the characteristics of liquid products or the dechlorination efficiency of CaCO3 sorbent. The halogen free liquid products can be used as a feedstock in refinery or fuel oil.

Application of Micro- or Small-Scale Biomass-Derived Fuel System for Power Generation

Biomass being world’s largest renewable fuel source is now considered as the best alternate for fossil fuels owing to the CO2 saving nature as well as more economical as compared to fossil fuels. Although, some pretreatment process is required in order to utilize the raw biomass for power generation. There are various systems to generate power but combined heat and power (CHP) generation has proved to be the most beneficial method to generate electricity as well as heat by recovering the surplus heat to make an overall efficiency of up to 90 %. Various types of CHP systems have been discussed and compared for their working and efficiency along with their applications in different dwellings depending upon their power capacities. Moreover, biomass CHP systems have been thoroughly overviewed for their economic, energy, and environmental aspects.