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Hydrometallurgical Waste Production and Utilization
Published in Sehliselo Ndlovu, Geoffrey S. Simate, Elias Matinde, Waste Production and Utilization in the Metal Extraction Industry, 2017
Sehliselo Ndlovu, Geoffrey S. Simate, Elias Matinde
In ideal situations, leaching gives rise to two end products: a solid residue that is in most cases devoid of valuable metals and is destined for the tailings dumps, and the other, a metal-laden solution that advances to the next stage of processing. In other situations, however, the solid residue can contain some valuable metals that, if unrecovered, can be lost to the environment. On the other hand, the residue can also contain some toxic components that, if left untreated, would have a negative impact on the environment. These toxic components will therefore need to be removed before disposal. Thus, modern developments in the hydrometallurgical flowsheet design consider the processing of waste streams in order to recover valuable metals if any and to reduce the level of toxicity of the final discharge stream.
A review on the co-processing of biomass with other fuels sources
Published in International Journal of Green Energy, 2021
Latex bearing plants can act as a substitute for crude out and thus these can be processed by extraction and cracking to get fuel oils. The stems and leaves of the latex bearing plants such as Tabernaemontana divaricata, Alstonia scholars, Euphorbia geniculata, and Thevetia peruviana were considered for the content of biocrude in them (Sharma and Prasad 1986). These studies presented a possible pathway of getting hydrocarbon oil, pyrolytic oil, and nonpolluting char from latex bearing plants. The biocrude so formed can be used as a substitute for petroleum crude. The spent residue itself can also be used to get tar oil, methanol, acetic acid and solid char as fuel (Ahmaruzzaman and Sharma 2007a; Sharma and Prasad 1986). Thermal cracking of Calotropis procera latex at 200–400°C was carried out and studies on dynamics of chemical reactions showed that the process was a hydrogen-transfer (H-T) hydrocracking under ambient pressure conditions (Sharma 1994a). The hydrogen-rich cracked triterpenoids act as the hydrogen donors during the process, where the nascent hydrogen atoms and the free radicals chemically plug the cracked moieties to stabilize them.
Fuel gas production from dusty tar pyrolysis
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2018
Dongdong Cao, Lin Du, Ze Wang, Wenli Song, Songgeng Li
Dusty tar from fast pyrolysis of a bituminous coal consists of 45% (wt%) dust and 55% tar (wt%). Tar is composed of light organic fraction (LF) and heavy organic fraction (HF). LF has a boiling point less than 360°C, while HF has a boiling point higher than that (Huang et al. 2014). In this work, the content of LF and HF with dust (HF + dust) in dusty tar was determined by heating the sample in a reactor from 25 to 360°C in N2 atmosphere, with a heating rate of 10°C/min. The residue is weighed. The vapors are condensed at −15°C and also weighed. Herein, the obtained (HF + dust) is 64.5% and LF is 35.5% (34.9% obtained + 0.6% loss). The proximate analysis of dusty tar was performed according to the National Standard of China (GB/T 212-2008). The ultimate analysis of dusty tar was conducted with an elemental analyzer (MACRO cube, Elementar Vario, Germany). The result is given in Table 1.
Dewatering and low-temperature pyrolysis of oily sludge in the presence of various agricultural biomasses
Published in Environmental Technology, 2018
Song Zhao, Xiehong Zhou, Chuanyi Wang, Hanzhong Jia
The potential effect of various biomasses, such as rice husk, walnut shell, sawdust, and apricot shell, on the dewatering and pyrolysis of oily sludge had been thoroughly studied. The presence of biomass significantly enhanced the dewatering performance, exhibiting a gradually increase in dewatering efficiency with the increase of biomass addition within 0–1.0 wt % in original oily sludge. During the co-pyrolysis process of dewatering oily sludge, the oil recovery increased by 5% in the presence of 0.2 wt % of biomass such as rice husk and sawdust. The improved oil recovery could be attributed to the participation of biomass in the prolysis process, which could eliminate the uneven heat transfer and provide more energy for pyrolysis. The recovery oil had higher C13–C19 aliphatic contents with less heterochain compounds compared with original oily sludge, which is in favor of its application as fuel such as diesel oil. In addition, the presence of biomass played an important role for the increase in calorific value of pyrolysis residue and controlled the pollution components of the exhaust gas discharged from residue incineration. According to analysis, the heavy metals of pyrolysis residue will be likely to be applied to the desulfurization material. The solid residue could be used as fuel in the incineration process. The obtained results provided valuable information on applying biomass as an additive agent in dewatering and prolysis processes of oily sludge.