Publication

Impact Factor: 8.0
https://www.sciencedirect.com/journal/journal-of-environmental-management

There is increasing attention on developing efficient processes including circular economyprinciples, and obtaining fuels from wastewater treatmentfeedstocks is among the most promising. As a wastewater treatment byproduct, sewage sludge is a source of lipids that can be converted to biodiesel in a transesterification process. Economic and environmental analysis have been applied to a 60 m3/h sewage sludge plant, exploring 32 process alternatives. Using solvent extraction from wet sewage sludge, the high cost associated with the drying step is skipped. The wet alternatives with low amounts of solvent and acid usage depicted higher performance compared to the dry ones. Incorporating additional extraction stages increases both the financial gains and environmental impacts. As a result, a multicriteria analysis is implemented to ascertain the optimum process based on different priorities. The case with 0.5:1 (v/v) of hexane to biomass ratio, 3-stage extractor, 60 min residence time and pH 4 was the optimum alternative in most criteria.

Impact Factor: 3.8
https://pubs.acs.org/journal/iecred

Natural gas conversion to liquid transportation fuels through Fischer–Tropsch synthesis (FTS) is an alternative approach compared to the conventional crude oil refining. In a gas-to-liquid (GTL) plant, natural gas is first converted to synthesis gas (syngas) and then to liquid fuels in an FT reactor. The distribution of liquid fuels being produced in the FT reactor depends on several factors including the catalyst, reactor type, operating pressure and temperature, chain growth probability (α), and so forth. The change in α along the FT fixed-bed reactor is affected by the temperature and H2/CO ratio. In this paper, a typical multitubular FT reactor was simulated with a variable α along the tube length. To do so, the reactor was discretized to 1000 small segments and the α model was modified to fit the wax concentration in the reference FT reactor data with a wax production capacity of 6900 kg/h. The developed FT reactor model was then used for the plantwide simulation of a GTL flowsheet with a larger wax production capacity of ca. 16,719 kg/h. The distribution of chemical species based on variable and constant α was compared. With a similar feed syngas composition, the wax mass fraction is 45.34% in the variable α scenario and is 41.02, 55.7, and 73.57% when α is fixed at 0.9, 0.92, and 0.95, respectively. In addition, sectioning of the FT reactor into two stages was considered to investigate the potential of volume reduction to produce ca. 16,719 kg/h of wax. The results suggest that the staged reactor has nearly 12% lower volume compared to the base case.