Studies on the Gasification Performance of Sludge Cake Pre-Treated by Hydrothermal Carbonization

Abstract

Proper treatment and careful management of sewage sludge are essential because its disposal can lead to adverse environmental impacts such as public health hazards, as well as air, soil, and water pollution. Several efforts are being made currently not only to safely dispose of sewage sludge but also to utilize it as an energy source. Therefore, in this study, initiatives were taken to valorize sewage sludge cake by reducing the moisture content and increasing the calorific value by applying a hydrothermal treatment technique for efficient energy recovery. The sludge cake treated at 200 °C for 1 h was found to be the optimum condition for hydrothermal carbonization, as, in this condition, the caloric value of the treated sludge increased by 10% and the moisture content removed was 20 wt.%. To recover energy from the hydrothermally treated sludge, a gasification technology was applied at 900 °C. The results showed that the product gas from hydrothermally treated sludge cake had a higher lower heating value (0.98 MJ/Nm3) and higher cold gas efficiency (5.8%). Furthermore, compared with raw sludge cake, less tar was generated during the gasification of hydrothermally treated sludge cake. The removal efficiency was 28.2%. Overall results depict that hydrothermally treated sewage sludge cake could be a good source of energy recovery via the gasification process.

Energy Analysis of an Integrated Plant: Fluidized Bed Steam Gasification of Hydrothermally Treated Biomass Coupled to Solid Oxide Fuel Cells

“…During the process the reactions of dehydration, dechlorination, denitrification, and coalification take place improving fuel properties of the treated substrates [46]. Hydrochars generally exhibit higher heating values, higher ash fusion temperatures, and reduced sulfur, chlorine, and nitrogen contents compared to the raw biomass [27,47,48]. Also, if the volatile matter content is reduced, then the produced syngas could have less tar [45].…”

“…Lee et al [27] carried out air gasification experiments on hydrochar produced by HTC of sewage sludge. The results demonstrated that the product gas increased its LHV by 0.98 MJ/Nm 3 and cold gas efficiency by 5.8% more, compared to the product gas obtained by the gasification of the non-treated feedstock.…”

Gasification Applicability of Korean Municipal Waste Derived Solid Fuel: A Comparative Study

“…Moreover, the gasification characteristics were compared by utilizing lower heating value (LHV) gas , which is the low heat generated by-product gas and yield of product gas from feedstock (Y gas ), which indicates the gas yield. Many studies [2,19,[22][23][24] have used the following formulas (1)-(4) to evaluate the gasification characteristics. Here, Q gas represents the total flow rate of the product gas and m feeding denotes the mass of the injected feedstock.…”

Syngas Production, Clean-Up and Wastewater Management in a Demo-Scale Fixed-Bed Updraft Biomass Gasification Unit

“…Gasification technologies for small-and medium-scale combined heat and power (CHP) generation from waste biomass have been significantly developed in the last decades [10]. Most of the attention is focused on fixed-bed downdraft processes, typically available for a capacity between 200 and 700 kW th [11][12][13], but few studies also consider bubbling [14,15] or circulating fluidised-bed [16] gasification processes, sometimes promoted with specific catalysts [17] or integrated with hydrothermal carbonisation to treat high-moisture biomass [18]. With respect to these technologies, fixed-bed updraft gasification allows a better conversion efficiency (thanks to the countercurrent heat exchanges) [4] and it is typically characterised by simple construction, easy operation, fuel flexibility in terms of type (biomass, coal, wastes, etc.…”