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Yu M.M.,University of British Columbia | Masnadi M.S.,University of British Columbia | Grace J.R.,University of British Columbia | Bi X.T.,University of British Columbia | And 2 more authors.
Bioresource Technology | Year: 2015

This work studied the feasibility of co-gasification of biosolids with biomass as a means of disposal with energy recovery. The kinetics study at 800°C showed that biomass, such as switchgrass, could catalyze the reactions because switchgrass ash contained a high proportion of potassium, an excellent catalyst for gasification. However, biosolids could also inhibit gasification due to interaction between biomass alkali/alkaline earth metals and biosolids clay minerals. In the pilot scale experiments, increasing the proportion of biosolids in the feedstock affected gasification performance negatively. Syngas yield and char conversion decreased from 1.38 to 0.47m3/kg and 82-36% respectively as the biosolids proportion in the fuel increased from 0% to 100%. Over the same range, the tar content increased from 10.3 to 200g/m3, while the ammonia concentration increased from 1660 to 19,200ppmv. No more than 25% biosolids in the fuel feed is recommended to maintain a reasonable gasification. © 2014 Elsevier Ltd. Source


Masnadi M.S.,University of British Columbia | Grace J.R.,University of British Columbia | Bi X.T.,University of British Columbia | Lim C.J.,University of British Columbia | And 4 more authors.
Renewable Energy | Year: 2015

Recent environmental sharp curbs on fossil fuel energy systems such as coal power plants due to their greenhouse gas emissions have compelled industries to include renewable fuels. Biomass/coal co-gasification could provide a transition from energy production based on fossil fuels to renewables. A low-ash coal and switchgrass rich in potassium were selected on the basis of previous thermogravimetric studies to steam co-gasify 50:50wt% coal:switchgrass mixtures in a pilot scale bubbling fluidized bed reactor with silica sand as the bed material at ~800 and 860°C and 1atm. With the switchgrass added to coal, the hydrogen and cold gas efficiencies, gas yield and HHV of the product gas were enhanced remarkably relative to single-fuel gasification. The product gas tar yield also decreased considerably due to decomposition of tar catalyzed by switchgrass alkali and alkaline earth metals. Switchgrass ash therefore can act as inexpensive natural catalysts for steam gasification and assist in operating at lower temperatures without being penalized by an increase in product tar yield. An equilibrium model over-predicted hydrogen and under-predicted methane concentrations. However, an empirically kinetically-modified model was able to predict the product gas compositions accurately. © 2015 Elsevier Ltd. Source


Masnadi M.S.,University of British Columbia | Grace J.R.,University of British Columbia | Bi X.T.,University of British Columbia | Lim C.J.,University of British Columbia | And 4 more authors.
Energy | Year: 2015

Recent regulatory sharp curbs on coal power plants have compelled industries to adopt alternative sources of fuels. Biomass/fossil fuel co-gasification could be a pathway through more sustainable energy production technologies. As a basis for co-gasification study, the characteristics of single-fuel switchgrass and coal steam gasification in an atmospheric pilot scale bubbling fluidized bed reactor were studied. Increasing the steam-to-fuel ratio at 860°C caused a moderate increase in the H2 and CO2 concentrations and decreases in the CO and CH4 concentrations, due to more steam-CH4 reforming and water-gasification reaction of CO. With increasing reactor temperature, the H2 concentration increased, whereas the CO, CH4, and CO2 concentrations fell slightly. Fall switchgrass gasification resulted in higher carbon, hydrogen and cold gas efficiencies than spring harvest gasification, possibly due to higher potassium concentration and hence, greater reactivity of the fall switchgrass. The equilibrium model was unable to predict the syngas composition properly. Adding an extra methanator stoichiometric reactor to produce methane based on the empirical CH4 concentration, and removing part of the carbon, hydrogen and steam before introducing the feed and gas agent streams to the reactor based on experimental carbon, hydrogen, and steam efficiencies, the kinetically modified model predicted the syngas composition accurately. © 2014 Elsevier Ltd. Source

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