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The application of biomass resources and sewage sludge is currently the most important issue in the field of coal combustion systems. The main drawback for operating a boiler system is its varied firing characteristics and low heating value. In this study, we have developed new synthetic fuels, namely hybrid sludge fuel (HSF), using coal and sewage sludge impregnated bioliquid (molasses) and evaluated their properties by comparison with conventional fuels. To prepare the HSF, it was treated in a carbonization system at 250 °C. Depending on the van Krevelen diagram, the fuel quality of HSF was superior to that of raw bioliquid and sewage sludge. In addition, its fuel characteristic was similar to sub-bituminous and bituminous coal. Thermogravimetric analysis (TGA) indicated only a single-stage combustion pattern for HSF during non-isothermal heating. To clarify the unburned carbon (UBC) content, an ultimate analysis was conducted. The amount of UBC of the HSF was much more than that of sewage sludge, but less than that of coal. To investigate the surface hydrophobicity of HSF, Fourier transform infrared spectroscopy (FT-IR) analysis and a moisture re-adsorption test were carried out. The HSF possessed high hydrophobicity and presented a low moisture re-adsorption rate compared to conventional fuels. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents results obtained from the industrial-scale co-firing of bioliquid fuels. The co-firing of bioliquid is an interesting alternative to the co-firing of solid biomass. The chemical and physical properties of the most abundant biofuels to be co-combusted in PC boilers, i.e. crude glycerine, palm oil and rapeseed oil, were determined. Glycerine was found to be the most attractive fuel because of its properties, availability and price. Therefore glycerine was chosen for the test co-firing in PC boilers with a capacity of 100MWth and 200MWe installed in respectively CHP ROKITA and PS Kozienice. The primary objective of the research was to determine whether crude glycerine can be used as a co-firing fuel for industrial boilers in utility plants. Preliminary laboratory-scale co-firing tests were carried out. On the basis of the test results two burner designs were developed. One is a gas-dynamic burner with steam-biofuel (submicron-fine) atomization. This burner can burn any “difficult” liquid fuel at a rate of 1.5t/h. The other design is a multi-jet burner with two-medium (steam and air) atomization, high outflow velocities and a capacity of 300–600kg/h depending on the atomization medium and glycerine pressure at the burner head inlet. The two types of burners differ in the extent of the liquid fuel spray area. Tests of crude glycerine co-firing in two PC boilers: OP-130 and OP-650 were carried out. The tests focused on the effect of the liquid biomass-glycerine combination on the combustion behaviour. An analysis of the burnout from the co-firing was carried out. The operating boiler parameters in the two tests were compared, taking into account the emission of such pollutants as NO x and SO2. [Copyright &y& Elsevier]

This study reports the results of a detailed analysis of 203 samples of bioliquid used as a substitute for heavy fuel oil in oil-fired power plants. Bioliquid is a mixture of various vegetable oils, animal fats and its byproducts. The heating value of bioliquid is approximately the same as that of heavy fuel oil; however, bioliquid has significantly less N and S components and exhibits better combustion reactivity. For a commercial electricity generation, demonstration tests firing bioliquid in 75, 90, and 100 MW oil-fired boilers were conducted, and the results were compared with those obtained by firing heavy fuel oil. Further, the impacts of bioliquid fuel characteristics on combustion and boiler operation were also investigated. During the bioliquid firing, the heat absorption in the furnace decreased and the furnace exit gas temperature increased in comparison to the heavy fuel oil firing. No serious problems occurred in the boiler operation, and NOx and SOx emissions remarkably decreased. With minor modifications on the fuel transfer system and atomization devices, bioliquid could successfully replace heavy fuel oil in the existing oil-fired boilers. The limited values for 18 fuel properties of bioliquid are suggested by considering the stable boiler operation and environmental safety. • The characteristics of 203 bioliquid samples are analyzed compared to heavy fuel oil. • Kinematic viscosity and heating value of bioliquid are 8 and 89% of heavy fuel oil. • Bioliquids can be burned in heavy fuel oil fired boilers with minor modifications. • Emissions are reduced by 30% for NOx and 93% for SOx with lower fuel-N and –S. • Specifications are proposed for bioliquid fuel used in heavy fuel oil fired boilers. [ABSTRACT FROM AUTHOR]

This study compared the combustion characteristics between bioliquid and heavy fuel oil using a 0.7 MWth pilot furnace and a 75 MWe power generation boiler. The bioliquid flame in the pilot furnace was clearer and more transparent, but higher gas temperature in the burner zone, compared to the heavy fuel oil flame. It might be due to higher sooting tendency of the heavy fuel oil flame. Due to the lower N and S contents in bioliquid, NOx and SOx emissions were significantly reduced in the bioliquid combustion tests. For the bioliquid demonstration in a 75 MWe power generation boiler, bioliquid firing led to decrease in heat flux to the furnace wall, so the furnace exit gas temperature was increased, comparing to the heavy fuel oil firing. Subsequently, the heat absorption in the first pass of the boiler was increased and finally it led to the increase in reheater de-superheating water spray flow rate. Significant reductions in NOx and SOx emissions were achieved with bioliquid firing. The operation and measured data in the bioliquid demonstration tests showed the successful operation of the unit, and no operational or emissions limitations were identified. • The combustion characteristics of bioliquid were compared to those of heavy fuel oil. • The bioliquid flame was clearer and more transparent due to lower sooting tendency. • Significant reductions in NOx and SOx were achieved with bioliquid firing. • Bioliquid firing tests at 79 MWe showed no operational or emissions limitations. [ABSTRACT FROM AUTHOR]