Investigation on co-firing of coal mine waste residues in pulverized coal combustion systems

Millions of tonnes of coal mine waste residues are piled up in dumping sites, causing serious environmental problems. Co-combustion in fluidized bed facilities is the most widespread alternative for the energy utilization of these by-products. However, no experiences have been so far reported of coal mine waste residues co-firing under pulverized fuel combustion technology. This work proves the technical feasibility of co-firing coal with up to 20% coal mine waste residues and investigates the impacts of transferring this co-firing alternative into a commercial unit. Experimental co-firing tests of coal mine waste residues were conducted on a 500 kWth pulverized fuel pilot plant. Regulated emissions (CO, CO2, SO2 and NOx) and visible flame radiation were monitored, obtaining regular and stable flicker and acceptable emissions levels for CO (200 mg/m3N) and NOx (700–800 mg/m3N). Finally, the impact analysis of co-firing coal mine waste residues in a full-scale pulverized fuel plant was performed by simulating the power cycle and combustion process in a 160 MWe pulverized coal combustion unit. Simulation results show the viability of this alternative in terms of plant efficiency, increase in power consumptions of auxiliary equipment and pollutant emissions for co-firing ratios under 10% in energy basis

Flame speed and Kst reactivity data for pulverised corn cobs and peanut shells.

Power generation using waste material from the processing of agricultural crops can be a viable biomass energy source. However, there is scant data on their burning properties and this work presents flame speed and explosion Kst data for two agricultural waste materials: corn cobs and peanut shells. Both parameters were measured on the ISO 1 m3 dust explosion equipment. Two coarse size fractions of corn cobs (CC) and peanut shells (PS) of size less than 500 μm were tested using the Leeds 1 m3 vessel and were compared with two pulverized coal samples. This is typical of the size fraction used in pulverized coal power stations and of pulverized biomass currently used in power generation. The explosion parameters minimum explosive concentration (MEC), rate of pressure rise (dP/dt), deflagration constant (Kst), peak to initial pressure rise (Pm/Pi), turbulent and laminar flame speeds were determined using a calibrated hemispherical disperser in the 1 m3 vessel. MEC were measured in the range of 0.6-0.85 in terms of burnt equivalence ratio, Øburnt, which were comparable to the coal samples. The measured Kst (25-60 bar m/s) and turbulent flame speeds (~1.3 m/s) were lower than for coal, which was a reflection of the lower calorific value. These results showed that these crop residues are technically feasible power plant fuels to burn alongside coal or as a renewable biofuel on their own

TORJREFACTION STUDIES OF VARIOUS OIL PALM BIOMASS

Oil palm biomass are the main agricultural wastes in Malaysia. However, biomass have relatively high moisture content, low energy density and durability against biodegradation. To overcome these problems, a pre-treatment method called as torrefaction process was applied in this work. Torrefaction process of empty fruit bunches (EFB), palm mesocarp fiber (PMF) and palm kernel shell (PKS) of size range 250-500 um were performed under inert atmosphere at mild torrefaction (200, 220 and 240 °C) and severe torrefaction (260, 280 and 300 °C) in the TGA and tube furnace. The objectives of this research work were to investigate the changes in the properties of torrefied biomass included CHNS content, calorific value, weight loss distribution, mass and energy yield, mass loss and internal structure. Torrefaction behavior and its kinetic have been studied and a model was proposed to predict the produced amount of torrefied biomass

Upgrading Bahan Bakar Jumputan Padat (BBJP) Sebagai Co firing Sistem Tenaga Uap Melalui Thermal Drying dan Fermentasi

The waste sorting process produces organic and inorganic waste. It can be converted into Solid Recovered Fuel with the addition of a maximum of 20% plastic, which can be used for co-firing coal combustion in steam power systems. High humidity levels and the condition of organic waste with its various constituent components require drying and other treatments to increase the calorie content. Types of organic waste treatment, methods of drying, and decomposition of organic waste went through a fermentation process. The research aims to identify the effect of fermentation, addition of biomass, and plastic shreds of BBJP products on density, ash content, chlorine, and calorific value. Dimensions of organic waste powder at a level of 50 mesh and plastic shreds of 5-10 mesh are aimed at increasing the pellet/SRF bond. Mechanical testing data in the form of compression testing resulted in a level of resistance that exceeded pellet strength requirements and increased by 67%. Chlorine and sulfur levels are approaching the limit, but ash levels are still high. The calorific value of pellets in the fermented organic waste specimen treatment produces a higher calorific value compared to other treatments. Research on converting waste into co-firing fuel in solid form with the criteria for calorific value and physical properties that comply with the technical requirements for co-firing steam-powered systems can still be optimized to produce fuel with a higher calorie content. Reducing chlorine, sulfur, and ash levels is done for a low-carbon and environmentally friendly combustion process

STUDY ON ASHES OF BLENDED COAL-BIOMASS FOR CO-FIRING SYSTEM IN A COAL FIRED BOILER

Biomass and coal blend combustion or co-firing is a promising combustion technology. However, significant development work is required before large-scale implementation can be realized. Issues related to successful implementation of coal biomass co-firing mainly for power generation should be identified. This paper presents the results of the study on blended coal-biomass characterisation, particularly the ash chemical composition and ash fusion temperature to predict the slagging and fouling propensity in a coal fired boiler. The coal used in this research has a calorific value of 5,067 cal/g and the ash fusion temperature of softening temperature in oxidation condition (softening temperature-ox) is 1,228ºC, while the biomass used was baggase, straw and rice husk with the calorific value of 4,144; 3,545; 3,301 cal/g and the softening temperature-ox of 1,303; 1,420 and >1,500ºC, respectively. Experimental results for some varieties of fuel blends indicate that the proportion of 95%-5% of coal and baggase has the highest softening temperature-ox of 1,225ºC. The blend of coal and straw resulted in the highest softening temperature-ox of 1,240ºC at 95%-5%, while the blend of coal and rice husk, the highest softening temperature-ox of 1,235ºC was reached at the proportion of coal and rice husk at 90%-10%. According to the slagging and fouling index, blended coal and straw shows the best performance compared to that of blended coal either with baggase or rice hus

Combustion of Agricultural Biomass - Issues and Solutions

Biomass is one of the oldest energy source known to mankind. Progress made so far in understanding of a rather complex direct combustion process allowed for a constant technology development. Increasingly stringent environmental requirements of the EU, especially in terms of the pollutant emissions, require development of new design solutions of the combustion system for residential hot water boilers fuelled by some form of solid biomass. The emissions are becoming even greater problem if, various residues from agricultural production are used instead of a wooden biomass, as they are becoming more desirable fuel due to their lower cost. In this paper, various issues related to the combustion of agricultural biomass are discussed. Attention is given to the problems associated with high volatile matter contents, presence of nitrogen, sulphur, chlorine and low ash melting temperatures. At the end, novel design modifications of a conventional residential biomass combustion system are proposed, as the well-known methodologies for combustion and emissions control applied in industrial-scale boilers are in most cases not suitable for small-scale units

Capacitance and Impedance Evaluations in Coconut Shells and Rice Husks Derived Activated Carbon Electrodes.

Solid polarisable activated carbon electrodes have been prepared from Coconut shells and Rice husks. The preparation process involved precursor pre-carbonizations and conversion to solid carbon discs, inert environment carbonization and C02 activation at 7500C. Electrochemical Impedance spectroscopy characterizations gave their Double layer Capacitances as 0.02Fg-1 and 0.17Fg-1 respectively. The electrodes developed polarization impedances were 627.9? for the coconut shells and 1316.5? for the rice husks units. Their XRD scans showed that the electrodes were principally carbon and silica. The low polarization impedance of the coconut shell electrode was attributed to the activated petroleum residue tar binding material. Keywords: Carbonization, Activation, Impedance spectroscopy, Polarization impedance, Double layer Capacitanc

Distillation of mallee biomass for eucalyptus oil extraction and thermochemical behaviour of the spent biomass

This thesis investigates eucalyptus oil extraction, nutrients release, carbon loss and structural changes of mallee leaf after steam distillation. Pyrolysis of the spent leaf was then conducted to study the biochar characteristics. The mallee leaf was also torrefied then combusted under pulverised fuel (PF) condition for examining the effect of torrefaction on particulate matter emission. The obtained knowledge and data significantly contribute to developing a mallee-based bioenergy system in the rural and regional Australia

Vegetable ashes as Supplementary Cementitious Materials

[EN] Approximately 140 billion metric tons of biomass are produced every year in the world from agriculture. The ashes resulting from firing agricultural wastes such as rice husk, sugar cane and others can be used as Supplementary Cementitious Materials (SCM). They can be mixed with lime alone or in ternary mixtures with Portland cement and lime. If fired at temperatures around 600-700 °C the agricultural ashes exhibit good reactivity. Despite extensive research work carried out on the use of agricultural ashes as source of SCMs, few success stories are reported on practical applications on an industrial scale. Details of the firing technology should be re-assessed, with special emphasis on the scale at which the technology begins to be economically suitable. Further research is also needed to understand the mechanisms of structural transformation of amorphous silica during calcination, and the impact of the ashes on cement hydration in blended systems.Martirena, F.; Monzó Balbuena, JM. (2018). Vegetable ashes as Supplementary Cementitious Materials. Cement and Concrete Research. 114:57-64. https://doi.org/10.1016/j.cemconres.2017.08.015S576411