The impact of torrefaction temperature on the ignitability, fuel ratio and ash fusion temperatures of two tropical deciduous woods (Teak and Melina) were investigated in a setup of tubular furnace. The properties considered are calorific value, fuel ratio, ignitability index, ash compositions and ash fusion temperatures of the biomass. Six different temperatures (220, 240, 260, 280, 300 and 320 C) at 60 min reaction time were considered. The results indicated that as torrefaction temperature increased, the calorific value, fuel ratio and ignitability index of the biomass also increased. The ignitability index of biomass (40-63) was better than the value (35) recommended for fuel applicable in thermal plants for power generation. The ash compositional analysis revealed that there was no variation in the quantity of SiO 2 , Al 2 O 3 , CaO along with other minerals for the raw and torrefied biomass. This implied that the temperature up to 320 C has no significant impact on the compositions of biomass ash during torrefaction. The ash fusion temperature test showed that the biomass ash softens at % 1200 C and finally fused at % 1300 C. The study concluded that an increase in torrefaction temperature increases the thermal properties of the torrefied biomass without affecting the compositions of biomass ash or lowering the ash fusion temperatures.
Coal processing industries generate millions of tons of fines (<3 mm) during mining operation and are often considered as wastes. These wastes have enormous potential in serving as energy and metallurgical operation feedstock. One avenue for its use is densification into briquettes or pelletizes. Various briquetting techniques have been adopted in the past few decades; however, the main issues upfront in commercializing these techniques are significant binder cost and poor mechanical integrity. Therefore, the present study concentrates on utilizing commonly available organic binder along with pretreated biomass in developing coal fine briquettes. Briquettes were produced after initial pretreatment of the raw materials under a load of 2 tons. Briquettes were cured in an inert environment and eventually characterized for its main litmus requirements (physical properties). It was observed that pitch-molasses bonded briquettes have better physical properties leading to good mechanical integrity than briquettes produced from individual binder. The proximate, ultimate and calorific value analyses of the briquettes do not deteriorate but mildly improved compared to the raw coal fines. With a density of 1.18–1.32 g/cm 3 , drop to fracture that is greater than 100 (times/2 m), impact resistance index well above 6000, water resistance index of 99% and cold crushing strength of 9 MPa, pitch-molasses bonded briquettes clearly surpassed recommended physical properties benchmarked for briquettes of industrial and domestic end use. The physical properties of the briquettes favorably meet requirements as feedstock for rotary kiln direct reduced iron and COREX iron-making processes as well as fuel for thermal operations.
The evaluation of thermal decomposition characteristics and kinetic parameters of melina wood were investigated. Proximate, ultimate and calorific value analyses of the melina wood were carried out based on standards. Melina wood was subjected to multiple heating rates (5-15 C/min) in thermogravimetric experiment. Two prominent isoconversional methods (Flynn-Wall-Ozawa and Starink) were adopted to obtain kinetic parameters from the non-isothermal thermogravimetric analysis curves. The ash, volatile matter and carbon contents of the melina were 2.15, 81.42 and 47.05%, respectively, while the calorific value was 18.72 MJ/kg. The main devolatilization stage of melina ranged from 220 C to 350 C while 80% weight loss was obtained below 400 C. The activation energy varied between approximately 15 and 162 kJ/mol as a function of degree of conversion. The pre-exponential factors varied between 1.60E þ 2 and 5.67 E þ 12/min. The decomposition kinetic mechanism of melina is concluded to be a multi-step reaction.
Summary Torrefaction and densification are crucial steps in upgrading biomass as feedstock for energy generation and metallurgical applications. This paper attempts to discuss essential basics on biomass torrefaction and densification, which can propel developing nation to take full advantage of them. The most promising clean energy sources that have found applications in various areas are biomass materials, that is, both the lignocellulosic and non‐lignocellulosic. However, high moisture contents, low energy density, hydrophilic nature, poor storage and handling properties are the major drawbacks limiting its usefulness. Therefore, torrefaction as one of the major thermal pre‐treatment processes to upgrade biomass in terms of improved energy density, hydrophobic, moisture content and grindability has been discussed. The influence of temperature, residence time, particle sizes and gas flow rates on the properties of torrefied biomass has also been discussed. The advantages and disadvantages of various torrefaction technologies have also been highlighted. The possible areas of application of torrefied biomass especially densification into pellets and briquettes alongside the equipment required for it have been reviewed in this paper. The torrefied biomass can be deployed in the metallurgical industries as reducing agent in the development of sponge iron from iron ores of various grade including lean ones. The information gathered in this paper from peer‐reviewed articles will reduce the burden of seeking to understand the preliminaries of torrefaction process and its importance.
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