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Coal is the main fuel for the direct reduced iron (DRI) plants of India, which are one of the major sources of fly ash generation. The generation of fly ash and its disposal has raised concern because of the environmental impacts. In the present study, two different fly ash samples were investigated to explore the scope of recovery of combustibles....
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... sample was placed on the top sieve and covered with a lid and a pan was placed after the bottom sieve to collect the finest fraction. The whole setup was then placed on a ro-tap sieve shaker, which rotates the entire stack of sieves along with gentle tapping ( Figure 3). Sieving was done for 15 min. ...
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Citations
... Discharges into the water by the rolling and pickling sections. [103] 15-16 (kg/ton liquid steel) [105] 10-20 kg/ton liquid steel [5] 12 kg/ton steel [104] 250 kg/ton DRI [106] ...
Steelmaking and ferrous metal processing companies are suppliers of great importance to a wide array of industries, thus being quintessential for the social and financial growth of regions and countries. Most used processes (i.e., blast furnace, basic oxygen furnace, and electric arc furnace-based) are, however, highly pollutant, generating hazardous wastes that were usually landfilled. Generated wastes are important sources of secondary raw materials such as zinc and iron, presenting interesting market value. Hence, aiming to develop green procedures, industries have been using diverse approaches to treat and detoxify hazardous wastes, extract and reuse added value components, or even use their existing infrastructures to convert the wastes generated by other industries into secondary raw materials for steel manufacturing. This paper reviews the main industrial processes, focusing on the waste-generating steps, and discloses the most recent and relevant industrial synergies toward a circular economy. The final contribution of this study consists of the compilation of industrial synergies and recovery technologies for the steelmaking and metal processes.
... Such high ash coal is available either as run of mine coal or as middling/reject coal from metallurgical coal washeries. Due to poor combustion characteristics of high ash coal, pollution level from Indian thermal power plants is on the higher side along with higher (35%) unburned carbon in ash [4]. To reduce environmental pollution and unburned carbon in ash, blending coal with suitable biomass or high VM coal has been recommended by various scientists [3,5]. ...
This work presents the combustion studies of high ash coal, wheat straw (WS), wheat husk (WH) and their blends to enhance the combustion performance of high ash coal. Coal, WS and WH were characterized by proximate analysis, ultimate analysis and gross calorific value (GCV) determination. Combustion performance of individual fuel and their blends were assessed by thermogravimetric (TGA) investigation followed by the study of various burning profile parameters such as ignition temperature (Ti), peak temperature (TP), burnout temperature (Tb), ignition index (IIX), combustion characteristics index (CIX) and burnout index (BIX). Experimental results show that coal has poor combustion characteristics compared to WS and WH. After the addition of 20% WS with coal Ti reduces from 383 °C to 257 °C, TP reduces from 452 °C to 287 °C, Tb reduces from 509 °C to 507 °C. Combustion performance indices analysis inferred that after the addition of 20% WH with coal, IIX improved from 2.81 to 5.14 mass²/min² OC³ and CIX improved from 3.58 to 8.11 mass/min² °C³. Activation energy (AE) analysis shows that coal having higher AE (82.13 kJ/mol) compared to WS (57.97 kJ/mol) and WH (56.56 kJ/mol). Based on ΔH, ΔG and ΔS analysis it was observed that individual combustion of coal is difficult compared to WS and WH combustion, whereas blending of WS/WH makes the combustion process significantly favorable.
... For example, in Finland, a tax price for one ton of FBCFA is 80 EUR. In addition, in populous countries such as India, there is a need to save agriculture and forest land from eventual fly ash dumping [4]. Hence, applications in which FBC fly ashes could be utilized efficiently have been studied widely and are reviewed in the current article. ...
... Some FBCFAs contain a high amount of unburnt carbon, which causes energy loss, prevents their utilization in concrete, for instance, and increases the fly ash total amount. Jain et al. [4] studied two different FBCFA samples to explore the scope of the recovery of combustibles. The first ash sample did not show any recovery potential, but the second ash sample indicated that about 40% of the material could be recovered, with 35% fixed carbon and a 10,841 kJ kg -1 gross calorific value. ...
Traditionally fly ash is thought to be glassy, spherical particle originating from pulverized coal combustion (PCC) at temperature up to 1700 °C. However, nowadays fluidized bed combustion (FBC) technology is spreading quickly around the world as it is an efficient and environmentally friendly method. FBC is also able to utilize mixtures of low-grade solid fuels (e.g., coal, lignite, biomass, and waste) that have fluctuating quality, composition, and moisture contents. However, this leads to a high variation in the produced fly ash quality, unlike PCC fly ash, and hence challenges when attempting to utilize this fly ash. In this study, the utilization of fluidized bed combustion fly ash (FBCFA) was reviewed using the Scopus database. The most promising utilization target for FBCFA from biomass combustion is as a fertilizer and soil amendment. In construction, the FBCFA from various fuels is utilized as cement replacement material, in non-cement binders, as lightweight aggregates and cast-concrete products. Other types of construction applications include mine backfilling material, soil stabilizer, and road construction material. There are also other promising applications for FBCFA utilization, such as catalysts support material and utilization in waste stabilization.
... Underground mining leads to surface subsidence and water pollution (Lechner et al., 2014;Xu et al., 2014;Bukowski, 2015). The coal gangue emitted from the process of coal mining and coal washing (Deshpande and Shekdar, 2005;Wei et al., 2010) and the fly ash produced by coal combustion (Oz et al., 2009;Shoumkova, 2011;Osmanlioglu, 2014;Jain et al., 2016;Mandal and Sinha, 2017) accumulated on the Earth's surface, occupied a lot of land and caused pollution to environment. Coal gangue and fly ash contains contaminants such as mercury, cadmium and arsenic (Wang et al., 2013). ...
Cemented coal waste backfill material (CCWBM) is made of coal gangue, fly ash and cementitious materials. It has been widely used in the field of backfill mining to control surface subsidence and protect the environment. A large number of unconfined backfill bodies without lateral support are formed in partial backfill mining. To study the failure characteristics of unconfined CCWBM body in partial backfill, the stress–strain curves of the CCWBM were obtained by uniaxial compression tests at different ages (1–28 d). The central pressure was measured by the embedded pressure sensors. The failure characteristics of the specimen were monitored by acoustic emission (AE) positioning technique. Three observations can be made.
1. The central pressure variation curves lag behind the mean stress change curves. The central pressure curve can be divided into three stages: slow increase stage, rapid growth stage and decline stage. It has two pressure manifestations: early appearance and peak appearance. They can be as the failure precursor and instability critical, respectively.
2. The specimen forms a central elastic bearing area in the process of compression. The plastic area develops to the inner side with the increase of pressure, and an upper and lower compound cone-shaped residual area is finally formed.
3. The embedded pressure sensor can be used to monitor the instability of the unconfined backfill body. The research results can provide guidance for the in-situ stability monitoring and reinforcement of unconfined CCWBM body in partial backfill.
