Small-scale forward smouldering experiments for remediation of coal tar in inert media (original) (raw)
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Fuel, 2015
This study presents the development and validation of a computational model which simulates the propagation of a smouldering front through a porous medium against unique experiments in coal tar and sand. The model couples a multiphase flow solver in porous media with a perimeter expansion module based on Huygens principle to predict the spread. A suite of two-dimensional experiments using coal tar-contaminated sand were conducted to explore the time-dependent vertical and lateral smouldering front propagation rates and final extent of remediation as a function of air injection rate. A thermal severity analysis revealed, for the first time, the temperature-time relationship indicative of coal tar combustion. The model, calibrated to the base case experiment, then correctly predicts the remaining experiments. This work provides further confidence in a model for predicting smouldering, which eventually is expected to be useful for designing soil remediation schemes for a novel technology based upon smouldering destruction of organic contaminants in soil.
Chemical Engineering Science, 2007
This work measured the rates of burning of three coal chars. This was done by adding small batches (∼ 3 mg; particle size 106-150 m) of a char to a hot bed of silica sand (diam. 90-126 m) fluidised by different mixtures of O 2 + N 2 , varying from 0 to 100 vol% O 2 . The bed was electrically heated and maintained at 700, 800, 900 or 950 • C. The concentrations of CO 2 and CO in the gases leaving the bed were continuously measured after adding a batch of char and used to derive the rate of oxidation of carbon. It was found that [CO]>[CO 2 ] in the off-gas. The indications are that C s + 1 2 O 2 → CO is a major reaction of a coal char, with the CO being oxidised in a fluidised bed to CO 2 either in bubbles or on top of the hot sand.
Modelling Heat Losses in a Tar Sand Formation during Thermal Recovery Processes
International Journal of Engineering Inventions (IJEI), 2014
Heat losses to adjacent formations jeopardize the efficiency of thermal recovery operations. Predicting these energy losses is important in the design of a thermal recovery project. The case study is a steam flood project where heat losses from a tar sand formation is mathematically modeled based on pertinent assumptions. The heat loss model was developed using the law of conservation of energy, with heat energy as a function of the properties of the tar sand formation and the heat-carrying fluid. Solutions of this model were obtained using the MATLAB software. Sensitivity analyses revealed that the rate of heat loss to the adjacent strata increased/decreased depending on the variation of the steam and tar sand formation properties. A variation of some properties had no significant effect on the rate of heat losses. Thus, it is vital in advance to gather adequate information especially of the tar sand formation so as to prepare an injection fluid whose properties would minimize heat losses to the cap and base rocks. This would increase the mobility of the oil and extend the life of the production well(s).
Flame behavior in heated porous sand bed
2007
This paper reports experimental and numerical investigations on the combustion characteristics of a lean methane–air mixture in a heated porous sand bed. The porous bed consisted of sand (SiO2) particles with a mean particle diameter of 0.56 mm. The horizontally placed quartz tube was heated externally to initiate the combustion reaction in the porous bed combustor. The stabilized flame location curve as a function of averaged mixture velocity was obtained for various equivalence ratios.
Analysis of Heating System in FBC of Sand Reclaimer
Thermal Science and Engineering, 2018
In recent years, the foundry sector has been showing an increased interest in reclamation of used sands. Grain shape, sieve analysis, chemical and thermal characteristics must be uniform while molding the sand for better casting characteristics. The problem that tackled by every foundry industry is that of processing an adequate supply of sand which has the properties to meet many requirements imposed upon while molding and core making. Recently, fluidized bed combustors are becoming core of ‘clean wastes technology’ due to their efficient and clean burning of sand. For proven energy efficient sand reclamation processing, analysis of heating system in fluidized bed combustor (FBC) is required. The objective of current study is to design heating element and analysis of heating system by calculation of heat losses and thermal analysis of fluidized bed combustor for improving efficiency.
Smoldering Remediation of Coal-Tar-Contaminated Soil: Pilot Field Tests of STAR
Environmental science & technology, 2015
Self-sustaining treatment for active remediation (STAR) is an emerging, smoldering-based technology for nonaqueous-phase liquid (NAPL) remediation. This work presents the first in situ field evaluation of STAR. Pilot field tests were performed at 3.0 m (shallow test) and 7.9 m (deep test) below ground surface within distinct lithological units contaminated with coal tar at a former industrial facility. Self-sustained smoldering (i.e., after the in-well ignition heater was terminated) was demonstrated below the water table for the first time. The outward propagation of a NAPL smoldering front was mapped, and the NAPL destruction rate was quantified in real time. A total of 3700 kg of coal tar over 12 days in the shallow test and 860 kg over 11 days in the deep test was destroyed; less than 2% of total mass removed was volatilized. Self-sustaining propagation was relatively uniform radially outward in the deep test, achieving a radius of influence of 3.7 m; strong permeability contras...
Testing of Fluidized Bed Combustor for Foundry Sand Reclamation
This paper studies thermal sand reclamation system. Also, study the need of compact thermal sand reclamation process for the smart foundry. This paper studies testing of newly developed fluidized bed combustor (FBC) for foundry sand reclamation. Here, chemically bonded No-bake Sand used for testing reclamation process. A fluidized bed combustor is a good alternative for small capacity foundry sand reclamation process. Fluidized bed combustor consists of inner-chamber, heating coil, insulation, nozzle and some standard size inlet and outlet pipes. This FBC system contains maximum 20 kg of foundry used sand which are chemically bonded No bake sand for testing. Testing of the system was done by using Taguchi technique. Process parameter selection for testing was temperature, sand holding time, and quantity of sand. And result checked for this three parameters was percent weight reduction of sand and required testing time or cycle time. By using Taguchi method we get optimum parameters combination to get the better result. We also test the required time to achieve temperature from atmospheric temperature to selected temperature for a test. We also check the grain size of reclaimed sand which comes from newly developed fluidized bed combustor. The requirement of such reclamation unit is very important than a previously developed sand reclamation unit. It generates alternative for small foundry sand reclamation process.
Effect of the Heat Transfer Surface on Prevention of Spontaneous Combustion of Coal
International Journal of Technology
The increased use of coal for power generation has increased the demand for low-rank coal, such as lignite and sub-bituminous coal, and during its supply, it may need to be stored for long periods. Because low-quality coal is more susceptible to spontaneous combustion than highquality coal, its storage could potentially cause work-related accidents. One method being developed to control the temperature of stored coal to prevent spontaneous combustion is the immersion of heat exchangers in coal piles. This method can be used to control the temperature during both the storage and transportation processes. The purpose of this study was to test this method and, in particular, study the effect of changes in the heat-exchange surface area on the effectiveness of temperature control. An experiment was set up to control the temperature of a laboratory-scale coal pile using a heat exchanger made from copper tubes. Coal samples were placed in a cylindrical container with a spiral-shaped heat exchanger, placed in the center of the cylindrical container, and cooled with ~27 o seawater. Tests were carried out using several configurations of heat exchanger dimensions to determine the effect of changing the ratio of heatexchange surface area to volume of combustible material. The test results showed that greater heat-exchange surface area produced a greater amount of cooling load and temperature difference.
Rudarsko-geološko-naftni zbornik
This study investigates the effect of variations of coal dust particles size on the rate of burning of coal dust particles in a 2-liter closed chamber. Coal dust was selected from three different mines with different sizes (149µm, 125µm, 105µm, 74µm, 63µm, 53µm, 44µm, 37µm) for explosion testing in a closed chamber of 2-liters. In this analysis, the concentration of coal dust was considered constant (10000 g/m 3), all tests were carried out at a pressure of 1.5 bar and the initial temperature was 25 °C. To calculate the burning rate, the explosion severity parameters of each sample, such as the maximum explosion pressure, the maximum rate of increase in pressure, and the explosion index must be determined during various tests. The results of the experiments show that by variating the size of the coal dust particles, the burning rate of the particles also changes and there is an inverse relationship between them. Coal dust particles with dimensions of 44µm and 37 µm have a higher burning velocity than other dimensions. Thus, with a reduction in the size of coal dust particles, the burning velocity of coal dust increases. The outcomes acquired in this examination are not just valuable in developing information on coal dust explosion processes, but also improve the measures needed to prevent coal dust explosions in coal mines.