Air Jigs Research Articles

A review of all aspects of dry coal cleaning methods and evaluation of widely used applications

Although there are many developments in the energy industry, coal still holds its vital place and seems to have a major role in future. That is why the direct utilisation of coal becomes impractical even impossible in those days. Thus, the aim of this review is for all aspects of dry coal cleaning methods be overviewed, analysed and evaluated, including the applicability to the industry in the face of wet methods. The density-based methods have potential than the other dry coal cleaning methods and have made great development within the coal preparation industry. The Ep values of air jigs or air tables are between 0.13 g/cm3 and 0.26 g/cm3, but fluidised bed separation method are between 0.03 g/cm3 and 0.07 g/cm3. It provides rivalry with wet methods and is a serious alternative for coal preparation. [Received: January 17, 2022; Accepted: July 20, 2022]

3D printed brachytherapy jig for Reference Air Kerma Rate calibration.

3D printing in modern radiotherapy allows users the ability to create custom devices which can be a valuable tool for use in brachytherapy source calibration. Radiotherapy centres may verify their brachytherapy source activity with a calibrated Farmer chamber. For this purpose, a jig was designed, 3D printed and commissioned for in-air source strength calibration. Measurements on four afterloaders with varied equipment and environments were completed. A full uncertainty budget was developed and measurements with the in-air jig were consistently within 3% of the certificate source strength, and within the 4.1% combined uncertainty for comparing a well chamber measurement (1.7%) with the in air jig (3.75%). By creating a jig that is able to be customised to multiple catheter sizes and cylindrical chamber designs, centres can be provided with the option of independently checking their source strength with ease and for little cost.

Construction and Demolition Waste Recycling through Conventional Jig, Air Jig, and Sensor-Based Sorting: A Comparison

The paper presents a comparison of the concentration methods conventional jig, air jig, and sensor-based sorting to treat construction and demolition waste. All tests were made with concrete, brick, and gypsum particles and the tests aim to separate these materials into different size ranges, depending on the method. The equipment tested, conventional jig, air jig, and sensor-based sorting present good results to concentrate construction and demolition waste particles, with different concentrations and mass recoveries. The results show particularly good mass recoveries and particle concentration for conventional jig, especially for concrete and gypsum particles. Sensor-based sorting should preferably use concentration circuits for best results.

Environmental performance of construction and demolition waste management strategies for valorization of recycled coarse aggregate

This study reports on a Life Cycle Assessment (LCA) comparison between two different Construction and Demolition Waste (CDW) management strategies to produce Recycled Coarse Aggregate (RCA): the current recycling strategy (RCA-C) versus air jig strategy (RCA-PR). Additionally, RCAs are compared to natural aggregate production. Air jig is proposed as a recycling strategy for CDW sustainable reuse and recycling. In contrast to RCA-C, air jig allows better CDW segregation, providing recycled materials with better quality. The results point out that recycling strategies differ in segregation efficiency, the quality of recycled material produced, and environmental performance. Both recycling strategies provided environmental benefits when compared to natural aggregate. RCA-PR presents better environmental performance due to the larger number of by-products generated as a result of using air jig and it is able to reduce the environmental impacts related to its management based on the benefits of its by-products. The results suggest that the production and transport of RCA are viable from an environmental point of view in larger urban centers. This study provides a better understanding of CDW management, enhancing knowledge on the environmental performance of the current practice and a future proposal recycling strategy. Moreover, it opens up a new perspective on the multifunctionality associated with recycling strategies of CDW and understanding about air jig environmental impacts.

COST ASSESSMENT OF THE BRAZILIAN CONSTRUCTION AND DEMOLITION WASTE RECYCLING PLANT: A CASE STUDY OF PORTO ALEGRE

The construction activities generate representative amount of Construction and Demolition Waste (CDW) around the world. Brazilian City Halls collected about 45 million tons/year. CDW recycling plants needs to be economically viable. The characteristics of recycling plants and future expectations vary around the world. Thus, the cost analysis needs to be adapted to the local reality and future scenarios should be evaluated. In this context, the objective of this paper is to evaluate the CDW recycling plant costs in Brazil. Two scenarios are tested, actual Scenario (1) and future Scenario (2), with air jig. Four steps are performed: literature review, inventory of the inputs, economic indicators analysis, and sensitivity analysis of alternative solutions. The results suggest that both scenarios do not reach positive economic indicators (IRR, NPV and Payback). The Fixed Costs are the main influence on the results, mainly due to the acquisition of Equipment. The Variable Costs represent, in Scenario 1 and 2, 18% and 10% of their Total Fixed Costs, respectively. Scenario 1, however, has possible conversion into positive IRR easier than for Scenario 2, once the Air Jig influence significantly in the increment of costs. A Government subsidy tested would not make the CDW Recycling Scenarios economically attractive. Only Scenario 1 can achieve positive results, however without the acquisition costs of Land, Equipment and Vehicles. Counterparts with the City Hall, in exchange for the supply of these inputs, would not influence the positive results. The use of new technologies maybe will be possible after the recycled aggregate market is consolidated in Brazil.

Destoning the Moatize Coal Seam, Mozambique, by Dry Jigging

This paper proposes pre-beneficiation studies by air jigs of the coal layers from a Moatize coal deposit. Pre-beneficiation, also called destoning, removes tailings before the beneficiation plant. The air jigs operate in the same granulometric size range as the heavy-media cyclones (HMCs) that are installed in the preparation plant. With the destoning, the heavy-media circuit operates with a lower coal feed and higher organic matter contents, increasing its cutting efficiency and lowering operational costs. The use of air jigs reduces the total water consumption in the plant, which is especially important for the region where the plant is installed, as water is particularly scarce. Four coal layers of the Moatize coal deposit were studied, which are currently exploited in the mine. As main results of the study, it is possible to say that the concentration of lights (feed of the preparation plant) and heavies (waste fraction) in air jigs can be carried out with reasonable efficiencies for all coal layers studied, making air jigs a feasible option for coal destoning.

Demolished concretes recycling by the use of pneumatic jigs

Large quantities of construction and demolition waste is generated annually around the world. Part of this material is processed in recycling plants. After removing metals, fines and lights, the construction and demolition waste is crushed and sized and can be used as aggregates for low resistance concrete, for road sub-base, city landfill and other low value-added applications. For their use as coarse aggregate in structural concretes, construction and demolition waste must exhibit high densities and regularity of the material. This material usually is presented in demolished concretes. About 20% of the particles from demolished concretes can be used as coarse aggregates substituting part of natural aggregates in structural concretes. This article presents studies of demolished concretes recycling by the use of a pneumatic jig. All jigging tests were carried out with three different concretes produced in three strength classes: C16/20, ordinary concrete; C50/60, high strength concrete; and C70/85, very high strength concrete. Based on density distribution of the three concretes, there are reasonable masses with densities over 2.7 g cm-3, particle density considered appropriate to the used as coarse aggregate for structural concretes. The concretes present different mass recoveries of the denser particles (different liberation). Coarse aggregates can be recovered with reasonable masses by the use of air jigs: About 65% for high strength concretes and about 75% for the low strength concrete. The jigging concentration efficiency depends on the concrete liberation, density and size distribution.

Development of dry coal gravity separation techniques

Dry separation method was used at the beginning of 20th century to separate coal separation process. First industrial applications of dry separation took place in the middle of 1930s. At that time air separator Frazer-Yankey, based on aero suspension was used in in Pittsburgh and Lundale, West Wirginia coal preparation plants. Later, some more constructions like RAW air jig, air table “V” type Birtley, air jig type Kirkup, air table “V” type Peale-Davis or air jig type Bruay-Soulary were constructed. Fast development of wet technologies of processes, especially jigging and heavy dense medium separation caused the discontinuation of the further development of dry separation methods and replacement of dry preparation plants with plants based on wet methods of enrichment. At the end of 20th century and beginning of 21st century dry separation method started once again to be widely used in the world. New types of equipment like FGX vibrating air table, TFX air jig or KAT process technology were introduced to wide applications in Asian countries. The paper describes few constructions of old air separators and new ones, used nowadays. It contains comparison of the separation results obtained by means of various equipment and shows possibility to separate coal in laboratory scale air jig.

Development of a new fine particle dry separator

Dry coal cleaning has generated renewed interest in scientific and coal mining communities alike due to water scarcity in many parts of the world and the numerous tailings ponds that have resulted from traditional wet coal preparation methods. Commercially available dry separation technologies such as air tables and air jigs are mostly effective in cleaning coarse coal with particle size larger than 6.35 mm. The smaller-than-6.35 mm fraction, which might be up to 20 to 40 percent of raw coal, is sent to the clean coal or tailings streams in a dry separation plant without any cleaning. The main objective of this study is to develop, design and fabricate a new density-based dry separator to effectively clean fine coal in the size range of smaller than 6.35 mm to larger than 1 mm. A difficult-to-clean coal sample with particle size smaller than 6.35 mm and flat-shaped shales as main rocks were used in this study. Using a laboratory-scale fluidization bed, the optimum air flow rate for fluidization of fine particles in air tables was found, which was much less than that for coarse coal. The perforations diameter and open area of the separating deck of the air table were also found to be critical for fine particle separation. These findings led to the development of a new air table named SIU Airtable for cleaning fine coal sized smaller than 6.35 mm and larger than 1 mm. The new air table has a unique air distribution and fluidization system for fine particles, along with adjustable vibration frequency and direction. It also has an optional extended section to lower the moisture content of high-moisture fine coal using part of the fluidization air. The experiments showed that an ash rejection of about 49 percent could be achieved with a combustible recovery of around 89 percent, indicating suitable separation. Furthermore, increasing ash rejection to 70 percent gives a combustible recovery of 72 percent, indicating that the separation performance of the new air table is close to the fine coal washability data.

Performance Optimization of a New Air Table and Flip-flow Screen for Fine Particle Dry Separation

ABSTRACT The mining industry has seen increased efforts toward achieving dry mineral separation owing to current and projected water scarcity and environmental problems associated with conventional wet processing methods. Commercially available dry coal separation technologies such as air tables and air jigs have proven effective in cleaning only the +6.35 mm while the −6.35 mm comprised of coal and impurities is discarded or used without further cleaning. To address this issue, a new density-based dry separator named SIU Airtable was developed. The main objective of this study was to evaluate the fine coal (6.35 × 1 mm) dry cleaning performance of the developed air table. The study also sought to evaluate the dry screening performance of the Liwell flip-flow screen to achieve efficient size separations at 1 and 2 mm. Two different Illinois No. 6 coal samples were used to optimize the new air table by varying its operating variables. The analysis of separation efficiency showed similar trends for both coal samples based on the cut point density (SG50) and probable error (Ep). Additionally, separation efficiency was significantly higher for the 6.35 × 3.36 mm size fraction and reduced when the size range was broadened to 6.35 × 1 mm. Product coal ash of 13.8–14.5% and tailings ash of 52.9–59.7% were achieved from the feed ash of 31–36%. Screening experiments on the Liwell flip-flow screen showed an efficiency of 88.7% and 85.1% achieved for the 1-mm and 2-mm polyurethane panels, respectively.

Usage of air jigging for multi-component separation of construction and demolition waste

The use of air jigging for performing multi-component separation in the treatment of mixed construction and demolition waste was studied. Sorting tests were carried out with mixtures of equal bulk volume of concrete and brick in which fixed quantities of unwanted materials - gypsum, wood and paper - were added. Experimental results have demonstrated the possibility to use air jigging to carry out both the removal of low-density contaminants and the concrete concentration in only one process step. In relation to the removal of contaminants only, the overall performance of jigging process can be comparable with that of commercial air classifiers and automatic sorting systems. Also, the initial content of contaminants seems does not have a significant effect on the separation extent. These results are of particular importance for recycling plants processing as they represent an alternative to optimize the use of air jigs. Further investigation is needed in order to evaluate the practical feasibility of such method.

Wall effects on particle separation in air jigs

This study investigates the influence of wall effects on particle separation in an air jigging device. Tests were conducted with a ternary mixture of concrete, brick and gypsum particles in the size range from 12 to 20mm for three different jigging times. It is shown that an unusual, remarkable segregation occurred in the direction perpendicular to the lateral walls, giving rise to a horizontal segregation pattern. In all cases, heavier particles concentrated more in the center of the particle bed while lighter particles concentrated along the side walls. Composition measurements of the stratified bed revealed that wall effects can significantly influence the composition of jig products. Linear predictions of jigging evolution suggest that stratification progress linearly after the first initial stages. Also, time evolution and analysis of local compacities indicate that stratification starts from the bottom to the upper layers of particle bed. Based on the experimental results, a mechanism for the pattern formation was proposed, which was enhanced by a geometry model of bed rearrangement. Prediction results for bed composition correlated well with experimental data and endorsed the role of lateral walls on the segregation pattern formed. The results obtained also show practical significance for the use of air jigging in the sorting of recycled aggregates.

Stratification in air jigs of concrete/brick/gypsum particles

This work deals with the separation of concrete, brick and gypsum particles from a CDW recycled aggregate mixture. Construction and Demolition Waste materials can be handled as an ore treatment problem. Efficient sorting processes of low quality CDW recycled aggregate could allow the reuse of concrete, brick and gypsum particles. The processes also improve the remaining mixed aggregates for recycling in unbound sub-base materials, by increasing their self-cementing properties and by reducing the sulfate content through the removal of gypsum. All tests were carried out in the size range between 4 and 20mm using a laboratory air jig. The aim of the work is to concentrate a high amount of gypsum (light material) and concrete (heavy material) particles. Three working parameters are relevant for the jigging processes control such as the sorting duration, the frequency and the expansion ratio. Each of them are studied. It was found that a quadratic model of the number of jig cycles, a product of the frequency and time, accurately predict well the sorting results, if the expansion is large enough. An optimal point seems achieved at about 320 jigging cycles. Concentrates with concrete contents higher than 90% and gypsum contents significantly lower than 1% were possible to be reached and can be an alternative in aggregates for the concrete market. Indeed, gypsum reduction in concrete concentrates was about 25 times. This level of reduction could be satisfactory in sorting real demolition products. On the other hand, contents of over 70% of gypsum concentrates were obtained, increasing the reuse and recycling abilities.

Effect of fluidizing characteristics on upgrading of lignitic coals in gravity based air jig

Two lignitic coals characterized by easy and difficult to wash were upgraded on a pneumatic semi-pilot scale Allair stratification jig. The fluidizing characteristics of lignites, i.e. apparent and cohesive minimum fluidizing air velocities, and Umfa and Umf-coh values were initially determined in a continuous system involving discharging units of the products (light and dense materials) in the presence of pulsed air. The effect of fluidizing conditions on separation conditions for −15+4mm coal samples was systematically investigated. Fluidizing air velocity and pulsation frequency were selected as the main parameters to determine the optimum separation efficiencies. The results reveal that separations at fluidizing air velocities of 1000–1200cm/s (approximately %100 of Umf-coh) yielded high separation performance. In addition, although easy to float coals exhibited good separation performance in a wide range of pulsation frequencies of 3–4s−1, particularly the difficult to float coal required a specific pulsation frequency of 3.5s−1. Under the optimum operational conditions, the ash contents of clean coal products were reduced down to the levels of 16–18% from 44% feed ash with the separation efficiencies of 41 and 53% for difficult and easy to float coals, respectively.

The potential of using air jigging to sort recycled aggregates

Abstract The recycling of inert construction and demolition materials (C&D) remains problematic if these materials are used to process high-quality recycled aggregates suitable for manufacturing new concrete. Even when selective demolition is employed, the crushing and classification of C&D produces recycled aggregates with an unacceptable level of impurities, with the content of gypsum being the biggest concern. Another concern is the percentage of brick content that decreases the density of the recycled aggregate as well as its homogeneity. The present work studies an air jig sorting method to separate out concrete particles from a C&D mixture that contains high amount of gypsum (22% mass) and brick (24% mass) particles. The mixture of aggregates studied had a 4–20 mm grading. After sorting, the bottom third of the mixture had less than 1% mass of gypsum and more than 90% mass of concrete particles. In contrast, the upper third of the sorted material contained gypsum in proportion of nearly 80% mass. The separation mechanism appears to be governed by both particle density and bulk density of individual components. These results are very encouraging and prove that the air jigging method is a promising technology for the use in C&D recycling plants. Further research is warranted.

A technique for calibrating a high dose rate 192Ir brachytherapy source

The reference air kerma rate of an ¹⁹²Ir high dose rate brachytherapy source is determined based broadly on the International Atomic Energy Agency (IAEA) TECDOC 1274 code of practice. Since the primary standards dosimetry laboratory at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) does not maintain a standard at ¹⁹²Ir quality, the air kerma calibration coefficient of an IBA FC65-G Farmer type ionisation chamber is calculated using coefficients determined at 300 kV and ⁶⁰Co qualities. The methodology proposed by Mainegra-Hing and Rogers [1] at 250 kV and ¹³⁷Cs qualities is used. The validity of this approach is tested by performing Monte Carlo simulations to determine the chamber's air kerma calibration coefficient at ¹⁹²Ir quality. Very good agreement is obtained between values using these two methods. The reference air kerma rate is measured using the Farmer chamber in an in air jig. In addition the necessary correction factors are applied to the measured value. The reference air kerma rate determined in this way is compared to the value stated by the vendor of the ¹⁹²Ir source on the source calibration certificate. Differences are with one exception less than 1%. It is concluded that because of the agreement between the values from the methodology used in this study and the source calibration certificate values this methodology can be used clinically.

Beneficiation of high-ash, Indian non-coking coal by dry jigging

Indian coals, which are of Gondwana origin, contain high amounts of mineral matter, wherein the extraneous material was intimately mixed in the coal matrix during the formation stage, causing a high level of impurity in the run-of-mine (ROM) material. These coals possess difficult to very difficult washability characteristics. Beneficiation of high-ash non-coking coals of India has become the prerequisite for improving the overall economics and efficiency of power generation. The use of dry cleaning systems in India for beneficiation of non-coking coals has gaining renewed interest recently. The benefit of the dry beneficiation process is to exploit the given resources while providing a more reliable and consistent quality fuel with a low operating cost. M/S Allmineral has introduced a technique for the dry beneficiation of coal, which is being tried in India for the treatment of high-ash non-coking coals. The first commercial air jig of 50 t/hr capacity was installed and commissioned to beneficiate high-ash coals of 40 × 5 mm feed with an ash content of 40%; a clean coal product of 33% ash was produced and is being used for a sponge iron plant.

DRY BENEFICIATION OF COAL—A REVIEW

Coal continues to play a major role in the economic development of a country, especially in metallurgical industries and conventional power generation plants. For effective utilization of high ash coals, it is necessary to beneficiate them. The wet beneficiation process for coal cleaning is currently the predominant method of purification of coal in the world. However, dry beneficiation of coal has obvious advantages over wet processes. The dry processes for coal are based on the physical properties of coal and its associated mineral matters. Different types of equipment for dry beneficiation have been developed, based on the exploitation of physical properties such as density, size, shape, magnetic susceptibility, and electrical conductivity. This article presents a summary assessment of different technologies and their performance in the beneficiation process of high ash coals with particular reference to Indian thermal coals. The literature on sorting, air jigs, magnetic separation, air-dense medium fluidized bed separation, and electrostatic separation is summarized and discussed.

Separation of sphalerite, silica and calcite from flourspar

The use of air jigging for performing multi-component separation in the treatment of mixed construction and demolition waste was studied. Sorting tests were carried out with mixtures of equal bulk volume of concrete and brick in which fixed quantities of unwanted materials - gypsum, wood and paper - were added. Experimental results have demonstrated the possibility to use air jigging to carry out both the removal of low-density contaminants and the concrete concentration in only one process step. In relation to the removal of contaminants only, the overall performance of jigging process can be comparable with that of commercial air classifiers and automatic sorting systems. Also, the initial content of contaminants seems does not have a significant effect on the separation extent. These results are of particular importance for recycling plants processing as they represent an alternative to optimize the use of air jigs. Further investigation is needed in order to evaluate the practical feasibility of such method.