Numerical simulation and experimental study on jet- pipeline-drop plate combined flotation enhancement device

Optimization of operating parameters for achieving maximum clean coal yield at the desired clean coal ash level is a major problem for all coal washeries. The problem is aggravated when the washeries receive raw coal from different seams/collieries with frequent variations in proportions and characteristics of individual coals. The problem is more severe in countries like India which have predominant reserves of difficult-to-wash coals. As a result, the yield of clean coal drops to a lower level compared to what can be achieved if necessary corrections are incorporated in the operating conditions. Hence, the present study involves development of a mathematical model, which would identify the enablers for optimizing the operating conditions and also to predict the actual yield based on the variations in proportion and characteristics of raw coal used. The model calculates theoretical yield and predicted yield of composite clean coal. The theoretical yield is calculated from the washability data of blended coarse coal and the ideal flotation response of blended fine coal. The predicted yield of coarse clean coal was calculated from the theoretical yield of coarse clean coal using a designed Ep value for a dense media (DM) cyclone. Similarly the predicted yield of fine clean coal was calculated from the theoretical yield of fine clean coal considering the designed process performance of a flotation plant. The predicted yield of composite clean coal was calculated from the predicted yield of coarse and fine clean coal. The developed model was validated and implemented in the Jamadoba washery.

Coal flotation using wash oil as a new type of collector

Fine coal (− 0.5 mm) is treated in a flotation circuit at Bhelatand washery of Tata Steel. The average ash content of the flotation feed, the fine clean coal, and the tailings of the flotation circuit are 18.5%, 12.5%, and 36%, respectively. The yield of clean coal from the flotation circuit is about 72%. However, the performance of the circuit in terms of clean coal yield is not satisfactory. The feed to the flotation contains 15–20% of oversize (+ 0.5 mm) fraction because of the inefficiency of the desliming screens. These oversize materials, which are of high carbonaceous value, are not efficiently recovered through the flotation process. Hence, the major challenge is to improve the flotation kinetics of the coal fines, especially the oversize particles. The way flotation reagents are distributed down a flotation bank can positively influence the flotation response of oversize particles. Hence, two-stage reagent distribution, with extra amount of reagent in the second stage, was studied in the laboratory. Results of laboratory-scale studies showed an improvement in yield of clean coal of 10–12% with a marginal increase of clean coal ash content. Based on encouraging laboratory findings, the idea was implemented in the plant, which showed a substantial improvement in the yield of clean coal from 74% to 84% with marginal increase in clean coal ash content.

Coating of fine particles by slime particles is inevitable in mechanized mining and transportation. These slime particles reduce the floatability and increase the ash content of clean coal. Ultrasonic pre-treatment method is used as a pre-treatment method to enhance the selectivity as well as kinetics of many minerals such as magnesite, complex sulphide ore, silica, coal, galena and zinc. However, the effect of ultrasonic pre-treatment time was not explored in literature and important for an energy intensive process. In the present investigation, ultrasonic pre-treatment time as well as reagent (collector and frother) dosages were optimized to achieve maximum clean coal yield. With ultrasonic pre-treatment, the clean coal yield increased for all the reagent dosages. Moreover, the clean coal yield obtained through ultrasonic pre-treatment is very close to the theoretical yield calculated from the release analysis. In the selectivity study, 8 unit increments in clean coal yield is observed with ultrasonic pre-treatment compared to the case without pre-treatment. Kinetic studies revealed that flotation rate increased from 0.026 to 0.049 s−1 with ultrasonic pre-treatment. Improvement in clean coal yield with ultrasonic pre-treatment is validated with the characterization studies such as XRD, zeta potential, petrographic and FTIR analysis.

At present, kerosene is one of the most widely used non-polar hydrocarbon oil collector agent in coal flotation in China, kerosene is difficult to dissolve in water, with good collector, but the dosage is comparatively large in the actual production.The drainage oil is from the dining recycled goods and the waste of animal flesh, can be used for preparation of fatty acid collector, which not only to reduce environmental pollution,but also to reduce the risk of food safety. At the same time, if drainage oil can replace the kerosene in coal collection, it will improve the coal preparation plant efficiency and solve the problem of shortage of national resources. In this study, we use Huangling coal as raw material for flotation experiment, use kerosene, diesel, drainage oil and emulsified drainage oil as collectors. Adding different collectors in the same flotation conditions to research the yield of clean coal, the clean coal ash and the yield of tailings by changing the dosage of collectors. The results show when adding to OP emulsifier and the proportion of water and oil is 6:4, flotation effects is the best, the yield of clean coal is 88.67%, the ash of clean coal is from 9.16% down to 8.63%, the yield of tailings is 11.32% .

The properties analyzing of flotation feed sample told that this fine coal sample is high-ash and hard-to-float coal slime. The ash reduction comparison of the step-by-step release flotation test with high intensity conditioning (HIC) or not, and the comparison of flotation test with HIC and adding depressant were made. The results showed that HIC can significantly improve the flotation effect for high-ash and hard-to-float coal slime. Comparing with the traditional step-by-step flotation process, if it meets the demand of ash content is 10.00% and 8.00%, the clean coal yield with HIC will increase 18 and 29 percentage points respectively; comparing with the effect of floatation adding depressant, HIC has more help to reduce the ash content and increase the yield of clean coal. In addition, HIC will save a lot of flotation reagents.

In this study, ash content lower than 1%, the ultraclean coal, using anthracite coal, is prepared by selective agglomeration flotation. ultraclean coal with lower ash is needed as electrode material and solid fuel, aim of obtaining lower ash content of ultraclean coal, dispersant is usually used to reduce ash content, but the yield will decrease. Therefore, clean coal yield can be further increased by regulator. For this purpose, the effects of stirring speed; dispersant (sodium hexametaphosphate) dosage, kerosene dosage, organic regulator (butyric acid; propionic acid; acetic acid; fumaric acid; maleic acid; ethylenediaminetetraacetic acid) on yield and ash content of clean coal were investigated in the experiments. The analyses of zeta potential, contact angle, x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), x-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), and Fourier transform infrared spectroscopy (FTIR) were used to illustrate the performance of the process. The results showed that the sodium hexametaphosphate and stirring speed had a significant effect on the reduction of clean coal ash content. Furthermore, adding acetic acid and propionic acid can improve the clean coal yield without increasing the clean coal ash content. Acetic acid was used as regulator, the yield of clean coal increased by 19.42%. At the same time, acetic acid and propionic acid are proposed as a method to produce microbubbles. This important discovery provides an optional method to obtain more target products for fine mineral flotation.

Preparation of renewable collector from waste engine oil for clean flotation of fine coal with different oxidation degree

Flotation of lean coal using trisodium citrate dihydrate as a dispersant in the presence of sodium oleate

Synergistically effective flotation enrichment of vitrinite by Na removal for high-Na high-inertinite low-rank Zhundong coal

Producing low-ash coal by microwave and ultrasonication pretreatment followed by solvent extraction of coal

ABSTRACTThe application of cyclonic microbubble flotation column (FCMC) from laboratory to industrial scale was investigated in this study. The FCMC was found to be superior to the standard self-aeration flotation cell for separating the fine coal (below 0.5 mm in size) as sampled from the Xiezhuang coal preparation plant (CPP), and tested under laboratory conditions. Compared with the flotation cell, the ash content of clean coal obtained by the FCMC was reduced by 1.34 percentage points, whereas the clean coal yield and the flotation efficiency index was increased by 2.90 and 6.64 percentage points, respectively. Under these industrial conditions, compared with the IF-45W flotation cell, the clean coal ash content obtained by the industrial FCMC-5000 (the column diameter was 5000 mm) was also reduced by 2.70 percentage points, whereas the clean coal yield and flotation efficiency index increased by 15.10 and 18.99 percentage points, respectively. Furthermore, annual profits of the Xiezhuang CPP increased by 46.773 million RMB by replacing the IF-4.5W flotation cell with the FCMC-5000. The results showed that the FCMC was an efficient coal flotation unit, and its application in separating fine coal has the potential to create significant profits for the enterprise.

Feed property and flotation operation parameters are critical factors influencing coal flotation performance. However, no previous studies have integrated machine learning SHAP (SHapley Additive exPlanations) analysis to simulate coal flotation outcomes and interpret the influence of relevant factors. To address this gap, several machine learning models are employed to predict coal flotation performance metrics (clean coal yield and ash content). Furthermore, the impact of excluding low clean coal yield data on prediction accuracy is systematically investigated. Additionally, Pearson correlation analysis and SHAP analysis are used to quantify the relative importance of feed properties and operational parameters on flotation performance, as well as their interactive effects. Results show that the linear model achieves the R2 of 0.2881 and 0.4348 for yield and ash content prediction, while the nonlinear models achieve the largest R2 of 0.6402 and 0.9312 for yield and ash content prediction, respectively. This proves that nonlinear models have higher accuracy than linear model. Importance analysis indicates that Ad of feed, fraction of −74 μm and Ad of −74 μm particles have a significant impact on both yield and ash content. The rest variables can only affect one output or have a minimal impact on results. This research can advance the mechanistic understanding of coal flotation processes and provide actionable insights for optimizing coal flotation.

Flotation cell and flotation column are widely used as the separation equipment for coal slime. In order to obtain better flotation results for different particle sizes, different turbulence intensity of flow field need to be created, but the turbulence intensity is not easy to adjust in conventional flotation equipment. In this paper, a new fluidized bed flotation column was designed to control turbulence intensity by the liquid velocity and static bed height. The effects of liquid velocities (0.198 m/s,0.226 m/s,0.254 m/s) and static bed heights (0.317 m,0.343 m,0.380 m) on coal slime flotation with different particle sizes were studied, which were evaluated by the combustible recovery, ash content, and the yield of clean coal. The research results showed that the flotation performance of coarse particles is better with low turbulence caused by low liquid velocity and great static bed height than that in high turbulence. Under the condition of high liquid velocity and low bed height, a high turbulence intensity environment is created, and the fine particle separation efficiency is better than that in low turbulence.

The strong hydrophilicity of fine-grained coal slime leads to poor flotation recovery. To enhance its surface hydrophobicity and flotation performance, octylphenol polyoxyethylene ether (OP-10), nonylphenol polyoxyethylene ether (NP-10), and their mixture (NP-OP) were compounded with kerosene as collectors. Surface free energy, adhesion force measurement, microcalorimetry, FTIR, SEM-EDS, and flotation tests were conducted. Compared with the kerosene, NP-10/kerosene has the best effect on improving the surface hydrophobicity of coal slime: the contact angle increases from 63.44°to 79.23°, the polar component of the surface free energy decreases from 9.33 mJ·m−2 to 2.98 mJ·m−2. When using kerosene alone, the flotation clean coal yield is 34.12% and the ash content is 21.49%. Compared with this, after using OP-10/kerosene, NP-OP/kerosene and NP-10/kerosene, the clean coal yield increased by 11.35%, 15.92% and 18.97%; and the ash content decreased by 6.16%, 10.4% and 10.5%. Mechanistically, polyoxyethylene ether groups formed hydrogen bonds with oxygen-containing functional groups on the coal surface, weakening hydrophilic groups, while hydrophobic carbon chains aligned directionally to reduce surface polarity and hydration film stability. Double adsorption of kerosene molecules enhances hydrophobicity. SEM-EDS analysis showed reduced Si and Al content, indicating removal of aluminosilicate minerals.