Component modification of steel slag in air quenching process to improve grindability

A new solution called component modification in-process was introduced to the difficult grinding of air quenching steel slag by a series of experiments. The results show that the fly ash added into the molten steel slag before air quenching can more effectively improve the slag's grindability than milltailings, which is the other modification agent tested under the same conditions. The role of fly ash is strengthened as its proportion increases, although the degree of promotion is gradually reduced. As a result of the reaction between fly ash and steel slag at high temperature, some new mineral phases and vitreous bodies with fine grindability promote the slag grinding easily. This work is helpful to making a comprehensive utilization of steel slag and maximize its economic efficiency in China.

Grindability, Grading and Wettability of Recycled Plaste

The changes of grindability, grading and wettability of recycled plaster(R-P)and the mechanisms of these changes were studied by using vickers hardness, particle size distribution(PSD), scanning electron microscope(SEM) and nitrogen adsorption porosimetry to reveal that R-P was obviously different from plaster of Paris(POP). At the same milling time, R-P had the characteristics of high specific surface area, fine particle diameter and uneven size distribution compared with POP, so R-P possessed both good grindability and poor grading. The water absorption, dissolution rate and mass loss in dry-wet cycle of the hardened recycled gypsum(hardened RG) increased, while the water saturated strength and dry-wet cycle strength decreased significantly compared with the hardened virgin gypsum(hardened VG). Therefore, poor wettability could be seen in R-P. The analyses indicated that the changes of grindability and grading could be attributed to the reduction in hardness and the increase in the porosity of hardened RG and that the poor wettability of R-P was caused by the increase of large pores and the changes of microstructure of hardened RG.

Application of a Fuzzy Analytical Hierarchy Process for Predicting the Grindability of Granite

The ranking system of grindability is the key technology for high-efficiency grinding granite. A new classification system is presented to evaluate and ranking the grindability of granite. On account of the complicated relation between the mineral composition and mechanical properties with the grindability of granite, a new method by the combination of Fuzzy Analytic Hierarchy Process (FAHP) method with TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) methods is developed to establish the dependence function and fuzzy relationship between SiO2 content, quartz content, Shore hardness, density, compressive strength, flexural strength and abrasion resistance of granite with grinding force. The grindability of ten types of granite was evaluated and classified by this method. With the fuzzy ranking system established and the grindability classification, it is very convenient to evaluate the grindability and select a suitable diamond tools and proper grinding parameters for a new granite type by only the petrographic analysis and mechanical properties testing.

Study and Modeling of the Grinding Kinetics of Reactive Rocks in a Cement Laboratory

This article focuses on the study of crushing rocks that can replace clinker in low-carbon cement. A laboratory ball mill was used, varying the duration of the grinding. It has been observed that the specific surface of rocks changes in a nonlinear way with time, due to the agglomeration of particles. To this end, a mathematical model describing this evolution, which considers van der Waals forces, has been proposed. And finally, the model was adjusted regarding the experimental data. The results found show that the present model is more accurate than the classical models, because it considers the agglomeration phenomenon.

Effects of Polycarboxylate-based Grinding Aid on the Performance of Grinded Cement

A molecular modified PCE-type GA was self-synthesized,and the grindability concerning grinding duration and particle size distribution of ground cement was evaluated.Setting time,flowability,hydration heat,mechanical properties and microstructure of the ground cement were also investigated.The results show that:PCE-type GA is effective in cement grinding.With 0.03%PCE-type GA added into cement clinker,the Blain surface area reaches to the highest at every ten minutes,and the volume percent of cement particles with size of(0-32μm)reaches the highest.Excessive amount of PCE-type GA seems to impair the grinding efficiency.The grinding efficiency promotes cement fineness and hence contributes to the cement hydration degree as well as improves the mechanical properties.

A NEW SIMULATING ALGORITHM FOR BALL MILLS--CONVERSION COEFFICIENT METHOD

The conversing relation among the Bond Work Index Wp specific output of mill and the energy efficiency of grinding were developed using dimensional analysis.The relations of which were proved and the value of the coversion coefficient i was also obtained using a new installed device for measuring grindability of ores.With the new simulating algorithm,the mill specifications,output and size distribution of griding products of industrial mills can be calculated based on laboratory measuring results.This algorithm is more accurate and simpler than any of the others.

Comparative assessment of force,temperature,and wheel wear in sustainable grinding aerospace alloy using biolubricant

The substitution of biolubricant for mineral cutting fluids in aerospace material grinding is an inevitable development direction,under the requirements of the worldwide carbon emission strategy.However,serious tool wear and workpiece damage in difficult-to-machine material grinding challenges the availability of using biolubricants via minimum quantity lubrication.The primary cause for this condition is the unknown and complex influencing mechanisms of the biolubricant physicochemical properties on grindability.In this review,a comparative assessment of grindability is performed using titanium alloy,nickel-based alloy,and high-strength steel.Firstly,this work considers the physicochemical properties as the main factors,and the antifriction and heat dissipation behaviours of biolubricant in a high temperature and pressure interface are comprehensively analysed.Secondly,the comparative assessment of force,temperature,wheel wear and workpiece surface for titanium alloy,nickel-based alloy,and high-strength steel confirms that biolubricant is a potential replacement of traditional cutting fluids because of its improved lubrication and cooling performance.High-viscosity biolubricant and nano-enhancers with high thermal conductivity are recommended for titanium alloy to solve the burn puzzle of the workpiece.Biolubricant with high viscosity and high fatty acid saturation characteristics should be used to overcome the bottleneck of wheel wear and nickel-based alloy surface burn.The nano-enhancers with high hardness and spherical characteristics are better choices.Furthermore,a different option is available for high-strength steel grinding,which needs low-viscosity biolubricant to address the debris breaking difficulty and wheel clogging.Finally,the current challenges and potential methods are proposed to promote the application of biolubricant.

Effect of process parameters on dry centrifugal granulation of molten slag by a rotary disk atomizer

Dry centrifugal granulation(DCG)experiments for blast furnace slag(BFS)were performed by means of a rotary disk atomizer since water quenching method can create a series of problems.The results showed that the DCG method can granulate the BFS,but the results are easily affected by the slag flow rate,disk rotating speed,disk radius,disk material and slag falling height.The granulating parameters with an excessive flow rate,low rotating speed,SiN–SiC disk,stainless steel disk and low slag falling height are detrimental to the granulation process.The most suitable parameters for granulation are a slag flow rate of 5.1×10^(−5) m^(3)/s,a disk rotating speed of 1500–2300 r/min,a slag falling height of 0.8 m and a smooth graphitic disk with the radius of 0.1 m.In the absence of an off-center flow,the overall best granulating effect produces round particles with mean diameter of 3.43 mm without creating slag fiber.The vitreous content of the BFS particles granulated by graphite disks is 92%,which meets the requirements of cement raw materials.The Bond work index of dry granulated BFS is 18.4 kWh/t,and the grindability of dry granulated slag and water-quenched slag is similar.

Experimental research on semi-coke for blast furnace injection

The combustion properties and grindability of Shenmu low-rank coal(SM)and its four different semi-cokes were studied by the self-designed equipment and Hardgrove method.The four semi-cokes were obtained under the pyrolysis temperature of 400,500,600 and 700℃,named as SM-400,SM-500,SM-600 and SM-700,respectively.The analyses of nitrogen adsorp-tion,Fourier-transform infrared spectroscopy(FTIR)spectra and Raman spectra were carried out to explain the change in combustion ratio and grindability.The result showed that the specific surface area of samples had an essential effect on the combustion ratio of SM-400 and SM-500.Meanwhile,the grindability depended on the strength of coal matrix,and the augment of pore amounts would increase the grindability.The functional groups and graphitization degree of the same sam-ple were identical with the combustion ratio.With the pyrolysis upgrading temperature increasing,the combustion ratio of sample decreased,corresponding to the decrease in the benzene ring and the increase in graphitization degree.In addition,the thermogravimetric analysis was carried out,and the result was compared against what was shown in the data of com-bustion ratio.For pulverized coal injection,the combustion ratio was more intuitive and more accurate than combustibility.