An Entrapment Model of Water Flow on Fine Coal Flotation

Jun.2004Journal of China University of Mining & TechnologyVol. 14 No. 1An Entrapment Model of Water Flowon fine coal flotationTAO YO-jmn(陶有俊),UMai-xi(路迈西)2, WANG Zho-ya(王卓雅)LIU Wen-li(刘文礼)2,ZHA0Ye-min(赵跃民)(1. School of Chemical Engineering and Technology, CUMT, Xuzhou, Jiangsu China2. School of Chemical and Engineering, CUMT, Beijing ChinaAbstract: Effect of entrapment of water flow on fine coal flotation was studied. The relation between constant ofrater flotation rate and flotation time was investigated and the water recycling model determined. The entrapmentdel of water flow about the relation bet ween the recovery of fine particle and that of water in concentration wasestablished. Finally, the equation about ash in fine clean coal at any time was derived by introducing a de-ashingKey words: fine coal; entrapment; flotation rate constantCLC number: TD 9Document code: A Article ID: 1006-1266(2004)01-0001-05mathematics models have befectedIntroductionfrom different points of view by many scholarsSince the first order flotation dynamIn recent years, some researches on fine coalequation was brought forward by H. G. Zuniga etflotation behavor and water recovery model of fineusing chemical reaction dynamics for reference, the coal flotation process have been done. For examplethematics models have been researched the <75 um fine coal flotation behavor has beenin depth. On the basis of the first order flotation studied by T C. RAO, B. GOViNdaRaTAN, Mdynamics equation, the basic form of flotation VANAGAMUDI et al adopting batch flotationdynamics equation was extended by N. Arbiter and process in the lab. The experiment results showR. T. Hukki for the progression of flotation that there is a definite correlative relation betweendynamics equation, which can bedc/ flotation rate constant and water recovery ratedtkc", where k is flotation rate constant, n is Before that. the relation curve of flotation rateflotation dynamics progression. After that, the constant and water rate constant of several usefulflotation rate constant distribution model was firstly minerals has also been studied by Tuoli(1976)andbrought forward by Imaizumi and E. T. Woodburn, the results show that the water rate constant willwho held that the initial distribution of flotation rate increase with the increase of flotation rate constantconstant of wide fraction materials obeyed I- of mineral materials, no mater the hydrophobicitydistribution. And the double-rate constant model of the mineral materials is good or notwas also put forward by simplifying the continuousThe flotation course is a very complex physicaldistribution flotation rate constants, in whichYH中国煤化工 is influenced by manyflotation materials were separated into two partsCNMHGtributionarticularfast flotation and slow flotation expressed by k, and Different size particle differs in flotation behvIorkw, respectively. After many years'researches, the which is very important for the flotation process andBiograph方数据ujm(1964-),mfrom Chuzhou. Anhui Province, associate professtudent for doctors deresearch on clean coal techniqueJournal of China University of Mining & TechnologyVol 14 No. 1results. In flotation practicea common water entering the froth. To further probe into thephenomenon in coal flotation that the fine coal has a behavior of the slurry during the flotationpoor selectivity and often contaminates the clean flotation tests in batches under different conditionscoal, so it becomes a difficult problem to be solved. were performed, and the relation between theThe behavior of fine coal in floatation is greatly recovery of <74 um size and the accumulated waternfluenced by entrapment of water flow, and this quantity in concentration was analyzed (Fig. 1)slime entrapment has much to do with the waterIt can be seen from Fig. 1 that almost all of thequantity entering the clean coal and little to do with test points locate in a straight line at the beginningsurface properties of minerals. The wetter the froth time, thus having a good linear relationship. At thebubble is (or the more the water contained in clean end of the flotation, there is an inflexion point ofpal), the more the non-target materials in clean the fine coal recovery in some experiment programscoal will be. Because this entrapment is poor in because there is an extreme value point, i.e. theselectivity, the finer the particles are, the greater maximum of <74 um size recovery, in this linethe probability of this entrapment is. This articlebased on the research on water recovery modelexplores the regularity of fine coal in flotation, thusstablishing the flotation mathematics model of fine少?coal 1-4. in batches2 Flotation Eexperiments in BatchesWater content in clean coal /kThe sample is the flotation feed of Linhuan coalFig 1 Relation between water content andpreparation plant. The screening test result of thepercentage of coal (<74 um)feed is showed as Table 1. The tests areOn the basis of the flotation dynamic theorycarried out on 8L XFD-12 model flotation machinehe relation between the recovery of slime and theequipped with the automatic froth-scavening system water quantity in concentration during the entireto reduce the experimental error. In thiflotation process can be expressed as followsthe pulp density is 100 g/L, and the flotation yz4 sm=yx74 um. max=(1-exp(-roQn)), (1)reagents are the same as the plant. Light diesel oil is where Qw is the mass of water in clean coal, gused as the collector and secondary alcohol as thY-74 um is the size content of <74 um particlesfrother. The experiments are carried out in batchesclean coal, % Y,4 gm, max is the maximum recovery ofder the condition of different reagent dosage<74 um size particles, % and ro, rI are modelTable 1 The screening test results of flotation feedparameters to be determined7/%(A)/%y/%x(A)/%From equation(1), we have0.5-0.2519.6413.7519.6413.75lim y.lim y0,25-0,12517,7616.3137,4015,490.125-0.07416.397253.79As a result, the recovery of <74 um0,074-0,04510,3318,8264,1216,34particles in concentration can be obtained as long as35.8824.7119.34thethe fl3 Dyamics Characteristic of Fine Coal中国煤化工Fer recycling modelFlotationCNMHri: I. e flotation feed. During3. 1 Relation between size content of <74 umthe flotation, the water is separated into two partsnd water quantityone into concentration and the other into tailing, asFlotatisi-wv1 ice indicates that the recovery of the flotation products. The water recovery infine particle has much to do with the recovery of concentration is influenced by many factorsTAO You-jun et alAn Entrapment Model of Water Flow on Fine Coal3especially the dosage of the flotation reagents, theThe dosage of frother/kgheight of the liquid surface in pulp, the pneumatic191001502002503003504004500volume, and the intensity of agitation. Due to itsKw vs the dosagecomplexity of those factors, it is very difficult toof frother8establish the mechanism model of the water豆09However, according to the research on flotationKw vs theprocess, the water recovery in clean coal can beneumatic volumeounted out by using the preliminary equation of the091,1flotation dynamics 5-7 From the test result ofor the dosage of collector/kflotation in batches. it is obvious that the relationig 2 Constant of water flotation rate kvsbetween water quantity in concentration and thedifferent operation variablesflotation time t is basically in accordance with thepreliminary equation of flotation rate3. 3. 2 Establishment of relation model between ko, this relation can be showed asd other operation variablesdThe data in above-mentioned Figs illustratethat the k has much to do thehere c is the pulp density in flotationtank at time t. and little to do with the dosage of the collector andfrother. The conclu(3)where Rw. max" is the maximum recovery of water, frother. So, the regression equation between kwwhich can be 95% according to the experience, kw is and pneumatic volume can be expressed asthe constant of flotation rate and R is the water0.488247+1.07708×Qar(6)recoverv at time tThe results of the regressionabouttheF=35.761>F.1(1,7)=12.2, multipleflotation tests as thecorrelation coefficient R is 0.914 5. and o is 0.106del of finentent and water volumetime t will beThe data of the accumulated water volume andTherefore, it can be deduced from equations (1)In1. These data are linearized in terms of the(3), and (4), that isNon-linear Equation (1 ), and then the model<7m(t)=7<74m(1-exp(-r0×(Qw,mxparameters ro and r are determined according to theRwmx×(1-exp)7)).(5)ulti-element regression analysis. So we can get theDetermination of the constant of watermathematics model about the relations bet ween theflotation raterecoveries of fine coal and water during the3. 3. 1 Relation between kw and different operationflotation. i.evariables(t)=y<74PmTo understand the relation between k. andexp(-0.000429×Q(7)different operation variables clearly, we comparedIts of the regression analysis aboutthe results of the tests, and concluded that the k中国煤化工Fa(1,4)=7.235,has much to do with the pneumatic volume and little mCNMH Gnt r is 0.943 andto do with t, the dosage of collector, and froth0.282.( Fig. 2). According to the analysis, thee ncreaseof 4 Calculation of Recovery of Concentra-absolute vo丹数据 air per minute through the pulption in flotationleads to an increase of water recovery velocityAt any flotation time t, the materials enteringJournal of China University of Mining & TechnologyVol 14 No. 1the concentration can be regarded as two paoneThrough the analysis of Equation (11),itis those particles of >74 um due to their good obvious that the smaller the de-ashing coefficient eafloatability, the other is those particles of <74 um is, the more distinctive the effect of mechanicdue to the mechanical entrapment of water floyntrapment of water flow is. To further determineThese can be written asthe de-ashing coefficient under different7(t)=>74m(t)+7<74m(t),(8)where ys74ym (t) can be counted out by using the involving the de-ashing coefficient Ea andflotation dynamic model according to the constant of experimental conditions are established based on theflotation rate which is a discrete distribution as experimental conditions and different values of de-follows 3ashing coefficients produced from Equation (11)Thi774m(t)=>7.m(1-e")Ea=76.532-4.8892×Qowhere k, is the constant of the flotation rate, the ith10.531×Q-9.134×Qsize in>74 um size coal; R;co is the maximumThe results of the regression analysis are: F=recovery of the ith size coal in the entire flotation14.89>F.(3,5)=12.1, multiple corfeed. But the recovery of the <74 um size cerelationcoefficient R is 0.931 3, and o is 1.4513Y 74 um can be obtained from the Equation (7)In the above, Qool, FRo are dosages of collectorBecause the parameters in above model havectively, and QAir is thealread been found, the yield of concentration y()atolume under the experimental conditionsany time t can be calculated out according to themaking some changEquation (11)constants of flotation rate of all size fractions andthe ash of <74 um size at any time t can be5 Prediction of Ash in Clean CoalA,(t)=100×A7()2(1-Ea)(13)Because the clean coal of flotation is made up ofwo parts which are>74 um size and <74 um concentration at any time t, which is the weightedze, the ash of >74 um size in clean coal can be average of the ash content in both >74 um size anddetermined from the ash of all size fractions in <74 um sizeflotation feed, that is to say, the ash of all fractionsin clean coal is in accord with those in flotation feed6 Testing and Verification of the ModelIt can be calculated by the following formulaTo further examine the reliability of the model∑7(1)×Athe results between test values and actual results of(10)are compareunder different(t)experimental conditions, and one comparison resulttermine the ash of <74 um size, weunder a certain experimental condition is showed inntroduce the de-ashing coefficient Eal6Fig. 3g100×A-y;×AFig. 3 shows that it is feasible to take thewhere A, is the ash of <74 um size in flotation a ation results as two parts, <74 um size and100×A中国煤化工rately. The calculatedfeed, % A, is the ash of <74 um size in vaof the expCNMHGconcentration,%; and r; is the recovery of <74luci is reliable for the fine coalTAO You-jun et alAn Entrapment Model of Water Flow on Fine CoalExpen_ recovery40Experi recovery08642clean coal ash906080100120140Fig 3 Prediction of the model and the value of batch experiments7 Conclusionsexp(-0.000429×Q:341) The floatation behavior of fine coal is3) The ash of fine coal can be obtained fromfluenced mainly by the entrapment of water flow the de-ashed coefficient equation as followse flotation100×AA,(t)=2) The relation model between fine particlerecovery and water volume in concentration is[1]丁立亲.浮选理论与实践[M].北京:煤炭工业出版社,1987[2]蔡璋浮游选煤与选矿[M].北京:煤炭工业出版社,19913 Lynch A J Mineral and coal flotation circuits their simulation and control[M]. Amsterdam: Elsevier Press, 1981.64-684]胡为柏,李松仁.数学模型在矿物工程中的应用[M].长沙:湖南科学技术出版社,19835]陶有俊,煤泥浮选数学模型的研究[.江苏徐州:中国矿业大学化工学院,19926」刘文礼.煤泥浮选数学模型及其仿真器的研究[D].北京:中国矿业大学化学与环境工程学院,19987]陶有俊,路迈西,蔡璋,等.细粒煤浮选动力学特性的研究[].中囯矿业大学学报,2003,32(6):694-697中国煤化工CNMHG