Calculating Method for Influence of Material Flow on Energy Consumption in Steel Manufacturing Proce

Available online at www.sciencedirect.com* ScienceDirectJOURNAL OF IRON AND STEEL RESEARCH, INTERNATIONAL. 2007， 14(2): 46-51Calculating Method for Influence of Material Flow on EnergyConsumption in Steel Manufacturing ProcessYU Qing bo,LU Zhong-wu，CAI Jiurju(School of Materials and Metallurgy，Northeastern University, Shenyang 110004， Liaoning, China)Abstract: From the viewpoint of systems energy conservation, the influences of material flow on its energy consump-tion in a steel manufacturing process is an important subject. The quantitative analysis of the relationship betweenmaterial flow and the energy intensity is useful to save energy in steel industry. Based on the concept of standard ma-terial flow diagram, all possible situations of ferrie material flow in steel manufacturing process are analyzed. The ex-pressions of the influence of material flow deviated from standard material flow diagram on energy consumption areput forward.Key words: steel manufacturing process; material flow; energy consumption; calculating methodThe theory of systems energy conservation em-unqualified product and other wastes are collectedphasizes both energy saving and non-energy (materi-and moved in opposite direction for their retreat-als) savingh2. The concept of steel ratio coefficientment. And, there are usually input and output of awas put forward to emphasize the importance of non-certain amount of iron containing materials in theenergy~3]. Energy consumption situation in Chinesemidway of the process10.11]. Therefore, the materialsteel industry was analyzed and energy consumptionflows in a steel manufacturing process are very com-amount in future was predicted by ep ( where e isplicated.energy intensity of unit process， kgce/t processThe practical steel manufacturing process couldproduct; p is steel ratio coefficient of unit process, tbe simplified to closed one- way process conformingprocess product/t billet) analysis method[4-9]. Butto following two conditions from balance of ferrice力analysis could not be applied in analysis of inter-material: (1) the only direction of the flow of iron-nal factors of composing steel ratio coefficient ircontaining materials is from each unit process to itseach unit process and influence of each factor on en-next downstream unit process, and finally to the ex-ergy consumption， which is of great importance tit of the manufacturing process; (2) there is no in-guide of steel enterprises to reduce steel ratio coeffi-put or output of iron-containing materials in thecient in each unit process and energy consumption.midway of the manufacturing process. The standardTherefore，how to calculate the influence of materialmaterial flow diagram (SMFD) of steel manufactur-flow on steel ratio coefficient in each process as welling process was defined as conforming above twoas its relationship with energy consumption is an im- conditions and bases on 1 t of final product[12]. In-portant subject.fluence of flow way, amount and distance of ferricSteel industry is a typical process industry， inmaterinal nrracs on energy consump-which iron ore and other iron-containing materialsion P中国煤化工energy consumptionare transformed into final product through a series ofper tdMYHC N M H Gy applying SMFD,unit processes. While qualified product of each unitand the method of calculating influence of ferricprocess goes downstream to its next unit process,material flow on energy consumption was intro-Foundation Item: Item Sponsored by National Basic Research Program of China (200002600)Biography: YU Qing-bo( 1966-)，Male, Doctor, Professor;E-mail: yuqbneu@ 163. com; Revised Date: September 11, 2006No.2Calculating Method for Influence of Material Flow on Energy Consumption in Steel Manufacturing Process● 47 ●duced in detail.General speaking， there is a main material flow1 Practical Material Flow Situation in Steelin steel manufacturing processes from the firstprocess to the last one. Obviously， the quantity ofManufacturing Processthis main material flow between each two adjacentSituation of iron- containing material flow inprocesses is not the same. .steel manufacturing process is very complicated. AsThere are also three types of material flow be-to every unit process， it is possible that there are side main material flow. The first flow, or a materi-kinds of different material flows at the same time. Ial flow, includes each material flow input from out-is shown in Fig. 1.side of processes in every unit process. The second(1) Qualified product in Process i-1 is addedflow, or β material flow, includes those recycling to .to Process i. Mass of ferrum is M,-1， ton iron/ tonthat process after output from each unit process andfinal product or steel;recycling to its upstream process after output from(2) Iron-containing materials from surrounding aseach process. The third flow, or γ material flow,raw material is added to Process i. Mass of ferrum is .includes each one that would not return after outputai，ton iron/ ton final product or steel;from each unit process.(3) Output of iron-containing materials to sur-The main material flow has close quantitativerounding in Process i. Mass of ferrum is γ;，ton i-relation with a, β and γ material flow. It is necessa-ron/ton final product or steel. Y;= r';十γ"i，γ; isry not only to make clear of eacha, β and γ materialthe ferric mass in qualified product for sale, and γ" isflow，but mutual relation between them with thethe ferric mass in unqualified product output inclu-main material flow to structure practical materialding waste for sale and production loss;flow diagram. Output and input balance of ferrum in(4) Unqualified product or waste in Process ieach unit process is the principle to comply with.return to itself or upstream process as raw material. .Although people noticed the influence of mate-The ferric mass is β，ton iron/ ton final product orrial flow on energy consumption， research in thissteel. β=.+j..m， m=1，2，.，i-1，B.. is thefield stays in qualitative analysis in which there isferric mass in material returning to itself processnot a relative criterion to carry out quantitative anal-(for example sinter return)， and p:r,m is the ferricysis. The concept of SMFD provides a reference cri-mass in material returning from Process i to Processterion for quantitative analysis of influence of mate-m (for example scrap steel from steel rolling to steelrial flow on energy consumption. It has the samemaking);importance as the concept of energy bearer1] that(5) Iron-containing unqualified product 01was put forward at the early beginning of foundation .waste in downstream process as raw material is re-of systems energy conservation theory.turned to Process i. The ferric mass is..(j=i+1,Structuring SMFD According to Practicali+2，..，n)，ton iron/ ton final product or steel;Steel Manufacturing Processes(6) Qualified product in Process i is moved toProcess i+1. The ferric mass is M;，ton iron/ton fi-Structuring SMFD of practical steel manufacturingnal product or steel.processes is important in influence analysis of materialAccording to the mass balance, the input and out-flow on energy consumption. Real material flow dia-put of iron-containing materials should obey Eqn. (1):gram (RMFD) could be compared with SMFD to as-M-1+a++...+..=M:+y.+β..+f..m .certain influence of each material flow factor on energy consumption. The SMFD is built from practical( Product for sale Yi[ron- containing materialsIUnqualified productmanufacturing processes, and different manufactur-m surroundinoutput to surroundings Y,"ing processes should have different SMFD. Produc-Product ofunitProducuof ution P中国煤化工ation of per ton mate-Unit process irial inYHCNMHGFDarethesamewith.B;Recycling to upstrearmthat in practical production. Final product ratio co-or itself processefficient and process energy intensity in each unit、 Recycling from unil processj 10 i upstream iprocess are calculated based on consumption index inFig. 1 Situation of Fe-containing materialspractical manufacturing process. Assume there are nflow in a unit processprocesses in one practical manufacturing process, in●48.Journal of Iron and Steel Research, InternationalVol. 14which process energy intensity in each unit processProcess i on RFPRC of unit Process i. The third itemand ferric concentration in material product are e;is the influence of ferric material output from down-(kgce/t process product) and C;(t ferrum/t qualifiedstream Process j on RFPRC of unit Process i. Theproduct) respectively. The input and output of fer-forth item is the influence of unqualified produced inric material in each unit process are shown in Fig. 1.downstream Process j recycling to its upstreamThe corresponding SMFD should have n processes,process on RFPRC of unit Process i. So Eqn. (4)and reference final product ratio coefficient and ref-could beerence process energy intensity in each unit processPw= po+Opμ (i=1,2,..,n)(5is as follows respectively:where Oppi is the influence of material flow on finalproduct ratio coefficient of each unit process whenpo;=(i=1,2,3...n)they deviated from SMFD. .t process product/t final product(2)It can be learned by comparison of Eqn. (4) andP(5):eoi= Ppw+r";7C;+p:/Ci(i=1,2,3,..n)Poip.=1(6kgce/t process productwhere Poi is the final product ratio coefficient of unit°°+°≥+°Sw,Process i in SMFD (standard final product ratio co-efficient in brief， SFPRC); C; is the ferric quantityOpm=0.(7)in qualified product in unit Process i; eoi is theFrom Eqn. (4) to Eqn. (7), it is shown that fi-process energy intensity of Processin SMFDnal product ratio coefficient of each unit process in a( standard process energy intensity in brief, SPEI);steel manufacturing processes varies not only withpr is the final product ratio coefficient of unitferric content in unit process product, but with theProcess i in practical process ( real final product ratiomaterial flow situation in each downstream process.coefficient in brief, RFPRC)，px=M./C;+r :/C.From Eqn. (3)，it can be seen that the SPEI3.2 Influence of material flow on energy intensitymeans that total energy consumption in a process isper ton final product in manufacturing processdivided into all material produced in that process in-Real energy intensity per ton final productcluding qualified and unqualified products. But real(REIP) in practical production has following calcu-process energy intensity ( RPEI) divides that intolating expression:qualified products produced in that process， whichEp=etpol+e2p+esps+.+epμ +..+means waste does not consume energy.enpm= Sepm(8)3 Calculating Influence of Material Flow onStandard energy intensity per ton final productEnergy Intensity for Each Ton Final Prod-(SEIP) in SMFD has following calculating expres-uct in Practical Manufacturing Processsion:Eop=eolpol+eo2po2+ eos po3 +..+eopoi +..+Energy intensity per ton final product is re-ferred to as energy consumed for producing 1 t quali-eompon= Zeoipa9)fied steel products in whole processes.Difference between REIP and SEIP can be ob-tained by subtracting Eqn. (9) from Eqn. (8).3. 1 Influence of material flow on PFPRCAssume there are n processes in a steel manu-OEp=E,- Eop= 2(e;pμ一eorpo)(10)facturing process in which any possible material flowSubstituting Eqn. (2) to Eqn. (7) into Eqn. (10),in each unit process is shown in Fig. 1，the RFPRCfollowing formula can he obtained:in each unit process is as follows :中国煤化工三.x,+三....+只2;+号_Br.mYHCN M H G-7+1j=i计1m- :Pr=C ,mC,hCt,CY,fβ)」(11)(i=1,2..,n-1) (4)Eqn. (11) can be used to calculate the influenceThe first item in right of the equal sign is referof material flow in practical manufacturing processence SFPRC. The second item is the influence ofon REIP.ferric material input from downstream Process j toAnalyzing Eqn. (3)，Eqn. (4) and Eqn. (11)，itNo.2Calculating Method for Influence of Material Flow on Energy Consumption in Steel Manufacturing Process● 49●can be learned that△E, is caused by two reasons. Irprocess on energy consumption could be obtained bythe first place, material flow in downstream processanalysis of Eqn. (11). For example，some practicalchanges RFPRC of upstream process. In the secondmanufacturing process has 8 unit processes ( seeplace，material flow in that process changes theFig. 2). Some ferric material bought outside of theprocess energy intensity. These two factors influ-process is added in the seventh process as raw mate-ence total energy consumption in process and fur-rial in which the ferric content is C, (ton ferrum perther influence energy intensity per ton final prod-ton material) and the ferric mass is a7 (ton ferrumuct.per ton qualified product in Process 8). The influ-The influence of each material flow in each unitence of that material flow on REIP ise06eqC12C2、3Cg4 IC45C6C↓71C8MI/C,(MP2 sI] CgIM] CaSM C;Cc ,C。tHR) coRjcMI- Mining;MP- Mineral processing; SI- Sintering;IM- Iron making;SM- Steel making;CC- Continuous casting; HR一 Hot rolling;CR- Cold rollingFig. 2 Standard material flow diagram for blast furnace converter processOE7=-areo1+ eo2⊥ eo3 + e04. 十eos. t eo6second to the fourth item are influences of materialCTC2TC3TCTC3TCflow in each unit process from downstream of(kgce/t qualified product of 8th unit process) (12)Process i to continuous casting process on steel ratioThe influence of adding every 1 kg that materialcoefficient of Process i. The fifth item is influence offlow on REIP could be obtained by total mass ofwaste produced in each process after continuousadded material dividing△Ep7:casting returning to the process before continuous△epor=一Ca7 |eol + eo2+ eo3.十eo4+ eos.十eoecasting，and after Process i on steel ratio coefficient1000(C1'C2'C3CCC。of Process i. .(kgce/ kg qualified product of 8th unit process) (13)(2) After continuous casting process4 Calculation of Influence of Material Flowp:s(k+1)=C + a:+1_ Y"k+1_ βa+1 .(15)Ck+1 Cr+1Ce+1 Ce+1on Energy Intensity Per Ton Steel in Prac-tical Manufacturing Processp。=上_②EB+Energy intensity per ton steel is a universally .applied evaluation index for energy consumption thatC;C;C(i=k+2,k+3,...n) (16)means energy consumed in producing 1 ton qualifiedSteel ratio coefficient in practical manufacturingcontinuous casting slab in all processes.process isp。=por+Op。，(i≠k)(17)4.1 Analysis of steel ratio coefficient in steel manu-px= pok=1，△px=0facturing processAssume there are n processes in a steel manufactur-4.2 Influence of material flow on energy intensitying process，in which Process k is continuous castingper ton steel in practical manufacturing processprocess and Process k- 1 is steel making process.The SMFD is taken as reference standard in analy-Ferric material flow in each process is also shown insis of energy consumption per ton steel in a practicalFig.1. The steel ratio coefficient in each unitmanufacturing process. Difference between practicalprocess has following expression:中国煤化工and reference energy(1) Before continuous casting processintens:1YHCNMHG,台iP# eotPor)(18)之点Br.m(i=1,2,..,k-1)(14)Substituting RFPRC pp in Eqn. (3) into steelratio coefficient p。and substituting Eqn. (14) toThe first item in right of the equal sign is refer-Eqn. (16) into Eqn. (18), the following formula canence steel ratio coefficient of Process i. From thebe obtained : .Journal of Iron and Steel Research, InternationalVol. 14△E,=△es+ Oex十Oe.(k+1)十Oe,(19)ferrum mass.where△ea is changes of energy intensity per ton(3) Revise balance of ferrum mass in data ofsteel caused by material flow in each unit process be-each unit process by subtracting ferrum mass leavingfore continuous casting; Oex is changes of energy in-out of process by ferrum mass entering into process.tensity per ton steel caused by material flow in con-The inadequate part is item for production loss astinuous casting process;△e,(k+1) is changes of energypart of output from process to environment, and it isintensity per ton steel caused by material flow in theinvolved in influential analysis of material flow onfirst process after continuous casting; Oex is chan-energy consumption. Surplus part can be recordedges of energy intensity per ton steel caused by mate-but it is not involved in influential analysis of mate-rial flow in each process after continuous casting.rial flow on energy consumption.Den=°[°"(-.三r,+_2y;+_....(4) Build material flow diagram for practical;-+1m-production process referenced on per ton final prod-二.3..+r":+p,)](20)uct. Quantity of each material flow in diagram equalsferrum mass in qualified final product divided by fer-Sex=*(r".+B&)(21)rum mass of each material flow in each unit process.(5) Build material flow diagram for practical△e(k+1)= = eo(k+1)(22)production process referenced on per ton steel. .Quantity of each material flow in diagram equals fer-Sea=_Eo(_a,-_z,y,-__+a;)]rum mass in qualified steel slab of continuous casting(23)process divided by ferrum mass of each material flowIt can be learned after analysis of Eqn. (20) toin each unit process.Eqn. (23) that influence of material flow on energy(6) Build SMFD based on RMFD.intensity per steel is different before and after con-(7) Calculate influence of material flow on energytinuous casting process. Steel ratio coefficient irconsumption per ton final product or per ton steel ac-each unit process before continuous casting is influ-cording to expressions given in Section 3 and 4.enced by material flow in each downstream process6Conclusionsso that material flow in that process only influencesprocess energy intensity in that process and finally(1) The influence expressions of materialthey influence energy intensity per ton steel togeth-flows deviated from standard material flow diagramer. Steel ratio coefficient in each unit process afteron energy consumption are put forward.continuous casting is influenced by material flow ir(2) The comparison between RMFD of a steeleach upstream process, so that material flow influ-manufacturing process and its corresponding SMFDences not only steel ratio coefficient but also processmakes the energy analysis quantitatively very clear.energy intensity in that process, and finally waste(3) Recycling of iron-containing materials inproduced in that process does not influence energysteel manufacturing process increases its energy in-intensity per ton steel. That is exactly the limitationtensity; for a definite amount of recycling， the lon-of energy intensity per ton steel as an evaluation in-ger the“distance”of recycling， the greater will bedex.the increase of energy intensity.The calculating expression of influence of each ma-(4) Output of iron-containing materials fromterial flow as well as adding or subtracting l kg on ener-any unit process to the surrounding increases the en-gy intensity per ton steel referenced by Eqn. (12) andergy intensity of final product; for a definite amountEqn. (13) is based on Eqn. (20) to Eqn. (23).of output, the larger the ordinal number of the unit5 Calculating Procedures in Analysis of Influ-process. the greater will be the increase of energyintens中国煤化工ence of Material Flow on Energy Consump-|YHC N M H Gng materials from thetionsurrounding to any unit process decreases the energy(1) Collect relative data in a practical manufac-intensity of final product; for a definite amount ofturing process and make each material flow clear.input，the larger the ordinal number of the unit(2) Multiply material mass in each materialprocess，the more will be the decrease of energy in-flow by corresponding ferric concentration to obtaintensity.No.2Calculating Method for Influence of Material Flow on Energy Consumption in Steel Manufacturing Process● 51●(6) For an enterprise, REIP of main productsceedings of the International Conference on Energy and Envi-ronment [C]. 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