Coupling Model of Energy Flow and Material Flow in SKS Lead Smelting

Transcription

1 Sed Orders for Reprits to The Ope Materials Sciece Joural, 2014, 8, Ope Access Couplig Model of Eergy Flow ad Material Flow i SKS Lead Smeltig Hogcai Wag *, Zhagmig Shi, Liufag Li ad Bo Che School of Eergy Sciece ad Egieerig, Cetral South Uiversity, Chagsha, , Chia Abstract: This paper studied the couplig model of material flow ad eergy flow i the productio process of lead smeltig eterprises, ad established the mathematical model for material flow ad eergy flow to resolve optimizatio problems. From the poit of eergy flow, the paper aalyzed three kids of eergy flow chages which have a effect o the eterprise products. Through calculatio ad aalysis, it has bee foud that there is 38.42% eergy-savig potetial i this eterprise. Separately from the material flow ad eergy flow agle, the paper put forward five aspects suggestios to reduce the eergy cosumptio of the eterprise products. Keywords: Eergy cosumptio, eergy flow, material flow, SKS lead smeltig. 1. INTRODUCTION The paper aalyzed the eergy system of lead smeltig eterprises, usig the process of SKS (Shui Kou Sha) lead smeltig. The SKS lead smeltig process is a lead smeltig techology i which oxyge blows from the bottom ito the blast furace. The key feature is that the Oxidatio-reductio reactios take place i differet meltig furaces. SKS lead smeltig process, which has bee widely applied i Chia, has may techical characteristics, such as low ivestmet, low productio costs, strog adaptability for raw materials, high level of automatio ad evirometal friedliess. Now the techology has reached iteratioal advaced level ad some coutries also adopt this method to smelt metals like copper, lead ad so o [1-3]. Research o the couplig model of SKS Lead Smeltig Process helps recogizig the associatio betwee material flow ad eergy flow i each process ad provides guidace for reducig the eergy cosumptio of lead smeltig eterprises [4-5]. A lot of researches o the theory ad optimizatio of eergy system have bee coducted i the metallurgy idustry [6-13]. At preset, the e-p aalysis method has bee put forward by Academicia Lu Zhogwu, which is widely applied i iro ad steel eterprises [14-15]. Comparig the research achievemet of system eergy coservatio i iro ad steel eterprises, i this research, both the material flow ad eergy flow i the lead smeltig corporatio are simultaeously aalyzed ad SKS lead smeltig process is broke dow ito material flow ad eergy flow which are related. With respect to the material flow, we framed a material flow diagram of productio process from graulatio of raw materials to crude lead productio ad built a lead flow model cotaiig lead materials; with respect to eergy flow, we framed a eergy flow diagram cotaiig eergy productio, trasformatio, use ad disuse emissio ad built a eergy model of lead smeltig *Address correspodece to this author at the Cetral South Uiversity, Research o Eergy System Egieerig; Tel: ; Fax: ; hogcai_001@163.com process; for the relatioship betwee material flow ad eergy flow, we built the couplig model. 2. ANALYSIS OF THE MATERIAL FLOW IN SKS LEAD SMELTING PROCESS I the SKS lead smeltig procedure, there is a mai material flow called lead flow that moves from the first process to the fial process all the way. It is possible that i each process, there are all five material flows or some of them as show i Fig. (1). (1) Iput material flow: the lead products i process i-1 are used i process i as raw materials, with lead flow as P i-1, t/t lead. (2) Exteral material flow: the lead raw materials are added to process i from the eviromet, with lead flow as i, t/t lead. (3) Discharged material flow: the lead materials are discharged from process i to the eviromet, with lead flow as i, t/t lead.( i = i + i, i -the lead weight of qualified products which are sold i process i, i -the lead weight of uqualified products which are outputted ito the eviromet, such as caterig waste, productio losses ad so o, t/t lead) (4) Cyclig material flow: the uqualified products i process i or the followig processes are retured to process i or the previous processes to be recycled, with lead flow as i t/t lead.( i,i -the lead weight of materials retured to the origial process; i,k -the lead weight of materials i process i retured to the previous process k, k=1,2,,i-1; j,i -the lead weight of uqualified materials i process j retured to process i as raw materials, j=i+1,i+2,,; i = i,i + j,i ) (5) Output material flow: the qualified products are trasferred from process i to process i+1, with lead flow as P i, t/t lead X/ Betham Ope

2 132 The Ope Materials Sciece Joural, 2014, Volume 8 Wag et al. It is foud that that there are three differet kids of material flows besides the mai material flow P i : the first material flow called material flow cotais the lead material flow iputted ito each process from the eviromet; the secod material flow called material flow cotais the lead material flow retured to the origial process ad the lead material flow is retured to each process from the followig processes; the third material flow called material flow cotais the lead material flow which does ot retur to the origial process after beig discharged to the eviromet. There is a close relatioship amog the mai material flow, material flow, material flow ad material flow i terms of quatity. I order to build a actual material flow model of each process, ot oly do we eed to aalyze all,, material flows, but also we eed to fid out the relatioship betwee them ad the mai material flow. For each process, the priciple that the weight is the balace of reveue ad expediture must be obeyed. (5) Recyclig eergy flow: the eergy is recycled to be used i the process or the other processes, such as fuel, thermal eergy ad so o (e i -the eergy recycled for the process itself, e i -the eergy recycled for other processes); From Fig. (2), we have a eergy equatio: E i!1 + e ",i + e #,i = E i + e $,i + e #,i + e %,i (2) As for the utilizatio of waste heat ad eergy i SKS lead smeltig process, ot oly should we cosider eergy dissipatio i time ad space, but also we should match the utilizatio of differet eergy levels. Whe we face the problem of the further utilizatio of eergy E i, we should judge whether the eergy ca be used i the followig processes. If it caot be used, heat ad eergy would be wasted which ca be recycled o the matchig utilizatio of eergy level priciple. If it ca be used, we should do our best to miimize the time ad space betwee processes ad prevet the eergy from depreciatio whe cosumed. Fig. (2). Eergy flow i productio process. Fig. (1). Material flow i productio process. Accordig to the lead balace, we have: P i!1 + " i + # i,i + # j,i = P i + $ i + # i,i + # i,k (1) 3. ANALYSIS OF THE ENERGY FLOW IN SKS LEAD SMELTING PROCESS Based o the product per uit, the eergy flow of lead productio process is show i Fig. (2). Accordig to the resource, destiatio ad role, eergy flow ca be classified ito five kids of eergy flows. (1) Iput eergy flow: the eergy called E i-1 i process i- 1 is itroduced ito process i, cotaiig chemical eergy, thermal eergy, kietic eergy ad so o; (2) Output eergy flow: the eergy called E i is trasferred from the i process to eviromet, such as thermal eergy ad chemical eergy; (3) Exteral eergy flow: the eergy called e i is added to process i from eviromet, such as fuel, electricity, steam ad so o; (4) Loss eergy flow: the eergy called e i is lost i process i ad the course of trasmissio; 4. ANALYSIS OF COUPLING OF SKS LEAD SMELTING PROCESS I SKS lead smeltig process, material flow merges with eergy flow ad fiishes the productio with the effect of eergy flow. The couplig effect is realized by the quality of the products (the ratio of each material flow is P i ) ad eergy cosumptio of each process (e i ); as a result of their chages, the ratio of each material flow ad eergy cosumptio of each process chage, ad both have a impact o the eergy cosumptio. The miimum eergy cosumptio per to lead is the object fuctio of the couplig model of the SKS lead smeltig process. Its decisio variables are flow rates of material flow ad eergy flow ad costrait equatio is the relatio betwee material flow ad eergy flow. The object fuctio is Mi E p =! e i (3) i=1 The costrait equatio is ( ); e i = ( e!,i + e ",i ) # e $,i + e ",i = C C i + "! j j=i+1 C i + i " " j=i+1 m=1 # j,m % j $ " ; C i j=i+1 C i

3 Couplig Model of Eergy Flow ad Material Flow i SKS Lead Smeltig The Ope Materials Sciece Joural, 2014, Volume 8 133! = f ( p 1, p 2,"""!1, +1,"""p ); e x,i = f ( ); > 0;! e x,i! 0(e x,i!"#!e ",i,e #,i,e $,i ). Further aalysis shows that whe the eergy cosumptio of each process, amely e i, is costat, the ifluece of material flow chages o eergy cosumptio per to lead ca be expressed by formula (4): - e!e p,p = i ' i * 0 $ / " $!# j + $!% j + $ $!& j,m +!& i,i C ), 2 (4) i=1./ i ( j=i+1 j=i+1 j=i+1 m=1 + 12! E p,p -the amout of eergy cosumptio chage per to lead caused by material flow chage, kj/t; e i -eergy cosumptio of each process, kj/t; C i -the lead-cotaiig rate of the productio i each process, %;! j,! j, m,! j -the amout of each material flow chage, t/t; I formula (4), the eergy cosumptio per to lead decreases whe exteral material flow icreases, cyclig material flow decreases ad discharge material flow also decreases. The ifluece of three flows is always greater i the later process tha i the former oes. Whe the lead coefficiet P i of each process is costat ad techology coditio of each eergy coversio process is determied, the ifluece of eergy flow o the eergy cosumptio ca be expressed by formula (5):!E p,e = [ [ ' " #!E i#1 + " q j,i!b j #!e $,i (5) i=1 m i j=1 ] ]! E i-1 -the amout of eergy chage moved to process i from previous process, kgce/t; m i -the umber of kid of eergy eeded to be iputted to produce oe to process products i process i; q j,i -the iput amout of j eergy eeded to produce oe to products i process i,j t/t (m 3 /t, kwh/t);! b j -the amout of j eergy chage, kj/t (kj/m 3, kj/kwh); -lead coefficiet of process i, t/t. Based o formula (5) ad from the perspective of eergy flow, we ca fid that the mai method to decrease the eergy cosumptio per to lead is: to make the eergy to be processed sooer i the products used i the followig process; to decrease the eergy value of differet eergy medium; to reuse differet kids of waste heat ad eergy promptly ad reasoably. 5. CALCULATION AND ANALYSIS OF ENERGY CONSUMPTION WHEN ENERGY FLOW CHANGES I some SKS lead smeltig processes, the eergy called! E i-1 which is carried by lead slag caot be trasferred i time because liquid lead slag produced at the bottom blowig furace must be set to blast furace for smeltig after it is cooled. Besides, the steam produced i the bottom blowig furace ad fumig furace is discharged ito the eviromet, so the eergy for self-use (! e,i )! e is zero. Based o the data of the year 2012 of this eterprise, we calculated that the average eergy cosumptio per to lead (E p,e ) is kj/t usig formula (5). From the eergy cosumptio data of 2012, its average eergy cosumptio per to lead is kj/t with the relative error beig 0.009%. Allowig for the ustable factors i the productio process, such as raw materials, eviromet, temperature ad so o, we ca coclude that the relative error is withi the allowable rage. So the model built i the paper is reasoable. I the right part of formula (5), the three items reflect the ifluece o the eergy cosumptio per to lead of the eergy flow chage i eergy trasmissio, eergy flow chage i eergy trasformatio ad recycled eergy flow chage respectively. The paper aalyzed the eergy coservatio potetial of the eterprise uder the effect of eergy flow i detail. We coverted the eergy carried by products ad waste heat ad eergy recycled i each process to equivalet heat, assumig that all of it is used. Next, the ifluece of the three eergy flow chages o the eergy coservatio per to lead is aalyzed i detail o the coditio that! E i-1 ad! e,i are ot zero i the productio process Ifluece of Waste Heat Recyclig for Self Use i Bottom Blowig Furace o the Eergy Cosumptio Per To Lead Fuel gas i bottom blowig furace is directly set ito the furace agai after gettig out of the furace i order to recycle its waste heat i the productio process. Statistic report shows that about to of steam was produced by bottom blowig-waste heat furace i Based o the related parameters of steam, to steam ca be coverted to kg of stadard coal with the same heat, amely, oe to of crude lead is produced alog with steam with the eergy of 92.93kg stadard coal. If the eergy of! e,2 is all itroduced ito the bottom blowig furace process as recycled eergy, the eergy cosumptio per to lead ca be decreased to kj/t with other factors beig costat, that is, the eergy cosumptio would be decreased by kj/t Ifluece of Waste Heat Recyclig for Use i Fumig Furace o the Eergy Cosumptio Per To Lead I SKS lead smeltig process, the fuctio of fumig furace is maily to deal with the slag i blast furace where there is a lot of heat. The waste heat ad eergy is recycled by waste heat furace as well. There is to steam ad all of which was coverted to kg stadard coal with the same heat i the year If we iput all the steam ito the blast furace, i other words, if 78.80kg

4 134 The Ope Materials Sciece Joural, 2014, Volume 8 Wag et al. Table 1. Ifluece of the maximum of recycled eergy o the eergy cosumptio per to lead [kj/t]. Factor Eergy Loss i Bottom Blowig Process Eergy Loss i Blast Furace Process Comprehesive Eergy Loss Bottom blowig furace Bottom blowig furace fumig furace Bottom blowig furace Bottom blowig furace Blastfurace fumig furace Blastfurace high lead slag Blastfurace stadard coal is put ito the blast furace while oe to crude lead is produced, the eergy cosumptio per to lead would decrease to kj/t with other factors beig costat. That is to say, the eergy cosumptio per to lead decreases by kj/t Ifluece of Sesible Heat Recovery of High Lead Slag o the Eergy Cosumptio Per To Lead There was to high lead slag from the bottom blowig furace ad the average tappig temperature was 1030 at the ed of Based o the characteristics of high lead slag, we ca calculate that the heat ivolved is kj, equally kg stadard coal. If this amout of eergy, as the eergy of the bottom blowig furace, is all itroduced to blast furace process, that is to say, there will be high lead slag carryig the eergy of 54.37kg stadard coal, the eergy cosumptio per to lead decreasig to kj/t with other factors beig costat. That is, the eergy cosumptio per to lead would decrease by kj/t Aalysis of Eergy Cosumptio Uder the Ifluece of Eergy Flow ad Eergy Coservatio Potetial From the above aalysis, it ca be observed that the steam released by the waste heat boilers i bottom blowig furace process ad fumig furace process, ad the sesible heat losses have a great ifluece o the eergy cosumptio per to lead i SKS lead smeltig process. Table 1 shows the ifluece o comprehesive eergy cosumptio of crude lead assumig that the eergy is all recycled i the productio process. Bottom blowig furace ad fumig furace reuse the same kid of waste heat ad eergy. The ifluece o eergy cosumptio varies i differet productio processes; however, the ifluece o eergy cosumptio i the whole productio process is the same. Table 1 shows that the total ifluece of the three eergy flow chages o eergy cosumptio per to lead is kj/t. Besides, decreased usage of coke powder ad smoke powered coal has a great ifluece o eergy cosumptio per to lead. I order to decrease eergy cosumptio per to lead, we should iput the eergy carried by high lead slag ito blast furace as much as possible ad recycle the waste heat ad eergy i the bottom blowig furace, blast furace ad fumig furace i reasoable time. CONFLICT OF INTEREST The authors cofirm that this article cotet has o coflict of iterest. ACKNOWLEDGEMENTS This work is supported by the Key Project of Sciece ad Techology Pla of Hua Provice, Chia; Project(Y ) Supported by Noferrous Metal Sciece Foudatio of HNG-CSU, Chia REFERENCES [1] Li D P, Zhag Z X. The applicatio of ew lead smeltig techology of oxidizig i bottom blowig furace ad reductio smeltig i blast furace. No-ferrous Metals (Smeltig Part) 2003; 4(5): [2] He S C, Li D Y. SKS copper smeltig process. Chia Noferrous Metallurgy 2006; 2(6): 6-9. [3] Zhag L R, et al. Advaced techology for lead ad zic Metallurgy, Hua: Hua Sciece ad Techology Press, [4] Wag H C, Research ad aalysis o eterprise eergy cosumptio system of SKS lead smeltig process. Chagsha: Cetral South Uiversity, [5] Wag H C, Shi Z M, She H, et al. Iflueces of material flow i SKS lead smeltig process o its eergy cosumptio. Joural of Cetral South Uiversity (Sciece ad Techology) 2012; 43(7), [6] Goto N, Tachibaa J, Fujie K. Evirometal maagemet system based o material flow aalysis to establish ad maitai eco tow. Joural of idustrial ad Egieerig Chemistry 2005; 11(6): [7] Lu Z W, Cai J J, Foudatio of systemic eergy coservatio, Beijig: Sciece Press, [8] Xu S B, Geeralized eergy, Hua: Hua People's publishig House, [9] Poleske K R, McMichael F C. A Chiese coke makig process flow model for eergy ad evirometal aalyses. Eergy Policy 2002; 7(30): [10] Cai J J, Wag J J, Lu Z W, et al. Material flow ad eergy flow i iro & steel idustry ad correlatio betwee them. Joural of Northeaster Uiversity (Natural Sciece) 2006; 3(9): [11] Wag J J, Cai J J, Zhag Q, et al. Study o eergy - flow modelig i iro ad steel eterprise. Chia Metallurgy 2006; 16(5), [12] Yu Q B, Lu Z W, Cai J J. Study o the method for calculatig ifluece of mass flow o eergy cosumptio i steel maufacturig process. Acta Metallurgica Siica 2000; 36(4):

5 Couplig Model of Eergy Flow ad Material Flow i SKS Lead Smeltig The Ope Materials Sciece Joural, 2014, Volume [13] LI Xiag, CUI Ji-feg, QI Jia-xu, YANG Shag-dog. Eergy trasmissio modes based o Tabu search ad particle swarm hybrid optimizatio algorithm. Joural of Cetral South Uiversity of Techology 2007; 14(1): [14] Robert D Doerig. Modelig a eergy maagemet system for a large cetral eergy plat complex. Idustrial Egieerig 1981; 13(7): [15] Starbek M, Meart D. The optimizatio of material flow i Productio. Iteratioal Joural of Machie Tools & Maufacture 2000; 40(14): Received: May 26, 2015 Revised: July 14, 2015 Accepted: August 10, 2015 Wag et al.; Licesee Betham Ope. This is a ope access article licesed uder the terms of the Creative Commos Attributio No-Commercial Licese ( by-c/4.0/) which permits urestricted, o-commercial use, distributio ad reproductio i ay medium, provided the work is properly cited.