Control Method for Low Oxygen Concentration in Reheating Furnace

Transcription

1 Chn Steel Techncl Report, No., Control pp. 7, Method () or Low Oxygen Concentrton n Rehetng Furnce Control Method or Low Oxygen Concentrton n Rehetng Furnce HENGHSING CHENG, YUANLIANG HSU, CHAOHUA WANG*, FUYUAN HSIA** nd TUNGTSAI OU** Iron nd Steel Reserch & Development Deprtment *New Mterls Reserch & Development Deprtment. **Rollng Mll Deprtment Ⅱ Chn Steel Corporton The rehetng urnce consumes most o the energy nd produces hgh mounts o crbon doxde n the hot rollng process. The oxygen concentrton n the urnce tmosphere s very mportnt becuse too much oxygen wll cuse greter uel consumpton nd wll nduce more scle on the slb surce nd more ntrogen oxdes n the combuston gs. Proper control o the oxygen concentrton enbles the urnce to ttn better producton cost perormnce n energy consumpton, slb scle loss nd NOx emsson. There re two sources o oxygen n the urnce tmosphere. One s the combuston r suppled to the burner nd the other s the outsde r nltrted nto the urnce durng door openng. In ths study, control technology ws proposed to nhbt the r nltrton nd to mnmze the oxygen concentrton n the urnce tmosphere by controllng the urnce pressure nd combuston r usng predcton method, whch could estmte the nluence rom the vrton n combuston lodng bsed on the stte o chnge n the control loop. The proposed control method hs been mplemented n the rehetng urnces o No. nd No. hot strp mll n Chn Steel Corporton. The results revel tht the control method could nhbt the r nltrton sgncntly through decrese n the urnce temperture drop ter the door openng. Moreover, the oxygen concentrton n the urnce tmosphere could be stbly mnmzed bsed on the better control perormnce. Also, the results o experments demonstrted tht ths method reduced the uel consumpton o the urnce, the scle loss o the heted slb nd therml NOx emsson. Keywords: Furnce pressure, Oxygen concentrton, Artouel rto, Fuel consumpton, Slb scle loss. INTRODUCTION In the hot strp mll, slbs re heted bove 5C or the subsequent rollng process, so the lowtemperture slbs re pushed nto the rehetng urnce rom the chrgng sde nd heted grdully v the prehetng zone, hetng zone nd sokng zone nd extrcted t the dschrgng door, s shown n Fg.. Oxygen s n essentl element or the combuston recton n the rehetng urnce, though the oxygen n the urnce lso prtcptes n some o the rectons, ncludng the ormton o ntrogen oxdes (NOx), or oxde lyer on the surce o the slb (see Fg.). Excess oxygen n the urnce not only ncreses the energy consumpton nd slb scle, but lso ncreses the slb scle nd therml NOx, nd other negtve eects suppressed durng Fg.. Rehetng urnce n hot strp mll.

2 HengHsng Cheng, YunLng Hsu, ChoHu Wng, FuYun Hs nd TungTs Ou oxygen decency. The best stuton s to ensure the complete combuston o the uel under the premse o mnmzng the resdul oxygen or, n other words, to mntn low level o oxygen concentrton n the exhust gs. On the other hnd, n the hghtemperture urnce re, such s the hetng zone nd sokng zone, to supply decent oxygen cn eectvely slow down the oxdton rte o steel slbs, so t s necessry to ensure tht ll the resdul uel s burnt n the downstrem zone. Fuel consumpton nd slb scle loss re the mjor costs n the hot rolled strp or plte producton lne n ddton to the mterl cost. Generlly, n the rehetng urnce the uel consumpton per ton o steel s bout 8 to 6 clores, nd the oxde scle cuses slb weght loss bout.6 to %. Thereore, the stble control o the oxygen n the urnce tmosphere nd the mntennce o low oxygen concentrton n the exhust gs re the mens to reduce uel consumpton nd scle loss. Combuston r Combuston r CO, NOx, O FeO, Dschrge Dschrge door composton. For exmple, the coecent or coke oven gs (C.O.G.), whch s usully used s the source o the hetng uel n the rehetng urnce, s bout.. The urnce temperture s controlled by djustng the uel low suppled to the burners nd the r low needed or complete combuston ccordng to the coecent. However, t s dcult to control the composton o C.O.G. precsely. Fgure shows tht the clorc vlue o C.O.G. chnges n the rnge o 8 to kcl/m. I the uel hetng vlue chnges, the mount o r needed or combuston o uel my be excessve or ndequte, resultng n vrton o the oxygen concentrton n the exhust gs. Oxygen Oxygen concentrton (%) Slb dschrgng Slb dschrgng Tme (mn) Tme (mn) Fg.. Ar nhlton durng dschrge door openng. Ar Slb Fg.. Recton o oxygen n the slb rehetng urnce. There re two sources or the oxygen n the urnce tmosphere. One s the combuston r suppled to the burner nd the other s the outsde r nhled nto the urnce durng the openng o the dschrgng door. Both result n vrton o the oxygen concentrton n the urnce tmosphere. Every ew mnutes, the dschrge door s opened brely to extrct the heted slbs. Snce there s derence n the mbent temperture nsde nd outsde the urnce, there exsts vertcl pressure drop. The vertcl pressure drop cuses negtve pressure t the bottom o the urnce whle the door s openng nd the outsde r s nhled nto the urnce. Thereore, the urnce temperture n the sokng zone s sgncntly decresed nd the oxygen concentrton o the exhust gs ppers to pek ter the door s opened, s shown n Fg.. Fgure lso revels tht r nhlton s derent ech tme becuse o the derent pek vlue o oxygen concentrton. Besdes the r nltrton, the luctuton o uel composton lso dsturbs the oxygen concentrton. The unt volume o r requred or complete combuston o uel s clled the theoretcl r consumpton coecent nd s bsed on the uel COG clorc vlue (kcl/m ) ) Tme Tme (dy) (dy) Fg.. Dly chnge o C.O.G clorc vlue. In generl, oxygen nlyzers my be nstlled n the roos o the prehetng zone, hetng zone nd sokng zone to mesure the oxygen content n the urnce tmosphere nd used to control the oxygen concentrton o wste gs by utomtclly djustng the rtouel rto (A/F rto) n every zone (). Some studes proposed other desgns o oxygen eedbck control wth tme dely compenston () or used some dvnced control technques such s uzzypid control (). However, n most urnces o Chn Steel, the oxygen nlyzer cn esly l n hgh temperture surroundngs such s those n the hetng zone or sokng zone nd the smplng tube cn esly become clogged becuse o sulde deposton. So the eedbck control o oxygen concentrton cnnot be used n every urnce zone t Chn Steel. However, t hgher tempertures, the oxdton rte o the slb n the ur

3 Control Method or Low Oxygen Concentrton n Rehetng Furnce nce my ncrese lmost exponentlly (56), so reducng the oxygen content n the hgh temperture zone cn eectvely reduce the slb scle s mentoned bove. In prctce, the combuston r suppled to the hetng zone nd sokng zone my be ndequtely controlled by mnully djustng the A/F rto less thn. (wth A/F rto lrger thn. t the prehetng zone). Thereore, the mesured oxygen concentrton t the hetng zone nd sokng zone would be zero nd cnnot be used to control the A/F rto utomtclly. Otherwse, some studes proposed tht reltme mesurng o the clorc vlue o C.O.G. to djust the A/F rto dynmclly n ccordnce wth n emprcl ormul to compenste or the eect o chnges n clorc vlue (7). However, ths method s knd o eedorwrd control tht s not ble to overcome other dsturbnces such s r nhlton. Becuse there s no esble nd stble method or oxygen control n the hgh urnce tmosphere, ddtonl uel consumpton nd scle loss result. In ths reserch, control method or low oxygen concentrton o wste gs n rehetng urnce s proposed. Frst, dschrge predcton control o the urnce pressure ws developed to predct quntttvely the level o r nhlton wthn ew seconds ter the dschrge door s opened. Then the urnce pressure cn be mmedtely controlled durng the whole perod o door openng (bout 5 seconds) to reduce the r nhled nto the urnce. Second, new control rchtecture or utomtclly djustng the A/F rto ws proposed to stbly mntn the wste gs t low oxygen stte. The new control rchtecture ncludes theoretcl zone A/F rto clculton by consderng the resdul uel gs or oxygen rom the upstrem zone, the low compenston when the burner s suppled wth excess r, nd nlly eedbck control bsed on the ctul oxygen concentrton mesured t the prehetng zone roo ner the chrgng door ( lowtemperture re n the urnce, where the relblty o the oxygen nlyzer s gretly enhnced) to correct ny error rom the theoretcl mode. The proposed control method hs been mplemented n the rehetng urnces o No. nd No. hot strp mlls t Chn Steel Corporton. The results revel tht the control method could nhbt the r nltrton sgncntly bsed on the decresng o the urnce temperture drop ter the door openng. Addtonlly, the oxygen concentrton n the urnce tmosphere could be stbly mnmzed bsed on the better control perormnce. Also, the results o experments demonstrte tht ths method mproves the unormty o slb temperture nd reduces the uel consumpton o the urnce, the scle loss o heted slb nd therml NOx emsson.. EXPERIMENTAL METHOD The method proposed n ths study or controllng the oxygen concentrton n wste gs s exhbted n Fg.5. The method ncludes two prts: the dschrge predcton control o the urnce pressure; nd the utomtc rtouel rto control wth the estmton o the zone oxygen concentrton.. Dschrge Predcton Control o Furnce Pressure Becuse the trnsent response o the temperture eld nd low eld n the rehetng urnce s complex when the dschrge door s opened, t s dcult to decouple the governng equton o urnce pressure by the theoretcl nlyss. Yet ny chnge o the low eld wll eventully be relected n chnges o the Oxygen concentrton estmton (Vrtul sensor) Feedbck Artouel rto control modcton Oxygen trget Trget Zone TF T cscde control Zone TF T cscde control Zone TF T cscde control O Anlyzer HZ Dmper Pressure control Pressure trget Trget Stte estmton Predcton control Fg.5. Low oxygen control o rehetng urnce.

4 HengHsng Cheng, YunLng Hsu, ChoHu Wng, FuYun Hs nd TungTs Ou equlbrum stte o the urnce pressure control. Ater the study o lrge mounts o dt through sttstcl nlyss the chrcterstcs o the pressure chnges durng the openng o the dschrge door were determned, s shown n Fg.6 nd Fg.7. The temperture drop t the sokng zone ter dschrgng door s opened cn ndcte the r nhlton s quntttve ndex. The dt shown n Fg.6 revels tht the temperture drop s quslner reltve to the verge error o urnce pressure control durng whole perod o dschrgng. Also, t ws ound tht the trend o the equlbrum stte chnge n the urnce pressure control s consstent throughout the whole perod o dschrgng, so tht the output chnge n the urnce pressure control loop wthn 5 seconds ter door openng hs negtve correlton wth the verge error o pressure control, s shown n Fg.7. The control output ws used to djust the lue dmper openng. Pressure control error durng dschrgng (mmho) Pressure control error durng dschrgng (mmho) T t d (d ) temperture drop (deg) temperture drop (deg) Fg.6. Quslner relton between temperture drop t sokng zone nd urnce pressure. control error durng dschrgng. Pressure control output chnge n 5s (%) Pressure control output chngen 55 (%) Pressure Pressure control error durng dschrgng (mmho) O) Fg.7. Quslner relton between pressure control error durng dschrgng nd control output chnge n 5s. On the bss o the bovementoned ndngs, the dschrgng predcton control ws desgned n ths study to utomtclly djust the urnce pressure. The control dgrm s exhbted n Fg.8. Bsclly, the urnce s kept t low postve pressure,.e..mm H O, nd then strts to dynmclly djust the pressure beore the openng o the dschrgng door. Due to the long dstnce rom pressure mesurement poston to the lue dmper, the response o the urnce pressure control s slow (bout seconds). So, bout seconds beore openng the door, the urnce pressure hs to be rsed by ollowng the predesgned pttern. The predcton control s then strted 5 seconds ter door openng. The lgorthm o the predcton control s to chnge preset temperture drop n the expected urnce pressure control error rst, n ccordnce wth the lner regresson equton n Fg.6. Then, the output ncrement o the pressure PI controller (Proportonl Integrl controller) wthn 5 seconds ter ech door openng s used to estmte the verge error o the urnce pressure control durng the whole dschrgng Dschrgng predcton control Expected temperture drop Expected FPC error Gn Dschrgng FPC error estmton Acton tme ΔMV clculton Trgger Pressure trget Acton tme Dschrgng PID control Dmper Furnce lmtton Dschrgng pttern Pressure sensor Dschrge door open FPC: Furnce pressure control loop Trgger: 5sec ter dschrge door OPEN Acton tme: rom 5sec ter dschrge door OPEN to door CLOSE Acton tme: rom sec beore dschrge door OPEN to sec ter door CLOSE Fg.8. Dschrgng predcton control o urnce pressure.

5 Control Method or Low Oxygen Concentrton n Rehetng Furnce perod ccordng to the lner regresson equton n Fg.7. The derence between the estmted error nd the expected error cn be used to djust the control trget o the urnce pressure drectly untl the dschrgng door s closed. So, the correcton o urnce pressure by the predcton control s derent nd cn control the r nhlton durng ech perod o slb dschrgng.. Automtc ArtoFuel Rto Control In generl, the rehetng urnce my be splt nto multple ndependent temperture control zones to grdully het slbs to set temperture. The gs n the urnce lows rom the sokng zone to the prehetng zone, so the resdul uel gs or r rom the upstrem zone my nluence the combuston recton n the current zone, s shown n Fg.9. For exmple, the suppled r sokng zone s ndequte,.e. the rtouel (A/F) rto o the sokng zone s set to.9, t mens tht bout % uel gs my not be burnt nd low to ts downstrem zone (the hetng zone.). The new control method s bsed on the expected rtouel rto n every zone to reclculte the requred zone A/F rto by consderng the resdul uel gs or r rom the upstrem zone. The lgorthm s shown n Equton, (V ~ V V, V ( V V ~ I...() ( )V ) V ) V, V,,...() In the nl zone o the low drecton, ll uel gs should be completely burnt to vod ny ddtonl uel consumpton or polluton, so the control trget n the prehetng zone s the expected oxygen concentrton ( ) n the wste gs. The theoretcl expresson s shown s Equton 5, V V V (%)...(5) w where s V w s the combuston gs n the prehetng zone nd s expressed s Equton 6 ccordng to the theoretcl combuston gs producton coecent ( ) nd then the expected rtouel rto cn be clculted s Equton 7. Also, the requred rtouel rto n the prehetng zone cn be obtned by the Equton. Combuston r V w (V ~ V ~ V ~ )... (6) HZ Combuston recton Resdul uel or r orm upstrem zone (V ~ V ~ ( ) (V ~ HZ V ~ V HZ )... (7) ) Fg.9. Illustrton o resdul uel gs or r orm upstrem zone. V V V ~ V ~ V V where V nd V re the volume low o r nd uel gs n the th zone; V nd V re the resdul r nd uel gs rom the upstrem zone; V ~ nd V ~ re the suppled r nd uel gs o the burner; s the expected zone rtouel rto nd η s the theoretcl r consumpton coecent o the uel gs. u s the requred rtouel rto or controllng the suppled r o burner s shown n Equton nd t cn be expressed s Equton, where the resdul r or uel gs re clculted s Equton. ~ ~ V V... () Accordng to the bovementoned lgorthm the requred A/F rto n ech zone cn be clculted, so tht the ctul rto o r nd uel gs prtcptng n the combuston recton cn meet the expected stuton. Besdes, ddtonl r s requred to ensure combuston... () ecency when the uel low suppled to the ( burner s low. The ddtonl r lso ects the combuston recton n the downstrem zone, so compenston method ws proposed to compenste or the extr r rom the burner. Fnlly, eedbck control method ws proposed to correct the error between the ctul oxygen concentrton mesured n the prehetng zone nd the estmted oxygen concentrton. The estmted oxygen concentrton s clculted by the mesured low rtes o uel gs nd r n ll combuston zones. It s ssumed tht ny vrton o the clorc vlue o C.O.G. results n percentge chnge o the theoretcl r consumpton coecent ( ( ) ). Substtutng nto Equton 5, the mesured oxygen concentrton ( ~ ) cn be expressed s Equton 8. Thereore, the percentge chnge o the theoretcl r consumpton coecent cn be estmted s Equton 9 nd used to correct the theoretcl zone

6 HengHsng Cheng, YunLng Hsu, ChoHu Wng, FuYun Hs nd TungTs Ou 5 rtouel rto nd low compenston v PI controller. Fgure depcts the bre control dgrm o the utomtc A/F control. To reduce the nluence o ny tme dely rom the low eld nd mesurement response, ll dt used n the eedbck correcton ws clculted v wndow verge wth the durton o 5 mnutes. ~ (%) (V ~ [(V ~ V ~ V ~ (V ~ V ~ V ~ ) ( ) )] V ~ V ~ ) [(V ~ HZ V ~ V ~ HZ ) ( ) (V ~ V ~ V ~ )] HZ ( ~ ) [(V ~ HZ... (8) V ~ V ~ (V ~ V ~ V ~ )] ~ (V ~ ) HZ (( ~ ) ~ ) (V ~ HZ V ~ V ~ ) HZ HZ V ~ HZ V ~... (9). RESULTS AND DISCUSSION The dschrgng predcton control cn predct the level o r nhlton ter the openng o the dschrgng door nd utomtclly djust the urnce pressure. Fgure shows the results o the dschrgng predcton control. The Fgure() shows the phenomenon o temperture drop t the sokng zone ter slb dschrgng wthout usng the predcton control. The temperture drop ter ech slb dschrgng s derent mens tht the level o r nhlton s lso derent. The Fgure revels tht the temperture drop s sgncntly mproved by usng the predcton control. The mesured oxygen concentrton n the wste gs shown n Fg. lso demonstrtes tht the r nhlton rom the dschrgng door s decresed. ) temperture (deg) (deg) temperture temperture (deg) (deg) Slb dschrgng 5 Tme Tme (mn) () () Slb dschrgng 5 Tme (mn) Fg.. Results o sokng zone temperture ()wthout nd wth dschrgng predcton control o urnce pressure. Oxygen Oxygen concentrton concentrton (%) Oxygen concentrton (%) Oxygen concentrton (%) Slb dschrgng 5 Tme (mn) (mn) () Slb dschrgng 5 Tme (mn) Fg.. Results o oxygen concentrton ()wthout nd wth dschrgng predcton control o urnce pressure. () O estmton Low uel bs Δ X Zone temperture control A/F rto trget Fuel low control X (=.) X Fuel low to zone Ar low control Ar low to zone Wndow verge Wndow length: 5mn estmton O mesured t prehetng zone PI control Ded bnd: ±.5 Lmt: ±.7 Zone A/F rto clculton Flow compenston X Fg.. Automtc A/F rto control t low oxygen concentrton.

7 6 Control Method or Low Oxygen Concentrton n Rehetng Furnce Fgure shows the sttstcl results o the predcton control n longterm demonstrton. The pek o mesured oxygen concentrton nd the mount o temperture drop re both ndces or quntyng the r nhlton durng door openng. Although there s no method to mesure the r nhlton drectly, the postve correlton shown n Fg.() revels tht the two quntttve ndces re relted to the r nhlton. Ater usng the predcton control, both the verges nd stndrd devtons n the two ndces re decresed s shown n Fg.. Also, the lower stndrd devton n the two ndces mens tht the predcton control ndeed nhbts the r nhled nto the urnce every tme the dschrgng door s opened. Oxygen concentrton concentrton pek (%) Oxygen concentrton pek (%) Oxygen concentrton pek (%) Men±xstd. =.7±x.9 Men± xstd. =.88 ± x.8 temperture drop (deg) () Men±xstd. =.±x. Men± xstd. = 7.8 ± x.79 temperture drop (deg) Fg.. Sttstcl results o temperture drop nd oxygen pek ()wthout nd wth dschrgng predcton control o urnce pressure. Fgure () shows the mesured oxygen concentrton o wste gs beore usng the low oxygen control. All A/F rtos n the prehetng zone, hetng zone nd sokng zone re xed, so tht ny chnge o uel het vlue or other dsturbnce my nduce vrnce o oxygen concentrton. Thereore, the A/F rtos were set hgher thn ormerly to ensure the complete combuston o the suppled uel. However, ths nevtbly results n n excess o suppled r nd cuses ddtonl uel consumpton nd scle loss. Fgure shows the result o low oxygen control. The mesured oxygen concentrton s more stble nd hs sgncntly smll stndrd devton, enblng the urnce to remn t stble low oxygen stte. Fgure 5 exhbts the sttstcl results o longterm testng n the our rehetng urnces o No. hot strp mll. The results o the trls wth low oxygen control ll show smller men vlues nd stndrd devtons n oxygen concentrton. The trls lso demonstrte tht the proposed control method s esble even when the new control used n derent urnce. Oxygen Oxygen concentrton concentrton (%) (%) Oxygen Oxygen concentrton concentrton (%) (%) 5 Men±std. =.8±.55%.55% 5 Tme (hour) () 5 Men±std. =.5±.%.% 5 Tme (hour) Fg.. Results o oxygen concentrton ()wthout nd wth low oxygen control. Oxygen concentrton Oxygen (%) concentrton (%) No. Furnce Wthout LOC Wth LOC Trl Trl Trl Trl No. Furnce Wthout LOC Wth LOC No. Furnce Wthout LOC Wth LOC Trl Trl Trl Trl No. Furnce Wthout LOC Wth LOC Trl Trl Trl Trl Trl Trl Trl Trl Fg.5. Sttstcl results o low oxygen control n derent urnces.

8 HengHsng Cheng, YunLng Hsu, ChoHu Wng, FuYun Hs nd TungTs Ou 7 Tble Benets o low oxygen control t Chn Steel Fuel consumpton Scle loss No. Hot Strp Mll No. Furnce.68%.58% No. Furnce.%.% No. Furnce.8%.5% No. Furnce.98%.99% No. Hot Strp Mll No. Furnce.575%.86% No. Furnce.6%.% Averge.9%.% To ncrese the controllblty o oxygen content n urnce tmosphere, the proposed control method n ths study rst nhbts the r nhlton rom the dschrgng door by usng predcton control, nd then utomtclly controls the A/F rto n ech combuston zone v zone A/F clculton, low compenston nd eedbck correcton. It s mportnt tht n the eedbck control loop, the control trget s not the expected oxygen concentrton. The control trget s the estmted oxygen concentrton clculted ccordng to the mesured low o suppled uel nd r. And, the results demonstrte tht ths knd o control method s useul to control the oxygen content. The proposed control method or controllng the oxygen content n urnce tmosphere hs been mplemented n the rehetng urnces o No. nd No. hot strp mlls t Chn Steel Corporton. Ater totl o sx urnce testng trls (the results re ndcted n Tble ), t s demonstrted tht usng the control method cn hve the benets o svng.9% n uel consumpton nd ncresng the yeld by.%. In other words, when ths low oxygen control method s used n the two hot strp mlls t s ble to nnully sve bout m o C.O.G. consumpton, reduce bout, tons o slb scle loss nd decrese bout 6, tons o CO emssons.. CONCLUSIONS In the rehetng urnce o hot rollng mll, therml energy rom uel combuston hets the slb v het trnser o rdton nd convecton. Thereore, the urnce consumes most o the energy nd produces hgh mounts o crbon doxde n the hot rollng process. The oxygen concentrton n the urnce tmosphere s very mportnt becuse too much oxygen wll cuse more uel consumpton nd wll nduce more scle on the slb surce nd more ntrogen oxdes n the combuston gs. Proper control o the oxygen concentrton cn enble the urnce to obtn better perormnce n terms o producton cost n energy consumpton, slb scle loss, nd NOx emsson. There re two sources o oxygen n the urnce tmosphere. One s the combuston r suppled to the burner nd the other s the outsde r nltrted nto the urnce durng the dschrge door openng. Also, the nltrton o cold r wll led to n nconsstent temperture decresng rte on both sdes o the slb nd cuse nonunormty o slb temperture. In ths study, control technology ws proposed to nhbt the r nltrton nd to mnmze the oxygen concentrton n the urnce tmosphere by controllng the urnce pressure nd combuston r wth predcton method, whch could estmte the nluence o the vrton o combuston lodng bsed on the stte chnge n the control loop. The proposed control method hs been mplemented n the rehetng urnces o No. nd No. hot strp mlls t Chn Steel Corporton. The results reveled tht the control method could sgncntly nhbt the r nltrton ter door openng. Moreover, the oxygen concentrton n the urnce tmosphere could be stbly mnmzed by the better control perormnce. Also, the results o experments demonstrted tht ths method could mprove the unormty o slb temperture nd reduce the urnce uel consumpton, the scle loss o heted slb, nd the therml NOx emsson. REFERENCES. L.J. Jng, J.G. Jng, T. Fu, nd Y.J. Yng: Shndong Metllurgy; 6, vol. 8, no., pp. 6.. H.Q. B: Journl o Astronutc Metrology nd Mesurement;, vol., no., pp X.Y. Lu, J. Sun, nd X.Y. L: Technques o Automton & Applctons; 5, vol., no. 9, pp X.Y. Lu, J.D. Zhng, nd X.Y. L: Control Systems; 6, vol., no., pp Z.Z. Lu, Z.P. Zheng, C.J. Dng, H.S. Zeng, nd D.M. Zhng: Energy or Metllurgcl Industry;, vol., no., pp.. 6. T.B. We: Reserch on Iron & Steel;, no., pp S.M. To: Bosteel Technology;, no., pp. 8.