Recycling EAF dust by heat treatment with PVC

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Minerals Engineering 20 (2007) 739–746

Recycling EAF dust by heat treatment with PVC

Gye-Seung Lee a, Young Jun Song b,*

a National Institute of Advanced Industrial Science and Technology, Onogawa, Tsukuba 305-8569, Japanb Department of Metallurgical Engineering, Samcheok Campus Kangwon National University,

253 Gyodong, Samcheok, Republic of Korea

Received 29 September 2006; accepted 15 March 2007Available online 4 May 2007

Abstract

This study investigated whether polyvinyl chloride (PVC) can be used as an additive for the treatment of electric arc furnace (EAF)dust. The PVC powder was mixed with the dust in order to test the synchronous treatment of two resources: waste PVC and EAF dust.The mixture was made into pellets and subjected to heat at various temperatures. The effects of the heat treatment and heating rate wereinvestigated. The PVC emitted hydrogen chloride gas by pyrolysis and generated chlorides of zinc, lead, and cadmium in the pellets.These chlorides can be recovered by volatilization or leaching after the heat treatment. The residual pellet of this process contained over45% iron, and it is expected that the residual pellet can be injected into the electric arc furnace.� 2007 Published by Elsevier Ltd.

Keywords: EAF dust; PVC; Recycle; Heat treatment; Volatilization

1. Introduction

Generation of the electric arc furnace (EAF) dust insteel-making companies has increased, and many researchstudies on its treatment have been published. Althoughmost of the researches focused on the recovery of metals,prior consideration about using the dust may be re-injec-tion into the furnace as the principal ingredient of the dustis iron. Therefore, the subject of those researches, like thisstudy, can be regarded as pretreatment for re-injection.

EAF dust refining methods can be classified as wet anddry, and their main target metals are zinc, lead, and cad-mium. A typical dry refining method involves mixing thedust with an additive and subjecting it to heat. The notice-able point is that lead and cadmium are recovered as chlo-rides. For example, the WAELZ kiln method mixes thedust with a reductant and roasts the mixture in about1200 �C. Zinc can be recovered as metal by deoxidationand volatilization. Although this method can recoveralmost all lead and cadmium in the dust, all of those are

0892-6875/$ - see front matter � 2007 Published by Elsevier Ltd.

doi:10.1016/j.mineng.2007.03.001

* Corresponding author.E-mail address: [email protected] (Y.J. Song).

recovered as chloride and the source of chlorine is the dustitself (Lee et al., 2000).

This research began from the idea that target metals ofthe dust can be recovered as chlorides by volatilization.We choose waste polyvinyl chloride (PVC) as the sourceof chlorine and tested whether PVC can be used as theadditive. PVC is composed of about 57% chlorine andabout 43% hydrocarbon. It begins emitting hydrogen chlo-ride gas by pyrolysis under 300 �C and remains hydrocar-bon. Hydrogen chloride gas may pose a problem duringthe incineration of waste, but it can be used as a providerof chlorine. Moreover, the residual hydrocarbon of PVCcan be used as a reductant.

Therefore, this research was carried out for the simulta-neous treatment of two kinds of resources: EAF dust andwaste PVC. The entire process of this research aimed torecover the zinc, lead, and cadmium from the dust andwas adjusted so that the residual dust can be injected intothe EAF.

Instead of using waste PVC, pure PVC powder was usedin this research. The characteristic of the dust and PVC wasinvestigated. The dust and PVC were mixed and made aspellets at various mixing ratios. The pellets were heat-treated

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740 G.-S. Lee, Y.J. Song / Minerals Engineering 20 (2007) 739–746

at various temperatures, and the effects of the heat treatmentand the heating rate were investigated.

2. Experimental

The EAF dust was collected from a baghouse of a steel-making company in Korea. Pure PVC powder (LS100S,LG Chem Co.) was used in experiments and was mixedwith the dust in various ratios. Prior to making pellets,the dust and PVC powder were blended by a rod mill forover 2 h. The mixture was injected into a cylindrical holeof a mold with an inner diameter of 11 mm. A hydraulicoil press machine compressed about 3 g of the mixture at200 kg f/cm2 for 30 s, producing cylindrical pellets. As thepellets generated by over 150 kg f/cm2 of compressive forcewere hard enough for the experiments to be performed, theuse of binder or cement to solidify was not needed.

Fig. 1 shows the schematic of the furnace used in thisresearch. To control the atmosphere inside the furnaceand draw out the volatilized gases, argon gas was injectedinto the furnace at a rate of 0.25 m3/h. Gases wereexhausted through a condenser for the recovery of chlo-rides from the exhaust gases. We used five pieces of pelletsin a crucible for each roasting experiment. The roasted pel-lets were immediately removed at the end of roasting timeand chilled in a cooling device, into which room-tempera-ture argon gas was injected. The weight of the chilled pelletwas measured and weight decrease was calculated.

Fig. 1. Schematic diagram of experimental apparatus.

Table 1Composition of the dust (unit: wt%)

ZnO Fe2O3 PbO CuO CdO A

27.39 32.46 4.48 0.31 0.07 1.

The solid samples were dissolved by an acid mixture foranalysis. The chemical composition of the prepared solu-tions was analyzed by ICP (VISTA-Pro, Varian) exceptchlorine and carbon. The content of chlorine was measuredby potentiometric method, which is the titration methodusing a silver electrode and silver nitrate titrant (Clesceriet al., 1998). To measure the carbon content of the sample,the sample was pulverized into under 45 lm and heated ina tube furnace at 800 �C. Oxygen gas was injected into thefurnace and the exhaust gas was drawn out through a car-bon dioxide gas absorber using sodium hydroxide. Carboncontent was calculated from the weight variations of theabsorber (Korean Industrial Standard, 2003).

The configuration of the samples and the distribution ofseveral elements in the sample were observed by SEM(JSM6300, JEOL) and EDX mapping technique. X-ray dif-fraction technique (D/max-2200, RIGAKU) was used forthe analysis of crystalline phases of samples. XRD patternswere compared with the list in the Joint Committee onpowder diffraction standards (JCPDS) data files.

3. Results and discussion

3.1. Characteristic of the EAF dust

Table 1 shows the composition of the dust. The princi-pal elements in the dust were iron and zinc. Lead, alkalimetals, and chlorine were minor elements. In this researchand chemical analysis, minor elements less than 0.1% wereignored except cadmium.

The X-ray diffraction technique was applied in the anal-ysis of the crystalline phases of the dust. Intensities andpositions of XRD patterns in Fig. 2 were collated withJCPDS and the results imply that the dust contains the fol-lowing crystals: ZnFe2O4 (franklinite), Fe3O4 (magnetite),ZnO (zincite), and SiO2 (quartz), KCl (Sylvite), NaCl(Halite). Table 1 and the XRD result imply that chlorinein the dust mainly makes compounds with alkali metals.

Fig. 3 shows the particle size distribution of the dust.Dust size was under 10 lm except approximately 8% ofover 9 lm. Photographs of SEM in Fig. 4 indicate that dustparticles were spherical in shape with a diameter of about1 lm, coinciding with the median size of the dust:1.07 lm. Therefore, particles of over 9 lm can be regardedas aggregate of other smaller particles.

3.2. Pyrolysis of PVC and reaction with the dust

Fig. 5 shows the size distribution and SEM photographof the PVC sample. As can be seen, the size of PVC parti-cles ranges from 70 lm to 200 lm.

l2O3 CaO MgO Na2O K2O Cl

27 3.23 2.69 3.11 5.23 5.95

10 20 30 40 50 60 70 80

F : Franklinite or MagnetiteZ : Zincite (ZnO)K : Sylvite (KCl)N : Halite (NaCl)

F

Inte

nsity

2θ

N

N

NKK

K

FZ

F

Z

Z

Z

Z

FF

F

F

F

Fig. 2. XRD patterns of the dust (Cu Ka).

0.1 1 10 1000

1

2

3

4

5

Diff

eren

tial f

requ

ency

(%

)

Particle size (μm)

Fig. 3. Particle size distribution of the dust.

Fig. 4. SEM photographs of the dust.

50 100 150 200 2500

2

4

6

8

10

12

14

16

Parti

cle

size

dis

tribu

tion

(%)

Particle size (μm)

Fig. 5. Particle size distribution and SEM photograph of PVC powder.

0 200 400 600 800 10000

20

40

60

80

100

-4

-2

0

2

4

6 TGA in Ar

TGA in air DTA in Ar DTA in air

TGA

(wt%

)

DTA, ΔT

Temperature (ºC)

Fig. 6. TG–DTA curves of PVC powder. (Heating rate of 10 �C/min.)

G.-S. Lee, Y.J. Song / Minerals Engineering 20 (2007) 739–746 741

For confirmation of the pyrolysis of the PVC sample,thermo-gravimetric and differential thermal analysis (TG–DTA) of PVC sample were performed. The tests were con-

ducted in the atmosphere of air and argon, respectively.Fig. 6 shows the result.

Both TGA curves commonly showed sudden weight lossof about 62% between 250 �C and 350 �C and those wereaccompanied with small endothermic peaks in both DTAcurves. It indicated that the PVC pyrolyzed and emittedhydrogen chloride with a little hydrocarbon, which was4% of weight loss and it was noticed as benzene or toluene(Saeed et al., 2004).

After the emission of hydrogen chloride, the residuebegan to decompose at about 400 �C. It lost only 28% ofits weight under the argon atmosphere. However, underthe air atmosphere, the entire residue burned with the exo-thermic peak of the DTA under 600 �C.

Consequently, the PVC began to emit hydrogen chloridegas under 300 �C and the hydrocarbon residue decomposedat over 400 �C. To confirm the pyrolysis of the PVC in thepellet, the PVC 10% pellet, the mixing ratio of the dust andPVC is 9:1 was heated at 300 �C for 1 h and its cross-sec-tion was observed by the EDX mapping technique ofSEM. Fig. 7 shows the distribution of the carbon and

Fig. 7. EDX mapping of the cross-section of the pellet (PVC 10% pellet roasted at 300 �C for 1 h). (a) SEM photograph, (b) carbon and (c) chlorine.

200 400 600 800 10000

100

200

300

400

500

600

700

800

FeC

l 2

Cd

Cl 2

Pb

Cl 2

Zn

Cd

FeC

l 3

Zn

Cl 2

Vapo

ur p

ress

ure

(mm

Hg)

Temperature (ºC)

Fig. 9. Variation of vapor pressure as temperature.


chloride on the cross-section with SEM photograph. Ascan be seen, the PVC particle decomposed in the pelletand had a hollow structure. Fig. 7b and c indicate thatthe residual PVC contained no chlorine and the hydrogenchloride reacted with the dust around that.

The effect of the heat treatment on the volatilization ofmetals is shown in Fig. 8. The PVC 30% pellets were heatedin temperatures varying from 300 �C to 1000 �C for 1 h.Because the pellets were quickly injected into the furnacewhen the internal temperature of the furnace reached thetarget temperature, the heating rate was very fast but couldnot be measured.

Volatilization of zinc, lead, and cadmium increased inproportion to the temperature, and particularly from600 �C, volatilization began to rapidly increase. Volatiliza-tion of cadmium finished at 800 �C, and those of lead andzinc were finished at 1000 �C.

However, 17% of iron was volatilized at 300 �C and thevolatilized amount hardly varied with the temperature.This result can be explained by vapor pressure of the chlo-rides as shown in Fig. 9 (The Chemical Society of Japan,1975). As can be seen in the figure, the form of iron which

300 400 500 600 700 800 900 10000

20

40

60

80

100

Vola

tiliz

ed ra

tio (%

)

Temperature (ºC)

Cd Pb Zn Fe

Fig. 8. Volatilized elements as temperature from PVC 30% pellets roastedat each temperature for 1 h.

can be volatilized at 300 �C is FeCl3,implying that the vol-atilization of iron was mainly caused by the generation ofFeCl3.

Vapor pressures of PbCl2 and CdCl2 can explain thatthe volatilization of lead and cadmium had rapidlyincreased from 600 �C, as shown in Fig. 8. However,although ZnCl2 could volatilize at a lower temperaturethan the chlorides of lead and cadmium, its volatilizationfinished at about 1000 �C. It implies that the generationof the zinc chloride is slower than other chlorides or some-thing interrupts the generation or volatilization of the zincchloride.

Fig. 10 is the XRD patterns of the pellets roasted from800 �C to 1000 �C shown in Fig. 8. As can be seen, the newpeak of K2ZnCl4 appeared at 800 �C. However, it vanishedat 1000 �C and, instead, the peak of KCl became bigger.This implies that potassium chloride can restrain zinc chlo-ride from volatilization until 900 �C by generatingK2ZnCl4.

Cross-sections of those pellets were observed by SEM.Fig. 11a is the SEM photograph of the pellet roasted at800 �C. The dust and PVC combined with each other andlost their original shapes.

There were needle-shaped materials around the residualPVC. This pellet was heated at 800 �C and much of volatilechlorides still remained inside it. Its volatilization wasstopped by sudden chilling at the end of the heat treatment.Therefore, the material can be regarded as the result of thesudden chloride growth.

10 20 30 40 50 60 70 80 90

PK

K

W

N

N

N

I

I

WN

N

N

N

W W

WK

P

P

NKIN

Z

Z

F : Fe3O4 or ZnFe2O4

W : FeO I : FeZ : ZnO K : KClN : NaCl P : K2ZnCl4

FI

I

F

NNFW

I

I

Z

I

K

I

K

1000 ºC

900º C

800 ºC

ZK

F

FFZ

K

K

Z

ZF

NZ

F

F

F

FFFZ

Z

W

W

Z

NN

K

PP

WW

W

N

N

FF

F

Z

Z

Z

Z

K

PP

P

Inte

nsity

2θ

NZF

Fig. 10. XRD patterns of PVC 30% pellet roasted as temperature (CuKa).


Fig. 11b shows the pellet heated at 900 �C. Residual dustgrew into plate-shaped crystals of very porous aggregation.

Fig. 11. SEM photographs of the cross-section of PVC 30% pellets. (a)

Although residual PVC was not found, about 100 lm spaceof the PVC particle remained vacant. Roasting at 1000 �Cin Fig. 11c sintered those crystals and reduced pores.

Fig. 12 shows the variation of appearance of the pellet asroasting time at 1000 �C. Fig. 11c shows the SEM of cross-section of this sample. As can be seen, the pellet had shrun-ken as the roasting time, caused by volatilization andsintering.

Consequently, the roasting of the PVC 30% pellets at1000 �C for 1 h can recover 97.2%, 99.5%, and 97.0% ofzinc, lead, and cadmium, respectively. However, about20% of iron was volatilized unsuitably.

3.3. Effect of heating rate

Fig. 13 shows the predictable chemical reactions in thepellet and the variation of the Gibbs free energy of thosereactions (Barin, 1995; Shimada et al., 1998). Reactions(1) and (2) are about the generation of FeCl3. As can beseen, because reaction (1) does not occur at the tempera-ture in which hydrogen chloride gas is emitted, reaction(2) can be regarded as the main reaction of generatingFeCl3.

However, the reactions from (5) to (9) have lower Gibbsfree energy than reaction (2). Reactions (5) and (6) areabout the generation of the zinc chloride, and those of(7) and (8) are about the generation of cadmium chlorideand lead chloride, respectively.

Therefore, although the chlorides of zinc, lead, and cad-mium can be generated earlier than FeCl3, some amount of

60 min at 800 �C, (b) 60 min at 900 �C and (c) 90 min at 1000 �C.

Fig. 12. Photograph of PVC 30% pellets roasted at 1000 �C for 5, 15, 30, 60, 90 min.

(1) Fe2O3(s) + 6HCl(g) = 2FeCl3(s,l,g) + 3H2O(g)

(2) ZnFe2O4(s) + 8HCl(g) =

ZnCl2(s,l) + 2FeCl3(g) + 4H2O(g)

(3) Fe3O4(s) + CO(g) = 3FeO(s) + CO2(g)

(4) Fe3O4(s) + 2HCl(g) = FeCl2(s,l) + Fe2O3(s) + H2O(g)

(5) ZnFe2O4(s)+2HCl(g)= ZnCl2(s,l) + Fe2O3(s) + H2O(g)

(6) ZnO(s) + 2HCl(g) = ZnCl2(s,l) + H2O(g)

(7) CdO(s) + 2HCl(g) = CdCl2(s,l) + H2O(g)

(8) PbO(s) + 2HCl(g) = PbCl2(s,l) + H2O(g)

(9) CaO(s) + 2HCl(g) = CaCl2(s,l) + H2O(g)

(10) FeCl2(s,l) + ZnFe2O4(s) = ZnCl2(l) + Fe3O4(s)

(11) FeCl2(l) + ZnO(s) = ZnCl2(g) + FeO(s)

(12) ZnCl2(g) + CdO(s) = CdCl2(l) + ZnO(s)

(13) FeCl2(l) + CdO(s) = CdCl2(l) + FeO(s)

(14) ZnCl2(l) + PbO(s) = PbCl2(l) + ZnO(s)

200 400 600 800 1000

-12

-8

-4

0

4

8

14 13

1211

10

6

98

54

3

7

2

1

ΔGo (

x 1

0 - 4 J

/mol

e)

Temperature (ºC)

Fig. 13. Variations of DG� as temperature.


iron volatilized due perhaps to the following reason. Underthe high heating rate, rapid pyrolysis of the PVC leads tothe partial high concentration of the hydrogen chloridegas, which increases the possibility of reaction (2). On thecontrary, it is expected that a low heating rate can avoidthe concentration of hydrogen chloride and proceed withthe reactions from (5) to (9).

Ferrous chloride can be generated as in reaction (4), andit can be also used as a chlorine provider. A Japanese patenthad tried to treat the EAF dust by using ferrous chloride(Sugawara, 1992), in which the mixture of ferrous chlorideand dust was mixed at 1000 �C, and asserted that ferrouschloride is a good chlorine provider to zinc, lead, and cad-mium in the EAF dust. Reactions (10), (11), and (13) indi-cate the chlorine exchange reaction between the ferrouschloride and others. Those are influential reactions, becausethe volatilization of ferrous chloride is possible at a highertemperature than other chlorides, as shown in Fig. 9. Thezinc chloride also can be used as chlorine provider to bothcadmium and lead as in reactions (12) and (14).

The possibility of the reaction (10) was tested by theexperiment in Fig. 14. The synthetic franklinite (ZnFe2O4)and FeCl2 were used in the test. The FeCl2 was prepared byroasting FeCl2 Æ 4H2O at 200 �C and this dehydration wasconfirmed through another preliminary test. The franklin-ite was prepared according to the following method. ZnCl3and FeCl3 Æ 6H2O were mixed as 1:2 of the mole ratio anddissolved in water. Sodium hydroxide was injected intothat solution until its pH becomes 9. The precipitated mix-ture of Zn(OH)2 and Fe(OH)3 was recovered and roastedat 600 �C for 17 h and at 800 �C for 1 h. The synthesizedfranklinite was confirmed by XRD.

The ZnFe2O4 and FeCl2 were mixed as 1:1 of the moleratio and injected into a furnace at room temperature. Itwas subjected to heat until the temperature reached1000 �C, at a heating rate of 2 �C/min. Each aliquot wascollected at each temperature at an interval of 100 �C.The samples were separated into soluble and insolublematerial as they were leached in water and analyzed. Thepercentage of zinc and iron shown in Fig. 14 was calculated

300 400 500 600 700 800 900 10000

20

40

60

80

100

Con

cent

ratio

n (%

)

Temperature(ºC)

Soluble Zn Volatilized Zn

FeCl2

Soluble Fe (FeCl2) Volatilized Fe

Fig. 14. Chlorine exchange between FeCl2 and ZnFe2O4 as temperature.


under the concept that soluble and insoluble materialsmake up 100%.

As can be seen, the chlorine exchange began at about600 �C and finished at about 800 �C. Dissolved and volatil-ized zinc increased in proportion to the decrease of FeCl2,but iron did not volatilize. The volatilization of zincincreased with the temperature and almost all zinc volatil-ized at 1000 �C.

The chlorine exchange between iron and zinc occurredas an equivalent mole ratio. In case of 700 �C, about 45%of soluble iron decreased and about 44% of zinc was dis-solved or volatilized.

The effect of the heating rate on the volatilization of ironwas tested in Fig. 15. The PVC 30% pellets were injectedinto the furnace at room temperature and heat-treated at400 �C for half an hour. The heating rate varied from2 �C/min to 60 �C/min.

The volatilization of iron decreased in proportion to thedecrease of the heating rate. About 3.9% of iron volatilizedat the heating rate of 10 �C/min and none of the iron vol-atilized at the heating rate of 4 �C/min.

0 10 20 30 40 50 600

5

10

15

20

25

Vola

tiliz

ed F

e (%

)

Heating Rate (ºC/min)

Fig. 15. Relation between the heating rate and volatilization of Fe fromthe PVC 30% pellet.

Therefore, from the above results, the following obser-vation can be made. Rapid heating rate makes excessiveconcentration of the hydrogen chloride gas and inducesto generated ferric chloride. However, the heating rateslower than 4 �C/min progresses the reactions in sequenceof Gibb free energy in Fig. 13.

Finally, the effect of the mixed PVC ratio was investi-gated. The PVC powder was mixed with the dust as theratio from 10% to 45%. The pellets were heated at 800 �Cfor 1 h and the heating rate was 2 �C/min.

The technique used in this research left much chlorideresidue in the roasted pellet. The chlorides of transitionmetals can be volatilized by heat treatment, but the chlo-rides of alkali metals and alkaline metals cannot. There-fore, for the re-injection of the residual pellet, the pelletwas washed after heat treatment.

When the washing step is included in the process, we donot need to increase the temperature until 1000 �C. Theheat treatment will be undertaken at 800 �C for the follow-ing reasons. All of the necessary reactions occur under800 �C, such as the pyrolysis of the PVC, hydrogen chlo-ride reactions, and chlorine exchange. When the excessPVC was mixed with the dust, heat treatment at 800 �C willbe safe because FeCl2 can still remain in the pellet. More-over, it can be noticed in the SEM photograph shown inFig. 11 that the state of the pellet heat-treated at 800 �Cis more suitable for washing than the pellet heat-treatedat 1000 �C, because the particles of the latter were sintered.

The heated pellets were pulverized under 150 lm andinjected into the dilute hydrochloric acid solution, whosepH was adjusted at 5. H2O2 was injected into the solutionas 0.05 mol/L for precipitating the residual ferrous chloridein the roasted pellet into Fe(OH)3.

Fig. 16 shows the recovery of zinc, lead, cadmium, andchlorine of the PVC. The volatilized amount of metals wasobtained by the analysis of the roasted pellet before thewashing. The amount of dissolved metals was obtainedby the analysis of the supernatant of the washing solution.

10 15 20 25 30 35 40 45

102030405060708090

100

Rec

over

y (%

)

Mixed PVC (%)

Dissolved Zn Volatilized Zn

Dissolved Pb Volatilized Pb

Chlorine of PVC

Dissolved Cd Volatilized Cd

Fig. 16. Recovery of metals as PVC mixing ratio by roasting at 800 �Cand washing.

10 15 20 25 30 35 40 450

10

20

30

40

50

60

Wei

ght r

atio

of r

esid

ue (%

)

Mixed PVC (%)

etc. Carbon Iron

Fig. 17. Content of the residual pellet after roasting at 800 �C andwashing.


The recovery of chlorine of the PVC was calculated underthe assumption that volatilized metals were recovered aschlorides.

The recovery of chlorine decreased in proportion to themixed PVC ratio, and that of the PVC 45% pellet wasabout 92%. The recovery of zinc and lead increased in pro-portion to the mixed PVC ratio and converged at 40% and30%, respectively. The recovery of cadmium was irrelevantto the PVC ratio and exceeded 92% at the 10% PVC mixingratio.

Fig. 17 shows the concentration of iron and carbon inthe washed residue. The concentration was calculatedunder the concept that the amount of each element in thepellet before roasting is 100%. For instance, the weight ofthe PVC 40% pellet was reduced to 29.6% of the originalpellet after the heat treatment and washing, and the con-centration of iron and carbon in the final residue were46% and 20.9%, respectively.

The principal ingredients in the final residue were ironand carbon. The concentration of those increased in pro-portion to the mixed PVC ratio.

The weight of residue decreased in proportion to themixed PVC ratio, but that of the PVC 45% pellet increased,which occurred because the ferrous chloride in the heat-treated pellet precipitated into ferric hydroxide duringwashing, implying that mixing 45% of PVC is excessive.

Consequently, the optimum condition identified in thisresearch is the following: 40% of the PVC mixing ratio,heat treatment at 800 �C, heating rate of 2 �C/min, and

washing. This process recovered 96.2% of zinc, 97.4% oflead, and 98.8% of cadmium. The final residue has 46%iron and 20.9% carbon, and it can be injected into theEAF.

This research can be used for synchronous treatment ofboth resources: EAF dust and plastic waste loaded withPVC. However, this process may create dioxin and it isnot investigated yet. Prior to practical application, itshould be considered.

4. Conclusion

The PVC powder was mixed with the dust in variousmixing ratios, and the mixture was made into pellets. Thepellets were subjected to heat treatment at various temper-atures, and the effects of the heat treatment temperatureand the heating rate were investigated.

Potassium chloride restrained the zinc chloride fromvolatilizing until 900 �C by generating K2ZnCl4. Ferrouschloride functioned as the chlorine provider to the zinc,lead, and cadmium of the dust.

Rapid heating rate generated ferric chloride in the pel-lets, but the heating rate lower than 4 �C/min did not.The PVC 40% pellets were heat-treated at 800 �C at a heat-ing rate of 2 �C/min, and the heat-treated pellets were pul-verized and washed. This process recovered 96.2% zinc,97.4% lead, and 98.8% cadmium. The final residue has46% iron and 20.9% carbon.

References

Barin, I., 1995. Thermochemical Data of Pure Substances, 3rd ed. VCHPub. Inc.

Clesceri, L.S., Greenberg, A.E., EATON, A.D., 1998. Standard Methodsfor the Examination of Water and Wastewater, 20th ed., pp. 4–69,ISBN 0-87553-235-7.

Korean Industrial Standard, 2003. General rules for determination ofcarbon in metallic materials, KSD 1789.

Lee, J., Kim, Y., Seo, S., Lee, K., Kim, Y., 2000. Reduction behavior ofZn, Pb, Cl, Fe, Cu and Cd compounds in EAF dust with carbon. J.Korean Inst. Resour. Recy. 9 (4), 3–15.

Saeed, L., Tohka, A., Haapala, M., Zevenhoven, R., 2004. Pyrolysis andcombustion of PVC, PVC-wood and PVC-coal mixtures in a two-stagefluidized bed process. Fuel Process. Technol. 85, 1565–1583.

Shimada, T., Kajinami, T., Kumagi, T., Takeda, S., Hayashi, J., Chiba,T., 1998. Characteristics of vaporization of coal ash minerals chlori-nated by gaseous hydrogen Chloride. Ind. Eng. Chem. Res. 37, 895.

Sugawara, K., 1992. Japanese Patent H04-159965.The Chemical Society of Japan, 1995. Chemical Handbook, second ed.,

MARUZEN Co., Ltd., pp. 702–705.

Documents

Recycling EAF dust by heat treatment with PVC