Fuel 85 (2006) 878–880
www.fuelfirst.com
Short Communication
Extraction of sulfur and vanadium from petroleum
coke by means of salt-roasting treatment
Habib Shlewit *, Moussa Alibrahim
Chemistry Department, Atomic Energy Commission, P.O. Box 6091, Damascus, Syrian Arab Republic
Received 1 March 2005; received in revised form 24 August 2005; accepted 25 August 2005
Available online 23 September 2005
Abstract
Syrian petroleum coke samples were characterized and submitted for salt-roasting treatment in an electric furnace to evaluate the convenience
of this procedure for the extraction of the vanadium and sulfur from coke.
The solution and solid residue remaining after salt-roasting both were separated by filtration and were analyzed for vanadium and sulfur. The
solution was analyzed by UV–vis spectroscopy and gravimetrically for vanadium and sulfur, respectively. The solid residue and the untreated
samples of petroleum coke were analyzed by XRF spectrometry. Results showed that more than 90 wt% of sulfur and 60 wt% of vanadium could
be extracted by the salt-roasting treatment. An alternative procedure has been suggested, in which, more than 80% of sulfur and a small percentage
of vanadium can be leached by 0.75 M of Na2CO3 solution at 70–80 8C.
q 2005 Elsevier Ltd. All rights reserved.
Keywords: Vanadium; Sulfur; Salt-roasting; Extraction
1. Introduction
The objective of salt-roasting of refractory metal ores is to
render the metal content water-soluble. Salt-roasting converts
the metal to an oxidic anion of its maximum valance state.
Vanadium in the feed materials is converted on roasting
with a source of sodium under oxidizing conditions to soluble
sodium salt [1–3]. The soluble vanadium values in the roasted
material is leached out with water, and then precipitated and
separated from the solution as insoluble vanadium compounds.
A water-soluble sodium vanadate is produced as follows [1]
2NaCl C O2 C H2 O C V2 O3 % 2NaVO3 C 2HCl
or
2NaCl C V2 O5 C H2 O% 2NaVO3 C 2HCl
NaVO3, sodium metavanadate is readily water-soluble. The
water leach liquor for these reactions, typically should be
slightly alkaline (pHZ7–8). The reaction given below occurs if
water is absent, and as compared to the previous reactions,
the formation of NaVO3, occurs more slowly [3,4].
3
2NaCl C O2 C V2 O5 % 2NaVO3 C Cl2
2
Acid leaching of the water-soluble vanadium decomposes
the vanadium compounds and causes the dissolution of
vanadium [5].
Several researchers have investigated microwave heating
procedures for the dissolution of wide variety of samples [6–
10]. The general conclusion reached from the studies is that
microwave heating achieves faster and safer dissolution than
conventional procedures, with minimal sample contamination
and reagent requirements.
Syrian petroleum refineries produce about 0.6 Mt/year of
petroleum coke. This work presented in this paper aims to
minimize the sulfur content of this coke to about 1% or less by
means of the salt-roasting treatment. That is, the treated coke will
be a valuable fuel resource for a number of the heavy industries
in Syria. Moreover, vanadium recovered by the proposed
process, as a co-product and using minimal reagent requirements, will improve the commercial viability of this process.
2. Experimental
* Corresponding author. Tel.: C963 11 6112289; fax: C963 11 2132580.
E-mail address: scientific@aec.org.sy (H. Shlewit).
2.1. Instrumentation
0016-2361/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.fuel.2005.08.036
Certified standards and petroleum coke samples were
processed using on electric furnace. The determination of
H. Shlewit, M. Alibrahim / Fuel 85 (2006) 878–880
the vanadium content of the solutions obtained after the saltroasting treatment of the petroleum coke samples was carried
out using an UV spectrophotometer as vanadium (V) after
oxidation by HNO3. Hydrogen peroxide was used as a
complexing agent [10]. X-ray fluorescence measurements
(XRF) of vanadium in the solid petroleum coke samples
were carried out using a 109Cd annular source XRF
spectrometer, with a Si(Li) detector.
2.2. Reagents
Certified coal reference standards AR-1800 from Alpha
Resource Inc. were used to check the extraction efficiency.
Working solutions were prepared in distilled water. All
reagents used were of analytical reagent grade.
2.3. Procedure
The petroleum coke samples were ground to an average
particle size of 150 mm, and were dried in air at 110 8C for
1 h. Samples were divided into four groups (a, b, c and d)
each group was treated separately as follows: (a) exact
amounts of the dried material (3.0 g) were mixed with
different amounts of NaCl, 0.25, 0.5, 0.75 and 1.0 g. A placed
in a ceramic crucible. Crucibles were heated in the electric
furnace to 200, 300, 400 and 850 8C. After the furnaceheating period of 1, 2, and 3 h, the contents of the crucibles
were transferred to 50 ml calibration flasks and the
volume adjusted with distilled water. After shaking, the
liquid and solid phases were separated by filtration and each
phase was taken for analysis; (b) an exact amount of the dried
petroleum coke (3.0 g) were placed in a ceramic crucible, to
which 0.5 g of sodium carbonate (Na2CO3) and 0.5 g of
sodium chloride were added. The crucible was heated by the
electric furnace to 200, 300, 400 and 850 8C; (c) exact
amount of dried coke (3.0 g) was placed in a ceramic
crucible, to which 0.5 g of sodium carbonate (Na2CO3) was
added and treated similarly in an electric furnace; (d) 3.0 g of
the dried petroleum coke samples were placed in 50 ml flasks
containing 25 ml of 0.25, 0.5, 0.75 and 1.0 M of Na2CO3.
Flasks were heated using a thermostatic hot plate provided
with magnetic stirrer. After heating for 1 h, at 70–80 8C, the
volume was adjusted distilled water. Liquids and solids were
separated after mixing by filtration, and each phase taken for
analysis.
3. Results and discussion
The original petroleum coke samples were first analyzed
and characterized by XRF. Table 1 shows their composition.
Samples of group (a) roasted with different amounts of
NaCl, showed that the extraction efficiency for vanadium and
sulfur was not significant and not really affected by the
roasting temperature change or by the amount of NaCl added
(Table 2).
Samples of group (b) roasted in electric furnace with a
mixture of sodium carbonate and sodium chloride, showed
879
Table 1
Syrian petroleum coke composition
Al
Si
S
Ca
V
Fe
Ni
Mo
Ba
Zn
415G8 mg/kg
1550G110 mg/kg
8.24G0.15%
672G20 mg/kg
917G20 mg/kg
200G14 mg/kg
241G6 mg/kg
19.8G1.0 mg/kg
7.2G2.0 mg/kg
3.0G0.3 mg/kg
Table 2
Effect of roasting temperature and amount of NaCl added on vanadium and
sulfur extraction efficiency
NaCl (g)
added to 3 g
petroleum
coke
0.25
0.50
0.75
1.00
Extraction
efficiency
wt% 2008 C
Extraction
efficiency
wt% 300 8C
Extraction
efficiency
wt% 400 8C
Extraction
efficiency
wt% 850 8C
V
S
V
S
V
S
V
S
1.3
1.8
1.7
1.8
1.7
1.9
1.95
1.8
2.1
2.2
1.9
1.95
2.1
2.2
1.9
2.0
2.5
2.4
2.5
2.0
1.7
1.9
1.8
1.95
–
–
–
–
–
–
–
–
that the extraction efficiency for vanadium and sulfur
increased as the roasting temperature was increased form
200 up to 400 8C, but the extraction efficiency for vanadium
decreased as the roasting temperature increased to 850 8C.
That is considered to be due to the decomposition of
Na2CO3, at high temperature, to form Na2O and CO2 and the
Na2O may then react with the vanadium compounds present
to form a vanadate which is insoluble in water solutions.
Table 3 shows the effect of roasting temperature on
vanadium and sulfur extraction efficiency from the samples
of group b.
The results for samples of group (c) roasted in presence of
0.5 g sodium carbonate only, and treated under the same
conditions as the previous samples showed Table 4 that the
extraction efficiencies for vanadium and sulfur were not
significantly different compared with results obtained using
coke samples roasted with Na2CO3 and NaCl.
Thus, it can be concluded that sodium chloride has no
significant effect on salt roasting of petroleum coke.
Adding 0.5 g of sodium salt (Na2CO3) is the stoichiometric amount needed to fix the pH of the process operation
to about 9.5.
Table 3
Effect of roasting temperature on vanadium and sulfur extraction efficiency
(samples of group b, roasted with Na2CO3CNaCl)
Roasting temperature
(8C)
Vanadium extraction
efficiency (wt%)
Sulfur extraction efficiency (wt%)
200
300
400
850
55
58
62
6.7
82
89
92
–
880
H. Shlewit, M. Alibrahim / Fuel 85 (2006) 878–880
Table 4
Effect of the roasting temperature on vanadium and sulfur extraction efficiency
(samples of group c, roasted with Na2CO3)
Roasting temperature
(8C)
Vanadium extraction
efficiency (wt%)
Sulfur extraction efficiency (wt%)
200
300
400
850
56.3
58.7
64.8
6.7
81.4
90.3
91.8
–
Table 5
Vanadium and sulfur extraction efficiency as a function of sodium carbonate
concentration (samples of group d)
Na2CO3 concentration
(M)
Vanadium extraction
efficiency (wt%)
Sulfur extraction efficiency (wt%)
0.25
0.50
0.75
1.0
1.2
8.2
13
21.2
43
62
83.2
83.3
4. Conclusion
Treatment of Syrian petroleum coke by salt-roasting
constitutes a very efficient method for sulfur extraction from
this type of coke, and more than 60% of vanadium can also be
extracted. Moreover, results obtained showed that, treatment
using 0.75 M of sodium carbonate solution at 70–80 8C for 1 h
is quite efficient to leach more than 80% of sulfur from the
petroleum coke.
Acknowledgements
The authors would like to express their thanks to Prof. I.
Othman, General Director of the Syrian Atomic Energy
Commission and Prof. G. Zayzafoon, head of the Chemistry
Department for their help and support. The authors would like
to extend their thank to Ms S. Alike and Mr A. Rezkalah for
their valuable help to carry out this work.
References
Some tests were also carried out to investigate the effect of
oxidation on the extraction efficiency of V and S. NaClO3 as
a strong oxidant, was added before roasting to the mixture of
petroleum coke and sodium salts. Results showed that
the extraction efficiencies were not significantly affected,
possibly due to efficient oxidation by air during the roasting
treatment at such high temperatures.
Coke samples of group (d) were submitted to heating for 1 h
at 70–80 8C in the presence of different concentrations of
sodium carbonate. The analyses given in Table 5, show that
vanadium and sulfur extraction efficiencies increased as the
sodium carbonate concentration increased. However, the
vanadium extraction efficiency is too low compared with
samples treated as in the groups b and c. However, sulfur
extraction efficiency is quite efficient when the sodium
carbonate concentration was 0.75 M.
[1] Merritt RobertC. The extractive metallurgy of uranium.: Colorado School
of Mines Research InstituteColorado School of Mines Research; 1971 pp.
52–8.
[2] Yom- Tov Z, Churchill M, Faur A. The roasting of Tete slag for the
extraction of vanadium, report No. 1602. Johannesburg: National Institute
for Metallurgy; 1976.
[3] Goddard JB, Fox JS. Salt roasting of vanadium ores. Warrendal, PA: The
Metallurgical Society of AIME; 1981 pp. 127–45.
[4] Gupta CK, Krishnamurthy N. Extractive metallurgy of vanadium.
Amsterdam: Elsevier; 1992.
[5] Fathi Habashi. Priciple of extractive metallurgy. vol. 2. London (New
York): Gordon and Breach; 1980.
[6] Abu-Samara A, Morris JS, Koirtyohann SR. Anal Chem 1975;47:1475.
[7] Matthes SA, Farrell RF, Mackie AJ. Bureau of mines technical progress
report, Albany, NY, USA 1983 [TPR120].
[8] Fernando LA, William DH, Gabrielli CC. Anal Chem 1986;58:511.
[9] Blust R, Van der Linden A, Decleir W. At Spectrosc 1985;6:163.
[10] Kingston MAE, Jassie LB. Anal Chem 1986;58:2534.