Heavy petroleum products as possible feedstocks for carbon black production

Heavy petroleum products as possible feedstocks for carbon black production Jabir

Shanshool,

Adnan

T. Zayona

and

Manhel

School of Chemical Engineering, University of Technology, PO Box 35010, Baghdad, Iraq (Received 30 April 1986; revised 24 November 1986)

M.

Awd

Tel Mohammad,

The possibility of producing carbon black from Iraqi refinery products has been investigated. The products considered as feedstocks included five different furfural extracts from lube oil processing in addition to vacuum residue, reduced crude and a heavy Qaiyarah crude oil. A laboratory-scale experimental apparatus based on the oil furnace process and operated at different air/feed ratio was used to compare the suitability of the feedstocks for carbon black production. The results indicate that the most suitable feedstocks were extracts LVI 60 and LVI 150, and vacuum residue. (Keywords:

petroleum

products;

carbon

black;

feedstocks)

Carbon black consists essentially of fine carbon particles, semi-graphitic in structure with varying amounts of volatile material and ash. Its main application is as a reinforcing agent in rubber; other uses are in printing inks, paints, plastics and dry electric cells’,‘. There are several types of carbon black, and their characteristics depend upon both the particle size and method of production. The important relevant characteristics of carbon black are pH and specific surface, which is governed by particle structure3q4. Carbon black is produced by partial combustion or pyrolysis of appropriate hydrocarbon raw materials. The usual feedstocks are heavy distillates or residual petroleum products, especially those with high aromatic contents. Natural gas and heavy liquid products produced by cracking processes or carbonization of coal are also used as raw materials2ss. The common processes for carbon black production are known as channel, thermal, acetylene and furnace processes. Of these, the oil furnace process, which is based on partial combustion of highly aromatic hydrocarbon fractions, is by far the most important today. Carbon black is formed in the furnace by partial oxidation and cracking of oil feedstock at 13W14OO”C and is carried by gas flow to a heat exchanger and a quench cooler, where the temperature is reduced to % 200°C. The product is then collected for finishing. The type of black thus produced depends to a large extent on the nature of the feedstock and the operating temperature. The live principal grades oil furnace black are designated (in order of decreasing particle size) as general purpose furnace (GPF), fast extruding furnace (FEF), high-abrasion furnace (HAF), intermediate superabrasion furnace (ISAF), and super-abrasion furnace (SAF) black. These designations broadly describe the behaviour of the blacks in rubber compounds’. The aim of the present work is to investigate possible local feedstocks for black production using a laboratory unit specially built for this purpose. Carbon black is consumed in Iraq by the rubber and other industries, but the demand is tilled at present by imports. 0016-2361/87/121664-03$3.00 0 1987 Butterworth & Co. (Publishers)

1664

Ltd.

FUEL, 1987, Vol 66, December

EXPERIMENTAL The feedstocks

used were as follows (Figure

1, Table 1):

‘Reduced crude’ (stream 1) - an atmospheric distillation bottom residue of Kirkuk crude (light crude oil; API gravity = 36). Furfural extracts (streams 2-6) of base lube oils derived from vacuum distillation of the reduced crude. Vacuum distillation bottom residue (stream 7). Qaiyarah crude oil (stream 8) - a heavy crude oil (API gravity z 15.4) with a high sulphur content (Z 7 wt %). A laboratory unit was designed and constructed to test the suitability of the different feedstocks for carbon black production; it was based on the oil furnace process and comprised mainly a furnace, a cooling system and a bag filter, as shown in Figure 24. The major component of the furnace is the burner; several burner designs were tested, and that shown in Figure 3 was found to operate satisfactorily for the different experimental conditions of this investigation. In a typical experiment, feedstock and air in a predetermined weight ratio were supplied to the burner continuously for 2 h and the resulting carbon black was collected. Feedstock flowrates were chosen within the range 1.8-2.8 g min-‘; the maximum capacity of the burner was z 75 g carbon black per hour.

RESULTS

AND DISCUSSION

The basic characteristics of the different feedstocks are shown in Table 1. The H/C ratio and the density indicate the aromaticity of the feedstock, which is considered the most important single property reflecting suitability for carbon black production. The sulphur contents of all the feedstocks were rather high, which is a disadvantage, especially so for the Qaiyarah crude and the vacuum residue. This could lead to severe corrosion and pollution problems during and following carbon black production. During operations involving feedstocks with high Conradson carbon residues, problems of plugging and

Heavy

petroleum

products

as feedstocks

for carbon

black

production:

J. Shanshool

et al.

discontinued combustion arose, particularly with the Qaiyarah crude and the vacuum residue. Feedstock quality has been rated according to a term known as the Correlation Index (C.I.)‘, defined by: C.I. = $$

+ 413.ld

- 456.8

(1)

where: t = the volumetric mid boiling point of the liquid feedstock in “C at 760 mm Hg; and d = the specific gravity at 15.6”C. An increased correlation index is associated8 with better yields and improved qualities of the black produced. Calculated values of C.I. for the feedstocks are given in Table I. It is seen that feedstocks with low H/C ratios have higher C.1. values, which leads to the conclusion that the extracts LVI 60 and LVI 150 and the vacuum residue should be the most suitable feedstocks for carbon black production in the present work. The results given in Table 2 show that higher maximum yields of carbon black are obtained from feedstocks with higher C.I. values, thus confirming the conclusion of previous work8. The greatest yield (44.5 %) was obtained from extract LVI 60, and this appears to be the most promising feedstock; extract LVI 150 and the vacuum residue could also be considered suitable, while the feedstocks with C.I. lower than 75 gave low yields (~20%). The yields from the three best feedstocks are similar to those expected from a large-scale oil furnace process’. Table 2 also gives the general properties of the carbon blacks produced. The best quality black (i.e., having high

Base oil 40

-

Stock

40

(2)

E!use oil 60

*x_

LVI HVI

60 60

(3) (4)

Bose oil 150

xx_

LVI HVI

150 150

(5) (6)

Vacuum residue (7)

Figure 1 Sources of feedstocks. *These streams had low C.I. values [see Equation (I)] and were therefore not considered as possible feedstocks. ** Furfural extracts were obtained via ordinary (LVI) or deep (HVI) extraction processes

Table 1

Basic characteristics

Stream no. (see Figure I)

“Correlation

*

1i3r

I

I

I

L-

I

--_---I

Water

1

7 ‘

@

Pressure

gauge

la

Flow meter

Figure 2 Laboratory unit for production of carbon black. 1, Tubular heat exchanger; 2, furnace; 3, burner; 4, LPG pilot flame; 5, heat exchanger; 6, quench cooler; 7, additional air duct; 8, bag filter; 9, fan

Figure 3 Details of burner. Inner cylinder: stainless steel; thickness, 2.5 mm; i.d., 180mm; height, 160mm; perforations, five rows of 1.5 mm holes (for primary air). Outer cylinder: tinplate; thickness, 1.5 mm; i.d., 220mm; height, 180mm; perforations, one row of 4mm holes (for secondary air)

of feedstocks

Feedstock

Sulphur (wt%)

Conradson carbon residue (wt %)

Specific gravity at 15.6”C

Mid boiling point (“C)

mol. ratio

C.I.”

Reduced crude Stock 40 LVI 60 HVI 60 LVI 150 HVI 150 Vacuum residue Qaiyarah crude oil

3.9 5 5.3 4.6 3.6 3.9 6 7

10.51 6.35 5.34 6.21 6.82 11.32 15.20 13.51

0.9500 1.002 1.0539 1.0175 1.0461 0.9756 1.0320 0.9631

400 325 405 430 460 460 510 460

1.6 1.4 1.3 1.4 1.4 1.6 1.4 1.5

66 91 107 89 96 60 95 75

index, as defined in Equation

H/C

(1)

FUEL, 1987,

Vol 66, December

1665

Heavy petroleum

products

as feedstocks

for carbon black production:

J. Shanshool

et al.

Table 2 Maximum yields and general properties of produced carbon blacks Stream no.

Feedstock

3 5 7 2

LVI 60 LVI 150 Vacuum residue Stock 40

4 8 1 6

HVI 60 Qaiyarah crude oil Reduced crude HVI 150

C.I.

Max. yield (wt%)

107 96 95 91 89 75 66 60

PH

Iodine no. (g kg-‘)

Heating loss W %I

Particle diameter Ash (wt%I (rm)

ASTM no.’

44.5 37.8 36.7 32.9

9.3 9.0 8.7 8.1

150.2 130.4 133.7 88.0

0.13 0.24 0.47 0.49

20 22 22 25

0.11 0.19 0.21 0.17

N N N N

30.1 19.9 18.9 17.4

8.7 7.3 5.1 6.8

38.5 37.1 34.7 32.2

0.21 0.98 0.92 1.92

40 50 80 80

0.11 0.20 0.27 0.32

N 550 N 660 _

110 220 220 340

Grade’ SAF ISAF ISAF HAFHS FEF GPF _

“See Ref. 6 bSee Refs. 1 and 9

6

8

IO A~r/feed

12 ratio [wt/wf)

14

16

Yield versusair/feed ratio for: 1, reduced crude; 2, stock 40; 3, LVI 60; 4, HVI 60; 5, LVI 150; 6, HVI 150; 7, vacuum residue; 8, Qaiyarah crude Figure 4

iodine number, small particle diameter and alkaline reaction) is seen to be produced from the three feedstocks giving the highest yields, as mentioned above. The types of black produced are super-abrasion furnace (SAF) and intermediate super-abrasion furnace (ISAF), which are equivalent to ASTM Grades N 110 and N 2206. These ASTM grades, in addition to N 300, are considered suitable products for rubber compounds. The variation of yield with air/feed ratio is shown in Figure 4. It is clearly seen that there is a maximum value of carbon black at a given feed/air ratio for each feedstock. This maximum is obtained within a range of 7-8.5 air/feed for all the feedstocks studied. It is worth noting that the feedstocks giving high yields required higher air/feed ratios than the other feedstocks. The calculated theoretical values for complete combustion lie within the range 14-16, about twice the values required to obtain a maximum yield for all the feedstocks. It was observed that carbon black could not be produced with air/feed ratios <4 because the amount of air was then insufficient for the combustion process to generate the heat required to pyrolyse the feed. Increasing the air/feed

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ratio to = 778.5 increased the carbon yield and also raised the furnace temperature appreciably, to 142&155o”C. Such a temperature range is the most suitable for carbon black formation, resulting in higher yields’. Increasing the air/feed ratio beyond 7-8.5 leads to lower yields because of increased combustion of the feed and also probably of the carbon itself. It should also be pointed out that air/feed ratios influence the general properties of the produced black. The better properties are possessed by the blacks produced at the optimum air/feed ratios; ratios outside the range 7-lOgive blacks with inferior properties such as large particle diameter and acidic reaction. It is concluded that feedstocks with low H/C ratios and high C.I. values give higher yields of carbon black with better properties. The maximum yield for all feedstocks appears to result when the air/fuel weight ratio is 2 50 y0 of the theoretical value for complete combustion. It is also concluded that extracts LVI 60 and LVI 150 and the vacuum residue (and perhaps extract stock 40) are suitable local feedstocks for carbon black production. Mixtures of these feedstocks would also probably be suitable for this purpose, providing good flexibility in feedstock availability.

ACKNOWLEDGEMENT The authors thank Dr Hazim S. Al-Najjar (Petroleum Research Center, Baghdad) for valuable discussions.

REFERENCES ‘Kirk-Othmer Encyclopedia of Chemical Technology’, John Wiley & Sons, New York, 1978 L. F. and Matar, S. ‘From Hydrocarbons to Hatch, Petrochemicals’, Gulf Publishing, 1981 Smith, W. R. ‘Petroleum Products Handbook’, McGraw-Hill, New York, 1960, chapter 15 Hydrocarbon Processing, in ‘Petrochemicals Handbook’, November 1975, 122 Stockes, C. A. and Guercio, V. J. Erdb;l und Kohle-ErdgasPetrochem. 1985, 38, 31 ASTM D24 (carbon black), American Society for Testing and Materials, Philadelphia, 1978 Nelson, M. L. Oil Gas J. 1955,53,47 Tsekhanovich, M. S., Surovikin, V. F., Popuggev, Ya. I. and Smakhitina, A. Z. Chem. Technol. Fuels Oils 1973, November, 112 CITCO, Cities Service Co., Columbian Chemicals Division, Technical Service Center, Hamburg B/77e, 1977