Ind. Eng. Chem. Prod. Res. Dev., Vol. 18, No. 3, 1979
227
Cold Flow Properties and Response to Cold Flow Improver of Some Typical Fuel Oils Lelf Idar Rossemyr Department of Chemistry, University of Bergen, N-50 14 Bergen-Universitet, Norway
The content and distribution of n-paraffins in heavy naphtha, kerosine, light gas oil, and heavy gas oil from Ekofisk crude oil are determined. The results have been used to calculate the n-paraffin content of 40 fuel oils made by mixing various amounts of these four fractions. Cold flow properties such as cloud point and cold filter plugging point (CFPP) and response to addition of varying amounts of one flow improver to these fuels have been examined in relation to the n-paraffin content and distillation range.
Introduction The n-paraffin content will greatly influence the cold flow properties-pour point, cloud point, and cold filter plugging point (CFPP)-of gas oils when these are cooled. This is caused by the fact that crystallization of the nparaffins into waxes occurs at low temperatures. Even if the wax constitutes not more than 1-2% of the total sample, it can still reduce the flow properties of the fuels (Pass et al., 1967). The wax impedes the flow of the oil by crystallizing into an interlocking network of fine sheets leading to cage-like structures entrapping the remaining oil. The cold flow properties may be improved by adding lighter refinery stock, but another, and in most cases less expensive method of improving the quality, is to add small amounts of a cold flow improver (Knepper and Hutton, 1975). The mechanism of crystal modification by flow improvers has been discussed in the literature (Holder and Winkler, 1965; Bucaram, 1967). Most of the previous experiments relating to cold flow properties deal with pour point depression, and very little has been done about the variations in CFPP by addition of flow improvers (Feldman, 1973; Pass et al., 1967; Coley et al., 1967). Our work is an attempt to throw light on how the CFPP varies with the n-paraffin content and the distillation range of fuel oils. (See Table I.) The n-paraffin content of heavy naphtha, kerosine, light gas oil (LGO) and heavy gas oil (HGO) from Ekofisk crude oil was determined by urea adduction and gas chromatography. The results were used to calculate the n-paraffin content and distribution in about 40 fuel oil samples consisting of varying amounts of these four fractions. Cloud points and CFPP were measured after addition of 250 and 500 ppm of the flow improver Keroflux M. (See Table 11.) Experimental Section Gas Chromatograph. The gas-liquid chromatograph used was a Hewlett-Packard Model 5720 A equipped with a hydrogen flame ionization detector. The column used was a 30 m X 0.5 mm commercial SCOT column couted with SE-30 (from S.G.E., Australia): carrier gas (He), 2 mL/min; hydrogen, 15 mL/min; air, 215 mL/min; injector temperature, 250 "C; detector temperature, 300 "C. Temperature Programming. Heavy naphtha, 50 "C, 4O/min; kerosine, 70 "C, 4O/min; LGO, 70 "C, 4"/min; HGO, 75 "C, 4"/min.
Table I. Density, Cloud Point, and Distillation Range of the Four Fractions from Ekofisk Crude Oil
*Continental Shelf Institute Haakon Magnussons Gt. 1B, P.O. Box 1883, N-7001 Trondheim, Norway.
CFPP. The CFPP analyzer Model 8121-000-00 (Walter Herzog) meets the specification of DIN 51 428 for the cold
h naphtha kerosine
LGO
HGO
0.8065
0.8397
0.8685
...
...
- 20
11
132 151 152 154 156 158 160 161 163 166 170 174 182
165 192 192 194 197 199 202 205 209 213 219 223 229
237 254 256 256 260 262 267 271 276 28 3 29 3 302 308
282 309 317 325 330 334 340 344 3 50 358 370 379
density, g/mL cloud point, "C
0.7866
ibp,"C 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 95% fbP
...
Table 11. The Total n-Paraffin Content is Determined by Three Methods: Planimeter (Plani.) and Disk-Integrator (Disk) from the Gas Chromatogram of the Pure Fraction, and by Urea Adducts h method naphtha kero. LGO HGO Total n-paraffin content, wt % percent by weight of each n-paraffin given by its carbon number
plani. disk urea
19.0 20.4
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
0.7 4.6 7.6 4.8 1.4 0.5 0.1
0019-7890/79/1218-0227$01.00/00 1979 American Chemical Society
22.4 18.5
18.9 14.3
0.1 1.5 < 0 . 1 6.1
