Determining the Sediment Content of Fuel Oil A New Method S. H. HULSE
AND
H. L. THWAITES, Standard Oil Development C o . , Linden, N. J .
A practical method has been developed fuel’s stability in contact n i t h so-called “bunker” fuel for determining the sediment content of p r e h e a t e r s u r f a c e s . As a oil of the present day contains matter of fact, a t present there residual fuel oil Tvithout the use of a diluent residual products from cracking is no generally accepted 1abor:i’vhich may dissolve Or disperse operations. This material varies tory method Tvliich seema to material* The method is useful i n Prenidely in character r i t h the nacorrelate with known ca~e. of ture of the crude oil from which dicting the storage performance of fuel preheater clogging. Variorioils and gives promise of value i n connectests have been propo>ed arid it is derived and the method and degree of cracking to which it tion luith tests for determining the problem is being studied inhas been submitted. tenqively in several lalioratot ies cracked residues are not altoward fouling of preheatem (1,3),including those with TT liich ways conipletely soluble in pethe writers are associated. t’roleum distillat’es or uncracked residues, thus complicating !Yew Developments the problem of preparing merchantable blends. They usually cont’ain solid or semisolid particles which are not The present’ report descrilm a nelv method for determining objectionable if dispersed, but which sometimes agglomerate sedinient which avoids certain theoretically o1ijection:ii)le in the form of troublesonie sludges or deposits if tlie fuels are features of the sedinient by extraction test and Tvliich has, up subjected to unfavorable conditions of storage anti u.e. to date, been found to correlate accurately with the :Ic.trial The solubility problem a t one time was most serious, when tentlency of fuel oils to settle. The new method has also i t v a s frequently necessary to blend cracked resiilues nith given promise as a tool for use in conducting te+ta for I)!’eparaffinic gas oils. Difficulties of this particular 1;ind are less dictiiig the tendency of fuels to clog preheaters. It can I I C frequent today, since the oil industry is plentifully supplied carried out in a shorter elapsed time than the sdinient l)y n i t h cracked distillates for blending purposes. Ilon-ever, the extractioii test. solubility probleni in lesser degrees still exists, ~ T - C tliough I~ it The nciv method involves filtering undiluted but Iientcil iiil may not be recognized as such. The problem of niiniinizing the through an asixstos niat in a apecial steam-jacketed filter precipitation of residues and sludges is still frequently troiiiilefunnel, washing the residue free of oil with a higli-fla4i-point some, and even the best informed technologists are not paraffinic naphtha (“Stoddard soliTent”), drying, and \\-eighah-ays able to predict whether or not, a given oil n-ill cause ing. It avoids the abnorninlities incident to the use of an difficulty. Practically all residual fuel oils deposit sediiiieiit mid ,37-4OMM OD A sludge in storage tanks (usually an emulsion of xi-ater, oil, anti insoluble material). The rate a t vliich these deposits , -T-accumulate is controlled in part by t’he character of the oil, *and t’liere is a definite need for a laboratory test’ method capable of evaluating this detail of practical quality. Storage tanks must, of course, be cleaned periodically, but it is coni31 25NM I D MINIMUM mercially advantageous t o perform this operation as infrequently as possible. Furthermore, accumulated sediments may cause serious difficulties by becoming dislodged and being carried into the burner, thus interfering with satisfactory operation. 6 - 8 M M. The actual use of bunker fuel oils generally involves either one or two heating operations. It is sometimes necessary SEAT GROUND TO FIT to warm the contents of storage tanks in order to facilitat’e I-INCH STANDARD GOOCH PORCELAIN pumping to boiler rooms, and it is pract’icallyah-ays necessary FILTER PLATE to p a s tlie fuel through a heat exchanger (preheater), which reduces its viscosity so as to ensure proper atomization by the burner. The surfaces of these preheaters are prone to become FIGERE1. STEAM-JACKETEDSUCTION fouled with deposits of insoluble material fornied in or sepaF I L E R FCNXEL rated from the fuel a t the elevated temperatures to diicli i t has been subjected. Such fouling is known to vary in inaromatic solvent such as the benzene employed in the seditensity with different oils, and a laboratory test is also needed ment by extraction test. The sediment contained in cracked to eTaluate this tendency. residues consists in part of aggregates of small primary particles held together by an asphaltic binder. The benzene Present Laboratory Test Jlethods solvent used in the sediment by extraction test is capable of The “sediment by extraction” test ( 2 ) is commonly applied dissoh-ing tlie hinder and dispersing aggregates which exist to bunker fuel oil and apparantly affords some degree of in the actual oil and which are capable of settling out as sludge, or in extreme cases of clogging strainers. Cracked protection against excessive deposition of sludge in storage, although i t does not always rate oils correctly with respect to fuel oil may also contain solid asphaltic material which is this tendency. It seems to be valueless in predicting a soluble in benzene but insoluble in the oil. The new sediment CCH of the heavy, viscous
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DECEILIBER 15, 1938
.INALI-TICAL EDITIOS
test simulates actual service conditions which involve heating the fuel but not thinning it with an aromatic solvent.
Apparatus and Reagents ASBESTOS. Medium-fiber, acid-washed asbestos suspended in distilled mater with a concentration of 6 prams per liter. WASH KAPHTHAS. A high-boiling petroleum naphtha having an initial boiling point of 149" C. (300"F,),or higher, and a final boiling point not exceeding 213" C. (415' F,). Theaniline point should be between 40" and 60" C. A commercial product sold as "Stoddard solvent" usually meets these requirements. -1.S.T. M. precipitation naphtha. FILTER FUNNEL.A steam-jacketed suction filter funnel of glass as shown in Figure 1, with a 2.5-cni. (1-inch) perforated porcelain filter plate, ground in to fit. (This device is available from the firm of Gottlieb Greiner, 50 Dey St., Sew York, S.T.) ACCESSORIE~. Suction flask adapter, rubber hose, pump, steam supply, etc. The pump should be capable of holding an absolute pressure of 254 mm. (10 inches) in the suction flask while liquid is on the
TABLE
679
I. REPRODUCIBILITY O F RESULTSO F HOT FILTRATION SEDIMEST L~ETHOD
Sample l 5 6 9 n - - c , Sample 1570b Lahora- Individual determinations Laboratory ' Individual determinations Laboratory tory (sediment number! average (sediment numher) average .i 0.20,0.21,0.23 0.213 0 . 1 6 . 0 . 1 8 . 0 . I6 0.166 I3 ............ 0.240 0.180 L 0.17,O.ZO 0.185 0.225 D 0.19.0.19 0.190 0.165 E 0 . 1 9 5 , 0 . 1 9 5 , 0 . 2 0 4 0.213 , 0.202 173 0 172 F 0.21S,O.215 0.217 0 167 G 0.196,O. 1 9 2 , O 203 0.197 0.177 H 0 . 2 0 9 , o . 199,o. 197, 0,208 0.203 136 0 136 0.208,0,203 I 0.206 0.118 0.18,0.20 J 0.19: 0.145 0 , 2 1 7 , O . 230, 0.224,0.229 R 1G7 0.2'2 0 , 2 1 9 . 0 . 2 1 5 . 0 . 2 2 0 0. . 2 2 2 0.15i 160 Grand average 0,206 ,...... 0 . 183 .irerage devFation among laboratories 0.009 ............ 0.026 4 Specific gravity, 0.883. Gravity, 12.4' A . P.I. h c o u i t y , 70.1 seconds Furol at 1220 F. b Specific gravity, 0.983. Grayity, 12.1' -4. P. I. Viscosity, 71.6 seconds Furol at 122' F. ~~
Procedure PREPARATION OF FILTER. The asbestos suspension is shaken thoroughly and a 50-ml. portion n-ithdran-n, xhich contains approximately 0.3 gram of asbestos. Without applying suction, the funnel is filled with the suspension and allowed to stand 15 to 20 seconds, after which light suction is applied. When the liquid froin this first portion of the suspension has passed through the plate, a thin pad of asbestos, having no holes, will be formed on the perforated plate. Full suction is then applied and the balance of the 50-ml. of asbestos suspension poured into the funnel. After the liquid has been filtered through, the asbestos mat is Tyashed with 50 ml. of distilled water and finally with 10 to 15 ml. of acetone or alcohol. The funnel is then dried in an oven at 120" C. (248" F.) for an hour and cooled in a desiccator before weighing. PREPARATION OF S . w P L E . Sample containers are warmed until their entire contents have come to a temperature of 49" to 52" C. (120" to 125' F,), The fuel oil in the sample container is thoroughly mixed, preferably with a suitable stirrer operated by hand or by power. F I L T R A T I O X OF FUELOIL. An adequate quantity of the !
