SO6
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 39 No 4
LITER LTURE CITED
Laboratory Machine for the Continuous Production of Grease J
DEVELOPMENT AND DESIGN HIS 1ahoratol.y has p l ~ q ~ ~ e t l T d i e i t e r greareh having improved evaporatioll rates, storage stat)ility, and luw-tenil~e~~xture To expedite utilicharwcteri.tics'. zation i i i naval equi1)nient. h t l i the Bureau of A4erimautiitsand thrs Bureau (Jf Ort1iianc.r reco~nniendetl t h a t raniples I J ~dist,ritiuted to cooperating activitie3 and equipnlent nianufacturel,s for tests and routint. use. Sanil)le +iwsvaried from a Feiv ounce' t o as muc4i as 50 pound., the larger aniountc being required f o r functional testing and field applkations. T h e fire kettle rnethod ~f ~ ~ l a k ing greaser and its use at this lahoratory have been desc8ril)ed'. When large batches of grease \vere made by this method, the lahoratorg' ventilation proved inadequate, and much di,vomfort \vas experienced, since the vapors given off by t h e hot grease were very irritating t o t h e mucous membranes;. This suggested t h e w e of a rlosed system for niaking t h e greases. Recause of the demand for large quantitiep of diester grease, the possibility of using a totally ericlosed continuous heating and cooling syzteni was investigated. .is suggested originally, thc ~ u e t h o dwas intended 'to make uniform batches of approximately 1 pound, hut t,he scale was later revised upward t o production of 50 1
Hain, G . hl., Jones, D. T., Alerker, I < .
I,,, and Zisrnan, W . .4.,ISD. ENQ.C H E M . . 39. 500 (1947).
G. \I. H\l\
i \ D E. E. STOAE
h c c l l Krwurc.h I,rrhorator,\. l r a s h i n g t o n , U . C .
Ii niachiiie i s
described for L h r coiitinuou. production of 100 pounds of grease per da? using a totall? enclo*ed s?steni. 4 Fiscose spiniierette piinip forces the material through the system. \ soap is heated in fluid slurry t o 200" i n a (,oil o f fine-hore ticbing whose w a l l - are heated 1)) a current of about 30 amperes. (:ooling to a gel and -hearing of the gel to a butter? grease are accompliqhed by forcing the hot liquid through a watercooled c-oil of the *dine dimensions as the heater. idditional %hearingtakes place in a worker section, using a gear piimp to cycle grease through a perforated plate or wreeti.
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4
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I
3
---"i' Figure I .
1.
2. 3.
4.
Agitator Feedtank Feedpump Heating coil
Flow Diagram 5. Cooling coil
6. Working pump 7. Working scrern 8. Check v a l v e
pounds per day. It \vas unique i n that t h e grease passed through miall-diameter tuhing, therehy P i fecting h e a r breakdown of tlie grease rtructure as the grease cwoleti. With this in mind it was I)r.opciml to huild a machine embodying the following features : 1. ('ontinunus flow heat irig ancl cmling. 2. Thin Layer heating and C O O l inp, using flow turbulence in tulling ( i f small cross section to act as a mixer and high pressure head t o s u p ply the necessary flow work. 3. Cniform heating by using t h e tutiing wall itself as the re.w's t a n w heating el(~rnent,
Yuvh a "tup !vas made t)reatllioard fashion on the lahorat,ory tatile. I t consisted of a heating coil follo~vedby a cooling coil and fed by a punip that wa.5 capable of exerting iereral hundred pounds pressure. .4 slurry of the diester and soap \vith the necessary additives was fed to this apparatus; the heating roil melted the slurry, while the cooliilg coil chilled the mixture tu a gel siniilar t o t h a t produced in the fire kettle method. This apparatus provrd t h a t grease could be made ..uwe?sfully in a closed system. Based uii information obtained Rith thi5 equipment, a plant was designed having a capacity of 100 pounds of grease per day. Figure 1 is a flow sheet and Figure 2 is a photograph of the plant. The apparatus was built up of standard parts, and no special or U I I U S U ~ ~ equipment used.
April 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
The portion of the apparatus subjected t o heat was built of 3/,,-inch stainless steel tubing (18 '8 type). -4luminum tubing and galvanized iron pipe were used throughout. As short a conneetion as possible was used between the feed tank, 2 , and the Zenith viscose spinnerette variablespecd feed pump, 3; this was to provide for adequate flow of feed. h safety valve, 9, was placed in the line from 3 t o the insulated stainless steel heating coil, 4. T h e heating coil, made from about 8 feet of tubing, was heated by passing a n electric current through the coil and using the resistance of the coil t o provide the heat. The line current (110-volt alternating current) was fed t o a low-voltage transformer, 10, through a continuously variable autotransformer ( 2 5 kv.-amp.), 11. T h e l o ~ vvoltage from 10 JYas connected t o the ends of 4. The cooling coil, 5 , of the same length as t h e heating coil, was a c o w centric pipe heat exchanger cooled with water, thtb water passing through t h e outer tuhc and the grease through the inner tube. T h e coaling ivater rate was measured by an orifirc meter insertrd in the water line. The worker unit, B, 7 , and 8, \vas built to recirculate the grease through a section containing ti scrwn, 7 , the object being t o break up thts gel structure of the grease. T h e gear pump, 6 ( 3 . 5 gallons per minute at 1800 r.p.m.), circulated the grease through the screen, 7 , and back to 6. A check valvr, 8, was providt,d for removing the worked grease. Thermocouples were installed at suitable points in the apparatus to control the heating and cooling of the grease. Pressure gages were placed on the high-pressure sides of the two 1. pumps: by-pass valves were provided for sam2. pling and cleaning purposes. 3. I n operation the diester soap slurry as charged 4. 5. into the feed tank, 2, and agitated until homogeneous, b y a variable-speed agitator, 1. T h e feed pump, 3, was regulated t o the desired speed and t h e heat control, 11, adjusted t o give the Drorm- temmrature t o the melted grease. T h e &ding water %vasturned on and the product from the cooling coil vented until a homogeneous product was obtained. \\-hen the apparatus had reached equilibrium, the worker was started and the cool grease fed t o the worker. As ttir incoming grease raised the pressure in the worker the check valve, 8, opened and alloweti the finished grease t o extrude. Typical of the greases made hy the machine n-ai the folloning: 14 0 1.0 1 0
02 1.0 a2 8
.ix.erage operating conditions Feed p u m p speed, r.p.m Flow r a t e of slurry. ml Der minute Feed p u m p pressire, po;nds per square i n r h Worker p u m p speed, r.p.n;. Worker p u m p pressure, pounds per square inrh Worker screen size, meshes per inch Production r a t e , pounds per hour Cooling water r a t e , gallons per m i n u t e Power consumed by heating coil, watts Heating transformer o u t p u t , amperes Temperatures, C. Feed slurry H o t slurry Chilled gel Inlet water Outlet water Tf'orker
130 7..R
400 36 125 30 8.5 1.2
630 15 82
200 20 6 12 28
'The machine i. not limited to the production of iitliiun] soap grea.sei, hut inay l i e used for other greases that can be made tJy rapid heating and cooling. K h e n making greases of high 3oap content 120 to 30C01 or using more vi.qcous fluids, the existing pump-driving mechanism may not have the power required t o overcome the increased friction of the grease. .Iny driving mechanism capable of forcing the grease through the cooling coil can be used. Grease can be made a t almost any feed pump speed. T h e driving mechnnkm used \vas variable from 0 to 220 r.p.m. -\t the higher speeds tlip slurry flow rate through the heating coil
Figure 2. Agitator Feed tank Feedpump Heating coil Cooling coil Worker pump Worker screen
507
Laboratory Grease Plant 8. Check valve 9. Safety valve 10. Transformer 11. Variable transformer 12. Potentiometer for temperature meanuremrnta 13. Pressure gage
may be too rapid to allo\v vomplete melting aiid mixing of the soap with the fluid. The method of heat,ing used gave very quick, uniform heating which could he easily regulated by means of the variable transformer. The cooling coil, while adequate, did not give uniform cooling; t h e molten grease Ivould (ahill arid a.dhere to the walls of the cooling coil, leaving a core through the center. The heat transfer a c r o s this layer of grease to the core, although very poor, proved sufficient and did not warrant changing the design. The working that the grease rereived in the worker unit was controlled by three factors: feed pump speed, Jvorker pump speed, and Xvorker screen size. The shear breakdown of the grease csaused by the grease working against itself was negligible because of the size of the piping (0.5 inch) wed. Before starting the n-orker unit was hand-packed with grease to eliminate the occlusion of air in the worked grease that n.oiild have been present had the unit been started empty. The grease produced in the machine \%-\-henoperated as described a h \ e contained a slight amount of "prickly heat"' and had a niii.rc)i)enetr3tion of 00 to 100. The machine could he started u p and put i n operation pruduc. ing worked grease within 40 minutes. I t had a holdup of ahout 3 pounds of grease. The grease produced was uniform and homogeneous and was as good a.: that pi,ocluc.ecl by the inore IahoriouP lahoratory methods;. ACKNOWLEDG3IE:RT
The authors wi.5h t o thank J. E. Brophy and R. 0. Militz for their suggestions and assistance in designing the necessary parts and fittings. THE opinions or assertions contained i n this paper are t h e authors' a n d are not t o he construed as official or reflecting t h e vi,?ws of the Navy Department
