CA1156449A

CA1156449A - Method of destruction of polychlorinated biphenyls

Info

Publication number: CA1156449A
Application number: CA000364406A
Authority: CA
Inventors: Oscar L. Norman; Laurence H. Handler
Original assignee: SUNOHIO A PARTNERSHIP OF SUN OIL POWER SERVICES COMPANY Inc AND SUN-OHIO Inc
Current assignee: SUNOHIO Inc
Priority date: 1979-11-30
Filing date: 1980-11-10
Publication date: 1983-11-08
Also published as: IT1141099B; IT8026288A0; GB2063908A; DE3044978A1; FR2470793A1; NL8006492A; GB2063908B

Abstract

ABSTRACT OF THE DISCLOSURE

A field method for removing polychlorinated biphenyls (PCB's) and similar halogenated aromatic hydrocarbons from silicone based oils and hydro-carbon fluids such as transformer oils contaminated with them by contacting the contaminated oil with a hydrocarbon dispersion of sodium, reacting the mixture of oil and sodium dispersion at a temperature above about 75°C, and passing the treated oil through a filter medium or other separating means to remove parti-culate and other contaminating material.

Description

As is well known, polyhalogerlated blphe~yls such as polychloro-biphenyls (PCB's) and polybromobiphenyls (P~B'~) are toxic ~aterial~ whose use has been curtailed for environmental reasons. Because of their thermally stable and nonflammable properties PCB's have been used as diclectric ~at~riala for transformers, capacitors, and as heat transfer agents, aQd th~ like.
Al~hough ~he PCB's and PBB's used heretof~re have, in ma~y ~ases, been replaced with different nonhazardous materialg, thege replacement materials have fte~
quently bee~ contaminated with residual PCB's or PBB's remainin~ iD the equip-ment. Thus, for example, when large tra~sformers containing PCB's are drai~ed and the liquid dielectric replaced with an environmentally acceptable dielectric (usually a hydrocarbon or silicone based oil) the new material becomes contami-nated wi~h residual PCB's which were not removed by the r~placement procedure.

Such transformer oils 9 heat tràn8fer a~ents, and the like are frequently serviced in the field a~ ~he point of use by mobile equipme~t whi~h removes accumulated foreig~ matter i~ the oil and otherwlse refine~ it for reuse in the system from w~ich it i8 removed. Since many of ~uch oil~ contai~
contaminating PCB's or PBB's it is desirable that the ~ervice iQ the field be able to remove them in an economical and expeditious ma~ner.

It is known that sodium disper~ions and high-surface sodiu~ are useful in eliminating impurities such as halides from petroleum fraction~ and other hydrocarbons (U.S.I. Industrial Chemi~als Co. brochure "Sodium Disper-sions"). Sodium l~aphthalene has also been used to dechlorinate polychlorinated biphenyls as disclosed by Akira Oku, et al (Chemistry and Industry, 4, November 1978). Generally the procedures employed are batch techniques at a fixed site and do not lend themselves to ~ield processing.

The present invention is directed to a field method for removing polyhalogenated aromatic compounds from hydrocarbon and silicone oils by contacting the contaminated oil with a sodium dispersion, reacting the mixture

2 ~ ~

1 15~4~3 at a temperature above 0bout 75C1 and separating particulate and other unwanted material.

It is believed that t~e reaetion re~ults in the polyhalogesated aromatic compounds being conver~ed to innocuous polyaro~a~ic compounds. Iu a preferred process the contaminated oil is pas~ed through a conduit equipped with mixing meansl a hydroearbon diBpersion of sodium ig introduced in~o the contaminated oil in the conduit at ~ poi~ to e~sure thorough mixlng, the mixture of oil ar.d sodium disper~ion is reacted at a temperature of at least about 75C, the treated oil i5 passed through a filter medium or other sepa-rating means to remove particulate and other contaminati~g material and prefer-ably, the treated oil i8 recycled to the system from which it was removed. I~
a fur~her preferred embodiment, a~y excess w diuD remaini~g ~fter the resction with the PCB's is re~oved from the system by reaction wlt~ a hydrated abaorbe~t material which is added to the syste~. ~he hydrated ab~or~ent reacts with an~
unreacted sodium and thus, upon discarding the w ed ~ilter bed ~o ~azardou~
materials are present a~d environmental standards are met.

The sodium dispersion used iQ the proce~s of the i~vention will be .
one where the particle size of the sodium particles i8 preferably on the order of about one to about ten microns. Sodi~m dispersions where the sodium particle i9 about twenty microns are operable for the process, but le8s time ef~icient.
Suitable dispersions are commercially available and are exemplified by Matheson Light Oil Sodium Dispersion. Reference is also made to the text by Fatt and Tashima entitled "Alkali ~etal Dispersions," D. Van Nostrand Company, Inc., New ~~

York, 1961, which describes the preparation of these dispersions in detail.

The amount of sodium dispersion used in the system depend~ upon the concentration of the PCB or PBB contaminants and other sodium reactive materials present. Prior to performing the proce8s, the contaminated oil is analyzed for the PCB's (or PBB's), water and acid number by conventional analytical procedures.

The results of such analysis provide a basis for calculation às to how much sodiu~ is needed to react ~toichiometrically with the ~odium-reaction com-ponents present, and usually a small sodium exces~ of ~bout 10% will be actually used. Since the flow rate of the oil ~h-rough the ~ystem will be controlled to be from about 5 to about 25 gallon~ per ~inute as determi~ed by the particular oil being treated, the rate of addition of the ~odium di~per3io~
to the contaminated oil can readily be detenmined As indicated, the method o the i~vention LS CO~tinllOU3 aQd will employ au apparatus similar to that shawn in the drawing. The tra~sformer oil or other system oil to be treated is taken through line 11 to a conduit 12 ant the appropriate amount of sodium digpersion uuder slight nitrogen pressure or by other positive displacement is metered into the conduit from dispersion storage tank 13. The mixture of oil and disp~rsion the~ p~oceed~ through th~
co~duit to a mixing zone 14 which may be a stirred a~itator, or preferably a~
interfacial surface generator mixing device exemplified by the types disclosed in U.S.2,747,844, 3,195,865, 3,394,924, and 3,632,090. These static mixers are preferred as they have no moving part~, require no maintenance or power, are compact, and can form an integral part of the conduit ~ystem. The drawing shows the mixed fluid then enterin8 a heating zone 15 in order to ensure essentially complete reaction of the halogen compound with the sodium metal in the dispersion. However, ~he heating zone may be positioned at other loca-tions; e.g. in the mixing stage or even b~fore the introduction of the sodiu~
dispersion. All that is required i8 that the mixture of sodium dispersion and oil be heated to a tempe~ature above about 75C for reaction to occur and completion of the reaction. In general, the temperature of the reaction mixture will be between about 100 and about 125C, this upper temperature having been chosen for safety purposes at 20C below the minimum flash point of the oil recommended by NEMA (National Electrical Manufacturers Aasociation).
The reacted fluid then passes to a holding zone 16 fro~ which it 1Owa to a separator such as a filter system 17. The filter system will use as the filter 4 a~ ~

medium any one of a number o filtering media including Fuller's earth, alu~ina, attapulgus clay, pqper, and the like. It will be understood that the particu-late material is separated by filtration, bu~ other unwanted mat~rials may be removed by sorption phenomena. The filtered oil which i~ clear and water white or slightly colored is then ready fo~ reuse and after cooling i~ recylced to the transformer or other system through line 18. Pump 19 is shown as a means to effect circulation of ~he liquid through ~he ~ystem.

.
The entire system described above is ea~ily mcunted on a pallet or flat bed truck and is resdily transported to the site where the hydrocarbo~ oil is to be treated. Thus, a highly effective, efficient and cost~effective ~ean~
is provided for purifying oil contaminated with polyhaloaromatic compounds and a valuable advance in the art has been achievet.

It is of interest to note that hi8h surface sodium on alumina i6 somewhat effective, but inefficient ~o remove PCB's to a sn~icien~ly low level. Only the sodium dispersion as described is sufficiently effective, and then only above about 75C, as below this tempecature, PCB's removal does not occur efficiently.

._ . . ..
In order to further illustrate the Lnvention, the following example~
are given:

Example 1 .. . . . . .
Following the procedures discussed above, a relatively clean hydro-carbon oil contaminated with PCB's containing 49.2ppm of chlorine i9 treated for fifteen minutes with an excess over the stoichiometric amount of sodium dispersion having sodium particles of one micron in size at 120 to 125C and passed through a ten-inch column of a one-inch diametec bed of Fuller's earth.
Five successive runs are made using the same previously used Fuller's earth bed. The following tabLe indicates the analytical results which are obtain~d on the product liquid.
TABLE I
m Run Chlorine ~ 3E~ Color 1 - <0.1 Colorle~s 2 1.3 <0.1 Colorless

3 -- <0.1 Colorles~

4 -- <0.1 Colarless 1.0 <0.1 Colorles3 It is to be noted that the colorles~ product liquid i8 low i~ both chlorine and sodium. The chlorine analysis in ~his exampl~ and all others followi~g were carried out by the Dohrmann microcoulo~retric method. T~c analytical bla~k ~th an uncontaminated hydrocarbon ba~ed transformer oil was normally 0.8-1.8ppm Cl.

Example 2 Following the procedure as discu~sed above, a very dirty transfonmer oil contaminated with PCB's containing 40.7ppm o~ chlorine is treated with a~
excess over the stoichiometric amount of a sodium disper~ion hsvi~g sodium particles of one micron a~ 120 to 125~ and passed through a te~ ch colu~n of a one-inch in dilmeter bed of Fuller's earth ab30rbent. ~he product oil obtained is colorlefis, has a power factor of 0.0017 at 100C, a resist~vity of 64 x 1012 ohm-cm at 100C and contai~ 2.6ppm of chlorine and le~s than O.lppm of sodium. When the run -is repeated and the sodiu~ treated material pa~sed through the previously used Fuller's earth, the product liquid l~ light y~llow and contains 8.0ppm of chlorine and 2.6ppm of sodium. A third passing of treated material through the Fuller's earth yields a cloudy, orange liquid, thus iadicating the need to replace the filter material when a highly impure oil is treated.

1 ~ 9 Example 3 This example ~hows the effect of ~emperature and i~ carried out with a test oil and sodium disper~ion as in Exa~ple 1. T~ble II show~ the re3ult~
obtained.
, TABLE II
Temperatu~e Time Cl (C) _ 73 - 75 15 25.9 100 - lOS 15 ~ 30.g 120 o 125 5 4.6 120 - 125 15 1.0 Thus it is clear from the above that the preferred operating temperatu~e i~
from about 120 to 125C.

This example illustrates the use of a "High Surface" ~odiu~ dispersed on alumina for PCB's removal and the effect of reaidenc~ time.

A standard test hydrocarbon oil containing PCB's analyzing for 49.2pp~ chlorine is heated to~l~5 to 110C. The data for this ~un-is ahown in Table III.

TABLe III
Residence ppm ppm Sample it Time (Min.) Chlorine Sodium 1 8.8 1.3 <1.0 2 8.8 . 1.5 . - -3 g.8 2.4 4 4.3 9.5 4 3 10.6 3.0 6 ~.3 6.6 7 1.6 3~.7 8 1.6 31.0 6.0 Although the "High Surface" aodium removes the chlorine content, Stoichiometric calculation of the data in Table IV shows that with continuing 4 ~

throughput the system does not e~ficiently reduce the PCB co~tent of the oil even at the p~efe~red temperature of 120-125.

TABL~ lY
Hi~h Surface Sodiu~
PCB R o o~al Proces~

Bed: 10% Na/A1203 (28-48 ~e~h, 12g-Ma, 12~g~A1203) Feed: Test Oil containiug 49ppm Cl (PCB's) Total AppYoximate Flow Rate Yolume Flow at Chlorine PCB Content Sample No. ~ S ~ ppmof Treated Oil Oil Temperature: 74-t7C
1 & 255 17.0 34.0 2 lO S30 24.0 48.0 3 1? 784 36.6 73.2 Oil Te~p~ture: ~00-110C
1 17 28~ 1.3 2.6 2 " 403 1.5 3.0 3 " 522 2.4 4.8 4 35 857 9.5 19.0 " 992 10.6 21.Z
6 " 1127 6.6 ~13.2 7 95 1477 34.7 69.4 8 " 1727 31.g 63.8 9 17 2~11 13.6 27.2 Oil Tem erature: 120-125C
P
1 17 180 7.0 14.0 Z " 527 ~.9 5.8 3 " . 985 . 1.8 3.6 4 " lg94 2.1 4.2 " 2760 2.7 5.4 6 " 3075 2.1 4.2 7 " 3380 8.1 16.2 8 " 3690 -13;2 26.4 ~ -9 " 4764 25.0 50.0 Example S

Using the technique of Example 1 at 100C with PCB contami~ated oil (40.7ppm chlorine) and with a sodiu~ dispersion where the particle size i~ 20 mierons, the -following Table V ~howfl the ine~ficiency of the process with such sodium particle stze:

TABLE V

Time (Hin.) ppm Chlorine 36.9 29.7 27.0 Example 6 When Example 1 i8 repeated but using alumina, Filtrol R 24 a~d Elorosil R as absorbent bed~, a reduction in PCB's i8 si~ rly obtained, but in most cases the product i~ so~ewhat colored. Wit~ both Flltrol 24 a~d Florosil the beds are quite effective, ~ut are quic~ly plugged. Thu~ these absorbents are less desirable th~n Fuller's earth.

Example 7 When Example 1 is repeated with a silicone ba ed tra~sformer oil contaminated with PCB's, the chlorine content is si~ilarl~ reduced to low levels of chlorine As indicated above in another embodiment of the inv~ntion the sep~ra-tion procedure involves reacting a hydr~ted absorbent material with the treated product taken from holding tank 16 in order to r~move any ~odium particle~ -still present. Thus an a~sorbe~t such a3 a hydrsted ~ilica or ~ilicate may be added to the product from the holding tank, agitated thoroughly while bein8 held for a short time (about l to 5 ~inute8~ and filtered through an industri31 filter before passing through filter 17. In this wa~, the exc~ss unreacted sodi~m particles react with the water in the hydrated absorbent and this permits easier filtration and gives a cleaner product. In an alternative method, the hydrated absorbent may simply be used alone as the filter media or placed in the bed of a different filter material; i.e the hydrated material may be a bottom, middle or top layer iQ the filter bed of non-hydrated filter A ~ 9 medium used in filteriDg the treated oiL. Other examples of hydrated absor-bents include finely divided RVM and LV~ types of attapulgus clay (mesh siæe of 200/up made by Engelhard Industries) and hydrated magnesium silicate (Brite~or~
90 made by Philadelphia Quartz Company). This embodiment is illustrated by th~
following examples.

Example 8 As in Example 1, 100ml of te~t oil containislg about 50p~m of chlori~e from PCB's present is treated with 20 drops of a sodium di~perfiion i~ light oil(1 micron particle size) fo~ fifteen minutes at 1Z0~^12S~. Thc~, o~e gra~ o finely divided hydrated silica (HiSil ~ 233 ~ade by PPG Industries) is added to the hot oil, stirred for three to four minutes ~nd allowed to stand for 45 ~inutes while cooling. The material is then filtered through a paper filter to give a water white oil product co~tainis~g le~s tha~ lpp~ of sodium; less tha~
lppm of chlorine and less than 1OPPM of silicon.

When a dirty oil is used in the above example (9Oml of the oil of Example 1 plus 10ml of a used, dirty transsormer oil) the results are essen-tially the same except that ~he filtered oil hss a slight yellow color.

With a very dirty oil under the same conditions the resultin~ filtered oil is a deep orange and contains 2.8ppm of csllorine, 116ppm of sodium and les6than lppm of sili COQ .
.
When Example 8 is repeated with the test oil but using one gram of 200/Up attapulgus clay islstead of the hydrated ~ilica, the resultant oil` is water white. With a dirty oil, two grams of the attapulgus clay gives a clear oil with an orange color.

4~1 ~xample g A test oil containing h9ppm of chlosine i8 ~reated wi~h a sodiu~
dispersion as in Example 8 a~d is pa~ed through a colum~ of 5Q/80 mesh XV~
type attapulgus clay. The resulting oil i8 clear and water white a~d greatly reduoed in ~hlorine content.

Exam21e 10 A run is made similar to that of Example 9, but using a column composed of a top one-third layer of RVM attapulgu~ clay and a lower two~third~
layer of LVM attap~lgus clay (both clays of S0/80 mesh). The oil effluent i8 somewhat hazy due to the presence of water and/or clay fines~ bu~ ~he chlori~e content of the treated oil i~ reduced fro~ 49ppm to 9.3pp~. A test of the oil with litmus paper i~dicates that it i8 neutral. Whe~ water i5 pre5eQt i~ the oil it is readily removed by vacuum stripping before reuse. Howev~r, by using a larger amount or a more efficient hydrated absorbe~t, the oil ~ay be treated without any water breaking through.

Claims

Claim 1. A field method to remove at the point of use, halogenated aromatic hydrocarbons from hydrocarbon transformer oils contaminated with said halogenated aromatic hydrocarbons which comprises removing said contaminated oil from the transformer and circulating said oil through a decontamination system at a flow rate of from about 5 to about 25 gallons per minute to effect decontamination by mixing the contaminated oil with a hydrocarbon dispersion of sodium wherein said sodium has a particle size of from about one to about twenty microns, reacting the mixture of oil and sodium dispersion at a temperature above about 75°C, passing the treated oil through separating means to remove particulate and other contaminating material and returning the treated oil essentially free of halogenated aromatic hydrocarbons back to the transformer.
Claim 2. The method of Claim l wherein the temperature is about l25°C.
Claim 3. The method of Claim 1 wherein the particle size of the sodium is from about 1 to about 10 microns.
Claim 4. A field method for removing polychlorinated biphenyls from hydrocarbon transformer oil contaminated with said biphenyls which comprises removing said contaminated oil from the transformer at the point of use and circulating said oil through a decontamination system at a flow rate of from about 5 to about 25 gallons per minute to effect decontamination by mixing the contaminated oil with a hydrocarbon dispersion of sodium wherein said sodium has a particle size of from about one to about twenty microns, reacting the mixture of oil and sodium dispersion at a temperature of from about 75°C. to about 125°C., passing the treated oil through a filter medium to remove particulate and other contaminating material and returning the heated oil essentially free of polychlorinated biphenyls to said transformer.
Claim 5. A field method for removing polyhalogenated biphenyls from hydrocarbon transformer oil contaminated with said biphenyls which comprises removing said contaminated oil from the transformer at the point of use and circulating said oil through a decontamination system at a flow rate of from about 5 to about 25 gallons per minute to effect decontamination by mixing the contaminated oil with a hydrocarbon dispersion of sodium wherein said sodium has a particle size of from about one to about twenty microns, reacting the mixture of oil and dispersion at a temperature above about 75°C, reacting the sodium particles remaining in the treated oil with a hydrated absorbent material, separating particulate and other contaminating material, and returning the treated oil essentially free of polyhalogenated biphenyls back to the transformer.
Claim 6. The method of Claim 5 wherein the halogenated biphenyls are polychlorinated biphenyls.
Claim 7. The method of Claim 6 wherein the temperature is from about 75°C to about 125°C.
Claim 8. The method of Claim 7 wherein the particle size of the sodium is from about 1 to about 10 microns.
Claim 9. The method of Claim 8 wherein the hydrated absorbent is a hydrated silica.
Claim 10. The method of Claim 9 wherein the hydrated absorbent is a attapulgus clay.
Claim 11. The method of Claim 8 wherein the hydrated absorbent is a hydrated magnesium silicate.

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