127
091
THS

 

A CONTINUOUS OXIDATION

PROCESS FOR. FLUX OILS USED

1N THE MANUFACTURE OF
ASPHALT ROOFING

Thesis for the Degree: of C. E.

James Allan Stone
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LCONTINUOUS OXIDATION PROCESS FOR FLUX OILS

USED IN THE MANUFACTURE OF ASPHALT ROOFING

THESIS
BY

JAMES AILAN STONE

IN PARTIAL FUIEILMENT OF THE REQUIREMENTS
FOR THE DEGREE OF

C. E.

MICHIGAN STATE COLLEGE
EAST LANSING

MICHIGAN

1955

"HESIS

 

 

DESCRIPTION OF PRESENT OXIDATION PROCESS

Definition of Petroleum Flux Oil

Petroleum flux oil is a residual oil in the
process of refining petroleum into gasolene, solvents,
lubricants, fuel oils, etc. It is comparable to the
natural asphalts in general prOperties end can be used
fer the same purposes. Throughout this design the
‘Iords flux oil and esphalt ere used synonymously.
Among its uses are those of road construction and
msnufeeture of roofing. Even et this residual stage
flux oil, like the originel petroleum, is e mixture
of oils, end by distilletion the properties of flux
oil my be chenged from that of a. liquid. at ordinary
temperetures to that of e pitch Iith e melting point
of 300 degrees Fehrenheit or more. However, if air is
introduced through the flux oil st the tempersture st
shich distilletion takes pleee, oxidetion of the lighter
oils occurs. This oxidation takes place more repidly
then dietilletion, end has not become the method hy
thich the melting point of flux oils is reised. In
the uses of flux oil the melting point characteristic
is most importent.

98894

Use of Petroleum Flux Oil
Asphalt roofing is composed of two types, built-up
roofing and prepared roofing. Ihe first is used on
factories, warehouses, and office buildings; while the
latter is used mainly on homes. Both types of roofing
are essentially alike. One, however, as its name ‘
implies, is built-up on the roof deck to be covered,
while the other is completely manufactured and only
needs to be laid. Both roofings are made up of’a
felt base which has been saturated with asphalt.
fihis is the body of the roofing. The built-up roofing
consists only of this saturated felt, a coating of
higher melting point asphalt, and a sprinkled layer of
gravel. hhe latter two items are applied on the Job.
The prepared roofing is also composed of this saturated
felt, a coating of higher melting point flux oil, and
a layer of granulated slate pressed.into the coating;
this process is completed at the fletory.
Saturant of Roofing Pelt

« rho melting point of flux oil used.as a saturant
is 100 degrees Elhrenheit, except in the case of shingles
when it is about 150 degrees lahrenheit. the reason for
a higher melting point saturant for shingles is to provide

8.

a more rigid base. The asphalt used as a coating for
built-up roofing has two ranges of melting points, the
lower for flat roofs and the higher for slaping roofs.
Coating on Prepared Roofing

Prepared roofings are composed of three types:
Scooth surface, slate rolls, and shingles. The smooth
surface roofing has only a dusted surface of mica or
soapstone on t0p of the coating. Slate rolls have
granulated slate imbedded in the coating. Shingles
are similarily made as slate rolls and then are cut
into shingle patterns. The coatings vary in melting
point from 200 degrees Fahrenheit on smooth surface
roofings to 240 degrees Fahrenheit on shingles. The
latter require a higher melting point to obtain rigidity.

Definition of Oxidation of Flux Oil

Asphalt of a melting point meeting the require-
ment for a saturant is usually purchased from the
refineries. This melting point is about 100 degrees
rahrenheit. The roofing manufacturer then oxidizes
this flux oil to raise the melting point to that
required for coatings and shingle saturant. Oxidation
in this case consists of heating up the asphalt and
passing air through it until the required melting
point is attained. This is accomplished by filling or

5.

charging a horizontal still with the flux oil. Some-
times two or more kinds of flux oil are used in making
a charge, depending upon the properties desired hy
specification. One source of flux oil may not be able
to meet all requirements. Blending with an asphalt
from another oil field is necessary to meet the
specification of penetration or prevent discoloration
of slate granules.
Present Method of Oxidation

.ifter charging heat is applied to the still
bottom heating the asphalt to a temperature of about
460 degrees Fahrenheit. Air is blown through the flux
oil from a series of vertical pipes with outlet holes
on the bottom, so that air bubbles rise through the
liquid. Oxidation between the air and lighter oils
occurs giving off heat during the chemical reaction,
raising the temperature of the charge. The oxidized
vapors are exhausted from the still by means of’a fan.
The air is produced hy low speed air compressors at a
pressure of about two pounds per square inch.

Experience in knowing when to stOp firing the
still bottom is necessary in order to control the
rise in temperature due to oxidation. The maximum

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safe temperature to oxidize is about 530 degrees
Fahrenheit; above this point there is danger of flash
or fire. Usually the rise during oxidation from the
initial temperature of 450 degrees Fahrenheit is
about 50 degrees to 70 degrees Fahrenheit, making a
total temperature of between cod degrees to 520 degrees
Fahrenheit. Samples are taken from time to time until
the required melting point is attained, at which time
the air is turned off and the completed coating pumped
to the supply tanks over the roofing machines. The total
time from charging to pumping, of course, varies with the.
melting point to be attained and the amount of flux oil
to be oxidized. The range is from twelve to
twentybfour hours.
Method of Charging

There are two methods of charging. One is to
pump the asphalt directly from the storage tank to the
still and then start firing the still. The other
method is to pump the flux oil through a tube heater
and preheat it before placing it in the still. How-
ever, even after this preheating, by the time the
still is charged it must be reheated to attain the

initial oxidizing temperature. Nevertheless the tube
heater having better heat contact is more economical
in the use of fuel. Also the still-time is reduced
because of less firing to attain the initial
oxidising temperature.

PROPOSED METHOD OF OXIDATION

The asphalt leaving the tube heater has a
temperature between 450 degrees and.500 degrees
Fahrenheit depending on the temperature of the heater
and the rate of pumping. Since this range of heat is
sufficient to start oxidation of the flux oil, if air
could be introduced through it, oxidation would occur
without heating in a still. The stills are of 5,000
and 10,000 gallon capacity. The pumping rate through
the heater is from 1,500 gallons to 2,000 gallons per
hour. This requires about three hours to charge a
small still and about six.hours for a large still. It
is during this period.that the asphalt cools down
requiring firing up in order to attain the initial
oxidizing temperature.

To oxidize the flux oil while it is sufficiently
hot would require that the air be blown through it
while it is in motion. After being pumped through the
heater and heated to 450 degrees Fahrenheit, if the
asphalt flowed through a small tank and air sea blown
through it oxidation.would.take place. Thus the flux
oil could be drawn from the storage tank, pumped

7.

continuously through the tube-heater and on through
an oxidizing tank, to the supply tanks above the
roofing machine.
Purpose of This Method

This would rednce heating to a minimum,eliminating
the firing of the still. h'requently the still charge
is finished long before it is needed at the roofing
machines. During this inteml the finished product
cools down so that then the time arrives to pump
out the still the charge is too cold and must be
reheated. By oxidizing the asphalt as it is needed,
continuously, this reheating could also be eliminated.

If the flux oil could be oxidized while it is
pumped, at a rate of 1,500 gallons per hour, it
would increase the capacity of a single unit by a
big margin. The large still has a capacity of 10,000
gallons requiring from 12 hours to 1'! hours to
oxidize, plus 6 hours to charge, making a total time
of 18 to 23 hours. While continuous oxidation at
1,500 gallons per hour would total 56,000 gallons in
24 hours.

The present still is charged a definite amount
which may be more or less than is needed in a day's
production at the machine. A continuous oxidizing

8.

unit sould.allow control of the amount to be
oxidised. this amount varies with the type of
roofing being produced.

rhe present still charge is oxidized to a definite
melting point. Continuous oxidising would permit
control of melting point by changing velocity of
flow or time of contact with the air so that
successive melting points might be produced. One unit
could produce different coatings, thereby replacing*
several stills.

Another benefit to the manufacture of roofing
would be the reduction in the amount of inventory of
finished products. At present it requires 34 hours
notice to prepare the coating for a machine run. .1
continuous oxidising process would.require only a few’
hours notice to schedule a machine run. This would
allow operating to customers' orders.

Cost Reduction

.Most important, a continuous oxidizing unit would
save money in its operation. Fuel in heating and
reheating would be greatly reduced. It would also
reduce still cleaning and operating labor. Firing of

a still causes a coke to form on the bottom. this

must be removed when the accumulation interferes with
the heat transfer from the still bottom to the asphalt.
Preheated charging has reduced the amount of coking.
It is reasonable to suppose that continuous oxidation
sould reduce this further by eliminating the still
firing.

Usually each machine operated requires a still
of coating. Daily production varies from two to four
stills normally. By using a single oxidising unit the
time for an operator to supervise the oxidation would
be greatly reduced allowing him to handle other
functions such as unloading asphalt from incoming
cars.

Power would be greatly reduced. Only one air
compressor would be needed for the continuous cxidiser
and one exhaust fan. At present one of each is used
for each still when oxidising.

Problem of Design

Oxidation of asphalt continuously by heating it
to 500 degrees Fahrenheit and introducing air through
it brings several problems to mind. How long is it
necessary for the air to be in contact with the flux

10.

oil to produce a definite melting point? How long
does it take to raise the melting point a definite
range in the present stills? Is there a relation
between the different melting points required and the
time necessary to oxidise to them?

is the temperature for all oxidising is fairly
constant and.the volume of air used remains the same,
only the time of'contact is variable. The temperature
ranges between 500 degrees and 530 degrees Fahrenheit,
and the volume of air passed through each charge is
600 cubic feet per minute. The different melting
points required.are: Shingle saturant, 145 to 165
degrees Fahrenheit; smooth surface roofing coating,
195 to 210 degrees Fahrenheit; slate roll roofing
coating, 210 to 220 degrees Fahrenheit; and shingle
coating, 250 to 240 degrees fiahrenheit. The flux oil,
used as regular saturant, from.which these are oxidised,
has a.melting point of 110 to 120 degrees Fahrenheit.
She average rise of shingle saturant is 40 degrees
Fahrenheit; of smooth surface roofing coating, as
determined by the maJority of charges which are to
195 to 200 degrees Fahrenheit, is 80 degrees Fahrenheit;

11.

of slate roll roofing is 100 degrees Fahrenheit; and
of shingles is 120 degrees Fahrenheit.

Also there is the question: Is there a relation
existing between the oxidising time of the 10,000
gallon still and the 5,000 gallon still? no first is
charged to a depth of 6 feet 6 inches, and the latter
to 5 feet 1 inch. The large still has a diameter of
9 feet 0 inches, while the diameter of the smaller
still is 7 feet 0 inches. the space between the level
of the liquid and the tap of the still is used to collect
the vapors and allow for the splash caused by the air
bubbling through the liquid. There is a difference in
the quantities oxidised, one is about 7,600 gallons
and the other 4,200 gallons.

The volume of air used in oxidising both sizes
of stills is constant, 600 cuhic feet per minute. the
temperature, of course, is the same for both. The
only variables then are the depth of material through
which the air passes and quantity of flux oil in each
to be oxidised.

The variable of quantity can be equalised by

reducing the oxidising time to that per 1,000 gallons.

12.

Ihis leaves only the variable of depth to consider as
a relation between the oxidizing time of the two sizes
or stills.

13.

DESIGN OF CONTINUOUS PROCESS

Analysis of Present Method

In order to have facts concerning the operation
of’the present system of'oxidising the asphalt in
horizontal stills a record.sas kept of each still
charge. Table #1 shows a sample of the record kept,
in this case 195 to 210 degrees Fahrenheit melting
point coating, shoeing data, size of still, total time
from charging to O.K. by laboratory, firing time,
oxidation time, and reheating time. These records
were grouped by melting points: 145 to 165 degrees
Fahrenheit group, 195 to 210 degrees Fahrenheit group,
210 to 220 degrees Fahrenheit group, and.230 to 240
degrees Fahrenheit group. .is indicated above these
groups sere divided into those for the large size stills
and those for the smaller stills.

These records sere kept over a period of a year
and.one-half before initial comparisons sere made.
There exists.a side difference in the figures of each
still charge. Seme of the higher figures are due to
charging a cold still or starting oxidation before a
high enough temperature had been reached. The low

14.

193°~210° F. melting Point Coating.

TABLE 1

Time in Hours.

 

 

 

 

 

 

 

 

 

 

 

 

Date Total Firing Oxidation Reheat
Small Large Small Large Small Large Small Large

2/3 11 4 95 3%

2/7 2 3% 16 3

2/8 11 2 3% 3

2/13 21 3 13 1

2/14 13% 1g 10 2

2/13 12 3 8 1

2/22 13 1 94' 1

3/7 13 3 8i 2

3/12 1 3 10 3

3/13 1 3 13 2

3/19 1 3% 12 1

3/20 15 10} 2

3/20 13 2 9 0

3/21 12 14 4 0

3/27 19 1} 14 0

3/28 is: 3 12 3

4/2 13} 22 2 3 12 19 25 2

4/3 13 2 10 0

4/3 10} 2 9 1

4/4 21 2 17 2

4/4 12 2 9g 1

4/3 184' 3 12 3

4/3 19 1g 1e 2%

4/7 134 17 1 3g 10 8% 2 1

4/7 17 1 14 1

4/8 13 1 1 0

4/8 14 1 1 1%

4/9 13% 20 3 24 13% 1 3

Lee. 13.0 17.0 2.3 2.9 10.8 12.1 1.4 2.1

 

 

figures are mainly due to leaving part of'a previous
charge in the still and "topping off" for the use
charge. Thus a charge in this case would have a higher
original melting point than 115 degrees Fahrenheit.

The records acre analysed by throwing out the unusual
figures, but the net average was close to the average
leaving in these figures.

Before analyzing these records it was assumed that
only a flea sbuld be necessary in the present horizon-
tal stills to make a continuous oxidising unit.
The charges in the 10,000 gallon stills were known
to require longer total time than the 5,000 gallon
stills. This seemed reasonable because the larger
still contained more asphalt to be oxidized.

Relation Betseen Melting Point Divisions

in.examination of Table #2, which is a summary
of‘still charges recorded.from.iugust l, 1932, to
March 1, 1935, reveals data.about oxidation of the
present stills. There are four main groups, in which
tso are to be analysed now. These are for the.4,200
gallon still charge and the 7,600 gallon still charge,
the normal charges. The total number of charges were

divided into the total oxidation hours, which gave the

15.

TABLE

2

 

3700 Gallon Still Charge

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Depth 4' 6"
Melt. Number Total Ave. Ave. Melt. Ave.
Point of Still Oxida- Oxida- Hours Point Time 0
Charges tion tion per Rise per 1 F.
Hours Hours 1,000 g. Rise
M312.
Point
per
1:0001g‘_
193-210 13 199.0 12.43 3.33 80° .0420
210-220 4 47.3 11.88 3.21 1003 .0321
230-240 13 231.0 13.39 4.24 120 .0333
Group Ave. .0363
4200 341133 Still Charge
Depth 5' 1"
143-133 37 327.3 4.888 1.13 403 .0290
193-210 237 2492.0 9.700 2.31 80 .0289
210-220 32 707.3 13.303 3.24 1003 .0324
230-240 89 1434.0 13.112 3.83 120 .0333
Group Ave . .0314
7000 341133 33111 Charge
Depth 3' 0n
193-210 20 241.0 12.03 1.72 80° .0214
210-220 22 332.0 13.83 2.41 100° .0241
230-240 22 391.0 17.79 2.34 120° .021g
Group Ave. .0222
7600 Gallon Still Charge
Depth 6' 5"
0
193-210 173 2121.3 12.034 1.39 80: .0199
210-220 132 2411.0 14.821 1.93 100 .0193
_230-240 212g 3849.3 18.130 2.39 120° .0199
Group Ave. .0194

 

 

 

average oxidation time per charge. These were further
reduced to the time per 1,000 gallons. On Chart #1
these figures were plotted for each melting point
division and a line drawn for each size charge from
the point for 230 to 240 degrees Fahrenheit melting
point to the 115 degrees Fahrenheit melting point
position. The line for the 7,600 gallon charge
approximates the plotted points indicating clearly a
relation existing between each melting point position.
The line for the 4,200 gallon charge, neglecting the
point for 195 to 210 degrees Fahrenheit melting point
division, also indicates that such a relation exists.
The discrepancy is the plotted point for the 195 to
210 degrees Fahrenheit melting point division, which
is low. Looking back to Table #2 it will be noted
that the number of charges for this division is several
times larger than for any of the others. Therefore,
this figure must be authentic.
Difference in Operation

The difference between this point and the normal
line is due to the difference in Operation of the
5,000 gallon still for this division. When the other
melting point divisions are oxidised the still may
:not be recharged immediately. This division, however,

16.

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is immediately recharged. Bo heat is lost in the still
shell. The reason for this difference lies in its use
as a coating, which contains 50 per cent sand filler,
which amount requires a hot coating at the roofing
machine in order to remain semi-liquid. To maintain
hot coatings, small amounts are pumped to the supply
tanks over the roofing machines and refilled as
depleted. The 5,000 gallon still is repeatedly
charged as soon as it is empty to keep pace with
production.

The oxidising conditions of this still, when the
195 to 210 degrees Fahrenheit melting point coatings
are being oxidised, approach closely the conditions
under~which continuous oxidation occurs, and are
evidently a more accurate figure on which to base
assumptions. The 145 to 165 degrees Fahrenheit
melting point division for this size still charge
also bears out the above conclusions, as these
oxidised saturant charges are immediately recharged
.and oxidised. The dotted.lines through these two
_points illustrate the result, if the other divisions
could be recharged as soon as finished; they indicate
further the margin of safe calculation.when compared

17.

.with the line for the 7,500 gallon still charge which
is used in the design of the oxidation tank, as will
he pointed out later.

On Table #2 the average oxidation hours per 1,000
gallons were further reduced to average time per one
degree Fahrenheit rise in melting point per 1,000
gallons. is Just pointed out the times for the 145 to
155 degrees Fahrenheit and 195 to 210 degrees Fahrenheit
melting point divisions are almost identical for the
4,200 gallon charge. The time for the other two
divisions of melting points for this size charge is,
of course, higher.

The average times per one degree Fahrenheit melt-
ing point rise for the 7,600 gallon charges are quite
similar. The 145 to 165 degrees Fahrenheit division
time is lower and in a say it corresponds in Operation
to the 195 to 210 degrees Fahrenheit and 145 to 165
degrees Fahrenheit melting point divisions for the
4,200 gallon charge.

Relation Between Depths of Charges

These final figures eliminate all variables except

depth of flux oil through which the oxygen passes.

If these times are preportional to the reciprocal of

18.

the depths, this last variable can be eliminated.

The group average for the depth of 5 feet 1 inch is
.0314 hours per one degree Fahrenheit rise in melting .
point per 1,000 gallons and the group average for the .
depth of 6 feet 6 inches is .0194.

e0314 : l .:. I : 1
5708 655

6.51 _-_ .omuswe
Therefore X.‘; .0245 hours, which is much higher
than the actual figure of .0194 hours.
Study ofoir Bubbles in a.Liquid

A.study was made of air bubbles passing through
water. A six inch diameter pipe was installed
vertically with a glass bulb on the bottom. .1
one-quarter inch diameter pipe was inserted in the
six inch pipe, so that it was only one inch above the
bottom of the glass bulb. Air was introduced through
the one-quarter inch pipe under enough pressure to
barely emerge from the bottom when the six inch pipe
was filled to various depths with water. As the
bubble left the one-quarter inch pipe it was observed
by an assistant who called out. A.st0p watch was
started by the observer and then stopped as the bubble

19.

reached the surface of the water. Table #3 gives

the results of this test. The 10 inch depth was used

as a base, and the times for the other depths calculated
by direct prOportion. These figures were close enough
to the test figures to assume such a proportion holds
true.

This test indicates that another factor must enter
into the difference in oxidation time per one degree
Fahrenheit rise in melting point per 1,000 gallons for
the depths of 5 feet 1 inch and 6 feet 6 inches. It was
noted during the test that as the depth of water was
increased, the pressure on the air was also increased by
opening the valve in order to release an air bubble.
also that the initial bubble size was approximately the
same siae, but at the surface as the depth increased the
size of the emerging air bubble increased.

in. Law of Depth

In oxidising flux oil, then, increasing the depth
through which the air bubbles pass not only lengthens
the time of contact, but also increases the pressure
contact. This indicates not a direct preportion,
but a preportion by the squares of the depths.

Now compare the group averages for the depths of

20.

TABLE

3

 

Air Bubbles Rising in Water.

 

 

 

Depth Ave. Time Calculated Time
9.5" 1.20 seconds 1.48 seconds
10.0" 1.56 " Base 1.56 "
19.5” 2.92 " 3.04 "
27.0" 4.02 " 4.21 "
29.5" 4.68 " 4.60 "
48.0" 7.50 " 7.49 "
76.0" 12.50 " 11.86 "
94.0" 15.00 " 14.66 "

 

 

 

 

5 feet 1 inch and 6 feet 6 inches.

.0314:( 112; 1::(1)2
(3:08) (675’)

.osiez'i -x:‘1
2578]?" 42723

42.25): .: .0314x25.81

Therefore 41 .0192 hours which is an error of

only'1.04 per cent to the actual average of .0194 hours.
New to be sure that the above formula is not
Just for these two depths, the still charges for the
large and small stills were lowered 6 inches for a
period of three months and a record kept. The
results are tabulated in Table f2 under the 3,700
gallon and 7,000 gallon charges at depths of 4 feet
6 inches and 6 feet 0 inches respectively. The average-
time per one degree Fahrenheit rise per 1,000 gallons
was computed.
In Table #4 all the charges are compared with
the 7,600 gallon charges for oxidation time per one
degree Fahrenheit rise per 1,000 gallons, using the
above formula. While the figures based on the 7,600
gallon still charges are higher than the actual,
nevertheless they indicate closely the relation
existing due to the depth of asphalt through which

the air bubbles pass.

21.

TABLE 4

2

Formula T1 : T2 :

 

2
( 1 ) .3
( 151)

(1)
(T5)

T1.: Oxidation hours per 10 F. rise in melting
point per 1,000 gal. at D1 depth.

_ 5' l" 01' 5.08 ft. depth.

12‘:_Calculated oxidation hours per 1° F. rise in
melting point per 1,000 gal. at D3 depth

 

 

 

 

 

 

 

Dg': Selected depth; either 4' 6", 6' 0" or 6' 6".
Still I Depth Melting Oxidation Calculated*
Capacity D2 Point Hours per Oxidation o
Gallons 10F. Rise Hrs. per 1
per 1,000 g. F. Rise per
1,000 gal.
Group
Ave.
3700 4' 6" 210-220 .0321) .0407
3700 4' 6" 230-240 .0353).0365 .0415
4200 .D1 145-165 .0290) .0300
4200 D1 195-210 .0289) .0325
4200 D1 210-220 .0324) .0319
4200 D1 230-240 .0320).03l4 .0325
7000 6' 0" 195-210 .0214 .0234
7000 6' 0" 210-220 .0241 .0229
7000 6? 0" 230-240 .0212).0222 .0234
7600 6' 6” 145-165 .0183)
7600 6' 6? 195-210 .0199)
7600 6' 6! 210-220 .0195)
7600 6‘ 69 230-240 .0199).0194

 

Increase.ETficient Oxidation

To increase the efficiency of an oxidizing unit,
the above relation suggests an increase in the depth
of flux oil through which the air passes. This change
of depth to increase efficiency has physical limits.
In shallow depths the air bubble emerging at the
surface still has a large portion of oxygen which has
not combined with the lighter oils. As the depth is
increased this percentage of free oxygen is reduced,
approaching zero as a limit. Since the change in depth
also causes a change in oxidation time, by the square
of the difference in depth, then a depth which is too
great would not give the calculated results because the
free oxygen available in the emerging bubble would be
negligible.

Design

Without knowing how much free oxygen is still
left in the bubble after it has travelled through the
charge in the present stills, but believing that it
is a high percentage, an arbitrary increase in the
depth of asphalt of the proposed oxidation tank is
selected. In Table #5 the depth is set at 10 feet
0 inches. Based on the group average oxidation time

22.

2 2
Formula 11:E-%-}3T3:)+)
1 - 3

Tl‘: Group average oxidation hours per 1° F. rise in
melting point per 1,000 gal. at D1 depth, .0194

D1 :- 6' " 5" or ‘05 fQOt depth.

Calculated oxidation hours per l0 E. rise in
melting point per 1,000 gal. at D3 depth.

D3 : 10' " 0" depth.

 

lblting Melting Calculated

Point Point Rise Oxidation hrs. Oxidation
per 1° F. rise hours per
per 1,000 gal. 1,000 gal.

 

 

 

 

 

o o
145 -165 40° I\ races
195°-210° 80° ) \.ooeeo/ .664
2100-220" 100° 3// \ .332

{2300-2400 120°

 

 

per one degree Fahrenheit rise in.melting point per
1,000 gallons for the 7,600 gallon charge, the oxidation
time is calculated for all divisions of melting points.
Knoeing that this group average time is higher than
for the actual oxidation time for the 195 to 210 degrees
Fahrenheit melting point division for 5,100 gallon
charge, a condition.ehich more closely approaches the
condition of continuous oxidation, the calculations
have a margin of safety.
Vertical Unit

The above analysis or the flacts concerning
oxidation time indicates the economical advantage or‘a
vertical oxidation unit. It is also apparent that if
this unit is too large the‘heat imparted to the flux
oil by the tube heater sill be reduced through cool-
ing. The loss due to radiation is the reason for the
present still charge being heated prior to oxidation,
in order to reattain.the oxidation temperature. 0n
the other hand, if the oxidizing unit is too small,
the element or time beteecn the flux oil and the
oxygen sill be too short.

Diameter of'Unit
The smallest diameter or an oxidizing tank, with

23.

a liquid level or 10 feet 0 inches, must be large enough
to permit any particle of a constant flow to be in
contact with oxygen for at least one hour. This is the
shortest span of time in which, by laboratory methods,
flux oil is oxidized from 115 degrees Fahrenheit melting
point to 235 degrees Fahrenheit melting point. Since
the average rate of the pumps feeding the asphalt
through the tube heater to a temperature or 500 degrees
Fahrenheit is 1,500 gallons per hour, then the smallest
capacity should be 1,500 gallons at a 10 feet 0 inches
level. The diameter of such a tank would be approxi-
mately 5 feet 0 inches.

The asphalt being pumped in a tank or the above
dimensions at 1,500 gallons per hour’would.be in contact
with air for one hour. An.examination of Table #5
shows that this would be sufficient for oxidation to
195 to 210 degrees Fahrenheit melting point.

1.0 hour e 1500 gallona‘; .667 hours per 1,000
gallons compared:gggh calculated .664 hours per 1,000
gallons. The other melting point divisions sould not
be taken care of by this procedure.

Mixing Action of Air Bubbles
To suppose that the flux.oil, after passing through

24.

the oxidising unit in this manner, would be raised to
195 to 210 degrees Fahrenheit melting point would lead
to an error. the air passing through the flux oil
provides a mechanical mixing action so that the flux
oil emerging is composed of particles which have been
in contact with the air the full hour and also of
particles which have been in the tank less than one
hour. rhe melting point of the resulting mixture
would be one-halt or 155 degrees Fahrenheit, the average
between the melting point of the asphalt charged and
finished.

115° plus 195° _-; 155°

This is because the average time for the entire
tankful in contact with the air is one-half hour.

Calculated;

.5 hour e 150 . :_ .353 hours per 1,000

gallons. ‘IUUUE.

Table #5 calculated time: .332 hours per 1,000
gallons 145 to 165 degrees Fahrenheit melting point.

As this melting point division is one-third.the
maximum melting point division, and one-half of the

195 to 210 degrees Fahrenheit melting point division,

25.

it becomes necessary to use three oxidizing tanks in
series to obtain the maximum.required melting point
235 degrees Fahrenheit, and two tanks in series to
obtain the 195 degrees Fahrenheit melting point.

For every instant of Operation beyond the first
hour the flux oil emerging from the oxidation tank is
also composed of particles which have been in the tank
more than one hour. It operation of the unit continued
for a long period it is reasonable to suppose an
equilibrium.would be reached when the average time
for the entire tankful in contact with the air is a
full hour. However, in starting up the oxidation unit
and continuing for only a few hours it is safe to
design the unit with the above calculation. For long
periods of operation the speed of the pump can be
controlled to produce the required melting point.

Using tanks 5 feet 0 inches in diameter and 10 feet
0 inches in liquid level makes a total capacity oi
4,500 gallons. If this capacity could be reduced,
the heat loss due to radiation would not be so great.
However, it is essential that the diameter of these

tanks be large enough for a man to enter and clean them.

26.

.1 diameter or 4 feet 0 inches is the smallest diameter
in which a man could.work without undue obstructions.

In Table #6 a tank 4 feet 1 inch in diameter is
'used, and comparison between actual oxidation hours
per 1,000 gallons and the calculated is tabulated.
The total capacity or three tanks in series is about
3,000 gallons. This table, further, shows the
calculations for the 210 to 220 degrees Fahrenheit
melting division, using two regular tanks in series,
and the third with a liquid level at 7 feet 0 inches
to obtain the desired result.

Operation of Unit

how to obtain coating and oxidized saturants the
asphalt is pumped through the tube heater, raising the
temperature to 500 degrees Fahrenheit, then through as
many oxidising tanks as are necessary to reach the
required melting point, and from there it is pumped to
the roofing supply tanks.

The pumps will operate at a constant rate of 1,500
gallons per hour and the tube heater will be fired at
a uniform temperature to impart to the flux oil a

temperature of 500 degrees Fahrenheit. Then if shingle

27.

 

TABLE_#6

 

Pump Speed - 1500 Gallons Per Hour, Air - 600 cu.ft./min.
Capacity of Tank - 10,070 Gallons Diameter - 4' 1"
Depth of Flux 011 - 10' 0" a

Time of Contact with Air - .57 hours/1000 ga .

Effective Time Contact with Air - .333 hours 1000 gal.

 

 

,Lctual Calculated, Tanks in Melting Resulting
Oxidation Oxidation Series Point Melting
Hours per Hours per Rise Point
1000 gal. 1000 gal.
.555 .552 1 40° _ l45°-155°
.570 .554 z 803 1950-2103
1.000 .996 3 120 230°~24O

 

 

 

 

 

 

For melting point 210°~220° use two tanks in series at

flux oil depth of 10' 0" and third tank at flux depth
of 7' 0".

- 2 2

T1 : ( 1 I ‘2 T4 : ( 1 )

(171‘) (‘15:)

D11: 6' 6" or 6.5'

T4‘: Oxidation hours per 1°F. rise in melting point
per 1000 gallons at D4 depth.

54'; 7' 1" or 7.08'
.0194 : ( l ’2': T4 : 2
(3.5)

00194 3 1 :
‘12:55

.82965

( 1 )
(7703)
1

T‘:
50.15 T4

Rise in melting point‘; 20°F.
.01555 x 20.: .551 hrs./1000 gal. oxidation.

(Cont.)

TABLE je ( cont .1

Capacity at 7‘ 1" level‘: 700 gallons

700 e 1500 G.P.H.‘:' .46 hours
.46 e 2 - .23 hours effective oxidation of 700 gal.

700 : .23 - 100 : I

700X - 236
X_:,.329 hours/1000 oxidation, comparing closely

with calculated .331 hours/1000.

saturant (145 to 165 degrees Fahrenheit melting point)
is desired the asphalt will be pumped into #1 oxidizing
tank. It overflows to #2 oxidizing tank and the bottom
valve is Opened to the suction line to another pump
which in turn pumps it to the roofing saturators. When
195 to 210 degrees Fahrenheit melting point coating is
required, the asphalt will be oxidized in #1 and f2
oxidizing tanks, overflowing into #3, thence by the
second pump to the roofing supply tanks. When 210 to
220 degrees Fahrenheit.ms1ting:point coating is required,
the asphalt will be oxidized in #1, #2 and #3 oxidising
tanks using, however, the 7 foot 1 inch overflow in
#3 oxidizer. When 230 to 240 degrees Fahrenheit melting
point coating is needed the flux oil.will be oxidized
in all three tanks at the levels of 10 feet 0 inches.
Control of Oxidation.

Since 600 cubic feet of air per minute are blown
through the 4,200 gallon and 7,600 gallon charges of
the present stills, it is reasonable to presume that a
large portion emerging from the flux oil is still
free air. The total capacity of the three oxidising
tanks is 3,000 gallons which is less than the present

28.

 

 

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still charges. Six hundred cubic’feet of air per
minute should be an ample quantity of air to accomplish
the calculated results for all three tanks. By the

use of valves and pressure guages the amount of air

is regulated to provide each tank with approximately
200 cubic feet of air per minute.

The degree of heat and rate of pumping is
supervised by an operator. The fly-wheel pump is
equipped with recording 5.13.11. indicators and speed
regulators. The discharge line of the tube heater and
each oxidising tank is equipped with recording
thermometers. Each overflow on the oxidising tanks
is equipped with sample valves and samples are taken
half hourly for laboratory check on the melting point
required. If the melting point is found to be higher
than required, the Operator speeds the pumping rate.
If the melting point is found to be lower than required,
the Operator slows the pumping rate.

The pump used in discharging the completed coating
or saturant Operates at a higher rate than the pump
feeding the oxidising tanks to avoid any danger of
completely filling the tanks and putting the sides

29.

under pressure or overflowing.

The preposed method is simple in construction and
Operation, and much more efficient than the present
stills. It now takes from 12 to 24 hours to charge,
oxidize and pump a still, and the charge is only
4,200 to 7,600 gallons. This new method would produce
at the rate Of 1,300 gallons an hour.

The cost of this oxidizing equipment is about
equal to that of a 10,000 gallon still. Yet on a
twenty-four hour basis the oxidizing tanks could
produce 36,000 gallons, while one 10,000 gallon still
would produce only 7,600 gallons. The new method
produces almost five times as much.

Specification of Oxidising Tank

The tanks will be welded one-half inch boiler
plate, 4 foot 1 inch inside diameter and 13 feet
0 inches high, and welded bottom.will be bolted to
anchor bolts in a concrete fOundation which is capable
Of sustaining a total load of 13,000 pounds. The tOp
of each tank will be equipped with a welded cover in
the middle of which is a flanged Opening 24 inches in
diameter. This is the connection for the reducing

cone to the 9 inch vapor pipe. Each tank will be

30.

equipped with a 24 inch flanged man-hole the bottom
Of which will be 1 foot 0 inches above the bottom
of the tank. This is to be used to clean the tanks
of accumulated coke.

Each oxidation tank.will be covered, in the field,
with a 3 inch thickness asbestos insulation. This
will be covered with smooth surface roofing and painted
with a tar water-proof paint.

All the pipe fitting will be completed in the
field. The pipe for the asphalt will be standard
weight, outside Jacketed, steel pipe, connected by
means of flanges. The pipe for the air lines will be
standard flanged steel pipe. The vapor lines will
be of welded light steel, one-eighth inch thick,
equipped with flanges.

31.

ESTIMATED COST

Oxidising tanks 3
4'1" inside diameter x 13'0"

high welded boiler plate,

flanged Openings

Concrete foundation

Insulation, 3" thick . 3
4" outside Jacketed pipe 40 ft.
4" Jacketed cocks 6
4" steel pipe 20 ft.
6" steel pipe 40 ft.
Reducing cones, 2'0" diam. to

0'9" diam. 3
9- welded pipe 1/8" thick «0 ft.
4" rising stem valves 5
Recording thermometers 3
Speed regulator & RsP.M.

indicator
Labor & overhead

Tbtal

61,000.00

300.00
450.00
80.00
90.00
10.00
30.00

50.00
40.00
100.00
300.00

200.00

1'350200

m

The exhaust fan.now used on the stills will be

installed for use with the oxidation tanks, and the

compressed air will be furnished.by the same

compressor that now provides air for the stills.

Estimated Annual Savings

The annual saving by the use of this continuous

oxidising process is enumerated as follows:

Fuel Oil. 3y eliminating the firing of a still,

which requires an average of 4 hours x 20 gallons of

Oil for each charge. In 1934 there were over 500

charges. 4x20x500x$.03 per~gallon.: $1,200.00

32.

Electric Power. By reducing the number of hours
per 1,000 gallons necessary to oxidize asphalt, the
use of the air compressor and exhaust fan would be
reduced saving electric power. Total annual power
consumed with present stills, 5880 oxidation hours x
22.5 K.W. per hour is 132,300 K.W. To produce the
same amount of coating and oxidized saturant with the
continuous process would require 2,000 hours. 2,000 x
22.5 K.W.‘:.45,000 K.W. Annual saving in power,
87,300 K.v. 0 $015 is approximately $1,300.00.

‘§§ggm. 'Steam is used to atomize the fuel oil in
the burner, the cost averaging $1.00 per still charge.
Annual saving, 500 still charges x $1.00‘; $500.00

‘Egbgg. By being able to oxidize the flux oil
into coating '. few hours before it is to be used on
the roofing machine, a labor saving will be realised.
At present the stills are charged 24 hours in advance
of their use. At the beginning of the week, Saturday
night, the stills are charged fer MOnday's machine
run. If the coating is prepared in the continuous
oxidizing tank Sunday night for Monday's run, then
there is a saving in being able to start the tube

heater 16 hours later. Since there are 3 men on each

33.

‘7

3')
b

A.

..f '7‘

K§l

s n
-a
1' l
I
s
. .
e

8 hour shift, this would.mean a saving of 6 men per
week. 6 x.$5.00 x 50 weeks ;_$l,500.00

The annual cost for cleaning still bottoms is
$600.00. This cost is largely due to the accumulation
of coke on the bottom of the still while firing
the still charge. The use Of the oxidation tanks
reduces this localized heating to a minimum, reducing
thereby the necessity for cleaning. Experience alone
could determine the amount of cleaning required, how-
ever, it is estimated at $200.00 annually. The labor
saving would be $400.00.

There are other possible labor savings. The
stillman at present looks after as many as six stills.
With only one unit requiring his attention, and
continuous pumping with one set-up he might be able to
perform other functions now requiring other men. The
present layout with.multiple stills and intermittent
pumping in or out of these stills requires the work
of’a pumpman in addition to the still Operator. With
the installation of the continuous oxidation unit the
work of the pumpman could be taken over by the still-
man, without any loss in efficient discharge of the
stillman's usual duties of supervising the oxidation

34.

of asphalt. It is reasonable to suppose that two Of
the three pumpmen per 24 hour period could be eliminated.
This saving in annual cost would amount to roughly
$1,500.00, not overlooking a substantial raise in
salary for each stillman.

TOTAL ANNUAL SAVING

Fuel Oil pl,200.00
Electric power 1,300.00
Steam 500.00
Labor 3 400.00

Total W

Thus it is quite evident that the continuous
oxidising process is economically sound, saving
$6,400.00 annually, against the initial installation
cost Of $4,000.00.

It is beneficial in other ways. Because the time
of oxidizing a given amount Of flux oil is so much
more rapid than in the present stills the planning
department is enabled to change machine schedules
to meet actual orders, instead of anticipating
demand, as at present. This would allow building up
the stock of standard products, and, also, being able
to produce within 24 hours the special orders that
the customers demand in style of roofing and colors

of slate. Being able to serve each customer's espe-

35.

cial demands promptly is sound.business. Quality
plus service is invaluable to good.will and repeat
orders.

Therefore, besides its measurable economy,
this continuous oxidizing unit would assist in.meet-
ing the policy of service by making the roofing machine
schedules more flexible.

36.

 

 

MICHIGAN STATE UNIVERSITY LIBRARIES

II III ILII lllllllll

3 1293 3 46 0722

In