H. M. CHELTON, R. N. TRAXLER,'
and J. W. ROMBERG
Research and Technical Department, Texaco, Inc., Port Neches, Tex.
Oxidized Asphalts In a Vertical Pilot Plant Controlled oxidation rate resulting from more even and intimate contact of air with asphalt base in vertical plants may yield products that are better and more uniform from batch to batch
4 Pilot converter for air-blowing asphalt
THE
air-blowing process has been used mainly to prepare asphalts having properties not obtainable by vacuum distillation. I n the work described here, several variables-i.e., temperature. air rate, pressure, and liquid level-kvere studied to determine their effect on reaction rate and properties of the resulting asphalts. I t was possible to produce oxidized asphalm having different properties from the same residuum by variation of oxidation temperature. pressure, and air rate.
a t the bottom, heating to the desired temperature, setting the control instruments to the run temperature, pressure, and air rate. and then admitting air to the vessel. Samples were removed periodically for testing. Unless otherwise stated. 10 gallons of residuum were used for each run. Results of the experiments were expressed by plots of the increase in softening point with time (oxidation rate) and the relationship of softening point to the penetration a t 77' F. (properties).
Experimental
Results
Experiments were conducted in a pilot converter in which 30 gallons of residuum could be processed. The vessel was constructed from a 12-foot section of 10inch, Type 304 stainless steel pipe, topped by a 2.5-foot length of 18-inch pipe of the same material, which acted as a knockout drum. A vapor treating section was provided to cool the off-gas to approximately 110' F. a n d to collect the liquids condensed a t this temperature. The vessel was heated electrically and contained a stainless steel coil fitted for thr use of steam or cooling water. Temperature, pressure, and air rate were controlled by instruments. A typical run consisted of pumping a weighed charge of residuum (Table I) into the converter through the opening
Temperature. Increasing the temperature increased the oxidation rate (Figure 1). T h e process temperature also affected the properties of the product
LL'
250
0 PS.1.G.
0
0
2
4
6
100
150 200 S O F T E N I N G P O I N T , RBB,OF.
Figure 2. Oxidation temperature affected properties of air-blown Residuum A
U' 0
8 1 0 1 2 1 4
HOURS ON A I R
Present address, Texas Transportation Institute, College Station, Tex.
0'
Figure 1 . Increasing the temperature increased the hardening rate
HOURS ON A I R
Figure 3. Rate of hardening was higher at higher air rates for Residuum A VOL. 51, NO. 1 1
NOVEMBER 1959
1353
0
450
(c (c
OF.
300
b
t K
50
z
I 4 5 0 OF. 100 S C F / M - T
Figure 6. Pressure affected the properties of air-blown Residuum A
100
w
a
250
0 100
1
1
150 200 S O F T E N I N G POINT, RBB,
OF.
loo 70 PS.lG.
Figure 4. Air rate affected the properties of air-blown Residuum A
150
300 0
a
the oxidation liquid level rate in and the converter properties had of airon blown Residuum A . Charges of 10, 20, and 30 gallons (2.5, 5 , and 7.5 feet) were used. T h e results (Figure 7) show the oxidation rate was increased with increasing liquid level, but the softening point-penetration relationship was unaffected. The increase in oxidation rate with increased liquid level is probably the reason for the predominant use of vertical vessels in new asphalt
Table
*
Residuum A (Louisiana) B (Texas)
,// 150
-
0 ?S.IP,
lJl
1 354
1
I
I
250 I
450
Li
OF.
0 FIS.1.G.
8i200 0 -
5
2 ~
f
E
'
150
100
I
I
I
' F.
16.4 10.4
540 530
4
Viscosity, Saybolt Fur01 at Component dnalysis ( 2 ) , 210' F. Asphaltics Paraffinics Cyclics 45
5
68
90
2
51
27 47
results in less susceptible products. The effects of all these variables in the air-blowing of Residuum A were accentuated because of its low viscosity and chemical composition. Thus, the degree to which temperature, air rate, and pressure, affect the reaction rate and properties of a particular residuum will have to be determined experimentally. Goppel and Knotnerus ( 7 ) found that the temperature of oxidation affects the tvpe of oxygen-containing compounds formed during the air-blowing of asphalt. Possibly the difference in such chemical reactions accounts for the variation in properties of asphalts. literature Cited
0
IO 0
Open Cup),
4PI
Figure 5. Oxidation rate of Residuum B increased with increasing pressure
(3
U
Gravity,
An increase in temperature results in a product more susceptible to temperature change (lower penetration at 77' F. for a particular Ring and Ball softening point). Incteasing air rate or pressure
2 I O I?S.l,G, (200 SCFN-T)
31 5
Properties of Asphaltic Residua
Discussion
g*oo i z 5
2
I.
Flash Point (Cleveland
450 O F . 100 S C F I W T
L'
250
Liquid Level. Experimental runs were-made to determine what effect
250 POINT, R@B,"F,
200
SOFTENING
obtained (Figure 2 ) . It was found that Residuum A oxidized to 100 penetration a t 77 F. might have any sofcening point between 130" and 180' F. depending upon the process temperature. The softening point of Residuum B could not be altered to the same degree, but the trend was the same. Air Rate. Increasing the air rate increased the oxidation rate (Figure 3). As with temperature, an upper limit was approached beyond which an increase in air rate did not effect a proportional increase in oxidation rate. Air rate had much the same effect on the rate of hardening of Residuum B as it did on Residuum A. By varying the air rate, a 100 penetration asphalt could be prepared from Residuum A (Figure 4) having any softening point between 130' and 150' F. Air rate had the same effect on the properties of air-blown Residuum B but to a smaller extent. Pressure. As pressure was increased the oxidation rate increased (Figure 5 ) . The property curves for oxidized Residuum A (Figure 6) show that by varying the pressure between atmospheric and 70 p.s.i.g., a 100 penetration oxidized asphalt can be prepared to any softening point between 140' and 180' F. Pressure affected the properties of air-blown Residuum B in the same direction as Residuum A but to a lesser extent.
1
I
1
oleo
I
I
(1) Goppel, J. M., Knotnerus, J., 4th World Petrol. Congr., Sect. I11 g, p. 399, Milan, Italy, 1954. (2) Traxler, R. N., Schweyer, H. E., Oil Gas J . 52, 158 (1953).
I
INDUSTRIAL AND ENGINEERING CHEMISTRY
RECEIVED for review January 2, 1959 ACCEPTED June 25, 1959
