Asphalt oxidation technique

Abstract

The present invention relates to a method for oxidizing asphalt which comprises dispersing an oxygen containing gas throughout an asphalt flux in an oxidation zone while the asphalt flux is maintained at a temperature which is within the range of about 400 F. to 550 F., wherein the oxygen containing gas is introduced into the oxidation zone through a recycle loop. The recycle loop pumps asphalt flux from the oxidation zone and reintroduces the asphalt flux into the oxidation zone as oxygen enhanced asphalt flux. The recycle loop will typically include a pump which pulls the asphalt flux from the oxidation zone and which pumps the oxygen enhanced asphalt flux into the oxidation zone, and wherein the oxygen containing gas is injected into the recycle loop at a point before the asphalt flux enters into the pump.

Claims

1. A method for oxidizing asphalt which comprises dispersing an oxygen containing gas throughout an asphalt flux in an oxidation zone while the asphalt flux is maintained at a temperature which is within the range of about 400 F. to 550 F., wherein the oxygen containing gas is introduced into the oxidation zone through a recycle loop, wherein the recycle loop pumps asphalt flux from the oxidation zone and reintroduces the asphalt flux into the oxidation zone as an oxygen enhanced asphalt flux, wherein the recycle loop further includes a pump which pulls the asphalt flux from the oxidation zone and which pumps the oxygen enhanced asphalt flux into the oxidation zone, and wherein the oxygen containing gas is injected into the recycle loop at a point before the asphalt flux enters into the pump.

2. The method of claim 1 wherein an oxygen containing gas is injected into the recycle loop to produce the oxygen enhanced asphalt flux.

3. The method of claim 1 wherein the recycle loop pumps the asphalt flux from the oxidation zone and pumps the oxygen enhanced asphalt flux into the oxidation zone, and wherein the oxygen enhanced asphalt flux is pumped into the oxidation zone at a lower point in the oxidation zone than the point at which the asphalt flux is pumped from the oxidation zone.

4. The method of claim 3 wherein the oxygen containing gas is air.

5. The method of claim 4 wherein the air is enriched with oxygen.

6. The method of claim 1 wherein said method results in the production of industrial asphalt, wherein the industrial asphalt has a softening point which is within the range of 185 F. to 235 F., and wherein the industrial asphalt has a penetration value which is within the range of 15 dmm to 35 dmm.

7. The method of claim 1 wherein said method results in the production of industrial asphalt, wherein the industrial asphalt has a softening point which is within the range of 190 F. to 220 F., and wherein the industrial asphalt has a penetration value which is within the range of 15 dmm to 25 dmm.

8. The method of claim 1 wherein the asphalt flux is maintained at a temperature which is within the range of about 425 F. to about 525 F., and wherein the asphalt flux is maintained in the oxidation zone for a period of about 2 hours to about 8 hours.

9. The method of claim 8 wherein the asphalt flux is maintained in the oxidation zone for a period of about 3 hours to about 6 hours.

10. The method of claim 1 wherein the asphalt flux is maintained at a temperature which is within the range of about 450 F. to about 500 F., and wherein the asphalt flux is maintained in the oxidation zone for a period of about 3 hours to about 6 hours.

11. The method of claim 1 wherein the oxidation zone is a blow still.

12. The method of claim 1 wherein the oxidation is conducted in the presence of an air blowing catalyst.

13. The method of claim 1 wherein the oxygen enhanced asphalt flux is pumped into the oxidation zone at a higher point in the oxidation zone than the point at which the asphalt flux is pumped from the oxidation zone.

14. The method of claim 1 wherein said method is carried out as a batch process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic drawing which depicts a conventional technique for introducing air into a blow still for oxidizing asphalt flux via a sparger located near the bottom of the blow still.

(2) FIG. 2 is a schematic drawing which depicts one embodiment of this invention where a recycle loop introduces asphalt flux having an enhance oxygen level into the oxidation zone at the bottom the oxidization zone (blow still).

(3) FIG. 3 is a schematic drawing which depicts another embodiment of this invention where a recycle loop introduces asphalt flux having an enhance oxygen level into a point near the top of the oxidization zone (blow still).

DETAILED DESCRIPTION OF THE INVENTION

(4) The process of this invention is particularly useful in treating hard asphalt flux to produce industrial asphalt that is useful in roofing applications. More specifically, hard asphalt flux can be treated by the process of this invention to produce industrial asphalt that has a softening point which is within the range of 185 F. (85 C.) to 250 F. (121 C.) and a penetration value of at least 15 dmm. In most cases, the industrial asphalt will have a penetration value which is within the range of 15 dmm to 35 dmm. Industrial asphalt that is made by the process of this invention for utilization in roofing applications will typically have a softening point which is within the range of 185 F. (85 C.) to 250 F. (121 C.) and a penetration value which is within the range of 15 dmm to 35 dmm. Industrial asphalt made by the process of this invention for roofing applications will preferably have a softening point which is within the range of 190 F. (88 C.) to 210 F. (99 C.) and a penetration value which is within the range of 15 dmm to 25 dmm.

(5) The asphalt flux is normally the petroleum residue from a vacuum distillation column used in refining crude oil. The asphaltic material used as the starting material can also be solvent extracted asphalt, naturally occurring asphalt, or synthetic asphalt. Blends of such asphaltic materials can also be treated by the process of this invention. The asphalt flux can also include polymers, recycled tire rubber, recycled engine oil residue, recycled plastics, softeners, antifungal agents, biocides (algae inhibiting agents), and other additives. Tar and pitch can also be used as the starting material for treatment by the technique of this invention. The hard asphalt flux is characterized in that it cannot be air blown to attain both a softening point which is within the range of 185 F. (85 C.) to 250 F. (121 C.) and a penetration value of at least 15 dmm. However, it should be understood that the process of this invention is also applicable to the treatment of virtually any asphaltic materials in addition to hard asphalt flux. The technique of this invention is of particular value in the treatment of hard asphalt flux that is difficult or impossible to air blow utilizing standard air blowing methods into industrial asphalt having properties suitable for use in roofing applications.

(6) In practicing the method of this invention, conventional asphalt oxidation techniques are employed with the exception of the oxygen containing gas is introduced into the oxidization zone (blow still) via a recycle loop. Two embodiments of this invention are depicted in FIG. 2 and FIG. 3. In the embodiment of the invention depicted in FIG. 2 a recycle loop 2 introduces asphalt flux having an enhanced oxygen level 3 into the oxidation zone 4 at the bottom the oxidization zone (blow still) 5. The oxygen containing gas is pumped into the recycle loop at an injection point 6 which is situated in the recycle loop 3 at a point before the asphalt flux flows through a pump 7 which circulates the asphalt flux through the recycle loop 3 from a point located near the top of the asphalt level 8 but which is below the dead space 9 above the top of the oxidization zone 5. In this embodiment of the invention the asphalt flux having an enhanced oxygen level is reintroduced into the bottom of the oxidization zone at an injection point 10. In the configuration illustrated in FIG. 2 the recycle loop pumps the asphalt flux from an area near the top the oxidation zone and pumps the oxygen enhanced asphalt flux into the oxidation zone at a point near the bottom of the oxidation zone. The area near the top of the oxidization zone is typically in the top 50% of the oxidation zone, is more typically in the top 30% of the oxidation zone, and is preferably in the top 10% of the oxidation. The area near the bottom of the oxidization zone is typically in the lower 50% of the oxidation zone, is more typically in the lower 20% of the oxidation zone, and is preferably in the lower 10% of the oxidation zone.

(7) In the embodiment of the invention depicted in FIG. 3 a recycle loop 2 introduces asphalt flux having an enhanced oxygen level 3 into the oxidation zone 4 at a point which is near the top the asphalt level 8 in the oxidaization zone 4. The oxygen containing gas is pumped into the recycle loop at an injection point 6 which is situated in the recycle loop 3 at a point before the asphalt flux flows through a pump 7 which circulates the asphalt flux through the recycle loop 3 from a point located near the bottom of the oxidization zone 11 in this embodiment of the invention the asphalt flux having an enhanced oxygen level is reintroduced into the top of the oxidization zone 4 at an injection point 12 which is located near the top of the asphalt level 8 but below the dead space 9 above the top of the oxidization. In a further embodiment of this invention the asphalt flux having an enhanced oxygen content is reintroduced into the dead space 9 above the oxidization zone 4. This configuration is advantageous in that it minimizes the amount of blow loss experienced in oxidizing an asphalt flux to a desired level while maintaining acceptable rates of oxidization. This is highly desirable since it is more environmentally friendly then conventional air blowing techniques and in that it increases the amount of oxidized product which is attained from a given amount of starting material.

(8) In the configuration illustrated in FIG. 3 the recycle loop pumps the asphalt flux from an area near the bottom the oxidation zone and pumps the oxygen enhanced asphalt flux into the oxidation zone at a point near the top of the oxidation zone. The area near the bottom of the oxidization zone is typically in the lower 50% of the oxidation zone, is more typically in the lower 30% of the oxidation zone, and is preferably in the lower 10% of the oxidation. The area near the top of the oxidization zone is typically in the upper 50% of the oxidation zone, is more typically in the upper 20% of the oxidation zone, and is preferably in the upper 10% of the oxidation zone.

(9) In the technique of this invention, the asphalt flux is air blown by heating it to a temperature which is within the range of 400 F. (204 C.) to 550 F. (288 C.) and blowing an oxygen containing gas through it. This air blowing step will preferably be conducted at a temperature which is within the range of 425 F. (218 C.) to 525 F. (274 C.) and will most preferably be conducted at a temperature which is within the range of 450 F. (232 C.) to 500 F. (260 C.). This air blowing step will typically take about 2 hours to about 8 hours and will more typically take about 3 hours to about 6 hours. However, the air blowing step will be conducted for a period of time that is sufficient to attain the ultimate desired softening point. In other words, the asphalt flux will be air blown until a softening point of at least 100 F. (38 C.) is attained.

(10) The oxygen containing gas (oxidizing gas) is typically air. The air can contain moisture and can optionally be enriched to contain a higher level of oxygen. Chlorine enriched air or pure oxygen can also be utilized in the air blowing step. Air blow can be performed either with or without a conventional air blowing catalyst. Some representative examples of air blowing catalysts include ferric chloride (FeCl.sub.3), phosphorous pentoxide (P.sub.2O.sub.5), aluminum chloride (AlCl.sub.3), boric acid (H.sub.3BO.sub.3), copper sulfate (CuSO.sub.4), zinc chloride (ZnCl.sub.2), phosphorous sesquesulfide (P.sub.45.sub.3), phosphorous pentasulfide (P.sub.25.sub.5), phytic acid (C.sub.6H.sub.6[OPO-(OH).sub.2].sub.6), and organic sulfonic acids. The asphalt oxidation of this invention can also be conducted in the presence of a polyphosphoric acid as described in U.S. Pat. No. 7,901,563. The teachings of U.S. Pat. No. 7,901,563 are incorporated by reference herein for the purpose of describing air blowing procedures which are conducted in the presence of a polyphosphoric acid.

(11) The industrial asphalt made can be used in making roofing products and other industrial products using standard procedures. For instance, the industrial asphalt can be blended with fillers, stabilizers (like limestone, stonedust, sand, granule, etc.), polymers, recycled tire rubber, recycled engine oil residue, recycled plastics, softeners, antifungal agents, biocides (algae inhibiting agents), and other additives.

(12) This invention is illustrated by the following examples that are merely for the purpose of illustration and are not to be regarded as limiting the scope of the invention or the manner in which it can be practiced. Unless specifically indicated otherwise, parts and percentages are given by weight.

EXAMPLE 1

(13) The method of this invention can be conducted as depicted in FIG. 2 wherein hot asphalt flux is maintained in a blow still at a temperature which is within the range of about 400 F. to 550 F. In this method air is injected into a recycle loop which recycles asphalt flux which is being drawn from the blow still at a point near the top of the blow still and reintroduces it as oxygen enhanced asphalt flux at a point located at the bottom of the blow still. In this method, the asphalt flux is maintained in the blow still until it is oxidized to a level which is sufficient to attain desired physical characteristics, such as the desired softening point and penetration value.

EXAMPLE 2

(14) In this experiment an asphalt flux was oxidized utilizing the method of this invention in a system of the type depicted in FIG. 2. The system was filled with approximately 6 gallons (about 20,000 grams) of asphalt flux having an initial softening point of about 92 F. Softening points were measured by the Mettler cup and ball method according to ASTM D3461 using a Mettler DP-70 tester. In this experiment oxygen was injected into the recycle loop at a rate of 3 standard cubic feet per minute (136 standard cubic feet per minute per ton of asphalt). This system consisted of a heated steel vessel having a diameter of 10.5 inches which was 25 inches tall. It had a band heater which was located at the bottom of the vessel to maintain a temperature within the range of 400 F. to 500 F. The heater was regulated by an external Watlow controller. The asphalt was pumped through the recycle loop with a Viking positive displacement pump which was operated at 431 rpm to attain a pumping rate of 6 gallons per minute.

(15) During the oxidization process the softening point of the oxidized asphalt was monitored. The increase in softening point as a function of oxidization time is reported in Table 1.

(16) TABLE-US-00001 TABLE 1 Time Softening Point 0 minutes (initial) 92 F. 48 minutes 105 F. 60 minutes 115 F. 80 minutes 125 F. 95 minutes 138 F. 110 minutes 155 F.

(17) As can be seen from Table 1, the technique of this invention proved to be successful in oxidizing the asphalt flux as exhibited by the increasing softening point of the asphalt over time. Accordingly, the technique of this invention can be used to replace conventional blow stills in air blowing asphalt flux to make industrial asphalt.

(18) While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention.