Process for the manufacture of Trinidad Lake Asphalt cold milled

Abstract

A method for producing a non-coalescing asphalt from raw natural asphalt herein referred to as TLA Cold Milled. Raw TLA is crushed into smaller particles and milled at ambient temperature. The milled TLA is passed through a first sieve to maintain the separation of the particles and to produce a damp milled TLA in a powdered state. The damp milled powdered TLA is dried by exposing it to heat and is thereafter cooled to ambient temperature. The dried and cooled powdered TLA is passed through the first sieve or another sieve to produce the TLA Cold Milled which may be packaged at ambient temperature in conventional bags. The milling of the asphalt results in each particle of inorganic matter within the asphalt being surrounded by bitumen and a thin film of inorganic material, producing asphalt in a non-coalescing form, i.e., the TLA Cold Milled.

Claims

1. A method for the manufacture of Trinidad Lake Asphalt (TLA) Cold Milled, comprising: obtaining raw TLA from the earth; crushing the raw TLA into smaller particles; milling the crushed raw TLA at ambient temperatures; passing the milled TLA through a first sieve to produce a damp milled TLA in a powdered state; drying the damp milled powdered TLA by exposing it to heat; cooling the dried powdered TLA to ambient temperature; passing the dried and cooled powdered TLA through the first sieve again or a second sieve to produce the TLA Cold Milled.

2. The method of claim 1 wherein the crushed and milled raw TLA particles are an average size of 841 m to 297 m.

3. The method of claim 1 wherein the crushed raw TLA is milled for 1-10 minutes at ambient temperature.

4. The method of claim 1 wherein the milled TLA is passed through a 20-50 mesh sieve.

5. The method of claim 4 wherein the sieve is 20 mesh.

6. The method of claim 1 wherein the damp milled powdered TLA is dried in an oven at 105 C. to 120 C. for 1-1.5 hours.

7. The method of claim 6 wherein the temperature is 110 C. and the time is 1.5 hours.

8. The method of claim 1 wherein the dried powdered TLA is passed through a 20-50 mesh sieve.

9. The method of claim 8 wherein the sieve is 20 mesh.

10. The method of claim 1 wherein the TLA Cold Milled is packaged at ambient temperature.

11. The method of claim 10 wherein the TLA Cold Milled is packaged in conventional bags.

12. The method of claim 1 wherein the TLA Cold Milled is used as a hot mix asphalt modifier and is mixed with hot mix Asphalt at a temperature of 88 C.-92 C.

13. The method of claim 12 wherein the percentage by weight of TLA Cold Milled is in accordance with ASTMD 6626.

14. The method of claim 12 wherein naturally occurring bitumen which surrounds inorganic matter of the TLA Cold Milled is solubilised by refinery bitumen in the hot mix.

15. The method of claim 1 wherein the milling produces a powdered product in which particles of a naturally occurring inorganic matter are coated with naturally occurring bitumen and a naturally occurring inorganic material present in raw asphalt is released which coats the outside of the bitumen-coated inorganic matter to render it non-coalescing.

16. The method of claim 1 wherein the milling of the crushed raw TLA serves to keep the meshed particles separate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block diagram of the process of the present invention for the manufacture of refined TLA Cold Milled;

(2) FIG. 2 is a diagrammatic illustration showing the inorganic matter of the TLA Cold Milled surrounded by bitumen and a thin film of inorganic material;

(3) FIG. 3 is a photograph of TLA as dug from the earth;

(4) FIG. 4 is a photograph of crushed or pre-milled raw TLA;

(5) FIG. 5 is a photograph of damp TLA powder after milling and sieving; and

(6) FIG. 6 is a photograph of the TLA Cold-Milled produced in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) As shown in the flow diagram of FIG. 1, into a mill is placed raw asphalt dug from the earth which has been crushed (pre-milled) to break up the chunks of raw asphalt into smaller pieces. The crushed sample is milled and passed through a 20-50 mesh sieve (e.g., 20 mesh). The sieved material is then placed in an oven at a temperature much less than 163 C. (105 C.-120 C. for 1.0-1.5 hours) to remove moisture, thus producing refined dry TLA Cold Milled.

(8) The % of unrefined asphalt material retained on the 20-50 mesh screen is <2% (1.22%-1.78%). The process produces little to no waste.

(9) The sample must be milled to a fine particle size to allow for: i) Maximum surface area of the bitumen surrounding the inorganic material. ii) Ease of release of moisture during the drying process. iii) Maximum surface area to allow for the inorganic released agent to coat the bitumen, so as to prevent coalescing, thus enabling the deposited film to be as thin as possible.

(10) The weight used in the mill depends on the capacity of the millweights can vary from 227 g ( lb) to 454 g (1 lb). The final milling time depends on the sizes of the pre-milled raw asphaltthe smaller the asphalt pieces, the less time required to produce the final product. The pre-milled material has different shapes e.g. rectangular, triangular etc. and is <0.5 in.sup.2 in particle size. After crushing (pre-milling), the asphalt is milled for 1-10 mins (depending on the weight and particle sizes of the raw asphalt used) to a particle size of 841 m-297 m before drying and sieving. The drying process takes a further 1.0-1.5 hours.

(11) The process can be batch or continuous.

(12) Results

(13) Physical Test Results:

(14) The refined TLA Cold Milled was independently tested and the results are as stated below:

(15) TABLE-US-00001 Refined TLA Cold Test Milled Refined Drummed TLA Softening Point, D 36 151.5 C. 89-99 C. Ash, ASTM D2415 36.79% 35-37.5%.sup. Solubility in TCE, 52.56% 53-55%.sup. ASTM D2172 Loss on Heating, 0.057% 1.58%.sup. ASTM D6 Water Content, ASTM 0.5% 0.3% D95 Asphaltenes, ASTM 31% 33% D4424 Maltenes 69% 67% Flash & Fire Point, 287 C. 255-260 C. ASTM D92 Penetration (100 g, 5 1 0-5 sec) Bulk Loose Density 0.64 Not applicable g/cc
Performance Grade Results:

(16) A comparison of the Performance Grade of the refined TLA Cold Milled and drummed TLA was independently tested and the results are as stated below:

(17) 25% by weight each of drummed TLA and TLA Cold Milled was added to refinery bitumen with a PG rating of 52-22.

(18) PG 52-22+25% TLA (drummed), produced a modified bitumen with PG 58-10.

(19) PG 52-22+25% TLA (Cold Milled), produced a modified bitumen with PG 64-16.

(20) PAH Tests:

(21) A comparison of the Poly-Aromatic Hydrocarbon (PAH) content of a modified refinery bitumen using TLA Cold Milled and Drummed TLA, was independently tested and the results are as stated below:

(22) TABLE-US-00002 RESULTS-PQL* is 17.8 for NFT, 20.2 for Ref Bit and 21.5 for DT TEST TLA Cold Milled Refinery Bitumen TLA Refined (Drummed) PROPERTY METHOD Results MDL Results MDL Results MDL PAH, ppm 1-Methylnaphthalene EPA 8270 BDL*** 6.3 BDL 7.2 BDL 7.6 2-Methylnaphthalene BDL 7.2 BDL 8.2 BDL 8.7 Acenaphthene BDL 6.5 BDL 7.4 BDL 7.9 Acenaphthylene BDL 5.6 BDL 6.3 BDL 6.7 Anthracene BDL 5.5 BDL 6.2 BDL 6.6 Benzo(a)anthracene BDL 5.2 BDL 5.9 BDL 6.2 Benzo(a)pyrene BDL 2.1 BDL 2.4 BDL 2.5 Benzo(b)fluoranthene BDL 13.5 BDL 15.2 BDL 16.2 Benzo(g,h,i)perylene BDL 6.4 BDL 7.3 BDL 7.8 Benzo(k)fluoranthene BDL 3.9 BDL 4.4 BDL 4.7 Chrysene BDL 6.4 BDL 7.2 BDL 7.7 Dibenz(a,h)anthracen BDL 9.0 BDL 10.2 BDL 10.9 Fluoranthene BDL 5.8 BDL 6.6 BDL 7.0 Fluorene BDL 8.1 BDL 9.1 BDL 9.7 Indeno(1,2,3- BDL 9.0 BDL 10.2 BDL 10.9 Naphthalene BDL 5.8 BDL 6.6 BDL 7.0 Phenanthrene 7.8 6.8 9.6 7.7 BDL 8.2 Pyrene BDL 9.0 BDL 10.2 BDL 10.9 PQLpractical quantitation limit; MDLminimum detection limit; BDLBelow minimum detection limit; NFTTLA Cold Milled; Ref BitRefinery Bitumen; DTTLA Refined (Drummed); TLA Cold MilledPG 52-22 + 25% TLA (Cold Milled); Refinery Bitumenrefinery bitumen PG 52-22; TLA Refined (Drummed)PG 52-22 + 25% TLA (drummed)

(23) In every instance, the polyaromatic hydrocarbon in question was lower with the TLA Cold Milled compared to TLA (drummed).

(24) Coalescing Results:

(25) It is imperative that the TLA Cold Milled does not coalesce during transportation to avoid the need for the complicated handling procedures (such as double handling) that are presently required for drummed TLA.

(26) To this end coalescing tests were conducted under worst case conditions. Taking into consideration the size of the bags to be used for transportation, the bulk density of the material, the number of bags which would fill a container, the temperature in a container, etc., stacking tests were conducted using a minimum of 837.67 kg/m.sup.2, a temperature of 60-70 C. and a time frame of at least 35 days.

(27) No coalescing of the TLA Cold Milled was observed after repeated stacking tests were conducted.

(28) Characteristics and Advantages of Present Invention:

(29) 1) A process for producing TLA which is milled at ambient temperature. 2) TLA Cold Milled is a hot mix asphalt modifier 3) TLA Cold Milled is 100% TLA. 4) TLA Cold Milled is manufactured with no external additive(s). 5) TLA Cold Milled is packaged in bags at ambient temperatureno silicone coated drums are needed. 6) TLA Cold Milled requires a manufacturing temperature of much less than 163 C. for production. 7) The process is simpler and safer than the manufacture of drummed TLAno saturated steam is needed. 8) The process requires less energy than the manufacture of drummed TLA. 9) A process which requires less manufacturing time <18 hours, than drummed TLA. 10) After the removal of moisture, the process is 98% efficient. 11) TLA Cold Milled is easier to mix with hot bitumen than drummed TLAmixing temperatures of 88-92 C. can be used. 12) A milling process which allows for the release of an inorganic material present in the natural asphalt. 13) The inorganic material on milling, sieving and drying in an oven at a temperature much less than 163 C., coats each powder grain. 14) The inorganic material prevents coalescing of the TLA Cold Milled. 15) The inorganic material does not prevent the TLA Cold Milled from being easily solubilised by the refinery bitumen. 16) The Cold Milled TLA mixes with the hot refinery bitumen at a much lower temperature 88-92 C. than drummed TLA which requires a temperature of 163 C. 17) Higher PG modified hot mix asphalts are possible with TLA Cold Milled for the same concentration levels versus traditional drummed TLA. 18) Lower PAH levels result when TLA Cold Milled is used as the modifier for the same bitumen at the same concentration levels in a hot mix when compared to traditional drummed TLA. 19) The manufacturing process can be used with other naturally occurring asphalts/bitumens.