METHOD FOR PREPARING BITUMEN SOLID AT AMBIENT TEMPERATURE, IN A FLUIDISED AIR BED

Abstract

A method for manufacturing granules of material usable as a road binder or as a sealing binder, including a core and a coating layer in a fluidized air bed facility, the core consisting of a first composition including at least one material selected from: a bitumen base, a pitch, a clear binder, and the coating layer consisting of a second composition including at least one viscosifying compound and at least one anticaking agent.

Claims

1-11. (canceled)

12. A process for manufacturing pellets of material that can be used as a road binder or as a sealing binder, comprising a core and a coating layer, in a fluidized air bed facility, said process comprising the following steps: (i) feeding the cores into the process chamber, (ii) fluidizing the cores present in the process chamber, by injecting an air stream, and (iii) feeding the coating layer precursor composition to the fluidized bed by means of at least one spray nozzle emerging from below into the fluidized bed, said facility comprising, in the process chamber, at least one insert delimiting a fluidized bed zone in which the air flow rate is higher relative to the rest of the process chamber, said core consisting of a first composition comprising at least one material selected from the group consisting of: a bitumen base, a pitch and a clear binder, and said coating layer consisting of a second composition comprising at least one viscosifying compound and at least one anticaking agent.

13. The process for manufacturing pellets of material as claimed in claim 12, in a fluidized air bed facility, the cores being placed in a process chamber of the fluidized air bed facility, wherein a coating layer precursor composition is fed to the fluidized bed by means of at least one spray nozzle emerging from below into the fluidized bed, and wherein an air stream is fed from below to the fluidized bed in order to maintain the fluidized bed and to dry and/or cool the cores placed in the fluidized bed, said process chamber of the fluidized air bed facility comprising at least one insert above each spray nozzle, wherein: a) the air stream is guided by an incoming air housing comprising at least one incoming air chamber, b) the zone of the fluidized bed formed by the incoming air chamber has a zone with a higher flow rate of the air stream applied to the cores, c) the coating layer precursor composition is sprayed into the zone operating at a higher flow rate, d) the cores originating from the zone at a higher flow rate are returned to the fluidized bed, e) a portion of the cores present in the fluidized bed is returned to the zone at a higher flow rate, so that a circulation of cores appears between the fluidized bed and the zone at a higher flow rate, and f) the insert(s) provided for in the process chamber of the fluidized bed facility above each spray nozzle are arranged in the form of facility pieces that can be adjusted in height and in width or diameter, the respective lower edges of which are adjustably spaced from the surface of the bottom of the fluidized bed, said cores consisting of a first composition comprising at least one material selected from the group consisting of: a bitumen base, a pitch and a clear binder, and said coating layer consisting of a second composition comprising at least one viscosifying compound and at least one anticaking agent.

14. The process as claimed in claim 12, wherein the insert is cylindrical in shape.

15. The process as claimed in claim 12, which is carried out at a temperature of less than or equal to 30 C.

16. The process as claimed in claim 15, which is carried out at a temperature of less than or equal to 25 C.

17. The process according to claim 12 which is carried out at a temperature greater than or equal to 0 C.

18. The process according to claim 17 which is carried out at a temperature greater than or equal to 10 C.

19. The process as claimed in claim 12, wherein the viscosifying agent is selected from the group consisting of cellulose derivatives, gelling compounds, polyethylene glycols, and mixtures thereof.

20. The process as claimed in claim 19, wherein the viscosifying compound is selected from the group consisting of cellulose ethers.

21. The process as claimed in claim 20, wherein the cellulose ether is selected from the group consisting of methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), hydroxyethylmethylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC), hydroxybutylmethylcellulose (HBMC), carboxymethylcellulose (CMC), sodium carboxymethylcellulose (Na-CMC), carboxymethylsulfoethylcellulose, and hydroxyethylmethylcarboxymethylcellulose.

22. The process as claimed in claim 21, wherein the cellulose ether is selected from the group consisting of hydroxyethylmethylcellulose, hydroxypropylmethylcellulose and hydroxybutylmethylcellulose.

23. The process as claimed in claim 22, wherein the cellulose ether is hydroxypropylmethylcellulose.

24. The process as claimed in claim 12, wherein the coating layer comprises: one or more viscosifying compounds and at least 10% of one or more anticaking agents, the percentages being expressed by weight relative to the total weight of the coating layer.

25. The process as claimed in claim 12, wherein the anticaking compound is selected from the group consisting of: talc; fines with the exception of limestone fines, sand; cement; carbon; wood residues; rice husk ash; glass powder; clays; alumina; silica; silica derivatives; plastic powder; lime; hydrated lime; plaster; rubber crumb; polymer powder,; and mixtures of these materials.

26. The process as claimed in claim 12, wherein the first composition has a needle penetrability measured at 25 C. according to the standard EN 1426 of from 5 to 330 1/10 mm.

27. The process as claimed in claim 23, wherein the first composition has a needle penetrability measured at 25 C. according to the standard EN 1426 of from 20 to 220 1/10 mm.

28. The process as claimed in claim 12, wherein the first composition also comprises at least one chemical additive selected from the group consisting of: an organic compound, a paraffin, a polyphosphoric acid, and mixtures thereof.

29. The process as claimed in claim 12, wherein the coating layer has an average thickness greater than or equal to 20 m.

Description

FIGURES

[0490] FIG. 1: Sectional view of the fluidized air bed facility

[0491] FIG. 1 represents a sectional view of a fluidized air bed facility.

[0492] Referring to FIG. 1, the fluidized air bed (12) facility (10) (also known as a granulator) comprises a fluidized air bed (12) process chamber (II) in which the cores of a bituminous material (14) are placed and in which an air stream (16) is fed from below to the fluidized bed (12) and through a perforated grid (13) in order to maintain the fluidized bed and in order to dry and/or cool the cores of a bituminous material (14). A coating layer precursor composition (18) is then fed to the fluidized bed (12) by means of a spray nozzle (20) emerging from below into the fluidized bed (12). The fluidized bed (12) process chamber (II) also comprises an insert (22) located above the spray nozzle (20) and in the form of a cylindrical facility piece that can be adjusted in height and diameter and the lower edges (15) of which are adjustably spaced from the perforated grid (13) of the bottom of the fluidized bed (12).

[0493] The filtration chamber (IV) comprises several filters (24) for recycling the fine particles emitted during the implementation of the process.

[0494] The air stream (16) fed to the fluidized bed (12) is guided by an incoming air housing (I) comprising an incoming air chamber (26).

[0495] The fluidized air bed (12) granulator (10) thus comprises 4 distinct zones: (I) the incoming air housing, (II) the process chamber, (III) the expansion chamber and (IV) the filtration chamber.

[0496] The zone of the fluidized bed formed by the incoming air chamber (26) has a zone (28) with a higher flow rate of the air stream (16) applied to the cores made of a bituminous material (14).

[0497] The coating layer precursor composition (18) is fed into the zone (28) operating ata higher flow rate.

[0498] The cores made of a bituminous material (14) originating from the zone (28) at a higher flow rate are returned to the fluidized bed (12).

[0499] A portion of the cores made of bituminous material (14) present in the fluidized bed (12) is returned to the zone (28) at higher flow rate, so that a circulation of cores made of bituminous material (14) appears between the fluidized bed (12) and the zone (28) at higher flow rate.

[0500] The invention is illustrated by the following examples, which are given without any implied limitation.

Experimental Section:

[0501] In these examples, the parts and percentages are expressed by weight unless otherwise indicated.

Materials and Methods:

Devices:

Facility 1:

[0502] Facility 1 is a fluidized air bed facility such as that used in the process according to the invention.

[0503] The following examples 2 to 8 were carried out in a fluidized air bed granulator sold by the company Glatt under the trade name ProCell and the sectional view of which is represented in FIG. 1.

Facility 2:

[0504] The following example 1 was carried out in a fluidized air bed granulator sold by the company Glatt under the trade name ProCell similar to facility 1 but with the following two differences: [0505] it is devoid of insert (22), and [0506] the air stream (16) fed to the fluidized bed (12) is constant throughout the granulator, i.e. there is no zone (28) at a higher flow rate.

Starting Materials:

[0507] The cores of bituminous material used as starting material in the examples below are composed of:

[0508] Bituminous base (B): a bitumen base of 50/70 grade, denoted B.sub.1, having a penetrability P.sub.25 of 58 1/10 mm and an RBSP of 49.6 C. and commercially available from the Total group under the brand name Azalt;

[0509] Additive: [0510] Additive A1 of formula (I): sebacic acid [0511] Additive A2 of formula (II): N,N-ethylenedi(stearamide) sold by the company Croda under the name Crodawax 140

[0512] Fillers: mineral fillers having a diameter less than or equal to 0.063 mm Preparation of granule cores

Composition:

[0513]

TABLE-US-00001 TABLE 1 composition of the bituminous binder constituting the granule core The amounts are expressed as percentage by weight of additive compound relative to the total weight of the composition. C1 Bitumen base B1 A1 1.5% A2 2.5%

Processes:

Preparation of the Binder Base:

[0514] The bitumen base B.sub.1 is introduced into a reactor maintained at 160 C. with stirring at 300 rpm for two hours. The additives are then introduced into the reactor. The contents of the reactor are maintained at 160 C. with stirring at 300 rpm for 1 hour.

Preparation of the Solid Binder Pellets

A. General Method for Preparing the Binder Cores of the Pellets According to the Invention

[0515] The binder composition is reheated at 160 C. for two hours in an oven before being poured into a silicone mold exhibiting different holes of spherical shape, so as to form the solid binder cores. After having observed the solidification of the binder in the mold, the surplus is leveled off using a blade heated with a Bunsen burner. After 30 minutes, the solid binder in the form of uncoated pellets is removed from the mold and stored in a tray covered with silicone paper. The binder cores are then allowed to cool to ambient temperature for 10 to 15 minutes.

B. General Method for Preparing the Bitumen Cores of the Pellets According to the Invention with an Industrial Process

[0516] For the implementation of this method, use may be made of a device and of a process as described in great detail in patent U.S. Pat. No. 4,279,579. Various models of this device are commercially available from the company Sandvik under the trade name Rotoform.

[0517] Bitumen pellets can also be obtained from the bituminous composition according to the invention poured into the tank of such a device and maintained at a temperature of between 130 and 160 C.

[0518] An injection nozzle or several injection nozzles make(s) possible the transfer of the bitumen composition according to the invention inside the double pelletizing drum comprising an external rotating drum, the two drums being equipped with slots, nozzles and orifices making possible the pelletizing of bitumen drops through the first stationary drum and orifices exhibiting a diameter of between 2 and 8 mm of the external rotating drum. The bitumen drops are deposited on the upper face of a horizontal conveyor belt driven by rollers.

[0519] Bitumen pellets were obtained from the bituminous composition C1 poured into the reservoir of such a device and maintained at a temperature of between 80 and 100 C.

[0520] One or more injection nozzles allow the transfer of the bituminous composition C1 inside the pelletizing twin drum including an external rotating drum, the two drums being equipped with slots, nozzles and orifices allowing the pelletizing of drops of bitumen through the first stationary drum and the orifices between 2 and 8 mm in diameter of the external rotating drum. The bitumen drops are deposited on the upper face of a horizontal conveyor belt driven by rollers.

Preparation of the Coating Layer

[0521] The coating layer precursor composition is an aqueous composition comprising: [0522] a viscosifying agent: hydroxypropylmethylcellulose introduced in the form of Sepifilm LP 010 commercially available from the company SEPPIC, and [0523] an anticaking agent: siliceous fines from La Noubleau.

[0524] It is prepared by mixing the components at ambient temperature in water with the contents set out in table 2.

Coating of the Pellets

[0525] The cores of bituminous material are loaded into the process chamber, the stream of air being in operation. The cores of bituminous material are thus fluidized by the stream of air injected into the process chamber. Finally, the coating layer precursor composition is sprayed into the process chamber by means of the spray nozzle.

Tests of Load Strength of the Pellets

[0526] This test is carried out in order to evaluate the load strength of the pellets at a temperature of 65 C. under a compressive stress. Specifically, this test makes it possible to simulate the temperature and compression conditions of the pellets on each other, to which they are subjected during transportation and/or storage in bulk in 10 to 100 kg bags or in 500 to 1000 kg big bags or in 200 kg drums, and to evaluate their strength under these conditions.

[0527] The load strength test is performed according to the following protocol: 5 ml of pellets are placed in a 20 ml syringe and the plunger is then placed on the pellets together with a weight of 208 g, representing a force applied as in a big bag. The whole is placed in an oven at 65 C. for at least 4 hours.

1. Preparation of the Coated Bitumen Pellets

[0528] Experiment 1 is carried out in device 2 (free of insert and in which the air flow rate is constant throughout the granulator).

[0529] Experiments 2 to 8 are carried out in device 1 (process according to the invention).

[0530] The implementation parameters of the various experiments are given in table 2 below. The spraying pressure (in bar) is from 1 to 3 bar.

TABLE-US-00002 TABLE 2 Examples 1 2 3 (*) 4 (*) 5 (*) 6 7 8 Coating layer precursor composition % of viscosifying agent 10 10 10 5 7.5 10 % of anticaking agent 20 20 15 12.5 10 Process implementation conditions Amount of cores fluidized (in g) 1050 937 1305 1142 1107 1123 Amount of precursor composition sprayed (in g) 1003 407 194 224 1101 1060 1000 Fluidization flow rate (in m.sup.3/h) 350 300 300 280 280 250 250 250 Product temperature (in C.) 14 35 35 35 35 17 17 17 Spraying flow rate (in g/min) 29.3 25.1 22.6 10.8 3.3 13.9 15.4 14.1 (*) following the agglomeration of the pellets during the process, said process was interrupted before having sprayed all of the precursor composition.

[0531] Examples 1 to 5 are counterexamples.

[0532] Examples 6, 7 and 8 are examples according to the invention.

2. Bitumen Pellets Obtained

[0533] The pellets obtained in examples 1 to 8 are then evaluated according to several criteria:

[0534] 1) the obtaining of bitumen pellets comprising a core and a coating layer,

[0535] 2) the homogeneity of the coating layer formed,

[0536] 3) the granule deformation,

[0537] 4) the presence of agglomerates, and

[0538] 5) their resistance to high temperature at 65 C.

[0539] The results are presented in table 3 below.

TABLE-US-00003 TABLE 3 Examples 1 2 3 4 5 6 7 8 Granule formation yes yes no no no yes yes yes Homogeneous deposition no yes yes yes yes Granule deformation x x Granule agglomeration x x x Resistance to ambient temperature at 65 C. + ++ +++ +++: the pellets retain their initial shape and do not adhere to one another. ++: the pellets do not adhere to one another but no longer exhibit their rounded shape. +: the pellets adhere slightly to one another. : the pellets are quite molten.

Coating Layer Comprising Exclusively an Anticaking Agent (Examples 1 and 2)

[0540] In examples 1 and 2, the coating layer precursor composition comprises only an anticaking agent.

[0541] It is noted that the bitumen pellets obtained according to examples 1 and 2 are not stable at high temperature.

[0542] The sole presence of an anticaking agent in the coating layer precursor composition does not make it possible to obtain bitumen pellets that are stable at high temperature.

Coating Layer Comprising Only a Viscosifying Agent (Examples 3, 4 and 5)

[0543] In examples 3, 4 and 5, the coating layer precursor composition comprises exclusively a viscosifying agent.

[0544] The cores and the coating layer precursor composition sprayed in the process chamber adhere to one another without however forming pellets. The cores agglomerate and make it impossible to form bitumen pellets.

[0545] The sole presence of a viscosifying agent in the coating layer precursor composition does not make it possible to obtain well-separated bitumen pellets.

Coating Layer Comprising Both a Viscosifying Agent and an Anticaking Agent (Examples 6, 7 and 8)

[0546] In examples 6, 7 and 8, the coating layer precursor composition comprises both a viscosifying agent and an anticaking agent.

[0547] The process according to the invention makes it possible to obtain bitumen pellets comprising a core made of a bituminous material and a homogeneous coating layer. These pellets are obtained in a separated manner.

[0548] Furthermore, the bitumen pellets formed in examples 6, 7 and 8 exhibit good resistance to conditioning at an ambient temperature of 65 C. insofar as they hardly adhere to one another.

[0549] The pellets formed in example 8 are particularly advantageous in that they retain their initial shape.

[0550] Thus, the handling and the transportation/storage of said pellets formed by means of the process according to the invention will be easy insofar as the pellets are obtained in the form of separated units by virtue of the formation of a homogeneous coating layer. More particularly, since these pellets do not melt and do not agglomerate together at high ambient temperature, their handling, their transportation and their storage are improved compared with the pellets of the prior art.