FR2791997A1 - Preparation of bitumen emulsion by mixing emulsifying composition and fluid bitumen under controlled pressure to form stable emulsion suitable for application to road surfaces - Google Patents

Abstract

Quantities of emulsifying agent and bitumen are metered out by mass counters and a controlled pressure in the system is established the mixture is fractionated in a colloid mill to form a stable emulsion. The process comprises the mechanical fractionation of a mixture comprising two constituents, fluid bitumen and an emulsifying composition, the preparation being carried out in a pressure zone of 1.5-10 bars. Independent claims are also included for the apparatus for the above process, and the product obtained.

Description

The present invention relates to a method and an installation for the

  manufacturing a bitumen emulsion, in particular road bitumen, which consists in mechanically breaking down a mixture composed of at least two major constituents, namely fluid bitumen and an emulsifying composition, and possibly constituents

  minor auxiliaries of treatment.

  By emulsifying composition is generally meant acidic water containing amines and / or

other chemicals.

  According to the standard technique, to reduce the natural viscosity of the bitumen and thus facilitate emulsification, the bitumen is added, in addition to an emulsifying composition, one or more fluxes, such as coal oil or oil, after which it is made pass the

  mixing, at ambient pressure, in a colloid mill.

  The known technique has a double disadvantage: on the one hand, the harmfulness of the added fluxes which are released when the bitumen solidifies; not only do these fluxes affect the environment but, in addition, some, such as petroleum oil, are carcinogenic; on the other hand, the colloid mill, under the conditions in which it is used, does not necessarily fractionate the bitumen as much as it would be necessary to return to the bitumen a sufficiently high viscosity

for spreading.

  The object of the invention is to propose a process and an installation which make it possible to avoid the use of the addition of chemicals to facilitate the emulsification while obtaining at the outlet of the colloid mill an emulsion of bitumen having a satisfactory viscosity. This object is achieved in that, according to the invention, the fractionation is carried out in an area where the constituents are at a pressure of between 1.5

and 10 bars.

  More specifically, the process consists of separately conveying said constituents to the fractionation zone and introducing them into it while said fluid bitumen is at a pressure of between 2 and 2.5 bars and that the emulsifying composition is at a temperature of

pressure of the order of 2 bars.

  This results in a much more extensive bitumen fractionation, which translates into an increase in

  viscosity and stability of the emulsion.

  As is known, the bitumen is treated while it is fluid, in this case, melted at a temperature of the order of 180 C. The expansion curve of the bitumen reflects a great sensitivity to temperature variations and it s then, when the proportion between bitumen and emulsifying composition is measured using volume meters, the actual dosage varies with temperature changes, and the resulting emulsion composition

  (hence its viscosity) fluctuates accordingly.

  To obtain an emulsion of constant composition and viscosity despite temperature variations, in a preferred embodiment of the process according to the invention, the constituents of

  the emulsion are dosed by means of mass counters.

  In practice, the process according to the invention consists in bringing each of said constituents to the desired pressure upstream of said mass counter and in keeping the fractionation zone at a pressure of between 1.5 and

bars.

  The invention also relates to an installation

  suitable for carrying out the method set out above.

  This installation comprises: for each of the constituents: a constituent tank, a mass counter, a constant flow pump connected to said tank and, by a so-called "upstream" pipe, to the upstream side of said mass counter, a pipe of recycling, the upstream end of which is connected to said upstream pipe and whose downstream end opens into said tank, to a pressure gauge and a valve interposed on said recycling line, to a servo-control circuit acting on said valve as a function of the pressure found by said manometer; To a pipe called "downstream", downstream of the mass meter; and for all the constituents: a colloid mill on which are connected, on the upstream side, said downstream pipes and, on the downstream side, an emulsion distribution pipe leading to the outlet of the installation, a pressure gauge and an interposed valve; on said distribution line between the colloid mill and the outlet of the installation, and a servo-control circuit acting on said valve as a function of the pressure observed by

said manometer.

  Preferably, the colloid mill has a variable air gap, which makes it possible to subject the mixture of

  constituents at a greater or lesser shear.

  The resulting emulsion has a pseudo-viscosity S.T.V.

  between 14 seconds and 120 seconds at 25 ° C. and a cationic emulsion rupture index of between 54.degree.

and 84.

  Pseuso-viscosity S.T.V. is measured according to standard NF T66-020 using a flow viscometer with a 4 mm diameter orifice and the rupture index of

  the cationic emulsion is measured according to standard NF T66-017.

  The invention will be better understood on reading the

  description hereinafter made with reference to the single figure

  of the attached drawing which schematically represents a shape

  execution of the installation according to the invention.

  As can be seen, the installation comprises an emulsifying composition supply circuit designated generally by E, a molten bitumen feed circuit generally designated by B and, optionally, an additive feed circuit ( s) designated as a whole by A, the three circuits having the same structure, so that only one of them (the circuit E) will be described in detail; the same references will be used from one circuit to another to designate the same components, the distinction between circuits being made by the addition, as the case may be, of the letters e, b and a to the references in question. If we examine the circuit E, we see that it comprises a reservoir containing an emulsifying composition, which reservoir is connected by a

  2nd pipe at the upstream side of a constant flow pump 3e.

  The downstream side of the constant flow pump 3e is connected by a pipe 4e, called upstream pipe, to the side

upstream of a mass counter 5e.

  A recycle line 6e connects the upstream line 4e to the tank 1 of emulsifying composition, with the interposition of a plug for a pressure gauge 7e and a valve 8e. A servo circuit 9e connects the manometer

7th at the 8th valve.

  On the downstream side, the mass meter 5e is connected to a pipe, called downstream, 10e itself connected to a colloid mill 11. Between the mass meter 5e and the colloid mill 11 are interposed, on the downstream pipe 10e, a valve 12e and a check valve 13th. A servo circuit 14e connects the mass counter 5e to the

12th valve.

  Colloidal mill 11 also terminates the downstream pipe 0b of the bitumen supply circuit B and the downstream pipe 10a of the optional supply circuit of additive (s) A. As an additive (s), it is possible, for example, to provide in a manner known per se, polymers whose role is to improve the resistance of the bitumen when exposed to

  very cold or hot weather.

  The outlet of the colloid mill 11 is connected to a distribution line 15 leading to the outlet of the installation and on which are interposed a manometer plug 16 and a valve 17. A circuit

  servocontrol 18 connects the pressure gauge 16 and the valve 17.

  The operation of the installation will be described below assuming that it comprises a circuit A. The tanks 1a, 1b and 1c are respectively charged with emulsifying composition, 180 C bitumen and additives. The constant flow pumps 3e, 3b and 3a respectively provide a mass flow rate of Qe, Qb and Qa

  respectively under a pressure of Pe, Pb and Pa.

  The mass counters 5e, 5b and 5a are respectively adjusted so that they provide a mass flow of qe <Qe, qb <Qb and qa <Qa. For example, if it is desired to obtain an emulsion without additive containing 65% of bitumen, it may be equal to 5.25 tonnes / hour and qb to 9.75 tonnes / hour. If the emulsion must contain

  additions, these figures will be revised accordingly.

  To ensure the flows qe, qb and qa above, the mass counters 5e, 5b and 5a respectively control the valves 12e, 12b and 12a via the circuits 14e, 14b and 14a. Moreover, the valves 8e, 8b and 8a are slaved respectively to the manometers 7e, 7b and 7a so that they are maintained, respectively, in the pipes

  4e, 4b and 4a, a pressure pe <Pe, pb <Pb and pa <Pa.

  If, for example, the mass counter 5e closes the valve 12e to reduce the amount of emulsifying composition sent to the colloid mill 11 so as to respect the fixed dosage, it follows a rise in pressure in the line 4e and the part of the bypass line 6e upstream of the valve 8e since the pump 3e is at a constant flow rate. When the pressure exceeds the threshold pe initially set, the servo-control circuit 9e between the pressure gauge 7e and the valve 8e controls the opening of said valve 8e and the emulsifying composition is recycled to the tank 1a until the pressure prevailing in the duct 4e and in the section of the duct 6e upstream of the valve 8e falls back to

  the value pe, causing the closure of said valve.

  The operation of the circuit B is identical to that of the circuit A, it being understood, however, that the control circuit 9b is set in such a way that the valve 8b opens when the pressure prevailing in the pipe 4b and the pipe section 6b in upstream of the valve 7b exceeds pb and closes when this pressure is lower or

equal to pb.

  The same is true of the optional circuit A which has its own setting of the mass counter, a function of the desired concentration of additive (s) in the emulsion, and its own adjustment of the servo circuit 9a resting

on a threshold pressure pa.

  The components of the mixture to be emulsified feed the

  Colloidal mill 11 via lines 10e, 10b and 10a.

  The colloidal mill may be a commercial device, such as a type PF 200 turbine, available from Pierre GUERIN (France). It comprises, as active parts, on the one hand, a fluted conical rotor rotating at 2950 revolutions / minute and to which four blades are fixed and, on the other hand, a fluted conical stator, the air gap between rotor and stator being adjustable. Means

  are incorporated in the turbine housing.

  Such a device is heretofore used to emulsify compositions at ambient pressure (with the exception of

  the mechanical effect due to rotation).

  The pressure prevailing in the colloid mill 11 is controlled by means of the valve 17 controlled by the servo-control circuit 18 as a function of the information coming from the manometer 16. If the pressure observed by the manometer 16 is below a threshold px, the circuit 18 controls the closing of the valve 17 until the desired pressure

be restored, and vice versa.

EXAMPLES

  The effect of setting the flow and pressure parameters, as well as the setting of the colloid mill gap, is shown in the table on the following page for two

  bitumen concentrations of the emulsion.

  The range of products produced covers needs ranging from soil impregnation for the lowest pseudo-viscosity to coatings on steep slopes for

higher viscosities.

  It follows from the foregoing description that

  performing an installation from commercial devices and by making appropriate adjustments of flow and pressure, and if necessary shear forces, the characteristics of the emulsion can be modified, in particular to vary the fineness and size of the emulsions. bitumen particles dispersed in the emulsifying composition.

  VARIATION OF VISCOSITY AND BREAKING INDEX OF

  CATIONIC EMULSION IN ACCORDANCE WITH PARAMETER ADJUSTMENT

  Concen- traine colloidal emulsion of resultant Example 1 emulsion in bitumen setting qb qe pb pe px pseudo- index interferen en en visco- de in t / h t / h bar bars bar sité rupture

-2 cm S.T.V.

in S

1 65% 50 9.75 5.25 2.5 2 2 14 84

2 65% 55 9.75 5.25 2.5 2 4 35 65

  3 65 t 55 8,45 4,55 2,5 2 4,5 39 58 4 65 t 55 9,75 5,25 2,5 2 2 14 84

69% 50 10.35 4.65 2 2 1.5 15 68

  6 69% 55 10.35 4.65 2.5 2 1.5 15 68

  7 69 t 55 10.35 4.65 2.5 2 5 80 58 8 69 t 54 8.97 4.03 2.5 2 5 120 54

Claims (8)

  1 - A process for manufacturing a bitumen emulsion which consists in mechanically breaking down a mixture composed of at least two constituents, namely fluid bitumen and an emulsifying composition, characterized in that said fractionation is carried out in an area where said constituents are at a pressure of between 1.5 and 10 bars.   2 - Process according to claim 1, characterized in that it comprises penetrating the fluid bitumen in said fractionation zone while said bitumen is at   a pressure of between 2 and 2.5 bars.   3 - Process according to claim 1 or 2, characterized in that it consists in causing the emulsifying composition to penetrate into said fractionation zone while said composition is at a pressure of the order 2 bars.   4 - Process according to any one of the claims   1 to 3, characterized in that it consists in separately dosing each of said constituents by means of counters Massive (5th, 5th).   - Process according to claim 4, characterized in that it consists in carrying each of said constituents to the desired pressure (pe, pb) upstream of said mass counter 5th, 5b).   6 - Process according to any one of the claims   1 to 5, characterized in that it further consists in varying the shear forces exerted on the mixture   in the fractionation zone (11).   7 - Installation for the implementation of the method   according to any one of claims 1 to 6,   characterized in that it comprises: - for each of the constituents: a constituent reservoir (1a, 1b), to a mass counter (5e, 5b), to a constant flow pump (3e, 3b) connected to said reservoir (the , lb) and, by a line (4e, 4b), called "upstream", on the upstream side of said mass counter (5e, 5b), a recycling line (6e, 6b) whose upstream end is connected to said pipe upstream (4e, 4b) and whose downstream end opens into said reservoir (1a, 1b), to a pressure gauge (7e, 7b) and a valve (8e, 8b) interposed on said recycling line (6e, 6b), 10. a servo control circuit (9e, 9b) acting on said valve (8e, 8b) as a function of the pressure observed by said manometer (7e, 7b); A pipe (10e, 0lb) called "downstream", downstream of the mass meter (5e, 5b); and - for all the constituents: to a colloid mill (11) on which are connected, on the upstream side, said downstream pipes (10e, 0lb) and, on the downstream side, an emulsion distribution pipe (15) leading to the outlet of the installation, 20. a manometer (16) and a valve (17) interposed on said distribution line (15) between the colloid mill (11) and the output of the installation, and a servo circuit ( 18) acting on said valve (17) according to the pressure   noted by said manometer (16).   8 - Plant according to claim 7, characterized in that the colloid mill (11) is at variable air gap.   9 - Emulsion of bitumen, characterized in that it has a pseudoviscosity S.T.V. between 14 and 120 seconds at 25 ° C. and a rupture index of the emulsion cationic value between 54 and 84.