CA1046792A - Method and apparatus for the continuous automatic analysis of the crystallization point of liquid substances - Google Patents
Method and apparatus for the continuous automatic analysis of the crystallization point of liquid substancesInfo
- Publication number
- CA1046792A CA1046792A CA248,262A CA248262A CA1046792A CA 1046792 A CA1046792 A CA 1046792A CA 248262 A CA248262 A CA 248262A CA 1046792 A CA1046792 A CA 1046792A
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- 239000000126 substance Substances 0.000 title claims abstract description 66
- 238000002425 crystallisation Methods 0.000 title claims abstract description 65
- 230000008025 crystallization Effects 0.000 title claims abstract description 65
- 238000000034 method Methods 0.000 title claims abstract description 31
- 239000007788 liquid Substances 0.000 title claims abstract description 22
- 238000004458 analytical method Methods 0.000 title claims abstract description 21
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims abstract description 59
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical group CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims abstract description 20
- URLKBWYHVLBVBO-UHFFFAOYSA-N Para-Xylene Chemical group CC1=CC=C(C)C=C1 URLKBWYHVLBVBO-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000010438 heat treatment Methods 0.000 claims abstract description 15
- 238000001816 cooling Methods 0.000 claims abstract description 14
- 239000002178 crystalline material Substances 0.000 claims abstract description 8
- 239000013078 crystal Substances 0.000 claims description 8
- 150000004945 aromatic hydrocarbons Chemical class 0.000 claims description 5
- 229910001220 stainless steel Inorganic materials 0.000 claims description 4
- 239000010935 stainless steel Substances 0.000 claims description 4
- 239000000110 cooling liquid Substances 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims 1
- 239000003921 oil Substances 0.000 description 11
- 238000005259 measurement Methods 0.000 description 5
- 238000011161 development Methods 0.000 description 4
- 235000011837 pasties Nutrition 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- KUGRPPRAQNPSQD-UHFFFAOYSA-N OOOOO Chemical compound OOOOO KUGRPPRAQNPSQD-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 125000003118 aryl group Chemical group 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 230000000750 progressive effect Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- RSPISYXLHRIGJD-UHFFFAOYSA-N OOOO Chemical compound OOOO RSPISYXLHRIGJD-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000002844 continuous effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/26—Oils; Viscous liquids; Paints; Inks
- G01N33/28—Oils, i.e. hydrocarbon liquids
- G01N33/2811—Oils, i.e. hydrocarbon liquids by measuring cloud point or pour point of oils
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N11/02—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material
- G01N11/04—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material through a restricted passage, e.g. tube, aperture
- G01N11/08—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material through a restricted passage, e.g. tube, aperture by measuring pressure required to produce a known flow
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/02—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering
- G01N25/04—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering of melting point; of freezing point; of softening point
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Immunology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Pathology (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Investigating Or Analyzing Materials Using Thermal Means (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
METHOD AND APPARATUS FOR THE CONTINUOUS
AUTOMATIC ANALYSIS OF THE CRYSTALLIZATION
POINT OF LIQUID SUBSTANCES
ABSTRACT OF THE DISCLOSURE
The method consists of passing the substance to be analyzed through a measuring circuit at a constant flow rate, the temperature therein being maintained at a value sufficiently below the assumed crystallization point of the substance. Heating means are provided along the flow path of the liquid substance in said circuit.
The substance in the course of cooling is kept in contact with an isomorphous crystalline material. The heating means is automatically turned on and off respectively at two characteristic temperatures, which are detected by measuring the pressure drop or difference of pressure of the substance at the inlet and at the outlet of the measuring circuit, variations of the pressure drop being effected as a function of temperature. The values thus measured of the pressure drop are utilised as control data for respectively turning on and off the heating means when the tempera-ture of the substance at the outlet reaches one of its two characteristic values, the first corresponding to the crystallization temperature level, whilst the other corresponds to a temperature sufficiently above said crystallization point. The temperature of the substance at the outlet of the circuit is continuously recorded, which constitutes a value representing the crystallization point of the substance. The method and the apparatus are particularly useful for determining the crystallization point of benzene, of paraxylene or of orthoxylene automatically and continuously.
AUTOMATIC ANALYSIS OF THE CRYSTALLIZATION
POINT OF LIQUID SUBSTANCES
ABSTRACT OF THE DISCLOSURE
The method consists of passing the substance to be analyzed through a measuring circuit at a constant flow rate, the temperature therein being maintained at a value sufficiently below the assumed crystallization point of the substance. Heating means are provided along the flow path of the liquid substance in said circuit.
The substance in the course of cooling is kept in contact with an isomorphous crystalline material. The heating means is automatically turned on and off respectively at two characteristic temperatures, which are detected by measuring the pressure drop or difference of pressure of the substance at the inlet and at the outlet of the measuring circuit, variations of the pressure drop being effected as a function of temperature. The values thus measured of the pressure drop are utilised as control data for respectively turning on and off the heating means when the tempera-ture of the substance at the outlet reaches one of its two characteristic values, the first corresponding to the crystallization temperature level, whilst the other corresponds to a temperature sufficiently above said crystallization point. The temperature of the substance at the outlet of the circuit is continuously recorded, which constitutes a value representing the crystallization point of the substance. The method and the apparatus are particularly useful for determining the crystallization point of benzene, of paraxylene or of orthoxylene automatically and continuously.
Description
~04679Z
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a method and apparatus for the continuous automatic analysis of the crystallization point of liquid substances, especially of aromatic hydrocarbons.
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a method and apparatus for the continuous automatic analysis of the crystallization point of liquid substances, especially of aromatic hydrocarbons.
2. Description of the Prior Art A method and an apparatus for the automatic continuous analysis of the filterability point of liquid substances, in particular of gas-oils during manufacture, has previously been described in a U.S. patent specification by applicant.
The method consists of passing a substance to be analyzed through a measuring circuit at a constant flow rate, the temperature therein being maintained at a value sufficiently below the assumed filterability point of the substance, heating means being provided along the flow path of the liquid substance in said circuit, and automatically turning on and off said heating means respectively at two characteristic temperatures detected by measuring the pressure drop or difference in pressure of the substance at the inlet and at the outlet of the circuit, the variation of said pressure drop being effected as a function of temperature, the values thus measured of the pressure drop being utilized as control data for respectively turning on and off the heating means, when the temperature at the outlet of the substance reaches one of the two characteristic temperatures, the first corresponding to a temperature slightly below the filterability point, whilst the other corresponds to a tempera-ture sufficiently above said filterability point, and in that the temperature of the substance at the outlet of the circuit is recorded continuously, which temperature constitutes a representative value of the filterability point of the substance.
1~4ti,79Z
A preferred embodiment of the apparatus for carrying out the aforementione~ method comprises a measuring circuit constituted by a capillary tube of stainless steel traversed by the substance to be analyzed, whose flow rate is kept constant by a small volumetric pump, the capillary tube having a large portion of its length immersed in a cooling liquid bath contained in a measuring well, the inlet and the outlet of the capillary tube in the well being connected, outside of the well, to two electrical leads of which one is directly connected to the power supply whilst the other is connected to differential pressure-responsive switching means, mounted between the inlet and the outlet of the capillary tube, whilst a thermosensitive element is positioned at the outlet of the measuring well along the flow path of the substance to be analysed and is connected to a recording device.
The aforementioned patent application also describes a method and an apparatus for the continuous measurement of the filterability temperature limit, the filterability point corresponding to the appreciable diminution of the flowability of a gas-oil when the temperature drops.
Devices have also already been described, enabling the determination of the crystallization temperature of a liquid. Reference may notably be made to U.S. Patent No.
The method consists of passing a substance to be analyzed through a measuring circuit at a constant flow rate, the temperature therein being maintained at a value sufficiently below the assumed filterability point of the substance, heating means being provided along the flow path of the liquid substance in said circuit, and automatically turning on and off said heating means respectively at two characteristic temperatures detected by measuring the pressure drop or difference in pressure of the substance at the inlet and at the outlet of the circuit, the variation of said pressure drop being effected as a function of temperature, the values thus measured of the pressure drop being utilized as control data for respectively turning on and off the heating means, when the temperature at the outlet of the substance reaches one of the two characteristic temperatures, the first corresponding to a temperature slightly below the filterability point, whilst the other corresponds to a tempera-ture sufficiently above said filterability point, and in that the temperature of the substance at the outlet of the circuit is recorded continuously, which temperature constitutes a representative value of the filterability point of the substance.
1~4ti,79Z
A preferred embodiment of the apparatus for carrying out the aforementione~ method comprises a measuring circuit constituted by a capillary tube of stainless steel traversed by the substance to be analyzed, whose flow rate is kept constant by a small volumetric pump, the capillary tube having a large portion of its length immersed in a cooling liquid bath contained in a measuring well, the inlet and the outlet of the capillary tube in the well being connected, outside of the well, to two electrical leads of which one is directly connected to the power supply whilst the other is connected to differential pressure-responsive switching means, mounted between the inlet and the outlet of the capillary tube, whilst a thermosensitive element is positioned at the outlet of the measuring well along the flow path of the substance to be analysed and is connected to a recording device.
The aforementioned patent application also describes a method and an apparatus for the continuous measurement of the filterability temperature limit, the filterability point corresponding to the appreciable diminution of the flowability of a gas-oil when the temperature drops.
Devices have also already been described, enabling the determination of the crystallization temperature of a liquid. Reference may notably be made to U.S. Patent No.
3,577,765, which relates to a method and an apparatus for determining automatically the crystallization temperature of a flowing liquid and more particularly, of aqueous solutions, for example of sodium benzenesulfona~e whose crystallization is not of the "clean" type, that is to say it manifests an increase in viscosity of the cooled liquid stream.
Such a method is not suitable for substances of high purity, such as, for example, benzene, paraxylene, or orthoxylene, since these substances having a crystallization of the "clean" type, exhibit a random undercooling phenomenon, described in more detail in the description which follows, and this phenomenon is a handicap for the automatic continuous analysis of the crystallization point.
OBJECTS AND GENERAL DESCRIPTION OF THE INVENTION
It is therefore an object of the present invention to provide an improved method and apparatus for the automatic continuous analysis of the crystallization point of liquid substances.
It is a further object of the present invention to provide a method and an apparatus specially adapted to the automatic continuous analysis of the crystallization point of substances with crystallization of the "clean" type.
It is another object of the present invention to provide a method and an apparatus for overcoming the above-mentioned drawbacks of the prior art method and apparatus, notably in that it overcomes the phenomenon of random under-cooling or supercooling of a substance with "clean" crystalliz-ation in the course of cooling.
~0 In cold testing, gas-oils undergo chanses of state.
It is therefore a further object of the present invention to provide a method and an apparatus well adapted to the contin-uous measurement and definition of the characteristics of a gas-oil.
It is a further object of the present invention to provide a method and an apparatus for the continuous measure-ment of the crystallization point of a gas-oil and more particularly of an aromatic hydrocarbon.
Other objects and advantages of the method and apparatus according to the present invention will emerge from the description which follows.
According to the invention, in its most general ~046792 form, there is provided a method for the automatic continuous analysis of the crystallization point of liquid substances, particuarly of aromatic hydrocarbons, characterized in that it consists of passing a constant flow rate of the substance to be analysed through a measuring circuit, whose temperature is kept at a value sufficiently below the assumed crystallization point of said substance, heating means being provided in the flow path of the liquid in said circuit, in that the liquid substance to be analysed is kept in the course of cooling in contact with an isomorphous crystalline material, and in that said heating means are automatically turned on and off respectively at two characteristic temperatures detected by measuring the pressure drop or pressure difference of the substance at the inlet and at the outlet of the measuring circuit, the variation of said pressure drop being effected as a function of temperature, the values thus measured of the pressure drop being utilized as control data for turning on and off respectively the heating means, when the temperature at the outlet of the substance reaches one of its two characteristic values, the first corresponding to the crystallization temperature level whilst the other corresponds to a temperature sufficiently above said crystallization point r and in that the temperature of the substance at the outlet of the circuit is recorded continuously, which constitutes a representative value of the crystallization point of the substance.
According to another aspect of the invention, in its most general form, there is provided an apparatus for carrying out the aforesaid method, which apparatus comprises a measuring circuit constituted by a stainless steel capillary tube traversed by the substance to be analysed, of which the flow rate is maintained constant by a small volumetric pump, the capillary tube having a large portion of its length immersed in a cooling liquid bath contained in a measuring well, the bottom of the latter being arranged in the form of a fluidYtight crystals chamber which contains an isomorphous crystalline material, a short portion of the capillary tube extending through said chamber, the isomorphous material being in contact with the substance to be analysed, by means of an opening formed in the portion of the tube situated in said chamber, the inlet and the outlet of the capillary tube in the well being connected externally of the well to two electrical leads of which one is directly connected to the differential pressure-responsive switching means, mounted between the inlet and the outlet of the capillary tube, whilst a thermosensitive element is positioned at the outlet of the measuring well on the flow path of the substance to be analysed and is coupled to a recorder.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more fully understood, several embodiments of the method and apparatus according to the invention are described below with reference to the accompanying drawings, given of course, purely by way of non-limiting example. In the drawings:
Figure 1 is a graph given by way of explanation;
Figure 2 is a diagram of an embodiment of the apparatus according to the invention;
Figure 3 is a graph showing the temperature/purity relationship for benzene;
Figure 4 is a graph showing the temperature/purity relationship for paraxylene;
Figure 5 is a graph showing the temperature/purity relationship for orthoxylene.
DESCRIPTION OF PREFERRED EMBODIMENTS
$here is of course a relative similarity for gas-~046792 oils in the course of cooling, between the change of statecorresponding to the filterability point and the crystalliæation.
However, it must be noted that there is a difference in crystallizing substances of the "pasty" type and those with "clean" crystallization.
Referring to Figure 1 of the accompanying drawings, the difference between "pasty" type crystallization and "clean"
type crystallization will now be defined.
Figure 1 is a graph showing the known temperature/
pressure drop relationship in the case of a gas-oil.
Curve A shows the development of the pressure drop in a circuit traversed by a gas-oil in the course of cooling, this gas-oil having progressive crystallization of the "pasty" type.
Curve B shows the development of the pressure drop in a circuit traversed by a gas-oil in the course of cooling.
this gas-oil having a "clean" crystallization. This "clean"
crystallization is the case for aromatic substances such as benzene, paraxylene and orthoxylene.
The dashed portion of curve B corresponds to the random undercooling which mostly precedes any clean crystal-lization. This phenomenon is a particularly constraining handi-cap in carrying out continuous analysis, but it is possible to eliminate the risk thereof completely by maintaining the liquid in the course of cooling in contact with an isomorphous crystalline material, that is to say of the same system of crystallization.
In the method according to the invention, generally, the flow rate of the substance to be analysed is kept constant, although the variation of the pressure drop is measured progressively as the temperature of the circulating substance drops, this substance being kept in contact with an isomorphous crystalline material in the part where its crystallization takes ~046792 place.
Figure 2 shows diagrammatically an embodiment of the apparatus according to the invention.
The analyser of the crystallization point comprises a measuring circuit cons~ituted by a capillary tube of stainless steel.
This capillary tube 1 is traversed by a substance to be analyzed suppliedat 21 and propelled by a volumetric pump 22 situated downstream. The tube 1 passes into a measuring lQ well 2. This measuring well 2 is a cavity of small volume formed in a solid mass 3 of steel. This measuring well comprises a fluid-tight chamber 4 in its lower part, said chamber 4 containing an isomorphous crystalline material 5, that is to say of the same system of crystallization as the substance to be analysed, a rhombic pyramid system, for example, if the substance to be analysed is benzene. The remaining part of the measuring well 2 is filled with a non-freezable product 6.
The solid steel mass 3 comprises means connected to a cooling unit and is heat-insulated.
The capillary tube 1 has an outer diameter of 1.5 mm and an inner diameter of about 1.2mm, and it is shaped so that it offers a fairly large surface in the measuring well 2 before the entry of said tube 1 into the arystals chamber 4; the tube 1 may for example have a substantially helicoidal shape. The capillary tube 1 penetrates the crystals chamber 4 through a fluid-tight and electrically insulating barrel 7a and re-emerges therefrom through a barrel 7b identical with the barrel 7a. The portion l_ of the capillary tube 1 passing into the crystals chamber 4 comprises a longitudinal opening 8 formed throughout the length of a generator of this portion of tube la. This opening 8 thus permits the liquid stream cir-culating in the capillary tube to be placed in communicationwith the isomorphous material 5, for example, benzene, stored in the chamber 4.
The capill~ry tube 1 has a length of about 100 cm and represents an electrical resistance of about 1 ohm. The inlet and outlet connections of the tube 1 are formed as insulating joints and are connected, through a switch 10, associated with differential pressure-sensing switch means 11, to a potential difference 12 (mains).
The differential pressure-sensing means 11 is mounted between the inlet 13 of the tube of the measuring circuit on the side of its high pressure connection and the ; outlet 14 of the measuring circuit on the side of its low pressure connection.
On the side of the outlet 14 of the measuring well, a thermosensitive element 15 dips into the outlet section of the capillary tube 1. This element 15 is constituted by a platinum resistance of 100~ at 0C, technically known as "pyrothenax"; its outer end is connected to a continuous temperature recorder 16.
At its outlet 14 from the measuring well 2, the capillary tube 1 is extended perpendicularly to the thermo-sensitive element 15 and its end is provided with a drain 17.
The dynamic behaviour of the whole of the apparatus will now be described.
At the inlet of the circuit, by means of the volumetric pump 21, the constant flow rate of the substance to be analysed is ensured, which permits continuous circulation of the substance in the capillary tube 1.
The analysis unit or measuring well 2 is kept at 0C and, the circulation being established in the capillary tube 1, the sequence of analysis cycles occurs in the manner ~04679Z
described below.
The temperature of the substance to be analysed 5, for example benzene, standing in the chamber 4, drops rapidly since this chamber is in direct thermal contact with the bottom of the cooling well. A~ter a possible, but single, initial overcooling, the product 5 crystallizes in the chamber 4. The liquid stream circulating in the capillary tube 1 is hence in physical contact with isomorphous crystals, which avoids over cooling during its crystallization. In fact, as soon as the liquid benzene flowing in the tube, as a result of its pro-gressive cooling, reaches cry~tallization temperature, there is a solidification of the capillary, or of a considerable portion of the latter without the appearance of a random under cooling phenomenon preceding "clean" crystallization. The stopping of the flow which results from the solidiication of the capillary causes a rise in pressure at the inlet of the capillary and results in closing the pressure-sensitive switch 10; the differential pressure-sensing means 11 connected to this capillary 1 then actuates the starting up of the re-heating sequence by applying an alternating potential differenceto the terminals of the capillary 1, which then behaves as a heating resistance.
The rise in temperature of the whole of the capillary circuit causes fusion of the crystals occurring therein, thus freeing the flow in the capillary, which permits instantaneous return to the initial pressure and thus causes the stopping of the heating.
The relatively large amount of crystals 5 immobilized in the chamber 4, and the fact that the latter are kept at a temperature sufficiently below their melting point, enables their permanence to be ensured, only the layers surrounding the capillary being liable to successive fusions and crystallization.
~046'79Z
Liquid/solid physical contact is thus ensured constantly in spite of the slight mobility of the transition zone.
The sequence of analyses then ~ollow, according to the procedure described above, at the rate of about three per minute. This frequency of recurrence is hence sufficient to permit the analysis to be compared with continuous analysis.
The development of the temperature thus recorded by the device 16 then presents itself in the form of a saw-tooth, whose lower crests locate accurately the successive values of the crystallization temperatures~
The envelope curve of these low crests enables the development of the latter to be followed, although it is of course possible to insert in the recording channel a memory device enabling only the continuous tracing of this low envelope to be recorded.
The apparatus according to the invention has been utilized for the continuous analysis of the crystalliztion point of benzene.
Of course, a relationship exists between the crystallization temperature and the purity of the benzene, whose graphic representation is shown in figure 3. This curve represents the crystallization temperature in degrees centigrade as ordinate, as a function of the purity of the benzene in % as abscissea.
The graph of figure 3 has been calcu ~ ted from cryoscopic constants according to the formula:
Log10 P = 2.00000 - (A/2.3026)(t~ -t~) [1 ~ B(t~ -t~]
where P = percentage of moles of benzene A = 0.01523 molar fraction per degree B - 0.0032 molar fraction per degree t p O= 5.333 ~ 0.010C
:~0467g2 tp - crystallization point in C of the inpure benzene.
By means o~ the apparatus according to the invention, table I given below has been recorded which enables the temperature of crystallization~purity of benzene relationship to be established.
TABLE I
PURITY OF THE BENZENE AS A FUNCTION OF THE
CRYSTALLIZATION POINT
Crystallization %Benzene Crystallization %Benzene point C. point C
-1.0 93.2 3.5 96.9 1.1 3.6 97.1 1.2 93.5 3.7 97.2 1.3 93.7 3.8 97.4 1.4 93.8 3.9 97.5 1.5 94.0 4.0 97.7 1.6 94.1 4.1 97.8 1.7 94.3 4.2 98.0 1.8 94.4 4.3 98.1 1.9 94.5 4.4 98.3 2.0 94.7 4.5 98.4 2.1 94.9 4.6 98.6 2.2 95.0 4.7 98.7 2.3 95.1 4.8 98.9 2.4 95.3 4.9 99.0 2.5 95.5 5.0 99.2 2.6 95.6 5.1 99.3 2.7 95.8 5.2 99.5 2.8 95.9 5.3 99.8 2.9 96.0 5.4 99.8 3.0 96.2 5-5 99 9 3.1 96.3 ~)4679Z
TAB~E I (co:ntin ed~
PURITY OF THE BENZENE AS A FUNCTION OF THE CRYST~LLIZATION POINT
Crystallization ~senzene Crystallization %senzene point C point C
.
3.2 96.5 3.3 96.6 3-4 96.8 From this recording, it appears overall that a fluctuation in purity of 0.15% is manifested by a fluctuation of 0.1C in the crystallization temperature.
For the continuous analysis of the crystallization point of benzene, the extent of measurement corresponds to 2.5C to 5.5C, namely to a purity of95-5 to 99.9%. Since the defined limit corresponds to 1/100 of the length of measurement, it is 0.3C. According to the method of the invention, the repeatability in measured purity is 0.05% and the response time with a momentary variation in purity of 1%
is about 15 minutes.
According to the method of the present invention, it is possible to carry out continuous analyses of the crystallization points of other aromatic substances such as paraxylene or orthoxylene, as well as any substances whose crystallization temperatures are situated between -30C and ambient temperature.
In figure 4, is shown the crystallization temperature in C as a function of the % of purity of paraxylene, this curve having been calculated from the cryoscopic constants.
Below, there is given in Table II the crystallization points recorded by the method according to the invention, as well as the % purity of paraxylene.
1~46792 .
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~04679Z
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1~?4679Z
In Figure 5, the crystallization temperature in C
as a function of the percentage purity of orthoxylene is shown by a curve calculated from the cryoscopic constants.
Below, is given in Table III the crystallization points read in a continuous analysis of orthoxylene according to the method of the invention and the percentage purity of the orthoxylene.
TABLE III
PURITY OF THE ORTHOXYLENE AS A FUNCTION OF THE
CRYSTALLIZATION POINT
Crystallization point % paraxylene -29.0 90.2 -29.1 90.~
-29.2 89.7 -29.3 89.5 -29.4 89.3 -29.5 89.0 -29.6 88.8 -29.7 88.5 -29.8 88.3 -29.9 88.1 ~30.0 87,8 -30.1 87.6 -30.2 87.3 ~30-3 87.1 86.9 -30.5 86.5 -30.6 86.4 ~30-7 86.2 -30.8 85.9 -30.9 85.7 ~04679Z
TABLE~III (continued) Crystallization point ~ paraxylene -31.0 85.4 -31.1 85~2 -31.2 85.0 The continuous analysis of the crystallization point of an aromatic hydrocarbon enables the purity of the analysed substance to be determined continuously and hence this data to be transmitted directly to a processing system for said hydrocarhon, for example a distillation column, in order to cause the parameters to vary correspondingly.
Such a method is not suitable for substances of high purity, such as, for example, benzene, paraxylene, or orthoxylene, since these substances having a crystallization of the "clean" type, exhibit a random undercooling phenomenon, described in more detail in the description which follows, and this phenomenon is a handicap for the automatic continuous analysis of the crystallization point.
OBJECTS AND GENERAL DESCRIPTION OF THE INVENTION
It is therefore an object of the present invention to provide an improved method and apparatus for the automatic continuous analysis of the crystallization point of liquid substances.
It is a further object of the present invention to provide a method and an apparatus specially adapted to the automatic continuous analysis of the crystallization point of substances with crystallization of the "clean" type.
It is another object of the present invention to provide a method and an apparatus for overcoming the above-mentioned drawbacks of the prior art method and apparatus, notably in that it overcomes the phenomenon of random under-cooling or supercooling of a substance with "clean" crystalliz-ation in the course of cooling.
~0 In cold testing, gas-oils undergo chanses of state.
It is therefore a further object of the present invention to provide a method and an apparatus well adapted to the contin-uous measurement and definition of the characteristics of a gas-oil.
It is a further object of the present invention to provide a method and an apparatus for the continuous measure-ment of the crystallization point of a gas-oil and more particularly of an aromatic hydrocarbon.
Other objects and advantages of the method and apparatus according to the present invention will emerge from the description which follows.
According to the invention, in its most general ~046792 form, there is provided a method for the automatic continuous analysis of the crystallization point of liquid substances, particuarly of aromatic hydrocarbons, characterized in that it consists of passing a constant flow rate of the substance to be analysed through a measuring circuit, whose temperature is kept at a value sufficiently below the assumed crystallization point of said substance, heating means being provided in the flow path of the liquid in said circuit, in that the liquid substance to be analysed is kept in the course of cooling in contact with an isomorphous crystalline material, and in that said heating means are automatically turned on and off respectively at two characteristic temperatures detected by measuring the pressure drop or pressure difference of the substance at the inlet and at the outlet of the measuring circuit, the variation of said pressure drop being effected as a function of temperature, the values thus measured of the pressure drop being utilized as control data for turning on and off respectively the heating means, when the temperature at the outlet of the substance reaches one of its two characteristic values, the first corresponding to the crystallization temperature level whilst the other corresponds to a temperature sufficiently above said crystallization point r and in that the temperature of the substance at the outlet of the circuit is recorded continuously, which constitutes a representative value of the crystallization point of the substance.
According to another aspect of the invention, in its most general form, there is provided an apparatus for carrying out the aforesaid method, which apparatus comprises a measuring circuit constituted by a stainless steel capillary tube traversed by the substance to be analysed, of which the flow rate is maintained constant by a small volumetric pump, the capillary tube having a large portion of its length immersed in a cooling liquid bath contained in a measuring well, the bottom of the latter being arranged in the form of a fluidYtight crystals chamber which contains an isomorphous crystalline material, a short portion of the capillary tube extending through said chamber, the isomorphous material being in contact with the substance to be analysed, by means of an opening formed in the portion of the tube situated in said chamber, the inlet and the outlet of the capillary tube in the well being connected externally of the well to two electrical leads of which one is directly connected to the differential pressure-responsive switching means, mounted between the inlet and the outlet of the capillary tube, whilst a thermosensitive element is positioned at the outlet of the measuring well on the flow path of the substance to be analysed and is coupled to a recorder.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more fully understood, several embodiments of the method and apparatus according to the invention are described below with reference to the accompanying drawings, given of course, purely by way of non-limiting example. In the drawings:
Figure 1 is a graph given by way of explanation;
Figure 2 is a diagram of an embodiment of the apparatus according to the invention;
Figure 3 is a graph showing the temperature/purity relationship for benzene;
Figure 4 is a graph showing the temperature/purity relationship for paraxylene;
Figure 5 is a graph showing the temperature/purity relationship for orthoxylene.
DESCRIPTION OF PREFERRED EMBODIMENTS
$here is of course a relative similarity for gas-~046792 oils in the course of cooling, between the change of statecorresponding to the filterability point and the crystalliæation.
However, it must be noted that there is a difference in crystallizing substances of the "pasty" type and those with "clean" crystallization.
Referring to Figure 1 of the accompanying drawings, the difference between "pasty" type crystallization and "clean"
type crystallization will now be defined.
Figure 1 is a graph showing the known temperature/
pressure drop relationship in the case of a gas-oil.
Curve A shows the development of the pressure drop in a circuit traversed by a gas-oil in the course of cooling, this gas-oil having progressive crystallization of the "pasty" type.
Curve B shows the development of the pressure drop in a circuit traversed by a gas-oil in the course of cooling.
this gas-oil having a "clean" crystallization. This "clean"
crystallization is the case for aromatic substances such as benzene, paraxylene and orthoxylene.
The dashed portion of curve B corresponds to the random undercooling which mostly precedes any clean crystal-lization. This phenomenon is a particularly constraining handi-cap in carrying out continuous analysis, but it is possible to eliminate the risk thereof completely by maintaining the liquid in the course of cooling in contact with an isomorphous crystalline material, that is to say of the same system of crystallization.
In the method according to the invention, generally, the flow rate of the substance to be analysed is kept constant, although the variation of the pressure drop is measured progressively as the temperature of the circulating substance drops, this substance being kept in contact with an isomorphous crystalline material in the part where its crystallization takes ~046792 place.
Figure 2 shows diagrammatically an embodiment of the apparatus according to the invention.
The analyser of the crystallization point comprises a measuring circuit cons~ituted by a capillary tube of stainless steel.
This capillary tube 1 is traversed by a substance to be analyzed suppliedat 21 and propelled by a volumetric pump 22 situated downstream. The tube 1 passes into a measuring lQ well 2. This measuring well 2 is a cavity of small volume formed in a solid mass 3 of steel. This measuring well comprises a fluid-tight chamber 4 in its lower part, said chamber 4 containing an isomorphous crystalline material 5, that is to say of the same system of crystallization as the substance to be analysed, a rhombic pyramid system, for example, if the substance to be analysed is benzene. The remaining part of the measuring well 2 is filled with a non-freezable product 6.
The solid steel mass 3 comprises means connected to a cooling unit and is heat-insulated.
The capillary tube 1 has an outer diameter of 1.5 mm and an inner diameter of about 1.2mm, and it is shaped so that it offers a fairly large surface in the measuring well 2 before the entry of said tube 1 into the arystals chamber 4; the tube 1 may for example have a substantially helicoidal shape. The capillary tube 1 penetrates the crystals chamber 4 through a fluid-tight and electrically insulating barrel 7a and re-emerges therefrom through a barrel 7b identical with the barrel 7a. The portion l_ of the capillary tube 1 passing into the crystals chamber 4 comprises a longitudinal opening 8 formed throughout the length of a generator of this portion of tube la. This opening 8 thus permits the liquid stream cir-culating in the capillary tube to be placed in communicationwith the isomorphous material 5, for example, benzene, stored in the chamber 4.
The capill~ry tube 1 has a length of about 100 cm and represents an electrical resistance of about 1 ohm. The inlet and outlet connections of the tube 1 are formed as insulating joints and are connected, through a switch 10, associated with differential pressure-sensing switch means 11, to a potential difference 12 (mains).
The differential pressure-sensing means 11 is mounted between the inlet 13 of the tube of the measuring circuit on the side of its high pressure connection and the ; outlet 14 of the measuring circuit on the side of its low pressure connection.
On the side of the outlet 14 of the measuring well, a thermosensitive element 15 dips into the outlet section of the capillary tube 1. This element 15 is constituted by a platinum resistance of 100~ at 0C, technically known as "pyrothenax"; its outer end is connected to a continuous temperature recorder 16.
At its outlet 14 from the measuring well 2, the capillary tube 1 is extended perpendicularly to the thermo-sensitive element 15 and its end is provided with a drain 17.
The dynamic behaviour of the whole of the apparatus will now be described.
At the inlet of the circuit, by means of the volumetric pump 21, the constant flow rate of the substance to be analysed is ensured, which permits continuous circulation of the substance in the capillary tube 1.
The analysis unit or measuring well 2 is kept at 0C and, the circulation being established in the capillary tube 1, the sequence of analysis cycles occurs in the manner ~04679Z
described below.
The temperature of the substance to be analysed 5, for example benzene, standing in the chamber 4, drops rapidly since this chamber is in direct thermal contact with the bottom of the cooling well. A~ter a possible, but single, initial overcooling, the product 5 crystallizes in the chamber 4. The liquid stream circulating in the capillary tube 1 is hence in physical contact with isomorphous crystals, which avoids over cooling during its crystallization. In fact, as soon as the liquid benzene flowing in the tube, as a result of its pro-gressive cooling, reaches cry~tallization temperature, there is a solidification of the capillary, or of a considerable portion of the latter without the appearance of a random under cooling phenomenon preceding "clean" crystallization. The stopping of the flow which results from the solidiication of the capillary causes a rise in pressure at the inlet of the capillary and results in closing the pressure-sensitive switch 10; the differential pressure-sensing means 11 connected to this capillary 1 then actuates the starting up of the re-heating sequence by applying an alternating potential differenceto the terminals of the capillary 1, which then behaves as a heating resistance.
The rise in temperature of the whole of the capillary circuit causes fusion of the crystals occurring therein, thus freeing the flow in the capillary, which permits instantaneous return to the initial pressure and thus causes the stopping of the heating.
The relatively large amount of crystals 5 immobilized in the chamber 4, and the fact that the latter are kept at a temperature sufficiently below their melting point, enables their permanence to be ensured, only the layers surrounding the capillary being liable to successive fusions and crystallization.
~046'79Z
Liquid/solid physical contact is thus ensured constantly in spite of the slight mobility of the transition zone.
The sequence of analyses then ~ollow, according to the procedure described above, at the rate of about three per minute. This frequency of recurrence is hence sufficient to permit the analysis to be compared with continuous analysis.
The development of the temperature thus recorded by the device 16 then presents itself in the form of a saw-tooth, whose lower crests locate accurately the successive values of the crystallization temperatures~
The envelope curve of these low crests enables the development of the latter to be followed, although it is of course possible to insert in the recording channel a memory device enabling only the continuous tracing of this low envelope to be recorded.
The apparatus according to the invention has been utilized for the continuous analysis of the crystalliztion point of benzene.
Of course, a relationship exists between the crystallization temperature and the purity of the benzene, whose graphic representation is shown in figure 3. This curve represents the crystallization temperature in degrees centigrade as ordinate, as a function of the purity of the benzene in % as abscissea.
The graph of figure 3 has been calcu ~ ted from cryoscopic constants according to the formula:
Log10 P = 2.00000 - (A/2.3026)(t~ -t~) [1 ~ B(t~ -t~]
where P = percentage of moles of benzene A = 0.01523 molar fraction per degree B - 0.0032 molar fraction per degree t p O= 5.333 ~ 0.010C
:~0467g2 tp - crystallization point in C of the inpure benzene.
By means o~ the apparatus according to the invention, table I given below has been recorded which enables the temperature of crystallization~purity of benzene relationship to be established.
TABLE I
PURITY OF THE BENZENE AS A FUNCTION OF THE
CRYSTALLIZATION POINT
Crystallization %Benzene Crystallization %Benzene point C. point C
-1.0 93.2 3.5 96.9 1.1 3.6 97.1 1.2 93.5 3.7 97.2 1.3 93.7 3.8 97.4 1.4 93.8 3.9 97.5 1.5 94.0 4.0 97.7 1.6 94.1 4.1 97.8 1.7 94.3 4.2 98.0 1.8 94.4 4.3 98.1 1.9 94.5 4.4 98.3 2.0 94.7 4.5 98.4 2.1 94.9 4.6 98.6 2.2 95.0 4.7 98.7 2.3 95.1 4.8 98.9 2.4 95.3 4.9 99.0 2.5 95.5 5.0 99.2 2.6 95.6 5.1 99.3 2.7 95.8 5.2 99.5 2.8 95.9 5.3 99.8 2.9 96.0 5.4 99.8 3.0 96.2 5-5 99 9 3.1 96.3 ~)4679Z
TAB~E I (co:ntin ed~
PURITY OF THE BENZENE AS A FUNCTION OF THE CRYST~LLIZATION POINT
Crystallization ~senzene Crystallization %senzene point C point C
.
3.2 96.5 3.3 96.6 3-4 96.8 From this recording, it appears overall that a fluctuation in purity of 0.15% is manifested by a fluctuation of 0.1C in the crystallization temperature.
For the continuous analysis of the crystallization point of benzene, the extent of measurement corresponds to 2.5C to 5.5C, namely to a purity of95-5 to 99.9%. Since the defined limit corresponds to 1/100 of the length of measurement, it is 0.3C. According to the method of the invention, the repeatability in measured purity is 0.05% and the response time with a momentary variation in purity of 1%
is about 15 minutes.
According to the method of the present invention, it is possible to carry out continuous analyses of the crystallization points of other aromatic substances such as paraxylene or orthoxylene, as well as any substances whose crystallization temperatures are situated between -30C and ambient temperature.
In figure 4, is shown the crystallization temperature in C as a function of the % of purity of paraxylene, this curve having been calculated from the cryoscopic constants.
Below, there is given in Table II the crystallization points recorded by the method according to the invention, as well as the % purity of paraxylene.
1~46792 .
Y
co ~1 r~l ~o CO ~1 ~ ~D 00 ~ ~ U~ X O ~ ~ 00 0 ~ In oO o ~ ~ co ~P
~, rl o ~1 ~ O r-l N ~ ~r 111 ~ t~ 00 ~ O ~1 ~1 ~ ~ Ln ~D 1~ CO ~ O ~1 ~
1 CO 0~ ~O 00 0~ CO OD CO a~ ct> a~ al ~ a~ a~ a~ ~ c~ ~ ~ o o o o o ~ O
D ~D ~ ~ r-- t` 0~ 00 00 OC 00 ~ ~ ~ ~ O O O O ~ ~1 ~1 ~ N ~
h ..... ..... ..... ..... .....
o~
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E~ ,,~ o ,~ ~
O ~1 ~ ~ ~ U~ o ,1 ~ ~ er u~ ~D t` 0~ a~ o _I ~ ~ ~r ..... ... -. .... - ..... .....
a) U~ CO O ~ ~ I~ O ~ ~ I~ ~ ~ ~ ~D ~ _I ~ D CO ~ ~ D 00 0 ~ ~ ~ O O O O ~ ~ ~ ~1 _I ~ ~ ~ ~ ~ ~ ~ ~ ~ er ~r ~r Is7 h ..... ..... ..... ..... .....
dP
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o ~ ~ ~ ~ In ~ r~ co c~ o ~ ~ ~ ~ ~ O ~ ~ ~ ~r ~o ..... ..... ..... ..... .....
c) ~04679Z
~C
1~ O ~ 1~ 0 0 ~ l ~ O t~l ~ I~ O ~1 ~r 1~ o t~ l~ O ~ Lr) 1~ O N ~r ~ O
S~ OOOO~ ~D~D~I` r~t~o~co ooo~ ~oooo ,~,1~
~ ..... ..... ..... ..... ..... .....
op N C~
rl O
~1 rl O O O O O t~ I~ 1` 1` 1` 1--r ~ t~ 1-- OD CO 00 0~ CO C~ 00 CO 00 0~ ~n a~ ~ ~:;~ ~
U~O .... - ..... .,....... ..... .-.- .. ' ~>1 P~ N N N t~ N tN N N N ~ l N N N ~ `l tN N ~ ~l N N N N N N N
C~
~1 ~ ~ 0 0 ~ IJ~ CC~ O ~ 1~ C~ O ~ u) t~ O N 11'1 1~ 0 ~ In 1` 0 N 11~ 1` 0 N 1 ~1 N N ~ ~'7 t~ 00 CO ~ ~ 0~ cn O O O O ~ 1 ~I N N N N 1`'7 ~) ~ ~ el~ ~r O
H ~
~ O
~ .~
~ N O
~ ~1 0 ~1 O ~ ~ ~ ~ ~ ~ ~ ~ ~ O ~ N~ ~ 0~
~r~ ~NN~N N~NNN NNNNN NN~NN NNNNN
~1 ~ON N~ON ~N~ ~ ~ ~o ~ ..... .---- --.- ..... ..... ~
N~
.,1 o r~
_I
O~N~ ~ O~N~ ~.~ O~N~
~NNNN ~NNNN
U~O ..... .. ~..... ..... ..... ..... .....
NN~N~ NNNNN ~NNNN N~N~N NNNNN
~04679Z
a) ~ ~-nro~ n~o~ l~o S~ N N N ~ ~)OO OO C5~ O
..... ..... ..
a~ ~ o u~ ~ ~ ~ cs~~ a~ a~ ~ ~ ~ o d~ ~1 N C.) ~1 IS) ~D ~ ) ~ O ~I N ~ ~r U~
~ cn a~ a~ ~ N N N N N N N
u~ O
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rd r~ O N It~ r~O N lo r~ O N 1~ ~` O N
... ,'. ..... .....
~ o~
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~ O
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N o H rl H _I
r l ~ In u~O ~I N ~ ~r u~ ~D 1~ ao a~
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(1~ ~ ~D 00 0 IY) Lll I` O N Ir) ~` O N 11~ 1`
t~
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.,1 o ~_1 ~ '~D r` ~) ~ O ~I N ~ ei~
~rl ~t~ OOOOO OOOOO
Ul O .......... .....
~1 Q N N N N ~ t~ ~ ~1 ~ ~) ~ ~ ~) ~ t''7 U
1~?4679Z
In Figure 5, the crystallization temperature in C
as a function of the percentage purity of orthoxylene is shown by a curve calculated from the cryoscopic constants.
Below, is given in Table III the crystallization points read in a continuous analysis of orthoxylene according to the method of the invention and the percentage purity of the orthoxylene.
TABLE III
PURITY OF THE ORTHOXYLENE AS A FUNCTION OF THE
CRYSTALLIZATION POINT
Crystallization point % paraxylene -29.0 90.2 -29.1 90.~
-29.2 89.7 -29.3 89.5 -29.4 89.3 -29.5 89.0 -29.6 88.8 -29.7 88.5 -29.8 88.3 -29.9 88.1 ~30.0 87,8 -30.1 87.6 -30.2 87.3 ~30-3 87.1 86.9 -30.5 86.5 -30.6 86.4 ~30-7 86.2 -30.8 85.9 -30.9 85.7 ~04679Z
TABLE~III (continued) Crystallization point ~ paraxylene -31.0 85.4 -31.1 85~2 -31.2 85.0 The continuous analysis of the crystallization point of an aromatic hydrocarbon enables the purity of the analysed substance to be determined continuously and hence this data to be transmitted directly to a processing system for said hydrocarhon, for example a distillation column, in order to cause the parameters to vary correspondingly.
Claims (5)
1. Method for the continuous automatic analysis of the crystallization point of liquid substances, comprising passing the substance to be analysed through a measuring circuit at a constant flow rate, the temperature therein being maintained at a value sufficiently below the assumed crystal-lization point of the substance, heating means being provided along the flow path of the liquid substance in said circuit, maintaining the substance in the course of cooling in contact with an isomorphous crystalline material, automatically turning on and off said heating means respectively at two characteristic temperatures, detected by measuring the pressure drop or difference of pressure of the substance at the inlet and at the outlet of the measuring circuit, variations of the pressure drop being effected as a function of temperature, the values thus measured of the pressure drop being utilized as control data for respectively turning on and off the heating means when the temperature of the substance at the outlet reaches one of its two characteristic values, the first corresponding to the crystallization temperature level, whilst the other corresponds to a temperature sufficiently above said crystal-lization point, and continuously recording the temperature of the substance at the outlet of the circuit, which constitutes a value representing the crystallization point of the substance.
2. Method according to Claim 1 wherein said substance is an aromatic hydrocarbon.
3. Method according to claim 2, wherein the liquid substance is benzene, paraxylene or orthoxylene.
4, Apparatus for carrying out a method for the continuous auto-matic analysis of the crystallization point of liquid substances, comprising a measuring circuit constituted by a capillary tube of stainless steel adapted to be traversed by the substance to be analysed, means for maintaining a constant flow rate by a small volumetric pump, the capillary tube having a large portion of its length immersed in a cooling liquid bath contained in a measuring well, the bottom of the latter being arranged in the form of a fluid-tight crystals chamber adapted to contain an isomorphous crystalline material, a short portion of the capillary tube extending through said chamber, the isomorphous material being able to contact the substance to be analysed, through an opening formed in the portion of the tube situated in said chamber, the inlet and the outlet of the capillary tube in the well being connected externally to the well, to two electrical leads of which one is connected directly to the supply whilst the other is connected to differen-tial pressure-responsive switching means, mounted between the inlet and the outlet of the capillary tube, whilst a thermosensitive element is posi-tioned at the outlet of the measuring well in the flow path of the substance to be analysed and is coupled to a recording device.
5. An apparatus according to claim 4, wherein the opening formed in the portion of the tube situated in the crystal chamber is a longi-tudinal opening along a generator of said portion of the tube.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7508934A FR2304913A2 (en) | 1975-03-21 | 1975-03-21 | METHOD AND DEVICE FOR THE AUTOMATIC CONTINUOUS ANALYSIS OF THE CRYSTALLIZATION POINT OF LIQUID PRODUCTS, IN PARTICULAR OF AROMATIC HYDROCARBONS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1046792A true CA1046792A (en) | 1979-01-23 |
Family
ID=9152909
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA248,262A Expired CA1046792A (en) | 1975-03-21 | 1976-03-19 | Method and apparatus for the continuous automatic analysis of the crystallization point of liquid substances |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5287091A (en) |
| BE (1) | BE839078R (en) |
| CA (1) | CA1046792A (en) |
| DE (1) | DE2610405A1 (en) |
| FR (1) | FR2304913A2 (en) |
| GB (1) | GB1527151A (en) |
| IT (1) | IT1057995B (en) |
| NL (1) | NL7602936A (en) |
| SE (1) | SE7603409L (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2521301A1 (en) * | 1982-02-11 | 1983-08-12 | British Petroleum Co | METHOD AND DEVICE FOR THE CONTINUOUS ANALYSIS OF THE OIL FLOW POINT |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3577765A (en) * | 1967-12-26 | 1971-05-04 | Monsanto Co | Apparatus for determining crystalization temperature |
| DE1958476C3 (en) * | 1969-11-21 | 1974-03-14 | Farbwerke Hoechst Ag, Vormals Meister Lucius & Bruening, 6000 Frankfurt | Device for measuring the solidification temperature of liquids |
| FR2244383A5 (en) * | 1973-09-19 | 1975-04-11 | Antar Petroles Atlantique |
-
1975
- 1975-03-21 FR FR7508934A patent/FR2304913A2/en active Granted
-
1976
- 1976-03-01 BE BE164764A patent/BE839078R/en active
- 1976-03-12 DE DE19762610405 patent/DE2610405A1/en not_active Withdrawn
- 1976-03-15 IT IT48571/76A patent/IT1057995B/en active
- 1976-03-18 SE SE7603409A patent/SE7603409L/en unknown
- 1976-03-19 CA CA248,262A patent/CA1046792A/en not_active Expired
- 1976-03-19 NL NL7602936A patent/NL7602936A/en not_active Application Discontinuation
- 1976-03-19 GB GB11168/76A patent/GB1527151A/en not_active Expired
- 1976-03-19 JP JP2939076A patent/JPS5287091A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB1527151A (en) | 1978-10-04 |
| BE839078R (en) | 1976-09-01 |
| FR2304913B2 (en) | 1978-03-17 |
| JPS5287091A (en) | 1977-07-20 |
| FR2304913A2 (en) | 1976-10-15 |
| NL7602936A (en) | 1976-09-23 |
| DE2610405A1 (en) | 1976-09-30 |
| SE7603409L (en) | 1976-09-22 |
| IT1057995B (en) | 1982-03-30 |
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