EP2419719A1

EP2419719A1 - Method and device for measuring the dew point temperature of a gaseous element

Info

Publication number: EP2419719A1
Application number: EP10723663A
Authority: EP
Inventors: Christophe Mathonat; Fabien Thomas; Christophe Hein
Original assignee: Total Raffinage Marketing SA; Societe dEtudes dAutomatisation de Regulation et dAppareils de Mesures SETARAM SAS
Current assignee: Societe dEtudes dAutomatisation de Regulation et dAppareils de Mesures SETARAM SAS; TotalEnergies Marketing Services SA
Priority date: 2009-04-14
Filing date: 2010-04-13
Publication date: 2012-02-22
Also published as: WO2010119220A1; FR2944353B1; FR2944353A1

Abstract

The invention relates to a device and to a method for the implementation thereof for measuring the dew point temperature of a gaseous element, alone or in a mixture, which can have a low calorific capacity and/or an aggressive chemical character like sulfur, circulating for example in a pipe, working at a range of temperatures varying from around 100 to 400°C and providing an optimized precision in the measure due to an optimized signal-to-noise ratio. For this purpose, the device includes in particular a calorimetric unit (2), two thermometric means (3, 4) and a measuring surface (8), each of the latter (3, 4, 8) being in direct thermal contact with the calorimetric unit and the gaseous element. Each thermometric means is capable of generating a signal representative of the thermal effect associated with the condensation and/or the evaporation of the gaseous element on said surface (8).

Description

DEVICE AND METHOD FOR MEASURING THE TEMPERATURE OF THE ROSED POINT OF A GAS ELEMENT

The present invention relates to a device and its associated method for measuring the dew point temperature of a gaseous element, alone or in a mixture, said device being based on the principle of differential calorimetry.

Many industrial applications require the measurement of the dew point temperature, in particular that of the dew point of water vapor in gases, for example for industrial drying applications in order to ensure the evaporation of the water. Such a measure may also concern, but not limitatively, an organic solvent contained in a product or a corrosion or frost alarm in installations.

More particularly, the field of use of the device and method of the present invention relates to the chemical, oil and gas industries, and in particular the CLAUS units for producing liquid sulfur from a gaseous element rich in hydrogen sulphide and carbon dioxide. sulfur, in which the knowledge of the dew point temperature of the sulfur element makes it possible to optimize the operation of the unit.

It is to this latter application that reference will be made more particularly in the remainder of the present description, but the device and method, objects of the present invention, apply to any type of measurements of the temperature of the point of contact. dew of a gas, alone or in mixture, in the turbulent or laminar state, for example in a pipe.

Subsequently and within the meaning of the present invention, the expression "dew point" or "dew point temperature" means the temperature below which, at the pressure considered, the vapor of a gaseous element, condenses.

With regard to sulfur, the temperature of its dew point is the temperature from which the first drop of liquid sulfur appears on a support considered. The CLAUS reaction, which converts hydrogen sulphide (H2S) from petroleum desulfurization to non-toxic elemental sulfur (S) and also useful raw material, being exothermic, conversion of I 2 S to liquid S is favored by low temperatures. . This being the case, it is nevertheless necessary to maintain the temperature of the catalytic reactor at a sufficient level, to avoid the appearance of liquid sulfur on the surface of the catalysts, which can lead to clogging of the support reactor of said catalysts.

Thus, it is necessary that the set temperature (Tc) imposed on the inlet of the catalytic reactor is set so that the outlet temperature (Ts) of the same catalytic reactor is greater than the dew point temperature of the sulfur at the outlet said reactor. This applies to each of the catalytic reactors that the CLAUS unit can count. Today, the adjustment of the Tc is done empirically, known to those skilled in the art, so that the Ts adopts the desired value significantly higher than the temperature of the dew sulfur.

Indeed, the dew point temperature of sulfur being unknown, and depending in particular on the composition of the gas which is not fixed, the temperature Tc is generally adjusted to a level which has several tens of degrees Celsius more than the temperature Ts expected at the outlet of this same reactor, that is to say, much higher than the sulfur dew point temperature. This allows the operator to have a "comfortable" safety margin with regard to the temperature of appearance of the first drops of sulfur dew. This technique, however, has the major disadvantage of being penalizing from an economic and environmental point of view, because, as the operation of the unit is not optimized, the conversion rate to sulfur does not reach, de facto, its optimum, which results in waste gas loaded with acid gases requiring a more important complementary treatment, also called in the profession, tail gas treatment.

A process for optimizing the step of CLAUS units has recently been proposed by the Applicant (WO 2007/096512) to optimize the operation of the process of converting I 2 S to liquid S from the precise knowledge of the dew point of sulfur, allowing to operate as close as possible to this value, thanks to its continuous measurement to optimize reactor temperatures and increase the efficiency of the CLAUS unit.

It therefore appears important to be able to have on the market a device allowing the precise on-line measurement of the sulfur dew point temperature in order to be able to work, for example for the CLAUS process units, as close as possible to this point. measured dew and therefore with a better conversion efficiency from IΗ2S to S liquid.

Several solutions have been proposed, such as EP 0 202 453 which describes a device for measuring the temperature of the dew point of a gas, in particular water vapor, comprising a calorimetric block, resistive type heating means, a cooling module and an outer envelope incorporating two thermopiles positioned on either side of the axis of symmetry of said block, one of the two thermopiles serving as a reference being thermally insulated from the calorimetric block by a thermal barrier. The heating means are arranged inside the calorimetric block, near the thermopiles.

The measurement of the dew point is then performed by a so-called direct method which consists in detecting the variation of the signal emitted by the thermopile, referred to as the measurement, as soon as the condensate appears on its condensation surface when the temperature decreases. of this surface, and to measure the corresponding temperature by means of a temperature sensor integrated on the surface of the thermopile. This method is furthermore carried out with a laminar gas flow in a controlled atmosphere by a fan disposed above the condensing surface.

EP 0542 582 describes a technical evolution of EP 0 202 453 comprising a calorimetric block, resistive type heating means, a cooling module and a single thermal probe integrated in the calorimetric block. The measurement of the dew point is carried out as in EP 0 202 453 by a direct method by detecting the condensation of the gas on the surface of the thermal probe and by measuring the temperature of the latter at this time.

These devices and methods have several drawbacks among which: the presence of a thermal barrier in the sensor which is conducive to a drift of the measurement signal, which can also be enhanced by the presence of several thermal bridges between the two thermopiles on the one hand, and the calorimetric block of somewhere else,

the measurement of the dew point temperature of the gaseous element is essentially based on the detection of the condensation of said gaseous element on the surface of the thermal probe, which condensation is considered to be homogeneous and which can not create a significant difference between the measured signals, for example by the two thermopiles,

the absence of use mentioned for an application to gaseous elements flowing in a turbulent type flow,

it is essentially the measurement of the temperature of the dew point of the water that is described, in particular for an industrial drying application,

the measurement of the dew point of a gaseous element with a low heat capacity, in particular with a heat capacity strictly lower than that of water and with an aggressive chemical character, as in the case of sulfur, is not mentioned,

- The use of a single thermal probe is drift generator for the measured signal, causing de facto an additional difficulty for the measurement of the dew point temperature.

In addition, if WO 2007/096512 describes a method for optimizing the operation of CLAUS units as indicated above, no technical element on the device for measuring the dew point temperature of sulfur and on a measurement method using such a device are described in the document.

There is therefore a need in the art relating to a device and its method of implementation for measuring the dew point temperature of a gaseous element, alone or as a mixture, which may have a low heat capacity and / or an aggressive chemical character such as sulfur, circulating for example in a pipe, allowing to work in a range of temperatures ranging from a hundred degrees to 400 ⁰ C and offering improved accuracy of measurement due to a ratio optimized signal / noise. To this end, a first object of the invention is a device for measuring the dew point temperature of a gaseous element, alone or as a mixture, comprising: at least one calorimetric block intended to regulate and homogenize the temperature of the device, at least two thermometric means, each thermometric means being in direct thermal contact with the calorimetric block, a measurement surface in direct thermal contact with the thermometric means and the gaseous element, in which each thermometric means is capable of generating a signal representative of the thermal effect associated with the condensation and / or evaporation of the gaseous element on said measuring surface, the calorimetric block and the thermometric means (3, 4) being contained in an outer envelope, one face of which comprises the measuring surface in direct thermal contact with the gaseous element, and wherein said measuring surface in thermal contact means and with the gaseous element is resistant to chemical corrosion.

Such a device makes it possible to optimize the measurement of the dew point due to the presence of two thermometric means in direct thermal contact with the measuring surface and the calorimetric block.

Advantageously, these elements are contained in an outer envelope, one face of which comprises the measurement surface in direct thermal contact with the gaseous element.

Direct thermal contact means a contact without thermal barrier or thermal bridge. Surfaces in direct thermal contact can thus be in physical contact with one another, or be separated by a thermal conductive material disposed in such a way between said surfaces that it excludes thermal barriers and thermal bridges.

Advantageously, the measurement surface is the external face of a flat plate integral with the outer casing, in thermal contact direct with the thermometric means, and allowing a thermal measurement through its thickness.

Such a plate will for example be used in an aggressive environment and may be secured to the outer casing so as to form a sealed enclosure.

In a variant, the flat plate is made in one piece with the outer casing, thus simplifying the production and mounting of the device.

Advantageously, the outer casing of the device is made of a material resistant to chemical corrosion, which allows the use of the device in an aggressive medium.

Alternatively, the measuring surface is part of the thermometric means.

Advantageously, the temperature regulation of the calorimetric block is performed by at least one heating means, preferably of the resistive type, and at least one cooling means associated with the calorimetric block.

Advantageously, the calorimetric block contains at least one probe for measuring the temperature.

The calorimetric block may be made of a material chosen from all suitable metallic materials, alloys, plastics or composites, alone or as a mixture, and preferably made of copper, and even more preferably silver.

Advantageously, the device contains two thermometric means positioned on either side of an axis of symmetry of the calorimetric block.

The thermometric means may be selected from thermocouples, fluxmeters, thermopiles, Peltier elements, also called thermoelectric modules. Advantageously, a computer processing chain of the signals generated by the thermometric means is associated with said device.

Another subject of the invention relates to a method for measuring the dew point temperature of a gaseous element, alone or as a mixture, by means of a device according to the invention, comprising the following steps:

the device is arranged in the gaseous flow comprising the gaseous element so that the measurement surface is positioned in thermal contact with said gaseous flow,

- Cooling and heating cycles of the calorimetric block are successively carried out so that the measuring surface in contact with the gaseous element can condense said gaseous element on itself during cooling, then evaporate it during heating,

the differential electrical signals emitted by the thermometric means are measured, these signals being representative of the temperature changes of the measuring surface due to the thermal effects associated with the effects of condensation or evaporation of the gaseous element,

the measured electrical signals are recorded,

- The electrical signals are then processed by computer means to deduce directly, or through a prior calibration, the temperature of the dew point of the gaseous element.

For example, a measurement cycle, corresponding to a cooling and heating cycle of the calorimetric block, consists of heating the measuring surface by means of the calorimetric block to a temperature T _sup greater than the dew point temperature. assumed, followed by cooling of this surface to a temperature T _m f below the presumed dew point temperature, and then reheating of the measurement surface to the temperature T _sup . Advantageously, the measuring surface is disposed substantially vertically.

By substantially vertically, it is understood that the measuring surface comprises an angle between +/- 20 °, preferably between +/- 10 ° and even more preferably between +/- 5 ° with respect to the direction of gravity.

The Applicant has indeed found that, due to this particular position of the thermometric means, the amplitude of the signal is greater, thus improving the accuracy of the measurement.

In particular, in the case of evaporation, it starts at one end of the measurement surface and ends at the other end.

Advantageously, the electrical signals representative of the temperature changes of the measuring surface are recorded for the evaporation effect of the condensed gas element.

In the implementation of the method, the temperature of the device may be varied between 100 ^° C. and 400 ^° C., and preferably between 150 ^° C. and 350 ^° C., during a cooling and heating cycle.

The invention also relates to the use of the device according to the invention and the method according to the invention for measuring the dew point temperature of a gaseous element, alone or as a mixture, preferably sulfur.

In particular, the device and the method according to the invention can be used to determine the dew point temperature of a gaseous element, alone or as a mixture, flowing in a laminar or turbulent type flow.

In particular, the gaseous element may have a low heat capacity, preferably less than that of water. The invention finally relates to the use of the device according to the invention and the method according to the invention for controlling a conversion unit, preferably for the conversion of hydrogen sulfide to liquid sulfur.

The invention has several advantages, and in particular that making it possible to accurately determine the dew point temperature of sulfur. Indeed, the presence of two thermometric means makes it possible to limit the drifts of the measured signals.

In addition, the device can be implemented to measure the dew point by evaporation, the amplitude of the signals emitted in the latter configuration is greater, hence de facto, a better accuracy of the measurement.

Thus, the heating temperature Tc at the inlet of a catalytic reactor of a CLAUS unit is adjusted so that the outlet temperature Ts of said reactor is greater than the dew point temperature of 5 °. C at 20 ^° C., and more advantageously from 5 ° C. to 10 ^° C. instead of several tens of degrees, or even greater up to 100 ^° C., at the supposed temperature of the dew point of the sulfur, as such is the case in Art.

This precise knowledge of the dew point of sulfur thus makes it possible to reduce the operating temperature of the reactors of the CLAUS units, while increasing the efficiency of said units. This increase in yield leads to a decrease in the quantity of untreated residual sulfur species, called tail gas, in particular H2S and SO2. Thus, the size of the complementary treatment units of these waste gases is also optimized, resulting in an additional energy and economic gain. In addition, the invention is not only applicable to new units, but also to pre-existing units.

Finally, another important advantage lies in enabling the conversion of sulfur to be facilitated, with easier respect for the environmental aspect, which becomes more and more restrictive with SO2 emission quotas are increasingly declining in number of days and cumulative.

The invention also relates to a hydrogen sulphide (H2S) partial combustion gas treatment plant comprising at least:

(i) a furnace supplied with H2S and producing said SO2-containing hydrogen sulfide partial combustion gas,

(ii) a catalytic bed reactor, and

(iii) a condenser of the oven exit gases; said gases successively circulating in the furnace, the catalytic bed reactor, and the capacitor, characterized in that it further comprises a device (1) for measuring the dew point temperature of a gaseous element, alone or in admixture, comprising:

at least one calorimetric block intended to regulate and homogenize the temperature of the device,

at least two thermometric means, each thermometric means being in direct thermal contact with the calorimetric block,

a measuring surface in direct thermal contact with the thermometric means and the gaseous element, in which each thermometric means is capable of generating a signal representative of the thermal effect associated with the condensation and / or evaporation of the gaseous element on said measuring surface; said device being placed between the catalytic bed reactor and the capacitor.

More particularly, the calorimetric block and the thermometric means are contained in an outer casing, one face of which comprises the measuring surface in direct thermal contact with the gaseous element, and wherein said measurement surface in direct thermal contact with the gaseous element is resistant to corrosion.

Advantageously, the installation may further comprise a partial combustion gas heater. In particular, the installation could comprise from 1 to 3 catalytic bed reactors, from 1 to 4 capacitors, from 0 to 3 gas heaters, the device being placed between the catalytic bed reactor farthest from the furnace and the capacitor the following immediately, it being understood that the catalytic bed reactor farthest from the furnace will be the one that will process the smallest amounts of H ₂ S.

The invention will be better understood on reading the detailed description of the device and the associated method with reference to the non-limiting drawings, in which:

FIG. 1 schematically represents a device that is the subject of the present invention,

FIG. 2 is a curve representing the signal resulting from the two thermometric means as a function of the temperature of the calorimetric block, obtained during the use of the device according to the invention for measuring the dew point of a gaseous mixture,

FIGS. 3 to 5 are curves similar to those of FIG. 3, each corresponding to the measurement of a gaseous composition of known dew point temperature, with a view to calibrating the device according to the invention.

The device represented in FIG. 1 comprises: a calorimetric block 2 intended to regulate and homogenize the temperature of the device 1,

two thermometric means 3, 4 capable of generating a signal representative of the thermal effect associated with the condensation and / or the evaporation of the gaseous element.

The thermometric means 3, 4 are each in direct thermal contact with the calorimetric block 2, in the example shown, in physical contact.

The thermometric means 3, 4 and the calorimetric block 2 are contained in an outer envelope 7, 9, one face of which has a measuring surface 8 in direct thermal contact with the gaseous element, the thermometric means 3, 4 also being in contact with each other. direct thermal with said measurement surface 8. In general, the device 1 is of cylindrical shape and the calorimetric block 2 is equipped with a heating means 5 and a cooling means 6.

These heating and cooling means 6 are in contact with the calorimetric block.

The heating means 5 is preferably a system consisting of one or more heating resistor (s) surrounding (s) the calorimetric block 2. This heating means makes it possible to raise the temperature of the calorimetric block, for example, up to 400 ^° C., at a speed that can vary from 10 ° C. to 50 ° C. per minute.

The cooling means 6, disposed on one face of the calorimetric block 2, makes it possible to lower the temperature of the latter, for example from 400 ^° C. to 100 ^° C., or less, at a speed of up to 10 ^° C. or 20 ⁰ C, or more, per minute. Said cooling means may be fed with a refrigerated fluid flowing respectively through the A and B inputs provided in the device 1, object of the present invention.

The main function of the calorimetric block 2 is to bring the device to a predetermined temperature and homogenize said temperature so that the thermometric means 3 and 4, and the measurement surface 8, reach the desired temperature. At least one probe, not shown in FIG. 1, for example of the thermocouple type, is installed within this calorimetric block 2 in order to measure and therefore regulate the temperature of said block, and consequently the temperatures of the thermometric means and the temperature. measuring surface 8.

The calorimetric block 2 is made of a material chosen from all suitable metallic materials, alloys, plastics or composites, alone or as a mixture, and preferably made of copper, and even more preferably of silver.

The two thermometric means 3 and 4 are arranged between the calorimetric block 2 and the gaseous element. These means are arranged on either side of the axis of symmetry of the calorimetric block 2, so that their two largest parallel faces are directly in thermal contact, without thermal barrier or thermal bridge, respectively with said calorimetric block 2 and the gaseous element, whose dew point temperature is to be determined. In the case of a corrosive chemical gas element, a thin, preferably planar, layer of chemically resistant metal is arranged in direct thermal contact with the thermometric means 3 and 4 and the gaseous element to be analyzed, the outer face of the thin layer of metal then constituting the measuring surface 8.

The thermometric means 3 and 4, the function of which is to measure the possible thermal effects due to condensation or evaporation of a gaseous element on their surface, or on a surface thermally in contact, may be, without limitation, thermocouples , fluxmeters, thermopiles, Peltier elements, also called thermoelectric modules.

The two thermometric means 3 and 4 cited above are held in position in a mechanical frame which is itself included, for the purposes of protection against possible external attack, in the outer casing made of a material resistant to corrosion, for example a austenitic stainless steel type 304 (18% Cr-8% Ni) and preferably type 316 (18% Cr-8% Ni-2% Mo).

This envelope can consist of two parts:

an enclosure which has a mechanical and chemical protection function, which comprises the outer casing 7 and its rear face 9,

- A thin flat metal plate whose outer face is the measuring surface 8, to allow a thermal measurement by the two thermometric means 3 and 4 through its thickness.

The constituent materials of the device described in this example have been specially selected to withstand a temperature of 350 ^° C., preferably 400 ^° C. The dimension of the device is calculated as a function of the size of the thermometric means used, for example a diameter of 100 mm, a total length of 140 mm and a weight of 5 kg, for thermometric means arranged inside with dimensions ranging from 10 to 50 mm.

Obviously, the device can evolve in its shape, but it will always consist of at least one calorimetric block 2 regulated in temperature and two thermometric means 3 and 4, directly in thermal contacts with said block and the gaseous element, also directly or by means of a thin metal plate, of a thickness of less than 5 mm and preferably of 2 mm, the outer face of which constitutes the measuring surface 8.

The outer casing may also have the particularity of being integral, the measuring surface 8 being integral with this casing.

In the case where the thermometric means 3 and 4 consist of a chemically robust material with respect to the corrosive gas to be analyzed, for example sulfur, it no longer becomes necessary to use a metal plate to constitute the measuring surface 8. The upper face of each of the thermometric means 3 and 4 would then constitute this measuring surface 8.

The device for detecting the dew point of sulfur, object of the present invention is a measuring instrument based on the principle of differential calorimetry. Its two thermoelectric modules 3 and 4 are intended to measure the thermal effect (the heat flux) associated with the condensation and / or the evaporation of the gaseous element, for example sulfur. The signals emitted by each of the two modules correspond to the difference in heat flux, and therefore temperature, between two points of their surface. These signals are then taken into account in a computer processing chain for their ultimate exploitation by humans or in an automated process.

The device is provided with an input-output C for the electrical cables supporting the measurement signals of the thermometric means, the thermocouple for measuring the heating of the calorimetric block and also the supply of the heating means 5.

The device 1, and more exactly its measuring surface 8, is positioned directly on the process line (for example the CLAUS process) in which the gaseous element to be analyzed flows in a flow, for example of the turbulent type, so as to the measuring surface is directly in contact with said gas flow, the device being oriented so that the measurement surface 8 is in a substantially vertical plane. The thermal effect associated with the condensations and / or evaporation will cause a heterogeneous temperature change along the metal support plate of the measuring surface 8 and therefore a variation of the amplitude of the generated signal different for each thermometric means.

The heterogeneity of the evaporation phenomenon will be preferred to the condensation. The heterogeneity of the evaporation phenomenon at the measuring surface 8 is measured in particular by virtue of the correct orientation of the thermometric means as indicated above. It causes a difference in temperature and heat flow between the two thermometric means, thereby generating differential electrical signals for the appearance of the evaporation peak of the gaseous element, signals becoming more easily usable by a computer processing chain of measurement. .

The method of implementing the device according to the present invention consists in successively carrying out cooling cycles and then heating the calorimetric block 2, thus the measuring surface 8, so as to condense the sulfur on the surface. measuring surface during cooling, then to evaporate said sulfur during heating. Generally starting from a "high" temperature level higher than the dew point temperature of the gaseous element, for example sulfur, to then cool in a linear manner, to cross the dew point and thus to condense the sulfur up to to reach a "low" landing. Then, the device is heated again to cross the dew point, evaporate the sulfur and again reach the "high" landing.

The differential electrical signals emitted by the two thermometric means 3 and 4 are recorded during the cooling and heating cycles.

Three methods of identifying the dew point can then be used:

1. the direct measurement of the dew point by detecting the phenomenon of condensation. This measurement is generally difficult because the condensation is a homogeneous low energy phenomenon which results in an electrical signal, coming from the thermometric means, weakly exploitable because of low amplitude.

2. the indirect measurement of the dew point by the detection of the phenomenon of evaporation which is, in the case of the present invention, a phenomenon of heterogeneous type. Evaporation causes local cooling at the surface of the Measurement 8. The evaporation takes place at slightly different times depending on the position on the measuring surface, the thermometric means then measuring a greater difference in heat flow. The phenomenon of evaporation is visible by the appearance of a peak of the differential signal corresponding to the signal difference between the two thermometric means 3 and 4, this peak corresponding to a break in equilibrium between the two thermometric means. The differential signal, due to evaporation, due to its amplitude (the higher the peak, the stronger the evaporation phenomenon, the more condensate and therefore the lower the dew point) and / or its position in time allows, thanks to a prior calibration, to go back to the dew point.

3. the iterative measurement through different cycles continuously by varying the temperature of the low plateau. There is obtained either a signal corresponding to the peak of evaporation in the case where the temperature of said low plateau is lower than the dew point, or no signal in the case where the temperature of the low plateau is greater than the dew point. This is an iterative all-or-nothing detection. Indeed, by iterating the cycles, one finds a temperature range in which is the dew point. This measurement method is longer than the two previously mentioned.

The second method of dew point identification is preferred since it relies on evaporation of the gaseous element, allowing a more significant measurement by a higher signal level.

The invention also relates to the use of the device and method of the present invention for measuring the dew point temperature of a gaseous element, preferably sulfur, in order to control a chemical unit of conversion, preferably conversion of hydrogen sulfide to liquid sulfur.

The use of the device installed on the charges of the various reactors of the CLAUS units and the implementation of the method, objects of the present invention, make it possible to determine the temperature of the sulfur dew point several times per hour in each of the reactors of the units. Claus, while facilitating the achievement of conversion imposed by the regulations on gaseous emissions, also allowing savings on the sizing of a tail gas treatment unit in the conversion chain.

Example

In a conversion unit of an H2S and SO2 mixture into

Liquid sulfur, CLAUS type of a petroleum refinery, the device according to the present invention is installed at the outlet of two reactors in which the sulfur compounds are converted into elemental sulfur.

The constitution of said device is in accordance with the present description and comprises in particular: a calorimetric block made of copper,

two thermometric means of thermopile type,

a resistive type heating means consisting essentially of a nickel-chromium heating wire, a water-radiator type cooling means, a casing made of a 316 stainless steel material,

- included in this envelope, a thin plate covering the thermometric means also made of stainless steel 316, having a thickness of 1 mm and whose outer face is the measurement surface of the device, - the device has a diameter of 140 mm, a height of 145 mm and a weight of 5 kg.

The device described above, and more precisely its measurement surface, is positioned directly on the outlet pipes of the reactors in which the gaseous element, the dew point temperature of which is to be measured, flows in a turbulent flow.

The measuring surface of the device is positioned in such a way that the thermometric means are preferably arranged on a vertical plane.

Heating and cooling cycles are carried out on both sides of the dew point. During a cycle, the temperature of the calorimetric block is first raised to 350 ^° C. and then cooled to 120 ^° C., and then heated to 350 ° C.

Sulfur condenses on the measurement surface that has become cold and then evaporates when the temperature rises.

The heating and cooling cycles are 3 per hour of operation or more.

The differential signals from the two thermometric means make it possible, after treatment in a calculation chain and prior calibration, to evaluate the dew point temperature of the sulfur.

In the example, the difference in electrical potential between the two thermopiles (in micro volts) is measured as a function of the temperature of the calorimetric block.

A / Use of the device and method objects of the present invention

FIG. 2 represents the recording of the signals coming from the thermometric means during a complete cycle of operation as described above, the arrows indicating the direction of unwinding of the cycle in time.

The sinusoidal signal S observed corresponds to the physical phenomenon of evaporation. The dew point temperature can be deduced after calibration of the device.

B / Calibration of the device

In order to determine the dew point temperature from a signal of the type recorded in FIG. 2, it is also essential to calibrate the device.

For this purpose, three operating cycles are carried out as described above, during which three gaseous compositions (or gaseous) standards are tested, the dew-temperature of which is known.

Figures 3, 4 and 5 show, respectively, the heating period during which the evaporation phenomenon is observed, for three cycles of operation in which the device is tested with gaseous compositions having known dewpoint temperatures, 160 ^° C., 170 ^° C. and 180 ^° C.

The position of the signal measured on each curve is marked for the corresponding dew point temperature and thus makes it possible to calibrate the device by establishing a curve representing the dew point temperature as a function of the temperature of the calorimetric block.

C / Online Measurements The measurement system placed in the gas pipeline provides the dew point temperature of the unit for a given moment.

Continuous measurements, taken at predetermined time intervals, for example of the order of 20 minutes, make it possible to drive the CLAUS unit as close as possible to the measured temperature of the dew point of the sulfur, in particular 5 ^° C. above ^zero . above this temperature.

Claims

Device (1) for measuring the dew point temperature of a gaseous element, alone or in a mixture, comprising:

at least one calorimetric block (2) intended to regulate and homogenize the temperature of the device (1), at least two thermometric means (3, 4), each thermometric means (3, 4) being in direct thermal contact with the block calorimetric (2),

a measuring surface (8) in direct thermal contact with the thermometric means and the gaseous element, in which each thermometric means (3, 4) is able to generate a signal representative of the thermal effect associated with the condensation and / or evaporation of the gaseous element on said measurement surface (8), the calorimetric block (2) and the thermometric means (3, 4) are contained in an outer envelope (7, 9), one of which comprises the measuring surface (8) in direct thermal contact with the gaseous element, and wherein said measuring surface (8) in direct thermal contact with the gaseous element is resistant to chemical corrosion.

2. Device according to claim 1, characterized in that the measuring surface (8) is the outer face of a flat plate integral with the outer casing and allowing a thermal measurement through its thickness.

3. Device according to claim 2, characterized in that the flat plate is made in one piece with the outer casing (7, 9).

4. Device according to one of claims 1 to 3, characterized in that the outer casing (7, 9) of the device (1) is made of a material resistant to chemical corrosion.

5. Device according to claim 1, characterized in that the measuring surface (8) is part of the thermometric means.

6. Device according to one of claims 1 to 5, characterized in that, at the calorimetric block (2), is associated at least one heating means (5), preferably resistive type, and at least one cooling means (6).

7. Device according to one of the preceding claims, characterized in that the calorimetric block (2) contains at least one probe for measuring the temperature.

8. Device according to one of the preceding claims, characterized in that the calorimetric block (2) is made of a material selected from all suitable metallic materials, alloys, plastics, or composites, alone or in a mixture, and preferably constituted copper and even more preferably silver.

9. Device according to one of the preceding claims, characterized in that the thermometric means (3, 4) are selected from thermocouples, fluxmeters, thermopiles, Peltier elements, also called thermoelectric modules.

10. A method for measuring the dew point temperature of a gaseous element, alone or as a mixture, by means of a device (1) according to claims 1 to 9, comprising the following steps: (1) in the gaseous flow comprising the gaseous element so that the measurement surface (8) is positioned in thermal contact with said gaseous flow,

- Cooling and heating cycles of the calorimetric block (2) are successively carried out so that the measuring surface (8) in contact with the gaseous element can condense said gaseous element on itself during the cooling, then the evaporate during heating,

the differential electrical signals emitted by the thermometric means (3, 4) are measured, these signals being representative of the temperature changes of the measuring surface (8) due to the thermal effects associated with the effects of condensation or evaporation of the gaseous element - the measured electrical signals are recorded, - The electrical signals are then processed by computer means to deduce directly, or through a prior calibration, the temperature of the dew point of the gaseous element.

11. The method of claim 10, characterized in that the measuring surface is disposed substantially vertically.

12. Method according to one of claims 10 or 11, characterized in that the electrical signals representative of the temperature changes on the measuring surface (8) are recorded for the evaporation effect of the condensed gas element.

13. Method according to one of claims 10 to 12, characterized in that the temperature of the device (1) is varied between 100 ⁰ C and

400 ^° C., and preferably between 150 ° C. and 350 ^° C., during a cooling and heating cycle.

14. Use of the device according to claims 1 to 9 and the method according to claims 10 to 13 for measuring the dew point temperature of a gaseous element, alone or in mixture, preferably sulfur.

15. Use according to claim 14, wherein the gaseous element, alone or in mixture, circulates in a laminar or turbulent flow type.

16. Use according to claim 14 or 15, wherein the heat capacity of the gaseous element is low, preferably lower than that of water.

17. Use of the device according to claims 1 to 9 and the process according to claims 10 to 13 for controlling a conversion unit, preferably for the conversion of hydrogen sulfide to liquid sulfur.

18. Hydrogen sulfide (H2S) partial combustion flue gas treatment plant, comprising at least: (i) a furnace fueled with H2S and producing said hydrogen sulfide partial combustion gas containing SO2, (ii) a reactor with a catalytic bed, and

(iii) a condenser of the oven exit gases; said gases successively circulating in the furnace, the catalytic bed reactor, and the capacitor, characterized in that it further comprises a device (1) for measuring the dew point temperature of a gaseous element, alone or in a mixture, comprising:

at least one calorimetric block (2) for regulating and homogenizing the temperature of the device (1),

at least two thermometric means (3, 4), each thermometric means (3, 4) being in direct thermal contact with the calorimetric block (2),

a measuring surface (8) in direct thermal contact with the thermometric means and the gaseous element, in which each thermometric means (3, 4) is capable of generating a signal representative of the thermal effect associated with the condensation and or evaporation of the gaseous element on said measuring surface (8); said device (1) being placed between the catalytic bed reactor and the capacitor.

19. Installation according to claim 18, wherein the calorimetric block (2) and the thermometric means (3, 4) are contained in an outer casing (7, 9), one face of which comprises the measurement surface (8) in thermal contact. direct with the gaseous element, and wherein said measuring surface (8) in direct thermal contact with the gaseous element is resistant to corrosion.

20. Installation according to claim 18 or claim 19, characterized in that it further comprises a partial combustion gas heater.

21. Installation according to any one of claims 18 to 20, characterized in that it comprises from 1 to 3 catalytic bed reactors, from 1 to 4 capacitors, from 0 to 3 gas heaters, and in that the device (1) is placed between the catalytic bed reactor furthest from the furnace and the capacitor immediately following it, it being understood that the bed reactor Catalyst farthest from the furnace will be the one that will process the lowest quantities of IHbS.