EP1147294B1 - Method and device for controlling a turbo-machine so as to limit clogging of the turbo-machine internal parts with impurities derived from a process gas - Google Patents

Description

The invention relates to a method and a device for operating a turbomachine comprising an inlet and an outlet for a process gas, so as to limit the fouling of internal parts of the turbomachine by dirt coming from the process gas.

The fouling of the internal parts of turbomachinery, and in particular of centrifugal compressors, is a phenomenon that the user can hardly control or prevent.

The deposition and agglomeration of dirt on the aerodynamic internal parts of turbomachinery can have completely undesirable consequences on performance.

On the one hand, the conduct of the process implemented in the turbomachine can be modified significantly. In the case of a centrifugal compressor, the pressure and temperature levels or the flow rates in the compressor can be modified due to the formation of deposits in the aerodynamic channels such as the blades or the diffusers of the compressor.

On the other hand, the mechanical elements of the turbomachine can be subjected to stresses leading to their deterioration. It is therefore necessary to protect these mechanical elements. In particular, unbalances, variations in axial thrust, or fouling of the internal linings generated by deposits on the dynamic parts of the turbomachine can induce vibrations which are detrimental to the proper functioning of the turbomachine.

The deposition and agglomeration of dirt on the internal parts of turbomachinery and in particular of centrifugal compressors are due to two main causes. First of all, the filters or the separators arranged upstream of the turbomachines cannot stop particles having a size of a few micrometers which are deposited on the internal parts of the turbomachine. In addition, the pressure and temperature levels reached in the compressor, as well as the nature of the gases for which compression is carried out, favor reactions of the polymerization type on the deposited materials or corrosion of the internal parts of the compressor under the effect of the materials. filed.

Generally, fouling of the internal parts of turbomachinery and in particular of centrifugal compressors is a general phenomenon which occurs in all cases during normal operation of the turbomachine. This fouling can reach a level such that it becomes necessary to stop the turbomachine and therefore the current production or manufacturing cycle. It is therefore entirely desirable to have means for removing dirt from the dirty internal part of a turbomachine or limiting the deposition of dirt in this internal part.

So far, no general process is known for cleaning the internal parts of turbomachinery regardless of the type of turbomachine concerned, the substance in circulation in these turbomachinery and the type and nature of the dirt likely to be deposited in their internal parts.

Each operator of turbomachinery tries to remedy the fouling problem it encounters, depending on the type of fouling or the organizational characteristics of production.

• démonter et sabler les parties encrassées des turbomachines,
• injecter périodiquement des particules solides ou liquides (en particulier sous forme de brouillard) pour éroder ou dissoudre les salissures,
• mélanger en continu des additifs avec le fluide circulant dans la turbomachine, substances empêchants ou retardant la polymérisation,
• enduire les parties internes de revêtement pour réaliser des surfaces anti-adhérentes.

Anti-fouling coating processes or solvents or chemical additives are known which make it possible to reduce or eliminate fouling, in certain specific cases (cf. for example the document: PATENT ABSTRACTS OF JAPAN vol. 007, no. 183 (M-235 & JP 58 085371 A (MITSUBISHI JUKOGYO KK), 21.05.83) In general, in order to optimize the availability of industrial equipment, the main methods used which can be combined with each other consist of:

• disassemble and sand the dirty parts of the turbomachinery,
• periodically inject solid or liquid particles (in particular in the form of a mist) to erode or dissolve dirt,
• continuously mixing additives with the fluid circulating in the turbomachine, substances preventing or delaying polymerization,
• coat the internal parts of the coating to produce non-stick surfaces.

All of these methods have drawbacks. In particular, these methods are expensive and their effectiveness is neither total nor lasting.

In addition, each of the methods is adapted to a particular case and no method is known which is of general application.

Cleaning processes are also known which are applied outside the sector of the operation of turbomachinery and which use a solvent constituted by a dense fluid under pressure such as carbon dioxide, in the liquid state or in the supercritical state. .

In such processes, carbon dioxide can be used in place of organic solvents.

Carbon dioxide CO ₂ has a critical point at a pressure of 73 bars (7.3 MPa) and at a temperature of 31 ° C.

These cleaning processes use carbon dioxide at a pressure higher than the critical pressure and at a temperature which can be lower than the critical temperature, the carbon dioxide then being liquid, or even at a temperature higher than the critical temperature, the carbon dioxide then being in a supercritical state intermediate between the liquid and gaseous states.

The critical CO ₂ pressure and temperature values, which are not very difficult to achieve, allow industrial application.

In the supercritical state, the properties of CO ₂ such as its density, its viscosity which is low, and its coefficient of diffusion which is high, as well as a very good solvent power with regard to many materials, make it an interesting solvent product for cleaning, purifying and treating materials.

In the supercritical state, CO ₂ dissolves in particular most of the organic compounds.

Other substances may have similar properties in the supercritical state, such as certain alkanes.

In the case of turbochargers which have an inlet into which a gas intervening in a process in which the gas undergoes a physical or chemical transformation is introduced, it is generally desirable to continuously carry out the removal of dirt inside the turbocharger , during the operation of this turbocharger. It has been proposed to introduce into the process gas stream, at the inlet of the turbocharger, a substance capable of dissolving the dirt deposited inside the turbocharger.

At the outlet of the turbocharger, a fluid is recovered consisting of the process gas and the substance in the supercritical state containing the soils in the dissolved state. A separation of the process gas and the fluid constituted by the substance containing the soils in the dissolved state must then be carried out.

To carry out cleaning of the compressor under economical conditions, it is obviously desirable to carry out the regeneration and recycling of the substance used to dissolve the dirt in the internal parts of the turbocharger. For this, it is necessary to separate from the substance used for cleaning, the impurities constituted by dirt which have been dissolved by the substance in the supercritical state. This separation of impurities cannot be carried out continuously, on the current of the dissolving substance circulating in the compressor, under conditions which are sufficiently economical to be accepted within the framework of an industrial process.

Indeed, to carry out the separation of impurities continuously on the stream of dissolving substance, it is generally necessary to bypass the critical point of the fluid by thermodynamic transformations in a well defined order. It is necessary to carry out an expansion of the substance to obtain its vaporization, the impurities in the liquid or solid state then being separated from the substance in the gaseous state.

It is then necessary to recompress the substance in order to reintroduce it into the process circuit, inside the compressor, in a supercritical state. To ensure the pressurization of the dissolution substance, a high-speed compressor or pump must be used, the cost of installation and use of which is generally incompatible with an economical implementation of an industrial process using gas. of process.

It is therefore desirable to have a method for operating the turbomachines which makes it possible to limit their fouling, without having to perform continuously, during the operation of the turbomachine, the regeneration and recycling of a cleaning substance.

The use of the compressor to circulate the dissolving substance is generally incompatible with the sizing of the compressor due to the level of pressure and developed power required for a constant rotational speed.

The object of the invention is therefore to propose a method for operating a turbomachine comprising an inlet and an outlet for a process gas put into circulation in a circuit called a process circuit, making it possible to limit fouling of the internal parts of the turbomachine by dirt coming from the process gas, without having to ensure the continuous circulation, regeneration and recycling of a cleaning substance, during all the operating phases of the turbomachine.

To this end, the method according to the invention is characterized in that between at least two successive phases of normal operation of the turbomachine during which only process gas is introduced into the compressor inlet and the process gas for its use, a cleaning phase is carried out during which a substance in the dense state capable of dissolving the dirt on the internal parts of the turbomachine is introduced into the process circuit the turbomachine and the process gas is separated from the substance in which the dirt is dissolved in the form of impurities in the liquid state.

In order to clearly understand the invention, a description will be given, by way of example, with reference to the attached figures, of a method of driving a turbocharger making it possible to limit fouling of the turbocharger and the device used for the implementation of the process.

The installations shown respectively in FIGS. 1 and 2 which make it possible to implement the method of the invention according to a first mode and according to a second embodiment differ only in the construction of the turbocharger cleaning circuit. In both cases, the same use circuit, or process circuit 1, is used. Therefore, only the process circuit relating to the embodiment of FIG. 1 will be described, the corresponding elements in Figures 1 and 2 showing the same references.

On the other hand, the cleaning circuits 2 and 2 ′ are different in the case of the first and in the case of the second embodiment of the method of the invention.

The cleaning circuit 2 of the embodiment shown in FIG. 1 makes it possible, during the cleaning phases of the turbocharger, to continuously regenerate the dense cleaning substance which is constituted by CO ₂ in the supercritical state.

In the case of the second embodiment shown in FIG. 2, the cleaning circuit 2 ′ does not perform any regeneration of the substance used which is also CO ₂ in the supercritical state, during the cleaning phases, the CO ₂ supercritical containing dissolved impurities being recycled in the process circuit 1. The supercritical CO ₂ containing impurities is recovered in a storage container at the end of the cleaning phase, before restarting a new normal operating phase of installation. During the normal operation phase of the installation following the cleaning phase, it is possible to evacuate the supercritical CO ₂ saturated with impurities to a regeneration installation.

The circuit of method 1, in the case of the first and second embodiment, comprises a turbocharger 3, the inlet part 4 of which is connected to a pipe 5 for supplying process gas to circuit 1. The process gas Reaching compressor 3 via line 5 contains dirt. A shut-off valve 6 makes it possible to shut off the supply of process gas to the circuit 1. The turbocharger 3 has an outlet part 7 connected to a pipe 8 for discharging the compressed gas in the turbocharger to a separator 9 and a line 10 for transferring the compressed gas to an installation for use. On the pipe 8, a heat exchanger 11 is arranged which makes it possible to cool the process gas at the outlet of the turbocharger 3. The pipe 8 is connected by a first branch on which is arranged a stop valve 13, to the first gas separator liquid 9 which is constituted by a filtration unit and, by a second branch on which is arranged a stop valve 14, to a second liquid gas separator 12 also constituted by a filtration unit.

During normal operation of the installation comprising the turbocharger, the process gas containing dirt is introduced into the inlet part 4 of the turbocharger, compressed and then evacuated by the outlet part 7 of the turbocharger in the pipe 8. During the phases normal use of the installation, the stop valve 14 is closed and the valve 13 is open. The compressed and cooled process gas is introduced into the separator 9 which makes it possible to separate from the process gas impurities constituted by condensates. The condensates are evacuated via line 15. The compressed process gas is evacuated via line 10 to an installation allowing its use.

The cooling of the process gas by the heat exchanger 11 is adjusted according to the end use of the process gas.

During normal operation of the turbocharger, pollutants contained in the process gas are deposited on internal parts of the turbocharger 3, such as blades or diffusers, these pollutants constituting dirt in the internal part of the compressor. The amount of dirt deposited on the internal parts of the compressor can increase with the time of use of the compressor, which leads to the drawbacks which have been mentioned above.

According to the invention, there is provided between two successive phases of normal operation of the compressor during which the internal part of the compressor is loaded with dirt, a cleaning phase which is carried out using in the process circuit, before entry. turbocharger 3, a soil dissolving substance consisting of a chemical compound in a dense and preferably supercritical state.

Preferably, supercritical CO ₂ is used for cleaning the compressor.

In the case of the installation shown in FIG. 1 and in the case of the installation shown in FIG. 2, a cleaning circuit 2 or 2 ′ is used which includes the second gas / liquid separator 12 and which can be completely isolated from the process circuit 1 by means of the stop valve 14 and by means of a stop valve 16 arranged on a line 18 itself connected to line 5 of the normal use circuit 1, downstream of the stop valve 6. The cleaning circuit 2 or 2 ′ is thus bypassed on the process circuit 1 on both sides other from inlet 4 and outlet 7 of the turbocharger 3.

To operate the cleaning circuit 2 or the cleaning circuit 2 ', the valve 13 of the process circuit is closed and the valves 14 and 16 of the cleaning circuit 2 or 2' are opened.

In the case of the installation shown in FIG. 1, making it possible to implement the method of the invention according to a first embodiment, use is made of a supply tank 20 containing CO ₂ in the supercritical state which is placed as a bypass on circuit 2, downstream of separator 12 on a line 21 leaving the separator 12. A three-way valve 19 makes it possible to put the supply tank 20 in communication with line 21 of the cleaning circuit 2, so as to introduce supercritical CO ₂ into the cleaning circuit 2 or to isolate the pipe 21 from the supply tank 20. At the start of the cleaning phase, clean supercritical CO ₂ is introduced into the storage tank 20 by the line 27. The cleaning circuit 2 is then supplied from the supply tank 20, by opening the three-way valve 19.

The supercritical CO ₂ introduced into the circuit 2 arrives in the pipe 18 to be introduced into the process circuit 1 and into the inlet part 4 of the turbocharger 3, mixed with process gas admitted into the process circuit by the driving 5.

The supercritical CO ₂ circulating with the process gas in the turbocharger 3 dissolves the dirt deposited on the internal parts of the turbocharger. Is recovered in the outlet part 7 of the turbocharger 3, compressed process gas containing CO ₂ containing dirt in the dissolved state.

The process gas containing the dirt dissolved in the CO ₂ is cooled in the heat exchanger 11 which produces a condensation of the CO ₂ containing the impurities contained in the process gas.

The mixture arriving at the inlet of the separator 12 constituted by a filtration unit, therefore comprises the compressed process gas and a liquid part constituted by the CO ₂ containing the dissolved impurities.

The second separator 12 separates the compressed process gas which is evacuated towards the installation for use by a line 17 and the liquid mixture of CO ₂ and impurities which is evacuated by the line 21 of the cleaning circuit 2.

The liquid phase consisting of CO ₂ and impurities undergoes an expansion produced by an expansion valve 22, so that downstream of the expansion valve 22, the fluid flowing in the cleaning circuit 2 is constituted by CO ₂ in gaseous form and impurities dissolved in the liquid state. The fluid passes through a separator 23 of the cleaning circuit 2 constituted by a gas / liquid separator filter. The separator 23 separates the gaseous CO ₂ which is sent via an outlet pipe into a compressor 24 and impurities dissolved in the liquid state or possibly in the solid state which are discharged from the separator 23, via a evacuation 25.

The purified CO ₂ gas is compressed by the compressor 24 and passes through a heat exchanger 26 which makes it possible to raise the temperature of the compressed CO ₂ , so that at the outlet of the heat exchanger 26, the fluid circulating in the cleaning circuit 2 consists of clean supercritical CO ₂ which can be returned to process circuit 1, via line 18.

The cleaning circuit can thus be operated continuously, until satisfactory cleaning of the internal parts of the turbocharger 3 is obtained.

At the end of the cleaning phase, the valves 14 and 16 are closed and the stop valve 13 of the process circuit is opened. This begins a new phase of normal operation of the turbocharger 3 and of the installation. The three-way valve 19 is placed in a position making it possible to recover the cleaning CO ₂ in the supply container 20.

In this way, the installation comprising the turbocharger 3 can operate continuously with intermittent cleaning phases making it possible to avoid excessive fouling of the turbocharger. 3. The duration of the normal operating phases and of the cleaning phases is adjusted so as to avoid excessive fouling of the turbocharger 3, while limiting the additional energy expenditure due in particular to the use of the compressor 24 on the cleaning circuit 2 .

In the case of the installation shown in FIG. 2, the process circuit 1 is identical to the process circuit implemented in the case of the first embodiment. In addition, the cleaning circuit 2 ′ comprises, as before, the shut-off valves 14 and 16 and the second separator 12 making it possible to recover from the line 21 ′ of the cleaning circuit 2 ′, during cleaning, a liquid phase constituted with CO ₂ containing dirt from the turbocharger 3 in the dissolved state.

The cleaning circuit according to the second embodiment in which regeneration of the dissolving substance is not carried out has a simpler structure than the cleaning circuit 2 of the first embodiment.

The cleaning circuit comprises, following the separator 12, a CO ₂ recovery tank 20 'and a pump 24'.

To carry out the cleaning, CO ₂ in the supercritical state is introduced into the CO ₂ recovery tank 20 ′, at the start of the cleaning phase. The supercritical CO ₂ is sent by the pump 24 'in the line 18 connected to the process circuit 1.

In line 5 of the process circuit, the supercritical CO ₂ is mixed with process gas.

The operation of the installation during the cleaning phase is identical to the operation which has been described above with regard to the first embodiment, until a liquid phase consisting of CO ₂ containing impurities is recovered in the line 21 'of the cleaning circuit 2'. However, the heat exchanger 11 is adjusted so as to recover the CO ₂ containing liquid impurities, in the supercritical state in the line 21 '.

The supercritical CO ₂ containing liquid impurities is collected in the storage tank 20 ′, the discharge pipe 25 ′ of which is closed by a valve. The CO ₂ in the supercritical state containing impurities is then sucked by the pump 24 'then discharged into the pipe 18 to be reintroduced into the process gas. Cleaning is thus carried out by circulation of CO ₂ in the supercritical state, in the process circuit 1 and in the cleaning circuit, until the time when the supercritical CO ₂ is saturated with impurities in the liquid state. The cleaning circuit 2 'is then isolated from the process circuit 1 and the supercritical CO ₂ containing liquid impurities is recovered in the recovery tank 20'. The installation is returned to normal operation. During the normal operating phase of the installation, the supercritical CO ₂ containing dirt in the liquid state is evacuated via the evacuation pipe 25 ′ from the recovery container 20 ′ and, if necessary, regenerated by separation of the CO ₂ and liquid impurities, for example by a process of expansion and vaporization of CO ₂ followed by filtration.

CO ₂ in the supercritical state is introduced into the container 20 ′ to carry out a subsequent cleaning step.

In the second embodiment, the installation can also operate continuously, the cleaning capacity of the turbocharger 3 being limited only by increasing the amount of impurities dissolved in the CO ₂ in the state supercritical and reaching saturation state.

The regeneration of CO ₂ in the liquid state or in the supercritical state could be carried out by decanting the liquid impurities inside a decanting container or possibly inside the recovery container 21 ′.

In order to be able to operate the turbocharger 3 continuously using the dirt removal method during cleaning phases interspersed between two normal operating phases, in the case of the second embodiment, it is necessary to perform the CO ₂ purification at a frequency sufficient to avoid unacceptable fouling of the turbocharger during the normal operating phase separating two successive cleaning phases.

In other words, the speed of separation of impurities from liquid or gaseous CO ₂ must be greater than the fouling speed of the turbocharger.

In the case of the first embodiment, the installation can be operated continuously, without excessive fouling of the turbocharger, by adjusting the duration of the successive phases of normal operation and cleaning. The method according to the first embodiment which has the advantage of greater flexibility of implementation, however has the disadvantage of requiring greater energy expenditure. This energy expenditure depends in fact on the duration of the cleaning phases interspersed between two phases of normal operation of the installation.

The invention is not limited to the embodiment which has been described.

In particular, it is possible to use other substances than CO ₂ in the supercritical state for dissolving the dirt in the turbocharger. Such substances can be, for example, water (H ₂ O), propane (C ₃ H ₈ ) or pentane (C ₅ H ₁₂ ), in the supercritical state.

It is also possible to envisage using the method according to the invention to carry out the cleaning of apparatuses or installations different from centrifugal turbochargers.

Claims (9)

1. Control process for a turbo machine (3) comprising an inlet (4) and an outlet (7) for a process gas so as to limit dirt accumulation on internal parts of the turbo machine (3) by dirt originating from process gas put into circulation in a process circuit (1) in which the turbo machine (3) is located, characterized by the fact that a cleaning phase is carried out between at least two successive normal operation phases of the turbo machine (3) during which process gas alone is added into the inlet (4) of the turbo machine (3) and the process gas is recovered for use, and during this cleaning phase a substance is added into the process circuit (1) at the inlet (4) to the turbo machine (3), the substance being in a dense state capable of dissolving dirt on the internal parts of the turbo machine (3), and the process gas and the substance in which dirt is dissolved in the form of impurities in the liquid state are separated.
2. Process according to claim 1, characterised by the fact that the pressure in the substance in which the dirt is dissolved in the form of impurities in the liquid state is continuously reduced during the cleaning phase so as to vaporize the substance, in that the substance in the gaseous state is separated from impurities in the liquid state, in that the continuously retrieved substance separated from the impurities is compressed and heated to bring it into a dense state, and that the substance is added into the process gas at the inlet (4) to the turbo machine (3) in the retrieved dense state.
3. Process according to claim 1, characterised by the fact that during the cleaning phase, the substance in the dense state containing impurities in the liquid state is recycled in the process gas, at the inlet (4) to the turbo machine (3), and that the substance is retrieved in the dense state containing impurities in the liquid state in a storage receptacle (20') at the end of the cleaning phase.
4. Process according to claim 3, characterised by the fact that impurities in the liquid state are separated from the substance during a normal operation phase of the turbo machine (3) after the cleaning phase.
5. Process according to any one of claims 1 to 4, characterised by the fact that the substance dissolving the impurities in the supercritical state is composed of carbon dioxide CO₂.
6. Process according to any one of claims 1 to 4, characterised by the fact that the substance dissolving dirt in the supercritical state is composed of at least one of the following substances - water (H₂O), propane (C₃H₈), pentane (C₅H₁₂).
7. Device for the control of a turbo machine (3) comprising an inlet (4) and an outlet (7) for a process gas, so as to limit dirt accumulation in the internal parts of the turbo machine due to dirt originating from the process gas, comprising a normal compressor usage circuit (1), a cleaning circuit (2, 2') bypassing the process circuit (1) on each side of the inlet (4) and outlet (7) of the turbo machine, the process circuit (1) and the cleaning circuit (2, 2') of the turbo machine comprising stop valves (14, 16) in order to put either the process circuit (1) or the cleaning circuit (2, 2') into service.
8. Device according to claim 7, characterised by the fact that between a connection part to the process circuit (1) on the output side of the outlet (7) from the turbo machine (3) and a connection part to the process circuit (1) on the input side of the inlet (4) to the turbo machine, the cleaning circuit (2) comprises a first stop valve (14), a gas-liquid separator (12) and a storage vessel (20) for the substance used to dissolve impurities in the dense state bypassing the cleaning circuit through a three-way valve (19), a pressure reduction valve (22), a gas / liquid filtration unit (23), a compressor (24), a heat exchanger (26) and a second stop valve (16), in this order,
      and in that the process circuit (1) comprises a heat exchanger (11) between the outlet (7) from the turbo machine (3) and the cleaning circuit (2).
9. Device according to claim 7, characterised by the fact that the cleaning circuit (2') comprises a first stop valve (14), a gas / liquid separator (12), a recovery vessel (20') comprising an exhaust duct (25'), a pump (24') and a second stop valve (16), in this order, between a connection part to the process circuit (1) on the output side of the outlet (7) from the turbo machine (3) and a connection part to the process circuit (1) on the input side of the inlet (4) to the turbo machine.