FR2922645A1 - Sampling system for liquid hydrocarbon effluent in petrochemical industry, has three valves placed in series and equipped with pneumatic or electric control system, where system implements opening and closing sequences of valves - Google Patents

Abstract

The system has three valves (5-7) e.g. on/off control valves, placed in series and equipped with a pneumatic or electric control system, where the system implements opening and closing sequences of the valves. The valve (5) is opened during a period to fill a volume of liquid between the valves (5, 6). The valve (5) is closed and the valve (6) is opened during a period to fill a volume between the valves (6, 7). The valves (6, 7) are respectively closed and opened during a period to transfer the volume of liquid between the valves (6, 7) towards a vial.

Description

Field of the invention

The field of the invention is that of chemical processes operating at high temperature and high pressure in general, and more particularly that of refining and petrochemical processes using reactions at high pressure and high temperature, that is to say up to approximately 30 MPa and 500 ° C, respectively. During the implementation of these methods, it is customary to monitor the progress of the reactions by taking samples, said samples making it possible to carry out the required chemical analyzes. The sampling system according to the invention aims at taking liquid samples which do not contain gas. It is possible to adapt the sampling system according to the invention to reactors of the "batch" type (in the English terminology) directly at the outlet of the reactor and more precisely at the bottom of the reactor to overcome the presence gas, and also on continuous type reactors, for example at the bottom of a gas-liquid separator placed downstream of the reactor.

The sampling system according to the invention is particularly suitable for pilot process development equipment or catalysts used in these processes. Indeed, the voluntarily reduced size of these reactor equipment implies that sampling can induce disturbances in terms of operation at the reaction zone since the sample volume is not negligible compared to the total volume of the reactor.

The Applicant has therefore developed an automated sampling system to ensure the stability of the operating conditions of the process, for example in terms of pressure and temperature, by taking a very small sample volume at a determined frequency.

Advantageously, when the sample is taken from an intermediate container, for example from a gas-liquid separator, the system according to the invention makes it possible to use a container of smaller size and by therefore improve the representativeness of the sample taken.

Another advantage of the invention is that it does not involve any human intervention in the manipulation of valves and thus ensures greater operator safety, given the pressure conditions and the high temperatures involved. 1 Summary of the invention

The subject of the invention is a sampling system for taking a liquid hydrocarbon effluent at high pressure and high temperature and degassed beforehand, said sampling system implementing opening and closing sequences of at least three valves arranged. in series and ordered automatically.

The sampling system according to the invention is particularly suitable for implementation on a pilot tool, that is to say for taking liquid samples from a reactor whose volume of the reaction zone is generally between 0, 05 and 10 liters.

Description of the Invention The invention relates to a sampling system for sampling a liquid hydrocarbon effluent at high pressure and high temperature and degassed beforehand, said sampling system implementing opening and closing sequences of at least three valves arranged in series and controlled automatically. Preferably, the number of valves is equal to 3, but depending on the pressure level of the effluent to be sampled, it may be advantageous to have more than three valves in series.

Said valves arranged in series can be any type of valve known to those skilled in the art that can be equipped with a pneumatic or electrical control system, for example, digital valves ("all or nothing") or even faucets .

By a set of closing and opening sequences of the different valves, according to a determined order and a determined duration, it is possible to take a sufficient sample volume to carry out the various required analyzes without disturbing the operation of the reaction zone and maintaining in it a good stability in terms of pressure and temperature.

The sampling system is placed either directly at the outlet of a reactor, at the bottom to have an effluent containing no gas, or at the outlet of a gas-liquid separator, and more specifically on a pipe liquid output. The sampling system according to the invention is particularly suitable for implementation on a pilot tool, that is to say for taking liquid samples from a reactor whose volume of the reaction zone is generally between 0.degree. , 05 and 10 liters, and preferably between 0.1 and 5 liters. It is also advantageously used for taking samples between two reactors, one of the advantages being that it does not interrupt the feed of the second reactor.

With regard to the sample volume taken, this generally represents less than 4% of the volume of the reaction zone, preferably from 0.5 to 2%.

The scope of the invention can be better understood from Figures 1, 2 and 3 and the example.

Figure 1 illustrates the use of the sampling system according to the invention, with three valves connected in series and in the case of a reactor operating continuously. Figures 2 and 3 relate to the example, Figure 2 showing the evolution of the temperature profile and Figure 3 the evolution of the pressure profile during sampling.

In FIG. 1, the feedstock (1) is introduced into the reactor (2) loaded with a catalyst operating in ascending mode. At the outlet of the reactor, the pipe (3) is used to feed a gas-liquid separator (4) continuously at the output of which the three valves (5), (6) and (7) are connected in series. For sampling, the opening and closing sequences of the valves are operated according to a well-defined order which is: opening of the first valve (valve (5)) for a duration At, making it possible to fill the volume understood. between the first valve and the second valve (valve (6)) by the liquid to be withdrawn; closing the first valve (valve (5)) and opening the second valve (valve (6)) for a duration At2 to fill the volume between the second valve and the third valve (valve (7)). Thus, the liquid is relieved by the fact that the volume between the first valve and the third valve is generally between 1.2 and 2.5 times the volume between the first and the second valve, preferably equal to 1 , 8 times the volume between the first and the second valve. closing the second valve and opening the third valve for a time At3 to transfer the volume of liquid between the second valve and the third valve to a bottle. The volume of liquid taken at each cycle is a function of the reaction volume. It is generally between 0.5 and 4% of the volume of the reaction zone, preferably between 0.5 and 2% of the volume of the reaction zone.

The valves are actuated by any type of actuator known to those skilled in the art, for example a pneumatic actuator and an automaton makes it possible to program the number of cycles and the time separating them. In addition, the controller manages the opening times At ,, At2 and At3, respectively first, second and third valves (valves (5), (6) and (7)), and their closure.

EXAMPLE

The sampling system according to the invention is implemented according to the diagram of FIG.

The reactor (2) with a volume of 0.2 liters is used to carry out hydrotreatment reactions and operates at a pressure of 16 MPa and a temperature of 150 ° C. The effluent leaving the reactor under the same conditions of temperature and pressure is sent to the gas-liquid separator (4) and is then returned to the reactor (2). At the bottom of the gas-liquid separator, the sampling system comprising three valves "T.O.R" is implemented. The sequences of opening and closing of the valves proceed as follows when the programmed cycle is started at the level of the automaton controlling the three valves: opening of the valve (5) for 5 seconds to fill the volume between the valve (5) and the valve (6) equal to 4 cm3 (1 cm3 = 10-6 m3); - closing the valve (5) and opening the valve (6) for 10 seconds to fill the volume between the valve (6) and the valve (7) equal to 6 cm3. The opening of the valve (6) induces an expansion of the liquid because the volume between the valve (5) and the valve (7) is 2.5 times the volume between the valve (5) and the valve (6), which results in a residual pressure of the liquid less than 0.5 MPa. - closing the valve (6) and opening the valve (7) for 20 seconds.

The volume of sample collected per cycle, in a bottle at the outlet of the valve (7), is about 3 cm3.

Four successive cycles were programmed at 4 minute intervals.

FIG. 2 illustrates the variation of temperature as a function of time within the reactor during the implementation of a conventional sampling (FIG. 2.a, not in accordance with the invention) and during the implementation of the control system. sampling according to the invention. Similarly, FIG. 3 illustrates the variation of pressure as a function of time within the reactor during the implementation of conventional sampling (FIG. 2.a, not in accordance with the invention) and during implementation. of the sampling system according to the invention.

There is thus a pressure drop of 0.3 MPa and a temperature drop of 2 ° C within the reaction zone when the sampling is done manually by successive opening of two valves only. These variations disrupt the operation of the reactor over a relatively long period (45 minutes). On the other hand, in the case of the implementation of the sampling system according to the invention, a good stability is observed, whether for the temperature or for the pressure within the reactor. The sampling does not induce any disturbance with respect to the operation of the reactor.5

Claims (8)

Sampling system for sampling a liquid hydrocarbon effluent at high pressure and high temperature from a reactor and degassed beforehand, said sampling system implementing opening and closing sequences of at least three valves arranged in series and controlled automatically, the liquid undergoing a relaxation at the second valve. 2. Sampling system according to claim 1 for which the number of valves is equal to 3. 3. sampling system according to one of claims 1 or 2 for which the opening and closing sequences of the valves are operated in a specific order which is: opening of the first valve for a duration At, allowing filling the volume between the first valve and the second valve with the liquid to be withdrawn; closing the first valve and opening the second valve Ott over a period of time to fill the volume between the second valve and the third valve, - closing the second valve and opening the third valve for a duration At3 to transfer the volume of liquid between the second valve and the third valve to a vial. 4. Sampling system according to any one of the preceding claims wherein the volume between the first and the third valve is between 1.2 and 2.5 times the volume between the first and the second valve. 5. Sampling system according to any one of the preceding claims wherein the volume between the first and the third valve is equal to 1.8 times the volume between the first and the second valve. 6. Sampling system according to any one of the preceding claims implemented on a pilot tool for taking liquid samples from a reactor whose volume of the reaction zone is between 0.05 and 10 liters. 7. Sampling system according to one of the preceding claims, said sampling system being located directly at the outlet of the reactor on a liquid outlet line. 8. sampling system according to one of the preceding claims, said sampling system being located at the outlet of a gas-liquid separator on a liquid outlet line.