TSA purification unit with a reduced number of valves

Abstract

A gas purification process by temperature-modulated adsorption comprises: - a step during which a first tank (R02) operates in adsorption mode, producing purified gas, which is directed via a first discharge valve (V4) to the common discharge manifold (3), the other tank (R01) being in regeneration mode and isolated from the common discharge manifold (3) by the other discharge valve (V3); - a pressurization step of the other tank (R01) between the regeneration pressure and the adsorption pressure, by supplying purified gas from the first tank (R02) to the other tank (R01) via one or the other of the discharge valves (V3, V4). Abbreviated figure: Fig. 9

Description

Title of the invention: TSA purification unit with a reduced number of valves

[0001] The present invention relates to a method for purifying a gas by temperature-modulated adsorption (TSA process), implementing a temperature-modulated adsorption purification unit (TSA unit). The process is particularly applicable to the pre-purification, specifically drying, of feed air for an air separation unit.

[0002] Such a unit typically comprises two adsorption tanks, a common manifold for supplying the tanks with a feed gas (e.g., air to be purified), a common manifold for discharging a purified gas (e.g., dried air) from the tanks, a common manifold for supplying a regeneration gas to the tanks, two supply valves arranged to direct the feed gas from the common supply manifold to one of the tanks and / or to the other tank, two discharge valves arranged to direct the purified gas from one and / or the other tank to the common discharge manifold, two regeneration valves arranged to direct the regeneration gas from the common supply manifold to one of the tanks and / or to the other tank, two purge valves, each arranged to vent a purge gas or the regeneration gas from one of the two tanks, two depressurization valves,Each tank is arranged to depressurize one of the two vessels, with a pressurization valve in fluidic communication between the two vessels, arranged to pressurize one of the vessels by supplying a portion of the purified gas from the other vessel.

[0003] The large number of valves required to implement these steps makes the unit relatively complex to install and bulky.

[0004] There is now a need for a more compact and simpler to install TSA unit.

[0005] The present invention aims to effectively overcome these drawbacks by proposing to eliminate the specific pressurization and / or depressurization valves and to use instead discharge valves that serve to direct the purified gas and / or purge valves. The valves used are, in particular, on / off (ON / OFF) valves.

[0006] The invention thus makes it possible to reduce the number of pieces of equipment in the TSA unit.

[0007] The invention thus relates to a method for purifying a gas by temperature-modulated adsorption, employing a temperature-modulated adsorption purification unit, said unit comprising: - two adsorption tanks, - a common manifold for supplying the tanks with a feed gas, - a common discharge collector for purified gas from the tanks, - a common manifold for supplying regeneration gas to the tanks, - two supply valves arranged to direct the supply gas from the common supply manifold to one of the tanks and / or to the other tank, - two discharge valves arranged to direct the purified gas from one or both of the tanks towards the common discharge manifold, - two regeneration valves arranged to direct the regeneration gas from the common supply manifold to one of the tanks and / or to the other tank, - two purge valves, each arranged to vent either a purge gas or the regeneration gas from one of the two tanks, the unit operating according to a temperature-modulated adsorption cycle, the cycle comprising an adsorption phase, during which the purified gas is produced at an adsorption pressure and a regeneration phase at a regeneration pressure lower than the adsorption pressure, the process comprising: - a stage during which a first tank operates by adsorption, producing the purified gas, which is directed via a first discharge valve to the common discharge manifold, the other tank being then in regeneration and isolated from the common discharge manifold by the other discharge valve, - a pressurization step of the other tank between the regeneration pressure and the adsorption pressure, by supplying purified gas from the first tank to the other tank via one or the other of the discharge valves, - a stage during which the other tank operates in adsorption, producing the purified gas, which is directed via the other discharge valve to the common discharge manifold, the first tank then being in regeneration and isolated from the common discharge manifold by the first discharge valve, - optionally an intermediate step, between the step during which a first tank operates in adsorption and the step during which the other tank operates in adsorption, an intermediate step during which the two tanks operate in parallel in adsorption.

[0008] The invention thus allows the implementation of the pressurization step with the discharge valves, without the pressurization valve normally present in the prior art TSA units.

[0009] The process advantageously includes a switching step between the step during which the first tank operates in adsorption and the step during which the other tank operates by adsorption, the said switching step being implemented using the discharge valves.

[0010] According to one embodiment, each of the purge valves is arranged to vent from one of the two tanks a purge gas or the regeneration gas to the atmosphere.

[0011] According to one embodiment, the pressurization step is implemented by actuating one and / or the other of the discharge valves according to a stepped opening ramp.

[0012] According to one embodiment, the process includes a step of depressurizing one of the tanks from the adsorption pressure to the regeneration pressure via one of the purge valves and a step during which a purge gas or the regeneration gas is evacuated from said tank, via said purge valve.

[0013] The invention thus allows the implementation of the depressurization step with one of the purge valves, without the depressurization valves normally present in prior art TSA units.

[0014] According to one embodiment, the depressurization step is implemented by actuating said purge valve according to a stepped opening ramp, in particular with an opening sequence different from the opening sequence according to which one and / or the other of the discharge valves is actuated.

[0015] According to one embodiment, the discharge valves and / or purge valves are electrically actuated valves.

[0016] According to one embodiment, the discharge valves and / or purge valves are butterfly type valves.

[0017] According to one embodiment, the discharge valves and / or drain valves have a maximum opening diameter that is the same as the diameter of the pipeline on which they are installed. Alternatively, the discharge valves and / or drain valves have a maximum opening diameter that is smaller than that of the pipeline on which they are installed.

[0018] According to one embodiment, the process is an air purification process. The process is, for example, a pre-purification process, in particular drying, of feed air to an air separation unit, for example a cryogenic air separation unit.

[0019] According to one embodiment, the adsorption pressure is less than 2 bara, preferably less than 1.5 bara.

[0020] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given only to illustrate, but in no way limit, the invention.

[0021] Figures 1 to 8 represent a TSA process according to the prior art of eight steps; and

[0022] Figures 9 to 12 represent a TSA process implemented according to the invention.

[0023] In the prior art process, unit TSA 1 comprises: - a ROI adsorption tank, - an R02 adsorption tank, - a common manifold 2 for supplying the ROI, R02 tanks with air to be purified, - a common manifold 3 for discharging the purified air from the ROI, R02 tanks, - a common manifold 4 for supplying a regeneration gas to the ROI, R02 tanks, - a heater 7 (for example electric), arranged to heat the regeneration gas, - two supply valves VI, V2, arranged to direct the supply gas from the common supply manifold 2 towards one of the tanks and / or towards the other tank, - two discharge valves V3, V4, arranged to direct the purified air from one and / or the other of the ROI, R02 tanks to the common discharge manifold 3, - two regeneration valves V5, V6 arranged to direct the regeneration gas from the common supply manifold 4 to one and / or the other tank, - two purge valves V7, V8, each arranged to vent either a purge gas or the regeneration gas from one of the two tanks, - two V9, VIO depressurization valves, each arranged to depressurize one of the two tanks, - a vent 6, arranged in fluidic communication with valves V7, V8, V9 and VIO, to evacuate the purge gas, the regeneration gas or to depressurize the ROI, R02 tanks to the atmosphere, - a pressurization valve Vil in fluidic communication between the two tanks ROI, R02, arranged to pressurize one of the tanks by supplying part of the purified air from the other tank.

[0024] Figure 1 represents a step during which the ROI tank is isolated at the high cycle pressure (adsorption pressure), while the R02 tank is operating in adsorption mode. Only valves V2 and V4 are open, and the other valves are closed. The heater 7 is not in operation. Air to be purified is supplied to the R02 tank for purification via manifold 2, and the purified air is discharged via manifold 3.

[0025] Figure 2 represents the depressurization step of the ROI tank via the valve Depressurization V9 (the R02 tank still operating in adsorption mode, valves V2 and V4 open). The pressurized gases are vented to the atmosphere via vent 6.

[0026] Figure 3 represents the blow-off stage of the ROI tank, this time with valve V7 open and valve V9 closed. The blow-off gas is vented to the atmosphere via valve V7 and vent 6. Valve V5 is opened to establish a regeneration flow rate. Heater 7 is activated in the next step, once a sufficient flow rate is established.

[0027] Valve V9 (respectively V10) is generally smaller in size compared to valve V7 (respectively V8).

[0028] Fig. 4 shows the ROI tank in regeneration, during a heating stage in which a regeneration gas (for example a nitrogen-rich residual gas) is heated by the heater 7 which is in operation, brought via the manifold 4 and sweeps the ROI tank via the open valves V5 and V7.

[0029] Following this heating step, the now regenerated ROI tank needs to be cooled in preparation for its operation in adsorption. This cooling step is shown in [Fig. 5]. The position of the valves has not changed compared to the heating step, but the heater 7 is switched off.

[0030] Figure 6 represents the next step, during which the regenerated and cooled ROI tank is isolated at the low cycle pressure (regeneration pressure), with valves V7 and V5 now closed. The R02 tank continues to operate in adsorption mode, with valves V2 and V4 open.

[0031] Figure 7 represents the repressurization step of the ROI tank from the low pressure to the high pressure of the cycle, in preparation for its operation in adsorption mode. To achieve this, a portion of the purified air exiting the R02 tank is redirected via the open valve V1 and fed to the ROI tank in a counter-current flow.

[0032] Valve Vil is generally small in size compared to valves V3 and V4.

[0033] Fig. 8 represents the next step, during which the re-pressurized ROI tank and the R02 tank operate in adsorption in parallel, before the R02 tank finishes its operation in adsorption, in order to be regenerated.

[0034] In the process according to the invention, valves V9, V10 and VI1 have been removed.

[0035] Figure 9 shows the depressurization step implemented in the process according to the invention. The ROI tank is depressurized via the purge valve V7, instead of via a dedicated depressurization valve. Valve V7 (respectively valve V8) is a butterfly-type on / off valve, comprising an electric actuator (not shown). An opening command with a value of "1" is sent to the actuator, which moves valve V7. If the command is "0", the actuator stops and valve V7 remains in an intermediate position. By varying the duration of the opening command ("1" or "0"), a stepped opening ramp can be simulated. This is shown in Figure 10, in which the x-axis represents time and the y-axis represents the degree of valve opening. Diagram 10 represents this degree of opening (stepped curve), while diagram 11 represents the order the opening oscillates between the state "1" and the state "0" (notched curve), with a variable duration for each state. The longer a value of 1 lasts, the more the valve opens.

[0036] Figure 11 represents the pressurization step of the ROI tank from the regeneration pressure to the adsorption pressure implemented in the process according to the invention. The ROI tank is pressurized via the discharge valves V3 and V4 instead of via a dedicated pressurization valve. The same principle is applied to the actuation of valves V3 and V4 as for valve V7 (or V8, if applicable, in the case of tank R02), in order to simulate a stepped opening ramp. The opening sequence of valve V3 and / or valve V4 will typically be different from that in which valve V7 is actuation. This is shown in Figure 11. 12], in the same way as in [Fig.10].

[0037] During the opening sequence, the number of steps and / or their duration can be adjusted to obtain the desired ramp and the desired pressurization, depressurization, or purging speed. This prevents overspeeding in the adsorbent bed, thus avoiding any risk of attrition and minimizing noise. In the case of pressurization, this notably involves limiting the amount of purified gas adsorbed from the other tank.

Claims

[Claim 1] Demands A process for purifying a gas by temperature-modulated adsorption employing a temperature-modulated adsorption purification unit (1), said unit (1) comprising: - two adsorption tanks (ROI, R02), - a common manifold (2) for supplying the tanks (ROI, R02) with a feed gas, - a common collector (3) for discharging purified gas from tanks (ROI, RO2), - a common collector (4) for supplying a regeneration gas to the tanks (ROI, R02), - two supply valves (VI, V2) arranged to direct the supply gas from the common supply manifold (2) to one of the tanks and / or to the other tank, - two discharge valves (V3, V4) arranged to direct the purified gas from one and / or the other of the tanks (ROI, R02) towards the common discharge manifold (3), - two regeneration valves (V5, V6) arranged to direct the regeneration gas from the common supply manifold (4) to one of the tanks and / or to the other tank, - two purge valves (V7, V8), each arranged to vent from one of the two tanks (ROI, R02) either a purge gas or the regeneration gas, the unit operating according to a temperature-modulated adsorption cycle, the cycle comprising an adsorption phase, during which the purified gas is produced at an adsorption pressure and a regeneration phase at a regeneration pressure lower than the adsorption pressure, the process comprising: - a stage during which a first tank (ROI) operates in adsorption, producing the purified gas, which is directed via a first discharge valve (V4) to the common discharge collector (3), the other tank (ROI) then being in regeneration and isolated from the common discharge collector (3) by the other discharge valve (V3), - a pressurization step of the other tank (ROI) between the regeneration pressure and the adsorption pressure, by supplying gas purified from the first tank (R02) to the other tank (ROI) via one or the other of the discharge valves (V3, V4), - a step during which the other tank (ROI) operates in adsorption, producing the purified gas, which is directed via the other discharge valve (V3) to the common discharge collector (3), the first tank (R02) then being in regeneration and isolated from the common discharge collector (3) by the first discharge valve (V4), - optionally an intermediate step, between the step during which a first tank (R02) operates in adsorption and the step during which the other tank (ROI) operates in adsorption, intermediate step during which the two tanks (ROI, R02) operate in parallel in adsorption.

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