Method for drying compressed gas

Abstract

To provide a method for drying compressed gas.SOLUTION: Method for drying compressed gas by means of a drying device (1) having an inlet (7) for compressed gas to be dried and an outlet (8) for dried compressed gas, comprising the following steps: Wherein the drying device (1) comprises at least two containers (2) filled with a regeneratable drying agent (3) and an adjustable valve system (4) consisting of a first valve block (5) and a second valve block (6) connecting an inlet (7) and an outlet (8), respectively, to the containers (2), the adjustable valve system (4) is adjusted so that at least one vessel (2) dries the compressed gas while the other vessel (2) is successively regenerated and cooled, each of the vessels (2) drying the compressed gas in turn by adjusting the valve system (4), the method consisting in calculating the duration (tads) for which the vessel (2) dries the compressed gas based on the formula tads = A * B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for drying compressed gas.

[0002] More specifically, the present invention is directed to a drying apparatus having an inlet for compressed gas to be dried and an outlet for dried compressed gas, the drying apparatus including at least two containers filled with a regenerable desiccant, and an adjustable valve system connecting the inlet and outlet to the containers, the adjustable valve system being adjusted so that at least one container dries the compressed gas while the other containers are successively regenerated and cooled, each of the containers drying the compressed gas in turn by adjusting the valve system. [Background technology]

[0003] A regenerable desiccant is a moisture absorbent or desiccant that can absorb moisture from a gas by adsorption and, once saturated with moisture, can be dried by passing a so-called regeneration gas through it. This process is also called desiccant regeneration. The regeneration gas is usually a hot gas.

[0004] This is the principle of adsorption, but the present invention can also be applied to the principle of absorption.

[0005] As the container dries, it will absorb moisture from the compressed gas that is drying it, saturating the desiccant.

[0006] The container is then regenerated, typically allowing warm air to pass through, which will extract moisture from the desiccant and regenerate it.

[0007] In known drying systems, the vessel is switched from drying to regenerating, i.e., the determination of the period for which the vessel is to dry or the length of the adsorption cycle is based on the measurement of the dew point.

[0008] The dew point at the outlet of the dryer shall be measured by a dew point sensor.

[0009] If the dew point rises above a predetermined threshold, this means that the desiccant in the associated vessel that dries the compressed gas is saturated.

[0010] At that time, the valve system is controlled so that the vessel with the saturated desiccant is regenerated while the other vessel dries the compressed gas.

[0011] Such known drying devices therefore have the disadvantage of being entirely dependent on the measurements of the dew point sensor for correct operation of the drying device.

[0012] However, dew point sensors are very sensitive sensors, which means that deviations in the measured dew point can occur very easily.

[0013] Furthermore, such sensors are very expensive and very fragile, requiring periodic replacement. Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention aims to overcome at least one of the above and other drawbacks by providing a method that makes it possible to determine the period of time during which a vessel is dry or the length of an adsorption cycle without the need for a dew point sensor. [Means for solving the problem]

[0015] The present invention comprises a method for drying compressed gas by a drying apparatus having an inlet for compressed gas to be dried and an outlet for dried compressed gas, the drying apparatus comprising at least two containers filled with a regenerable desiccant, and an adjustable valve system comprising a first valve block and a second valve block connecting the inlet and outlet to the containers, respectively, the adjustable valve system being adjusted so that at least one container dries the compressed gas while the other container is successively regenerated and cooled, and by adjusting the valve system, each of the containers dries the compressed gas in turn, the method comprising the steps of: t ads =A*B and calculating the period of time for the container to dry the compressed gas based on: -t ads = the period during which the container dries the compressed gas; -A = given adsorption time; -B = product of one or more of the following coefficients: and this coefficient is C ΔP = correction factor for the average pressure drop over the dryer compared to the reference pressure drop over the dryer; C P = correction factor for the mean inlet pressure compared to the reference inlet pressure; C T = correction factor for the average inlet temperature compared to the reference inlet temperature; · C = fixed correction factor; and The reference pressure drop, reference inlet pressure, and reference inlet temperature are values ​​measured or determined on the dryer when operated under reference conditions.

[0016] The above reference conditions are dryer dependent and are often design parameters for which the dryer is designed.

[0017] The reference conditions are, for example, a predetermined pressure and temperature at full flow of the compressed gas to be dried. Under these conditions, the reference pressure drop, inlet pressure, and temperature are then determined.

[0018] These values ​​only need to be determined once. The advantage is that this method makes it possible to calculate the period during which a container dries compressed gas, i.e., the time when this container must stop drying and other containers must be used to dry compressed gas.

[0019] This eliminates the need for a dew point sensor to determine when a container should stop drying and another container should be used for drying.

[0020] Only temperature and pressure sensors are required, which are more reliable and less expensive sensors.

[0021] In order to better illustrate the features of the present invention, some preferred embodiments of the method according to the invention for drying compressed gas will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0022] [Figure 1] 1 shows a schematic representation of a drying device for drying compressed gas by the method according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0023] The drying device 1 for drying compressed gases, shown diagrammatically in FIG. 1, essentially comprises two containers 2 filled with moisture-absorbing material 3 .

[0024] This renewable moisture absorbent 3 is also called a desiccant.

[0025] Of course, the number of containers 2 can be three or more.

[0026] The drying apparatus 1 further comprises a valve system 4 consisting of a first valve block 5 and a second valve block 6 .

[0027] A first valve block 5 will connect the container 2 to an inlet 7 for dry compressed gas and a second valve block 6 will connect the container 2 to an outlet 8 for dry compressed gas.

[0028] The valve blocks 5, 6 are systems of different pipes and valves that can be adjusted so that at any one time at least one vessel 2 is being regenerated while one or more other vessels 2 are drying the compressed gas; by adjusting the valve system 4, each of the vessels 2 will dry the compressed gas in turn.

[0029] Further, according to the present invention, the drying apparatus 1 comprises a four-way valve 9, a blower 10 for drawing in ambient air, and a gas discharge port 11 for discharging gas, which are configured such that, in a first position of the four-way valve 9, the blower 10 is connected to the container 2 via the first valve block 5, and in a second position of the four-way valve 9, the gas discharge port 11 is connected to the container 2 via the first valve block 5, as shown in FIG.

[0030] As shown in FIG. 1, the drying apparatus 1 is configured such that, in the first position of the four-way valve 9, ambient air drawn in by the blower 10 through the four-way valve 9 and the first valve block 5 can enter the container 2 to be cooled.

[0031] Of course, the valve block 5 is adjusted in an appropriate manner to allow the correct flow path of the gases.

[0032] In the example of FIG. 1, the drying device 1 comprises a cooling pipe 12 connecting the second valve block 6 to the inlet side 13 of the blower 10, although this is not essential to the invention.

[0033] It can be seen from FIG. 1 that when the four-way valve 9 is in the first position, a closed cooling circuit 14 is formed in series by the blower 10, the four-way valve 9, the first valve block 5, the container 2, the second valve block 6, and the cooling pipe 12.

[0034] As can be seen in the drawing, the cooling pipe 12 includes a cooler 15. This cooler 15 may be, for example, an air-to-air cooler 15.

[0035] The closed cooling circuit 14 described above will be used to cool the vessel.

[0036] In addition, the drying apparatus 1 comprises a regeneration pipe 16 connecting the four-way valve 9 to the second valve block 6 .

[0037] In the second position of the four-way valve 9, when the four-way valve 9 connects the gas discharge port 11 to the first valve block 5, the four-way valve 9 connects the blower 10 to the regeneration pipe 16 and therefore to the second valve block 6.

[0038] This regeneration pipe 16 is equipped with a heater 17, in this case an electric heater 17.

[0039] In the second position of the four-way valve 9, a regeneration circuit 18 is formed, comprising the blower 10, the four-way valve 9, a regeneration pipe 16 with a heater 17, the second valve block 6, the vessel 2 to be regenerated, the first valve block 5, the four-way valve 9 and the gas discharge port 11.

[0040] The regeneration circuit 18 will be used to regenerate the vessel.

[0041] As can be seen from the drawing, in this case the regeneration pipe 16 and the cooling pipe 12 are partially coincident.

[0042] In this case, only one pipe 19 exits the second valve block 6, but this pipe also contains the heater 20. The pipe 19 branches into two separate pipes 19a, 19b, one of which leads to the inlet side 13 of the blower 10, which contains the cooler 15, and the other of which leads to the four-way valve 9.

[0043] Of course, when implementing the closed cooling circuit 14 and regeneration circuit 18, in addition to the valve blocks 5, 6 and the four-way valve 9 being appropriately adjusted, the heater 17 and cooler 15 mentioned above are also appropriately adjusted.

[0044] Finally, the drying device 1 in this case, although not essential to the present invention, has an inlet temperature T in a temperature sensor 20 for measuring the inlet pressure P in and outlet pressure P out The pressure sensor 21 includes two pressure sensors 21 and 22 for measuring the pressure, respectively.

[0045] Based on the measurements of the pressure sensors 21 and 22, the inlet pressure P in and outlet pressure P out It will be apparent that the pressure drop ΔP on the drying device 1 can be determined by calculating the difference between

[0046] The operation of the drying device 1 and the method according to the invention for drying compressed gas using the drying device 1 is very simple and is as follows.

[0047] During operation of the drying apparatus 1, compressed gas to be dried enters the drying vessel 2 through the inlet 7, hereinafter referred to as vessel 2a.

[0048] When passing through this container 2a, the desiccant 3 adsorbs moisture and extracts it from the gas.

[0049] The dry compressed gas leaves the drying device 1 through outlet 8 .

[0050] The other vessel 2, which has already dried the gas in the previous cycle, contains moisture and is meanwhile regenerated. This vessel 2 will be referred to as vessel 2b below.

[0051] A regeneration cycle is used, which consists of heating ambient air, passing it through vessel 2b and then discharging it.

[0052] For this regeneration cycle, the regeneration circuit 18 described above is used.

[0053] For this purpose, the four-way valve 9 is placed in the second position and the valve blocks 5, 6 are adjusted so that a regeneration circuit 18 is realized. The heater 17 is also switched on.

[0054] The blower 10 draws in ambient air which passes through a regenerative pipe 16 along with a heater 17 where the gas is heated.

[0055] Via the second valve block 6, the heated gas is fed to the container 2b, and extracts moisture from the desiccant 3 as it passes through the container 2b.

[0056] Via the first valve block 5 , the hot moist gas will exit the drying device 1 through the gas discharge port 11 .

[0057] After the regeneration cycle, the heater 17 will be turned off.

[0058] As the desiccant 3 is regenerated, the container 2b will cool.

[0059] A closed cooling circuit 14 is used, whereby ambient air is passed through the vessel 2b to be cooled.

[0060] Ambient air drawn in by blower 10 is circulated through a closed cooling circuit 14, passes through vessel 2b and is then cooled by cooler 15. This cooled gas then passes through vessel 2b again via blower 10.

[0061] After cooling of vessel 2b is complete, it can be used to dry compressed gas, while the other vessel 2a, previously used for drying, can now be regenerated and cooled.

[0062] If container 2b cools container 2a even after cooling, container 2b will be in standby after cooling, which means that container 2b will not dry, regenerate or cool.

[0063] The switching moment, ie the moment when regeneration of the vessel 2a begins, is determined by the method according to the invention.

[0064] According to the present invention, the period during which the container 2 dries the compressed gas (t ads ) is calculated based on the following formula: t ads =A*B where: -t ads = the period during which the container 2 dries the compressed gas; -A = given adsorption time; -B = product of one or more of the following coefficients: and this coefficient is C ΔP = Reference pressure drop ΔP on dryer 1 ref Average pressure drop ΔP over dryer 1 compared to gem Correction factors for; C P = Reference inlet pressure P ref The mean inlet pressure P compared to gem Correction factors for; C T =Reference inlet temperature T ref The average inlet temperature T compared to gem Correction factors for; · C = fixed correction factor; is.

[0065] In the following, B=C ΔP *C p *C T * Assume that C. But, for example, B=C ΔP *C p Or B=C T Or any other possible combination of one to four of these factors.

[0066] Calculated period t adsAfter this time, vessels 2a and 2b will be switched: vessel 2a will be regenerated, while vessel 2b will dry the gas.

[0067] The method described above is repeated, but the functions of the vessels 2a, 2b are reversed.

[0068] As mentioned above, the reference pressure loss ΔP ref , reference inlet pressure P ref , and reference inlet temperature T ref are the pressure loss ΔP on the drying device 1, and the inlet pressure P in and inlet temperature T in is a value measured or determined for the drying device 1 when operated under reference conditions.

[0069] These reference conditions are fixed values ​​of the temperature of the compressed gas to be dried, for example 35° C., at full flow rate, and the pressure of the compressed gas, for example 7 bar.

[0070] When the dryer 1 operates under these reference conditions, the pressure difference ΔP on the dryer 1 and the inlet pressure P in and inlet temperature T in is determined, which is ΔP ref , P ref and T ref Corresponds to.

[0071] Reference pressure difference ΔP ref , reference inlet pressure P ref and reference inlet temperature T ref These values ​​for are fixed values.

[0072] Preferably, the above-mentioned t ads The parameter A from the equation is equal to the adsorption time that the vessel 2 can adsorb when the drying device 1 is operated under the reference conditions.

[0073] In other words, this parameter A is determined in the same manner as the reference value described above and is a fixed value.

[0074] Preferably, the parameter C, which is a fixed correction factor, is equal to a number greater than zero and less than or equal to 1. In practice, C will typically have a value between 0.8 and 0.9.

[0075] This means that vessel 2 does not adsorb for a very long time, and vessel 2 is switched in time. ads is a safety factor to limit

[0076] Other parameters C ΔP , C p , C T is not a fixed value, but is the time ads is recalculated during each adsorption cycle so that

[0077] Preferably, C ΔP The following formula is used for C ΔP =(ΔP ref / ΔP gem ) 1 / 2 where ΔP ref is the reference pressure drop over the dryer 1, and ΔP gem is the average pressure drop over the dryer 1 measured over the drying cycle.

[0078] Alternatively, C ΔP can be determined or measured using a measured or determined flow rate. For this purpose, for example, a flow rate sensor can be used. This is flow is called, where C flow =Flow rate ref / Flow rate gem and Flow rate ref is the reference flow rate through the dryer 1, and gem is the measured flow rate through the dryer 1 during the drying cycle.

[0079] Another alternative is to calculate the C based on the rpm of the compressor to which the dryer is connected. ΔPThe purpose is to determine or calculate

[0080] Preferably, C P The following formula is used for C P =P gem / P ref where P ref is the reference inlet pressure, and P gem is the average inlet pressure measured over the drying cycle.

[0081] Preferably, C T The following formula is used for C T =(T ref in m 3 of gas) / (T gem in m 3 (moisture content of gas) where T ref is the reference inlet temperature, and T gem is the average inlet temperature measured over the drying cycle.

[0082] Unit m at a given temperature 3 The moisture content of the gas can be read from tables or curves known in the literature.

[0083] Average pressure drop ΔP gem , mean inlet pressure P gem and average inlet temperature T gem is the inlet temperature T in The measurement value of the temperature sensor 20 to determine the inlet pressure P in and outlet pressure P out can be easily determined from the measurements of the two pressure sensors 21 and 22 to determine the pressure difference.

[0084] Using the above formula, after each adsorption cycle, t for the next cycle is calculated based on the measurements of sensors 20, 21, and 22. ads can be calculated

[0085] Preferably, the container 2 dries the compressed gas for a calculated period t ads is equal to the so-called minimum half cycle time.

[0086] A complete cycle consists of regenerating the first vessel 2 and regenerating the second vessel 2 .

[0087] That is, a half cycle regenerates one vessel 2. The half cycle time is the time required to regenerate one vessel 2.

[0088] The half-cycle time, ie the time during which at least one vessel 2 must be regenerated, is in principle also equal to the adsorption time or the time during which the vessel 2 will dry the gas.

[0089] Calculated period t ads is equal to the minimum half cycle time, i.e. the minimum adsorption time of vessel 2.

[0090] This means that the adsorption time must be at least the calculated period t ads This means that it must be equal to

[0091] If a dew point sensor is present, e.g., the calculated period t ads If the dew point is still high enough after the end of the process, the adsorption in the vessel 2 can continue for a longer period of time.

[0092] Although the example shown and described above refers to two containers 2, it is not excluded that there are more than two containers 2. There is always at least one container 2 in which the compressed gas is dried.

[0093] If there are two or more containers 2 for drying compressed gas at the same time, t ads can be valid for both containers.

[0094] If the two containers 2 do not start drying the compressed gas at the same time, t ads will be calculated for each of these containers 2.

[0095] The invention is not limited to the exemplary illustrated embodiments, and such methods can be implemented in various modifications without departing from the scope of the invention.

Claims

1. A method for drying compressed gas by a drying device (1) having an inlet (7) for compressed gas to be dried and an outlet (8) for dried compressed gas, the drying device (1) comprising at least two containers (2) filled with a regenerable desiccant (3), and an adjustable valve system (4) consisting of a first valve block (5) and a second valve block (6) connecting the inlet (7) and the outlet (8) to the containers (2), respectively, the adjustable valve system (4) being adjusted so that at least one container (2) dries the compressed gas while the other container (2) is successively regenerated and cooled, and by adjusting the valve system (4), each of the containers (2) dries the compressed gas in turn; The method comprises reacting a compound of formula t ads =A*B Based on this, the period (t ads ), where: -t ads = the period during which the container (2) dries the compressed gas; -A = predetermined adsorption time; -B = product of one or more of the following coefficients: and the coefficients are ・C ΔP = Reference pressure drop (ΔP) on the drying device (1) ref ) compared to the average pressure drop (ΔP gem ) correction factor; ・C P = Reference inlet pressure (P ref ) compared to the mean inlet pressure (P gem ) correction factor; ・C T =Reference inlet temperature (T ref ) compared to the average inlet temperature (T gem ) correction factor; C = fixed correction factor; and Standard pressure loss (ΔP ref ), reference inlet pressure (P ref ), and the reference inlet temperature (T ref ) is a value measured or determined in said drying device (1) when operated under reference conditions.

2. C ΔP The following formula is used for C ΔP =(ΔP ref / ΔP gem ) 1 / 2 Here, ΔP ref is the reference pressure drop (ΔP ref ) and ΔP gem is the average pressure drop (ΔP) over the drying device (1) measured over the drying cycle. gem ) or C ΔP is determined or measured using a measured or determined flow rate, where: C ΔP =C flow =Flow rate ref / Flow rate gem and the Flow rate ref is the reference flow rate through the drying device (1), and gem is the measured flow rate through the drying device (1) during a drying cycle, or C ΔP 2. The method according to claim 1, wherein is determined or calculated based on the rpm of a compressor to which the drying device (1) is connected.

3. C P The following formula is used for C P =P gem / P ref Here, P ref is the reference inlet pressure (P ref ) and P gem is the average inlet pressure (P) measured over the drying cycle gem 3. The method according to claim 1 or 2, wherein

4. C T The following formula is used for C T = (T ref in units of m 3 moisture content of gas) / (T gem in units of m 3 (moisture content of gas) Here, T ref is the reference inlet temperature (T ref ) and T gem is the average inlet temperature (T gem 4. The method according to claim 1, wherein

5. 5. The method according to any one of claims 1 to 4, wherein A is equal to the time that the container (2) can adsorb when the drying device (1) operates under reference conditions.

6. 6. The method of claim 1, wherein C is greater than zero and less than or equal to 1.

7. The calculated period (t ads 7. The method of claim 1, wherein the minimum half cycle time is equal to the minimum half cycle time.

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