System for removing residual solvent in acetylene gas

Abstract

The invention provides a solvent purification system for removing solvent impurities in gas. A removal system (1) is provided with a gas source unit (11) provided with a storage container, a purifier unit (121) for removing a residual solvent, which is an organic solvent, from an unpurified acetylene gas supplied from the gas source unit (11), a flow divider (123) for distributing the acetylene gas supplied from the gas source unit (11), a flow converging device (124) for converging the acetylene gas supplied from the gas source unit (11), and a control unit (CU) for controlling the flow converging device (124). The flow divider (123) is capable of diverting the acetylene gas to the demand point (P0), the flow converging device (124) is capable of converging the purified acetylene gas treated by the purifier unit (121) and the unpurified acetylene gas supplied by the gas source unit (11), and the control unit (CU) determines the purity of the acetylene gas delivered from the flow converging device (124) and controls the flow divider (123) and the flow converging device (124) so that the acetylene gas delivered to the demand point (P0) has a target purity.

Description

Technical Field

[0001] The present disclosure relates to a system for removing residual solvents from acetylene gas, and more particularly to a system for removing trace amounts of residual solvents from acetylene gas taken out from a storage container. Background Art

[0002] Low-pressure vacuum carburizing technology is a heat treatment under low-pressure vacuum used to modify the surface of metal components made of iron, steel or other metals and alloys. In addition, low-pressure vacuum carburizing method produces less coal than other carburizing methods (such as high-concentration carburizing method and gas carburizing method), so it has attracted attention (for example, see Patent Document 1).

[0003] However, in carburizing technology, as a carbon source, acetylene (C2H2) is the most widely used carbon source (for example, refer to Patent Document 2).

[0004] In the low-pressure vacuum carburizing process, a certain flow rate of acetylene is required to be introduced into the chamber. However, compared with other hydrocarbon gases, acetylene cannot be safely compressed at a pressure higher than 1.5 barg (gauge pressure). Therefore, as a storage technology for acetylene, for example, an organic solvent (such as acetone or dimethylformamide (DMF)) in which acetylene is dissolved is infiltrated into a porous material (such as a porous calcium silicate material).

[0005] When acetylene in an organic solvent is recovered from a porous material, a certain amount of the organic solvent is inevitably present in the acetylene gas.

[0006] In the carburizing process, it is necessary to set up a plurality of storage containers (such as cylinders) for storing acetylene, and control the acetylene supply amount according to the process requirements in the chamber.

[0007] The acetylene gas taken out from the storage container contains a certain amount of organic solvent (also called "residual solvent"). The concentration of the organic solvent in the acetylene gas depends on the nature of the solvent, the temperature, the residual pressure in the cylinder, and the extraction rate of the acetylene gas (see, for example, Patent Document 3).

[0008] The concentration (content) of the organic solvent in the acetylene gas is, for example, in the range of about 0.01% (100 ppm) to about 1% (10,000 ppm) when the organic solvent is dimethylformamide (DMF), or in the range of about 1% to about 10% when the organic solvent is acetone.

[0009] In the carburizing process, the presence of organic solvents may deteriorate the uniformity and quality of the process and may also affect maintenance, etc. Therefore, it is desirable to control the concentration of organic solvents in the acetylene gas to be not higher than a predetermined concentration.

[0010] On the other hand, an organic solvent is required to store acetylene in a storage container, and the organic solvent is also included in order to take out the acetylene gas from the storage container. Furthermore, it is difficult to take out the entire amount of acetylene from the storage container.

[0011] In addition, the content of dimethylformamide (DMF) in acetylene gas is about 10 to 100 times less than that of acetone. Therefore, dimethylformamide (DMF) is preferably used rather than acetone (see, for example, Patent Document 4).

[0012] On the other hand, the use of DMF is restricted by laws and regulations in certain regions, safety guidelines, etc. Therefore, acetone is sometimes recommended as an organic solvent.

[0013] As a method for removing residual solvent from acetylene gas, for example, a cold trap (for example patent documentation 5) or a solvent removal device consisting of an adsorbent (for example, with reference to patent documentation 3, 6) can be cited. Such a solvent removal device (also referred to as a purifier) ​​requires close monitoring and needs to limit the flow rate of the acetylene gas imported. In addition, the organic solvent in acetylene, its content may change over time, or it may change in use. That is, it is difficult to properly set the size, setting conditions, operating conditions, etc. of the solvent removal device (purifier). Therefore, when using acetylene gas (comprising organic solvent) in the purposes of carburizing process, it is expected that the above-mentioned solvent removal device (purifier) ​​determines the best size and carries out the best maintenance management (setting conditions, operating conditions, etc.).

[0014] When acetylene gas is taken out from a storage container (e.g., a cylinder), the residual pressure in the storage container gradually decreases, which means that the acetylene content in the storage container decreases. In the past, in order not to increase the residual solvent concentration, only less than 70% of the acetylene in the total acetylene storage was taken out.

[0015] In addition, the residual pressure in the storage container decreases due to use, and thus the flow rate per unit time of acetylene gas taken out from the storage container also decreases. This results in that the acetylene in the storage container cannot be fully used, thereby reducing the utilization rate.

[0016] Prior Art Literature

[0017] Patent Document 1: U.S. Patent No. 5702540

[0018] Patent Document 2: U.S. Patent Publication No. 2003 / 0168125

[0019] Patent Document 3: International Patent Publication No. WO2008120160

[0020] Patent Document 4: U.S. Patent No. 8915992

[0021] Patent Document 5: U.S. Patent No. 8309473

[0022] Patent Document 6: U.S. Patent No. 8398747 Summary of the invention

[0023] Problems to be solved by the invention

[0024] The present disclosure provides a system capable of appropriately removing a trace amount of residual solvent (solvent traces) in acetylene gas and supplying controlled acetylene (residual solvent at a low concentration) in accordance with the specification conditions of a carburizing process.

[0025] In addition, the present disclosure provides a system capable of using DMF and acetone as organic solvents.

[0026] In addition, the present disclosure provides a system that can increase the supply amount of acetylene gas from a storage container, reduce the amount of acetylene remaining in the storage container compared to the past, and improve the utilization rate (reduce the residual rate).

[0027] In addition, the present disclosure provides a system capable of maintaining a high flow rate per unit time of acetylene gas from a storage container.

[0028] Means for solving problems

[0029] A removal system (1) for removing residual solvent from acetylene gas comprises a gas source unit (11), a purifier unit (121), a flow splitter (123), a flow combining device (124) and a control unit (CU).

[0030] The gas source unit (11) is provided with at least one storage container (e.g., an acetylene storage cylinder), wherein the storage container stores acetylene dissolved in an organic solvent.

[0031] The purifier unit (121) includes at least one purifier (residual solvent removal device) for removing the residual solvent as the organic solvent from the unpurified acetylene gas supplied from the gas source unit (11).

[0032] The flow divider (123) distributes (transmits completely to either side, or distributes at a predetermined flow rate) the acetylene gas supplied by the gas source unit (11),

[0033] The merging device (124) is capable of merging the purified acetylene gas processed by the purifier unit (121) with the unpurified acetylene gas supplied by the gas source unit (11).

[0034] The control unit (CU) determines the purity or solvent content of the acetylene gas delivered from the merging device (124), and controls the flow splitter (123) and the merging device (124) so ​​that the acetylene gas delivered to the demand point (P0) has a target purity.

[0035] The system (1) for removing residual solvent in acetylene gas comprises a first pipe (L1), a first branch pipe (L1a), a second branch pipe (L1b), a bypass pipe (L2) and a lead-out pipe (L3).

[0036] The first pipe (L1) is used to transport the unpurified acetylene gas from the gas source unit (11) to the diverter (123).

[0037] The first branch pipe (L1a) is used to transport the unpurified acetylene gas from the diverter (123) to the purifier unit (121).

[0038] The second branch pipe (L1b) is used to transport purified acetylene gas from the purifier unit (121) to the merging device (124).

[0039] The bypass pipe (L2) is used to transport unpurified acetylene gas from the flow splitter (123) to the flow combining device (124).

[0040] The outlet pipe (L3) is used to transport acetylene gas from the confluence device (124) to a demand point (P0) at a subsequent stage.

[0041] The control unit (CU) can calculate the purification ratio (X) based on one or more data including the concentration of acetylene gas supplied from the storage container, the concentration of residual solvent in the acetylene gas, the residual pressure of the final use condition of the storage container, the flow rate of acetylene gas, the temperature of acetylene gas, and the accumulated supply time of acetylene gas.

[0042] The control unit (CU) can control the acetylene gas supplied by the gas source unit (11) to switch between the following (1) to (4),

[0043] (1) Proportional purification according to the change of purification ratio (X),

[0044] (2) Fixed ratio purification with a fixed purification ratio,

[0045] (3) Complete purification of the entire amount,

[0046] (4) Non-purification without purification of the entire amount.

[0047] Another removal system for removing residual impurities in gas according to the present disclosure may include a gas source unit, a purifier unit, a flow splitter, a confluence device, and a control unit.

[0048] The gas source unit has at least one storage container.

[0049] The purifier unit includes at least one purifier that removes the residual impurities from the unpurified gas supplied from the gas source unit.

[0050] The flow divider distributes the gas supplied by the gas source unit,

[0051] The merging device can merge the purified gas processed by the purifier unit with the unpurified gas supplied by the gas source unit.

[0052] The control unit determines the purity or impurity content of the gas delivered from the flow combining device, and controls the flow splitter and the flow combining device so that the gas delivered to the demand point has a target purity.

[0053] The gas may be another gas such as natural gas (NG) containing variable impurities such as carbon dioxide or water, or a mixture of gases containing impurities.

[0054] (Effect)

[0055] (1) Acetylene gas of a certain purity can be taken out from a plurality of gas cylinders (storage containers) storing acetylene.

[0056] (2) In the case where the organic solvent is DMF, in order to prevent the solvent content in the acetylene gas from increasing to more than 500 ppm, the acetylene gas may be not taken out from the cylinder when the residual pressure drops below about 5 barg. Thus, when the residual pressure drops, the total usage of the cylinder is limited. In the present disclosure, about 70% to 80% of the acetylene in the total acetylene storage can be supplied (in the past, only less than about 70% could be used).

[0057] (3) A purifier (solvent removal device) is provided, and control such as feeding / non-feeding / partial feeding to the purifier is performed, thereby appropriately controlling the concentration (content) of the residual solvent in the acetylene gas.

[0058] (4) The supply amount of acetylene gas from the storage container can be increased, so that the residual amount of acetylene in the storage container is less than before, thereby improving the utilization rate (reducing the residual rate).

[0059] (5) The flow rate per unit time of acetylene gas from the storage container can be maintained at a high level.

[0060] (6) Even when propanol is used as the organic solvent, the quality (residual solvent concentration) equivalent to that of DMF can be maintained.

[0061] (7) The residual solvent in the acetylene gas can be completely or partially removed to increase the acetylene purity to a predetermined allowable concentration level (the concentration of the residual solvent can be suppressed to below a certain value). BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a diagram showing the function of the removal system.

[0063] Figure 2 It is a diagram showing cases A, B, and C of the purification ratio X.

[0064] Figure 3 This is a diagram showing an example of a piping structure for purification processing and non-purification processing.

[0065] Figure 4 This is a diagram showing an example of the relationship between the residual pressure in the storage container and the ideal usage amount of acetylene.

[0066] Figure 5 It is a graph showing the relationship between DMF content and residual pressure.

[0067] Figure 6 It means Figure 5 A graph showing the relationship between the residual DMF content and the amount of acetylene gas used.

[0068] Figure 7 It is a diagram showing purification treatment examples at different target solvent contents.

[0069] Description of Reference Numerals

[0070] 1 Residual solvent removal system in acetylene gas

[0071] 11 Gas source unit

[0072] 121 Purifier Unit

[0073] 121a Purifier

[0074] 123 Shunt

[0075] 124 confluence equipment

[0076] CU Control Unit DETAILED DESCRIPTION

[0077] Hereinafter, several embodiments of the present invention will be described. The embodiments described below illustrate an example of the present invention. The present invention is not limited to the following embodiments, but also includes various variations implemented within the scope of not changing the gist of the present invention. In addition, the structures described below are not all necessary structures of the present invention.

[0078] (Implementation Method 1)

[0079] Reference Figure 1 , basic functions of the removal system 1 for removing the residual solvent in the acetylene gas according to the first embodiment will be described.

[0080] The removal system 1 includes a gas source unit 11 , a purifier unit 121 , a flow divider 123 (also referred to as a “distribution device”), a flow merging device 124 , and a control unit CU.

[0081] The gas source unit 11 includes at least one storage container. The gas in Embodiment 1 is acetylene gas. In the storage container, acetylene is dissolved in an organic solvent (DMF) and then contained in a porous material and stored.

[0082] The purifier unit 121 includes at least one purifier 121a for removing residual solvent as an organic solvent from the unpurified acetylene gas supplied from the gas source unit 11. The one or more purifiers 121a may be configured to have a purification adsorbent column or a condenser system connected in series or in parallel.

[0083] The flow divider 123 is a device for distributing (transmitting completely to either side, or distributing at a predetermined flow rate) the acetylene gas supplied by the gas source unit (11). The flow divider 123 can be composed of a three-way valve 123a, a damping mechanism, a control valve, a flow control valve, a proportional flow control valve, a solenoid valve, etc.

[0084] The merging device 124 is a device that can merge the purified acetylene gas processed by the purifier unit 121 with the unpurified acetylene gas supplied by the gas source unit 11. The merging device 124 can deliver only the purified acetylene gas to the downstream section, can deliver only the unpurified acetylene gas to the downstream section, and can mix the two at a predetermined mixing ratio (purification ratio) and deliver them to the downstream section.

[0085] The merging device 124 mixes the unpurified acetylene gas with the purified acetylene gas purified by the purifier unit 121 at a predetermined purification ratio (X=0-1). The merging device 124 may be composed of a downstream three-way valve 124a, or may be composed of a T-shaped pipe and an isolation valve or a flow control valve.

[0086] The merging device 124 may be configured to include a mixer 124a or a buffer tank. The mixer 124a or the buffer tank may be configured to mix the gas purified by the purifier 121a and the unpurified gas, and to send the gas with the purification ratio (X) downstream.

[0087] The mixing area of ​​the confluence device 124 may be composed of a mixing chamber or a buffer chamber. In the case of a buffer chamber, the purified acetylene gas and the directly delivered unpurified acetylene gas may be introduced simultaneously at a controlled flow rate, or may be introduced into the buffer chamber in sequence based on a set volume fraction. The mixing area may have one or more sampling ports, and the solvent and / or other impurities in the acetylene gas may be measured by an analysis device.

[0088] The control unit CU calculates the concentration of the gas delivered from the merging device (124), and controls the splitter (123) and the merging device (124) so ​​that the acetylene gas (unpurified gas, completely purified gas, mixed gas) delivered to the demand point (P0) reaches the target concentration (for example, the acetylene purity required by the demand point, the concentration of residual solvent, etc.).

[0089] The control unit CU can control the diverter 123 to deliver acetylene gas to only one pipe, or can control the diverter 123 to distribute and deliver acetylene gas to the purifier unit 121 and the converging device 124 at a predetermined purification ratio (X=0~1).

[0090] The control unit CU may determine the concentration of the acetylene gas supplied from the storage container, the concentration (content) of the residual solvent in the acetylene gas (η source ), the purification ratio (X) is determined based on one or more data including the residual pressure of the final use conditions of the storage container, the flow rate of acetylene gas, the temperature of acetylene gas, and the accumulated supply time of acetylene gas.

[0091] The control unit CU may control the flow control valve or isolation valve provided on the flow divider 123, the flow combining device 124, and each pipe (L1, L1a, L2, L1b, L3, etc.) based on the purification ratio (X).

[0092] The control unit CU can determine whether to deliver the acetylene gas to the purifier unit 121 for treatment and determine the delivery period (the total flow rate of the purified acetylene gas) corresponding to the requirements of the carburizing process at the demand point P0.

[0093] The control unit CU can determine whether to feed the acetylene gas to the bypass pipe L2 and determine the feeding period (the total flow rate of the unpurified acetylene gas) according to the requirements of the carburizing process at the demand point P0.

[0094] The control unit CU may determine switching information corresponding to the requirements of the carburizing process at the demand point P0 and including at least the total flow rate of the purified acetylene gas and the total flow rate of the unpurified acetylene gas.

[0095] The control unit CU can determine the mixing ratio (mixing ratio per unit time) of the acetylene gas processed by the purifier unit 121 and the acetylene gas fed to the bypass pipe L2.

[0096] The control unit CU may determine the ratio of the purified acetylene gas (purification ratio X) to the unpurified gas (1−X), and may also determine the ratio at which they are mixed by the combining device 124 .

[0097] The control unit CU may monitor a change in the state of the purifier unit 121 (eg, in use, in regeneration, in standby) or maintain the state, and may control the purifier unit 121 .

[0098] The control unit CU may determine which purifier (adsorbent column) or purifiers (adsorbent columns) among the at least one purifier 121a constituting the purifier unit 121 is to be used or regenerated, and perform control required for the use or regeneration.

[0099] The control unit CU may include: an accumulation amount calculation unit for calculating the amount of residual solvent (also called "impurities") removed (purified) from the acetylene gas by the purifier unit 121 and accumulated in the purifier (adsorption column, etc.); a regeneration and replacement period calculation unit for calculating the regeneration period and / or replacement period of each purifier 121a of the purifier unit 121 based on the accumulation amount of the residual solvent calculated by the accumulation amount calculation unit; and a regeneration control unit for controlling the regeneration device (not shown) corresponding to the regeneration period and / or replacement period of each purifier 121a calculated by the regeneration and replacement period calculation unit.

[0100] The regeneration equipment may include: a heating device for heating the adsorbent in the purifier, a regeneration gas supply device for supplying a regeneration gas for regenerating the adsorbent to the pipe, and an automatic isolation valve provided on the pipe.

[0101] The regeneration control unit may control the ON / OFF of an automatic isolation valve that switches the passage of gas between the regeneration purifier and the used purifier. The regeneration control unit may control the heating device for heating the adsorbent of the regeneration purifier to be turned on. The heating device may be an electric heating jacket provided on the outer wall of the storage container. The regeneration control unit may issue a command to the regeneration gas supply device to control the timing and supply time of the regeneration gas to the piping.

[0102] The first pipe L1 is a pipe for conveying unpurified acetylene gas from the gas source unit 11 to the diverter 123. The first branch pipe L1a is a pipe for conveying unpurified acetylene gas from the diverter 123 to the purifier unit 121. The second branch pipe L1b is a pipe for conveying purified acetylene gas from the purifier unit 121 to the confluence device 124. The bypass pipe L2 is a pipe for conveying unpurified acetylene gas from the diverter 123 to the confluence device 124. The outlet pipe L3 is a pipe for conveying acetylene gas from the confluence device 124 to the demand point P0 in the rear section.

[0103] The storage container and / or each of the pipes may be provided with valves (e.g., isolation valves, flow control valves), a gas flow meter for measuring gas flow, a gas pressure gauge for measuring gas pressure, a gas thermometer for measuring gas temperature, a gas concentration measuring device for measuring gas concentration, an impurity concentration measuring device (trace solvent analysis device) for measuring the concentration of impurities (solvents) in the gas, etc. The measured data may be sent to the control unit CU in association with the respective measurement time and the respective device identification information, or may be stored in a storage unit (not shown).

[0104] The gas source unit 11 or the control unit CU can determine the acetylene gas (Q source ) in the residual solvent content (concentration) (η source ).

[0105] The upstream three-way valve 123a and the downstream three-way valve 124a may be automatically driven valves or manual valves.

[0106] The upstream three-way valve 123a and the downstream three-way valve 124a can be controlled according to the control instruction from the control unit CU. The isolation valves and the flow control valve can also be controlled according to the control instruction from the control unit CU.

[0107] The control unit CU calculates the residual solvent content (concentration) (η) in the acetylene gas based on the residual solvent content (concentration) (η source ), the residual pressure of the cylinder under the final use condition, the flow rate of acetylene gas, the temperature of acetylene gas, and the accumulated supply time, and calculate the purification ratio (X).

[0108] The control unit CU controls the flow control valves or isolation valves provided on the flow divider 123, the confluence device 124, and each pipe L1, L1a, L2, L1b, L3, etc. based on the purification ratio (X). The control unit CU controls the branch device or various valves in accordance with the purification ratio X. The amount of gas sent to the purifier and the amount of gas sent to the bypass pipe L2 are controlled.

[0109] Each pipe may be provided with a gas flow meter, a gas pressure meter, a gas thermometer, a gas concentration measuring device, and an impurity concentration measuring device. The measured data may be sent to the control unit CU in association with the respective measurement time and the respective device identification information, or may be stored in the storage unit.

[0110] (Method for determining the ultimate residual pressure)

[0111] The control unit CU and / or the gas source unit 11 determine the limit residual pressure of the storage container corresponding to the specific use conditions (flow rate, temperature). The content of the residual solvent (impurities) in the acetylene gas that can be allowed is predetermined according to the use conditions, and the residual pressure at which the target carburizing process quality cannot be obtained is determined.

[0112] When the internal pressure measured in the storage container in use is lower than the limit residual pressure, switch to another storage container. This switch is called a switch point (use limit point). The use limit point can be used to determine the start and end timing of the purification process in the purifier unit 121.

[0113] In addition, the switching point can be determined based on the measurement data (monitoring) of various measuring devices, the residual pressure or temperature in the storage container, etc. The switching point is calculated based on measurable information such as the residual pressure or temperature of the storage container, the solvent content in the acetylene gas, the cumulative supply time, the total supply amount of acetylene, and the flow rate of acetylene per unit time.

[0114] By determining the switching point, the purification system can be optimized (the number of purifiers, the size of the adsorption columns, etc.).

[0115] The acetylene gas concentration (residual solvent concentration) taken out of the container corresponding to the residual pressure and temperature can be measured in advance, an approximate function can be determined based on the measured data, and the approximate function (which can be a linear function) can be stored in the storage unit. Using this approximate function, the acetylene gas concentration (residual solvent concentration) can be calculated based on the measured values ​​of the residual pressure and temperature.

[0116] In accordance with the acetylene concentration and flow rate required at the demand point P0, replacement of a storage container, use of a purifier, use of a bypass pipe, use of a mixing device, and the like can be determined.

[0117] In addition, the purifier does not need to be used all the time, and can be made smaller than a system that uses the purifier continuously. Since the purifier can be made smaller, the regeneration energy of the purifier can also be reduced.

[0118] Corresponding to the switching point, three types of purification processing are performed.

[0119] (1) Proportional purification

[0120] According to the change of the calculated purification ratio (X), the amount of purified gas and the amount of non-purified gas are changed and mixed in real time or at predetermined time intervals (1 minute unit, 10 minute unit, etc.). The maximum fixed content of the residual solvent in the acetylene gas is set as the upper limit, and the purification of the acetylene gas is set to be variable.

[0121] (2) Fixed ratio purification

[0122] When it is determined that purge is necessary, purge processing corresponding to a preset fixed purge ratio is performed.

[0123] (3) Complete purification (or non-purification)

[0124] When it is determined that purification is required, the acetylene gas is 100% purified (the gas is not sent to the bypass pipe, but to the purifier unit). When it is determined that purification is not required, the acetylene gas is not purified, but 100% is sent to the back stage (the gas is not sent to the purifier, but to the bypass pipe).

[0125] In determining the switching point, a predetermined function can be used to define the relationship between the residual pressure of the storage container during use and the concentration of the extracted acetylene gas (solvent concentration) based on the initial value of the storage container (volume, filling pressure and solvent amount) and the acetylene solubility. This function can be used to determine the ideal acetylene supply available for the subsequent carburizing process.

[0126] (a) The normally used operating pressure limit is determined by the residual pressure in the storage container.

[0127] (b) Depending on the target final use conditions (residual pressure) and the use conditions (flow rate and temperature), the amount of acetylene gas that can be used can be increased by 10% to 60%. For example, when using a DMF cylinder (extended use from 5 barg to 2 barg), the amount of acetylene that can be used can be increased by about 20% to 30%, and when using an acetone cylinder (extended use from 6 barg to 2 barg), the amount of acetylene that can be used can be increased by about 35% to 40%.

[0128] Figure 4 Represents the relationship between the residual pressure in the storage container and the ideal amount of acetylene used. As a function of the residual pressure in the storage container (cylinder) at 20°C, Figure 4 (a) shows the case of a standard B50 cylinder filled with acetylene gas with DMF as the solvent, Figure 4 (b) shows the case of a standard B50 cylinder filled with acetylene gas with acetone as the solvent.

[0129] (1) indicates that the switching point is determined by the limit value of each residual solvent (impurity).

[0130] DMF: 500ppm / 5barg

[0131] Acetone: 2.2% / 6barg (assuming flow rate is 10slm)

[0132] The amount of solvent in the acetylene gas is determined based on general recommendations regarding the use of storage containers.

[0133] (2) Figure 4 The horizontal axis represents the residual pressure, the right vertical axis represents the utilization rate of the storage container during standard use, and the left vertical axis represents the ideal usable amount of acetylene gas.

[0134] In terms of utilization rate, the utilization rate in the previous standard use is set to 100%. According to the removal system 1 disclosed in the present invention, the storage container replacement time can be extended to the minimum residual pressure (2 barg), and the utilization rate can be increased to 130% (DMF Figure 4 (a)) and 140% (acetylene Figure 4 (b)), and the amount that can be used is also increased.

[0135] The target purification ratio (X) is determined based on the estimated solvent content (η direct ) and user requirements (target solvent content η target The control unit CU may be determined by various methods.

[0136] Figure 2 Two methods are shown. Ratio purge (cases A and B) or full purge (case C) are exemplified. The main difference between the two methods is that in ratio purge, a portion of the acetylene gas from the storage container is purified (at a purification ratio X), whereas in full purge, all of the acetylene gas from the storage container is purified after switching.

[0137] (1) Case A: After reaching the switching point, purification is performed with a variable purification ratio (X) according to the evaluation results ( Figure 2 (a))

[0138] (2) Case B: After reaching the switching point, purification is performed at a fixed purification ratio (X) ( Figure 2 (a))

[0139] (3) Case C: After reaching the switching point, all acetylene gas is purified.

[0140] ( Figure 2 (b))

[0141] Figure 2 (a) shows proportional purge in which acetylene gas is distributed at a purge ratio (X) so that only a portion of the acetylene gas is purge. Figure 2(b) shows complete purification where all acetylene gas from the storage container (cylinder) is purified by the purifier unit 121 .

[0142] The fixed purge ratio (X) can be set to, for example, a fixed ratio corresponding to the requirement of the final demand point P0. The variable purge ratio (X) is determined using the maximum fixed content of the residual solvent in the acetylene gas as a target value.

[0143] (Proportional purification)

[0144] The control unit CU determines the amount (ratio) of gas purified by the purifier unit 121. Then, the purified gas is mixed with the unpurified gas to generate a mixed gas. The solvent (impurity) content in the mixed gas corresponds to the requirements of the subsequent process side.

[0145] The removal system 1 has an advantage in that the size of the purifier unit can be reduced compared to a purifier system that purifies the entire acetylene gas supplied to a subsequent process.

[0146] In one embodiment, the purification ratio X of the purified gas may be a fixed value. The purification ratio may also be evaluated and determined again. A variable purification ratio may be evaluated and determined dynamically.

[0147] In another embodiment, the purge ratio X or whether to perform full purge may be determined based on a fixed value such as the target final residual pressure (before replacement of the storage container). In this case, the purge ratio X is determined as a single value by a predictive method. In addition, a constant purge ratio X may be estimated based on a predetermined range of usage times, gas volume, or residual pressure (intermediate situations between situations A and B may be considered).

[0148] The proportion of gas that is purified (purification ratio X) is ideally based on the solvent (impurity) content (η) of the storage container being evaluated. source ), target solvent (impurity) content (η target ) and the solvent (impurity) content (η) in the purified acetylene gas after purification purified ) to determine.

[0149] The solvent (impurity) content of the purified mixed gas can be determined, or the solvent (impurity) content caused by switching to full-amount purification can be determined. Figure 3 An example of purification processing of the removal system 1 is shown. This system can purify all or part of the acetylene from the acetylene gas source unit 11 by the purification unit 121, and mix it with unpurified acetylene gas to generate acetylene gas of a predetermined purity.

[0150] The concentration of each solvent and the purification ratio X are related by formula (1).

[0151] (Formula 1)η output =(1-X)·η source +X·η purified

[0152] The total gas flow Q total (=Q source =Q output ) is expressed by equations (2), (3) and (4). The state before the switching point corresponds to X=0.

[0153] (Formula 2)Q total =Q purified +Q direct

[0154] (Formula 3)Q purified =X·Q total

[0155] (Formula 4)Q direct =(1-X)·Q total

[0156] Flow rate of acetylene gas from storage container: Q source (=Q total )

[0157] Solvent content in acetylene gas from storage container: η source

[0158] The flow rate of acetylene gas purified by the purifier: Q purified

[0159] The solvent content (concentration) in the acetylene gas after purification by the purifier: η purified

[0160] Flow rate of acetylene gas bypassing the purifier: Q direct

[0161] Solvent content in acetylene gas bypassing the purifier: η direct

[0162] Flow rate of acetylene gas output from removal system 1: Q output

[0163] The solvent content in the acetylene gas output from the removal system 1: η output

[0164] Target solvent content according to user requirements: η target

[0165] Pressure regulating valve with pressure gauge: PR1

[0166] Upstream flow control valve: V1

[0167] Flow control valve installed on purifier piping line L1 (L1a): CV2

[0168] Flow control valve installed in bypass piping line L2: CV1

[0169] The function of the branch device 123 can be realized by using CV1 and CV2.

[0170] The removal system 1 is capable of diluting residual solvent (and impurities) in the acetylene gas taken from the storage container.

[0171] (1) The purifier unit 121 may be configured to include one or more adsorbent-filled columns or solvent condensers. The purifier unit 121 may convert the acetylene gas delivered from the storage container into an acetylene gas stream with higher purity (eg, at least 50% of the solvent vapor is removed).

[0172] (2) The conditions under which purified acetylene gas and unpurified acetylene gas are mixed or used can be controlled.

[0173] The removal system 1 is capable of utilizing most of the acetylene gas in the storage container while reducing the amount of residual solvent in the acetylene gas provided to the downstream process.

[0174] The predetermined content (or tolerance) of DMF is 500 ppm (target solvent content η target ) of a standard DMF solvent storage container, it was previously necessary to stop using it when the residual pressure reached 5 barg. Assuming that the storage container in use is properly stopped, only about 60% to 70% of the total capacity of the storage container can be used. On the other hand, in the removal system 1, it is possible to target In the case of working to a residual pressure of 2 barg, 70% to 80% of the total capacity of the storage container can be used. Therefore, the use of on-site storage containers (cylinders, gas bottles, etc.) can be extended, and the replacement frequency and replenishment of storage containers can be reduced.

[0175] The control unit CU determines in which state and amount the purge is to be performed.

[0176] Acetylene purity in supply gas < acetylene purity in target purge gas

[0177] Solvent content in supply gas > Solvent content in purge gas (mixed gas)

[0178] The control unit CU can control each isolation valve to completely stop the flow from the gas source unit 11 (storage container) when the quality of the acetylene gas is lower than the reference value and cannot be switched to other storage containers.

[0179] The control unit CU can estimate the total amount of acetylene gas used based on (i) the usage conditions (residual pressure of the storage container at the beginning, residual pressure during use) and (ii) the integral of the flow rate of acetylene gas delivered to the demand point process.

[0180] The control unit CU can obtain or determine information related to the current utilization rate of the storage container (cylinder), the predicted time to the switching point, and the remaining time (usable time, replacement time) for replacing the storage container (cylinder) based on either the pre-recorded processing time of the carburizing process, an average value based on its usage or recorded data.

[0181] The control unit CU can output an alarm to the user when an adverse condition occurs due to cooling of the storage container accompanying the removal of acetylene gas. It can output a warning to the user when the change in the use conditions is too large (flow rate problem, temperature, residual pressure is too low). In addition, in order to support the user's inventory management and distribution, the warning can be output when the storage container reaches a predetermined usage rate.

[0182] The control unit CU may include one or more processors, and the processors read various data and control commands from the storage unit and execute various processes required for control.

[0183] The control unit CU can send and receive various data and command signals with external devices. The external devices may be, for example, the gas source unit 11, the splitter 123, the purifier unit 121, the confluence device 124, a storage device, a cloud server, a cloud storage, a control device of the demand point P0, a user's management device, etc.

[0184] Examples of the various data include the above-mentioned measurement data, confirmed data, purification ratio X, switching point (use limit point), estimation of replacement time of storage container, residual pressure, various process data, control command data, and the like.

[0185] This data can be used to improve various management methods such as inventory management and quality management.

[0186] The control unit CU can control and monitor the entire removal system 1. Table 1 shows an example of the purification process.

[0187] Residual pressure of storage pressure in use: P residual

[0188] Switching point: Sp = the limiting residual pressure in normal use. In the present disclosure, the residual solvent amount is controlled by performing purification at a relatively low residual pressure.

[0189]

Table 1

[0190]

[0191] (a): Purification rate X: the amount of purified acetylene gas purified by the purifier unit / the total amount of unpurified acetylene gas taken out from the storage container

[0192] (b): Temperature, residual pressure, or other measured parameters that have a significant change from the normal value or estimated value from the control unit.

[0193] (Implementation Method of Purification)

[0194] The control unit CU can be used with a purity level (lower limit concentration, or target solvent content η) which is less than a predetermined limit in the carburizing process at the required point. target ) Correspondingly, the limit residual pressure before replacement of the storage container and the surplus pressure range (offset value) higher than the limit residual pressure are determined.

[0195] Figure 3 , different purification treatment examples are shown. Examples include proportional purification (case A), fixed ratio purification (case B), and complete purification (case C). In proportional purification, only a portion of the acetylene gas is purified (purification ratio X). In complete purification, all of the acetylene gas is purified. The purification treatment can be set based on the switching point (including offset).

[0196] (Proportional purification)

[0197] Ratio purge purifies a portion of the acetylene gas taken from the storage container.

[0198] The control unit CU determines the amount of acetylene gas purified by the purifier 121a. The purified acetylene gas is mixed with the unpurified acetylene gas in the confluence device 124. As a result, the residual solvent content (solvent concentration) in the acetylene gas is reduced. By performing partial purification, the purifier unit can be miniaturized compared to other systems that always perform purification.

[0199] Figure 5 The relationship between DMF content and residual pressure is shown. The acetylene gas flow rate is 10 slm and the temperature is 20°C. In this embodiment, the target solvent content η in the acetylene gas is target Set to 500ppm. It can be seen that as the residual pressure decreases, the DMF content in the acetylene gas increases. Using this relationship curve, the purification ratio X, proportional purification, fixed ratio purification, and complete purification can be determined.

[0200] Figure 5 (a) shows that proportional purge is started at the switch point (Switch point: 5 barg), whereby the DMF content (500 ppm) in the acetylene gas can be kept constant even when the residual pressure is reduced from 5 barg to 2 barg. Figure 5(b) shows the results of performing fixed ratio purge (fixed purge ratio increased as pressure decreased) at 5, 4, and 3 barg so that the DMF content did not exceed 500 ppm. Figure 5 (c) shows the result of setting the minimum residual pressure indicating the timing of replacing the storage container to 2 barg and performing complete purification so that the DMF content does not exceed 500 ppm at this value.

[0201] The purge ratio X can be re-evaluated (re-set) by the control unit CU. The re-evaluation (re-setting) depends on the accuracy of the distribution of the flow divider 123, for example.

[0202] Figure 6 Shown with Figure 5 The relationship between the corresponding residual DMF content and the amount of acetylene gas used.

[0203] As the cumulative amount of acetylene gas taken out from the storage container increases, the residual DMF content in the acetylene gas increases. Figure 5 (a) Corresponding Figure 6 In (a), the residual DMF content is a constant value of 500 ppm from the switching point (5 barg) to the final minimum residual pressure (2 barg). Figure 6 (b) corresponds to Figure 5 (b) Figure 6 (c) corresponds to Figure 5 (c).

[0204] The portion of the purified acetylene gas delivered from the purifier unit 121 (purification ratio X) and the portion of the unpurified acetylene gas (1-X) delivered directly to the carburizing process of the demand point P0 are controlled to provide a total flow rate (V) suitable for one or more carburizing processes. total ). In addition, the purified acetylene gas component (purification ratio X) and the unpurified acetylene gas component (1-X) are sent to the demand point P0 in a state of being mixed in the merging device 124 (mixer 124a, etc.).

[0205] Solvent content in purified acetylene gas: η purified

[0206] Amount of purified acetylene gas: V pured

[0207] Amount of unpurified acetylene gas delivered directly: V direct

[0208] (Formula 11)

[0209] V total =V purified +V direct

[0210] (Formula 12)

[0211] V purified =X·V total

[0212] (Formula 13)

[0213] V direct =(1-X)·V total

[0214] (Formula 14)

[0215] η total =(1-X)·η total +X·η purified

[0216] The solvent content (η) in acetylene gas taken from a standard storage container (acetylene cylinder) direct ), can be appropriately expressed as a function of the residual pressure of the storage container. The function may be, for example, a logistic function or a linear function in a region of the residual pressure limited at a fixed temperature and a fixed gas flow rate.

[0217] That is, the solvent content (η) in the acetylene gas taken out from the storage container can be calculated based on the data such as the acetylene gas flow rate, residual pressure, temperature, etc. direct ).

[0218] Figure 7 The results for three target solvent contents (η target ) for each of the following purification processes. The flow rate is 10slm and the temperature is 20°C. Figure 7 In the experiment, the target solvent content (η target ) is set to 350ppm, purification starts from a residual pressure of 7barg, when it is set to 500ppm, purification starts from a residual pressure of 5barg, and when it is set to 650ppm, purification starts from a residual pressure of 4barg. Figure 7 (a) corresponds to Figure 5 (a) Figure 7 (b) corresponds to Figure 5 (b) Figure 7 (c) corresponds to Figure 5 (c).

[0219] (with conditional purification)

[0220] Conditional purification ( Figure 2 (b)) It is conditional on whether the acetylene gas is fully purified or not purified.

[0221] The conditions are determined by the control unit based on process requirements, gas flow, storage container temperature, residual pressure, etc. The timing of switching the flow switch to achieve full purge or non-purge is determined to a specific value of residual pressure (e.g. 5 barg). Figure 3 In the removal system of the structure of (a) (b), purification treatment is performed.

[0222] The acetylene gas delivered from the removal system to the carburizing process is either fully purified or non-purified.

[0223] Before switching: Solvent content in the output gas and η direct 、V direct same.

[0224] After switching: the solvent content in the output gas is η purified , V purified ≈V direct .

[0225] The control unit CU controls and monitors various valves, such as electromagnetic valves, pneumatic valves, or pneumatic or electromagnetic three-way valves.

[0226] (Purifier Unit)

[0227] The purifier unit 121 includes one or more purifiers 121a. The purifier 121a may include a first refining device for removing a trace amount of solvent as a liquid, a removal device or purifier (second refining device) for taking out a trace amount of solvent such as a mechanical trap (mechanical trap) or a cold trap (cold trap), and a third refining device for removing other trace impurities (sulfur or phosphine compounds, etc.).

[0228] The purifier 121a may be composed of a column containing one or more fillers. The filler may be, for example, one or more of zeolite, exchanged zeolite, activated carbon, treated (or impregnated) activated carbon, metal organic framework (MOF), covalent organic framework (COF), polymer, silica-based material, etc. The filler may be, for example, in the form of a film, a monolith, a pellet, a bead, a block, or a powder.

[0229] The purifier 121a may be composed of columns arranged in series, columns arranged in parallel, or a combination of the two.

[0230] Formula 15 represents a calculation formula for obtaining the amount of purified acetylene gas.

[0231] Q additional : Total amount of acetylene that meets the quality requirements

[0232] Q direct : The total amount of acetylene gas delivered from the storage container

[0233] Q purified: The amount of purified acetylene gas purified after the switching point (Sp)

[0234] P f : The final minimum residual pressure of the storage container

[0235] q C2H2 : The amount of acetylene gas delivered within a specific pressure range

[0236] q C2H2 An ideal time and heat transfer during use can be assumed to be the difference in solubility of acetylene in the solvent volume.

[0237] (Formula 15)

[0238]

[0239] Formula 16 is a calculation formula for determining the amount of solvent removed, and can be expressed as a function of pressure under ideal conditions of constant temperature and constant gas flow rate.

[0240] Q solvent removed : The amount of solvent removed in the purifier unit

[0241] η total : The total amount of solvent in the acetylene gas sent to the carburizing process

[0242] η direct : Solvent content in unpurified acetylene gas

[0243] (Formula 16)

[0244]

[0245] Compared with the conventional purification system that purifies the storage container (cylinder or gas bottle) from the initial pressure to the final pressure, the removal system 1 can reduce the gas source unit 11 by 2 to 50 times, thereby reducing the adsorbent dosage, installation area, regeneration times, regeneration energy, maintenance, etc.

[0246] The purification capacity is defined as the volume of acetylene gas of any solvent content that can be purified by a certain amount of adsorbent.

[0247] For example, "10%·m 3 kg -1 The purification capacity H" means that 1 kg of the substance M as the adsorbent can purify 10 m3 of acetylene with a solvent content of 1%. 3 This is similar to being able to use the same 1 kg of adsorbent material to purify 1 m 3 are the same. 3 kg -1 and 18%·m3 kg -1 The two substances M1 and M2 used to purify the solvent (acetone) in acetylene, as shown in Table 2, can be estimated based on the model content relative to the flow rate of 10 slm at 20°C, and the size of each single column purifier relative to the purification target concentration of acetone is 2.3%.

[0248] Table 2 shows the ideal amount of adsorbent required for the full purification of a B50-type cylinder, based on the acetone content modeled at a flow rate of 10 slm at 20°C and the corresponding size ratio (purification capacity H(M1) = 8%·m 3 kg -1 And purification capacity H(M2) = 18%·m 3 kg -1 ) comparison.

[0249]

Table 2

[0250] M1 quantity (kg) M2 quantity (kg) Relative amount of adsorbent used Full use (full purification) 12.8 5.7 100％ Situation A 0.4 0.2 3％ Case B-1 0.5 0.2 4％ Case B-2 0.7 0.3 5％ Case C 1.3 0.6 10％

[0251] Using the estimated adsorbent amounts in Table 2, it is possible to determine the size reduction of the purifier (adsorbent column, condenser, etc.). Compare full use with cases A to C. Ratio purification (case A) uses less adsorbent than the other cases.

[0252] One or more of the situations A to C can be applied based on the solvent content limit determined by the user of the demand point. In addition, each situation can be selected to improve the efficiency of the removal system 1. A higher acetylene utilization rate can be achieved, and acetylene that meets the pre-required quality (purity) can be delivered to the demand point. In addition, the removal system 1 can reduce the frequency of acetylene gas being delivered from the storage container and reduce the cost of acetylene gas supply.

[0253] The control unit CU can record, manage and transmit the system status and information in one or more storage devices. The control unit CU can predict the usage rate of the storage container and the necessity of replacement period, maintenance, regeneration of the purifier. The prediction data can be sent to the control center for predictive troubleshooting in case of necessity.

Claims

1. A removal system for removing residual solvent from acetylene gas, comprising a gas source unit 11, a purifier unit 121, a splitter 123, a confluence device 124 and a control unit CU, The gas source unit 11 includes at least one storage container, which stores acetylene dissolved in an organic solvent. The purifier unit 121 includes at least one purifier for removing the residual solvent as the organic solvent from the unpurified acetylene gas supplied from the gas source unit 11. The flow divider 123 distributes the acetylene gas supplied by the gas source unit 11. The merging device 124 can merge the purified acetylene gas processed by the purifier unit 121 with the unpurified acetylene gas supplied by the gas source unit 11. The control unit CU determines the purity or solvent content of the acetylene gas delivered from the merging device 124 and controls the flow splitter 123 and the merging device 124 so that the acetylene gas delivered to the demand point P0 has a target purity.

2. The removal system according to claim 1, comprising a first pipe L1, a first branch pipe L1a, a second branch pipe L1b, a bypass pipe L2 and a lead-out pipe L3, The first pipe L1 is used to transport the unpurified acetylene gas from the gas source unit 11 to the diverter 123. The first branch pipe L1a is used to transport the unpurified acetylene gas from the diverter 123 to the purifier unit 121. The second branch pipe L1b is used to transport the purified acetylene gas from the purifier unit 121 to the merging device 124. The bypass pipe L2 is used to transport the unpurified acetylene gas from the splitter 123 to the converging device 124. The outlet pipe L3 is used to transport acetylene gas from the confluence device 124 to the demand point P0 at the subsequent stage.

3. The removal system according to claim 1, The control unit calculates the purification ratio X based on one or more data of the concentration of acetylene gas supplied from the storage container, the concentration of residual solvent in the acetylene gas, the residual pressure of the final use condition of the storage container, the flow rate of acetylene gas, the temperature of acetylene gas, and the accumulated supply time of acetylene gas.

4. The removal system according to claim 1, The control unit controls the acetylene gas supplied by the gas source unit 11 and switches between the following (1) to (4). (1) Proportional purification according to the change of purification ratio X, (2) Fixed ratio purification with a fixed purification ratio, (3) Complete purification of the entire amount, (4) Non-purification without purification of the entire amount.

5. A removal system for removing residual impurities in gas, comprising a gas source unit, a purifier unit, a splitter, a confluence device and a control unit, The gas source unit has at least one storage container. The purifier unit includes at least one purifier that removes the residual impurities from the unpurified gas supplied from the gas source unit. The flow divider distributes the gas supplied by the gas source unit, The merging device can merge the purified gas processed by the purifier unit with the unpurified gas supplied by the gas source unit. The control unit determines the purity or impurity content of the gas delivered from the flow combining device, and controls the flow splitter and the flow combining device so that the gas delivered to the demand point has a target purity.

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