System for removing residual solvent in acetylene gas

Abstract

To provide a solvent removal system that removes solvent impurities in gas.SOLUTION: A removal system 1 includes: a gas source unit 11 that includes a storage container; a purifier unit 121 that removes a residual solvent, which is an organic solvent, from an unpurified acetylene gas supplied from the gas source unit 11; a flow split 123 that distributes the acetylene gas supplied from the gas source unit 11; flow mix means 124 capable of mixing the purified acetylene gas processed in the purifier unit 121 with the unpurified acetylene gas supplied from the gas source unit 11; and a control unit CU that determines the purity of the acetylene gas delivered from the flow mix means 124 and controls the flow split 123 and the flow mix means 124 so that the acetylene gas delivered to a demand point P0 has target purity.SELECTED DRAWING: Figure 1

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 removed from a storage container. [Background technology]

[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. Low pressure / vacuum carburizing is attracting attention because it generates less soot than other carburizing methods (e.g., high concentration carburizing and gas carburizing) (see, for example, Patent Document 1). In the carburizing technology, for example, acetylene (C 2 H 2 ) is the most widely used carbon source (see, for example, Patent Document 2).

[0003] Low pressure / vacuum carburization processes require a constant flow of acetylene to be introduced into the chamber. However, in contrast to other hydrocarbon gases, acetylene cannot be safely compressed above 1.5 barg (gauge pressure). Therefore, storage techniques for acetylene include, for example, impregnating a porous material (e.g., porous calcium silicate-based material) with acetylene dissolved in an organic solvent (e.g., acetone or dimethylformamide (DMF)). When acetylene in an organic solvent is recovered from a porous material, a certain amount of organic solvent is inevitably present in the acetylene gas.

[0004] In the carburization process, a number of storage vessels (eg, cylinders) for storing acetylene are installed, and the amount of acetylene supplied needs to be controlled according to the process requirements in the chamber.

[0005] The acetylene gas extracted from the storage vessel 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 speed of the acetylene gas (see, for example, Patent Document 3). 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), and in the range of about 1% to about 10% when the organic solvent is acetone.

[0006] In the carburization process, the presence of organic solvents can deteriorate the homogeneity and quality of the process and can also affect maintenance, etc. Therefore, it is desired to control the concentration of organic solvents in the acetylene gas so that it does not exceed a certain concentration. On the other hand, an organic solvent is required to store acetylene in a storage container, and in order to extract acetylene gas from this storage container, the organic solvent is also carried along with it, and furthermore, it is difficult to extract the entire amount of acetylene from the storage container.

[0007] Furthermore, the content of dimethylformamide (DMF) in acetylene gas is about 10 to 100 times less than that of acetone, and therefore it is preferable to use dimethylformamide (DMF) rather than acetone (see, for example, Patent Document 4). On the other hand, DMF may be restricted in use due to local laws, safety guidelines, etc. Therefore, acetone may be recommended as an organic solvent.

[0008] Methods for removing residual solvents from acetylene gas include, for example, a cold trap (see, for example, Patent Document 5) or a solvent removal device made of an adsorbent (see, for example, Patent Documents 3 and 6). Such a solvent removal device (also called a purifier) ​​requires strict monitoring and the flow rate of the acetylene gas introduced must be limited. Furthermore, the content of the organic solvent in the acetylene may change over time or during use. That is, it is difficult to appropriately set the size, installation conditions, operating conditions, etc. of the solvent removal device (purifier). Therefore, when acetylene gas (including organic solvents) is used for applications such as carburization processes, there is a demand for optimal size determination and optimal maintenance (installation conditions, operating conditions, etc.) of the above-mentioned solvent removal device (purifier).

[0009] When acetylene gas is taken out of 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. Conventionally, in order to avoid high residual solvent concentration, less than 70% of the acetylene in the total acetylene storage is taken out.

[0010] In addition, the residual pressure in the storage container decreases with use, and the flow rate of acetylene gas taken out of the storage container per unit time also decreases, which means that the acetylene in the storage container cannot be fully used, resulting in a lower utilization rate. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 5,702,540 [Patent Document 2] US Patent Publication No. 2003 / 0168125 [Patent Document 3] International Patent Publication No. WO2008120160 [Patent Document 4] U.S. Patent No. 8,915,992 [Patent Document 5] U.S. Patent No. 8,309,473 [Patent Document 6] U.S. Patent No. 8,398,747 Summary of the Invention [Problem to be solved by the invention]

[0012] The present disclosure provides a system that can adequately remove traces of residual solvent in acetylene gas and can supply a controlled amount of acetylene (low concentration of residual solvent) in accordance with the specifications of the carburization process. The present disclosure also provides a system that can use DMF and acetone as organic solvents. The present disclosure also provides a system that can increase the amount of acetylene gas supplied from the storage container and reduce the amount of acetylene remaining in the storage container compared to conventional methods, thereby improving utilization rate (reducing remaining amount rate). The present disclosure also provides a system that can maintain a high flow rate of acetylene gas per unit time from the storage vessel. [Means for solving the problem]

[0013] The system for removing residual solvents from acetylene gas (1) is as follows: a gas source unit (11) comprising at least one storage vessel (e.g., an acetylene storage cylinder) for storing acetylene dissolved in an organic solvent; a purifier unit (121) including at least one purifier (residual solvent remover) for removing a residual solvent, which is an organic solvent, from the unpurified acetylene gas supplied from the gas source unit (11); a flow splitter (123) for distributing (sending completely to one side at a predetermined flow rate) the acetylene gas supplied from the gas source unit (11); a joining means (124) by which the purified acetylene gas treated in the purifier unit (121) and the unpurified acetylene gas supplied from the gas source unit (11) can join together; a control unit (CU) for determining the purity or solvent content of the acetylene gas sent from the joining means (124) so ​​that the acetylene gas to be sent to the demand point (P0) has a target purity, and for controlling the flow splitter (123) and the joining means (124); The device may include:

[0014] The system (1) for removing residual solvent from acetylene gas comprises: a first pipe (L1) for delivering the unpurified acetylene gas from the gas source unit (11) to the flow split (123); a first branch pipe (L1a) for conveying the unpurified acetylene gas from the flow split (123) to the purifier unit (121); a second branch pipe (L1b) for sending the purified acetylene gas from the purifier unit (121) to the joining means (124); a bypass pipe (L2) for sending unpurified acetylene gas from the flow split (123) to the joining means (124); an outlet pipe (L3) for sending acetylene gas from the joining means (124) to a downstream demand point (P0); The device may include:

[0015] The control unit (CU) may calculate the purification ratio (X) based on one or more types of data from the concentration of acetylene gas supplied from the storage container, the concentration of residual solvent in the acetylene gas, the residual pressure of the storage container under final use conditions, the flow rate of the acetylene gas, the temperature of the acetylene gas, and the cumulative supply time of the acetylene gas.

[0016] The control unit (CU) controls the acetylene gas supplied from the gas source unit (11) as follows: (1) Proportional purification, which purifies according to changes in the purification ratio (X); (2) Fixed ratio purification, which purifies at a fixed purification ratio; (3) Complete purification, which purifies the entire amount; (4) Non-purification, where the entire amount is not purified; may be controlled so as to switch between

[0017] Another disclosed system for removing residual impurities from a gas includes: a gas source unit comprising at least one storage vessel; a purifier unit including at least one purifier for removing the residual impurities from the unpurified gas supplied from the gas source unit; a flow split for distributing gas supplied from the gas source unit; a confluence means for confluence of the purified gas treated in the purifier unit and the unpurified gas supplied from the gas source unit; The gas supply system may further include a control unit that determines the purity or impurity content of the gas sent from the joining means and controls the flow split and the joining means so that the gas sent to the demand point has a target purity. The gas may be other gases such as natural gas (NG) containing variable impurities such as carbon dioxide or water, or a mixture of gases containing impurities.

[0018] (effect) (1) Acetylene gas of a constant purity can be extracted from multiple cylinders (storage containers) that store acetylene. (2) When the organic solvent is DMF, in order to avoid an increase in the solvent content in the acetylene gas to more than 500 ppm, the system may be configured not to extract acetylene gas from a cylinder whose residual pressure has dropped below about 5 barg. This limits the total amount of cylinder usage when the residual pressure drops. In the present disclosure, about 70% to 80% of the acetylene in the total acetylene storage can be supplied (conventionally, only about 70% or less could be used). (3) By providing a purifier (solvent removal device) and controlling whether or not to send the gas to the purifier, or sending only a portion of the gas to the purifier, the concentration (content) of residual solvent in the acetylene gas can be appropriately controlled. (4) The amount of acetylene gas supplied from the storage container can be increased, and the amount of acetylene remaining in the storage container can be reduced compared to conventional methods, thereby improving utilization rate (reducing remaining amount rate). (5) A high flow rate of acetylene gas per unit time can be maintained from the storage container. (6) Even when acetone is used as the organic solvent, the same quality (residual solvent concentration) as DMF can be maintained. (7) Residual solvents in acetylene gas can be completely or partially removed, and the acetylene purity can be increased to an acceptable specified concentration level (the concentration of residual solvents can be kept below a certain level). [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 illustrates the function of the removal system. [Diagram 2] FIG. 13 is a diagram showing cases A, B, and C of a purification ratio X. [Diagram 3] FIG. 2 is a diagram showing an example of a piping configuration for a purification process and a non-purification process. [Figure 4] FIG. 1 is a diagram showing an example of the relationship between the residual pressure in a storage container and the ideal amount of acetylene to be used. [Diagram 5] FIG. 1 is a graph showing the relationship between DMF content and residual pressure. [Figure 6] FIG. 6 is a graph showing the relationship between the residual DMF content and the amount of acetylene gas used, which corresponds to FIG. 5. [Figure 7] FIG. 1 shows an example of a purification process at different target solvent contents. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Several embodiments of the present invention will be described below. The embodiments described below are merely examples of the present invention. The present invention is not limited to the following embodiments, and includes various modified forms that are implemented within the scope of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0021] (Embodiment 1) The basic function of the system 1 for removing residual solvent in acetylene gas according to the first embodiment will be described with reference to FIG. The removal system 1 includes a gas source unit 11, a purifier unit 121, a flow splitter 123 (also called a "distribution means"), a confluence means 124, and a control unit CU.

[0022] The gas source unit 11 includes at least one storage container. The gas in the first embodiment is acetylene gas. In the storage container, acetylene is dissolved in an organic solvent (DMF) and then impregnated in a porous material and stored.

[0023] The purifier unit 121 includes at least one purifier 121a for removing residual organic solvents from the raw acetylene gas supplied from the gas source unit 11. The one or more purifiers 121a may be configured with a series or parallel system of adsorbent columns or condensers for purification.

[0024] The flow splitter 123 is a means for distributing (sending completely to one side, distributing at a predetermined flow rate) the acetylene gas supplied from the gas source unit 11. The flow splitter 123 may be composed of a three-way valve 123a, a damper mechanism, a control valve, a flow control valve, a proportional flow control valve, a solenoid valve, etc.

[0025] The confluence means 124 is a means by which the purified acetylene gas treated in the purifier unit 121 and the unpurified acetylene gas supplied from the gas source unit 11 can be confluenced. The confluence means 124 can send only the purified acetylene gas to the subsequent stage, or can send only the unpurified acetylene gas to the subsequent stage, or can mix the two at a predetermined mixing ratio (purification ratio) before sending them to the subsequent stage. The confluence means 124 mixes unpurified acetylene gas with purified acetylene gas purified by the purifier unit 121 at a predetermined purification ratio (X=0 to 1). The confluence means 124 may be composed of a downstream three-way valve 124a, or may be composed of a T-shaped pipe and a gate valve or a flow control valve. The confluence means 124 may be configured to include a mixer 124a or a buffer tank. In the mixer 124a or the buffer tank, the gas purified by the purifier 121a and the unpurified gas are mixed, and the gas with the purification ratio (X) is sent downstream. The mixing region of the confluence means 124 may be comprised of a mixing chamber or a buffer chamber. In the case of a buffer chamber, the purified acetylene gas and the directly fed unpurified acetylene gas may be introduced simultaneously at a controlled flow rate, or may be introduced sequentially into the buffer chamber based on a set volume fraction. The mixing region may include one or more sampling ports, and the solvent and / or other impurities in the acetylene gas may be measured by an analyzer.

[0026] The control unit CU calculates the concentration of the gas sent from the confluence means (124) and controls the flow split (123) and the confluence means (124) so ​​that the acetylene gas (unpurified gas, fully purified gas, mixed gas) sent to the demand point (P0) has a target concentration (e.g., acetylene purity, residual solvent concentration, etc. required at the demand point). The control unit CU may control the flow split 123 to send the acetylene gas completely to only one of the pipes, or may control the flow split 123 to distribute and send the acetylene gas to the purifier unit 121 and the confluence means 124 at a predetermined purification ratio (X=0 to 1).

[0027] The control unit CU controls the concentration of acetylene gas supplied from the storage container, the concentration (content) of residual solvent in the acetylene gas (η sourceThe purification ratio (X) may be determined based on one or more of the following data: residual pressure of the storage container under end-use conditions, flow rate of acetylene gas, temperature of acetylene gas, and cumulative supply time of acetylene gas. The control unit CU may control the flow split 123, the confluence means 124, and the flow control valves or gate valves provided in each pipe (L1, L1a, L2, L1b, L3, etc.) based on the purification ratio (X).

[0028] The control unit CU may determine whether to send acetylene gas to the purifier unit 121 for processing and may determine the sending period (total flow rate of purified acetylene gas) in response to the demand of the carburization process at the demand point P0. The control unit CU may determine whether or not to feed into the bypass pipe L2 in response to a request from the carburization process at the demand point P0, and may determine the feed period (total flow rate of unpurified acetylene gas). The control unit CU may determine switching information including at least a total flow rate of purified acetylene gas and a total flow rate of unpurified acetylene gas corresponding to the demand of the carburization process at the demand point P0.

[0029] The control unit CU may determine the mixing ratio (mixing ratio per unit time) of the acetylene gas treated in the purifier unit 121 and the acetylene gas sent to the bypass pipe L2. The control unit CU may determine the ratio of the purified acetylene gas (purification ratio X) to the unpurified gas (1-X), and may further determine the ratio at which they are mixed in the confluence means 124.

[0030] The control unit CU may monitor the purifier unit 121 for changes in status (eg, in use, regenerating, standby) or maintenance status and may control the purifier unit 121 . The control unit CU may determine which purifier (adsorbent column) or multiple purifiers (adsorbent columns) to use or regenerate among at least one or more purifiers 121a constituting the purifier unit 121, and perform the control necessary for the use or regeneration. The control unit CU may include an accumulation amount calculation unit that calculates the amount of residual solvent (also called "impurities") removed (purified) from the acetylene gas by the purifier unit 121 and accumulated in the purifier (such as an adsorption column), a regeneration / replacement time calculation unit that calculates the regeneration time and / or replacement time of each purifier 121a of the purifier unit 121 in accordance with the accumulation amount of residual solvent calculated by the accumulation calculation unit, and a regeneration control unit that controls a regeneration means (not shown) in response to the regeneration time and / or replacement time of each purifier 121a calculated by the regeneration / replacement time calculation unit 302.

[0031] The regeneration means may include a heating device for heating the adsorbent in the purifier, a regeneration gas supply means for supplying a regeneration gas used for regenerating the adsorbent to a piping, and an automatic gate valve provided in the piping. The regeneration control unit may control the ON / OFF of an automatic gate valve that switches gas passage between the purifier for regeneration and the purifier in use. The regeneration control unit may control the ON of a heating device that heats the adsorbent in the purifier for regeneration. The heating device may be an electric heating jacket provided on the outer wall of the storage container. The regeneration control unit may instruct the regeneration gas supply means to control the timing and supply time for supplying the regeneration gas to the piping.

[0032] The first pipe L1 is a pipe for sending unpurified acetylene gas from the gas source unit 11 to the flow split 123. The first branch pipe L1a is a pipe for sending unpurified acetylene gas from the flow split 123 to the purifier unit 121. The second branch pipe L1b is a pipe for sending purified acetylene gas from the purifier unit 121 to the junction means 124. The bypass pipe L2 is a pipe for sending unpurified acetylene gas from the flow split 123 to the junction means 124. The outlet pipe L3 is a pipe for sending acetylene gas from the junction means 124 to a downstream demand point P0.

[0033] The storage container and / or each of the pipes may have a valve (e.g., a gate valve, a flow control valve), a gas flowmeter for measuring the gas flow rate, a gas pressure gauge for measuring the gas pressure, a gas thermometer for measuring the gas temperature, a gas concentration measuring device for measuring the gas concentration, an impurity concentration measuring device (trace solvent analyzer) for measuring the concentration of impurities (solvents) in the gas, etc. In these, each measured data may be sent to the control unit CU in association with each measurement time and each device identification information, or may be stored in a storage unit (not shown).

[0034] The gas source unit 11 or the control unit CU detects the amount of acetylene gas (Q) taken out of the storage container, which is measured by an impurity concentration measuring device (trace solvent analyzer). source Residual solvent content (concentration) in (η source ) may be determined.

[0035] The upstream three-way valve 123a and the downstream three-way valve 124a may be automatically operated valves or may be manually operated valves. The upstream three-way valve 123a and the downstream three-way valve 124a may be controlled by a control command from the control unit CU. Each gate valve and each flow control valve may be controlled by a control command from the control unit CU.

[0036] The control unit CU measures the residual solvent content (concentration) (η source ) The purification ratio (X) is calculated based on one or more of the following data: residual pressure under final cylinder conditions, flow rate of acetylene gas, temperature of acetylene gas, and cumulative supply time. The control unit CU controls the flow control valves or gate valves provided in the flow split 123, the merging means 124, and the respective pipes L1, L1a, L2, L1b, and L3, etc., based on the purification ratio (X). The control unit CU controls the branching means and various valves in response to 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. 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. In these, the measured data may be associated with the respective measurement times and respective device identification information, and may be sent to the control unit CU or may be stored in a memory unit.

[0037] (Method of determining limit residual pressure) The control unit CU and / or the gas source unit 11 determine the limit residual pressure of the storage vessel corresponding to the specific operating conditions (flow rate, temperature). The allowable content of residual solvents (impurities) in the acetylene gas according to the operating conditions is predetermined, and the residual pressure at which the desired carburizing process quality cannot be obtained is determined. When the measured internal pressure of the active storage vessel falls below a threshold residual pressure, a switch is made to another storage vessel, called the switching point, which can be used to determine when to start and stop the purification process in the purifier unit 121. The switching point can be determined based on measurement data (monitoring) from various measuring devices, data such as the residual pressure and temperature in the storage container, etc. The switching point is calculated based on measurable information such as the residual pressure and temperature in the storage container, the solvent content in the acetylene gas, the cumulative supply time, the total amount of acetylene supplied, and the flow rate of acetylene per unit time. Determining the switching points allows optimization of the purification system (number of purifiers, adsorption column size, etc.). The acetylene gas concentration (residual solvent concentration) taken out of the container corresponding to the residual pressure and temperature may be measured in advance, an approximation function may be determined from the measurement data, and the approximation function (which may be a linear function) may be stored in the memory unit. The acetylene gas concentration (residual solvent concentration) may be calculated from the measured values ​​of the residual pressure and temperature using this approximation function. Depending on the acetylene concentration and flow rate required by the demand point P0, it may be decided to replace the storage container, use a purifier, use a bypass pipe, use a mixing means, etc. In addition, the purifier does not need to be used all the time, and can be made smaller than in systems where the purifier is used continuously. The smaller size of the purifier also reduces the regeneration energy required for the purifier.

[0038] Three types of purification processes are carried out depending on the switching points. (1) Proportional purification According to the change in the calculated purification ratio (X), the amount of gas to be purified and the amount of gas not to be purified are changed and mixed in real time or at a specified time interval (1 minute, 10 minutes, etc.). The purification of acetylene gas is made variable with the upper limit set to the maximum fixed content of residual solvent in the acetylene gas. (2) Fixed ratio purification When it is determined that purification is necessary, purification processing is carried out according to a preset fixed purification ratio. (3) Complete purification (or non-purification) When purification is judged to be necessary, 100% of the acetylene gas is purified (the gas is sent to the purifier unit, not to the bypass piping). When purification is judged to be unnecessary, 100% of the acetylene gas is sent to the subsequent stage without purification (the gas is sent to the bypass piping, not to the purifier).

[0039] In determining the switching point, based on the initial values ​​of the reservoir (volume, filling pressure and solvent amount) and the acetylene solubility, a function can be defined that defines the relationship between the residual pressure in the reservoir during use and the concentration of acetylene gas (solvent concentration) taken out. This function can be used to determine the ideal acetylene supply available for the downstream carburization process. (a) The commonly used working pressure limit is determined by the residual pressure in the storage vessel. (b) Depending on the targeted end-use conditions (residual pressure), it allows an increase in available acetylene gas of 10% to 60%, depending on the use conditions (flow rate and temperature). For example, for DMF-based cylinders (extended use from 5 barg to 2 barg), the available amount of acetylene increases by about 20% to 30%, and for acetone-based cylinders (extended use from 6 barg to 2 barg), the available amount of acetylene increases by about 35% to 40%.

[0040] Figure 4 shows the relationship between the residual pressure in the storage vessel and the ideal amount of acetylene to be used, as a function of the residual pressure in the storage vessel (cylinder) at 20°C. Figure 4(a) shows the case of a standard B50 cylinder filled with acetylene gas in the solvent DMF, and Figure 4(b) shows the case of a standard B50 cylinder filled with acetylene gas in the solvent acetone. (1) We show that the switching point is determined by the limit value of each residual solvent (impurity). DMF: 500ppm / 5barg Acetone: 2.2% / 6barg (assuming a flow rate of 10slm). The content of solvents in acetylene gas is determined based on general recommendations for the use of storage containers. (2) The horizontal axis of Figure 4 shows the residual pressure, the right vertical axis shows the utilization rate of the storage container under standard use, and the left vertical axis shows the ideal amount of acetylene gas that can be used. The usage rate is 100% in the conventional standard usage. According to the removal system 1 of the present disclosure, the timing for replacing the storage container can be extended to the minimum residual pressure (2 barg), and the usage rate can be increased to 130% (DMF, FIG. 4(a)) and 140% (acetylene, FIG. 4(b)), and the usable amount can also be increased.

[0041] 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 can be determined in various ways. Two approaches are illustrated in Figure 2. Proportional purification (cases A and B) or total purification (case C) are illustrated. The main difference between these two approaches is that in proportional purification, a portion of the acetylene gas from the storage vessel is purified (purification ratio X), whereas in total purification, all the acetylene gas from the storage vessel is purified after switching. (1) Case A: After reaching the switching point, purification is performed with a variable purification ratio (X) based on the evaluation results (Figure 2(a)). (2) Case B: After reaching the switching point, purification is performed at a fixed purification ratio (X) (Figure 2(a)). (3) Case C: After the switching point is reached, the entire amount of acetylene gas is purified (Figure 2(b)). Figure 2(a) shows proportional purification, where the acetylene gas is distributed such that only a portion of the acetylene gas is purified, at a purification ratio (Χ), and Figure 2(b) shows total purification, where the acetylene gas from the storage vessel (cylinder) is completely purified by the purifier unit 121. The fixed purification ratio (X) may be set to a fixed ratio according to the requirements of the final demand point P0, for example. The variable purification ratio (X) is determined by targeting a fixed maximum content of residual solvents in the acetylene gas.

[0042] (Proportional Purification) The control unit CU determines the amount (proportion) of gas to be purified by the purifier unit 121. The purified gas is then mixed with the raw gas to produce a mixed gas, the solvent (impurity) content of which corresponds to the requirements of the downstream process. An advantage of the removal system 1 is that the size of the purifier unit can be minimized compared to a purifier system that purifies the entire amount of acetylene gas supplied to a downstream process. In one embodiment, the purification ratio X of the gas to be purified may be a fixed value. The purification ratio may be re-evaluated and determined. A variable purification ratio may be dynamically evaluated and determined. In another embodiment, the purification ratio X or whether or not to perform full purification may be determined based on a fixed value such as a target final residual pressure (before the storage vessel is replaced). In such a case, the purification ratio X is determined as a single value in a predictive manner. Furthermore, a constant purification ratio X may be estimated based on a predetermined range of the number of uses, gas volume, or residual pressure (intermediate cases between cases A and B may be considered).

[0043] The fraction of gas that is purified (purification ratio X) is ideally proportional to the solvent (impurity) content (η source ), target solvent (impurity) content (η target ) and the solvent (impurity) content in the purified acetylene gas after purification (η purified ) is determined based on The solvent (impurity) content of the mixed gas after purification can be determined, or the solvent (impurity) content by switching to full purification can be determined. Figure 3 shows an example of the purification process of the removal system 1. This system can purify all or a part of acetylene from an acetylene gas source unit 11 using a purification unit 121, and mix it with unpurified acetylene gas to generate acetylene gas of a predetermined purity.

[0044] The relationship between each solvent concentration and the purification ratio X is expressed by formula (1). (Equation 1) η output = (1-X)·η source + X η purified Total gas flow rate Q total (=Q source =Q output ) are shown in equations (2), (3), and (4), where the state before the switching point corresponds to X=0. (Formula 2) Q total = Q purified + Q direct (Formula 3) Q purified =X Q total (Formula 4) Q direct =(1-X) Q total Flow rate of acetylene gas from storage vessel: Q source (=Q total ) Solvent content in acetylene gas from a storage vessel: η source Flow rate of acetylene gas purified by the purifier: Q purified Solvent content (concentration) in acetylene gas after purification by the purifier: η purified Flow rate of acetylene gas bypassing the purifier: Q direct Solvent content in acetylene gas bypassing the purifier: η direct Flow rate of acetylene gas output from removal system 1: Q output Solvent content in the acetylene gas output from removal system 1: η output Target solvent content according to user requirements: η target Pressure regulator with pressure gauge: PR1 Upstream flow control valve: V1 Flow control valve installed in purifier piping line L1 (L1a): CV2 Flow control valve installed in bypass piping line L2: CV1 The function of the branching means 123 can be realized by CV1 and CV2.

[0045] The removal system 1 is capable of diluting residual solvent (and impurities) in the acetylene gas removed from the storage vessel. (1) The purifier unit 121 may be configured with one or more adsorbent packed columns or a solvent condenser. The purifier unit 121 can convert the acetylene gas coming from the storage vessel into an acetylene gas stream of higher purity (e.g., removal of at least 50% of the solvent vapor). (2) The conditions under which purified and unpurified acetylene gas are mixed or used can be controlled.

[0046] The removal system 1 allows for the use of most of the acetylene gas in the storage vessel while reducing the amount of residual solvent in the acetylene gas provided to a downstream process. The specified content (or tolerance) of DMF is 500 ppm (target solvent content η target For example, in the case of a standard DMF solvent storage vessel with a residual pressure of 5 barg, conventionally, it would be necessary to stop use. This means that, assuming proper deactivation of the storage vessel during use, only about 60% to 70% of the acetylene gas can be used at the full capacity of the storage vessel. On the other hand, the removal system 1 can use acetylene gas at a target solvent content η target It can operate down to a residual pressure of 2 barg without exceeding 100% and can use 70% to 80% of the full capacity of the storage vessel, thus extending the life of the storage vessel (cylinders, bottles, etc.) on-site and reducing the frequency of storage vessel change-out and refilling.

[0047] The control unit CU decides under what conditions and in what amount the purification takes place. Acetylene purity in supply gas < acetylene purity in target purified gas Solvent content in supply gas > Solvent content in purified gas (mixed gas) The control unit CU may control each gate valve to completely stop the flow from the gas source unit 11 (storage container) when the quality of the acetylene gas drops below a reference value and switching to another storage container is not possible.

[0048] The control unit CU may estimate the total amount of acetylene gas used based on (i) the conditions of use (residual pressure in the storage vessel at start, residual pressure during use) and (ii) the integral of the flow rate of acetylene gas delivered to the demand point process. The control unit CU may obtain or determine information regarding the current utilization rate of the storage container (cylinder), the predicted time until the switching point and the remaining time for replacing the storage container (cylinder) (usable time, replacement time) according to either the pre-registered processing time of the carburizing process, its usage or average values ​​based on recorded data. The control unit CU may output an alert to the user when a problem occurs due to cooling of the storage vessel as the acetylene gas is removed. A warning may also be output to the user in situations where the usage conditions fluctuate too much (flow rate problems, temperature, residual pressure too low), etc. Also, to assist the user in inventory management and delivery, it may output an alert when the storage vessel reaches a certain usage rate.

[0049] The control unit CU may have one or more processors, and the processors may read various data and control commands from the storage unit and execute processes required for various controls. The control unit CU may transmit and receive various data and command signals to and from an external device, which may be, for example, the gas source unit 11, the flow splitter 123, the purifier unit 121, the merging means 124, a storage device, a cloud server, a cloud storage, a control device of the demand point P0, a user management device, etc. The various data include, for example, the above-mentioned measurement data, determined data, purification ratio X, switching point (usage limit point), estimated replacement time of the storage container, residual pressure, various process data, control command data, and the like. These data may be used to improve inventory control, quality control, and other site controls.

[0050] The control unit CU may control and monitor the entire removal system 1. Table 1 shows an example of a purification process. Residual pressure of storage pressure during use: P residual Switching point: Sp = limit residual pressure under normal use. In this disclosure, purification is performed even at a residual pressure lower than that to control the amount of residual solvent. [Table 1] (a): Purification rate X: Amount of purified acetylene gas purified by the purifier unit / Total amount of unpurified acetylene gas taken out from the storage container (b): Temperature, residual pressure, or other measured parameters that have a significant change from normal or estimated values ​​from the control unit.

[0051] (Embodiments of purification) The control unit CU is a unit that controls the purity level (lower limit concentration or target solvent content η target ) may be determined a limit residual pressure before replacement of the storage container and a marginal pressure range (offset value) higher than the limit residual pressure. Figure 3 shows examples of different purification processes. These 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 process can be set based on the switching point (including offset).

[0052] (Proportional Purification) Proportional purging purifies a portion of the acetylene gas removed from the storage vessel. The control unit CU determines the amount of acetylene gas to be purified by the purifier 121a. The purified acetylene gas is mixed with unpurified acetylene gas in the merging means 124. This reduces the residual solvent content (solvent concentration) in the acetylene gas. The partial purification process allows the purifier unit to be made smaller than other systems that purify the gas constantly.

[0053] FIG. 5 shows the relationship between the DMF content and the residual pressure. The acetylene gas flow rate is 10 slm and the temperature is 20° C. In this example, the target solvent content η target was set to 500 ppm. It can be seen that the DMF content in the acetylene gas increases with the decrease in residual pressure. Using this relationship curve, the purification ratio X, proportional purification, fixed ratio purification, and complete purification can be determined. Figure 5(a) shows that by starting proportional purification at the switching point (5 barg), the DMF content (500 ppm) in the acetylene gas can be kept constant even if the residual pressure drops from 5 barg to 2 barg. Figure 5(b) shows the results of fixed ratio purification (increasing the fixed purification ratio as the pressure drops) at 5, 4, and 3 barg so that the DMF content does not exceed 500 ppm. Figure 5(c) shows the results of full purification, where the minimum residual pressure, which indicates the timing for replacing the storage vessel, is set to 2 barg, so that the DMF content does not exceed 500 ppm at that value.

[0054] The clearance ratio X may be re-evaluated (re-set) by the control unit CU, depending for example on the accuracy of the distribution of the flow split 123.

[0055] FIG. 6 shows the relationship between the residual DMF content and the amount of acetylene gas used, which corresponds to FIG. As the cumulative amount of acetylene gas removed from the storage vessel increases, the residual DMF content in the acetylene gas increases. Figure 6(a), which corresponds to Figure 5(a), shows that the residual DMF content is constant at 500 ppm from the switching point (5 barg) to the final minimum residual pressure (2 barg). Similarly, Figure 6(b) corresponds to Figure 5(b), and Figure 6(c) corresponds to Figure 5(c).

[0056] The amount of purified acetylene gas sent from the clarifier unit 121 (purification ratio Χ) and the amount of unpurified acetylene gas sent directly to the carburization process at the demand point P0 (1-Χ) determine the total flow rate (V total The purified acetylene gas (purification ratio X) and the unpurified acetylene gas (1-X) are mixed in a merging means 124 (such as mixer 124a) and sent to the demand point P0. Solvent content in purified acetylene gas: η purified Amount of purified acetylene gas: V pured Amount of unpurified acetylene gas sent directly: V direct (Formula 11) V total = V purified + V direct (Formula 12) V purified = X V total (Formula 13) V direct = (1-X) V total (Formula 14) η total = (1-X)·η total +X·η purified

[0057] The solvent content (η) in acetylene gas taken from a standard storage vessel (acetylene cylinder) direct) can be conveniently expressed as a function of the residual pressure in the storage vessel, such as a logistic function or a linear function in a region of limited residual pressure at a fixed temperature and fixed gas flow rate. In other words, the solvent content (η direct ) can be obtained.

[0058] Figure 7 shows the three target solvent contents (η target ) are shown. The flow rate is 10 slm and the temperature is 20°C. In FIG. 7, the target solvent content (η target ) is set to 350 ppm, purification will start from a residual pressure of 7 barg, when set to 500 ppm, when the residual pressure is 5 barg, when set to 650 ppm, when the residual pressure is 4 barg. Figure 7(a) corresponds to Figure 5(a), Figure 7(b) corresponds to Figure 5(b), and Figure 7(c) corresponds to Figure 5(c).

[0059] (Conditional Purification) Conditional purification (Figure 2(b)) determines whether acetylene gas is completely purified or not purified under certain conditions. The conditions are determined by the control unit based on measurements such as process demand, gas flow rate, storage vessel temperature, residual pressure, etc. The timing of the flow switch to achieve full purification or no purification is determined as a specific value of residual pressure (e.g. 5 barg). The purification process is carried out by the removal system configured as shown in Figure 3(a)(b). The acetylene gas sent from the removal system to the carburization process may be fully purified or unpurified. Before switching: The solvent content in the output gas is η direct , V direct is the same as: After switching: The solvent content in the output gas is η purified , V purified ≒V direct It is. The control unit CU controls and monitors various valves, such as solenoid valves, pneumatic valves, or three-way pneumatic or solenoid valves.

[0060] (Purifier unit) The purifier unit 121 comprises one or more purifiers 121a, which may comprise a first purifier for removing trace solvent as liquid, a remover or purifier (second purifier) ​​for removing trace solvent such as a mechanical trap or cold trap, and a third purifier for removing other trace impurities (such as sulfur or phosphine compounds). The purifier 121a may be comprised of a column containing one or more packings. The packings may be, for example, one or more of zeolites, exchanged zeolites, activated carbon, treated (or impregnated) activated carbon, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), polymers, silica-based materials, etc. The packings may be in the form of, for example, films, monoliths, pellets, beads, blocks, or powders. The purifier 121a may be composed of columns arranged in series, columns arranged in parallel, or columns arranged in both series and parallel configurations.

[0061] Equation 15 shows the calculation formula for calculating the amount of purified acetylene gas. Q additional : The total amount of acetylene that satisfies the quality requirement. Q direct :Total amount of acetylene gas sent from the storage tank Q purified : Amount of purified acetylene gas purified after switching point (Sp) P f : The final minimum residual pressure in the storage vessel q C2H2 : Amount of acetylene gas delivered at a specific pressure range q C2H2 can be assumed to be the difference in solubility of acetylene in the amount of solvent, assuming ideal time and heat transfer over the duration of use.

number

[0062] Equation 16 is the calculation for the amount of solvent removed, which can be expressed as a function of pressure in the ideal case of constant temperature and constant gas flow rate. Q solvent removed : the amount of solvent removed by the clarifier unit η total : The total amount of solvents in the acetylene gas sent to the carburizing process η direct : Solvent content in unpurified acetylene gas

number

[0063] In comparison with a conventional purification system that constantly purifies a storage container (gas cylinder or bundle) from the initial pressure to the final pressure, the removal system 1 can reduce the size of the gas source unit 11 by 2 to 50 times. It can also reduce the amount of adsorbent, the installation area, the number of regenerations, the regeneration energy, and the maintenance. Purification capacity is defined as the volume of acetylene gas of a given solvent content that can be purified by a given amount of adsorbent. For example, "10% m 3 ·kg -1 The purification capacity H" is the capacity of 1 kg of adsorbent material M to purify 10 m of acetylene with a solvent content of 1%. 3 This shows that the same 1 kg of adsorbent material can purify 1 m of acetylene with a 10% solvent content. 3 It is also possible to purify the solvent (acetone) in acetylene to 8% m 3 ·kg -1 and 18%·m 3 ·kg -1 For two types of substances M1 and M2 that can be purified by 2.3%, respectively, the purifier size for a single column for a purification target concentration of 2.3% acetone can be estimated based on the model content for a flow rate of 10 slm at 20°C, as shown in Table 2.

[0064] Table 2 shows the ideal amount of adsorbent required (purification capacity H(M1) = 8% m2) based on the modeled acetone content for a flow rate of 10 slm at 20 °C and the corresponding size ratio, compared to the ideal amount of adsorbent required for full purification of a B50 type gas cylinder. 3 ·kg -1 and purification capacity H(M2) = 18% m 3 ·kg -1 ) comparison is shown below. [Table 2]

[0065] Using the estimated adsorbent amounts in Table 2, the sizing reduction of the clarifier (adsorbent column, condenser, etc.) can be determined. Full use is compared to cases A through C. Proportional clarification (case A) requires less adsorbent amount than the others. Based on the solvent content limit determined by the user at the demand point, one or more of cases A to C can be applied. Also, each case can be selected to improve the efficiency of the removal system 1. It is possible to enable a higher utilization rate of acetylene and deliver acetylene of a quality (purity) that meets the prior requirements to the demand point. Also, the removal system 1 can reduce the frequency of pumping acetylene gas from the storage vessel, thereby reducing the cost of acetylene gas supply.

[0066] The control unit CU may record, manage, and communicate system status and information in one or more storage devices. The control unit CU may predict the usage rate and replacement timing of the reservoir, maintenance, and the need for purifier regeneration. Predicted data may be sent to and used by a control center to predict troubleshooting if the need arises. [Explanation of symbols]

[0067] 1. System for removing residual solvents from acetylene gas 11 Gas source unit 121 Purifier Unit 121a Purifier 123 Flow Split 124 Merging means CU Control Unit

Claims

1. A system for removing residual solvent from acetylene gas, comprising: a gas source unit (11) comprising at least one storage vessel for storing acetylene dissolved in an organic solvent; a purifier unit (121) including at least one purifier for removing residual solvent, which is the organic solvent, from unpurified acetylene gas supplied from the gas source unit (11); a flow split (123) for distributing acetylene gas supplied from the gas source unit (11); a joining means (124) for joining the purified acetylene gas treated in the purifier unit (121) and the unpurified acetylene gas supplied from the gas source unit (11); a control unit (CU) that determines the acetylene gas purity or solvent content sent from the joining means (124) so ​​that the acetylene gas to be sent to a demand point (P0) has a target purity, and controls the flow split (123) and the joining means (124).

2. a first pipe (L1) for delivering the unpurified acetylene gas from the gas source unit (11) to the flow split (123); a first branch pipe (L1a) for conveying the unpurified acetylene gas from the flow split (123) to the purifier unit (121); a second branch pipe (L1b) for sending purified acetylene gas from the purifier unit (121) to the joining means (124); a bypass pipe (L2) for sending unpurified acetylene gas from the flow split (123) to the joining means (124); an outlet pipe (L3) for sending acetylene gas from the joining means (124) to a downstream demand point (P0); The removal system of claim 1 , comprising:

3. the control unit calculates a purification ratio (X) based on one or more kinds of data among the concentration of acetylene gas supplied from the storage container, the concentration of residual solvent in the acetylene gas, the residual pressure of the storage container under final use conditions, the flow rate of the acetylene gas, the temperature of the acetylene gas, and the cumulative supply time of the acetylene gas; The removal system of claim 1 .

4. The control unit controls the acetylene gas supplied from the gas source unit (11) as follows: (1) Proportional purification in response to changes in the purification ratio (X); (2) Fixed ratio purification, which purifies at a fixed purification ratio; (3) Complete purification, which purifies the entire amount; (4) Non-purification, where the entire amount is not purified; The removal system according to claim 1 , wherein the control is for switching between:

5. 1. A system for removing residual impurities from a gas, comprising: a gas source unit comprising at least one storage vessel; a purifier unit including at least one purifier for removing the residual impurities from the unpurified gas supplied from the gas source unit; a flow split for distributing gas supplied from the gas source unit; a confluence means for confluence of the purified gas treated in the purifier unit and the unpurified gas supplied from the gas source unit; a control unit that determines the gas purity or impurity content sent from the joining means and controls the flow split and the joining means so that the gas sent to a demand point has a target purity.

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