Method and system for monitoring the flammability of various flows during vinyl acetate production.

Abstract

This invention provides a method and system for producing vinyl acetate. [Solution] A method and system for producing vinyl acetate can use a combustion limit (FL) formula with improved efficiency at one or more locations in the vinyl acetate production process. In this invention, FL can be used in one or more of the four parts of the vinyl acetate production process: the reactor, the inter-process heat exchanger, the carbon dioxide removal system, and the ethylene recovery system. Such FL is a function of the operating state and includes at least one interaction term that represents the interrelationship of two or more operating states (e.g., temperature, pressure, and component concentration) with respect to FL.

Description

[Technical Field]

[0001] Priority Claim

[0001] This disclosure claims priority under U.S. Provisional Patent Application No. 62 / 950264, filed on 19 December 2019. background

[0002] This disclosure relates to a method and system for producing vinyl acetate. [Background technology]

[0002]

[0003] Vinyl acetate is conventionally produced by a gas-phase reaction of ethylene, oxygen, and acetic acid, in which ethylene is acetoxylated. The reaction is usually carried out in a fixed-bed catalytic reactor. The catalyst may include palladium or a palladium / gold mixture supported on a silica or alumina base. In addition to the production of vinyl acetate, undesirable combustion of ethylene also occurs, forming carbon dioxide and water. Other undesirable impurities that may be formed include acetaldehyde, ethyl acetate, methyl acetate, acetone, ethylene glycol diacetate, acrolein, and crotonaldehyde.

[0003]

[0004] The selectivity and conversion rate of a reaction are functions of several variables, including reactor temperature, component concentrations, and catalyst state. Catalyst deactivation, which routinely occurs over time due to the accumulation of tar and polymeric substances on the catalyst surface and / or structural changes in the catalyst metal, can adversely affect the reaction process, particularly in terms of selectivity. These changes in reactor performance can ultimately lead to changes in the composition of the liquid flow entering the refining section of a vinyl acetate plant.

[0004]

[0005] Acetoxylation of ethylene produces a crude vinyl acetate product containing vinyl acetate, water, carbon dioxide, and excess unreacted ethylene and acetic acid. The ethylene and acetic acid are recycled back to the reactor from the unit's reaction and purification sections. The vinyl acetate product is recovered, purified in the purification section, and sent to a storage tank. Wastewater is sent to a treatment facility, and carbon dioxide is sent to a pollution control unit. Inert gases such as nitrogen and argon may accumulate over time; in such cases, they can be removed from the reaction section to minimize accumulation.

[0005]

[0006] Generally speaking, the rate of acetoxylation increases as the oxygen concentration in the reactor increases. However, the amount of oxygen that can be introduced into the reactor is limited by the flammability limit of the reaction mixture. The flammability limit is typically defined as the minimum concentration of oxygen in the mixture that causes a pressure increase when in contact with an ignition source. If the oxygen concentration exceeds this flammability limit, a fire or explosion may occur.

[0006]

[0007] Various steps are taken to minimize the risk of such fire or explosion. For example, in the fixed-bed reactor of European Patent No. 0845453, the concentration of oxygen in the inlet gas composition is strictly monitored and maintained at or near a threshold. The mathematical approximation method used to determine this threshold is described in European Patent No. 0845453, which is incorporated herein by reference. If the inlet oxygen concentration exceeds this threshold, a shutdown signal is activated, quenching the reaction by stopping the entry of new oxygen into the reactor.

[0007]

[0008] However, conventional calculations of the flammability limit and / or the setting of flammability ranges can be inherently inaccurate. Conventional experimental techniques and methods used to develop mathematical correlations generally calculate lower flammability limits. These correlations act as a buffer from the true flammability limit. This provides safety, but reaction efficiency is compromised due to operation at oxygen concentrations lower than those indicated by the true combustion limit. [Overview of the Initiative]

[0008]

[0009] This disclosure relates to a method and system for producing vinyl acetate.

[0010] According to one aspect of the present disclosure, the method involves reacting a feed stream containing acetic acid, ethylene, oxygen, carbon dioxide, alkane, and water in a reactor to produce a crude vinyl acetate stream containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkane; cooling the crude vinyl acetate stream in a heat exchanger; measuring and / or determining the pressure of the feed stream or reactor, the temperature of the feed stream or reactor, and the concentration of at least one component in the feed stream; measuring and / or determining the oxygen content ([O2]) of the feed stream; and AFL min >When FL-[O2] is true, the procedure includes initiating a shutdown procedure or repair step, where the minimum approach to the flammability limit (AFL) is true. min The combustion limit (FL) equations are state-based, and the FL equation includes at least one interaction term.

[0009]

[0011] According to one aspect of the present disclosure, the method involves reacting a feed stream containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor to produce a crude vinyl acetate stream containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, where the tail gas stream contains ethylene, carbon dioxide, alkanes, and oxygen; the flash gas stream contains ethylene, carbon dioxide, alkanes, and oxygen; and the vinyl acetate stream contains vinyl acetate, water, and acetic acid; heating the tail gas stream in a heat exchanger; measuring and / or determining the pressure of the heated tail gas stream, the temperature of the heated tail gas stream, and the concentration of at least one component in the heated tail gas stream; measuring and / or determining the oxygen content ([O2]) of the heated tail gas stream; and AFL min >When FL-[O2] is true, the procedure includes initiating a shutdown procedure or repair step, where the minimum approach to the combustion limit (AFL) is true. minThe combustion limit (FL) equations are state-based, and the FL equation includes at least one interaction term.

[0010]

[0012] According to one aspect of the present disclosure, the method involves reacting a feed stream containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor to produce a crude vinyl acetate stream containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, where the tail gas stream contains ethylene, carbon dioxide, alkanes, and oxygen; the flash gas stream contains ethylene, carbon dioxide, alkanes, and oxygen; and the vinyl acetate stream contains vinyl acetate, water, and acetic acid; removing at least a portion of the carbon dioxide from the flash gas stream to produce a CO2 removal overhead stream; measuring and / or determining the pressure of the CO2 removal overhead stream, the temperature of the CO2 removal overhead stream, and the concentration state of at least one component in the CO2 removal overhead stream; measuring and / or determining the oxygen content ([O2]) of the CO2 removal overhead stream; AFL min >When FL-[O2] is true, the procedure includes initiating a shutdown procedure or repair step, where the minimum approach to the combustion limit (AFL) is true. min The combustion limit (FL) equations are state-based, and the FL equation includes at least one interaction term.

[0011]

[0013] According to one aspect of the present disclosure, the method involves reacting a feed stream containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor to produce a crude vinyl acetate stream containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; and separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, where the tail gas stream contains ethylene, carbon dioxide, alkanes, and oxygen; the flash gas stream contains ethylene, carbon dioxide, alkanes, and oxygen; and the vinyl acetate stream contains vinyl acetate. including rue, water and acetic acid; heating the tail gas stream in a heat exchanger; removing at least a portion of the carbon dioxide from the flash gas stream to produce a CO2 removal overhead stream; mixing the evaporated acetic acid with the heated tail gas stream and the CO2 removal overhead stream in an evaporator to produce an evaporation stream; adding oxygen to the evaporation stream to produce a feed stream; measuring and / or determining the conditions of (a), (b) and / or (c), that is, (a) the pressure of the feed stream or the reactor, the temperature of the feed stream or the reactor, and the concentration of at least one component in the feed stream, (b) the pressure of the heated tail gas stream, the temperature of the heated tail gas stream, and the concentration of at least one component in the heated tail gas stream, (c) the pressure of the CO2 removal overhead stream, the temperature of the CO2 removal overhead stream, and the concentration of at least one component in the CO2 removal overhead stream, wherein (a) is related to a first minimum approach (AFL min )(a first minimum approach to flammability limit) and a first flammability limit (FL) equation, (b) is related to a second minimum AFL min and a second FL equation based on the conditions of (b), (c) is related to a third minimum AFL min and a third FL equation based on the conditions of (c), one or more of the first FL equation, the second FL equation, and the third FL equation includes at least one interaction term; measuring and / or determining the oxygen content ([O2]) of the stream selected from the group consisting of the feed stream, the heated tail gas stream, the CO2 removal overhead stream, and any combination thereof; starting a shutdown procedure or a repair step when AFL min >FL - [O2] is true for one or more of (a), (b) or (c).

[0012]

[0014] According to one aspect of the present disclosure, the method involves reacting a feed stream containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor to produce a crude vinyl acetate stream containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream; transporting a portion of the flash gas stream to an ethylene recovery process having a vent stream; measuring the pressure of the vent stream, the temperature of the vent stream, and the concentration of at least one component in the vent stream, where the state is defined as the minimum approach to the combustion limit (AFL). min ) and related to the combustion limit (FL) equation including at least one interaction term; measuring the oxygen content ([O2]) in the vent flow; and AFL relative to the vent flow. min >When FL-[O2] is true, change the operating state of the ethylene recovery process and change the ethylene recovery process to AFL min This includes returning to ≤FL-[O2].

[0013]

[0015] The following figures are included to illustrate an embodiment of a particular aspect and should not be considered an exclusive embodiment. The disclosed subject matter can be modified, altered, combined, and equivalent in form and function by a number of people skilled in the art who are interested in this disclosure. [Brief explanation of the drawing]

[0014] [Figure 1]

[0016] The figure shows a process flow diagram of an example of the vinyl acetate production process of this disclosure. [Modes for carrying out the invention]

[0015]

[0017] As already explained, vinyl acetate reactors operate based on flammability limits, which achieve safety but greatly reduce reaction efficiency and therefore increase manufacturing costs. Furthermore, when manufacturers monitor flammability at additional locations along the vinyl acetate production process, the same conventional calculation of flammability limits and / or setting of non-flammability ranges are often used, even though the conditions (e.g., temperature and pressure) and components in the corresponding compositions differ at different locations along the production process. Therefore, there is a need for a vinyl acetate production process that utilizes more accurate flammability limit relationships throughout the vinyl acetate production process, providing safety management and improved operating efficiency.

[0016]

[0018] This disclosure relates to a method and system for producing vinyl acetate using a combustion limit (FL) formula with improved efficiency at one or more locations in the vinyl acetate production process. In the present invention, FL can be used for four parts of the vinyl acetate production process: the reactor, the inter-process heat exchanger, the carbon dioxide removal system, and the ethylene recovery system (as described in further detail herein).

[0017]

[0019] As described herein, FL is a function of operating conditions and includes at least one interaction term that expresses the interrelationship between two or more operating conditions (e.g., temperature, pressure, and component concentration) to FL. FL is typically expressed in units of mole percent oxygen. However, as will be apparent to those skilled in the art, other units are acceptable.

[0018]

[0020] This specification describes four types of interaction terms: component-component interaction terms, temperature-component interaction terms, pressure-component interaction terms, and pressure-temperature interaction terms. Each FL formula described herein includes at least one interaction term. Furthermore, for each interaction term included, each FL formula described herein may include one or more of the aforementioned interaction terms. For example, a first FL may include one component-component interaction term, two temperature-component interaction terms, and a pressure-temperature interaction term, but may not include a pressure-component interaction term. Furthermore, a second FL may include three component-component interaction terms, two temperature-component interaction terms, and two pressure-component interaction terms, but may not include a pressure-temperature interaction term. Preferably, at least one (more preferably at least three) component-component interaction terms are included in the FL formula.

[0019]

[0021] Equation 1a is a general formula for calculating the flammability limits described herein.

[0020]

number

[0021] In the formula, FL is the combustion limit; α, β, γ, δ i and ε j [C] is a factor that can be experimentally determined for a given range of composition, pressure, and temperature; P is pressure; T is temperature; [C] i ] is the concentration of each of the i-th C component considered in the composition; I j is the j-th interaction term I to be considered; a, b, and c are exponents (usually 1 or 2).

[0022]

[0022] For Formula 1, the number i of C components considered in the composition may be in the range of 0 to 10 or more, or 1 to 10, or 2 to 7. For Formula 1, the number j of I components considered in the composition may be in the range of 1 to 20 or more, or 1 to 15, or 2 to 10, or 4 to 12.

[0023]

[0023] The interaction term can be two or more operating states that multiply each other (for example, I=P d *[C] e (d and e are exponents, usually 1) is an example of a pressure-component interaction term, where I=T f *[C] g (f and g are exponents, usually 1) is an example of a temperature-component interaction term, where I=[C1] h *[C2] k (h and k are exponents, usually 1) is an example of a component-component interaction term, where the two components may be the same or different, and I=P l *T m (l and m are exponents, typically 1) is the pressure-temperature interaction term. In this specification, the states of the interaction term are shown as multiplicative, but other mathematical relationships may be used. For example, if an inverse relationship is found between the two components, the interaction term may not be multiplicative as shown in the example above, but rather include a first state divided by a second state.

[0024]

[0024] The FL formula may include concentration terms for one or more components in the composition under consideration. Not all components in the composition being considered need to be included in the FL formula.

[0025] The FL formula may include at least one interaction term. Preferably, FL includes at least one of each of the four interaction terms. More preferably, FL includes (a) two or more component-component interaction terms, (b) one or more temperature-component interaction terms, (c) one or more pressure-component interaction terms, (d) a pressure-temperature interaction term, or (e) any two or more combinations of (a)-(d).

[0025]

[0026] For example, equation 2-5 is an example of the FL formula.

[0026]

number

[0027]

[0027] Approach to the flammability limit (AFL) is defined as the difference between the flammability limit of the composition and the oxygen content ([O2]) in the composition, as shown in Formula 6. AFL is usually expressed in units of mole percent oxygen in a particular gas. However, as will be apparent to those skilled in the art, other units are acceptable, and the units of FL, AFL and [O2] should be identical with respect to Formula 6.

[0028]

number

[0029]

[0028] When AFL is 0, the oxygen content is equal to the combustion limit.

[0029] Each FL has a corresponding minimum AFL. Minimum AFL (AFL min ) is safe operation AFL min AFL is a threshold value that provides a value that allows the system to approach FL while operating safely, provided that ≤FL-[O2] is true. min Methods for determining the approach to the combustion limit are known in the art and may include considerations such as the uncertainty of the FL formula, the sensor detection limit, and the sensor measurement accuracy (or error). European Patent Application Publication No. 0845453 describes a method for determining the approach to the combustion limit and is incorporated herein by reference.

[0030]

[0030] Each location in the system where FL is monitored corresponds to the AFL min and the FL formula (abbreviated as "AFL" in this specification) min It has a combination called " / FL combination" (AFL). min The / FL combination is generally unique to different locations in the vinyl acetate production process due to the different considerations at each location. However, in some cases, two locations may have the same AFL min It has / FL.

[0031]

[0031] The system and method of the vinyl acetate production process comprises four parts: reactor AFL for one or more of the inlet, interprocess heat exchanger, carbon dioxide removal system, and ethylene recovery system min / FL combinations may be (as described in further detail herein). Preferably, two or more of the aforementioned parts of the vinyl acetate production process are each AFL min The / FL combination is more preferably three or four of the parts of the vinyl acetate production process are each AFL min The / FL combination is most preferably all four of the aforementioned parts of the vinyl acetate production process are each AFL min It has a / FL combination.

[0032]

[0032] The figure shows a process flow diagram of an example of vinyl acetate production process 100 of the present disclosure. Additional components and modifications can be made to process 100 without changing the scope of the present invention. Furthermore, as will be apparent to those skilled in the art, the description of process 100 and the associated system uses flow to describe fluids passing through various lines. For each flow, the associated system has a corresponding line (e.g., a pipe or other passage through which the corresponding fluid or other material can easily pass), and optionally valves, pumps, compressors, heat exchangers or other equipment, whether explicitly stated or not, to ensure the proper operation of the system.

[0033]

[0033] Furthermore, the descriptive terms used for individual flows do not limit the composition of the flow to those consisting of the descriptive terms. For example, an ethylene flow does not necessarily consist only of ethylene. Rather, an ethylene flow may include ethylene and a diluent gas (e.g., an inert gas). Alternatively, an ethylene flow may consist only of ethylene. Or, an ethylene flow may include ethylene, another reactant, and optionally an inert component.

[0034]

[0034] In the illustrated process 100, the acetic acid stream 102 and the ethylene stream 104 are introduced into the evaporator 106. Optionally, ethane may also be added to the evaporator 106. In addition, one or more recycle streams 130, 158 (each further described herein) may also be introduced into the evaporator 106. Optionally, one or more of the recycle streams 130, 158 may be combined with the acetic acid stream 102 before being introduced into the evaporator 106 (not shown).

[0035]

[0035] The temperature and pressure of the evaporator 106 can vary over a wide range. The evaporator 106 preferably operates at temperatures of 100°C to 250°C, or 100°C to 200°C, or 120°C to 150°C. The operating pressure of the evaporator 106 is preferably 0.1 MPa to 2.03 MPa, or 0.25 MPa to 1.75 MPa, or 0.5 MPa to 1.5 MPa. The evaporator 106 generates an evaporated feed stream 108. The evaporated feed stream 108 exits the evaporator 106 and combines with the oxygen stream 110 to generate a mixed feed stream 112. The mixed feed stream 112 is analyzed by a sensor 114 before being supplied to the vinyl acetate reactor 116.

[0036]

[0036] Sensor 114 includes a water sensor for determining the concentration of water in the mixed feed stream 112. Sensor 114 may optionally include a temperature sensor, a pressure sensor, a flow rate sensor, a composition sensor (e.g., gas chromatography, infrared spectroscopy, and oxygen analyzer), and any combination thereof. Each of the individual sensors may be present alone or in multiples. Having multiple sensors of a particular type provides overlapping functions, minimizing downtime for sensor replacement and mitigating safety issues resulting from a faulty or malfunctioning calibration sensor. Sensor 114 is generally located upstream of the vinyl acetate reactor 116, but the sensor may be located at other locations where calculations can be performed to assess conditions at the reactor inlet (e.g., temperature, pressure, or component concentration) or at the first AFL min The / FL combination may be placed in any other appropriate location where it is applied.

[0037]

[0037] As described herein, many locations within process 100 contain compositions that may become flammable if not monitored and their conditions adjusted as necessary. Parts of the 100 and related systems should be operated to mitigate the risk of fire and explosion. One such location is the mixed feed stream 112 under reaction conditions. Thus, the composition of the mixed feed stream 112, the temperature of the mixed feed stream 112 and / or the vinyl acetate reactor 116, and the pressure of the mixed feed stream 112 and / or the vinyl acetate reactor 116 can be adjusted to provide safe operation of the vinyl acetate reactor 116.

[0038]

[0038] The operating state of the vinyl acetate reactor 116 can be adjusted based on the composition of the mixed feed stream 112. Generally, a suitable range for the operating state of the vinyl acetate reactor 116 is provided below.

[0039]

[0039] Regarding the general operating conditions of the vinyl acetate reactor 116, when producing vinyl acetate, the molar ratio of ethylene to oxygen is preferably less than 20:1 in the vinyl acetate reactor 116 (e.g., 1:1 to 20:1, or 1:1 to 10:1, or 1.5:1 to 5:1, or 2:1 to 4:1). Furthermore, the molar ratio of acetic acid to oxygen is preferably less than 10:1 in the vinyl acetate reactor 116 (e.g., 0.5:1 to 10:1, 0.5:1 to 5:1, or 0.5:1 to 3:1). The molar ratio of ethylene to acetic acid is preferably less than 10:1 in the vinyl acetate reactor 116 (e.g., 1:1 to 10:1, or 1:1 to 5:1, or 2:1 to 3:1). Thus, the mixed feed stream 112 contains ethylene, oxygen, and acetic acid in the aforementioned molar ratios.

[0040]

[0040] The vinyl acetate reactor 116 may be a shell and tube reactor that absorbs the heat generated by the exothermic reaction via a heat exchange medium and can control the temperature therein within a temperature range of 100°C to 250°C, or 110°C to 200°C, or 120°C to 180°C. The pressure inside the vinyl acetate reactor 116 can be maintained at 0.5 MPa to 2.5 MPa, or 0.5 MPa to 2 MPa.

[0041]

[0041] Furthermore, the vinyl acetate reactor 116 may be a fixed-bed reactor or a fluidized-bed reactor, preferably a fixed-bed reactor containing a catalyst suitable for the acetoxylation of ethylene. Catalysts suitable for the production of vinyl acetate are described, for example, in U.S. Patents 3,743,607; 3,775,342; 5,557,014; 5,990,344; 5,998,659; 6,022,823; 6,057,260; and 6,472,556, each of which is incorporated herein by reference. Suitable catalysts may include palladium, gold, vanadium, and mixtures thereof. Particularly preferred catalysts are palladium acetate / potassium acetate / cadmium acetate and palladium acetate / barium acetolaurate / potassium acetate. Generally, the palladium content of the catalyst is 0.5 wt% to 5 wt%, or 0.5 wt% to 3 wt%, or 0.6 wt% to 2 wt%. When gold or one of its compounds is used, it is added in amounts of 0.01 wt% to 4 wt%, or 0.2 wt% to 2 wt%, or 0.3 wt% to 1.5 wt%. The catalyst also preferably contains a refractory support, preferably a metal oxide, such as silica, silica-alumina, titania, or zirconia, more preferably silica.

[0042]

[0042] The operating state in which the vinyl acetate reactor 116 is operated is the first AFL min The first FL can be obtained based on the / FL combination. The first FL can be obtained based on the pressure in the mixed feed stream 112 or vinyl acetate reactor 116, the temperature in the mixed feed stream 112 or vinyl acetate reactor 116, and the concentrations of the individual components in the mixed feed stream 112. Process 100 uses one or more recycled streams 130, 156, 168 and may contain diluents, so the components in the mixed feed stream 112 are greater than ethylene, acetic acid, and oxygen. Examples of components in the mixed feed stream 112 whose concentrations can be used (individually and / or in interaction terms) in the first FL formula (e.g., one of formulas 1-5) include, but are not limited to, ethylene, acetic acid, methane, ethane, propane, water, and nitrogen. , argon and carbon dioxide are also present.

[0043]

[0043] The concentrations of components in the various flows described herein can be measured directly or calculated based on measurements of different components. For example, the acetic acid content (explanating dimerization) in the flow can be calculated based on measurements. The acetic acid content can then be derived from the water content. Furthermore, the measurements or values ​​derived from measurements do not have to be of the location of interest. For example, the water content at the reactor inlet can be derived from the water content of the recycled flow (mentioned in paragraph 55 but not shown in the diagram) originating from the purification process 148. Thus, when state values ​​(e.g., temperature values, pressure values, or concentrations of components in the flow) are described herein, the state values ​​are not limited to direct measurements at the location, but include values ​​derived for the location based on measurements at that location or other locations within process 100.

[0044]

[0044] A discussion of the derivation of the FL formula is provided in the Examples section. The first FL can be based on the pressure in the vinyl acetate reactor 116, the temperature in the vinyl acetate reactor 116, and the concentrations of the individual components in the vinyl acetate reactor 116 at the inlet. Here again, generally, the first FL formula may include at least one interaction term. Preferably, the first FL formula includes at least one of each of the four interaction terms. More preferably, the first FL formula includes (a) two or more component-component interaction terms, (b) one or more temperature-component interaction terms, (c) one or more pressure-component interaction terms, (d) a pressure-temperature interaction term, or (e) any two or more combinations of (a)-(d). The components that may be included in the interaction term of the first FL equation are, but are not limited to, the concentrations of ethane ([C2H6]), methane ([CH4]), carbon dioxide ([CO2]), acetic acid ([HAc]), water ([H2O]), ethylene ([C2H4]), propane ([C3H8]), and any combination thereof. Therefore, examples of interaction terms that may be included in the first FL formula are not limited to, but include P*T, P*[C2H6], P*[CH4], P*[CO2], P*[HAc], P*[H2O], P*[C2H4], P*[C3H8], T*[C2H6], T*[CH4], T*[CO2], T*[HAc], T*[H2O], T*[C2H4], T*[C3H8], [C2H6]*[CH4], [C2H6]*[CO2], [C2H6]*[HAc], [C2H6]*[H2O], [C2H6]*[C2H Examples include [4], [C2H6]*[C3H8], [CH4]*[CO2], [CH4]*[HAc], [CH4]*[H2O], [CH4]*[C2H4], [CH4]*[C3H8], [CO2]*[HAc], [CO2]*[H2O], [CO2]*[C2H4], [CO2]*[C3H8], [HAc]*[H2O], [HAc]*[C2H4], [HAc]*[C3H8], [H2O]*[C2H4], [H2O]*[C3H8], [C2H4]*[C3H8], and any combination thereof. Inert gases may be included if they affect the heat capacity of the gas mixture.Therefore, examples of interaction terms that may be included in the first FL formula, though not limited to them, include P*[inert], T*[inert], [inert]*[C2H6], [inert]*[CH4], [inert]*[CO2], [inert]*[HAc], [inert]*[H2O], [inert]*[C2H4], [inert]*[C3H8], [inert a]*[inert]. b) and any combination thereof are examples. Examples of inert gases used in vinyl acetate production include, but are not limited to, argon, nitrogen, and any combination thereof. In the above examples of interaction terms (both lists), the corresponding exponent listed above for each component of the interaction term is 1. However, other exponents (e.g., -2, -1, -0.5, 0.5, 1, 2, etc.) may be used.

[0045]

[0045] The state of the vinyl acetate reactor 116 may be monitored and used to calculate a first FL and to check for breaches of the first minimum AFL. For example, during operation, to account for fluctuations in the operating conditions (e.g., pressure, temperature, and the concentration of individual components in the mixed feed stream 112) The FL of 1 is calculated continuously, and the operation within the smallest AFL (i.e., AFL) min To ensure ≤FL-[O2]), the oxygen content (molar percent oxygen) in the mixed feed stream 112 is continuously measured. If the minimum AFL is compromised (i.e., if the real-time AFL is less than the minimum AFL, or if AFL min >If FL-[O2], process 100 may enter a shutdown procedure or undergo a repair step to ensure that the minimum AFL is not compromised.

[0046]

[0046] Referring again to the figure, the vinyl acetate reaction in reactor 116 produces a crude vinyl acetate stream 118. Depending on the conversion rate and reaction state, the crude vinyl acetate stream 118 may contain 5 wt% to 30 wt% vinyl acetate, 5 wt% to 40 wt% acetic acid, 0.1 wt% to 10 wt% water, 10 wt% to 80 wt% ethylene, 1 wt% to 40 wt% carbon dioxide, 0.1 wt% to 50 wt% alkanes (e.g., methane, ethane, or mixtures thereof), and 0.1 wt% to 15 wt% oxygen. In some cases, the crude vinyl acetate stream 118 may also contain 0.01 wt% to 10 wt% ethyl acetate. The crude vinyl acetate stream 118 may contain methyl acetate, acetaldehyde, acrolein, propane, and other compounds such as inert substances, such as nitrogen or argon. Generally, these other compounds, with the exception of inert substances, are present in very small amounts.

[0047]

[0047] The crude vinyl acetate stream 118 passes through the heat exchanger 120 to lower its temperature and then enters the separator 122 (e.g., a distillation column). Preferably, the crude vinyl acetate stream 118 is cooled to a temperature of 80°C to 145°C or 90°C to 135°C before being introduced into the separator 122. Preferably, no condensation of liquefiable components occurs, and the cooled crude vinyl acetate stream 118 is introduced into the separator 122 as a gas.

[0048]

[0048] The energy for separating the components of the crude vinyl acetate flow 118 can be provided by the heat of reaction in reactor 116. In some embodiments, there may be an optional reboiler to increase the separation energy in separator 122.

[0049]

[0049] The separator 122 separates the crude vinyl acetate stream 118 into at least two streams: an overhead stream 124 and a bottom stream 126. The overhead stream 124 may contain ethylene, carbon dioxide, water, alkanes (e.g., methane, ethane, propane, or mixtures thereof), oxygen, and vinyl acetate. The bottom stream may contain vinyl acetate, acetic acid, water, and potentially ethylene, carbon dioxide, and alkanes.

[0050]

[0050] The overhead flow 124 is transported to the scrubber 128 to remove vinyl acetate from the overhead flow 124. As a result, the scrubber 128 has a tail gas flow 130 and a bottom flow 132. Vinyl acetate scrubbing can be achieved by passing the overhead flow 124 through a mixture of water and acetic acid.

[0051]

[0051] The tail gas flow 130 contains ethylene, carbon dioxide, alkanes, and oxygen. The state of the tail gas flow 130 (e.g., temperature, pressure, and / or composition of components) can be measured using a sensor 134. Sensors 134 are not limited to, but include, temperature sensors, pressure sensors, flow sensors, composition sensors (e.g., gas chromatography, infrared spectroscopy, and oxygen analyzers), and any combination thereof. Each individual sensor can be present alone or in multiples. Having multiple sensors of a particular type provides overlapping functions, minimizing downtime for sensor replacement and mitigating safety issues resulting from a faulty or malfunctioning calibration sensor. Sensors 134 are generally shown along the tail gas flow 130 as downstream of the scrubber 128, but the sensors may be placed at other locations where calculations can be performed to evaluate the state of the tail gas flow 130 after the scrubber 128 (e.g., temperature, pressure, or component concentration).

[0052]

[0052] The tail gas flow 130 (also called the recycle flow) is transported and returned to the evaporator 106 through a heat exchanger 120 in which the crude vinyl acetate flow 118 heats the tail gas flow 130. If applicable, the tail gas flow 130 may be augmented by other flows, including other recycle flows (not shown) and feed flows in the process, or otherwise these other flows are added. As shown, the ethylene feed flow 136 and the methane feed flow 138 (or other ballast gas flows) are combined with the tail gas flow 130 (e.g., mixed or encompassed).

[0053]

[0053] Furthermore, other processes (not shown) may be performed on the tail gas flow 130 between the scrubber 128 and the heat exchanger 120. For example, at least a portion of the carbon dioxide may be removed from the tail gas flow 130.

[0054]

[0054] The tail gas flow 130 after being heated in the heat exchanger 120 is potentially flammable and / or explosive. Therefore, the second AFL min The / FL combination can be used in the methods and systems disclosed herein to monitor the flammability of the tail gas flow 130 before it is introduced into the evaporator.

[0055]

[0055] Thus, between the heat exchanger 120 and the evaporator 106, the tail gas flow 130 is analyzed by the sensor 140. Examples of the sensor 140 include, but are not limited to, temperature sensors, pressure sensors, flow sensors, composition sensors (e.g., gas chromatography, infrared spectroscopy, and oxygen analyzers), and any combination thereof. Each individual sensor can be present alone or in multiples. Having multiple sensors of a particular type provides overlapping functions, minimizing downtime for sensor replacement and mitigating safety issues resulting from a faulty or malfunctioning calibration sensor. Although the sensor 140 is generally shown between the heat exchanger 120 and the evaporator 106, the sensor may be located at other locations or a second AFL where calculations can be performed to evaluate the conditions (e.g., temperature, pressure, or component concentration) between the heat exchanger 120 and the evaporator 106. min The / FL combination may be placed in any other appropriate location where it is applied.

[0056]

[0056] A consideration of the derivation of the FL formula is provided in the Examples section. The second FL can be based on the pressure of the line containing the tail gas flow 130, the temperature of the tail gas flow 130, and the concentrations of the individual components in the tail gas flow 130. Here again, generally, the second FL formula may include at least one interaction term. Preferably, the second FL formula includes at least one of each of the four interaction terms. More preferably, the second FL formula includes (a) two or more component-component interaction terms, (b) one or more temperature-component interaction terms, (c) one or more pressure-component interaction terms, (d) a pressure-temperature interaction term, or (e) any combination of two or more of (a)-(d). Examples of components in the vinyl acetate reactor 116 whose concentrations may be used in the second FL formula (e.g., one of formulas 1-5) include, but are not limited to, ethylene, methane, ethane, propane, and carbon dioxide. The components that may be included in the interaction term of the second FL equation are, but are not limited to, the concentrations of ethane ([C2H6]), methane ([CH4]), carbon dioxide ([CO2]), ethylene ([C2H4]), propane ([C3H8]), and any combination thereof. Therefore, examples of interaction terms that may be included in the second FL equation are, but are not limited to, P*T, P*[C2H6], P*[CH4], P*[CO2], P*[C2H4], P*[C3H8], T*[C2H6], T*[CH4], T*[CO2], T*[C2H4], T*[C3H8], [C2H6]*[CH4], [C2H6]*[CO2], [C2H6]*[C2H4], [C2H6]*[C3H8], [CH4]*[CO2], [CH4]*[C2H4], [CH4]*[C3H8], [CO2]*[C2H4], [CO2]*[C3H8], [C2H4]*[C3H8], and any combination thereof. Inert gases are gases that are gases If it affects the heat capacity of the mixture, it may be included depending on the circumstances. Therefore, examples of interaction terms that may be included in the second FL formula, but are not limited to, include P*[inert], T*[inert], [inert]*[C2H6], [inert]*[CH4], [inert]*[CO2], [inert]*[HAc], [inert]*[H2O], [inert]*[C2H4], [inert]*[C3H8], [inert a]*[inert b], and any combination thereof. Examples of inert gases used in vinyl acetate production, but are not limited to, include argon, nitrogen, and any combination thereof. In the above examples of interaction terms (both lists), the corresponding exponent listed above for each component of the interaction term is 1. However, other exponents (e.g., -2, -1, -0.5, 0.5, 1, 2, etc.) may be used.

[0057]

[0057] The state of the tail gas flow 130 may be monitored and used to calculate a second FL and to check for breaches of the second minimum AFL. For example, during operation, the second FL is continuously calculated to account for fluctuations in the operating conditions (e.g., pressure, temperature, and concentrations of individual components in the tail gas flow 130), and the oxygen content (mol percent oxygen) of the tail gas flow 130 is used to check for breaches of the second minimum AFL (i.e., AFL min It is measured continuously to ensure that ≤FL-[O2]). If the second minimum AFL is compromised (i.e., if the real-time AFL is less than the minimum AFL, or AFL min >If FL-[O2], process 100 may enter a shutdown procedure or undergo a repair step to ensure that the minimum AFL is not compromised.

[0058]

[0058] Referring again to the figure, the bottom flow 126 from the separator 122 and the bottom flow 132 from the scrubber 128 are combined and can be supplied to the unpurified tank 142. Generally, the flow entering the unpurified tank 142 is reduced to a pressure of 0.1 MPa to 0.15 MPa. When the incoming flow is reduced in pressure, ethylene, carbon dioxide, inert gas (e.g., nitrogen and / or argon) and acetic acid flash to produce a flash gas flow 144. The bottom of the unpurified tank 142 contains mainly vinyl acetate, water and acetic acid, and some ethyl acetate byproducts. The bottom is transported as a vinyl acetate flow 146 and purified by various processes 148 to produce a purified vinyl acetate product flow 150. Examples of purification processes 148 include, but are not limited to, azeotropic distillation, water stripping, distillation, phase separation, and any combination thereof. Examples of various processing methods and systems are described in U.S. Patents No. 6,410,817, No. 8,993,796, and No. 9,045,413, and U.S. Patent Application Publication 2014 / 0066649, respectively, which are incorporated herein by reference.

[0059]

[0059] Furthermore, the purification process 148 may cause additional flows to be recycled individually or in any combination and returned to the evaporator 106, tail gas flow 130, flash gas flow 144 and / or other flows in process 100.

[0060]

[0060] In some cases (not shown in the figure), a portion of the tail gas slip flow 130 may be combined with (for example, mixed with or encompassed with) the flash gas flow 144.

[0061] At least a portion of the carbon dioxide in the flash gas flow 144 (which may optionally be combined with a portion of the tail gas slip flow 130) is removed before it is recycled and returned to the evaporator 106. As shown in the figure, the flash gas flow 144 first passes through the CO2 scrubber 152 and then the CO2 absorber 156 to generate a CO2 removal overhead flow 158. Between the CO2 scrubber 152 and the CO2 absorber 156, ethylene can be added to the flash gas flow 144 from the ethylene flow 154.

[0061]

[0062] CO2 removal overhead flow 158 has an oxygen content as described herein. It is yet another potentially flammable or explosive composition that can be monitored for the system. Thus, the third AFL min The / FL combination can be used in the methods and systems of this disclosure to monitor the flammability of the CO2 removal overhead flow 158.

[0062]

[0063] Therefore, after the CO2 absorber 156, the CO2 removal overhead flow 158 is analyzed by the sensor 160. Examples of the sensor 160 include, but are not limited to, temperature sensors, pressure sensors, flow rate sensors, composition sensors (e.g., gas chromatography, infrared spectroscopy, and oxygen analyzers), as well as any combination thereof. Each of the individual sensors can exist alone or in multiples. Having multiple sensors of a particular type provides overlapping functions, minimizing downtime for sensor replacement and mitigating safety issues resulting from a faulty or malfunctioning calibration sensor. Although the sensor 160 is generally shown as downstream of the CO2 absorber 156, the sensor 160 may also be located at other locations or a third AFL where calculations can be performed to evaluate the conditions downstream of the CO2 absorber 156 (e.g., temperature, pressure, or component concentration). min The / FL combination may be placed in any other appropriate location where it is applied.

[0063]

[0064] A discussion of the derivation of the FL formula is provided in the Examples section. A third FL can be based on the pressure of the line containing the CO2 removal overhead flow 158, the temperature of the CO2 removal overhead flow 158, and the concentrations of the individual components in the CO2 removal overhead flow 158. Here again, generally, the third FL formula may include at least one interaction term. Preferably, the third FL formula includes at least one of each of the four interaction terms. More preferably, the third FL formula includes (a) two or more component-component interaction terms, (b) one or more temperature-component interaction terms, (c) one or more pressure-component interaction terms, (d) a pressure-temperature interaction term, or (e) any combination of two or more of (a)-(d). Examples of components in the vinyl acetate reactor 116 whose concentrations may be used in the third FL formula (e.g., one of formulas 1-5) include, but are not limited to, ethylene, methane, ethane, propane, and carbon dioxide. The components that may be included in the interaction term of the second FL equation are, but are not limited to, the concentrations of ethane ([C2H6]), methane ([CH4]), carbon dioxide ([CO2]), ethylene ([C2H4]), propane ([C3H8]), and any combination thereof. Therefore, examples of interaction terms that may be included in the third FL formula are, but are not limited to, P*T, P*[C2H6], P*[CH4], P*[CO2], P*[C2H4], P*[C3H8], T*[C2H6], T*[CH4], T*[CO2], T*[C2H4], T*[C3H8], [C2H6]*[CH4], [C2H6]*[CO2], [C2H6]*[C2H4], [C2H6]*[C3H8], [CH4]*[CO2], [CH4]*[C2H4], [CH4]*[C3H8], [CO2]*[C2H4], [CO2]*[C3H8], [C2H4]*[C3H8], and any combination thereof. Inert gases may be included if they affect the heat capacity of the gas mixture.Therefore, examples of interaction terms that may be included in the second FL formula, but are not limited to, P*[inert], T*[inert], [inert]*[C2H6], [inert]*[CH4], [inert]*[CO2], [inert]*[HAc], [inert]*[H2O], [inert]*[C2H4], [inert]*[C3H8], [inert a]*[inert b], and any combination thereof. Examples of inert gases used in vinyl acetate production, but are not limited to, argon, nitrogen, and any combination thereof. In the above examples of interaction terms (both lists), the corresponding exponent listed above for each component of the interaction term is 1. However, other exponents (e.g., -2, -1, -0.5, 0.5, 1, 2, etc.) may be used.

[0064]

[0065] The tail gas flow 130 and the CO2 removal overhead flow 158 have similar components. Therefore, the second FL formula and the third FL formula may be the same. However, since different sensors may be used, the second minimum AFL and the third minimum AFL may be different.

[0065]

[0066] The state of the CO2 removal overhead flow 158 may be monitored and used to calculate a third FL and to check for breaches of the third minimum AFL. For example, during operation, the third FL is continuously calculated to account for fluctuations in the operating conditions (e.g., pressure, temperature, and concentrations of individual components of the CO2 removal overhead flow 158), and the oxygen content (molar percent oxygen) of the CO2 removal overhead flow 158 is used to check for operation within the third minimum AFL (i.e., AFL min It is measured continuously to ensure that ≤FL-[O2]). If the third minimum AFL is compromised (i.e., if the real-time AFL is less than the minimum AFL, or AFL min >If FL-[O2], process 100 may enter a shutdown procedure or undergo a repair step to ensure that the minimum AFL is not compromised.

[0066]

[0067] Referring again to the diagram, the CO2 removal overhead flow 158 can then pass through the heat exchanger 162 and be supplied to the evaporator 106. Furthermore, the slip flow 164 from the flash gas flow 144 and / or the CO2 removal overhead flow 158 is used to purge inert material from the system. This slip flow 164 can be sent through the ethylene recovery process 166. The ethylene recovery process 162 generates the ethylene vent flow 168 and the recycle flow 172.

[0067]

[0068] Examples of ethylene recovery processes 166 include, but are not limited to, scrubbing systems, membrane recovery processes, and any combination thereof.

[0069] The ethylene recovery process 166 can generate a vent flow 168 and an additional flow 172 for recovering the ethylene in other processes or recycling it back into this process 100.

[0068]

[0070] The vent stream 168 and associated output stream of the ethylene recovery process 166 are additional potentially flammable or explosive compositions whose oxygen content can be monitored for the processes and systems described herein. Thus, the fourth AFL min The / FL combination can be used in the methods and systems of this disclosure to monitor the flammability of the ethylene vent stream 168.

[0069]

[0071] Therefore, after the ethylene recovery process 166, the ethylene vent flow 168 is analyzed by the sensor 170. Examples of the sensor 170 include, but are not limited to, temperature sensors, pressure sensors, flow rate sensors, composition sensors (e.g., gas chromatography, infrared spectroscopy, and oxygen analyzers), as well as any combination thereof. Each individual sensor may be present alone or in multiples. Having multiple sensors of a particular type provides overlapping functionality, minimizing downtime for sensor replacement and mitigating safety issues resulting from a faulty or malfunctioning calibration sensor. Although the sensor 170 is generally shown along the ethylene vent flow 168, the sensor 170 may also be located at other locations or a fourth AFL where calculations can be performed to assess the state of the ethylene vent flow 168 (e.g., temperature, pressure, or component concentration). min The / FL combination may be placed in any other appropriate location where it is applied.

[0070]

[0072] A discussion of the derivation of the FL formula is provided in the Examples section. The fourth FL can be based on the pressure of the line containing the ethylene vent flow 168, the temperature of the ethylene vent flow 168, and the concentrations of the individual components in the ethylene vent flow 168. Here again, generally, the fourth FL formula may include at least one interaction term. Preferably, the fourth FL formula includes at least one of each of the four interaction terms. More preferably, the fourth FL formula includes (a) two or more component-component interaction terms, (b) one or more temperature-component interaction terms, and (c) one or more pressure-component interaction terms. (e) includes an action term, (d) a pressure-temperature interaction term, or any combination of two or more of (a)-(d). Examples of components in vinyl acetate reactor 116 whose concentrations may be used in the fourth FL formula (e.g., one of formulas 1-5) include, but are not limited to, ethylene, methane, ethane, propane, and carbon dioxide. Components that may be included in the interaction term of the second FL formula include, but are not limited to, the concentration of ethane ([C2H6]), the concentration of methane ([CH4]), the concentration of carbon dioxide ([CO2]), the concentration of ethylene ([C2H4]), the concentration of propane ([C3H8]), and any combination thereof. Therefore, examples of interaction terms that may be included in the second FL equation are, but are not limited to, P*T, P*[C2H6], P*[CH4], P*[CO2], P*[C2H4], P*[C3H8], T*[C2H6], T*[CH4], T*[CO2], T*[C2H4], T*[C3H8], [C2H6]*[CH4], [C2H6]*[CO2], [C2H6]*[C2H4], [C2H6]*[C3H8], [CH4]*[CO2], [CH4]*[C2H4], [CH4]*[C3H8], [CO2]*[C2H4], [CO2]*[C3H8], [C2H4]*[C3H8], and any combination thereof. Inert gases may be included if they affect the heat capacity of the gas mixture. Therefore, examples of interaction terms that may be included in the second FL formula, but are not limited to, P*[inert], T*[inert], [inert]*[C2H6], [inert]*[CH4], [inert]*[CO2], [inert]*[HAc], [inert]*[H2O], [inert]*[C2H4], [inert]*[C3H8], [inert a]*[inert b], and any combination thereof. Examples of inert gases used in vinyl acetate production, but are not limited to, argon, nitrogen, and any combination thereof. In the above examples of interaction terms (both lists), the corresponding exponent listed above for each component of the interaction term is 1. However, other exponents (e.g., -2, -1, -0.5, 0.5, 1, 2, etc.) may be used.

[0071]

[0073] The state of the ethylene recovery process 166 and / or the ethylene vent flow 168 may be monitored and used to calculate the fourth FL and to check for breaches of the fourth minimum AFL. For example, during operation, the fourth FL is continuously calculated to account for fluctuations in the operating conditions (e.g., pressure, temperature, and concentrations of individual components in the ethylene vent flow 164), and the oxygen content (molar percent oxygen) of the ethylene vent flow 164 is used to ensure operation within the fourth minimum AFL (i.e., AFL min It is measured continuously to ensure that ≤FL-[O2]). The ethylene recovery process 166 and / or ethylene vent stream 168 are somewhat independent from the rest of process 100, so the fourth minimum AFL is violated (i.e., the real-time AFL is less than the minimum AFL, i.e., AFL min >FL-[O2]) may result in a less severe measure than stopping process 100. In general, the operating state of the ethylene recovery process 166 can be altered to return the ethylene recovery process 166 and / or the ethylene vent flow 168 to safe operation. For example, the flow rate of the slip flow 164 may be altered, and / or a diluent gas (e.g., an inert gas such as nitrogen or argon) may be added to flow 168. Other appropriate actions that can be taken to return the ethylene recovery process 166 and / or the ethylene vent flow 168 to safe operation will be apparent to those skilled in the art.

[0072]

[0074] While the figures illustrate process 100 in general terms, those skilled in the art will recognize how the teachings of this disclosure should be adapted to other vinyl acetate production processes that may differ from the illustrated process 100. Examples of different vinyl acetate production processes and systems are described in U.S. Patents No. 6,410,817, No. 8,993,796, and No. 9,045,413 and U.S. Patent Application Publication 2014 / 0066649, respectively, which are incorporated herein by reference.

[0073] Example Embodiment

[0075] A first non-limiting exemplary method of this disclosure involves reacting a feed stream 112 containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; measuring and / or determining the pressure of the feed stream 112 or the reactor 116, the temperature of the feed stream 112 or the reactor 116, and the concentration state of at least one component in the feed stream 112; measuring and / or determining the oxygen content ([O2]) of the feed stream 112; and AFL min >When FL-[O2] is true, the procedure includes initiating a shutdown procedure or repair step, where the minimum approach to the combustion limit (AFL) is true. min The combustion limit (FL) equations are state-based, and the FL equation includes at least one interaction term.

[0074]

[0076] A second non-limiting exemplary method of this disclosure involves reacting a feed stream 112 containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; and separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, where the tail gas stream 130 contains ethylene, carbon dioxide, alkanes, and The flash gas stream 144 contains ethylene, carbon dioxide, alkanes, and oxygen, and the vinyl acetate stream 146 contains vinyl acetate, water, and acetic acid; the tail gas stream 130 is heated in the heat exchanger 120; the pressure of the tail gas stream 130 after heating, the temperature of the tail gas stream 130 after heating, and the concentration state of at least one component in the tail gas stream 130 after heating are measured and / or determined; the oxygen content ([O2]) of the tail gas stream 130 after heating is measured and / or determined; AFL min >When FL-[O2] is true, the procedure includes initiating a shutdown procedure or repair step, where the minimum approach to the combustion limit (AFL) is true. min The combustion limit (FL) equations are state-based, and the FL equation includes at least one interaction term.

[0075]

[0077] A third non-limiting exemplary method of this disclosure involves reacting a feed stream 112 containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; and separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, where the tail gas stream 130 contains ethylene, carbon dioxide, alkanes, and oxygen, and the flash gas stream 144 contains ethylene The vinyl acetate stream 146 contains len, carbon dioxide, alkanes, and oxygen, and vinyl acetate stream 146 contains vinyl acetate, water, and acetic acid; remove at least a portion of the carbon dioxide from the flash gas stream 144 to produce a CO2 removal overhead stream 158; measure and / or determine the pressure of the CO2 removal overhead stream 158, the temperature of the CO2 removal overhead stream 158, and the concentration state of at least one component in the CO2 removal overhead stream 158; measure and / or determine the oxygen content ([O2]) of the CO2 removal overhead stream 158; AFL min >When FL-[O2] is true, the procedure includes initiating a shutdown procedure or repair step, where the minimum approach to the combustion limit (AFL) is true. min The combustion limit (FL) equations are state-based, and the FL equation includes at least one interaction term.

[0076]

[0078] Two or more of the first, second, and third exemplary methods may be performed together. For example, the first and second exemplary methods may be performed together. In another example, the first and third exemplary methods may be performed together. In yet another example, the second and third exemplary methods may be performed together. In yet another example, the first, second, and third exemplary methods may be performed together. In addition, the flow recycling and other process steps described herein may be performed in combination with one or more of the first, second, and third exemplary methods.

[0077]

[0079] A fourth non-limiting exemplary method of this disclosure involves reacting a feed stream 112 containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, where the tail gas stream 130 contains ethylene, carbon dioxide, alkanes, and oxygen; the flash gas stream 144 contains ethylene, carbon dioxide, alkanes, and oxygen; and the vinyl acetate stream 146 contains vinyl acetate, water, and acetic acid; heating the tail gas stream 130 in a heat exchanger 120; removing at least a portion of the carbon dioxide from the flash gas stream 144 to produce a CO2 removal overhead stream 158; and adding the evaporated acetic acid. Mix the heated tail gas flow 130 and the CO2 removal overhead flow 158 in the evaporator 106 to produce the evaporative flow 108; add oxygen to the evaporative flow 108 to produce the feed flow 112; measure and / or determine the following conditions: (a), (b), and / or (c), where (a) the pressure of the feed flow 112 or reactor 116, the temperature of the feed flow 112 or reactor 116, and the concentration of at least one component in the feed flow 112; (b) the pressure of the heated tail gas flow 130, the temperature of the heated tail gas flow 130, and the concentration of at least one component in the heated tail gas flow 130; (c) the pressure of the CO2 removal overhead flow 158, the temperature of the CO2 removal overhead flow 158, and the concentration of at least one component in the CO2 removal overhead flow 158, where (a) is the first minimum approach (AFL) to the combustion limit based on the conditions in (a). min ) and the first combustion limit (FL) formula, where (b) is the second minimum AFL based on the conditions of (b) min And related to the second FL formula, (c) is the third minimum AFL based on the state of (c) minand in relation to the third FL formula, one or more of the first FL formula, the second FL formula and the third second FL formula include at least one interaction term; measure and / or determine the oxygen content ([O2]) of the flow selected from the group consisting of the feed flow 112, the post-heated tail gas flow 130, the CO2 removal overhead flow 158, and any combination thereof; and for one or more of (a), (b), or (c), AFL min >Includes initiating an operation shutdown procedure or repair step when FL-[O2] is true. A fourth non-limiting exemplary method may further include one or more of the following: Element 1: A first FL formula, a second FL formula and / or a third FL formula according to formula 1. Element 2: A first AFL min The second AFL min Unlike and / or the first AFL min The third AFL min Unlike and / or the second AFL min The third AFL minElement 3: The first FL formula differs from the second FL formula, and / or the first FL formula differs from the third FL formula, and / or the second FL formula differs from the third FL formula. Element 4: At least one interaction term is selected from the group consisting of component-component interaction terms, temperature-component interaction terms, pressure-component interaction terms, pressure-temperature interaction terms, and any combination thereof. Element 5: The second first formula, the second FL formula, and / or the third FL formula include one or more terms selected from the group consisting of constants, temperature, pressure, and concentrations of components in the corresponding composition. Element 6: The first FL formula and / or the second FL formula and / or the third FL formula include at least two component-component interaction terms. Element 7: The first FL formula and / or the second FL formula and / or the third FL formula include at least one pressure-component term, at least one temperature-component interaction term, pressure-temperature interaction term, and at least two component-component interaction terms. Element 8: At least one interaction term is between 3 and 15. Element 9: The method includes combining a portion of the tail gas slip flow 130 with the flash gas flow 144 before further removing at least a portion of carbon dioxide from the flash gas flow 144. Element 10: Separation of the crude vinyl acetate flow 118 involves separating the crude vinyl acetate flow 118 into an overhead flow 124 and a first bottom flow 126 in a separator 122; separating the overhead flow 124 into a tail gas flow 130 and a second bottom flow 132 in a scrubber 128; combining the first and second bottom flows 126, 132; and combining the first and second bottom flows 126. , 132 into unrefined tank 142, flash gas stream 144 and vinyl acetate stream 146 Element 11: The method further comprises purifying the vinyl acetate stream 146 into a purified vinyl acetate product stream 150. Element 12: The method further comprises purifying the vinyl acetate stream 146 into a purified vinyl acetate product stream 150 and one or more additional streams; recycling at least one of the additional streams back to the evaporator 106, tail gas stream 130 or flash gas stream 144. Element 13: The method further comprises adding ethylene and / or methane to the tail gas stream 130 upstream of the heat exchanger 120. Element 14: The method further comprises removing at least a portion of carbon dioxide from the tail gas stream 130 upstream of the heat exchanger 120. Element 15: The method further comprises adding ethylene and / or acetic acid to the evaporator 106. Element 16: The method further involves transporting a portion of the flash gas flow 144 to an ethylene recovery process 166 having a vent flow 168; measuring the pressure of the vent flow 168, the temperature of the vent flow 168, and the state of the concentration of at least one component in the vent flow 168, where the state is the fourth minimum approach (AFL) to the combustion limit. min ) (a fourth minimum approach to flammability limit) and at least one interaction In relation to the fourth combustion limit (FL) equation including the term; the oxygen content ([O2]) of vent flow 168 is measured; and AFL is compared to vent flow 168. min >When FL-[O2] is true, change the operating state of the ethylene recovery process 166 to AFL min This includes returning to ≤FL-[O2]. Element 17: In element 16, the fourth AFL min However, the first AFL min and / or the second AFL min and / or the third AFL minThe following are different. Element 18: In element 16, the fourth FL formula is different from the first FL formula and / or the second FL formula and / or the third FL formula. Element 19: In element 16, at least one interaction term for the fourth FL formula is selected from the group consisting of component-component interaction terms, temperature-component interaction terms, pressure-component interaction terms, pressure-temperature interaction terms, and any combination thereof. Element 20: In element 16, the second first formula, the second FL formula, and / or the third FL formula include one or more terms selected from the group consisting of constants, temperature, pressure, and the concentration of components in the corresponding composition. Element 21: In element 16, the fourth FL formula includes at least two component-component interaction terms. Element 22: In element 16, the fourth FL formula includes at least one pressure-component term, at least one temperature-component interaction term, a pressure-temperature interaction term, and at least two component-component interaction terms. Element 23: In element 16, at least one interaction term for the fourth FL expression is an interaction term of 3-15. Examples of combinations are not limited to, but include: element 1 combined with one or more elements 2-22; combinations of elements 2 and 3; combinations of elements 4 and 5; two or more combinations of elements 2-8; two or more combinations of elements 9-15; one or more elements 2-8 combined with one or more elements 9-15; element 16 combined with one or more elements 17-23; one or more elements 2-8 combined with element 16, and possibly further combined with one or more elements 17-23; and one or more elements 9-15 combined with element 16, and possibly further combined with one or more elements 17-23, and possibly further combined with one or more elements 2-8.

[0078]

[0080] A fifth non-limiting exemplary method of this disclosure is: reacting a feed stream 112 containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146; transporting a portion of the flash gas stream 144 to an ethylene recovery process 166 having a vent stream 168; measuring the pressure of the vent stream 168, the temperature of the vent stream 168, and the state of the concentration of at least one component in the vent stream 168, where the state is the minimum approach to the combustion limit (AFL). min ) and related to the combustion limit (FL) equation including at least one interaction term; measuring the oxygen content ([O2]) of vent flow 168; and AFL relative to vent flow 168 min >When FL-[O2] is true, change the operating state of the ethylene recovery process 166 to AFL min This includes returning to ≤FL-[O2]. A fifth non-limiting example method is further The following may be included: Element 24: The FL formula is given by Equation 1. Element 25: At least one interaction term is selected from the group consisting of component-component interaction terms, temperature-component interaction terms, pressure-component interaction terms, pressure-temperature interaction terms, and any combination thereof. Element 26: The FL formula includes at least two component-component interaction terms. Element 27: The FL formula includes at least one pressure-component term, at least one temperature-component interaction term, a pressure-temperature interaction term, and at least two component-component interaction terms. Element 28: At least one interaction term is an interaction term between 3 and 15.

[0079]

[0081] To aid in a better understanding of embodiments of the present invention, examples of preferred or representative embodiments are given throughout this specification. These examples should not be read to limit or restrict the scope of the present invention in any way. [Examples]

[0080]

[0082] The following describes non-limiting examples for deriving various FL formulas.

[0083] The general formula for FL is given by Equation 1.

[0081]

number

[0082]

[0084] Factors α, β, γ, δ i and ε j The value of can be determined experimentally. Generally, the experimental determination of such a factor involves setting a reasonable range of possible operating states for the position to which the FL formula should be applied.

[0083]

[0085] Next, the maximum oxygen concentration before flammability (molar percent oxygen relative to the total gas) is experimentally determined under various conditions within the operating range. Based on the accumulated data, the FL equation is derived using one of the data-fitting models. Multiple equations that fit the data may be obtained. Each equation derived from the data-fitting model can have any number for i and j in Equation 1. The numbers for i and j, and whether C or I is included in each equation, can be set by the operator before data fitting. Alternatively, the numbers for i and j, and whether C or I is included in the equation, may originate from the data-fitting model itself. Statistical analysis of multiple equations may be used to determine which equation should be used during operation.

[0084]

[0086] In the first embodiment, the possible operating state ranges shown in Table 1 were analyzed for reactor state and reactor inlet composition. Wherever possible, the concentration limits for flammability to oxygen were determined according to ASTM E918-09 (2015).

[0085] [Table 1]

[0086]

[0087] Numerous FL equations, including Equation 7-10, were derived. Here, FL is the flammable oxygen composition expressed in mol% in the dry gas; P is the pressure expressed in psig; T is the temperature expressed in °C; [C2H6], [CH4], and [CO2] are the ethane, methane, and carbon dioxide concentrations expressed in mole percent in the oxygen-free dry gas; [Hac] is the acetic acid concentration expressed in weight percent in the oxygen-free gas; [H2O] is the water concentration expressed in weight percent in the oxygen-free gas; the dry gas is the composition of the mixed feed stream 112 excluding water and acetic acid; the oxygen-free dry gas is the composition of the mixed feed stream 112 excluding water, acetic acid, and oxygen; and the oxygen-free gas is the composition of the mixed feed stream 112 excluding oxygen. Formula 7:

[0087]

number

[0088] Formula 8:

[0089]

number

[0090] Formula 9:

[0091]

number

[0092] Equation 10:

[0093]

number

[0094]

[0088] Statistical analysis can be used when determining which of the FL formulas (e.g., formulas 7-10 or others) should be used in operation. Here again, formulas 7-10 provided in the present invention are derived from data generated from the states in Table 1 and are specific to the vinyl acetate system / process configuration and state as defined in the corresponding experimental design. As will be recognized by those skilled in the art, formulas 7-10 cannot necessarily be used in any vinyl acetate process / system. Furthermore, those skilled in the art who have come into contact with this disclosure will recognize, without excessive experimentation, how to measure flammability data points within a suitable state range for different reactors and how to consider the vinyl acetate system / process configuration.

[0095]

[0089] In the second embodiment, an inter-process heat exchanger and / or carbon dioxide removal system We analyzed the possible operating state ranges listed in Table 2 that may be applicable to the system. Wherever possible, we determined the concentration limits for flammability relative to oxygen according to ASTM E918-09 (2015).

[0096] [Table 2]

[0097]

[0090] Numerous FL formulas, including formulas 11-14, were derived. Here, FL is the flammable oxygen composition expressed in mol% in the dry gas; P is the pressure expressed in psig; T is the temperature expressed in °C; [C2H6], [CH4], and [CO2] are the ethane, methane, and carbon dioxide concentrations expressed in mole percent in the oxygen-free dry gas; the oxygen-free dry gas is the composition of the flow excluding water, acetic acid, and oxygen. Equation 11:

[0098]

number

[0099] Equation 12:

[0100]

number

[0101] Equation 13:

[0102]

number

[0103] Equation 14:

[0104]

number

[0105]

[0091] Statistical analysis can be used when determining which of the FL formulas (e.g., formulas 11-14 or others) should be used during operation. Here again, formulas 11-14 provided in the present invention are derived from data generated from the states in Table 2 and are specific to the vinyl acetate system / process configuration and state as defined in the corresponding experimental design. As will be recognized by those skilled in the art, formulas 11-14 cannot necessarily be used in any vinyl acetate process / system. Furthermore, those skilled in the art who have come into contact with this disclosure will recognize, without excessive experimentation, how to measure flammability data points within a suitable state range for different reactors and how to consider the vinyl acetate system / process configuration.

[0106]

[0092] Unless otherwise indicated, all numbers used herein and in the accompanying claims to represent quantities of components, properties, such as molecular weight and reaction conditions, should be understood in all cases to be modified by the term “approximately.” Therefore, unless otherwise indicated, The numerical parameters described herein and in the appended claims are approximations that may vary depending on the desired properties to be obtained in embodiments of the invention. While we do not intend to limit the application of the doctrine of equivalents to the claims, each numerical parameter should be interpreted by taking into account at least the number of significant figures reported and by applying common rounding techniques.

[0107]

[0093] One or more exemplary embodiments incorporating embodiments of the present invention disclosed herein are presented herein. For the sake of simplicity, not all features of physical practices are described or shown herein. In developing physical embodiments incorporating embodiments of the present invention, it is understood that numerous implementation-specific decisions must be made in each implementation, and over time, such as compliance with system-related, business-related, government-related, and other constraints, in order to achieve the developer's goals. The developer's efforts may be time-consuming, but such efforts are routine work for those with ordinary skill in the art and who benefit from this disclosure.

[0108]

[0094] Although compositions and methods are described herein as "including" various components or steps, compositions and methods may also "essentially consist of" or "consist of" those various components and steps.

[0109]

[0095] Accordingly, the present invention may be modified as appropriate to achieve the stated objectives and advantages and their inherent nature. The particular embodiments disclosed above are merely examples, as the present invention may be modified and practiced in different but equivalent ways that will be obvious to those skilled in the art and who have an interest in the teachings of the present invention. Furthermore, except for the following claims, there is no intention to limit the invention to the structural or design details shown herein. Accordingly, it is obvious that the particular exemplary embodiments disclosed above may be modified, combined or altered, and all such variations are considered to fall within the scope and spirit of the present invention. The present invention disclosed herein as examples may be adequately practiced in the absence of any elements not specifically disclosed herein and / or any optional elements disclosed herein. Compositions and methods are described as “containing,” “encompassing,” or “incorporating” various components or steps, but compositions and methods may also “essentially consist of” or “consist of” those various components and steps. All the number and scope disclosed above may vary to some extent. Wherever a range of numbers with lower and upper limits is disclosed, all numbers that fall within that range and all ranges that are included are specifically disclosed. In particular, any range of values ​​disclosed herein (in the form of "about a to about b" or equivalently "about a to b" or equivalently "about ab") should be understood to describe all numbers and ranges that are included within that broader range of values. Furthermore, terms used in the claims have their obvious and ordinary meanings unless otherwise clearly defined by the patentee. Moreover, the indefinite article "a" or "an" used in the claims is defined to mean one or more of the elements it introduces in the present invention. The claims of the original application of this application are transcribed below. (Aspect 1) A step of reacting a feed stream 112 containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; The step of cooling the crude vinyl acetate flow 118 in a heat exchanger 120; The step of separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, wherein the tail gas stream 130 contains ethylene, carbon dioxide, alkanes, and oxygen; the flash gas stream 144 contains ethylene, carbon dioxide, alkanes, and oxygen; and the vinyl acetate stream 146 contains vinyl acetate, water, and acetic acid; The step of heating the tail gas flow 130 in the heat exchanger 120; A step of removing at least a portion of the carbon dioxide from the flash gas flow 144 to generate a CO2 removal overhead flow 158; A step of mixing the evaporated acetic acid with the heated tail gas flow 130 and the CO2 removal overhead flow 158 in the evaporator 106 to generate the evaporation flow 108; A step of adding oxygen to the evaporation flow 108 to generate the supply flow 112; (a) the pressure of the feed flow 112 and / or the reactor 116, the temperature of the feed flow 112 and / or the reactor 116, and the concentration of at least one component in the feed flow 112 and / or the reactor 116; (b) the pressure of the tail gas flow 130 after heating, the temperature of the tail gas flow 130 after heating, and the concentration of at least one component in the tail gas flow 130 after heating; (c) Pressure of the CO2 removal overhead flow 158, temperature of the CO2 removal overhead flow 158, and concentration of at least one component in the CO2 removal overhead flow 158 A step of measuring and / or determining the conditions of (a), (b) and / or (c), wherein (a) is a first minimum approach (AFL) to the combustion limit based on the conditions of (a). min ) and the first combustion limit (FL) formula, where (b) is the second minimum AFL based on the aforementioned state of (b) min And relating to the second FL formula, (c) is the third minimum AFL based on the aforementioned state of (c). minand related to a third FL equation, wherein one or more of the first FL equation, the second FL equation, and the third FL equation include at least one interaction term; measuring and / or determining the oxygen content ([O2]) of a stream selected from the group consisting of the feed stream 112, the heated tail gas stream 130, the CO2 removal overhead stream 158, and any combination thereof; and (a), (b), or (c) for one or more of AFL MIN starting a shutdown procedure or a repair step when AFL > FL-[O2] is true A method comprising. (Aspect 2) The first AFL min is different from the second AFL min and / or the first AFL min is different from the third AFL min and / or the second AFL min is different from the third AFL min The method according to Aspect 1, wherein. (Aspect 3) The first FL equation is different from the second FL equation, and / or the first FL equation is different from the third FL equation, and / or the second FL equation is different from the third FL equation, the method according to Aspect 1 or 2. (Aspect 4) The at least one interaction term is selected from the group consisting of a component-component interaction term, a temperature-component interaction term, a pressure-component interaction term, a pressure-temperature interaction term, and any combination thereof, the method according to any one of Aspects 1 to 3. (Aspect 5) The first FL equation, the second FL equation, and / or the third FL equation include one or more terms selected from the group consisting of a constant, a temperature, a pressure, and the concentration of a component in the corresponding composition, the method according to any one of Aspects 1 to 4. (Aspect 6) The first FL equation and / or the second FL equation and / or the third FL equation include at least two component-component interaction terms, the method according to any one of Aspects 1 to 5. (Aspect 7) The method according to any one of aspects 1 to 6, wherein the first FL formula and / or the second FL formula and / or the third FL formula includes at least one pressure-component term, at least one temperature-component interaction term, a pressure-temperature interaction term, and at least two component-component interaction terms. (Aspect 8) The method according to any one of aspects 1 to 7, wherein the at least one interaction term is one of 3 to 15 interaction terms. (Aspect 9) Furthermore, The method according to any one of embodiments 1 to 8, further comprising the step of combining a portion of the tail gas slip flow 130 with the flash gas flow 144 before removing at least a portion of the carbon dioxide from the flash gas flow 144. (Aspect 10) The step of separating the crude vinyl acetate flow 118 is, The step of separating the crude vinyl acetate flow 118 into an overhead flow 124 and a first bottom flow 126 in a separator 122; The step of separating the overhead flow 124 into the tail gas flow 130 and the second bottom flow 132 within the scrubber 128; The step of combining the first and second bottom flows 126, 132; and The step of separating the combined first and second bottom flows 126 and 132 into the flash gas flow 144 and the vinyl acetate flow 146 in the unpurified tank 142. The method according to any one of embodiments 1 to 9, including the method described herein. (Aspect 11) Furthermore, The step of purifying the vinyl acetate stream 146 into a purified vinyl acetate product stream 150. The method according to any one of embodiments 1 to 10, including the method described above. (Aspect 12) Furthermore: The steps of purifying the vinyl acetate stream 146 into a purified vinyl acetate product stream 150 and one or more additional streams; and The step of recycling at least one of the additional flows back into the evaporator 106, the tail gas flow 130, and / or the flash gas flow 144. The method according to any one of Aspects 1 to 10, comprising (Aspect 13) Further, Adding ethylene and / or methane to the tail gas stream 130 upstream of the heat exchanger 120 The method according to any one of Aspects 1 to 12, comprising (Aspect 14) Further, Removing at least a portion of the carbon dioxide from the tail gas stream 130 upstream of the heat exchanger 120 The method according to any one of Aspects 1 to 13, comprising (Aspect 15) Further, Adding ethylene and / or acetic acid to the evaporator 106 The method according to any one of Aspects 1 to 14, comprising (Aspect 16) Further, Conveying a portion of the flash gas stream 144 to an ethylene recovery process 166 having a vent stream 168; Measuring the pressure of the vent stream 168, the temperature of the vent stream 168, and the concentration of at least one component in the vent stream 168, wherein the state is a fourth minimum approach (AFL min ) to the combustion limit and is related to a fourth combustion limit (FL) equation including at least one interaction term; Measuring the oxygen content ([O2]) in the vent stream 168; and When AFL min > FL - [O2] is true, changing the operating state of the ethylene recovery process 166 to return the ethylene recovery process 166 to AFL min ≦ FL - [O2] The method according to any one of Aspects 1 to 15, comprising (Aspect 17) The fourth AFL min is different from the first AFL min and / or the second AFL min and / or the third AFL min The method according to Aspect 16. (Aspect 18) The method according to aspect 16 or 17, wherein the fourth FL formula is different from the first FL formula and / or the second FL formula and / or the third FL formula. (Aspect 19) The method according to one of aspects 16 to 18, wherein the at least one interaction term for the fourth FL formula is selected from the group consisting of a component-component interaction term, a temperature-component interaction term, a pressure-component interaction term, a pressure-temperature interaction term, and any combination thereof. (Aspect 20) The method according to one of the aspects 16 to 19, wherein the first FL formula, the second FL formula and / or the third FL formula includes one or more terms selected from the group consisting of constants, temperature, pressure and the concentration of a component in the corresponding composition. (Aspect 21) The method according to one of the aspects 16 to 20, wherein the fourth FL formula includes at least two component-component interaction terms. (Aspect 22) The method according to one of the aspects 16 to 21, wherein the fourth FL formula includes at least one pressure-component term, at least one temperature-component interaction term, a pressure-temperature interaction term, and at least two component-component interaction terms. (Aspect 23) The method according to one of the aspects 16 to 22, wherein the at least one interaction term for the fourth FL formula is one of the 3 to 15 interaction terms. (Aspect 24) A step of reacting a feed stream 112 containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; The step of cooling the crude vinyl acetate flow 118 in a heat exchanger 120; The step of separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146; A step of transporting a portion of the flash gas flow 144 to an ethylene recovery process 166 having a vent flow 168; A step of measuring the pressure of the vent flow 168, the temperature of the vent flow 168, and the concentration of at least one component in the vent flow 168, wherein the state is the minimum approach to the combustion limit (AFL). min) and a step associated with the combustion limit (FL) equation including at least one interaction term; A step of measuring the oxygen content ([O2]) in the vent stream 168; and AFL for the aforementioned vent flow 168 min When >FL-[O2] is true, the operating state of the ethylene recovery process 166 is changed to AFL min Steps to return to ≤FL-[O2] A method that includes this. (Aspect 25) The method according to aspect 24, wherein the at least one interaction term is selected from the group consisting of a component-component interaction term, a temperature-component interaction term, a pressure-component interaction term, a pressure-temperature interaction term, and any combination thereof. (Aspect 26) The method according to aspect 24 or 25, wherein the FL formula includes at least two component-component interaction terms. (Aspect 27) The method according to one of aspects 24 to 26, wherein the FL formula includes at least one pressure-component term, at least one temperature-component interaction term, a pressure-temperature interaction term, and at least two component-component interaction terms. (Aspect 28) The method according to one of the aspects 24 to 27, wherein the at least one interaction term is one of the 3 to 15 interaction terms.

Claims

[Claim 1] A step of reacting a feed stream 112 containing acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 containing vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; The step of cooling the crude vinyl acetate flow 118 in a heat exchanger 120; The step of separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, wherein the tail gas stream 130 contains ethylene, carbon dioxide, alkanes, and oxygen; the flash gas stream 144 contains ethylene, carbon dioxide, alkanes, and oxygen; and the vinyl acetate stream 146 contains vinyl acetate, water, and acetic acid; The step of heating the tail gas flow 130 in the heat exchanger 120; At least a portion of the carbon dioxide is removed from the flash gas stream 144 to CO ２ Steps to generate a removal overhead flow 158; The evaporated acetic acid is heated and then the tail gas flow 130 and the CO ２ The step of mixing the removed overhead flow 158 with the evaporator 106 to generate the evaporation flow 108; A step of adding oxygen to the evaporation flow 108 to generate the supply flow 112; (a) the pressure of the feed flow 112 and / or the reactor 116, the temperature of the feed flow 112 and / or the reactor 116, and the concentration of at least one component in the feed flow 112 and / or the reactor 116; (b) the pressure of the tail gas flow 130 after heating, the temperature of the tail gas flow 130 after heating, and the concentration of at least one component in the tail gas flow 130 after heating; (c) The CO ２ The pressure of the removed overhead flow 158, the CO ２ The temperature of the removal overhead flow 158, and the CO ２ Concentration of at least one component in the removed overhead flow 158 A step of measuring and / or determining the conditions of (a), (b) and / or (c), wherein (a) is a first minimum approach (AFL) to the combustion limit based on the condition of (a). ｍｉｎ ) and in relation to the first combustion limit (FL) formula, where (b) is the second minimum AFL based on the aforementioned state of (b) ｍｉｎ And relating to the second FL formula, (c) is the third minimum AFL based on the aforementioned state of (c) ｍｉｎ and relating to a third FL formula, one or more of the first FL formula, the second FL formula and the third second FL formula include at least one interaction term; The oxygen content ([O]) of a stream selected from the group consisting of the feed stream 112, the heated tail gas stream 130, the CO ２ removal overhead stream 158, and any combination thereof is measured and / or determined; and ２ )); and AFL for one or more of (a), (b), or (c) ＭＩＮ >FL-[O ２ Step to initiate an operation shutdown procedure or repair step when ] is true. A method that includes this.

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