A method for allocating symbiotic products in evaluating the carbon footprint of a distillation process

Abstract

The present application provides a method for evaluating the distribution of symbiotic products in the carbon footprint of a distillation process, the method comprising: determining the carbon emissions of the distillation process based on the carbon footprint of the feed, the carbon emissions of the reboiler at the bottom of the tower, and the carbon emissions of the condensation and cooling process at the top of the tower; determining the correlation between the carbon footprint of the top product and the carbon footprint of the bottom product based on the heat relationship between the gas and liquid phases of each plate in the distillation tower; and calculating the carbon footprints of the top product and the bottom product based on the carbon emissions of the distillation process, the output of the top product and the bottom product, and the above-mentioned correlation based on the carbon emission footprint balance.

Description

Technical Field

[0001] The present invention relates to a method for allocating carbon emissions to co-products in the carbon footprint evaluation of distillation process products, and is particularly suitable for industries such as oil refining and petrochemicals. Since the distillation process inputs one raw material and outputs multiple products, the use of the present invention to allocate carbon emissions is more accurate and objective. Background Art

[0002] The concept of "carbon footprint," derived from "ecological footprint," refers to the total direct and indirect greenhouse gas emissions generated by a product (or service) over its life cycle, typically expressed as CO2 equivalents. Compared to an organization's carbon emissions, a carbon footprint evaluates the lifecycle carbon emissions of a product's acquisition process.

[0003] As an entity sector that ensures national energy security and the supply of basic raw materials, the petrochemical industry has large carbon emissions. Conducting carbon footprint evaluation of petrochemical industry products can not only grasp the carbon emission distribution of each production link in the industry, but also obtain the carbon emissions of the product's life cycle, providing important guidance for the industry to achieve low-carbon transformation.

[0004] The production process of petrochemical products often uses a single input feedstock and produces multiple products. Therefore, carbon footprint assessments of petrochemical products require allocating carbon emissions from the production process to each product, i.e., allocating carbon emissions from co-products. Distillation, a typical chemical unit operation, separates feedstock into a high-purity overhead product and bottoms product. The distillation process requires significant energy input to the bottom reboiler and energy-consuming media such as circulating water and air cooling in the overhead condenser. These energy-consuming processes generate carbon emissions and are the direct source of these emissions. Therefore, the amount of energy consumed in the production of the overhead and bottoms products during the distillation process determines their respective carbon footprints. The method for allocating carbon emissions from this process to the overhead and bottoms products must be based on the energy consumption of the product production process. Currently, the relevant standards for product carbon footprint assessments, including PAS 2050, "Greenhouse gas emissions assessment of goods and services over their life cycle," and ISO 14067, "Greenhouse gas product carbon footprint quantification requirements and guidance," do not include methods for allocating carbon emissions from distillation processes based on energy consumption.

[0005] Based on this, an embodiment of the present application provides a method for evaluating the distribution of co-products in the carbon footprint of a distillation process. Summary of the Invention

[0006] The purpose of this application is to provide a method for evaluating the distribution of co-products in the carbon footprint of a distillation process. Figure 2The figure shows a typical flow chart of a distillation process. The distillation process consists of a distillation tower, a reboiler, and a condenser. The feed is added from the middle of the distillation tower. The liquid phase in the distillation tower flows downward layer by layer along the tower plates, flowing out from the bottom of the tower and entering the reboiler. The liquid is heated to boil and vaporize, and the vaporized gas phase returns to the tower, forming a gas phase that rises layer by layer along the tower plates. The rising gas phase contacts the downward-flowing liquid phase, and the light components in the liquid phase are transferred to the gas phase, while the heavy components in the gas phase are transferred to the liquid phase. As a result, the heavy component content in the downward-flowing liquid phase gradually increases, and a high-purity heavy component product can be obtained at the bottom of the tower.

[0007] As the gas phase flows upward within the tower, it comes into contact with the liquid phase, and light components are continuously transferred to the gas phase, thereby gradually increasing the light component content in the rising gas phase. At the top of the tower, a gas phase material with a very high purity of light components can be obtained. After flowing out of the top of the tower, this gas phase material enters the condenser, is condensed and cooled, and becomes a liquid phase. Part of it is extracted as the top product, and part of it is returned to the distillation tower from the top of the tower as the reflux liquid phase.

[0008] The carbon emissions from the distillation process are mainly caused by the heat consumption of the reboiler at the bottom of the tower (generally using steam, heating furnace fuel gas, and sometimes heat medium), and the electricity consumption of air cooling and water cooling at the top of the tower. These energy-consuming processes can be converted into carbon emissions according to their energy values. When evaluating the carbon footprint of the distillation process, the carbon emissions converted from energy need to be allocated to the products at the top and bottom of the tower.

[0009] This application proposes a method for evaluating the distribution of symbiotic products in a distillation process carbon footprint, the method comprising:

[0010] 1. Determine the carbon emissions of the distillation process based on the carbon footprint of the feed, the carbon emissions of the reboiler at the bottom of the tower, and the carbon emissions of the condensation and cooling process at the top of the tower.

[0011] The carbon emissions of the reboiler can be calculated based on the energy consumption and the carbon emission factor of the corresponding energy, as shown in the following formula:

[0012] E b =Q R ·E

[0013] Where: E b ——Carbon emissions from the bottom reboiler, kgCO2;

[0014] Q R ——Reboiler energy consumption, MJ;

[0015] E——Carbon emission factor of reboiler energy consumption, kgCO2 / MJ;

[0016] 2. Determine the correlation between the carbon footprints of the top product and the bottom product based on the heat relationship between the gas and liquid phases on each tray in the distillation tower;

[0017] 3. Based on the carbon footprint balance, the carbon footprints of the top product and bottom product can be calculated according to the above correlation, carbon emissions, and the output of the top product and bottom product.

[0018] For the distillation process, the carbon footprint balance satisfies the following equation: carbon emissions from feed + process = carbon footprint of overhead product × amount of overhead product + carbon footprint of bottom product × amount of bottom product, i.e., the following equation:

[0019] C F ·F+E b +E t =D·C D +W·C W

[0020] Where: C F ——Feed carbon footprint, kgCO2 / t;

[0021] F——feed amount, t.

[0022] E t ——Carbon emissions from the tower top condensation cooling process, kgCO2;

[0023] D——tower top product output, t;

[0024] W——tower bottom product output, t;

[0025] C D ——Carbon footprint of tower top product, kgCO2 / t;

[0026] C W ——Carbon footprint of tower bottoms, kgCO2 / t.

[0027] The above correlation between the carbon footprints of the top product and the bottom product is determined based on the heat relationship between the gas and liquid phases on each plate of the distillation tower, including:

[0028] 1. Based on the fact that the liquid phase at the bottom of the distillation tower is the bottom product, the carbon footprint of the bottom product C W kgCO2 / t, as the liquid phase at the bottom of the distillation tower L N Carbon footprint kgCO2 / t.

[0029] 2. Determine the carbon footprint of the rising gas phase at the bottom of the distillation tower based on the carbon footprint of the liquid phase at the bottom of the distillation tower, the carbon emissions from the reboiler, and the amount of gas phase vaporized from the reboiler.

[0030] Since the reboiler at the bottom of the tower consumes energy and produces carbon emissions, the gas phase V generated by the reboiler heating and vaporization of the liquid phase at the bottom of the tower is N+1 , its carbon footprint is increased compared to the liquid phase at the bottom of the tower. The carbon footprint of the rising gas phase at the bottom of the tower can be calculated by energy balance as follows:

[0031]

[0032] Where: ——Gas phase carbon footprint of reboiler (N+1th tray), kgCO2 / t;

[0033] ——Carbon footprint of distillation tower bottom product (liquid phase at the bottom of the tower), kgCO2 / t;

[0034] V N+1 ——The amount of gas phase vaporized in the reboiler of the distillation tower (equivalent to N+1 plate), that is, the gas phase load at the bottom of the tower, t;

[0035] The amount of gas phase vaporized in the reboiler at the bottom of the tower V N+1 It can be calculated from the vaporization heat of the bottom material and the reboiler heat.

[0036] 3. Calculate the carbon footprint of the gas phase on the lower tray of the feed tray based on the heat relationship between the gas phases on each tray in the stripping section of the distillation tower and the carbon footprint of the rising gas phase at the bottom of the tower.

[0037] When the heat of vaporization of the components being separated during distillation differs minimally, and the sensible heat caused by temperature differences on different trays is ignored, the amount of liquid vaporized on each tray is equal to the amount of gas liquefied. In a distillation tower without feed or discharge, the molar flow rate of the gas phase entering each tray (gas phase load) is equal to the gas phase load leaving that tray; the molar flow rate of the liquid phase entering each tray (liquid phase load) is equal to the liquid phase load leaving that tray. Therefore, for each tray in the distillation tower, the liquid phase load flowing downward and the gas phase load flowing upward are both constant, conforming to the constant molar flow law.

[0038] When there is feed in the distillation tower, the section below the feed is the stripping section, and the section above the feed is the rectifying section. The gas and liquid phase loads of the rectifying section and the stripping section will change due to the different feeds and their thermal states, so the carbon footprints should be calculated separately.

[0039] In the stripping section of the distillation tower, the gas phase rises along the tower and the temperature continues to decrease. The gas phase carbon footprint of the lower tray of the feed plate can be determined by the rising gas phase V N+1 The carbon footprint is calculated from the enthalpy difference between the gas phases on the trays as follows:

[0040]

[0041] Where: ——Gas phase carbon footprint of the lower tray below the feed tray (j+1 tray), kgCO2 / t;

[0042] j——the tray number of the feed tray;

[0043] ——Enthalpy of vaporized gaseous material in the bottom reboiler, MJ;

[0044] ——Gas phase enthalpy of the tray below the feed tray, MJ;

[0045] E - Carbon emission factor per unit heat of the distillation process, kgCO2 / MJ.

[0046] 4. Determine the carbon footprint of the feed plate gas phase based on the amount of gas phase in the distillation tower feed and the carbon footprint of the gas phase on the lower tray of the feed plate.

[0047] For the feed of the distillation tower, its thermal state will affect the gas and liquid phase loads of each section of the distillation tower. The feed of the distillation tower includes five thermal conditions: (1) cold liquid feed with a temperature below the bubble point; (2) saturated liquid feed below the bubble point; (3) gas-liquid two-phase feed with a temperature between the bubble point and the dew point; (4) saturated gas phase feed below the dew point; (5) superheated gas phase feed with a temperature above the dew point.

[0048] Due to the different feed and its thermal conditions, the gas and liquid phase loads of the feed plate and the gas and liquid phases of the lower tray will change. Figure 3 The influence of feed thermal state on gas and liquid phase loads is shown, including: (a) subcooled liquid feed; (b) saturated liquid feed; (c) gas-liquid mixed feed; (d) saturated steam feed; (e) superheated steam feed.

[0049] The feed F contains qF of liquid phase and (1-q)F of gas phase. After passing through the feed plate, the carbon footprint of the gas phase Vj of the feed plate can be calculated from the (1-q)F gas phase in the feed and the gas phase Vj+1 of the lower tray and their carbon footprints, as follows:

[0050]

[0051] Where: ——Gas phase carbon footprint of the feed tray (j trays), kgCO2 / t;

[0052] V j+1 ——Gas phase load on the tray below the feed tray, t;

[0053] q——the proportion of liquid phase in the feed, %;

[0054] 5. Determine the carbon footprint of the tower top gas phase based on the feed plate gas phase carbon footprint and the heat relationship between the feed plate gas phase and the tower top gas phase.

[0055] Gas phase carbon footprint from feed plate The carbon footprint of the top gas phase can be calculated by the enthalpy difference between the feed plate gas phase and the top gas phase, as follows:

[0056]

[0057] Where: ——Gas phase carbon footprint at the top of the tower (first tray), kgCO2 / t;

[0058] ——enthalpy of the gas phase on the feed plate (the jth tray), MJ;

[0059] ——Gas phase enthalpy at the top of the tower, MJ;

[0060] 6. Determine the carbon footprint of the top product based on the carbon emissions from the top condensation cooling process and the carbon footprint of the top gas phase.

[0061] Since the gas phase at the top of the tower is cooled and liquefied by the condenser, the electricity consumption and circulating water consumption of the condenser using air cooling or water cooling will generate carbon emissions. This part of carbon emissions should be included in the carbon footprint of the tower top product, as shown in the following formula:

[0062]

[0063] Where: C D ——Carbon footprint of tower top product, kgCO2 / t;

[0064] E t ——Carbon emissions from the gas phase condensation and cooling process at the top of the tower, kgCO2;

[0065] D——tower top product output, t.

[0066] In this way, the correlation between the carbon footprints of the tower top product and the tower bottom product can be determined.

[0067] The technical solution of the present application includes the following beneficial effects: determining the carbon emissions of the distillation process based on the feed carbon footprint, the carbon emissions of the bottom reboiler and the carbon emissions of the top condensation cooling process; determining the correlation between the carbon footprints of the top product and the bottom product based on the heat relationship between the gas and liquid phases of each plate in the distillation tower; and calculating the carbon footprints of the top product and the bottom product based on the carbon emission footprint balance according to the correlation, carbon emissions, and the output of the top product and the bottom product. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the technical solution of the present application, the following briefly introduces the drawings required for use in the embodiments.

[0069] Figure 1 A process diagram for determining the carbon footprint correlation between the tower top product and the tower bottom product provided in this application is shown;

[0070] Figure 2 A schematic diagram of a distillation process provided by the present application is shown;

[0071] Figure 3 The following figure shows the effect of feed state on the gas and liquid load of a tray provided by the present application; wherein, (a) subcooled liquid feed; (b) saturated liquid feed; (c) gas-liquid mixed feed; (d) saturated steam feed; (e) superheated steam feed;

[0072] Figure 4 A schematic diagram of gas phase flow rate change provided in an embodiment of the present application is shown;

[0073] Figure 5 Another schematic diagram of gas phase flow rate change provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0074] The following describes some embodiments of the present application in detail. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Figure 1 A process diagram for determining the carbon footprint correlation between the tower top product and the tower bottom product provided in this application is shown; Figure 2 A schematic diagram of a distillation process provided in this application is shown.

[0075] Example 1

[0076] A distillation tower (gasoline stabilization tower) separates the liquefied gas shown in Table 1 and the stabilized gasoline shown in Table 2. The bottom of the stabilization tower uses the first middle section of a distillation tower to take heat as the reboiler heat source. The main operating conditions are shown in Table 3.

[0077] Table 1 Composition of liquefied gas

[0078]

[0079] Table 2 Stable gasoline distillation range

[0080]

[0081] Table 3 Main operating conditions of the stabilization tower

[0082]

[0083] 1. The bottom of the stabilization tower uses the first intermediate cycle of a distillation tower as a heat source, extracting 82.95 GJ / hr of heat. This is converted to 1.0 MPa steam in this case, with a steam enthalpy of 2.6 GJ / t. The carbon emission factor for 1.0 MPa steam is 226.82 kgCO2 / t, resulting in a reboiler carbon emission of 7236.43 kgCO2. There is no heat output from the top of the tower, and the power consumption for the air and water cooling at the top is 60 kWh / hr, corresponding to a carbon emission of 58 kgCO2.

[0084] 2. Calculate the reboiler gas phase volume based on the bottom product composition and reboiler heat. The simulation shows that the latent heat of vaporization of the bottom material is 0.3856GJ / t, so the bottom gas phase load = 82.95GJ / hr ÷ 0.3856GJ / t = 215.1t / hr, and the bottom gas phase carbon footprint is

[0085] 3. The feed plate of this tower is the 26th plate. However, in actual operation, the mass transfer and heat transfer of the plates above and below the feed plate do not meet the requirements of the ideal plate. Therefore, considering the influence of the plate efficiency, it can be assumed that the 26th to 34th plates are the feed plates (i.e., a theoretical plate). The gas phase load changes below the feed plate as shown in the figure below. Figure 4 As shown in the figure, it can be seen that the gas phase load below plate 34 changes little, so it can be considered to comply with the constant molar flow assumption.

[0086] The return temperature of the gas phase at the bottom of the tower is 179°C, and the temperature of the feed plate is 115.06°C. From the simulation, it can be seen that the enthalpy change of the gas phase in the tower is 0.1326GJ / t (the gas phase composition is calculated based on the feed composition). The carbon footprint of the gas phase on the tower plate below the feed plate is

[0087] 4. The feed to the fractionator has a certain impact on the gas-liquid load. The simulation results show that the liquid load in the rectification section is L = 1868 kmol / hr (tray 24), and the liquid load in the stripping section is L' = 5677 kmol / hr (tray 34). The feed rate is F = 3998 kmol / hr. Therefore, the liquid flow rate in the feed = 5677 kmol / hr - 1868 kmol / hr = 3809 kmol / hr, q = 3809 kmol / hr ÷ 3998 kmol / hr = 0.95, and the feed carbon footprint can be calculated as zero.

[0088] Since the feed is a two-phase feed of gas and liquid, the gas phase in the feed will enter the feed plate together with the gas phase of the lower tray of the feed plate. Calculate the feed plate

[0089] 5. Changes in the gas phase load in the distillation section are as follows: Figure 5 As shown in the figure, it can be seen that the gas phase load of each tower plate in the distillation section is stable, so the carbon footprint of the top gas phase can be calculated from the heat relationship from the feed plate to the top gas phase.

[0090] The feed plate temperature is 115°C and the tower top temperature is 54.83°C. The enthalpy change from the feed plate to the tower top is 0.1716 GJ / t. The carbon footprint of the tower top gas phase is:

[0091]

[0092] 6. Since the top gas phase flows out of the distillation tower and enters the condenser, the carbon footprint of the top product can be calculated based on the carbon emissions of the condensation and cooling process.

[0093] The carbon footprint of the tower top product can be calculated based on the tower top product output:

[0094]

[0095] 7. The carbon footprint of the distillation process satisfies the following balance:

[0096] Feed carbon footprint + bottom reboiler carbon emissions + top condenser cooling carbon emissions = top product carbon footprint × top product output + bottom product carbon footprint × bottom product output.

[0097] Based on the carbon footprints of the tower top and tower bottom products and the above balance relationship, the product carbon footprint can be calculated, that is: From this we can get the carbon footprint of the bottom product :

[0098] The carbon footprint of the tower top product is 0.93×21.23+9.17=28.91kgCO2 / t.

[0099] The above results show that for gasoline stabilizers, the overhead product has a higher carbon footprint than the bottom product. This is primarily because the overhead product exits the fractionator in the vapor phase, carrying with it a significant amount of latent heat energy. This energy is then condensed and cooled at the top of the fractionator, consuming significant amounts of circulating water, air cooling fans, and other energy-consuming media. During fractionator operation, energy fed into the reboiler at the bottom of the fractionator is continuously transferred to the top of the fractionator via the vapor phase load within the fractionator, ultimately being carried away by the overhead vapor phase. Therefore, the overhead product consumes more energy than the bottom product.

[0100] Example 2

[0101] The feed composition of a depropanizer is shown in Table 4. The tower separates C3 and C4 in the feed. 1.0 MPa steam is used as the reboiler heat source at the bottom of the tower. The main operating conditions are shown in Table 5.

[0102] Table 4 Composition of liquefied gas

[0103]

[0104] Table 5 Main operating conditions of the depropanizer

[0105]

[0106] The depropanizer bottom reboiler consumes 10.9 t / hr of 1.0 MPa steam. The enthalpy of 1.0 MPa steam is 2.6 GJ / t, resulting in a heat consumption of 28.4 GJ / hr. The steam carbon emission factor is 226.82 kgCO₂ / t, resulting in a reboiler carbon emission of 2477.57 kgCO₂. There is no heat output from the top of the tower. Air and water cooling consumes 30 kWh / hr of electricity, resulting in a carbon emission of 29 kgCO₂.

[0107] 2. Based on the feed composition, its bubble point temperature is calculated to be 73.99°C. The actual feed temperature is 68.46°C, indicating that the feed is subcooled. The heat required to raise the separation tower feed temperature from 68.46°C to the bubble point of 73.99°C is 0.928 GJ. Simulations show that the feed's latent heat of vaporization is 0.351 GJ / t. Therefore, the amount of gas phase that can condense from 68.46°C to the bubble point is 0.928 GJ ÷ 0.351 GJ / t = 2642.57 kg. Based on the feed volume of 54.27 t, the feed state q = -2642.57 kg ÷ 54270 kg = -0.049. The feed carbon footprint is assumed to be 0.

[0108] 3. Carbon footprint of tower bottom products The carbon footprint of the gas phase at the bottom of the tower can be calculated. According to the simulation, the latent heat of vaporization of the material at the bottom of the tower is 0.2426GJ / t, so the gas phase load = 28.4GJ / hr ÷ 0.2426GJ / t = 117.08t / hr, and the carbon footprint of the rising gas phase at the bottom of the tower is

[0109] 4. The bottom temperature of the depropanizer is 103℃ and the feed plate temperature is 68.4℃. The simulation shows that the enthalpy change of the gas phase in the stripping section is 0.0685GJ / t, so the gas phase carbon footprint of the tray below the feed plate is

[0110]

[0111] 5. Since the feed is supercooled, the gas phase on the lower tray of the feed plate will partially liquefy when it rises to the feed plate, and the heat released is the heat required to heat the feed to the bubble point. However, in this example, the feed temperature is higher than the feed plate temperature, that is, the feed thermal state is supercooled, but the feed temperature is higher than the feed plate temperature. When the two temperatures are close, it can be considered that the carbon footprint of the gas phase below the feed plate does not change after passing through the feed plate, and remains

[0112] 6. The feed plate temperature is 68.4°C and the tower top temperature is 46.6°C. The enthalpy change from the feed plate to the tower top gas phase can be calculated by simulation to be 0.0257GJ / t. The carbon footprint of the tower top gas phase is

[0113] 7. Based on the tower top reflux flow and tower top product output, the tower top gas phase flow rate is calculated as 18.75t / hr + 67.43t / hr = 86.18t / hr. The carbon emissions converted from the air cooling and water cooling power consumption is 29kgCO2. The carbon footprint of the tower top product is:

[0114] 8. The carbon footprint of a product can be calculated from the balance equation of carbon emission footprint, as follows:

[0115]

[0116] From this, the carbon footprint of the bottom product can be obtained

[0117] Then, the carbon footprint of the top product is 40.90kgCO2 / t+15.29kgCO2 / t=56.19kgCO2 / t 。

[0118] From the above calculations, it can be seen that the carbon footprint of the top product is higher than that of the bottom product, which means that the carbon emissions of obtaining the top product are greater. Therefore, when the same equipment is separating two feeds with different compositions, the lower the content of the light component, the lower the carbon emissions of the process.

[0119] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solution of the present application rather than to limit it. The scope of protection of the present application is not limited thereto.

Claims

1. A method for evaluating the distribution of symbiotic products in a distillation process carbon footprint, characterized by: The carbon emissions of the distillation process are determined based on the feed carbon footprint, the carbon emissions of the tower bottom reboiler, and the carbon emissions of the tower top condensation and cooling process; Determine the correlation between the carbon footprints of the top product and bottom product based on the heat relationship between the gas and liquid phases on each plate of the distillation tower; Based on the carbon footprint balance, the carbon footprints of the overhead product and the bottom product are calculated according to the correlation, the carbon emissions of the distillation process, and the output of the overhead product and the bottom product; Determining the correlation between the carbon footprints of the tower top product and the tower bottom product, including: Determining the carbon footprint of the tower bottom gas phase based on the tower bottom product carbon footprint, the reboiler carbon emissions, and the tower bottom gas phase volume; The carbon footprint of the top gas phase is determined based on the heat relationship between the gas phases of each tray of the distillation tower and the carbon footprint of the feed gas phase; Based on the carbon footprint of the tower top gas phase and the carbon emissions of the tower top condensation and cooling process, the carbon footprint of the tower top product is determined, that is, the correlation between the carbon footprints of the tower bottom product and the tower top product; Based on the heat relationship between the gas phases on each tray of the distillation tower and the carbon footprint of the feed gas phase, the carbon footprint of the top gas phase is determined, including: The carbon footprint of the gas phase on the tray below the feed tray is determined based on the carbon footprint of the gas phase at the bottom of the tower and the heat relationship between the gas phases on each tray in the stripping section of the distillation tower. According to the thermal state of the feed, the gas phase carbon footprint of the feed plate is determined by the gas phase carbon footprint of the feed and the gas phase carbon footprint of the tray below the feed plate; The carbon footprint of the tower top gas phase is determined from the carbon footprint of the feed plate gas phase according to the heat relationship between the feed plate gas phase and the tower top gas phase.

2. The method according to claim 1, characterized in that Based on the carbon footprint of the tower bottom product, the carbon emissions of the reboiler, and the amount of the tower bottom gas phase, the carbon footprint of the tower bottom gas phase is determined, including: Determine the amount of gas phase at the bottom of the tower based on the heat consumption of the tower bottom reboiler and the latent heat of vaporization of the tower bottom material; The carbon footprint of the rising gas phase at the bottom of the distillation tower is determined based on the carbon footprint of the liquid phase at the bottom of the distillation tower and the carbon emissions from the reboiler.

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