Complex rectifying tower product carbon footprint calculation method based on energy balance

Abstract

The invention provides a complex rectifying tower product carbon footprint calculation method based on energy balance, and relates to the technical field of oil refining industry product carbon footprint evaluation. The complex rectifying tower product carbon footprint calculation method is as follows: product carbon footprint = feeding carbon footprint-(complex rectifying tower product unit heat release * unit calorific value carbon emission factor); wherein the unit heat release amount of the complex rectifying tower product is equal to the heat release amount in the product tower / the product yield. According to the method for calculating the carbon footprint of the complex rectifying tower product, the carbon footprint of the complex rectifying tower product is calculated according to the energy change of the product material in the production and processing process, and the method has better scientificity.

Description

Technical Field

[0001] The invention relates to the technical field of carbon footprint evaluation of products in the oil refining industry, and in particular to a method for calculating the carbon footprint of complex distillation tower products based on energy balance. Background Art

[0002] The product carbon footprint is a calculation of the greenhouse gas emissions generated by the product during the raw material acquisition, transportation, production, and use stages according to the life cycle method. For the petroleum and petrochemical industry, since there are many unit processes that input one raw material and output multiple products, such as distillation and reaction processes, in the product carbon footprint evaluation, it is necessary to allocate the carbon emissions of the production process to each co-product. The relevant principles and standards guiding the product carbon footprint evaluation at present - "PAS2050 Specification for the Assessment of Greenhouse Gas Emissions of Goods and Services during the Life Cycle" and "ISO14067" do not involve scientific and reasonable rules for the allocation of carbon emissions from chemical unit processes.

[0003] Figure 1 It is a schematic diagram of a crude oil distillation process with multiple parallel distillation towers;

[0004] Figure 2 Schematic diagram of the flow of the atmospheric tower as a complex distillation tower.

[0005] According to the general multi-component distillation method, petroleum (or petroleum fractions) are separated and cut into N product components such as gasoline, kerosene, diesel, heavy oil, etc., and N-1 distillation towers are required to complete the above separation and cutting tasks. Figure 1 shown.

[0006] However, in the distillation of petroleum (or petroleum fractions), the various products themselves are a complex mixture, and the separation accuracy between them does not require very high, and the number of plates required between two products is not many. Therefore, these towers can be combined into one tower. This tower is actually equivalent to overlapping several simple distillation towers. Its distillation section is equivalent to the combination of the four distillation sections of the original four simple towers, and its lower section is equivalent to the stripping section of tower 1. Such a tower is called a composite distillation tower or a complex distillation tower. Figure 2 As shown. Due to the large processing capacity of the complex tower, in addition to the top cold reflux, the reflux method also has top circulating reflux and 2 to 4 mid-section circulating refluxes. The heat from each reflux of the tower is used to control the distillation point temperature of the side-line extracted material.

[0007] Since a complex distillation tower is obtained by overlapping several simple distillation towers, carbon footprint evaluation of each side product of the process requires allocation of carbon emissions among the products.

[0008] In view of this, the present invention is proposed. Summary of the invention

[0009] The object of the present invention is to provide a method for calculating the carbon footprint of complex distillation tower products based on energy balance.

[0010] Since the complex distillation tower has only a distillation section but no stripping section, there is no reboiler at the bottom of the tower; at the same time, it has multiple product side-line extractions and mid-section heat extraction. After being heated in the heating furnace, the feed enters the bottom of the tower in two phases of gas phase. The gas phase rises along the tower and is condensed through the mid-section circulation heat extraction to form a side-line extraction. Therefore, the feed vaporization rate of the complex distillation tower is equal to (slightly greater than) the sum of the yields of the top product and each side-line product. The heat source of the complex distillation tower is almost entirely provided by the feed heating furnace. That is, when the feed temperature, vaporization rate, etc. are determined, the excess heat in the complex distillation tower, that is, the reflux ratio, is actually determined by the heat balance of the entire tower. It can be seen from this that in the operation process of the complex distillation tower from feed to product, there is a corresponding energy evolution law: the product component in the feed will vaporize after absorbing heat in the heating furnace. After entering the fractionation tower, the gas phase component will condense to form a side-line extraction when it flows upward along the tower through the mid-section circulation heat extraction, and release heat. The heat is generally recovered through heat exchange in the device. Therefore, in the distillation process of the complex distillation tower, the feed amount (F F ), feed enthalpy (H F ) and product output (F pi ), product enthalpy (H pi ) and mid-cycle heat extraction (Q j ) has a relationship with the energy balance of the whole tower.

[0011] This application evaluates the product carbon footprint through the energy evolution process of the product material, that is, calculates the carbon footprint of the complex distillation tower product through the feed carbon footprint, the unit heat release of the complex distillation tower product and the unit calorific value carbon emission factor, so as to better reflect the scientific nature of the product carbon footprint.

[0012] Figure 3 The process flow chart of the complex distillation tower provided by the present invention.

[0013] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0014] S1: Calculate the heat carried out by the product according to the product output of the complex distillation tower. The calculation formula is as follows:

[0015] Heat carried out by the product = product output × (product outflow temperature - tower top reflux temperature) × mass heat capacity of the product;

[0016] S2: Calculate the heat released by the product in the tower and the unit heat released by the product in the tower based on the heat brought out by the product. The calculation formula is as follows:

[0017] Heat released in the product tower = (heat carried by the feed / feed flow) × product output - heat released by the product;

[0018] Unit heat release in product tower = heat release in product tower / product output;

[0019] S3: Based on the energy balance of the whole tower, the carbon footprint of the complex distillation tower product is calculated by the unit heat release of the product in the tower. The calculation formula is as follows:

[0020] The carbon footprint of complex distillation tower products = feed carbon footprint - (unit heat release in the product tower × carbon emissions per unit calorific value).

[0021] The present invention provides a method for calculating the carbon footprint of complex distillation tower products based on energy balance, wherein the complex distillation tower products include tower top products and side products; the feed amount, feed enthalpy value and product output, product enthalpy value and mid-stage circulation heat extraction have a relationship of full tower energy balance;

[0022] Furthermore, the feed carbon footprint includes: crude oil carbon footprint, feed heat exchange carbon footprint and heating furnace fuel consumption carbon footprint.

[0023] Furthermore, the complex distillation tower includes any one of an atmospheric pressure tower and a vacuum tower of a atmospheric and vacuum distillation unit, a main distillation tower of a catalytic cracking unit and a delayed coking unit, and a product distillation tower of a hydrocracking unit.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: the carbon emissions are calculated according to the energy changes of the product materials during the production and processing process, which can better reflect the scientific nature of the carbon footprint of complex distillation products. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation of the present invention or the technical solution in the prior art, the drawings of the specific implementation are briefly introduced below.

[0026] Figure 1 A schematic diagram of a crude oil distillation process with multiple parallel distillation towers provided by the present invention;

[0027] Figure 2 A schematic flow diagram of an atmospheric tower as a complex distillation tower provided by the present invention;

[0028] Figure 3 A process flow chart of a complex distillation tower provided by the present invention;

[0029] Figure 4 This is the energy balance calculation boundary diagram of the product distillation tower provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments.

[0031] The technical terms of the application text and various calculation formulas can be expressed using formula symbols, and the specific meanings of the formula symbols are as follows:

[0032] F F —Feed rate, t / hr;

[0033] H F —Feed enthalpy, MJ / t;

[0034] H pi —Enthalpy of product i flowing out of a complex distillation tower, MJ / t;

[0035] F pi —Product i output, t / hr;

[0036] C pi —Carbon footprint of product i, kgCO2 / t;

[0037] Q j —Heat taken from the jth middle cycle, GJ / hr;

[0038] Q ri —Heat released in product i tower, MJ / hr;

[0039] C F —Feed carbon footprint, kgCO2 / t;

[0040] E h —Carbon emission factor per unit of heat;

[0041] According to the present invention, the feed rate (F F ), feed enthalpy (H F ) and product output (F pi ), product enthalpy (H pi ) and mid-cycle heat extraction (Q j ) has the energy balance of the whole tower, that is, it satisfies:

[0042]

[0043] The carbon footprint of the complex distillation tower product (C pi ) = Feed carbon footprint (C F )-(unit heat release of complex distillation tower products × unit calorific value carbon emission factor (E h )), as follows:

[0044]

[0045] Where: the unit heat release of the complex distillation tower product = the heat release in the product tower (Q ri ) / Product output (F pi ).

[0046] In a preferred embodiment of the present invention, the calculation formula for the heat release in the product tower is as follows:

[0047] Q r,i =F P,i ·(H F -H p,i )

[0048] That is, the amount of heat released in the product tower = (heat brought in by the feed / feed flow) × product output - heat brought out by the product.

[0049] In the above preferred embodiment, the heat brought by the feed includes feed latent heat and feed sensible heat.

[0050] In the above preferred embodiment, the calculation formula of the heat brought out by the product is as follows:

[0051] Heat carried out by the product = product output × (product out-tower temperature - tower top reflux temperature) × mass heat capacity of the product.

[0052] In a preferred embodiment of the present invention, the feed carbon footprint includes: feed oil carbon footprint, feed heat exchange carbon footprint and heating furnace fuel consumption carbon footprint.

[0053] Since the energy source of the complex tower is almost entirely brought in by the feed, that is, provided by the feed heating furnace, this application evaluates the carbon footprint of the feed heating furnace and the complex tower as a whole. The carbon emission sources of this process are mainly emissions from the feed heating furnace, tower top air cooling, water cooling, and electricity consumption.

[0054] In a preferred embodiment of the present invention, the complex distillation tower comprises any one of an atmospheric pressure tower and a vacuum tower of a atmospheric and vacuum unit, a main fractionation tower of a catalytic cracking unit and a delayed coking unit, and a product fractionation tower of a hydrocracking unit.

[0055] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0056] Example 1

[0057] (I) This embodiment takes a product fractionation tower of a hydrocracking unit as an example. The tower separates the debutanizer bottom oil into naphtha, jet fuel, diesel and tail oil. The material balance is shown in Table 1.

[0058] Table 1 Product fractionation tower material balance (t / hr)

[0059]

[0060] As shown in Table 1, only the tail oil in the feed is liquid. The product carbon footprint of the complex distillation tower can be calculated based on the heat balance. The main operating conditions of the tower are shown in Table 2.

[0061] Table 2 Product fractionation tower operating conditions:

[0062]

[0063]

[0064] (II) Carbon footprint of product fractionation tower feed:

[0065] 1. The feed of the product distillation tower comes from the bottom oil of the debutanizer tower. After heat exchange and heating, the carbon footprint of the product distillation tower feed can be calculated to be 75.382kgCO2 / t.

[0066] (III) The mass heat capacity of each fraction in the product distillation tower is 2.5 MJ / (t·℃), the unit latent heat of vaporization of naphtha is 300 MJ / t, the unit latent heat of vaporization of jet fuel is 210 MJ / t, and the unit latent heat of vaporization of diesel is 168 MJ / t. The energy balance of the entire tower is calculated based on the top reflux temperature of 51℃.

[0067] (1) Heat brought into the feed:

[0068] After the product fractionator feed enters the fractionator gasification section, the naphtha, jet fuel and diesel components in the feed will be vaporized, and the total amount of vaporized material is 139.7t / hr.

[0069] Since the vaporization process of the above-mentioned materials will absorb heat, the temperature of the feed in the vaporization section will drop. The temperature after the drop can be considered to be the tower bottom temperature of 285°C. From this, the heat of the feed in the vaporization section can be calculated, including the latent heat and sensible heat of the vaporized material. The latent heat is calculated from the vaporization amount and the vaporization heat. The results are shown in Table 3.

[0070] Table 3 Latent heat of feed in the vaporization section

[0071]

[0072] It can be seen from Table 3 that the total latent heat of feed vaporization is 33.068 GJ.

[0073] The sensible heat of the feed can be calculated from the flow rate and mass heat capacity, 214t / hr×(285℃-51℃)×2.5MJ / (t·℃)=125204MJ / hr,

[0074] From this, it can be calculated that the energy carried by the feed is 33068MJ / hr+125204MJ / hr=158271MJ / hr, and the unit heat is 739.6MJ / t.

[0075] (2) Bring out heat:

[0076] Figure 4 The energy balance calculation boundary diagram of the product distillation tower provided for this embodiment.

[0077] For the product fractionation tower, the heat output includes the heat taken out by each side product, the heat of the tower top condensation cooling, and the heat taken out by the first middle section cycle and the second middle section cycle. Figure 4 shown.

[0078] 1) The heat brought out by the side-line products can be calculated based on their outlet temperature, flow rate and mass heat capacity. For example, the heat brought out by aviation fuel = 44.3t / hr×(208℃-51℃)×2.5MJ / (t·℃)=17387.8MJ. The heat brought out by other side-line products can be calculated in the same way.

[0079] 2) The condensation heat at the top of the tower can be calculated from the top reflux flow, product volume and product vaporization latent heat, (72t / h+58.6t / hr)×300MJ / t=39180.0MJ;

[0080] 3) The cooling heat of the tower top is the heat released when the temperature of the oil and gas at the top of the tower is further cooled to 51°C after condensation. Assuming that the bubble point temperature of naphtha is 90°C, the cooling heat of the tower top = (72t / h+58.6t / hr)×(90°C-51°C)×2.5MJ / (t·℃)=12733.5MJ.

[0081] 4) The heat intake of the middle cycle can be calculated by the middle cycle flow rate, the tower outlet temperature and the tower inlet temperature. For example, the heat intake of the first middle cycle = 191t / h×(208℃-180℃)×2.5MJ / (t·℃)=11937.5MJ.

[0082] (3) Heat balance of the whole tower:

[0083] The heat output of the product flowing out of the distillation tower calculated in step (2) is combined with the heat input calculated in step (1) to obtain the heat balance of the entire tower, as shown in Table 4.

[0084] Table 4 Heat balance of product fractionation tower

[0085]

[0086]

[0087] From the heat balance of the distillation tower listed in the table above, it can be seen that the total heat brought into the distillation tower by the feed is 158.27 GJ / hr, the total heat taken away by the product is 80.39 GJ / hr, and the heat removed from the top and middle circulation of the tower is 77.90 GJ / hr.

[0088] (4) Heat released in the product tower:

[0089] During the operation of the fractionation tower, the heat released by the product in the tower is the difference between the heat brought in by the feed and the heat brought out by the product, that is:

[0090] Heat released in the product tower = (heat brought in by the feed / feed flow) × product output - heat released by the product.

[0091] For example: For jet fuel products, the heat released in the tower = (158271.1MJ / hr÷214t / hr)×44.3t / hr-17387.8MJ / hr=15376.5MJ / hr. Similarly, the heat released in the tower by other products can be calculated, as shown in Table 5.

[0092] Table 5 Heat release of each product in the distillation tower

[0093]

[0094]

[0095] Note: Unit heat release = heat release / output.

[0096] It can be seen from Table 5 that different products release different amounts of heat in the tower, which is mainly due to the different condensation temperatures corresponding to different products.

[0097] For example, the condensation temperature of the diesel side line is 263°C, and the heat released in the tower includes two parts:

[0098] The first is the sensible heat released by the temperature drop of the diesel gas phase component in the vaporization section when it rises through the tower plate by plate, and the second is the latent heat of the diesel gas phase component condensing at the extraction plate position. The sensible heat released by the diesel gas phase is the heat when the temperature drops from 285°C to 263°C. Since the heat of the tower has been used by the cold material heat exchange in the device, the thermal utility consumption of the device can be reduced, which is directly reflected in the reduction of fuel consumption of the heating furnace and the reduction of carbon emissions.

[0099] Therefore, based on the carbon emissions per unit calorific value of 77.525kgCO2 / GJ, the carbon footprint of the product after deducting carbon emissions from heat release can be calculated as follows:

[0100]

[0101] For example, the carbon footprint of diesel = 75.382kgCO2 / t-209.58MJ / t×77.525kgCO2 / GJ÷1000MJ / GJ=59.134kgCO2 / t. The carbon footprints of other products are shown in Table 6.

[0102] Table 6 Carbon footprint of distillation tower products

[0103]

[0104] It can be seen from Table 6 that for the hydrocracking product fractionation tower, the carbon footprint of its product naphtha is the lowest and the tail oil is the highest. This is mainly because when all products leave the tower in liquid state, the outlet temperature of naphtha is the lowest and the heat released in the tower is the largest, so the carbon emissions deducted are the largest, resulting in the lowest carbon footprint.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit it.

Claims

1. A method for calculating the carbon footprint of complex distillation tower products based on energy balance, It is characterized in that The method comprises: S1: Calculate the heat removed by the product based on the output of the complex distillation tower product: Heat carried out by the product = product output × (product outflow temperature - tower top reflux temperature) × mass heat capacity of the product; S2: Calculate the heat released by the product in the tower and the unit heat released by the product in the tower based on the heat brought out by the product: Heat released in the product tower = (heat carried by feed / feed flow) × product output - heat released by the product; Unit heat release in product tower = heat release in product tower / product output; S3: Based on the energy balance of the whole tower, the carbon footprint of the complex distillation tower product is calculated by the unit heat release of the product in the tower: The carbon footprint of complex distillation tower products = feed carbon footprint - (unit heat release in the product tower × carbon emissions per unit calorific value).

2. The carbon footprint calculation method according to claim 1, It is characterized in that The complex distillation tower products include top products and side products; the feed amount and feed enthalpy value of the complex distillation tower have an energy balance relationship with the product output, product enthalpy value and mid-stage circulation heat extraction of the complex distillation tower.

3. The carbon footprint calculation method according to claim 1, It is characterized in that The heat carried by the feed includes the latent heat of the feed and the sensible heat of the feed.

4. The carbon footprint calculation method according to claim 1, It is characterized in that The feed carbon footprint includes: feed oil carbon footprint, feed heat exchange carbon footprint and heating furnace fuel consumption carbon footprint.

5. The carbon footprint calculation method according to claim 1, It is characterized in that The complex distillation tower includes any one of the atmospheric pressure tower and vacuum tower of the atmospheric and vacuum distillation unit, the main distillation tower of the catalytic cracking unit and the delayed coking unit, and the product distillation tower of the hydrocracking unit.

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