KR101171986B1 - Method for recovering heat quantity of Benzene Recovery Unit - Google Patents

Abstract

The present invention comprises a first step of performing a heat exchange of the benzene recovery unit distillation column top product and fruit; And a second step of performing heat exchange of the fruit and the naphtha cracking plant distillation column bottom product in which the heat exchange was performed in the first step. According to the present invention, the heat generated from the benzene recovery unit can be reused in other facilities in the naphtha cracking plant, such as ethane separation tower, propane separation tower, butane separation tower, C3 hydrocarbon separation tower and / or oligomer separation tower. The overall energy cost can be reduced.

Naphtha cracking plant, benzene recovery unit, fruit, heat exchanger, benzene separation tower, regeneration tower, ethane separation tower, propane separation tower, C9 hydrocarbon separation tower

Description

Method for recovering heat quantity of Benzene Recovery Unit

The present invention relates to a calorie recovery method that makes it possible to utilize the calorie generated in the benzene recovery unit at another facility in a naphtha cracking plant.

The Naphtha Cracking Center (hereinafter referred to as "NCC") thermally decomposes gasoline naphtha (nathpha) at a temperature of about 750 to 800 ° C, which is the basic raw material for petrochemical products ethylene, propylene, butylene and BTX. It is a facility that produces benzene, toluene, and xylene.

Among the units constituting the naphtha cracking plant, the Benzene Recovery Unit (BRU) is a raw pyrolysis gasoline (RPG) which is a by-product of producing ethylene and propylene from naphtha as raw materials. Benzene), and the process carried out in the unit is largely referred to as gasoline hydrogenation (GHT) process or prefractionation (PF). ), Extraction (hereinafter referred to as "EXT") process, and dealkylation (hereinafter referred to as "HDA") process.

The GHT process is a process of separating hydrocarbons having 5 carbon atoms and hydrocarbons having 6 or more carbon atoms after hydrogenation and desulfurization reaction using RPG as a raw material. The GHT process is performed in various ways, the representative examples of which are as follows. The first method is a first GHT reactor in which the hydrogenation reaction is carried out; A secondary GHT reactor in which hydrogenation and desulfurization reaction proceed; And RPG which is a raw material in a pentane separator having a hydrocarbon of 5 carbon atoms separated therefrom. In addition, the GHT process is the first GHT reactor in which the hydrogenation reaction proceeds; A pentane separation column in which hydrocarbons having 5 carbon atoms are separated; A secondary GHT reactor in which the hydrogenation reaction proceeds; And a stripper in which the desulfurization reaction proceeds, in a sequential manner via the RPG. As described above, the GHT process may be performed in various ways, but in any case, hydrocarbons having 5 carbon atoms and hydrocarbons having 6 or more carbon atoms are produced, the latter of which is sent to a hexane separator of the PF process.

The unit performing the PF process consists of a hexane separation column and a C9 hydrocarbon separation column. The raw material introduced from the GHT process is first introduced into a hexane separation column, where it is separated into hydrocarbons having 6 carbon atoms and hydrocarbons having 7 carbon atoms or more. The hydrocarbon having 6 carbon atoms is introduced into the EXT process, and the hydrocarbon having 7 or more carbon atoms is separated into a hydrocarbon having 10 or more carbon atoms and a hydrocarbon having 7 to 9 carbon atoms in the C9 hydrocarbon separation tower, and then the latter is introduced into the HDA process.

The EXT process is a process for producing benzene and the like from hydrocarbons having 6 carbon atoms produced in the PF process, and the process is performed by using an apparatus such as an extractor, a stripper, and a recovery tower. In addition, the HDA process uses hydrocarbons having a carbon number of 7 or more introduced from the PF process as a raw material, and produces benzene through a dealkylation process in a high temperature and high pressure reactor, and then introduces the benzene into a benzene separation tower together with the benzene produced in the EXT process. Is the process of producing benzene.

The most important of the components of the unit performing the above-described benzene recovery process is a separation tower (distillation tower) for separating the multi-component materials included in the raw materials by their respective boiling point differences, which are generally shown in FIG. It is composed together. With reference to Figure 1 will be described schematically the operating principle of the separation column. When the feed is introduced into the separation column, the vapor evaporated in the reboiler 1 rises in the upper direction (tower) inside the tower, and the liquid condensed in the condenser 2 is refluxed to the bottom (bottom). Direction. When the vapor and the liquid contact inside the column, the vapor condenses and the liquid evaporates. At this time, the low boiling point component tends to evaporate, and the high boiling point component tends to condense, which leads to the low boiling point component. Concentration increases. This results in a pure low boiling point steam at the top of the separation tower, which is condensed by the condenser 2, partly produced as a product, and partly refluxed back to the column top. On the other hand, the refluxed condensate (reflux) is used to condense the high boiling point components coming up to the bottom. In addition, some of the high-boiling components discharged from the tower bottom are also produced as products, while others are evaporated again in the reboiler and then sent to the bottom of the separation tower to be used to evaporate components inside the tower.

In the separation tower, the raw material inflow, evaporation by the reboiler (1) and condensation and reflux by the condenser (2) are repeated, producing a high-purity product. Energy, steam, is used. Therefore, the benzene recovery unit composed of a plurality of such separation towers is also required a large amount of steam, the amount is more than 80,000 tons for the benzene recovery unit, 260,000 tons per year combined with the other units constituting the plant. .

However, in the actual production process, as described above, most of the large amount of steam required by the purchase from the outside, resulting in a large economic loss. As a way of compensating for this economic loss, one can think of reusing the calorific value of the heat produced by the benzene recovery unit that is being forcibly cooled for process reasons. However, such a method is not easy to realize due to problems such as lack of calories of the BRU emissions and difficulty in changing the operating conditions, and thus there is no technology capable of recycling the calories generated from the BRU.

The present invention has been made in consideration of the above-described problems, and provides a calorie recovery method for reducing the energy cost of the entire plant by reusing the calorie which has been forcibly cooled in the benzene recovery unit in another facility in the plant. It aims to do it.

The present invention as a means for solving the above problems, the first step of performing a heat exchange of the benzene recovery unit distillation column top product and fruit; And a second step of performing heat exchange of the fruit and the naphtha cracking plant distillation column bottom product having the heat exchange performed in the first step.

In the calorie recovery method of the present invention, the fruit used is preferably water or an organic solvent.

In addition, the benzene recovery unit distillation column heat exchanged in the first step of the calorific recovery method of the present invention may be one or more selected from the group consisting of benzene separation tower, regeneration tower, hexane separation tower and C9 hydrocarbon separation tower.

In the calorie recovery method of the present invention, the calorie exchanged in the first step is preferably in the range of 3 Gcal / hr to 30 Gcal / hr.

In addition, the first step of the calorie recovery method of the present invention further comprises maintaining the upper temperature of the benzene recovery unit distillation column from 90 ℃ to 125 ℃ and / or pressurizing the heat-exchanged fruit in the first step can do.

In the heat recovery method of the present invention, the naphtha cracking plant distillation column of the second step may be at least one selected from the group consisting of an ethane separation tower, a propane separation tower, a butane separation tower, a C3 hydrocarbon separation tower, and an oligomer separation tower. The amount of heat exchanged in two steps is preferably in the range of 3 Gcal / hr to 30 Gcal / hr.

The calorie recovery method of the present invention may further include the step of recovering the fruit subjected to the heat exchange in the second step to the benzene recovery unit.

According to the method of the present invention, the amount of heat generated in a benzene recovery unit that has been discarded because it has not been found to be used in a naphtha cracking plant such as an ethane separation tower, a propane separation tower, a butane separation tower, a C3 hydrocarbon separation tower and / or an oligomer separation tower. It can be used at other facilities within the plant, reducing the energy costs of the entire plant.

The present invention comprises a first step of performing heat exchange of a BRU distillation column overhead product and fruit; And

It relates to a BRU calorie recovery method comprising a second step of performing a heat exchange of the fruit and the NCC column bottom product subjected to the heat exchange in the first step. According to the method of the present invention, it is possible to utilize the heat of the BRU, which was previously forcedly cooled due to process reasons, in another facility in the NCC, thereby reducing the energy cost of the entire plant.

Hereinafter, the calorie recovery method of the present invention will be described in more detail, and the meaning of symbols used for this purpose is defined as follows. That is, the symbol "Cn" used in the specification of the present invention means a hydrocarbon having n carbon atoms, "Cn-m" means a hydrocarbon having n to m carbon atoms, and "Cn +" and "Cn-" each represent n carbon atoms. The above and n or less hydrocarbons are meant.

The present invention is characterized by recovering the heat of the upper column of the product carrying out the benzene recovery process, which can be utilized in other facilities in the NCC, for a more clear understanding of the present invention in the BRU with reference to the accompanying drawings A schematic description of the process performed is as follows. That is, the main processes performed in the BRU may include a GHT process, a PF process EXT process, and an HDA process. Among them, the process of performing the GHT and PF processes is shown in FIG. 2 and the process of performing the EXT process is shown in FIG. And, the process of performing the HDA process is shown in FIG.

As shown in FIG. 2, in the GHT process, RPG is first introduced into the primary GHT reactor 3 to proceed with a hydrogenation process, whereby diolefin in the raw material is converted into paraffin. Subsequently, some of the bottom products of the primary GHT reactor 3 are introduced into the secondary GHT reactor 4 via the separator F1 and the like, and some are forcedly cooled in the cooler C1 to the primary GHT reactor 3. ) Is recovered. In the secondary GHT reactor 4, unreacted olefins in the raw materials are converted to paraffins by hydrogenation, and sulfur is converted into hydrogen sulfide and removed by a desulfurization process. Subsequently, the bottom product of the secondary GHT reactor 4 passes through a plurality of heat exchangers E1, E2, E3, E4, and then sequentially passes through the cooler C2 and the separator F2, and then the pentane separation tower 5 Is introduced. In the pentane separation tower 5, the introduced raw material is separated into C5 and C6 +, of which C6 + is introduced into the PF process.

In the PF process, C6 + is first introduced into the hexane separation column 6, which is separated into C6 and C7 + in the hexane separation column 6. The separated C6 is then introduced to the EXT process and C7 + is introduced to the HDA process via the C9 hydrocarbon separation tower 7. In the EXT process, the C6 produced in the PF process is extracted in the extractor 8; Extraction in stripper 9 and regeneration in recovery tower 10 are converted to benzene which is introduced into benzene separation tower 13 and purified to high purity benzene (FIG. 3). Meanwhile, in the HDA process, benzene is produced using the latter of C10 + and C7-9 separated from the C9 hydrocarbon separation tower 7 as a raw material. Specifically, the raw material C7-9 is introduced into the HDA reactor 11 while being circulated by a pump to produce benzene through a dealkylation reaction. The benzene thus produced is passed through a stabilizer 12 again, and then introduced into the benzene separation tower 13 together with the benzene produced in the EXT process, which is recycled through a recycle tower 14 or the like. Purified with high purity benzene (see FIG. 4).

Although each process performed in the BRU has been schematically described, the above is only one aspect of the BRU process to which the calorific recovery method of the present invention can be applied. That is, the BRU process can be modified and performed in various ways. For example, the GHT process may include a primary GHT reactor in which RPG, which is a raw material, is hydrogenated; Pentane separation column in which separation of C5 and C6 + is performed; A secondary GHT reactor in which a hydrogenation reaction proceeds with respect to C6 +; And it may be carried out in such a way as to pass sequentially through the stripping apparatus in which the desulfurization process proceeds. In addition, in the BRU process, a separation process may be performed by connecting a plurality of separation towers such as a benzene separation tower in view of separation efficiency.

The first step of the present invention is a step of performing heat exchange by transferring the heat of the BRU distillation column top product to the fruit in the BRU process performed as described above. In the present invention, the method of performing such heat exchange is not particularly limited. For example, the heat exchange may be performed by installing a heat exchanger in a pipe through which a BRU distillation column top product having a heat quantity to be recovered flows and passing the fruit through the heat exchanger. The average person skilled in the art can easily select the desired type of heat exchanger, its installation place and method, and the like.

In addition, the kind of fruit used for heat exchange in the first step of the present invention is not particularly limited. For example, in the present invention, any fruit conventional in the art such as water or an organic solvent can be used without limitation. The specific type of organic solvent is also not particularly limited as long as it can be used at 100 ° C. or higher. For example, Dowtherm (manufactured by Dow Chem), Therminol VP-1 (Therminol VP-1) (Solutia) And biphenyl mixtures, including Diphyl (Lanxess) and / or Therm S300 (Nippon Steel), and the like, and 100 Common fruits that can be used at high temperatures above ℃ can be used without limitation.

Specific examples of the BRU distillation column in which the heat exchange is performed in the first step may include at least one selected from the group consisting of a benzene separation tower, a regeneration tower, a hexane separation tower, and a C9 hydrocarbon separation tower. One aspect of the existing design conditions of the typical BRU distillation column is shown in Table 1 below (design conditions shown in Table 1 may vary depending on the size and output of the entire plant, etc.).

[Table 1]

BRU  Design conditions Temperature before cooling
(° C) Cooling calories
( Gcal Of hr ) Refrigerant Temperature after cooling
(° C) First benzene Separation tower 99 3.88 Air 71 Secondary benzene Separation tower 99 2.59 CW 71 Play tops 121 1.41 Air / CW 86 Hexane Separation tower 99 3.91 CW 77

As shown in Table 1, in the existing BRU design conditions, the heat amount of the product on the top of the BRU distillation column was cooled by air or cooling water, but in the present invention, the reconstruction of the heat exchange loop between the BRU and the NCC is performed. Through the heat treatment to cool the heat is recycled. In addition, the type of heat exchanger BRU distillation column in the present invention is not limited to the above, and if necessary, the heat exchange loop may be designed so that additional heat amount may be supplied to the NCC from the GHT reactor and the benzene product cooler.

Although not particularly limited, in the first step of the present invention, the calorie range exchanged with the fruit in the BRU distillation column is preferably 3 Gcal / hr to 30 Gcal / hr. If the above range is less than 3 Gcal / hr, the payback period of the investment is long, so the economic efficiency of the investment is low, and it may be difficult to be utilized in other facilities in the factory. If the range is more than 30 Gcal / hr, additional equipment for power supply is provided. There is a fear that the economy will fall due to the need for investment.

In the calorific recovery method of the present invention may also be further performed to control the temperature of the top of the BRU distillation column in the range of 90 ℃ to 125 ℃. This BRU distillation column top temperature control is performed to ensure that the heat exchanged to fruit in the first step falls within the optimum range that can be preferably used in other facilities in the NCC. That is, one of the reasons why the heat recovery of the BRU is difficult because the heat generated from the BRU is insufficient to be utilized in other facilities in the NCC. Accordingly, in the present invention, the temperature control step may be further performed as one of means for replenishing the heat amount previously lacked. After performing this temperature control step, one aspect of each BRU distillation column top temperature and the range of calories that can be recovered is shown in Table 2 below (the ranges shown in Table 2 may vary depending on the size and output of the entire plant, etc.). Can).

[Table 2]

After temperature control BRU  Design conditions Temperature (℃) calorie ( Gcal Of hr ) First benzene Separation tower 100.6 4.1 Secondary benzene Separation tower 101.3 2.8 Play tops 121 1.41 Hexane Separation tower 100.1 4.1

Such BRU distillation column top temperature control may be particularly preferably used when the fruit is an organic solvent. At this time, the control method is not particularly limited, and for example, the BRU distillation column may be appropriately operated by pressurization. In this case, specific driving conditions, such as pressurization conditions, are not particularly limited depending on the type of each distillation column and / or the desired separation efficiency, and an average technician in the art may describe the above-described distillation column temperature without compromising the desired separation efficiency. Conditions that can fall within a range can be easily selected.

In the present invention, as another means for replenishing the calories of the fruit, the step of pressurizing the heat exchanged fruit may be further performed. This pressing step of the fruit can be particularly preferably used when the fruit is water. The method of performing such pressurization is not particularly limited, and for example, a steam compressor may be installed at an appropriate position of a pipe in which heat exchanged fruit flows, and a method of pressurizing the fruit may be used. As such, when pressurizing the fruit (preferably water (steam)), the pressurized fruit has a temperature of 110 ° C. to 147 ° C., and a pressure of 1.5 KCA (kg / cm ² a) to 4.5 KCA (kg / cm ² a). Is preferably. If the temperature and / or pressure of the fruit is out of the above-mentioned range, the heat content of the fruit may be insufficient, making it difficult to use in other facilities or deteriorating economic efficiency.

The second step of the present invention is to transfer the fruit heat exchanged in the first step to another distillation column in the NCC plant, performing a heat exchange of the fruit and the bottom product of the distillation column. At this time, the method of performing heat exchange is not particularly limited, and for example, may be performed using a suitable heat exchanger as in the first step.

NCC is a facility that uses naphtha to produce products through decomposition, quenching, compression and refining processes, and is also a methane separator, a ethane separator, a deethanizer, a propane separator, butane It is composed of a number of distillation towers such as debutanizer, C3 hydrocarbon separation tower and oligomer separation tower. Looking at one aspect of the existing design conditions of the typical separation tower of the above is shown in Table 3 (the design conditions shown in Table 3 may vary depending on the size and output of the entire plant, etc.).

[Table 3]

NCC  Design conditions Feed  flux
(T / H) Scraping  Temperature
(° C) Heat source calorie
( Gcal Of hr ) ethane Separation tower 187.2 93 LS 9.33 Propane Separation tower 91.5 85 LS 6.11 butane Separation tower 46.2 100 LS 5.01 C3  hydrocarbon Separation tower 44.5 52.3 QW 35.08 Oligomer Separation tower 45.5 52 LS 3.30

LS; Low-pressure steam

QW: Quench Water

In the second step of the present invention, the fruit recovering the heat amount of the BRU distillation column in the first step is transferred to the NCC plant, and the heat amount is supplied to all or part of the distillation column as described above. Although not particularly limited, the NCC distillation column in which calories are exchanged in the second step of the present invention is preferably at least one selected from the group consisting of ethane separation tower, propane separation tower, butane separation tower, C3 hydrocarbon separation tower, and oligomer separation tower. .

In addition, the amount of heat exchanged in the second step is preferably in the range of 3 Gcal / hr to 30 Gcal / hr. If the above range is smaller than 3 Gcal / hr, the payback period of the investment may be too long, and if it exceeds 30 Gcal / hr, additional equipment investment is required and the economy is inferior.

In the present invention, it may further comprise the step of recovering the fruit subjected to heat exchange in the above-described second step to the distillation column of the BRU. The fruit recovered in this way can be used again for heat exchange with the top of the BRU distillation column, there is an advantage that can be further improved the process efficiency.

Hereinafter, with reference to the accompanying drawings, one aspect of the calorie recovery method of the present invention will be described schematically. 5 is a schematic diagram illustrating a heat exchange loop between an NCC and a BRU constructed according to one aspect of the present invention.

That is, according to one aspect of the invention the heat exchange loop connecting the NCC and the BRU may be configured as shown in FIG. First, the heat exchanger (E5, E5) in a pipe through which the upper part of the BRU distillation column (benzene separation tower 13-1, 13-2, regeneration tower 14, and / or hexane separation tower 7, etc.) to which heat exchange is performed flows. E6, E7, E8) are installed. Meanwhile, the pipes in which the fruits heat-exchanged in the first step are combined and flow through the heat exchangers E9 and E10 installed below the NCC distillation column (ethane separation tower 15 and / or propane separation tower 16, etc.). It is installed to be connected. In the present invention, a separate heat exchanger E11 is also installed on the pipe for the purpose of temperature control of the fruit or steam production, or a steam compressor for pressurizing the heat exchanged fruit is not shown in the drawing. Can be installed as

In the first step of the present invention, the BRU distillation column top product flows through a pipe in which heat exchangers E5, E6, E7, and E8 are installed to perform heat exchange with the fruit. Fruits undergoing heat exchange in the heat exchanger flow along the pipe and merge with each other, and the combined fruits are introduced into the NCC. Subsequently, in the second step of the present invention, the heat introduced to the NCC distillation column bottom product is performed while the fruit introduced into the NCC passes through the heat exchangers E9 and E10 below the NCC distillation towers 15 and 16 along the pipe. In the present invention, it is also possible to further improve the process efficiency by designing the pipe A so that the fruit whose heat exchange with the NCC distillation column bottom product is completed is recovered back to the BRU.

The above-described BRU calorie recovery method is only one aspect of the present invention, and in the present invention, the conditions such as the connection state of the pipe, the number of heat exchangers, and / or the type of distillation column are freely changed within the scope of not impairing the object of the present invention. BRU calorie recovery can be performed

1 is a schematic diagram showing the shape of a general separation column (distillation column).

Figure 2 is a schematic diagram showing the schematic flow of the GHT and PF process performed in the BRU.

3 is a schematic diagram showing a schematic flow of an EXT process performed in a BRU.

4 is a schematic diagram showing a schematic flow of an HDA process performed in a BRU.

Figure 5 is a schematic diagram showing the state of the loop configured for the calorie recovery method according to an aspect of the present invention.

Claims (12)

A first step of performing heat exchange of the column top product and fruit of the benzene recovery unit; And A heat recovery method of a benzene recovery unit comprising a second step of performing a heat exchange of the fruit and naphtha cracking plant distillation column bottom product subjected to the heat exchange in the first step. The method of claim 1, The fruit is water or an organic solvent. The method of claim 2, The organic solvent is a biphenyl mixture. The method of claim 1, Wherein the distillation column of the benzene recovery unit is at least one selected from the group consisting of a benzene separation column, a regeneration tower for recovering benzene from a mixture of benzene and a solvent and regenerating the solvent, a hexane separation column, and a C9 hydrocarbon separation column. The method of claim 1, The amount of heat exchanged in the first step is 3 Gcal / hr to 30 Gcal / hr. The method of claim 1, And further controlling the top temperature of the distillation column of the benzene recovery unit of the first stage in the range of 90 ° C to 125 ° C. The method of claim 1, Pressurizing the heat exchanged fruit in the first step. The method of claim 7, wherein Pressurization of the fruit is carried out using a steam compressor. The method of claim 7, wherein Pressed fruit is characterized in that the temperature is 110 ℃ to 147 ℃, the pressure is 1.5 KCA to 4.5 KCA. The method of claim 1, The distillation column of the naphtha cracking plant is at least one selected from the group consisting of ethane separation tower, propane separation tower, butane separation tower, C3 hydrocarbon separation tower and oligomer separation tower. The method of claim 1, The amount of heat exchanged in the second step is 3 Gcal / hr to 30 Gcal / hr. The method of claim 1, Recovering the fruit having undergone the heat exchange in the second step to a benzene recovery unit.

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