JPH0346037B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a petroleum distillation apparatus having a main distillation column and a pre-distillation column, and further equipped with a naphtha rectification system consisting of a stabilizer and a splitter. It is something. More specifically, the present invention relates to a petroleum distillation apparatus equipped with an optimal naphtha rectification system configuration depending on the distillation performance of a pre-distillation column. In this specification, petroleum typically means crude oil, but generally refers to petroleum-based compounds from which LPG and naphtha can be obtained by distillation. <Prior art> Various types of equipment have been considered for distilling crude oil at normal pressure to extract various fractions. from crude oil preheated by a heat recovery system.
Part of the mixed fraction of LPG and naphtha (light + heavy) is distilled in a pre-distillation column, and the top fraction of the pre-distillation column is directly transferred to the naphtha rectification system consisting of a stabilizer and a splitter to the main distillation column. There is an atmospheric distillation unit for crude oil that is sent together with the overhead fraction. This apparatus will be explained based on the process diagrams of FIGS. 3 and 4. First, as shown in FIG.
After being preheated in a heat recovery system consisting of one or more heat exchanger groups E1 and E2 using the column bottom residual oil 30e as a heat source, it is supplied to the pre-distillation column 20. Each of these heat exchanger groups has a method in which crude oil is sequentially exchanged heat with one or more heat sources (one-through type), and a method in which crude oil is distributed according to the number of heat sources and merged with each heat source after heat exchange (split type). Alternatively, it is a collection of heat exchangers arranged in a combination manner. The pre-distillation column 20 is equipped with a reflux mechanism such as a side line reflux system, an external reflux system at the top, or a combination of both. When the side line reflux system is adopted, the heat of the side line reflux 20a can be used as a heat source for the heat recovery system, as shown in the figure. The heat required for the rectification of crude oil in the pre-distillation column 20 is normally the heat brought in by the crude oil by preheating the crude oil in the heat recovery system, and a reboiler for the pre-distillation column is not particularly required. Although not shown, stripping steam is introduced into the bottom of the pre-distillation column as needed in order to enhance the rectification effect of the pre-distillation column. The crude oil preheated by the heat recovery system heat exchanger groups E1 and E2 is rectified in the pre-distillation column 20, and the pre-distillation column top fraction 20f, which is a part of the LPG/naphtha mixed fraction, is taken out from the top of the column. On the other hand, the pre-distillation column bottom residual oil 20e is further heated in the heating furnace 70 via the heat recovery system heat exchanger group E3, and then supplied to the main distillation column 30. Main distillation column 30
In 30 different fractions with different boiling point ranges,
c and 30d, and the main distillation column top fraction 30f, which is the remainder of the LPG/naphtha fraction that was not taken out in the previous distillation column, is taken out from the top of the main distillation column. Residual oil 30e is obtained. The top mechanisms of both the pre-distillation column 20 and the main distillation column 30 include condensers 21 and 31, a top receiving tank 22,
It consists of an overhead reflux system equipped with 32, and the condensed water is
The LPG/naphtha mixed fractions 20f and 30f are
As shown in the figure, the mixture is sent to the naphtha rectification system, first separated into LPG and naphtha by the stabilizer 40, and then the naphtha fraction is sent to the splitter 50 where it is separated into light naphtha and heavy naphtha. .
In FIG. 4, symbols F1 and F2 indicate the top reflux paths of the stabilizer 40 and the splitter 50, respectively, and both include a condenser, a top receiving tank, and a pump. Although not shown, the pre-distillation column, the main distillation column, the stabilizer, and the splitter are each provided with a gas venting pipe and a regulating valve for adjusting the operating pressure of the column at the top of the receiving tank. In the crude oil atmospheric distillation equipment as described above,
The preheating temperature of the crude oil supplied to the pre-distillation column 20 is determined by the amount of LPG and naphtha (light + heavy) fractions obtained from the top of the pre-distillation column and the amount of kerosene fraction mixed into the fractions. The premise is that the temperature is such that rectification can be achieved in the pre-distillation column at a level that does not impair the product specifications of the heavy naphtha obtained from the naphtha rectification system. In addition, the operating pressure in the pre-distillation column 20 varies slightly depending on the type of crude oil, preheating temperature, etc., but is usually 1 to 5.
It is operated in the range of Kg/cm ² G. By the way, in both the stabilizer 40 and the splitter 50 in the naphtha rectification system, most of the heat required for the distillation operation is obtained from heating by the reboilers 41 and 51, as shown in FIG. As shown in Figure 3, usually the bottom residue 30e of the main distillation column 30 or the side line reflux 30
Part of b is used. In Figure 3,
The heat source of the reboiler 41 of the stabilizer 40 is the residual oil 30e from the bottom of the main distillation column, and the splitter 50
The heat source of the reboiler 51 is the side line reflux 3 of the main distillation column.
0b, but both reboilers are arranged so that the main distillation column bottom residual oil 30e is used as a heat source, and furthermore, the reboilers are arranged so that the bottom oil 30e of the main distillation column is used as a heat source, and the fractions 30c and 3 from the column side of the main distillation column are
0d may be used as a heat source for these reboilers. However, the heating temperature by each reboiler in the stabilizer and splitter in a naphtha rectification system, in other words, the amount of heat required for the reboiler, varies depending on the throughput of LPG/naphtha fraction supplied to the stabilizer and splitter, and is not necessarily constant. Not. The throughput of the stabilizer or splitter depends mainly on the distillation performance of the pre-distillation column and the main distillation column, especially the top yield and fractionation degree of the pre-distillation column. The amount of LPG and naphtha fraction to be processed also changes, and if the amount to be processed is reduced, the amount of heat required for the stabilizer and splitter reboiler will also be reduced. On the other hand, the degree of rectification in the pre-distillation column changes depending on the crude oil type and the preheating temperature of the crude oil supplied to the pre-distillation column, and as a result of this change, the fraction at the top of the pre-distillation column and the top fraction of the main distillation column are The yield and composition also change. For example, an LPG fraction, a light naphtha fraction, and a part of a heavy naphtha fraction are obtained from the top of a pre-distillation column, and a relatively large amount of light naphtha fraction is present in the bottom oil. When operating at the rectification degree of the pre-distillation column, the top fraction of the pre-distillation column and the top fraction of the main distillation column can be mixed and sent to the naphtha rectification system as shown in Figure 4. It is not necessarily suitable for reducing the throughput in stabilizers and splitters. <Problems to be Solved by the Invention> Therefore, the present invention aims at dissolving LPG from the top of the pre-distillation column in the conventional crude oil atmospheric distillation apparatus as described above.
When operating at a rectification degree of the pre-distillation column such that a fraction, a light naphtha fraction, and a part of the heavy naphtha fraction are obtained, and a relatively large amount of the light naphtha fraction is present in the bottom oil. By configuring a naphtha rectification system that is particularly suitable for The purpose of this invention is to provide a crude oil atmospheric distillation apparatus that can save energy as a whole by allocating heat to other heat recovery systems. <Means for Solving the Problems> In order to achieve the above object, the naphtha rectification system of the present invention includes a pipe that leads the top fraction of the pre-distillation column to the stabilizer, and a pipe that leads the bottom fraction of the stabilizer to the naphtha rectification system. A pipe leading to the splitter and a pipe leading the top fraction of the main distillation column to join the pipe leading the stabilizer bottom fraction to the splitter are provided. By this,
LPG can be taken out from the top of the stabilizer tower, light naphtha can be taken out from the top of the spritzator tower, and heavy naphtha can be taken out from the bottom of the splitter tower. If we talk about the degree of rectification of the pre-distillation column here, the degree of rectification of the pre-distillation column is generally determined by the number of trays and internal reflux amount of the distillation column, and the number of trays is determined at the time of construction of the column. Therefore, it can be said that the internal recirculation amount is the operational condition that affects the degree of rectification. This amount of internal reflux is determined by three factors: a) the amount of heat brought in by the supplied crude oil (amount of preheating in the crude oil preheating system), a) the ratio of the amount of overhead distillate withdrawn to the amount of crude oil supplied, and a) the amount of heat removed by condenser, side line reflux, etc. It can be decided. The rectification degree of the pre-distillation column for which the equipment configuration of this invention is optimal is, for example, when processing a certain type of crude oil, and as shown in Figure 2, the degree of rectification of the pre-distillation column is as follows:
This is a case in which all the fractions, a light naphtha fraction, and only a part of the heavy naphtha fraction are obtained, but a relatively large amount of the light naphtha fraction is still present in the column bottom residue. <Examples> Examples of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a drawing conceptually showing a distillation apparatus of the present invention consisting of a naphtha rectification system 60 having a pre-distillation column 20, a main distillation column 30, a stabilizer 40 and a splitter 50, and a heat recovery system heat exchanger group. , the heating furnace, the stabilizer, the reboiler of the splitter, each distillation column, the distillation pipe, the side wire reflux route, and their piping, etc., are substantially the same as the conventional equipment shown in Figs. 3 and 4, so illustrations are omitted. , or the third
The same reference numerals as in FIGS. 4 and 4 are used to omit the explanation. The crude oil preheated by a heat recovery system heat exchanger group (not shown) is introduced into the pre-distillation column 20 and is separated into a pre-distillation column top fraction and a column bottom residue, and the pre-distillation column bottom residue is It is supplied to the main distillation column 30 via a group of heat exchangers and a heating furnace (none of which are shown). The top fraction 20f of the pre-distillation column 20 is sent to the condenser 2.
1. The water is directly guided to the stabilizer 40 by the pipe 1 via the tower top receiving tank 22 and the pump 23. In this stabilizer, the top pressure is generally 5 to 12 Kg/cm ²
Distillation operation is carried out in G, and the top fraction of the pre-distillation column is
The LPG fraction is fractionated, and butane and lighter components are taken out as LPG from the top of the stabilizer tower via the top reflux route F1 and from pipe 2, while naphtha (light + heavy) is extracted from the bottom fraction of the stabilizer tower. is obtained and guided to the splitter 50 through the pipe 3. Note that the stabilizer tower overhead fraction is usually taken out as a liquid, but if it contains a large amount of light components such as methane, a portion of it may also be taken out as a gas. The column fraction 30f of the main distillation column 30 is the condenser 3
1. This fraction 30f is led to the naphtha rectification system via pipe 4 through the top receiving tank 32 and pump 33.
(Heavy naphtha fraction) contains a light naphtha fraction that exceeds the allowable amount of heavy naphtha products, so it cannot be made into a heavy naphtha product as it is, so it is combined with the stabilizer bottom fraction and sent to the splitter. Supply to 50. . In this splitter, the distillation operation is performed at a tower top pressure of about 0.1 to 2.0 Kg/cm ² G, but the vapor pressure of light naphtha may cause a negative pressure in the tower receiving tank, and the fuel gas etc. Sometimes it is introduced into a receiving tank to compensate for the pressure. A light naphtha product is taken out from the top of the splitter column via the top reflux path F2 through pipe 5, and from the bottom of the splitter column via pipe 6.
The heavy naphtha product is removed by By configuring the naphtha rectification system as described above, it is possible to reduce the throughput in the stabilizer and splitter and to reduce the amount of heat required for the reboiler. The reboiler heat source for the stabilizer and splitter is obtained from the side line reflux of the main distillation column or the bottom oil, as in the conventional naphtha rectification system (Fig. 4). 52 and the temperature control TC, surplus heat due to the reduction of the reboiler heat source obtained by employing this invention can be directed to the heat recovery system heat exchanger group. Note that a heat exchanger using the splitter tower bottom distillate flowing through the pipe 6 as a heat source is installed in the pipe 4 downstream of the confluence of the pipes 4 and 3, and preheats the raw material oil supplied to the splitter 50, respectively. The amount of heat required by the reboiler of the splitter may be further reduced. <Effects of the Invention> As explained above, according to the present invention, an LPG fraction, a light naphtha fraction, and a part of a heavy naphtha fraction are obtained from the top of the pre-distillation column, and the residual oil at the bottom of the column contains Optimal naphtha rectification that minimizes the amount of treatment in the stabilizer and splitter of the naphtha rectification system when the pre-distillation column has a rectification degree where a relatively large amount of light naphtha fraction exists. Because of the system configuration, the heat source required for the reboiler for the stabilizer and splitter can be kept to the minimum necessary. As a result, it becomes possible to allocate the surplus heat of the reboiler heat source to, for example, crude oil preheating, thereby further reducing the heating furnace load on the main distillation column. EXAMPLES The effects of this invention will be specifically explained below with reference to Examples. Experimental example: In a crude oil atmospheric distillation apparatus with a capacity of 100,000 BPSD (barrel/day), which is equipped with a pre-distillation column, a main distillation column, and a naphtha rectification system, Middle Eastern crude oil is processed at 100,000 BPSD, and the naphtha rectification system is as shown in Figure 1. We compared the throughput of the stabilizer and splitter and the amount of heat in the reboiler using the apparatus of this invention and the case in which a conventional naphtha rectification system (Figure 4) was used. We calculated the profit from reduction in distillation column heating furnace fuel and the increase in heat exchanger construction cost due to the increase in the required heat transfer area due to the increase in the amount of heat recovered in the crude oil preheating system. Furthermore, the amount of reduction in the construction cost of the naphtha rectification system apparatus according to the present invention (the difference in construction cost between the conventional apparatus (FIG. 4) and the apparatus of the present invention (FIG. 1)) was also calculated. The results are shown in the table below. From this table, it can be seen that by adopting this invention, the construction cost of the heat exchanger increased by 11 million yen, while the construction cost of the naphtha rectification system decreased by 7 million yen.
Although the equipment cost will increase by 4 million yen, the profit from the reduction in heating fuel for the main distillation column will be 101 million yen per year, so it is recognized that the energy saving effect is fully realized compared to the increase in equipment cost. 【table】

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of the distillation apparatus of this invention; Fig. 2 is an explanatory diagram showing the rectification degree of the pre-distillation column that is optimal for this inventive apparatus; Figs. 3 and 4 are illustrations of conventional distillation equipment. It is an explanatory view showing a device. 1-6...Piping, 20...Pre-distillation column, 30...
Main distillation column, 40... stabilizer, 50... splitter, 60... naphtha rectification system, 70... heating furnace.

Claims (1)

[Claims] 1 Equipped with a pre-distillation column, a main distillation column, and a naphtha rectification system having a stabilizer and a splitter, the bottom residue of the pre-distillation column is distilled in the main distillation column, and the top fraction of the pre-distillation column and the main distillation column are distilled. In a petroleum distillation apparatus for producing LPG, light naphtha, and heavy naphtha by treating the top fraction of the column with a naphtha rectification system, the naphtha rectification system processes the top fraction of the pre-distillation column to a stabilizer. a pipe that leads the bottom fraction of the stabilizer to the splitter, and a pipe that joins the top fraction of the main distillation column with the pipe that leads the stabilizer bottom fraction to the splitter; A petroleum distillation apparatus characterized in that LPG is obtained from the top of the stabilizer column, light naphtha is obtained from the top of the splitter column, and heavy naphtha is obtained from the bottom of the splitter column.