JPH06116568A - Method of controlling processing in separating furnace for olefin production - Google Patents

Abstract

In a process for controlling the transition temperature between the convection zone and radiant zone in cracking furnaces for olefin production from different hydrocarbon feedstocks, the feed stream is divided into two part streams before introduction into the convection zone, the first part stream is first preheated and then mixed with process steam, subsequently mixed with the second part stream untreated up to this point in time, and the resulting total process stream is passed after further heating and/or vaporisation into the radiant zone. The mixing of the first part stream with the process steam can take place before or after internal or external super-heating of the process steam. <IMAGE>

Description

Detailed Description of the Invention

[0001]

This invention relates to a separation furnace (Spaltofe) for producing olefins from various hydrocarbon inputs.
n) a method of adjusting the transition temperature between the convection zone and the radiation zone.

[0002]

In the thermal separation of hydrocarbons for the production of olefins, the hydrocarbons are heated to a high temperature of approximately 550 ° C. to 900 ° C. in a separation zone called the radiation zone,
It is necessary to allow the desired conversion to take place by the brief passage of hydrocarbons through this zone. To do this, the hydrocarbon must already be preheated to a relatively high temperature before it is introduced into the radiant zone. Since the separation is carried out in the presence of water vapor as an inert diluent, it must be preheated to the inlet temperature of the radiant zone.

The required elevated temperatures in the separation zone are usually achieved by passing the charge through a separation tube (spartrohre) which is arranged in the radiant section of the separation furnace heated by the combustion device. The hot flue gases produced during combustion, after leaving the radiant zone, still form a large reservoir of heat, which is used for the preheating of the hydrocarbon charge and possibly further fluids, It is intended to be guided through a convection zone provided with a heat exchanger for the purpose.

In the ideal precondition that a precisely defined, unchanging hydrocarbon charge is operated under unchanging, steady-state driving conditions, the convection zone as well as the radiating zone is designed with the number of heat exchangers, the conduits. Can be ideally determined in terms of length, residence time, etc. However, even with inputs that are almost constant in terms of time and composition, the interplay of adjustments during operation is due to the interrelationship of the individual operating parameters, which in practice is complex and has not yet been fully studied. It indicates that it is unavoidable to occur. Furthermore, the actual conditions of operation vary in almost all cases in the greater extent of the composition of the product of the hydrocarbon charge, which leads to a suitable adaptation of the conditions of separation, in particular the temperature curve (Temperattu).
It shows that the adaptability of rprofl) appears desirable.

German publication 15 68 966 gives the doctrine of how such an adjustment is possible. The tenet is that the transition temperature between the convection and radiant sections of the separation furnace is controlled such that a portion of the hot flue gas or a portion of the preheated hydrocarbons is directed around the convection zone. The present invention relates to an adjusting method for separating hydrogen.

This known method is directed to controlling the temperature curve inside the separation tube through the convection zone and the subsequent radiation zone. In this case, the greater steepness of the temperature curve in the radiant zone means that the preheating of the separate charge in the convective zone is reduced and the transition temperature from the convective zone to the radiant zone is reduced, first of all in the radiant zone. It is obtained by continuing preheating. The essential aspect of this method is that the adjustment made in this case operates in such a way that it reaches a fixed end temperature T _E at the outlet end of the separation tube. However, the German publication cited above does not give any suggestion to the changes to be made in the implementation of the process when making the transition to a completely different separation input, for example the transition from benzine to gas oil. Of.

Because of the ever-increasing demand for olefins which can lead to starvation of inputs and / or price increases, methods have been developed to enable the best utilization of various hydrocarbon inputs over the years. In particular, efforts have been made.

However, exchanging hydrocarbon inputs almost always required changing the course of the process. In addition to that, it was necessary to change the vapor dilution. Such changes cause large changes in the flow-through through heat exchangers located in the convection zone, which can lead to drive engineering problems.

German Patent Publication 28 54 061 discloses a method of preheating hydrocarbons prior to heat separation in the essential area of a separation furnace which is heated by combustion, in which method: Hydrocarbons and other fluids are intended to be heated by the flue gas through a heat exchanger located in the convection zone of the separation furnace. The design of a separation furnace for the separation of various hydrocarbon inputs is to direct hydrocarbons and other fluids through a heat exchanger divided into a series of tube bundles, in which flow sequence and / or individual tube bundles are used. The possibility of allowing the fluid flowing through the device to be changed in relation to the separation charge by means of a switching device. This is made possible by the fact that the tube bundles of the heat exchanger are connected to each other by a conduit provided at least in part with a switching mechanism.

Between the convection zone and the radiation zone of a separation furnace, a pyrolysis furnace or a fractionation furnace, in order to obtain the best possible yield from the hydrocarbon charge in each case with the least energy consumption. It is necessary to adjust the transition temperature, which is also referred to as the crossover temperature.

[0011]

Accordingly, the present invention provides a method of the kind set forth above in such a way that the transition temperatures between the convective zone and the radiant zone in the various hydrocarbon inputs are technologically simple. The aim is to adapt the process progress to be possible with further improved economics.

[0012]

According to the invention, the abovementioned object is to divide the input stream into two substreams prior to their introduction into the convection zone, first preheating the first substream and subsequently And then mixed with a second, unprocessed partial stream which has not been processed up to this point, and further heats and / or vaporizes the entire processed stream produced in this way before radiating It is solved by introducing it in the area.

One configuration of the process according to the invention consists in superheating the process vapor before mixing it with the first partial stream.
On the one hand, the superheating of this process steam is
It can be carried out in hot, countercurrent heat exchange with the flue gas coming from the radiant zone of the separation furnace, and on the other hand outside the separation furnace in any other kind and manner. The first configuration utilizes, among other things, a liquefied hydrocarbon charge. Because in this case a partial vaporization of the first partial stream first occurs and is almost not begun by the application of heat of the superheated treated steam to the hydrocarbons by mixing with the superheated treated steam and the first partial stream. This is because complete evaporation is performed.

Yet another configuration of the process according to the invention is that the process vapor and the first partial stream are first mixed and the gas mixture thus produced is subsequently introduced into a heat exchanger,
It is contemplated that the heat exchanger will be heated until it causes superheating of the gas mixture.

Yet another configuration of the method according to the invention is the first
The possibility of preheating the partial stream of (1) in one stage or in multiple stages before mixing with the process steam.

Similarly, in yet another aspect of the present invention, heating of the entire process stream formed after mixing both partial streams can occur in one or multiple stages. It is done.

Still another configuration of the method according to the present invention is as follows:
The preheating of the partial streams and the further heating of the total process stream formed by the mixture of both partial streams consists of indirect heat exchange with the hot flue gas coming from the radiant zone.

The process according to the invention comprises ethane, propane,
It is applicable to various hydrocarbon inputs such as butane, liquefied gas, naphtha, kerosene, atmospheric gas oil, hydrogenated atmospheric gas oil and hydrogenated vacuum gas oil. It is worth noting in this regard that, with the above, almost all known hydrocarbon inputs are applicable.

The process according to the invention allows a relatively inexpensive technological adaptation of the separation process to a great variety of hydrocarbon inputs. This means the least energy consumption, in this case especially the amount and temperature of the heating gas and the resulting flue gas for driving the combustion device into the radiant zone. In terms of consumption, the best, and therefore maximum, utilization of the hydrocarbon input can be achieved. In this way, the structural and drive costs can be significantly reduced compared to the state of the art cited above.

The process according to the invention thus has the following improvements, namely the best utilization in the case of different hydrocarbon inputs, and the heating medium required for the production of olefins from different hydrocarbon inputs. Also, due to the structural simplification of the convection zone of the separation furnace, the equipment costs and operating costs can be reduced.

In addition, the precise adjustment of the transition temperature between the convection zone and the radiant zone finally makes it possible to reduce the buildup of coke in the heat exchanger through which the entire process gas stream flows. The coking rate of the gas conduit is essentially not only the temperature of the gas mixture being separated, but also the fractionation performance. This means that the initiation of the original separation process in the last heat exchanger is avoided. Rapid coking of gas conduits can significantly shorten the operating life of the separation furnace.

The adjustment of the transition temperature makes it possible to adjust the temperature selected so as not to cause just any coking in the convection zone for the respective hydrocarbon feed used. . Avoiding drive interruptions due to coke stripping operations in the convection zone leads to improved economics of the separation furnace.

[0023]

The invention is explained in more detail below by means of the two schematically illustrated embodiments shown in the accompanying drawings.

FIG. 1 shows the principle of the method according to the invention. This figure shows the convection zone of a separation furnace for the pyrolysis of various hydrocarbon inputs.

A stream of hydrocarbon charge is led through the conduit 1 before the convection zone and is split in the desired ratio into a first partial stream (conduit 2) and a second partial stream (conduit 3). . The first partial stream is then introduced into heat exchanger B via conduit 2 and is heated countercurrently with the flue gas to be cooled (indicated by the dashed arrow) from the radiant zone of the separation furnace. , Is discharged through the conduit 2a. The process vapors required for the dilution of the hydrocarbon charge are introduced into the heat exchanger C via the conduit 4 and are superheated in the heat exchanger countercurrently with the flue gas to be cooled. The superheated process vapor is subsequently discharged through conduit 4a, mixed with the heated first partial stream from conduit 2a and passed through conduit 2c to a second, untreated partial stream. It is guided with the inside of the conduit 3. The total process stream thus formed is subsequently introduced into the heat exchanger D via the conduit 5, where it is further heated or vaporized by the flue gas to be cooled. After bypassing the intermediately located heat exchanger E as described further below, the entire process stream is introduced through the conduit 6 to the last heat exchanger F in the convection zone, which heat exchanger E Inside, it is heated by the hot flue gas to be cooled to the desired transition temperature between the convection zone and the radiation zone, and is then led through the conduit 7 to the radiation zone.

In the heat exchanger A, the feed water introduced through the conduit 10 is heated and then through the conduit 11 a high pressure steam cylinder (Hochdruck, not shown).
-Dampftrommel). This feed water serves as a coolant for quenching the separated gas, and for that purpose the feed water is introduced into the quench cooler. The heat exchange with the hot separated gas produces steam, which is collected in the upper part of the quench cooler and returned to the steam chamber of the high-pressure steam cylinder.
From here, the steam passes through the conduit 12 and accumulates in the heat exchanger E,
Here the steam is superheated by the hot flue gases. The superheated steam is discharged through conduit 13 so that it can be used, for example, to drive a turbine for energy recovery.

The flue gas has a temperature of 1000 ° C. to 1200 ° C. at the transition from the radiant zone to the convection zone, and exits the convection zone (not shown) at the upper end at a temperature of about 130 ° C., optionally After being cleaned, it is discharged through the chimney.

FIG. 2 shows a further configuration of the method according to the invention. As already explained in FIG. 1, the hydrocarbon charge is split into the first partial stream (conduit 2) and the second partial stream (conduit 3) in the desired ratio. This first partial stream is again directed via conduit 2 to heat exchanger B, where it is heated by the flue gas to be cooled and discharged via conduit 2a. The process vapors required for dilution are introduced through conduit 4 and mixed in this conduit 2a with the first, already heated partial stream, the gas mixture thus formed passing through conduit 2b. And then introduced into another heat exchanger C,
In this heat exchanger, the gas mixture is heated until the process vapor components are superheated. The gas mixture is subsequently discharged through conduit 2c and mixed in conduit 3 with a second, previously untreated partial stream. The total process stream thus formed is directed into the radiant zone through conduits 5, 6 and 7 as in FIG. 1 and through heat exchangers D and F.

Points 21 and 22 represent measuring points for flow control in both partial flows in conduit 2 and conduit 3, respectively. Points 23 to 28 indicate six temperature measurement points.

Table 1 shows in which range the transition temperature corresponding to the temperature of the measuring point 28 varies depending on the ratio of the two differently selected partial flows. Ethane has been chosen as the hydrocarbon input.

[0031]

[Table 1]

The advantageous operating modes of the method according to the invention are explained below by means of three examples. As the hydrocarbon input, atmospheric gas oil with a partial flow ratio of 100/0 was selected in the first example, and in Examples 2 and 3 respectively 3
Ethane has been selected with partial flow ratios of 0/70 and 60/40. A description of these three examples is given by FIG.

Example 1 Liquid gas oil having a pressure of 5.4 bar and a temperature of 82 ° C. was introduced into heat exchanger B through conduits 1 and 2. This already half steamed gas oil after being heated to 357 ° C. was discharged through conduit 2a at a pressure of 5.4 bar. Steam at a temperature of 179 ° C. was introduced into the heat exchanger C through the conduit 4 at a pressure of 5.6 bar. After superheating had taken place, this steam was discharged through conduit 4a at a pressure of 5.4 bar and a temperature of 449 ° C. and mixed with the gas oil from conduit 2a. The dust mixing results in the complete evaporation of the produced mixture and leads to the conduit 2c.
Through 5 and 5 into heat exchanger D at a pressure of 5.0 bar and 3
A mixture having a temperature of 61 ° C. was introduced. This further heated mixture exited heat exchanger D at a pressure of 4.9 bar and a temperature of 449 ° C. and was subsequently introduced via conduit 6 into heat exchanger F at the end of the convection zone. At a pressure of 4.8 bar and a temperature of 540 ° C., which corresponds to the transition temperature between the convection zone and the radiation zone, this mixture is withdrawn from the heat exchanger F through the conduit 7 and introduced into the radiation zone. It
Further, the feed water preheated from 110 ° C. to 140 ° C. in the heat exchanger A, the high pressure steam in the heat exchanger E is 629 ° C.
To 527 ° C. The hot flue gas had a temperature of 1124 ° C. at the inlet to the convection zone and was discharged from the convection zone at a temperature of 122 ° C. after passing through seven heat exchangers AF.

Example 2: Gaseous ethane having a pressure of 3.9 bar and a temperature of 68 ° C. was introduced as hydrocarbon input through conduit 1. 30% of this charge is introduced into heat exchanger B through conduit 2 and in this heat exchanger 646
It was heated to 0 ° C. and discharged via conduit 2a at a pressure of 3.9 bar. Steam having a pressure of 3.9 bar and a temperature of 175 ° C. is introduced into the heat exchanger C through the conduit 4,
Superheated to 629 ° C., discharged at constant pressure through conduit 4a and mixed with heated ethane from conduit 2a. The gas mixture thus formed is led through conduit 2c with 70% of the remainder of the hydrocarbon charge which has not been treated so far, the mixture thus formed having a pressure of 3.5 bar and It was introduced into heat exchanger D through conduit 5 at a temperature of 347 ° C. 49 in this heat exchanger
Further heating up to 6 ° C. was carried out, after which the gas mixture was introduced into heat exchanger F through conduit 6 at a pressure of 3.4 bar. It was heated here to a transition temperature of 649 ° C., after which the mixture passed through conduit 7 and reached the radiation zone. Further, the feed water was preheated from 110 ° C. to 309 ° C. in the heat exchanger A, evaporated and superheated to high pressure steam from 330 ° C. to 504 ° C. in the heat exchanger E. The hot flue gas had a temperature of 1182 ° C. at the inlet of the convection zone and exited the convection zone at a temperature of 183 ° C. after passing through one of the heat exchangers AF.

Example 3: Gaseous ethane having a pressure of 4.0 bar and a temperature of 68 ° C. was introduced as hydrocarbon input through conduit 1. 60% of the charge was introduced into heat exchanger B via line 2, heated in this heat exchanger to 643 ° C. and discharged via line 2a at a pressure of 3.9 bar. Steam having a pressure of 3.9 bar and a temperature of 175 ° C. is introduced into the heat exchanger C through the conduit 4 and 6
It was superheated to 36 ° C., discharged at constant pressure through conduit 4a and mixed with the superheated ethane from conduit 2a.
The gas mixture thus formed, together with the remaining 40% of the untreated hydrocarbon charge, was passed through conduit 2
The mixture, which was led through c and thus formed, was introduced into heat exchanger D through conduit 5 at a pressure of 3.5 bar and a temperature of 482 ° C. 58 more in this heat exchanger
Heating was carried out to 1 ° C., after which the gas mixture was introduced into the heat exchanger F through the conduit 6 at a pressure of 3.5 bar.
Heating was here carried out to a transition temperature of 709 ° C., after which the mixture passed through conduit 7 to the radiation zone. Further, in the heat exchanger A, the feed water is preheated from 110 ° C. to 256 ° C., evaporated, and then in the heat exchanger E, 329 ° C. to 527 ° C.
Overheated to high pressure steam. The hot flue gas had 1166 ° C. at the inlet to the convection zone and exited the convection zone at a temperature of 162 ° C. after passing through seven heat exchangers AF.

[0035]

Since the present invention is constructed as described above, in order to enable the best utilization of the hydrocarbon input, the hydrocarbon input in each case can be used with the least energy consumption. The transition temperatures between the convective and radiant zones of various hydrocarbon inputs are technologically simple to process so that good yields can be achieved, further improving process progress and increasing economics. It can be done.

[Brief description of drawings]

FIG. 1 is an illustration of a circulation circuit showing a process according to the invention in which the process vapor is first superheated and subsequently mixed with a first partial stream.

FIG. 2 a process according to the invention in which the process vapor and the first partial stream are first mixed and subsequently heated until the process components of the gas mixture thus formed are superheated. Explanatory diagram of the circulation circuit showing.

[Explanation of symbols]

 A heat exchanger B heat exchanger C heat exchanger D heat exchanger E heat exchanger F heat exchanger

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Wolfgang Schwab Federal Republic of Germany Day 8190 Wolf Ratshausen Astern Valk 18

Claims (9)

[Claims] 1. A method of adjusting the transition temperature between convection and radiant zones in a separation furnace for producing olefins from various hydrocarbon inputs, prior to introducing an input stream into said convection zone. Into two sub-streams, the first sub-stream is first preheated and subsequently mixed with the process vapor, after which the second sub-stream is mixed.
Mixing process with a partial stream that has not been treated up to this point, and further heating and / or evaporating the entire treated stream thus formed before directing it to the radiation zone. 2. Process according to claim 1, characterized in that the process vapor is superheated and subsequently mixed with the first partial stream. 3. Process according to claim 2, characterized in that the treated steam is superheated in the heat exchanger of the convection zone by hot flue gases coming from the radiant zone of the separation furnace. 4. Process according to claim 2, characterized in that the process steam which has already been superheated outside the separation furnace is introduced. 5. The first partial stream and the process vapor are mixed first, and the gas mixture thus formed is subsequently heated to a superheated state. How was done. 6. The preheating of the first partial stream can be performed in one step or in multiple steps before being mixed with the process vapor. The method described in. 7. A further heating of the total process stream formed after mixing both said partial streams can be carried out in one or more stages.
The method described in any one of 1. 8. Preheating of the first partial stream as well as further heating of the total process stream formed after mixing both partial streams is indirect with hot flue gas coming from the radiant zone. The method according to claim 1, wherein the method is performed by heat exchange. 9. Ethane, butane as hydrocarbon input,
A liquefied gas, naphtha, kerosene, atmospheric pressure gas oil, hydrogenated atmospheric pressure gas oil, and hydrogenated vacuum gas oil can be utilized.
A method according to any one of claims 8 to 8.