JPH0765052B2 - Method for producing olefins from hydrocarbons - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing olefins such as ethylene by thermal decomposition of hydrocarbons such as naphtha,
More specifically, when producing olefins such as ethylene by the thermal decomposition of hydrocarbons such as naphtha, it is possible to reduce the occurrence of fouling in a rectification column or the like for separating olefins from the pyrolysis product gas. And a method for producing olefins by thermal decomposition of hydrocarbons such as naphtha that can reduce the oxygen content in the obtained olefins.

TECHNICAL BACKGROUND OF THE INVENTION AND PROBLEMS THEREOF Olefins such as ethylene and propylene are very important compounds as starting materials for petrochemistry. Such olefins are mainly produced by thermal decomposition of hydrocarbons such as naphtha, kerosene and gas oil.

However, when producing olefins such as ethylene and propylene by thermally decomposing hydrocarbons such as naphtha in a pyrolysis furnace, a device for separating olefins from the pyrolysis product gas of hydrocarbons such as naphtha. For example, in a compressor of a pyrolysis product gas or a rectification tower such as a deethane tower and a depropanizer, a polymer such as a diene or acetylene adheres to the inner surface of the device, and the device is contaminated. There was a problem.

Therefore, at present, chemicals called anti-fouling agents such as naphtha AF-17Y manufactured by Kurita Industry Co., Ltd. and Hakuto Chemical C-276 manufactured by Hakuto Kagaku Co. Although the contamination of the above device is prevented by injecting, there is a problem that this chemical has a risk of adversely affecting the human body during handling, and the cost is not negligible because it is required in large quantities. there were. In addition, the anti-fouling agent has a problem that the effect varies depending on the type.

On the other hand, in olefins such as ethylene and propylene obtained by thermal decomposition of hydrocarbons such as naphtha, oxygen is present as a small amount of impurities, and this oxygen is produced by polymerizing ethylene, propylene and the like into polyethylene,
It acts as a catalyst poison for the polymerization catalyst when producing polypropylene and the like. For this reason, it is desirable that the obtained products of ethylene, propylene, etc. contain oxygen as little as possible.

To solve these problems all at once, prevent the generation of polymers such as dienes or acetylenes without using an anti-fouling agent, and make sure that oxygen is not contained in products such as ethylene as much as possible. I have to The inventors of the present invention have made extensive studies to solve these problems all at once, and found that oxygen dissolved in hydrocarbons such as naphtha as a raw material produces contaminants due to polymerization of dienes or acetylenes. Therefore, it is sufficient to reduce this oxygen, and in order to reduce the oxygen dissolved in hydrocarbons such as naphtha as a raw material,
Before supplying hydrocarbons such as naphtha to the pyrolysis furnace,
The amount of oxygen contained in the olefin obtained by reducing the dissolved oxygen in hydrocarbons such as naphtha and hydrocarbons such as naphtha, and reducing the dissolved oxygen in the hydrocarbons such as naphtha The inventors have found that this is the case, and have completed the present invention.

OBJECT OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and it is possible to obtain olefins from hydrocarbons such as naphtha without using chemical agents such as anti-fouling agents. Carbonization such as naphtha, which can reduce the generation of pollution in the equipment for producing olefins and reduce the amount of oxygen contained as impurities in the obtained olefins such as ethylene. It is an object of the present invention to provide a method for producing olefins from hydrogens.

SUMMARY OF THE INVENTION A method for producing olefins from hydrocarbons according to the present invention is a method in which hydrocarbons are pyrolyzed in a pyrolysis furnace, and olefins such as ethylene are separated and purified from the resulting pyrolysis product gas to produce olefins. When producing a class of hydrocarbons,
After contacting with a light gas containing no oxygen, the oxygen dissolved in the hydrocarbons is expelled to reduce the amount of dissolved oxygen in the hydrocarbons, and then the hydrocarbons are supplied to the pyrolysis furnace. It has a feature.

In the present invention, when producing olefins such as ethylene from hydrocarbons, the hydrocarbons and the light gas containing no oxygen are brought into contact with each other before supplying the hydrocarbons such as naphtha to the thermal cracking furnace. Dissolved oxygen in hydrocarbons is expelled to reduce the amount of dissolved oxygen in hydrocarbons, and thus equipment contamination due to polymerization of dienes or acetylenes without the use of chemical agents such as anti-fouling agents The amount of oxygen contained as impurities in the obtained olefins such as ethylene can be reduced.

DETAILED DESCRIPTION OF THE INVENTION The method for producing olefins from hydrocarbons such as naphtha according to the present invention will be specifically described below.

In the present invention, hydrocarbons such as naphtha, kerosene and gas oil are pyrolyzed in a pyrolysis furnace, and olefins such as ethylene and propylene are separated and purified from the obtained pyrolysis product gas to produce olefins. However, such a method for producing olefins by thermal decomposition of hydrocarbons is conventionally known, and a device for producing olefins by simply thermally decomposing hydrocarbons, that is, a steam cracker device will be described below. To do.

The steam cracker device is a well-known device for producing ethylene, propylene, and butadiene from hydrocarbons such as naphtha, kerosene, and gas oil. Any type of steam cracker device such as that shown by Kogyosha can be used, an example of which is shown in the flow chart in FIG. In this steam cracker device 1, raw material hydrocarbons such as naphtha are steam 2
Together with this, it is introduced into the thermal decomposition furnace 3 and thermally decomposed at a temperature of about 800 ° C. The hydrocarbons discharged from the thermal cracking furnace 3 are rapidly cooled to prevent polymerization, then guided to a rectification column 4, where tar is separated from the top and bottom and gas oil is separated from the top and the hydrocarbons are obtained from the top of the tower. The thus-obtained hydrocarbons are sent to a compressor 6 equipped with a drive unit 5 and compressed. The compressed hydrocarbons are then passed through a sulfur removal facility consisting of an alkali cleaning section 7 and a drying section 8, and then a depropanizer, a hydrogen separator such as a deep cooling unit, a demethanizer, a deethane tower,
It is sent to an olefin recovery section 9 including an ethylene separation column, a propylene separation column, a debutanization column, etc., and 99.95% high purity ethylene, 99.0% high purity propylene, olefins such as butadiene are separated and recovered, and Methane, ethane, propane, hydrogen, etc. are also recovered.

In the present invention, when using such a steam cracker apparatus 1, hydrocarbons such as naphtha are pyrolyzed in a thermal cracking furnace, and olefins such as ethylene and propylene are produced from the resulting pyrolysis product gas. Prior to supplying the hydrocarbons to the thermal decomposition furnace 3, the hydrocarbons are brought into contact with a light gas containing no oxygen to expel the oxygen dissolved in the hydrocarbons to dissolve the hydrocarbons in the hydrocarbons. After reducing the amount of oxygen, the naphtha is supplied to the thermal decomposition furnace 3.

Explaining naphtha as an example of hydrocarbons below,
To remove dissolved oxygen dissolved in naphtha by bringing naphtha into contact with a light gas containing no oxygen, for example,
It can be performed as shown in the figure. That is, naphtha is supplied to the upper part of the degassing column 11 having the tray 10, while light gas containing no oxygen is supplied to the lower part of the degassing column 11 to bring the naphtha and the light gas into countercurrent contact. By doing so, the dissolved oxygen dissolved in the naphtha reaches the upper part of the degassing tower together with the light gas, while the naphtha having the reduced dissolved oxygen content is taken out from the bottom part of the degassing tower. At this time, if the bottom of the degassing tower 11 is heated by the steam heater 12, the amount of dissolved oxygen in naphtha can be further reduced.

As the light gas containing no oxygen, an inert gas such as nitrogen can be used, but a combustible gas is preferably used. This is because, when the combustible gas is used, the combustible gas can be used as it is as the fuel gas in the thermal cracking furnace of the steam cracking device.

As the flammable light gas containing no oxygen, specifically, hydrogen gas, methane gas, ethane gas, propane gas, or a mixture thereof is used, but especially a mixed gas of methane and hydrogen by-produced in the steam cracking device. Is preferred.

Instead of the vertically long degassing tower 11 having the trays 10, a horizontally long degassing tower 11 having a light gas jet port 15 at the bottom as shown in FIG. 3 can be used.

Further, when the naphtha and the light gas are brought into contact with each other to expel the dissolved oxygen dissolved in the naphtha, as shown in FIG. 4, after supplying the light gas into the raw naphtha, these are mixed with a mixer 13
After stirring in the inside, a light gas and naphtha having a reduced dissolved oxygen content may be separated in the separation tower 14. At this time, the raw material naphtha can be preheated by the preheater 15.

Effect of the Invention In the present invention, when producing olefins such as ethylene from naphtha, before the naphtha is supplied to the thermal decomposition furnace, naphtha and oxygen-free light gas are contacted with oxygen dissolved in the naphtha. Since the amount of dissolved oxygen in naphtha has been reduced by removing the naphtha, it is possible to significantly reduce the pollution of the equipment due to the polymerization of dienes or acetylenes without using chemical agents such as anti-fouling agents. The amount of oxygen contained as impurities in the olefins can be reduced.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Examples 1-2 Normal temperature light naphtha stored in a floating roof type tank (specific gravity: 0.
68) is supplied to the upper part of a degassing column (plate type, number of stages = 10) with a reheater under the following conditions, and a mixed gas of methane and hydrogen at room temperature containing no oxygen from the bottom of the column. A methane-rich gas (96 mol% of methane, 4 mol% of hydrogen) was injected. While the light naphtha and methane-rich gas were in countercurrent contact, the treated light naphtha was taken out from the bottom of the tower and the gas stream was taken out from the top of the tower.

As a result, the oxygen concentration in naphtha taken out from the bottom of the tower is 1 ppm.
(Weight) The conditions of this operation are shown in Table 1.

The naphtha obtained from the bottom of the degassing tower by the above operation was heated to 800 ° C.
Pyrolysis was carried out in a pyrolysis furnace heated to the above. The obtained pyrolysis product gas was cooled and then supplied to the compressor 6, but the decrease in the efficiency (polytropic efficiency) of this compressor was reduced as shown in FIG.

In FIG. 5, the region A is the case where the dissolved oxygen in the naphtha was reduced according to the present invention and then the naphtha was supplied to the thermal decomposition furnace, and the region B is the thermal decomposition as it is without reducing the dissolved oxygen in the naphtha. This is the case when supplied to the furnace. From FIG. 5, it can be seen that the compression efficiency in the region A decreases gradually, whereas the compression efficiency in the region B decreases rapidly.

Further, the amount of oxygen as an impurity contained in the olefins separated and purified from the obtained pyrolysis product gas has also been reduced by the treatment according to the present invention.

If the reduction in polytropic efficiency could be reduced by 1%, the annual power saving for ethylene production of 300,000 tons / year would reach 1000MWH, and the effect is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a steam cracker device,
2 to 4 are explanatory views of an apparatus for expelling oxygen dissolved in raw material hydrocarbons, and FIG. 5 is a case where olefins are produced from hydrocarbons according to the present invention and conventionally known. FIG. 3 is a diagram showing a decrease in compression efficiency in a compressor when olefins are produced from hydrocarbons by the method described above. 1 ... Steam cracker device, 2 ... Steam 3 ... Thermal decomposition furnace, 4 ... Fractionation tower, 6 ... Compressor 9 ... Olefin recovery section, 11 ... Degassing tower

Claims (3)

[Claims] 1. When hydrocarbons are pyrolyzed in a thermal cracking furnace and olefins such as ethylene are separated and purified from the resulting pyrolysis product gas to produce olefins, hydrocarbons and oxygen are included. Characterized in that the hydrocarbons are supplied to a thermal cracking furnace after the oxygen dissolved in the hydrocarbons is expelled to reduce the amount of dissolved oxygen in the hydrocarbons by contacting with a non-light gas. , A method for producing olefins from hydrocarbons. 2. The method according to claim 1, wherein the hydrocarbon is naphtha. 3. The method according to claim 1, wherein the light gas containing no oxygen is a mixed gas of methane and hydrogen.