JPH0361715B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for separating and recovering useful components such as ethylene and propylene contained in light gas by-produced from a catalytic cracker. Technical background of the invention and its problems The catalytic cracking method removes the high-boiling point content of petroleum, which is higher than kerosene.
BACKGROUND OF THE INVENTION Dynamic catalyst beds or moving catalyst beds are known as methods for producing high octane gasoline by decomposition at high temperatures in the presence of a catalyst. The gases produced by such catalytic crackers, especially fluid catalytic crackers, contain large amounts of lower hydrocarbons such as ethylene and propylene, and it is desirable to effectively separate and recover these lower hydrocarbons. It is rare. In order to recover useful components such as ethylene or propylene from the light gas produced as a by-product from such a catalytic cracker, it is necessary to install dedicated separation and purification equipment such as a drying tower, cryogenic separation equipment, and distillation equipment. This was economically difficult to implement due to the high cost. For this reason, the light gas by-produced from the catalytic cracker contains useful components such as ethylene or propylene, but at present they are only consumed as fuel. In addition, from the light gas produced by the catalytic cracking equipment,
It is also possible to recover useful gas containing ethylene or propylene by a separation and recovery method using an adsorbent, but in this case, only a mixed gas of ethylene and propylene is obtained, and the resulting mixed gas contains contains dienes, acetylene, etc. Therefore, it was necessary to further separate these components, and dienes, acetylene, etc. had to be removed by hydrogenation or the like. It is also conceivable to use an absorbent to recover useful gas containing ethylene or propylene from the light gas by-produced from the catalytic cracker, but this also has the same problems as described above. Although the light gas produced as a by-product from catalytic cracking equipment contains significant amounts of useful components such as ethylene and propylene, it is difficult to separate these components and recover them in high purity. It could not be used effectively and was simply consumed as fuel. Recently, a method for producing gasoline or fuel oil by bringing light obtained from the above-mentioned catalytic cracker into contact with a zeolite catalyst has been disclosed in Japanese Patent Application Laid-Open No. 1983-1999.
Although it is proposed in Publication No. 108090, it is not a process for recovering olefin as a chemical raw material. Purpose of the Invention The present invention aims to solve the above-mentioned problems associated with the prior art, and aims to reduce the amount of ethylene, propylene, etc. Developing a method for separating and recovering useful components from the above-mentioned light gases, which allows each useful component of olefins to be recovered with high purity without the need for new dedicated separation and purification equipment such as cryogenic separation equipment and distillation equipment. is intended to provide. Summary of the Invention In order to solve the above-mentioned technical problems, the present inventors conducted extensive research and focused on a steam cracker apparatus equipped with cryogenic separation and distillation purification equipment for olefins. This equipment is installed in an oil refining/petrochemical complex and is often located close to a catalytic cracker, achieving an organic connection between the catalytic cracker and the steam cracker, resulting in cheaper olefin production. They found that this is possible, and after further detailed study, they completed the present invention. The method for separating and recovering olefins from light gas by-produced from a catalytic cracker according to the present invention is to separate and recover light gas containing olefins such as ethylene and propylene, which are by-produced from a catalytic cracker, from hydrocarbons such as ethylene, It is introduced between the outlet of the pyrolysis furnace of a steam cracker device for producing propylene, etc. and a point in the compressor that has a pressure lower than 12 kg/cm ² G, and the steam cracker device is used to produce ethylene. It is characterized by the ability to separate and recover olefins such as and propylene with high purity. In the present invention, the light gas containing olefins produced as a by-product from the catalytic cracking device introduced into a specific part of the steam cracker device is It is preferable to concentrate the light gas by adsorption, absorption, membrane separation, etc., and it is also preferable to remove harmful components such as arsenic compounds and carbonyl sulfide contained in the light gas. In the method for separating and recovering olefins from light gas by-produced from a catalytic cracker according to the present invention, the light gas is introduced into a specific location of a steam cracker device for producing ethylene, propylene, etc. from hydrocarbons. However, since this steam cracker equipment is used to separate and recover olefins, it is possible to recover olefins such as ethylene and propylene from light gas with high purity, and the existing equipment can be used as is. Therefore, there is no need to newly install a cryogenic separation device, a distillation device, etc., and an extremely excellent effect can be obtained in that olefins such as ethylene and propylene can be recovered at low cost. DETAILED DESCRIPTION OF THE INVENTION A method for separating and recovering olefins from light gas by-produced from a catalytic cracking apparatus according to the present invention will be specifically described below. In the present invention, light gas by-produced from a catalytic cracker is used as the raw material gas from which olefins such as ethylene and propylene are recovered, and this light gas contains hydrogen, nitrogen, and lower carbonized carbon atoms having 1 to 3 carbon atoms. Hydrogen such as ethylene, propylene, methane, ethane, propane, etc. Catalytic cracking is a well-known process for producing high-octane gasoline by decomposing petroleum with a boiling point higher than that of kerosene in the presence of a catalyst at high temperatures. This catalytic cracking method can be divided into a fluidized bed method and a moving bed method depending on the state of use of the catalyst, but in the present invention, light gas produced as a by-product of either catalytic cracking method can be used as a raw material. I can do it. Examples of fluid catalytic cracking methods include the ESSO method, SHELL method, KELLOG method,
Light gas produced as a by-product from any method such as the TEXACO method can also be used as a raw material. In these catalytic cracking methods, the composition of the by-product light gas varies slightly depending on the type of raw material or catalyst used, but any of them can be used as the raw material gas in the present invention. In the catalytic cracking method, hydrocarbons catalytically cracked in a reaction tower are generally fractionated in a main rectification tower, with heavy fractions being extracted from the bottom of the tower and various gas oils as side distillation products, and then being extracted from the top of the tower. Gas and naphtha (gasoline) are distilled out. The gas and naphtha are cooled in a condenser and separated into non-condensable gas and liquid. Among these, the non-condensable gas is then pressurized to approximately 10 to 15 Kg/cm ² G by a wet gas compressor, and is usually further sent to an absorption tower to separate the propane and butane fractions in the gas, and the top gas is It is sent to a sponge absorber where a small amount of propylene and butane fractions are further separated. The top gas from the absorption tower is contacted with a solution such as diisopropanolamine in an additive scrubber to remove hydrogen sulfide, if necessary, and then discharged as tail gas. This tail gas is generally a light gas produced as a by-product by the catalytic cracking method used in the present invention. In the present invention, tail gas discharged from the catalytic cracker as described above is preferably used, but in some cases, gas obtained at an appropriate location after the exit line of the wet gas compressor may also be used. Such gases include, for example, the outlet of a wet gas compressor, the overhead gas of an absorption tower, or the overhead gas of an additive scriber. Table 1 shows an example of the composition of light gas produced as a by-product from a catalytic cracker.

[Table] In the present invention, the light gas by-produced from the catalytic cracker as described above is introduced into a specific part of the steam cracker equipment for producing ethylene, propylene, etc. from hydrocarbons. First, the Kratzker device will be explained. The steam cracker equipment is capable of converting hydrocarbons such as naphtha, kerosene, and gas oil into ethylene,
The present invention uses a steam cracker of a type which is a well-known apparatus for producing propylene and butadiene, such as the one shown in Revised Manufacturing Process Chart Complete Collection, 1978 Edition, Published by Kagaku Kogyosha. An example flowchart is shown in FIG. In this steam cracker device 1, raw material hydrocarbons such as naphtha are introduced into a thermal cracking furnace 3 together with steam 2, and about
It is thermally decomposed at a temperature of about 800℃. The hydrocarbons discharged from the thermal cracking furnace 3 are rapidly cooled to prevent polymerization, and then led to a rectification column 4, where tar is separated from the top and bottom, and gas oil is separated from the top, while oil is separated from the top of the column. The hydrocarbons thus obtained are sent to a compressor 6 equipped with a motor 5 and compressed. The compressed hydrocarbons then pass through a sulfur removal equipment consisting of an alkali washing section 7 and a drying section 8, and are then sent to a hydrogen separation device such as a depropanizer, a deep cooling device, a demethanizer, a deethanizer, and an ethylene separation tower. , a propylene separation tower, a debutanizer, etc. are sent to the olefin recovery section 9, where high purity ethylene of approximately 99.95% is produced.
Olefins such as propylene and butadiene with a high purity of approximately 99.0% are separated and recovered, as well as methane, ethane, propane, hydrogen, etc. In the present invention, the light gas produced as a by-product from the catalytic cracker is transported between the pyrolysis furnace outlet 3 of the steam cracker and the compressor 6 at a point having a pressure lower than 12 kg/cm ² G. This steam cracker equipment is used as is to separate and recover olefins such as ethylene and propylene with high purity. In the present invention, the light gas by-produced from the catalytic cracker is transferred to the steam cracker device 1.
When introducing between the pyrolysis furnace outlet 3 and the compressor 6 where the pressure is lower than 12 kg/ ^{cm 2 G} , it is necessary to introduce the It is preferable to introduce it into This is because the light gas produced as a by-product from the catalytic cracker is generally
This is because it has a pressure of up to about 15 kg/cm ² G. In the present invention, it is also possible to recover olefins with high purity by supplying only the light gas produced by the catalytic cracker to the steam cracker device 1, but normally, olefins can be recovered from hydrocarbon raw materials such as naphtha The light gas is supplied to the steam cracker device 1 which is being operated and supplied with the light gas, and the two components are combined to recover olefins with high purity. By the way, the light gas by-produced from the catalytic cracker generally has the above-mentioned composition, but it is also possible to increase the olefin concentration in the light gas before introducing it into the steam cracker.
Any conventionally known method can be used to increase the olefin concentration in the light gas. For example, when olefins contained in light gas are adsorbed on an adsorbent at high pressure and then desorbed at low pressure, the hydrocarbons adsorbed on the adsorbent are lowered to an intermediate pressure between the high pressure and the low pressure for at least one hour. An adsorption method typified by a pressure swing method can be employed, in which a portion of hydrocarbons is removed, and then olefins are desorbed from an adsorbent and recovered at low pressure. Alternatively, the concentration of olefins in the light gas may be reduced by employing a method disclosed in JP-A No. 60-25939, that is, a method in which the light gas is brought into contact with an adsorbent consisting of a copper halide salt and activated carbon. It can also be increased. Furthermore, the concentration of olefins in the light gas may be increased by employing the method disclosed in JP-A No. 57-10316, that is, the method of bringing the light gas into contact with a separation membrane such as an ion exchange membrane. can. Furthermore, the concentration of olefins in the light gas can be increased by employing a method such as that disclosed in JP-A-59-55839, that is, a method in which the light gas is brought into contact with an absorption liquid. Light gas produced as a by-product from a catalytic cracker usually contains impurities such as carbon dioxide, carbon monoxide, hydrogen sulfide, carbonyl sulfide, oxygen, water, and nitrogen. Furthermore, when there are arsenic compounds in the feed of the catalytic cracker, the gas may contain arsenic compounds such as arsine. For example, if light gas contains a large amount of carbon dioxide, it may condense in the deep cooling device in the olefin recovery section of the steam cracker, and the line may become clogged. Furthermore, carbonyl sulfide or arsenic compounds may poison the catalyst used in the acetylene hydrogenation section of the olefin recovery section. Therefore, it is preferable to remove such harmful components to a concentration below a permissible value before or after introduction into the steam cracker device. Carbon dioxide is also present in the pyrolysis products at the outlet of the pyrolysis furnace in the steam cracker, and the water portion of this carbon dioxide is generally removed in the alkaline washing section in the steam cracker, and some of it is removed by the steam. It is converted into methane along with carbon monoxide in the methanator inside the Kratzker device. This carbon dioxide concentration is preferably about 10 ppm or less before being sent to the olefin recovery section 9 of the steam cracker device.
It is desirable that it be suppressed to about 1 ppm or less. Like carbon dioxide, carbon monoxide is also present in the pyrolysis products at the outlet of the pyrolysis furnace of the steam cracker equipment, and this carbon monoxide is mixed into the hydrogen or methane gas and is converted to methane in the methanator in some cases. Although it is discharged outside the system, it also passes through the hydrogenation reaction tower of the olefin recovery section 9 on the way. Palladium catalysts are generally used in the hydrogenation reaction tower, and carbon monoxide was considered undesirable because it has a temporary poisoning effect. However, in recent years it has become clear that the presence of a suitable amount of carbon monoxide or the pretreatment of the catalyst with carbon monoxide actually improves the water washing selectivity of acetylenes/dienes.
(Refer to JP-A-59-59634, JP-A-57-84745, etc.) Therefore, the tolerance level for carbon monoxide is not necessarily constant depending on the hydrogenation catalyst used, but generally it is Before being sent to the recovery section 9, it is sufficient that the concentration is about 500 ppm or less. In addition, if you want to avoid contamination with carbon monoxide, you can adsorb the light gas produced by the catalytic cracker.
Carbon monoxide can be easily reduced by using an absorption process. Hydrogen sulfide is removed in the alkaline cleaning section 7 in the steam cracker, but the hydrogen sulfide concentration is preferably about 1 ppm or less before being sent to the olefin recovery section in the steam cracker.
It is desirable that it be suppressed to around 0.1 ppm. Carbonyl sulfide (COS) is partially removed in the alkaline cleaning section 7 in the steam cracker, but the concentration of carbonyl sulfide is reduced to 1 ppm before being sent to the olefin recovery section 9 in the steam cracker. It is preferable that the amount is suppressed to about 0.1 ppm or less, preferably about 0.1 ppm or less. If oxygen is mixed into ethylene and exceeds the product specification limit, it must be removed, and the concentration of oxygen should be moderately below 10 ppm before being sent to the olefin recovery section in the steam cracker equipment. is preferably suppressed to about 1 ppm or less. It doesn't matter how much water is contained in light gas. This is because the pyrolysis products from the steam cracker device contain saturated steam, which is removed in the drying section 8. Even if nitrogen is contained in the light gas, it does not pose any particular problem in the operation of the steam cracker device 1. As described above, the arsenic compound may poison the hydrogenation catalyst such as acetylene in the olefin recovery section 9 of the steam cracker device 1. Therefore, the arsenic concentration in the gas sent to the olefin recovery section in the steam cracker equipment is
It is preferable that the content be suppressed to 1 ppm or less, preferably 0.1 ppm or less. As mentioned above, the light gas produced as a by-product from the catalytic cracker contains impurities, and among these, arsenic compounds and carbonyl sulfide, in particular, cannot be removed to below allowable levels in the steam cracker. There are many such substances, and moreover, these may poison the hydrogenation catalyst. Therefore, arsenic compounds and carbonyl sulfide are extracted from light gases.
It is preferable to unload the steam cracker before introducing it into the steam cracker device 1. To remove the above impurities, especially oxygen and carbonyl sulfide, from light gas,
Although the method disclosed in Japanese Patent No. 59-14453 can be employed, any conventionally known method can be employed. Specifically, the above-mentioned impurities can be removed from the light gas by passing the light gas through an amine cleaning tower, a sulfide removal tower, a deoxygenation tower, a CO conversion tower, or the like. Known methods can also be used to remove arsenic compounds (mainly arsine compounds). In other words, reaction adsorption using chemical catalysts (manganese chloride, etc.)
(Japanese Unexamined Patent Publication No. 1982-238144), adsorption removal using activated carbon supporting monochrome copper (Japanese Patent Application Laid-Open No. 60-238144), etc. can be used. The above-mentioned impurities may be removed from the light gas at any time before it is introduced into the steam cracker equipment. For example, when performing an operation to increase the olefin concentration in the light gas, , may be before or after the operation. In addition, if an existing steam cracker equipment can be equipped with a device for removing these arsenic compounds or carbonyl sulfide, in such a case, the equipment for removing arsenic compounds etc. can be used for olefin recovery in the steam cracker equipment. It can be provided at a location up to part 9. Effects of the Invention In the method for separating and recovering olefins from light gas by-produced from a catalytic cracking apparatus according to the present invention, the light gas is used to specify a steam cracker apparatus for producing ethylene, propylene, etc. from hydrocarbons. Since the steam cracker equipment is used to separate and recover olefins, it is possible to recover olefins such as ethylene and propylene from light gases with high purity, and the existing equipment can be used to separate and recover olefins. Since it can be used as is, there is no need to newly install cryogenic separation equipment, distillation equipment, etc., and an extremely excellent effect can be obtained in that olefins such as ethylene and propylene can be recovered at low cost. In addition, in the method for separating and recovering olefins from light gas by-produced from a catalytic cracker according to the present invention, the light gas having a pressure of about 10 to 15 kg/cm ² G is transferred to the cracking furnace outlet of the steam cracker device. Since the light gas is introduced between the light gas and the point where the pressure is lower than the 12 kg/cm ² G of the compressor, it is possible to omit the installation of a compressor required to increase the pressure of the light gas. EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. Example The following impurities in light gas saturated with water vapor by-produced from a fluid catalytic cracker were treated in advance with a removal device. Impurities: H ₂ S 10ppm COS 8ppm O ₂ 80ppm That is, after passing the light gas through a COS hydrolysis tower (packed with activated alumina catalyst) under the conditions of GHSV 1000V/H/V temperature 110℃ pressure 10Kg/cm ² G, H _2S
Passed through a removal column (filled with zinc oxide) under the same conditions and removed H ₂ S
GHSV2000V/H/ V, temperature 110℃
The O ₂ in the purified gas was passed under a pressure of 10 Kg/cm ² G.
The solubility was set to 1 ppm or less. After the purified gas was cooled to room temperature, it was used as feed in Examples 1 to 3 below. Example 1 The above-mentioned light gas is introduced into the inlet of the cracked gas compressor of the steam cracker (pressure 2 Kg/cm ² G), combined with the cracked gas of the steam cracker, and subjected to rectification separation. Table 2 shows the composition and flow rate of light gas as a raw material, the composition of light gas after impurity removal, and the flow rate of recovered ethylene, ethane, propylene, etc. (However, water is not included in Table 2.) Example 2 Light gases are dehumidified and olefins (mainly ethylene and propylene ) is concentrated and introduced into the first stage of the cracked gas compressor of the steam cracker with a pressure of 2 kg/cm ² G. As in Example 1, Table 3 shows the composition of the light gas as a raw material. Example 3 After drying and cooling the above-mentioned light gas, using -4〓 volatile oil as an absorbent, _C3 mainly composed of propylene was prepared.
The fraction is concentrated and introduced into the cracked gas compressor of the steam cracker at a pressure of 2 kg/cm ² G. As in Example 1, Table 4 shows the composition of the light gas as a raw material. Above, the volatile oil is 15% pentane, 25% pentane.
%, cyclopentadiene 10%, isoprene 10%,
It is a cracked naphtha consisting of 10% C ₈ , 28% BTX fraction, and 2% styrene. Absorption tower is 5Kg/cm ² G tower top 30
The absorber is operated at the bottom of the column at 46 mm, and the volatile oil at the bottom of the absorption columns that has absorbed the olefin fraction is sent to a stripping column of 4 kg/cm ² G, where it is heated, and concentrated gas is recovered from the top of the column.

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【table】 [Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a steam cracker device. 1... Steam cracker device, 2... Steam, 3... Thermal decomposition furnace, 4... Rectification column, 6... Compressor, 9... Olefin recovery section.

Claims (1)

[Scope of Claims] 1. Light gas containing olefins such as ethylene and propylene by-produced from a catalytic cracker is used as a pyrolysis furnace outlet of a steam cracker device for producing ethylene, propylene, etc. from hydrocarbons. and the compressor where the pressure is lower than 12 kg/cm ² G, and using this steam cracker equipment, olefins such as ethylene and propylene can be separated and recovered with high purity. A method for separating and recovering olefins from light gas produced as a by-product from catalytic cracking equipment. 2 After performing an operation to condense the olefins contained in the light gas, which is produced as a by-product from the catalytic cracker and contains olefins such as ethylene and propylene, the light gas is converted from hydrocarbons to ethylene. It is introduced between the outlet of the pyrolysis furnace of a steam cracker equipment for producing propylene, etc. and a point in the compressor that has a pressure lower than 12 kg/cm ² G, and using this steam cracker equipment, A method for separating and recovering olefins from light gas produced as a by-product from a catalytic cracker, which is characterized by separating and recovering olefins such as ethylene and propylene at high purity. 3. The method according to claim 2, wherein the operation for concentrating the olefins contained in the light gas is an adsorption method, an absorption method, or a membrane separation method. 4 After performing an operation to remove impurities contained in the light gas containing olefins such as ethylene and propylene as by-products from the catalytic cracking equipment, the light gas is converted from hydrocarbons to ethylene, olefins, etc. It is introduced between the outlet of the pyrolysis furnace of a steam cracker device for producing propylene, etc. and a point in the compressor that has a pressure lower than 12 kg/cm ² G, and the steam cracker device is used to produce ethylene. A method for separating and recovering olefins from light gas produced as a by-product from a catalytic cracking device, which is characterized by separating and recovering olefins such as and propylene with high purity. 5 The impurities contained in the light gas and removed are
5. The method according to claim 4, wherein the compound is carbonyl sulfide, carbon dioxide, carbon monoxide, hydrogen sulfide, oxygen or arsenic compound.