JPS6310693A - Method of separating and recovering olefins from low boiling gas formed as by-product in catalytic cracker - Google Patents

Abstract

PURPOSE:To separate and recover high-purity olefins from a low boiling gas at a low cost, by introducing a low-boiling gas prepd. as a by-product in a catalytic cracker from a particular portion. CONSTITUTION:If necessary, the olefin concn. of a low-boiling gas contg. olefin gases, such as ethylene or propylene, prepd. as a by-product in a catalytic cracker is increased, followed by removal of impurities such as carbonyl sulfid, CO2, CO, H2S, oxygen, water, nitrogen, and arsenic compd. The low-boiling gas is then introduced between the outlet of a thermal decomposition furnace 3 and the portion having a pressure of 12kg/cm<2>G of a compressor 6 of a steam cracker 1, thereby separating and recovering olefins such as ethylene or propylene through utilization of the cracker 1 in itself.

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 advantages of the invention and its problems The catalytic cracking method is a method for producing high-octane gasoline by decomposing seafood with a boiling point higher than that of petroleum kerosene at high temperatures in the presence of a catalyst. Mobile catalyst beds are known.

The gas by-produced from such catalytic crackers, especially fluid catalytic crackers, contains large amounts of lower hydrocarbons such as ethylene and propylene, and it is desirable to efficiently separate and recover these lower hydrocarbons. ing.

In order to recover useful components such as ethylene or propylene from the light gas produced by 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, and the equipment is required. It was difficult to implement economically 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 currently it is only consumed as fuel.

It is also possible to recover useful gas containing ethylene or propylene from the light gas by-produced from the catalytic cracker by a separation and recovery method using an adsorbent, but in this case, a mixed gas of ethylene and propylene can be obtained. Moreover, the resulting mixed gas contains dienes, acetylene, etc. For this reason, each of these components had to be roughly separated, and dienes, acetylene, etc. had to be removed by hydrogenation or the like.

It is also conceivable to use an absorbent to recover useful gases containing ethylene or propylene from the light gas by-produced from the catalytic cracker, but this also has the same problems as above.

In this way, the light gas produced as a by-product from the catalytic cracking equipment contains
Although it contains a considerable amount of useful components such as ethylene or propylene, it is not possible to separate these components, recover them in high purity, and use them effectively, and they are simply consumed as fuel. It's just a simple thing.

Recently, Japanese Patent Application Laid-open No. 108090/1983 has proposed a method for producing gasoline or fuel oil by contacting 1q of light gas produced from the above-mentioned catalytic cracker with a zeolite catalyst. olefin recovery process.

Purpose of the Invention The present invention aims to solve the problems associated with the prior art as described above, and aims to reduce the amount of ethylene, propylene, A method for separating and recovering useful components from the above-mentioned light gases, such that each useful component of the olefins can be recovered with high purity without the need to newly install a dedicated separation and purification device such as a cryogenic separation device or a distillation device. 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 cracking equipment, achieving an organic combination of the catalytic cracking equipment and the steam cracker equipment, and producing inexpensive olefins. They found that it was possible to build A-type products, 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 cracking device according to the present invention is to separate and recover light gas containing olefins such as ethylene and propylene by-produced from a catalytic cracking device from hydrocarbons such as ethylene, propylene, etc. 12 at the pyrolysis furnace outlet and compression filtration of the steam cracker equipment for producing! The steam cracker is used to produce olefins such as ethylene and propylene at high temperatures. T! The feature is that it can be separated and recovered at once.

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 adsorbs the olefins contained in the light gas before being introduced into the steam cracker device. It is preferable to concentrate the light gas by absorption, membrane separation, etc., and it is also preferable to remove harmful components such as H-L 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 cracking apparatus according to the present invention, the light gas is introduced into a specific part of a steam cracker apparatus for producing ethylene, propylene, etc. from hydrocarbons, Since olefins are separated and recovered using this steam purifier, olefins such as ethylene and propylene can be recovered from light gas with high purity, and 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.

Hereinafter, the method for separating and recovering olefins from the light gas by-produced from the catalytic cracking apparatus according to the present invention will be specifically described.

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. Hydrogen such as ethylene, propylene, methane, ethane, propane, etc.

Catalytic cracking is a well-known process in which seafood with a boiling point higher than that of petroleum kerosene is decomposed at high temperatures in the presence of a catalyst to produce high-octane gasoline. This catalytic cracking method is 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 by either catalytic cracking method can be used as a raw material. Examples of fluid catalytic cracking methods include the ESSO method, 5HELL method, KELLOG method, T
Light gas produced as a by-product from any method such as the EXACO 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 coming out from the bottom of the tower, various gas oils as side distillation products, and 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 about 10-15 KgZc112G by a wet gas compressor, and usually
The gas is roughly sent to an absorption tower where the propane and butane fractions in the gas are separated, and the top gas is sent to a sponge absorber where a small amount of propane 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 of the catalytic cracking process used in the present invention.

In the present invention, tail gas discharged from a catalytic cracker as described above is preferably used, but in some cases,
It is also possible to use gas obtained at any suitable point after the wet gas compressor outlet line.

Examples of such gases include wet gas compressor outlet gas, absorption tower overhead gas, and additive scriber overhead gas.

Table 1 shows an example of the composition of light gas by-produced from a catalytic cracker.
Shown below.

Table 1 In the present invention, the light gas produced as a by-product from the catalytic cracker as described above is introduced into a specific part of a steam cracker for producing ethylene, propylene, etc. from hydrocarbons. First, let me explain.

A steam cracker is a well-known device for preparing ethylene, propylene, and butadiene from hydrocarbons such as naphtha, kerosene, and gas oil. Any type of steam cracker apparatus, such as that shown in Kagaku Kogyosha, 2006, may be used; an exemplary flowchart is shown in FIG. In this steam cracker device 1, raw material hydrocarbons such as naphza are introduced into a thermal cracking furnace 3 together with steam 2, and are thermally cracked at a temperature of about 800°C. 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
It is sent to the compressor 6 where it is compressed. The compressed hydrocarbons then pass through a sulfur removal equipment consisting of an alkali washing section 7 and a drying section 8, and then are sent to a depropanizer tower,
It is sent to the olefin recovery section 9, which consists of a hydrogen separation device such as a deep cooling device, a demethanizer, a deethanizer, an ethylene separation tower, a propylene separation tower, a debutanizer, etc., and 99.95%
Olefins such as ethylene with a high purity of about 99.0%, propylene with a high purity of about 99.0%, and butadiene are separated and recovered, and methane, ethane, propane, hydrogen, etc. are also recovered.

In the present invention, the light gas produced as a by-product from the catalytic cracker is distributed between the pyrolysis furnace outlet 3 of the steam cracker as described above and the point 12 in the compressor 6 where the pressure is lower than 'j/cm2G. 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 pyrolysis furnace outlet 3 of the steam cracker device 1 and the compressor 6 at a rate of 2 kg/kg.
The light gas is preferably introduced upstream of the alkaline cleaning section 7 of the steam cracker, and the light gas is generally between 10 and 1 cm2G.
This is because the pressure is up to about 5 kg/cm2G.

In the present invention, olefins can be recovered with high purity by supplying only the light gas produced as a by-product from the catalytic cracker to the steam cracker @1, but normally, hydrocarbon raw materials such as naphza are supplied. The light gas is supplied to the steam cracker apparatus 1 which is being operated, 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 can also be introduced into the steam cracker after increasing the olefin concentration in the light gas. Any conventionally known method can be employed 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 time. 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 under low pressure.

Further, for example, a method as 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, is employed to remove olefins in the light gas. It is also possible to increase the concentration of

For example, by employing a method as disclosed in JP-A No. 57-10316, that is, a method in which the light gas is brought into contact with a separation membrane such as an ion exchange membrane, the degree of olefins in the light gas is increased. You can also do that.

Furthermore, it is also possible to increase the 11 degrees of olefins in the light gas by employing a method such as that disclosed in JP-A No. 59-55839, that is, a method of bringing the light gas 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. Further, when an arsenic compound is present in the feed of the catalytic cracking apparatus, the gas may contain an arsenic compound such as arsine.

For example, if the light gas contains carbon dioxide, it may condense in the deep cooling device in the η reflex recovery section of the steam cracker, and the line may become blocked. 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 apparatus.

Carbon dioxide is also present in the pyrolysis products at the outlet of the pyrolysis furnace of the steam cracker, and most of this carbon dioxide is generally removed in the alkaline cleaning section within the steam cracker, with some remaining in the steam cracker. It is converted into methane along with carbon monoxide in the methanator inside. It is desirable that this carbon dioxide concentration is suppressed to about 10 pl)m or less, preferably about 11)l)m or less, before being sent to the olefin recovery section 9 of the steam cracker apparatus.

- Carbon monoxide, like carbon dioxide, also exists in the thermal decomposition products at the outlet of the thermal cracker of the steam cracker equipment, and this carbon monoxide is converted into methane in hydrogen or methane gas) and, if necessary, in a methanator. It is then discharged out of the system, but it also passes through the water washing reaction tower of the olefin recovery section 9 on the way.

Generally, a palladium catalyst is used in the water-washed 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 an appropriate amount of carbon monoxide or pretreatment of the catalyst with carbon monoxide actually improves the selectivity of acetylene/dienes in water washing. (Unexamined Japanese Patent Publication No. 59-596
See Publication No. 34, Publication No. 57-84745, etc. ) Therefore, the tolerance of this carbon monoxide is not necessarily constant depending on the main catalyst used, but in general, 500 p.
It suffices if it is about pm or less. Also, if you want to avoid contamination with -1m carbon, contact molecules/? Carbon monoxide can be easily reduced by treating the light gas produced by the equipment with an adsorption and absorption process.

Hydrogen sulfide is removed in the alkaline washing section 7 in the steam cracker device, but this hydrogen sulfide reservoir is preferably cleaned by about 11)I)m or less before being sent to the olefin recovery section in the steam cracker device. It is desirable that it be suppressed to about 0.1DI)m.

A portion of carbonyl sulfide (CO3) is removed in the alkaline cleaning section 7 in the steam cracker, but the concentration of carbonyl sulfide is reduced to about lppm or less before being sent to the olefin recovery section 9 in the steam cracker. Preferably, it is suppressed to about 0.01 ppm or less.

Oxygen must be removed if it is mixed into the ethylene and exceeds the product specification limit, and the concentration of hydrogen must be kept below 1101)p before being sent to the olefin recovery section in the steam cracker unit. It is preferable that the amount is suppressed to about 1 pI)m 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 apparatus 1.

As mentioned above, the arsenic compound is
There is a possibility that the hydrogenation catalyst such as acetylene in the olefin recovery section 9 may be poisoned. For this reason, the arsenic concentration in the gas sent to the olefin recovery section in the steam cracker device is preferably 11) l) m or less, preferably o, lpp.
It is preferable that it is suppressed to less than m.

As mentioned above, the light gas by-produced from the catalytic cracker contains impurities, and among these, arsenic compounds and carbonyl sulfide, in particular, cannot often be removed to below allowable levels in the steam cracker. Moreover, these may poison the hydrogenated melting medium. Therefore, it is preferable to remove arsenic compounds, carbonyl sulfide, and the like from the light gas before introducing it into the steam cracker apparatus 1.

In order to remove the above-mentioned impurities such as nitrate and carbonyl sulfide from light gas, for example, Japanese Patent Publication No. 59-1445
Although the method disclosed in Publication No. 3 can be employed, any conventionally known method can be employed. Specifically, amine cleaning towers, sulfide removal towers, deoxygenation towers,
By passing light gas through a co conversion tower etc.
The above impurities can be removed from light gas.

Known methods can also be used to remove arsenic compounds (mainly arsine compounds). That is, reaction adsorption using an oxidizing catalyst (such as manganese oxide) (Japanese Patent Publication No. 17772/1983);
Adsorption removal using copper-chromium supported activated carbon (JP-A-60-2
38144) etc. can be used.

The timing to remove the above impurities from light gas is as follows:
It can be done at any time as long as it is before it is introduced into the steam cracker equipment; for example, when performing an operation to increase the olefin concentration in light gas, it can be done before or after the operation. .

In addition, if an existing steam cracker equipment is equipped with a device for removing these arsenic compounds or carbonyl sulfide, in such a case, the equipment for removing arsenic compounds etc. is installed in the olefin recovery section 9 of the steam cracker equipment. It can be installed in locations up to .

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 separated from a specific part of 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 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 or a distillation device, and an extremely excellent effect is achieved in that olefins such as ethylene and propylene can be recovered at low cost.

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 produced as a by-product from a fluid catalytic cracker were treated in advance with a removal device.

Impurities: HS 1oppm COS 8 ppm 02 aoppm That is, the light gas was transferred to a CO8 hydrolysis tower (packed with activated alumina catalyst) at GASV 1000 Vl'tl/V temperature 110'C pressure 10 K! After passing it under the conditions of J/cm2G, it passed through the H2S removal tower (filled with zinc oxide) under the same conditions to remove traces of Machi S and 0.00% COS. 1 ppm or less, and then GH3V 2000V/H/V, temperature 110'C was placed in an oxygen removal column (packed with a catalyst containing 2 wt% silver supported on alumina: prepared by the method described in Example 1 of Japanese Patent Publication No. 14454/1983). It was passed under a pressure of 10 kg/cm2G, and the 0° solubility in the purified gas was 1 ppI11 or less.

The above purified gas was cooled to room temperature and then used for 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 (at a pressure of 2! J/cm2G), and is combined with the cracked gas of the steam cracker to perform rectification separation.

Composition and flow rate of light gas as raw material, composition of light gas after impurity removal, and recovered ethylene, ethane,
Table 2 shows the flow rates of 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 the pressure of the cracked gas compressor of the steam cracker is 2 to 9.
/aiG in the first stage.

As in Example 1, the raw material I! Table 3 shows the composition of the quality gas.

After drying and cooling the light gas above, -4°F volatile oil is used as an absorbent to concentrate the C3 fraction mainly consisting of propylene, and the pressure of the cracked gas compressor of the steam cracker is 2 kg/
Introduce it to the site containing Cl1IG.

As in Example 1, the composition of the light gas that is the raw material is shown in Table 4.
Shown below.

The above volatile oil is 15% pentane, 25% pentene, 10% cyclopentadiene, 10% isoprene, CB10
%, a cracked naphtha consisting of 28% BTX fraction and 2% styrene. The absorption tower is operated at 5tJ/cm2G at 30"F at the top and at 646°F, and the volatile oil at the bottom of the absorption tower that has absorbed the olefin fraction is sent to the stripping tower 4! I/CIR2G where it is heated and straightened. Collect concentrated gas from the top.

Leaving -2 Inspection

[Brief explanation of drawings]

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

Claims (1)

[Scope of Claims] 1) A pyrolysis furnace outlet of a steam cracker device for producing ethylene, propylene, etc. from hydrocarbons by using light gas containing olefins such as ethylene and propylene as by-products from a catalytic cracker. and 12K in compressor
Catalytic cracking is characterized in that it is introduced between a point having a pressure lower than g/cm^2G and uses this steam cracker equipment to separate and recover olefins such as ethylene and propylene with high purity. A method for separating and recovering olefins from light gas produced as a by-product from equipment. 2) After performing an operation to concentrate 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 separated from hydrocarbons. It is introduced between the pyrolysis furnace outlet of a steam cracker equipment for producing ethylene, propylene, etc. and a point in the compressor that has a pressure lower than 12Kg/cm^2G, and the steam cracker equipment is used to produce ethylene. A method for separating and recovering olefins from light gas produced as a by-product from a catalytic cracking unit, which is characterized by separating and recovering olefins such as and propylene with 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 produced as by-products from the catalytic cracker, the light gas is converted from hydrocarbons to ethylene, olefins, etc. It is introduced between the pyrolysis furnace outlet of a steam cracker equipment for producing propylene and the compressor at a point with a pressure lower than 12Kg/cm^2G, and the steam cracker equipment is used to produce ethylene and propylene. 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 olefins with high purity. 5) The method according to claim 4, wherein the impurity contained in the light gas and removed is carbonyl sulfide, carbon dioxide, carbon monoxide, hydrogen sulfide, oxygen, or an arsenic compound.