JPS6046153B2 - Heavy oil pyrolysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for thermally decomposing heavy oil, and more specifically, a product obtained by thermally decomposing heavy oil is introduced into a fractionating column, and a high boiling point by-product is produced as a by-product. The exhaust gas containing naphthalene, etc., produced when it is further fractionated in a vacuum separation tower, is led to a condensation tower and condensed once, and the condensed liquid is circulated to the fractionation tower etc. This invention relates to a thermal decomposition method that prevents equipment from being blocked by naphthalene and allows stable operation over a long period of time.

In general, the thermal decomposition products produced by thermally decomposing various heavy oils such as atmospheric distillation residue oil and vacuum distillation residue oil in the presence of steam are fractionated in a fractionating column, and the bottom of the column is distilled.

The high-boiling by-product obtained from the process contains a relatively large amount of naphthalene as well as trace amounts of gasoline and water. Therefore, when this is further separated into a fraction containing naphthalene as the main component and a bottom fraction containing heavy components other than these in a vacuum separation column, the top gas of the vacuum separation column contains Water and gasoline present in the bottom oil are present along with the naphthalene. Therefore, if this exhaust gas is directly discharged outside the equipment system, it will cause blockage of pipes and deterioration of the environment, so first it is led to a naphthalene condensation tower to condense the naphthalene, and then steam and gasoline are removed from the top of the condensation tower. It is necessary to drain it into the ejector drainage system or out of the system from the bottom of the tower. in this case,
Regarding the temperature of the naphthalene condensation tower, if the temperature is too low, the moisture in the gasoline will not evaporate, and if it is too high, the naphthalene will evaporate while remaining dissolved in the gasoline, and the amount of naphthalene entrained in the mist will also increase. This may cause blockage of the ejector cooler, and even blockage of piping and instrumentation equipment. In this way, in order to evaporate and extract only the moisture and gasoline from the top of the naphthalene condensation tower, it is necessary to pay close attention to the temperature control of the condensation tower, and the operation is complicated. On the other hand, when extracting moisture and gasoline from the bottom of the naphthalene condensation tower, the specific gravity of the condensate containing naphthalene and gasoline is 1.000 to 1.040 (50/4°C), Since the specific gravity is very close to that of water, it is extremely difficult to separate and extract the water and gasoline components only by controlling the water-oil interface.

As mentioned above, it is extremely difficult to completely capture the naphthalene in the exhaust gas coming out of the top of the vacuum separation tower while extracting moisture and gasoline from the system, and various methods have been proposed so far. However, none of them were satisfactory.

One method is to recycle the condensate at the bottom of the naphthalene condensation tower to a vacuum separation tower, and extract water and gasoline only from the top of the condensation tower. The amount of water coming in is overwhelmingly larger than the amount of gasoline and gasoline, and as a result, water accumulates from the top of the vacuum separation tower to the naphthalene condensation tower, eventually causing fluctuations in the operation of the vacuum separation tower. There is a drawback. The present invention is a heavy oil that can be operated stably for a long period of time with simple operations and equipment, without troubles such as blockage of various equipment due to naphthalene or troubles such as operational fluctuations and overflow of the vacuum separation tower due to water accumulation. The purpose of this project is to develop a method for thermally decomposing heavy oil in the presence of steam.The thermal decomposition products obtained by thermally decomposing heavy oil in the presence of steam are passed through a quencher and then introduced into a fractionating column. In the fractionation column, the main cracked products, mainly cracked gas and cracked gasoline, are separated from the top of the column, and the cracked byproducts, mainly cracked heavy oil, are separated from the bottom of the column, and then the separated cracked byproducts are separated. The product is introduced into a vacuum separation tower and separated into each fraction, and the exhaust gas discharged from the top of the vacuum separation tower is led to a condensation tower and condensed, and the resulting condensate is passed through the quencher and/or This is a method for thermally decomposing heavy oil, which is characterized by returning it to a fractionation column.

First, there are various types of heavy oil that can be used as feedstock oil for thermal cracking in the method of the present invention, and although there are no particular controls, examples include various types of atmospheric distillation residue oil, vacuum distillation residue oil, and petroleum naphtha. There is cracked heavy oil, which is a by-product when fractions are thermally decomposed.

Next, the method of the present invention will be explained in more detail based on the drawings.

FIG. 1 is a schematic diagram showing an example of an apparatus used in the method of the present invention. According to the method of the present invention, heavy oil, which is a raw material oil, is introduced into the cracking reaction tower 1 together with steam or separately. In this decomposition reaction tower 1, the introduced heavy oil is thermally decomposed in the presence of steam. The conditions for this thermal decomposition may be determined as appropriate depending on the type of heavy oil used, the desired product, etc., but are usually 650°C to 850°C, preferably 72°C.
The temperature should be approximately 0 to 780°C. Next, the product obtained by this thermal decomposition (mixed with steam) is transferred to a quencher 2.
where it is rapidly cooled. Although the cooling temperature varies depending on various conditions, it is usually cooled to about 200 to 400°C. After cooling, the pyrolysis products are led to the fractionation column 3, where the main cracking products mainly consisting of cracked gas and cracked gasoline and steam are separated from the top of the column, while the main cracking products mainly consisting of cracked heavy oil are separated from the top of the column. Decomposition by-products are separated from the bottom of the column. The main decomposition product generally has a boiling point of about 150-250°C or less, and the decomposition by-product has a boiling point of about 150-250'C or more. Note that the operating conditions in this fractionating column 3 may be determined as appropriate, but generally the column top pressure is 0.4 to 1.0.
kgIcIt-G1 The top temperature is 90 to 120°C, and the bottom temperature is 180 to 250'C. In addition, the decomposition byproducts separated from the bottom of the fractionator 3 contain relatively large amounts of naphthalene, anthracene, phenanthrene, etc.
It also contains small amounts of gasoline and water. Subsequently, the decomposition reaction by-products are heated in a heating furnace 4 for 300 min as required.
After heating to ~400° C., the mixture is introduced into a vacuum separation column 5 and separated into each fraction, and each fraction is separated from an appropriate position on the column side, the bottom of the column, etc.

The type of fraction to be separated here may be determined as appropriate, but in general, from the upper column side, boiling point 2
00~270℃ cracked light gas oil, boiling point 270~3 containing mainly anthracene, phenanthrene, etc. from the middle stage of the tower side
The cracked heavy gas oil at 50°C is separated and recovered, and the cracked heavy oil with a boiling point of 350°C or higher is extracted from the bottom of the column. The operating conditions in the vacuum separation column 5 may be determined as appropriate depending on various conditions, but are usually under a reduced pressure of O-0.8k9d-A1, preferably 0.05 to 0.4k91d-A. Should. As described above, when the decomposition byproducts from the fractionator 3 are fractionated in the vacuum separation column 5, exhaust gas is discharged from the top of the column.

This exhaust gas contains moisture, gasoline, naphthalene, etc., and it is not preferable to discharge it as it is out of the system. In addition, the pressure inside the vacuum separation tower 5 is normally achieved by an ejector 7 using steam, and if left as is, naphthalene contained in the exhaust gas from the top of the tower will precipitate in the ejector 7 etc., causing blockage problems. There is a risk of pipe strain, so there is a condensation tower 6 for naphthalene etc.
It is necessary to install Therefore, according to the method of the present invention, the exhaust gas discharged from the top of the vacuum separation tower 5 is led to the condensation tower 6 and condensed.

In this condensation tower 6, it is possible to condense the naphthalene while leaving the gasoline and water in the exhaust gas as vapor, but it is difficult to control the temperature, and some naphthalene still escapes to the ejector etc. as vapor. In addition, there is a problem in that it takes time and effort to separate the water and gasoline components. Therefore, in the method of the present invention, most of the gasoline, water, and naphthalene in the exhaust gas are condensed in the condensation tower 6, and the naphthalene in particular is prevented from flying out to the ejector or the like. Next, the condensate obtained in the condensation column 6 can be directly extracted from the system, but since it contains useful components such as gasoline and naphthalene, it is necessary to fractionally distill it again. is preferred.

Therefore, it is conceivable to circulate the condensate to the vacuum separation tower 5 (see broken line B in Figure 1), but if the operation continues for a long time with such a circulation system, a large amount of moisture will accumulate in the condensation tower 6. This may cause driving problems. Therefore,
In the method of the present invention, the condensate in the condensation tower 6 is returned to either or both of the aforementioned quencher 2 and fractionation tower 3. The returned condensate is sent to the fractionator 3, where most of the moisture and gasoline are separated from the top of the column 3, and further, most of the naphthalene is separated from the reduced pressure separation column 5. Therefore, even if continuous operation is performed for a long period of time, there is no fear that condensate containing water and other components will accumulate in the condensation tower 6, and no operational trouble will occur. Further, as in the method of the present invention, returning the condensate to the quench cooler 2 or the fractionating column 3 is extremely beneficial in the following respects.

That is, in general, the *1 bottom liquid in the fractionating column 3, that is, the cracked byproducts mainly composed of cracked heavy oil, has a very high viscosity, and if left as it is, there is a risk of clogging various equipment such as the heat exchanger. Therefore, it is necessary to reduce the viscosity by diluting it with some kind of liquid. However, according to the method of the present invention, since the condensate is returned to the fractionating column 3, etc., this condensate greatly contributes to reducing the viscosity of the decomposition byproducts, and the diluent (
lights, diesel distillate, etc.) can be omitted or saved. As described above, according to the method of the present invention, stable continuous operation can be performed over a long period of time with simple operation and economical operating costs.

Next, the effects of the method of the present invention will be specifically explained based on Examples and Comparative Examples. Comparative Example Heavy oil was thermally decomposed using the apparatus shown in FIG. 1 (however, the line indicated by the broken line B was used instead of the line indicated by the solid line A as the condensate circulation line).

Various conditions and results are shown in Table 1. The following can be seen from this result. (1) The condensate at the bottom of the condensation tower contains 10 WL% or more of accumulated water.

Further, the specific gravity of this condensate is 0.998, which is very close to the specific gravity of water, which is 0.978. (2)
Approximately 30 wt% of oil is present in the ejector drainage water, but the properties of this oil are almost the same as those of the condensate at the bottom of the condensation tower, indicating that a considerable amount of this condensate had leaked out into the ejector drainage water. Recognize.

EXAMPLE Heavy oil was thermally decomposed using the apparatus shown in FIG. 1 (where the solid line A was used as the condensate circulation line).

Various conditions and results are shown in Table 2. The following can be seen from this result. The two major operational differences between the example and the comparative example are that the temperature of the condensation tower 6 is lower in the example and that the circulation line for the condensate at the bottom of the condensation tower 6 is different. It is. (1) The amount of oil contained in the ejector waste water is extremely reduced.

This indicates that the amount of naphthalene leaking from the top of the condensation tower to the Eddy and Ector drainage systems has become negligible. (2) The specific gravity of the condensate at the bottom of the condensation tower is large and the initial boiling point is high, resulting in a small water/oil ratio.

This indicates that water and light oil no longer accumulate in the condensation tower. (3) Even if the amount of diluent oil supplied to the lower part of the fractionating column 3 is zero, the viscosity of the bottom oil of the fractionating column does not increase, but rather decreases.

This indicates that the condensate circulated from the condensation tower to the fractionation tower effectively reduces the viscosity of the bottom oil of the fractionation tower. FIG. 1... decomposition reaction tower,
2... Rapid cooler, 3... Fractionating column, 4...
... Heating furnace, 5 ... Vacuum separation tower, 6 ...
... Condensation tower, 7... Ejector, A...
...Circulation line used in Examples, B...Circulation line used in Comparative Examples.

Claims (1)

[Claims] 1. The thermal decomposition product obtained by thermally decomposing heavy oil in the presence of steam is passed through a quencher and then introduced into a fractionating column,
In the fractionation column, cracked main products, mainly cracked gas and cracked gasoline, are separated from the top of the column, and cracked byproducts, mainly cracked heavy oil, are separated from the bottom of the column, and then the separated cracked byproducts are separated. is introduced into the vacuum separation tower and separated into each fraction, and the exhaust gas discharged from the top of the vacuum separation tower is led to the condensation tower and condensed, and the resulting condensate is passed through the quencher and/or the fractionator. A method for thermally decomposing heavy oil, which is characterized by returning it to a column.