JPS5925886A - Method for obtaining thermal cracked oil from heavy oil by two-stage thermal cracking - Google Patents

Abstract

PURPOSE:To obtain a thermal cracked oil in high yield, by thermally cracking a heavy oil at a high temperature in the first stage, taking out the resultant thermal cracked oil and decomposition residue, thermally cracking the thermal cracking residue at a high temperature in the second stage, mixing the thermal cracking product with the thermal cracking oil, distilling the resultant mixture, and circulating the resultant residue through the thermal cracking step. CONSTITUTION:A heavy oil is introduced through a line 1 into the first thermal cracking reactor 15 and thermally cracked at 400-500 deg.C. The resultant thermal cracked oil is then taken out of a line 3, sent to a distillation column 17, and the thermal cracking residue is taken out of a line 9 and introduced into the second thermal cracking reactor 16 and thermally cracked at 510-650 deg.C. The resultant thermal cracked oil obtained in the second thermal cracking step is taken out of a line 7 and sent to the distillation column 17. The thermal cracked oil in the first step and the above-mentioned thermal cracked oil are distilled to give the aimed purified thermal cracked oil. The resultant residue after the distillation is then circulated through the first thermal cracking reactor 15 by a line 11 and further thermally cracked.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining pyrolysis oil from heavy oil in high yield by two-stage pyrolysis.

In recent years, as the use of natural gas and coal as fuel has increased, demand for heavy oil has decreased, while demand for light oil such as gasoline and naphtha has increased.
How to produce pyrolysis oil or lightened oil with good yield has become an important technical issue. Conventionally, the method for obtaining pyrolysis oil from heavy oil with the highest yield is the flute coat method.
The King method is known. In this method, for example, as seen in Japanese Patent Publication No. 31-9136, heavy oil is introduced into a thermal decomposition reactor in which coke particles are fluidized, and the heavy oil is thermally decomposed there. Pyrolysis oil and pyrolysis gas are generated, a thermal polymerization product (coke) is attached to the surface of fluidized coke particles in the reactor, and the fluidized coke particles with coke attached are extracted from the reactor. This is a method to continuously thermally decompose heavy oil by extracting it.

At present, this flute caulking method is
It is thought that the highest yield is given for the production of pyrolysis oil, for example, when pyrolysis is performed using Iranian heavy vacuum residue (Conradson carbon 21.4%) as the raw material heavy oil. , cracked gas (04 or less) 11%
(by weight), 618% cracked oil (05-540°C) and 264% coke are reported to be obtained. However, even in this method, a considerable portion of the feedstock (approximately 40
%) is converted into coke and cracked gas with low added value, and is still unsatisfactory from the point of view of process efficiency. In particular, in such a thermal cracking process, the magnitude of the cracked oil yield is a factor that determines the quality of the process, so further improving the cracked oil yield is extremely important.

In view of the prior art as described above, the present inventors have conducted intensive research to develop a heavy oil pyrolysis process that provides a higher cracked oil yield, and have developed a special two-stage pyrolysis method. found that by adopting it, the purpose could be achieved,
The present invention has now been completed.

That is, according to the present invention, when thermally decomposing heavy hydrocarbon oil, (a) a first thermal decomposition step of thermally decomposing the heavy oil at a temperature of 400 to 500°C; (b) the first thermal decomposition step; The pyrolysis oil and molten state first from the decomposition process
a step of extracting the first thermal decomposition residue in a molten state from 510 to 650°C;
a second pyrolysis step of pyrolysis at a temperature of , (v) extracting pyrolysis oil and pyrolysis residue from the second pyrolysis step, (e) the first pyrolysis step and the second pyrolysis step. a step of distilling the pyrolysis oil from the heavy oil to separate it into a distillate and a distillation residue; (f) circulating the distillation residue through the first pyrolysis step; A method of obtaining pyrolysis oil is provided.

The raw material heavy oil used in the present invention is generally 56
Konradsonker S? It contains 710 weight units or more, usually 15 to 25 weight units. Examples of such heavy oil include distillation residue oil, vacuum distillation residue oil, coal liquefied oil, sierre oil, oil sand oil, and the like. In addition, this heavy oil
If necessary, it can be diluted with light hydrocarbon oil such as FOO cycle oil, cracked oil, or coal-based solvent.

In the present invention, the above-mentioned heavy oil is first
It is thermally decomposed at a relatively low temperature of 500°C, preferably 410-430°C (first thermal decomposition).

This low-temperature pyrolysis is performed under conditions where the continuous phase is a liquid phase, and a normal liquid phase pyrolysis reactor is employed. To perform this thermal decomposition preferably, for example, the feedstock oil is preheated to 450 to 500°C and then continuously introduced into a low-temperature liquid phase reactor. A reactive gas, such as steam or nitrogen gas, is injected in a dispersed state into the liquid heavy oil forming a continuous liquid phase, and the decomposition products, pyrolysis oil and pyrolysis gas, are transferred to the reactor. The vapor phase is continuously withdrawn from the top, while the decomposition residue is continuously withdrawn from the bottom of the reactor. The temperature inside the reactor is 400~
Set in the range of 500℃. If the temperature is lower than 400°C, the decomposition of the feedstock oil will not proceed smoothly, and if the temperature exceeds 500°C, although the thermal decomposition will proceed smoothly, a large amount of thermal decomposition gas will be generated, which is not preferable. The residence time of the liquid in the reactor is preferably set in the range of 15 minutes to 120 minutes, preferably 30 minutes to 60 minutes. If the residence time is less than 15 minutes, the thermal decomposition will not proceed sufficiently. On the other hand, if the residence time is too long, the thermal decomposition residue will become coke-like and difficult to handle as a liquid. The reaction pressure ranges from 0 to I Kg/cm2. In the present invention, the thermal decomposition yields a thermal decomposition residue having properties such as a fixed carbon content of 30 to 60% by weight, preferably 30 to 45% by weight, and a viscosity of 200 centipoise or less at 350°C. It is better to do it like this.

Next, the thermal decomposition residue obtained from the first thermal decomposition step is thermally decomposed at a high temperature of 510 to 650°C, preferably 550 to 600°C (second thermal decomposition). This high-temperature thermal decomposition can be carried out using a solid-gas fluidized bed reactor in which the continuous phase is a gas phase, which is employed in the usual Flue P coking method. That is, this solid gas fluidized bed reactor contains a solid fluidized bed in which solid particles are fluidized by a fluidizing gas, for example, a high temperature gas such as steam, nitrogen gas, or carbon oxide. As solid particles in this case, in addition to coke, heat-resistant inorganic particles such as alumina, silica/alumina, etc. are generally used, and the particle diameter is usually about 0.01 to 1 rMl. The temperature in the reactor is preferably set in the range of 510-650°C; temperatures below 510°C will cause problems such as the fluidized particles sticking to each other, while temperatures exceeding 650°C will This is not preferable because it increases the amount of pyrolysis gas generated. The reaction pressure ranges from 0 to IK17 cm2.

In the present invention, when the pyrolysis residue from the low-temperature pyrolysis reactor is supplied to the second pyrolysis step, the pyrolysis residue is cooled to 300 to 400°C on New Year's Day as necessary, and then molten via a pump. can be sent to a second pyrolysis step, and
When the pyrolysis residue is introduced into the second pyrolysis reactor, it is mixed with a non-reactive gas such as water vapor, and the pyrolysis residue is introduced into the second pyrolysis reactor in a finely divided state.
It is best to blow it into the reactor.

By performing the second pyrolysis step as described above, the pyrolysis residue from the first pyrolysis step is further pyrolyzed to produce pyrolysis oil and pyrolysis gas as steam 4. At the same time, coke is produced as a decomposition residue. The cracked oil is extracted from the top of the reactor along with non-reactive gases such as water vapor introduced from the bottom of the reactor, while the coke produced stays in the reactor for a certain period of time and is then removed from the reactor together with fluidized particles. being taken outside.

The pyrolysis oil extracted from the first pyrolysis step and the second pyrolysis step is sent to a distillation step, where it is separated into distillate oil and distillation residue oil. The pyrolysis oil from the first pyrolysis step is also fed to this distillation step and subjected to distillation treatment. The properties of the pyrolysis oil distillate are generally as follows.

It contains at least 40% by weight, usually 40 to 60% by weight, of substances having a boiling point of 566°C or higher.

In the present invention, the distillation residue oil obtained in the distillation step is circulated to the first thermal decomposition step. The circulation of this distillation residue increases the yield of light pyrolysis oil. Generally, the circulation ratio of distillation residue oil is 0 to 1 part by weight of raw material heavy oil.
．． The proportion is from 1 to 0.5 parts by weight, preferably from 0.2 to 0.4 parts by weight.

Next, the present invention will be explained in more detail with reference to the drawings.

The drawing shows a flow sheet of the method of the present invention, in which feedstock oil is introduced from line 1 into a first pyrolysis reactor 15, and for this first pyrolysis reactor, a non-heat source is introduced from line 2. A reactive gas, for example steam, is blown in and recycled distillation residue is introduced through line 11. Preferable conditions in this first thermal decomposition step are as follows.

Reaction method: Liquid phase continuous reaction temperature = 420-440°C Reaction time: 30 minutes to 120 minutes (liquid phase basis) Pyrolysis oil is extracted from line 3 together with pyrolysis gas and non-reactive gas, and sent to the distillation column. Sent to 17th.

9- Meanwhile, the pyrolysis residue is withdrawn from line 9 and introduced into a second pyrolysis reactor 16 equipped with a solid fluidized bed.

In this case, a non-reactive gas such as steam is blown into the reactor together with the pyrolysis residue through line 10, and the pyrolysis residue is brought into contact with the fluidized bed in the form of a spray. A fluidizing gas is introduced from line 6 to the second pyrolysis reactor, and solid particles for forming a fluidized bed are supplied from line 4. Preferred conditions in this second thermal decomposition step are as follows.

Reaction method: solid-gas fluidized bed continuous reaction temperature = 550-600°C reaction time = 1-10 seconds (based on gas phase) Pyrolysis oil is extracted from line 7 together with pyrolysis gas and non-reactive gas, and sent to the distillation column. Sent to 17th.

On the other hand, the coke produced by this thermal decomposition is extracted from line 5 together with solid particles for fluidization.

Distillation column 17 is preferably operated under the following conditions.

Column top temperature = 130 to 160°C -l〇 - Column bottom temperature = 340°C In the distillation column 17, gas consisting of vaporized pyrolysis oil, pyrolysis gas and non-reactive gas is extracted from the top of the column, Relatively light pyrolysis oil is extracted from line 13 and relatively heavy pyrolysis oil is extracted from line 14. The distillation residue is extracted from the bottom of the column through a line 11, and is transferred to the first thermal decomposition reactor 1.
It is cycled to 5.

According to the present invention, an increased pyrolysis oil yield can be obtained compared to the conventional flute coking method. For example, in the case of the flute coking method, the pyrolysis oil yield at 05 to 540°C Regarding this, while the relationship is about 62 times, in the case of the method of the present invention, it reaches about 70% by weight. Still, the pyrolysis oil of the present invention has the advantage that it has less unsaturation, exhibits a lower bromine number, and requires less hydrogen consumption when hydrorefining. For example, 0. Regarding light pyrolysis oil at ~19°C, the flute coking method shows a bromine number of 130, while the method of the present invention shows a bromine number of only about 80.

11- Next, the present invention will be explained in more detail with reference to Examples.

Example 1 (1) First thermal decomposition step Container 1: 'Sonkerbov 21.4% by weight vacuum residual oil was charged into a reactor equipped with a stirrer, nitrogen gas was blown from the bottom of the reactor, the reaction temperature was 420°C, The thermal decomposition reaction was carried out under the conditions that normal pressure was employed as the reaction pressure and the reaction time was 30 to 1.20 minutes. The results are shown in Table 1.

Table 1 12- Next, regarding the pyrolysis residue, its fixed carbon content (a),
Examining the relationship with the viscosity of the residue at 350°C, it is found that when the fixed carbon content is 45% or less, the viscosity of the residue is at most 30 centipoise, but when the fixed carbon content exceeds 50%, the viscosity increases rapidly and the fixed carbon At 55% content, viscosity is 20
0 centipoise and 2 at fixed carbon content of 60 LIO.
．． It reaches up to 000 centipoise. Therefore, in order to obtain a pyrolysis residue with low viscosity and easy handling, the fixed carbon content should be 45% or less, and in the case of the present invention, the fixed carbon content of the pyrolysis residue from the first pyrolysis step is 30 to 30%. A selection in the range of 45% is advantageous.

(2) Second pyrolysis step The pyrolysis residue of the door 3 obtained in the first pyrolysis step is fluidized by steam at a reaction temperature of 600°C and normal pressure to obtain a particle size of 04 to 0.6 m. Thermal decomposition was carried out by spraying it onto a solid-gas fluidized bed consisting of solid particles (alumina particles). The results are shown in Table 2.

13- Table 2 Example 2 Conradson Case 2254% by weight vacuum residual oil was charged into a reactor, and steam was blown into the reactor from the bottom. first,
The first thermal decomposition was performed under the conditions of the reaction temperature of 420° C. and normal pressure for 30 to 120 minutes. Subsequently, the reactor was thermally decomposed under the second thermal decomposition conditions, that is, the reaction temperature was raised to 600°C. The results are shown in Table 3.

14- Third Comparative Example 1 For comparison, the same starting material was directly decomposed at 600° C. without passing through the first thermal decomposition step.

As a result, the yield of gas (04 or less) was 8%, the cracked oil (aS
~540<0>C) yield of 59% and coke yield of 33% were obtained.

A comparison between <, /, 2.3 of Example 2 and Comparative Example 1 shows that the cracked oil yield is high in the case of the present invention.

Example 3 Decomposition residual oil obtained in Example 1 (2) lτ Awkward Soil 39 One Nose ξ space experiment (540°C or higher, fixed carbon 37%)
Using 100 parts by weight as raw material, in the first thermal decomposition step, it was heated to 420°C.
, decomposed for 120 minutes.

The product yield at this time was 4% for gas (04 or lower), 14% for cracked oil (05 to 540°C), and 82% for cracked residual oil (540°C or higher, fixed carbon 48%). This cracked residual oil was further thermally decomposed in a second thermal cracking step to obtain 30 parts by weight of coke.

Comparative Example 2 The same raw material (540°C or higher, fixed carbon 37%) was directly
When pyrolyzed in the pyrolysis process, 5% gas and cracked oil (05~
540℃) 17%, cracked residual oil (540℃ or higher) 66%
, 12 parts by weight of coke.

From the above, by recycling the raw material to the first pyrolysis step, 30 parts by weight of coke can be obtained in one pass, whereas in Comparative Example 2, only 12 parts by weight can be obtained. Therefore, the amount of recirculation is smaller when recycled to the first pyrolysis step than when recycled to the second pyrolysis step.

[Brief explanation of drawings]

The drawing shows an example of a 70-sheet for carrying out the invention. 15... First thermal decomposition reactor, 16... Second thermal decomposition reactor, 17... Distillation column. Patent Applicant Chiyoda Corporation Agent Patent Attorney Toshiaki Ikeura 17-

Claims (1)

[Claims] (1) When pyrolyzing heavy oil, (a) a first pyrolysis step in which the heavy oil is pyrolyzed at a temperature of 400 to 500°C; (b) pyrolysis oil is removed from the first pyrolysis step; (c) a second pyrolysis step of pyrolyzing the first pyrolysis residue at a temperature of 510 to 650°C; d) pyrolysis oil from the second pyrolysis step; (e) a step of distilling the pyrolysis oil from the first pyrolysis step and the second pyrolysis step to separate it into a distillate and a distillation residue; A method for obtaining pyrolysis oil from heavy oil, comprising the step of circulating the distillation residue to the first pyrolysis step.