JPS6355559B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for pyrolyzing heavy hydrocarbon oil by passing it through a heating zone and a soaking zone. [Prior art] Conventionally, in order to obtain light oil from heavy hydrocarbon oil such as petroleum residue oil, shale oil, and tar sand oil, heavy hydrocarbon oil was pyrolyzed by passing it through a heating zone and a soaking zone. It is known to do. In this pyrolysis method, the heating zone consists of a tubular coil, and the heavy hydrocarbon oil is heated to the pyrolysis temperature, and the pyrolysis is carried out in the soaking zone. , consists of a rigid drum with a large inner diameter, that is, a simple empty tower vessel, and this empty tower vessel is not equipped with a heating burner.
Thermal decomposition in such an open column vessel is a low-salt reaction decomposition, so the coking phenomenon is mild, and stable continuous operation is said to be about one year. However, such thermal decomposition within the vessel has the drawback that the stability of the thermally decomposed oil is poor. This is a large-diameter sky tower Bethcell,
This is due to the back-mixing flow of the hydrocarbon oil and the large distribution of residence times of the hydrocarbon oil within the vessel, resulting in the formation of material that has undergone excessive thermal history. In order to improve this drawback, a method was proposed in which multiple small-capacity Betsu cells were connected in series (Japanese Patent Laid-Open No.
65302 and JP-A-53-119903), and a method of arranging internal materials such as fillers or horizontal perforated plates inside the empty tower Betsu cell (JP-A-55-12198). I still wasn't satisfied with it.
In addition, during such thermal decomposition inside the Vessel, a large amount of coke is generated, and when the operation is stopped and a decoking operation is performed, there is no heating means such as a burner, so the decoking operation (air and steam The problem is that the decoking operation cannot be carried out (method of introducing a method to burn off coke and remove coke), and the decoking operation must be performed by input, and as a result, the decoking operation takes a lot of time and requires significant expense. It was hot too. [Objective] It is an object of the present invention to overcome the above-mentioned drawbacks of the conventional methods when pyrolyzing heavy hydrocarbon oil by passing it through a heating zone and a soaking zone. [Structure] According to the present invention, when a heavy hydrocarbon oil is thermally decomposed by passing through a heating zone and a soaking zone, the heating zone and the soaking zone are each configured with a tubular coil, and the soaking zone is The length/inner diameter ratio of the constituting tubular coil is 100 or more,
The flow of heavy hydrocarbon oil passing through both zones is maintained in a substantially piston flow state, and the heating zone is maintained at a zone outlet temperature of 380 to 520°C and a residence time of 20 minutes or less, and the soaking zone is maintained at a zone inlet temperature. temperature
The heating zone was operated under the conditions of 380 to 520°C, liquid linear velocity of 0.5 to 10 m/sec, and residence time of 2 to 60 minutes to determine the lightening rate _P1 of the heating zone relative to the total lightening rate Pf of heavy hydrocarbon oil. A method for thermally decomposing hydrocarbon oil is provided, which is characterized in that the ratio P ₁ /Pf is maintained at 1/2 or less. In the present invention, since both the heating zone and the soaking zone are constructed from tubular coils, the heavy hydrocarbon oil flows through the heating zone and the soaking zone in a fluid state that is considered to be a piston flow, and undergoes a thermal decomposition reaction during that time. Therefore, it is possible to obtain a thermally decomposed oil with good stability without the disadvantages caused by back mixing seen in the conventional method as described above. The heating zone in the present invention consists of a tubular coil, in which the heavy hydrocarbon oil is heated to its thermal decomposition temperature, usually 380-520°C, preferably
It is rapidly heated to a range of 420-480℃. In this case, the pressure is 1 to 250 Kg/cm ² G, preferably 5 to 200
Kg/cm ² G, residence time [coil volume (m ³ )/liquid flow rate (15°C) (m ³ /min)] is usually 20 minutes or less,
Thermal decomposition in the heating zone is limited as much as possible. The temperature and residence time in this heating zone are determined by the lightening rate
It is preferable to select P ₁ so that it is equal to or less than 1/2 of the lightening rate of the produced oil obtained from the soaking zone, that is, the final lightening rate Pf. In this case, the lightening rate P ₁ in the heating zone is defined as follows. P ₁ = (1-B/A) x 100 P ₁ : Lightening rate of heating zone (%) B: Weight of fraction of 538°C or higher in oil produced from heating zone A: 538°C in feedstock oil Weight of the above fraction In the present invention, the heating zone is, as described above,
The heating furnace used in this heating zone is compact because it is implemented to suppress coking in the heating tube, the residence time is short, and the heat flow rate can be increased. In addition, introducing high-temperature steam or a gaseous substance such as hydrogen into this heating furnace increases the liquid flow rate in the pipe and reduces the hydrocarbon partial pressure, which has a more favorable effect in suppressing the coking phenomenon. be done. The ratio of this gaseous substance to the raw material oil is 50 to 2000 N/, preferably 100 to 500 N/. The product oil obtained from the heating zone is introduced into the soaking zone where it is pyrolyzed. In the case of the present invention, this soaking zone is composed of a tubular coil, and in this case, the tube diameter (inner diameter) of the tubular coil of this soaking zone is generally the same as the tube diameter (inner diameter) of the tubular coil of the heating zone. diameter or larger diameter is selected. The linear velocity of the liquid hydrocarbon oil within this tubular coil is preferably in the range of 0.5 m/sec to 10 m/sec, preferably 1.5 m/sec to 5 m/sec.
A liquid linear velocity below this range is undesirable because the kinetic energy of the fluid is small and the polycondensate resulting from the reaction tends to coagulate and adhere to the wall surface of the reaction tube.
A liquid linear velocity greater than the above range significantly increases the pressure loss within the reaction tube and is not practical. Note that the liquid linear velocity is expressed by the following formula. R=l/ρ×A R: Liquid linear velocity (m/sec) l: Hydrocarbon oil supply amount (Kg/sec) ρ: Density of hydrocarbon oil at 15°C (Kg/m ³ ) A: Interruption of flow in the pipe Area (m ² ) Length of tubular coil making up the soaking zone/
The inner diameter ratio (L/D) is preferably 100 or more. The inlet temperature in this soaking zone is between 380 and 520
The temperature is preferably controlled within the range of 420 to 480°C. In this case, if the temperature is lower than 380°C, the decomposition rate is very low and it becomes uneconomical, and if the temperature is higher than 520°C, coking is extremely likely to occur as described above. In conventional empty column Betssel type soaker decomposition, the soaker outlet temperature is lower than the inlet temperature by at least about 20°C. This temperature reduction naturally varies depending on the raw material oil properties and cracking severity. Therefore, in the conventional empty column Betssel type soaker decomposition, control of decomposition severity is complicated.
The outlet temperature of the heating zone and the residence time in the soaker (vessel) must be adjusted. but,
Controlling the exit temperature of the heating zone is difficult due to the large capacity of the heating furnace burner, and in particular local fine adjustment is difficult. On the other hand, the residence time in the soaker can be adjusted by adjusting the pressure at the soaker outlet or by adjusting the liquid level at the gas-liquid interface, but in the former case the adjustment range is small, and in the latter case the liquid level None of these methods can be said to be advantageous because the reliability of the interface detector is problematic. The pyrolysis reactor (soaker) used in the soaking zone of the present invention is composed of a tubular coil as described above, and this reactor is equipped with a heating means such as a burner as a decoking burner, and this heating means is It can advantageously be used for temperature control purposes in the soaking zone. In this case, the capacity of the heating means attached to this soaking zone is sufficient to be about 20% of the capacity of the heating means of the heating zone, which sufficiently compensates for the temperature drop accompanying the thermal decomposition reaction (endothermic reaction) in the soaking zone. can do. In the case of the present invention, by adding this heating means to the soaking zone, the reaction conditions can be easily controlled, and the control can be controlled within a range of 1/2 to 2 times in terms of reaction time compared to the thermal decomposition reaction in a steady state. It can be performed. Further, since the burner attached to the soaking zone can be made independent of the heating zone, it is possible to adjust the flame temperature, and it is also easy to control the increase in the reaction tube surface temperature due to radiation. The residence time in the soaking zone has a close relationship with the reaction temperature, and for a particular feedstock, in order to maintain the same lightening rate, it is necessary to decrease the residence time as the reaction temperature increases. Although the lightening rate at which stable product oil can be obtained differs depending on the properties of the feedstock oil, the residence time in this soaking zone is
For a reaction temperature of 380-480°C, it ranges from 2 to 60 minutes, preferably from 5 to 30 minutes. If the residence time is shorter than this, high temperatures are required to obtain an economical lightening rate, making coking more likely to occur.
On the other hand, a residence time longer than the above is not practical because the length of the reaction tube becomes significantly long. The final lightening rate achieved in the present invention varies depending on the properties of the raw oil, the purpose of lightening, etc., but is generally 20 to 40%. The final weight reduction rate in this case is expressed by the following formula. Pf = (1-C/A) x 100 Rf: Final lightening rate (%) A: Weight of fraction of 538°C or higher in raw oil C: Fraction of 538°C or higher in produced oil from soaking zone Weight In the present invention, the ratio P ₁ /Pf of the lightening rate P ₁ of the heating zone to the final lightening rate Pf is 1/2 or less, preferably 1/5 to 2/5. The pyrolysis apparatus used in the present invention may have a heating zone and a soaking zone, and both zones can be placed in the same heating furnace or in separate independent furnaces. . When both zones are placed in the same heating furnace, a partition wall such as a brick wall is provided in the furnace to form two compartments, a heating burner is provided in one of the compartments, and a tubular coil is installed. The other compartment may be provided with a small heating burner and a tubular coil to form the soaking zone.
In this case, the radiant heat from the burners in the heating zone is blocked by the partition wall, and the tubular coil in the soaking zone is prevented from being directly heated by the radiant heat from the burners in the heating zone. When the heating zone and soaking zone are configured as separate devices, each zone can be formed using a tubular heating furnace. [Effects] According to the pyrolysis method of the present invention, both the heating zone and the soaking zone are configured with tubular coils, and the flow of hydrocarbon oil passing through both zones is made into a piston flow state, which is different from conventional methods. The disadvantages of Betssel-type soaker cracking can be overcome, and a stable and high quality pyrolysis product oil can be obtained. The thermal decomposition method of the present invention is applied to various heavy hydrocarbon oils, such as petroleum vapor distillation residue oil, vacuum distillation residue oil, sier oil, tar sand oil, coal liquefied oil, etc. [Example] Next, the present invention will be explained in more detail with reference to Examples. Example A Middle Eastern vacuum residue oil having the properties shown below was used as a raw material oil. Table-1 Specific gravity (d15/4℃): 1.0404 Viscosity (cp) (100℃): 8800 Conradson residual carbon content (wt%) (CCR): 23.1 Heptane insoluble content (wt%): 12.6 Toluene insoluble content (wt%) ): 0.01 or less The raw material oil described above was introduced into a heating furnace having a tubular coil and heated there, and then introduced into a heating furnace (soaker) having another tubular coil, where it was thermally decomposed. In this case, the tube diameters of the heating furnace and the tubular coil used in the soaker are the same, both having an inner diameter of 4 mm, and the length of the tubular coil used in the heating furnace is 200 cm, and the length of the tubular coil used in the soaker is 4 mm. The length of the tubular coil is 300cm. The experimental conditions and results are shown in the table below. Note that Examples No. 1 and No. 2 show the results when no decoking burner was used. Also, examples
No. 2 shows the result of supplying raw material oil together with hydrogen, increasing the flow rate of the raw material oil in the pipe, and suppressing polycondensation due to hydrogen. Comparative Examples 1 to 4 The feedstock oils shown in the examples were thermally decomposed using only a heating furnace (No. 1) and using a combination of a heating furnace and a soaker consisting of an empty column vessel (No. 2). Ivy. In addition, in these Comparative Examples No. 1 and No. 2, the raw material oil was supplied together with hydrogen to perform thermal decomposition, respectively (No. 3 and No. 4). These experimental conditions and results are shown in Table 2.

【table】

[Table] In Table 2 above, the thermal stability was measured by the thermal decomposition test method ASTM D1661, and the evaluation criteria are as follows. 1...Stable 2...Slightly stable 3...Unstable From the test results in Table 2, in the case of the present invention, the thermally decomposed oil obtained suppresses the formation of toluene-insoluble components of polycondensation compounds that are the cause of sludge formation. It is clear that the stability is excellent.

Claims (1)

[Claims] 1. When a heavy hydrocarbon oil is thermally decomposed by passing through a heating zone and a soaking zone, the heating zone and the soaking zone are each constituted by a tubular coil, and the length of the tubular coil constituting the soaking zone is The inner diameter ratio is set to 100 or more, the flow of heavy hydrocarbon oil passing through both zones is maintained in a substantially piston flow state, and the heating zone is controlled at a zone outlet temperature of 380 to 520°C and a residence time of 20 minutes or less. The soaking zone was operated under the conditions of zone inlet temperature of 380 to 520°C, liquid linear velocity of 0.5 to 10 m/s, and residence time of 2 to 60 minutes, and the total lightening rate of heavy hydrocarbon oil was determined.
Ratio P ₁ / of the lightening rate P ₁ of the heating zone to Pf
A method for thermally decomposing hydrocarbon oil, characterized by maintaining Pf at 1/2 or less.