JPS6246594B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coking method capable of producing product coke of good quality from raw material heavy oil of various properties. Delayed coking equipment is widely used to obtain coke from petroleum-based or coal-based heavy oil. Generally, this delayed coking equipment basically consists of a heating furnace for raw material heavy oil and two or more coking tanks installed in parallel with each other, which are connected in series in this order. The raw material heavy oil is heated by a pump, and when it reaches a thermal decomposition temperature of 450 to 500℃, it is sent to one of the coking tanks and retained for a relatively long time, and the heavy oil is stored inside the coking tank. The delayed coking method is carried out by accumulating coke produced by the cracking of coke and distilling the cracked oil from the top. However, one problem with this delayed coking method is that high-quality coke cannot be obtained from materials other than raw material heavy oil with limited properties. For this reason, several techniques have been proposed for producing high-quality coke from a variety of raw material heavy oils. Such technology involves, for example, subjecting petroleum-based heavy oil to appropriate thermal decomposition in advance using a pyrolysis device, and then producing a blended oil using the resulting tar as a raw material or as part of the raw material in a coking tank. (Japanese Unexamined Patent Publication No. 49-33901, etc.), a method using clarified oil from a catalytic cracker as a blending raw material (Japanese Patent Publication No. 35-33901, etc.)
No. 18176, etc.), a two-stage coking tank is used in series, with inferior coke produced from early coking components in the feedstock oil being produced in the first stage tank, and remaining oil is removed in the second stage tank. Method for producing high quality coke from minced water (Japanese Patent Application Laid-open No. 1989-89902)
and so on. The former two methods belong to the range of raw material selection or pretreatment in the delayed coking method, while the latter focuses on the removal of inferior components in the raw material oil, and in any case, it is widely used to It can be said that this technology is characterized by adjusting the composition of oil. In a broad sense, the present invention can be said to relate to technology for adjusting feedstock oil, but by relatively simple modification of equipment, the operating range of reaction conditions can be expanded and high-quality coke can be produced from feedstock oils of various qualities. The aim is to provide technology to In conventional delayed coking equipment, a fluid heated to a predetermined temperature by a heating furnace is simply transferred to an insulated coking tank. Moreover, the coking tank requires a huge volume in order to proceed with the desired thermal decomposition and coking, and it is virtually impossible to heat and control the temperature of such a huge coking tank. Therefore, the temperature of the coking bath is only maintained at a natural temperature that balances the amount of heat introduced by the fluid heated in the furnace. That is, the temperature of the coking bath depends only on the furnace outlet temperature. Of course, there are other operating variables such as the flow rate and pressure of feedstock oil, but in actual industrial manufacturing, the operating range is limited to an extremely narrow range due to design constraints, and it is difficult to improve the quality of product coke. Not free enough to be effective. On the other hand, as a result of many years of engaged in coke production and repeated research, the present inventors have found that product coke quality is determined not only by the temperature conditions in the coking tank but also by the initial coking or pyrolysis conditions of the feedstock oil, especially the heating It was discovered that the pyrolysis conditions from the furnace to the coking tank have a very significant influence. In other words, they have discovered that it is possible to control coke quality by controlling the preliminary thermal decomposition conditions, rather than by controlling the reaction conditions in the coking tank, which are difficult to control. Moreover, since the preliminary pyrolysis step is accomplished in a relatively short time, its control is significantly simpler than in huge coking tanks. The method for coking heavy oil according to the present invention is based on such knowledge, and more specifically,
The process of introducing raw material heavy oil into the heating area and raising the temperature to the pyrolysis temperature.The heated heavy oil is introduced into the intermediate heat treatment area and is maintained at a pressure equal to or higher than that of the next coking process. The method is characterized by comprising a step of pre-pyrolyzing heavy oil by controlling the temperature, and a step of obtaining coke by introducing the pre-pyrolyzed heavy oil into a coking region and heat-treating it. be. Hereinafter, the present invention will be explained in more detail based on the drawings. The drawing is a layout diagram of each part of the coking apparatus used in the present invention. This device includes a heating furnace 1, an intermediate tank 2, a pair of coking tanks 3a arranged in parallel,
3b, the fractionating column 4 is connected in this order to the pipes 12, 23,
34, which are connected almost in series. Further, a raw material supply pipe 5 is connected to the heating furnace 1 from a raw material heavy oil tank (not shown), and a circulation pipe 41 from the bottom of the fractionating column 4 is connected to this pipe 5. Further, a superheated steam introduction pipe 6 is connected to the lower part of the intermediate tank 2, and a cooling oil introduction pipe 7 is connected to the upper part thereof, and furthermore, a pressure control valve 8 is provided at the outlet pipe of the intermediate tank 2. The volume of the intermediate tank 2 is equal to that of the coking tank 3a.
Alternatively, about 1 to 5% of the volume of 3b is appropriate. A typical operating mode of the above device will be explained. First, raw material heavy oil consisting of petroleum-based normal pressure or vacuum direct distillation residue oil, pyrolysis residue oil, coal star, etc. is supplied from piping 5, and heated to 450 to 500°C through heating furnace 1. , into the intermediate tank 2, where preliminary thermal decomposition is performed for a residence time of about 100 to 300 seconds. At this time, if the outlet temperature of the heating furnace 1 is too low for the raw material oil type used, superheated steam or the like is introduced from the pipe 6 to heat the contents, and if it is too high, the contents are heated. Cooling oil heated to a lower temperature is introduced to cool the contents. In this way, temperature control is performed again in the intermediate tank 2 instead of the outlet temperature of the heating furnace 1.
Once the factors such as the capacity of the heating furnace 1 and the heating pattern are set for the standard oil type, they cannot be changed accordingly even if the raw oil type changes.
This is because ideal preliminary thermal decomposition conditions may not be adopted using only the heating furnace 1. Furthermore, the pressure in the intermediate tank 2 is controlled to 5 to 30 Kg/cm ² G, which is equal to or higher than the pressure in the coking tanks 3a and 3b, by opening and closing the control valve 8. As shown in the example below, it was found that increasing the pressure for preliminary pyrolysis within a certain limit is advantageous for improving the quality of coke product (see example below). Controlling the pressure not only adjusts the pressure as a pre-pyrolysis reaction condition, but also has the effect of adjusting the residence time in the intermediate tank 2. In addition, since the volume of the intermediate tank 2 is significantly smaller than that of the coking tanks 3a and 3b, the same initial pyrolysis pressure can be applied to the coking tank 3.
Carrying out the process in intermediate tank 2 instead of in a and 3b is far more advantageous in terms of the economics of the device as a pressurized container. The heavy oil subjected to the initial pyrolysis treatment in the intermediate tank 2 is
Similar to the normal delayed coking method, the coking process is further carried out in coking tanks 3a and 3b. That is, the heavy oil from the intermediate tank 2 is transferred to the pipe 23.
After that, it is charged from the bottom into one of the coking tanks 3a and 3b, for example 3a, and is further subjected to thermal decomposition and coking treatment while being held in the tank 3a for a total of 24 to 48 hours while gradually increasing its amount. When tank 3a is almost full, transfer the heavy mass to tank 3b.
to be introduced. On the other hand, in the tank 3a, thermal cracking and coking continue for a while, and the cracked oil is introduced into the fractionating column 4 from the pipe 34, and is cracked from the top and intermediate stages via pipes 9a, 9b, 9c, etc. In addition to recovering gas or product light oil,
From the bottom of the tower, heavy oil is circulated upstream of the heater 1 through a pipe 41. After holding the coke in the tank 3a for a required period of time, the tank 3a is opened and the product coke produced is recovered. Although preferred embodiments of the device used in the present invention have been described above, various modifications are possible within the scope of the present invention. For example, in the above example, additional heating and cooling means are provided in the intermediate tank 2, but this may be either heating or cooling means, and the heating and cooling may be indirect heat rather than direct heat exchange. It may also be through exchange. Furthermore, the intermediate tank 2 may have any shape or structure as long as the above objective is achieved. Therefore, in addition to the above-mentioned tank type, there may be a tubular type or a type in which a tube is arranged in a coiled manner. As mentioned above, according to the present invention, it is possible to follow various changes in feedstock heavy oil by simply modifying a conventional delayed coking unit by providing an intermediate tank equipped with independent pressure and temperature control means. This makes it possible to set optimal initial pyrolysis conditions and improve the quality of product coke obtained from the same raw material heavy oil. Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 Heating furnace 2 equipped with a heating tube with an inner diameter of 3 mm and a length of 9 m
A coking plant on a pilot plant scale was constructed, consisting of a base, an intermediate tank with an internal volume of 2 connected to this heating furnace, and a coking tank with an internal volume of 80 connected to this intermediate tank. This intermediate tank had a high temperature steam supply device as a heating means, a quenching oil supply device as a cooling means, and a control valve as a pressure control means. Table 1 shows the properties of the raw material heavy oil used. Note that the raw material heavy oil shown in Table 1 was also used in Example 2 and Comparative Examples 1 and 2 below.

[Table] 200g/200g of raw material heavy oil with these properties
Table 3 shows the results of delayed coking performed under the conditions shown in Table 2 by supplying the material to the heating furnace at a rate of 10 minutes. Example 2 Delayed coking of feedstock heavy oil was carried out under the conditions shown in Table 2 in the same manner as in Example 1 except that the intermediate cracking tank pressure in the intermediate tank was changed, and the results are shown in Table 3. Comparative Example 1 A pilot plant similar to Example 1 was constructed except that an intermediate tank was not provided, and Table 2 was prepared in the same manner as Example 1.
Delayed coking of raw material heavy oil was carried out under the conditions shown in Table 3, and the results are shown in Table 3.

【table】

[Table] Looking at the results in Table 3, it can be seen that Examples 1 and 2, in which initial thermal decomposition was performed under pressure in intermediate tank 2, had the optimum conditions for the raw material oil used as a normal delayed coking method. Compared to the comparative example carried out in
It can be seen that high-quality coke with an improved apparent specific gravity and a small coefficient of thermal expansion was obtained as a product coke. Comparative Example 2 Using the pilot plant of Comparative Example 1, which does not have an intermediate tank, delayed coking of feedstock heavy oil was carried out at a heating furnace temperature of 490°C and a coking temperature of 460°C. 5Kg/ ^cm2
The pressure was increased from G to 7 Kg/cm ² G. The coke obtained has an apparent specific gravity (g/cm ³ ) of 1.25 and an apparent specific gravity of 2.0
had CTE. This shows that coke with good properties cannot be obtained simply by increasing the pressure in the coking tank without providing an intermediate tank.

[Brief explanation of the drawing]

The drawing is a layout diagram of each part of a coking apparatus according to an embodiment used in the present invention. 1... Heating furnace, 2... Intermediate tank, 3a, 3b...
Coking tank, 4... Fractionation tower, 6... Superheated steam piping, 7... Cooling oil piping, 8... Pressure control valve.

Claims (1)

[Claims] 1. A step of introducing raw material heavy oil into a heating region and raising the temperature to a pyrolysis temperature, and introducing the heated heavy oil into an intermediate heat treatment region, which is equivalent to or equivalent to the next coking step. The process consists of a process of pre-pyrolyzing heavy oil by controlling the temperature while maintaining a high pressure, and a process of obtaining coke by introducing the pre-pyrolyzed heavy oil into a coking area and heat-treating it. A method for coking heavy oil, which is characterized by: 2 The pressure in the intermediate heat treatment region is 5 to 30
Kg/cm ² G. 3. The method according to claim 1, wherein the residence time of the heavy oil in the intermediate heat treatment region is 100 to 300 seconds.