JPS5844107B2 - Method and apparatus for thermal decomposition of hydrocarbons - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for thermally decomposing hydrocarbons, particularly heavy hydrocarbons, to convert them into active ingredients such as light fuel oil and fuel gas.

Crude oil, which is the raw material for industrial fuel, often has a high sulfur content, and therefore requires treatment such as hydrodesulfurization, but fuel oil and other heavy oils contain asphaltene fractions and heavy metals such as vanadium and nickel. It cannot be desulfurized sufficiently because it contains a large amount of

Conventionally, thermal cracking methods such as hydrocracking, partial oxidation at high temperatures, and coking are known as methods for converting heavy hydrocarbons into non-polluting fuels.

However, in the case of the hydroxyl decomposition method, hydrogen consumption is enormous and complete decomposition is difficult even when operated under high pressure.

In the case of coking methods, dilate coking, fluid coking, etc. are known, but for example, in filled coking, the equipment is complicated, the residence time in a part of the coker is long, and the reactor is large. There are disadvantages such as the high sulfur content of the cracked oil and the low porosity of the coke produced, making reprocessing such as gasification difficult.

Also, in the case of the partial oxidation method, oxygen consumption is large and only low-calorie fuel gas can be produced.

As a method to improve these drawbacks, a method in which molten salts such as alkali metal salts are added during coking of hydrocarbons and gasification of produced coke is disclosed in U.S. Pat. No. 2,780.
, No. 587, No. 3,387,941, No. 3,179,
It is described in each specification of No. 584.

The invention described in U.S. Patent No. 2,780,587 involves filling a seed reactor with molten salt, feeding heavy hydrocarbons from the bottom to cause coking, and then making it fluid in the top of the reactor. This method allows coke and molten salt to be extracted, but this method does not allow sufficient contact time during coking, and it is difficult to completely extract the generated coke from the system, resulting in coke accumulating in the molten salt. In addition, excess fluidizing gas is required to create a fluidized state in the upper part of the reactor, which limits the throughput.

In the invention described in U.S. Pat. No. 3,387,941, desulfurization of coke is carried out with sodium carbonate, and in the invention described in U.S. Pat. No. 3,179,584, a coking apparatus is It is disclosed that the amount of hydrogen produced by coking can be increased by mixing raw materials with sodium carbonate.

However, these methods also have the above-mentioned problems and have not been put into practical use.

The object of the present invention is to overcome the drawbacks of these methods and provide an improved method and apparatus capable of completely treating hydrocarbons, especially heavy hydrocarbons, and converting them into useful fuel oil, fuel gas, etc. It's about doing.

Other objects of the invention will become apparent from the description below.

The present invention aims to achieve such an object, and includes a coking process in which hydrocarbons are thermally decomposed by the sensible heat of gas generated in the molten salt regeneration process in the coexistence of steam and molten salt, and a thermal decomposition process in the coking process. After separating the decomposition products from the mixing section, the recovered molten salt is brought into contact with a mixed gas such as carbon dioxide and steam generated in the molten salt decoking process to desulfurize it, and the resulting gas is supplied to the coking process for molten salt regeneration. and a molten salt decoking step in which the desulfurized molten salt containing coke from the molten salt regeneration step is contacted with oxygen or air and water vapor to remove coke and the resulting gas is supplied to the molten salt regeneration step. This is a thermal decomposition method for hydrocarbons, which consists of two steps, and is characterized in that the molten salt from the molten salt decoking step is recycled to the coking step.

Furthermore, the apparatus of the present invention includes a preheater for hydrocarbons, a molten salt container, a reactor for thermally decomposing the hydrocarbons, and a separator for separating the thermal decomposition mixture into decomposition products and recovered molten salt, The reactor has a hollow cylindrical shape and has a coking section in the upper part of the white material, a molten salt regeneration part in the middle part, and a molten salt decoking part in the lower part, and the inlet side of the coking part is connected to the preheater and the molten salt container. , the outlet sides are respectively connected to the separator, and the molten salt regeneration section has a tray provided with a slot, on which the molten salt recovered from the separator is received and the molten salt is transferred to the molten salt regeneration section. An overflow pipe was installed to guide the molten salt, an air or oxygen supply pipe and a steam supply pipe were provided in the molten salt decoking section, and a gas discharge pipe was provided at the top of the reactor to connect the bottom of the reactor and the molten salt container. This is a hydrocarbon thermal decomposition device characterized by the following.

Moreover, in the present invention, it is preferable that the caulking part is tubular.

The invention will now be explained with reference to the drawings.

The figure is a system diagram illustrating one embodiment of the present invention.

The raw material heavy oil is preheated to 200 to 420°C in a preheater 1, and steam is also entrained to prevent coking in areas where no salt exists, and molten salt is supplied from a molten salt container 2 at the inlet of the coking section. It also enters the tubular coking section 3 of the reactor 15.

The reactor 15 has a hollow cylindrical shape and has a coking section 3 in the upper part, a molten salt regenerating part 7 in the middle part, and a molten salt decoking part 10 in the lower part.

The tubular coking section 3 is externally heated by hot gas from the molten salt regeneration section 7 below, and the humidity is 450 to 600°C.
is maintained.

The raw material hydrocarbon introduced into the coking section 3 undergoes thermal decomposition in the presence of molten salt and steam. At the same time, a part of the sulfur substances contained in the raw material reacts with the molten salt and coking occurs. After sufficient retention time to accomplish the
It is led to a separator 4.

In the separator 4, thermal decomposition products such as cracked gas and cracked oil are separated from coke and molten salt.

Separated oil, cracked gas, and steam are extracted from the extraction line 5 to the outside of the reactor through a cooler 6.

These products are desulfurized to produce clean fuel oil and high strength fuel gas.

After the cracked gas, cracked oil, and steam are separated in the separator 4, the recovered molten salt, that is, the molten salt containing coke, flows down and is led to the molten salt regeneration section 7.

This reproducing section 7 is provided with a tray having a slot 8 .

Co, CO rising from the molten salt decoking section 10 below
,.

Gas such as steam is bubbled through the slot 8 into the recovered molten salt on the tray, passing through the recovered molten salt while being in gas-liquid contact with the recovered molten salt, and leakage of the recovered molten salt from the slot 8 is prevented.

Sulfur reacted with the molten salt by this CO2 and steam is converted into hydrogen sulfide and transferred into the mixed gas.

The regenerated molten salt and coke are led to a molten salt decoking section 10 through an overflow pipe 9.

In this molten salt decoking section 10, the coke dispersed in the molten salt is removed from the oxygen or air and steam supply ports 13.
The coke is completely gasified by oxygen or air from 14 and steam.

After the coke has been gasified, the molten salt is extracted from the reactor bottom 11, and a portion of the molten salt is sent to the vanadium and nickel recovery section to remove metals such as vanadium and nickel mixed into the molten salt. The salt is transported by steam or air through the lift pipe 12 to the upper molten salt vessel 2 and recycled again to the coking section 3.

Further, the coke dispersed in the molten salt in the molten salt decoking section 10 is gasified and passed through the molten salt regeneration section 7 and the coking section 3, and then from the upper part to produce low-calorie fuel gas or hydrogen. It is extracted as gas for use.

Raw materials used in the practice of the present invention include, but are not limited to, hydrocarbons, particularly heavy fractions such as heavy hydrocarbons, crude oil containing sulfur, heavy oil, and the like.

In addition, the molten salt used in the practice of the present invention has a melting point of 4
It is preferably 50°C or lower, and its viscosity is 5 to 10
One with 0 cp is most preferably used.

Examples of molten salts include alkali metal hydroxides such as NaOH and KOH, K2CO3, Na2CO3゜Li2CO3
Alkali metal carbonates such as or mixtures thereof, and in some cases alkaline earth metal hydroxides, carbonates, etc. are also used.

When these alkali metal compounds are used, they react with the sulfur compounds present in heavy hydrocarbon materials,
A part of the molten salt becomes sulfide.

The present invention provides three improved methods and equipment for the molten salt method in the production of useful fuel oil and fuel gas by thermal decomposition of hydrocarbons, as described above, and the features of the present invention are as follows: It also lies in the combination of each element, and the contents will be explained in detail next.

The first feature of the present invention resides in the coking section of the reactor.

The caulking part is, for example, taken over by a group of coiled pipes, and inside these pipes there is a
~100 cp of molten salt is allowed to flow down, and the raw material heavy hydrocarbon material is made to coexist with steam, and is sent in a spray state or liquid state into a coiled pipe in which the molten salt coexists,
The O coking reaction, so-called thermal decomposition reaction, which causes coking while the molten salt flows down the pipe, is an endothermic reaction, so the heat necessary for the reaction must be supplied.

In the present invention, as the heat required for this, the sensible heat of the mixed gas that is removed from the gasification of coke in the molten salt decoking section is used, and the sensible heat is used to heat the coiled pipe of the coking section. This provides the necessary heat for caulking.

Since the molten salt used for coking is recycled, it is necessary to regenerate the generated sulfide into the original molten salt.

This is because this sulfide contributes to an increase in melting temperature,
Furthermore, the viscosity of the molten salt increases, which impairs the flow of the substance within the coiled pipe.

Therefore, the molten salt used for coking is separated into recovered molten salt containing cracked gas, cracked oil, and coke in a separation chamber, and the recovered molten salt containing separated coke is introduced into the molten salt regeneration section of the reactor. be done.

A second feature of the present invention resides in a molten salt regeneration section having a tray structure.

Some of the molten salt becomes sulfide in the coking area, so it needs to be regenerated.

In the present invention, this regeneration section has a tray structure, and the CO2 and unreacted steam generated in the lower coke gasification section are converted into a mixture of molten salt and coke on the tray in a tray such as used in a distillation apparatus, for example. Hydrogen sulfide is generated and regenerated from the sulfide by passing it through the sulfide.

Therefore, in the regeneration section, the molten salt is regenerated using CO2 and steam in the mixed gas generated by gasification of coke, so there is no need to separately introduce a molten salt regeneration gas.

Although it is desirable that such regeneration is optionally carried out at a relatively low temperature, the regeneration temperature is preferably about 10 to 100°C since it is necessary to use the mixed gas that has passed through the regeneration section as a heat source for coking.

However, it is not limited to this. The third feature of the present invention is the molten salt decoking section.

The mixture of coke and molten salt that has passed through the molten salt regeneration section is led to the molten salt decoking section located below.

Oxygen and H2O are fed into the molten salt decoking section, and the reaction temperature is about 700-1100°C, more preferably about 850°C.
Partial oxidation is induced at ~950°C.

Normally, such partial oxidation reactions are carried out at temperatures higher than 1100°C, but when molten salts, especially alkali metal compounds, are present, they have a catalytic effect on this gasification reaction, lowering the reaction rate to that of conventional methods. It can be made about 10 to 100 times larger or more than that.

It is known that oxides of iron, nickel, etc. are also suitable for this effect of increasing the reaction rate.

The coke dispersed in the molten salt in the molten salt decoking section is gasified by the following reaction, and after passing through the regeneration section and the coking section, is taken out from the upper part of the reactor.
It is used as a fuel gas for low force 01J- or hydrogen production gas.

Here, +Q and -Q indicate exotherm and endotherm.

In this molten salt decoking section, all of the coke generated during coking is gasified, but all of the sulfur contained in the feedstock heavy oil becomes gaseous substances and is added to the lightened fuel oil. Since it exists as a simple sulfur molecule, sulfur can be recovered through a simple desulfurization process.

In addition, heavy metal substances such as vanadium and nickel remain in the molten salt, but when the molten salt is recycled, some of them are extracted and these can be easily recovered in the vanadium, nickel, etc. recovery process.

According to the present invention, a reactor including a coking section, a molten salt regeneration section, and a molten salt decoking section is used, and the coking section passes through a separator to produce fuel oil and high-calorie fuel gas. In the desalting and decoking section, low-calorie fuel gas or gas suitable for hydrogen production can be produced, and hydrocarbons can be easily converted into various active ingredients in a series of steps.

In addition, conventionally, when heavy hydrocarbons were thermally decomposed in a pipe, the inside of the pipe was clogged with produced coke, making it difficult to effectively treat the heavy hydrocarbons, but the molten salt method of the present invention Since the inner wall of the pipe is coated with the molten salt and the coke produced is dispersed within the molten salt, it is possible to extract it from the reaction system without causing coke blockage inside the pipe.

Since the coking reaction can be assumed to be a first-order reaction, a plug flow type reaction in a pipe reactor like the one of the present invention is more advantageous in increasing the final reaction rate than a complete mixing tank type like a normal seed type reactor. It is.

Furthermore, the present invention can be fully applied to heavy oils containing high amounts of asphaltene substances, sulfur, vanadium, nickel, etc., as well as raw materials containing impurities such as waste oil, and these can be converted into active ingredients. It is possible to convert.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Practical Example 1 The experiment was carried out using Gatsuchi Saran vacuum residue oil having the properties and composition shown in Table 1 as the raw material and using the apparatus shown in the above figure.

Table 2 shows the respective operating conditions in the coking section, regeneration section and decoking section.

The product yield and produced gas composition obtained as a result are shown in Tables 3 and 4, respectively, and the evaporation curve of the cracked oil is shown numerically in Table 5, The active ingredient was efficiently obtained from the raw material residue oil without any coking troubles.

Example 2 Under the same conditions as Example 1, when the humidity in the coking area was raised to 550°C, the cracked oil yield (relative to the raw material) was
is 64.2% by weight, and the cracked gas yield (relative to the raw material) is 1
The amount was 1.5% by weight.

Additionally, the equipment was able to operate without any problems.

Example 3 Operation was carried out under the same conditions as in Example 1, with a temperature of 600°C in the molten salt regeneration part and a humidity of 750°C in the gasification part.

As a result, CO2 in the gas composition of the gasification section increases and
decreased.

Additionally, the equipment was able to operate without any problems.

Example 4 A test was carried out under the same conditions as in Example 1, except that 5% by weight of sulfur hydroxide was added to the molten salt.

The cracked oil yield, cracked gas yield, and partial oxidation reaction gas yield were almost the same, and the system could be operated for a long time.

Comparative Example When the supply of molten salt to the coking section was stopped under the operating conditions of Examples 1 and 2, the coking section became clogged with coke within a few minutes, making operation impossible.

[Brief explanation of drawings]

The figure is a system diagram illustrating one embodiment of the present invention. 1... Preheater, 2... Molten salt container, 3
... Caulking part, 4 ... Separator, 5
...Extraction line, 6...Cooler, 7.
... Molten salt regeneration section, 8 ... Slot, 9
...Downcomer, 10... Molten salt decoking section, 11... Reactor bottom, 12...
... Lift pipe, 13 ... Supply port, 14.
... Supply port, 15 ... Reactor.

Claims (1)

[Claims] 1. A coking step in which hydrocarbons are thermally decomposed by the sensible heat of gas generated in the molten salt regeneration step in the coexistence of steam and molten salt, and separation of decomposition products from the thermal decomposition mixture of the coking step. After that, the recovered molten salt is brought into contact with a mixed gas such as carbon dioxide and steam generated in the molten salt decoking step to desulfurize it and the resulting gas is supplied to the coking step, and the molten salt regeneration step a molten salt decoking step which removes coke by contacting the desulfurized molten salt containing coke from the molten salt with oxygen or air and water vapor and supplies the resulting gas to the molten salt regeneration step; A method for thermal cracking of hydrocarbons, characterized in that molten salt from a coking process is recycled to the coking process. 2 The melting point of the molten salt is 450℃ or less and the viscosity is 5 to 100℃
The thermal decomposition method for hydrocarbons according to claim 1, wherein p. 3 Consists of a preheater for hydrocarbons, a molten salt container, a reactor for thermally decomposing the hydrocarbons, and a separator for separating the thermal decomposition mixture into decomposition products and recovered molten salt, and the reactor has a hollow cylindrical shape. It has a coking part in the upper part, a molten salt regeneration part in the middle part, and a molten salt decoking part in the lower part, and the inlet side of the coking part is connected to the preheater and the molten salt container, and the outlet side is connected to the separator. The molten salt regeneration section has a tray provided with slots, and an overflow pipe is installed on the tray to receive the recovered molten salt from the separator and to guide the molten salt to the molten salt regeneration section, Hydrocarbons characterized in that an air or oxygen supply pipe and a steam supply pipe are provided in the molten salt decoking section, the bottom of the reactor and the molten salt container are connected, and a gas discharge pipe is provided at the top of the reactor. pyrolysis equipment. 4. The hydrocarbon pyrolysis apparatus according to claim 3, wherein the coking part is tubular.