JPS60202191A - Refining of gas oil - Google Patents

Abstract

PURPOSE:To prepare high-purity aromatic hydrocarbons efficiently, by fractionating tar-based raw material gas oil into low-boiling, heavy oil and light oil cuts and hydrogenating a mixt. of refined light oil obtained from the light oil cut and the low-boiling cut. CONSTITUTION:A tar-based light oil fraction is fed to a preliminary distillation tower for fractionation into a low boiling cut, a heavy oil cut and a light oil cut having a boiling point of 100-145 deg.C. The light oil cut is subjected to treatment for base removal by acid extraction and neutralization with alkali to remove residual acid components. Refined light oil cut obtained by removal of remaining alkali components is mixed by confluence with the low-boiling cut and the mixt. is led into a hydrogenation reaction process, followed by distillation for refining. The preliminary distillation should pref. be performed in such a way that a low-boiling cut having a boiling point below 100 deg.C may be extracted at the top of distillation tower, a heavy oil cut having a boiling point of above 145 deg.C may be extracted at the bottom and a light oil cut may be extracted in the middle as side cut.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is directed to refining tar-based light oil obtained during coke production, that is, gas light oil derived from coke oven gas and tar light oil derived from coal tar. This article covers the refining method of gas oil used to produce aromatic products such as benzene, toluene, and xylene.

(Prior art) Gaseous light oil obtained from coke oven gas recovered during coke production and tar light oil obtained from rutal contain large amounts of useful aromatic products such as benzene, toluene, and xylene. On the other hand, it also contains impurities such as dienes, olefins, sulfur compounds, tar bases, etc. When producing aromatic products from these tar-based raw gas oils, it is necessary to separate and remove the impurities in the raw gas oil. Purification treatment is required.

The method for refining this feedstock gas oil is to first pre-distill the feedstock gas oil to remove dissolved gases such as oxygen, moisture, heavy components such as low boiling point components such as C5, and high boiling point components of C9 or higher. The components are adjusted, and then the various impurities contained in the raw gas oil are hydrogenated or hydrogenolyzed by reacting with hydrogen gas, and then heated for purification.

However, in conventional refining methods, useful tar bases such as pyridine and α-picoline are not only subjected to hydrogenation or hydrogenolysis in the hydrogenation process of raw gas oil;
An increase in hydrogen consumption occurs.

[Purpose of the invention]

The present invention was devised in view of the above points, and its purpose is to obtain a highly pure aromatic hydrocarbon product, to consume less hydrogen, and to reduce consumption of acids, alkalis, etc. The object of the present invention is to provide a light oil refining method that allows useful tar bases to be recovered easily and efficiently.

(Structure of the Invention) That is, in the present invention, tar-based raw material light oil is charged into a preliminary lid column, and the low-boiling point portion, the heavy oil surface portion, and the boiling point 100~
The light oils and fats obtained at 145°C are separated into light oils and fats, and the resulting light oils and fats are debased by pickling and extraction, then neutralized with alkali to remove residual acidic components, and then residual alkaline components are removed. This is a light oil refining method in which the purified light oil distillate obtained by removing the distilled light oil and the above-mentioned low boiling point fraction are combined and charged into a hydrogenation reaction step, and the refining cap section is performed after hydrogenation.

In the present invention, the raw material light oil is heated to a boiling point of 100°C by preliminary distillation.
The oil is divided into a lower boiling point portion, a heavy oil portion with a boiling point higher than 145°C, and a light oil and fat portion with a boiling point of 100 to 145°C. There are almost no tar bases such as pyridine and α-picoline, which are targets for recovery, in the low boiling point portion below 100℃ and the heavy oil surface fraction with a boiling point above 145℃, and almost no other tar bases are present. . In addition, if the concentration of heavy oil with a temperature higher than 145°C increases, sludge is likely to be generated when it comes into contact with an acid aqueous solution, and the acid and alkali will disappear! ! [Hanging also increases.

Pre-distillation of feedstock gas oil may be carried out using multiple lid columns, but if light oils and fats containing useful tar bases such as -pyridine and α-picoline come into contact with oxygen in the air for a long time, The generation of sludge in the debasing treatment process by pickling and extraction is increasing. Therefore, preferably, the low-boiling point portion with a boiling point lower than 100° C. is extracted from the top of the column, and the heavy oil surface portion with a boiling point higher than 145° C. is extracted from the bottom of the column, and
It is preferable to carry out this by using a lid column which is adapted to extract light fats and oils having a boiling point of 100 to 145° C. from the side cup 1 as a side cut tank. In addition, the proportions of low-boiling parts, light oils and fats, and heavy oils in the pre-distillation of raw gas oil vary depending on the composition of the raw gas oil, but the low-boiling parts are 20 to 20 parts per 100 parts of raw gas oil. 30 parts, the light fat content is within the range of 55 to 72 parts, and the heavy oil content is within the range of 8 to 15 parts.

It is better to do so.

” Debasing treatment by pickling and extraction of light oil distillates can be carried out by conventionally known methods, but it suppresses the generation of sludge, increases the recovery rate of useful tar bases, and In order to prevent equipment corrosion problems, it is preferable to recirculate a portion of the extract extracted from the lower layer of the column to the debasing treatment process and to add the required amount to this recycled extract. The free acid concentration of the extract is maintained at about 5-10% by additionally replenishing the acidic solution. In addition, 1. To mix the light oil reservoir and the extract liquid, install a line mixer such as a pipe mixer, orifice mixer, or static mixer in the piping line that charges the light oil surface into the separation column. It is better to do so. Furthermore, the light oil surface fraction and the extract are mixed and then separated into layers in a stationary separation column.
Abasic oil is extracted from the two layers, a base extract is extracted from the lower layer, and a small amount of sludge is extracted from the middle layer. In addition, in this debasing treatment step, the separation tower is preferably operated under an inert gas atmosphere such as nitrogen gas in order to reduce the chance of contact with oxygen in the air as much as possible and suppress the generation of sludge. Alternatively, by operating with full liquid, it is possible to prevent contact with oxygen and provide a head for the next process, thereby saving energy.

The upper layer of debasic oil is neutralized to remove residual acid content. Neutralization treatment is performed while avoiding contact with a caustic alkali such as NaOH or KOH or an alkaline aqueous solution such as ammonia. The concentration of this alkaline aqueous solution is not particularly limited, but if acidic components remain in the light oil distillate after debasing treatment, problems such as corrosion and decreased catalyst activity may occur in the hydrogenation process. Preferably, the alkaline content should be approximately equal to or slightly in excess of the residual acidic content.

The light oil surface fraction after the neutralization treatment is then charged to a step for separating and removing the alkaline components remaining in the light oil fraction. This residual alkaline content can be separated and removed by water washing or adsorption, but if the alkaline content remains in the hydrogenation process, it will cause a decrease in catalyst activity and corrosion of the equipment in this hydrogenation process. It is necessary to separate and remove the alkaline content, which is preferably carried out by evaporating the light oil surface content using an evaporator and separating and removing the residual oil containing the remaining alkali content.

When the above-mentioned evaporator evaporates the light oil content and separates and removes the residual alkaline content, the evaporator may be operated using steam from the preliminary lid column as the heating source in order to save energy, as will be described later. It is best to do this under as much pressure as possible, e.g.
If the preliminary lid column is operated at normal pressure, the evaporator is 300sH
Operated under reduced pressure below Q. Furthermore, although there are no particular restrictions on the reboiler for the evaporator, since contamination tends to cause a decrease in heat transfer, it is preferable to use a falling film type reboiler that has a high heat transfer coefficient and is less likely to cause a decrease in heat transfer due to contamination. Good.

The residual oil, which is recovered from the bottom of the column of the evaporated product and contains residual alkaline content, can be used as a fuel oil.
For example, benzene, toluene, xylene, etc. are charged into a water washing process to be recovered again and returned to the water washing preliminary lid tower. The water washing step carried out for this purpose is not particularly limited either, and any method may include a mixing means for mixing the residual oil and washing water, and an oil-water separation means for separating oil and water. Bye. In this water washing step, preferably "-
The water separated by the oil distribution water separation means is regenerated by the water evaporator,
In addition to using the recycled water again as washing water to reduce the amount of wastewater discharged outside the system, the heavy oil tank with a boiling point of 145°C or higher extracted from the bottom of the preliminary lid tower is used as a heat source for this water evaporator. In addition, as for the reboiler, a falling film type is used which has a high heat transfer coefficient and is less likely to cause a decrease in heat transfer due to dirt.

The purified light oil distillate after the above-mentioned residual alkali separation and removal step is combined with the low boiling point distillate taken out from the top of the preliminary lid column, and is charged into the hydrogenation reaction process. Impurities are hydrogenated or hydrogenolyzed by the method described in the following. At this time, it may be charged to the hydrogenation process together with other light oil fractions, such as aromatic-rich cracked gasoline or reformed gasoline. After hydrogenation and purification, the product is capped in a capping step to obtain purified aromatic products such as benzene, 1-toluene, and xylene.

Next, the method of the present invention will be specifically explained according to a 70-sheet according to an example of implementation.

In Fig. 1, raw gas oil is charged from line (1) to preliminary cap column (2), and low boiling point fraction with a boiling point of 100°C or less is extracted from the top of the column in this preliminary cap column (2). , heavy oil with a boiling point of 145°C or higher extracted from the bottom of the tower, and heavy oil with a boiling point of 100 to 14°C extracted from the side cut.
It is separated into a light oil fraction at 5°C.

The light oil fraction is charged from the line (3) to the fraction N1 column (4) for debasing it and recovering useful tar bases. In this abasic treated culm, the above separation tower (4
) The N111 [M extract with a concentration of 5-10% used for debasing treatment is extracted from the bottom of the column through line (5),
A part of this extract passes through the extract circulation line (7) together with the acidic liquid that is additionally replenished from the line (6), and then passes through the above line (
3), mixed with light oil reduction in a line mixer (8) installed in line (3), and charged into a separation column (4). The remainder of the extract extracted from the bottom of the separation column (4) is introduced through a line (9) to a tar base recovery step (not shown), where useful tar bases are recovered. In addition, in the PIl basin (4), the sludge generated between the debased light oil fraction in the upper layer and the extract in the lower layer is removed from the sludge extraction line (10) provided at the interface between the upper and lower layers. It is designed to be extracted continuously. Note that the separation column (4) in this debasing treatment step is operated under a nitrogen gas atmosphere or under pressure with full liquid.

The light oil reduced by the debasing treatment in the above debasing treatment process is
It is extracted from the top of the separation tower (4), charged into the neutralization tower (12) through line (11), and neutralized with an aqueous alkali solution charged through line (13). In this neutralization step, the light oil reduction and the alkaline aqueous solution are mixed in a line mixer (14) installed in the line (11),
Mak.

A part of the alkaline aqueous solution extracted from the bottom of the neutralization tower (12) is circulated from the alkaline aqueous solution circulation line (15) to the line (11), and further,
The sludge generated in the neutralization tower (12) is continuously or intermittently extracted from a sludge extraction line (16) provided in the neutralization tower (12).

The light oil □ portion after being neutralized is extracted from the top of the neutralization tower (12) and introduced into the evaporation process through the line (17). In this evaporation culm, line (17)
The light oil fraction introduced from is first charged into a falling film glue boiler (18), heated, and then evaporated! (19). This evaporator (19)
is operated under reduced pressure lower than the pre-cap column operating pressure, and the heat supply to the reboiler (18) is withdrawn from the top of the pre-cap column (2) via line (20). This is carried out by circulating a part of the low boiling point fraction with a boiling point of 100° C. or less to the reboiler (18) via the low boiling point fraction circulation line (21). Also in this evaporation step, a part of the residual oil extracted from the line (22) at the bottom of the evaporator fi (19) is circulated through the residual oil circulation line (23) to the reboiler (18), and the light oil reduction is It is intended to increase evaporation efficiency.

The refined light oil distillate evaporated in this evaporation process is evaporated! (1
9) It is extracted from the top of the column through line (24), merges with the low-boiling fraction flowing through line (20), and is charged into a hydrogenation reaction step (not shown) to undergo hydrogenation or hydrogenolysis. It is purified in one culm of the purification cap to produce aromatic products such as bempine, 1-luene, and xylene.

Furthermore, in this flow sheet, -C is the evaporated M (
The residual oil extracted from the line (22) at the bottom of the column in step 19) is introduced into the water washing process, mixed with washing water in the line mixer (25), and then charged into the oil/water #1 tank (26). Oil and water are separated, and the oil is returned to the preliminary lid tower (2) through the line (27), and the water is returned to the preliminary lid tower (2) through the line (28).
).

A part of it is transferred from the line (29) to the line mixer (25).
) and the remainder is evaporated from the line (30) with a boiler (31)! (32),
This water evaporates! (32) to be recirculated and used as washing water. , 'The produced water is re-injected into the line mixer 4J- with additional water charged from the line (34).
(25) Also, for the reboiler (31), a falling film type is used which has a high heat transfer coefficient and is less likely to deteriorate heat transfer due to dirt. The heavy oil distillate with a boiling point of 145° C. or more extracted from the bottom of the column 2> is used by being circulated through the line (33).

(Example) Gas light oil was used as tar-based light oil, and this gas light oil was purified according to the above flow sheet. The proportions of heavy oil reservoirs are 27%, 62% and 1, respectively.
It was 1%. In addition, Table 1 shows the composition of the gaseous light oil, the composition of the Zydka distillate, and the composition of the refined light oil reservoir (not shown) introduced into the hydrogenation reaction step.

Further, the impurity cans after the purification lid were as shown in Table 2. As a comparative example, a case is shown in which the lid is used as it is without being subjected to debasing treatment. The recovery rates of pyridine and α-picoline were 95% and 100%, respectively.

Table 1 Table 2 [Effects of the Invention] According to the present invention, tar-based light oil is purified to efficiently obtain aromatic products such as high-purity benzene, toluene, and xylene, and at the same time, pyridine Useful tar bases such as α-picoline and α-picoline can be easily and efficiently recovered.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet for a light oil refining method according to an example of the implementation of the present invention.

Claims (8)

[Claims] (1) Tar-based raw material light oil is charged into a pre-distillation tower and separated into a low boiling point distillation, a φ quality oil distillation, and a light oil distillation with a boiling point of 100 to 145°C, and the obtained light oil distillation After debasing by pickling and extraction, the remaining acidic content was removed by neutralization with an alkali, and the remaining alkali content was then separated and removed to obtain a purified light oil fraction and the low boiling point distillate described in 1. A method for refining light oil, which is characterized in that it is charged into a culm for a hydrogenation reaction, and then subjected to purification and distillation after hydrogenation. (2) The light oil tank is a side cut tank of the distillation tower, which extracts the low boiling point tank whose boiling point is lower than 100°C from the top of the tower, and the heavy oil tank whose boiling point is higher than 145°C from the bottom of the tower. A method for refining light oil according to claim 1. (3) The method for refining light oil according to claim 1 or 2, wherein the separation and removal of residual alkali content is carried out by washing with water or adsorption. (4) The method for refining light oil according to claim 1 or 2, wherein the separation and removal of the residual alkali content is carried out by evaporating in an evaporator C to separate and remove the residual oil containing the residual alkali content. (5) The method for refining light oil according to claim 4, wherein the side cut distillation tank is continuously processed from its debasing treatment step to its neutralization treatment step and evaporation step using an evaporator. (6) The scope of the patent claims that the flow rate control when charging the light oil reservoir after neutralization treatment to the evaporation process is performed by liquid level control and cascade control in the far-flow tank at the top of the evaporation section. The method for refining light oil according to item 5.・ (7) The light oil refining method according to any one of claims 4 to 6, wherein the evaporator is operated using discharged steam from the preliminary distillation column as a heat source. (8) The heating method of the evaporator uses a falling film or thin film evaporator.
A method for refining light oil according to any of paragraphs.