JPH0598267A - Method of controlling stably feeding solvent in coal liquefaction process - Google Patents

Abstract

PURPOSE:To provide the title method comprising using an improved valve which can be used as a level control valve of a high-pressure tank or the like and in such a case can be prevented from being stopped by the solid matter contained in a solvent in a coal liquefaction process in which coal is liquefied under high-temperature high-pressure conditions. CONSTITUTION:The title method comprises using a valve having a short valve plug with a cut lower end as a level control valve of a high-pressure tank in a coal liquefaction process ad thereby fully opening the valve when it is stopped with solid matter. Although this valve keeps an ordinary Cv (valve capacity) at an ordinary degree of opening, the clearance between its seat ring and the lower end of the plug increases when the degree of opening exceeds a given value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquefaction reaction of coal carried out in the presence of high-temperature hydrogen under high pressure and a part of the solvent obtained by the liquefaction reaction of coal under high temperature and high pressure. In a coal liquefaction process that circulates and uses this solvent, the present invention relates to a method for controlling the stable supply of solvent by modifying the liquid level control valve of each tank that requires a minute flow rate control, Also in the field, it can be widely applied to a process that requires control of a small amount of liquid flow rate under high pressure.

[0002]

2. Description of the Related Art A coal liquefaction method in a coal liquefaction process is a method in which a slurry prepared by mixing coal and a solvent is mixed with hydrogen under high temperature and high pressure in the presence of a catalyst to effect hydrocracking. After depressurizing the obtained solvent, liquefied oil such as light oil, medium oil, heavy oil is produced from this.

Of the liquefied oils thus obtained, heavy oils are obtained by carrying out a solvent hydrogenation reaction by adding hydrogen at high temperature and high pressure in the presence of a catalyst in the solvent hydrogenation reaction step. After depressurizing the solvent, it is circulated as a circulating solvent in the liquefaction reaction step and used as a solvent for preparing a coal slurry.

[0004]

In each of these steps, high temperature (300 to 450 ° C.) and high pressure (10
It is indispensable to stably supply the solvent to each high-pressure tank at a pressure of 0 to 200 kg / cm ² ) using a liquid level control valve in order to carry out the continuous operation of the coal liquefaction process.

However, the liquid level control valve of each high-pressure tank has an extremely small flow rate (5 to 200
Since it is necessary to control the flow rate in the state of (kg / hr), it is unavoidable that the clearance between the liquid level control valve plug and the seat ring is made small and the valve capacity (hereinafter referred to as the C _v value) is made small.

On the other hand, in each reaction step, in order to remove unreacted coal particles contained in the solvent, solids such as exfoliated material from the liquefaction reaction tower, and scattered sludge from the vacuum distillation tower, each tank and coal are removed. Although the solids are removed by a strainer before and after the slurry supply pump, the solvent supply pump, etc., it is impossible to completely remove the solids.

As a result, these solids block the minute gaps in the liquid level control valve of each tank of the high-pressure system, making it impossible to continue the stable supply of the solvent and often stopping the operation. It was Therefore, it has been necessary to modify the liquid level control valve and to control the flow rate based on the modification so that the solvent supply failure due to these solids does not occur.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to improve the above-mentioned problems, and as a result, as a result, the solid matter is liquid A method for controlling the stable supply of a solvent by modifying the liquid level control valve and controlling the flow rate based on the modification so that the blockage of solid matter can be released immediately without stopping the operation even if the surface control valve is blocked. Devised.

That is, the present invention relates to a liquid level control valve for a high pressure system, which requires a stable small flow rate in a coal liquefaction process in which a coal liquefaction reaction and a solvent hydrogenation reaction are performed under high temperature and high pressure. This is related to remodeling and accompanying flow rate control.For the liquid level control valve of high-pressure tanks, use a valve with a valve plug with a short tip and a short length. It is characterized by doing.

[0010]

The function of the present invention will be described in detail below together with its function.

The coal used in the present invention is lignite, lignite, subbituminous coal or bituminous coal usually used for coal liquefaction.

The solvent used in the present invention means a solvent consisting of light oil, medium oil, heavy oil, which is produced in the coal liquefaction reaction step under high temperature and high pressure using a catalyst, and the heavy oil. It is a hydrogenation solvent obtained by hydrogenating a part of a heavy oil in a solvent hydrogenation process under high temperature and high pressure.

FIG. 1 shows the flow of the coal liquefaction process. The raw material coal is usually pulverized by the pulverizer 1 in consideration of the properties of the coal slurry, the reactivity of coal liquefaction, etc. so that the yield of 100 mesh or less is 80% or more.

The crushed coal is mixed with a circulating solvent for coal liquefaction in the slurry adjusting tank 2 to form a slurry. The slurry concentration is usually adjusted in the range of the solvent / coal ratio of about 1.0 to 3.0.

Further, in order to increase the yield of liquefied oil from coal, iron-based disposable catalysts (synthetic iron sulfide catalyst, natural iron ore catalyst, etc.) are used, and the amount of addition is based on anhydrous ashless base material coal. 1 to 5% is preferable. In addition, sulfur may be added as a co-catalyst in order to increase the activity of the iron-based catalyst.

Subsequently, the coal slurry is reacted with hydrogen gas in the liquefaction reaction tower 3 kept under high temperature and high pressure for a predetermined time to cause a hydrocracking reaction. The conditions for hydrocracking are a temperature of 430 to 470 ° C. and a pressure of 150 to 170.
place in kg / cm ^2, the liquefaction reaction of raw coal progresses by such decomposition reaction.

The product after the reaction is separated into gas, water and oil by the high temperature separator 4, the medium / low temperature separator 5 and the oil / water separator 6. Of the separated oils, light oil and medium oil are separated by the distillation facility 7 and recovered as predetermined product oils.

The heavy oil is vacuum-distilled in the vacuum distillation facility 9 through the slurry vacuum tank 8 and the distillation facility 7, and the one having a boiling point fraction of 538 ° C. or higher is discharged out of the system as a liquefaction residue.
Here, the flow rate control between the high temperature separator 4 and the slurry decompression tank 8 is controlled by the liquid level control valve 10. The flow rate of the medium / low temperature separator 5 and the oil separated by the oil / water separator 6 via the medium / low temperature separator 5 are controlled by a liquid level control valve 11.

Of the liquefied oils obtained, the heavy oils are:
The hydrogen donating property is enhanced by reacting with hydrogen gas in a fixed-bed solvent-hydrogen reaction tower 12 of a fixed bed, which is kept under high temperature and high pressure and is filled with a catalyst, for a predetermined time to enhance the hydrogen donating ability, and this is a circulating solvent. Is circulated to the slurry adjusting tank 2 for use.

In the operation of these circulation systems, the liquid level control valve is often clogged by solids, and at that time, the operation is temporarily stopped and the liquid level control valve is disassembled and cleaned. I had to do it.

The solid matter generated in the system includes liquefaction reaction tower 3
The unreacted coal particles generated when the liquefaction reaction is carried out in the liquefaction process, and the sludge component that has been peeled off after adhering to the liquefaction reaction tower 3 and the chlorine component and the nitrogen component contained in the coal react under high temperature and high pressure. This corresponds to ammonium chloride crystals generated thereby, a liquefaction residue mixed in the solvent hydrogenation reaction system from the top of the vacuum distillation column when a bumping phenomenon occurs in the vacuum distillation column, and the like.

In order to remove these solids, the preparation process at the start of operation and the inside of the system at the end of operation are cleaned, and strainers are installed before and after each tank and each solvent supply pump.

However, 100% of these solids
It was impossible to completely remove it, and the solid level that was not removed frequently caused the liquid level control valve to be blocked.

The present inventors have solved these problems,
As a result of various studies on the modification of the liquid level control valve that can release the blockage of the liquid level control valve without stopping the operation and the flow rate control based on it, even when the sludge is blocked while securing the required flow rate in steady operation, The inventors have invented a valve remodeling method and a flow rate control method that can immediately remove the blocked solid matter by fully opening the valve.

FIG. 2 is a schematic view of a typical liquid level control valve used in the present liquefaction process, and FIG.
Shows a schematic view of the liquid level control valve plug for two types A and B. Since the liquid level control valve used in a high-pressure system has a very small flow rate in a steady state, the valve capacity (C _v value) is very small, and the foreign matter having a slightly large particle size is blocked.

Table 1 shows the specifications of a typical liquid level control valve. A high-pressure liquid level control valve functionally needs to control a fluid whose flow rate is extremely small under high pressure, so simply increasing the clearance between the valve and the guide will block the valve due to solid matter. Even if it can be prevented, it is impossible to perform flow control of a predetermined minute flow rate.

That is, it is necessary to remodel the device so that it is possible to deal with a blockage while ensuring a predetermined C _v value. The present inventors have invented the following modification method in consideration of the above problems.

That is, although the C _v value is the same at a normal valve opening, the tip of the valve plug is cut so that the clearance with the seat ring becomes larger at a certain opening or more, and the length of the plug is increased. Shortened.

FIG. 4 shows a method of remodeling the valve. In the valve structure before the remodeling, depending on the type and particle size of the solid matter, even if the valve opening is fully opened when the obstruction due to the solid matter occurs, It is not possible to remove the clogged solids, so the solids had to be removed by shutting down and dismantling and cleaning the valve.

In the structure of the valve after the modification, when the solid matter is clogged, the valve control mode is changed from automatic operation to manual operation and the valve is fully opened to increase the clearance between the valve plug and the seat, thereby closing the solid matter. By flowing out, the blockage can be immediately released without stopping the operation.

That is, while securing the flow rate in the steady state, when the blockage due to solid matter occurs, the control mode is changed from automatic to manual and the valve opening is fully opened to release the blockage of solid matter. Is.

By the modification according to the present invention, it becomes possible to release the blockage of the solid matter, and it is possible to avoid the shutdown of the liquefaction plant due to the blockage trouble.

[0033]

EXAMPLES Next, the method of the present invention will be described more specifically by way of examples.

[0034]

Example 1 The liquefied oil separated by the high temperature separator 4 in FIG.
Although decompression treatment is performed from g / cm ² to normal pressure, the clearance between the liquid level control valve and the valve plug is 161 μm even when fully opened due to the small flow rate, and unreacted coal and liquefaction reaction in the liquefaction reaction tower 3 The solid matter peeled off from the tower wall of the tower 3 often caused clogging trouble.

With the introduction of the method of the present invention, the number of clogging troubles became zero. As a result, it was possible to avoid an increase in costs for dismantling and cleaning the liquid level control valve during operation, stopping operation, and restarting operation (see Table 2).

[0036]

Second Embodiment The liquefied oil separated from the high temperature separator 4 by the medium / low temperature separator 5 is separated via the oil / water separator 6. The clearance of the liquid level control valve 11 that controls the flow rate of the liquefied oil separated through the oil-water separator 6 is 12.5 μm even when fully opened, and the unreacted coal in the liquefaction reaction tower 3 and the tower wall of the liquefaction reaction tower 3 Occasionally, a clogging trouble occurred due to the solid matter peeled off from.

With the introduction of the method of the present invention, the number of clogging troubles became zero. As a result, it was possible to avoid an increase in costs for dismantling and cleaning the liquid level control valve during operation, stopping operation, and restarting operation (see Table 2).

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

By modifying the liquid level control valve and utilizing the flow rate control method of the present invention, it can be applied to all liquid level control valves that need to prevent solids from being blocked while controlling a minute flow rate under high pressure. it can.

Further, in a chemical plant other than the coal liquefaction process as well, it is a method applicable to a place where solid matter generation is predicted under high pressure and fine flow rate control is required.

[Brief description of drawings]

FIG. 1 is an overall flow diagram of a coal liquefaction process.

FIG. 2 is a schematic view of a liquid level control valve. Type A is a liquid level control / let down valve (ON-
(OFF type), Type B is a liquid level control valve.

FIG. 3 Control valve (Type A and Type B)
FIG.

FIG. 4 is an explanatory diagram showing an example of a method for modifying the liquid surface control valve according to the present invention. (A) shows that the sludge does not flow before the modification, and (B) shows that the plug completely comes out of the valve seat and the sludge flows out after the modification.

[Explanation of symbols]

 1 Crusher 2 Slurry adjustment tank 3 Liquefaction reaction tower 4 High temperature separator 5 Medium / low temperature separator 6 Hot water separation 7 Distillation equipment 8 Slurry decompression tank 9 Decompression distillation equipment 10 Liquid level control valve 11 Liquid level control valve 12 Solvent hydrogenation reaction Tower

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Kato Kimitsu, Kimitsu No. 1 Kimitsu, Nippon Steel Co., Ltd. Kimitsu Tsu Works (72) Inventor Yoshiaki Doi Kimitsu, Kimitsu No. 1 Nippon Steel Co., Ltd. Tsu Steel Works (72) Inventor Hisaka Yamamoto 1-6-6 Totsukahigashi, Kawaguchi City, Saitama Prefecture (72) Kenji Iguchi 7-26-1 Makuhari Hongo, Chiba City, Chiba Prefecture

Claims (1)

[Claims] 1. Coal, a coal liquefaction solvent, and a coal liquefaction catalyst are mixed to form a slurry, and the coal slurry is pressurized and heated in the presence of hydrogen to hydrocrack to obtain a liquefied oil obtained. A coal liquefaction step of separating into a solvent and a residue, and in the presence of a solvent hydrogenation catalyst, a part of the solvent obtained in the coal liquefaction step is pressurized, heated and hydrogenated, and then depressurized to liquefy the coal. In a coal liquefaction process that has a solvent hydrogenation process that is circulated as a solvent for use, a valve with a valve plug with a short tip and a short length is used as a liquid level control valve for high-pressure tanks A method for controlling stable supply of a solvent in a coal liquefaction process, which comprises fully opening the valve.