JPS5959787A - Dehydration of coal tar - Google Patents

Abstract

PURPOSE:To insure dehydration of coal tar under stabilized conditions, by subjecting water-containing raw coal tar to a preliminary flushing process to remove a part of water and a part of gas oil. CONSTITUTION:Crude coal tar introduced through a line 1 is passed through heat exchangers 2 and 4 for heating. It is further heated to a predetermined temperature in a heater 5 under pressure and is fed into a flushing tank 7. The heated and pressurized coal tar is flushed in the flushing tank 7, where a greater portion of volatile matters such as water and gas oil contained in it are vaporized and they are fed into the heat exchanger 2. The coal tar from the flushing tank 7 which still contained gas oil and a small amount of water is discharged through a line 15, heated to a predetermined temperature in a heat exchanger 16 and fed into a dehydrating tower 14 for separation of remaining low-boiling fractions such as water and gas oil.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dehydrating coal tar. More specifically, the present invention relates to an improved dehydration treatment method that can reliably remove water in coal tar in a stable state and eliminates the problem of sludge removal.

Coal tar is usually distilled into light oil, carpol oil,
It is fractionated into various fractions such as naphthalene oil, cleaning oil, anthracene oil, and pitch. However, coal tar usually contains 3 to 10% water, and this water causes bumping phenomena during distillation, bubbles that impede rectification, and exhibits high vapor pressure, making pressure and temperature control difficult. It is necessary to remove as much moisture as possible beforehand, not only to reduce the amount of moisture, but also to unnecessarily increase the consumption of fuel necessary for heating.

However, as a method for dehydrating coal tar, 1tli
A commonly used method is to heat tal and dehydrate it in a dehydration tower using gas-liquid equilibrium. In such dehydration, moisture is completely expelled from the liquid phase, and the column top temperature is +-1, s and 5 to 100"C in atmospheric pressure operation.
The koji is 4g, +ifl. However, if the water content in the coolant fluctuates and increases to 2% or more, the V balance of a type of azeotrope that is thought to be formed in water pots, etc. will be disrupted. Bumping phenomenon in the dehydration tower may cause problems with safe operation, such as boiling and temperature control becoming difficult. For this reason, it is desirable to reduce the water content in the tar by 1 to less than 2 as a pretreatment step in the dehydration tower. As such a pretreatment force method, a pressurized dehydration method has conventionally been adopted.

This pressurized dehydration method is;
By pressurizing and dehydrating the coal cool heated to ~I 50 "C," and leaving it to stand for about 30 minutes to 1 hour at 14i, the water in the coal cool will form into two layers due to the difference in specific gravity. This is to reduce the moisture content in the lower layer of coal cool.

However, since the pressurized dehydration tank used in the pressurized dehydration tank is a pressure vessel, it is necessary to conduct an internal open inspection once a year. In recent years, with the increase in the size of coke ovens, the amount of sludge such as coke powder and coal powder in tar has increased due to the smokeless coking method, and as a result, it is necessary to remove the sludge that accumulates in the pressurized dehydration tank. Problems arose, such as the work being complicated and requiring a long time. However, as the amount of coal tar to be processed increases, the pressurized dehydration tank requires a tank with a large capacity sufficient for retention for 30 minutes to 1 hour, so the installation area only increases. Therefore, the construction cost would be enormous. Furthermore, heavy oil is dispersed and dissolved in the water separated from the upper layer of the pressure dehydration tank, which poses problems in river water treatment, such as increasing the burden of waste liquid treatment. Furthermore, the moisture content in coal tar varies considerably and can reach around 10% in some cases. For this reason, the moisture that could not be separated in the pressure dehydration tank increases by more than 2 times, and that amount is vaporized in the heating furnace or heat exchanger in the next step, and when supplied to the dehydration tower, the gas-liquid Δ1 / Stable operation of the dehydration tower is not possible due to bumping occurring in the liquid under pressure. In other words, in order to operate the dehydration tower stably, it is desirable that the water content in the coal cool is 2% or less, but due to the above-mentioned reasons, it is extremely difficult to maintain the water content at 2% or less at all times. .

The present invention C solves the drawbacks of the conventional method as described above.
A method of distillation of coal tar, which has been developed for the purpose of ζ, and is characterized by flashing part of the water content and part of the light oil content in the furathon process before dehydrating the water-containing raw material coal tar in a dehydration tower. It's a method.

Next, one embodiment of the present invention will be described with reference to the drawings. As shown in the drawing, the crude coal tar introduced from line I is preheated in heat exchanger 2 by the latent heat of condensing gaseous substances such as steam and light oil supplied from line 8. , is heated in a heat exchanger 4 via a line 3, further heated under pressure in a heater 5 to a predetermined temperature, for example, 110 to 200°C, and then transferred via a line 6 to a flap tank 7 under approximately atmospheric pressure. Supplied. The coal tar heated under pressure is flashed at a temperature of 100 to 30"C; in this tank 7, most of the volatile components such as water and light oil in the coal tar are vaporized and sent to the line 8. The most part is condensed by heat exchange with crude coal tar in the heat exchanger 2, and is converted into crude coal tar by the latent heat of condensation. For example, air fin cooler)
After being added, the oil/water mixture is sent to the first light oil separation tank 11 via line 10. The water (ammonia water) separated by standing in this first light oil separation tank 11 is discharged from the line 12 to the outside, while the light oil passes through line 13 to the dehydration tower 14.
is supplied to the top of the column as part of the reflux liquid in the dehydration column 14.

The boiling point range of the oil distilled from the flattening tank 7 together with water is wider than the boiling point range of the oil coming out from the top of the dehydration tower 14. For example, Q of dehydration tower 14: Does Ji J come out? The main components are benzene, turquonin, xylene, and trinotylbenzene, which have 6 to 9 carbon atoms. Once upon a time,
Tar gas oil with a narrow boiling point range is used as the reflux liquid of the dehydration tower 14, and the entire amount of the oil distilled from the flash tank is used as the reflux liquid of the dehydration tower 14. It is desirable to collect light oil and L7. That is, the oil distilled from the flash tank 7 is transferred to the dehydration tower 14.
By refluxing the oil, heavy components in this oil are removed from the dehydration tower.
The temperature range of the oil distilled from the top of the dehydration tower 14 is kept narrow, making it possible to recover high-quality tar light oil.

The coal tar from which most of the volatile matter has been separated and removed in the flash tank 7 still contains a small amount of water in addition to light oil, so it is discharged from the line 5 through the heat exchanger 16 at a predetermined level. (Heated to 1 m degree, and then supplied to the bottom of the dehydration tower through line 17) 4.

The dehydration tower 14 is a distillation tower that uses gas-liquid equilibrium to separate and remove remaining water, light oil, and other low-boiling fractions from the coal tar. In this case, the temperature at the bottom of the dehydration tower 4 is determined by passing the bottom liquid through a line 26 to a heating means 28 such as a reboiler or heating furnace using steam heating.
After heating, it is kept at 150 to 200'' (L:) by circulating through the dehydration tower 14-\ through line 29.

The low-boiling fraction discharged from the top of the tower is sent to a heat exchanger (line 18) and then to an appropriate cooling unit (for example, an air fin cooler). It is sent to the light oil component tank 21.This second light oil separation j
1!72 ], the stationary fraction p (L) is discharged from the system through line 22 and line 12 to the water (ammonia water). On the other hand, the light oil component is discharged from line 23 and sent to another process.
\1 is reduced or a part thereof is separated from +4 line 24 and supplied to the top of the dehydration tower 14 as a reflux liquid.

The coal tar thus dehydrated is discharged from the bottom of the dehydration tower 14 through the line 25, and a part of it is heated to a predetermined humidity in the heating means 28 through the line 26 as described above, and then the coal tar is discharged through the line 25. 29 to the dehydration tower 14, or the residue is heated in a heat exchanger 2H;
It is then supplied to a coal tar distillation column (not shown) via line 32.

In the following, the method of the present invention will be explained in further detail by giving examples.
to change to. In the following examples, 1%J means 1° by weight, unless otherwise specified.
For treatment with 35,050 parts h+ of crude coal tar at ℃,
If a conventional preliminary dehydration method were to be adopted, a pressurized dehydration tank (pressure resistance: Okg/ffl, capacity 60 m') would be required; however, in this embodiment, instead of the pressurized dehydration tank, a
g' (6.8 m' flash tank 7 is attached and preliminary dehydration is carried out) ζ case is shown. That is, coal tar is supplied from line 1 to heat exchanger 2 and heated to approximately +03"C [1, then supplied to heat exchanger 4 through line 3] and heated to 28"C. Then, it is further pressurized and heated with steam in the inn heater 5, and then heated to 0.01 k! from the line 6. ? /cyl-G] 20"C crude coal tar was sent to the flash tank 7 and was flattened at 20"C. The component flattened from this flash tank 7 is a mixed vapor of 1679 parts/1]r consisting of 87% moisture and 13% light oil, which is discharged from lie/8 and condensed in a heat exchanger (condenser) 2. 100℃
The condensate of? It was cooled to 50''C in a cooling device 9 and sent to 8g1 light oil separation tank]1.

Light oil (benzene,
Toluene/, xylene 45 parts, other heavy components (parabolic with a boiling point lower than naphthalene) 25 parts, naphthalene 26 parts
and other heavy components (5) were sent to the top of the dehydration tower 14 via line 13.

As a result, 835% of water in the coal tar phase was removed.

In this way, the flushed saliva 7W I 2
(Coal tar at 1°C has a water content of [chi] or more and is discharged from line] 5, heated further to 175°C in heat exchanger 16, and then passed through line 17 to the bottom of dehydration tower 14. In this dehydration tower] 4, the bottom liquid was circulated and heated by the reboiler 28 heated by steam, thereby maintaining the bottom rsy + degree at 180° 0 and carrying out atmospheric distillation.Moisture/122 The layer top fraction at 90°C with a light oil content of 578% was discharged from line 19, cooled to 50°C in a cooler 20, and sent to the second light oil separation tower 22. ε1Mo2 light oil separation Gas oil (79% benzene, toluene, xolene) separated by standing in tank 22
, naphthalene, 2% of other heavy components, and 19% of other heavy components) are discharged from the line 24 to the outside, and the remainder is sent to the dehydration tower 14 along with the light oil from the first light oil separation tank 11. The reflux ratio of the distillation operation in the dehydration tower 14 was maintained at about 3 by feeding the mixture at the top. On the other hand, water containing ammonia separated from the first and second light oil separation tanks 1.1 and 22 was discharged to the outside of the system from the d line 12 at a ratio of 1,750 parts/11. It was confirmed that there was no problem in the operation of tower I4, and that stable operation was possible.

As mentioned above, in the method for dehydrating coal tar according to the present invention, before dehydrating the water-containing raw material coal tar in the dehydration tower, part of the water and part of the light oil are removed in advance in the flage unit stage. First of all, the flashing process is carried out under approximately atmospheric pressure, so there is no need to use a large-capacity pressure vessel unlike the conventional pressurized dehydration tank. In addition, since it is a continuous flat/yuka type, even if the throughput of coal tar distillation is large, the weight can be kept small. In addition, unlike a pressurized dewatering tank, separation is not performed by standing still, so there is no need for sludge removal work. Furthermore, by performing flash treatment, the dehydration efficiency increases, so the water content in the coal tar supplied to the dehydration tower becomes extremely small, and as a result, there is no bumping phenomenon in the dehydration tower, making safe operation possible. .

In addition, since the vapors evaporated during the fludge process are used as a heating source for the coal tar phase, heat can be recovered.

[Brief explanation of drawings]

The drawing is a flow no. 1 showing an embodiment of the method for distilling coal tar according to the present invention. 2.4, 17, 30, 35, 39, 41. 42... Heat exchanger, 5 Heater, 7 Flash tank, I], 12.
・Light oil separation (・Tos, +6,3]・・Tube furnace, 14 Dehydration tower.

Claims (1)

[Claims] u, + a゛When dehydrating Suwon F4 coal tar in a dehydration tower, it is characterized in that part of the water and part of the light oil are flashed in advance in a furanite stage. Coal tar dehydration treatment method. (2) The method according to claim 1, in which water-containing prefectural coal tar is heated under pressure and is introduced into flat/yellow I8. (3) The method according to claim 1 and claim 2, wherein the water content of the coal tar after being subjected to the fludge treatment and being led to the dehydration tower is 2 H or less. (4) The method according to any one of claims 1 to 3, wherein the flash temperature of the flap unit is 100 to 20°C under atmospheric pressure. ) The method according to any one of claims 1 to 4, wherein the components flashed in the flage unit stage are condensed and then separated into water and oil by standing separation. (6) Standing. 6. The method according to claim 5, wherein the separated oil is supplied as a reflux liquid to a dehydration tower.