JPH075894B2 - How to separate ash from slurry - Google Patents

Description

TECHNICAL FIELD The present invention relates to separating ash from a by-product unburned carbon slurry produced when a petroleum coke or a petroleum pitch-water slurry is partially oxidized by an oxygen-containing gas. It is about.

[Prior Art] In the prior art and the present invention, the solid content consists of unburned carbon content and ash content, and when this solid content is suspended in water, a slurry is formed.

Conventionally, using a vertical gasifier having a gasification reaction chamber in the upper part and a generated gas quenching chamber in which cooling water is spread in the lower part,
A method for partially oxidizing gasification raw materials such as natural gas, naphtha, crude oil, heavy oil C, heavy oil such as vacuum residue oil, coal and petroleum coke is known as a so-called Texaco method. In this method, generally, the gas generated in the gasification reaction chamber is cooled in the quench chamber, and the generated gas from which the entrained unburned components have been washed and removed is extracted from the side wall of the vapor phase section in the upper part of the quench chamber, The unburned component is discharged as a slurry from the lower side wall of the quenching chamber.

Of the above gasification raw materials, the unburned substances (mainly carbon content) during the gasification reaction of natural gas, naphtha, crude oil, C heavy oil, heavy oil (vacuum residue oil, etc.) are 0 to 3% by weight (in the raw material). Carbon content)
Although the amount of ash varies with the degree, the amount of ash is far less than that of petroleum coke described later, and it was not necessary to separate the ash content in the slurry and recycle only the unburned carbon content.

However, when petroleum coke is used as a raw material, it is inferior as a gasification raw material, that is, the residual carbon content is as high as 70 to 90% (generally 20 to 35% in the case of vacuum residue oil), and the volatile content is 8%. -14% (generally 65-75% in the case of vacuum residue oil) is low, and the rate of unburned substances is usually around 15% by weight (carbon content in raw material), which is higher than heavy oil. Most of the unburned materials are coarse particles of several tens to several hundreds of mesh, and have a property of large sedimentation. Note that 90% or more of this unburned material is carbon.

When the partial oxidation reaction of petroleum coke was carried out using the above-mentioned ordinary gasifier, the unburned carbon content and the ash content in the raw material increased as compared with the residual oil gasification, and it was installed on the lower side wall of the quenching chamber. From the ash slurry outlet, fine slag mainly containing 90% or more of unburned carbon is discharged out of the reaction system in the form of a slurry, and then heat exchange is performed by a heat exchanger and then supplied to the settler.

So-called solid-liquid separation is performed in which the solid and liquid components, which are composed of unburned carbon components and ash components, are separated in the settler. The slurry supplied to the central part of the setra is separated into solid content and water while flowing from the central part to the outer peripheral part in the setra, and the clear water separated in the upper part of the setra is reused as process water. In addition, the mixture of unburned carbon and ash that settled in the lower part of the settler is not deposited on the bottom of the settler by continuously driving the rake provided on the settler at a constant speed, and the solid content is high. The slurry is discharged to the outside of the settler system through a pipe arranged at the bottom of the settler. In addition, a part of the discharged slurry is once stored as a recycled slurry in a recycling tank to reuse the unburned carbon content, and is then supplied to a grinding device such as a mill together with petroleum coke. Wet milled into petroleum coke-water slurry.

This petroleum coke-water slurry is supplied to the burner in the upper part of the gasification reaction chamber, and the high temperature partial oxidation reaction is performed in the gasification reaction chamber by the oxygen supplied at the same time. Further, among the slurries having a large amount of solids discharged from the lower part of the settler, the remaining slurry is squeezed by a filter press to separate into solids and water, and the separated solids are discharged as a fine slag out of the system. It

[Problems to be Solved by the Invention] However, the recycled slurry discharged from the lower part of the settler and stored in the recycling tank is recirculated as it is without separating the ash content and the unburned carbon content. When attempting to reuse the unburned carbon contained, the ash slurry containing 10% or more of ash must be recirculated, and the ash contained in petroleum coke contains vanadium and nickel. There is a problem that it tends to adhere to the wall of the reaction chamber, which hinders stable operation of the gasifier.

[Means for Solving the Problem] In order to solve such a problem, in the present invention, at least 7% by weight of solid matter obtained by partially oxidizing petroleum coke or petroleum pitch in a gasifier and cooling it is used. The slurry containing the above is taken out from the gasifier, diluted with water so that the solid content becomes 1 to 5% by weight, and then the ash content in the solid content is separated and removed in a separation / concentration tank to contain a large amount of carbonaceous fuel. I got a slurry.

[Operation] According to the method of the present invention, the slurry taken out from the side wall of the quenching chamber at the lower part of the gasifier is the clear water separated by a settler provided on the downstream side of the separation and concentration tank before entering the separation and concentration tank. Circulate and mix with the slurry that enters the separation / concentration tank to dilute the concentration of solids in the slurry, and more efficiently separate the ash content and unburned carbon content of the residue in the separation / concentration tank. It is possible to obtain a recycled slurry containing a large amount of unburned carbon from the lower part of the concentrating tank and recirculate it back into the gasifier to increase the carbon conversion rate and reduce the recycling of ash to the gasifier.

[Examples] FIG. 1 is a system diagram of an apparatus suitable for carrying out the method of the present invention, and FIG. 2 shows an example of an apparatus for separating ash and unburned carbon in a separation / concentration tank and its separation state. A schematic diagram and FIG. 3 show a correlation diagram between the concentration of the slurry supplied to the separation and concentration tank and the ash separation rate.

In FIG. 1, petroleum coke is introduced into a crusher 2 through a line 1 and the slurry discharged from the gasifier 11 is efficiently separated into ash and unburned carbon in a separation / concentration tank 30 described later. After mixing with the recycled slurry, the petroleum coke is wet-milled.

The conditioned water slurry of petroleum coke is sent to the slurry tank 5 through the line 4. The slurry of water and petroleum coke is sent to the burner 9 through the line 8 by the slurry supply pump 7, and is introduced into the burner 9 through the line 10 together with high-purity oxygen (99.6 mol% oxygen) in the gasifier 11.
The gasification reaction chamber 12 is supplied from the top of the.

The gasifier 11 is a reaction chamber 1 lined with refractory 12a in the upper stage.
2, a cooling chamber 14 filled with water for quenching the generated gas is provided at the lower stage, and the reaction chamber 12 and the quenching chamber 14 are communicated with each other at the throat portion 13. Water is stretched to an appropriate height in the quenching chamber 14, and a cylindrical dip tube 14a and a draft tube 14b are coaxially provided so that the lower end is immersed in the water.

The gas generated above is sent to the lower part of the carbon scrubber 16 via a carbon collector (not shown) from the gas outlet 14c provided in the water surface upper region of the quenching chamber 14 through the line 15. The water supplied from a line 17 disposed above the carbon scrubber 16 is contacted with the liquid by gas-liquid contact to be washed, and then sent from the top of the carbon scrubber 16 through a line 18 to the next step. Further, at the bottom of the carbon scrubber 16, a part of the clear water of the settler 60, which will be described later, is refluxed through the line 20 so as to keep the liquid level at the bottom of the carbon scrubber 16 constant, and at the same time, part of the bottom liquid. A pipe is provided so as to be returned to the quenching chamber 14 through a line 19.

On the other hand, in the lower region of the quenching chamber 14, slurry can be formed by mixing water with ash and unburned carbon produced during gas generation, but a lock hopper arranged at the bottom of the quenching chamber 14
A relatively coarse particle called coarse slag is mainly discharged to the outside of the gasifier 11 system through the line 21 by opening and closing valves above and below the lock hopper 22.

On the other hand, in the lower part of the quenching chamber 14, a slurry of fine slag containing relatively finer particles than the above-mentioned coarse slag is taken out from the discharge port 14d through the line 23, and the heat exchanger 2
After heat exchange with the clear water discharged from Setra 60 in 4, it is sent to the separation / concentration tank 30 through line 26.
In order to dilute the concentration of solids in the slurry entering 30 to reflux some of the clear water discharged from Setra 60,
Line 27 is connected in the middle of 28. The diluted slurry is supplied to the separation / concentration tank 30 through the line 28.

As shown in FIG. 2, the slurry supplied through the line 28 is first discharged to the liquid receiver 31. Slurry is a receiver
It flows down toward a liquid disperser 32 provided coaxially with the liquid receiver 31 at the bottom of the liquid receiver 31, and radially flows out from holes of vertical slits 33 provided at equal intervals on the circumference of the liquid disperser 32. It is supposed to be done.

The lower end of the liquid disperser 32 is coaxially provided with a partition-shaped partition plate 34 having an outer diameter somewhat smaller than the inner diameter of the dispersion concentration tank 30, and the slurry flowing out from the slit 33 of the liquid disperser 32 is a partition plate. 34 In the separation zone 41 in the upper area, a residence time is set so that only unburned carbon content settles down, and the horizontal angle is 20 to 30 degrees so that it flows downward without depositing. .

On the upper inner wall of the separation / concentration tank 30, an overflow weir 35 having an annular groove is arranged so that the liquid can be extracted at a constant flow rate, and the ash content solid-solid separated in the separation zone 41 is arranged. The overflow water containing the is flowed down by the overflow, through the rectangular flow holes 42 formed at equal intervals in the upper side wall of the separation / concentration tank 30, and annularly along the upper outer wall of the separation / concentration tank 30. It flows down to the disposed overflow liquid receiver 36 and is discharged from the line 52.

Furthermore, the upper water of the concentration zone 38 in the lower area of the partition plate 34,
It is a supernatant zone in which the amount of solids is very small, and the ash fraction separated by the particle size difference in the concentration zone 38 is mainly contained and removed. Here, one end of a middle-stage withdrawing pipe 37 that is horizontally arranged penetrating the partition plate 34 and the side wall of the separating and concentrating tank 30 is provided in the vicinity of the concentrating tank rake shaft 43, and the other end is a middle-stage withdrawing having a weir. The water discharged from the middle stage is sent to the settler 60 through the line 53 along with the water in the line 52 by being conducted to the flow rate adjusting weir 40.

The lower end of the concentration tank rake shaft 43 arranged on the axis of the separation concentration tank 30 is such that the concentration tank rake 39 is left-right symmetrically around the concentration tank rake shaft 43 with a slight clearance from the bottom surface of the separation concentration tank 30. One pair is provided, the upper end of which is fixed to a motor for driving the concentration tank rake 39 and is rotated in a certain direction at an appropriate speed.

With the rotation of the concentrating tank rake 39, it is possible to smoothly discharge from the line 50 while preventing the accumulation of solids at the bottom of the separating and concentrating tank 30, and the recycled slurry discharged from the line 50 is pumped by the pump 61. After passing through, it is arranged so as to be supplied to the crushing device via line 3.

Also, the water with a large amount of ash, which has been supplied to the Setra 60 through the line 53, is separated into solid and liquid in the Setra 60, and the Setra 60 is separated.
The clear water from the top is discharged via line 54. The discharged clear water is used as process water in the slurry dilution line 27 entering the separation / concentration tank 30 in the previous step, the line 25 extending to the bottom of the carbon scrubber 16, and the like. In addition, the separated solid slurry is lined from the bottom of the Setra 60.
It is discharged through 57 and sent to the next process for processing.

Gasifier for petroleum coke treatment configured as described above
Explain how the ash content in the slurry from 11 is separated.

Petroleum coke, which is a starting material, has a composition of 85 to 90% by weight of carbon and 0.3 to 1.0% by weight of ash, and has a volatile content of 8 to 14%.
Low weight%, poor reactivity, normal gasification temperature (1300
(~ 1400 ℃), only about 85% of the carbon in petroleum coke is gasified, and the remaining about 15% is not gasified and is left as unburned carbon in the slurry, leaving the gasifier 11 system. Is discharged. Therefore, the slurry discharged to the outside of the gasifier 11 system is separated into as much ash and unburned carbon as possible in the separation / concentration tank 30, and the separated unburned carbon is recovered and recycled to produce petroleum as a raw material. By wet grinding with coke to produce petroleum coke-water slurry and gasifying it with the gasifier 11, finally about 95% of the carbon content of petroleum coke is obtained.
Will be gasified.

That is, the composition of the slurry that is recycled to reuse unburned carbon is 17.1% unburned carbon and 1.2% ash.
% Content, crusher with petroleum coke 2
And at least about 60% by weight of petroleum coke-water slurry is supplied to the slurry tank 5.

Pump 7 for petroleum coke-water slurry in slurry tank 5
Then, the pressure is increased by means of spraying from the burner 9 to the gasification reaction chamber 12 together with high-purity oxygen (concentration of 99.6 mol%). The petroleum coke particles have a temperature of 1,000 to 1,700 ° C., a pressure of 1 to 200 kg / cm ² , preferably 1,100 to 1,500 ° C., and a pressure of 10 to 80 kg / cm ² under the operating conditions of reacting petroleum coke particles with oxygen by partial oxidation. A gasification rate of 85% is obtained.

The generated gas passes through the throat section 13 and the dip tube 14a.
After passing through the inside, the gas is discharged from the gas discharge port 14c through the gap between the draft tube 14b and the dip tube 14a while cleaning the gas in the quenching chamber 14 with the quenching water that is stretched to a certain level, and further inside the carbon scrubber 16. Ascending, the gas is cleaned by gas-liquid contact with the water (boiler water) supplied from the top of the carbon scrubber 16, and the gas is sent from the top of the carbon scrubber 16 to the next step.

On the other hand, in the quenching chamber 14 at the lower part of the gasifier 11, ash components generated during the partial oxidation reaction of petroleum coke particles in the gasification reaction chamber 12 at the upper part, and unburned carbon components are suspended in the quenching water. It becomes a slurry.

In the lower part of the quenching chamber 14, 14% of unburned carbon
A large amount of unburned carbon, called coarse slag having a particle size of mesh or more, is settled and deposited, but these are from the lock hopper 22 connected to the lower part of the gasifier 11 to the lock hopper 22. By opening and closing the valves provided above and below, it is sent to the next process discharged intermittently and processed.

Also, from the side wall of the quenching chamber 14, unburned carbon content of less than 14 mesh called fine slag 6.6%, ash content 0.6%
A slurry with a concentration of 7.2% containing is extracted. Under normal operation, the slurry concentration in the quenching chamber 14 will be 7% or slightly above 7%.
The slurry concentration changes depending on the operating conditions of 11. That is, the condition that the slurry concentration is 7% or less is that the amount of quench water supplied from the bottom of the carbon scrubber 16 to the cooling chamber 14 increases, or the gasification temperature in the gasification reaction chamber 12 is increased and unreacted. This is the case when the carbon content is reduced. Further, the condition that the slurry concentration is 7% or more is opposite to the condition that the slurry concentration is 7% or less, or the quench water supplied from the bottom of the carbon scrubber 16 to the cooling chamber 14 is decreased, or This corresponds to the case where the gasification temperature in the gasification reaction chamber 12 is lowered to increase the amount of unreacted carbon.

In the separation / concentration tank 30 of the next step, in order to more efficiently perform the sedimentation separation, in this embodiment, the clear water in the settler 60, which will be described later, is partially refluxed so that the solid content concentration in the slurry is 7.2%. To 4.5%. This is because by diluting, the cohesive action between particles is weakened, and conversely by increasing the separation action, the separation utilizing the physical property that the unburned carbon particle size is larger than the ash particle size is more effective due to the synergistic effect. This is to make it easier to raise.

Further, when the concentration of the slurry taken out from the side wall of the cooling chamber 14 is diluted to 1 to 5% by weight by partially refluxing the clear water, as the slurry concentration approaches 1%, the separation and concentration tank 30
As a result of the increase in the volume of the separation zone 41 in the upper part of the above, the volume of the separation / concentration tank 30 itself becomes relatively large, and therefore the average retention time of the solid content in the separation / concentration tank 30 also becomes long. In particular,
This tendency becomes remarkable when the slurry concentration is 1% or less. Further, as the volume of the separation / concentration tank 30 increases, the settler 60 also becomes larger. In addition, as the slurry concentration approaches 5%, in the separation / concentration tank 30, the agglomeration action between particles is strengthened and a blocking phenomenon occurs, so the dispersion action of unburned carbon content and ash is weakened, and unburned carbon particles are Separation using the physical property that the diameter is larger than the ash particle diameter becomes difficult, and this phenomenon becomes more remarkable when the slurry concentration is 5% or more.

From the above, the slurry discharged from the cooling chamber 14 is diluted with the partially refluxed clear water from the settler 60, and the slurry concentration becomes 1
In the vicinity of%, the volume of the separation / concentration tank 30, in particular, the volume of the separation zone 41 above the separation / concentration tank 30 becomes large, and as a result, the total volume of the separation / concentration tank 30 becomes large.
Therefore, the average residence time spent for the sedimentation separation of the unburned carbon content in the concentration zone 38 becomes large, and the separability of the unburned carbon content from the slurry concentration decreases.

On the other hand, the slurry discharged from the cooling chamber 14 is diluted with the partially refluxed clear water from the setra 60, and the slurry concentration is 5%.
When it becomes close, the agglomeration action between particles becomes strong, and it becomes difficult to separate the unburned carbon content and the ash content by the physical properties depending on the particle size, so the slurry concentration supplied to the separation concentration tank 30 in the present invention is , Desirably 2 to 4%.

FIG. 3 is a graph showing an example of the present invention.

In the figure, as the slurry concentration supplied to the separation / concentration tank 30 becomes lower than about 5%, the ash separation rate increases, and
When the residence time in the separation / concentration tank 30 is increased from 1.4 minutes to 2.6 minutes, the ash separation rate increases.

However, the concentration of the slurry supplied to the separation and concentration tank 30 is 5.5%.
When the above is reached, the ash separation rate becomes about 10% or less, and it can be seen that no further improvement in ash separation is observed.

The solid / solid separation of the ash content and the unburned carbon content is performed mainly by the difference in particle size between the two, rather than the difference in specific gravity.

That is, if the particle size is 325 mesh or more, about 93% has unburned carbon content, 4% has ash content, and if the particle size is 325 mesh or less, about 78% has unburned carbon content and 19% has ash content. Have a composition.

Utilizing such a difference in particle diameter, solid / solid separation is performed in the separation / concentration tank 30 as follows.

That is, in the separation / concentration tank 30, solid and solid separation of ash and unburned carbon is performed in two zones. First, the first solid and solid separation for separating a large amount of ash is carried out first. After being carried out in the separation zone 41, the second solid-solid separation for separating the remaining ash as much as possible is carried out in the concentration zone 38.

The slurry containing 4.1% unburned carbon and 0.4% ash diluted to a solids concentration of 4.5% was first separated into a separation and concentration tank 30.
Of the vertical slit formed in the liquid disperser 32 while being supplied to the liquid receiver 31 and flowing down to the liquid disperser 32 while overflowing.
Radially flows from 33 to the separation zone 41 at a velocity of about 0.1 m / s, and solid / solid separation in the separation / concentration tank 30 is started.

In the separation zone 41, while the slurry flowing out from the slits 33 flows down along the partition plate 34, a part of the water becomes an upward flow, and ascending components having a small particle size are mainly entrained in the upward flow. , Overflow weir in the upper area of separation zone 41
It flows from 35 to the next process, Setra 60. However, the unburned carbon content having a large particle size that does not accompany the ascending flow is separated by the partition plate
And is sent to the concentration zone 38 which is the second separation zone, and the first solid / solid separation is completed.

In the above-mentioned separation zone 41, the efficiency of separating the ash content and the unburned carbon content depends on the slit 3 as a factor depending on the device shape.
3. The partition plate 34 and the average liquid depth from the partition plate 34 to the interface of the overflow weir greatly influence.

The slurry flowing down from the separation zone 41 is the concentration zone.
At 38, the final solid / solid separation is performed.

The water containing a large amount of ash separated in the concentration zone 38 is discharged from the middle extraction pipe 37 in the upper area of the concentration zone 38, and the ash content discharged from the overflow weir 35 in the upper area of the separation zone 41 described above. Together with water containing a large amount of water, it is sent to Setra 60 in the next step as overflow water having a solid content concentration of 1.3%. At this time, the overflow water contains 1.2% of unburned carbon and 0.2% of ash.

Thus, the slurry containing a large amount of unburned carbon separated in the separation / concentration tank 30 with an average residence time of 5 minutes in the separation zone 41 and 2.4 hours in the concentration zone 38 is separated and concentrated.
Although it deposits on the bottom of 30, the concentration tank rake 39 is driven at a speed of 0.24 rpm, so the solid content deposited on these bottoms is separated and concentrated as a 18.3% recycled slurry within the range that does not hinder the sedimentation separation effect. It is discharged from the bottom of the tank 30. The recycled slurry at this time had an unburned carbon content of 17.1%,
The ash content becomes 1.2% and is returned to the crushing device 2 via the pump 61.

From the above, the ash separation rate in the separation and concentration tank 30 is 20%.

Thus, while the newly supplied petroleum coke and the above-mentioned recycled slurry are mixed in the crushing device 2,
It is pulverized to a desired particle size and supplied to the gasifier 11 again, and about 95% of the carbon content of the petroleum coke is gasified.

Furthermore, the supernatant from the separation / concentration tank 30 is used for the next step settler.
Solid / liquid separation is performed at 60, and the separated supernatant is used as dilution water for diluting the solid content concentration of 7.2% taken out from the quenching chamber 14 to 4.5%.

Further, the solid content settled in the lower part of the Setra 60 is forcibly separated from water and the solid content by a filter press in the next step, and is taken out as a solid content containing 12.7% of ash content and treated in an incinerator or the like. .

In this embodiment, the separation and concentration tank 30 is used for separating the ash content and the unburned carbon content in the slurry taken out from the quenching chamber 14.
However, the present invention is not limited to this, and the liquid cyclone and the separation / concentration tank 30 may be combined, or the separation / concentration tank 30 may be arranged in series.

Furthermore, in the present embodiment, the case of petroleum coke gasification was described, but it can also be adopted in the case of petroleum pitch gasification.

[Effects of the Invention] As is clear from the above description, according to the present invention, if the concentration of the slurry taken out from the quenching chamber is diluted to at least 5% or less, the ash content and the unburned carbon content are separated in the separation / concentration tank. Are efficiently separated. By returning the separated slurry containing a large amount of unburned carbon to the gasifier again, it is possible to increase the carbon conversion rate in the gasifier by about 10%.

[Brief description of drawings]

FIG. 1 is a system diagram of an apparatus suitable for carrying out the method of the present invention, FIG. 2 is a schematic diagram showing the separation state of ash and unburned carbon in a separation and concentration tank, and FIG. 3 is a separation and concentration tank. The correlation diagram between the supplied slurry concentration and the ash separation rate is shown. 2 ... Grinding device, 5 ... Slurry tank, 11 ... Gasification device, 12 ... Gasification reaction chamber, 14 ... Quenching chamber, 16 ... Carbon scrubber, 22 ... Rock hopper, 30 ... Separation and concentration Tank, 60 ... Setra.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Morio Togame, Morio Togame 2575, Fujimagari, Ube City, Yamaguchi Prefecture Ube Ammonia Industry Co., Ltd. Yoshihiko Funaoka Examiner, Ube Head Office

Claims (1)

[Claims] 1. A slurry containing at least 7% by weight of solid content obtained by partially oxidizing petroleum coke or petroleum pitch in a gasifier and cooling it is taken out from the gasifier and has a solid content of 1 to 5% by weight. After diluting with water so that it becomes 100%, the ash content in the solid content is separated and removed in a separation and concentration tank,
A method for separating ash from a slurry, characterized in that a slurry containing a large amount of carbonaceous fuel is obtained.