CN103550946A - Crude styrene separating method for reducing scale formation of crude styrene separation tower still - Google Patents
Crude styrene separating method for reducing scale formation of crude styrene separation tower still Download PDFInfo
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- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 title claims abstract description 320
- 238000000926 separation method Methods 0.000 title claims abstract description 66
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- 238000006116 polymerization reaction Methods 0.000 description 55
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- OWZPCEFYPSAJFR-UHFFFAOYSA-N 2-(butan-2-yl)-4,6-dinitrophenol Chemical compound CCC(C)C1=CC([N+]([O-])=O)=CC([N+]([O-])=O)=C1O OWZPCEFYPSAJFR-UHFFFAOYSA-N 0.000 description 14
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- 239000012808 vapor phase Substances 0.000 description 4
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- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
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- 238000004140 cleaning Methods 0.000 description 3
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- 230000036961 partial effect Effects 0.000 description 3
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- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
The invention provides a crude styrene separating device for reducing scale formation of a crude styrene separation tower still. According to the crude styrene separating device, an easy-to-scale part in the tower still is provided with an anti-scaling safety device, and the anti-scaling safety device is a high-temperature anti-scaling system, wherein the high-temperature anti-scaling system comprises one or a plurality of flow dividing devices, and one or a plurality of reverse spray systems, the flow dividing devices are used for dividing 10-30wt% of liquid phase materials in the tower still and returning to the tower still, the reverse spray system are used for spraying the divided materials to the inner wall of the tower still according to required directions; the high-temperature anti-scaling system is started when a scaling critical point of the crude styrene in the tower still is achieved. The invention further provides a crude styrene separating method for reducing scale formation of the crude styrene separation tower still.
Description
Technical Field
The invention relates to a method for producing styrene, in particular to a problem of fouling of a tower bottom of a separation tower frequently occurring in a crude styrene separation process. In particular to a method for solving the problem of scaling of a tower bottom of a crude styrene separation tower.
Background
Styrene is an important organic chemical raw material, is widely used for preparing various synthetic materials by homopolymerization or copolymerization, and is an easily polymerizable (self-polymerizing) compound.
Commercially, about 90% of the styrene production is produced by the catalytic dehydrogenation of ethylbenzene. The ethylbenzene catalytic dehydrogenation process is a process for the catalytic dehydrogenation of ethylbenzene to styrene in the presence of steam in an adiabatic reactor system. The ethylbenzene dehydrogenation reaction mixture is cooled and separated to obtain a hydrocarbon phase (DM, ethylbenzene dehydrogenation liquid or crude styrene) which mainly contains styrene, unreacted ethylbenzene, byproducts of benzene, toluene, high-boiling residues and the like, and the crude styrene is rectified and separated to obtain a polymerization-grade styrene product. In fact, the crude styrene obtained, whether by ethylbenzene catalytic dehydrogenation process or by oxidative dehydrogenation process and co-oxidative dehydrogenation of the POSM process, etc., generally needs to be purified by rectification separation.
In the rectification process of crude styrene, in order to reduce the polymerization reaction of easy-to-polymerize styrene in the process to reduce the styrene yield and block process equipment and a system, negative pressure operation is usually adopted in design to reduce the system pressure and further reduce the operation temperature so as to achieve the purpose of reducing the polymerization rate; meanwhile, various polymerization inhibitors are required to be added in the rectification process to prevent and slow down the polymerization of the styrene so as to ensure the safety, reliability and economy of the system operation and improve the yield of the styrene to the maximum extent.
In response to the polymerization problem of crude styrene distillation, process patentees have employed the addition of polymerization inhibitors to the feed to prevent and slow the polymerization of styrene during the distillation process; there are also some patents which propose different improvements, such as US005910232A which proposes to improve the effect of inhibiting polymerization by adding a nitrated radical compound to the material; the Chinese patent CN101157083 proposes to increase the scale formation in the spray cleaning pipeline in the gas phase flow pipeline. However, according to the above patents and techniques, either the crude styrene distillation process is not suitable or the fouling of the polymer wall build-up during operation still often occurs inside the equipment which presents the surface of the gas phase space through which no liquid material flows, and the equipment often needs to be shut down to clean the polymer, reducing the operation efficiency of the equipment.
Therefore, in order to stably perform device production for a long period, the existing process and equipment need to be improved, the long-period, safe and stable operation of the production device is met, and potential safety hazards in production are eliminated.
Disclosure of Invention
The first purpose of the invention is to solve the problem of scaling of the tower bottom of the separation tower in the crude styrene rectification process, meet the requirements of long period, safety and stable operation of a production device and eliminate potential safety hazards in production.
The second purpose of the invention is to solve the problem of scaling of the tower bottom of the separation tower in the crude styrene rectification process, meet the requirements of long period, safety and stable operation of a production device and eliminate potential safety hazards in production.
The third purpose of the invention is to solve the problem of scaling of the tower bottom of the separation tower in the crude styrene rectification process, meet the requirements of long period, safety and stable operation of a production device and eliminate potential safety hazards in production.
In a first aspect of the invention, a crude styrene separation device for reducing scaling of a tower kettle of a crude styrene separation tower is provided, wherein a scaling prevention safety device is arranged at a position which is easy to scale in the tower kettle, and a high-temperature scaling prevention system is arranged in the scaling prevention safety device; wherein,
the high temperature anti-fouling system comprises:
one or more shunting devices, wherein the shunting devices shunt 10-30 wt% of the liquid-phase material in the tower kettle and return the liquid-phase material to the tower kettle; and
one or more reverse spraying systems, wherein the reverse spraying systems spray the shunted materials to the inner wall of the tower kettle according to a required direction;
and the high-temperature anti-scaling system is started when the scaling critical point of the crude styrene is reached in the tower kettle.
In a specific embodiment, the flow dividing device divides 20-30 wt% of the liquid-phase material in the tower kettle and returns the liquid-phase material to the tower kettle
The "separation device" may include: the distillation column required for refining styrene includes, for example, an ethylbenzene-styrene separation column, an ethylbenzene recycle column, a high-pressure ethylbenzene recycle column, and a low-pressure ethylbenzene recycle column.
In one embodiment of the present invention, wherein the fouling-prone part comprises the bottom of the column bottom.
In the present invention, the "bottom" includes the part below the lower half of the column bottom, especially the outer surface of the bowl-shaped structure and the joint between the column wall and the bowl edge.
In one embodiment of the present invention, the fouling critical point of the crude styrene is 115 to 120 ℃.
In one embodiment, the critical point is 118 ± 0.5 ℃.
In an embodiment of the present invention, in the high-temperature anti-scaling system, the reverse spraying system sprays the diverted material to the inner wall of the tower kettle in a reverse direction.
In the present invention, the "reverse direction" includes: the spraying direction and the general flow direction of the materials are in opposite positions; or the direction of the spray is at an angle to the general flow direction of the material. In general, the "reverse" position allows the return stream to be flushed to a location where the styrene polymer is prone to wall fouling.
In one embodiment of the invention, in the diversion system, the liquid-phase material in the tower kettle is guided to the outside of the tower kettle and then is diverted and introduced into the spraying system.
The split stream may be 2-4 but is not limited thereto.
In one embodiment of the present invention, the shunt system comprises:
a tower kettle pump arranged at the downstream of the tower kettle outlet;
and a branch line for returning part of liquid-phase materials into the tower is arranged at the downstream of the tower kettle pump, and the number of the branch lines is 2-4, but not limited to this.
In one embodiment of the invention, the back spray system is of a ring, linear or grid type construction.
In one embodiment of the present invention, the reverse spray system comprises:
a circular structure spray device; a linear structure spray device; a grid-type structure spray device; and
the combination of the above spraying devices.
In a specific embodiment, a polymerization inhibitor-containing tower kettle material is introduced into a tower from a tower kettle pump outlet pipeline (namely a branch line), wherein one path is provided with a DN 25-DN 80 ring pipe and 2-4 feed inlets, the polymerization inhibitor-containing tower kettle material is upwards and reversely sprayed to a joint of a tower wall and a bowl edge through 18-72 nozzles on an annular pipeline in the tower, an angle is 50-80 degrees, and the flow rate of each nozzle is 3-12 liters/minute. And the other path is also provided with a DN 25-DN 80 ring pipe and 1-2 feed inlets, the materials are upwards and reversely sprayed to the bowl-shaped bottom through 16-64 nozzles on the grid-type pipeline in the tower, the wide angle is 100-130 degrees, and the flow of each nozzle is 3-12 liters/minute.
The second aspect of the present invention provides a crude styrene separation method for reducing scaling at the bottom of a crude styrene separation column, comprising the steps of:
shunting part of the liquid-phase material in the tower kettle and returning the liquid-phase material to the tower kettle; and
and reversely spraying the shunted materials to the inner wall of the tower kettle.
In a specific embodiment, the liquid-phase material in the tower kettle is divided into 2-4 parts and then is subjected to reverse spraying.
In a specific embodiment, a polymerization inhibitor-containing tower kettle material is introduced into a tower from a tower kettle pump outlet pipeline (namely a branch line), wherein one path is provided with a DN 25-DN 80 ring pipe and 2-4 feed inlets, the polymerization inhibitor-containing tower kettle material is upwards and reversely sprayed to a joint of a tower wall and a bowl edge through 18-72 nozzles on an annular pipeline in the tower, an angle is 50-80 degrees, and the flow rate of each nozzle is 3-12 liters/minute. And the other path is also provided with a DN 25-DN 80 ring pipe and 1-2 feed inlets, the materials are upwards and reversely sprayed to the bowl-shaped bottom through 16-64 nozzles on the grid-type pipeline in the tower, the wide angle is 100-130 degrees, and the flow of each nozzle is 3-12 liters/minute.
A third aspect of the present invention provides the use of a crude styrene separation unit according to the present invention for reducing fouling in the bottom of a crude styrene separation column.
Drawings
FIG. 1 is a schematic diagram of a separation column of a crude styrene separation process typical of current styrene industrial plants.
FIG. 2 is a schematic diagram of a separation column of a crude styrene separation process using the technical solution of the present invention.
Figure 3 is a schematic diagram of a spray system using the solution of the invention.
In fig. 1, 101 is a rectifying column, 102 is a column bottom pump, 1 is a rectifying column feeding material, i.e. crude styrene, 2 is a rectifying column top discharging material, and 3 is a rectifying column bottom discharging material, which is used in the next step and contains styrene, polymerization inhibitor, weight and the like. Styrene rectification inhibitor 4(DNBP or similar functional chemical agent) and/or second rectification inhibitor 5 (real inhibitor) are injected into the rectification column along with the rectification column feed 1 or into the upstream column system feed.
In fig. 2, 101 is a rectifying column, 102 is a column bottom pump, 1 is a rectifying column feeding material, i.e. crude styrene, 2 is a rectifying column top discharging material, and 3 is a rectifying column bottom discharging material, which is used in the next step and contains styrene, polymerization inhibitor, weight and the like. Styrene rectification inhibitor 4(DNBP or similar functional chemical agent) and/or second rectification inhibitor 5 (real inhibitor) are injected into the rectification column along with the rectification column feed 1 or into the upstream column system feed. And 6 is tower bottom material of a newly added spraying system which is led out from an outlet pipeline of the tower bottom pump 102 and enters a gas phase space of the tower bottom.
In fig. 3, 101 is a rectifying tower, 103 is a tower kettle bowl type structure, 104 is a tower bottom reboiler inlet pipeline, 105 is a circular ring-shaped spray pipeline, and 106 is a grid-shaped spray pipeline; a1 is 7600mm of the inner diameter of the crude styrene separation tower in the embodiment, A2 is 4300mm of the diameter of the bowl bottom of the bowl-shaped structure;
Detailed Description
The inventor of the invention has extensively and deeply researched, and by improving the preparation process, the problem of wall-hanging scaling of the styrene polymer at the tower bottom of the rectifying tower, which is caused in the crude styrene rectifying process, is solved, the requirements of long-term, safe and stable operation of a production device are met, and the potential safety hazard in production is eliminated. The present invention has been completed based on this finding.
As used herein, the term "comprising" or "includes" means that the various ingredients can be used together in a mixture or composition of the invention. Thus, the terms "consisting essentially of and" consisting of are encompassed by the terms "comprising" or "including".
Various aspects of the invention are described in detail below:
crude styrene separation device
In a first aspect of the invention, a crude styrene separation device for reducing scaling of a tower kettle of a crude styrene separation tower is provided, wherein a scaling prevention safety device is arranged at a position which is easy to scale in the tower kettle, and a high-temperature scaling prevention system is arranged in the scaling prevention safety device; wherein,
the high temperature anti-fouling system comprises:
one or more shunting devices, wherein the shunting devices shunt 10-30 wt% of the liquid-phase material in the tower kettle and return the liquid-phase material to the tower kettle; and
one or more reverse spraying systems, wherein the reverse spraying systems spray the shunted materials to the inner wall of the tower kettle according to a required direction;
and the high-temperature anti-scaling system is started when the scaling critical point of the crude styrene is reached in the tower kettle.
At present, about 60 percent of styrene rectifying devices are scaled and even need to be stopped.
The inventor realizes that a bidirectional reversible process of scaling and washing actually exists in the rectification process of the styrene through a great deal of experiments, and for this reason, the inventor designs the combination of a conventional scaling prevention system and a high-temperature scaling prevention system to ensure that the bidirectional reversible process of scaling and washing is controlled in the flow direction of a forward circulation, so that the system ensures that no scaling is generated.
Specifically, in the invention, the anti-scaling safety device is set as a high-temperature and low-temperature (relatively speaking) part, and the scaling critical point (about 118 ℃ and set as 115-120 according to the equipment) of crude styrene is taken as the critical point; the low-temperature part is a conventional part; the high-temperature part adopts washing and reverse flow, thereby effectively avoiding the scaling problem of the crude styrene.
In the usual case, the reversible process of "fouling" and flushing is intervened by conventional anti-fouling systems.
At high temperatures, the fouling rate is much greater than the washing rate, and the balance of the "fouling" and washing reversible process is disrupted. At the moment, the high-temperature anti-scaling part is started under the specific condition, and the bidirectional reversible process can be quickly returned to V by spraying a specific amount of material into the interior of the tower kettle in a specific direction and angle at a specific position at a specific temperatureScale formation<VRinsingThus, the problem of scaling at high temperature in the bottom of the styrene separation column is solved very well.
In addition, the high-temperature anti-scaling system is started when needed, so that the energy-saving effect is achieved. In a specific embodiment, the problem of tower kettle scaling can be better solved by combining the flow dividing mode.
In the invention, the content of the styrene in the crude styrene in the tower kettle is not less than 50 percent based on the weight of the material flow in the tower kettle. Typically, the bottoms stream (i.e., crude styrene) also contains ethylbenzene, styrene, alpha-methylstyrene, polymer, high boilers, and polymerization inhibitors. In the present invention, the "polymerization inhibitor" includes DNBP (Chinese 4, 6-dinitro-o-sec-butylphenol) or a similar functional chemical agent, and is suitable for refining to qualified styrene. In particular, the content of the polymerization inhibitor DNBP or similar functional chemical agents is generally between 680ppm and 1500 ppm.
The content of the inhibitor DNBP or similar functional chemical may be between 680ppm and 2500ppm, usually between 680ppm and 1500 ppm. Such "functional-like chemical agents" include, but are not limited to: DNBP (4, 6-dinitroo-sec-butylphenol) and DNPC (2, 6-dinitro-p-methylphenol).
In the present invention, the "separation device" includes: the distillation column required for refining styrene includes, for example, an ethylbenzene-styrene separation column, an ethylbenzene recycle column, a high-pressure ethylbenzene recycle column, and a low-pressure ethylbenzene recycle column.
In the invention, in the flow dividing process, the weight proportion of the partial liquid phase material in the total material is 10-30%, and can be determined according to the degree of scaling, the number and the flow of the nozzles and the area needing to be washed.
In one embodiment of the present invention, wherein the fouling-prone part comprises the bottom of the column bottom.
In the present invention, the "bottom" includes the part below the lower half of the column bottom, especially the outer surface of the bowl-shaped structure and the joint between the column wall and the bowl edge.
In one embodiment of the present invention, the fouling critical point of the crude styrene is 115 to 120 ℃.
In one embodiment, the critical point is 118 ± 0.5 ℃.
In an embodiment of the present invention, in the high-temperature anti-scaling system, the reverse spraying system sprays the diverted material to the inner wall of the tower kettle in a reverse direction.
In the present invention, the "reverse direction" includes: the spraying direction and the general flow direction of the materials are in opposite positions; or the direction of the spray is at an angle to the general flow direction of the material. In general, the "reverse" position allows the return stream to be flushed to a location where the styrene polymer is prone to wall fouling.
In the invention, a part of liquid phase material in the tower kettle is preferably sprayed to the inner wall of the tower kettle in a reverse direction by a spraying system in the tower kettle of the crude styrene separation tower, particularly to a place where the styrene polymer is easy to be hung on the wall and scaled. The spraying system sprays liquid materials containing polymerization inhibitor to scour the surface of the gas phase space (the inner wall of the tower kettle and the outer surface of the internal component), so that the retention time of liquid styrene condensed on the surface of the gas phase space is reduced, the liquid on the surface of the gas phase space is kept in a flowing state all the time, and the liquid is fully mixed with the polymerization inhibitor in the sprayed materials (flushing liquid). The spraying system sprays out the liquid material containing the polymerization inhibitor to flush the surface of the gas-phase space, and even if the polymer is formed, the polymer formed can be dissolved or can not grow because of the existence of the flushing of the liquid material containing the polymerization inhibitor. Based on the above method, the problems that the skilled person always wants to solve are solved.
In one embodiment of the invention, in the diversion system, the liquid-phase material in the tower kettle is guided to the outside of the tower kettle and then is diverted and introduced into the spraying system.
The split stream may be 2-4 but is not limited thereto.
In one embodiment of the present invention, the shunt system comprises:
a tower kettle pump arranged at the downstream of the tower kettle outlet;
and a branch line for returning part of liquid-phase materials into the tower is arranged at the downstream of the tower kettle pump, and the number of the branch lines is 2-4, but not limited to the number.
In one embodiment of the invention, the back spray system is of a ring, linear or grid type construction.
In one embodiment of the present invention, the reverse spray system comprises:
a circular structure spray device; a linear structure spray device; a grid-type structure spray device; and
the combination of the above spraying devices.
In a specific embodiment, a polymerization inhibitor-containing tower kettle material is introduced into a tower from a tower kettle pump outlet pipeline (namely a branch line), wherein one path is provided with a DN 25-DN 80 ring pipe and 2-4 feed inlets, the polymerization inhibitor-containing tower kettle material is upwards and reversely sprayed to a joint of a tower wall and a bowl edge through 18-72 nozzles on an annular pipeline in the tower, an angle is 50-80 degrees, and the flow rate of each nozzle is 3-12 liters/minute. And the other path is also provided with a DN 25-DN 80 ring pipe and 1-2 feed inlets, the materials are upwards and reversely sprayed to the bowl-shaped bottom through 16-64 nozzles on the grid-type pipeline in the tower, the wide angle is 100-130 degrees, and the flow of each nozzle is 3-12 liters/minute.
Crude styrene separation method
The second aspect of the present invention provides a crude styrene separation method for reducing scaling at the bottom of a crude styrene separation column, comprising the steps of:
shunting part of the liquid-phase material in the tower kettle and returning the liquid-phase material to the tower kettle; and
and reversely spraying the shunted materials to the inner wall of the tower kettle.
In a specific embodiment, the liquid-phase material in the tower kettle is divided into 2-4 parts and then is subjected to reverse spraying.
In a specific embodiment, a polymerization inhibitor-containing tower kettle material is introduced into a tower from a tower kettle pump outlet pipeline (namely a branch line), wherein one path is provided with a DN 25-DN 80 ring pipe and 2-4 feed inlets, the polymerization inhibitor-containing tower kettle material is upwards and reversely sprayed to a joint of a tower wall and a bowl edge through 18-72 nozzles on an annular pipeline in the tower, an angle is 50-80 degrees, and the flow rate of each nozzle is 3-12 liters/minute. And the other path is also provided with a DN 25-DN 80 ring pipe and 1-2 feed inlets, the materials are upwards and reversely sprayed to the bowl-shaped bottom through 16-64 nozzles on the grid-type pipeline in the tower, the wide angle is 100-130 degrees, and the flow of each nozzle is 3-12 liters/minute.
A third aspect of the present invention provides the use of a crude styrene separation unit according to the present invention for reducing fouling in the bottom of a crude styrene separation column.
PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic diagram of a separation column of a crude styrene separation process typical of current styrene industrial plants.
In fig. 1, 101 is a rectifying column, 102 is a column bottom pump, 1 is a rectifying column feeding material, i.e. crude styrene, 2 is a rectifying column top discharging material, and 3 is a rectifying column bottom discharging material, which is used in the next step and contains styrene, polymerization inhibitor, weight and the like. Styrene rectification inhibitor 4(DNBP or similar functional chemical agent) and/or second rectification inhibitor 5 (real inhibitor) are injected into the rectification column along with the rectification column feed 1 or into the feed of the upstream column system. At present, most devices use DNBP or similar functional chemical agents to be matched with a real polymerization inhibitor for use, so that the polymerization inhibition effect is better, the DNBP is not consumed in the using process, and the DNBP can be repeatedly used; the real polymerization inhibitor is consumed in the using process and can not be reused.
In the crude styrene rectification process, the temperature of the bottom of the rectification tower is generally 85-125 ℃, and the styrene content of partial bottom materials of the rectification tower is more than 50 wt%. In the course of refining crude styrene, the styrene is heated and evaporated under high temperature in the tower kettle material containing high-concentration styrene, or the styrene gas phase reaching vapor-liquid equilibrium in the larger gas phase space in the tower kettle meets the internal components of the tower kettle and is condensed to form a styrene liquid film without polymerization inhibitor, part of the liquid styrene can generate polymerization reaction to generate polymer, and part of the polymer can be accumulated in a proper place.
In actual production operation, the phenomenon of wall-hanging scaling of styrene polymers can occur in a tower kettle of a crude styrene rectifying tower, a discharge pipeline of the tower kettle can be blocked under severe conditions, stable operation of the tower is affected, and even the tower needs to be stopped for cleaning.
Therefore, in order to stably perform device production for a long period, the existing process and equipment need to be improved, the long-period, safe and stable operation of the production device is met, and potential safety hazards in production are eliminated.
In response to the polymerization problem of crude styrene distillation, process patentees have employed the addition of polymerization inhibitors to the feed to prevent and slow the polymerization of styrene during the distillation process; there are also some patents which propose different improvements, such as US005910232A which proposes to improve the effect of inhibiting polymerization by adding a nitrated radical compound to the material; the Chinese patent CN101157083 proposes to increase the scale formation in the spray cleaning pipeline in the gas phase flow pipeline. However, according to the above patents and techniques, either the crude styrene distillation process is not suitable or the fouling of the polymer wall build-up during operation still often occurs inside the equipment which presents the surface of the gas phase space through which no liquid material flows, and the equipment often needs to be shut down to clean the polymer, reducing the operation efficiency of the equipment.
The present invention has been accomplished in view of the above circumstances and the practical success of production, and the present invention provides a feasible method for solving this problem, enabling a production apparatus to operate safely, continuously and stably.
The invention aims to solve the technical problem that the wall built-up scaling of styrene polymers at the bottom of a rectifying tower occurs in the traditional crude styrene rectifying process, because a separating tower bottom in the crude styrene rectifying process has a certain gas phase space, the surface of the space is not directly contacted with liquid materials at the bottom of the rectifying tower, vapor phase formed after styrene in the liquid materials at the bottom of the rectifying tower is heated and evaporated or vapor phase balanced with the liquid materials at the bottom of the rectifying tower reaches the surface of the gas phase space at the bottom of the rectifying tower and is condensed to form liquid drops, and because the boiling point of a polymerization inhibitor in the liquid materials at the bottom of the rectifying tower is higher, the saturated vapor pressure is low and the polymerization inhibitor is hardly volatilized, the formed styrene liquid drops hardly contain any polymerization inhibitor. As the residence time is prolonged, the styrene droplets slowly polymerize to form polymer, and the polymer grows up day by day and month to form wall-hanging polymer similar to stalactite, namely the fouling of the tower kettle occurs. The tower kettle of the rectifying tower is often characterized by high temperature, generally between 85 ℃ and 125 ℃; another characterization is that the styrene content is high, typically around 50% wt. In order to solve the problem of wall-hanging scaling of styrene polymers generated in the rectifying tower in the process of crude styrene rectification, the invention adopts the following technical scheme: the method for solving the fouling of the crude styrene separation tower comprises the following steps:
1. a tower bottom material flow is led out from a tower bottom discharge pipeline of the crude styrene separation tower, and the material flow is pumped out from a tower bottom. The tower bottom material flow contains ethylbenzene, styrene, alpha-methyl styrene, polymer, high boiling point matter, polymerization inhibitor DNBP or similar functional chemical agent, and is suitable for refining qualified styrene, and the content of the polymerization inhibitor DNBP or similar functional chemical agent is 680-1500 ppm.
2. One or more sets of spraying systems are added in the tower kettle of the crude styrene separation tower, and the annular type, the linear type or the grid type can be adopted according to the structural forms of different tower kettles
3. Part of the liquid phase material in the tower kettle is reversely sprayed to the inner wall of the tower kettle through a spraying system in the tower kettle of the crude styrene separation tower, in particular to a place where styrene polymer is easy to be hung on a wall and scaled.
4. The spraying system sprays liquid materials containing polymerization inhibitor to wash the surface of the gas phase space, so that the retention time of styrene condensed on the surface of the gas phase space is reduced, the liquid on the surface of the gas phase space is kept in a flowing state all the time and is fully mixed with the polymerization inhibitor in the sprayed materials (flushing liquid).
5. The spraying system sprays out the liquid material containing the polymerization inhibitor to flush the surface of the gas-phase space, and even if the polymer is formed, the polymer formed can be dissolved or can not grow because of the existence of the flushing of the liquid material containing the polymerization inhibitor.
6. Spray system for dividing tower kettle material flow of crude styrene separation tower into 2-4 points and introducing into tower kettle
The invention provides a method for solving the problem of wall-hanging scaling of styrene polymers generated in a rectifying tower in the process of rectifying crude styrene. In the method, a part of the tower bottom discharge of the crude styrene separation tower is introduced into the tower bottom, and is reversely sprayed to the bottom of the tower bottom through a special spraying device to dissolve and flush styrene or styrene polymers staying on the surface of the tower bottom, so that the polymer wall hanging and scaling phenomenon of the tower bottom disappears or is slowed down. The invention takes a separation tower in the crude styrene rectification process in figure 1 as an example to describe the content of the patent invention, and is also applicable to other types of rectification towers and solutions to similar problems of chemical devices of related processes.
Technical effects
The invention solves the problem of the wall-hanging scaling of the styrene polymer at the bottom of the high-temperature tower system which is caused in the crude styrene rectification process for a long time, and meets the requirements of long-period, safe and stable operation of a production device; the potential safety hazard in production is eliminated, the device is suitable for being popularized and used in the existing similar devices and newly-built devices, and considerable economic benefits are generated.
Unless otherwise specified, various starting materials of the present invention are commercially available; or prepared according to conventional methods in the art. Unless defined or stated otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention.
Other aspects of the invention will be apparent to those skilled in the art in view of the disclosure herein.
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental methods of the following examples, which are not specified under specific conditions, are generally determined according to national standards. If there is no corresponding national standard, it is carried out according to the usual international standards, to the conventional conditions or to the conditions recommended by the manufacturer. Unless otherwise indicated, all parts are parts by weight, all percentages are percentages by weight, and the length units are millimeters.
Unless defined or stated otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention.
Examples
In accordance with the present invention, a crude styrene splitter fouling solution process is used for a 50 ten thousand ton year styrene plant, as shown in figure 2.
In the ethylbenzene-styrene separation tower 101 in the crude styrene separation and rectification process, a tower kettle has a bowl-shaped structure, the inner diameter of the tower is 7600mm, the height of a bottom gas phase space is 6800 mm, and the volume of the bottom gas phase space is about 250 cubic meters.
The ethylbenzene styrene splitter 101 has a column bottom temperature of 120 deg.C and a pressure of 40.5kpa, and the column bottom stream typically has the following composition:
the main part that styrene polymer wall built-up scale deposit is at the bottom of the bowl of bowl type structure between the top edge of tower cauldron bowl type structure and the tower wall, bowl type side evenly distributed 8 ~ 20 mm's hole so that contain polymerization inhibitor's liquid dashes and rinses bowl type lateral surface in the bowl in the conventional scale formation device that prevents, but receive the restriction of hole quantity, unlimited trompil is impossible, have partial area to dash and rinse by the liquid that contains polymerization inhibitor all the time between the top edge of tower cauldron bowl type structure and the tower wall and at the bottom of the bowl of bowl type structure, styrene polymer forms gradually here.
It can be said that the styrene polymer is mainly generated in liquid phase styrene without polymerization inhibitor, and the liquid phase styrene containing polymerization inhibitor rarely forms wall-hanging polymer in the operation period, even no wall-hanging polymer is generated. The gas phase space at the bottom of the ethylbenzene-styrene separation tower 101 is relatively large, the vapor phase formed after the styrene is heated and evaporated or the vapor phase balanced with the liquid phase reaches the bowl-shaped side surface and the bottom of the tower kettle and is condensed to form liquid drops, and the formed styrene liquid drops hardly contain any polymerization inhibitor due to the fact that the boiling point of the polymerization inhibitor is relatively high, the saturated steam pressure is low, and the polymerization inhibitor hardly volatilizes. Because the residence time of liquid drops at the joint of the tower wall and the bowl edge and in the bowl-shaped bottom area is long, meanwhile, the liquid-phase styrene with polymerization inhibitor in the bowl-shaped inner part with the bowl-shaped side surface coming from the hole can not completely wash the styrene drops formed below or some liquid drops can not contact the liquid-phase styrene with polymerization inhibitor at all, therefore, the styrene drops slowly polymerize to form polymer, and the polymer is accumulated in the day and the month to form wall-hanging polymer similar to stalactite, namely the tower kettle is scaled.
According to the above-described wall built-up polymer formation mechanism,
the invention provides a crude styrene separation device for reducing scaling of a tower kettle of a crude styrene separation tower, wherein an anti-scaling safety device is arranged at a position which is easy to scale in the tower kettle, and the anti-scaling safety device comprises a conventional anti-scaling system and a high-temperature anti-scaling system; wherein,
the conventional anti-scaling system comprises 8-20 mm pores uniformly distributed on the bowl-shaped side surface, so that liquid containing polymerization inhibitor in the bowl can wash the bowl-shaped side surface; and
the high-temperature anti-scaling system comprises one or more reverse spraying systems, and the reverse spraying systems spray the shunted materials to the inner wall of the tower kettle according to a required direction;
and the high-temperature anti-scaling system is started when the scaling critical point of the crude styrene is reached in the tower kettle.
Specifically, a polymerization inhibitor-containing tower kettle material 6 is introduced into the tower from a tower kettle pump outlet pipeline, wherein one path is provided with a DN 25-DN 80 ring pipe, and the diameter of the ring pipe is selected to be matched with the flow required by spraying. 2-4 feed inlets, wherein the number of the feed inlets is mainly set in consideration of the uniformity of the sprayed liquid; the spraying water is upwards and reversely sprayed to the joint of the tower wall and the bowl edge through 18-72 nozzles on an annular pipeline in the tower, and the number of the nozzles depends on the area needing spraying and the minimum number needed for fully covering the area needing spraying; the flow rate of each nozzle is 3-12 liters/minute, and the flow rate of the nozzle depends on the form of the nozzle, the pressure of the pipeline and the total flow allowed by the process. And the other path is also provided with a DN 25-DN 80 ring pipe and 1-2 feed inlets, the materials are upwards and reversely sprayed to the bowl-shaped bottom through 16-64 nozzles on the grid-type pipeline in the tower, and the flow rate of each nozzle is 3-12 liters per minute.
The high temperature anti-fouling system was started at 118 ℃.
Comparative example 1
The crude styrene rectifying device which is the same as the crude styrene rectifying device in the embodiment 1 is not provided with the method for solving the scale formation of the crude styrene separating tower, and as a result, after the device runs for six months, the polymer blockage phenomenon gradually occurs on the inlet pipeline of the tower kettle pump of the ethylbenzene styrene separating tower 101, and the shutdown inspection shows that the stalactite-shaped styrene polymer wall-hanging scale formation is formed between the upper edge of the bowl-shaped structure of the tower kettle and the tower wall and the bowl bottom of the bowl-shaped structure, and the scale formation is caused by the fact that the crude styrene polymer wall-hanging scale formation enters the inlet pipeline of the tower.
Example 2
The bottom of the ethylbenzene-styrene separation tower 101 was modified according to the steps and conditions of example 1, and the improved process is shown in fig. 2, so that the ethylbenzene-styrene separation tower 101 was still in good condition after 26 months of operation, and the parameters, equipment and meters showed no sign of polymer formation.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the scope of the invention, which is defined by the claims appended hereto, and any other technical entity or method that is encompassed by the claims as broadly defined herein, or equivalent variations thereof, is contemplated as being encompassed by the claims.
All documents referred to herein are incorporated by reference into this application as if each were individually incorporated by reference. Furthermore, it should be understood that various changes and modifications can be made by those skilled in the art after reading the above disclosure, and equivalents also fall within the scope of the invention as defined by the appended claims.
Claims (10)
1. A crude styrene separation device for reducing scaling of a tower kettle of a crude styrene separation tower is disclosed, wherein an anti-scaling safety device is arranged at a position which is easy to scale in the tower kettle, and a high-temperature anti-scaling system is arranged in the anti-scaling safety device; wherein,
the high temperature anti-fouling system comprises:
one or more shunting devices, wherein the shunting devices shunt 10-30 wt% of the liquid-phase material in the tower kettle and return the liquid-phase material to the tower kettle; and
one or more reverse spraying systems, wherein the reverse spraying systems spray the shunted materials to the inner wall of the tower kettle according to a required direction;
and the high-temperature anti-scaling system is started when the scaling critical point of the crude styrene is reached in the tower kettle.
2. The crude styrene separation unit of claim 1, wherein the fouling prone portion comprises a bottom of the column bottom.
3. The crude styrene separation apparatus as claimed in claim 1, wherein the crude styrene has a fouling critical point of 115 to 120 ℃.
4. The crude styrene separation unit of claim 1, wherein in the high temperature anti-scaling system, the counter-current spraying system sprays the diverted material to the inner wall of the column bottom in a counter-current direction.
5. The crude styrene separation unit of claim 1, wherein the liquid phase material in the bottom of the column is introduced to the outside of the bottom of the column and then introduced to the spray system.
6. The crude styrene separation unit of claim 5, wherein the split stream system comprises:
a tower kettle pump arranged at the downstream of the tower kettle outlet;
and 2-4 branch lines for returning part of liquid-phase materials into the tower are arranged at the downstream of the tower kettle pump.
7. The crude styrene separation apparatus of claim 1, wherein the counter current spray system is of a ring type, linear type or grid type configuration.
8. The crude styrene separation unit of claim 1, wherein the reverse spray system comprises:
a circular structure spray device; a linear structure spray device; a grid-type structure spray device; and
the combination of the above spraying devices.
9. A crude styrene separation method for reducing the scale formation of a tower kettle of a crude styrene separation tower comprises the following steps:
shunting part of the liquid-phase material in the tower kettle and returning the liquid-phase material to the tower kettle; and
and reversely spraying the shunted materials to the inner wall of the tower kettle.
10. Use of a crude styrene separation unit as defined in claim 1 for reducing fouling in the bottom of a crude styrene separation column.
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