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Abstract: This article discusses the use of the valve in the catalyst regeneration section of the catalytic reforming process in the oil refining industry and the problems that have arisen. Based on the comparative analysis, the valve structure has been improved to improve the serviceability of the valve and prolong the service life of the valve purpose.
Improvement of crude oil refining is an important process that must go through after the exploitation of crude oil. Over the years, the research and optimization of various refining processes have never stopped, and the purpose is to improve the quality of products , Reduce energy consumption, improve economy and enhance safety. In a variety of processes, the catalytic reforming process is a more mature process, after a series of improvements, its process performance has been significantly improved, but there are still some problems to be solved, in particular, the catalyst Regeneration process improvement, is directly related to whether a substantial increase in productivity, reduce costs, reduce downtime and other issues. In this paper, the actual conditions of the catalytic reforming process and customer feedback, focusing on the process of some important positions in the valve in the use of existing problems, and provide targeted solutions.
1 Catalytic reforming process and catalyst regeneration process Catalytic reforming process is widely used in petroleum and petrochemical industry, is a chemical process converting naphtha distilled from crude oil into high octane reformate. This process converts low octane linear hydrocarbons to branched paraffins (isoparaffins) and naphthenes, which are partially dehydrogenated to produce high octane aromatics. The dehydrogenation process also produces large amounts of by-product hydrogen that can be supplied to other refinery processes such as hydrocracking to produce lower molecular weight hydrocarbons such as methane, ethane, propane, and butane. In addition to being the main source of petrol blending, reforming or aromatics bulk chemicals such as stupid, toluene, xylene (BTX) and ethylbenzene, they have a variety of uses, most importantly as plastic conversion raw materials.
The performance of the catalyst is crucial in the reforming reaction. Its selectivity, activity and stability are critical to the yield and yield of the final product. However, as the reaction continues, the catalyst gradually cokes and inactivates the reaction performance Deteriorate, and the reaction efficiency is lowered. Therefore, the catalyst needs to be regenerated and renewed after being used for a period of time. UOP (American Global Quality Company) in 1971 to develop and commercialize the catalyst continuous regeneration process (CATALYST Co nTINUOUS REGENERATION), referred to as CCR (see Figure 1). In the process, the catalyst can be continuously removed from the last stage reactor, regenerated in a specific environment and returned to the first stage reactor. The CCR process achieves a gradual improvement of the reforming technology. Due to the repeated regeneration, the coke can be continuously burned off and the catalyst has been continuously repaired, so the coke deposition is no longer a difficult point. Meanwhile, the CCR process can reduce the reaction pressure, increase the octane number of gasoline products and increase the hydrogen production.
2 regeneration process requirements, features and issues 2.1 process requirements CCR process includes separation, charcoal, halogenation, drying and reduction of four parts. The reacted catalyst flows out from the bottom of the reactor, is lifted to the separation hopper at the top of the regenerator, removes the dust in the separation zone, burns the coke on the catalyst surface through the charcoal burning zone, and then increases the acidity of the catalyst surface through the halogenated zone Part, and then drying to remove moisture, through the reduction zone in the hydrogen environment reduction reaction to complete the regeneration process. The regenerated catalyst was collected in a lock hopper, sent to the bottom riser in batches and then to the top of the reactor.
The catalyst continuously flows through each part of the regeneration process and is sent in batch to the reactor in the bottom lock hopper according to a preset amount. The regeneration amount of each batch of the catalyst determines the regeneration cycle rate of the catalyst, which also determines the weight The reaction rate of the entire process reactor therefore requires the installation of a valve cooperating lock hopper between each of the links throughout the regeneration system to accurately control the amount of catalyst flowing through each reaction section. Which need to select the appropriate valve according to working conditions.
2.2 Blocking hopper block valve features of the operating conditions Located upstream of the hopper catalyst contains hydrogen, so the valve has a higher anti-leakage performance.
The catalyst is granular during use, about 0.6 mm in diameter, requiring the catalyst not to be crushed during valve opening and closing.
The catalyst contains a certain amount of dust, requiring the valve parts have a high anti-wear performance.
The process environment in the lock hopper area is ≤ 100 PSI, temperature ≤ 200 ° C, seal class ≤ ANSI Class IV, bi-directional seal.
2.3 valve problems In the valve opening and closing the use of the process, some of the catalyst particles are crushed to form a powder, and the catalyst in a certain amount of dust accumulation in the valve seat and seat sealing position both wear and tear, the valve loss Sealing performance; powder and dust will also accumulate in the gap between the drive shaft and bearing to increase the opening and closing torque, reducing control performance; dust accumulation between the drive shaft and the filler will cause wear on the filler and drive shaft surface resulting in filler failure , Causing the medium to leak into the atmosphere as a result of the presence of hydrogen in the catalyst upstream of the hopper, resulting in a fire; Fig. 2 shows the surface wear of the drive shaft.
3 General valve design 3.1 Material Selection Sealing ring and the valve flap to choose anti-erosion, but also has a certain anti-corrosion materials, general-purpose materials for the austenitic stainless steel, in order to increase the anti-abrasion performance, the need to use some coatings to increase the hardness of materials such as chrome, Chromium, tungsten carbide and nickel-boron alloys are also used to enhance wear resistance, but their applications are limited due to their general corrosion resistance.
Drive shaft material needs both toughness and wear resistance at the same time, common materials for the precipitation of hardened steel chrome or surfacing cobalt-based hard alloy.
3.2 Structure Design In order to avoid the catalyst being crushed in the flow process, there is a gap between the valve sealing ring and the valve disc so as to ensure the smooth flow of the catalyst. Because the gap can not seal the valve, the valve with the shut-off function needs to be used in combination.
In order to ensure that the reduction reaction hydrogen does not leak to the atmosphere, a pre-loading system is designed in the packing part to ensure that the load is automatically compensated for the purpose of preventing the leakage after the wear-relaxation of the packing is performed for a long time.
4 valves to improve the design 4.1 Material Selection Ceramic materials with the industrialization in recent years to improve the wider application in the valve industry, its excellent resistance to abrasion and corrosion resistance to meet a variety of conditions, the type is quite extensive, such as oxidation Aluminum Ceramics, Zirconia Ceramics, Silicon Carbide Ceramics, etc. The disadvantage is that it is sensitive to tensile stress and shear stress. The internal structure state is sensitive to process stability and difficult to process.
Ion nitriding process can make the coating hardness of 67 HRC, the effective coating hardness greater than 50 HRC. But because carburizing nitriding process will reduce the corrosion resistance of the material, so it is only suitable for non-corrosive conditions.
Cobalt-based hardfacing on the drive shaft surface can effectively increase the wear resistance of the surface. In addition, chrome plating is also an effective method.
4.2 Structural Design In order to avoid catalyst dust accumulation in the valve seal area, the use of global design than the partial ball design has the advantage of fixed ball design than the floating ball design has the advantage of the back seat in the design of pre-tensioned elastic module should be Avoid semi-enclosed areas to eliminate the possibility of dust accumulation and reduce the risk of increased torque and even jamming. In the design of seals to reduce the structure easy to dust accumulation. Seal should be designed as symmetrical structure to facilitate replacement, reduce costs.
The packing structure should give priority to the design scheme with the dish spring. When the packing is loosened after being used for a period of time, the disc spring automatically deforms to achieve the compensation of the packing load. This design scheme can prevent the hydrogen gas timely and effectively without human intervention In the filler at the leak; In addition, the filler should also be used negative pressure leakproof design, which is characterized by: the use of double packing layout, the middle of the metal separator ring will be placed on the two sets of packing, the next two sides, the location of the ring The side wall of the valve body is provided with a through hole through which the connecting pipe fittings are arranged, the other end of the pipe fittings is connected with the gas container, and the pressure in the container is set to negative pressure. When hydrogen reaches the partition ring through the under packing, The formation of external leakage, while under the action of negative pressure, hydrogen automatically into the gas container for preservation. This packing structure design to further reduce the risk of hydrogen leakage, but also ruled out security risks.
Summary Through the use of special materials and the use of special structural design, can effectively improve the efficiency of the valve to extend the service life and reduce maintenance downtime, but also significantly reduce the owners of spare parts and reduce the cost of inventory. The new packing structure design greatly reduces the chance of hydrogen leakage, avoids the occurrence of fire, provides security for on-site operations, reduces personnel inspection time and reduces labor costs.
references:
[1] "HYDROCARBON PROCESSING'S REFINING PROCESSES 2006 HANDBOOK"
[2] "TECHNOLOGY EVOLUTION IN REFINING AND PETROCHEMICALS"
Improvement of crude oil refining is an important process that must go through after the exploitation of crude oil. Over the years, the research and optimization of various refining processes have never stopped, and the purpose is to improve the quality of products , Reduce energy consumption, improve economy and enhance safety. In a variety of processes, the catalytic reforming process is a more mature process, after a series of improvements, its process performance has been significantly improved, but there are still some problems to be solved, in particular, the catalyst Regeneration process improvement, is directly related to whether a substantial increase in productivity, reduce costs, reduce downtime and other issues. In this paper, the actual conditions of the catalytic reforming process and customer feedback, focusing on the process of some important positions in the valve in the use of existing problems, and provide targeted solutions.
1 Catalytic reforming process and catalyst regeneration process Catalytic reforming process is widely used in petroleum and petrochemical industry, is a chemical process converting naphtha distilled from crude oil into high octane reformate. This process converts low octane linear hydrocarbons to branched paraffins (isoparaffins) and naphthenes, which are partially dehydrogenated to produce high octane aromatics. The dehydrogenation process also produces large amounts of by-product hydrogen that can be supplied to other refinery processes such as hydrocracking to produce lower molecular weight hydrocarbons such as methane, ethane, propane, and butane. In addition to being the main source of petrol blending, reforming or aromatics bulk chemicals such as stupid, toluene, xylene (BTX) and ethylbenzene, they have a variety of uses, most importantly as plastic conversion raw materials.
The performance of the catalyst is crucial in the reforming reaction. Its selectivity, activity and stability are critical to the yield and yield of the final product. However, as the reaction continues, the catalyst gradually cokes and inactivates the reaction performance Deteriorate, and the reaction efficiency is lowered. Therefore, the catalyst needs to be regenerated and renewed after being used for a period of time. UOP (American Global Quality Company) in 1971 to develop and commercialize the catalyst continuous regeneration process (CATALYST Co nTINUOUS REGENERATION), referred to as CCR (see Figure 1). In the process, the catalyst can be continuously removed from the last stage reactor, regenerated in a specific environment and returned to the first stage reactor. The CCR process achieves a gradual improvement of the reforming technology. Due to the repeated regeneration, the coke can be continuously burned off and the catalyst has been continuously repaired, so the coke deposition is no longer a difficult point. Meanwhile, the CCR process can reduce the reaction pressure, increase the octane number of gasoline products and increase the hydrogen production.
2 regeneration process requirements, features and issues 2.1 process requirements CCR process includes separation, charcoal, halogenation, drying and reduction of four parts. The reacted catalyst flows out from the bottom of the reactor, is lifted to the separation hopper at the top of the regenerator, removes the dust in the separation zone, burns the coke on the catalyst surface through the charcoal burning zone, and then increases the acidity of the catalyst surface through the halogenated zone Part, and then drying to remove moisture, through the reduction zone in the hydrogen environment reduction reaction to complete the regeneration process. The regenerated catalyst was collected in a lock hopper, sent to the bottom riser in batches and then to the top of the reactor.
The catalyst continuously flows through each part of the regeneration process and is sent in batch to the reactor in the bottom lock hopper according to a preset amount. The regeneration amount of each batch of the catalyst determines the regeneration cycle rate of the catalyst, which also determines the weight The reaction rate of the entire process reactor therefore requires the installation of a valve cooperating lock hopper between each of the links throughout the regeneration system to accurately control the amount of catalyst flowing through each reaction section. Which need to select the appropriate valve according to working conditions.
2.2 Blocking hopper block valve features of the operating conditions Located upstream of the hopper catalyst contains hydrogen, so the valve has a higher anti-leakage performance.
The catalyst is granular during use, about 0.6 mm in diameter, requiring the catalyst not to be crushed during valve opening and closing.
The catalyst contains a certain amount of dust, requiring the valve parts have a high anti-wear performance.
The process environment in the lock hopper area is ≤ 100 PSI, temperature ≤ 200 ° C, seal class ≤ ANSI Class IV, bi-directional seal.
2.3 valve problems In the valve opening and closing the use of the process, some of the catalyst particles are crushed to form a powder, and the catalyst in a certain amount of dust accumulation in the valve seat and seat sealing position both wear and tear, the valve loss Sealing performance; powder and dust will also accumulate in the gap between the drive shaft and bearing to increase the opening and closing torque, reducing control performance; dust accumulation between the drive shaft and the filler will cause wear on the filler and drive shaft surface resulting in filler failure , Causing the medium to leak into the atmosphere as a result of the presence of hydrogen in the catalyst upstream of the hopper, resulting in a fire; Fig. 2 shows the surface wear of the drive shaft.
3 General valve design 3.1 Material Selection Sealing ring and the valve flap to choose anti-erosion, but also has a certain anti-corrosion materials, general-purpose materials for the austenitic stainless steel, in order to increase the anti-abrasion performance, the need to use some coatings to increase the hardness of materials such as chrome, Chromium, tungsten carbide and nickel-boron alloys are also used to enhance wear resistance, but their applications are limited due to their general corrosion resistance.
Drive shaft material needs both toughness and wear resistance at the same time, common materials for the precipitation of hardened steel chrome or surfacing cobalt-based hard alloy.
3.2 Structure Design In order to avoid the catalyst being crushed in the flow process, there is a gap between the valve sealing ring and the valve disc so as to ensure the smooth flow of the catalyst. Because the gap can not seal the valve, the valve with the shut-off function needs to be used in combination.
In order to ensure that the reduction reaction hydrogen does not leak to the atmosphere, a pre-loading system is designed in the packing part to ensure that the load is automatically compensated for the purpose of preventing the leakage after the wear-relaxation of the packing is performed for a long time.
4 valves to improve the design 4.1 Material Selection Ceramic materials with the industrialization in recent years to improve the wider application in the valve industry, its excellent resistance to abrasion and corrosion resistance to meet a variety of conditions, the type is quite extensive, such as oxidation Aluminum Ceramics, Zirconia Ceramics, Silicon Carbide Ceramics, etc. The disadvantage is that it is sensitive to tensile stress and shear stress. The internal structure state is sensitive to process stability and difficult to process.
Ion nitriding process can make the coating hardness of 67 HRC, the effective coating hardness greater than 50 HRC. But because carburizing nitriding process will reduce the corrosion resistance of the material, so it is only suitable for non-corrosive conditions.
Cobalt-based hardfacing on the drive shaft surface can effectively increase the wear resistance of the surface. In addition, chrome plating is also an effective method.
4.2 Structural Design In order to avoid catalyst dust accumulation in the valve seal area, the use of global design than the partial ball design has the advantage of fixed ball design than the floating ball design has the advantage of the back seat in the design of pre-tensioned elastic module should be Avoid semi-enclosed areas to eliminate the possibility of dust accumulation and reduce the risk of increased torque and even jamming. In the design of seals to reduce the structure easy to dust accumulation. Seal should be designed as symmetrical structure to facilitate replacement, reduce costs.
The packing structure should give priority to the design scheme with the dish spring. When the packing is loosened after being used for a period of time, the disc spring automatically deforms to achieve the compensation of the packing load. This design scheme can prevent the hydrogen gas timely and effectively without human intervention In the filler at the leak; In addition, the filler should also be used negative pressure leakproof design, which is characterized by: the use of double packing layout, the middle of the metal separator ring will be placed on the two sets of packing, the next two sides, the location of the ring The side wall of the valve body is provided with a through hole through which the connecting pipe fittings are arranged, the other end of the pipe fittings is connected with the gas container, and the pressure in the container is set to negative pressure. When hydrogen reaches the partition ring through the under packing, The formation of external leakage, while under the action of negative pressure, hydrogen automatically into the gas container for preservation. This packing structure design to further reduce the risk of hydrogen leakage, but also ruled out security risks.
Summary Through the use of special materials and the use of special structural design, can effectively improve the efficiency of the valve to extend the service life and reduce maintenance downtime, but also significantly reduce the owners of spare parts and reduce the cost of inventory. The new packing structure design greatly reduces the chance of hydrogen leakage, avoids the occurrence of fire, provides security for on-site operations, reduces personnel inspection time and reduces labor costs.
references:
[1] "HYDROCARBON PROCESSING'S REFINING PROCESSES 2006 HANDBOOK"
[2] "TECHNOLOGY EVOLUTION IN REFINING AND PETROCHEMICALS"
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