06-03-2013, 04:47 PM
Modeling of catalytic reactor for a Sulfuric acid production
[attachment=52805]
Abstract
The raw material for sulfuric acid manufacture is clean SO2 gas. Its comes from (i) burning molten by-product sulfur ; (ii) roasting or smelting metal sulphide concentrates, and (iii) decomposing contaminated organic chemical process sulfuric acid catalyst. Efficient gas cleaning is required for metallurgical and contaminated acid decomposition gasses, especially the former. Sulfuric acid is made from SO2 gas by (i) oxidising the SO2 to SO3 in contact with supported liquid phase catalyst then (ii) reacting the resulting SO3 with the water component of 98 mass% H2SO4 , 1.5 mass% H2O acid.
This paper discusses the reason for these process steps and indicates how acid making can be controlled and optimised. Special emphasis is placed on SO2 oxidation efficiency and how it is influenced by feed gas composition, feed gas temperature catalyst composition, catalyst bed pressure, number of catalyst beds, and double versus single contact acid mocking. In addition review of various other treatment methods for SO2 bearing gasses is the provided. A brief description of each process is included along with commentary on there technical and economic on their technical and economic applicability for use at metallurgical facilities
Introduction
As the increase demand of a fertilizer world -wide Sulfuric acid demands also increase. It is a main raw material for a manufacturing of phosphate fertilizer for high level of crop production. Around 200 million metric tons of sulfuric acid is manufactured per year most of it from strong SO2 gas. India produces and consumes around 12 million tons per year of Sulfuric acid. A majority of the acid is used for making phosphate fertilizer, but it has a myriad of other uses.[ Carison, et al.(2002)]
The raw material for sulfuric acid manufacture is clean SO2 gas. Its comes from (i) burning molten by-product sulfur ; (ii) roasting or smelting metal sulphide concentrates, and (iii) decomposing contaminated organic chemical process sulfuric acid catalyst. Efficient gas cleaning is required for metallurgical and contaminated acid decomposition gasses, especially the former. Sulfuric acid is made from SO2 gas by (i) oxidising the SO2 to SO3 in contact with supported liquid phase catalyst then (ii) reacting the resulting SO3 with the water component of 98 mass% H2SO4 , 1.5 mass% H2O acid.
CATALYTIC REACTOR:
Catalytic reaction and reactors have wide spread applications in the production of chemicals in bulk, petroleum and petrochemicals, pharmaceuticals, speciality chemicals etc.
The wide spread application of the fixed bed reactors , they are as reactors with moving catalyst like fluidised bed reactors and effect of heat and mass transfer and high pressure operation in multiphase fluidised bed reactors .
Application of the bio catalytic reactions in various fields, methods of immobilization and advantages of using immobilized reactors & unconventional reactors like membrane reactor, photocatalytic reactor, moving bed and chromatographic reactors, monolytic reactors, reactive distillation cum catalytic reactors and microstructured catalytic reactors. [Jayaraman, et al. (2005)]
CATALYST:
Vanadium Oxide are very important industrial heterogeneous catalyst.V2O5 catalyst has been employed for oxidation of SO2 to SO3.Oxidation of SO2 over supported vanadia catalysts has been carefully studied ,and conclusive mechanisms have been drawn based heavily on O=V-(O-) structural models. Very recent theoretical and experimental studies. However ,strongly suggest that the catalyst should possess an 020=V-O- support structure Gas vanadium oxide cluster are excellent model system to help elucidate and understand molecular level processes occurring in the above mentioned reactions using vanadium catalysts. [He, et al. (2008)]
The characteristics of the catalyst which can be used are mentioned as follows:
1) Porous carrier having large surface area, controlled pore size and resistance to process gases at high temperature; in pellet form if used in fixed bed and powdered form if used for fluidized bed. Ex- Alumina, silica gel, zeolites.
2) Active catalytic agent: Vanadium pentaoxide in this case. Preparations are generally kept secret for the competitive reasons but they usually consist of adding water soluble compounds to gels or porous substrates and firing at temperature below the sintering point.
3) Promoter: Alkali and/or metallic compounds added in trace amounts to enhance the activity of the catalytic agent. [ Zhenxing, et al. (2003)]
FACTOR AFFECTING CATALYST LIFE
There are a number of factor which can impact the life of sulphuric acid catalyst. The catalyst life can be shortened through the following mechanisms:
Vanadium Loss: Dust accumulation in the bed; iron oxide corrosion product; chlorides in the gas streams; and acid contact with catalyst.
Moisture Contact: leaching of the active salts; decreased catalyst hardness.
Poison: arsenic
Carrier Degradation: fluorine attack; thermal cycling. [ Winkler, (2009)]
TEMPERATURE EFFECT IN CATALYST
In general, within a catalyst bed, catalyst damage will only occur if the bed temperature has been at least 100 higher than the initial operating temperature for the extended time period. The damage that can occurring is more physical that chemical in nature. At the high temperature, the structure of the catalyst support can change with subsequent decrease in surface area. The active ingredients within a sulfuric acid catalyst will vary from bed to bed as the level of SO3 in the gas stream is dependent on the overall conversion. Also, the SO2/SO3 ratio in the gas phase has a large effect on the composition of the active catalyst phse. The more highly sulphated lower bed catalyst will always performs very well in the upper beds, but both temperature and chemical effects on the upper bed catalyst prevent it from operating properly in the lower beds. [ Winkler, (2009)]
[attachment=52805]
Abstract
The raw material for sulfuric acid manufacture is clean SO2 gas. Its comes from (i) burning molten by-product sulfur ; (ii) roasting or smelting metal sulphide concentrates, and (iii) decomposing contaminated organic chemical process sulfuric acid catalyst. Efficient gas cleaning is required for metallurgical and contaminated acid decomposition gasses, especially the former. Sulfuric acid is made from SO2 gas by (i) oxidising the SO2 to SO3 in contact with supported liquid phase catalyst then (ii) reacting the resulting SO3 with the water component of 98 mass% H2SO4 , 1.5 mass% H2O acid.
This paper discusses the reason for these process steps and indicates how acid making can be controlled and optimised. Special emphasis is placed on SO2 oxidation efficiency and how it is influenced by feed gas composition, feed gas temperature catalyst composition, catalyst bed pressure, number of catalyst beds, and double versus single contact acid mocking. In addition review of various other treatment methods for SO2 bearing gasses is the provided. A brief description of each process is included along with commentary on there technical and economic on their technical and economic applicability for use at metallurgical facilities
Introduction
As the increase demand of a fertilizer world -wide Sulfuric acid demands also increase. It is a main raw material for a manufacturing of phosphate fertilizer for high level of crop production. Around 200 million metric tons of sulfuric acid is manufactured per year most of it from strong SO2 gas. India produces and consumes around 12 million tons per year of Sulfuric acid. A majority of the acid is used for making phosphate fertilizer, but it has a myriad of other uses.[ Carison, et al.(2002)]
The raw material for sulfuric acid manufacture is clean SO2 gas. Its comes from (i) burning molten by-product sulfur ; (ii) roasting or smelting metal sulphide concentrates, and (iii) decomposing contaminated organic chemical process sulfuric acid catalyst. Efficient gas cleaning is required for metallurgical and contaminated acid decomposition gasses, especially the former. Sulfuric acid is made from SO2 gas by (i) oxidising the SO2 to SO3 in contact with supported liquid phase catalyst then (ii) reacting the resulting SO3 with the water component of 98 mass% H2SO4 , 1.5 mass% H2O acid.
CATALYTIC REACTOR:
Catalytic reaction and reactors have wide spread applications in the production of chemicals in bulk, petroleum and petrochemicals, pharmaceuticals, speciality chemicals etc.
The wide spread application of the fixed bed reactors , they are as reactors with moving catalyst like fluidised bed reactors and effect of heat and mass transfer and high pressure operation in multiphase fluidised bed reactors .
Application of the bio catalytic reactions in various fields, methods of immobilization and advantages of using immobilized reactors & unconventional reactors like membrane reactor, photocatalytic reactor, moving bed and chromatographic reactors, monolytic reactors, reactive distillation cum catalytic reactors and microstructured catalytic reactors. [Jayaraman, et al. (2005)]
CATALYST:
Vanadium Oxide are very important industrial heterogeneous catalyst.V2O5 catalyst has been employed for oxidation of SO2 to SO3.Oxidation of SO2 over supported vanadia catalysts has been carefully studied ,and conclusive mechanisms have been drawn based heavily on O=V-(O-) structural models. Very recent theoretical and experimental studies. However ,strongly suggest that the catalyst should possess an 020=V-O- support structure Gas vanadium oxide cluster are excellent model system to help elucidate and understand molecular level processes occurring in the above mentioned reactions using vanadium catalysts. [He, et al. (2008)]
The characteristics of the catalyst which can be used are mentioned as follows:
1) Porous carrier having large surface area, controlled pore size and resistance to process gases at high temperature; in pellet form if used in fixed bed and powdered form if used for fluidized bed. Ex- Alumina, silica gel, zeolites.
2) Active catalytic agent: Vanadium pentaoxide in this case. Preparations are generally kept secret for the competitive reasons but they usually consist of adding water soluble compounds to gels or porous substrates and firing at temperature below the sintering point.
3) Promoter: Alkali and/or metallic compounds added in trace amounts to enhance the activity of the catalytic agent. [ Zhenxing, et al. (2003)]
FACTOR AFFECTING CATALYST LIFE
There are a number of factor which can impact the life of sulphuric acid catalyst. The catalyst life can be shortened through the following mechanisms:
Vanadium Loss: Dust accumulation in the bed; iron oxide corrosion product; chlorides in the gas streams; and acid contact with catalyst.
Moisture Contact: leaching of the active salts; decreased catalyst hardness.
Poison: arsenic
Carrier Degradation: fluorine attack; thermal cycling. [ Winkler, (2009)]
TEMPERATURE EFFECT IN CATALYST
In general, within a catalyst bed, catalyst damage will only occur if the bed temperature has been at least 100 higher than the initial operating temperature for the extended time period. The damage that can occurring is more physical that chemical in nature. At the high temperature, the structure of the catalyst support can change with subsequent decrease in surface area. The active ingredients within a sulfuric acid catalyst will vary from bed to bed as the level of SO3 in the gas stream is dependent on the overall conversion. Also, the SO2/SO3 ratio in the gas phase has a large effect on the composition of the active catalyst phse. The more highly sulphated lower bed catalyst will always performs very well in the upper beds, but both temperature and chemical effects on the upper bed catalyst prevent it from operating properly in the lower beds. [ Winkler, (2009)]