Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/69—Sulfur trioxide; Sulfuric acid
  • C01B17/74—Preparation
  • C01B17/76—Preparation by contact processes
  • C01B17/765—Multi-stage SO3-conversion
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/69—Sulfur trioxide; Sulfuric acid
  • C01B17/74—Preparation
  • C01B17/76—Preparation by contact processes
  • C01B17/78—Preparation by contact processes characterised by the catalyst used
  • C01B17/79—Preparation by contact processes characterised by the catalyst used containing vanadium
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/69—Sulfur trioxide; Sulfuric acid
  • C01B17/74—Preparation
  • C01B17/76—Preparation by contact processes
  • C01B17/80—Apparatus

Definitions

• the invention relates to a process and a plant for sulfuric acid production, wherein a sulfur dioxide-containing product gas stream is produced, which is fed to a reaction space in which a reaction of sulfur dioxide to sulfur trioxide takes place on a catalyst and the resulting sulfur trioxide is converted into further plant parts to sulfuric acid.
• Sulfuric acid is one of the most important basic chemicals. Their large-scale production takes place in three steps: 1. Production of sulfur dioxide (SO2),
• raw material for the sulfuric acid production can serve elemental sulfur. It is used in the desulphurisation of crude oil or natural gas in refineries or in the scouring of sulphidic ores, as well as in the desulphurisation of the flue gases of coal-fired power stations. If sulfur is used as raw material, the production of sulfur dioxide takes place by the combustion of sulfur in atomising burners, whereby the liquid sulfur is pressed under high pressure into the burner nozzle. Sulfur dioxide can also be generated by combustion or catalytic conversion of hydrogen sulfide-containing exhaust gases, which are obtained, for example, in the purification of coke oven gases.
• the raw gas produced in the first production step usually has an SO 2 content of between 3 and 12% by volume.
• the raw gas is usually cooled in a waste heat boiler and diluted to adjust a superstoichiometric O2 / S ⁇ 2 ratio, if necessary with air.
• the exothermic reaction of SO 2 to SO 3 occurs on catalysts, such as vanadium pentoxide (V 2 O 5), at temperatures from 400 to 650 0 C.
• V 2 O 5 vanadium pentoxide
• the conversion of SO 2 to SO 3 is driven with a large excess of air. There are two reasons. On the one hand, a high oxygen concentration shifts the reaction equilibrium in the direction of sulfur trioxide. On the other hand, the air is used to cool the gas between two reactor beds, which heat exchangers can be saved.
• the SO 3 formed in the second production step is cooled and passed into an absorber.
• the absorber contains a packed bed, which is sprinkled from above with circulated sulfuric acid. That in countercurrent
• the object of the invention is to provide a process in which a high yield of sulfuric acid is achieved with a small amount of catalyst. Furthermore, the apparatuses used should be as small as possible and therefore cost-effective in relation to the amount of sulfuric acid produced. This object is achieved in that the reaction space in alternation with the product gas stream, an oxidizing gas stream is supplied.
• the SO 2 in the product gas stream reacts with the oxygen bound to the catalyst to form SO 3.
• the first phase is therefore also referred to as the reaction phase.
• the metal phase of the catalyst is previously saturated with oxygen in the cycle.
• the reaction phase only small amounts of oxygen are present in the product gas stream.
• the product gas stream contains an oxygen content of less than 1 mol%, preferably less than 0.5 mol%.
• the product gas stream may also be completely free of oxygen. The oxygen required for the oxidation extracts the SO2 from the catalyst.
• the sulfur dioxide content in the product gas stream is preferably more than 1 mol% and less than 20 mol% at the entry into the reaction space.
• the product gas stream at the inlet contains a sulfur dioxide content of more than 3 mol% and less than 12 mol%.
• the catalyst in the reaction chamber is overflowed according to the invention by an oxidizing gas stream.
• the influx of product gas into this reaction space is stopped during the second phase.
• the oxidation gas stream contains an oxygen content of more than 10% by volume.
• air is used as the oxidizing gas stream.
• Gas mixtures with an oxygen content of more than 21% by volume or pure oxygen can also be used.
• the oxidizing gas stream preferably does not contain any gas components which reduce the catalyst. In particular, it proves to be advantageous if the oxidation gas stream is free of sulfur dioxide.
• Part of the oxygen contained in the oxidant gas stream is bound by the catalyst during the second phase.
• the second phase is therefore also referred to as the oxygen saturation phase.
• a temperature of 300 ° C. liquefaction of the hitherto solid metal phase on the catalyst surface can occur in the catalyst beds.
• Still bound sulfur trioxide may be present on the catalyst surface from the reaction phase, which now becomes free.
• the oxygen from the oxidation gas stream passes into the metal phase. This oxygen transport continues until the metal phase of the catalyst is saturated.
• a catalyst bed is arranged in the reaction space.
• the catalyst bed is preferably designed as a catalyst bed.
• the catalyst bed may consist of extrudates on which a thin layer of active catalyst substance is applied.
• Also conceivable is the use of monolithic molded bodies. The monoliths can be crossed by channels,
• the surface of the channels is coated with the active catalyst substance.
• the catalytically active substance used is preferably vanadium pentoxide V 2 O 5 , at which the conversion of SO 2 to SO 3 takes place on an oxygen-saturated liquid metal phase, Saturated Metal Phase (SMP).
• SMP Saturated Metal Phase
• the method has at least one further reaction space. In a phase while the oxidizing gas stream is passed through the first reaction space, the product gas stream flows through the second reaction space. In this way, a continuous operation of the sulfuric acid production plant is made possible. If the first reaction space flows through the oxidizing gas stream, the second reaction space takes over the conversion of SO 2 to SO 3 in the product gas stream.
• the oxidation gas stream is fed to the second reaction space.
• the leadership of the gas streams is changed so that the first reaction chamber of the oxidizing gas stream and the second reaction chamber, the product gas stream is supplied. This cycle repeats cyclically.
• the reaction spaces are each independent reactors.
• more than two reactors can be used, with an even number recommends, since they can always be operated in pairs in alternating operation.
• the large-scale implementation of the method according to the invention can thus take place either via two contact towers or via integrated reactor concepts such as multi-bed towers or ring reactors.
• reaction spaces are operated alternately between a reaction phase and an oxygen saturation phase. While the sulfur dioxide-containing product gas stream is supplied to the first reaction space, the oxygen-containing oxidation gas stream flows through the second reaction space. After that, the guidance of the gas flows is exchanged.
• One cycle thus comprises one reaction phase and one oxygen saturation phase per reaction space.
• the reaction rate is very high despite the low oxygen supply.
• the amount of catalyst needed to achieve a particular reaction equilibrium can be significantly reduced. As a result, a significantly smaller reactor volume is required compared to conventional methods.
• the gas stream which is fed to the downstream processes after the conversion of SO 2 to SO 3 is reduced, since the product gas stream contains only small amounts of oxygen.
• the apparatuses used in the downstream processes such as, for example, heat exchangers or gas scrubbers, can be made smaller, which leads to a cost reduction.
• the oxidizing gas stream is used after flowing through a reaction space for the production of the sulfur dioxide-containing gas stream.
• the catalyst is saturated with oxygen from the oxidation gas stream. This reduces the oxygen content in the oxidation gas stream.
• the oxidizing gas flow has an average oxygen content of only 15 mol .-%. Due to the lower oxygen content, the temperature generated during the conversion of the sulfur source to SO2 is lowered. This reduces the formation of nitrogen oxides (NO x ).
• the sulfuric acid layer according to the invention is equipped to control the gas flows with fittings.
• three-way valves are used.
• the valves can be actuated via actuators.
• electric, pneumatic or hydraulic actuators can be used.
• the valves are inventively controlled so that the reaction chambers in mutual alternation to the product gas stream, an air flow can be supplied.
• valves which control the guidance of the gas streams are switched such that the respective reaction spaces are respectively flowed through by the product gas stream and the oxidizing gas stream in the opposite direction.
• Fig. 1 a is a circuit diagram of two reaction spaces for the conversion of SO2
• 1 b shows a circuit diagram in which the flow of product gas flows through the left-hand reaction space
• 1 c is a circuit diagram in which the right reaction space is flowed through by the product gas stream
• FIG. 5 an online concentration measurement with a Raman spectroscope during the warm-up phase and the start of the reaction
• FIG. 6 temperature profiles measured at a pilot plant during a warm-up phase, a reduction phase and a reaction phase.
• Fig. 1a the reaction chambers 1 and 2 are shown, which are part of a process for sulfuric acid production.
• the reaction chambers 1, 2 a conversion of SO2 to SO3 takes place.
• the reaction chambers 1, 2 are as
• the catalysts 3, 4 are as beds in the
• reaction spaces 1, 2 introduced and form two catalyst beds, where the reaction proceeds to sulfur trioxide.
• the reaction chambers 1, 2 are in mutual alternation of the product gas stream 5 and the oxidation gas stream
• valves serve 13, 14 of the steering of the gas streams (5, 6).
• 1 b shows an operating phase in which the product gas stream 5 is fed to the reaction space 1.
• the three-way valves 7, 8 pass the product gas stream 5 to the reaction space 1.
• the catalyst 3 reacts with the sulfuric acid.
• the product gas stream 5 leaves the reaction space 1 and flows through the three-way valve 9 and the valve 14 to the plant part, in which the reaction of the sulfur trioxide takes place to sulfuric acid.
• the reaction space 2 flows through the oxidizing gas flow 6.
• the oxidizing gas stream 6 in the exemplary embodiment is a pure air stream.
• the catalyst 4 in the reaction chamber 2 is loaded during this phase of operation with the oxygen from the air to saturation.
• the oxygen content in the oxidation gas stream 6 decreases as it flows through the reaction space 2.
• the oxygen-depleted oxidizing gas stream 6 is fed to the combustion chamber, in which the sulfur dioxide is produced.
• FIG. 1 c shows an operating phase in which the oxidation gas stream 6 is fed to the reaction space 1.
• the three-way valves 10, 9 conduct the oxidation gas stream 6 to the reaction space 1.
• the reaction chamber 1 is flowed through in the reverse direction to the product gas guide.
• the catalyst 3 absorbs oxygen from the oxidation gas stream 6.
• the proportion of oxygen in the oxidation gas stream 6 drops as it flows through the reaction space 1.
• the oxygen-depleted oxidation gas stream 6 leaves the reaction space 1 and flows through the three-way valve 8 and the valve 13 to the combustion chamber, in which the production of sulfur dioxide takes place.
• FIG. 1 c shows an operating phase in which the oxidation gas stream 6 is fed to the reaction space 1.
• the three-way valves 10, 9 conduct the oxidation gas stream 6 to the reaction space 1.
• the reaction chamber 1 is flowed through in the reverse direction to the product gas guide.
• the catalyst 3 absorbs oxygen from the oxidation gas stream 6.
• the reaction space 2 flows through the product gas stream 5.
• the product gas stream is fed to the reaction space 2 via the three-way valves 7, 12.
• the reaction space 2 is flowed through in the reverse direction to the oxidation gas guide.
• the sulfur dioxide present in the product gas stream is converted to sulfur trioxide during this phase of operation.
• FIG. 2 shows a periodic reactor operation realized in a pilot plant. In the reaction space of the pilot plant four catalyst beds are arranged one above the other. In the diagram shown in FIG. 2, the gas temperature T G is plotted in ° Celsius over the time t in minutes. The lines drawn in the diagram represent the following curves:
• One cycle of pilot plant operation is 20 minutes. Per cycle, the reactor is flowed through during a first phase of 10 minutes with the product gas stream 5 containing sulfur dioxide.
• the product gas stream 5 entering the reactor is composed of 95.5 mol% of nitrogen, 4 mol% of sulfur dioxide and 0.5 mol% of oxygen.
• the oxidizing gas stream 6 is fed to the reactor.
• the stream of oxidizing gas 6 entering the reactor is composed of 79 mol% of nitrogen and 21 mol% of oxygen.
• the oxidizing gas stream 6 contains no sulfur dioxide.
• FIG. 3 shows temperature profiles measured on the technology in a start-up process.
• the gas temperature T G is plotted in ° Celsius over the time t in seconds.
• the designation of the curves corresponds to that of the diagram of FIG. 2.
• the reaction starts at time t 0 .
• the measured gas temperature reaches a maximum that is up to 50 Kelvin above the temperature reached at the stationary point.
• the SMP effect Saturated Metal Phase Effect
• the plant is operated with compressed air until it reaches a stationary temperature profile in the reactor. From a temperature above 300 ° C. in the catalyst beds, the formation of a slight sulfuric acid mist in a bubble column can be observed. The appearance of this mist indicates a liquefaction of the hitherto solid metal phase on the catalyst surface.
• sulfur trioxide from previous experiments is released and reacts with the water in the bubble column to sulfuric acid.
• the oxygen starts to move from the compressed air (xo2> 20 vol.%) Into the metal phase. This mass transport continues until the metal phase is saturated, the oxygen supply is interrupted or sulfur dioxide enters the reactor.
• Fig. 4 shows the reaction mechanism of sulfur dioxide oxidation on vanadium pentoxide. All recent studies on sulfur dioxide oxidation on vanadium pentoxide assume that the reactions take place in the liquid metal phase. In the publication "Oxidation of Sulfur Dioxide to Sulfur Trioxide over Supported Vanadium Catalysts, Applied Catalysis B: Environmental," Vol. 19, pp. 103-1 17, 1998, Dünn provides a widely accepted reaction mechanism of sequential and parallel reaction. Reaction 5, the oxidation of V 3+ to V 5+ , is considered by the mechanism to be the rate-limiting reaction step. Under the conditions which were set in the pilot plants in the pilot plant shown in FIG.
• FIG. 5 shows an online concentration measurement with a Raman spectroscope during the warm-up phase and the start of the reaction.
• the oxygen mole fraction X02 at the reactor outlet is plotted in percent over time t in seconds.
• the concentration measurement is already started during the warm-up phase with compressed air. From a temperature of 315 0 C, the oxygen content at the reactor outlet drops abruptly to about 10 mol .-%. After the start of the reaction, at time t 0 , the oxygen content decreases even more clearly. The reaction is aborted shortly after the start.
• FIG. 6 shows temperature profiles measured at the pilot plant during a warm-up phase, a reduction phase and a reaction phase.
• the gas temperature T G is plotted in degrees Celsius over the time t in seconds.
• the designation of the curves corresponds to that of the diagram of FIG. 2.
• the gas flow is composed of 79 mol% nitrogen, 21 mol% oxygen and 0 mol% sulfur dioxide.
• the gas flow is composed of 96 mol% nitrogen, 0 mol% oxygen and 4 mol% sulfur dioxide.
• the reaction phase which is shown in section III of the diagram, the gas flow is composed of 90 mol .-% nitrogen, 6 mol .-% oxygen and 4 mol .-% sulfur dioxide.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Catalysts (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Treating Waste Gases (AREA)

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• 2009
  • 2009-08-06 DE DE102009036289A patent/DE102009036289A1/de not_active Withdrawn
• 2010
  • 2010-07-12 RU RU2012108371/04A patent/RU2012108371A/ru not_active Application Discontinuation
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