CA1102997A - Method and apparatus for the thermal cracking of sulfuric acid - Google Patents
Method and apparatus for the thermal cracking of sulfuric acidInfo
- Publication number
- CA1102997A CA1102997A CA245,308A CA245308A CA1102997A CA 1102997 A CA1102997 A CA 1102997A CA 245308 A CA245308 A CA 245308A CA 1102997 A CA1102997 A CA 1102997A
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- Prior art keywords
- fuel
- sulfuric acid
- oxygen
- ultrasonic field
- combustion
- Prior art date
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Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K5/00—Whistles
-
- 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
- C01B17/48—Sulfur dioxide; Sulfurous acid
- C01B17/50—Preparation of sulfur dioxide
- C01B17/58—Recovery of sulfur dioxide from acid tar or the like or from any waste sulfuric acid
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
- F23D11/10—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour
- F23D11/12—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour characterised by the shape or arrangement of the outlets from the nozzle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
- F23G7/008—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals for liquid waste
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Organic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Combustion & Propulsion (AREA)
- Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Acoustics & Sound (AREA)
- Gasification And Melting Of Waste (AREA)
- Treatment Of Sludge (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE Sulfuric acid and fuel are passed to an ultrasonic field which atomizes sulfuric acid. Fuel is combusted in the ultrasonic field to provide sulfuric acid thermal cracking tem-peratures, and thermal cracking of sulfuric acid occurs in the ultrasonic field in the presence of combustion of fuel. The sulfuric acid and fuel may be mixed to form a fuel in acid dis-persion prior to passing to the ultrasonic field, or the sulfuric acid and fuel may be separately passed to and mixed in the ultra-sonic field.
Description
This inYention relates to a method for thermal cracking sulfuric acid wherein sulfuric acid is passed into an ultrasonic field provided by an ultrasonic atomizer while simultaneously combusting fuel to provide sulfuric acid thermal cracking temperatures, and to ultrasonic atomizers useful in practicing the method for thermal cracking sulfuric acid.
In a number of chemical processes, waste sulfuric acid containing varying amounts of impurities are obtained. The lmpurities may be organic or inorganic such as the ammonium, iron, and sodium sulfate salts, and water. Generally, these impurities can only be removed from the waste sulfuric acid by expensive procedures. It has been proposed that sulfur values can be recovered from waste sulfuric acid by thermal cracking the sulfuric acid to provide a sulfur dioxide gas which can be removed from the impurities. The sulfur dioxide-containing gas can be conventionally processed, e.g. by the contact method, to obtain concentrated sulfuric acid or oleum.
Heretofore, thermal cracking of waste sulfuric acid has been accomplished by, for instance~ injecting the waste acid into a reaction chamber which is maintained at thermal cracking temperatures, e.g. 800 to 1300C., by the simultaneous combustion of fuel in the rea¢tion chamber. ~he acid is gener-ally in;ected into the reaction chamber by means of pressure ato-mizers or rotary atomizers. A number of, for example~ oil burners are provided in the reaction chamber to provide the necessary thermal energy for thermal cracking of sulfuric acid. Frequently, the reaction chamber is cylindrical and vertical, and the waste acid is injected centrally at the ceiling with the burners being disposed radially or tangentially into the reaction chamber.
Problems occurred with the use of pressure or rotary atomizers in that they tended to clog rapidly and thus were prone to dis-turbances, especially since a flnely-divided ~istribution of sulfuric acid is desired for efficient thermal cracking.
Ultrasonic atomizers operating with an ultrasonic generator (Hartman generator) are known and have found applica-tion as ultrasonic oil burners~ Unlik~ heating oil which is a practically h~mogeneous li~uid, contaminated waste sulfuric acids which are subjected to thermal cracking re~uently either initially contain solids or precipitate solids during atomiza-tion. Consequently, waste sulfuric acid must be introduced in a considerably larger layer thickness into the ultrasonic field than the thicknesses emploved wi~h heating oil. Moreover, the presence of solid c~mponents in as well as changes in the composition of waste acid as well may affect the degree of ato-mization. Irregular atomization may cause the thermal cracking to be susceptible to disturbances such as flame cooling.
My prior U. S. Patent No. 3,908,904, issued September 30, 1975, with Friedrich Mahler and Heinrich Petexs as co~
inventors, discloses usin~ ultrasonic atomiæers for atomizing waste sulfuric acid in acid cracking furnaces. In ul~rasonic atomization, the effec~ of mechanical injection thxough a nozzle is further intensi~iëa by an ultrasonic field in the zone in front of the nozzle. Thus, a desirably fine dispersion of the waste acid can be obtained using a coarse spray. The dispersion of the waste acid may be subjected to thermal cracking by ~hermal energy provided by fuel burners disposed within the furnace. The fuel burners may be placed axially on the ceiling of the furnace such that already hot gases en~er the thermal cracking zone parallel ~o the acid mist. In this manner, there is no danger of flame subcoolin~.
, ~ ' J
When the cracked gas is processed to obtain sul~uric acid or oleum, the amounts of gaseous diluents in the cracked gas is of substantial concern. A highly diluted cracked gas may require increased expenditures for additional and larger apparatus in the sulfllric acid plant to process the larger vol-ume of gas and will require increased power costs. The use of more concentrated oxygen-providing gases for combustion with fuel to reduce the amount of diluent gases from that providing using air as the oxygen source, may lead to the production of high temperatures, for instance, in excess of 2000C. using oxygen as the oxygen source, which may result in damage to con--ventional oil burners and the lining of the combustion chamber.
Moreover, since the cracked gases are generally cooled and cleaned before they are fed to the sulfuric acid plant, unre-duced sulfuric acid, and in some cases sulfuric acid compounds in the cracked gases, together with other gas impurities, can lead to corrosive attacks on treating equipment. Furthermore, during scrubbing~ hexavalent sulfuric moieties in the gas may at least partially be dissolved in the scrubbing water and thus 20 are lost from the system. Consequently, it is desired to provide -essentially complete thermal cracking of sulfuric acid with minimal dilution of the thermal cracked product with inert gases.
By the method of this invention, sulfuric acid, which may be waste sulfuric acid, for instance, containing suspended solids or dissolved salts which precipitate upon atomization of the acid, and fuel are passed into an ultrasonic field whereby the ultrasonic field atomizes sulfuric acid. Combustion of -fuel with oxygen is conducted within the ultrasonic field to pro-j 30 vide sulfuric acid thermal cracking temperatures, e.g. about ~ 800 to 1300C., preferably about 900 to 1100C. Thermal cracking yields of SO2 provided by the method of this inve~ltion may be high, e.g. at least about 99 or about 99.5%, and the thermal cracking is not unduly susceptible to disturbances.
Since the thermal cracking is almost complete, corrosion in the processing equipment downstream from the thermal cracking may be minimal. External fuel burners such as employed in conven-tional sufluric acid thermal cracking furnaces may be omitted, resulting in a reduction of equipment costs and elimination of periodic conventional maintenance. Conveniently, an ultrasonic atomizer for providing the ultrasonic field is adapted to inject fuel and waste acid into the ultrasonic field. In view of the finely~divided form of the liquid, combustion of fuel with oxy-gen and thermal cracking of sulfuric acid to provide sulfur di-oxide occurs quickly and requires a thermal cracking zone of less volume than if the entire source of thermal energy were provided by fuel burners outside the ultrasonic field. The ultrasonic field may also be employed for atomization of waste solutions containing salts, e.g. ammonium salts, of sulfur-containing acids.
In one aspect of this inventiong a mixture of fuel and sulfuric acid is prepared, and the mixture is injected into the ultrasonic fieId. The fuel may desirably be liquid, e.g. fuel oil, and may be dispersed in the acid by means of conventional apparatus for dispersing a liquid in a second liquid which is immiscible with the first liquid. Such apparatus include mixing nozzles for liquids, e.g. Venturi-type mixing nozzles. The fuel is often employed in amounts less than the amounts of sulfuric acid to be thermally cracked~ and thus an oil-in-water dispersion is generally formed.
In another aspect of this invention, the fuel and sulfuric acid to be thermally cracked may be passed through separate nozzle openings into the ultrasonic field. In this manner, fuel and sulfuric acid are separately, but simulta-neously, injected into the ultrasonic field. An ultrasonic atomizer for use in this aspect of the method o~ this invention provides for the separate injection of fuel, sulfuric acid, and sound gas, i.e. operating medium, which is gas passed through the atomizer to provide ultrasonic vibrations. The fuel and sulfuric acid may be released from the nozzle in, for instance, concentric patterns, into the ultrasonic field, and the patterns in the ultrasonic field may conveniently overlap. The liquid passing to the ultrasonic field may be ln the form of finely-divided drops, ; for instance, having a size of about 0.2 to 2 millimeters.
Advantageously, the fuel is injected into the ultrasonic field concentrically around a separate, central injection of sulfuric acid; however, the sulfuric acid may be concentrically injected around a separate, central injection of fuel. Conveniently, the ultrasonic field surrounds both the sulfuric acid nozzle and the fuel nozzle.
The method of this invention enables oxygen and air-enriched with oxygen as well as air to be used as the oxygen-containing gas to support combustion of the fuel without such high temperatures occurring as to damage the combustion chamber or the ultrasonic atomizer. Due to inkimate mixing of fuel and sulfuric acid by the method of this invention, the endothermic thermal crackin~ of the sulfuric acid serves as a heat sink, without undue subcooling, to the interspersed exothermic fuel combustion thereby tending to abate undeslrable peaks of high temperature on even a local basis in the combustion zone. The dispersion of fuel and sulfuric acid may be essentially uniform, but in any event, the mixing is sufficient to avoid localities in the ultrasonic field of excessively high temperature which may be deleterious to the equipmenf,. The oxygen-containing gas is preferably employed in an amount in excess of that re-quired for complete combustion of the fuel, i.e. for hydrocarbon-containing fuels, to carbon dioxide and water or for elemental sulfur-containing fuels, to sulfur dioxide, on a stoichiometric basis. The gases from the thermal cracklng zone may fequently contain about 1 to 9, preferably about 2 to 4, volume percent free oxygen. The oxygen-containing gas may, for instance, con-tain at least about 25 volume percent free, or molecular, oxygen.The capability Or employing oxygen or air enriched with oxygen as the oxygen-containing gas provides numerous advantages to the method of this invention. For instance, since the oxygen-con-taining gas may contain less inert gases than air, the amount of fuel employed can be reduced while still maintaining the same thermal cracking temperature. Particularly in conventional sulfuric acid thermal cracking units employing air as the oxygen-containing gas, it has been necessary to provide a preheater ror the air. Such an air preheater may not be required in meth-ods of thls invention in view of the reduced amounts of gas toheat and hi8her combustion kemperatures which can be achieved using more oxygen rich oxygen-containing gases than air. ~y using oxygen as the oxygen-¢ontaining gas, the volume of effluent gases from the thermal cracking zone may be about 40% lower than the amount of gases provided when air is used. Since the con-centration of sulfur dioxide is correspondingly greater in the effluent gases, the volume of~ for instance, a ~onventional sulfuric acid plant to convert sulfur dioxide to concentrated sulfuric acid or oleum may be substantially less and may result in a cost savings of about 30 percent over the costs required for the sulfuric acid plant to treak effluent gases when air , ; -6-.
-;:' - ' ., ' ' ~ ' , ~ h~
is used as the oxygen-containing gas. A savings o~ about 30 percent in electrical energy costs may also be real~zable.
The ultrasonic field is provided by the action of the ultrasonic atomizer on the passage therethrough of compressed operating medium, i.e. sound gas. The frequency of the ultra-sonic field is suitably bet~een about 10 and 1000 kilohertz, especially between about 20 and 100 kilohertz. The sound gas may be generally provided at a pressure of about o.6 to 10, pre~erably o.6 to 4, atmospheres absolute. The ultrasonic field atmoizes liquids passing therethrough and droplets in the range of between about 1 and 200 microns, especially between about 50 and 80 microns, may be obtained. Conveniently, the oxygen-containing gas for combustion with fuel is employed as the sound ; gas although other gases may also be employed such as steam which can be condensed from the effluent gases prior to passing to a sulfuric acid plant. Oxygen-containing gas may also be supplied by secondary oxygen supply ports, but preferably the oxygen-containing gas is supplied ln whole or part as the sound gas. `
Ultrasonic atomizers which may be beneficially employed in the method of this in~ention generally contain feed duct or ducts centrally arranged in the sound generation portion of the ultrasonic atomizer. Inkegral with the feed duct is a nozzle through which ~eed enters the ultrasonic field. Surrounding the feed duct or ducts is a sound gas conduit. At the operative end ~ face of the sound generator is positioned a deflector for the - sound gas for guiding the sound gas from the sound gas conduit into a resonance chamber whereat ~ibrations are for~ed. The deflector and resonance chamber are preferably disposed concen-trically around the nozzIe portion of the feed duct, and the resonance chamber includes an outlet opening into the operative end face. In one aspect of the apparatus of this invention, a single feed duct is preceded by a mixer which mixes and provides a fine dispersion of liquid ruel in sulfuric acid ~or passing to the ultrasonic field. The mixer may be a mixing nozzle such as a Venturi-type mixer. In another aspect, two concentric feed ducts are provided, one for sulfuric acid, e.g. the inner duct, and the other for fuel. The fuel and acid are separately inJected into the ultrasonic field and are mixed in the ultra-sonic field.
A furnace for thermal cracking of sulfuric acid which may beneficially be employed in accordance with this invention comprises one or more ultrasonic atomizers centrally arranged in the furnace. The furnace, which may be brick-lined, may conveniently be of a cylindrical configuration and be vertically oriented with the ultrasonic atomizer positioned on the ceiling.
The furnace may contain a furnace body constriction at a spacing from the furnace ceiling of about 1 to 4, preferably 1.5 to 3, times the diameter of the furnace. By this arrangement of the furnace, ultrasonic atomizer and furnace body constriction, a gaseous flow is achieved in the furnace which enables almost all of the sulfuric acid to be thermally cracked in a relatively small furnace volume. The residence time of the gases in the thermal cracking zone may be from about 0.1 to 5, preferably 1 to 4, seconds. The ultrasonic atomizer may also be selected to provide a beneficial configuration of the mixture of sulfuric acid and fuel for thermal cracking of the acid.
Various liquid or gaseous fuels under the conditions of injection into the furnace may be employed in the method of this inventi~n. Typical ~uels include hydrocarbon-containing liquid fuels such as fuel oil~ molten sulfur, or hydrocarbon-containing gaseous fuels such as fuel gas. The fuel selected - ' s..Juld in any ev~nt be capable of pr~vidlng surriclent h~zt to maintain thermal cracklng temperatures ln the furnace during operation.
The invention is further illustrated with reference to the drawings in which Figure 1 is an axial schematic sectional representa-tion of a thermal cracking furnace for sulruric acid, and Figure 2 is an axial schematic sectional representa-tion Or a head of an ultrasonic atomizer for atomization and mixing of separate streams Or fuel and sulfuric acid.
With reference to Figure 1, ultrasonic atomizer 12 ls centrally positioned on the ceiling 10~ of vertical thermal c;racking furnace 10. Air is supplied to the ultrasonic atomizer as the sound gas via line 16 by means of blower 14 ~hich draws air through filter 1~. Waste sulfuric acid to be atomized is supplied to mixing nozzle 13 via line 18, and is intimately mixed therein with fuel oil passing to the mixing nozzle through pipe 17 to form an oil-in-acid dispersion. The oil-in-ac~d dispersion passes through feed duct 12a to the head of ultra-sonic atomizer 12 and is injected into the ultrasonic field in - thermal cracking zone lOb. Fire bridge, or furnace body con-striction, 11 is provided in the furnace to enhance thermal cracking of sulfuric acid to provide sulfur dioxide. The sulfur dioxide-containing effluent is discharged from the furnace through line 19~ The effluent may be transported to a sulfuric acid plant to convert sulfur dioxide to sulfuric acid or oleum.
Figure 2 illustrates head 1 of an ultrasonic atomizer for separately injecting sulfuric acid and ~uel~ e.g. fuel gas~
into the ultrasonic field, Central feed duct 2 is adapted to pass sulfuric acid to the thermal cracking zone. At the front of central duct 2 is pressure atomizer nozzle 5. Annular feed ,'i. .
duct 3 is adapted to pass ~uel gas to and through annular open-ing 6 at face of the ultrasonic atomizer. The sound gas is passed via outer annular sound gas conduit 4 to the face of the ultrasonic atomizer ~here it impinges on deflector surface 8 and is deflected into resonance chamber 7 to provide ultrasonic vibrations and ultrasonic field for atomizing and mixing the fuel and sulfurlc acid.
The invention may be further understood by reference to the following examples. A sulfuric acid thermal cracking operation of the prior art is provided in Example 1.
A cylindrical, vertical waste sulfuric acid thermal cracking furnace is provided with an ultrasonic atomizer for waste acid disposed centrally on the ceiling of the furnace and six conventional oil burners directed radially into the furnace chamber. Approximately 23.1 tons per hour of waste sulfuric acid are passed through the ultrasonic atomizer into the furnace chamber. The waste sulfuric acid is obtained from a methyl methacrylate production plant and contains about 11.3 weight percent sulfuric acid, 53.5 weight percent ammonium bisulfite, 1.0 weight percent ammonium sulfate, 2 weight percent disul-fonic acid, 1.6 weight percent other organic components, and 30.6 weight percent water. Air ls passed to the thermal crack- -ing zone at a rate of 11,570 Nm3 (cubic meters at standard temperature and pressure) per hour. The total consumption of fuel oil including the oil required in preheating the air is 4,120 kilograms per hour. Approximately 72,700 ~m3 per hour of wet effluent from the thermal cracking zone are obtained, 3o and the wet effluent contains about 4.2 volume percent sulfur dioxide and about 3.1 volume percent molecular oxygen. The wet , .
effluent is dried to provide about 50,380 Nm3 per hou.r of dried gas containing 6.o volume percent sulfur dioxide and 4.5 volume percent molecular oxygen. The energy consumption inclusive of a sulfuric acid plant is about 40,000 kilowatt hours per day.
The following examples are illustrative of sulfuric acid cracking operations in accordance with the method of this invenkion.
EX~MPLE 2 A sulfuric acid cracking furnace of the type described in connection with Figure l is employed in connection with this example. A wa~te sulfuric acid stream having essentially the same composition and flow rate as described in Example 1 is intimately admixed with 2.38 tons per hour of fuel oil to pro-vlde a fuel oil in acid dispersion. The dispersion is fed to the reaction chamber through an ultrasonic atomizer. The sound gas for the ultrasonic atomizer is a mixture of 8,100 Nm3 per ; hour of air and 5,300 Nm3 per hour of molecular oxygen. Free oxygen comprises about 51 volume percent of the sound gas. ~bout ~ 20 36,725 Nm3 per hour of wet effluent containing 8.4 volume per-; cent sulfur dioxide and 2.3 volume percent molecular oxygen are obtained. No oil burners are provided, and the necessary thermal energy is provided by combuskion of fuel in the ultrasonic field.
~fter drying, about 16,350 Nm per hour of effluent containing 18.9 volume percent sulfur dioxide and 5.2 volume percent molecular oxygen are obtained. The energy consumption inclu-sive of a sulfuric acid plant is about 25,000 kilowatt hours per day. The cost of the waste sulfuric acid thermal cracking unit and sulfuric acid plant is estimated to be about 67 percent of the cost of the installakions for Example 1.
~9 ~
~XAMPLE 3 Essentially the same procedure as described in Example
In a number of chemical processes, waste sulfuric acid containing varying amounts of impurities are obtained. The lmpurities may be organic or inorganic such as the ammonium, iron, and sodium sulfate salts, and water. Generally, these impurities can only be removed from the waste sulfuric acid by expensive procedures. It has been proposed that sulfur values can be recovered from waste sulfuric acid by thermal cracking the sulfuric acid to provide a sulfur dioxide gas which can be removed from the impurities. The sulfur dioxide-containing gas can be conventionally processed, e.g. by the contact method, to obtain concentrated sulfuric acid or oleum.
Heretofore, thermal cracking of waste sulfuric acid has been accomplished by, for instance~ injecting the waste acid into a reaction chamber which is maintained at thermal cracking temperatures, e.g. 800 to 1300C., by the simultaneous combustion of fuel in the rea¢tion chamber. ~he acid is gener-ally in;ected into the reaction chamber by means of pressure ato-mizers or rotary atomizers. A number of, for example~ oil burners are provided in the reaction chamber to provide the necessary thermal energy for thermal cracking of sulfuric acid. Frequently, the reaction chamber is cylindrical and vertical, and the waste acid is injected centrally at the ceiling with the burners being disposed radially or tangentially into the reaction chamber.
Problems occurred with the use of pressure or rotary atomizers in that they tended to clog rapidly and thus were prone to dis-turbances, especially since a flnely-divided ~istribution of sulfuric acid is desired for efficient thermal cracking.
Ultrasonic atomizers operating with an ultrasonic generator (Hartman generator) are known and have found applica-tion as ultrasonic oil burners~ Unlik~ heating oil which is a practically h~mogeneous li~uid, contaminated waste sulfuric acids which are subjected to thermal cracking re~uently either initially contain solids or precipitate solids during atomiza-tion. Consequently, waste sulfuric acid must be introduced in a considerably larger layer thickness into the ultrasonic field than the thicknesses emploved wi~h heating oil. Moreover, the presence of solid c~mponents in as well as changes in the composition of waste acid as well may affect the degree of ato-mization. Irregular atomization may cause the thermal cracking to be susceptible to disturbances such as flame cooling.
My prior U. S. Patent No. 3,908,904, issued September 30, 1975, with Friedrich Mahler and Heinrich Petexs as co~
inventors, discloses usin~ ultrasonic atomiæers for atomizing waste sulfuric acid in acid cracking furnaces. In ul~rasonic atomization, the effec~ of mechanical injection thxough a nozzle is further intensi~iëa by an ultrasonic field in the zone in front of the nozzle. Thus, a desirably fine dispersion of the waste acid can be obtained using a coarse spray. The dispersion of the waste acid may be subjected to thermal cracking by ~hermal energy provided by fuel burners disposed within the furnace. The fuel burners may be placed axially on the ceiling of the furnace such that already hot gases en~er the thermal cracking zone parallel ~o the acid mist. In this manner, there is no danger of flame subcoolin~.
, ~ ' J
When the cracked gas is processed to obtain sul~uric acid or oleum, the amounts of gaseous diluents in the cracked gas is of substantial concern. A highly diluted cracked gas may require increased expenditures for additional and larger apparatus in the sulfllric acid plant to process the larger vol-ume of gas and will require increased power costs. The use of more concentrated oxygen-providing gases for combustion with fuel to reduce the amount of diluent gases from that providing using air as the oxygen source, may lead to the production of high temperatures, for instance, in excess of 2000C. using oxygen as the oxygen source, which may result in damage to con--ventional oil burners and the lining of the combustion chamber.
Moreover, since the cracked gases are generally cooled and cleaned before they are fed to the sulfuric acid plant, unre-duced sulfuric acid, and in some cases sulfuric acid compounds in the cracked gases, together with other gas impurities, can lead to corrosive attacks on treating equipment. Furthermore, during scrubbing~ hexavalent sulfuric moieties in the gas may at least partially be dissolved in the scrubbing water and thus 20 are lost from the system. Consequently, it is desired to provide -essentially complete thermal cracking of sulfuric acid with minimal dilution of the thermal cracked product with inert gases.
By the method of this invention, sulfuric acid, which may be waste sulfuric acid, for instance, containing suspended solids or dissolved salts which precipitate upon atomization of the acid, and fuel are passed into an ultrasonic field whereby the ultrasonic field atomizes sulfuric acid. Combustion of -fuel with oxygen is conducted within the ultrasonic field to pro-j 30 vide sulfuric acid thermal cracking temperatures, e.g. about ~ 800 to 1300C., preferably about 900 to 1100C. Thermal cracking yields of SO2 provided by the method of this inve~ltion may be high, e.g. at least about 99 or about 99.5%, and the thermal cracking is not unduly susceptible to disturbances.
Since the thermal cracking is almost complete, corrosion in the processing equipment downstream from the thermal cracking may be minimal. External fuel burners such as employed in conven-tional sufluric acid thermal cracking furnaces may be omitted, resulting in a reduction of equipment costs and elimination of periodic conventional maintenance. Conveniently, an ultrasonic atomizer for providing the ultrasonic field is adapted to inject fuel and waste acid into the ultrasonic field. In view of the finely~divided form of the liquid, combustion of fuel with oxy-gen and thermal cracking of sulfuric acid to provide sulfur di-oxide occurs quickly and requires a thermal cracking zone of less volume than if the entire source of thermal energy were provided by fuel burners outside the ultrasonic field. The ultrasonic field may also be employed for atomization of waste solutions containing salts, e.g. ammonium salts, of sulfur-containing acids.
In one aspect of this inventiong a mixture of fuel and sulfuric acid is prepared, and the mixture is injected into the ultrasonic fieId. The fuel may desirably be liquid, e.g. fuel oil, and may be dispersed in the acid by means of conventional apparatus for dispersing a liquid in a second liquid which is immiscible with the first liquid. Such apparatus include mixing nozzles for liquids, e.g. Venturi-type mixing nozzles. The fuel is often employed in amounts less than the amounts of sulfuric acid to be thermally cracked~ and thus an oil-in-water dispersion is generally formed.
In another aspect of this invention, the fuel and sulfuric acid to be thermally cracked may be passed through separate nozzle openings into the ultrasonic field. In this manner, fuel and sulfuric acid are separately, but simulta-neously, injected into the ultrasonic field. An ultrasonic atomizer for use in this aspect of the method o~ this invention provides for the separate injection of fuel, sulfuric acid, and sound gas, i.e. operating medium, which is gas passed through the atomizer to provide ultrasonic vibrations. The fuel and sulfuric acid may be released from the nozzle in, for instance, concentric patterns, into the ultrasonic field, and the patterns in the ultrasonic field may conveniently overlap. The liquid passing to the ultrasonic field may be ln the form of finely-divided drops, ; for instance, having a size of about 0.2 to 2 millimeters.
Advantageously, the fuel is injected into the ultrasonic field concentrically around a separate, central injection of sulfuric acid; however, the sulfuric acid may be concentrically injected around a separate, central injection of fuel. Conveniently, the ultrasonic field surrounds both the sulfuric acid nozzle and the fuel nozzle.
The method of this invention enables oxygen and air-enriched with oxygen as well as air to be used as the oxygen-containing gas to support combustion of the fuel without such high temperatures occurring as to damage the combustion chamber or the ultrasonic atomizer. Due to inkimate mixing of fuel and sulfuric acid by the method of this invention, the endothermic thermal crackin~ of the sulfuric acid serves as a heat sink, without undue subcooling, to the interspersed exothermic fuel combustion thereby tending to abate undeslrable peaks of high temperature on even a local basis in the combustion zone. The dispersion of fuel and sulfuric acid may be essentially uniform, but in any event, the mixing is sufficient to avoid localities in the ultrasonic field of excessively high temperature which may be deleterious to the equipmenf,. The oxygen-containing gas is preferably employed in an amount in excess of that re-quired for complete combustion of the fuel, i.e. for hydrocarbon-containing fuels, to carbon dioxide and water or for elemental sulfur-containing fuels, to sulfur dioxide, on a stoichiometric basis. The gases from the thermal cracklng zone may fequently contain about 1 to 9, preferably about 2 to 4, volume percent free oxygen. The oxygen-containing gas may, for instance, con-tain at least about 25 volume percent free, or molecular, oxygen.The capability Or employing oxygen or air enriched with oxygen as the oxygen-containing gas provides numerous advantages to the method of this invention. For instance, since the oxygen-con-taining gas may contain less inert gases than air, the amount of fuel employed can be reduced while still maintaining the same thermal cracking temperature. Particularly in conventional sulfuric acid thermal cracking units employing air as the oxygen-containing gas, it has been necessary to provide a preheater ror the air. Such an air preheater may not be required in meth-ods of thls invention in view of the reduced amounts of gas toheat and hi8her combustion kemperatures which can be achieved using more oxygen rich oxygen-containing gases than air. ~y using oxygen as the oxygen-¢ontaining gas, the volume of effluent gases from the thermal cracking zone may be about 40% lower than the amount of gases provided when air is used. Since the con-centration of sulfur dioxide is correspondingly greater in the effluent gases, the volume of~ for instance, a ~onventional sulfuric acid plant to convert sulfur dioxide to concentrated sulfuric acid or oleum may be substantially less and may result in a cost savings of about 30 percent over the costs required for the sulfuric acid plant to treak effluent gases when air , ; -6-.
-;:' - ' ., ' ' ~ ' , ~ h~
is used as the oxygen-containing gas. A savings o~ about 30 percent in electrical energy costs may also be real~zable.
The ultrasonic field is provided by the action of the ultrasonic atomizer on the passage therethrough of compressed operating medium, i.e. sound gas. The frequency of the ultra-sonic field is suitably bet~een about 10 and 1000 kilohertz, especially between about 20 and 100 kilohertz. The sound gas may be generally provided at a pressure of about o.6 to 10, pre~erably o.6 to 4, atmospheres absolute. The ultrasonic field atmoizes liquids passing therethrough and droplets in the range of between about 1 and 200 microns, especially between about 50 and 80 microns, may be obtained. Conveniently, the oxygen-containing gas for combustion with fuel is employed as the sound ; gas although other gases may also be employed such as steam which can be condensed from the effluent gases prior to passing to a sulfuric acid plant. Oxygen-containing gas may also be supplied by secondary oxygen supply ports, but preferably the oxygen-containing gas is supplied ln whole or part as the sound gas. `
Ultrasonic atomizers which may be beneficially employed in the method of this in~ention generally contain feed duct or ducts centrally arranged in the sound generation portion of the ultrasonic atomizer. Inkegral with the feed duct is a nozzle through which ~eed enters the ultrasonic field. Surrounding the feed duct or ducts is a sound gas conduit. At the operative end ~ face of the sound generator is positioned a deflector for the - sound gas for guiding the sound gas from the sound gas conduit into a resonance chamber whereat ~ibrations are for~ed. The deflector and resonance chamber are preferably disposed concen-trically around the nozzIe portion of the feed duct, and the resonance chamber includes an outlet opening into the operative end face. In one aspect of the apparatus of this invention, a single feed duct is preceded by a mixer which mixes and provides a fine dispersion of liquid ruel in sulfuric acid ~or passing to the ultrasonic field. The mixer may be a mixing nozzle such as a Venturi-type mixer. In another aspect, two concentric feed ducts are provided, one for sulfuric acid, e.g. the inner duct, and the other for fuel. The fuel and acid are separately inJected into the ultrasonic field and are mixed in the ultra-sonic field.
A furnace for thermal cracking of sulfuric acid which may beneficially be employed in accordance with this invention comprises one or more ultrasonic atomizers centrally arranged in the furnace. The furnace, which may be brick-lined, may conveniently be of a cylindrical configuration and be vertically oriented with the ultrasonic atomizer positioned on the ceiling.
The furnace may contain a furnace body constriction at a spacing from the furnace ceiling of about 1 to 4, preferably 1.5 to 3, times the diameter of the furnace. By this arrangement of the furnace, ultrasonic atomizer and furnace body constriction, a gaseous flow is achieved in the furnace which enables almost all of the sulfuric acid to be thermally cracked in a relatively small furnace volume. The residence time of the gases in the thermal cracking zone may be from about 0.1 to 5, preferably 1 to 4, seconds. The ultrasonic atomizer may also be selected to provide a beneficial configuration of the mixture of sulfuric acid and fuel for thermal cracking of the acid.
Various liquid or gaseous fuels under the conditions of injection into the furnace may be employed in the method of this inventi~n. Typical ~uels include hydrocarbon-containing liquid fuels such as fuel oil~ molten sulfur, or hydrocarbon-containing gaseous fuels such as fuel gas. The fuel selected - ' s..Juld in any ev~nt be capable of pr~vidlng surriclent h~zt to maintain thermal cracklng temperatures ln the furnace during operation.
The invention is further illustrated with reference to the drawings in which Figure 1 is an axial schematic sectional representa-tion of a thermal cracking furnace for sulruric acid, and Figure 2 is an axial schematic sectional representa-tion Or a head of an ultrasonic atomizer for atomization and mixing of separate streams Or fuel and sulfuric acid.
With reference to Figure 1, ultrasonic atomizer 12 ls centrally positioned on the ceiling 10~ of vertical thermal c;racking furnace 10. Air is supplied to the ultrasonic atomizer as the sound gas via line 16 by means of blower 14 ~hich draws air through filter 1~. Waste sulfuric acid to be atomized is supplied to mixing nozzle 13 via line 18, and is intimately mixed therein with fuel oil passing to the mixing nozzle through pipe 17 to form an oil-in-acid dispersion. The oil-in-ac~d dispersion passes through feed duct 12a to the head of ultra-sonic atomizer 12 and is injected into the ultrasonic field in - thermal cracking zone lOb. Fire bridge, or furnace body con-striction, 11 is provided in the furnace to enhance thermal cracking of sulfuric acid to provide sulfur dioxide. The sulfur dioxide-containing effluent is discharged from the furnace through line 19~ The effluent may be transported to a sulfuric acid plant to convert sulfur dioxide to sulfuric acid or oleum.
Figure 2 illustrates head 1 of an ultrasonic atomizer for separately injecting sulfuric acid and ~uel~ e.g. fuel gas~
into the ultrasonic field, Central feed duct 2 is adapted to pass sulfuric acid to the thermal cracking zone. At the front of central duct 2 is pressure atomizer nozzle 5. Annular feed ,'i. .
duct 3 is adapted to pass ~uel gas to and through annular open-ing 6 at face of the ultrasonic atomizer. The sound gas is passed via outer annular sound gas conduit 4 to the face of the ultrasonic atomizer ~here it impinges on deflector surface 8 and is deflected into resonance chamber 7 to provide ultrasonic vibrations and ultrasonic field for atomizing and mixing the fuel and sulfurlc acid.
The invention may be further understood by reference to the following examples. A sulfuric acid thermal cracking operation of the prior art is provided in Example 1.
A cylindrical, vertical waste sulfuric acid thermal cracking furnace is provided with an ultrasonic atomizer for waste acid disposed centrally on the ceiling of the furnace and six conventional oil burners directed radially into the furnace chamber. Approximately 23.1 tons per hour of waste sulfuric acid are passed through the ultrasonic atomizer into the furnace chamber. The waste sulfuric acid is obtained from a methyl methacrylate production plant and contains about 11.3 weight percent sulfuric acid, 53.5 weight percent ammonium bisulfite, 1.0 weight percent ammonium sulfate, 2 weight percent disul-fonic acid, 1.6 weight percent other organic components, and 30.6 weight percent water. Air ls passed to the thermal crack- -ing zone at a rate of 11,570 Nm3 (cubic meters at standard temperature and pressure) per hour. The total consumption of fuel oil including the oil required in preheating the air is 4,120 kilograms per hour. Approximately 72,700 ~m3 per hour of wet effluent from the thermal cracking zone are obtained, 3o and the wet effluent contains about 4.2 volume percent sulfur dioxide and about 3.1 volume percent molecular oxygen. The wet , .
effluent is dried to provide about 50,380 Nm3 per hou.r of dried gas containing 6.o volume percent sulfur dioxide and 4.5 volume percent molecular oxygen. The energy consumption inclusive of a sulfuric acid plant is about 40,000 kilowatt hours per day.
The following examples are illustrative of sulfuric acid cracking operations in accordance with the method of this invenkion.
EX~MPLE 2 A sulfuric acid cracking furnace of the type described in connection with Figure l is employed in connection with this example. A wa~te sulfuric acid stream having essentially the same composition and flow rate as described in Example 1 is intimately admixed with 2.38 tons per hour of fuel oil to pro-vlde a fuel oil in acid dispersion. The dispersion is fed to the reaction chamber through an ultrasonic atomizer. The sound gas for the ultrasonic atomizer is a mixture of 8,100 Nm3 per ; hour of air and 5,300 Nm3 per hour of molecular oxygen. Free oxygen comprises about 51 volume percent of the sound gas. ~bout ~ 20 36,725 Nm3 per hour of wet effluent containing 8.4 volume per-; cent sulfur dioxide and 2.3 volume percent molecular oxygen are obtained. No oil burners are provided, and the necessary thermal energy is provided by combuskion of fuel in the ultrasonic field.
~fter drying, about 16,350 Nm per hour of effluent containing 18.9 volume percent sulfur dioxide and 5.2 volume percent molecular oxygen are obtained. The energy consumption inclu-sive of a sulfuric acid plant is about 25,000 kilowatt hours per day. The cost of the waste sulfuric acid thermal cracking unit and sulfuric acid plant is estimated to be about 67 percent of the cost of the installakions for Example 1.
~9 ~
~XAMPLE 3 Essentially the same procedure as described in Example
2 is repeated except 6,900 Nm3 per hour of molecular oxygen are employed as the sound gas. The total fuel oil consumption is 2.3 tons per hour. The thermal cracking apparently proceeds without deleterious effects from combusting fuel with essentially pure oxygen. ~bout 30,180 Nm3 per hour of wet effluent containing 10.2 volume percent sulfur dioxide and 2.8 volume percent molecular oxygen are obtained, and upon drying the gas, 10,100 Nm3 per hour o~ a gas containing 30.5 volume percent sul.fur dioxide and 8.4 volume percent molecular oxygen are provided.
Examples 2 and 3 illustrate that the method for thermal cracking sul~uric acid Or this invention provides a sulfur dioxide-containing gas which can be of substantially higher con-centration than that o~ conventional thermal cracking units.
'rhus, lesser operational and equipment costs are incurred by employing the method of this invention, especially when the sul-fur dioxide is processed to provide sulfuric acid or oleum.
:
' .
Examples 2 and 3 illustrate that the method for thermal cracking sul~uric acid Or this invention provides a sulfur dioxide-containing gas which can be of substantially higher con-centration than that o~ conventional thermal cracking units.
'rhus, lesser operational and equipment costs are incurred by employing the method of this invention, especially when the sul-fur dioxide is processed to provide sulfuric acid or oleum.
:
' .
Claims (13)
1. A method for thermal cracking of waste sulfuric acid to provide a sulfur dioxide-containing gas comprising providing an ultrasonic field, passing sulfuric acid, fuel, and oxygen-containing gas to the ultrasonic field whereby the ultrasonic field atomizes sulfuric acid, combusting fuel with oxygen in the ultrasonic field to provide sulfuric acid thermal cracking temperatures, and thermally cracking sulfuric acid in the ultrasonic field during combustion of fuel.
2. The method of claim 1 wherein the combustion of fuel provides a temperature of about 800° to 1300°C. for thermal cracking of sulfuric acid.
3. The method of claim 2 wherein fuel and sulfuric acid are mixed to provide a fuel in acid dispersion prior to being passed to the ultrasonic field.
4. The method of claim 2 wherein fuel and sulfuric acid are separately passed to the ultrasonic field and are admixed in the ultrasonic field.
5. The method of claim 4 wherein sulfuric acid is passed through a nozzle into the ultrasonic field and fuel is passed through a nozzle concentrically around the nozzle for sulfuric acid into the ultrasonic fuel.
6. The method of claim 2 wherein oxygen-containing gas is provided as sound gas for producing the ultrasonic field.
7. The method of claim 2, 3 or 6 wherein the oxygen-containing gas is air enriched with oxygen.
8. The method of claim 2, 3 or 6 wherein the oxygen-containing gas is oxygen.
9. The method of claim 2 or 6 wherein oxygen-containing gas is provided in an amount such that about 1 to 9 volume percent molecular oxygen is in the sulfur dioxide-containing gas from the thermal cracking.
10. The method of claim 2 or 6 wherein the oxygen-containing gas is provided in an amount such that about 2 or 4 volume percent molecular oxygen is in the sulfur dioxide-containing gas from the thermal cracking.
11. The method of claim 2, 3 or 5 wherein the fuel is fuel oil.
12. A method for thermal cracking waste sulfuric acid to provide a sulfur dioxide-containing gas consisting essentially of generating an ultrasonic field, injecting said waste sulfuric acid, a fuel, and a gas supporting the combustion of the fuel into said generated ultrasonic field, said ultrasonic field being generated substantially co-axially with and near said injections, the combustion-supporting gas being selected from the group consisting of oxygen and oxygen-containing gas having at least about 25 volume percent free oxygen, said acid and said fuel in said ultrasonic field being atomized in intimate mixture with said combustion-supporting gas, initiating burning in said generated ultrasonic field of the atomized fuel with said combustion-supporting gas to thereby thermally crack said acid said injection, burning and thermal cracking serving to maintain the tempera-ture in the combustion zone produced by the exothermic fuel combustion and the endothermic acid cracking in the range from about 800 to 1,300°C.
13. A method for thermal cracking waste sulfuric acid to provide a sulfur dioxide-containing gas consisting essentially of generating an ultrasonic field by using a combustion-supporting gas to produce said ultrasonic field, injecting said waste sulfuric acid, combustion-supporting gas in an amount sufficient to provide an excess of oxygen and a fuel into said generated ultrasonic field, said ultrasonic field being generated substantially co-axially with and near said injections, the combustion-supporting gas being selected from the group consisting of oxygen and oxygen-containing gas having at least about 25 volume percent free oxygen, said acid and said fuel in said ultrasonic field being atomized in intimate mixture with said combustion-supporting gas, initiating burning in said generated ultrasonic field of the atomized fuel with said combustion-supporting gas to thereby thermally crack said acid, said injection, burning and thermal cracking serving to maintain the temperature in the combustion zone produced by the exothermic fuel combustion and the endothermic acid cracking in the range from about 800 to 1,300°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2506438.4-41 | 1975-02-15 | ||
| DE19752506438 DE2506438C3 (en) | 1975-02-15 | 1975-02-15 | Process for the thermal cracking of waste sulfuric acid |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1102997A true CA1102997A (en) | 1981-06-16 |
Family
ID=5938972
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA245,308A Expired CA1102997A (en) | 1975-02-15 | 1976-02-09 | Method and apparatus for the thermal cracking of sulfuric acid |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS51149195A (en) |
| CA (1) | CA1102997A (en) |
| DE (1) | DE2506438C3 (en) |
| FR (1) | FR2300740A1 (en) |
| GB (1) | GB1527661A (en) |
| NL (1) | NL7600702A (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4256721A (en) * | 1979-02-23 | 1981-03-17 | Boc Limited | Combustion method and apparatus |
| US4376107A (en) | 1981-06-11 | 1983-03-08 | Morgenthaler John H | Process for the regeneration of spent sulfuric acid |
| EP0071078A1 (en) * | 1981-07-25 | 1983-02-09 | Bayer Ag | Process for producing sulfuric acid |
| US4490347A (en) * | 1983-02-07 | 1984-12-25 | E. I. Du Pont De Nemours And Company | Process for sulfuric acid regeneration |
| GB8610856D0 (en) * | 1986-05-02 | 1986-06-11 | Boc Group Plc | Treatment of waste material |
| GB2190909B (en) * | 1986-05-02 | 1990-05-02 | Boc Group Plc | Treatment of waste material |
| US4715300A (en) * | 1987-04-27 | 1987-12-29 | Stauffer Chemical Company | Method of disposing of materials by dissolving in acid and then incinerating |
| DE10045320A1 (en) * | 2000-09-12 | 2002-03-28 | Messer Griesheim Gmbh | Process for the regeneration of sulfur-containing residue and for carrying out the process of suitable atomizing burners |
| DE10045322C2 (en) * | 2000-09-12 | 2002-07-18 | Messer Griesheim Gmbh | Atomizing burner for the thermal splitting of sulfur-containing residues |
| DE102009054312A1 (en) * | 2009-11-24 | 2011-05-26 | Air Liquide Deutschland Gmbh | Method and device for burning liquids |
| CN106524185B (en) * | 2016-11-28 | 2019-07-02 | 查都（上海）科技有限公司 | A kind of processing Waste Sulfuric Acid and organic liquid waste system and process flow |
| CN107975812A (en) * | 2017-10-21 | 2018-05-01 | 上海英保能源化工科技有限公司 | L-type spent acid pyrolysis furnace |
| US20230339752A1 (en) * | 2022-04-25 | 2023-10-26 | Messer Industries Usa, Inc. | Process and apparatus for acid regeneration |
-
1975
- 1975-02-15 DE DE19752506438 patent/DE2506438C3/en not_active Expired
-
1976
- 1976-01-23 NL NL7600702A patent/NL7600702A/en not_active Application Discontinuation
- 1976-02-09 CA CA245,308A patent/CA1102997A/en not_active Expired
- 1976-02-10 GB GB513176A patent/GB1527661A/en not_active Expired
- 1976-02-13 JP JP1475476A patent/JPS51149195A/en active Pending
- 1976-02-13 FR FR7604002A patent/FR2300740A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE2506438B2 (en) | 1978-09-07 |
| NL7600702A (en) | 1976-08-17 |
| FR2300740A1 (en) | 1976-09-10 |
| FR2300740B1 (en) | 1980-11-21 |
| GB1527661A (en) | 1978-10-04 |
| DE2506438A1 (en) | 1976-08-26 |
| DE2506438C3 (en) | 1979-04-26 |
| JPS51149195A (en) | 1976-12-21 |
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| MKEX | Expiry | ||
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Effective date: 19980616 |