WO1993014026A1 - Procede et appareil de desulfuration d'un gaz - Google Patents

Procede et appareil de desulfuration d'un gaz Download PDF

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Publication number
WO1993014026A1
WO1993014026A1 PCT/US1993/000319 US9300319W WO9314026A1 WO 1993014026 A1 WO1993014026 A1 WO 1993014026A1 US 9300319 W US9300319 W US 9300319W WO 9314026 A1 WO9314026 A1 WO 9314026A1
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WO
WIPO (PCT)
Prior art keywords
sulfite
magnesium
alkaline earth
bicarbonate
reactant
Prior art date
Application number
PCT/US1993/000319
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English (en)
Inventor
Nobuyasu Hasebe
Nobukatsu Hasebe
Original Assignee
Nobuyasu Hasebe
Nobukatsu Hasebe
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nobuyasu Hasebe, Nobukatsu Hasebe filed Critical Nobuyasu Hasebe
Priority to JP5512653A priority Critical patent/JPH07505603A/ja
Priority to EP93904493A priority patent/EP0621854A4/en
Publication of WO1993014026A1 publication Critical patent/WO1993014026A1/fr

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    • 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
    • C01B17/60—Isolation of sulfur dioxide from gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/73—After-treatment of removed components

Definitions

  • This invention relates to the treatment of gases for the removal ' of sulfur therefrom and more particularly to a continuous method for the treatment of flue gases and the like 5 to remove sulphur dioxide.
  • SO ⁇ sulphur oxide products
  • one method involves the creation of a water solution of sodium sulfite which is then contacted with the flue gas to produce acid sodium sulfite.
  • the acid sodium sulfite is then treated with calcium carbonate or calcium hydroxide to
  • Another method involves contacting the flue gas with a
  • Another object of the present invention is to provide a method for the treatment of flue gases and the like which substantially reduces the consumption of the reactant products.
  • Yet another object of the present invention is to provide 5 a method for the treatment of flue gases and the like in which the efficiency of the sulphur removal is substantially enhanced.
  • Another object of the invention is to provide improved apparatus for carrying out the treatment of sulfur containing 10 gases.
  • Still another object of the present invention is to provide improved apparatus for the thermal decomposition of sulfite produced in order to efficiently regenerate the reactants and substantially reduce the consumption of the
  • an alkaline earth bicarbonate is solubilized in water and contacted by a flue gas.
  • the solubilized alkaline earth 20 bicarbonate reacts with the S0 2 in the flue gas to form an alkaline earth sulfite which readily precipitates from the water solution and is efficiently separated therefrom.
  • the slurry exiting the desulfurization step is subjected to a heating step which causes the soluble bisulfite to be 30 converted to the insoluble sulfite.
  • the slurry is then subjected to a separation step to --_, recover the solid phase of the slurry from the aqueous phase.
  • the aqueous phase is then preferably recycled to the ⁇ ⁇ desulfurization step or may be disposed of.
  • the solids are subjected to thermal degradation to recover the alkaline earth oxide and S0 2 .
  • the alkaline earth oxide can be recirculated and reused in the desulfurization process to reduce the consumption of the alkaline earth reactant while the S0 2 , which has practical uses as a precursor in various chemical processes and therefor is of commercial value, is liquified.
  • Thermal degradation of the solids from the desulfurization step is carried out in apparatus which includes a preheater zone, an ignition and heating chamber and a degradation zone.
  • the thermal degradation is carried out in the presence of heated pellets which are themselves inert to the degradation reaction.
  • the pellets are heated in the ignition and heating chamber prior to contact with the solids from the desulfurization step.
  • the alkaline earth sulfite which is relatively insoluble in water is more readily precipitated and more easily separated when an alkali metal sulfite is also present. Consequently it is highly preferred that the reactant solution contain an alkali metal bicarbonate which will also be converted into an alkali metal sulfite and will enhance precipitation of the alkaline earth sulfite via the common ion effect.
  • the solids separated in the process are essentially the sulfites of both the alkaline earth metal or the alkali metal and thus the bulk of material is substantially decreased and less expensive equipment can be used for thermally decomposing the sulfites.
  • the method of the present invention is advantageously carried out in a continuous counter current fashion in one or more reaction columns.
  • the columns are divided into a bicarbonation zone and a desulphurization zone and the reactants introduced at the bicarbonation zone travel countercurrent to the flue gas so that the treated gas exits at one end of the column and a liquid phase and sulfite produced by contact with the flue gas exit as a slurry at the opposite end of the column.
  • the zones may be defined in separate columns.
  • the slurry is conveyed to a heated vessel for conversion of soluble bisulfate to insoluble sulfite. Since the solid byproduct is essentially alkaline earth or alkali metal sulfite, the bulk of the material relative to the volume of - * » flue gas being treated is less than with conventional methods
  • Fig. 1 is a block diagram of the steps of the method of 20 the present invention.
  • Fig. 2 is a schematic diagram of a single column apparatus for carrying out the method of the present invention
  • Fig. 3 is a schematic diagram showing an apparatus for 25 thermally decomposing magnesium sulfite
  • Fig. 4 is another embodiment illustrating a use of two columns for thermally decomposing magnesium sulfite.
  • the present invention provides an improved method for the •30 stripping of S0 2 from gases produced by the combustion of sulphur containing fossil fuels such as high sulphur oil, coal -> and the like.
  • Sulphur in such exhaust gases hereinafter referred to as flue gas
  • flue gas is oxidized to S0 2 and if released to the atmosphere in will produce a harmful complex of sulfur 35 compounds, commonly referred to as S0 ⁇ , which react with moisture in the air to form the so called acid rain which is so harmful to the environment as well as contributing to smog which is common in urban locations throughout the world.
  • S0 ⁇ harmful complex of sulfur 35 compounds
  • the invention is illustrated hereinafter in connection with the use of magnesium reactants although it will be clearly understood that the other members of the alkaline earth group can be utilized in the present invention.
  • the first step in the method is the bicarbonization step in which an aqueous slurry of magnesium in the form of an oxide, carbonate or hydroxide is reacted with carbon dioxide to produce magnesium bicarbonate which is water soluble in accordance with the following:
  • the magnesium oxide, hydroxide or carbonate or mixtures thereof are added to water to form a slurry of the essentially water insoluble magnesium compounds.
  • the amount of the oxygen containing magnesium compound added in the initial slurry is not critical although it will be seen from
  • the solids portion of the reactant slurry becomes substantially solubilized in the aqueous phase as the insoluble oxygen containing magnesium compounds react with the CO- to form the soluble magnesium bicarbonate. Since no such reaction is 100% efficient, it will be understood that after contact with the CO- the reactant still will contain some solids although far less than in the original slurry. These solids will comprise unreacted oxygen containing magnesium compounds as well as magnesium bicarbonate which is not been solubilized in the water bas_e. These solids may be separated from the reactant at this point, although such separation is not required.
  • the second step in the method is the desulfurization step in which at least the aqueous phase of the slurry containing the solubilized magnesium bicarbonate is contacted with the
  • reaction 4 there is a mole to mole reaction between the solubilized bicarbonate and the S0 2 and intimate contact between the bicarbonate in solution and the
  • S0 2 of the gas being treated provides a highly efficient desulfurization operation.
  • the magnesium sulfite produced by the reaction of the bicarbonate and S0 2 is relatively insoluble in water and is thus readily separated for recovery of the magnesium sulfite using conventional liquid/solid separation equipment.
  • the carbon dioxide formed in the desulfurization step is preferably recirculated back to the bicarbonization step to provide the C0 2 for the bicarbonization of the magnesium oxide, carbonate or hydroxide.
  • magnesium sulfite formed during the desulfurization step will react with the S0 2 in the flue gas to form magnesium bisulfite in accordance with the following:
  • magnesium bisulfite is soluble in the aqueous phase of the reactant and, unless treated, will be lost in the aqueous phase. It has been found that from between about 0.2 to about 0.6 mols of the bisulfite per mol of sulfite will be formed in the reactant during the desulfurization step.
  • the third step of the process is to heat the liquid phase of the reactant to a temperature sufficient to convert the bisulfite back to the insoluble sulfite. It has been found that heating the liquid phase-to between about 60°C and about 140*C will effect the conversion in accordance with the following:
  • the MgS0 3 is then subsequently separated from the aqueous phase and recovered as described below.
  • the liquid phase of the reactant slurry can be heated as described to effect the conversion of the soluble bisulfites to insoluble sulfites, it is preferred to subject the entire slurry exiting from the reaction column to the heating step prior to separating solids from the acqueous phase. It will be apparent that, unless treated as described herein, as much as one half of the magnesium compound may be lost in the process as soluble bisulfite.
  • magnesium sulfite may be oxidized to magnesium sulfate (MgS0 4 ) which is also soluble in water and which represents additional loss of magnesium in the process because it is not easily separated from the liquid phase.
  • MgS0 4 magnesium sulfate
  • This reaction represents a potential loss of magnesium from the process and must be made up by the addition of fresh magnesium oxide, carbonate or hydroxide at the bicarbonization step.
  • the loss of magnesium due to oxidation of the sulfite to sulfate can be reduced by the addition of anti-oxidants to the reactant either at the bicarbonization ste or just prior to desulfurization.
  • the anti-oxidant serves to prevent the oxidation of magnesium sulfite to magnesium sulfate in the presence of oxygen in the flue gas.
  • the anti-oxidant should be soluble in water and have a low vapor pressure so as to maintain its anti-oxidant 5 effect over a substantial period of time in the presence of relatively high temperatures.
  • the anti-oxidants which have been found useful in the present invention are hydrazine and hydrazine salts.
  • aryl- and alkyl- hydroxylamine containing materials such as p-, o-, or m-amino phenol are
  • Carboxylic acid such as tartaric and citric can serve as anti-oxidants in the method of this invention as well as aromatic polyamines such as ortho-, meta- or para-diaminobenzene.
  • Aromatic hydroxy compounds such as pyrocatechol, pyrogallol and 1,2,4, trioxybenzene have also
  • the anti-oxidant is preferably added in concentrations of between about 50ppm to about 500ppm with the exact amount being a matter of choice depending upon the oxygen content of the flue gas being treated.
  • magnesium sulfite is insoluble in water and thus precipitates out of the liquid phase in the desulfurization step.
  • the fourth step of the process involves the separation of the insoluble sulfite from the liquid phase of the reactant.
  • the alkali metal sulphite is prepared by the addition of an alkali bicarbonate to the liquid phase of the reactant slurry or can be added as the carbonate, oxide or hydroxide to the slurry of oxygen containing magnesium compounds for reaction in the bicarbonization step in the same manner as the magnesium compounds.
  • the alkali bicarbonate reacts with * the S0 2 in the flue gas accordingly to the following:
  • alkali sulfite will further react with a mole of S0 2 in accordance with the following:
  • the alkali sulfite also helps to remove the S0 2 from the flue gas.
  • the alkali metal be added in the form of an oxide, carbonate or hydroxide for reaction in the bicarbonation step to form the bicarbonate of the alkali metal.
  • excellent results have been achieved using natural alkali minerals such as nahcolite, trona, and natron.
  • Nahcolite is a mineral whose major component is sodium bicarbonate and which is found in saline mineral deposits.
  • Trona (Na 3 H(C0 3 )-.2H 2 0 is also a natural soda.
  • Nahcolite is a mineral comprising hydrated sodium bicarbonate.
  • the quantity of alkali metal bicarbonate which is present in the reactant should be sufficient to provide between about 0.1 to about 3 moles of alkali sulfite per mole of magnesium sulfite present after desulfurization.
  • a highly preferred range is about 0.4 mole to about 1 mole of alkali sulfite per mole of magnesium sulfite.
  • the fifth step in the process involves the thermal degradation of the sulfite (both the magnesium and alkali metal) for recovery of MgO, alkali earth oxide, if present, and S0 2 . Since magnesium oxide is decomposed at a temperature of between about 800°C and 1200"C which is well above the decomposition of any of the alkaline earth metal sulfites or alkali metal sulfites, the degradation temperature is carried out below the degradation temperature of Mg
  • S0 2 of high purity is formed as a byproduct of the sulfite decomposition and is separated and liquified for subsequent use for the production of sulphur containing products such as, for example, sulfuric acid production.
  • the method of the present invention is preferably carried
  • FIG. 2 there is schematically illustrated apparatus for carrying out the method of the present invention.
  • a reaction column 12 is provided with an inlet 14 at its lower end for flue gas and an outlet 16 at its top for treated gas.
  • a spray head 18 is disposed in the top of the reaction column 12
  • reaction column 12 and is connected by a line 20 and a line 22 to a mixing tank 24 in which the alkali metal oxide containing slurry is prepared.
  • the spray head 18 serves to evenly distribute the slurry in the reaction column 12.
  • the reaction column 12 is divided into zones 26 and 28 by a partition 30
  • the 25 including an open ended cylinder 32 which defines a passage 34 through the column 12 for communication between the zones, 26 and 28 respectively.
  • the cylinder 32 is partially closed off by a member 36 which permits gaseous communication between the zones but essentially prohibits liquid communication
  • magnesium oxide is added at the heating tank 48 to ensure an excess of the oxide for reaction with S0 2 formed during bisulfite conversion to reduce or eliminate the necessity of processing S0 2 formed during the bisulfite conversion step.
  • the slurry is sent to a liquid/solid separator 50 for separation of the solids from the liquid phase.
  • the solids are moved by a line 52 to a thermal degradation unit 54 as will be described hereinafter as will be described in detail in connection with Fig.3.
  • the liquid phase is conveyed by a pump
  • the reaction column 12 is further subdivided by fluid permeable packing supports 60, for example movable trays, screens or the like.
  • Each of the packing supports support packing materials 62 which serve to diffuse both the flue gas and the reactant to ensure intimate contact therebetween.
  • Permeability is provided by openings in the supports 60.
  • the size of the openings is not critical so long as packing material 62 can be retained by the supports 60
  • the packing material 62 may comprise any of the conventionally used materials such as Raschig rings or Berl saddles.
  • the packing material 62 comprises a plurality of hollow balls 64 which, as illustrated in FIG.5 are provided with openings 66 and edge portions of which describe inwardly extending contoured baffles 68.
  • the design and function of the hollow balls 64 is set forth in Japanese patent publication 54-37586, dated Nov 15, 1979.
  • the use of the hollow balls 64 as the packing material of choice is preferred since the hollow balls 64 are constantly agitated and moving by the action of the flue gas and the counterflowing reactant in the openings 66 and against the baffles 68 to cause the balls to oscillate and vibrate so that the build up of sulfite 5 on the surface of the ball is avoided.
  • the separated magnesium sulfite is pumped to a heating unit 70 for thermal degradation at a temperature of between about 800°C to about 1200"C.
  • the thermal degradation is achieved using a column heater in which the magnesium sulfite is heated in the presence of alumina 10 pellets.
  • the apparatus may comprise a single unit or multiple units.
  • a single column thermal degradation unit 54 which comprises a hollow column 72 having closed ends defining a top wall 71 and 15 a bottom wall 78.
  • Magnesium sulfite is introduced to the column through an inlet port 74.
  • the alumina pellets are separately added through an inlet port 75 in the top wall 71 opposite the port 74.
  • a depending partition 80 extends across the diameter of the column 72 in the upper portion thereof and
  • top and bottom walls 71 and 78 terminate in cooperation with the top wall 71 and side wall of the column 72 a drying and pre-heating zone 73 and an ignition and heating zone 76.
  • Fuel and air are introduced to the ignition zone 76 through inlet 82.
  • Alumina pellets are heated
  • 35 86 is located in the column 72 and the mixer 86 is driven through a shaft 88 and motor 90 to mix the pellets and the sulfite solids which are thermally degraded by the heated pellets to produce finely divided magnesium oxide.
  • the finely divided magnesium oxide and the alumina pellets are separated by a vibrating screen 92 located at the bottom of the column 72 and the magnesium oxide is sent to the make up tank 24 for reuse in the process.
  • the alumina pellets are returned by a line 94 to the port 74 and reintroduced in the column 72 for reheating and reuse in the thermal degradation process.
  • S0 2 is separated and exits the column 72 at line 96 for liquification and storage for use in other chemical operations in accordance with known procedures.
  • Fig. 4 there is illustrated a pair of reaction columns 98 and 100 designed for the thermal degradation of larger volumes of magnesium sulfite in large S0 2 stripping operations.
  • the columns are paired with the column 98 serving as the degradation column and the column 100 serving as the ignition and heating column.
  • the ignition column 100 includes a pair of inlets 102 and 103 for receiving fuel and pellets to be heated, respectively. Flue gas generated during the ignition of the fuel is conducted out of the column 100 through an outlet 104.
  • a rotating mixing element 106 of the type described above in connection with Fig.3 is provided to intimately mix the pellets and the fuel which are ignited in the midsection of the column 100 just below the mixing element 106.
  • a vibrating screen 108 is provided at the bottom of the column 100 for separating ash, if any, from the heated pellets and the heated pellets are then transferred by a line 110 to the degradation column 98.
  • the degradation column 98 is provided with inlet ports 112 and 114 for receiving magnesium sulfite and the heated pellets, respectively.
  • An outlet port 116 for S0 2 is provided in the upper portion of the degradation column 98 and a rotating power driven mixing element 118 is provided in the column 98.
  • the magnesium sulfite and the heated pellets are intimately mixed by the mixing element 118 to cause the degradation of the magnesium sulfite to magnesium oxide and SO.,.
  • a vibrating screen 120 is provided at the bottom of the column 98 for separating finely divided magnesium oxide from the alumina pellets.
  • the pellets are then returned by a line 122 to the ignition column 100 for reuse in the process and the magnesium oxide is transferred by a line 133 to the make up tank 24 for reuse in the sulfite stripping process. 5
  • the following examples are illustrative of specific modes of practicing the invention and are not intended as limiting the scope of the invention as defined by the appended claims.
  • Example 1 The following example illustrates the S0 2 efficiency of
  • a single reaction column 12 comprising a bicarbonation zone and a desulfurization zone.
  • a glass column 380cm in height and 10 cm in diameter was partitioned into an upper zone 160cm in length and a lower zone 220cm in length.
  • the upper zone was further divided into
  • 15 two 15cm coaxial sections by permeable supports consisting of screen having 7.25mm openings and the lower zone was divided into three 15cm sections by the screens.
  • Each section contained a plurality of hollow polypropylene packing balls of 10 mm diameter.
  • Each ball had a surface wall thickness of 0 0.03 mm and was provided with five through running openings, each 2mm in diameter.
  • Each section contained sufficient number of packing balls to fill it to a depth of 30 cm.
  • a gas comprising 0.2% SO-, 15% CO., 84.8% N- and no oxygen was introduced into the column at a flow rate of 1.18 nm 3 /min. 5
  • a reaction slurry comprising 4.5 gr of magnesium bicarbonate and 5.7 gr of the mineral trona in water was charged to the column at an initial flow rate of about 8.4 liters per minute.
  • 0.6 gr of magnesium carbonate and 0.7gr of trona were added on an hourly basis to the reactant to 0 compensate for any lost magnesium or sodium bicarbonate.
  • the exiting material from the reaction column was filtered to separate magnesium sulfite from the liquid phase and the liquid phase analyzed for its bisulfite content.
  • the ratio of magnesium bisulfite in the liquid phase to magnesium sulfite solids was found to be in the mole ratio of between 0.2:1 to 0.6:1.
  • the liquid phase was heated to about 65°C to convert the magnesium bisulfite salt to insoluble magnesium sulfite and refiltered to recover the magnesium sulfite.
  • the magnesium sulfite was thermally decomposed in the presence of alumina pellets heated to approximately 800°C and the magnesium oxide in finely divided form was separated from the alumina pellets. Recovery of the magnesium oxide was on the order of 99.5% of the magnesium oxide introduced to the thermal degradation.
  • a series of operations were performed to determine recovery efficiency of MgO in the thermal degradation operation using a pellet heater of the type described herein.
  • the heater was 1 meter in height and had an inside diameter of 2 meters.
  • the inner surface of the heater was lined with magnesium chrome bricks and the outside was lined with insulating brick, 25 mm in thickness.
  • a pellet hopper was provided at the top of the apparatus for feeding pellets to the interior.
  • the inner wall of the hopper was lined with a mortar consisting of a mixture of magnesium oxide and alumina to avoid contaminating the thermal degradation unit with metal particles from the sidewalls of the hopper.
  • An electrically powered vibrating screen (3.9mm openings) was installed at the outlet of the apparatus for separating the pellets and the magnesium oxide.
  • a test material comprising magnesium sulphite (58.14% moisture) was supplied to the apparatus through the feeding hopper at the rate of 10.37 kilograms an hour.
  • Alumina pellets (about 5mm in diameter and length) were fed to the thermal degradation unit at the rate of about 50kg/hr. Temperatures inside the apparatus were measured at 700°C. at the top, 990°C. at the midsection, and 850°C. at the bottom of the apparatus.
  • the fuel used was propane which was fed at the rate of 4 kilograms per hour.
  • the amount of magnesium oxide recovered was 1.59 kg. per hour which represented a mol percent yield of 94.84% of the magnesium sulfite introduced.
  • magnesium sulfite (68.28% moisture) was introduced at the rate of 10.08 kg/hour while the pellets were introduced at 50kg/hr . Temperatures inside the apparatus were measured as at 788°C. at the top, 998°C. in the midsection and 845°C at the bottom of the apparatus. Propane fuel was fed at the rate of 4 kil. per hour. The amount of magnesium oxide recovered was 1.5 kil. per hour with a mol yield efficiency of 92.99%.
  • a third run was made in the same manner as described above using magnesium sulfite test material (66.57% moisture) fed at the rate of 13.87 kg/hr.
  • the pellets were fed at the rate of about 70 kg/hr.
  • Temperatures measured inside the apparatus were 775°C. at the top, 998"C. at the midsection and 827°C at the bottom.
  • Propane was utilized at the rate of 4kg/hr as the fuel.
  • the amount of magnesium recovered was 1.76 kil. representing a mol yield efficiency of 98.28%.
  • the desulfurization process of the present invention was utilized on a flue gas from a boiler utilizing the apparatus illustrated in Fig. 1.
  • the reaction column was 12 meters in height and had an inside diameter of 1.5 meters.
  • the column was divided into a carbonization zone and a desulfurization zone with each zone being further divided in sections by screens having 38mm openings, each section included hollow plastic balls to a depth of 50 centimeters.
  • Each plastic ball was 45mm in diameter, had a surface wall thickness of 0.1mm, was provided with fourteen through running holes of 4 mm in diameter and provided with inwardly extending contoured baffles as illustrated in Fig. 5.
  • a reactant slurry comprising 3.2 kg/1 of magnesium carbonate and 3.6 kg/1 of the mineral trona (C0 3 23%, HC0 3 17%) was prepared in water to a salt concentration of 0.0759 kmols/kl.
  • the slurry was heated to a temperature of about 50"C. and introduced through a spray head into the bicarbonation zone of the reaction column.
  • the reactant in the form of a thin slurry was led into the desulfurization zone of the reaction column through a spray head as shown in FIG. 2.
  • the slurry was introduced at a rate of about 2 kl/min which resulted in a magnesium compound supply of about 1.6 mols per hour and a trona supply of about 0.8 mols per hour.
  • Example 4 Utilizing the apparatus of the foregoing example, the flue gas was modified by the addition of oxygen to provide an oxygen content of 10%.
  • the desulfurization operation was run as described in Example 4 above and the process was operated or two hours .
  • the sulphate content of the liquid phase after separation of the magnesium sulphite was measured and reported as a percent of magnesium sulphite recovered.
  • antioxidant 100 ppm
  • the sulphate ion concentration of the liquid phase was determined as a percent of the magnesium sulphite recovered.
  • a second 2 hour run was then conducted using a different antioxidant. Runs were repeated as described above for a total of six different antioxidant compositions.
  • the antioxidants tested were hydrazine, hydroxylamine, sodium polythionate and diaminodiphenyl, p-phenylenediamine and o- phenylenediamine. At the end of each run of each of the antioxidants the sulphate ion content was of the liquid phase was measured and reported as a percentage of the magnesium sulphite recovered. The results- are set forth in Table 3 below.

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Abstract

On dissout du bicarbonate de terre alcaline dans de l'eau et on le met en contact avec des gaz de fumée. Le bicarbonate de terre alcaline dissous réagit avec le SO2 se trouvant dans les gaz de fumée pour former un sulfite de terre alcaline qui se sépare par précipitation de la solution aqueuse. Selon l'invention, la boue sortant de l'étape de désulfuration est soumise à une étape de chauffage qui provoque la conversion du bisulfite de terre alcaline soluble formé pendant l'étape de désulfuration en sulfite insoluble. Les solides sont séparés de la phase aqueuse et sont soumis à une dégradation thermique afin de récupérer l'oxyde de terre alcaline et SO2. L'oxyde de terre alcaline peut être recyclé et réutilisé dans le processus de désulfuration tandis que SO2, qui présente des utilités pratiques comme précurseur dans divers processus chimiques et par conséquent a une valeur commerciale certaine, est liquéfié. La dégradation thermique des solides de l'étape de désulfuration s'effectue dans un appareil qui comprend une zone de préchauffage, une chambre d'allumage et de chauffage et une zone de dégradation. La dégradation thermique s'effectue en présence de pellets chauffés qui sont eux-mêmes inertes à la réaction de dégradation. De préférence, les pellets sont chauffés dans la chambre d'allumage et de chauffage avant d'entrer en contact avec les solides provenant de l'étape de désulfuration.
PCT/US1993/000319 1992-01-13 1993-01-13 Procede et appareil de desulfuration d'un gaz WO1993014026A1 (fr)

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JP5512653A JPH07505603A (ja) 1992-01-13 1993-01-13 ガス脱硫の方法と装置
EP93904493A EP0621854A4 (en) 1992-01-13 1993-01-13 Method and apparatus for desulfurization of a gas.

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US81928892A 1992-01-13 1992-01-13
US07/819,288 1992-01-13

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007031552A1 (fr) * 2005-09-15 2007-03-22 Solvay Chemicals, Inc. Elimination de trioxyde de soufre d’un flux de gaz de combustion
CN113184973A (zh) * 2021-04-25 2021-07-30 南京奇诺自控设备有限公司 一种so2碱吸塔含盐废水处理工艺

Citations (6)

* Cited by examiner, † Cited by third party
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EP0621854A4 (en) 1995-08-30
JPH07505603A (ja) 1995-06-22
EP0621854A1 (fr) 1994-11-02

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