CA1099489A - Method of removing mercury-containing contaminations in gases - Google Patents
Method of removing mercury-containing contaminations in gasesInfo
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- CA1099489A CA1099489A CA267,780A CA267780A CA1099489A CA 1099489 A CA1099489 A CA 1099489A CA 267780 A CA267780 A CA 267780A CA 1099489 A CA1099489 A CA 1099489A
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- sulfide
- mercury
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Abstract
ABSTRACT OF THE DISCLOSURE
The present invention relates to a method of removing mercury-containing contaminations from gases by passing the gas to be purified through a filter bed which is devised to make effective gas contact. The method is characterized in that the filter bed is comprised of specific material prepared by binding, onto a carrier substance such as granulated pumice, a sulfurous substance as contamination absorbin agent. The sulfurous substance may be a naturally occurring or synthetic sulfide of lead, cadmium, antimony, arsenic, iron, nickel and zinc and may be subjected to a surface activation pretreatment. The invention is specially adapted to remove contaminations in refinery effluent gases, especially those containing vaporized mercury metal, together with absorption on the filter bed material. The process uses a mechanism by which mercury, which has a high vapour pressure, is converted into its sulfide, which shows very low vapour pressure, by contacting the gas with sulfides of other metals.
The present invention relates to a method of removing mercury-containing contaminations from gases by passing the gas to be purified through a filter bed which is devised to make effective gas contact. The method is characterized in that the filter bed is comprised of specific material prepared by binding, onto a carrier substance such as granulated pumice, a sulfurous substance as contamination absorbin agent. The sulfurous substance may be a naturally occurring or synthetic sulfide of lead, cadmium, antimony, arsenic, iron, nickel and zinc and may be subjected to a surface activation pretreatment. The invention is specially adapted to remove contaminations in refinery effluent gases, especially those containing vaporized mercury metal, together with absorption on the filter bed material. The process uses a mechanism by which mercury, which has a high vapour pressure, is converted into its sulfide, which shows very low vapour pressure, by contacting the gas with sulfides of other metals.
Description
1~9~9 The present invention relates to a method of removal of metals and their compounds, especially mercury and its compounds, from gases in which they are contained as contaminants.
In refinery of non-ferrous metals, mercury contained in the raw sulfide ore or in the slag in small amounts will be discharged in a form of compound or metal vapour hy thermal treatment procedures, such as heating, roasting and so on, and will be included in gases.
Since the vapour pressure of mercury is relatively high, it is often contained in the exhaust gas in gaseous or finely dispersed state, and therefore, if these gases are exhausted without treatment, the atmosphere will be polluted when such gases are used for the production of sulfuric acid, and the sulfuric acid so obtained will be contaminated with mercury due to absorption.
In general, for removing metals or its compounds in gases, there have been many previously proposed procedures, which may be employed separately or in combination, for example, using scrubber or bag filter, cyclone separation, gravity setting and Cottrell precipitation. While it will be possible to remove, for example, mercury compounds in finely dispersed state by these procedures, they cannot attain a - complete removal of gaseous substance, such as mercury vapour, since all these procedures are based on a physical dust removal principle.
On the other hand, in order to remove small amounts of mercury by chemical means, several methods have been proposed. For example, a solution having oxidizing property, .~
1~99~89 such as a solution containing sulfuric acid, is used as a scrubber liquid, and a chemical reaction with iodide ion etc.
is utilized. In these methods, however, the effectiveness of mercury removal by oxidation will vanish by reduction by sulfurous acid gas for example, so that they cannot be considered wholly satisfactory for removing mercury in gases from the thermal treatment processes, such as heating, burn-ing and so on in refining non-ferrous metals.
For removing mercury there has further been proposed a method in which the gases are passed through an aqueous solution containing a substance which absorbs mercury easily, such as thiourea or the like. However, in this method, the pressure loss is considerably large due to the forced passage of gases through the aqueous solution, so that this is pPDblematic in the apparatus.
The present invention provides a novel process for removing contaminants from gases, which overcomes or at least reduces some of the aforementioned disadvantages.
Thus according to the present invention, there is provided a method for removing mercury-containing contaminants from gases, which comprises passing the gases through a filter bed, the filter bed including an absorbent comprising a carrier and at least one sulfide material absorbing agent, said at least one sulfide material being substantially insoluble in the components of said gas and being selected from naturally occurring and synthetic sulfides of the metals lead, cadmium, antimony, arsenic, iron, nickel and zinc.
A compound of mercury is subject to be converted into metallic form, so that it changes easily into metallic mercury by, for example, a small amount of reducing agent or even by heating. Metallic mercury has a relatively high .~ .
~- .; .
1~999~9 vapour pressure and volatilizes easily. The vapour pressures of mercury at various temperatures are as follows:
~3~ at 20 to 30 C
10-2 mH at 50 to 60 C
10 1 mmHg at about 100 C
1 to 2 mmHg at 120 to 130 C
10 to 20 mmHg at 180 to 190 C (~ee Chemical Handbook) . .
Thu.~, mercury may often be contained in ga~es in the form of metal vapour, so that in many cases it cannot be removed by employing a physical treatment such as scrubbing or settling.
In the present invention, there is taken into consideration the fact that mercury sulfide has a very low solubility product, and also a very low vapour pressure. In this invention, removal of mercury is undertaken by a mechanism in which mercury is removed by fixing it by substitution with a metal sulfide having greater solubility li product than that of mercury sulfide. The order of formation of sulfides of metals is given, according to so-called ZO Schurmann series, as follows: Pd, ~g, Ag, Cu, Bi, Cd, Sb, Sn, Pb, Zn, Ni, Co, Fe,........... As can be seen, mercury will form its sulfide more easily than many other metals.
As to the solubility products for various metal sulfides, the following data are available:
~ ' , .
10994~9 Sulfides Soly Prod. Sulfides Soly Prod.
HgS -52 2 3 -29 Hg2S10-47 Fe2S lo-18 PbS -23 NiS -19 CdS ~33 ZnS -22 sb2S31o~29 The solubility product of mercury sulfide is, as shown above, very small as compared to other metal sulfides~ though the values may vary in accordance with the pH of the solution.
Since raw materials ~or non-ferrous metals exist mainly as sulfides~ which may contain some sulfates and chlorides, the refinery exhaust gas thereof is an acidic gas containing S02 and S03 besides C02~ N2, H20, 2~ etc, Therefore, when such refinery exhaust gas is dissolved in water, or whe~ it reaches its dew point~ an acidic or weakly acidic pH value will be shown.
For the purpose of the present invention, it i8 permissible to use any metal sulfides when the ga~ will present a neutral atmosphere. However, the suitable metal sulfides are restricted when refinery exhaust exhibits an acidic property. Some sulfides, for example, synthetic zinc sulfide and iron sulfide, may dissolve in such cases.
However, natural minerals of zincblende and pyrrhotite can be used as a mercury absorbing agent, because these are not dissolved by weak acid.
In the following, reaction equations for mercury and other metal ions with various sulfides are shown.
.
1~399489 Hg (metal) ~ PbS + S02 + 2 = HgS + PbS04 . I .
~ 2Hg (metal) ~ PbS ~ S02 ~ 2 = Hg2S + PbS04 Hg++ + PbS = HgS + Pb++ .
2HG~ + PbS = Hg2S + Pb Hg (metal) + ZnS -~ S02 + 2 = HgS I ZnS04 2Hg (metal) ~ ZnS + S02 + 2 = Hg2S + ZnS04 Hg~+ + ZnS = HgS + Zn++
2Hg~ + ZnS = Hg2S + Zn Pb+ + ZnS = PbS + Zn . .
Pb++ + FeS = PbS + Fe Cd +. + ZnS . = CdS + Zn 2As ~ 3ZnS 2 3 3 Similar reactions are performed with other sulfides.
From these considerations, it can be seen that mercury present in gases can be removed in such a manner that mercury, which reveals high vapour pressure, is converted into mercury sulfides, which show very low vapour pressure.
Even mercury compounds present in gases which do not contain sulfur dioxide can be removed by fixing them by converting into mercury sulfide by means of a substitution react-ion in accordance with the equations above. Such will also apply for various other metal sulfides: they can be removed by substitution independent of the existence of sulfur dioxide.
In the case of mercury vapour, it undergoes also a strong absorption reaction together with the substitution reaction.
Thus mercury vapour in the air containing no sulfur dioxide can be removed by using lead sulfide to absorb it.
Thére are to preferred methods for the preparation of ~"t.j ., .J
1~)99489 the active substance to be used as absor~ent according to the present invention. Firstly, the sulfide or simple sulfur substnace may be bound to a carrier substance. Secondly, a carrier may ~e impregnated with a soluble salt of a metal and then hydrogen sulfide gas or an aqueous solution of sodium sulfide may be passed therethrough to deposit the metal sulfide onto the carrier substance.
As carrier substance, inorganic or organic porous substances can advantageously be utilized. Those which are la light and easily granulated into homogeneous particle size with having porous surface, such as pumice, are preferred Pumice is a porous volcanic ejecta material. The deposition of the absorbing agent thereon is easy to accomplish, and the deposited ¦
substance can only be removed therefrom by shocks with difficulty.
Among organic substances, sponge, spongy rubber, polyurethane foam and the like may be used.
When the temperature of the exhaust gas is high, or when the corroding tendency of the exhaust gas is great, an inorganic silicic porous substance, such as zeolite or pumice is suitable for the carrier. When the temperature of the exhaust gas is low and its corrosive tendency is small, other inorganic and organic substance may be used for the carrier.
The smaller the particle size of the carrier, the ; -greater the surface area thereof, so that the contact surface area becomes large and thereby the extraction of mecury is facilitated. Thereby however, the pressure loss may rq 1~99~9 become uneconomically large, so that a particle size of from several millimeters to several centimeters may be desirable.
In preparation of the absorbent, synthetic sulfides may be prepared By blowing hydrogen sulfide gas into an aqueous solution of various salts of metals. For example, lead sulfide and zinc sulfide can be prepared by blo~ing hydrogen sulfide gas into aqueous solution of, for instance, lead acetate or zinc sulfate and filtering off the precipitate of sulfide thus formed, which is further processed into the absorbent. The absorbent to be used according to the present invention can also be prepared from natural sulfide minerals, such as galena, zincblende, pyrite, pyrrhotite and chalcopyrite, etc., by washing them sufficiently with water and subse~uently further subjecting to a surface treatment with dilute sulfuric acid or by washing them with dilute sulfuric acid and thereafter further subjecting to sulfurizing with hydrogen sulfide.
The surfaces of various sulfide ores from mines are covered in general with dressing agent and slimes and, in many cases, are covered with salts, such as sulfate, due to oxidation by air. Thus, these ores as such are ineffective in using for scavenging mercury in gases, because the surface ; thereof does exist not as the mineral itself, such as galena or zincblende, but it exists, for instance, in sulfatized state.
Therefore, it may be necessary to subject the surface of the ore to an activation treatment such as sulfurizing with - hydrogen sulfide, in order to provide the absorbent according to the present invention.-1~99~89 .
Accord~ng to one preferred aspect of the present invention, a synthetic sulfide or a natural sulfide mineral selected from the aforementioned group sub~ected to a pre-treatment of surface cleaning, is used for the a~sor~ing agent and a porous material, for example, pumice, ~s employed for the carrier.
According to the present invention~ in one preferred process of operation, an exhaust gas containing mercry or metal compound is passed through an absorption col D , in which the aBsorbent made by comBining the absorbing agent with the carrier is packed, to contact the gas with the absorbing bed and thereby to fix the mercury or metal compound either by converting it into sulfide or by absorbing it.
- I The carrier may be combined with a single absorbing agent or with two or more kinds of absorbing agent in admixture.
The method of removing metal contamination in gases according to the present invention has many advantages. For example, the absorption apparatus is simple, because it is possible to remove mercury or other metal compounds from a gas by merely contacting the gas with the absorbent packed in an absorption col D . Moreover, the pressure loss in the flow of the gas is small. Further, the absorbent is stable enough to permit an easy operation even for acidic gases such as factory exhaust gas and non-ferrous metal refining exhaust gas.
1~99489 In the following, the invention ~s further explained by Examples.
Example 1 500 gms. of pumice (size 3 - 6 mm) are soaked in 1 Q of aqueous solut~on of lead acetate and taken out to dry. After drying, it is packed in a column and is then sulfurized by passing hydrogen sulfide through it. The lead content in the so treated pumice was 7%. Using the thus prepared absorbent, efficiency of removal of mercury in gas, was investigated in such a manner that the absorbent is packed in a column having a sectional area of 5 x 5 cm and 20 cm height and gas mixtures containing various amounts of mercury are passed therethrough.
Thb gas mixture used for the experiments consisted of 95% air and 5~ sulfur dioxide, based on volume, in which mercury was admixed in various concentrations- The rate of gas flow through the column was 16Q/min.
The results are summarized below, wherein the concentrations of mercury are given in mg/m3.
concentration of mercury ratio Or removal of (mg/m ) mercury (~) original after treatment 0.42 0.005 98.7 1.37 0.012 99.1 1.98 0.031 98.4
In refinery of non-ferrous metals, mercury contained in the raw sulfide ore or in the slag in small amounts will be discharged in a form of compound or metal vapour hy thermal treatment procedures, such as heating, roasting and so on, and will be included in gases.
Since the vapour pressure of mercury is relatively high, it is often contained in the exhaust gas in gaseous or finely dispersed state, and therefore, if these gases are exhausted without treatment, the atmosphere will be polluted when such gases are used for the production of sulfuric acid, and the sulfuric acid so obtained will be contaminated with mercury due to absorption.
In general, for removing metals or its compounds in gases, there have been many previously proposed procedures, which may be employed separately or in combination, for example, using scrubber or bag filter, cyclone separation, gravity setting and Cottrell precipitation. While it will be possible to remove, for example, mercury compounds in finely dispersed state by these procedures, they cannot attain a - complete removal of gaseous substance, such as mercury vapour, since all these procedures are based on a physical dust removal principle.
On the other hand, in order to remove small amounts of mercury by chemical means, several methods have been proposed. For example, a solution having oxidizing property, .~
1~99~89 such as a solution containing sulfuric acid, is used as a scrubber liquid, and a chemical reaction with iodide ion etc.
is utilized. In these methods, however, the effectiveness of mercury removal by oxidation will vanish by reduction by sulfurous acid gas for example, so that they cannot be considered wholly satisfactory for removing mercury in gases from the thermal treatment processes, such as heating, burn-ing and so on in refining non-ferrous metals.
For removing mercury there has further been proposed a method in which the gases are passed through an aqueous solution containing a substance which absorbs mercury easily, such as thiourea or the like. However, in this method, the pressure loss is considerably large due to the forced passage of gases through the aqueous solution, so that this is pPDblematic in the apparatus.
The present invention provides a novel process for removing contaminants from gases, which overcomes or at least reduces some of the aforementioned disadvantages.
Thus according to the present invention, there is provided a method for removing mercury-containing contaminants from gases, which comprises passing the gases through a filter bed, the filter bed including an absorbent comprising a carrier and at least one sulfide material absorbing agent, said at least one sulfide material being substantially insoluble in the components of said gas and being selected from naturally occurring and synthetic sulfides of the metals lead, cadmium, antimony, arsenic, iron, nickel and zinc.
A compound of mercury is subject to be converted into metallic form, so that it changes easily into metallic mercury by, for example, a small amount of reducing agent or even by heating. Metallic mercury has a relatively high .~ .
~- .; .
1~999~9 vapour pressure and volatilizes easily. The vapour pressures of mercury at various temperatures are as follows:
~3~ at 20 to 30 C
10-2 mH at 50 to 60 C
10 1 mmHg at about 100 C
1 to 2 mmHg at 120 to 130 C
10 to 20 mmHg at 180 to 190 C (~ee Chemical Handbook) . .
Thu.~, mercury may often be contained in ga~es in the form of metal vapour, so that in many cases it cannot be removed by employing a physical treatment such as scrubbing or settling.
In the present invention, there is taken into consideration the fact that mercury sulfide has a very low solubility product, and also a very low vapour pressure. In this invention, removal of mercury is undertaken by a mechanism in which mercury is removed by fixing it by substitution with a metal sulfide having greater solubility li product than that of mercury sulfide. The order of formation of sulfides of metals is given, according to so-called ZO Schurmann series, as follows: Pd, ~g, Ag, Cu, Bi, Cd, Sb, Sn, Pb, Zn, Ni, Co, Fe,........... As can be seen, mercury will form its sulfide more easily than many other metals.
As to the solubility products for various metal sulfides, the following data are available:
~ ' , .
10994~9 Sulfides Soly Prod. Sulfides Soly Prod.
HgS -52 2 3 -29 Hg2S10-47 Fe2S lo-18 PbS -23 NiS -19 CdS ~33 ZnS -22 sb2S31o~29 The solubility product of mercury sulfide is, as shown above, very small as compared to other metal sulfides~ though the values may vary in accordance with the pH of the solution.
Since raw materials ~or non-ferrous metals exist mainly as sulfides~ which may contain some sulfates and chlorides, the refinery exhaust gas thereof is an acidic gas containing S02 and S03 besides C02~ N2, H20, 2~ etc, Therefore, when such refinery exhaust gas is dissolved in water, or whe~ it reaches its dew point~ an acidic or weakly acidic pH value will be shown.
For the purpose of the present invention, it i8 permissible to use any metal sulfides when the ga~ will present a neutral atmosphere. However, the suitable metal sulfides are restricted when refinery exhaust exhibits an acidic property. Some sulfides, for example, synthetic zinc sulfide and iron sulfide, may dissolve in such cases.
However, natural minerals of zincblende and pyrrhotite can be used as a mercury absorbing agent, because these are not dissolved by weak acid.
In the following, reaction equations for mercury and other metal ions with various sulfides are shown.
.
1~399489 Hg (metal) ~ PbS + S02 + 2 = HgS + PbS04 . I .
~ 2Hg (metal) ~ PbS ~ S02 ~ 2 = Hg2S + PbS04 Hg++ + PbS = HgS + Pb++ .
2HG~ + PbS = Hg2S + Pb Hg (metal) + ZnS -~ S02 + 2 = HgS I ZnS04 2Hg (metal) ~ ZnS + S02 + 2 = Hg2S + ZnS04 Hg~+ + ZnS = HgS + Zn++
2Hg~ + ZnS = Hg2S + Zn Pb+ + ZnS = PbS + Zn . .
Pb++ + FeS = PbS + Fe Cd +. + ZnS . = CdS + Zn 2As ~ 3ZnS 2 3 3 Similar reactions are performed with other sulfides.
From these considerations, it can be seen that mercury present in gases can be removed in such a manner that mercury, which reveals high vapour pressure, is converted into mercury sulfides, which show very low vapour pressure.
Even mercury compounds present in gases which do not contain sulfur dioxide can be removed by fixing them by converting into mercury sulfide by means of a substitution react-ion in accordance with the equations above. Such will also apply for various other metal sulfides: they can be removed by substitution independent of the existence of sulfur dioxide.
In the case of mercury vapour, it undergoes also a strong absorption reaction together with the substitution reaction.
Thus mercury vapour in the air containing no sulfur dioxide can be removed by using lead sulfide to absorb it.
Thére are to preferred methods for the preparation of ~"t.j ., .J
1~)99489 the active substance to be used as absor~ent according to the present invention. Firstly, the sulfide or simple sulfur substnace may be bound to a carrier substance. Secondly, a carrier may ~e impregnated with a soluble salt of a metal and then hydrogen sulfide gas or an aqueous solution of sodium sulfide may be passed therethrough to deposit the metal sulfide onto the carrier substance.
As carrier substance, inorganic or organic porous substances can advantageously be utilized. Those which are la light and easily granulated into homogeneous particle size with having porous surface, such as pumice, are preferred Pumice is a porous volcanic ejecta material. The deposition of the absorbing agent thereon is easy to accomplish, and the deposited ¦
substance can only be removed therefrom by shocks with difficulty.
Among organic substances, sponge, spongy rubber, polyurethane foam and the like may be used.
When the temperature of the exhaust gas is high, or when the corroding tendency of the exhaust gas is great, an inorganic silicic porous substance, such as zeolite or pumice is suitable for the carrier. When the temperature of the exhaust gas is low and its corrosive tendency is small, other inorganic and organic substance may be used for the carrier.
The smaller the particle size of the carrier, the ; -greater the surface area thereof, so that the contact surface area becomes large and thereby the extraction of mecury is facilitated. Thereby however, the pressure loss may rq 1~99~9 become uneconomically large, so that a particle size of from several millimeters to several centimeters may be desirable.
In preparation of the absorbent, synthetic sulfides may be prepared By blowing hydrogen sulfide gas into an aqueous solution of various salts of metals. For example, lead sulfide and zinc sulfide can be prepared by blo~ing hydrogen sulfide gas into aqueous solution of, for instance, lead acetate or zinc sulfate and filtering off the precipitate of sulfide thus formed, which is further processed into the absorbent. The absorbent to be used according to the present invention can also be prepared from natural sulfide minerals, such as galena, zincblende, pyrite, pyrrhotite and chalcopyrite, etc., by washing them sufficiently with water and subse~uently further subjecting to a surface treatment with dilute sulfuric acid or by washing them with dilute sulfuric acid and thereafter further subjecting to sulfurizing with hydrogen sulfide.
The surfaces of various sulfide ores from mines are covered in general with dressing agent and slimes and, in many cases, are covered with salts, such as sulfate, due to oxidation by air. Thus, these ores as such are ineffective in using for scavenging mercury in gases, because the surface ; thereof does exist not as the mineral itself, such as galena or zincblende, but it exists, for instance, in sulfatized state.
Therefore, it may be necessary to subject the surface of the ore to an activation treatment such as sulfurizing with - hydrogen sulfide, in order to provide the absorbent according to the present invention.-1~99~89 .
Accord~ng to one preferred aspect of the present invention, a synthetic sulfide or a natural sulfide mineral selected from the aforementioned group sub~ected to a pre-treatment of surface cleaning, is used for the a~sor~ing agent and a porous material, for example, pumice, ~s employed for the carrier.
According to the present invention~ in one preferred process of operation, an exhaust gas containing mercry or metal compound is passed through an absorption col D , in which the aBsorbent made by comBining the absorbing agent with the carrier is packed, to contact the gas with the absorbing bed and thereby to fix the mercury or metal compound either by converting it into sulfide or by absorbing it.
- I The carrier may be combined with a single absorbing agent or with two or more kinds of absorbing agent in admixture.
The method of removing metal contamination in gases according to the present invention has many advantages. For example, the absorption apparatus is simple, because it is possible to remove mercury or other metal compounds from a gas by merely contacting the gas with the absorbent packed in an absorption col D . Moreover, the pressure loss in the flow of the gas is small. Further, the absorbent is stable enough to permit an easy operation even for acidic gases such as factory exhaust gas and non-ferrous metal refining exhaust gas.
1~99489 In the following, the invention ~s further explained by Examples.
Example 1 500 gms. of pumice (size 3 - 6 mm) are soaked in 1 Q of aqueous solut~on of lead acetate and taken out to dry. After drying, it is packed in a column and is then sulfurized by passing hydrogen sulfide through it. The lead content in the so treated pumice was 7%. Using the thus prepared absorbent, efficiency of removal of mercury in gas, was investigated in such a manner that the absorbent is packed in a column having a sectional area of 5 x 5 cm and 20 cm height and gas mixtures containing various amounts of mercury are passed therethrough.
Thb gas mixture used for the experiments consisted of 95% air and 5~ sulfur dioxide, based on volume, in which mercury was admixed in various concentrations- The rate of gas flow through the column was 16Q/min.
The results are summarized below, wherein the concentrations of mercury are given in mg/m3.
concentration of mercury ratio Or removal of (mg/m ) mercury (~) original after treatment 0.42 0.005 98.7 1.37 0.012 99.1 1.98 0.031 98.4
2.39 0.019 99.8 2.61 0.025 99.6
3.88 0.040 99.0 C
lV994~9 Example 2 An absorbent was prepared by blowing hydrogen sulfide gas into an aqueous solution of lead acetate to form lead sulfide, washing the so obtained precipitate with water, filtering it off and binding it onto granulated pumice. The lead content of the so prepared absorbent was 9.5 % by weight.
Tlle experiment was carried out using gas of 100 ~ air at a flow rate of 16 R/min. and specific velocity of 20~0.
Results obtained are summarized as follows:
: . .concentration of mercury ratio of removal Or (mg/m3) mercury (~) original after treatment . _ 7.19 0.012 99.8 7.38 0.017 99.8 7.44 0 023 99.7 9.66 0.095 99.0 .65 o ol3 99-6 5.48 0.021 99.6 Example 3 A column of 4 x 4 cm and 60 cm height was filled with absorbent prepared from pumice (size about 10 mm) and synt~letic lead sulfide. The height of packing (bed depth) was 16 cm. Mercury removal ratio was examined by passing a mercury-containing gas through the column Experimental conditions were:
gas used : 95 % air ~ 5 % sulfur dioxide; gas flow rate: 5.25~/min.; S V : 1230 r~ -- 10 --l~99~W
"
mercury conc. volume of gas ratio of removal (mg/m3) treated of mercury 'I
original after (m') (~) treat.
.30 o.o56 4.41 98.3 2. 37 0.017 8.19 99.3
lV994~9 Example 2 An absorbent was prepared by blowing hydrogen sulfide gas into an aqueous solution of lead acetate to form lead sulfide, washing the so obtained precipitate with water, filtering it off and binding it onto granulated pumice. The lead content of the so prepared absorbent was 9.5 % by weight.
Tlle experiment was carried out using gas of 100 ~ air at a flow rate of 16 R/min. and specific velocity of 20~0.
Results obtained are summarized as follows:
: . .concentration of mercury ratio of removal Or (mg/m3) mercury (~) original after treatment . _ 7.19 0.012 99.8 7.38 0.017 99.8 7.44 0 023 99.7 9.66 0.095 99.0 .65 o ol3 99-6 5.48 0.021 99.6 Example 3 A column of 4 x 4 cm and 60 cm height was filled with absorbent prepared from pumice (size about 10 mm) and synt~letic lead sulfide. The height of packing (bed depth) was 16 cm. Mercury removal ratio was examined by passing a mercury-containing gas through the column Experimental conditions were:
gas used : 95 % air ~ 5 % sulfur dioxide; gas flow rate: 5.25~/min.; S V : 1230 r~ -- 10 --l~99~W
"
mercury conc. volume of gas ratio of removal (mg/m3) treated of mercury 'I
original after (m') (~) treat.
.30 o.o56 4.41 98.3 2. 37 0.017 8.19 99.3
4.68 0.017 13. 23 99.6 2.38 0.021 17.01 99.1 .41 o.ol6 22. 68 98.9 1.61 ~. 014 31.50 99.1 Example 4 Efficiency of mercury removal was examined under the same conditions as in Example 4, except that an absorbent prepared by binding pretreated zincblende onto pumice (size: about 10 mm) was used.
mercury conc. volume of gas ratio of removal (mg/m~) treated of mercury _ 3 original after (m ) (~) treat.
3.15 0.043 5.67 98.6 : 1.68 o. 0338.19 98.0 2~ 5.5 0.034 13.54 99.3
mercury conc. volume of gas ratio of removal (mg/m~) treated of mercury _ 3 original after (m ) (~) treat.
3.15 0.043 5.67 98.6 : 1.68 o. 0338.19 98.0 2~ 5.5 0.034 13.54 99.3
5.69 -3 17. 64 99.5 .31 o.oO5 22.68 99. 8 4.52 0.021 27.09 99.5 .
1q~9~4~99 Example 5 Efficiency of mercury removal was examined under the same conditions as in Example 3, except that an absorbent prepared by binding pretreated galena onto pumice (size: aboui 10 mm) was used.
:' mercury conc. volume of gas ratio Or rcmoval (mg/m ) treated of mercury ~r~r~l = (m3) (%) 1.28 0.022 8.19 98.~
5.2~ 0.047 11.97 99.1 5.5 0.057 16.0~ 98.07 4.27 0.027 22.68 99.4 4.34 0.023 26.46 99.5 `
4.52 o.o46 31.50 99.0 Example 6 Efficiency of mercury removal was examined under the same conditions as in Example 3 except that an absorbent prepared by binding pretreated galena and synthetic lead sulfide in weight ratio of 9 : 1 onto pumice (about 10 mm) was used.
, . .~.
mercury conc. volume of gas ratio of removal (mg/m3) treated of mercury (rn3) (~) original atrteart.
5.5 o.oO5 ` 4.73 99.9 3.16 o . oO3 6.62 99.9 5.69 0.002 9.45 99.9 5.42 o.ool 17.64 99.9 4,38 o.oO3 27.09 99.9 3.26 ' 0.002 32.05 99.9 .
In all the Examples above, mercury waR added a~
vapour formed by heatin~ liquid mercury metal.
FB
1q~9~4~99 Example 5 Efficiency of mercury removal was examined under the same conditions as in Example 3, except that an absorbent prepared by binding pretreated galena onto pumice (size: aboui 10 mm) was used.
:' mercury conc. volume of gas ratio Or rcmoval (mg/m ) treated of mercury ~r~r~l = (m3) (%) 1.28 0.022 8.19 98.~
5.2~ 0.047 11.97 99.1 5.5 0.057 16.0~ 98.07 4.27 0.027 22.68 99.4 4.34 0.023 26.46 99.5 `
4.52 o.o46 31.50 99.0 Example 6 Efficiency of mercury removal was examined under the same conditions as in Example 3 except that an absorbent prepared by binding pretreated galena and synthetic lead sulfide in weight ratio of 9 : 1 onto pumice (about 10 mm) was used.
, . .~.
mercury conc. volume of gas ratio of removal (mg/m3) treated of mercury (rn3) (~) original atrteart.
5.5 o.oO5 ` 4.73 99.9 3.16 o . oO3 6.62 99.9 5.69 0.002 9.45 99.9 5.42 o.ool 17.64 99.9 4,38 o.oO3 27.09 99.9 3.26 ' 0.002 32.05 99.9 .
In all the Examples above, mercury waR added a~
vapour formed by heatin~ liquid mercury metal.
FB
Claims (9)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for removing mercury-containing contaminants from gases, which comprises passing the gases through a filter bed, the filter bed including an absorbent comprising a carrier and at least one sulfide material absorbing agent, said at least one sulfide material being substantially insoluble in the components of said gas and being selected from naturally occurring and synthetic sulfides of the metals lead, cadmium, antimony, arsenic, iron, nickel and zinc.
2. The method of claim 1 wherein the carrier is made of an inorganic or organic porous substance selected from silicic minerals, sponge, spongy rubber and plastics foams.
3. The method of claim 2 wherein the sulfide material is a natural or synthetic sulfide of lead or zinc.
4. The method of claim 3 wherein the porous carrier is made of pumice.
5. The method of claim 1 wherein the gases include acidic sulfurous gases and the sulfide material is selected from natural and synthetic lead sulfides, zincblende and pyrrhotite.
6. The method of claim 1 wherein the absorbing agent is comprised of natural sulfide mineral which has been subjected to a pretreatment of surface activation.
7. The method of claim 1 wherein the absorbent is prepared by binding the absorbing agent onto the carrier.
8. The method of claim 1 wherein the absorbing agent consists of a natural lead sulfide mineral which has been washed with water and subsequently surface treated with dilute sulfuric acid and with hydrogen sulfide.
9. A method for removing mercury-containing contaminants in an acidic gas containing sulfur dioxide and sulfur trioxide which comprises flowing the gas containing the said contaminants through an absorption column packed with an inorganic porous pumice having lead sulfide bound to the surface thereof, and thereby substituting mercury sulfide for said lead sulfide and thus removing mercury-containing contaminants from the gas.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA267,780A CA1099489A (en) | 1976-12-14 | 1976-12-14 | Method of removing mercury-containing contaminations in gases |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA267,780A CA1099489A (en) | 1976-12-14 | 1976-12-14 | Method of removing mercury-containing contaminations in gases |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1099489A true CA1099489A (en) | 1981-04-21 |
Family
ID=4107495
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA267,780A Expired CA1099489A (en) | 1976-12-14 | 1976-12-14 | Method of removing mercury-containing contaminations in gases |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1099489A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5352647A (en) * | 1990-05-02 | 1994-10-04 | Ftu Gmbh | Composition for separating out noxious substances from gases and exhaust gases |
-
1976
- 1976-12-14 CA CA267,780A patent/CA1099489A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5352647A (en) * | 1990-05-02 | 1994-10-04 | Ftu Gmbh | Composition for separating out noxious substances from gases and exhaust gases |
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