Title: Method for removing acidic gases from waste gas
Abstract: A method for removing acidic gases from waste gases is disclosed. The invention relates to a method for removing acid gases, in particular from SO.sub.2 and NO.sub.x, by contacting the waste gas with an emulsion of water in organic sulfoxides, in particular of water in oil-derived-sulfoxides. The organic sulfoxide phase can be regenerated after the emulsion is loaded with polluants, by letting the emulsion to settle down and separate into two phases. The aqueous phase obtained after the separation contains sulfate and nitrate ions which can be collected and used as valuable chemicals.
Patent Number: 6,881,243 Issued on 04/19/2005 to Khitrik, et al.
| Inventors:
|
Khitrik; Adolf (Katzrin, IL);
Pipko; Gregori (Kazrin, IL);
Doron; Benjamin (Jerusalem, IL)
|
| Assignee:
|
Lextran Ltd. (Katzrin, IL)
|
| Appl. No.:
|
110311 |
| Filed:
|
August 13, 2002 |
| PCT Filed:
|
October 6, 2000
|
| PCT NO:
|
PCT/IL00/00632
|
| 371 Date:
|
August 13, 2002
|
| 102(e) Date:
|
August 13, 2002
|
| PCT PUB.NO.:
|
WO01/26784 |
| PCT PUB. Date:
|
April 19, 2001 |
Foreign Application Priority Data
| Current U.S. Class: |
95/188; 95/190; 95/206; 95/232; 95/235; 423/235; 423/242.2; 423/243.01; 423/243.03 |
| Intern'l Class: |
B01D 053//14 |
| Field of Search: |
95/188,189,190,197,205,206,235,232
423/235,242.1,242.2,243.01,243.03,243.06
|
References Cited [Referenced By]
U.S. Patent Documents
| 3607004 | Sep., 1971 | Deachamps et al.
| |
| 3784478 | Jan., 1974 | Kolak et al.
| |
| 4039304 | Aug., 1977 | Bechthold et al. | 95/66.
|
| 4140651 | Feb., 1979 | Burnell et al. | 252/188.
|
| 4418044 | Nov., 1983 | Kulik.
| |
| 4885146 | Dec., 1989 | Lassmann et al.
| |
| 4923688 | May., 1990 | Iannicelli | 423/224.
|
| 5433934 | Jul., 1995 | Chang et al. | 423/235.
|
| 5601632 | Feb., 1997 | Jensen | 75/743.
|
| 6187277 | Feb., 2001 | Kirschner | 423/220.
|
Other References
SU 602, 212 A Abstract, Mar. 15, 1978, Nikitin Yu E.
SU 606 606 A Abstract, Apr. 12, 1978, As Bashkir BR Chen.
|
Primary Examiner: Smith; Duane S.
Attorney, Agent or Firm: Lowe, Hauptman, Gilman & Berner, LLP.
Claims
What is claimed is:
1. A method for simultaneously removing acidic gases of sulfur and nitrogen
oxides from waste gas before it is emitted to the atmosphere by contacting
said waste gas with a scrubbing agent comprising an emulsion of water in
organic sulfoxides in the presence of a stream of air or of ozonated air.
2. A method according to claim 1 wherein the waste gas is a combustion flue
gas.
3. A method according to claim 1 wherein the waste gas is a gas mixture
released from a chemical process.
4. A method according to claim 1 wherein the organic sulfoxides are oil
derived sulfoxides.
5. A method according to claim 4 wherein the oil derived sulfoxides are
derived from the diesel fraction of oil.
6. A method according to claim 1 wherein the weight ratio of water:organic
sulfoxide in the emulsion is in the range 10:90 to 90:10.
7. A method according to claim 1 wherein the scrubbing agent is regenerated
after it is loaded, by letting said scrubbing agent to separate into two
phases, collecting the upper sulfoxide phase and adding to said sulfoxide
phase a fresh amount of aqueous solution.
8. A method according to claim 7 wherein the aqueous phase obtained after
the separation of phases contains nitric and/or sulfuric acids and is
collected to be used as useful acid solutions.
9. A method according to claim 8 wherein ammonium salts are added to the
acid solution obtained after the separation of phases to obtain a solution
of ammonium nitrate and/or ammonium sulfate useful as a fertilizer.
10. A method for cleaning fuel gas from acid gases according to claim 1
wherein an aqueous phase of the emulsion further contains ammonium ions
and wherein a solution of ammonium nitrate and/or ammonium sulfate
obtained after separation of the emulsion is collected to be used as a
fertilizing solution.
11. A method according to claim 9 wherein the source for the ammonium ions
is selected from the group consisting of ammonia, ammonium carbonates and
ammonium carbamate.
12. A method according to claim 1 wherein contacting the waste gas with
said scrubbing agent is conducted in a tower embedded with inert particles
and wherein the waste gas is passed upward through the tower and the
emulsion is circulated downward in a rate which ensures complete wetting
of inert particles.
13. A method according to claim 1 wherein contacting the waste gas with
said scrubbing agent is conducted in a tower through which the waste gas
is passed in an upward direction and the emulsion is sprayed into the
tower from the upper opening of the tower forming a fog of said emulsion
inside the tower.
14. A method according to claim 6 wherein the weight ratio of water:organic
sulfoxide in the emulsion is in the range of 10:90 to 50:50.
Description
FIELD OF THE INVENTION
The present invention relates to a method for removing acidic gases from
waste gases. More specifically the present invention relates to a method
for removing acid gases, in particular from SO.sub.2 and NO.sub.x, by
contacting the waste gas with an emulsion of water in organic sulfoxides,
in particular of water in oil-derived-sulfoxides. The organic sulfoxide
phase can be regenerated after the emulsion is loaded with pollutants, by
letting the emulsion to settle down and separate into two phases. The
aqueous phase obtained after the separation contains sulfate and nitrate
ions which can be collected and used as valuable chemicals.
BACKGROUND
Industrially developed countries generate billions of tons of air
pollutants, a great part accounts to the combustion of coal, oil, and
gasoline in electric power plants. Other major air pollution sources
include petroleum refineries, cement plants and petrochemical plants.
Among the most troublesome air pollutants emitted into the atmosphere are
acid gases and in particular SO.sub.2 and NO.sub.x. These gases are the
major cause for acid rain, for smog and for human discomfort and
disability. Sulfur dioxide is released into the atmosphere from the
combustion of sulfur containing compounds in fossil fuels, such as gas,
petroleum, and coal. SO.sub.2, is a heavy, colorless gas with a
characteristic, suffocating odor. In moist air it is slowly oxidized to
sulfuric acid and contributes to acid rain. NO.sub.x gases, on the other
hand, partly originate from the combustion of nitrogen containing
compounds but mostly they originate from the reaction between elementary
oxygen and nitrogen present in the air at the elevated temperatures at
which various industrial processes (and combustion) take place. Therefore,
the problem of NO.sub.x is even more difficult to overcome as it is a
problem inherent to these processes and its generation cannot be avoided.
Nitrogen oxides, in addition to their contribution to acid rain, breaks
down to form ozone and reacts with other atmospheric pollutants to form
photochemical smog which irritates sensitive membranes and damages plants.
The increasing environmental awareness during the last decades has led in
many countries to governmental regulations, enforcing standards for
maximum air pollutants emission on power plants and industries, in order
to achieve air quality standards for various hazard materials. For
example, in the U.S., the Clean Air Act of 1967 as amended in 1970, 1977,
and 1990 is the legal basis for air-pollution control throughout the U.S.
The 1990 amendments to the Clean Air Act of 1967 put in place regulations
to reduce the release of sulfur dioxide from power plants to 10 million
tons per year by Jan. 1, 2000. This amount is about one-half the emissions
of 1990. In 1988, as part of the United Nations-sponsored Long-Range
Transboundary Air Pollution Agreement, the United States, along with 24
other nations, ratified a protocol freezing the rate of nitrogen oxides
emissions at 1987 levels.
The need to obey these regulations has led to the development of
diversified methods for controlling and reducing the emission of air
pollutants. In general, these methods include removing the hazardous
material before it is used (for example, using low-content sulfur coal) or
removing the pollutant after it is formed. For some air pollutants, (e.g.,
NO.sub.x) only methods of the second class can be employed.
The present invention relates to methods of the second class.
Industrially emitted pollutant gases can be entrapped by liquids or solids
traps that adsorb the harmful gases before they are released into the
atmosphere. These traps are usually in the form of tower tanks contactors
through which the waste gas is passed upward while the liquid, or a
slurry, i.e. a mixture of liquids and solids, is descending downward. The
agent which absorbs the pollutants and prevent their emitting into the
atmosphere is called the scrubbing agent. When this agent is a liquid, it
is sometimes the practice to fill the tower with inert particles in order
to increase the contact surface between the scrubbing agent and the waste
gas and to increase the residence time of the gas inside the reactor. In
such cases it is also the practice to circulate the liquid scrubbing agent
through the reactor until it is loaded with the pollutants.
Wet flue gas desulfurization, i.e., the removal of SO.sub.2 processes
typically involve the use of an alkaline cleansing liquid, such as a
calcium-based slurry or a sodium-based or ammonia-based solution. These
processes however are not suitable for the removal of nitrogen oxides. The
currently used methods for the removal of NO.sub.x from flue gas are
mainly of the king that is based on the reaction of NO and NO.sub.2 with
ammonia, with or without a catalyst, forming nitrogen and water. These
methods are effective only within a narrow flue gas temperature range, are
relatively high cost and involve the risk of ammonia leakage to the
atmosphere. In the presence of catalyst the process is more efficient but
its cost is even higher and the catalyst tends to be poisoned. In any case
these methods require a special equipment useful only for the removal of
NO.sub.x.
U.S. Pat. No. 3,6707,004 discloses a process for removing traces of
hydrogen sulfide (H.sub.2 S) contained in gases. The process consists of
passing the hydrogen sulfide-containing gas through a liquid phase
consisting essentially of iodine dissolved in an organic solvent.
U.S. Pat. No. 3,784,478 teaches a process for removal of nitrogen oxides
from the gaseous effluents of combustion processes utilizing gas-liquid
absorption.
Russian patent No. 2099789 describes a process for removing sulphur dioxide
from gasses by absorption with sulphoxides.
The processes described in U.S. Pat. Nos. 3,6707,004, 3,784,478 and Russian
patent No. 2099789 are disadvantageous since by these processes only one
gas (NO.sub.x or SO.sub.2 or H.sub.2 O) can be removed from waste gases.
Therefore a great effort is put into developing new NO.sub.x control
methods which will remove simultaneously NO.sub.2 and SO.sub.2 from
combustion flue gas. For example, U.S. Pat. No. 4,418,044 teaches a
scrubbing agent consisting of a solution of Fe(II) ions and thiosulfate in
a miscible mixture of water and alcohol. U.S. Pat. No.4,885,146 teaches a
similar scrubbing agent consisting of Fe(II) ions but in non-aqueous
solvent (only up to 10% water). According to U.S. Pat. No. 4,885,146 the
scrubbing agent can be regenerated for reuse.
The cost of pollution reduction processes and equipment is, however, still
very high and therefore intensive efforts are put into research in order
to increase the efficiency of known processes and in order to find new
more efficient and less energy consuming methods. These efforts
concentrate on the following points: simplicity of process (i.e., involve
low-cost equipment), the use of low-cost materials and the recycling of
these materials, universality of process, i.e., removing as many
pollutants as possible by the same process. Other, no less important,
efforts are dedicated to finding processes in which the end products, not
only are harmful, but can also be collected and be sold as useful
materials (i.e., converting the harmful air pollutants into valuable
materials) so that at least part of the investment will be earned back.
Therefore there is still a need for developing simple, more efficient and
relatively low-cost, methods for air pollution control, especially methods
which will clean fuel gases from both SO.sub.2 and NO.sub.x simultaneously
in one process and with the same equipment.
It is the aim of the present invention to provide a method for removing
acid gases, in particular SO.sub.2 and NO.sub.x, simultaneously.
Yet it is another aim of the present invention to provide such a method
which involves low-cost materials and equipment.
It is yet another aim of the present invention to provide such a method in
which the scrubbing material is regenerated easily for further use.
It is another aim of the present invention to provide such a method which
will also results in conversing the SO.sub.2 and NO.sub.x into useful
materials with commercial value.
SUMMARY OF THE INVENTION
The present invention relates to a method for removing acidic gases, in
particular SO.sub.2 and NO.sub.x, from waste gases by contacting the waste
gas with an emulsion of water-in-organic sulfoxides. The waste gas can be
any waste gas containing acidic gases, such as combustion flue gas and
waste gases generated in various chemical processes. The organic
sulfoxides are preferably oil-derived sulfoxides and in particular
sulfoxides derived from diesel. The weight ratio of the water: organic
sulfoxide in the emulsion is in the range 10:90 to 90:10, preferably in
the range 10:90 to 50:50.
The process of the present invention is carried out in an oxidation
environment. Therefore if the waste gas mixture does not contain enough
oxygen, an additional stream of air enriched with ozone (ozonated air) is
added to the waste gas.
The scrubbing agent can be regenerated after it is loaded, by letting said
scrubbing agent to separate into two phases, collecting the upper
sulfoxide phase and adding to said sulfoxide phase a fresh amount of
aqueous solution The aqueous phase which is obtained after the separation
of phases contains nitric and/or sulfuric acids and can be collected to be
used as useful acid solutions or ammonium ions can be added acidic
solution until neutralization occurs to obtain a solution of ammonium
nitrate and/or ammonium sulfate salts useful as a fertilizer.
In another embodiment of the present invention the aqueous phase of the
scrubbing agent is an aqueous solution of ammonium having pH equals or
lower than 6 and after the separation of the emulsion the aqueous phase is
a solution of ammonium nitrate and/or ammonium sulfate salts useful as a
fertilizer. The source for the ammonium ions can be ammonia or ammonium
carbonates (and bicarbonates) and ammonium carbamate.
According to the present invention, contacting the waste gas with the
scrubbing agent can be conducted in a tower embedded with inert particles,
wherein the waste gas is passed upward through the tower and the emulsion
is circulated downward in a rate which ensures complete wetting of inert
particles or can be conducted in a tower through which the waste gas is
passed in an upward direction and the emulsion is sprayed into the tower
from the upper opening of the tower forming a fog of said emulsion inside
the tower.
DETAILED DESCRIPTION OF THE INVENTION
The main problem of entrapping acid gases in aqueous solutions is the
instability of the intermediate species formed upon the dissolution of the
acidic gases in water (e.g., HNO.sub.2, H.sub.2 SO.sub.3), before they are
oxidized into stable species. The instability results in the decomposition
of the species and the releasing of the noxious gases from the solution.
The present invention overcomes this problem by introducing an agent which
binds the unstable species and forms a stable complex. Upon oxidation, a
stable ion is formed and the complex decomposes, leaving the agent
molecules free to bind to new dissolved pollutant molecules.
According to the present invention, this stabilizing agents are organic
sulfoxides. Organic sulfoxides are known for their acid extraction
properties. Of special interest are oil derived sulfoxides that are
obtained by the oxidation of organic sulfides contained in oil. By
oxidizing and extracting different fractions of oil, a mixture of
sulfoxides is obtained, having molecular weight and boiling temperature
according to the oil fraction from which they are derived. The diesel
fraction (boiling temperature 190-360.degree. C.) is in particular a good
source for oil-derived-sulfoxides, since this fraction is relatively rich
in sulfur and the sulfoxide mixture so obtained is a liquid of low-cost.
Sulfoxides form a complex with the unstable dissolved acidic gases thus
stabilizing these species and preventing their decomposition as explained
in the following.
a. NO.sub.x Entrapping
The total concentration of NO.sub.x produced in combustion processes is
typically 200-1000 ppm, most of it in the form of nitric oxide (NO) and
about 5% as nitrogen dioxide (NO.sub.2).
NO is a relatively inert gas. It does not dissolve in water and forms no
chemical compound with water or with alkalis, therefore it cannot be
absorbed by basic aqueous solutions. In order for NO to be absorbed by
aqueous solutions, it needs to be oxidized first by oxygen or by ozone:
(1) 2NO+O.sub.2 {character pullout}2NO.sub.2
or
(2) NO+O.sub.3 {character pullout}NO.sub.2 +O.sub.2
When both NO and NO.sub.2 present in the gas mixture they react to give:
(3) NO+NO.sub.2 {character pullout}N.sub.2 O.sub.3
The interaction of NO and NO.sub.2 with water occurs according to the
following possible reaction routes:
(4) 2NO.sub.2 +H.sub.2 O{character pullout}HNO.sub.2 +HNO.sub.3
(5) 3HNO.sub.2 {character pullout}HNO.sub.3 +2NO+H.sub.2 O
(6) 3NO.sub.2 +H.sub.2 O{character pullout}2HNO.sub.3 +NO
and
(7) N.sub.2 O.sub.3 +H.sub.2 O{character pullout}2HNO.sub.2
(8) 3HNO.sub.2 {character pullout}HNO.sub.3 +2NO+H.sub.2 O
(9) 3N.sub.2 O.sub.3 +H.sub.2 O{character pullout}2HNO.sub.3 +4NO
It is obvious from reactions (4-9) that in all cases, upon interaction of
NO.sub.2 (or NO and NO.sub.2) with water, HNO.sub.2 is formed and
decomposed to give NO.
The present invention provides a way to avoid the decomposition of nitrous
acid and the release of NO from the solution, by using organic sulfoxides,
having the structure:
##STR1##
The free electron pair on the sulfur atom forms a bond with HNO.sub.2 (J.
Applied Chemistry, vol 4, 1986, 900-903):
##STR2##
Thus, the sulfoxide binds the HNO.sub.2 and its decomposition is prevented.
In the presence of oxidant, the bound nitrous acid is oxidized to nitric
acid and loses its capability to bind to the sulfoxide. HNO.sub.3, whose
water solubility is very high, moves into the aqueous phase and the
sulfoxide molecules can adsorb another molecule of nitrous acid.
b. SO.sub.2 Entrapping
The combustion of coal, oil and other sulfur containing fuels produces a
flue gas in which 98-99% of the sulfur is in the form of sulfur dioxide
(SO.sub.2) and 1-2% is sulfur trioxide (SO.sub.3). For low and high sulfur
coals the total concentration of SO.sub.x is usually in the range of
1,000-4,000 ppm.
SO.sub.2 dissolved in water forms sulfurous acid:
(10) SO.sub.2 +H.sub.2 O{character pullout}H.sub.2 SO.sub.3
Sulfurous acid is unstable, it exists only in aqueous solutions and as the
temperature increase the equilibrium of reaction (10) shifts to the left
and SO.sub.2 is released. The solubility of SO.sub.2 in water is 9.61% at
20.degree. C. and decreases with temperature. At 80.degree. C. its
solubility is only 2.98%.
In the presence of oxidants, sulfurous acid oxidized gradually to sulfuric
acid. In the presence of ozone the SO.sub.2 dissolved according to the
following:
(11) 2SO.sub.2 +O.sub.3 +H.sub.2 O{character pullout}H.sub.2 S.sub.2
O.sub.6 +O.sub.2
and the dithionic acid is decomposed according to:
(12) H.sub.2 S.sub.2 O.sub.6 {character pullout}SO.sub.2 +H.sub.2 SO.sub.4
In the presence of NO.sub.x in water:
(13) H.sub.2 SO.sub.3 +NO.sub.2 {character pullout}H.sub.2 SO.sub.4 +NO
And the formed NO is oxidized again to NO.sub.2 and reaction (13) is
repeated. Thus, NO acts as a catalyst, accelerating the oxidation of
SO.sub.2.
In the presence of sulfoxides, SO.sub.2 forms a complex with the sulfoxide
group. (Nieftiechimija vol. 18, No. 2 p. 325-327). Infra-red studies show
that a 1:1 complex of sulfoxide with SO.sub.2 is formed through
coordination bond of the oxygen of the SO group with the free electron
pair on the sulfur atom of the sulfur dioxide.
##STR3##
Thus, using sulfoxides, simplifies and enhances the removing of sulfur
dioxide from waste gases. Our studies show that in the presence of oil
sulfoxide and water, SO.sub.2 absorption is enhanced and the decomposition
of H.sub.2 SO.sub.3 to release SO.sub.2 according to reaction 10 does not
occur.
EXAMPLES
The following experiments demonstrate and clarify the present invention and
do not intend to limit the scope of the invention by any way.
Example 1
A glass column of 400 mm height and 30 mm diameter was heated by an outer
electric heater to 80.degree. C. The glass column was filled with glass
rings of 4 mm height and 4 mm diameter and with 100 g emulsion of water in
diesel derived sulfoxides comprising of 30 g water in 70 g sulfoxides. A
stream of air containing 1.9% (mass percent) NO.sub.2 was bubbled
continuously through the bottom of the column at a rate of 0.29 l/min for
42 hours continuously. About 75-90% of NO.sub.2 was consumed.
After 42 hours, the liquid in the column was collected and separated into
two phases. The concentration of nitric acid in the aqueous phase was 20.3
wt. %.
The amount of nitrous and nitric acid in the sulfoxide phase was determined
by potentiometric titration in non-water medium and was found to be 21% of
the total acid. In order to destroy the nitrous acid--sulfoxide complex,
water were added to the organic phase and oxygen was bubbled into the
liquid in order to oxidize all nitrous acid molecules, converting them
into nitric ions which pass to the aqueous phase.
The sulfoxide phase obtained after the phase separation was combined with a
fresh amount of water and reused as a scrubbing agent. After a large
number of recycling the scrubbing agent by this procedure, no reduction in
its absorption power was observed.
This experiment demonstrates that at concentration of more than 20% of
nitric acid in the aqueous component of the emulsion, the scrubbing agent
of the present invention still has capability of absorbing more
pollutants.
Example 2
SO.sub.2 absorption was conducted under the same conditions as in
Experiment 1. SO.sub.2 concentration in the input gas was 2000 ppm. The
process was carried out for 42 hours during which more than 90% of
SO.sub.2 were absorbed without observing loss of absorption capability.
The aqueous phase obtained at the end of the process contained only
sulfuric acid. No sulfite ions (SO.sub.3) were detected.
Example 3
NO.sub.2 and SO.sub.2 absorbtion was conducted simultaneously with the same
reactor and emulsion composition as in Example 1 but at temperature of
20-25.degree. C.
The concentration of NO.sub.2 was 1000 ppm and that of SO.sub.2 800 ppm.
The process was carried out the for 8 hours continuously and during this
time no reduction in the absorption capability of the scrubbing agent was
observed. The average concentrations of NO.sub.2 and SO.sub.2 at the
output were less <10 ppm and <2 ppm respectively.
The aqueous phase obtained after collecting and separating the emulsion
contained a mixture of nitric and sulfuric acids.
Example 4
A stream of 1% NO diluted in N.sub.2 (0.188 l/min) was combined with a
stream of pure nitrogen (1.69 l/min) and a stream of ozonated air (2.2
l/min) and the gas mixture was passed through a two-section column reactor
of 0.04 m diameter. Each section has a perforated disk on which a packed
glass rings of 6 mm diameter and 6 mm height were placed. The height of
the packed glass rings in each section was 0.38 m.
The gas mixture was passed upward through the bottom of the reactor and the
scrubbing agent, oil-derived sulfoxide:water=70:30 (weight ratio) was
supplied dropwise into the column from its upper opening obtaining
complete and uniform wetting of the glass rings by the liquid. The
scrubbing agent was circulated through the reactor
The residence time of the gas in the reactor was 12 s.
The process was carried out for 29 hours.
The ozone was supplied into the reactor at a rate of 0.2 g/h, providing 40%
of the molar amount required for complete oxidation of NO into NO.sub.2.
The oxidation took place in the reactor simultaneously with the absorption
of NO.sub.2 by the scrubbing agent.
The concentrations of NO and of NO.sub.2 were measured by an automatic
analyzer at the input and at the output of the reactor.
The average input concentrations were: 600 ppm NO and 20 ppm NO.sub.2
The average output concentrations were: 7.2 ppm NO and 1 ppm NO.sub.2
The average absorption of NO was 88% and of NO.sub.2 95%.
The calculated amount of NO passing through the reactor during 29 hours is
4.38 g (0.1 13 l/h.times.29 h=3.277 l=(30 g/mole.times.3.277 l)/(22.4
l/mole) ). Since only 88% of NO was absorbed, the calculated amount of
HNO.sub.3 that should have been formed in the aqueous phase is 7.6 g. The
experimental result was 7.42 g, i.e., 97.6% yield.
Example 5
The removal of NO from the waste gas produced in a nitric acid production
process was carried out in a glass reactor of 9.09 cm diameter. The
reactor of 1 m height had a perforated plate at its bottom on which a
packing of 9 mm diameter and 9 mm height glass rings had been placed. The
packing layer volume was equal to 0.023 m.sup.3.
The waste gas from the chemical process was supplied to the reactor at a
rate of 9.7 l/min. Ozonated air was supplied to the reactor at a rate of 5
l/min by an ozonator with an output of 0.1 5 g ozone per hour, providing
40.5% of the stoichiometric amount required for full oxidation of NO into
NO.sub.2.
The absorbent (oil sulfoxide:water=70:30) was dosed into the reactor from
its upper opening at a rate of of 1530 ml/h.
The residence time of the gas inside the reactor was 9.4 s.
The concentrations of NO and of NO.sub.2, measured by an automatic analyzer
at the input and at the output of the reactor were as follows:
average input concentrations: NO=300 ppm, NO.sub.2 =50 ppm
average output concentrations: NO=40 ppm, NO.sub.2 =2 ppm
NO absorption 87%, NO.sub.2 absdorption 96%.
Under the same conditions, but without ozone supply, 187 ppm of NO and 4
ppm of NO.sub.2 were detected at the output, i.e., the NO absorption was
37.7% and the NO.sub.2 absorption was 92%.
Example 6
In order to receive a complex fertilizing--ammonium nitrate and ammonium
sulfate mixture, the aqueous phase received after one of the tests was
separated from the organic phase (oil sulfoxides) and neutralized by
aqueous solution of ammonium according to the following procedure:
10.2 g of NH.sub.4 OH solution with 13% NH.sub.3 concentration were added
on agitation to 30.0 g aqueous phase which contained 6.0% of HNO.sub.3 and
6.0 g of H.sub.2 SO.sub.4. After neutralization, the pH of the solution
was equal to 6.5.
The obtained solution was boiled at 100.degree. C. and the obtained mixture
was dried out at 150.degree. C. degrees, obtaining 4.46 g of salts
mixture. The analysis of the salts mixture gived the following
composition:
2.1 g of NH.sub.4 NO.sub.3 (92% of theoretical yield) and 2.36g of
(NH.sub.4).sub.2 SO.sub.4 (97.5% of theoretical yield).
*
