Title of Invention	"A PROCESS FOR PRODUCING DEOXYGENATED AIR"
Abstract	The present invention provides a process for producing deoxygenated air, which comprises mixing 0.1 to 4 wt % of sodium carbonate to water, reacting the mixture so obtained in a closed reactor with 0.2 to 8 wt. % of sodium sulphide in presence of 101 to 122 vol. % air, adding fresh air, if require, to avoid creation of vacuum conditions till oxygen deficient air of the desired level is obtained.

Full Text

This invention relates to a process for producing deoxygenated air, The invention particularly relates to an economical chemical method that removes oxygen from air in a closed vessel. In many anaerobic reactions, oxygen acts as an inhibitor. To minimise the inhibitory effect of oxygen, it is replaced by some inert gas. For this, cylinder of inert gas is required. In spite of this if there is leakage in the system air gets in and oxygen of air inhibits the reaction. It is also known that less than 10X oxygen in air will normally not support fire in goaf area in a mine. It is proposed to flush the goaf with existing fire or likely to have fire with an air having less than 8X oxygen. Existing technique of using solid carbon dioxide or liquid nitrogen is expensive and cumbersome. There are a few known methods for removing oxygen from the air i e i) at high temperature metals like gold, silver, platinum and palladium absorbs oxygen giving deoxygenated air but this method is not economical as expensive metals and continuous heating is required, ii) alkaline solution of pyrogallol also absorbs oxygen but handling of highly alkaline solution is cumbersome and it can not be used for biological reactions as they are pH and nutrient dependent. Production of large quantity of such an oxygen deficient air with less than 8X oxygen may work out easier and less expensive, particularly in minimising/controlling mine fires. The main objective of the present invention is to provide a produce for producing deoxygenated air. Another objective of the present invention is to provide a process which produces oxygen deficient air economically. Accordingly, the present invention provides a process for producing deoxygenated air, which comprises mixing 0.1 to 4.0 wt. % of sodium carbonate to water, reacting the mixture so obtained in a closed reactor with 0.2 to 8.0 wt. X of sodium sulphide in the presence of 101 to 122 vol. % air, adding fresh air, if required, to avoid creation of vacuum conditions till oxygen deficient air of the desired level is obtained. The chemicals used may be of laboratory/ commercial grade. The process of the present invention removes oxygen from air leaving behind a small quantity of oxygen depending upon the quantity of chemicals used and time taken. It is reported that sodium sulphide is very reactive with water giving hydrogen sulphide gas that is poisonous to the living beings. To check this reaction sodium carbonate is used. The reaction take place as below: Na2 S + 2H2O→H2S + 2NaOH (1) H2 S + Na2CO → Na2 S + H2 CO3 (2) H2CO3 + 2NaOH → Na2 CO3 + 2H2 O (3) In presence of moisture Na2 S reacts with oxygen according to the following reaction. 2[2Na2 S+H2O+20 → Na2 S2 O3 + 2NaOH] -(4) 2Na2 S2 O3 +O2 → 2 Na2 S2 O4 (5) 2Na2 S2O4 + 3O2 + 2H2 O → 2Na2 SO4 + 2H2 SO4 -(6) 2[2NaOH + H2SO4 → Na2 SO4 + 2H2 O] (7) Overall there is reaction of oxygen with sodium sulphide forming sodium sulphate. Na2 S + 2O2 → Na2 SO4 Sodium sulphide reacts with oxygen that is dissolved in water and oxygen of the air in the head space gets dissolved in water. Thus air of the head space becomes oxygen deficient due to which a vacuum ia created in the closed set. To break this vaouum fresh air is given in the set by opening the stop cock for few seconds. This process is to be repeated till no vacuum is created due to absorption of the oxygon. By this method anaerobic conditions can be maintained for a longer time even if there is slight leakage through any of the stopcock or Joint. The following examples are given by way of illustration and should not be construed to limit the scope of the present invention. Example 1 For this study four sets [Set-1, Set-2, Set-3, Set-4] were set up. In each set a flask with ground glass joint and two stop cocks were used. Total volume of the sets was 605 ml, 610 ml, 610 ml and 665 ml respectively. In all the four flasks 300 ml water along with a crystal of resazurine (an indicator for oxygen- in presence of oxygon colour of the solution is red otherwise blue) was taken. To the water of the flasks sodium carbonate added was 0.3 g, 0.6 g, 0.9 g and 1.2 g respectively and then sodium sulphide added was 0.6 g, 1.2 g, 1.8g and 2.4g respectively. adding sodium sulphide flasks were closed immediately. The initial oxygen in the room atmosphere was 20.90. Air in the head space of all four sets was analysed periodically for oxygen contents by Haldane apparatus. Results are shown in TABLE-1. TABLE—1 : Percentage of oxygen in air of head space (Serics 1) (Table Removed) From the results shown in TABLE-1, it is found that when lowest concentration of sodium carbonate and sodium sulphide i e 0.1% and 0.2X respectively taken, the reduction in oxygen 6ontent was from 20.9X to 9.55X in 15 days and that remained constant till 100 days of experimentation, when concentration of both the salts doubled and tripled, oxygen content of the air got reduced to 6.44X and 5.17X respectively in 37 days and then reduced to 1.99X and 1.7X respectively in 80 days and further reduced to 1.27X and IX respectively in 100 days. When concentration of salts increased to four times, the oxygen content of air reduced to 3.84X in 42 days and to 1% in 80 days and remained constant till 100 days of experimentation. Example-2 In second series of experiments another four sets [Set-5, Set-6, Set-7 Set-4] were set up with higher concentrations of salts. The total volume of the sets was 551 ml, 555 ml, 551 ml and 555 ml respectively. This time water added was 250 ml in each flask to maintain the volume of air to about 300 ml. In first two flasks sodium carbonate and sodium sulphide taken were 6 g and 12 g respectively. Set-5 was kept stationary and Set-6 was agitated in a shaker at 200 rpm for about 6 hours on five working days. In set-7 and set-8 sodium carbonate added was 7.5 g and 10 g respectively and sodium sulphide added was 15 and 20 g respectively. Rest of the conditions were same as example 1. The results are shown in TABLE-2 TABLE-2 Percentage of oxygen in air of head abace (aeries 2) (Table Removed) From the results shown in TABLE-2, it is found that with 2.4X of sodium carbonate and 4.8X of sodium sulphide concentration in water, oxygen content of air at stationary and agitated conditions reduced to 15X and 10.95% respectively in one day, then to 7.14 X and 4.57 X respectively in 5 days further reduced to 5,81 X and 3.82 X respectively in 15 days and in 27 days it got reduced to 2.94 X and 2.91 respectively. When oonoentration of salts further increased in set-7 and set-8 i e sodium carbonate to 3X and 4X respectively and sodium sulphide to 6X and 8X respectively. At stationary condition the oxygen content of set-7 and set-8 got reduced to 13.35 X and 13.18 X respectively in one day then reduced to 10.69 X and 8.87 X respectively in 7 days, further reduced to 5.07 X and 4.02 X respectively in 20 days and then to 3.32 X and 2.9 X respectively in 27 days. From the all eight experiments it is inferred that with lower concentration of salts, rate of reduction in Oxygen percentage is low. For quick reduction of oxygen percentage of air higher oonoentration of salts is required. There is a very little effect of agitation in the beginning but no effect of agitation after attaining the oxygen concentration below 10X. The main advantages of the process of the present invention are: 1. The chemical used in the process are easily available. 2. The process does not involve pressure. 3. The process does not involve temperature. 4. The process does not require agitation. 5. The process works even if there is some leakage through stop cocks or joints and maintains the anaerobic conditions for different biological processes. 6. The process is useful for anaerobic fermentation. 7. The chemicals, sodium carbonate and sodium sulphide are easily available. 8. The process removes more than 90 X oxygen from the air (reduction of oxygen in the air is from 20.9 X to 2 %). 9. The deoxygenated air containing less than 10X oxygen could be used in the mine goaf where fire is likely to take place. We Claim: 1. A process for producing deoxygenated air, which comprises mixing 0.1 to 4 wt % of sodium carbonate to water, reacting the mixture so obtained in a closed reactor with 0.2 to 8 wt. % of sodium sulphide in presence of 101 to 122 vol. % air, adding fresh air, if require, to avoid creation of vacuum conditions till oxygen deficient air of the desired level is obtained. 2. A process for producing deoxygenated air substantially as herein described with reference to the examples accompanying the specification.

Documents:

2387-del-1998-abstract.pdf

2387-del-1998-claims.pdf

2387-del-1998-correspondence-others.pdf

2387-del-1998-correspondence-po.pdf

2387-del-1998-description (complete).pdf

2387-del-1998-form-1.pdf

2387-del-1998-form-19.pdf

2387-del-1998-form-2.pdf