15 minute read
Oxygen Challenge and the Way Forward
A couple of caveats and a disclosure at the beginning:
• I am not a doctor or a virologist or an epidemiologist. So I will not dwell into Covid and the requirement of oxygen for a Covid patient.
• I have used approximation for calculations but the essence is to get the message across.
• I manage Kirloskar Pneumatic Company, which is one of the largest producers of compressors that go into making oxygen.
Plenty but Scarce
Oxygen is the third most prevalent element in the universe and the most prevalent element on earth. Yet, we don't have oxygen in the form and place that we need. It is like what Coleridge said in a poem, "Water, water everywhere, nor any drop to drink." That's the story of oxygen today.
21% of our biosphere is oxygen. But we need it in the form and place by which we can consume it, particularly for medical reasons. Oxygen is used extensively in manufacturing—for cutting and making steel, making nonferrous material, plastics and in textiles, brazing, welding, oxygen therapy, etc. 85% of oxygen that is produced, is used in engineering and manufacturing. Only about 10 to 15% is used for medical purposes.
The other challenge that we have to understand is that oxygen in many cases is the byproduct. The bigger thing that people look for is actually nitrogen. When we produce nitrogen, oxygen gets expelled and it is corrosive. You will see more corrosion in places near the air separation plants where oxygen is expelled.
The Oxygen Tracker
Now let's go to some numbers which are interesting. There is a website and tool to track the oxygen needs. (https://www.path.org/programs/ market dynamics/covid19oxygenneedstracker). It is a smart site where you can see the dynamic requirements every day. According to this, the low and middle income countries alone require 23 million cubic meters of oxygen per day or 33 lakh cylinders. That's a huge quantity. India needs about half of this—15 to 20 lakh cylinders per day (Based on our peak requirement on 23rd May). Estimated cost for this is Rs 40,000 crores. Being altruistic to this scale of money is not going to be sustainable over a period of time. We need to build a business case around it. The global oxygen market is about 5 billion dollars and it will be galloping to 30 billion dollars in a year. It is both an emerging business opportunity as well as a crying social need.
What we give a patient is certain litres of oxygen, delivered at a particular pressure, generally 0.5 bar. An oxygen cylinder is black in colour with a whitecap and a regulator. But now, due to shortage of cylinders and the emergency, we use all colours of cylinders and paint ‘O’ (oxygen) on them. As per Indian standards, it is 1.5mtr tall. A blue colour at the top is for nitrogen and yellow for argon.
Each oxygen cylinder has about 7cubic metres (7000 litres approx) of oxygen at 150 bar pressure. It has approximately 9.2 kilos of oxygen. A patient normally needs 3 to 4 litres a minute but most patients during Covid times need anywhere between 7 to 10litres a minute and in terms of cylinders, each patient requires one to two cylinders a day, at peak requirement.
Need vs. Capacity
We have always kept saying that we have enough oxygen capacity. It is not true. India produces 7,500 tons of cryogenic oxygen per day. This is assuming that we stop all industrial usage that accounts for 85% usage and divert all for medical use. It translates to 8.2 lakh cylinders. Again assuming that we have no shortage of cylinders and that everything can be perfectly bottled without any wastage, we can produce 8.2 lakh cylinders. If we divide this by 2, we can manage around 4 lakh beds, which is really not that much.
It is not just a question of logistics. It is impossible to achieve an ideal scenario where there is no cylinder shortage, no wastage of oxygen, etc. There are so many other challenges.
On record, India has 2.7 lakh oxygenated beds, i.e. beds which have oxygen supply. We have approximately 4,500 ICU beds. Apart from these official ones, we have created many Covid camps and temporary Covid beds, many of which have oxygen cylinders with regulators and temporary pipeline connections. During the peak, we had thousands of such beds with oxygen requirements. We really did not have oxygen for such a large requirement, in spite of banning all industrial requirements and converting them to medical grade.
We had to bring in cryogenic tankers, move oxygen in these tankers to different places and then fill it in bottles. The bottles can be switched very quickly. Even today, we have a shortage of empty cylinders. Many Covid Care Centres do not return empty cylinders and that's a big challenge. As a result, we do not have enough cylinders to rotate.
Atmospheric air contains three gases —78% nitrogen, 21% oxygen and 1% argon. We can separate these and get them out broadly by three processes.
A normal human being breathes about 2,000 litres a day and it comes in a form that is most comfortable. We get oxygen and nitrogen. Oxygen burns while nitrogen is a lazy gas. It slows us down a little bit and allows us to consume oxygen. Pure oxygen by itself is harmful. So we need to get it in a mix.
Air Separation Methods
The three ways of separation are:
1) The cryogenic separation
2) Membrane separation
3) The Pressure Swing Adsorption (PSA) method
In India, we are very familiar with 1 and 3. To give a comparison between these three methods, we can take the example of power generation. A cryogenic distillation plant or separation plant is like having a large thermal power station. A PSA is like having a generator. Having a membrane is like having a small two-stroke Honda engine for power supply at home. That is the kind of scale difference we are talking of.
In addition, oxygen is generated by electrolysis of water for space travel. When we go in for electrolysis for making hydrogen, we get oxygen as a by-product from water, as 89% by weight of water is oxygen. This oxygen has to be blended with nitrogen. These are not practicable for bulk production. So I am excluding this from our discussions.
Difficult to Compress
Oxygen is one of the most difficult gases to compress. It is easier to liquefy and pump, but to compress oxygen per se is exceptionally difficult. We don't actually compress oxygen. We compress air. Oxygen has to be compressed in a very different way. It is most difficult and expensive.
That is the reason why we have this light oxygen easily available from the electrolysis process but to collect that oxygen and compress will be exceptionally expensive and difficult. That is a technical challenge that we don't have an efficient solution for at the moment.
Decoding the Myth
Another myth is that we think scuba divers and mountaineers carry oxygen tanks. Actually, they carry air tanks that have just 21% oxygen. Pure oxygen is very rarely used in medical requirements such as hyperbaric oxygen therapy. So when we say that somebody needs oxygen, it is not pure oxygen, which is very harmful. What they get through a ventilator or canola is generally between 60 and 90 percent oxygen.
The Cryogenic Process
Now let us come to the known ways by which we can make oxygen for our current or near foreseeable requirements. We are all familiar with the cylinders. These are filled from cryogenic tanks. What do we do in a cryogenic plant?
We compress air by using two methods—using central, centrifugal compressors for large volumes or reciprocating compressors for high intensity, smaller volumes. We compress air and suddenly expand it. During this process of compression and sudden expansion, it dramatically cools. Once it is cooled, it is separated in three stages:
a) At minus 183 degree C, oxygen first condenses into a light blue liquid
b) At minus 186 degree C, Argon getscondensed into liquid and
c) At minus 196 degree C, Nitrogengets condensed into liquid.
Of these three, oxygen is easier to handle like LPG. Using cryogenic pumps, it is filled into bottles. This is how the whole thing works.
Concentrators ﴾PSA﴿
During our peak crisis, we sawpanic buying of membrane drivenoxygen concentrators. These are also aform of PSA but these are small onesrun with very light single phasecompressors (say 0.5 KW). These arefor short periods of time before you getto something more serious.
Oxygen Plant ﴾PSA﴿
The PSA plants are more scalable and will eventually be there all over the country. Here we have two PSA tanks with zeolite. Filtration of air happens by molecular sieves which are generally zeolite. The earlier versions had sodium zeolite. Now we have lithium zeolite.
The PSA Plant Process
When the compressed air is sent through this system, nitrogen being a lazy gas, does not go through easily. Oxygen rushes through and nitrogen is filtered out. The process swings from one tank to the other so as to allow the filtered nitrogen to be expelled. That is why we call it the Pressure Swing Adsorption (not absorption) process. The oxygen that goes through is compressed and delivered through a central pipeline system or via cylinders refilled by the plant.
What are the advantages of each of them?
The scalable, large ones are the cryogenic plants which will take one or two years to set up. No new plant has come up in the last two months. We have been delivering compressors for almost 85% of them. We ship at the rate of 10 compressors a month.
In many of these plants, the original intent is for getting nitrogen and expelling oxygen. But due to the emergency, we have switched the application by bottling oxygen and letting go of nitrogen. Out of the 7500 tons of cryogenic plant capacity available in India, almost a significant part were forced to be converted for medical oxygen production. This is filled in large quantities in cryogenic tanks, transported to various places and bottled there. Through this switching, we were able to get through the crisis.
Cryogenic plants will be used for large volumes and long term. But they would always have huge logistics challenges. They can operate on a continuous basis and cannot take ups and downs. These are like large thermal plants and meet the base load requirement, at a low cost.
PSA—The Need of the Hour
What is being built now in large numbers are the PSA machines. Eventually my submission would be that every hospital would have and should have a PSA machine, which will locally produce oxygen from electricity. You just plug in a compressor. It will take air from the atmosphere, put it through two zeolite tanks and get you oxygen, which you can just pipe it and deliver it to the patients.
While cryogenic plants are suited for the long term and per unit cost is much cheaper, in a crisis, every hospital should be mandated to have a PSA system.
The big thing that has to develop and come in quickly, not only in India, but across the world is the PSA system. The pressure swing adsorption (or it could be vacuum swing adsorption) system is like having a local generator. It would be a top up power or power that comes in when the cryogenics are either not available or cannot be made available on a continuous basis. This would become a mandated requirement for all hospitals, even large housing societies, etc.
The advantages of the PSA system which we don't have in any significant numbers today In India are:
a) Localized generation.
b) Needs only power supply.
c) No need for transportation, pressurized cylinders and cryogenic storage.
d) It is the easiest, safest and cleanest way to do things.
We already have PSA systems in India but they were largely used for producing nitrogen and which has many uses as an inert gas such as for blanketing fuel tanks, control panels, tires, gravity suits, etc. Many such nitrogen PSAs have been converted to get oxygen now.
The membrane or smaller concentrator would continue to be available for people who can afford it, like they have an air conditioner at home. It will give some comfort but it is only a temporary solution and for a short period of time. India used to get about 40,000 of it in a year. Today, we are probably getting that quantity in a month. Most of it comes from China and Europe and this will continue to come in and it is pretty cheap. There is not much of a manufacturing base for this in India, but eventually they will make this in India as well.
The membrane concentrators have rubber pistons and are not meant for rugged, long duration application. It is for one patient, to be used for a short period of time. That's all. It has a small compressor, a small cooling system, solenoid valves and zeolite membrane sieves. The nitrogen gets expelled out and you get oxygen. You take it to a canola and breathe through it.
A Caution
If you are running the membrane system or PSA plant in an airconditioned room, you must be mindful of the fact that you are enriching the room with nitrogen (which is getting expelled from the machine). Nitrogen being a lazy gas does not move quickly. This is very harmful for the others in that room who are not breathing oxygen.
In the PSA systems, the zeolite sieves use lithium ions. Sodium ions are not used anymore. In future, we may use activated carbon or graphene. Silica gel is used as a dryer to remove traces of moisture and oil in the air.
On a Mission Mode
For the last three to four months, we are on mission mode, being monitored and tracked. The government has put DRDO as the nodal agency to push these things.
For the PSA plant, the compressor and all the moving parts are built by us. The zeolite tanks and the other parts are being made locally by several people. You just have to plugandplay. You connect them up and then you can get oxygen which you can feed to various patients through the manifold.
The other worrying aspect is that in large makeshift Covid care centres, the oxygen supplied through cylinders is not continuously monitored or regulated. The cylinders are also not returned promptly. Of course, they have managed the crisis somehow.
If you look backwards, the oxygen for these centres would have been separated from air in a cryogenic plant situated in Jharkhand. Then they would have moved in cryogenic tankers by either train or road, brought into Madhya Pradesh for bottling and sent out to patients. The logistics are a nightmare and unsustainable.
As compared to this, the PSA system can be just connected wherever you have power. You can regulate the oxygen content and the oxygen air mixture. You can feed it in each location. This would be more sustainable.
Way Forward
Going forward, this is likely to be a big thing. There is a push to get as many of these things working as possible. We don't have too many of PSA at the moment but they are getting up quickly. It does not cost that much. To give you an idea, for a 60 bed hospital, delivering 10 litres per minute of oxygen, it will not cost more than 15 lakhs. This is something which is very affordable.
Large steel plants and process plants use huge centrifugal compressors. They use liquefied gas for the process. During the crisis, they were also pressed into use for generating oxygen but only a small part of the gas here is converted to oxygen.
Today oxygen is seen as a medical supply in a crisis. We are now taking a very altruistic stand and forgetting the cost. Quite honestly, it is unsustainable. It is costing billions of dollars and if you run it for long enough, it will be impossible.
This has to move into a more ethical, professional business activity. The consumer must get oxygen in the right place, at the right time and at the right price. That is the reason it must be talked about in a business school, because everything is a supply and demand issue.
What is the future likely to be? I believe that the large cryogenic plants are like the large thermal power stations; they would exist, have a purpose and have the lowest cost per unit. But it cannot meet the peaks and valleys and has huge logistic and other challenges. So just like we have mandated that gensets must be kept for commercial activity or hospitals, now hospitals must be mandated to have a PSA oxygen generator for them to get their license.
We will have the smaller, membrane concentrators at homes.
That is what the future is likely to be in oxygen. I don't think we will go back to living only out of the large cryogenic plants. We would have to get to a mixture of all the three and we have to do it all pretty quickly, to take on the future waves that we may face.
We have seen that most of the food that we consume goes through some level of processing. Most of the water we consume goes through some level of treatment. Eventually, we will come to a stage where most of the air that we consume, at least for critical requirements, would have a level of processing.
So the way ahead will definitely be through a molecular sieve based Pressure Swing Adsorption system, at least to start with. That will also get improved over a period of time.
