1.Zeolite oxygen concentrators: chemistry in three dimensions

At the heart of this technology are synthetic frameworks of silica and alumina with nanometer-sized pores that are rigid and inflexible

Chemists, when they are designing or building new molecules, can be thought of as architects and builders. An organic chemist can plan a blueprint for a new molecule, and synthesize it with precision out of atoms of carbon, oxygen, hydrogen and so on. After centuries of fine-tuning this skill, chemists in the early 20th century moved up to synthesizing long, thread-like one-dimensional polymers. The polyethylene of plastic bags is made from repeating units of the ethylene molecule, (importantly, the units are linked by the same firm chemical bonds as are seen within an organic molecule. This provides the stability that ensures that a shirt made from polyester-mixed yarn is long lasting). In biological systems, proteins are 1-dimensional polymers of amino acids.

Adding new dimensions

In recent years, this has been taken to a new level by the creation of extended 2- or 3-dimensional structures from linking together molecular units just as was done for polymers, but in two or three dimensions. The basic units go on fitting together to form large networks, like a wire mesh fence. The network is constructed by repeated additions of a molecule with symmetry. A few such networked sheets, when stacked one over another, form a functional 2-D entity. Because words like polymer do not do justice to this complex arrangement of atoms, such molecular networks are called frameworks.

Uses for these Covalent Organic Frameworks (COFs) take advantage of their stability, large surface area, controlled pore sizes, and tunable chemical environments. Just as you choose the size of the ‘pore’/hole in a wire mesh, frameworks can be designed to act as sieves in separating out molecules of a specified size. The smallest whiff of a toxic gas could be sensed – in an industrial environment, or in airline baggage. They are also suitable for both storing energy (as capacitors) and for conducting it (along membranes in fuel cells).

Metal Organic frameworks (MOFs) are structured like COFs but have metals in complexes with organic entities. The choice of metals is wide, from Beryllium to Zinc, though relatively abundant metals are preferred for economic and environmental reasons. They offer great advantages: for gas storage, as in the case of hydrogen storage in fuel cells; in catalysis, where they replace very expensive metals; in sensors; and in drug-delivery – anti-cancer and other drugs with severe side effects can be trapped in the porous confines of MOFs, to be released in small and steady doses.

Use of zeolites

Zeolites are highly porous, 3-D meshes of silica and alumina. In nature, they occur where volcanic outflows have met water. Synthetic zeolites have proven to be a big and low-cost boon. One biomedical device that has entered our lexicon during the pandemic is the oxygen concentrator. This device has brought down the scale of oxygen purification from industrial-size plants to the volumes needed for a single person. At the heart of this technology are synthetic frameworks of silica and alumina with nanometer-size pores that are rigid and inflexible. Beads of one such material, zeolite 13X, about a millimeter in diameter, are packed into two cylindrical columns in an oxygen concentrator.

The chemistry here is tailored to the task of separating oxygen from nitrogen in air. Being highly porous, zeolite beads have a surface area of about 500 square meters per gram. At high pressures in the column, nitrogen is in a tight embrace, chemically speaking, with the zeolite. Interaction between the negatively charged zeolite and the asymmetric nucleus (quadrupole moment) of nitrogen causes it to be preferentially adsorbed on the surface of the zeolite.

Oxygen remains free, and is thus enriched. Air has 78% nitrogen, 20.9% oxygen and smaller quantities of argon, carbon dioxide, etc. Once nitrogen is under arrest, what flows out from the column is 90%-plus oxygen. After this, lowering the pressure in the column releases the nitrogen, which is flushed out, and the cycle is repeated with fresh air.

Global volunteer efforts have made available very detailed instructions on building your own oxygen concentrator, with locally available resources. In India, IISc has transferred the technology of making oxygen concentrators to over 20 companies.

What are Zeolites?

• Zeolites are aluminosilicate minerals. They are microporous material that is used as adsorbents and catalysts.
• They can accommodate cations such as K⁺, Na⁺, Ca²⁺, Mg²⁺. When the zeolite minerals come in contact with a solution, they exchange these cations for other ions in the solution. The most common zeolite minerals are stilbite, phillipsite, natrolite, heulandite, chabzite, analcime.

Natural Zeolites

• The Zeolites are naturally formed when the volcanic rocks react with alkaline ground water.
• They also crystallize in marine basins for thousands to millions of years.
• The naturally occurring zeolites are contaminated with other minerals like quartz. They are rarely pure. For this reason, the naturally occurring Zeolites are excluded from commercial applications where purity is essential.
• The Zeolites transform into other minerals under hydrothermal alteration, weathering and metamorphic conditions. Weathering is breaking down of rocks through contact with water, atmospheric gases and biological organisms.

Artificial Zeolite

The zeolites are also produced by the process of slow crystallisation of silica-alumina gel.

Application

They are mainly used in commercial water purification. Also, they are used as sorbents and catalysts.

Zeolites in Oxygen Production

• Zeolites are used as adsorbent material in Pressure Swing Adsorption.
• An oxygen concentrator uses Zeolites to adsorb atmospheric nitrogen and then vents out the nitrogen. This leaves oxygen gas remaining to be used for patients.
• In high pressure, the surface area of zeolites increases and thus is capable of adsorbing large quantities of nitrogen.

2.What is the extent of India’s coal crisis?

Has domestic production stagnated? Why is supply insufficient? How are power companies placed?

The story so far: India could be on the verge of a power crisis as the stock of coal held by the country’s thermal power plants has hit critically low levels. Many power plants are operating with zero reserve stock or with stocks that could last just a few days. Some States have witnessed partial load-shedding aimed at saving power. Finance Minister Nirmala Sitharaman, however, is reported to have termed worries about a possible shortage of coal and power supplies “absolutely baseless” and is said to have asserted during the course of a trip to the U.S. that India is now a power-surplus country.

How bad is the problem?

According to data released by the Central Electricity Authority, as of Wednesday, India’s 135 thermal power plants overall had on average coal stock that would last just four days. In all, 112 of the 135 power plants are operating with stocks that are at critical or super-critical levels. The government usually mandates the power plants to hold stocks that would last at least two weeks. It has, however, reduced this requirement to 10 days now to avoid hoarding and ensure more equitable distribution of coal among the plants. India relies on coal to meet over 70% of its power needs, and Coal India Limited (CIL) supplies over 80% of the total coal. The current coal crisis comes amid a broader energy crisis across the world with the prices of natural gas, coal and oil rising sharply in the international market.

What has caused it?

The current crisis in the availability of coal has been the result of lacklustre domestic production and a sharp drop in imports over the last few years. According to BP Global Energy Statistics, domestic coal production in India has stagnated since 2018. It peaked at 12.80 exajoules (EJ) worth of coal in 2018. At the same time, the amount of coal imported from other countries to meet domestic demand, too, has dropped significantly. Coal imports have dropped from the peak of 6.46 EJ in 2016 to 4.22 EJ in 2020. Stagnating supply did not cause trouble last year with the economy shut down to tackle the COVID-19 pandemic. But the rise in power demand this year has exposed the government’s inability to push domestic production or compensate for insufficient domestic production by increasing imports. In fact, the government last year said it would stop all coal imports by FY24.

Many factors have been blamed for the insufficient supply of coal this year. These include short-term issues like flooding in coal-mining areas, transport issues, labour disruptions in major coal-mining countries and the sudden rise in power demand as the economy revives from the pandemic. But it should be noted that deeper structural problems have plagued the power industry in general for long. Populist politics has ensured that the price that many consumers pay for power is not commensurate with the production costs. In FY19, for instance, the revenues of distribution companies covered only about 70% of their total costs. This has discouraged private investment in power generation and distribution even as the demand for power continues to rise each year. It has also increased the debt burden on public sector distribution companies as they have not been compensated for the losses they incur while selling power at subsidised rates. According to the credit rating agency ICRA, the consolidated debt of public sector distribution companies is expected to hit ₹ 6 trillion in FY22.

It should also be noted that the mining of raw materials such as coal is nearly monopolised by public sector companies like CIL that are not run primarily for profits. In fact, CIL has kept the price of its coal low even as international prices have risen significantly this year. It has also been forced to share some of the pain of power generation and distribution companies.

According to the government, indebted power generators and distributors owe over ₹21,000 crore to CIL. So, overall, there is very little financial incentive that major producers across the supply chain, including miners, possess to ramp up production.

What lies ahead?

In recent years, many countries have been trying to cut down on their fossil fuel consumption in order to meet emission targets. But with the current energy crunch, which is prevalent not just in India, fossil fuels are likely to make a strong comeback. India and China, the top two consumers of coal in the world, are expected to further increase production of fossil fuels. The Indian government has been pushing CIL to ramp up production to meet the rising demand and cut down on the country’s reliance on imported coal. However, it is expected to ease restrictions on imported coal in the near future to tide over the crisis. The government last week mandated the thermal power plants to blend imported coal with domestic coal up to a limit of 10%. Meanwhile, China, which consumes half of the world’s coal output and has committed itself to reducing its carbon emissions by 65% by 2030, is set to install more coal-powered power plants to meet its rising energy needs. Structural problems that have plagued the Indian power industry, however, are unlikely to be resolved anytime soon. Allowing the price that consumers pay for power to be determined by market forces is likely to remain politically unpopular, so fundamental pricing reform is unlikely. But with coal selling at high prices in the international market and CIL unable to meet production targets, many power generators may be unable to increase their output unless they are allowed to price their output freely.

Background

India’s thermal power plants are facing a severe coal shortage, with coal stocks having come down to an average of four days of fuel across an increasing number of thermal stations.

Reasons:

• Eruption in Power Demand:
  • Economy recovering from the Covid-19 pandemic coupled with supply issues have led to the current coal shortage.
  • India is suffering from the impacts of a sharp surge in electricity demand, a squeeze on domestic mine output and surging prices of seaborne coal.
  • Increased Share of Thermal Power Plants:
    • Coal fired thermal power plants have also supplied a higher proportion of the increase in demand leading the share of thermal power in India’s power mix increasing to 66.4% from 61.9% in 2019.
  • Flooding and Rainfall:
    • Lower than normal stock accumulation by thermal power plants in the April-June period and continuous rainfall in coal bearing areas in August and September which led to lower production and fewer despatches of coal from coal mines.
  • Lowering Imports:
    • A consistent move to lower imports coupled with high international prices of coal have also led to plants cutting imports.
• Impact:
  • If Industries face electricity shortages, it could delay India’s economic reopening.
  • Some businesses might downscale production.
  • Providing India’s population and underdeveloped energy infrastructure, the power crisis could hit long and hard.
• Steps that can be Taken:
  • Ram-up Mining:
    • Government is working to closely monitor stocks and also State run Coal India and NTPC are working to raise output from mines to boost supply.
  • Supply Controls:
    • Rationing domestic power supplies, especially in rural and semi-urban areas, may emerge as one of India’s easiest solutions.
    • Indian power distributors do typically cut supplies to certain areas on a rotational basis when generation is lower than demand, and an extension of load-shedding would likely be considered if power plants take any further hits.
  • Increase Imports:
    • India will need to amplify its imports despite the financial cost. From Indonesia for instance, the price rose from USD 60 per tonne in march to 200 per tonne in September.
  • Hydro-Power Generation:
    • The same monsoon rains that have flooded coal mines are likely to boost hydro-power generation.
    • Large hydro-electric projects on dams are India’s major electricity source after coal and the sector performs at its peak around the rainy season which typically extends from June to October.
  • Turn to Natural Gas Powered Generators:
    • There could be a larger role for natural gas to play, even with global prices currently surging.
    • In a desperate situation, the gas-powered fleet could help prevent any widespread power outages. State-run generator NTPC Ltd., for example, has idle capacity that can be fired up in around 30 minutes if needed and is connected to a gas grid.

Coal

• This is the most abundantly found fossil fuel. It is used as a domestic fuel, in industries such as iron and steel, steam engines and to generate electricity. Electricity from coal is called thermal power.
• The coal which we are using today was formed millions of years ago when giant ferns and swamps got buried under the layers of earth. Coal is therefore referred to as Buried Sunshine.
• The leading coal producers of the world include China, US, Australia, Indonesia, India.
• The coal producing areas of India include Raniganj, Jharia, Dhanbad and Bokaro in Jharkhand.
• Coal is also classified into four ranks: anthracite, bituminous, subbituminous, and lignite. The ranking depends on the types and amounts of carbon the coal contains and on the amount of heat energy the coal can produce.