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Coal-water-slurry – a new source of Hydrogen?

Dirty coal is still a popular choice for power generation around the world, irrespective of the status of the country, whether industrially advanced or backward. The abundant availability and cheap cost, makes coal more attractive from investor’s point of view; they care less for the environment, while Governments turn a blind eye to all the emissions and pollutions. It is a question of survival for millions of people who work in coal mines and industries. It is one of the toughest challenges many Government are facing. Take for example India; about 65% of power generation still comes from coal. The import of coal increases year after year and there is no immediate solution in sight. Indian coal is a low-grade coal with very high ash content. Each coal-fired power plant generates a huge amount of fly ash and they stockpile them; supposed to be used in the production of Portland cement. It is a big business.

China and Indonesia too uses coal as a major fuel for power generation. But they have come out with an innovative and pragmatic method of using coal. They use coal-water-slurry (CWS), a finely pulverized high  grade coal (calorific value 5100-6100Kcal/kg) in water. They use some chemical additives that make the slurry a homogeneous fluid, similar to a Hydrocarbon such as Heavy fuel oil (HFO).The advantage with CWS is it can be easily pumped and injected into a furnace or boiler using ceramic nozzles, obviously to avoid erosion due the abrasive nature of coal, just like firing diesel or heavy oil. According to the literature, 1.8 -2.2 tons of CWS is equal to 1 ton of Heavy fuel oil (HFO) and it costs about the same. It cost only US$ 62 million to retrofit an existing coal-fired power plant with CWS system and the yearly savings are estimated at US$ 41 mil per year, an attractive rerun on investment.

The beautiful aspect of this method is it generates Hydrogen rich Syngas according to the following chemical reaction.

2C + O2+2 H2O ——– 2H2+2 CO2 when the mixture is subject to Gasification instead of mere Combustion.

The combustion efficiency is about 96-99% and the boiler efficiency of more than 90%. It generates less Sulfur dioxide and Nitrogen oxide emissions and good for the environment compared to conventional coal-fired power plants. It is a good technology that needs the attention of Governments especially India, China and Indonesisa.Even coal rich countries like US, Australia should focus on this technology apart from their persuasion such as carbon sequestration.

In fact this will open new avenues for India and China to switch over to Hydrogen economy without making large investments. The coal water slurry fluid has a property similar to a Hydrocarbon as shown below.

Density 65-70% ,Viscosity -1000Cp, Size d< 50 microns, Ash content <7, Sulfur<0.5%. It is easy to handle a liquid than solid coal. pulverized coal is pneumatically conveyed and fired in rotary cement kilns for so many years. There is nothing new about it. Similarly coal water slurry can be a game changer for  the power industry,  if it is combined with Gasification and combined cycle;  it will lead  into Hydrogen based power generation industry using Fuel cell such as Molten Carbonate Fuel cell (MCFC). I believe there is a clear opportunity for the Governments and private industries  to seriously look into CWS technology which I believe, is a ‘precursor’ for Hydrogen economy of the future.

Hydrogen from Coal

Coal is an important fuel that helped industrial revolution. It is still a main fuel for power generation in many parts of the world. It is also an important raw material for number of chemicals and they directly compete with Hydrocarbons such as Naptha.It is abundantly available and it is cheap. We are still able to generate electricity at 5 cents per kwhr using coal. But, now we are entering into a new phase of energy generation and distribution, due to changing environmental and climatic issues of the twenty-first century. We need completely a new fuel to address these issues; a fuel that has a higher heat content, which can generate more power per unit value of fuel, and yet, generates no pollution. It is a challenging job and the world is gearing up to meet these challenges. They affect the world because any issues about energy impacts each and every one of us. Many industrialized countries around the world are reluctant to sign an agreement that compels them to cut their greenhouse emission to an acceptable level set by UN panel of scientists.

Governments such as US, China and India are reluctant to sign such an agreement because their economy and growth depends upon cheap energy, made from coal. Such an agreement will be detrimental to their progress, and the leaders of these nations are not ready to sign such an agreement. They also understand that world cannot afford to continue to use coal as they have used in the past. It is simply unsustainable. It is a precarious situation and they need to carefully plan their path forward. On one hand, they need to keep up their industrial and economic growth, and although they need to cut their emissions and save the world, from catastrophic consequences of global warming.

A simple analysis of the fuel will show that Hydrogen is a potential energy source for the future. It has energy content at least five times more than a coal for a unit value. Coal has an average heat content of 5000 kcal /kg while Hydrogen has an average heat content of 39,000 kcal/kg. Coal has a number of impurities such as ash, sulfur, phosphorous, other than carbon. Burning coal will emit greenhouse gases with toxic fumes that have to be removed. Therefore, these industrialized countries are now looking ways to generate Hydrogen from coal; that too at a cost which will be comparable to other current fuels such as natural gas. It is not an easy task because natural gas is formed by Mother Nature over several hundred thousand years. It is readily available and there is no manufacturing cost except processing cost. We are used to free energy from Mother Nature. This is the crux of the issue.

Hydrogen is the most abundantly available element on earth; yet it is not available in a free form. It is available as a compound, such as, joined with oxygen forming   water H2O molecule; or joined with Carbon forming Methane CH4 molecule.This Hydrogen should be separated in a free form, and this separation requires energy. How can coal, which is just a Carbon, generate Hydrogen?  It requires an addition of water in the form of steam.  When coal is gasified with air and steam, a mixture of Hydrogen and Carbon dioxide is generated, known as Syngas (synthesis gas).

2C + H2O+O2  ———  2H2 +2 CO2

The syngas is separated into Hydrogen and carbon dioxide using various methods using their difference in densities. The Hydrogen can be stored under pressure for further use. Research work is now under way to capture carbon dioxide for sequestering. Carbon sequestration is a method of capturing carbon dioxide and storing it in a place where it cannot enter the atmosphere. But the technical feasibility and economic viability of such a system is yet to be established.

Carbon sequestration is a new concept and the cost of sequestration can potentially increase the cost of energy derived from Hydrogen despite the fact, Hydrogen has energy content five times more the carbon. However, there is no quick fix for our energy problems, and we have to reconcile to the energy cost will increase in the future but eventually cut the greenhouse emissions. These developed countries should at least show to the rest of the world, how they plan to cut their emissions and their action plans; such disclosure should be subject to inspection by UN panel. In the absence of any concrete mechanism, it will be impossible to stop the global warming in the stipulated time frame considering the fact that a number of coal/oil/gas-fired power plants are already under implementation.

Carbon and human survival

Carbon is the backbone of an organic life on earth. Every life from the smallest microorganism to human beings is made up of carbon. A cycle  called ‘carbon cycle’ that decomposes carbon into carbon dioxide which is used to synthesis Carbohydrates by the  process known as  ‘photosynthesis’ in presence of water and sunlight, as described in the following equation:

6CO2+ 6H2O   + sunlight →  C6H12O6 + 6O2

The oxygen generated during the above process and carbohydrates sustains life of animals and microorganism on earth. These lives consume oxygen and carbohydrates and releases Carbon dioxide by respiration into the atmosphere. The released carbon dioxide breaks down carbohydrates and other organic matters and regenerates carbon dioxide for reuse by animals and other lives. Not all organic matters are decomposed and part of it is stored as carbon biomass in the roots of plants and other organic matters and buried under earth. After millions of years these organic matters turns into fossil fuels under pressure and higher temperature. Carbon is distributed on earth, in water and in atmosphere. Due to increase in population and industrial growth over several decades the carbon dioxide increased gradually in soil, water and atmosphere. Carbon dioxide is also released by natural events like volcanic eruptions.

But the level of carbon dioxide in the atmosphere increased rapidly after industrialisation, when industries unearthed buried fossil fuels and burnt. In fact we are burning carbon at a faster rate than it is regenerated. It is purely man-made and it increases the presence of carbon dioxide both in atmosphere as well as in oceans. The rapid increase of green house emission started 240 years ago when industrial revolution started. The consequences of this unabated greenhouse gases due to combustion has caused ‘global warming’ with many consequences.

As I have mentioned in my previous articles, power generation and transportation are the two major industries that emit bulk of the greenhouse emission. Both industries use age-old technologies of combustion. The world has been complacent about fossil fuels and grossly indifferent to industrial pollution for decades. Global warming is looming as the biggest threat of the twenty-first century, yet we are not acting. Politicians deny global warming and they want to carry on the business as usual, at the peril of the future generations.

Powerful countries like US, China and India are reluctant to pass a unanimous resolution to set target for carbon emission, while smaller nations remain as powerless onlookers. These powerful nations can drag the rest of the world with them to face the wrath of the Mother Nature with disastrous consequences for their inaction.

It is quite obvious that world have no choice but switch to cleaner energy sources and leave the fossil fuels buried deep under the earth. A new paradigm shift in the way we generate energy and use them is the key for the survival of mankind. We need to develop Hydrogen as an alternative fuel source and Government should encourage innovations in such technologies, while they simultaneously price carbon. In the absence of a concrete legislation and mechanism to penalize polluters, industries will continue to use fossil fuels. A simple cost benefit analysis will show that taxing on polluters and simultaneously introducing renewable technologies will benefit the world in the long run.

 

 

 

 

 

 

 

” Water and Clean Energy -Two sides of the same coin”

Why I say “water and clean energy, are two sides of the same coin?” At the outset, it may sound odd, but in reality, these two are closely interconnected. Let us examine, step by step, how they are connected, to each other, and what are the implications, in terms of cost, and environmental issues.

Take for example, power generation industries. The two basic materials, any power plant require, are, fuel and water. It does not matter, what kind of fuel is used, whether it is a coal based power plant or liquid fuel based plant like Naphtha, or gas based plants, like piped natural gas or LNG Of course, this statement is applicable only, for existing, conventional power generation technologies, and not for PV solar or wind energy, technologies. Let us consider, only power generation, involving conversion of thermal energy, into electrical energy. Today, more than 80% of power generation in the world, is based on thermal power, including nuclear plants. What is the usage of water in power plants? All thermal power plants use steam, as the prime motive force, to drive the turbines, (gas turbine is an exception, but, even in gas based plants, the secondary motive force,  is steam, using waste heat recovery boilers, in combined cycle operations). The quality of water for conversion into steam is of high quality, purer, than our drinking water. The second usage of water is for cooling purpose. The water consumption by power plants, using once through cooling system is 1 lit/kwhr, and by closed circuit cooling tower, it is 1.7lit/kwhr .Only about 40% power plants in Europe, for example, use closed circuit cooling towers, and the rest use only ‘once through’ cooling systems. The total power generated in 2010, by two largest users, namely US and China, were 3792Twhrs and 3715 Twhrs  respectively. The total world power production, in 2008 was 20,262 Twhrs, using following methods.

Fossil fuel: Coal 41 %, Oil 5.50%, Gas 21%, Nuclear 13% and Hydro 16%.

Renewable: PV solar 0.06%, PV thermal 0.004%, Wind 1.1%, Tide  0.003 %, Geothermal 0.3%, Biomass &others 1.30%.

(1Twhrs is = 1,000,000,000 kwhrs)

The above statistics, gives us an idea, on how much water, is being used, by power generating plants, in the world. Availability of fresh water, on planet earth, is only 2.5% (96. 5% oceans, 1.70% ground water, 1.7% glaciers and ice caps, and 0.001% in the air, as vapor and clouds).The world’s precious water source, is used for power generation, while millions of people, do have water, to drink. The cost of bottled drinking water is US$ 0.20 /lit, in countries like, India. This situation is simply unsustainable.

The prime cause, for this situation, is lack of technology, to produce clean power, without using water. The power technology, we use today, is based on the principle of electromagnetism, invented, by Michael Faraday, in the year 1839. That is why, renewable energy, is becoming critically important, at this juncture, when the world is, at the cross road.

In order to overcome, the shortage of fresh water, many countries are now opting, for seawater desalination. Desalination, again, is an energy intensive process. For example 3-4 kwhrs of power is used, to desalinate 1 m3 of water. This  power has to come, from fossil fuel fired, thermal power plants, which are often co-located, with desalination plants, so that, all the discharge, from both the plants, can be easily pumped into the sea. Since, the world is running out of fresh water, we have to look for attentive source of water. In countries like India, the ground water is being exploited, for agricultural purpose, and the ground water is getting depleted. Depleting water resources is a threat to agriculture production. It is a vicious circle.

That is why, distributed energy systems, using Hydrogen as an alternative fuel,  is an important step, towards sustainability. One can generate Hydrogen from water, using renewable energy source, like solar or wind, and store them, for future usage. The stored Hydrogen can be used to generate power, as and when required, at any remote location (even where there is no grid power).The water is regenerated, during this process of power generation using Fuelcell, which can be recycled. There is no large consumption of water, and there is no greenhouse emission. It is a clean and sustainable solution. The same stored Hydrogen can also be used as a fuel for your car! Therefore; (The above statics are based on Wikipedia data).

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