Science Current Events | Science News |

Hybrid system could cut coal-plant emissions in half

April 04, 2016

CAMBRIDGE, MA -- Most of the world's nations have agreed to make substantial reductions in their greenhouse gas emissions, but achieving these goals is still a considerable technological, economic, and political challenge. The International Energy Agency has projected that, even with the new agreements in place, global coal-fired power generation will increase over the next few decades. Finding a cleaner way of using that coal could be a significant step toward achieving carbon-emissions reductions while meeting the needs of a growing and increasingly industrialized world population.

Now, researchers at MIT have come up with a plan that could contribute to that effort by making it possible to generate electricity from coal with much greater efficiency -- possibly reaching as much as twice the fuel-to-electricity efficiency of today's conventional coal plants. This would mean, all things being equal, a 50 percent reduction in carbon dioxide emissions for a given amount of power produced.

The concept, proposed by MIT doctoral student Katherine Ong and Ronald C. Crane (1972) Professor Ahmed Ghoniem, is described in their paper in the Journal of Power Sources. The key is combining into a single system two well-known technologies: coal gasification and fuel cells.

Coal gasification is a way of extracting burnable gaseous fuel from pulverized coal, rather than burning the coal itself. The technique is widely used in chemical processing plants as a way of producing hydrogen gas. Fuel cells produce electricity from a gaseous fuel by passing it through a battery-like system where the fuel reacts electrochemically with oxygen from the air.

The attraction of combining these two systems, Ong explains, is that both processes operate at similarly high temperatures of 800 degrees Celsius or more. Combining them in a single plant would thus allow the two components to exchange heat with minimal energy losses. In fact, the fuel cell would generate enough heat to sustain the gasification part of the process, she says, eliminating the need for a separate heating system, which is usually provided by burning a portion of the coal.

Coal gasification, by itself, works at a lower temperature than combustion and "is more efficient than burning," Ong says. First, the coal is pulverized to a powder, which is then heated in a flow of hot steam, somewhat like popcorn kernels heated in an air-popper. The heat leads to chemical reactions that release gases from the coal particles -- mainly carbon monoxide and hydrogen, both of which can produce electricity in a solid oxide fuel cell.

In the combined system, these gases would then be piped from the gasifier to a separate fuel cell stack, or ultimately, the fuel cell system could be installed in the same chamber as the gasifier so that the hot gas flows straight into the cell. In the fuel cell, a membrane separates the carbon monoxide and hydrogen from the oxygen, promoting an electrochemical reaction that generates electricity without burning the fuel.

Because there is no burning involved, the system produces less ash and other air pollutants than would be generated by combustion. It does produce carbon dioxide, but this is in a pure, uncontaminated stream and not mixed with air as in a conventional coal-burning plant. That would make it much easier to carry out carbon capture and sequestration (CCS) -- that is, capturing the output gas and burying it underground or disposing of it some other way -- to eliminate or drastically reduce the greenhouse gas emissions. In conventional plants, nitrogen from the air must be removed from the stream of gas in order to carry out CCS.

One of the big questions answered by this new research, which used simulations rather than lab experiments, was whether the process would work more efficiently using steam or carbon dioxide to react with the particles of coal. Both methods have been widely used, but most previous attempts to study gasification in combination with fuel cells chose the carbon dioxide option. This new study demonstrates that the system produces two to three times as much power output when steam is used instead.

Conventional coal-burning power plants typically have very low efficiency; only 30 percent of the energy contained in the fuel is actually converted to electricity. In comparison, the proposed combined gasification and fuel cell system could achieve efficiencies as high as 55 to 60 percent, Ong says, according to the simulations.

The next step would be to build a small, pilot-scale plant to measure the performance of the hybrid system in real-world conditions, Ong says. Because the individual component technologies are all well developed, a full-scale operational system could plausibly be built within a few years, she says. "This system requires no new technologies" that need more time to develop, she says. "It's just a matter of coupling these existing technologies together well."

The system would be more expensive than existing plants, she says, but the initial capital investment could be paid off within several years due to the system's state-of-the-art efficiency. And given the importance of reducing emissions, that initial capital expense may be easy to justify, especially if new fees are attached to the carbon dioxide emitted by fossil fuels.

"If we're going to cut down on carbon dioxide emissions in the near term, the only way to realistically do that is to increase the efficiency of our fossil fuel plants," she says.

Massachusetts Institute of Technology

Related Carbon Dioxide Current Events and Carbon Dioxide News Articles

Better combustion for power generation
In the United States, the use of natural gas for electricity generation continues to grow. The driving forces behind this development?

Hydrothermal vents, methane seeps play enormous role in marine life, global climate
The hydrothermal vents and methane seeps on the ocean floor that were once thought to be geologic and biological oddities are now emerging as a major force in ocean ecosystems, marine life and global climate.

Deep, old water explains why Antarctic Ocean hasn't warmed
The waters surrounding Antarctica may be one of the last places to experience human-driven climate change.

Researchers identify critical factors that determine drought vulnerability of wheat, maize
Researchers led by Lixin Wang, assistant professor of earth sciences in the School of Science at Indiana University-Purdue University Indianapolis, have identified critical information about the environmental variables and agronomic factors that determine the vulnerability of maize and wheat production to drought.

A planet 1,200 light-years away is a good prospect for a habitable world
A distant planet known as Kepler-62f could be habitable, a team of astronomers reports.

Scientists discover methane-producing microbes in California rocks
Deep in vents on the ocean floor, methane-producing microbes feed off chemical reactions between water and rock. Now evidence of this process has been found on land in a freshwater spring in California.

Researchers find higher than expected carbon emissions from inland waterways
Washington State University researchers have found that greenhouse-gas emissions from lakes and inland waterways may be as much as 45 percent greater than previously thought.

New study captures ultrafast motion of proteins
A new study by an international team of researchers, affiliated with Ulsan National Institute of Science and Technology (UNIST) has announced that they have succeeded for the first time in observing the structural changes in carbonic anhydrase.

Rutgers scientists help create world's largest coral gene database
Coral reefs - stunning, critical habitats for an enormous array of prized fish and other species - have survived five major extinction events over the last 250 million years.

Natural regeneration of tropical forests helps global climate mitigation and forest restoration
Climate scientists have long recognized the importance of forest conservation and forest regrowth in climate mitigation and carbon sequestration -- capturing carbon dioxide (CO2) from the atmosphere.
More Carbon Dioxide Current Events and Carbon Dioxide News Articles

In Praise of Carbon: How We’ve Been Misled Into Believing that Carbon Dioxide Causes Climate Change

In Praise of Carbon: How We’ve Been Misled Into Believing that Carbon Dioxide Causes Climate Change
by David Bennett Laing (Author)

If you wring all the water out of us, you and I consist of a little over two thirds carbon dioxide, dry weight, as do all other living things on Earth. Still, more than a few people claim that if we pour this life-giving gas into our atmosphere, we’ll burn up the planet. Is this really true? Many of those people would say, righteously, that I should be ashamed of myself for even asking the question, but that is in fact what this book is all about, asking the question. With “In Praise of Carbon,” I burrow beneath all the doomsday propaganda, scientific and otherwise, in search of the right answer to this question. In doing so, I’ve exposed some rather interesting things. Did you know, for example, that in 1900, the leading atmospheric physicist of the day, Knut Ångström,...

Miracle Molecule: Carbon Dioxide, Gas of Life

Miracle Molecule: Carbon Dioxide, Gas of Life

The astonishing story of a simple chemical that made life on Earth possible and continues its work today. Tiny amounts of this miracle molecule not only make life on Earth possible, but rising atmospheric CO2 levels also spur forest and crop growth, help plants survive heat and drought, and feed the world.

The Carbon Dioxide Syndrome

The Carbon Dioxide Syndrome
by Jennifer Stark and Russell Stark (Author)

Learn why changing your breathing can improve your health and well-being through the Butekyo Method. This method will help those with sleep disorders, panic attacks, allergies, hypertension and asthma.

Why It's Not Carbon Dioxide After All

Why It's Not Carbon Dioxide After All
by Douglas J Cotton (Author)

Climate Change is not caused by any Greenhouse Effect. This book explains the basics of thermodynamic physics in a way that will help you understand how the world has been so seriously misled into believing carbon dioxide is to blame for the observed global warming. The author presents a sound argument and outline of the "heat creep" process which is what must be supporting surface temperatures on Earth and other planets and he highlights the serious errors in the greenhouse conjecture. This is a "must read" book for anyone who is concerned that mankind is causing the world to warm. It explains natural climate cycles and predicts future global cooling.

Carbon Dioxide Utilisation: Closing the Carbon Cycle

Carbon Dioxide Utilisation: Closing the Carbon Cycle
by Peter Styring (Editor), Elsje Alessandra Quadrelli (Editor), Katy Armstrong (Editor)

Carbon Dioxide Utilisation: Closing the Carbon Cycle explores areas of application such as conversion to fuels, mineralization, conversion to polymers, and artificial photosynthesis as well as assesses the potential industrial suitability of the various processes. After an introduction to the thermodynamics, basic reactions, and physical chemistry of carbon dioxide, the book proceeds to examine current commercial and industrial processes, and the potential for carbon dioxide as a green and sustainable resource. While carbon dioxide is generally portrayed as a "bad" gas, a waste product, and a major contributor to global warming, a new branch of science is developing to convert this "bad" gas into useful products. This book explores the science behind converting CO2 into fuels for our cars...

Greenhouse Gas Carbon Dioxide Mitigation: Science and Technology

Greenhouse Gas Carbon Dioxide Mitigation: Science and Technology
by Martin M. Halmann (Author), Meyer Steinberg (Author)

Any mention of the "greenhouse effect" tends to ignite controversy. While the rising atmospheric concentrations of greenhouse gases-especially carbon dioxide- are certainly among the most pressing issues today, theoretical and perceived consequences have been subject to conjecture and misinformation.
That raging debate has obscured an important fact: scientists and engineers are hard at work on methods to reduce CO2 emissions, and devise practical methods for their remediation.
Greenhouse Gas Carbon Dioxide Mitigation: Science and Technology
sheds light on the most recent advancements, documented by two of the world's leading researchers on CO2.
Aware of the complexity and still-unknown factors behind climatic change, the authors consider the need to make CO2 mitigation viable...

Carbon Dioxide Emissions: Between the Sword and the Wall

Carbon Dioxide Emissions: Between the Sword and the Wall
by WBP

The international community has agreed on the Copenhagen Accord that “climate change is one of the greatest challenges of our time.” For them Carbon Dioxide emissions are the greatest reason for this change (Zhao and Du 39). Others argue that it is not a cause, that it is just a coincidence, that actually the Carbon Dioxide emissions are not a threat to the world. During an event hosted by the United States Energy Association, Roger Bezek, a consultant to energy companies, said, “CO2 is basically plant food, and the more CO2 in the environment the better plants do” (Milbank). Even though this is a hot topic nowadays the more fundamental question is: Are we taking care of our planet? And the answer is a very concise NO. There have been efforts to stop the relentless increase in...

Carbon Dioxide Capture and Acid Gas Injection (Advances in Natural Gas Engineering)

Carbon Dioxide Capture and Acid Gas Injection (Advances in Natural Gas Engineering)
by Ying Wu (Editor), John J. Carroll (Editor)

This is the sixth volume in a series of books on natural gas engineering, focusing carbon dioxide (CO2) capture and acid gas injection. This volume includes information for both upstream and downstream operations, including chapters on well modeling, carbon capture, chemical and thermodynamic models, and much more. Written by some of the most well-known and respected chemical and process engineers working with natural gas today, the chapters in this important volume represent the most cutting-edge and state-of-the-art processes and operations being used in the field.  Not available anywhere else, this volume is a must-have for any chemical engineer, chemist, or process engineer working with natural gas.    There are updates of new technologies in other related areas of natural gas, in...

Carbon Democracy: Political Power in the Age of Oil

Carbon Democracy: Political Power in the Age of Oil
by Timothy Mitchell (Author)

Does oil wealth lead to political poverty? It often looks that way, but Carbon Democracy tells a more complex story. In this magisterial study, Timothy Mitchell rethinks the history of energy, bringing into his grasp as he does so environmental politics, the struggle for democracy, and the place of the Middle East in the modern world. 

With the rise of coal power, the producers who oversaw its production acquired the ability to shut down energy systems, a threat they used to build the first mass democracies. Oil offered the West an alternative, and with it came a new form of politics. Oil created a denatured political life whose central object – the economy – appeared capable of infinite growth. What followed was a Western democracy dependent on an undemocratic Middle East....

Natural Extracts Using Supercritical Carbon Dioxide

Natural Extracts Using Supercritical Carbon Dioxide
by Mamata Mukhopadhyay (Author)

Synthesizing research from a wide variety of sources, this work offers a convenient guide to a clean, safe, inexpensive, non-toxic, non-polluting solvent that performs better than most conventional solvents. Natural Extracts Using Supercritical Carbon Dioxide reviews recent development in the technology and its applications to the food, flavor, fragrance, and pharmaceutical industries. It outlines the many advantages the method has over traditional methods like steam distillation, solvent extraction, and molecular distillation and it supports the popular trend toward the use of natural products in these industries.

© 2017