Coal for hydrogen: Experiments examine hydrogen-production benefits of clean coal burning

“While some day we may be able to produce hydrogen by breaking up water molecules in association with the high-temperature heat from nuclear power reactors, or through renewable energy technologies, right now the most cost-effective way to produce hydrogen is with coal,” says Chris Shaddix, principal investigator for clean coal combustion at Sandia’s Combustion Research Facility.

Shaddix and his colleagues are involved in a number of experiments to optimize the combustion of coal to produce the most energy and the least possible pollution. While traditional coal combustion produces harmful emissions, modern plants can meet environmental regulations for burning coal cleanly, Shaddix says. As the cost of competing fuels — particularly natural gas — climb, burning clean coal becomes cost competitive.

Add in the possible benefits of separating and storing carbon dioxide (CO₂) emissions from the power plant stacks and coal looks very promising for generating both electricity and hydrogen to provide a bridge to that future technology. “Utilities are starting to invest in coal,” says Shaddix.

Two approaches

Two different approaches to burning coal are now under study:

-- The first, called oxy-combustion, combines coal with pure oxygen.
-- The second, called gasification, burns coal only partially to create a fuel-gas.

The first approach is driven by concern over emissions of CO₂ and other pollutants. The burning of coal in oxygen is a near-term solution that with current knowledge can produce exhaust streams that are close to pure CO₂, says Shaddix. Harmful pollutants like nitrogen oxides, sulfur compounds, and mercury are virtually eliminated.

The oxy-combustion approach is favored by companies in Japan, Canada, Germany, and elsewhere, where pilot plants are under construction.

U.S. companies tend to favor gasification technologies, which offer higher efficiency and low pollution formation. One of these technologies, called steam reformation, combines the coal with steam in a hot environment to produce a “syngas,” composed mostly of carbon monoxide (CO) and hydrogen.

Once the syngas is produced it can be burned directly in a turbine to produce power. Or the syngas can be further reacted with more steam to shift the remaining CO to CO₂ and produce more hydrogen.

The CO₂ can be stored in oil and gas fields and the hydrogen can be used in many potential applications: to power a car in an engine or fuel cell, to power a turbine to produce electricity, or to fly an airplane.

The DOE has already demonstrated gasification technology in two pilot projects. Now, several commercial proposals are afoot in the U.S. for utilities to build plants without government support.

CRF role

Working with the National Energy Technology Lab in Morgantown, W. Va., the CRF is focused on understanding the chemistry and physics of coal combustion using state-of-the-art diagnostic capabilities and modeling expertise. “We apply computational models of reacting particles to the data to understand why we see the results we see,” says Shaddix.

Shaddix and Alejandro Molina, a Sandia postdoctoral student, have been working in a small-scale lab to analyze coal combustion.

“It is very important to understand how fast [coal] burns and releases energy,” Molina says. Burning coal in pure oxygen instead of air eliminates some separation problems, leaving water and CO₂, which can be stored, or sequestered, Molina says.

One problem with this oxygen approach has been a high flame temperature, he continues, which can rapidly destroy the metal burner materials. “The question is: what is the right proportion of oxygen and CO₂?”

After two years of small-scale research, work is now under way to bring two other CRF facilities into the research. A gasification lab will help the researchers study the behavior of coal gas under pressure. A two-story flow reactor that will help the team study the oxygen-coal combustion with recycled CO₂. Tests in this reactor are expected to begin in a few months.

Source: Sandia National Laboratories

Turning Waste Material into Ethanol
(PhysOrg.com) -- Say the word “biofuels” and most people think of grain ethanol and biodiesel. But there’s another, older technology called gasification that’s getting a new look from researchers at the U.S. Department of Energy’s Ames Laboratory and Iowa State University. By combining gasification with high-tech nanoscale porous catalysts, they hope to create ethanol from a wide range of biomass, including distiller’s grain left over from ethanol production, corn stover from the field, grass, wood pulp, animal waste, and garbage.
Closing the hydrogen economic loop
The inventor of the nickel metal hydride (NiMH) technology used for building batteries for countless portable electronic gadgets and now hybrid gas-electric cars believes the hydrogen economy is already upon us.
Scientists aim to boost world energy supplies -- with microbes
British and Canadian scientists expect to begin trials next month (May) to find out whether microbes can unlock the vast amount of energy trapped in the world's unrecoverable heavy oil deposits. An estimated six trillion barrels of oil remain underground because the oil has become either solid or too thick to be brought to the surface at economic cost by conventional means.
Single-celled bacterium works 24-7, converting light to energy by day, moonlighting at night
Researchers at Washington University in St. Louis have gained the first detailed insight into the way circadian rhythms govern global gene expression in Cyanothece, a type of cyanobacterium (blue-green algae) known to cycle between photosynthesis during the day and nitrogen fixation at night.
Coal gasification -- myths, challenges and opportunities
There is a growing consensus that increased demand for electricity will cement coal’s place in the energy portfolio for years to come. In fact, more than half of the electricity produced in the United States comes from coal. With demand for electricity expected to double by 2050 and renewable resources still years away from offsetting increased demand, it is clear -- coal is here to stay.
UC San Diego begins trading greenhouse gas credits on Chicago Climate Exchange
The University of California, San Diego has become the first campus on the West Coast to join the Chicago Climate Exchange (CCX), North America’s only voluntary, legally binding trading system to reduce emissions of greenhouse gases. UC San Diego is only the seventh university in the nation to join the climate exchange.
Team to chemically transform carbon dioxide into carbon-neutral liquid fuels
Using concentrated solar energy to reverse combustion, a research team from Sandia National Laboratories is building a prototype device intended to chemically “reenergize” carbon dioxide into carbon monoxide using concentrated solar power. The carbon monoxide could then be used to make hydrogen or serve as a building block to synthesize a liquid combustible fuel, such as methanol or even gasoline, diesel and jet fuel.
Scientists developing clean energy systems from micro-algae
An international consortium established by an Australian scientist is developing a clean source of energy that could see some of our future fuel and possibly water needs being generated by solar-powered bio-reactors and micro-algae while absorbing CO₂.

Coal for hydrogen: Experiments examine hydrogen-production benefits of clean coal burning

Related stories:

News discussion: