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Thermal Power

Coal in our Energy Mix

Around 40 percent of the world's generated energy is produced from coal. According to predictions by the IEA, energy production will rise to approximately 33,000 TWh by the year 2030, in spite of advances in the efficiency of energy usage (2006: 19,000 TWh). Due to its large reserves, numerous supplier countries and relatively low fuel costs, coal will be significantly involved in this increase and thus will make an important contribution to safe and cost-effective energy provision.

The major part of electricity generated from coal at EPCS venture is allotted to coal power plants that boasted an added output capacity of 22.4 GW in 2009. Alongside regular coal, lignite is also still used for electricity generation. Lignite power stations churn out large amounts of carbon dioxide, with a comparably low level of efficiency. Thus they hold little meaning for EPCS venture In 2009 they constituted only a small part of the total energy production, with a power output of 2.3 GW.

For environmental reasons, emissions from coal energy production must be reduced, and measures must be taken to convert methods of energy production over to lower emission technologies. EPCS venture has set itself the goal of halving the CO2 emissions of its energy production by 2030 at the latest, compared with 1990. EPCS venture is following a double strategy to reduce the CO2 emissions of its coal power plants, namely by means of an efficiency enhancement of the 700 degree technology and by using CCS technology.

Carbon Capture and Storage: A Vital Tool to Help Tackle Climate Change

To tackle climate change effectively, global carbon dioxide (CO2) emissions must be radically reduced. In view of the continued increase in energy demand worldwide, EPC VENTURE's efforts to achieve technological advances in conventional generation make an important contribution to the avoidance of carbon emissions. Fossil fuels like coal provide much of the world's electricity but won't be fully replaced by low-emission generating technologies for decades to come. That's why the utility industry is focusing its research and development on an innovative process called carbon capture and storage (CCS), which would make it possible to generate electricity from coal with nearly zero emissions. That would mean that the world's coal reserves (which estimates predict will last for more than 100 years) could be used to provide a secure, affordable, and climate-friendly supply of electricity. These processes are developed to supplement coal-fired power plants but will also be used at gas and biomass plants; to use them with biomass will create a negative emission output.

Three promising carbon-capture method are currently being developed for coal-fired power plants: post-combustion capture, pre-combustion capture, and oxyfuel combustion. EPC VENTURE is actively involved in the development of all three. Our main focus is on post-combustion capture because it's suitable for retrofitting onto existing power plants.

Carbon transport and storage are, along with carbon capture, essential components of our strategy for climate-friendly power production. We're therefore conducting R&D projects in these areas, as well. The pages that follow provide detailed information about these promising technologies and about our many CCS projects.

CCS - Supporting Emission Reduction

A coal-fired power plant that emits almost no CO2? In the not-too-distant future, it could be a reality. There are already three promising methods for capturing CO2 for low-emission coal-fired power generation: post-combustion capture, pre-combustion capture, and oxyfuel combustion.

In post-combustion capture, CO2 is chemically washed out of flue gas. In pre-combustion capture, coal is first transformed into a gas called syngas; CO2 is then removed from the syngas prior to combustion. In oxyfuel combustion, coal is burned in pure oxygen instead of air, which results in a significantly higher concentration of CO2in the flue gas. The flue gas must then be scrubbed of its remaining components such as oxygen, sulfur dioxide, and nitrous oxides.

Post-combustion capture is the only capture method that can be retrofitted onto existing power plants without significant modifications.

But no matter which capture method is used, it's essential that we find efficient and safe ways to transport and store CO2. Porous, geological formations called aquifers represent a particularly promising solution for storing CO2 deep underground. Strata of nonporous cap rock above the aquifer ensure that the CO2 doesn't escape.

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Post-Combustion Capture: CO2 Scrubbing

CO2 accounts for about 15 percent, by volume, of the flue gas of a coal-fired power plant. To capture it, conventional flue-gas purification equipment, which has been in use for decades, is enhanced by an additional process in which the flue gas column is exposed to a solvent that absorbs CO2.

The CO2-saturated solvent is piped into a second fractionating column and heated with steam until the CO2 is separated and washed out. The regenerated solvent is recycled into the carbon-capture process, resulting a closed scrubbing cycle.

The chemical industry already uses CO2 scrubbing processes but in applications that differ significantly (in terms of gas composition and volumes) from the operating conditions of a large coal-fired power plant. In addition, heating the solvent to absorb CO2 consumes energy. A key R&D task is to minimize this energy drain and thus reduce operating costs.

The decisive advantage of post-combustion over other capture methods is that it can be easily retrofitted onto existing power plants. One prerequisite, of course, is that plants have enough room on site to install capture equipment. Overview of post-production capture:

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Post-Combustion Capture Projects for a Cleaner Future of Energy

As one of the world's leading power and gas companies, EPC VENTURE is spurring the development of CCS technology and is supporting more than 80 promising R&D projects along the entire CCS value chain. Some of these projects we're conducting ourselves, and some are partnerships with renowned companies and research institutes. We plan to spend about EUR100 million on CCS research in the years ahead. Our top R&D priority is post-combustion capture.

We believe our focus on post-combustion capture makes sense for three reasons.

1. Post-combustion capture is compatible with proven, and highly developed generation technologies and processes.

2. It can be retrofitted onto existing power plants, which will reduce the emissions of fossil-fuel-fired generation more rapidly.

3. We're convinced that it has significant potential and that our intensive R&D effort will help pave the way to commercial viability in the foreseeable future.

Overview of the Most Important EPC VENTURE-Projects

Although post-combustion capture is a very promising technology, it's not yet mature enough for use in coal-fired power plants. For it to be viable on a commercial scale, advances need to be made in the solvents and processes involved in scrubbing CO2from flue gas, which would reduce fuel consumption and operating costs.

EPC VENTURE is investing in numerous R&D projects related to post-combustion capture, mainly to maximize thermal efficiency and perfect the scrubbing process. To give our R&D the best chances for success, we're working with the world's leading equipment manufacturers and with internationally renowned research institutes.

Below are the projects EPC VENTURE is actively engaged in to help ensure that post-combustion capture is ready for commercial operation in coal-fired power plants by 2020.

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Turning Coal into Clean Hydrogen: Pre-Combustion Capture

As the name suggests, pre-combustion capture involves capturing CO2 before a fuel is burned. The first step of this process is to separate air into nitrogen and oxygen. The second step is to combust coal at high temperatures using insufficient oxygen and steam. This step, called coal gasification, creates syngas, which consists mainly of CO2, carbon monoxide (CO), and hydrogen (H2).

Next, a catalytic converter uses steam to transform CO into a mixture of CO2 and H2. The CO2 is then washed out of this gas mixture and pressurized for transport to a storage facility. The hydrogen that remains can be used to generate electricity in a combined-cycle gas turbine (CCGT), which operates at a high level of thermal efficiency.

Gasification of solid fuels is already used to produce various chemical compounds and synthetic fuels. Before pre-combustion capture can be used on a utility scale, it must first be tested in demonstration plants. The focus of R&D is currently on hydrogen-fueled CCGTs and on optimizing the integration of gasification equipment, gas-purification equipment, and the CCGT itself.

Overview of pre-combustion capture

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Oxyfuel: Using Pure Oxygen to Produce Pure CO2

In the oxyfuel process, a fuel like coal is combusted with pure oxygen instead of air, with exhaust gas added to regulate the combustion temperature. The resulting flue gas consists of almost pure CO2 along with some steam.

Cooling the flue gas enables the CO2 to be separated from the steam, which condenses to water at low temperatures. The CO2-dense flue gas is then scrubbed using conventional equipment, which removes the minimal amounts of dust, sulfur dioxide, and nitrogen oxides it contains. The success of the oxyfuel method depends to a considerable degree on determining how thoroughly these gases must be scrubbed from the CO2 before it can be safely transported and stored.

It takes a lot of energy to produce the pure oxygen with which the fuel is combusted, but comparatively little to scrub the CO2 after combustion. Another challenge is to improve control of the combustion process in the boiler. Innovative solutions to meet these challenges will be important milestones towards rolling out the oxyfuel process on a utility scale.

Overview of oxyfuel combustion

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Transporting CO2 from Power Plants to Storage

Power plants are rarely located near a suitable underground storage facility, so captured CO2 must be transported to such a facility. Trucks are  suitable for transportation of small amounts and ships for transportation over long distances. But because power plants will continually capture large amounts of CO2, it makes economic and environmental sense to use pipelines to transport CO2. To reduce its volume, CO2 will be compressed (which will require additional energy) and piped to the storage facility in a highly dense, liquid-like form.

Pipelines for transporting CO2, which are similar to natural gas pipelines, will have to be planned, approved by regulators, and built in order to create a carbon transport infrastructure. Pipeline carbon transport is a proven technology. CO2 pipelines stretching several thousand kilometers have been in operation in the United States for some time.

Safe Solutions for Permanent CO2 Storage

Capturing CO2 can only make an effective, sustained contribution to climate protection if the CO2 can be stored safely and permanently. Finding viable storage solutions is a must for the success of CCS.

Storage Options Saline aquifers are suitable for permanent underground carbon storage. Typically more than 800 meters below the earth's surface, these rock formations consist of microscopic cavities filled with saltwater. CO2 would be injected into deep porous formations under high pressure, where it would displace and partially dissolve in the saltwater in a process similar to the carbonation of mineral water. This is an attractive solution because these formations have the capacity to store the quantities of CO2 that would be captured at power plants.

Depleted natural gas reservoirs represent another option for permanent carbon storage. Gas accumulated and was conserved in such formations for millions of years, providing a naturally created storage facility for CO2. Pressurized CO2 is already injected into oil reservoirs around the world in order to boost their production and extend their operating lives (Enhanced Oil Recovery, EOR). Now, we can benefit from this experience for carbon storage.

Depleted oil and gas reservoirs in Germany could store a lot of carbon although not enough on their own to store the amount of carbon that would be captured in power plants.

How It Works

Safe and permanent underground carbon storage would help prevent the CO2concentration in the earth's atmosphere from increasing. The nature of the geological structures suitable for storage and their depth below the earth's surface render impossible the sudden release of quantities of CO2 large enough to impair breathing. Porous formations, for example, are several thousand meters below ground and have been insulated from surrounding formations for very long periods of geological time.

A viable geological storage facility needs to consist of a porous rock formation for CO2storage and at least one impermeable stratum (known as cap rock) above it to prevent the CO2 from escaping. The quality of the cap rock is decisive for a storage facility's integrity and thus a key criterion for site selection.

What would happen to the CO2 stored in such a facility over the next several millennia? Most, and perhaps all, of the CO2 would dissolve in the water contained in the rock formation in a process similar to the carbonation of mineral water. Because it's denser, this CO2-infused water would sink to the formation's floor. Mineral processes would then crystallize the CO2 and bind it to the rock formation. Thus, with the aid of nature and time, CO2 can be permanently sequestered far below ground.

Earthquakes pose no serious threat to underground storage facilities. No storage facilities are planned for seismically active regions along the borders of the continental plates. And in seismically stable regions, effects are imperceptible or so small that they would not damage the integrity of the cap rock.

Storage facilities must offer sufficient natural safeguards against the escape of CO2. Their integrity would also be monitored continuously. The utility industry has decades of operational and institutional experience storing natural gas underground, experience that would help ensure safe and reliable carbon storage. Moreover, all facilities would be subject to regulatory consent and oversight.

The technology available today allows installations such as gas pipelines to be fully monitored and safely operated at all times. Sophisticated early warning systems have made it possible to reliably detect any gas leak, and there are safety devices to prevent an uncontrolled release of large quantities of gas in the event of a pipeline failure. This experience can be used when defining the requirements for the transportation of CO2by pipeline.

The future role of CSS Technology

We've set a clear target: to reduce our generation fleet's average CO2emissions to 360 grams per kilowatt-hour by 2020, less than half the 1990 figure. We expect CCS technologies to play a significant role in this effort.

The development of CCS is one of the biggest challenges facing our industry today. The first path breaking projects to utilize CCS technologies are under way. Together, the energy industry and equipment manufacturers must increase the efficiency and cost-effectiveness of carbon capture while reducing the additional energy it requires.

Our R&D focus is on refining post-combustion capture. This technology is particularly promising compared with other capture processes because it can be easily retrofitted onto existing power plants. It also offers considerable improvement potential through continued R&D.

 

 

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