December 03, 2015

China plans Ultracritical coal and coal plant retrofits to reduce coal plant emissions by 60% by 2020

China’s cabinet announced Wednesday that it would try to cut pollution from coal-fired power plants by 60 percent by 2020 through upgrades to plants, according to a report by Xinhua, the state news agency. If successful, the plan for upgrades would reduce carbon dioxide emissions from such plants by 180 million metric tons, the report said.

The announcement formalizes a step China is taking to try to reach broader coal-use and emissions goals to decrease some of the world’s worst levels of air pollutants and to help in limiting climate change. China is by far the world’s largest coal consumer and emitter of carbon dioxide and other greenhouse gases.

In parts of Beijing, levels of deadly, fine particulate matter called PM 2.5 were 40 times as high as the recommended daily exposure limit set by the World Health Organization.

Upgrades to coal-fired power plants would mean a reduction in raw coal use of around 100 million metric tons.

Newer power plants in China emit less pollution and carbon dioxide than older ones. Plants in the power industry are less polluting on average than those that produce heavy commodities like steel and cement, as well as heating boilers for wintertime warmth in north China.

In November 2014, Mr. Xi announced that China would try to reach a carbon emissions peak by around 2030, and China has said it is setting a cap on coal use in 2020 of 4.8 billion tons. China’s coal consumption was flat in 2014 compared with 2013 when measured by energy generation, and some scientists say China may already be reaching its peak in coal use.

This year, China has been releasing numbers that adjust its coal consumption of the past decade upward.

There is an IEA paper on reducing emissions by upgrading coal plants (58 pages)

Coal ranks second only to oil as the world’s leading energy source and is the world’s principal fuel for the generation of electrical power. Today, coal-fired power plants with a total capacity of 1 700 gigawatts (GWe) produce over 41% of the world’s electricity. Looking to the future, if no new policies are implemented, global demand for coal used in power generation is projected to rise by more than one-third by 2035 – and in China by almost 50%.

The global average efficiency of coal-fired power plants currently in operation is roughly 33%, much lower than for power plants that rely on other fossil fuel sources and significantly lower than the 45% efficiency possible with modern, ultra-supercritical coal-fired power plants. Over the operational lifetime of a typical coal-fired power generation unit, each percentage point increase in efficiency results in reduced CO2 emissions totalling many millions of tonnes. If coal-fired units currently in operation around the world could be upgraded to operate at an average of 42% efficiency, annual CO2 emissions would fall by more than 2 billion tonnes

China's capital Beijing suffered choking pollution this week, triggering an "orange" alert, the second-highest level, closing highways, halting or suspending construction and prompting a warning to residents to stay indoors.

The smog was caused by "unfavourable" weather, the Ministry of Environmental Protection said. Emissions in northern China soar over winter as urban heating systems are switched on and low wind speeds meant that polluted air does not get dispersed.

The hazardous air, which cleared on Wednesday, underscores the challenge facing the government as it battles pollution caused by the coal-burning power industry and raises questions about its ability to clean up its economy.

Reducing coal use and promoting cleaner forms of energy are set to play a crucial role in China's pledges to bring its greenhouse gas emissions to a peak by around 2030.

Beijing has pledged to reduce the share of coal in total energy consumption to 60 percent by the end of the decade. It has banned the use of low-grade coals.

Premier Li Keqiang has said China would set an efficiency "bottom line" of 310 grams of coal per kilowatt-hour for plants across the country, according to the government website.

The average for the first 10 months of 2015 was 318 grams, according to official data.

The hotter coal (or any thermal plant - natural gas and nuclear) can run then the more efficient they can be.

Upgrading existing plants and building new high-efficiency, low-emissions (HELE) coal-fired power plants addresses climate change concerns in two important ways. In the near term, emissions can be reduced by upgrading existing plants or building new HELE plants. Such plants emit almost 20% less CO2 than a subcritical unit operating at a similar load. Over the longer term, HELE plants can further facilitate emission reductions because coal-fired plants operating at the highest efficiencies are also the most appropriate option for CCS retrofit.

The best new coal plants in China are in the Ultra-supercritical 44-46% efficiency range.

Developments in AUSC steam cycles are expected to continue this trend. AUSC coal-fired plants are designed with an inlet steam temperature to the turbine of 700–760°C. Average metal temperatures of the final superheater and final reheater could be higher, up to about 815°C. Nickel-based alloy materials are needed to meet this demanding requirement. Various research programs are underway to develop AUSC plants. If successful, a commercial AUSC-based plant would be expected to achieve efficiencies in the range of 45–52% (LHV [net], hard coal). A plant operating at 48% efficiency (HHV) would emit up to 28% less CO2 than a subcritical plant, and up to 10% less than a corresponding USC plant. Commercial AUSC plants could be widely available by 2025, with the first units coming online in the near future.

Ultracritical coal reactor turbines in China

China is the premier example of a country benefitting from an actively pursued HELE upgrade policy. By utilizing state-of-the-art USC plants for new and replacement capacity, and with the retirement of older, less efficient units, CO2 emissions are projected to rise less steeply than the increase in demand for coal-based electricity; emissions are projected to reach 6136 Mt in 2040. If China continues to adopt the best technology and retire older units on a roughly 25-year timescale, a largely AUSC-based coal fleet would see projected CO2 emissions actually fall between 2035 and 2040; in this case the CO2 emissions are projected to be 5153 Mt in 2040 (a 16% reduction over the base case scenario), despite a continuing increase in demand. If the most effective CO2 abatement pathway is followed (25-year plant retirement, AUSC upgrades after 2025, CCS installation) emissions could fall to 750 Mt in 2040. Although the analysis presented here does not incorporate China’s recent announcement to peak coal utilization by 2020, such a policy approach would certainly require continued aggressive deployment of HELE coal-fired power plants.

On July 23, 2010, the Chinese National Energy Administration announced the establishment of a “National Innovation Union of 700°C Ultra-supercritical Coal-fired Power Generation Technology,” formally launching China’s 700°C ultra-supercritical technology development plan. This plan is mainly focused on research related to the optimal design of unit systems and major equipment as well as the development of the necessary thermally resistant alloys. Construction of the 700°C steam temperature demonstration project is expected to begin in 2018; the targeted demonstration completion date is approximately 2020

Carbon capture and storage should be technically feasible but will need

* massive investment
* a cross country pipeline network to run CO2 from plants to underground storage
* it will also cost energy which reduces plant efficiency by 10% or more

The USA has older coal plants and is looking at tweaking efficiency to go from 32% efficient to about 37% efficient.

Natural gas is close to double the CO2 efficiency versus Coal

The data below is for average heat rates for US steam-electric generators in 2013 using those fuels.
Each could get about 50% better with the best technology that could be available in 10-20 years.
They each can be about 30% better with the best technology in the world today.

Natural gas plants are pushing towards 65% efficiency.

SOURCES - Cornerstone, IEA, FAS, NY Times, Reuters

Форма для связи


Email *

Message *