Coal proponents and climate skeptics often cite China’s current and future reliance on coal power to bolster talking points. What is little discussed is the recent, massive transformation of China’s vast coal fleet, which is aimed at keeping the country on track to meet stringent emissions and climate goals.
The U.S. has officially announced it will exit the Paris Agreement, which leaves China—an economic powerhouse with a population of 1.3 billion people and a colossal demand for electricity—at the helm of the world’s efforts to mitigate climate change. But while China has been criticized for its reliance on coal—it remains the world’s largest producer, consumer, and importer of coal today—over the past five years the country has embarked on a remarkable transition to ramp up environmental measures, driven largely by a desperate effort to tamp down rampant air pollution in some of its major cities.
Through considerable progress to implement ambitious programs to increase the energy efficiency of power generation and a rapid scale-up of renewables and nuclear power, the country has transformed its power sector into one of the cleanest in the world at a breakneck pace. Today, its new highly efficient coal fleet is equipped with domestically developed and imported technologies that seek to meet some of the world’s strictest emission limits for sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM), and mercury—and which make America’s much smaller but highly beleaguered coal fleet look like a relic from the past.
Mandatory Emissions Reductions
The stunning pace of development of environmental technology innovation in China can be attributed to policies that the country has put in place relatively recently. China’s period of profound economic growth, urbanization, and demographic change began nearly three decades ago as the country embarked on reforms to “open up” its economy to foreign investors after the Cultural Revolution, which was embedded on fiercely anti-capitalist elements. The reforms prompted development of energy-intensive heavy industrial sectors, including steel and cement. But the country’s power supply couldn’t keep up, owing to a lack of capital investment. Between 1978 and 2003, the government encouraged reform of the investment systems to raise funds for a power plant expansion, and in the 1990s alone, China boosted its power generation capacity from 17 GW to 227 GW—mostly from new plants that were small coal-fired units outfitted with subcritical steam cycles. Most had few or no air pollutant emission controls, so inevitably—along with soaring power generation that fueled its budding economy—China saw an intense increase of air pollutants, spurring smog and haze, along with rampant acid rain problems across large swathes of southern China.
The ramp-up of air pollution prompted the government in the late 1990s to issue a notice on “strict control of small thermal power equipment manufacturing construction,” which banned construction of power units under 25 MW and forced some small, inefficient power units under 50 MW to close. One of the first strict pollution measures came in 2004, when the National Development and Reform Commission (NRDC), the key government agency that leads program implementation at a national level, issued new requirements for coal plant planning and construction. The rules mandated that any new coal plants larger than 600 MW or with a coal consumption rate of less than 286 grams (g)/kWh should have PM removal and flue gas desulfurization (FGD) systems installed. It also encouraged the use of supercritical and ultrasupercritical technology, as well as combined heat and power plants. In 2007, the country then launched the “Large Substituting Small” program, which meant every new and existing coal plant of more than 135 MW needed FGD systems. Emission standards strengthened in 2012, meanwhile, prompting the installation of electrostatic precipitators (ESPs) and selective catalytic reduction (SCR) units at more than 80% of the coal fleet. All these strict policies forced the decommissioning of an estimated 95 GW of small thermal generating units between 2005 and 2014.
According to Qian Zhu of the International Energy Agency’s (IEA’s) Clean Coal Centre, the resulting environmental gains were stunning. “By the end of 2014, the share of units ≥300 MWe in the installed thermal power capacity was 77.7% and the share of units ≥600 MWe reached 41.5%,” she wrote in a recent IEA overview of China’s clean coal innovations. “The share of [combined heat and power] units increased from 13.3% in 2000 to almost 29% of thermal power generation capacity in 2013. The national average coal consumption rate for power supply in 2015 was 315 g/kWh, which is a 55 g/kWh reduction from the 2005 level. The total amount of [PM], SO2 and NOx emitted from thermal power plants in 2014 was halved compared to that of 2006.” Also as significant, by 2014, 100 GW of China’s total coal capacity of 907 GW featured ultrasupercritical technology, a figure that has grown exponentially. Today, according to data from S&P Global Platts, of China’s 920-MW coal fleet, 19% uses ultrasupercritical technology, 25% uses supercritical technology, and 56% uses subcritical technology (Figure 1).
|1. A controlled shift. Between 1980 and 2016, the technology employed at new coal-fired power plant builds in China has shifted. Courtesy: Center for American Progress|
Stepping up Efficiency
China’s environmental vision is rooted in a national energy policy, typically set out as five-year plans, Qian noted. In 2014, for example, China published the “Action Plan on Upgrade and Reconstruction of Coal-Fired Power Plants for Energy Conservation and Emission Reduction,” which sets technical standards for new and existing coal plants to meet by 2020 (or by 2017 for plants in eastern China and 2018 in central China) for higher power generation efficiency and pollutant emission levels that are on par with gas-fired generation. The standards are stricter than comparable ones in both the European Union and in the U.S. (Table 1).
|Table 1. Conventional air pollution standards for new and existing plants in milligrams per cubic meter (mg/m3). Source: Center for American Progress|
It also mandates that new pulverized coal units of more than 600 MW be outfitted with ultrasupercritical technology, and that pulverized heating units and circulating fluidized bed (CFB) units of more than 300 MW adopt supercritical technology. To drive the adoption of high-efficiency, low-emission technology, the government has offered, since 2016, feed-in tariffs for power generated from low-emission plants.
The measures have paid off in a big way, as Melanie Hart, Luke Bassett, and Blaine Johnson of the Center for American Progress point out in a report on China’s coal generation that was released in May. “By 2020, all coal-fired units nationwide must achieve the following efficiency standards or shut down: 300 [g/kWh] for all new plants and 310 [g/kWh] for all existing plants.” The 100 most efficient coal-fired power plants in China range from 271.56 [g/kWh] to 294.88 [g/kWh]. “No plant on the U.S. top 100 list can currently meet these efficiency standards,” the authors noted.
A Technology Vision
According to Qian, achievements in efficiency have also been driven in large part by China’s giant investments in research and development (R&D) of new technologies and processes. Strategic objectives set out in its 11th Five-Year Plan (2006–2010), 12th Five-Year Plan (2011–2015), and 13th Five-Year Plan (2016–2020) prioritized technology development for large-scale ultrasupercritical and CFB units, as well as for carbon-capturing integrated gasification combined cycle (IGCC) units. These comprehensive plans also take into account domestic intellectual property rights and funding initiatives.
The result: China has both adapted and improved on technologies developed abroad, but also achieved cost reductions through process innovation, incremental manufacturing, and deployment at scale. But China’s development of domestic technologies and optimized engineering designs that are applicable to various parts of its power generation process, on both new and existing power plants, are also laudable. Some examples of significant progress follow.
Double-Reheating Ultrasupercritical Technology. A noteworthy example is the Guodian Taizhou Phase II Project, an ultrasupercritical plant consisting of two 1,000-MW units put online between September 2015 and January 2016 that demonstrated indigenously designed double-reheat technology (Figure 2). Compared to a conventional gigawatt-level single-reheating unit, the double-reheating unit adds another level of reheating to allow the system to reach a higher thermal cycle efficiency, adding to gains in power generation efficiency while slashing coal consumption and generation costs, says the plant’s owner China Guodian Corp. Unit 3 has a plant efficiency of 47.82%, one of the highest in China and in the world, and its emissions of PM, SO2, and NOx are 2.3 mg/m3, 15 mg/m3, and 31 mg/m3, respectively, noted Qian. The demonstrated technology has since been applied to at least two other power plants.
Circulating Fluidized Bed Technology. China now has a total of more than 3,000 CFB boiler units, a technology that suits China’s high-sulfur coal resources. In 2013, China commissioned the 600-MW supercritical Baima CFB demonstration power plant, which continues to be one of the largest units of its type. The steam parameters adopted by the Baima CFB unit are 25.4 MPa/571C/569C. The emissions of SO2, NOx, and PM (192, 112, and 9 mg/m3, respectively) are reportedly much lower than designed values for burning low-quality coal.
Integrated Gasification Combined Cycle Technology. Also in 2013, China put online its first IGCC plant, the 250-MW Huaneng Tianjin demonstration plant (Figure 3). The project in Tianjin province uses subbituminous coal. The gasifier is a dry-feed, oxygen-blown, pressurized two-stage reactor. Modifications in 2014 improved project reliability and availability significantly, said the plant’s majority owner, China Huaneng Group. In July 2016, the plant’s owners completed 72 hours of continuous operation during full-load commissioning tests on the carbon capture system, which uses an absorption chemical solvent-based process.
Air-Cooled Power Plants. In response to water scarcity, China has sought to vastly expand the use of air-cooled thermal power technology since around 2005. An indigenously built 600-MW air-cooling system was scaled up to a 1-GW ultrasupercritical air-cooling unit and installed at the Huadian Ningxia Lingwu Power Plant in Northwest China in 2010. The technology now reportedly equips 66 GW of China’s fleet.
Particulate Matter Control Technologies.China’s strong concerns about its widespread fine particulate issues have spurred a number of innovations. According to the Chinese Academy of Engineering, researchers at Tsinghua University have developed novel technologies, including in situ low-intensity phase-selective laser-induced breakdown spectroscopy, an in-flame two-stage diluted sampling system, and a thermophoretic sampling system to tamp down ultrafine PM formation at an early stage of the pulverized coal combustion process for plants burning high-sodium lignite and anthracite coal. The academic institution also says that stricter emission standards have prompted the use of “multi-field coupled control technologies,” including hybrid conventional approaches involving acoustic force, electrostatic force, chemical bonds, and thermophoretic force. These technologies are used alongside the widely applied use of wet ESPs, low-temperature ESPs, and hybrid ESP/bag systems.
Carbon Capture, Utilization, and Storage (CCUS). China’s commitment under the Paris Agreement is to reduce its carbon intensity 60% to 65% from the 2005 level by 2030, peaking its carbon emissions by 2030, and boosting the share of non-fossil-fueled power to 20%. In 2012, China became the world’s largest emitter of greenhouse gases—responsible for 23% of the global total. The country has been exploring a number of ways to capture CO2, including with precombustion methods such as the GreenGen IGCC project. It has so far completed three demonstration post-combustion carbon capture projects. In 2014, it also put online a 35 MWth oxyfuel boiler in Hubei province as part of a long-term plan to launch oxyfuel boilers of 200 MW to 600 MW after 2020. That project is supported by the Huazhong University of Science and Technology, along with a number of power generators and plant equipment makers. Projects are also underway to explore deep saline aquifer carbon storage, micro algae cultivation, and for long-term enhanced oil recovery. According to experts, China is on track to demonstrate the entire CCUS process and is determined to accelerate its commercial application.
A number of initiatives are ongoing in parallel to develop even higher-efficiency power technology solutions, as well as to increase the flexibility of coal plants, so that they can support the high penetration of renewables. On the emissions front, research continues on multi-field fine particulate control technologies, as well as on control technologies for heavy metals and volatile organic compounds. Several programs are also examining utilization of byproducts from pollutant removal.
The technologies would be beneficial to a number of countries bent on expanding their coal fleets. According to some experts, however, conditions in the U.S. may not support an expansion of highly efficient coal generation, taking into account lessons learned in China. One reason is that the U.S., unlike China, has access to cheap and plentiful shale gas, which has put coal-fired generation at a competitive disadvantage. Additionally, emissions regulations and the general public perception that coal is a dirty fuel have effectively halted the development of any new coal-fired power plants in the U.S.
“If China is going to reduce emissions substantially, more efficient coal generation has to be part of its equation, at least for the near to medium term. In the United States, investing in next-generation clean coal plants is not a good solution because natural gas is cheap, plentiful, and lower-emitting than all but the most expensive coal-fired power,” the authors of the May overview from the Center for American Progress noted. ■
—Sonal Patel is a POWER associate editor.