• Refurbishment and Rehabilitation of Existing Power Plants
Due to the large number of small power plants in use, China’s average thermal efficiency in power plants is lower than that in industrialized countries. Transfer of skills and techniques for incremental improvement in these small plants can lead to a significant reduction in emissions from coal-fired facilities. Technical measures include optimizing the turbine; replenishing advanced control systems; improving firing techniques; modifying the condenser and cooler; implementation of better maintenance regimes etc.
When selecting the refurbishing or rehabilitating technologies, one of the principles is to choose the suitable technologies, taking the comprehensive factors into consideration. One of the effective ways in which existing Chinese facilities can be improved involves the replacement of old coal-fired boilers with technically mature and economic-efficient fluidized bed boilers, which are already well proven. For older vintages of plants, the scope for such
improvements is limited. So, the preferred course of action may be to replace them completely with modern facilities.
• Circulating Fluidized Bed Combustion
Fluidized bed combustion has the capacity to burn low grade and difficult fuels and meet emission limits at reasonable efficiency. It also has the advantage to reduce emissions of other pollutants. In order to apply fluidized bed combustion technology on a large scale, further development of CFB technology with great economic and social benefits is needed, being focused on wider utilization of low-grade coal.
A number of ‘industrial-scale’ fluidized beds have been constructed or planned in China as a result of licensing agreements between Chinese and international suppliers. 6 CFBC demonstration plants, supported by the Japanese Green Aid Plan, have been built. The types of coal in use include high-ash (at Liaoyuan), anthracite (at Jinzhou) and coal mine sludge (at Zaozhuang). The lowest energy value coal is less than 8 MJ/kg at Zhejiang, where the coal has approximately 70% ash. The highest energy value is 25 MJ/kg at Fangshan, where ash levels are approximately 5%. At Zibo, Shangdong province, a mixture of coal plus mining waste is used (IEA, 1998: 16).
The other CFBC projects include one in Dalian, assisted by UNIDO, with boilers coming from Foster Wheeler. In Neijiang power plant, the largest coal-fired CFBC boiler in China has been installed by Ahlstrom, a division of Foster Wheeler, with China’s Dongfang Boiler Works being responsible for the manufacture of some components. It provides a total output of 285 MW, including up to 100 MW of electricity, and was commissioned in 1996. The 300 MW CFBC unit in Sichuan Baima Power Plant was approved by the State Development Planning Commission in March 1999 after some years delay (Editon, 2001)
The clean coal diffusion working group report listed some examples for CFBC projects, which have been carried out in cooperation with international suppliers (Watson et al, 2000: 9). Those include:
• A series of the Deutsche Babcock (German) design ‘Circofluid’ fluidized bed boilers have been constructed by Beijing Boiler Works. At least 14 units went into service between 1993 and 1996 (approximate sizes vary from 20-40 MWe).
• A 50 MW fluidized bed plant has recently been constructed for the Sichuan Aixi Power Generating Company by Shanghai Boiler Works (a subsidiary of Shanghai Electric Corp.).
The plant was built under a license agreement with Foster Wheeler of the USA and due to commission in 1998.
According to widely accepted technical argumentation and analysis, CFBC technology is relatively low in cost, simple in technical configuration and easy to be domesticated. It is commonly considered as one of the clean coal combustion technologies suitable to China's current situation.
• Coal Gasification
Experimental work on coal gasification started fairly early in China. Through a combination of indigenous research and international cooperation, China has worked on pressurized and atmospheric coal gasification and fixed-bed, fluidized-bed and pneumatic-bed gasification with different kinds of coal supply. The gas obtained is mainly used in industrial and household applications. It is used to produce synthetic gas and fuel gas.
At present, there are over 8000 gasifiers in China, 4000 of which gasify coal using atmospheric fixed-bed technology (Watson et al, 2000: 9). There are already cleaner, more advanced gasifier designs that were introduced to China at some industrial sites. These include Texaco gasification technology for large-scale chemical feedstock gas production; fixed bed gas gasifiers for industrial gas production; Lurgi pressured gasification technology for civil gas production. The imported Lurgi gasification technology was successfully used in the Yilan project in Harbin province with a capacity of 1.6 million m3 per day and the Lanzhou gasification project with a capacity of 0.6 million m3 per day (op cit.: 10).
• Supercritical Pulverized Power Plants
The designs of supercritical power plants are now regarded as commercially proven. The use of higher steam temperatures and pressures to increase the thermal efficiency of coal-fired power plants is an established practice in China.
Shidonkou No.2 was the first super-critical power plant in China. The units were ordered in the late 1980s and put into operation in the early 1990s, utilizing ABB boilers & turbines. The units have been highly reliable in operation and have achieved a boiler efficiency of over 93% with a yearly net standard coal consumption of 312 g/KWh. There are currently 9 supercritical plants in operation in China, with 16 under construction and a further 8 planned, altogether totaling over 21 GW of coal-fired capacity (World Coal Institute, 2004: 9). In 2003, two supercritical units of 800 MW were commissioned (Fangneng, 2003: 22). Units with large capacity in operation include the plants of Nanjing (2*300MW), Panshan
(2*500MW), Yingkou (2*300MW), Yimin (2*500MW), Suizhong (2*800MW), Waigaoqiao (2*1000MW), Fuyang (2*600MW) and Wangqu (2*600MW) (IEA, 1998: 16).
China is also considering to import more advanced ultra-supercritical technology from Denmark. Luaneng Group, from Shangdong Province, is now in negotiations with the Danish- Italian boiler company BWE. Detailed information is yet not disclosed.
• End-of-Pipe Technologies
End-of-pipe technologies include electrostatic precipitators to remove dust from flue gases, flue gas desulfurization (FGD) units and low-NOx burners. There is a big potential for international suppliers to transfer these technologies to Chinese firms or to collaborate in the development of cheaper, simplified designs, which are more likely to be deployed in China. The use of emission control devices, such as FGD, is new and fitted to a small number of Chinese power plants and industrial facilities. Utilization of FGD will be of significant benefit in addressing local and regional environmental problems. The majority of these units use imported technology. At the end of 1998, there were 10 units in operation, and a further 10 in various stages of planning or construction (World Bank, 2000b: 3). Six of the operational units use Japanese equipment financed by the Japanese Government. Three of the more recent plants have been constructed with the help of German overseas aid.
Many of the large coal-fired power plants that are being built in China by foreign developers have already installed electrostatic precipitators and low-NOx burners fitted as standard (Watson et al, 2000: 10). The government has set strict regulations for the large deployment of the technology. However, some of those that have been built and financed within China do not incorporate these features. Instead, they are fitted with less efficient particulate removal systems based on domestic scrubbers. A recent report mentioned that in the coming ten years, FGD and de-NOx equipment are going to be installed within 40 GW of China’s electricity generation capacity.
• Coal Liquefaction
Coal can be transformed into refined oil after a series of processes of high pressure and temperature. It provides an efficient way to reduce China's reliance on crude oil imports. There are two approaches for liquefaction: direct liquefaction and indirect liquefaction. The large-scale direct liquefaction project is now under construction by Shenhua Group Corp. Limited. The project consists of two phases of construction: the first phase is expected to start operation in 2007, with an initial annual oil output topping 1 million tons. The second phase
aims at yielding 5 million tons of oil products annually. In December 2004, Shenhua Group signed a contract valued at US$ 6.6 million with Honeywell International in order to introduce optimized Honeywell equipment to the coal liquefaction project. It is estimated that by 2013, 10 per cent of oil imports will be replaced by coal-liquefied oil (People’s Daily Online, 2005).