Characteristics and Utilization of fly ash from coal-fired power plant in CHINA

Transcription

1 2015 World of Coal Ash (WOCA) Conference in Nasvhille, TN - May 5-7, Characteristics and Utilization of fly ash from coal-fired power plant in CHINA Yajuan WEI 1,2*, Qunying WANG 1, Guangwei YING 1, Zhongyang LUO 2 and Yoshihiko NINOMIYA 3. 1 Department of environment and resource circularly utilization technology, China HuaDian Electric Research Institute, Hangzhou, , China 2 Department of energy engineering, Zhejiang University, Hangzhou, , China 3 Department of applied chemistry, Chubu University, Kasugai, Aichi, , Japan KEYWORDS: CFBC/pf ash; characteristics; radioactivity; classify; utilization; ABSTRACT: The amount of solid residues, released by factories and thermal power plants has been increasing throughout the world, and the disposal of the large amount of fly ash has become a serious environmental problem, especially in developing country. According to the survey statistics, the main problems with fly ash utilization In China are: 1) Utilization ratio of CFBC ash is very low; 2) The ways of using fly ash is limited, mainly in cement and concrete; 3) Utilization ratio of clinker is not high. In this study, the chemical and physical characteristics of more than 30 ash samples, including CFBC ash and pf ash, were investigated. Consequently, their potential utilization ways were estimated. Submitted for consideration in the World of Coal Ash 2015 Conference, held May 5-7, 2015.

2 Introduction: The amount of solid residues, released by factories and thermal power plants has been increasing throughout the world, and the disposal of the large amount of fly ash has become a serious environmental problem, especially in developing country. In 2010, about 480 million tones of fly ash were produced in China[1]. It is 10 times of EU15[2]. The production in China is estimated to be about 570 million tones by the end of The quantity of fly ash from thermal plants is massive. Figure1. Development of fly ash production in China from The majority of the coal fly ash are produced to meet certain requirements of standards or other specifications with respect to utilization in certain areas: firstly, it can lower disposal costs; secondly it need less areas for disposal; thirdly, there may be financial returns from the sale of the by-product or at least an offset of the processing and disposal costs; and fourthly, the by-products can replace some scarce or expensive natural resources[3]. By now, coal fly ash are mainly utilized as a replacement for natural materials in the building material industry, in civil engineering, in road construction, for construction work in underground coal mining as well as for recultivation and restoration

3 purposes in open cast mines. The power industry will take all efforts to provide always good quality products to the downstream market. Fly ash can be considered as the world s fifth largest raw material resource[4]. In China, fly ash utilization ratio is 35% in 1994, and it is up to 68% by the end of 2011[1]. However, it is still has very large development room. Fluidized bed combustion ash is produced in fluidized bed combustion boilers (CFB). Typically, fuels are burned in a CFB boiler with the addition of limestone to capture SO 2 in a solid form at temperature of 800 to 900 o C. CFB ash is rich in free calcium oxide (f-cao ) and sulphur, and sometimes its colour is different from cement. It can hardly be used as cement additive. Beneficial use for construction purpose is one of the most common markets for CFB ash. These uses include soil stabilization, road base, structural fills, and synthetic aggregate. Beneficial use for construction purpose is one of the most common markets for CFB ash. These uses include soil stabilization, road base, structural fills, and synthetic aggregate. Ordinary fly ash Cement CFB fly ash According to the survey statistics, the main problems with fly ash utilization In China are: 1) Utilization ratio of CFBC ash is very low; 2) The ways of using fly ash is limited, mainly in cement and concrete; 3) Utilization ratio of clinker is not high. In this study, the chemical and physical characteristics of more than 30 ash samples, including CFBC ash and pf ash, were investigated. Consequently, their potential utilization ways were estimated.

4 Experiments and analysis 30 fly ash samples evaluated in this study were got from CFB boilers and pulverized coal-fired boilers firing diverse fuels such as bituminous, low volatile bituminous, anthracite as well as coal gangue. Characterization of fly ash in terms of composition, mineralogy, surface chemistry and reactivity is of fundamental importance in the development of various applications of fly ash. Firstly, the chemical composition for selected fly ashes as determined by x-ray fluorescence, and the results were list in Table1.

5 Table1: Chemical composition of ash samples as oxides (wt.%) NO. Samples SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O SO3 P2O5 TiO2 1 XJS WD BJ FX ZP YA HS SJT GX PZH BM SJT DH ZZ YD

6 NO. Samples SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O SO3 P2O5 TiO2 16 JR DL DF ZX KM TZ HM FXN TLF HYC XJ WRMQ CJ KS LW

7 Samples NO.1 to No.6 is CFB ash and others are pf ash. As shown in this table, the fly ashes has significantly different chemical compositions as would be expected considering the types of fuels being fired and the boiler types. The results shows that the CaO content of CFB ash is varied from %. Future work includes identify ash mineralogical composition, fly ash diameter distribution, microstructure of fly ash, and deterring the controls on heavy metals leaching from fly ash under various environmental conditions as well as their utilization ways, especially for CFB ash. [1] 18/ shtml. [2] Fernando Caldas-Vierira, Hans-Joachim Feuerborn. Impact of Political decisions on Prodcution and use of coal combustion products in Europe World of coal ash(woca) conference-april 22-25, 2013 in Lexington, KY [3] M.Ahmaruzzaman. A review on the utilization of fly ash. Progress in Energy and combustion Science. 36(2010) [4]Mukherjee AB, Zevenhoven R, Bhattacharya P, et al.mercury flow via coal and coal utilization by-products: a global perspective. Resour Conserv Recycl 2008;52(4):