Application of thermal plasma technology for the treatment of solid wastes in China: An overview

doi:10.1016/j.wasman.2016.06.011

Waste Management

Volume 58, December 2016, Pages 260-269

https://doi.org/10.1016/j.wasman.2016.06.011 Get rights and content

Highlights

•
Plasma technology has great potential to serve as a viable alternative in solid wastes management.
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Lab- and industrial-scale plasma solid wastes treatment technology in China are reviewed.
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Existing challenges of plasma technology and recommendations for future works are analyzed.
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Plasma in solid wastes management is still in initial stage but possesses huge market space in China.

Abstract

With its enormous social and economical development, China is now experiencing a rapid increase in solid wastes generation and growing pressure for solid wastes management. Today solid wastes in China are mainly managed by a combination of landfill, incineration, and composting. Within different possible treatment routes, thermal plasma technology (TPT) offers the advantages of efficiently gasifying the organic contents of solid wastes into syngas that can be used for heat and power generation, and vitrifying the inorganics simultaneously into glassy slag with very low leachabilities. This process makes it feasible for near-zero emission into the environment while making use of all the useful components. Encouraged by the industrial operations of solid wastes treatment plants using TPT in some countries, several plasma demonstration projects have already been undertaken in China. This paper provides a preliminary overview of the current laboratory researches and industrial developments status of TPT for the treatment of solid wastes in China and analyzes the existing challenges. Furthermore, the future prospects for TPT in China are also discussed.

Introduction

As the second largest economy in the world, China has become the largest solid wastes generator in the world since 2004 owing to the unprecedented rate of urbanization, industrialization and steadily improving living standards (Chen et al., 2014). According to the Chinese law on the solid wastes prevention and control of environment pollution, solid wastes are classified into three types: municipal solid waste (MSW), industrial solid waste (ISW), and hazardous waste (HW). In 2010 (China Statistical Yearbook, 2011), China produced 158.0 million tons of MSW (the total quantity collected and transported), 2409.4 million tons of ISW, and 15.9 million tons of HW, whereas in 2014 (China Statistical Yearbook, 2015), the survey estimates were 178.6 million tons of MSW, 3256.2 million tons of ISW, and 36.3 million tons of HW. Hence, the solids production increased by 13%, 35%, and 128%, respectively in five years, which means solid wastes in China grow so fast that should be a cause for serious concerns to all.

The harmless management of solid wastes is very important to build a resource-saving and eco-friendly society (Zhao et al., 2016a, Zhao et al., 2016b). In response, the Chinese government is seeking effective ways of waste treatment processes during ‘the 13th Five-Year Plan’ period (2016–2020). Today solid wastes in China are managed by a combination of landfill, composting, and thermal treatment. Among them, sanitary landfill is the dominant form for solids disposal. However, this method suffers from the problems of releasing toxics and occupying vast expanses of land. Composting is the biological decomposition of organic wastes by bacteria, fungi, worms and other organisms under controlled aerobic conditions (Sánchez-García et al., 2015). The drawbacks of this process are the slow degradation rate and the limitation to only organics (Ojha et al., 2012). Hence landfill and composting are neither sufficient nor efficient solutions.

Thermal waste processing technologies, including incineration, pyrolysis, gasification, hold promises in more efficient treatment and energy recovery from the wastes. In recent years, interest in the utilization of advanced thermal plasma technology (TPT), as one of the thermal processing technologies, for wastes treatment has increased enormously (Agon et al., 2016, Materazzi et al., 2013, Materazzi et al., 2015, Morrin et al., 2012, Morrin et al., 2014, Tang et al., 2010, Wang et al., 2010), primarily because of high destruction efficiency and environmental compatibility. By gasifying the combustible parts of the solids into syngas for heat and power generation, and vitrifying the noncombustible parts simultaneously into dense, inert, leach-resistant vitrified slags, pollutants emission could be reduced to almost zero and valorization of all the components of the wastes could be achieved.

For similar reasons, plasma technology is gaining increasing popularity in China. This paper provides an overview of the current status of TPT for the treatment of solid wastes in China. The major barriers facing the growth of plasma industry are discussed and the perspective of plasma technology in China is also presented.

Section snippets

Brief overview of TPT

Plasma is considered to be the fourth state of matter, consisting of a mixture of electrons, ions and neutral particles, although overall it is electrically neutral (Jiang et al., 2014). Plasma can be categorised into three types, thermal plasma, cold plasma and warm (intermediate) plasma. Thermal plasma attains high temperatures, although not as high as ‘hot plasma’ found in thermo-nuclear research and astrophysics, and is in thermal equilibrium (Ruj and Ghosh, 2014). Bogaerts et al. (2002)

Brief overview of TPT for solid wastes management around the world

Table 1 lists some of the typical solid wastes TPT treatment facilities around the world. Most facilities are established in U.S. and Japan. Generally speaking, these plants operate successfully on a single, low moisture feedstock, the composition and characteristics of which are well understood and do not vary much over time (such as MSW incinerator fly ash or bottom ash – MSWI FA or BA, HW, and medical waste). These systems range in capacity from 1 t/d to 100 t/d, with most in the range of 5–30

Preliminary economic and environmental analysis of plasma plant

The successful operation of plasma plants around the world proves plasma technology worth in economic grounds though the initial investment and operating cost are very high (Ducharme, 2010, Zhao et al., 2016a, Zhao et al., 2016b). The primary income of plasma plant lies in the tipping fees and the added value of the potentially reusable by-products and the end-products. The plasma process has a major disadvantage in the form of high electricity consumption which makes it costly to operate.

Possible barriers to TPT industrialization in China and recommendations

The barriers to industrialization of waste-derived energy using TPT exist in both developed countries and developing countries. However, the magnitude and characteristics are different. Based on realistic assessment of the situation in China, some barrier factors to the successful industrialization of plasma technology presently can be identified as follows:

(1)
Technical scope

The supply of feedstock is crucial to the success of plasma processes. Currently, plasma application to the solid wastes

Future prospects of TPT in China

In other countries, TPT is continuing to grow both in the acceptance of the wider community as a process that has a positive impact on the environment and from a business aspect where it is a profitable solution. Also, in China, it is foreseeable that the TPT will possess incomparably wide market relative to the other technologies, as reflected in the following aspects:

(1)
From the viewpoint of environmental protection, the operation and emission standards of waste-to-energy plants are

Conclusions

Plasma technology shows great promise for the treatment of solid wastes without negative impact to the environment, and also for the useful by-products reclamation. It is in accordance with the principle of the ‘circular economy’ in China. Today, China faces serious resource shortages. On the other hand, China is the largest solid wastes producer in the world, therefore, it is anticipated that China has a great potential to develop waste-to-energy industry using the thermal plasma technology.

Conflict of interest

Authors disclose that there are no conflicts of interest that could inappropriately influence the outcome of the present study.

Acknowledgements

Special thanks to Alec Xu in Brown University from U.S.A. for proof-reading and editing.

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Application of thermal plasma technology for the treatment of solid wastes in China: An overview

Highlights

Abstract

Introduction

Section snippets

Brief overview of TPT

Brief overview of TPT for solid wastes management around the world

Preliminary economic and environmental analysis of plasma plant

Possible barriers to TPT industrialization in China and recommendations

Future prospects of TPT in China

Conclusions

Conflict of interest

Acknowledgements

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