Ethylene production increases rapidly in recent years in China, which promotes the growth of energy consumption and CO2 emissions. Ethylene industry is a technology-intensive industry, for which steam cracking, coal to olefins and methanol to olefins are three main production ways. In view of energy-efficient and lowcarbon technology selection, this study aims to find a suitable roadmap to achieve the targets under current policies for China’s ethylene industry by utilizing National Energy Technology model. With this roadmap, we find that the policy goal for steam cracking could be achieved and the energy consumption and CO2 emissions of producing one-ton ethylene could decrease effectively. Specifically, for producing per ton ethylene, energy consumption could be reduced by 16.8% and 17.1% in 2030 compared to 2015 for steam cracking and coal to olefins respectively, and the values of CO2 emissions are 18.1% and 14.8%. In addition, this study makes a discussion about how to achieve a more sustainable development for ethylene industry in China and it is found that both of energy consumption and CO2 emissions could be reduced by about 20% in 2030 compared to the reference scenario. It is proposed that structure of feedstock in steam cracking could be optimized with more light materials and ethylene producing ways need to be planned well. Especially, environmental effect of coal to olefins should be taken into consideration in its process of development. Steam cracking with ethane and methanol to olefins with imported methanol could be encouraged as they can reduce energy consumption and CO2 emission directly.

Introduction

Ethylene is a versatile chemical material and is generally considered as the building block of the chemical industry together with propylene and aromatics [1,2]. With demand growing steadily, China’s capacity of ethylene has ranked second in the world. From 2005 to 2016, the yield of ethylene increases at a rate of 8.1% annually to 17.81 million tons in China (Fig. 1a) [3]. Ethylene equivalent, which also consider the demand for ethylene’s downstream products like polyethylene, ethylene glycol and so on, is always considered as the real demand of ethylene, while its self-sufficiency1 is under 50% in long term. It is predicted that quantity of ethylene equivalent would keep increasing at a rate of 3.6% annually during year 2016–۲۰۲۰ [۴]. This would promote the yield of ethylene to increase at a rate of 11.5% annually during the 13th Five-Year Plan to 30 million tons in year 2020 [5]. China plans to construct seven petrochemical industrial bases during ۱۳th Five-Year Plan, which would increase 7.2 million tons of ethylene capacity2 . Steam cracking, coal to olefins3 via methanol (CTO), methanol to olefins directly (MTO) and catalytic pyrolysis process (CPP) are four ways to produce ethylene in China. Among which, steam cracking is the most important way which always accounts for more than 80% of the total yield, followed by CTO and MTO, which are two alternative ways but with part of production process similar. While the capacity of CPP only accounts for nearly 2% in 2015.