The main direction and technical path of green and low-carbon development of ethylene industry

CO2 emissions from China's petrochemical and chemical industries account for about 8% of China's total CO2 emissions in 2021, with the ethylene industry accounting for about 8% of the industry. Steam cracking production of ethylene is the most important production route of ethylene in China, accounting for about 84% of the total ethylene capacity in China. The main sources of carbon emissions are cracking furnace fuel combustion CO2 emissions, indirect emissions from heat and electricity consumption and flare emissions, among which direct emissions from fuel combustion and indirect emissions from heat and electricity consumption are the two main sources of CO2 emissions. Therefore, improving the thermal efficiency of crackers, adopting efficient separation technology, intelligent energy empowerment, and transforming steam-driven to electric-driven is one of the effective paths for energy saving and emission reduction in steam cracking units.

01 Cracker tube enhanced heat transfer technology can reduce fuel consumption and carbon emissions by changing the internal structure or material of the cracker tube and changing the fluid flow state inside the tube to enhance heat transfer.

The finned tube developed by Lummus and other companies in the U.S. can increase the thermal efficiency of ordinary furnace tubes by 20% to 30%, and is relatively mature. Canada Kubota developed the MERT series spiral tube can improve the heat transfer efficiency by more than 40%, and has been widely used. Scope series furnace tube developed by Schmidt + Clemens, Germany, uses HT-E alloy to improve thermal efficiency through uniform circulation pattern, thus reducing fuel consumption.

02 Cracker tube coating technology extends cracker operating cycles and tube life, significantly reduces coking rates, and reduces fuel gas consumption.

According to the function, it can be divided into barrier coating and catalytic coating. Barrier coating mainly plays the role of inert barrier to inhibit coking; catalytic coating catalyzes the removal of coke through steam gasification reaction on the basis of barrier effect.

03 High-efficiency separation technology can improve the separation efficiency of cracking products and significantly reduce process energy use, which is one of the key measures for energy saving and emission reduction in ethylene plants.

In addition to the continuous optimization of the traditional distillation separation process by using advanced recovery systems (ARS) and binary/tertiary refrigeration technologies, scientists are also actively exploring new separation materials. For example, MAF-49 and PCN-250 have been proved to have good ethylene/ethane selectivity; in addition, the new hydrogen-bonded-organic framework materials (HOFs) researched by Zhejiang University are a better ethane-based adsorbent. However, these materials are still in the laboratory stage and need to be continuously researched for early industrial application.

04 The intelligent control system models the relationship between input variables and output variables through data recognition, predicts the trend of output variables and realizes closed-loop control, which can improve the smooth operation of the device and the stability of product quality and reduce the energy consumption of the device.

There are already companies applying artificial intelligence (AI) technology to the ethylene production process, and information technology will help optimize the traditional chemical production process more in the future and further realize fine and green production.

05 Cracking furnace electrification will become an important path to reduce carbon emissions in ethylene cracking units.

A number of global companies as well as large domestic petroleum and petrochemical companies and others are conducting research on electrically heated cracking furnaces. Technical breakthroughs need to be achieved, including long-life and high-power electric furnace design, new high-efficiency electric heater material technology, and advanced control systems. In addition, the Finnish company Coolbrook, in cooperation with the University of Cambridge, has developed a rotating dynamic reactor (RDR) technology with a 20,000r/min rotor at the center of the reactor, which is expected to be industrialized by 2025.