Recently, China's environmental newspaper published the article "Can the development of plastic industry" turn white into green "? Do a good job in carbon reduction and pollution control of plastics, high value utilization and waste into treasure is the best choice". Many experts interviewed affirmed the role of plastic chemical recovery method in carbon reduction and pollution control of plastics. Some experts pointed out that chemical recycling can eradicate plastic pollution.

So at present, what is the stage of chemical recovery in China and other countries? Can it be applied on a large scale? The reporter interviewed the relevant business leaders of Sinopec Group and learned that the chemical recovery of plastics, which is different from the simple energy recovery of incineration, is a method of converting low-value waste plastics into high-quality oil fuel or chemical raw materials. It is becoming the focus of scientific and technological research and development around the world, and is expected to become one of the main options to control plastic pollution, help the circular economy, and achieve high-quality, safe and sustainable development.

Chemical recovery can reduce the new demand for fossil fuels

Waste plastics can be converted into high-quality oil fuel or chemical raw materials

According to the report released by the Recycled Plastics Branch of the China Material Recycling Association, the amount of waste plastics produced in China will be about 62 million tons in 2021. How to effectively deal with waste plastics is a major issue that China is trying to break. It is understood that at present, the effective treatment methods of waste plastics mainly include physical recovery and chemical recovery.

The main process of physical recovery of waste plastics includes collection, classification, crushing, cleaning, drying, granulation and production of corresponding products. It solves the problem of recycling relatively high value waste plastics that are easy to handle.

"Physically recovered products are generally difficult to reach the quality of raw plastics, and their recycling is mostly degraded. In the treatment of low-value, mixed, and contaminated plastic waste, this technology is difficult, economic, and not suitable." Gao Yongping, deputy manager of the Synthetic Resin Department of Sinopec Chemical Sales Company, told the reporter that various kinds of composite films, plastic bags, and other disposable packaging materials mixed with domestic waste, It accounts for a large proportion of plastic waste, which is the "backbone" of plastic pollution control, and is also an urgent problem to be solved in the recycling and high-value utilization of plastic waste.

Chemical recovery refers to changing the molecular structure of plastics into liquid or gas low molecular or even monomer small molecules, which can be used to manufacture new petrochemical products such as plastics, thus reducing the new demand for fossil fuels and reducing the impact of the production of plastics on the environment. When the chemical recycling of waste plastics is for the purpose of fuel and raw materials, a closed cycle is formed, which is called the chemical cycle of waste plastics.

Gao Yongping pointed out that the chemical recovery of plastics is a method of converting waste plastics into high-quality oil fuel or chemical raw materials, and is becoming the focus of scientific and technological research and development worldwide. At present, there are mainly pyrolysis, gasification, depolymerization and other technologies, among which pyrolysis technology has attracted the attention of researchers.

To what stage does plastic chemical recovery develop?

At present, the scale of the plant is difficult to be large-scale and the long-term continuous and stable operation is difficult

In recent years, under the background of global carbon emission reduction goals, the process of recycling waste plastics has been continuously promoted, and the chemical recovery technology of plastics has shown its vitality and innovation.

According to the data research of McKinsey Consulting, it is expected that the global plastic recycling rate will increase to 50% by 2030, and the proportion of chemical recycling may increase to about 17%.

Relevant foreign companies have started the layout of chemical recycling of plastics. As early as 2020, the renewable energy company Neste successfully carried out several test runs of liquefied waste plastics in the refinery in Finland.

ExxonMobil, an American oil and gas producer, has built the first large plastic waste chemical recovery facility in Texas. After putting into operation, the initial planning capacity is to recover 30000 tons of plastic waste annually.

Many enterprises in China are also developing plastic chemical recovery technology. Li Mingfeng, Chairman of Sinopec Research Institute of Petroleum and Chemical Technology (hereinafter referred to as "Sinopec Research Institute of Petroleum and Chemical Technology"), told our reporter: "At present, China and foreign counterparts are actively exploring the technology of chemical recovery and pyrolysis of waste plastics. The difficulties and main problems lie in the low yield of pyrolysis oil, the high content of impurities in oil, and the difficulty of large-scale and long-term continuous and stable operation of the unit."

It is reported that in order to solve these problems, Sinopec Institute of Petroleum Sciences has developed a complete set of chemical cycle technologies including the new continuous pyrolysis RPCC technology. In the RDC (stepped volume reduction and efficient liquefaction and dechlorination technology) unit, the mixed waste plastics are first subjected to stepped rapid liquefaction, at the same time, they are deeply dechlorinated, and then sent to the RPCC continuous pyrolysis unit for pyrolysis. The obtained pyrolysis oil is further processed to produce raw materials of plastic monomers, and then plastic products are produced, truly forming a closed cycle of plastics-waste plastics-olefins-plastics.

"At present, the complete set of chemical recycling technology for waste plastics has been tested in the laboratory and is ready to be transferred to the industrial side-line test stage." Zhang Zhemin, the project manager of Sinopec Institute of Petroleum Sciences, said that this technology can be applied to waste plastics produced in the production and living processes of waste plastics from landfills, waste plastics from paper mills, agricultural films, etc., and is expected to completely solve the problem of "white pollution" and the recycling of low-value waste plastics. These waste plastics are low-value waste plastics that cannot be physically regenerated or whose physical regeneration cost is too high.

When can China's plastic chemical recovery be applied in a large scale?

There are many types of waste plastics, and different technical schemes need to be adopted

"The world is doing technical research on the treatment of waste plastics by chemical recycling, but it has not yet achieved large-scale application, especially in terms of the large-scale treatment capacity of the plant," said Cai Zhiqiang, a senior expert of Sinopec Group. "Because there are so many types of waste plastics, different technical solutions need to be adopted, and the technology is very complex, and further research is needed."

According to Cai Zhiqiang, general plastic packaging includes plastic products made of pure polyethylene and polypropylene, such as automobiles, home appliance accessories, etc. There is also a considerable part of composite packaging, such as plastic-plastic composite, aluminum-plastic composite, paper-plastic composite, etc., which contains a variety of plastic, paper or metal materials. This kind of plastic waste has high requirements for recycling and treatment technology, and requires joint research on process development and equipment manufacturing.

"At present, the relevant tests of chemical recycling of plastics are being carried out, but the recycling system of low-value waste plastics in China still needs to be improved. How to collect and recycle low-value waste plastics and realize low-cost and efficient recycling is challenging and needs to be explored." Gao Yongping said, "The plastic components of plastic film residue are relatively simple and large, and it is easy to be recycled in a centralized way. Sinopec has started with the recovery and utilization of plastic film residue, and is planning to build a 10000-ton industrial experimental device in Xinjiang."

It is reported that because Xinjiang is relatively dry, cotton fields, corn and other crops need to be covered with film to keep water and moisture. If all the anti-aging plastic film specified in the national standard is used, the cotton field alone needs nearly 300000 tons of plastic film every year. The residue of plastic film residue in the farmland affected the growth of cotton roots, resulting in the yield of cotton seed per mu decreased from 500 kg to 600 kg to about 300 kg to 400 kg now.

In order to solve this problem, Xinjiang governments at all levels encouraged farmers and farms to recycle plastic film residues and replace old ones with new ones by building residual film recycling stations and combining with relevant subsidy policies. In 2021, the recovery rate of mulching film in Xinjiang has reached 81%, and the pollution of cotton field caused by the residual film of incremental mulching film has been effectively controlled.

"After the plastic film residue has been recycled and concentrated and professionally sorted by the partners, we will consider recycling it through chemical recovery technology and equipment." Cai Zhiqiang said frankly, "At present, this technology is relatively mature. I believe that with the support of the government, social attention and the efforts of scientists, it is only a matter of time before the chemical recovery and large-scale utilization of low-value waste plastics in other fields in the future."