China: recycling of vinyl chloride - new technologies? 

When do you hear about “new technologies?” in PVC recycling, I immediately want to check where the real developments are and where they are just repackaging old ideas for grants. There is a lot of noise in the industry, but the bottom line often comes down to pyrolysis and chemical recycling - the issue is the efficiency and economics of the process, especially for complex wastes like vinyl chloride.

Where do the main difficulties lie?

The problem is not to decompose PVC thermally - this has been done for a long time. The difficulty is in chlorine. When heated, it splits off, forming hydrochloric acid, which corrodes equipment and requires complex gas cleaning systems. Many ?innovations? In recent years, they have been trying to solve this problem: either selectively remove chlorine at an early stage, or convert it into safe salts immediately in the reactor. But lab results often fall apart when scaled up. I remember one project with a circulating fluidized bed never reached a continuous cycle due to problems with erosion of internal elements - chlorine did its job.

Another point is the heterogeneity of raw materials. In practice, vinyl chloride waste is rarely clean. These can be mixtures with plasticizers, fillers, and other polymers. Pure PVC technology may produce unpredictable product yields in a real waste stream. Therefore, many developments now include a stage of pre-sorting or modification of the process for “dirty” processing. raw materials. This increases capital costs, which becomes critical for many plants.

And of course, the economy. The most advanced method costs nothing if the cost of disposal of a ton of waste exceeds the cost of primary raw materials or penalties for disposal. In China, this is interesting: environmental regulation is becoming stricter, and many enterprises are looking for solutions that are not “the most advanced,” but rather effective and at the same time cost-effective. This stimulates the emergence of hybrid systems, where, for example, pyrolysis is combined with the production of commercial HCl or the solid residue is used in building materials.

Experience from design work: from drawing to workshop

In our practice, inChengdu Yizhi Technology Co.(this is a design institute created by Huaxi Technology), you often come across a request for a “full cycle”: not just to sell an installation, but to design a system for the customer’s specific waste. One of the latest projects is the modernization of a recycling line for a cable insulation manufacturer. There was a complex composite: PVC, polyethylene, traces of copper. Standard pyrolysis produced low-quality oil and problems with gas purification.

We had to combine: mechanical separation to remove metal, then two-stage low-temperature pyrolysis with the supply of additives that bind chlorine into the solid phase at the first stage. This made it possible to reduce corrosion and obtain cleaner pyrolysis oil from the second stage. But the key was not the equipment, but the modes - they were selected for almost six months at the pilot installation. Information about such integrated approaches can sometimes be found in materials onhttps://www.yzkjhx.ru, where we share some non-confidential case studies.

Not all attempts are successful. There was experience with the introduction of catalytic hydrochlorination to obtain chlorobenzene from the gas phase. The technology is beautiful, but the catalyst turned out to be extremely sensitive to sulfur impurities in the waste. The project was frozen at the stage of semi-factory testing - the economic calculations no longer converged. Such failures, by the way, are more important than many successful reports. They show where the limits of applicability of “paper” are. technologies.

What's really new on the market?

If you filter marketing, several areas look promising. The first is combined processes, where PVC recycling is integrated into a larger technical process, for example, in cement kilns or metallurgy. Here chlorine is not a problem, but a resource. But this requires synergy between different industries, which is gradually being developed in China through eco-industrial parks.

The second is solvent-selective methods. There are developments where, using certain solvents at moderate temperatures, PVC is selectively extracted from mixed plastics or dechlorinated. This is more energy efficient than high temperature processes. So far, this is mostly laboratory work, but several Chinese scientific groups, including collaborations with institutes like ours, are already conducting pilot tests.

And the third thing is numbers. Not the recycling itself, but its management. The implementation of IoT systems for monitoring process parameters in real time (temperature, pressure, gas composition) allows you to optimize modes for changing raw materials. This is not a revolution in chemistry, but a serious step towards stability and profitability. In some projects we use such systems to control pyrolysis reactors - this reduces the percentage of rejects (substandard oil or residue).

Practical nuances that are rarely written about

The implementation of any technology comes up against “low” limits. matter. For example, preparation of raw materials. PVC waste often comes in large pieces or rolls. They need to be crushed to a homogeneous fraction. Crushers and shredders for PVC are a different story: the plastic is viscous, the knives wear out quickly, especially if there are abrasive fillers. Equipment suppliers rarely focus on this, but it is a direct item of operating costs.

Another question about leftovers. Even after effective pyrolysis, a carbon residue (coke) remains. It needs to go somewhere. Ideally used as a sorbent or filler. But to sell it, it must meet standards. In practice, it is often simply sent to a landfill as inert waste, which eats up part of the profit from disposal. Real projects consider the economy taking into account this “tail”.

And the human factor. Plant operators are not engineers. The technological map must be extremely clear. There were cases when a shift, trying to increase the oil yield, arbitrarily increased the temperature in the reactor. The result is a sudden release of hydrogen chloride and the gas cleaning system is down for repairs. Therefore, now new projects include not only hardware, but also detailed regulations and simulators for operators.

Looking ahead: where the industry is heading

I think that in the next 5-10 years we will not see one “breakthrough” one. technology that will solve everything. There will be evolution and adaptation of existing methods. The focus will shift to flexible, modular, mid-capacity plants that can be placed close to the waste source, reducing logistics. This is especially true for China, with its dispersed industry.

The second trend is deep processing of waste products. Not just pyrolysis oil as fuel, but its purification into chemical raw materials. Or the use of the gas phase for synthesis. This increases the margin of the entire process.Chengdu Yizhi Technology Co., Ltd.With its registered capital of 120 million yuan and the experience of its parent Huaxi Technology in chemical technology, it is precisely oriented towards such complex turnkey projects. - from laboratory to operating production.

Finally, tightening environmental regulations will be a driver. Not only burial bans, but also standards for emissions of dioxins and furans when processing chlorine-containing waste. This will automatically weed out artisanal methods and create a market for technologies with guaranteed purity of the process. Those who invest in research and pilot lines now will set the standards tomorrow. The main thing is not to chase the big word “new”, but to consider the full life cycle of the technology, from the loading of raw materials to the fate of the last gram of residue.