Treatment after styrene polymerization
Thread Content
Although the polymerization of styrene can be well controlled in theory, many non-human factors can still cause polymerization in pipelines or equipment. Once polymerization occurs, what is usually done to deal with it? Our factory once experienced a power outage, which led to the polymerization of a pipeline and a circulation pump. No matter how many times it was rinsed with ethylbenzene or styrene, the polymer content remained above the allowed limit (the purity of high-quality styrene should be at least 99.7%, while the polymer content should be below 10 PPM). It might be within acceptable limits for a few hours after rinsing, but this did not solve the problem fundamentally. We asked many experts, and all of them said there was no solution other than replacing the pipelines and the pump! That’s why styrene plants become increasingly difficult to operate as they progress further; just thinking about polymerization that can be carried out visually is terrifying! ! ! I hope that experts and friends have good solutions; I would be grateful for your advice!
Styrene polymerization is indeed the most challenging issue in styrene production, one that requires serious attention from relevant experts. Our production technicians should also draw lessons from actual production experiences, encourage everyone to share these insights, and work together to improve styrene production!
I know that in our styrene storage tanks, a buildup once formed at the breather valve; it was removed by hitting it with a hammer. The antipollution agent we use is TBC. It would be better if your circulation pump had a backup generator, so it can keep working even in case of a power outage
Styrene is the easiest to polymerize; it is theoretically possible to fully control its polymerization, but this is impossible in actual production. The best way to achieve control is by starting from the design of the entire process. For the dehydrogenation pipeline after ethylbenzene dehydrogenation, it is preferable to keep it as short as possible; I think using the foreign Fina technology (with an external intermediate heat exchanger between the two reactors and a set of three-stage vertical combined heat exchangers) is a good option. Improved quencher--------In a very short period of time, styrene crosses its temperature range where self-polymerization is most likely to occur, thus providing an improved effect in preventing the self-polymerization of styrene. Improve the layout of the entire device to make it more rational. ----------------------The above are some of my own views; they are rather general and incomplete, so I hope others will add to them.
The dehydrogenation gas pipeline in FINA technology should be longer, as the intermediate heat exchanger is located externally and there are two additional large elbows that help to position the three-in-one heat exchanger upright. However, styrene in the dehydrogenation gas does not polymerize; polymerization of styrene mainly occurs in the liquid phase, especially at higher temperatures in the distillation unit, where polymerization is more likely to take place. It is hoped that better polymerization inhibitors can be developed. Additionally, process improvements should be considered to reduce dead zones. For components that do not tend to polymerize under normal operating conditions but may do so after shutdown, such as the three-in-one heat exchanger and compressors, it is necessary to consider using ethylbenzene and polymerization inhibitors after shutdown
Polymerization is inevitable; my equipment has also encountered issues with polymerized styrene in pumps, vent valves in storage tanks, and steam-water mixers. There isn’t a very good way to address this problem. Especially after polymerization occurs, it’s impossible to remove the polymer completely. The solution is to open the equipment for cleaning; if the polymerization isn’t complete, it’s usually still possible to clean it. If the polymerization is complete, the only option is to replace the equipment.
Our company has a highly effective styrene polymerization inhibitor, BL-628D, which is used at Qilu Petrochemical, Daqing Petrochemical, and Lanzhou Petrochemical. Dushanzi Petrochemical has already used it, and the results are excellent; you might consider giving it a try.
I’ve encountered the same problem as well; I’ve been driving for almost a year now but still haven’t experienced any aggregation, probably because the time period is too short and there are no devices for rapid cooling.
What is the temperature range in which self-polymerization occurs most easily?
To answer everyone’s questions better, take a look at some technical articles from Shanghai University of Petrochemical Technology. I hope it can be inspiring to everyone. New Technology for Styrene Quenching Systems I. Overview Styrene is one of the important basic organic chemical raw materials, and its main use is as a material for producing synthetic materials, particularly styrene-based synthetic resins. The catalytic dehydrogenation of ethylbenzene is the most important industrial method for producing styrene today. As shown in Figure 1, the basic principle of the ethylbenzene dehydrogenation process used in China to produce styrene is as follows: Steam is superheated to 800°C and fed into the reactor together with the raw material; the dehydrogenation reaction takes place at temperatures of 550–650°C, under normal or reduced pressure, with a water-to-oil ratio (by mass) of 1.0–2.5. The reaction products then pass through a condenser and a compressor before entering the separation tower. The dehydrogenation gas exiting the ethylbenzene dehydrogenation reactor has its temperature reduced to around 120°C after passing through a combined heat exchanger. To prevent polymerization, the temperature of the dehydrogenated gas in the quencher is rapidly lowered to the dew point temperature to pass through the styrene polymerization stage. Therefore, poor quenching efficiency of the quencher will directly lead to the polymerization of styrene, block the pipes, and at the same time cause the saturation temperature of the dehydrogenated gas to be too high, increasing the load on the main cooler. The styrene quenchers used in the past generally suffered from poor quenching efficiency and a tendency to clog, which affected the progress of subsequent processing stages. The main reason for the unsatisfactory quenching effect of the quencher is the poor atomization of the quenching water, which affects the heat and mass transfer between vapor and liquid ； At the same time, the coverage area of the spray nozzles using a simple linear distributor is limited, and the arrangement pattern of these spray nozzles needs further improvement ； Furthermore, the styrene quenchers used in the past were prone to clogging, which severely affected their service life. Therefore, it is highly necessary to develop and design efficient new types of quenching equipment. II. Main Technical Specifications and Features The development of the new styrene quencher began in early 2002. We applied theories and principles such as chemical engineering and fluid mechanics, and adopted a method that combines cold model testing with CFX simulation calculations, to develop a new type of styrene quenching device technology. The new type of quencher utilizes an optimally designed tube-type distributor in combination with specially designed nozzles, which ensures uniform flow distribution and excellent atomization effects. **This improves the heat and mass transfer between gas and liquid within the quencher, enabling uniform mixing of the two phases. At a system pressure range of 0.28–0.35 Kg/cm2, the temperature of the dehydrogenation gas can be instantly reduced from around 120°C to 70–75°C, effectively solving the problem of poor quenching efficiency that is common in styrene quenchers in China. At the same time, the nozzles used in the new type of quencher have been specially designed and manufactured, which effectively solves the problem of easy clogging of the nozzles and can **extend the service life of the quencher. It can meet the requirements of the styrene process well. III. Industrial Application The new type of styrene quencher was put into use in November 2004 at Qilu Petrochemical’s 60,000-ton/year styrene production facility. Under system pressures of 0.3–0.35 Kg/cm2 and an inlet dehydrogenation gas temperature of 119–123°C, the outlet dehydrogenation gas temperature could be reduced to 71–75°C. Since its introduction, the new type of quencher has been operating smoothly without any blockages, and it meets the requirements of the styrene production process very well. IV. Awards and Intellectual Property Two Chinese patents have been applied for for the new styrene quenching technology.