What is the application status of advanced control?

In many practical engineering projects, advanced control is still used very little; instead, simpler control systems are more commonly employed. Most are still in the laboratory stage; the technology is fairly mature, but their transplantability is poor, which makes it difficult to promote them. The specific implementation must be configured according to the particular industrial process. Many of the advanced control techniques we learn in school aren’t useful in some companies. I think the maintenance effort for advanced control systems is considerable; although they are quite intelligent in terms of control, their implementation and maintenance are also complex. There’s a petrochemical project in our lab that requires frequent on-site maintenance!

Implementation of advanced process control (APC) technology in ethylene cracking furnaces: The relationship between the APC system and the interlock system – Operations of the APC system do not trigger system interlocks; when an interlock is activated due to feed rate issues, the temperature balance and overall load control functions of the APC system are automatically disabled. Relationship between the advanced control system and the original control system: The advanced control system for the cracking furnace is developed by building upon the original control system, introducing new control concepts and methods, correcting the issues present in the original system, and upgrading it as a result. The operation process is designed to be simple and clear; the entire procedure is logical and easy to understand, allowing operators to adapt to the new pre-control system operations quickly. The new control method is primarily COT control, with the control mechanism changing from one based on calorific value to one based on the flow rate of fuel gas. To counteract the effects of fluctuations in the calorific value of fuel gas on COT, the calorific value of the fuel gas (obtained through soft sensing) is used as a feedforward signal for the COT controller. This approach not only helps to mitigate the impact of delays in the signals generated by the calorific value meter on COT and reduces the system’s dependence on such meters, but it also allows the soft sensing algorithm to predict changes in calorific value in case of a malfunction of the meter, thereby ensuring the stable operation of the temperature control system. The new control system also enhances the operational flexibility and adaptability of the temperature equalization and total load control systems. Since the equalization of temperatures across the various groups of furnace tubes has a significant impact on the operating cycle of the entire cracking furnace, the new system places greater emphasis on achieving such equalization; it allows for a greater variation in the feed flow rates for different groups. Moreover, the activation and deactivation of the advanced control system can be done with just one button, making the operation simple. The hardware environment for implementing advanced control technologies is fully integrated into the operating environment of the HONEYWELL TDC-3000 distributed control system. All advanced control software is written in the CL control language and runs within the APM or HPM modules of the TDC-3000; as a result, very few requirements are placed on the automatic control hardware devices.

Advanced control sounds great, but it isn’t being used in our company. We are currently building a new plant for our project; it’s quite new.

Although numerous studies have reported the successful application of various advanced control technologies in catalytic cracking units, and although several companies in China have purchased advanced control software packages for such units or carried out upgrades to implement advanced control systems, very few of these systems can be used on a long-term basis; they often have to be shut down shortly after acceptance. The reason for this is that these operational advanced control systems share common drawbacks: to obtain the dynamic model of the actual production plant, these systems require a series of large-scale tests, which are not only costly but may also pose a risk of unstable operation of the production plant over extended periods of time. At the same time, when the equipment ages or is upgraded, during device maintenance, or when there are significant changes in the properties of the raw materials, it is also necessary to update the original dynamic model, which means conducting a series of new field experiments. Such experiments cannot be carried out by ordinary engineering and technical personnel, which poses significant difficulties in the use and maintenance of these software systems

It’s all just for show; advanced control systems are installed and a lot of money is spent, but in the end they’re not put into use. Waste.

When done well, the benefits of APC are evident within 3 years, in terms of improved control levels, reduced energy consumption, and less workload for operators. It is undeniable, however, that high-performing APC systems are a minority among all APC systems, as the effectiveness of APCs also depends on the basic control level of each plant as well as the skills of the maintenance staff (not only those responsible for the engineering implementation of APCs). APCs represent a trend in the process industry, but it is relatively difficult to implement them in Chinese process enterprises under the current conditions. This is also one of the reasons why companies such as ASPEN and HONEYWELL have reduced their focus on APC engineering implementation. At present, companies like Zhenhai Refining & Chemical Co. are doing well in this area!