【Ten Years of Rapid Development in Chemical Equipment】687-2022: Domestic production of the country’s largest alkylation unit with IPC intelligent control
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This post was last edited by Desert Fish on 2022-12-16 at 09:05. Witness the decade-long development of chemical processing equipment; praise the prosperity and strength of modern China. Replies are rewarded; discussions are welcome. ------------------------------------------- On December 11, in the central control room of the alkylation unit at the second refining production department of Guangdong Petrochemical Company, operator Liang Weiyong kept a close eye on the DCS control system, carefully monitoring the performance of various control parameters. Based on production requirements, it is easy to control the reaction pressure through operations such as one-click automatic control, one-click manual control, one-click cascade control, and one-click volume adjustment. Wang Heng, production manager of the Second Refining Production Department, explained that Guangdong Petrochemical’s 600,000 tons per year alkylation unit is currently the largest alkylation production facility of its kind in China, and its two circulation processes were brought online on December 11th. This set of devices has numerous and complex control circuits, including 107 regular control circuits and 24 complex control circuits. “The greatest operational challenge in the alkylation control loop is that the feed to the reaction units is controlled using a pressure control point to regulate the olefin feed flow to the 6 reactors; the flow rates of the 6 coolant feeds are controlled via a liquid level sensor on the coolant side. The reactor pressure is controlled through proportional control of the inlet flow rates at the reactor tubes. ”Wang Heng said. At the initial stage of operation, this device is prone to issues such as inaccurate calibration of flow meters and malfunctioning instruments. If the conventional traditional flow series PID control method is used, the flow rates of the six feed streams entering the reactor will be uneven, leading to pressure fluctuations in the acid sedimentation tank. Moreover, uneven amounts of coolant fed into each reactor will result in inconsistent temperatures within those reactors. Additionally, manual operation on a long-term basis places a high workload on the operators. To ensure the smooth start of pilot production in the alkylation unit, through technical discussions, the company’s management provided full support for the use of the IPC intelligent control system developed by Beijing Century Longbo Technology Co., Ltd., for the 600,000 tons per year alkylation facility. The company’s manager explained that IPC can be integrated deeply with other control systems, thereby fully leveraging the potential of Distributed Control Systems (DCS). Through efforts to address related challenges, it was decided to change the pressure control for the 6 reactor feed streams from one control point to six separate control points, one for each reactor feed stream. Similarly, the liquid level control for the 6 coolant feed streams was changed from one control point to six separate control points, each controlling its own stream. This approach effectively overcame the problems associated with uneven flow distribution, enabling precise control of the feed to the alkylation reactors and ensuring stable operation of the reactor temperatures and pressures. Developed to address issues such as inaccurate calibration of flow meters and instrument malfunctions that often occur during the initial stages of trial production, the PRD technology perfectly solves these problems related to malfunctioning flow meters, enabling automatic operation even when the flow measurement is inaccurate. Furthermore, the production process of this unit generates significant amounts of energy and material consumption. Coupled with a shortage of personnel, the successful application of IPC greatly enhances the stable operation of the unit by reducing the workload associated with repeated adjustments by operators as well as fluctuations in control parameters. It provides strong technical support for the feeding of olefins into the alkylation reactor and for the steady operation of the unit in the subsequent stages, thereby creating conditions for long-term and efficient operation of the unit.
APC (Advanced Process Control) is an abbreviation for advanced control systems; it enables an improvement in the stability of processes and a reduction in operational intensity. Yunnan Petrochemical has implemented this technology in seven of its main production units, with significant positive results. IPC (Intelligent Process Control) is an abbreviation for intelligent control systems; it represents an upgraded version of APC and features powerful intelligent functions. It serves as an important indicator and trend in the development of intelligent factories.
In 2021, Yunnan Petrochemical’s 13 million tons per year atmospheric and vacuum distillation unit was equipped with an IPC intelligent control system! On January 22, the atmospheric and vacuum distillation unit was put into operation for the first time using a fully integrated intelligent control system; the operation proceeded safely and smoothly, with a successful start-up on the first attempt. On January 24, temperature fluctuations due to thermal siphonage back into the tower occurred in the stripping tower of the atmospheric and vacuum distillation unit. Through optimization, adjustment, analysis, and processing by the intelligent control system, the fluctuations were eliminated in just 2 hours. For fluctuations like these, manual adjustment used to take a long time. The oxygen content in atmospheric-pressure and reduced-pressure furnaces has always been a key indicator for energy saving and consumption reduction in such installations. Through continuous optimization by the staff, this level has been maintained at around 2.5%. After the implementation of IPC intelligent control, it has now been reduced to 2%. Just this alone allows for the savings of 100 tons of fuel gas per year, while the target set for IPC intelligent control is 1.5%. Previously, the temperature deviation among the three circuits for heat exchange with crude oil after separation was 15°C; now, with intelligent control, this deviation is no more than 3°C, thereby improving the heat exchange efficiency.
IPC intelligent control is a new technology that has emerged under the guidance of the strategic plan for \"digital transformation and intelligent development.\" Compared to previous black-screen operations, the algorithms of its control system have undergone fundamental changes, and the development and application of new technologies require a process of exploration. The core of IPC intelligent control is to mimic human operations; it must be based on large amounts of production data, with more data leading to greater accuracy. Through the operations during its first cycle, Yunnan Petrochemical’s atmospheric and vacuum distillation units have accumulated a large amount of operational data and experience. It has also been identified which operational bottlenecks need to be addressed urgently, thereby creating the conditions for implementing intelligent control modeling. The application of IPC intelligent control in ten-million-ton atmospheric and vacuum distillation units is a first. “Thousand-ton atmospheric and vacuum distillation units feature numerous control loops, complex processes, and long workflows, presenting challenges in terms of multi-level structure, high dimensionality, strong non-linearity, and strong coupling that hinder their widespread application. ”Dr. Wang Wenxin, who was involved in the system development, said that overcoming these challenges requires a great deal of solid foundational work. The relevant parties analyzed production big data to determine the coupling relationships, upgraded 206 PID basic control loops to intelligent PID control, and innovatively carried out intelligent modeling.