Application of DeLtaV DCS in the water-coal slurry pressurized gasification unit of our plant

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The slurry coal gasification unit in our plant’s gasification workshop is the first set of production equipment in China to adopt the \"slurry coal gasification for syngas production\" process developed by Texaco. This process features strong adaptability to different types of coal, low raw material consumption, high carbon conversion efficiency, and minimal generation of waste, making it one of the mainstream approaches in modern coal gasification technology. 1 Introduction to the DeLtaV DCS Control System: The slurry coal gasification unit features a high level of instrument automation, with numerous complex logical automatic control systems in place, such as the gasifier safety system, lockhopper system, flash vaporization system, and oxygen-to-coal ratio control. To implement the above complex control scheme, the DCS control system requires a high level of software programming capability and system stability. Our plant’s water-coal slurry pressurized gasification unit uses the DeltaV control system from Fisher-Rosemount in the United States. The DeltaV control system is a large-scale distributed control system developed by Fisher-Rosemount. It utilizes the state-of-the-art fieldbus technology available today, and features high reliability and excellent cost-performance ratios. A large DeltaV control system can consist of multiple servers, thereby dividing the system into several domains. Each domain can be composed of an independent server, a system network, and multiple field control stations, enabling relatively independent data acquisition and control functions. Operator stations and advanced computer stations can log in to different domains using domain names to perform operations. The network of the DeltaV control system is divided into three layers from top to bottom: the management network, the system network, and the control network. The system network enables the interconnection between the engineer station, operator station, system servers, and field control stations, while the control network facilitates communication between the main control unit and the process I/O units. ? 1.1 Technical features of the field control station: (1) Each field control station is equipped with two controllers, one primary and one secondary, which provide redundancy to ensure system reliability and enable seamless switching. (2) 1:1 redundancy for power supplies to ensure the stability and reliability of the power system. (3) I/O card redundancy ensures the reliability of the data acquisition and transmission system. (4) Network redundancy: Each field control station is equipped with two sets of system network interfaces, enabling a dual-redundancy structure for the system network and ensuring the reliability of the network system. (5) Dispersed isolation measures to ensure the safety and reliability of the system. (6) It features live plug-and-play functionality, facilitating operation and maintenance while ensuring safety and reliability. (7) It has the capability for self-diagnosis of system faults as well as a fault indication function, which facilitates fault troubleshooting. (8) Control solutions are implemented using a variety of configuration programming tools to meet the different requirements on site, thereby satisfying the customer’s control needs. 1.2 Internal structure of the field control station (as shown in Figure 1)? http://www.nmtech.com.cn/jishuwang/upload/060123936443458.jpg Figure 1: Internal structure of the field control station. 2 Hardware configuration of the DCS control system for the water-coal slurry pressurized gasification unit: The DCS control system for this unit consists of 3 pairs of controllers along with corresponding power supply units and I/O units, 5 operation stations (OP1–OP5), 1 engineer station (PLUS), 1 communication workstation, two HUBs, and a redundant communication network. The system network structure is shown in Figure 2. http://www.nmtech.com.cn/jishuwang/upload/060123937315909.jpg Figure 2 Network structure diagram of the DCs control system; solid lines represent the main network ； Dashed line — Secondary network. 2.1 Controller: The controller is based on a high-performance microprocessor and is capable of performing various process control calculations such as PID, ratio, and integral control, in accordance with the user’s configuration. It obtains information from the field through sub-expansion buses and related I/O cards, and outputs control signals that are sent to the field to carry out process control. It is the core of implementing process control and can be regarded as the brain of the system. The system is equipped with 3 pairs of controllers, with each pair serving as a redundancy for the other. Among them, Controller 1# controls the A# gasification furnace system, Controller 2# controls the B# gasification furnace system and the old flash vaporization system, while Controller 3# controls the C# gasification furnace system, the new flash vaporization system, and the gasification utility systems. The field control station is composed of 3 controllers along with the corresponding power supply units and I/O units; it performs functions such as collecting field signals, performing unit conversions, and transmitting data and diagnostic results to the operator station via the system network. 2.2 Operation Station? The operation station is the human-machine interface of the system. DELL industrial PCs are used, with a structure that is largely similar to that of ordinary PCs. It can perform various functions such as process monitoring, operation, call trend analysis, event logging, and the generation of printable reports. 2.3 PLUS Station: The PLUS Station is the main station of the system. Each system has only 1 PLUS station, and the system’s database is located on that PLUS station. Most of the work for instrument engineer configuration is also carried out at the PLUS station. After the configuration is completed, it needs to be downloaded to the controller to update its program. 2.4 System Network The DCS control system network is divided into two levels, from top to bottom, namely the system network and the control network. The system network enables the interconnection between the field control station and the system operator station. The control network enables communication between the field control station and the I/O units. The communication station is configured for future network scheduling. 2.5 Field Control Station (see Table 1) http://www.nmtech.com.cn/jishuwang/upload/060123938178725.jpg 3 System Software: The DeltaV system software is installed on Windows NT 4.0 and includes various applications, which can be divided into two main categories: engineering control configuration tools and operator operation configuration tools. 3.1 Engineering Control Configuration Tool The DeltaV system engineering control configuration tool is a development platform used for creating configured engineering control solutions; it includes a control solution editor and a simulation debugger, forming a complete software package for control editing and debugging. The instrument I/O measurement points of the water-coal slurry pressurized gasification unit are divided into five categories: analog input (AI), analog output (AO), digital input (DI), digital output (DO), thermocouple input (TC), and resistance temperature detector input (RTD). It features single-loop PID control, as well as various control schemes such as oxygen-to-coal ratio adjustment, cascade control, stratified control, median value selection, and temperature and pressure compensation. The control scheme design is implemented using programming tools such as FBD function blocks and ST language. ? 3.2 Operator Configuration Tool The DeltaV system operator configuration tool is a software application used to create operator monitoring interfaces; it is employed for drawing flowcharts, trend reports, alarms, operation logs, etc., providing operators with a platform that facilitates the monitoring of the system’s operational status. It is possible to assign usage permissions to the control stations, creating users with different levels of access such as supervisors, operators, and engineers, so that various operation control functions can be implemented based on those respective permissions. The operation records and historical trends generated by the system facilitate the analysis and determination of fault causes. 3.3 Steps for configuring the DeltaV system? (1) System configuration: The physical network of the system is established by adding nodes, I/O cards, and defining I/O channels. (2) Configuration of the control scheme: Design the control scheme based on the control requirements, divide the areas and establish modules, and set the module parameters. (3) Flowchart configuration: Static flowcharts are created using the drawing software provided by the system or other drawing tools; PowerPoint was used to achieve a better visual appearance, followed by the establishment of dynamic data links. (4) Trends, report configuration. 4 System Debugging (1) Single-channel debugging of I/O measurement points: For all channels on all I/O cards, analog signals are sent using a signal generator for testing; the measurement accuracy is high and the measurement errors are within acceptable limits. (2) The manual and automatic control in the control room of the control circuit operates properly; the valves move to their intended positions accurately. Smooth switching between manual and automatic control is possible, meeting the process requirements. (3) Special control schemes such as cascade control, median selection, and ratio control have been tested successfully and meet the process requirements. (4) The redundant switching tests for the controller and power supply card proceeded normally and stably, enabling long-term stable operation of the system. 5 Conclusion The application of the DeltaV DCS control system in the water-coal slurry pressurized gasification unit of our plant’s gasification workshop has shown that this system is easy to operate, stable in performance, and its control strategies are safe and reliable, fully meeting the process requirements.