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Currently, as water environments deteriorate increasingly and people become more aware of the need to protect the environment and reduce pollutant emissions, water treatment technologies and their efficiency have become even more important. The membrane process is considered to be the most advanced and cost-effective water treatment technology available today. Below is an application example of PLC control for a mobile container water truck using the MF+NF process, with a daily processing capacity of 360 tons. I. Introduction to Membrane-Based Water Treatment Processes Membrane filtration refers to the phenomenon in which, as a liquid passes through a membrane, some of its components are retained. In the water treatment industry, membranes generally refer to solid membranes with filtration pore sizes ranging from 0.0001 microns to 10 microns. Based on the manufacturing materials, membranes can be divided into organic membranes and inorganic membranes ； From a geometric perspective, they can be divided into flat membrane, spiral-wound membrane, tubular membrane, and hollow fiber membrane ； In terms of structural composition, they can be divided into single-layer membranes and composite membranes ； Based on the flow direction through the membrane, they can be divided into isotropic (symmetric) membranes and anisotropic (asymmetric) membranes. A filtration unit composed of multiple membrane units is called a membrane module. Due to differences in the molecular weight of the cut-offs, membranes are classified into reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF). It is roughly as shown in the figure below. Throughout the years, coagulation-sedimentation filtration and coagulation filtration have been widely used as pre-treatment methods in areas such as tap water, purified water for industrial use, ultra-pure water for semiconductors and power generation, refined water for pharmaceuticals and food, and seawater desalination. The aforementioned treatment method has been developed through years of technical accumulation, and it is capable of removing suspended solids from raw water sources such as river water, well water, lake and swamp water, as well as seawater. But at the same time, many problems have gradually arisen, such as: changes in water quality on rainy days complicating the addition of flocculants ； Deal with the increase in aluminum and iron ions as well as sludge production resulting from the use of flocculant agents in water treatment ； Equipment such as flocculation sedimentation tanks, sedimentation basins, and sand filtration systems occupy a large amount of space. To address the aforementioned issues, membrane-based water treatment processes were developed. Large MF membrane modules can not only replace coagulation-sedimentation filtration and coagulation filtration methods, but also purify industrial water through filtration (decontamination and clarification), thereby making it possible to replace the use of purified water as process water; this in turn promises to reduce the costs associated with process water. Compared with traditional water treatment processes, membrane processes have the following advantages: 1) High-quality water can be produced. Regardless of how the quality of the incoming water changes, it is possible to filter out water with a turbidity of less than 0.01 NTU. 2) Can operate automatically and is simple to use. 3) No coagulant is required; if one is used, only a small amount is needed. 4) The device occupies a small area. 5) The construction time is short. 6) It has a long service life. In normal use, there is no need to worry about membrane rupture caused by chemical corrosion or biological degradation. Figure 1: Comparison between membrane filtration and traditional sand filtration methods. II. Process flow of the membrane treatment system. The process flow of the membrane treatment system consists of three stages: filtration, backwashing, and air scouring and rinsing. Figure 2 shows the filtration process flow of the membrane treatment system. This system is an external-pressure circulating filtration system; the raw water does not require coagulation pretreatment. (However, in cases where components such as color that cannot be removed by membrane treatment alone need to be removed to achieve the desired removal rate, coagulants can be added.) ), large debris contained in the raw water (especially fibrous debris that tends to get entangled around the hollow fibers and make it difficult to remove) can be removed through pre-filtering before it is fed to the membrane modules. Figure 2: Filtration process flow. For long-term and stable operation, equipment that uses sodium hypochlorite (NaClO) solutions for backwashing along with air scrubbing also needs to be available. See Figure 3. Figure 3 shows the process flow for backwashing and air scrubbing. Figure 4 illustrates the flushing process flow of the membrane treatment system. Figure 4: Flushing process flow III. PLC control system At the request of the foreign party, the PLC uses a MITSUBISHI FX2N M80R CPU, along with 4 4AD and 1 4DA expansion modules. The touch screen uses a PRO-FACE GP2500T 10.4-inch color screen (with TCP/IP interface). The frequency converter uses the ABB ACS350 series. SCHNEIDER low-voltage electrical equipment is used. In actual use, it is found that the SIEMENS S7-200 PLC combined with a TP270 touch screen offers greater technical and functional advantages. Control functions of PLC: 1) Use of step programs to implement logical sequence control for the processes of filtration, backwashing, air scouring, and rinsing. 2) PID function. The built-in PID function block of the FX2N is utilized to control the input setpoint of the inverter via 4DA, thereby adjusting the frequency of the filter pump and achieving constant flow control. 3) Operation status and fault signals of various equipment, as well as the acquisition of temperature, pressure, flow rate, and level signals, and the control of various pumps, air compressors, and pneumatic valves. Control functions of the touch screen: 1) Manual/automatic control via the touch screen; 2) Display of the process flow; 3) Manual operation; 4) Display and adjustment of process parameters; 5) Setting of PID parameters; 6) Operation for checking membrane leaks; 7) Manual CIP cleaning operation; 8) Alarm display, storage, retrieval, and printing functions; 9) Display, retrieval, and printing of analog signal trends; 10) Data recording, display, retrieval, and printing functions; 11) Optional remote monitoring via TCP/IP. Figure 5: Main process flow screen; Figure 6: Process parameter setting screen; Figure 7: Trend curve screen
1. Introduction The central control system of the CNPC Hai 9/10 jackup drilling platform uses a PKS system. This is the first time that Honeywell’s automation system has been applied on a drilling platform. Certified by CCS (China Classification Society) and meets the certification standards. 2. System Introduction PKS (Process Knowledge System) is the abbreviation for Process Knowledge System. The PKS control system is a new medium-sized control system introduced by Honeywell in June 2002. It is a completely new DCS control system that combines the convenient configuration features of the Plantscape system with the hardware advantages of the TPS control system. 2.1 The framework of this system is as follows: In this PKS system, there are 2 FSC (FAIL SAFE CONTROLLER) cabinets and 1 PCS cabinet. The FSCs are used for the logical shutdown of the fire and gas protection systems, while the PCS cabinet is used for monitoring the condition of the ship’s hull. The systems are connected to each other via FTE (Fault-Tolerant Ethernet connections). There are two redundant servers, as well as two stations for monitoring purposes. (1) Server redundancy: The servers in the PKS process system can be configured in a redundant manner to provide a higher level of reliability. A pair of servers with identical configurations are used to support each other in a primary/secondary configuration. When the main server fails, data is collected from the secondary server, which then provides data services to the operation station. The primary server transmits all data processing information from the database to the secondary servers via a redundant network, thereby ensuring synchronization between them. (2) Network redundancy \ Switch redundancy: Devices are connected to each other using HONEYWELL’s fault-tolerant Ethernet technology (i.e., the H-type configuration, which ensures 4 communication paths). 2.2 Hardware configuration （1）The hardware of the FSC system consists of a Central Part card and I/O cards. The Central Part, abbreviated as CP, includes the CPU, COM (communication card), WD (system status monitoring card, also known as watchdog card), DBM (diagnosis and battery card), and VBD (vertical bus drive card). I/O cards include DI cards, DO cards, AI cards, and AO cards. The communication between the central card and the I/O cards is as follows: VB is connected to VBUS (the vertical bus), VBUS is connected to HBD (the horizontal bus drive card), HBD is connected to HBUS (the horizontal bus), and HBUS is then connected to the I/O cards. There are also terminals and relays inside the cabinet. (2) PCS cabinet hardware configuration It consists of one FTEB (fault-tolerant Ethernet bridge) card, one C200 (controller) card, two CNI (CONTROL NET) cards, and I/O components. The image above is the card status monitoring page. In the figure, FTEB01: FTEB card ； PRS021: C200 card ； CCN014: CNI card ； IAH161: AI card ； IDD321: DI card ； ODD321: DO card ； (3) Network structure 1) Ethernet (TCP/IP) Transmission rate: 100M/10M baud rate ； Network nodes: server, station, printer (switch, hub), etc ； Transmission medium: Twisted pair: connector (RF45, network card), distance within 100m ； 2) I/O Controlnet Transmission speed: 5M baud rate ； Network nodes: PMIO (I/O card), SIM, etc ； Transmission medium: Coaxial cable ； A 75Ω resistor must be added to the network terminal ； Transmission protocol: IEEE8023, token-based ； 2.3 Software Introduction (1) Control Builder – Control Builder is a graphical, object-oriented, window-based engineering tool used for the design, configuration, and implementation of control strategies in both the control execution environment of process system controllers and the application control environment. It is used to configure hardware such as networks, I/O modules, controllers, and fieldbus devices, as well as control points such as regulation control, device (motor) control, logic control, sequence control, and special user-defined functions. (2) QUICK Builder — QUICK Builder enables users to configure third-party controllers/RTUs, as well as their points, configuration workstations, and printers. Quick Builder uses a relational database engine, offering user-friendly views for filtering databases, multi-point editing tools, and an intuitive window-based user interface, which greatly improves configuration efficiency. Relational databases also provide user-defined fields that can be used to set scheduling deadlines, record wiring numbers, etc., and they also offer standard reports. Additions and modifications to the ExperiOn PKS process system database can be performed online. (3) HMIWeb Display Builder —— HMIWeb Display Builder is an object-oriented, fully integrated user interface configuration tool used to generate customized display graphics for users. Dynamic displays can be quickly generated simply by a mouse click. The system also provides a graphics library containing common industrial equipment such as containers, pipes, valves, tanks, motors, etc., to help users further accelerate the speed of graphic design. Furthermore, for similar images that are used in multiple places, the template image feature can be used to reduce configuration time. The provided process objects and palette functions enable users to create user objects quickly and easily, with 3D effects. By using script program (VBScript and JScript) components, the functionality of graphical interfaces can be significantly enhanced; tasks such as high-speed animations, tooltips, and control over the execution of station programs can all be accomplished through script programs. Many types of ActiveX components, such as those for playing sound and video images, can be inserted into the screen and invoked there. (4) Knowledge Builder —— Knowledge Builder is an online electronic resource that can be viewed in a browser using HTML format; it offers comprehensive content, including detailed information on FSC, PKS, and more. 2.4 System Openness Integration with Honeywell’s previous products: TDC2000, TDC3000, Plantscape, S9000, Logix60 Communication with PLCs (such as SIMENSE, AB, ABB) Integration with fieldbus technologies (Profibus-DP, Fieldbus, Modbus, HART, etc.) Standardized data access procedures AEC: High-performance servers for direct data exchange with OPC servers or clients. 3. System Applications The system is applied on drilling platforms and mainly has two functions: hull monitoring and logical shutdown. Hull monitoring: includes the condition monitoring of generators, mud pits, cement tanks, barite tanks, seawater ballast tanks, airlocks, fans, fire pumps, and utility equipment. Logical shutdown: Includes the logical shutdown resulting from alarms such as those from the fire detection system and manual alarms. Main interface: (1) Hull monitoring Hull monitoring connects the signals from hull equipment to the PCS cabinet via hardwired connections. The status of the device is then monitored through the display on the host computer. The figure below shows the monitoring of the generator and TANK: (2) Logical shutdown: The probe types are as follows: The fire probes, smoke probes, manual alarms, and heat sensors shown in the above figure collect data via on-site probes, which are then sent to the logical system within the FSC in WORD format through the MODBUS protocol. Hydrogen sulfide probes and combustible gas probes are connected to the FSC system via hard wiring. Depending on their location, the probes are divided into various fire zones; each fire zone has different alarms, and the devices that are shut down in response to those alarms also vary. The specific shutdown process is shown in the figure below: 4. Conclusion The Honeywell PKS system has entered the drilling platform manufacturing industry thanks to its robust performance, and has achieved certain results. Let’s witness together its development prospects in this industry!