1. Introduction Guangdong Southern Alkali Co., Ltd. is a large-scale state-owned chemical enterprise in Guangzhou. It is the only large-scale soda ash producer south of the Yangtze River with an annual output exceeding 200,000 tons, ranking among the top ten soda ash producers in China. It is also the only enterprise in China that integrates salt and alkali production. Due to its regional advantages, resource advantages, and geographical advantages, it possesses strong market competitiveness. Currently, enterprise informatization is too superficial, and further in-depth informatization faces serious challenges. To further promote enterprise informatization, this paper proposes that the solution lies in integrated management and control. Therefore, a PROFIBUS-based remote monitoring process automation network system was established for Guangdong Southern Alkali Co., Ltd., and integrated with the information network, realizing integrated management and control and remote monitoring of the production process. 2. System Requirements The control network system of Guangdong Southern Alkali Co., Ltd. networks 14 monitoring and control points across 6 production workshops in the plant area. Nearly 2,000 analog quantities of temperature, pressure, flow rate, and liquid level, as well as various actuator switch quantities and analog quantities, are centrally monitored during production scheduling; the monitoring results are sent to the main computer in the central control room. The control stations are allocated as follows: Lime Workshop: Lime Station; Heavy Alkali Workshop: Carbonation Station, Evaporation Station; Calcination Workshop: Calcination Station; Compression Workshop: Compression Station, Brine Station; Thermal Power Workshop: Boiler Station #1, Boiler Station #2, Boiler Station #3, Turbine Station #1, Turbine Station #2; Salt and Nitrate Workshop: Salt Production Station, Nitrate Extraction Station, Refrigeration Station. Each control station is required to adopt a distributed I/O design to reduce system cabling, minimize system failures, and facilitate inspection and maintenance. The main controller can independently monitor the actual parameter values ​​of field equipment and instruments in its assigned workshop, and can also automatically and independently control the equipment. The industrial computer connected to each field controller can locally display the production process, instrument parameters, equipment status, and other operating conditions of its assigned workshop. It can also be manually or automatically controlled by field operators and can provide audible and visual alarms. 3 System Design and Implementation Based on the above requirements, when selecting the structure of the control network, we focused on studying the advantages and disadvantages of the currently popular DCS and FCS. We examined many aspects such as the feasibility of implementation, performance-price ratio, ease of maintenance, and system scalability. Finally, we selected FCS, based on PROFIBUS, and used Siemens S7-300 series to form a distributed monitoring network. 3.1 System Network Structure Slave workstations of the control network are set up at the control points of each workshop. Each workstation is equipped with an industrial control computer, an S7-300 series PLC CPU315-2DP, and an I/O interface module. The slave workstations are connected to the control center using a PROFIBUS bus. A monitoring server is set up in the control center as the master workstation of the control network. Its network structure is shown in Figure 1. 3.2 System Composition (1) Enterprise Local Area Network Using web technology, the homepage of Guangdong Nanfang Alkali Manufacturing Co., Ltd. (www.nfsoda.com) is built to realize: a) Information release. Information is released to the outside world through the web server; b) Internal information exchange. Internal documents, notices, phone books, address books and news, etc.; c) Workflow processing platform. Scheduling, resource reservation and collaborative work; d) Email; e) BBS technical forum; f) E-commerce. The network system of Guangdong Southern Alkali Co., Ltd. should meet the requirements of C/S application and web-based B/S application. The local area network should be an intranet. The enterprise local area network server connected to the monitoring network can carry 124 terminals to realize the connection between the enterprise and the world. (2) Data acquisition and monitoring system design According to the characteristics of the data acquisition and monitoring system of Guangdong Southern Alkali Co., Ltd., it is proposed to use Siemens' fully integrated automation products. The data acquisition subsystem is constructed using Siemens' fully integrated automation products, using the S-300 series CPU315-2DP and PROFIBUS-DP communication module, expansion I/O module, etc., and is integrated through the PROFIBUS bus; it is connected to the Internet through the Win CC control center. The Win CC production process data is transmitted to the company's homepage in B/S mode through our self-developed information system public service platform. This allows all network workstations to browse real-time production process data. a) A Win CC-based server serves as the master workstation. A Win CC-based server is set up in the production scheduling and control center, connecting the PROFIBUS bus to the industrial Ethernet. Win CC is used to configure the industrial processes of all slave stations, enabling monitoring of real-time production data from all workshops. The Win CC-based server directly connects to the company-level information resource server. Through our self-developed data exchange platform, real-time production data is published on the information resource server in a B/S (Browser/Server) manner. Remote access and monitoring can be achieved via the network, similar to a scheduling center. The monitoring software running on the main computer in the central control room can display the entire plant's production process diagram, dynamically displaying the status and parameters of all equipment and instruments, and monitoring the production process. It tracks trends for important parameters and provides system alarms. The system also allows for on-site equipment control and parameter modification, enabling centralized scheduling of the enterprise's production process. This system can simulate and display alarms for pressure, temperature, and liquid level in the chemical production process. It displays the operating status and provides fault alarms for valves, fans, and pumps. The flowcharts on the monitoring screen are designed based on the actual production process, greatly facilitating operators. b) Siemens S7-300 PLC as a slave workstation. The powerful functions of Siemens S7-300 enable it to perform complex control functions whether operating independently or connected in a network. Therefore, S7-300 has a very high performance/price ratio. Due to the large number of points detected by the system, the slave station is composed of an industrial control computer connected to the S7-300 PLC and a distributed I/O ETT200M. The industrial control computer is configured with Protool to control the production process, and the operator can achieve local control. c) Profibus fieldbus realizes the connection between master and slave stations. All slave workstations are connected by Profibus. The total length of the bus is 2878m. Two bus RS 485 repeaters are set between the two longer slave stations. Due to the harsh environment of the factory area (severe salt and alkali pollution on the ground), the overhead wiring method is adopted and protected by composite PVC pipes. All buses and shielding layers are connected together and grounded at one end for lightning protection. (3) Enterprise information exchange platform. In information-based enterprises, there are multiple data sources. For data such as ERP data, financial data, and warehouse management data, based on the current status and technological foundation of information technology and industrial automation in my country, we have developed this platform for information-based enterprises. This resulted in the development of a commercially available, embedded database management system with independent intellectual property rights, designed for large-scale data querying and processing. This system can run on multiple platforms, including DOS, Windows, Unix, Linux, and embedded operating systems. It should feature low resource consumption, high operating efficiency, and fast logical query speed. The successful development of this system can solve many problems of "using databases but not actually using databases," and has excellent application and commercial prospects. Simultaneously, the commercialization of real-time databases can compensate for the deficiencies in my country's system software, promoting the realization of the goal of domestically produced system software. The main research contents include: • Public data interfaces for project and process management systems of ERP, CRM, and SCM; • Data exchange middleware for product data management systems of CAD, CAE, CAPP, and CAM; • Service platforms for office automation and decision support systems; • Interfaces for inter-enterprise collaboration and visualization tools; • Model library exchange software for knowledge base models, including persistence analysis models, decision models, enterprise collaboration models, visualization models, IPR models, and network models; • A database engine based on a C/S computing model and parallel algorithms, enabling fast querying and processing of ultra-large-scale databases, especially addressing the rapid response issue when a large number of users simultaneously access the system; • Efficient command and result caching algorithms; • Seamless coupling between database language and host language; • Provision of API function libraries, providing debugging and development environments; • Implementation technologies under multiple operating systems (Linux and embedded operating systems); • Implementation of internet query middleware based on real-time distributed databases. This platform solves the "data silo" phenomenon in enterprises, truly realizing information integration. 3.3 Industrial process monitoring uses Win CC and the industrial main computer of the monitoring center to form a production process monitoring system, which can display and alarm the pressure, temperature, flow rate and liquid level in the chemical production process. It can also display the operation and alarm the fault of valves, fans and pumps. Since the flowchart on the monitoring screen is drawn according to the production process, it can be understood by the operators at a glance and also brings convenience to the maintenance personnel. The system design adopts two-level monitoring software and Win CC. Win CC software is suitable for monitoring level applications and is set in the control center. Protool is used for field level and is set in each control station. Some operation interfaces are shown in Figure 2. (1) Software performance The software is divided into four levels of management: project, screen, window and target; there is no limit to the number of projects, and each project can have up to 1000 screens; each screen can include up to 100 windows, 256 dynamic targets, 256 controllable targets, 16 historical operation charts, 16 current trend charts, and 16 alarm windows; it supports monitoring features such as marking, prescription, panel, and symbol; it supports 9 alarm types; the software scan cycle is customized, and we set the shortest to 50ms. (2) System Integration and Debugging After configuring all stations in the laboratory, the control cabinet was installed and some functions were debugged. After several modifications, it was then installed and debugged on-site. Some problems were encountered during the debugging process. The main problem was that each CPU could only support a maximum of 2 ET200s (theoretically, it could support 3). In the design, 3 ET200s were set in several stations with more control points, which caused frequent system instability during debugging. After reducing the number of ET200s, the system worked normally. As it is a chemical enterprise, according to the characteristics of the industry, the system is required to have high reliability and stability. In terms of bus structure, we adopted isolation between each control station to solve the vulnerability of the bus and fully ensure the independence of each station to improve the reliability of the system. 4 Conclusion The above system design has a large number of stations and a long PROFIBUS bus. It is not common in China to use it for real-time monitoring in chemical enterprises (to realize analog quantity monitoring, which is more complex than other industries). The main contribution of this paper is to build a control network based on the PROFIBUS bus and realize resource sharing and seamless connection with the IT network. After nearly a year of use, the results were good, meeting the design requirements and greatly improving the enterprise's informatization and management levels. References [1] Zhou Ming. Fieldbus Control [M]. Beijing: China Electric Power Press, 2002. [2] Deng Zeming, Kuang Suifang, Cheng Lianglun. Application Technology of Electrical Appliances and Programmable Controllers [M]. Beijing: Machinery Industry Press, 2002.