1、英文原文Cementing the relationship between DCS and PLC: A review of emerging trends in plant control systems. Author:Moin ShaikhCompany: Siemens Energy & Automation, Inc.Abstract This paper explores the changing roles of traditional distributed control systems (DCS) and programmable logic controllers (P
2、LC) used to automate cement manufacturing processes. The two technologies initially served two different control requirements. However, improvements in microprocessor-based controllers created conditions for two technologies to merge.The shift toward commercial, off-the-shelf automation technology,
3、software-based control verses hard control and use of non-proprietary networks has created a new class of systems called hybrid process automation systems. In addition, the role of the plant control system has been expanded from just process visualization and control to include process optimization,
4、 plant asset management, energy management, and inventory control. Cement plants can now use the process control systems to improve operational and energy efficiency. Control system vendors have adopted unique terms to differentiate their systems from the traditional definition of a DCS or PLC. Some
5、 have expanded their process ontrol systems to offer vertical integration with IT systems and horizontal integration with intelligent drives, motors, process instrumentation and discrete control technologies. This paper addresses a number of requirements placed on the cement automation systems as a
6、result of these developments and identifies technologies that offer the best solution to meet the challenges faced by cement producers. Introduction The process of manufacturing cement has gone through many changes over the years. The wide acceptance of the dry process of cement making rather than t
7、he wet and pre-calcinations processes are among these changes. In any case, the manufacturing process continues to have the most significant, quantifiable influence on overall cement quality and efficiency, sustainability, and environmental impact of the plant. The automation requirements of the cem
8、ent industry are unique, even though on the surface they may seem similar to other industrial processes. Legacy automation systems installed in existing cement plants have not kept pace with new technologies now available to the process industry. The growing size and complexity of the cement manufac
9、turing process have placed new demands on automation system vendors. By understanding these requirements and the control and automation technologies available today, we can effectively select the best platform for the automation of applications in the cement industry. Cement Plant Automation Require
10、ments What is unique about automating the cement manufacturing process? Cement production involves the transformation of material through crushing and grinding. Limestone is the primary ingredient. The raw meal undergoes physical change through the calcinations process in the kiln where it is heated
11、 up to 1600o C. The automation systems convey material through different stages of the process and routes. The automation system manages the starting and stopping sequences of the conveying and material handling systems. Cement production can be considered as a combination of individual processes su
12、ch as blending and preparation of raw meal, temperature and speed control of the kiln and kiln feed control. Clinker cooling process recovers the heat and lowers the temperature of the clinker so it can be stored. Speed control of pre-heater fan and the exhaust fan maintain negative pressure inside
13、the kiln hood and ensure the correct flow of hot gases. Feed control of the Finish Mills to maintain throughput and blending of the cement with additives in the Finish Mills to produce different types of cement. Basic temperature, air flow and pressure control are very critical to the production pro
14、cess and are applied at various places in the process. The cement industry also uses large motors and drives that control large pieces of mechanical equipment. Interlock requirements for this type of equipment are unique when compared to the equipment used in typical process industries, such as chem
15、ical. The motors and mechanical equipment needs to be protected from operator mistakes and incorrect operation. For this purpose two types of interlocks are programmed in the control systems. The first type is called soft interlocks, implemented using logic in the control system, and second type of
16、interlocks are implemented using hard wiring and are called hard interlocks. There are also different types of interlocks effective in different modes of operation of the mechanical equipment. Improving energy efficiency in the cement production is a big challenge for cement industry since it is a big consumer of electricity, oil, coal, and natural gas. The cement industry is also the third largest emitter of greenhouse
