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One of the most practical optimization design methods in process system design—narrow point technology. In the 1980s, Professor B. Linnhoff of Manchester University of Technology in the United Kingdom proposed an overall energy-saving optimization design method for process systems—narrow point technology—in his doctoral thesis. This method has the characteristics of clear physical meaning, no need for complex mathematical models, flexible and simple method, and easy to be mastered by engineering and technical personnel. Once this method was introduced, it was valued and adopted by the engineering community, and was continuously developed and improved in practice. At present, this method has been adopted in the new design and renovation of large-scale projects in Europe and the United States, and has achieved huge economic benefits. The investment cost recovery period for general renovation projects is within two years. Since the energy crisis, countries * * and enterprises began to pay attention to energy conservation. The development of energy conservation work has gone through several processes:: The first stage is mainly reflected in heat recovery. This stage focuses on the waste heat recovery of a single device rather than the heat recovery of the entire system. ； The second stage considers the energy saving of individual equipment, such as changing the evaporation equipment from double-effect to triple-effect, using a heat pump device, strengthening the heat transfer of the heat exchanger, etc. ； The third stage, which is the current stage, considers process system energy saving. This is because the development of process system science since the 1980s has made people realize that in order to design a process industry factory with the lowest energy consumption, lowest cost and lowest environmental pollution, the entire system must be integrated and treated as an organic whole to achieve the optimal overall design. Therefore, in the era of process system energy conservation, process integration has become a hot topic. The most practical of the process heat integration methods is the narrow point technology. Narrow point technology has successfully achieved significant energy savings around the world. Using this technology, for new factory design, it can save 30% to 50% of energy and save about 10% of investment compared with traditional methods. ； For the renovation of old factories, energy savings can usually be 20% to 35%, and the payback period for renovation investment is generally only 0.5 to 3 years. Because narrow-point technology can achieve obvious energy saving and cost reduction effects, it has attracted more and more attention from various countries. Hoechst, Bayer, Union Carbide, Monsanto, DuPont, ICI, etc. have all adopted narrow point technology. Famous large engineering design companies such as Kellogg, Lummus, Chiyoda, Toyo, etc. have all established narrow point technology groups. Nowadays, when some large companies in the world bid, it has become a necessary condition to conduct narrow point technical analysis first. It can be seen that since the narrow-point technology takes the entire system as the starting point, compared with the previous energy-saving technology that only focused on the local area and only considered the recovery of certain heat flows and the transformation of a certain equipment or workshop, the energy-saving effect and economic benefits are much more significant. The current forefront of the thermal energy profession is the optimization control problem, which is a dynamic optimization problem. Its corresponding mathematical model is a set of differential equations, the objective function is in integral form, and the optimal solution is a function of time. The narrow point analysis method introduced in this article is a static optimization problem, and its corresponding mathematical model is a set of algebraic equations, so this method is simpler. The core technology of the process system optimization method is narrow point technology, which mainly optimizes the design of the entire process system, including the appropriate matching between hot and cold logistics, and the selection of types and energy levels of hot and cold utilities. ； Appropriate placement of heaters, coolers and some equipment in the system such as separators, evaporators and other equipment in the network ； Three-dimensional trade-off between energy saving, investment and operability. The final optimization goal is to minimize the sum of total annual operating costs and initial investment costs. In terms of optimization goals, narrow-point technology initially took energy as the system goal, and then developed to take total cost as the goal, and further considered non-quantitative process goals such as the safety, operability, adaptability to different working conditions, and impact on the environment of the process system. Therefore, narrow point technology can not only be used for the optimization and integration of heat recovery and heat exchange networks, but also can be used to rationally set up heat engines and heat pumps, determine the level and amount of public works, remove "bottlenecks", improve production capacity, integrate separation equipment, reduce production water, reduce waste gas pollution emissions, etc. Narrow point technology is suitable for the design and energy-saving renovation of process systems. Process systems are industries whose purpose is to process energy flows, such as chemical industry, metallurgy, oil refining, papermaking, cement, food, medicine, electric power and other industries. In the production system of the process industry, the entire production process from raw materials to products is always accompanied by energy supply, conversion, utilization, recycling, production, disposal and other links. For example, the feed needs to be heated and the product needs to be cooled. The heat exchange between cold and hot fluids constitutes a heat recovery heat exchange system. The part that is insufficiently heated must consume fuel or steam provided by the hot utility project, and the part that is insufficiently cooled must consume cooling water, cooling air or cold energy provided by the cold utility project. ； The operation of pumps and compressors requires electricity or is directly driven by steam turbines, etc. This post was last edited by mjs0222 on 2008-1-7 16:37 ]