Research On Pinch Method Of Heat Exchanger Network Synthesis Based On Nonlinear Relationship Between Enthalpy And Temperature

As an important energy recovery system of oil refining, chemical process industry, the utility targeting will provide an important basis for the energy saving potential of the heat exchanger network. When spread out the energy-saving job, if firm up a similar energy saving target for all industrial, it is unreasonable. The target of energy saving may be very easy on a badly designed and operated plant where there are many opportunities for energy saving, and a much higher target would be appropriate. However, on a "good" plant, where continuous improvement has taken place over the years, the target may be impossible to achieve. So heat exchanger network integration is very important guiding significance to carry out the energy conversation.The utility targeting as an important link of heat exchange network synthesis, some existing methods still have some problems and defects, need further research urgently. The pinch method is regarded as a mature technology. But it has been to assume the heat capacity flow rate to be contact. In fact, the specific heat capacity of streams is concerned with temperature, so its enthalpy is a function of temperature. This paper aims at pinch analysis of heat exchanger networks based on temperature and enthalpy nonlinear relationship. Around this theme, the main research work is carried out as follows:1. Analysis of the influence that average heat capacity instead of the actual heat capacity of streams on heat exchanger network energy integration, using improved STEP to get optimized heat exchanger network.2. Develop a algorithm of pinch method based on the nonlinear relationship between enthalpy and temperature, and has given the detailed steps of heat exchanger network pinch analysis.3. Using Aspen Plus property analysis to calculate the enthalpy under the certain temperature, and to fit the stream temperature and enthalpy relationship polynomial coefficient. Algorithm based on the nonlinear relationship between temperature and enthalpy has come true the heat exchanger network synthesis.4. This paper develops the software HEN Integration System is based on MATLAB GUI. The software provides a test and comparing platform for this paper’s theory research.5. Two cases are analyzed and studied. The first case from a chemical plant, second case studies from a refinery crude oil distillation system. The results show that when be applied to the heat exchanger network consist streams that nonlinear relationship between enthalpy and temperature is noticeable, There are obvious differences between pinch method and the method of this paper proposed. Considering the relationship between temperature and enthalpy of streams, can accurately reflect the distribution and transmission of the heat in the network, thus avoiding the heat exchanger network unreasonable design. Subsequently, the effectiveness and practicability of software system are tested by case studies.