Energy saving optimization of heat exchanger network in formamide production

Li Zhuoqian 1 Guo Yan1 Li Zhongli 2 Li Kegen 2 Huang Yong 2

(1. College of Biological and Chemical Engineering, Guangxi University of Science and Technology, Liuzhou 545005;

2. Chengdu Kete Ruixing Technology Co., Ltd., Chengdu 610037)

abstract

By using Aspen Plus software, the heat exchange network of a formamide production plant with an annual output of 10000 tons is simulated. The results show that the average error between the simulation value and the design parameters is XX%. Based on pinch technology, the energy consumption of the existing heat exchanger network in the whole process is analyzed to find out the unreasonable use of energy, and the transformation scheme of the heat exchanger network is proposed. Through comparative analysis and economic benefit evaluation, the results are obtained Excellent heat exchanger network optimization scheme. The results show that after optimization, the heat recovery is increased by XX kW, the utility is reduced by XX kW, the energy is saved by XX%, and the consumption is reduced significantly.

1. Preface

2. Formamide production process

3. Full process simulation and

3.1 Model establishment

3.2 Verification of simulation methods

3. Energy consumption analysis of existing heat exchanger network

4. Optimization of heat exchange network

4.1 Logistics data

4.2 Determination of optimal pinch point temperature difference (determination of pinch point position of heat exchange network)

The pinch point temperature difference △ Tmin is an important parameter of the heat exchange network. The smaller △ Tmin is, the more heat can be recovered, and the less heating and cooling utilities are required; However, pinch point temperature difference is the driving force of the system heat transfer, and the reduction of the driving force will lead to heat transfer difficulties, increase the heat exchange area, and thus increase the equipment investment cost. Therefore, for the heat exchange network to be modified or the heat exchange network to be newly designed, the pinch point temperature difference corresponding to the required economic goal is. optimal pinch point temperature difference.

4.3 Economic benefit analysis

4.4 Optimization of heat exchanger network

5. Conclusion

With the deepening of energy crisis, process integration has become a hot topic. As a practical method in process integration, pinch technology is widely used. this paper

Among the energy-saving methods of process systems, Pinch Technology is widely used internationally because of its practical, simple, intuitive and flexible advantages. For example, ICI in the United Kingdom, Unicarbon, Monsanto and DuPont in the United States, Chiyoda and Toyo in Japan, Sinopec Group and many other internationally renowned enterprises have adopted pinch point technology and achieved significant energy saving results. According to statistics, using pinch analysis technology to design new plants can save 30%~50% of energy and more than 10% of investment compared with traditional methods; For the technical transformation of the old plant, the pinch point technology can save energy by 20%~35%, and the payback period of the transformation investment is only half a year to two years. The good performance of pinch point analysis technology makes the application of pinch point technology as a necessary condition for bidding in many projects [2]. At the same time, with the development of computer technology, there are corresponding software to assist the design of pinch technology. Among these software, Aspen software has been widely used [3].

This paper simulates and optimizes the distillation section and heat exchange network in the process flow of vinyl acetate production with an annual output of 200000 tons, simulates the process flow with Aspen Plus software, optimizes the process operating parameters, designs the tray with CUP Tower software, and optimizes the heat exchange network of the unit with pinch technology. The main work is as follows:

According to the distillation process of vinyl acetate, this paper uses NRTL thermodynamic model and simple (DSTWU) and strict (RADFRAC) distillation modules for simulation calculation to determine the basic logistics data, which lays the foundation for the design of tray and the optimization of heat exchange network; At the same time, the process operating parameters (feed temperature, number of trays, feed position, etc.) were optimized, which not only reduced the investment cost of distillation tower equipment, but also reduced energy consumption. After optimization, the energy consumption of distillation section was 2857.34 kW saved.

The pinch technology was used to analyze the energy consumption of the heat exchanger network of the vinyl acetate distillation unit. With the pinch point temperature difference of 10 ℃, find out that the average pinch point temperature of the heat exchange network of the device is at 80 ℃ and 70 ℃ through the problem table method,

According to the calculation, the thermal utility consumption of the unit is reduced from 18141.28 kW to 16201.72 kW, saving energy

The force reaches 10.69%. Without changing the size of the original distillation column, F1 round float valve tray is selected to design the distillation column tray, and the structural parameters of the tray are calculated, which can fully meet the hydraulic requirements.

According to the process heat exchanger network, the dual flow heat exchanger (Hextran) model and Hextran software are selected for simulation calculation. The original process heat exchanger network is optimized using the three principles and design rules of pinch technology, and four energy saving optimization schemes are proposed. Passing heat load, number of heat exchange units, heat exchange area and circulating water

Use these design objectives to compare and analyze the four optimization schemes The equipment investment cost of the final optimization scheme I is reduced by 567500 yuan compared with the original process, and the energy cost can be saved by 617900 yuan annually, showing good economic benefits.