As a high energy-consuming industry, refining and chemical industry accounts for about 15% of the national total. Refining and chemical enterprises are basically rebuilding and expanding on the basis of old plants. Due to the limitation of technology and capital, and the rapid development of business, the operation optimization of reformed devices, reasonable energy exchange and utilization between new devices and original devices, and energy optimization between production devices and public engineering systems are not fully considered in the process of rebuilding and expanding, resulting in insufficient optimization of operating conditions, unreasonable heat exchange network, insufficient utilization of heat between devices, and no optimal allocation of thermoelectric energy, resulting in more and more low-temperature heat to be recovered in refining and chemical enterprises. Facing the severe energy situation and the challenge of climate change, with the inferior quality of processed crude oil, the improvement of added value of products and the continuous upgrading of oil quality, the pressure of energy saving and emission reduction in refining and chemical enterprises is gradually increasing. In the past, the single energy-saving technology and local energy analysis method for a single device and a single device can no longer meet the requirements of energy-saving and emission reduction indicators under the new situation.

2. Technical principle

Refinery energy system optimization technology is a promising energy-saving technology gradually developed in recent years, which integrates many technologies such as process simulation, process energy integration, system optimization and optimal control, and is a complex system engineering integrating refinery technology, information technology application, mathematical planning, technical and economic analysis and engineering construction. On the basis of accurately simulating the refining production process, this technology applies system engineering technologies such as pinch technology and "three-link" method and advanced optimization analysis methods, and combines with actual production management and operation experience to systematically analyze the process energy consumption, find out the "bottleneck" of energy consumption, and put forward an optimization scheme to improve the energy utilization ratio, so as to rationalize the heat exchange process, maximize the equipment efficiency, optimize the operating conditions, optimize the system operation, and realize energy saving while improving the economic benefits of enterprises.

3. Actual cases

In 2008, China Petroleum set up a major science and technology project for refining and chemical energy system optimization, and made important achievements in the research of energy system optimization through introducing absorption, development, integration, typical demonstration and popularization and application. He has mastered and created 38 international advanced simulation optimization technologies with independent intellectual property rights, including off-line simulation optimization technology for oil refining, off-line and on-line simulation optimization technology for ethylene and public works; Innovatively established seven practical and efficient working methods and platforms; In Jinzhou Petrochemical, Lanzhou Petrochemical, Jilin Petrochemical, Karamay Petrochemical and Changqing Petrochemical, six benchmark projects with outstanding energy saving and efficiency improvement have been formed.

The energy system optimization demonstration project of 46× 104t/a ethylene plant in Lanzhou Petrochemical Company has developed the ethylene cracking depth model, the Aspen Plus simulation model of post-treatment separation system and the utility system model of the plant, built a complete ethylene whole process simulation platform, and independently developed and applied the energy management system (EMS) of the ethylene plant. In the project research, the project measures of 12 with no investment or less investment were put forward and implemented, and the energy consumption per ton of ethylene was reduced by 65kg of standard oil. The demonstration project of energy optimization of public works system established the steam power system model of refining and chemical integration and the energy management EMS system, and realized the functions of real-time monitoring of KPI of energy system, statistical analysis of energy consumption, online optimization of public works system, performance tracking of energy-saving projects and so on.

By introducing and absorbing international advanced technology, Jinzhou Petrochemical studied the energy system optimization of existing production devices and public engineering systems, and vigorously implemented energy-saving and water-saving technological transformation, and the overall energy consumption level was significantly improved. 72 sets of process simulation models were established, 94 optimization opportunities for energy saving and efficiency improvement were identified, and 24 optimization schemes with no investment or less investment were implemented, achieving energy saving of 3.79 kg of standard oil per ton of crude oil.