## 1 Introduction  
Energy is an important guarantee for human social and economic development. Driven by rapid industrialization and urbanization, the energy problems are becoming increasingly acute, especially in the fields of geotherm, metallurgy, chemistry, electrical, and machinery [1]. The consumption of primary fossil fuels and the discharge of pollutants are increasing. So, it is crucial to increase the recovery efficiency of energy sources, one of which is the waste heat from industries. The waste heat sources are generally classified by temperature into three categories: Low-grade, medium-grade, and high-grade. The medium-grade and high-grade waste heat can be easily utilized by steam Rankine cycle or heating other streams. However, the low-grade waste heat, which accounts for half of the total, is hard to recycle. In addition, the waste heat should be condensed by cooling water or cooling air, which results in higher cost. Compared with the ordinary steam Rankine cycle, the organic ranking cycle (ORC) replaces the working fluid with an organic medium with a lower boiling point, which could make use of the low-grade heat. That heat is then used to create organic vapor, which in turn drives an expander to generate electricity. The types of energy available for the ORC energy recovery system includes internal combustion engine waste heat [2; 3], industrial waste heat [4], solar energy [5], biomass [6; 7],water desalination [8], and geothermal energy [9]. The usage of ORC for low-temperature waste heat recovery has many advantages such as: Simple mechanical structure, low pressure, convenient maintenance, remarkable economic benefit, and high recovery efficiency. Therefore, ORC is one of the hot topics in the field of low temperature waste heat recovery. The ORC system is more suitable for recovering waste heat from low and medium temperatures resources. However, the thermal efficiency of the cycle is still low. It is still a challenge to improve the thermodynamic performance of the ORC system. Secondly, due to the high investment in generating units, it is often necessary to rely on economies of scale to have better economic value [10]. Previous research has found that it is important to improve cycle performance, select a working fluid, and determine the best operating parameters. [PERSON] et al. [11] modified a hybrid waste-driven CHP-ORC plant with exhaust heat recovery using the flue gas condensation loop. Which led to an efficiency enhancement compared to its primary design. [PERSON] et al. [12] propose the most influential thermo-physical characteristics of working fluids were critical state, sensible heat and ratio of vaporization latent heat. They believe the mixing of different working fluids is an effective way to improve these thermo-physical properties. Mixed fluids compared to pure fluids have shown better performance on average but their compositions and mass fractions heavily change the cycle performance, and should be optimized in the design process of ORC plants. [PERSON] et al. [13] analyzed the sensitivity of operation parameters on the system performance of ORC system using orthogonal experiment, which shows that the temperature at the inlet of the expander is the most significant factors for the system performances. As for the application of ORC in chemical industry, [PERSON] et al. [14] analyzed and optimized a comprehensive ORC recovery system utilizing five waste heat sources distributed in different temperature levels, from a 1.2 million ton-level reforming and extraction unit in Shijiazhuang Refining & Chemical Company of China. Four schemes are presented in continuous optimization progress with the aim of simplifying the entire system and achieving both the robust thermal performance and economic benefit. More parametric optimization of the ORC was studied by researchers around the world. [PERSON] et al. [15] established a mathematical model of low-temperature ORC system, and investigated several factors influencing the exergy efficiency.