## 1 Introduction  
The total amount of municipal solid waste (MSW) in China reached 191.4 million tons in 2015 [1], and production is predicted to increase to 480 million tons in 2030 as a result of economic development and a growing population [2; 3; 4]. This has caused very serious environmental and social problems. Among these MSW disposal technologies, the incineration technology is widely applied due to its advantages of large reducing capacity and energy recovery for power generation. However, traditional direct incineration entails high investment and operating costs while producing a wide variety of pollutants. Gasification is becoming an increasingly attractive alternative to convert solid waste into a clean syngas (CO, H\({}_{2}\), and CH\({}_{4}\)) because it can reduce emissions of carcinogens, such as dioxins and furans [5], and also achieve higher overall efficiency and lower investment cost than direct combustion [6]. Despite its many advantages, there are some inherent disadvantages, such as the high moisture, lower heating value, and complexity of the MSW components. These drawbacks can lead to a lower calorific value of syngas, which may also contain impurities that restrict the development of MSW gasification technology. Because of the abundant fossil fuel consumption in China, the coal has a higher heating value and can be co-gasified with MSW to improve the syngas quality, and the relatively high temperature of the co-gasification process can also accelerate the decomposition of waste pollutants. Therefore, the co-gasification of MSW and coal has potential as a promising method to overcome the above disadvantages. On the other hand, as a nonrenewable resource, coal will be exhausted in the future, and co-gasification of MSW and coal can also reduce the fossil fuel consumption and emissions. Besides, the co-gasification technology has some other advantages that were established by the research of [PERSON] et al. [7], such as reduced fossil-based CO\({}_{2}\), NOx, and SO\({}_{x}\) production; higher production of CO, CH\({}_{4}\), and hydrocarbons; increased carbon conversion; and reduction in H\({}_{2}\)S and NH\({}_{3}\) production compared to coal gasification alone. Historically, there have been a few studies that have focused on the performance of MSW and coal co-gasification. [PERSON] et al. [8,9] performed a co-gasification experiment on coal blending with wastes and researched the effects of catalysts on the tars, heavy metals, and sulfur produced from co-gasification; the gasifying agent was a mixture of steam and oxygen. It was found that the presence of catalysts facilitates the reduction of hydrocarbons and tars, heavy metals, and H2S. [PERSON] et al. [10] investigated the overall performance efficiency of the air co-gasification process (coals, plastics, and wood) by a pre-pilot scale bubbling fluidized bed gasifier. They found that the lower heating value (LHV) progressively increased from 5.1 to 7.9 MJ/Nm\({}^{3}\) when adding the plastic waste proportion. [PERSON] et al. [11] performed co-gasification experiments on coals of different grades mixed with different types of biomass waste, and found that co-gasification is beneficial in reducing the negative characteristics of coals; the type of feedstock was a key factor for initial syngas composition. [PERSON] et al. [12] reviewed the co-gasification of waste and biomass to energy conversion, and concluded that co-gasification was beneficial in enhancing product quality and yield compared with wastes gasification alone; additionally, they attested its environmental-friendly character with lower greenhouse gas emissions. The fluidized beds were the most suitable reactors for co-gasification. [PERSON] et al. [13] set an innovative three-stage gasifier system for co-gasification of MSW with high alkali coal char. The effects of temperature and equivalence ratio on the concentration of tar and HCl have been evaluated experimentally.