## 1 Introduction  
Over the past few years, with the development of the global economy, energy shortages and environmental pollution have become two important issues facing humankind. The development of efficient and clean combustion of fossil energy, the comprehensive utilization of renewable fuels, and the reduction of environmental pollution have become inevitable requirements for sustainable social development. The brewing industry produces a large amount of distillers' waste of about 100 million tons per year [1] in China. Large amounts of sludge are produced in this process; for example, the wastewater treatment after brewing of Wuliangye Group, Sichuan Province, China, produces sludge with a daily output of about 70-80 tons, which greatly pollutes the environment, causes a waste of resources, and increases the burden on brewing enterprises [2, 3]. How to reasonably deal with these sludge has become an urgent problem to be solved. Blended biomass combustion is one of the effective ways for coal-fired power plants to eliminate solid waste from industrial sources, as it can reduce pollutant emissions, improve fuel flexibility and coal performance, and improve conversion efficiency as well [4, 5]. In order to investigate the combustion behavior of blended biomass, abundant research has been carried out regarding ignition, burnout, NOx emissions, and so on. In addition, the combustion characteristics of coal and biomass fuels, as well as sludge, have been studied extensively by thermo-analytical techniques such as thermo-gravimetric(TG), derivative thermo-gravimetry (DTG), and differential thermal analysis (DTA) [6; 7]. [PERSON] et al. [6] used TG, DTG and DTA to study the combustion of sludge, coal, and two types of biomass, as well as biomass and sludge mixed with coal as their co-firing conditions. Their results showed that the influence of heating rate on the TG curve varies and coal co-combustion with biomass and sludge can obtain economic benefits. [PERSON] et al. [8] studied coal and biomass fuel's volatile yield and the nitrogen distribution of fuel. They found that most of the fuel nitrogen released by biomass samples is volatile (80-95%), whereas for coal, volatile nitrogen varies considerably with different coal samples. [PERSON] et al. [9] used anthracite and sludge for co-combustion in a fluidized bed burner. The research illustrated that the metal concentration (such as Cu, Ni, Cr, Pb, etc.) of the ash formed by co-combustion is higher and the co-combustion soot shows a lower level of physiological toxicity. [PERSON] et al. [10] used differential scanning calorimetry to study the pyrolysis behavior of dry sludge. The main gases are CH\({}_{4}\), CO, CO\({}_{2}\), and other volatile organic compounds (VOCs). Except for CO\({}_{2}\), the concentration of other gases increases steadily as the pyrolysis temperature increases from 450 to 650 \({}^{\circ}\)C. [PERSON] et al. [11] used differential scanning and thermogravimetric analysis to study the difference in characteristics between sludge and coal. Studies have shown that a small sludge blending ratio has a limited effect on coal's heat release and weight loss. [PERSON] et al. [12] conducted an experimental study on the mixed combustion of coal and dry sludge and concluded that compared with coal, the sludge has two weight loss peaks; after the sludge is blended, the maximum fuel weight loss ratio is advanced and increased. At the same time, the flammability index increases and is between that of the combustion of coal and sludge alone. [PERSON] et al. [13] used a thermobalance analysis device to reveal the combustion of rice husk and rice straw combined with pre- and post-treatment strategies. The results show that the combustion characteristics of the mixed biomass are improved. [PERSON] et al. [14] used a tubular electric furnace to conduct mixed combustion experiments on municipal sludge and ferro-bituminous coal.