# Study on the Ash Deposition Characteristics for Co-Combustion of Zhundong Coal with Cotton Stalk
## 1 Introduction
[15] investigated the ash deposition characteristics of switchgrass and hardwood in a 17.58 kW biomass combustion system and demonstrated that switchgrass exhibited significantly lower ash deposition and slagging tendencies compared with hardwood. Additionally, varying excess air ratios had negligible effects on ash deposition for both fuels. [PERSON] et al. [16] studied ash transformation and deposition during pulverized wood combustion with and without the addition of coal fly ash. The results showed that the formation of deposits at the location with a high flue-gas temperatures was characterized by a slow and continuous growth of deposits. At the location with a low flue-gas temperature, the deposit grew slowly, and the number of deposits became almost constant after a few hours. Although the addition of fly ash increased the ash's settling rate at the location with the higher flue-gas temperature, it also significantly improved the sediment's ability to be removed However, most existing research is centered around small-scale bench testsand pilot-scale stand tests; limited reports exist on the slagging and fouling behaviors of coal-biomass blends in full-scale industrial boilers. Due to the diversity of raw materials and experimental costs, an increasing number of researchers are turning to CFD (computational fluid dynamics) methods to study ash deposition in full-scale industrial boilers [17; 18]. To predict slagging and fouling in such combustion processes, researchers have developed numerous ash deposition models to predict ash deposition phenomena, ranging from laboratory-scale facilities to full-scale industrial boilers [19; 20; 21]. [PERSON] et al. [22] proposed a model of deposit growth under slagging conditions, which was combined with a comprehensive combustion program to predict the flow field, temperature field, and growth of the deposit. The predictions indicated that numerical models can be used for the optimized design and operation of pulverized coal furnaces. By combining a gas-solid two-phase flow model, a combustion model, and a slagging model, [PERSON] et al. [23] conducted a numerical study on the slagging characteristics of a 300 MW W-type furnace and found that slagging was considerable on the side wall of the lower furnace. However, there are few studies on the characteristics of ash deposition during the co-combustion of coal and biomass in actual boilers. Relevant research results show that the melting behavior of ash components and the collision of melted ash particles on the heating surface are the main factors affecting ash deposition in the actual combustion process. Additionally, the movement of ash particles is closely related to the flow characteristics of flue gas in the furnace [24; 25]. The tangential circle diameter of the boiler is an important parameter of tangential combustion, which has an important effect on the steadiness of the combustion and the deviation of the flue gas's temperature at the furnace outlet. Therefore, the problem of slagging and fouling can be alleviated by adjusting the actual tangential circle diameter. In this work, the cotton stalks, which are abundant in the Xinjiang region, were selected and blended with Zhundong coal. The change trend of ash composition under different blending ratios was analyzed, and the melting proportions of mixed ash under different conditions were calculated by Factsage. The ash deposition model was established by the user-defined function, and the ash deposition characteristics in the furnace under different blending ratios were obtained. The influence of the tangential circle diameter on the ash deposition characteristics in the furnace was further explored. These research results can provide guidance for the practical blending of Zhundong coal and cotton stalks.