# Development of a Novel Shaft Dryer for Coal-Based Green Needle Coke Drying Process
## 1 Introduction
In addition, the dehydration tanks, with a height of approximately 10 m and a diameter of 2 to 4 m, and the large inclination belt conveyor occupy a large land area with a resultant capital investment cost. Thus, a new drying system should be developed to accelerate the drying process and stabilize the final moisture content of green cokes. Several drying methods are widely used in high energy-consuming industrial processes [21], including rotary dryer [22; 23], tubular drier [24], airflow dryer [25], fluidized-bed dryer [26], and microwave dryer [27]. Table 1 summarizes the characteristics of the drying methods mentioned in previous studies when they used for drying green coke. It is indicated that the dryers widely used in other industries are not suitable for green coke drying. Given the advantageous material flow and heat transfer of shaft facilities [28; 29; 30], this work aims at designing a novel efficient drying system with a shaft dryer that is suitable for green coke drying, with sound energy usage [31] and low environmental impact [32; 33]. In addition, key characteristics of the green coke, including particle size distribution [34], initial moisture content, vertex angle, pressure drop scheme [35], and the discharge characteristics, are essential to determine the parameters of the designed dryer [36]. However, little information can be found on this topic. This work investigates these characteristics experimentally and provides detailed data that are important to design the proposed shaft dryer for drying green coke. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Method** & **Advantage** & **Disadvantage** & **Operation and Maintenance** & **Quality of Green Coke** & **Energy Efficiency (\%)** & **Productivity** & **Capital Investment Cost** \\ \hline standing dehydration & & & uneven drying effect; low drying & & & & & \\ dehydration & & & efficiency; unstable moisture content; & & & & \\ tank & consumption; high safety & & large area occupied; high capital & & & & \\  & & investment cost & & & & & \\ \hline \multirow{4}{*}{rotary dryer} & good drying effect: wide & multiple transmission components of & & & & & \\  & applicability; easy to achieve & the dryer, which need continual & & & & & \\  & mechanization and automation; & running repairs large device, large & & & & & \\  & good uniformity of green coke; & area occupied, high capital investment & & & & & \\  & simple operation & cost; serious burning loss of green coke & & & & \\ \hline \multirow{4}{*}{tubular drier} & sound safety; light abrasion of & crushing is needed to meet the & & & & \\  & green coke & frequent on green coke particle size; & & & & \\  & & & poor drying effect high failure rate of & & & \\  & & the dryer & & & & \\ \hline \multirow{4}{*}{airflow dryer} & short drying time; good drying & high energy consumption; poor safety; & & & & \\  & effect big drying capacity; simple & serious dryer wear, short service life; & & & & \\  & dry structure, small area & refractory waste gas crushing is & & & & \\  & occupied; easy for manufacture; & needed to meet the requirement on & & & \\  & low capital investment cost & green coke particle size & & & & \\ \hline \multirow{4}{*}{fluidized-bed} & \multirow{4}{*}{big drying capacity; simple dryer} & wall accretion and bed blocking easily & & & & \\  & & occur; serious dust entrainment in & & & & \\ dryer & structure & waste gas; uneven drying of green & & & & \\  & & coke; crushing is needed to meet the & & & & \\  & requirement on green coke particle size & & & & \\ \hline microwave & & & underdeveloped technology; & & & \\ dryer & good drying effect & high electricity consumption; & & & & \\  & safety concerns & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of different green coke drying methods.