Modeling of Multiprocess Behavior for Feedstock-Mixed Porous Pellet: Heat and Mass Transfer, Chemical Reaction, and Phase Change

Abstract

Insight into the complicated energy-mass transfer and hierarchical reaction in metallurgical industry is of particular value in improving productivity and reducing energy consumption. This work proposes a coupled multiphysical reaction-transport (c-MPRT) model that is based on the implicit finite difference method for the promising bisolid porous pellet to investigate its dynamic characteristics concerning heat transfer, chemical reaction, and phase change. This model successfully reveals a negative influence on the heat conduction from the outer layers to the inner layers of the pellet, due to the enormous heat absorption of the chemical reacting and physical melting process. Compared to the ex situ heat conduction, the in situ Joule heat plays a dominant role during the heating of the inner layers. Additionally, there appears to be a decline in the temperature in the inner layers of the pellet during the reaction process, corresponding to a decreasing reaction rate resulting from the insufficient energy input to the inner layers. The maximum decrement in the temperature and the reaction rate are 35 K and 7.86 mol/s, respectively. In contrast with the chemical reaction process, the fusion process costs less time because the latent heat is lower than the enthalpy of the chemical reaction. It was found that a critical time point at which the fusing region enlarges abruptly exists and is about 1230 s, while the entire multiprocess in the pellet consumed about 1477 s. This coupled multiphysical model contributes to revealing the reaction-transport details and is of great significance to the bisolid porous pellet.

Towards Sustainable Carbon Return from Waste to Industry via C2-Type Molecular Unit

“…Industrial carbide manufacturing technology is based on electrodes that supply power to the furnace. In the mixture, heat transfer is significantly hindered [ 57 , 63 , 64 ], and considering the high enthalpy of carbide formation according to the equation, the process is carried out at high temperatures up to 2100–2200 °C to melt supplied portions of reagents immediately and reduce the reaction time. The decomposition of carbide at high temperatures is compensated by the fast rate of smelting and sufficient heating of outlying zones of the reaction mixture [ 65 ].…”

“…In addition to the well-established large-scale manufacturing of acetylene, carbide is also used directly, skipping gaseous acetylene, in many fundamental processes [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. Currently, calcium carbide is a valuable product of the chemical industry and is produced from natural limestone and fossil carbon [ 52 , 53 , 54 , 55 , 56 , 57 , 58 ]. The initial reagents in the manufacturing of carbide remained the same until, in 2010, Zhang and co-authors presented a powerful approach based on biochars [ 59 ], which were obtained by pyrolysis of biomass and successfully used instead of mined carbon.…”

The single-particle model of calcium carbide production and strengthening mechanism of the novel pelletizing process

“…纪雷鸣 [6] 针对钙碳球团反应控速问 题建立了数学模型, 分析了球团内部的转化率和温度 分布, 认为钙碳球团的控速步骤为表面化学反应. Xu 等人 [7] , 通过统计和拟合获得, 如式(3): Calcium carbide (CaC 2 ) is an important chemical raw material and China is the world's largest producer and consumer of CaC 2 , with more than 90% of the world's total production capacity. The equipment for producing CaC 2 by electric arc method is commonly known as submerged arc furnace (SAF).…”

Reengineering of the carbon-to-acetylene process featuring negative carbon emission

“…However, because of the highly endothermic nature of CaC 2 formation, this seemingly simple chemical reaction has to be performed industrially in an electric arc furnace at 2000-2300 °C for approximately 2 h to overcome dynamic and thermodynamic restrictions ( poor mass and heat transfer as well as a slow reaction rate). [23][24][25][26] In addition, con-siderable carbon dioxide (CO 2 ) emissions generated from the conversion of limestone (CaCO 3 ) to CaO, as well as a large amount of solid waste of the by-product CaC 2 slag (the main component is insoluble Ca(OH) 2 ), 27 originated from C 2 H 2 generation, have exacerbated the calcium-based carbon-toacetylene process. 28,29 The disadvantages of high temperature, high energy consumption, and high waste emissions in calcium carbide-based C 2 H 2 production have seriously restricted the whole acetylene chemical industry.…”