Comparative Study Of Different Routes From Low-Rank Coal To Low Carbon Unsaturated Hydrocarbons

Low-rank coal accounts for a large proportion of China's proven coal reserves. How to use it in a low carbon emission and high effective way is very interested. Using low-rank coal to manufacture low carbon unsaturated hydrocarbons, such as acetylene and ethylene, which are basic organic monomers, becomes a concern for researchers in recent years.Focusing on exploring a more suitable technical route from low-rank coal to low carbon unsaturated hydrocarbons, the acetylene route, which is based on the low-rank coal pyrolysis and oxygen-thermal calcium carbide preparation technologies, and the ethylene route, which is based on the low-rank coal gasification and methanol to olefins technologies, are established and compared.A series of multi-product evaluation indexes were proposed to assess multi-product systems with different products.These indexes contain 1)effective atom yield which represents the material conversion efficiency of the system,2) multi-product comprehensive energy consumption (MCEC) which reveals the energy consumption character of the system,3) multi-product comprehensive exergy loss (MCEL) which indicates the thermodynamic irreversibility of the system, and 4) multi-product comprehensive carbon emission (MCCE) which shows the environment-friendly performance of the system. The concept of the product weighting factor was especially defined to character the contributions of different products to the indexes.Based on the same low-rank coal input, the acetylene route and the ethylene route were simulated by Aspen Plus software. The mass and energy data of each stream and each model were obtained. The good consistency between simulation data and literature data assured that the simulation program was reliable. By comparison, it is shown that the effective atomic yield, MCEC, MCEL, and MCCE of the AR is 3.7 times,35.4%,11.5%, and 14.9% in correspondence to that of the ER, respectively. The essence of progressiveness of the AR was also clarified. Namely, it takes full advantage of properties of the chemical structure of the low-rank coal molecules and realizes energy cascading utilization.The study concludes that the AR is a more suitable way from low-rank coal to unsaturated hydrocarbon, and is worthy to be fully researched and developed.