Simulation And Integration Of Direct Synthesis Olefins From Coal-based Syngas Process

Use to the increasing price and the shortage of crude oil, producing ofefins from coal has become a hotspot topic worldwide, especially in China, which has abundant coal resource but poor crude oil reserves. The new technology of syngas to olefins (STO) is considered as a potential and competitive route compared with the commercial methanol to olfins (MTO) technology. However, the studies of STO mainly focus on the development of catalyst with high activity, there is almost no report published on the simulation and economic analysis of STO, which is a key role on the process design and development. Therefore, the aim of the study is to design a STO conceptual flowsheet, then obtain its mass and energy balance of the new process, as well as its economic possibility. The major work and innovative results for this dissertation are as follows.1. Based on the thermodynamic and kinetic analysis in key units of reactions and separations, an integrated coal-based syngas to olefins route was designed and simulated using Aspen Plus. As to avoid the restriction on ASF product distribution, we added an olefins cracking unit in process design where the hight olefins are converted into lower olefins and others hydrocarbons, and the percentage of C2~C4 olefins in products is improved approach 13.6%.2. For the coal-based direct synthesis of olefins from syngas route, the atom utilization efficiency of carbon to products is only 23.2% (12~14% for olefins and 10% for gasoline). While, the methanol to olefins route which the atom utilization efficiency of carbon is reach to 26.6% is much higher than STO routes, about 25.4% in olefins, only 1.2% in gasoline.3. The carbon flow balance results reveals that there are two main reasons for carbon loss: water gas shift to adjust the ratio of H2/CO result in that about 51.8% of the total carbon is converted into CO2. About 14.4% carbon is loses in olefins synthesis caused by water gas shift and methanation. While, the hydrogen atom utilization efficiency is only 34.1%, about 17.4% becomes waste water and is emitted to environment. 4. A proposal for recycled waste water to gasification unit was considered to improve the atom utilization efficiency of hydrogen and relieve the environment pollution. The result shows that organic contaminates in waste water are conversed into water, CO2, CO and H2 which are main compositions in syngas.5. Take the caol treatment capacity of 6400t/d as a cased study, the coal consumption of methanol to olefins route is about 4.63t per tone olefins that is much lower than that of the 5.26t for STO-OT and 5.03t for STO-RC routes. The total plant investment for the three routes are 1.5, 1.45 and 1.7 billion dollar (2007$), respectively. Compared with the economic performances of three routes, the production cost of OT-STO route is about $605/t that is approximately $50/t lower than that of the RC-STO route, and roughly $120/t lower than that of the MTO route.