Conceptual Design of an Oil Shale Comprehensive Refinery Process with High Resource Utilization

With the decrease of conventional energy reserves, countries such as China began to explore efficient ways to use oil shale as an alternative energy source. The refinery technology used for oil shale is retorting. However, in this process, fine-particle shale, semi-coke, and retorting gas are not used efficiently; rather, they are dismissed as solid and gaseous wastes. Resource utilization is extremely low in retorting. In addition, the price of crude retorting oil is very low, making the whole retorting process suffer from a low economic benefit. In this paper, a new oil shale comprehensive refinery process is proposed, aiming to process shale particles from all ranges of sizes. The new process includes a gas circulation shale retorting unit, a Dagong shale retorting unit, an oil–gas separation unit, a retorting gas steam reforming unit for hydrogen production, and a shale oil hydrogenation unit. Fine-particle shale from the gas circulation shale retorting unit is used as raw material in the Dagong shale retorting unit. A part of the retorting gas from the oil–gas separation unit is converted into hydrogen in the retorting gas steam reforming unit. The heat balance of the retorting gas steam reforming unit is provided by burning semi-coke from the gas circulation shale retorting unit. Hydrogen from the retorting gas steam reforming unit is used for shale oil hydrogenation, in order to upgrade crude retorting oil for an increased economic benefit. The new process is modeled using Aspen Plus software. Based on the simulation, a techno-economic analysis is carried out to explore its strengths over the conventional gas circulation shale retorting process. Results show that the oil yield is increased by 2.3%. The capital investment is higher, and the production cost for producing 1 t of oil is 1–1.3 times that of the conventional process, but the return on investment increases by 14%.