Bingjian Zhang

Thermodynamic analysis and modeling for typical feed-preheating and fractionating processes in delayed cokers

Abstract Delayed coking is one of the main processes for heavy oil processing with higher energy consumption in refineries. The present analysis includes the energy and exergy balance of the de-superheating section, the heat exchanging process of the feeds, etc. An approach to optimize the heat exchanger network through integrating the fractionating process is illustrated. A much higher feed temperature is usually considered better for an energy-use optimization retrofit. However, considering the limit of the energy integration within the whole plant, determining the feed preheating temperature is usually an optimization problem. Finally, a model is built that the annual cost is set as an objective function which is subject to the restrictions mentioned above.

An optimization procedure for retrofitting process energy systems in refineries

Abstract An optimization procedure is proposed in this paper for total site energy systems and is applied to industrial refinery complexes based on the insight of process production and energy utilization. Firstly, all process plants in the total site are optimized to target the minimum individual utilities, where processes and HENs are improved for better energy utilization and recovery. As a result, the efficiency of energy utilization is guaranteed for a single plant. Secondly, heat integration between plants is employed to recover surplus heat, which can transfer some heat below the pinch points of supplier plants into other receiver plants to decrease utility requirements. This may not change the first step, but can reduce the cold utilities of the supplier plants and the hot utilities of the receiver plants. Thirdly, low-temperature heat recovery and utilization systems are established with considering the layout and distribution of energy sources and sinks. The recovered low-temperature heat can be used to heat storage tanks and pipelines, preheat boiler feed water, and even to be low-temperature electricity generation. Finally, steam power systems are optimized in the new condition of steam and firedamp balance in the total site. A real industrial example for total site energy optimization is taken to demonstrate the performance of the presented method, and the energy requirement decreases more than 16%.

An exergy grand composite curve based procedure for arranging side exchangers on distillation columns

Abstract This paper presents an exergy grand composite curve based procedure for arranging a side-exchanger on a distillation column. The novel method is proposed to identify the original value of the location, heat duty of the side-exchanger and the criterion of modifying the column stage number. A benzene-toluene column is used to demonstrate the performance of the procedure. The results show that the location, heat duty of the side-exchanger, stage number modification on the column can be effectively identified, and the feeding stage optimization is also considered as the stage number modified. The procedure can guide the arrangement of a side-exchanger in a relatively simple, systemic and reliable way.

Thermal integration of a hot process stream on distillation columns through a side-reboiler

Abstract This paper presents a novel procedure to effectively integrate a hot process stream on a distillation column. The original value of the side-reboiler heat duty is identified through a comparison of the available heat duty of the hot process stream with the required heat duty of the side-reboiler. A benzene-toluene column is used to demonstrate the performance of the procedure. The results obtained demonstrate that the available heat duty of the hot process stream, the place location, heat duty of the side-reboiler, and stage number modification for the column could be identified by using the proposed procedure in a relatively simple and reliable way.