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Two-stage flow synthesis of isobutyl-modified MAO using 3D printing.

Stricter environmental regulations and policies are leading to increasing requirements for the quality of the oil product. Hydrogen fluctuation in the hydrofining process of refineries remains a considerable problem that may affect the quality of refinery products and increase operating costs. As hydrogen supply across multiple refineries is common in the process industry, the optimal design of interplant hydrogen networks (multi-refinery hydrogen networks) is inevitable in improving the stability of hydrogen supply and reducing the utility consumption of the entire system. This paper introduces the Worst-Case Conditional Value at Risk (WCVaR) concept for the synthesis of the interplant hydrogen network system with hydrogen source flowrate fluctuations. WCVaR is adopted to indicate the expected value of the pure hydrogen content in hydrogen networks in the worst case. Considering the adjustability of hydrogen utility in the realistic production process, this paper studies the stability of interplant hydrogen networks under constant and adjustable hydrogen utilities. The Monte Carlo simulation verifies that the multi-refinery hydrogen network structures obtained by this method are more robust.

The gas–solid vertical single helical ribbon agitated reactor (G-S-VSAR) is a gas–solid dense-phase agitated reactor, in which the interaction between the agitator and the dense granules dominates the flow field and transfer behavior. The particle movement characteristics are essential for determining the reactor space–time yield and product quality. In this work, the particle residence time distribution (RTD) was measured through magnetic-particles pulse experiment to investigate the overall movement and mixing characteristics of a G-S-VSAR, with the effects of rotation speed and gas velocity studied. The RTD curves were featured by time lag, bypass peak and exponential tail, and thus a model of ‘PFR + double parallel CSTRs’ was established. Results showed that the increase in rotation speed could eliminate the bypass, but only reduce the lag time. The lag time adversely influenced the mixing. Photography was applied to characterize the local particle movements near the reactor wall. It was found that the particles spiraled upwardly along the wall in laminar-like flow and the fully mixed state reached after one circulation. During the spiraled process, the undulating displacement in the vertical direction was induced by agitation in the ribbon-wall gap, which inhibited the radial mixing. Therefore, a narrow gap was recommended for reducing such undulating movements and promoting radial mixing.

When the liquid is injected into a gas-solid fluidized bed, particles are easily wetted and prone to form liquid bridges among them, further leading to particle agglomeration. Wet particle agglomeration induced by liquid bridge is dynamic and unstable, and its evolution behavior affects the stable operation of fluidized bed reactor. Therefore, based on the formation-fragmentation competition mechanism, a wet agglomeration evolution model is proposed to predict the evolution characteristics of wet agglomerates under different conditions. Furthermore, a modified drag force model which attributed the effect of wet agglomerates into the drag force was established and applied to the CFD simulation of a fluidized bed with wet agglomerates under the liquid spray-evaporation equilibrium state. Meanwhile, the particle image velocimetry (PIV) technology is applied in this work, and it was found that the vertical solid velocity simulated by CFD is in good agreement with the PIV measurement results.

The design of refinery hydrogen networks minimizing the total annualized cost is a computationally hard optimization problem. This is mainly due to the highly nonlinear compression power constraint and the nonconvexities of the problem. To decrease the nonlinearities, we propose in this work a concept of pressure discretization, and therein the pressure variables of new makeup compressors make discrete choices among the specified pressures of hydrogen origin and destination units. Based on this concept, the constraint of compression power is linearized without losing rigors. Then, hydrogen networks design is formulated as a mixed integer nonlinear programming model that is applicable to both grass-roots synthesis and retrofit problems. We develop a global optimization algorithm to solve the proposed model to global optimality. Two grass-roots synthesis and three retrofit examples are tested for illustration purposes. The total annualized cost and computing time of our solutions compare favorably to those of literature solutions.

Heat integrated water allocation networks (HIWAN) can be recognized as a nexus between water and energy within the process industry. Water and energy are so tightly related in this kind of networks that water saving options may cause more energy consumption or vice versa. Various mathematical programming methods have been proposed to simultaneous optimize HIWAN. However, this problem is believed to be difficult to solve. Compared to the traditional HEN, the direct heat transfer of stream mixing is more flexible in this problem and the actual number of heat exchangers can be much smaller than the traditional HEN. This paper takes advantage of these two features to build up a novel superstructure to simultaneously design HIWAN. Stream splitters and mixers are considered for every water-using operations and heat exchange units, so that possibilities of stream mixing can be fully explored and there are more series and parallel modes between heat exchangers than that of stage-wise superstructure. The proposed model is solved under given different number of heat exchange units. A small to large iteration strategy is introduced to find the best solutions. Applying this proposed approach, the better results are obtained in large-scale problems compared with the previous papers.