Search

This work investigates the possibility of commercialization of a recently proposed nano calcium carbonate production process as an improved process. The analyzed process uses steel slag instead of limestone as the calcium source to produce nano calcium carbonate and comprises a calcium carbonation process and a NaCl electrolysis process. CO2 reduction impact and techno-economic feasibility of the system are analyzed to investigate its feasibility. The new process is expected to reduce the CO2 emission by about 8 %, compared to the conventional process of making the nano calcium carbonate. In addition, unit cost of production for the new process is 484 USD/ton indicating that it is economically feasible. Sensitivity and scenario analyses are performed with respect to the type of electricity sources and the capital cost of the electrolysis system, which are the key contributors to the overall cost.

Heterotrophic cultivation can be a preferred option for commercial microalgal biorefinery owing to its significantly higher productivity and lipid content leading to high value products. However, l...

Microalgal biomass is considered to be a promising renewable energy source to replace fossil fuel given its simple growth mechanism and high productivity per unit area. Nevertheless, microalgal bio...

Increasing the lipid production rate stands as one of the challenges for achieving economic feasibility of microalgal biorefinery. Various bioreactor operation strategies have been considered for culturing microalgae, including batch, continuous, fed-batch, semi-batch, and two-stage operations. However, since the previous studies used different experimental criteria, it is hard to draw a conclusion about their relative performances. Motivated by this, the present study compares lipid productivity performances and capital expenditures of the various operation strategies after their operating conditions are optimized. The optimal condition for each strategy is determined by performing a model-based optimization to maximize lipid productivity, which is a good indicator of the overall economics. The two-stage operation with continuous-batch serial connection (w/ stress condition) and the semi-batch operation (w/o stress condition) show outstanding performance compared to the other types of operation. Also, start-up, initial cell concentration, and chemical consumption, which are critical factors in large-scale cultivation, are analyzed.

This study presents the synthesis of FexSn1-x alloys (0 ≤ x ≤ 1)/reduced graphene oxide (RGO) using a dry plasma reduction method. The formation of bimetallic FeSn nanoparticles on the surface of RGO was confirmed through TEM and XRD measurements. In the results, FeSn ranging from 1 to 5 nm in size is shown to be successfully immobilized on the RGO surface. The developed materials are then applied as Pt-free counter electrodes (CEs) in liquid-junction photovoltaic devices. To get efficient CEs, we have carefully controlled the chemical composition of the FexSn1-x/RGO through changing the volume ratio of the Fe and Sn precursors during synthesis. The catalytic activity of the electrodes follows the sequence of Fe0.1Sn0.9/RGO > Fe0Sn1/RGO > Fe0.3Sn0.7/RGO > Fe0.5Sn0.5/RGO > Fe0.7Sn0.3/RGO > Fe0.9Sn0.1/RGO > Fe1Sn0/RGO, with the Zw values of the developed electrodes lower than those of Sn/RGO and Fe/RGO electrodes. Accordingly, the highest efficiency was 5.0% for the device using Fe0.1Sn0.9/RGO CE, which is also higher than those of devices using Sn/RGO (4.6%) and Fe/RGO (3.8%). The proposed strategy is simple and efficient and is, therefore, promising for the fabrication of cost-effective CE materials for next-generation solar cells and lithium-ion batteries.

Previous batch control methods, such as iterative learning control (ILC) or run-to-run (R2R) control, can significantly improve the control performance of the batch process. However, to guarantee the expected good control performance, a fairly accurate process model is required for these controllers. Also, the implementation is numerically complicated so that it is difficult to be applied to real manufacturing processes. To overcome these problems, a new batch proportional-integral-derivative (PID) control method is proposed, which borrows the concept of the conventional PID control method. Simulation studies confirm that the proposed method shows acceptable performance in tracking a setpoint trajectory, rejecting disturbances, and robustness to noises and variation of process dynamics. The application to the commercial batch process of a single crystal grower verifies that the proposed method can significantly contribute to improving the control performances of real batch processes.