Advanced combustion,cooling and refrigeration,waste gas treatment,heat integrated separation and case studies

This is an overview of a Special Issue that has been dedicated to the 8th conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction – PRES’05. Twelve papers from the conference have been selected and peer-reviewed and cover various subjects of advanced combustion, cooling and refrigeration and waste gas treatment. These have been supplemented with heat integrated separation and case studies.     

Challenges and solutions of optical-based nondestructive quality inspection for robotic fruit and vegetable grading systems: A technical review

BackgroundOptical techniques, including computer vision, spectral imaging, near-infrared technology and other emerging imaging and spectroscopy techniques, have been rapidly developing and widely applied in fruit and vegetable grading systems for nondestructive quality inspecting and grading over the past decades. However, automatic detection of quality and grading is still difficult due to some still existing challenges, which are the key of blocking their commercialization in robotic fruit and vegetable grading systems. The challenges include the following aspects: the influence of physical and biological variability, whole surface detection, discrimination between defects and stems/calyxes, unobvious defect detection, robustness of the features and algorithms, as well as rapid optical detection system development. These challenges can reduce the fruit or vegetable quality inspection accuracy, thus greatly reducing automatic level of the quality inspecting and grading machines.Scope and approachAs agricultural engineers with about eight years of technical experience in fruit grading systems, we believe the ultimate goal of each scientific research should seek its task in serving the engineering. So, we have made many attempts to solve the challenges and increase the automation of the grading machines.Key findings and conclusionsThe review gives a detailed summary about the challenges and solutions of optical-based nondestructive quality inspection for fruit or vegetable grading systems from the perspective of engineering. Particular attention has been paid to the techniques that can improve the automation degree of the grading robot in this review. The advantages and disadvantages of the solutions are compared and discussed. Additionally, the remaining engineering challenges and future trends are also discussed.     

Facile synthesis of anatase/rutile TiO2/g-C3N4 multi-heterostructure for efficient photocatalytic overall water splitting

Rational design of high-efficiency heterostructure photocatalyst is an effective strategy to realize photocatalytic H₂ evolution from pure water, but remains still a considerable challenge. Herein, an anatase/rutile TiO₂/g-C₃N₄ (A/R/CN) multi-heterostructure photocatalyst was prepared by a facile thermoset hybrid method. The combination of two type-II semiconductor heterostructures (i.e., A/R and R/CN) significantly improve the separation and transfer efficiency of photogenerated carriers of anatase TiO₂, rutile TiO₂ and g-C₃N₄, and A/R/CN photocatalyst with high activity is obtained. The optimal A/R/CN photocatalyst exhibits significantly increased photocatalytic overall water splitting activity with a rate of H₂ evolution of 374.2 μmol g⁻¹h⁻¹, which is about 8 and 4 times that of pure g-C₃N₄ and P25. Moreover, it is demonstrated to be stable and retained a high activity (ca. 91.2%) after the fourth recycling experiment. This work comes up with an innovative perspective on the construction of multi-heterostructure interfaces to improve the overall photocatalytic water splitting performance.     

Synthesis of multiphase Au/Cd0.6Zn0.4S/ZnS photocatalysts for improved photocatalytic performance

Novel composite photocatalysts consisting of a cadmium and zinc sulfide solid solution (Cd_0.6Zn_0.4S) and zinc sulfide (ZnS) nanoparticles were successfully prepared by a simple hydrothermal treatment of suspended Cd_0.3Zn_0.7S at 120 °C. The as-obtained materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and UV-VIS diffuse reflection spectroscopy. The obtained photocatalysts were tested in the photocatalytic evolution of hydrogen from a Na₂S/Na₂SO₃ aqueous solution under visible light irradiation (λ = 450 nm). It is shown that the hydrothermal treatment of Cd_0.3Zn_0.7S at 120 °C increases the activity by a factor of 7.5 due to the phase transformations of the solid solution with the formation of the multiphase Cd_0.6Zn_0.4S/ZnS sample. The deposition of gold on the surface of Cd_0.6Zn_0.4S/ZnS leads to a further increase in activity: the achieved photocatalytic activity and quantum efficiency (450 nm) for 1%Au/Cd_0.6Zn_0.4S/ZnS are 17.4 mmol g⁻¹ h⁻¹ and 42.6%, respectively. This excellent performance is found to be attributable to the transformation of Cd_1-xZn_xS from the cubic to the hexagonal phase during the hydrothermal treatment. Additionally, photoelectrodes based on Cd_0.6Zn_0.4S/ZnS and FTO were synthesized and tested in a two-electrode cell. A high value of the photocurrent equal to 0.5 mA/cm² is achieved for the Cd_0.6Zn_0.4S/ZnS/FTO electrode. An investigation by means of impedance spectroscopy reveals the longer lifetime of photogenerated charge carriers in the Cd_0.6Zn_0.4S/ZnS/FTO photoelectrode if to compare with Cd_0.3Zn_0.7S/FTO system.     

Monitoring of firmness evolution of peaches during storage by combining acoustic and impact methods

Firmness is a very important quality property in peach. The storage of peach affects its subsequent softening process and shelf life. The temperature and duration of storage mainly influence the firmness of stored fruit, and monitoring the evolution of fruits enables producers to manage its commercial life. The objective of the present study was to use non-destructive acoustic and impact tests to estimate firmness of peaches and to elucidate the influence of storage temperature and of time on the softening process of peach. Continuous and classification models based on variables obtained from non-destructive methods were developed. Parameters obtained from non-destructive methods were compared to destructive reference tests. The maximum force in ball compression correlated well with the maximum acceleration from impact test (r² = 0.75), and with a band magnitude parameter from acoustic test (r² = −0.71). Combining impact and acoustic parameters, the multiple correlation coefficient increases up to 0.91 (adjusted R² = 0.82) in the prediction of the maximum force in ball compression. Classification models based on both non-destructive parameters and sorting peaches into two classes of firmness, showed scores of well classified higher than 90%.     

Feasibility analysis of a newly developed multifunctional mastication simulator

Food oral mastication is a highly complicated dynamic process which involves multiple sequential or simultaneous operations. Ethical complication and technical difficulties for oral access make in situ studies of food oral processing highly challenging and, therefore, feasible instrumental techniques are highly desirable in order to be able to conduct food oral processing research in vitro instead. In this work, a newly developed mastication simulator equipped with 3D printed teeth, controlling units, and various probes have been developed. The device is capable of simulating chewing actions by using two step motors controlling transverse and longitudinal movements. The mastication units sits inside an airtight and properly temperature controlled chamber made of aluminum alloy. The chamber has various small ports to allow the addition of artificial saliva and access of probes monitoring of the temperature, conductivity and pH of the collected saliva. Fractured food particles can be collected for size distribution analysis and to quantify the kinetics of food mastication. Conductivity and pH of the collected fluid (artificial saliva + food juice) can be measured as a function of mastication time or chewing cycles. Air inside the chamber can be collected regularly for composition analysis so that the kinetics of aroma release of a food can be monitored during mastication. Nuts and food gels have been used for feasibility tests of the device. Results demonstrate that the current design provides a feasible tool for in vitro oral mastication analysis during food oral processing.