The stringent international regulations on marine emission abatement have exerted a huge push on the development of marine desulfurization and denitrification technologies. However, for the traditional vessels driven by large two-stroke diesel engines, simultaneous removal of NO_x and SO₂ is still a big challenge at present. Here, a one-stage ozone oxidation combined with in-situ wet scrubbing for simultaneous removal of NO and SO₂ is proposed. A series of experiments were performed based on a bench-scale reaction system. The results showed that in-situ wet scrubbing could effectively decrease flue gas temperature, and then suppress the thermal decomposition of ozone, which was beneficial for improve oxidant utilization. Meanwhile, the in-situ combination of ozone injection and wet scrubbing was in favor of improving the selectivity oxidation of NO over SO₂ by ozone, which was possibly due to the high aqueous solubility of SO₂ in water. Aiming to reduce the electric power consumption by an ozone generating system, O₃/NO molar ratio was kept as low as possible. A complete removal of SO₂ and a high NO_x removal efficiency could be achieved through the introduction of other oxidative additives in scrubbing solution. This integrated system designed for marine application was of great significance.

The paper presents an experimental investigation of a steam ejector in a single-effect thermal vapor compression (S-TVC) desalination system driven by a low-temperature (below 100 °C) heat source. To investigate the performance of the steam ejector in the S-TVC desalination system, an experimental steam ejector system was designed and built. The influences of the nozzle exit position (NXP), operating temperatures, and the area ratio of the ejector (AR) on the steam ejector performance were investigated at primary steam temperatures ranging from 40 °C to 70 °C, and at secondary steam temperatures ranging from 10 °C to 25 °C. The experimental results showed that the steam ejector can work well in the S-TVC desalination system driven by a low-temperature heat source below 100 °C. The steam ejector could achieve a higher coefficient of performance (COP) by decreasing the primary steam temperature, increasing the secondary steam temperature, and increasing the AR. The steam ejector could also be operated at a higher critical condensation temperature by increasing the primary steam temperature and secondary steam temperature, and decreasing the AR. This study will allow S-TVC desalination to compete with adsorption desalination (AD).

Er-modified FeMn/TiO₂ catalysts were prepared through the wet impregnation method, and their NH₃-SCR activities were tested. The results showed that Er modification could obviously promote SO₂ resistance of FeMn/TiO₂ catalysts at a low temperature. The promoting effect and mechanism were explored in detail using various techniques, such as BET, XRD, H₂-TPR, XPS, TG, and in-situ DRIFTS. The characterization results indicated that Er modification on FeMn/TiO₂ catalysts could increase the Mn⁴⁺ concentration and surface chemisorbed labile oxygen ratio, which was favorable for NO oxidation to NO₂, further accelerating low-temperature SCR activity through the “fast SCR” reaction. As fast SCR reaction could accelerate the consumption of adsorbed NH₃ species, it would benefit to restrain the competitive adsorption of SO₂ and limit the reaction between adsorbed SO₂ and NH₃ species. XPS results indicated that ammonium sulfates and Mn sulfates formed were found on Er-modified FeMn/TiO₂ catalyst surface seemed much less than those on FeMn/TiO₂ catalyst surface, suggested that Er modification was helpful for reducing the generation or deposition of sulfate salts on the catalyst surface. According to in-situ DRIFTS the results of, the presence of SO₂ in feeding gas imposed a stronger impact on the NO adsorption than NH₃ adsorption on Lewis acid sites of Er-modified FeMn/TiO₂ catalysts, gradually making NH₃-SCR reaction to proceed in E–R mechanism rather than L–H mechanism.

The submerged cavitation jet is suitable for ocean engineering activities such as ship fouling cleaning, organic wastewater treatment, offshore oil drilling, and natural gas hydrate extraction due to its superior hydraulic performance and erosion capacity. As an intuitive analysis method, image processing is widely used to investigate the characteristics of submerged cavitation jets. However, due to the lack of quantitative evaluation of the cavitation cloud in image processing, it is difficult to establish the relationship between cavitation cloud image and cavitation performance. Therefore, a novel image processing method based on dimensionless grayscale intensity is proposed in this paper. This method was used under different sample spaces to obtain the maximum mass loss of the sample. The results showed that the method could accurately calculate the maximum mass loss of the sample based on the image processing results. When the sample space is 200 images and the working pressure is 20 MPa, the calculation error of the image processing method for the maximum mass loss of the sample is 1.26%. For the sample spaces of 10–5000 images, the maximum calculation error of the image processing method for the maximum mass loss of the samples is 3.29%. The image processing method proposed in this paper establishes the relationship between the cavitation cloud image and the maximum mass loss of the samples, which provides help for further understanding and application of submerged cavitation jets.

Ship fouling not only increases ship resistance and fuel consumption but is equally a type of biological invasion, which causes severe ecological damage. Submerged cavitation jet cleaning is an environmentally friendly, high-efficiency, and energy-saving cleaning method. The nozzle structure has an essential influence on the cleaning effect. Thus, a two-throat nozzle was designed for application in submerged cavitation jet cleaning. To investigate the cavitation characteristics of the two-throat nozzle, a high-speed photographic visualization experiment and an erosion experiment concerning the submerged cavitation jet were carried out in this study. The frame-difference method (FDM) was used to analyze the dynamic changes in the cavitation cloud in a single period. The dynamic changes in the cavitation cloud and the characteristics of the submerged cavitation jet were investigated under different inlet pressures. The sample mass loss and the macroscopic and microscopic changes in surface morphology were used to evaluate the cavitation intensity of the two-throat nozzle submerged jet. The experimental results demonstrate that the two-throat nozzle has a good cavitation effect, and the cavitation cloud of the submerged jet has obvious periodicity. With the increase in inlet pressure, the length, width, and area of the cavitation cloud continue to increase, and the shedding frequency of the cavitation cloud continues to decrease. The intensity of cavitation erosion is related to target distance and impact time. There is an appropriate target distance by which to achieve the optimal cavitation effect. The collapse of cavitation bubbles near the sample surface is related to the erosion distribution on the sample surface. Moreover, the magnitude of the absolute values of the root-mean-square surface roughness and surface skewness increase with cavitation intensity. The results in this paper are helpful for a better understanding of the cavitation characteristics of the two-throat nozzle submerged jet.

A steam ejector refrigeration system with a movable primary nozzle was developed to study the optimum nozzle exit position (NXP) in the ejector system. Three nozzles and two diffusers were fabricated to investigate the nozzle and diffuser effect on the optimum NXP. Experimental results show that an optimum NXP exists for an ejector system. In addition, the effects of boiler temperature and evaporator temperature on the system coefficient of performance (COP) were studied. The results indicate that the optimum NXP is not related to the operating temperature and the nozzle dimension and diffuser size. The investigation provides a better understanding of optimum NXP in a steam ejector refrigeration system.