Monitoring lime and cement improvement using spectral induced polarization and bender element techniques

Spectral induced polarization(SIP)and bender element(BE)techniques show a high sensitivity to particle size,particle distribution and content of generated hydration products,which essentially govern the efficiency of ground improvement.In this context,both SIP and BE were integrated on a column setup to monitor the processes of lime and cement stabilization.A 5 mmol/L Na2CO3 solution was injected into the sand-lime mixture to produce CaCO3 precipitation,while deionized water was injected into the sandcement mixture to induce the hydration of cement.The average diameters of the precipitated particles or clusters were calculated from the relaxation time,which was a significant parameter of SIP signals,via the Schwarz equation.Two pairs of BE were used to demonstrate the heterogeneity of the product precipitation,which was probably caused by the location of the inflow and outflow on the SIP-BE column.SIP and BE showed the capability of nondestructively monitoring the spatiotemporal chemical evolution processes,which could be helpful for engineering applications.

Characteristics of Particulate Matter Emissions for Low-Sulfur Heavy Oil Used in Low-Speed Two-Stroke Diesel Engines of Ocean-Going Ships

In this work,particulate matter(PM) emissions from a large two-stroke,low-speed marine diesel engine were investigated when the engine was operated with low-sulfur heavy fuel oil(HFO) at various loads.Particle samples were collected in situ from the engine exhaust to determine the detailed physical and chemical properties.The nanostructure and morphology of the nanoparticles were analyzed using transmission electron microscopy images(TEM).The results show that volatile organic carbon(OC) accounts for more than 80% in the HFO particles and leads to an increase in particle size.The thermodynamic conditions of a low-speed engine favor the behavior of capturing the soluble organic components.A large number of spherical char HFO particles with aerodynamic diameters of 0.2 μm-0.5 μm and a suspected inner metal core were detected.The two peak aerodynamic diameters of the HFO nanoparticles are 15 nm and 86 nm.The morphological differences among the HFO nanoparticles in varied engine conditions represent the formation process from primary nascent particles to mature graphitized particles caused by thermodynamics.The above study will be valuable for understanding the characteristics of PM emissions from low-sulfur HFO to achieve the ship PM emissions reduction target.