In most countries, sanitary landfill is the most commonly used method to eliminate municipal and industrial solid waste, but landfill produces seriously polluted landfill leachate. Landfill leachate contains many kinds of pollutants: such as refractory organic compounds and heavy metals. In general, there are three methods to treat landfill leachate: leachate transfer, biological processes, chemical and physical methods and membrane processes. Membrane processes can be divided into four types: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). Membrane process has the advantages of stable effluent and high rejection rate for refractory organic matter. But high treatment cost and membrane fouling problem affect the applications of membrane in practice.
In order to ensure the welding quality of the butt weld of the supercritical unit pipeline, ultrasonic testing is often used as a nondestructive testing method for the quality evaluation of the butt weld.In this paper, phased array testing technology, Ultrasonic time-of-flight diffraction(TOFD) testing technology and conventional A-type pulse ultrasonic testing technology were used to test the simulated test block. Experiments showed that the three methods can effectively detect slag inclusion, incomplete penetration and cracks. TOFD inspection technology had certain advantages in measuring the height of defects. Phased array ultrasonic testing technology had more intuitive test results. Combined with A-scan signal, it had certain advantages in defect characterization. Conventional A-type pulse ultrasonic testing technology has certain advantages in operability, and can effectively detect complex parts and workpieces.
The comprehensive failure analysis of the fractured LP rotor blade was carried out by means of appearance morphology analysis, SEM morphology analysis, mechanical property analysis, chemical composition analysis and microstructure detection. The results show that the second and last stage blades at the low-pressure rotor turbine side are damaged by mechanical collision, resulting in damage and deformation at the steam outlet side of the blades and generating stress concentration areas. The blades are prone to generate crack sources in the stress concentration areas of mechanical damage under the working load, and the cracks continue to expand on the condition of alternative stress, eventually leading to fatigue cracking and fracture of the blades. It is recommended to carefully check the blades at other positions of the LP rotor and deal with the mechanical damage and cracking problems in time. Secondly, foreign matters shall be prevented from entering the turbine with the steam to damage the blades, and the fixed parts inside the cylinder shall be ensured to be firm and not fall off, so as to prevent the recurrence of similar blade fracture.
The research focuses on slow sand filtration (SSF) simulation system for salty, phosphate and zinc removal. Salty, phosphate and zinc are all the polluted compostions of rainwater runoff. SSF system is an ideal way to purify the rainwater runoff due to its simplicity of construction and low cost. The paper also introduces the practical applications of SSF system nowadays. With the remarkable economic and human pupulation developments, our world faces the challenges of water scarcity. SSF system has great potential in filtering rainwater to provide no-potable water even potable water.
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