Lingjun Gao

Online particle size measurement through acoustic emission detection and signal analysis

Accurate determination of particle size distribution is critical to achieving optimal combustion efficiency and minimum pollutant emissions in both biomass and coal fired power plants. This paper presents an instrumentation system for online continuous measurement of particle size distribution based on acoustic emission (AE) method. Impulsive AE signals arising from impacts of particles with a metallic waveguide protruding into the flow carry information about the particle size. The relationship between the particle size and the peak AE voltage has been established through physical modeling of particle impact. A particle sizing algorithm is developed using peak detection techniques. Experimental results obtained with glass beads demonstrate the capability of the system to discriminate particles of different sizes from the recorded AE signals. The system has several appealing features such as online measurement, high sensitivity, simple structure, minimum invasiveness and low cost, which make it well suited for industrial applications.

On-Line Nonintrusive Detection of Wood Pellets in Pneumatic Conveying Pipelines Using Vibration and Acoustic Sensors

This paper presents a novel instrumentation system for on-line nonintrusive detection of wood pellets in pneumatic conveying pipelines using vibration and acoustic sensors. The system captures the vibration and sound generated by the collisions between biomass particles and the pipe wall. Time-frequency analysis technique is used to eliminate environmental noise from the signal, extract information about the collisions, and identify the presence of wood pellets. Experiments were carried out on an industrial pneumatic conveying pipeline to assess effectiveness and operability. The impacts of various factors on the performance of the detection system are compared and discussed, including different sensing (vibration sensor versus acoustic sensor), different time-frequency analysis methods (wavelet-based denoising versus classic filtering), and different system installation locations.

On-line measurement of particle size distribution using piezoelectric sensors

In many industrial processes involving gas/solid two-phase flows it is desirable to measure various parameters relating to the solid particles. Particle size is one of the most important features relating to process efficiency, pollutant emissions and product quality. In this paper, a novel instrumentation system is proposed to achieve on-line continuous measurement of particle size distribution based on a polyvinylidene difluoride (PVDF) piezoelectric film sensor. The sensor is attached to an impact bar intruding into solid particle flow. The impact events, between the impact bar and the particles, generate a sensor output signal. The relationship between the sensor output and the particle size is modeled mathematically, which can be used to infer the size distribution. Experimental work is undertaken to evaluate the effectiveness of the on-line particle sizing system and the validity of the mathematical model.

Contour-based image segmentation for on-line size distribution measurement of pneumatically conveyed particles

Pneumatic conveyance of particulate materials is an important technique widely used in many industries. This paper is concerned with image processing algorithms in an optical instrumentation system that is used to measure the size distribution of particles in a pneumatic suspension. A CCD camera is used to capture the images of the particulate flow field. — which is illuminated by a 650nm solid state laser. The size distribution of particles is then determined by processing the particle images through contour-based image processing algorithms including embedded pre-processing and particle detection. An artificial particle generator, for the first time, is implemented to generate comparative dataset. A relative comparison is made between the artificial dataset and real dataset obtained from power plant trials.

On-line Sizing of Pneumatically Conveyed Particles Through Acoustic Emission Detection and Signal Analysis

Accurate measurement of the particle size distribution of pneumatically conveyed pulverized fuel is critical to achieving optimal combustion efficiency and minimum pollutant emissions at coal and biomass-fired power plants. This paper presents a prototype instrumentation system for the on-line continuous measurement of particle size distribution through acoustic emission (AE) detection. The proposed method extracts particle size information from the impulsive AE signals arising from impacts of particles with a metallic waveguide protruding into the flow. The relationship between the particle size and the peak AE voltage is established through mathematical modeling of the particle impact process. Identification of the peak AE voltage is achieved with an energy-based peak detection algorithm. Experimental results obtained with glass beads demonstrate the capability of the system to discriminate particles of different sizes from the recorded AE signals. The system performs better in terms of accuracy for higher speed, lower concentration particles as the impact signals are stronger and better separated in the time domain.

On-line automatic detection of wood pellets in pneumatically conveyed wood dust flow

This paper presents a piezoelectric transducer based system for on-line automatic detection of wood pellets in wood dust flow in pneumatic conveying pipelines. The piezoelectric transducer senses non-intrusively the collisions between wood pellets and the pipe wall. Wavelet-based denoising is adopted to eliminate environmental noise and recover the collision events. Then the wood pellets are identified by sliding a time window through the denoised signal with a suitable threshold. Experiments were carried out on a laboratory test rig and on an industrial pneumatic conveying pipeline to assess the effectiveness and operability of the system.

In-line continuous sizing of biomass particles in gas-solid two-phase flow at a biomass-fired power plant

Gas-solid two-phase flows are widely seen in many industrial processes. A good exampleis the pneumatically conveyed pulverised fuel flow in the power generation industry. As a significant renewable fuel source, biomass has been widely adopted in electrical power generation. The particle size distribution of pneumatically conveyed biomass correlates closely with combustion efficiency and pollutant emissions and should therefore be monitored on anin-line, continuous basis. In this paper an integrated instrumentation system using both a piezoelectric sensorand anelectrostatic sensor arrayis proposed to measure the size distribution and flow velocity of biomass particles. A prototype system was tested on a 250mm bore pipe at a biomass-fired power plantand its performance has been evaluated under industrial conditions.

Online sizing of pneumatically conveyed particles by acoustic emission method

Accurate determination of particle size distribution is critical to achieving optimal combustion efficiency and minimum pollutant emissions in both biomass and biomass/coal fired power plants. This paper presents an instrumentation system for online continuous measurement of particle size distribution based on acoustic emission (AE) method. Impulsive AE signals arising from impacts of particles with a metallic waveguide protruding into the flow carry information about the particle size. With detailed information about the generation, propagation and detection of impact AE signals, the particle size can be quantitatively characterized. Experimental results obtained with glass beads demonstrate the capability of the system to discriminate particles of different sizes from the recorded AE signals. The system has several appealing features such as online measurement, high sensitivity, simple structure, minimum invasiveness and low cost, which make it well suited for industrial applications.

In-line particle sizing of pneumatically conveyed particles using a piezo film sensor

The pneumatic conveyance of granular or pulverised materials is widely seen in many industries. The size distribution of pneumatically conveyed particles should be monitored to ensure product quality, improve process efficiency and reduce atmospheric emissions. For instance, particle size distribution of pulverised fuel in the power generation industry is an important parameter in relation to combustion efficiency and pollutant emissions and should therefore be monitored in-line continuously. In this paper, a technique for in-line continuous measurement of particle size distribution based on a piezo film sensor has been proposed and evaluated. Basic measurement principle and mathematical model of the sensing process are introduced. Experimental work is undertaken on a particle flow test rig to evaluate the effectiveness of the particle sizing system and the validity of the mathematical model. Glass beads are used in the experiments as test particles. The results demonstrate the technique is effective for the in-line continuous measurement of glass beads greater than 300μm.