Feed Pipe Research Articles

Novel intermittent solid slug feeder for fast pyrolysis reactors: Fundamentals and modeling

To prevent plugging and help the raw biomass particles effectively penetrate and spread into the pyrolysis fluidized beds, one could inject the particles using intermittent slugs created by propelling loosely packed particles with gas pulses and transporting them along horizontal or inclined feeding pipes into the fluidized bed section of the reactor; this would combine the advantages of the low gas consumption of the screw feeders and the short residence time in high temperature zones of dilute phase feeders.Dried distillers' grain (DDG) and meat and bone meal residues (MBM) were selected as model feedstocks for experimental testing and modeling of a novel intermittent solid slug feeder technology. These feedstocks were chosen as much work has been done to attempt to process them into value-added products via fast pyrolysis, but they also possess very challenging flow characteristics and properties that are very different from each other (particle size, cohesivity, temperature sensitivity, density). As a result, creating a predictive model that can successfully model these challenging feedstocks is the basis to model any biomass of interest.The biomass flow in the feeding tube begins as an induced dense-phase flow and develops into a high velocity ‘aerated bed flow’. Gas leakage, solid friction and force-momentum balances were considered in the model. The model was developed from experimental data collected with simplified plugs (modified nylon ball), as well as real biomass slug flow.Several important variables were identified. They included the material flow properties, the gas capacitance pulse pressure and volume, and the length and material of feeding tube. The goals of this study were to (a) characterize the fundamental dynamic behavior of the biomass slugs in the feeder, (b) maximize the solid-to-gas feeding ratio, and thus minimize energy consumption, (c) minimize the accumulation of “straggler” biomass material in the feeding tube between pulses, and thus preventing biomass pre-cooking in the feeding tube and plugging (d) develop and validate a predictive model for the slug velocity at any point in the feeding tube (and thus the maximum feeding tube length), that can be applied for feeder and reactor design for any biomass feedstock, and (e) identify future areas of work for the ICFAR intermittent solid feeder.

Hydrogen production by supercritical water gasification of biomass: Particle and residence time distribution in fluidized bed reactor

Particle distribution and residence time distribution (RTD) in supercritical water fluidized bed reactor (SCWFBR) greatly affect the hydrogen yield through determining the two phase mixing and reaction time. A Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the solid distribution and RTD of feeding materials. The effect of four types of feeding methods and feeding rates on solid distribution and RTD were evaluated based on the simulation results. Results showed that double symmetrical feeding pipe with an feeding mouth angle of 45° provides more uniform solid distribution and longer residence time compared with those of other three types. A nonlinear relationship between feeding rate and RTD was observed, and an optimum feeding rate was found to be related to the best solid-fluid mixing in the study.

Mixing time and kinetic energy measurements in a shaken cylindrical bioreactor

The mixing dynamics in a cylindrical shaken bioreactor are investigated by means of velocity and kinetic energy and mixing time measurements obtained with phase-resolved PIV and a dual pH indicator system, respectively. The objective of the work is to correlate the kinetic energy of the flow and the mixing number measured under different operating conditions. The results provide evidence that the onset of a laminar-turbulent flow transition occurs when the previously reported transition to out-of-phase flow takes place, and that the mixing number is highly dependent on the position of the feeding pipe. Insertion close to the vessel walls and thus outside the vortical structures present near the centre of the reactor can enhance mixing.

Combined experimental and numerical approach for wear prediction in feed pipes

Within this work, a combined experimental and numerical approach to fundamentally understand erosive wear in feed pipes was initiated. By experimental lab-scale testing, it was shown that erosion rates strongly depend on the material's properties and testing conditions. Steel wear was more pronounced at higher impact angle, whereas low impact angle was more critical for rubber. Lab-tests results distinguish from empirical erosion models because material dependent critical impact energies and fatigue phenomena cannot be considered there. A CFD–DEM approach was conducted for simulation of particulate flow in pipes. In addition, long term wear measurements were done to gain data of the wear progress. Although further validation and testing are necessary, very promising results on erosion prediction could be achieved.

Discontinuous addition of small volumes of liquids in an intensive mixer to animal supplement feed with different particle size distributions

Abstract Animal compound and supplement feed can generally be characterised as dispersible multi-ingredient mixtures in which particles differ in size, density and shape and tend to segregate. The segregation of animal compound and supplement feed is frequently a reason for customer and official complaints. To avoid segregation, usually small volumes of liquids – e.g. molasses or vegetable oils – are added in the main mixer of a feed production line to cause fractional agglomeration of fine particles. The presence of small volumes of liquids will affect the distribution behaviour of particles during mixing and it may also influence the material and technological properties. However, the mixing homogeneity of typical compound feeds that can be achieved when small volumes of liquids are present is not adequately characterised at the moment. There is insufficient knowledge of the process design and specifically the time of the liquid application in the mixing sequence. This study aimed to investigate the effect of adding liquids in customary amounts to animal supplement feed on the achievable mixing homogeneity as well as its dependency on the time of the liquid application in the mixing sequence. Major material properties, namely flowability and dusting potential, were determined to evaluate both the results and the product quality. An intensive mixer equipped with a feed pipe for liquid application was used as test facility. The results show that, under certain conditions, the addition of liquids in an intensive mixer may have a positive effect on the achievable mixing homogeneity of mineral feeding stuffs.

Diagnosis of the ageing of water pipe systems by water quality and structure of iron corrosion in supplied water

To develop a method for screening ageing of water supply systems by analysing the supplied water's quality, water samples were collected from a water treatment plant, a delivery pump station, two distribution reservoirs and two feed pipes along a water pipe system. Principal component analysis of the water was conducted. In the first principal component, many elements exhibited high factor loadings, whereas the major contributor for the second principal component was iron (Fe). The unlined steel pipe, which was beyond its working lifetime, had a significantly high Fe content in suspended solids. X-ray absorption fine structure (XAFS) analysis showed differences in the abundance ratios of Fe3O4 and α-FeOOH among the sampling points. It was concluded that the concentration and speciation of Fe in supplied water can be a useful index for detecting the ageing of pipes.

Turbidity and pH dissipations in a dosage of high concentration NaOH solution to seawater

It is sometimes necessary to dose into a desalination feed stream a caustic solution to achieve a controlled pH increase, as, for example, in the application of boron suppression measures. To restrict the size of the caustic feed system, the NaOH is dosed from a high concentration solution. The solution is injected at the center of the raw water feed pipe and its concentration dissipates as it mixes with the main flowing solution. The problem is that desalination feed waters usually contain ions of a sparingly soluble salt such as CaCO3 and Mg(OH)2, which tend to precipitate at high pH levels. The very high local concentrations of the dosed NaOH at the injection region can lead to very high local supersaturations and induce the nucleation and precipitation of scale particles. The main goal of the present work was to delineate flow and concentration conditions at which dosage of a concentrated NaOH solution to seawater concentrates will not induce significant precipitation of CaCO3 and Mg(OH)2.

Generation of monodispersed microdroplets by temperature controlled bubble condensation processes

This work introduces a microfluidic method for the generation of monodispersed microdroplets by using temperature controlled bubble condensation processes. In this method, the dispersed phase is first vaporized in the feeding pipe and ruptured to monodispersed bubbles in a coflowing stream. These bubbles are then condensed in the downstream pipe, where monodispersed microdroplets are obtained. This method ensures the narrow distribution of droplet diameters and prepares microdroplets less than 200 μm in sub-millimeter fluidic devices.

Numerical simulation of thermal processes in the elements of MHD-pumps used for transferring liquid metals

The paper is devoted to numerical simulation of the non-stationary thermophysical processes occurring in the liquid metal feed pipe of MHD pumps. The non-stationary heat-conduction problem is formulated and solved numerically by the finite element method using ANSYS software. The results of numerical simulations are compared with the previously obtained experimental data. A series of numerical computations have been carried out to estimate the influence of different parameters on the process of pipe heating, which allowed us to determine the optimal parameters ensuring effective operation of MHD-pumps.

FEM modeling of the piezoelectric driving system in the design of direct-acting diesel injectors

A detailed mathematical model of a direct-acting prototypal piezo-injector has been developed to help experimentation, design and component optimization. The thermo-fluid dynamics of the hydraulic circuit components, including the injector feeding pipe, injector drilled pipes and nozzle, was modeled in conjunction with the mechanics of the mobile elements in the injector. A Finite Element Method (FEM) model of the piezo-stack has been developed to predict the temporal distribution of the elongation of the piezo-actuator. The piezoelectric submodel was based on the experimental trace of the current provided to the piezo-stack and was verified to correctly reproduce the dynamic response of the injector piezoelectric driving system.The complete numerical tool was then validated through an extensive comparison with experimental data taken for different injector working conditions. Finally, the validated model was applied to help develop the direct-acting prototypal injector through a better understanding of the cause and effect relationships in the analysis of the performance of the injection system. An upgraded version of the injector has been set up on the basis of the indications of the model and tested on the hydraulic test rig. The hydraulic performance of the modified injector has proved satisfactory and to be in line with the model predictions.

Quantitative characterization of pulverized coal and biomass–coal blends in pneumatic conveying pipelines using electrostatic sensor arrays and data fusion techniques

Quantitative data about the dynamic behaviour of pulverized coal and biomass–coal blends in fuel injection pipelines allow power plant operators to detect variations in fuel supply and oscillations in the flow at an early stage, enable them to balance fuel distribution between fuel feeding pipes and ultimately to achieve higher combustion efficiency and lower greenhouse gas emissions. Electrostatic sensor arrays and data fusion algorithms are combined to provide a non-intrusive solution to the measurement of fuel particle velocity, relative solid concentration and flow stability under pneumatic conveying conditions. Electrostatic sensor arrays with circular and arc-shaped electrodes are integrated in the same sensing head to measure ‘averaged’ and ‘localized’ characteristics of pulverized fuel flow. Data fusion techniques are applied to optimize and integrate the results from the sensor arrays. Experimental tests were conducted on the horizontal section of a 150 mm bore pneumatic conveyor circulating pulverized coal and sawdust under various flow conditions. Test results suggest that pure coal particles travel faster and carry more electrostatic charge than biomass–coal blends. As more biomass particles are added to the flow, the overall velocity of the flow reduces, the electrostatic charge level on particles decreases and the flow becomes less stable compared to the pure coal flow.

Assessment of Quantitative Perfusion Parameters by Dynamic Contrast-Enhanced Sonography Using a Deconvolution Method

The purpose of this study was to investigate the impact of the arterial input on perfusion parameters measured using dynamic contrast-enhanced sonography combined with a deconvolution method after bolus injections of a contrast agent. The in vitro experiments were conducted using a custom-made setup consisting of pumping a fluid through a phantom made of 3 intertwined silicone pipes, mimicking a complex structure akin to that of vessels in a tumor, combined with their feeding pipe, mimicking the arterial input. In the in vivo experiments, B16F10 melanoma cells were xenografted to 5 nude mice. An ultrasound scanner combined with a linear transducer was used to perform pulse inversion imaging based on linear raw data throughout the experiments. A mathematical model developed by the Gustave Roussy Institute (patent WO/2008/053268) and based on the dye dilution theory was used to evaluate 7 semiquantitative perfusion parameters directly from time-intensity curves and 3 quantitative perfusion parameters from the residue function obtained after a deconvolution process developed in our laboratory based on the Tikhonov regularization method. We evaluated and compared the intraoperator variability values of perfusion parameters determined after these two signal-processing methods. In vitro, semiquantitative perfusion parameters exhibited intraoperator variability values ranging from 3.39% to 13.60%. Quantitative parameters derived after the deconvolution process ranged from 4.46% to 11.82%. In vivo, tumors exhibited perfusion parameter intraoperator variability values ranging from 3.74% to 29.34%, whereas quantitative ones varied from 5.00% to 12.43%. Taking into account the arterial input in evaluating perfusion parameters improves the intraoperator variability and may improve the dynamic contrast-enhanced sonographic technique.

IMPACT OF THERMOMECHANICAL REFINING CONDITIONS ON FIBER QUALITY AND ENERGY CONSUMPTION BY MILL TRIAL

Fiber thermomechanical refining is a critical step for the manufacturing of medium density fiberboard (MDF). To increase productivity and improve fiber quality with a reduction in energy consumption during refining, it is essential to determine appropriate refining conditions, such as the chips retention time (accumulated chip height, CH) in the pre-heater, feeding screw revolution speed (SR) in the chip feeding pipe, and the opening ratio of the discharge valve (OV) in the discharge pipe. Using multiple regression analysis, relationships between the response variables (the total fibers, the specific energy consumption obtained by the motor power consumption/the total amount of dry fibers, and the percentage of qualified fibers) and the predictor variables (OV, CH, and SR) were modeled. Specific energy consumption decreased with an increase in CH. When more chips were stored in the pre-heater, the chips were softened by the extended steam-treatment time, reducing the energy consumption. There were negative relationships between the percentage of qualified fibers and the predictor variables (OV and SR). It was reasoned that a greater proportion of coarse fibre was produced when the discharge valve opening ratio or the feeding screw speed increased. This resulted in a reduction in the percentage of qualified fibers. Due to the large sample size (1667 measurements for each variable) in this study, the resulting regression equations can be applied to estimate the productivity, energy consumption, and fiber quality during refining in an MDF mill.

Numerical Characterization of Aerodynamic Losses of Jet Arrays for Gas Turbine Applications

Jet array is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooled region of gas turbine airfoils or in the turbine blade tip clearances control of large aero-engines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In this work, an aerodynamic analysis of jet arrays for active clearance control was performed; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The data were taken from a set of CFD RANS simulations, in which the behavior of the cooling system was investigated over a wide range of fluid-dynamics conditions. Furthermore, several different holes arrangements were investigated in significant detail, with the aim of evaluating the influence of the hole spacing on the discharge coefficient distribution. Tests were conducted by varying the jet Reynolds number in a wide range of effective engine operative conditions (Re = 2000-12,000, Pressure- Ratio = 1.01-1.6). To point out the reliability of the CFD analysis, some comparisons with experimental data, measured at the Department of Energy Engineering of the University of Florence, were drawn. An in-depth analysis of the numerical data set has underlined the opportunity of an efficient reduction through the mass velocity ratio of hole and feeding pipe: the dependence of the discharge coefficients from this parameter is roughly logarithmic.

Numerical studies on flow behavior of composite propellant slurry during vacuum casting

Rockets are powered by composite solid propellant, which is a heterogeneous system consisting of solid oxidizer and metallic fuel dispersed in a polymeric fuel binder matrix. The slurry casting technique under vacuum/ gravity condition is well-established for performing a different class of large sized case bonded rocket motors. During propellant casting, the flow rate of slurry is a very critical parameter as it affects the product quality. The casting rate is governed by suficient degassing and viscosity buildup due to the progress of cure reaction. In the present study, casting rate and casting time have been numerically evaluated for fixed and varying percentages of valve opening, different viscosity of slurry, and different pressure drop (driving force). The velocity profile of propellant slurry inside feeding pipe and valve has also been evaluated. Furthermore, to get a flawless grain and to predict the slurry casting rate, a microscopic analysis has been carried out to model the flow behaviour of composite propellant slurry, where the momentum conservation law has been applied to express the mathematical model in an analytical form. The resulting differential and algebraic equations have been solved numerically using MATLAB, computing software. The numerical analysis is useful for designing new casting set-up and for giving the idea of maximum casting rate, which is achievable for given casting set-up and rheological properties of propellant slurry.

Development and performance assessment of the new-generation CF fuel injection system for diesel passenger cars

An innovative hydraulic layout for high-pressure fuel injection systems has been developed. The rail has been removed from the high-pressure circuit of standard Common Rail injection apparatus in order to have: reduced production costs, easy installation on the engine and a fast dynamic response of the injection system during engine transients. The innovative high-pressure pump has been machined with extra delivery ports in order to obtain direct connection with each of the injector feeding pipes. A special pump delivery-chamber, featuring an adequate volume, was designed to provide the minimum hydraulic capacitance required for a proper control of the high-pressure in the system. A prototype of the new-concept Common Feeding (CF) injection system was set up at the Politecnico di Torino laboratory and subjected to an extensive experimental campaign on an advanced hydraulic test rig. The hydraulic performance of the new apparatus was compared with that of standard Common Rail system, in terms of injected flow-rate time histories, cycle-to-cycle dispersion and multiple injection dependence on dwell time. Finally, the new-generation system was installed on a Euro 5 diesel engine and tested in a dynamometer-cell. Pollutant emissions were measured at some reference working conditions as well as along the NEDC and compared to analogous data obtained for the same engine, but set up applying the standard Common Rail.

Study on fluid-structure interaction in liquid oxygen feeding pipe systems using finite volume method

The fluid-structure interaction may occur in space launch vehicles, which would lead to bad performance of vehicles, damage equipments on vehicles, or even affect astronauts’ health. In this paper, analysis on dynamic behavior of liquid oxygen (LOX) feeding pipe system in a large scale launch vehicle is performed, with the effect of fluid-structure interaction (FSI) taken into consideration. The pipe system is simplified as a planar FSI model with Poisson coupling and junction coupling. Numerical tests on pipes between the tank and the pump are solved by the finite volume method. Results show that restrictions weaken the interaction between axial and lateral vibrations. The reasonable results regarding frequencies and modes indicate that the FSI affects substantially the dynamic analysis, and thus highlight the usefulness of the proposed model. This study would provide a reference to the pipe test, as well as facilitate further studies on oscillation suppression.

Improved Design for the Device of Biomass Pyrolysis

On account of the problems which often appeared in the biomass pyrolysis device, a new set of improved biomass pyrolysis device was designed. It contains four parts: feed system, fluidized bed, cyclone separation system and condenser system. It has mainly solved the problems through the improved equipment as below: blind arch phenomenon in feed bucket, feed pipe jammed and the feed system leakage; when it makes pyrolysis experiment, the sand grains are easy to be carried out of the fluidized bed ; the cyclone separator separation efficiency is low; the condensation speed is slow and so on.

Pulverized coal stream ignition delay under conventional and oxy-fuel combustion conditions

The coal stream ignition process is critical to the performance of modern pulverized coal burners, particularly when operating under novel conditions such as experienced in oxy-fuel combustion. However, experimental studies of coal stream ignition are lacking, and recent modeling efforts have had to rely on comparisons with a single set of experiments in vitiated air. To begin to address this shortfall, we have conducted experiments on the ignition properties of two U.S. and two Chinese coals in a laminar entrained flow reactor. Most of the measurements focused on varying the coal feed rate for furnace temperatures of 1230–1320 K and for 12–20 vol.% O 2 in nitrogen. The influence of coal feed rate on ignition with a carbon dioxide diluent was also measured for 20 vol.% O 2 at 1280 K. A second set of measurements was performed for ignition of a fixed coal feed rate in N 2 and CO 2 environments at identical furnace temperatures of 1200 K, 1340 K, and 1670 K. A scientific CCD camera equipped with a 431 nm imaging filter was used to interrogate the ignition process. Under most conditions, the ignition delay decreased with increasing coal feed rate until a minimum was reached at a feed rate corresponding to a particle number density of approximately 4 × 10 9 m −3 in the coal feed pipe. This ignition minimum corresponds to a cold flow group number, G, of ∼0.3. At higher coal feed rates the ignition delay increased. The ignition delay time was shown to be very sensitive to (a) the temperature of the hot coflow into which the coal stream is introduced, and (b) the coal particle size. The three high volatile bituminous coals showed nearly identical ignition delay as a function of coal feed rate, whereas the subbituminous coal showed slightly greater apparent ignition delay. Bath gas CO 2 content was found to have a minor impact on ignition delay.

Further Studies of Micromixing: Scale-Up, Baffling and Feed Pipe Backmixing

Micromixing has been studied in a semi-batch reactor agitated by a Rushton turbine using two different reaction schemes. With one scheme, the selectivity was similar at the same mean specific energy dissipation rate and feed location at the 3.6 L scale to that found earlier at the 25 L scale. Also, at the 3.6 L scale, a study of backmixing at different feed locations showed that it was greatest when feeding into the trailing vortex, which is also the best feed location to improve micromixing. At that location, all pipes gave a similar selectivity at the same exit velocity. Comparison with the limited literature showed that one of the two criteria for predicting backmixing fitted the present results quite well but the other was out by two orders of magnitude. The other reaction scheme was used to compare micromixing in a 3 L vessel under baffled conditions with that without them. Such a comparison has only been made once before at a larger 25 L scale and with a different reaction scheme. The earlier surprising result was confirmed, namely that the mean specific energy dissipation rate required for equivalent selectivity without baffles was less than that required with them.