Nozzle Blockage Research Articles

Research on Key Technologies of 38CrMoAl Steel Produced by BOF-LF-RH-CC Process

Nozzle blockage is easy to take place in continuous casting process when producing 38CrMoAl steel due to high content of aluminum ([Al]=0.7%~1.1%). Slag-steel reaction will lead to large transformation for composition of molten steel and performance of slag on the condition of traditional high content of SiO2 in slag. And it will reduce the cleanliness of steel as well. The control target of refining slag and tundish powder has been gotten through the analysis of refining & continuous casting characteristics of high aluminum steel. Based on this, the content of Si and Al in molten steel can be controlled accurately, and the cleanliness of steel has gone to a higher level. Moreover, mold powder with high basicity and vitrification ensures the stability of slag after sorbing Al2O3 inclusions in theory. Continuous casting can be carried out successfully with the control of inclusion morphology through slag washing during tapping. Industrial practice shows that Si content is 0.25%~0.40%, Al content is 0.80%~1.00%, S content is below 0.004% and T[O] is below 0.0015% in steel products. Moreover, casting bloom with good surface quality is achieved, and the rate of bloom without cleaning is as high as 100%. With all these countermeasures, 38CrMoAl steel can be continuously cast for more than 6 heats.

An attempt to compare the performance of bioscrubbers and biotrickling filters for degradation of ethyl acetate in gas streams

AbstractThis study presents a comparison of the efficiency of a bioscrubber and a biotrickling filter (BTF) for the removal of ethyl acetate (EA) vapour from a waste gas stream, under the same operating conditions. The maximum EA elimination capacity achieved in the bioscrubber was 550 g m−3 h−1 with removal efficiency higher than 96%. For higher EA loadings the bioscrubber was oxygen limited, which caused incomplete EA biodegradation. When pure oxygen was fed to the bioscrubber at a rate of 0.02 L min−1, the bioscrubber recovered and could treat higher EA loadings without any oxygen limitation. The BTF achieved EA elimination capacity of 600 g m−3 h−1 with removal efficiency higher than 97% and the dissolved oxygen concentration remained substantially higher than in the bioscrubber. However, severe channelling and blockage of the spray nozzle occurred due to the excessive biomass growth. Overall, the bioscrubber system was easier to operate and control than the BTF, while an enhancement of the oxygen mass transfer in the bioscrubber could potentially increase its performance by up to three times. Copyright © 2005 Society of Chemical Industry

Fluid flow and mixing characteristics in RH degasser of Companhia Siderúrgica de Tubarão, and influence of bottom gas injection and nozzle blockage through physical modelling study

A physical model based on similarity principles has been constructed for simulating the RH degasser of Companhia Siderúrgica de Tubarão (CST), Vitória, ES, Brazil. The influence of gas injection through nozzles in the upleg with simultaneous bottom injection of gas, as well as the influence of nozzle blockage, on the circulation rate has been investigated. In addition, mathematical relationships for mixing characteristics in the process have been evaluated.

A Novel Amylose Corn-Starch Dispersion as an Aqueous Film Coating for Tablets

A novel aqueous coating dispersion of amylose-rich corn starch (Hylon VII) was evaluated in an aqueous film-coating process of tablets using an instrumented laboratory-scale pan-coating apparatus. The influence of two independent process variables, the coating temperature and the atomizing air pressure, on the properties of the coated tablets were investigated. The pre-use stability of aqueous coating dispersion (i.e., amylose corn-starch precipitate) was studied using a powder X-ray diffraction (XRD) technique. The crystallinity of amylose starch in the coating dispersion was found to increase slightly during 9 months of storage (in a refrigerator 6±2°C). The film coatings of an aqueous amylose-rich starch dispersion were successfully applied onto tablets without any significant drawbacks, such as nozzle blockage or related problems. It was found that the temperature in the coating pan had a significant influence on the film surface roughness, mechanical strength, and drug release in vitro. When the lowest coating temperature (30°C) was used, rougher film coatings were obtained due to overwetting. At higher temperatures (up to 50–60°C), lower surface roughness and higher mechanical strength values for the coated tablets were obtained. With the present amylose starch dispersion, the atomizing air pressure had a minor influence on the quality of the coating. Under appropriate coating conditions, a smooth tablet film coating was produced with this new, natural, and inexpensive amylose starch dispersion.

Reactivity of superfine aluminum powders stabilized by aluminum diboride

Al nano-particle (ANP) is vulnerable to external oxidation environment due to its high reactivity. To overcome such drawback, we coat ANPs with organic materials: ethanol and diethyl ether. Comparative discussions are raised from the coating to combustion process between bare ANP and other ANPs with different organic coating layers. Our results show the structure of organic coating layer is different for ethanol and diethyl ether molecules. ANPs prefer adsorbing ethanol molecules for its relatively simple structure and molecular polarity. In the heating stage, the presence of organic coating layers is beneficial for ANPs to attract external oxygen molecules, but the content of active Al atoms is reduced. The combustion stage can be divided into four stages according to the rate of temperature change. ANPs coated with organic compounds show a better combustion performance: they sacrifice ignition time but dramatically increase the combustion temperature which leads the whole ANP into a gas-phase combustion. Such improvement will enable ANPs to release more heat, obtain higher burning rate and effectively prevent nozzle blockage.

Solid Freeforming of Silicon Carbide by Inkjet Printing Using a Polymeric Precursor

Preceramic polymers can be dissolved in solvents to form low‐viscosity fluids. This makes them suitable for solid freeforming by direct inkjet printing. Two ways of using polycarbosilane (pcs) were investigated. In the first, it was dissolved in n‐heptane at up to 30 vol% and printed as a single‐phase material. In the second, it was used as an organic binder for silicon carbide powder suspended in an homologous series of hydrocarbon solvents ranging from n‐heptane to n‐decane. Polyisobutene succinimide was used as a surfactant. In both cases, components could be rendered successfully but pyrolysis of the unfilled pcs resulted in cracking. Components printed with powder suspensions did not crack on pyrolysis, retained overall near net shape, and underwent low shrinkage (8.2 vol%). The molecular weight of the n‐paraffin solvents influenced the viscosity and hence the maximum powder loading while the volatility, a property also related to molecular weight, influenced the quiescence time and the drying time needed between layers. Octane gave the best compromise between speed of printing, the quality and knitting of droplet relics, and the avoidance of nozzle blockage caused by too rapid drying.

Industrial application of a thermodynamical modelto predict inclusion composition

A model to predict microinclusion volume and chemistry, based on thermodynamics and mass balance, was developed for aluminium-killed calcium treated steels. The model turned out to be a useful tool in helping to solve many different problems at several steelworks. In this work, examples of such application are given, covering nozzle blockage by calcium sulphides in boron steels, macroinclusion formation by calcium attack on refractories, and chemical evolution of microinclusion with temperature.

Simple filtration system improves efficiency of a hydropneumatic root elutriator

Separating roots from soil is a laborious and costly process, but a commercially available hydropneumatic root elutriator can semi‐automate the job. Hydraulic and pneumatic systems elutriate the roots from the soil, while the electrical system controls the on/off functions of the hydraulic system. The extruded steel frame of the elutriator serves a dual purpose; structural support and transport of water and compressed air. Water is transported in the lower and air in the upper part of the hollow inner cavity of the extruded steel frame. They exit the frame into polyethylene tubes that extend to the base of the elutriator. After prolonged use, however, this design feature can become problematic because flow to the elutriator of either system can be blocked at the nozzle inlets with rust particles that originate from the steel frame's inner walls. The blockage increases sample processing time due to dismantling, clearing, and reassembling, which eventually degrades the elutriator. To resolve these problems a 40‐mesh (420 micron) in‐line stainless steel water filter and a 40‐micron in‐line bronze air filter were installed in the polyethylene tube lines between the extruded steel frame and the base of the elutriator. These filters were found to reduce nozzle blockage, thereby increasing sample processing efficiency by 10% and improving sample quality.

Safe sorting of GFP-transduced live cells for subsequent culture using a modified FACS Vantage

A stream-in-air cell sorter enables rapid sorting to a high purity, but it is not well suited for sorting of infectious material due to the risk of airborne spread to the surroundings. A FACS Vantage cell sorter was modified for safe use with potentially HIV infected cells. Safety tests with bacteriophages were performed to evaluate the potential spread of biologically active material during cell sorting. Cells transduced with a retroviral vector carrying the gene for GFP were sorted on the basis of their GFP fluorescence, and GFP expression was followed during subsequent culture. The bacteriophage sorting showed that the biologically active material was confined to the sorting chamber. A failure mode simulating a nozzle blockage resulted in detectable droplets inside the sorting chamber, but no droplets could be detected when an additional air suction from the sorting chamber had been put on. The GFP transduced cells were sorted to 99% purity. Cells not expressing GFP at the time of sorting did not turn on the gene during subsequent culture. Un-sorted cells and cells sorted to be positive for GFP showed a decrease in the fraction of GFP positive cells during culture. Sorting of live infected cells can be performed safely and with no deleterious effects on vector expression using the modified FACS Vantage instrument.

Safe sorting of GFP‐transduced live cells for subsequent culture using a modified FACS Vantage

Background: A stream-in-air cell sorter enables rapid sorting to a high purity, but it is not well suited for sorting of infectious material due to the risk of airborne spread to the surroundings. Methods: A FACS Vantage cell sorter was modified for safe use with potentially HIV infected cells. Safety tests with bacteriophages were performed to evaluate the potential spread of biologically active material during cell sorting. Cells transduced with a retroviral vector carrying the gene for GFP were sorted on the basis of their GFP fluorescence, and GFP expression was followed during subsequent culture. Results: The bacteriophage sorting showed that the biologically active material was confined to the sorting chamber. A failure mode simulating a nozzle blockage resulted in detectable droplets inside the sorting chamber, but no droplets could be detected when an additional air suction from the sorting chamber had been put on. The GFP transduced cells were sorted to 99% purity. Cells not expressing GFP at the time of sorting did not turn on the gene during subsequent culture. Un-sorted cells and cells sorted to be positive for GFP showed a decrease in the fraction of GFP positive cells during culture. Conclusions: Sorting of live infected cells can be performed safely and with no deleterious effects on vector expression using the modified FACS Vantage instrument. Cytometry 37: 284–290, 1999. © 1999 Wiley-Liss, Inc.

Launch Vehicle Dynamic and Control Effects from Solid Rocket Motor Slag Ejection

The effects of the ejection of slag from a Titan IV solid rocket motor upgrade (SRMU) are analyzed for the maximum dynamic pressure time. It is assumed that the 2500 Ibs of slag on board at that time is ejected, and the corresponding thrust perturbation is determined using existing theory for the discharge of an inert body. The slag ejection event causes sharp thrust transients during blockage of the nozzle throat and blow-down of the motor internal pressure. Control simulations indicate a worst-case SRMU gimbal angle change of 0.51 deg during the event, and small-amplitude limit cycles after the excitation. An aeroelastic analysis yields yaw shear loads and bending moments as high as 13600 Ibf and 5.1x 106 Ibf-in, respectively, at the aft end of the vehicle. It is shown that the degree of the nozzle throat blockage primarily defines the lateral load magnitudes. The Titan IV has adequate structural and control margins, and slag ejection does not pose a concern for its missions. Nomenclature A* =

The MV Robert LeMeur Ice/Propeller Interaction Project: Full-Scale Data

An experimental program was conducted in which ice/propeller interaction data were collected on a twin-shaft shrouded controllable pitch propeller vessel with 3500 kW per shaft line. The tests were conducted in late June 1984 in the seasonal ice of the Canadian Beaufort Sea. Collected data illustrate the phenomena occurring in the Kort nozzle. A number of observations were made: interaction forces during nozzle blockage are of the same magnitude as during ice-blade impact; the maximum ice-induced blade force is not a function of ship speed; maximum ice-induced blade force occurs near relative radius 0.8. Ice interactions cause significant movement of the shaft relative to the shaft bearing; in ahead mode the blade is bent forward during ice interactions. Ice-induced shaft torque transients reached twice nominal and ice-induced shaft thrust transients reached four times nominal value. The largest blade impact forces are associated with the short-duration impacts.

Rare Earth Additions in Continuously Cast Steel

Rare earth (lanthanide metals) addiiions to continuously cast steel are particularly advantageous because of their ability to refine as-cast structures, reduce segregation and increase hot ductility at temperatures just below that of solidification. The complete shape control of sulfides in steels containing Rare Earth Metals (REM), whether continuously cast or ingot cast, is primarily responsible for improvements in ductility related mechanical properties, weldability, fatigue resistance and resistance to hydrogen damage. Complete sulfide shape control can be obtained with REM additions at sulfur levels as high as.020%. The greatest improvements, however, are obtained with REM additions to low sulfur steels. However, to achieve full operational advantages afforded by REM, nozzle blockage problems must be circumvented. Water model studies indicate a possible solution.

Ejecta pulsing of subscale solid propellant rocket motors

This paper presents results obtained in a program designed to develop guidelines for pulsing solid propellant rocket motors to determine their susceptibility to finite amplitude disturbances. A series of motor firings was conducted in which sphetes of different sizes and materials were ejected through the nozzle to simulate inf light partial nozzle blockage due to igniter, propellant or other combustion chamber material fragments. Simple laboratory scale solld rocket motors with full and partial length grains were utilized. All of the motors tested were triggered into sustained nonlinear instability. A simple analysis was developed to calculate the velocity of the ejecta and pulse duration. Gaod ogreement between predicted and measured pulse durations was obtained. Two methods were developed for predicting initial ejecta induced pulse amplitudes: a simple model based on linear wave propagation theory and the assumption of quaslsteady nozzle behavior, and a numerical model which utillzes the quasi-steady nozzle assumption to provide a nozzle entrance boundary condition to a comprehensive combustion chamber nonlinear instability analysis. Comparisons of theoretical predictions with experimental data for both pulse amplitude and the motor response to pulsing are presented. Tht nonlinear instability analysis was found to be capable of predicting the complete range of nonlinear behavior observed in motor response to ejecta pulsing. Good agreement between measured and predicted initi pulse (amplitude and harmonic content), waveform evo ution, growth and decay rates, and DC shift was obtained. p'

Thermodynamics of nozzle blockage in continuous casting of calcium-containing steels

Thermodynamics of nozzle blockage in continuous casting of calcium-containing steels

Thermodynamics of nozzle blockage in continuous casting of calcium-containing steels

Calcium-bearing material is added commercially to remove sulfur and to control sulfide shape. Few steelmakers, however, have used calcium additions to cast aluminum-killed steels successfully through metering nozzles. In a development program to cast aluminum-killed steels at Inland's No. 1 Electric Furnace and Billet Caster Shop, calcium-silicide injection at first resulted in nozzle blockage in both aluminum-killed and silicon-killed steels. This paper discusses the thermodynamics of iron containing silicon, aluminum, calcium, oxygen, and sulfur, as well as analyses of the nozzle deposits. The thermodynamic calculations show that, in iron containing aluminum, the calcium content can be too high, so that solid calcium sulfides form. In iron containing silicon without aluminum, with similar calcium contents, solid calcium silicates and calcium sulfides can form. The results of the analyses from plugged nozzles were in agreement with these thermodynamic predictions.

A mathematical model of nozzle blockage by freezing—II. Turbulent flow

Hot molten metal flowing through a cylindrical pipe is frozen by the cold walls of the pipe and forms a solid crust on the walls. A model is presented to describe the growth of this crust given that the flow through the pipe is turbulent. Criteria which determine whether or not the pipe will block are investigated and some results from the theoretical analysis are presented for flows with Reynolds number between 2000 and 100,000 appropriate to those fluids with Prandtl numbers in the range 0.007–0.1.

A mathematical model of nozzle blockage by freezing

A mathematical model is presented which describes the formation of a crust on the inside of a cold pipe through which a fluid is flowing. A numerical/analytical treatment of the inward solidification problem is given and criteria presented which predict conditions under which blockage will occur.

Solidification of a liquid metal flowing through a circular pipe: a prediction of nozzle blockage

A description of a mathematical model is presented which deals with the freezing, and possible blockage, of a hot fluid as it flows through a pipe which is maintained at a subfreezing temperature. Full details of an interactive Fortran program are given. The program output provides full details of the time development of the crust, fluid pressure, local Reynolds number and inward crust speed. The program includes consideration of laminar or turbulent flow. The structure of the program consists of modules which can be modified to suit the end users system. In particular an option is provided to provide for graphical output.

Effect of silicone oil on solid propellant combustion in small motors

The feasibility of reducing troublesome nozzle blockage (by condensation deposits) in laboratory-scale solid rockets by addition of a silicone oil as a propellant ingredient was explored experimentally. An aluminized composite propellant and its counterpart with 1% silicone oil replacing part of the binder were fired in a 63.5 mm diameter, end-burning, all-metal burner. Pressure-time histories were recorded for all of the tests by a Taber gauge mounted at the downstream end of the chamber; temperature-time data at the nozzle throat were obtained in some of the runs by thermocouples having junctions positioned at the wall but insulated from the metal. Deposition of condensables on the nozzle walls causing a progressive increase in the chamber pressure with time was noted. The fraction of firings exhibiting practically no condensation was 59% with silicone and 32% without. On the average, temperature readings at the nozzle throat were higher with the silicone propellants. Although various phenomena may contribute to these findings, the results are not understood completely.