Analysis of the Flow Field and Impact Force in High-Pressure Water Descaling

This study aims to improve the performances of the high-pressure water descaling technology used in steel hot rolling processes.In particular,a 2050 mm hot rolling line is considered,and the problem is investigated by means of a fluid–structure interaction(FSI)method by which the descaling effect produced by rolling coils with different section sizes is examined.Assuming a flat fan-shaped nozzle at the entrance of the R1R2 roughing mill,the outflow field characteristics and the velocity distribution curve on the strike line(at a target distance of 30–120 mm)are determined.It is found that the velocity in the center region of the water jet with different target distances is higher than that in the boundary region.As the target distance increases,the velocity of the water jet in the central region decreases.Through comparison with experimental results,it is shown that the simulation model can accurately predict the impact position of the high-pressure water on the impact plate,thereby providing a computational scheme that can be used to optimize the nozzle space layout and improve the slabs’descent effect for different rolling specifications.

STUDY ON BLASTING DESCALING IN THE SOOT-DELIVERY PIPE

An experiment model, scaled 1: 1, designed for studying a blasting method to clear away soot in a soot-delivery pipe in coal-burning power plant is described. By mixing RDX and Nitramon on a particular scale and sticking the explosive cartridge on the outwall surface of the pipe, the experimental result makes clear that the controlled blasting method can get rid of the soot effectively. Under the action of the blasting compression wave and reflectance tension wave,the soot is destroyed effectively in the region of - 60° ~60° around the bIasting site, that creates a condition for the second blasting in the surplus soot.

Influence of a Protective Coating Slurry on Enhancing the Descaling Ability and Oxidation Resistance of 9% Nickel Steel

A kind of ceramic slurry was prepared and sprayed onto the surface of 9Ni steel at room temperature. The coating layer will not only reduce the depth of the formed Ni-enriched entanglement at high temperature but also have an excellent ability to resist oxidation of the 9Ni steel. Compared to bare specimen, the depths of the entanglement of the coated 9Ni specimen could be successfully reduced by 74.1% and the oxidation loss be decreased by 62.3% by heating at 1 250 ℃ for 60 min. In addition, the coated specimen indicates no trace of oxide pegs. It proves that the coating has outstanding improvement to internal oxidation resistance. Some characterization methods such as metalloscopy, XRD, XPS, SEM and EDX have been used to reveal a possible protective mechanism. The result shows that the coating layer reacts with the iron oxide to form Mg Fe2O4 on the surface of the coated specimen, which could provide a smaller diffusion coefficient rate of Fe ion. The coating with a low cost and easy implementation is promisingly applicable in the slab-reheating process of the 9Ni steel.

Impact Pressure Distribution in Flat Fan Nozzles for Descaling Oil Wells

The suitability of high pressure nozzles in terms of impact upon targeted surfaces has indicated its effectiveness for the cleaning of oil production tubing scale, which has recently attracted wider industrial applications considering its efficiency, ease of operation and cost benefit. In the oil and gas production, these nozzles are now used for cleaning the scale deposits along the production tubing resulted mainly from salt crystallization due to pressure and temperature drop. Detailed characterizations of flat-fan nozzle in terms of droplet sizes and mean velocities will benefit momentum computations for the axial and radial distribution along the spray width, with the view of finding the best stand-off distance between the target scale and the spray nozzle. While the droplet sizes and the velocities determine the momentum at impact, measuring droplet sizes has been known to be difficult especially in the high density spray region, still laboratory characterization of nozzles provides a reliable data especially avoiding uncontrollable parameters. While several researches consider break up insensitive to the cleaning performance, this research investigates the experimental data obtained using PDA （phase doppler anemometry） which led to established variation in momentum across the spray width thus, non-uniformity of impact distribution. Comparative model was then developed using Ansys Fluent code, which verifies the eroded surfaces of material using the flat-fan atomizer to have shown variability in the extent of impact actions due to kinetic energy difference between the center and edge droplets. The study＇s findings could be useful in establishing the effect of droplet kinetic energies based on the spray penetration, and will also add significant understanding to the effect of the ligaments and droplets, along the spray penetration in order to ascertain their momentum impact distribution along the targeted surface.

Directional amine-based solvent extraction for simultaneous enhanced water recovery,salt separation and effective descaling from hypersaline brines

The feasibility of simultaneous water recovery,salt separation and effective descaling of hypersaline brine was investigated by diisopropylamine(DIPA)-based directional solvent extraction(DSE),using diluted/concentrated seawater with initial saline concentration range of 12–237 g/L at extraction temperatures of 5 and 15℃,respectively.The water recovery shows an obvious boundary at saline concentration of 115 g/L under dual effect of specific water extraction efficiency and extraction cycles.High Cl^(–) ion concentration in product water is in sharp contrast to the nearly complete removal of SO_(4)^(2–)and hardness ions,indicating that DIPA-based DSE process indeed achieved efficient separation and purification of Cl^(–) ion from hypersaline brines.Especially,the radical precipitation of Mg^(2+)and Ca^(2+)ions in form of Mg(OH)_(2)and CaCO_(3)demonstrates effective descaling potential,although it leads to more DIPA residues in dewatered raffinate than product water.Moreover,an exponential correlation between the Cl^(–) removal efficiency and specific water extraction efficiency further reveals the intrinsic relationship of water extraction process and transfer of Cl^(–) ion to the product water.Overall,the study provides a novel approach for integrating the water recovery and separation of Cl^(–) ion from ultra-high-salinity brines with radical precipitation of Mg^(2+)and Ca^(2+) ions in one step.

Descaling Behavior of 430 Hot-rolled Stainless Steel in HCl-based Solution

Descaling of hot-rolled stainless steel is generally implemented through pickling process in HNO_3-HF mixed acids,which induces severe environmental concerns of nitrogen oxide（NOx）gases and nitrites.According to the electrochemical measurement,the mass loss test and the appearance analysis,a new pickling process which employed HCl-based solution was proposed and evaluated to provide theoretical basis for the development of environment-friendly and highly effective pickling process.Under the experimental condition,the HCl-based solution can compete with ordinary HNO_3-HF mixed acids in terms of pickling efficiency,surface integrity and the removal of Crdepleted layer.The descaling process of 430hot-rolled stainless steel in the HCl-based solution consisted of three steps.The descaling solution penetrated the oxide scales into the underlying metal,dissolving the Cr-depleted layer and part of substrates.The oxide scales peeled off from the stainless steel and a polished and smooth surface was exposed.The descaled stainless steel was dissolved uniformly in the HCl-based solution;therefore,the pickling duration was vital for desired surface integrity.Under the static condition,the appropriate descaling time of 430 hotrolled stainless steel in HCl-based solution was 400 s.

Pressure Drop of Liquid–Solid Two-Phase Flow in the Vertical Tube Bundle of a Cold-Model Circulating Fluidized Bed Evaporator

A cold-model vertical multi-tube circulating fluidized bed evaporator was designed and built to conduct a visualization study on the pressure drop of a liquid–solid two-phase flow and the corresponding particle distribution.Water and polyformaldehyde particle(POM)were used as the liquid and solid phases,respectively.The effects of operating parameters such as the amount of added particles,circulating flow rate,and particle size were systematically investigated.The results showed that the addition of the particles increased the pressure drop in the vertical tube bundle.The maximum pressure drop ratios were 18.65%,21.15%,18.00%,and 21.15%within the experimental range of the amount of added particles for POM1,POM2,POM3,and POM4,respectively.The pressure drop ratio basically decreased with the increase in the circulating flow rate but fluctuated with the increase in the amount of added particles and particle size.The difference in pressure drop ratio decreased with the increase in the circulating flow rate.As the amount of added particles increased,the difference in pressure drop ratio fluctuated at low circulating flow rate but basically decreased at high circulating flow rate.The pressure drop in the vertical tube bundle accounted for about 70%of the overall pressure drop in the up-flow heating chamber and was the main component of the overall pressure within the experimental range.Three-dimensional phase diagrams were established to display the variation ranges of the pressure drop and pressure drop ratio in the vertical tube bundle corresponding to the operating parameters.The research results can provide some reference for the application of the fluidized bed heat transfer technology in the industry.

A Scale-Invariant Fifth Order WCNS Scheme for Hyperbolic Conservation Laws

In this article,a robust,effective,and scale-invariant weighted compact nonlinear scheme(WCNS)is proposed by introducing descaling techniques to the nonlinear weights of the WCNS-Z/D schemes.The new scheme achieves an essentially non-oscillatory approximation of a discontinuous function(ENO-property),a scaleinvariant property with an arbitrary scale of a function(Si-property),and an optimal order of accuracy with smooth function regardless of the critical point(Cp-property).The classical WCNS-Z/D schemes do not satisfy Si-property intrinsically,which is caused by a loss of sub-stencils’adaptivity in the nonlinear interpolation of a discontinuous function when scaled by a small scale factor.A new nonlinear weight is devised by using an average of the function values and the descaling function,providing the new WCNS schemes(WCNS-Zm/Dm)with many attractive properties.The ENO-property,Si-property and Cp-property of the new WCNS schemes are validated numerically.Results show that the WCNS-Zm/Dm schemes satisfy the ENO-property and Si-property,while only the WCNS-Dm scheme satisfies the Cp-property.In addition,the Gaussian wave problem is solved by using successively refined grids to verify that the optimal order of accuracy of the new schemes can be achieved.Several one-dimensional shock tube problems,and two-dimensional double Mach reflection(DMR)problem and the Riemann IVP problem are simulated to illustrate the ENOproperty and Si-property of the scale-invariant WCNS-Zm/Dm schemes.

Deformation Uniformity of Cold-Rolled Q235 Steel Rebar by FEM in Bending and Rolling Processes

An analytic model based on ANSYS/LS-DYNA has been developed on the cold rolling process for Q235 steel rebar with 12 mm in diameter. The elastic-plastic finite element method (FEM) and the cold deformation resistance model of Q235 steel were adopted in this model. Deformation uniformity of the final product has been analyzed using this model. The results indicate that the uniformity of the final product is obtained only as the centerline of the bending rolls is vertical to the centerline of the driven roll and parallel to the centerline of the drive roll in the whole rolling process. Besides, the number of the bending rolls must even realize the continuous bending and reverse bending process. Also, the number of the bending rolls must match the deformation degree of the workpiece in the cold rolling process. The validity of this finite element model was verified by the size and distribution of grains from the billet to the rebar in a practical cold rolling process.