Fouling and fouling mitigation on heated metal surfaces

In this work, short carbon fibers were blended with poly(vinyl chloride) (PVC) plastisol forming a conductive network of the fibers in the composite. The effects of concentration and initial length of the carbon fibers on the conductivity of the network were studied. For an initial fiber length of 3 mm (L/D = 428), the volume resistivity of the network decreased rapidly from 4.3 × 10 5 to 5.1 × 10 0 Ω‐m for a change in the fiber concentration of 0.5 to 1.0 phr. The samples prepared by the plastisol method also showed excellent antistatic properties at very low fiber concentration (e.g. 1.0 phr), better than the samples that were prepared by mill mixing. Observation of the morphology showed that the short carbon fibers maintained their initial length in the PVC plastisol‐carbon fiber composite, without obvious breakage. This is why a conductive network in the plastisol‐carbon fiber composite can be formed at very low fiber concentrations.

Liquid-into-liquid jets in short cylindrical vessels have been investigated under conditions of uniform flow by using an aqueous blue tracer solution in conjunction with tránsparent cylindrical tanks. The vessels had diameters D of 3, 6, 12 and 24in., length-to-diameter ratios L/D of 1, 2 and 3 and inlet diameters d between ¼ and 1 in. Reynolds numbers in the inlet tube, Rei, ranged between 100 and 28,000. Four main types of jet were observed: \[ \begin{array}{@{}l@{\qquad}l@{\quad}l@{}} & \hbox{dissipated-laminar jets} & (Re_i < 300\;\hbox{approx}.);\\ & \hbox{fully laminar jets} & (300 < Re_i < 1000\;\hbox{approx}.);\\ & \hbox{semi-turbulent jets} & (1000 < Re_i < 3000\;\hbox{approx}.);\\ \hbox{and} & \hbox{fully turbulent jets} & (Re_i > 3000). \end{array} \]The laminar length a of sub-turbulent jets was investigated and correlated with Rei and the geometric parameters by the equation \[ a/d = 9.97 \times 10^7 Re_i^{-2.46}(D/d)^{-0.48} (L/d)^{0.74}. \]

The kinetics of calcium sulfate dihydrate (CaSO4.2H2O, gypsum) scale formation on heated metal surface from aqueous solution has been studied by a highly reproducible technique. It has been observed that gypsum growth takes place directly on heated metal surface without any bulk or spontaneous precipitation in the supersaturated solution. A variety of maleic acid based polymers with different functional groups have been examined for their inhibitory effect on gypsum growth. The results indicate that amount of gypsum scale formed on heated metal surface is strongly affected by polymer dosage and the functional groups present in the polymer. Scanning electron microscopic investigations of the gypsum crystals grown in the presence of anionic polymeric additives show that structures of these crystals are highly modified. Results on the performance of various surfactants and biocides are presented.

Investigation of the initial period of sulphate scale formation Part 1. Kinetics and mechanism of calcium sulphate surface nucleation at its crystallization on a heat-exchange surface

Relationship between the residual gas pressure and the lowest temperature keeping metal surfaces essentially clean in high vacua

Tall forage soybean [Glycine max (L.) Merr.] cultivars in maturity groups V, VI, and VII have been developed to supply forage. Our objective was to determine the effect of harvest date and row spacing on the forage yield and quality of these new soybean cultivars. We grew forage and standard grain soybean in Minnesota with harvests in early and late September. Average maturity of tall forage soybean was R3 (early harvest) to R4 or R5 (late harvest) and average maturity of grain soybean was R6 (early harvest) to R7 (late harvest). Herbage of forage soybean was mostly leaves and stems at both harvests, whereas herbage of grain soybean contained an average of 400 and 595 g kg−1 pods at the early and late harvests, respectively. There was no harvest date × soybean entry interaction for forage yield or forage quality. Forage and grain soybean had similar forage yields (∼8.8 Mg ha−1). Because adapted grain soybean was more mature and had a greater pod proportion than forage soybean, grain soybean had greater crude protein (CP) and lower fiber concentration than forage soybean. Average forage CP for forage and grain types was 146 and 218 g kg−1, respectively, while neutral‐detergent fiber (NDF) concentration was 523 and 400 g kg−1, respectively. Decreasing row width from 76 to 25 cm increased forage yield 0.8 Mg ha−1 but had no effect on total herbage quality.

Classical dynamics calculations are performed for O((3)P) + H2O((1)A1) collisions from 2 to 10 km s(-1) (4.1-101.3 kcal mol(-1)), focusing on product internal energies. Several methods are used to produce ro-vibrationally state-resolved product cross sections and to enforce zero-point maintenance from analysis of the classical trajectories. Two potential energy surfaces are used: (1) a recently developed set of global reactive surfaces for the three lowest triplet states which model OH formation, H elimination to make H + OOH, O-atom exchange, and collisional excitation and (2) a non-reactive surface used in past classical and quantum collision studies. Comparisons to these previous studies suggest that for H2O vibrational excitation, classical dynamics which include gaussian binning procedures and/or selected zero-point maintenance algorithms can produce results which approximate quantum scattering cross sections fairly well. Without these procedures, the classical cross sections can be many orders of magnitude greater than the quantum cross sections for exciting the bending vibration of H2O, especially near threshold. The classical cross section over-estimate is due to energy borrowing from stretching modes which dip below zero-point values. For results on the reactive surfaces, the present calculations show that at higher velocities there is an unusually large amount of product internal excitation. For OOH, where 40% of available collision energy goes into internal motion, the excited product vibrational and rotational energy distributions are relatively flat and values of the OOH rotational angular momentum exceed J = 100. Other product channel distributions show an exponential fall-off with energy consistent with an energy gap law. The present detailed distributions and cross sections can serve as a guide for future hyperthermal measurements of this system.

Near-neutral pH stress corrosion cracking (NNpHSCC) continues to be a concern for existing high pressure pipelines used to transport oil and gas in Canada. Although several studies have focused on the role of pipe steel microstructure on the initiation and growth of NNpHSCC, most used specimens machined from sub-surface locations that did not preserve the original pipe surface, which is the material that ultimately exposed. In the present work, a series of test specimens were designed to preserve the external pipe surface and allowed shallow 0.05 mm root radius surface notches with depths from 0.1, 0.2 and 0.3 mm to be machined and tested. All specimens were machined in the hoop (transverse) direction from a 1067 mm diameter, 12.5 mm thick X80 pipe. The specimens were subjected to a constant load of 95% of the specified minimum yield strength (SMYS) (equivalent to 80% of the actual pipe hoop yield strength) using proof rings for extended durations, e.g., 110, 220, 440 or 660 days. The results show that there was no apparent SCC developed on the smooth specimens with the original surface even after being tested for up to 660 days. In contrast, SCC were found to have initiated at the machined notches, irrespective of their depth after testing for 220 days. To provide further understanding of specimen design, the same SCC testing conditions were applied to smooth round-bar test specimens machined in the hoop direction of this same pipe close to the external surface and the mid-wall locations. While minor SCC initiation was found in the near surface specimens, significant SCC was observed in the specimens taken from the mid-wall location. This finding suggests that the heterogeneous or variable microstructure through the pipe wall thickness plays a critical role in SCC initiation for the X80 pipe investigated. It also suggests that careful attention must be paid to the design of test specimens as well as the location that they are removed from a test pipe in order to realistically assess the SCC susceptibility of pipe steels.

Monitoring of scale formation in a pneumatic conveying system operating in a metal production plant

In this study, we have an object to investigate the piping system buried in the ground at ground subsidence. Therefore, we conduct bending test of bellows pipes for buried piping using experimental equipment which is simulator for assumed ground subsidence. Grade of bellows pipe is stainless steel. We measure load and displacement and calculated stress and strain appeared at bellows pipe. We conduct bending test at four kinds of experiment conditions for outer surface of bellows pipe, that conditions are non-restraint, soil or gypsum are filled around outer surface of bellows pipe, buried piping system is set in the box in which soil is filled. By analyzing these experimental results, we clarify deformation characteristic of bellows pipes for buried piping at ground subsidence, and we verify the application of bellows pipe to buried piping.

Grid selection was investigated as a means of reducing environmental variation prior to selection for low neutral detergent fiber (NDF) concentration in smooth bromegrass (Bromus inermis Leyss.). Eleven populations of 350 plants each were arranged into 10 grids of 35 plants each. Adjustment of NDF concentration by block means and standard deviations reduced the phenotypic variation to 50 to 94% of the original variance. Adjustment also reduced or eliminated spatial patterns of phenotypic variation in five of eight populations with significant patterns to original NDF values. Selection for low NDF tended to identify plants from blocks with a low mean NDF in some populations. When selection was based on t-scores, the number of plants representing each block was a random variable in each population. Use of grid selection with a t-score adjustment should increase the efficiency of phenotypic recurrent selection for low NDF concentration.

Kinetics of growth of calcium sulfate crystals at heated metal surfaces

A variety of individual aerosol particles can be detected by causing them to impinge onto a heated metal surface where they pyrolyze and transfer surface-ionizable constituents to the surface within times of 10/sup -6/--10/sup -2/ sec, depending on the filament temperature. These surface-ionizable constituents then become ionized and are released from the surface as a burst of ions. For particles of similar composition, the number of ions per pulse is related to the particle size. This technique has been studied and has been applied to the continuous monitoring of submicron urban particulate matter.

The addition of metal oxides to silumin‐hexachloroethane pyrotechnic smoke mixtures makes ignition on a hot plate more difficult in the order aluminium oxide < zinc oxide < magnesium oxide. Evidence is presented that suggests that aluminium oxide inhibits ignition by acting as an inert diluent separating the active reactants whereas the effect of magnesium oxide is believed to be chemical in nature. The addition of small amounts of ferric oxide or potassium iodide has little effect on the onset of smoke formation in a silumin‐hexachloroethane‐zinc oxide composition but promotes the transition from smoke to flame reaction. In contrast small amounts of either iodine or trityl chloride inhibit the onset of the smoke reaction. A mechanism is proposed for the ignition of silumin‐hexachloroethane compositions that accounts for these observations.

The formation of trace moisture by exposure of dry heated surfaces of 316 L stainless-steel, Restek Silcosteel®, and nickel 1/8 in. outer diameter line segments to purified Ar and H2 was studied using atmospheric pressure ionization mass spectrometry at flow rates of 2 slpm. Prior to H2 exposure, adsorbed moisture was removed by heating incrementally to 500 °C in an argon matrix, where the Restek Silcosteel® material released a maximum of 50 ppb moisture at 300 °C and moisture spikes from the Ni and stainless-steel surfaces reached several 100 ppb. Upon exposure to H2, persistent low ppb moisture emissions due to the reduction of surface oxide species were observed at temperatures as low as 100 °C. Spikes at 300–500 °C ranged from ∼100 ppb for the stainless-steel lines to 400 ppb for the Restek Silcosteel® material. The observed moisture emissions have to be considered as a potential contamination source for high-purity processes utilizing H2 purge at elevated temperatures.