Spray Ice Research Articles

Studies of periodic seawater spray icing with unilateral NMR

Sea water ice has a complicated pore structure consisting of brine-filled pockets within a solid ice matrix. In this work, an unilateral Nuclear Magnetic Resonance instrument was used to characterize the evolution of sea-ice brine inclusions in two types of ice: stationary seawater ice and seawater spray ice formed by periodic spraying on horizontal and vertical surfaces. The portable unilateral NMR was capable of measuring very low amounts of brine (<10% of the water-filled volume). CPMG experiments were performed to extract the information on brine content and T2 distribution at temperatures between −6 °C and −16 °C. 1D imaging was used to spatially resolve the ice brine accumulation. The results show that the seawater spray ice growth, brine content (greater for the horizontal orientation than for the vertical one), and T2 distribution (unimodal for stationary ice and bimodal for spray ice) depend on temperature and surface orientation.

MRI monitoring of sea spray freezing.

Sea spray icing is a common hazard for vessels and offshore structures in cold climates. In this paper, quantitative 3D MRI and T1-T2 mapping of the formation of sea spray ice were performed. Three different freezing regimes were employed. During freezing, changes in both relaxation times and signal intensity were greater than an order of magnitude. Results show strong differences in brine intensity and distribution for the three freezing regimes. The observed ranges of spin densities and relaxation times during freezing are well suited to measurements with portable NMR devices. There is a considerable potential for the use of MRI in studies of sea spray ice.

Removal of organic contaminants and toxiciy from industrial effluents using freezing processes

Removal efficiency of organic contaminants and reduction of toxicity (Microtox) in the secondary petroleum refinery and pulp mill effluents using two freezing processes, unidirectional downward freezing (UDF) and the spray freezing, was evaluated in this experimental study. The effect of the freezing temperature, initial feed water impurity concentration, mixing of the freezing liquid and the duration of freezing on the impurity removal efficiency was examined. Effective removal of chemical oxygen demand (COD) and total organic carbon (TOC) causing materials from both effluents, color causing materials in the pulp mill effluent, and removal of linoeic and abietic acids in the meltwater of the spray ice was achieved by freezing only 70% of the feed water. Close association of effluent toxicity with TOC and COD concentrations was observed when EC 20 was used to measure the toxicity. Mixing of the freezing liquid significantly improved the impurity removal efficiency of the UDF process, reduced the influence of freezing temperature and initial feed water impurity concentration. Greater impurity removal efficiency was observed for the spray ice with longer storage time. The impurity removal efficiency of the spray freezing process was similar to that of the UDF without mixing.

Unusual lake ice phenomena observed in Lake Inawashiro, Japan: spray ice and ice balls

Unusual lake ice phenomena observed in Lake Inawashiro, Japan: spray ice and ice balls

Petroleum Refinery Secondary Effluent Polishing Using Freezing Processes—Toxicity and Organic Contaminant Removal

A petroleum refinery secondary effluent was treated using two freezing techniques--spray freezing and unidirectional downward freezing (UDF). The freezing processes were effective to remove toxicity and total organic carbon (TOC)- and chemical oxygen demand (COD)-causing materials in the effluent. Agitation of the liquid during UDF significantly improved the impurity separation efficiency; 85 to 96% removal of TOC and COD was achieved without any pretreatment and freezing only 70% of the feed water. The treatment efficiency of the spray freezing was at the same level as that of UDF without mixing. The spray ice with longer storage time released more contaminants with early meltwater. The initial contaminant concentration of the feed water and the freezing temperatures (-10 degrees C and -25 degrees C) had no significant influence on the treatment efficiency. A small fluctuation in effluent TOC concentration caused a dramatic change in effluent toxicity (Microtox). The effective concentration (EC20) (Microtox) was effective in detecting effluent toxicity.

Laboratory study on the sliding resistance of level ice and rubble on sand

Abstract An experimental set-up was constructed to study the friction behaviour of level ice and ice rubble on different seabeds at large scale and realistic stress levels. This paper presents the results of loading on a sand seabed. The tests were performed with a 4 m 2 footprint with vertical stress levels up to 17 kPa. The ice was moved horizontally a distance of about 120 mm with displacement rates from 0.003 to 0.342 mm/s. Four position transducers measured vertical displacements. A total of 47 tests were conducted with level ice and another 24 with ice rubble. Friction coefficients of 0.47 and 0.39 for peak and steady shear stresses, respectively, were obtained with level ice. Those produced with ice rubble were 0.65 and 0.62 for the peak and steady shear resistance, respectively, which represents an increase of about 50% in shear resistance compared with level ice. Shear failure is believed to have occurred at the ice–sediment interface, although the sand's internal friction may have been fully mobilized by the ice rubble. Sediment freeze-up caused a substantial increase in sliding resistance. During this process, the failure plane is believed to have migrated downward and laterally along the freezing front, into the sand bed, with a concurrent increase in shear resistance up to levels comparable to the sand's internal friction. Sand compaction may have contributed also in increasing sliding resistance. These results may be useful for the design of spray ice pads and to assess the stability of grounded ice features.

Effects of Freezing on the Survival of Escherichia coli and Bacillus and Response to UV and Chlorine After Freezing

Escherichia coli (E. coli) and Bacillus megaterium bacteria were frozen at -15 degrees C using a freezer and a spray freezing method. The frozen Bacillus spores were also exposed to UV and free chlorine. An average of 4.7-log inactivation was obtained from the spray ice with 2-day storage time, while the freezer freezing only caused 0.84-log reduction with the same storage time. Significantly higher inactivation levels were observed for the E. coli cells with 2-day storage compared with those without storage. The spray freezing was found more effective in killing the E. coli cells, while more cells were sublethally injured by the freezer freezing. Freezing did not kill the Bacillus megaterium spores, but affected their response to UV and chlorine. Greater inactivation levels were observed at higher free chlorine doses or longer contact time, and the UV fluence-response curve showed initial rapid kill followed by tailing for the frozen spores.

Natural freezing as a wastewater treatment method: E. coli inactivation capacity

Inactivation capacity of E. coli (strain ATCC 15597) in water by natural freezing was examined via two freezing methods: spray freezing and freezing in a freezer. The effect of freezing temperature (−5, −15 and −35 °C), storage time, freeze–thaw cycles on the survival of the test organism were investigated. In addition, the number of cells injured by the freezing process was also examined by using different growth media. The bacteria frozen at the warmer temperature (−5 °C) was most sensitive to storage and freeze–thaw cycles as compared to those frozen at −15 and −35 °C. In general, greater inactivation efficiencies were achieved under longer storage time and warmer freezing temperature conditions. Freezing and thawing caused cell injury. More cells were injured when frozen at −15 °C. The percentage of cells injured decreased as freeze–thaw cycles increased. The spray-freezing process was found more effective in killing the cells. On average, the log reduction rate for the spray ice with two-day storage time was about 4 log units higher than those without any storage after freezing. The results indicated that the natural freezing processes are not only cost-effective techniques for chemical and physical contaminant removal from wastewater or enhancing sludge dewaterability in cold regions but also effective in reducing E. coli concentration.

Spray freezing decontamination of tailings water at the Colomac Mine

A field pilot scale experiment was conducted to evaluate the efficiency of spray freezing to remove dissolved chemicals from the tailings lake water at the Colomac Mine, NWT. Cores of the spray ice were then taken to the University of Alberta. The distribution of chemicals in the ice cores were determined, then a 1 m long core sample was thawed in a controlled manner to simulate thawing in the field to examine the concentrations of chemicals in the melt water as the columns thawed. For the pilot scale project approximately 30% of the water pumped was frozen, with the remaining water returned to the tailings pond as runoff. Analysis of the water collected from an ice core melted under controlled laboratory conditions showed dissolved chemical removal of 87–99% (depending on the chemical species) after 39% of the spray ice column had melted. Arsenic concentrations were reduced from approximately 19 μg/L to approximately 5 μg/l. Cyanide had 99.2% removal but still remained at a concentration of approximately 350 μg/L. Approximately 60% of the treated water released at the end of the melt contained only 1–17% of the dissolved species. This melt water at the end of thaw would only require minor further treatment, which may significantly reduce overall treatment costs.

Network images of drainage channels in sea spray icing by MR microscopy

An MR imaging system was developed to visualize brine drainage channels in sea spray icing. Brine pockets trapped in spray-ice matrices during ice growth are structural features of sea spray icing. Brine in the spray ice sample had drained out; therefore, using a suction pump, we filled the air gaps in the drainage channels with dodecane. In the experiments, 0.5-1.0 h was necessary to accumulate signals sufficient to obtain a 3-D micro-image; the image matrix comprised 128(3) voxels (each voxel was 200 microm per side). The MIP view showed that sea spray icing has a developed drainage-channel network structure.

Release of Contaminants from Melting Spray Ice of Industrial Wastewaters

This study was carried out to investigate organic and inorganic contaminant removal from melting spray ice produced from aerated stabilization basin treated pulp mill wastewater and the oil sands t...

Treatment of pulp mill and oil sands industrial wastewaters by the partial spray freezing process

The spray freezing process, a natural freezing technology, was used to treat pulp mill effluent and oil sands tailings pond water. The wastewaters froze partially or completely (i.e. with or without runoff generation) during the spraying operation. Greater than 60% impurity reduction in the spray ice was obtained when 30% of the total volume of the sprayed water was released as runoff. Organic and inorganic contaminants were rejected with different efficiencies. The impurities were uniformly distributed within the ice columns when the spray ice was produced without generating any runoff. While a significant increase in impurity concentration was observed at the bottom of the ice formed with runoff production. The spray freezing process is an effective and economically feasible technique for wastewater treatment in cold regions. To achieve higher impurity removal efficiency, the wastewater should be only partially frozen during spray ice production.

Crystalline structure and physical properties of ship superstructure spray ice

In February and March 1990 the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL) made measurements of superstructure ice on a US Coast Guard cutter in the Bering Sea. Twenty–three ice samples were removed from bulkheads, decks and icicles during two icing events. Ice crystal measurements included crystal size, shape, orientation, brine–pocket location, size and shape, internal layering, and air–bubble sizes. Ice property measurements included salinity, density and temperature, with computed estimates of air and brine volume. This paper describes crystal and physical properties of the accreted ice and their relationship to ice sample position on the ship. Texturally, accreted ice resembled frazil ice that forms from the consolidation of freely nucleated ice crystals in sea water. This resemblance is also reflected in bulk salinities, ranging from 24‰ to 7‰, compared with frazil formed during the initial stages of freezing of sea water, where bulk salinities can exceed 10‰. Crystalline structures of accreted ice ranged from rounded to polygonal. Generally, rounded crystals would be expected for ice formed from sea–spray droplets, polygonal crystals may be attributed to thermally driven modification. No trend towards reorientation of crystallographic c–axes in either freshly accreted or thermally modified ice was observed. Mean crystal sizes ranged from 0.56 mm to 1.15 mm, with even larger crystals in icicles. Ice salinity averaged ca .12‰ on bulkheads and ca .21‰ on decks. Ice densities ranged from 0.69 to 0.92 Mg m −3 and were generally higher on decks. Bulkhead ice had larger computed total porosity and air volume and lower brine volume than deck ice. Samples taken from decks and bulkheads generally compared well with Russian and Japanese measurements.

Creep and strength tests on warm dry spray ice

Cet article presente des resultats d'essais de laboratoire destines a mesurer les proprietes de resistance et de fluage de la glace pulverisee, a des temperatures proches du point de fusion. Cette information est necessaire pour la conception des iles en glace pulverisee dans les regions cotieres deltaiques dans l'Arctique, ou les temperatures de l'eau sont souvent superieures a -1°C. Les resultats de laboratoire sont discutes et les parametres de resistance et de fluage utilises lors de la conception de l'ile Nipterk P-32 en mer de Beaufort canadienne sont presentes.

A case history of the Nipterk P-32 spray ice island

A case history of the Nipterk P-32 spray ice island

Creep and strength tests on warm dry spray ice

Creep and strength tests on warm dry spray ice

Construction and characterization of a spray-ice pad, Tuktoyaktuk, Northwest Territories

During the winter of 1990–1991, a field research program was undertaken to investigate the in situ properties of spray ice, since information on the mechanical and physical properties of undisturbed field-produced spray ice is scarce. The main objective of this research was to retrieve undisturbed field samples for laboratory characterization and to make field measurements to assist in studying the formation processes and physical properties after formation. For this purpose, a spray-ice pad was constructed in the freshwater Tuktoyaktuk Harbour, Northwest Territories, Canada. The 4.3 m thick pad was partly grounded in water depths of 3–6 m and had a maximum freeboard of 2.2 m. The spray-ice pad was constructed using a mobile spray-ice system placed on the first-year ice sheet. The ice production efficiency of the system was measured and found to give an ice content higher than 50%. A total of 11.8 m of cores of nonsaturated undisturbed spray ice were retrieved from three locations on the pad and transported to a cold room facility for density, shear wave velocity, and mechanical behavior testing. In addition, surface wave testing of the in situ spray ice and first-year ice was performed. This paper describes the field study and the methodologies employed to carry out this research. Key words : spray ice, construction, sampling, density, Rayleigh wave velocity.

Prediction of spray ice island settlement with the pressuremeter : Shields, D H; Domaschuk, L; Funegard, E; Osiowy, K B Proc 3rd International Symposium on Pressuremeters, Oxford, 2–6 April 1990P415–424. Publ London: Thomas Telford, 1990

Prediction of spray ice island settlement with the pressuremeter : Shields, D H; Domaschuk, L; Funegard, E; Osiowy, K B Proc 3rd International Symposium on Pressuremeters, Oxford, 2–6 April 1990P415–424. Publ London: Thomas Telford, 1990

Pressuremeter creep tests in spray ice : Shields, D H; Domschuk, L; Funegard, E G; Azizi, F Proc 12th International Conference on Soil Mechanics and Foundation Engineering, Rio de Janeiro, 13–18 August 1989V1, P313–317. Publ Rotterdam: A A Balkema, 1989

Pressuremeter creep tests in spray ice : Shields, D H; Domschuk, L; Funegard, E G; Azizi, F Proc 12th International Conference on Soil Mechanics and Foundation Engineering, Rio de Janeiro, 13–18 August 1989V1, P313–317. Publ Rotterdam: A A Balkema, 1989

Activation Energy for Creep of Spray Ice

The activation energy must be known in order to relate creep rate to temperature according to the Arrhenius equation. In this note the activation energy for man-made spray ice is determined from primary and secondary (minimum rate) creep data taken from settlement readings and in situ pressuremeter tests at Mars spray ice island. Spray ice is used to construct drilling platforms in the Arctic Ocean, and the creep settlement is an important engineering consideration in design. The value of the activation energy determined from secondary (minimum rate) creep of spray ice was found to be 78 kJ/mol, for a temperature range of -2 to -22°C. This activation energy is within the range of activation energies reported for the creep of polycrystalline ice. The activation energy determined from primary creep data was highly variable and had a value of about 50 kJ/mol.