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Cleaning
Published in Christoph Gerhard, Optics Manufacturing, 2018
Precision cleaning of glass surfaces can also be performed by dry-ice blasting (a.k.a. carbon dioxide snow cleaning). Here, either solid carbon dioxide snow pellets or liquid carbon dioxide is used. In the first case, removal of contaminants is a purely mechanical process, whereas the latter procedure can be described as follows: liquid carbon dioxide is mixed with compressed air and sprayed onto the work piece surface. Due to an abrupt relaxation during mixing, the liquid carbon dioxide becomes solid, resulting in the formation of small dry-ice crystals. These crystals then sublime at the work piece surface; cleaning is thus due to both thermal and mechanical effects, where the process temperature is given by the dry-ice temperature of approximately −79°C. The mechanical impact can be adjusted by the choice of the geometry of the used spray nozzles. Since dry ice features a comparatively low hardness of approximately 2 Mohs,2 this method is also suitable for cleaning sensitive surfaces.
Demolition
Published in Erik K. Lauritzen, Construction, Demolition and Disaster Waste Management, 2018
The blasting agent is solid CO2, which is pressed to pellets and blasted on the surface by a special gun. The cleansing effect is based on the thermal cracking of the surface material (coatings, dirt on surface, dyes) and the partial removal of cracked matter by the expansion of CO2 through evaporation. The dry ice blasting technique is applicable to craggy surfaces and fit for the removal of soft/flexible materials. It holds no risk of damages to sub-surface materials through vibrations or concussions. From the waste management point of view, it has the advantage that no toxic residuals of treatment agents are produced. Like the treatment with liquid nitrogen, it is comparatively expensive and not applicable to homogeneous materials.
Removal of Paint and Coatings
Published in E. Higgins Thomas, Hazardous Waste Minimization Handbook, 2018
The Lockheed Company investigated dry ice blasting for removing aircraft paint.9Dry ice or carbon dioxide pellets were used as a blasting media. The attractive aspect of this technology is that dry ice pellets vaporize after being used and the only waste product is the dry paint chips. There are, however, questions concerning the potential damage to surfaces, effectiveness of paint removal, and operation costs. One problem is that the generation of carbon dioxide displaces oxygen in a room, necessitating the use of a contained air supply when blasting. Production of fog from humid air is also a problem.
A review on sustainable alternatives for conventional cutting fluid applications for improved machinability
Published in Machining Science and Technology, 2023
D. J. Hiran Gabriel, M. Parthiban, I. Kantharaj, N. Beemkumar
In a cramped, poorly ventilated room, dry ice poses a significant risk. As dry ice sublimates, CO2 gas is produced. In a confined environment, this gas may accumulate, presence of sufficient CO2 gas a person may fall unconscious and, in extreme situations decease. Dry ice blasting technique also leaves the machined burrs airborne. The technique requires special delivery systems for usage, hence may not be suitable for small scale industries. Table 7 provides a comparative summary of the Dry ice blasting-based machining.
Extraction of asphalt mastic from mixture without chemical agent
Published in Road Materials and Pavement Design, 2023
Yun Su Kim, Michael P. Wistuba, Johannes Büchner
The use of compressed air with cyclone and dry ice is based on the principle of a dry ice blasting mechanism (see Figure 5). This mechanism is used to separate the cohesive layers on the basis of induced kinetic and thermal energy and sublimation energy by simultaneously injecting compressed air and dry ice pellets from the nozzle (Spur et al., 1999). This process is widely used to cleaning and machining the surfaces of rubber, plastics and steel without special chemical solvents. In particular, it is known that after the work there are no chemical residues to be treated separately and the material under the adhesive layer is not damaged compared to sandblasting or hydro blasting (Jamil et al., 2022; Máša et al., 2021). The size of the blasting nozzle, the force of the compressed air, the working distance, and the angle between the nozzle and the target surface can be changed differently according to the surface to be treated (Dzido et al., 2021). The produced dry ice has a temperature of about −75 °C and causes the temperature of the asphalt surface to drop very quickly, increasing the temperature difference between the asphalt surface and the aggregates and causing cracks on the surface (Artamendi et al., 2012). The aim of the utilisation of dry ice is that these cracks can separate the mastic from the aggregates. By means of the cyclone, all processed samples, including the fine flyable aggregates and mastics, are collected without any loss. Freezer: A commercial electrically regulated laboratory freezer is used for conditioning asphalt mixtures to a temperature of −20 °C.Oven: A standard forced-draft oven, thermostatically controlled, capable of maintaining a desired temperature setting from room temperature to 300 °C within a range of ±3 °C.Sieves: A set of sieves is used consisting of nominal sieve sizes of 0.075, 0.125, 0.250, 1.0, 2.0, 5.6, 8.0 and 11.2 mm. Note that the nominal sieve size of 0.075 mm is used instead of 0.063 mm which is typically used in Europe, to take into account also filler particles soiled from residual binder that sticks on filler particles (Elseifi et al., 2008; Karim et al., 2021; Li et al., 2020). The use of dry ice during sieving will overcome the problem that asphalt binder or mastic may adhere to the mesh and prevents accurate sieving.
Substrate pre-treatment by dry-ice blasting and cold spraying of titanium
Published in Surface Engineering, 2018
Figure 4 shows typical cross-sectional morphologies of Ti coatings deposited on stainless steel and aluminium substrates by cold spraying under different conditions. It is obvious that Ti coatings could be obtained on both the metallic substrates (stainless steel and aluminium). However, all the Ti coatings exhibit a porous structure in spite of the application of dry-ice blasting. All the coatings exhibit a high porosity (Table 1) and the average porosity is estimated to be more than 10%. This is consistent with the porosity values reported in other literatures [12–14]. Compared with cold-sprayed Cu and Zn coatings, Ti coatings generally have a relatively higher porosity due to the minor extent of deformation and the surface reactivity of the deposited Ti particles [12]. Ti particles are loosely connected with each other through a limited contact area. Similar phenomena could be observed more clearly for Ti–6Al–4 V coatings. Even if helium was used as the driving gas, the density of Ti coating was significantly increased but the top layer of the Ti coating was still porous as reported by Li et al. [12]. Moreover, no obvious boundary can be distinguished for all the coatings in this work, by which Ti coating can be divided into top porous region and inner dense region. Such result suggests that the accumulatively tamping effect of the following particles on the underlying material is not intensive, induced by the low kinetic energy of particles. All the coatings have a homogeneous pore distribution. In addition, it can be found that Ti coating sprayed with dry-ice blasting still have many pores, although the dry-ice blasted Ti coating presents a relatively low roughness as shown in Figure 5. It seems that dry-ice blasting does not exhibit any additional peening effect on the porous structure of cold-sprayed Ti coatings. The average roughnesses (Ra) of cold-sprayed Ti coatings without and with dry-ice blasting are 22.49 ± 0.9 and 20.13 ± 0.2 μm, respectively. The interconnected open-pores at the top layer significantly contribute to the high roughness. Considering the potential of peening effect of dry-ice blasting during cold spraying, Ti coatings with dry-ice blasting were prepared with more pass-numbers compared with those without dry-ice blasting. Thus, the thickness of Ti coating prepared by cold spraying without dry-ice blasting in this work is less than that with dry-ice blasting. Nevertheless, the deposition efficiency calculated on basis of the mass difference exhibit no much change after the application of dry-ice blasting during cold spraying of Ti particles whether on stainless steel or aluminium substrates. Moreover, it can be seen that the deposition efficiency of Ti particles on stainless steel substrates is higher than that on aluminium substrates. In all cases, the deposition efficiency of Ti particles is higher than 85% during cold spraying (Table 2). The high-deposition efficiency of Ti particles is associated with the metallurgical bonding at some interfaces between the deposited particles or the surface reactivity of the deposited particles as reported in the literature [13].