Dry ice blast cleaning technology protects workers from cleaning agents and eliminates the hassle of disposing of used contaminated cleaning agents. This makes dry ice blast cleaning technology a very green mold cleaning method, this process has been approved by the (US) Environmental Protection Agency and (US) Food and Drug Administration.
Just as dry ice blast cleaning technology can be used to clean machinery or other contaminated surfaces, this technology can also be used to clean industrial molds. When the dry ice particles hit the surface of the hot object, they will elevate into the gas, and there will be no residue in the entire cleaning process. Dry ice is a by-product of other industrial processes. Because it is made from recycled CO2, it will not generate CO2 again or increase the amount of CO2 in the atmosphere, so it will not exacerbate the greenhouse effect.
Manipulation rules
The following is the flow of the entire operation process and how this technology is applied to various production processes. First, dry ice is made by pressurizing liquid CO2 and then releasing it to normal atmospheric pressure. This converts liquid CO2 into a gas and a solid snow. This snow is compressed into a block or granular object. The equipment for producing dry ice requires a liquid CO2 container and a pelletizer or block.
Carbon dioxide is a colorless gas that is a by-product of breathing. Its density at 25 degrees Celsius is 1.98 kilograms per cubic meter-about 1.65 times the density of air. This means that CO2 gas can replace oxygen (CO2 gas sinks, oxygen rises).
This characteristic of carbon dioxide is very important, so it should be used and stored in a place with good ventilation (whether solid or liquid CO2). Moreover, the liquid CO2 needs to be stored in a sealed and pressurized container, so that it can prevent its state from changing. Because CO2 is a product of complete oxidation, it is not easy to produce chemical reactions, especially it is not easy to burn.
When the temperature is below -78 degrees Celsius, carbon dioxide will directly change from a gaseous state to a white solid called dry ice through desublimation. Carbon dioxide will only liquefy when the pressure reaches 5.1 atmospheres or more; under normal atmospheric pressure, it will directly convert from solid to gaseous through a sublimation process.
The equipment used in dry ice blast cleaning technology can store block dry ice and granular dry ice. Block dry ice machines are used for cleaning processes with lower power requirements. At this time, the pressure is only 50 psi; granular dry ice blasting machines with pressures from 120 psi to 300 psi are used for higher power cleaning processes. The application of dry ice can be said to be unlimited. When cleaning the mold, you don't have to wait for the mold to cool before cleaning. In most cases, it can be cleaned without disassembling the equipment.
The dry ice blast cleaning process should include high speed (supersonic) nozzles for surface treatment and paint removal. Since the kinetic energy impact force is a common product of dry ice particle mass, speed, and action time, the jet system can obtain the maximum impact force only by ejecting solid CO2 particles at the maximum speed in the sandblasting process. Particles can reach speeds of 900 feet per second.
Even with high-speed impact and right-angle impact, compared with other media (steel sand, gravel, PMB), the impact of solid CO2 particles is minimal. This is due to the relative softness of the solid CO2 particles which makes them unable to reach the density and hardness of other impactors.
Also, the particles transform from solid to gaseous state almost immediately at the moment of impact, which makes the recovery coefficient in the shock equation almost zero. This advantage is that almost no impact can be transmitted to the coating or substrate, so the entire spraying process is thought to not cause wear on the mold.
Dry ice blast cleaning technology is very effective. This is because the temperature of the particles is extremely low, and the particles rise from the solid state to the gas state immediately after the impact, which brings thermal shock. These ultra-cold particles at 110 degrees Fahrenheit quickly absorb heat from the contaminated surface, which creates a huge temperature difference between the continuous and trace thin layers of the coating.
This huge gradient of heat produces local high shear stresses between trace thin layers. The generation of shear stress also depends on the thermal conductivity of the coating and its coefficient of thermal expansion and contraction, as well as the thermal mass of the substrate.
The high shear stress generated in a very short time can cause the rapid increase of fine cracks between the layers. This reaction thus results in the decomposition of contaminant ions or the coating on the surface of the substrate.
These thermal and kinetic energy effects of dry ice particles can basically break the combination of surface contaminants, causing them to fall off the mold. Energy dissipation impact and rapid heat transfer between the dry ice particles and the mold surface caused the solid CO2 to rapidly rise to the gaseous state. During this process, the volume of the particles expanded by nearly 800 times within milliseconds, and microbursts were effectively generated at the point of impact.
Because these dry ice particles have no rebound force, these microbursts further detach the coating particles that have been separated from the substrate due to temperature differences. The CO2 gas expands outward along the surface, and the resulting explosion impact is concentrated between the surface of the mold and the particles that are cracked due to the temperature difference, which effectively creates a high-pressure region. The resulting effective lifting force can remove these particles from the mold surface.
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