Learn about a cost-effective way to achieve required particle sizes and production rates.

The Fundamentals of Cryogenic Grinding Webinar



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Q&A from the Webinar

  • How long is the process to install a system from trial to the first production run?

    The time from installation to production varies based on type and size of the mill and other equipment needed, whether your area is already set up or if utilities and other modifications are needed. There are certain pieces of equipment that if needed, may have some lead time. The optimal way to determine this is to have one of our engineers contact you. We have designed many systems across a very broad range of materials and can work with you to optimize for cost and quality.
  • What is the footprint of the system you showed? Internal and external to the building.

    Footprint is dependent upon the system that is recommended for your specific process. Speaking from our many years of experience, we can provide some examples of what is needed. As discussed in the presentation, a typical system will need a liquid nitrogen bulk tank located externally. Internally, a system could range from around a 6 x 6 foot area for the smallest system, such as a hammermill and a mini conveyor. One of Air Products’ lab systems has around a 40 x 20 foot footprint and even larger sizes exist. Our engineers can walk you through the equipment and safety requirements that best suit your needs.
  • What is the hardest material you have ground?

    UHDPE – Ultra high density polyethylene which can be used in many applications where tough, hard materials are required such as in automotive or conveyor parts, rods, plates or even sprockets and bearings. We have also worked with PEEK (Polyether ether ketone) another very amorphous crystalline material.
  • What types of mills do you offer or recommend?

    Our mill recommendation will depend on your system needs. We want our applications to be beneficial operationally and financially to our customers and their operations. Air Products offers a PolarFit® turbo mill in various sizes. We also have vendor relationships across the varieties of different mills. We would be pleased to talk to you about your needs and help select the appropriate mill and system to meet your needs.
  • How much does it cost to do a trial at your facility? Or, can I just rent a system?

    We’d be happy to have one of our engineers call you to discuss conducting a trial. It’s difficult to provide an estimate without discussing your project first.
  • What size particles are you capable of producing? How fine can I grind?

    We are able to produce excellent yields at particle sizes of 30 – 250 micron (325 – 60 US Mesh).
  • How fast can I grind?

    This is material dependent. We have run over 1,000 trials and can provide a good starting estimate for grinding rates. However, a lab trial can help us better understand the answer for your particular situation.
  • What kind of end use applications would use this? What kids of materials does this work on?

    • Plastics
    • Rubber
    • Spices, herbs and other foods
    • Pharmaceuticals
    • Waxes
    • Hot melt adhesives
    • Pigments and powder coating materials
    • Thermoplastic elastomers
  • How dangerous is liquid nitrogen? Can you also elaborate on safety concerns? What kind of venting do I need? How can I prevent creating an asphyxiating environment?

    Nitrogen makes up the major portion of the atmosphere (78.03% by volume, 75.5% by weight). Nitrogen is inert and will not support combustion. However, as we discussed during the presentation, there are a few safety concerns to be aware of when using liquid nitrogen that can be easily addressed. The first is asphyxiation where nitrogen will rapidly displace oxygen in the air. The asphyxiation hazard can be mitigated with proper venting and an oxygen monitor as we discussed in our webinar. The other is that it is a cryogenic liquid and can cause burns if it comes in contact with skin. Pressure hazards must also be considered. If trapped or valved in, boiling liquid nitrogen will produce enormous pressure, purely from the heat gained from its surroundings. This hazard is mitigated by using thermal relief valves. Again, Air Products is a world-recognized safety leader in the chemical industry and we can provide training and support to help you apply the proper equipment and procedures for handling liquid nitrogen.
  • How is liquid nitrogen delivered to the site and does it ever make sense to generate nitrogen on our site?

    As for liquid nitrogen delivery, it is routinely delivered via truckload to your tank. Air products has a large fleet of delivery trucks and plants located around the world to enable prompt delivery when you need it. It really depends on the liquid nitrogen usage rates for your system and other liquid nitrogen needs at your site to determine if on-site generation is a better option for you. Again, this is something our technical specialists can help with.
  • Can you retrofit an existing system or do I have to buy new equipment?

    This is where Air Products experience and knowledge in cryogenic grinding comes into play. Our applications engineers can help you determine system requirements.
  • Will the temperature damage my product?

    In fact it is just the opposite. The cold temperature of liquid nitrogen helps retain product integrity and quality. Nitrogen is inert and does not react with the product. A good example of this is spices. Spices are temperature sensitive. The heat generated from the actual grinding can cause spices to lose their essential oils, distort their aroma and flavor and alter their color—all of which reduce the quality of the spices. Additionally, if the spices are not processed at a low enough temperature, the oils and fats in the spices can cause agglomeration and clog up the mill. Good control of the operating temperature via liquid nitrogen flow control can help prevent these issues.
  • Why is temperature control so expensive? Can’t I just manually control temp/flow myself with a simple valve?

    As we discussed in the safety considerations part of our webinar, the type of valves used in a cryogenic grinding system is very important to mitigate pressure hazards associated with liquid nitrogen. As we discussed, if trapped or valved in, boiling liquid nitrogen will produce enormous pressure purely from the heat gained from its surroundings. This hazard can be mitigated by using thermal relief valves.
  • Have you worked with particles used in or polydispersions specific to the Agriculture sector?

    We are not aware of any work in our labs that was done specific to polydispersions of particles for agricultural uses. As we work with many different customers, sometimes details cannot be shared so we may have been unaware of the end use at the time. However, we would be happy to discuss your specific needs in applications following this webinar.

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