Cryogenic grinding is a method of powdering herbs at sub-zero temperatures ranging from 0 to minus 70°F. The herbs are frozen with liquid nitrogen as they are being ground. This process does not damage or alter the chemical composition of the plant in any way. Normal grinding processes which do not use a cooling system can reach up to 200°F. These high temperatures can reduce volatile components and heat-sensitive constituents in herbs.

1. CRYOGENIC GRINDING TECHNOLOGY
Speaker- Sunil Meena
Class- M.Tech. (Dairy Technology)
DairyTechnologyDivision
ICAR-NationalDairyResearch Institute
(DeemedUniversity)
Karnal- 132001(Haryana),India

2. • Introduction
• Problems With Convention Grinding
• Traditional V/S Cryogenic Grinding
• Cryogenic Grinding System
• Design Of Cryogenic Grinding System
• Advantages Of Cryogenic Grinding
• Applications Of Cryogenic Grinding
OUTLINES

3. INTRODUCTION
• Grinding is process in reducing size of solid material by mechanical
action,dividing them into small size particles
• Time also plays a part in fracturing process and it appears that material will
fracture at stress concentration if this can be maintained for longer period of
time . The energy required depends upon the hardness of material and also upon
the tendency of the material to crack its friability
• Heat is generated when energy is used to fracture a particle into a smaller size.
• The most extensive application of grinding in the food industry is in the milling
of grains to make flour, but it is used in many other processes.

4. • High heat generation
• Less tool life
• Loss of etheric oil
• Clogging and gumming of the mill
• Oxidation and related degradation

5. INTRODUCTION
• “Cryogenics” - Greek word – meaning: creation or production by means of cold
• Method of powdering herbs at sub-zero temperature (0 to - 70 °F)
• Does not damage or alter the chemical composition of the plant or seeds in any
way
• The herbs and spices are frozen with liquid nitrogen as they are being ground.
• Cryogenic grinding technology can efficiently grind most tough materials and
can also facilitate Cryogenic recycling of tough composite materials and multi
component scrap
• Cryogenics are applied in different fields of production, transportation,
medicine, aerospace, physics research etc.

6. CRYOGENIC GRINDING SYSTEM

7. Schematic Flow Chart Of Cryogenic Grinding
Feeding in Cryogenic screw conveyor
Chilling of product with liquid nitrogen
Feed of product in grinder
Ground product at low temp and inert atmosphere
Extracting low temperature form ground product
Packing of product
Loading in Hopper through vacuum conveyor

9. DESIGN OF A CRYOGENIC GRINDING SYSTEM
• The Cryogenic Grinding
System Consists Of Two
Main Units, Namely
• Precooling Unit
• Grinding Unit

10. PRECOOLING UNIT
• The cryogenic precooler is a cooling device made up of a screw conveyor
enclosed in a properly insulated barrel and a system to introduce liquid
nitrogen into the barrel, thereby providing refrigeration (liquid and cold gas)
within the system.
• The function of the cryogenic precooler is to remove the heat from the material
before it enters the grinder.
• The particle temperature must be low enough to absorb the heat generated in
the grinder and still fracture.
• Cryogenic precoolers, therefore, must have the ability to reduce the
temperature of the seed below its brittle point as well as the freezing point of
its oil, before it enters the grinder
• There must be provision to control the temperature of the precooler and the
feed rate to the grinder for the obvious purpose of controlling the grinding
process.
• The precooling unit consists of a screw conveyor assembly, an air compressor,
a liquid nitrogen (LN2) Dewar, a power transmission arrangement and control
panels.

11. SCREW CONVEYOR
• Screw conveyor A horizontal screw conveyor was designed to meet the
requirement of feeding to the grinder and metering.
• The capacity of a screw conveyor mainly depends on the screw diameter,
pitch of the screw, and rotational speed.

12. GRINDER
• Rotor contained 8 or 12 number of fixed ribs. Depending upon the requirement, the
rotor containing 8 and 12 number of ribs could be selected.
• Rotor was surrounded by a sieve ring of trapezoidal opening of uniform size. Sieve
rings of different opening sizes (0.08, 0.12, 0.2, 0.5 and 1.0 mm) were available.
• Sieve opening size controlled the final product size.
• Grinding operation was performed by impact and attrition.
• The impact was achieved by the material being struck with rotor ribs, whereas the
attrition was achieved while the seeds were present between the stationery sieve
ring and the fast moving rotor.
• The speed of the rotor could be controlled through an in-built control mechanism.
• The ground powder was collected in the collector pan from an outlet. A nylon bag
was attached to the outlet with a locking clamp. The nylon bag retained the
particles and allowed the nitrogen vapour to escape from the grinder.

13. ADVANTAGES OF CRYOGENIC GRINDING
• More uniform particle size distribution
• Efficient process
• Process cooling/temperature control
• Inertness
• Can grind smaller rubber particles down to below 200 micron
• Regular particle size
• Increased throughput
• Low capacity motors required
• Reduced power consumption
• Smaller size particles
• Minimal loss of volatile components
• Improves the aroma by minimizing the loss of essential oils when compared
• with grinding at normal temperature
• Approx. 2 - 3 times higher grinding capacity

14. APPLICATIONS OF CRYOGENIC GRINDING
• CryoGrinding of steel
• Thermoplastics
• Thermo sets
• Adhesives & Waxes
• Explosives
• Spices

15. BIBLIOGRAPHY
• Singh,K.K. , Goswami,T.K.; Design Of A Cryogenic Grinding System For
Spices; Journal of Food Engineering: 39 (1999)
• Saxena,Rohit, Soni, Adithi(2013);Cryogenic Grinding: A Physical
Technique To Retain Volatile Content In Natural Products; World
Scientific Publishing Company: Vol. 22 (2013) 589–592.
• Technical Paper on Cryogenic Grinding by Dharmendra Kumar Madhuka

16. THANK YOU