Solutions for Critical & Special Chemical Handling

1) Heat Sensitive Chemicals –

Criticality

• Particle size control is the main aim for chemical milling applications, but there is a subtle balance between milling size reduction and heat generation. Even a small rise in temperature can affect the properties of the material and result in product deprivation, decreased ingredient efficiency, and in severe cases, melting or burning of material.

Care Taken

• Grinding under controlled temperature with the help of cool air can be implemented while grinding heat sensitive materials. You can use any of the following systems to exercise control over the chemicals:
• Closed loop systems come with nitrogen purging. In this system, the material is ground with nitrogen air which maintains the lower temperature of the entire system and product while handling.
• Cryogenic grinding is action of chilling a feed material and then reducing it into a smaller particle size. Liquid nitrogen of subzero temperature is used to cool down the feed material preceding to and during grinding to prevent material from getting heated.

2) Hygroscopic Chemicals –

Criticality

• A hygroscopic material is one that readily absorbs water / moisture (usually from the atmosphere). Most of the chemicals such as fertilizers and salts tend to show hygroscopic properties. After/During grinding, this tendency increases even more because of the exposure of more surface area to the atmosphere. This condition increases the chances of choking material during operation, which can affect the overall efficiency of the system.

Care Taken

• Dry, cool and conditioned air is circulated with material in the mill, which prevents chances of material to absorb water / moisture from atmosphere and ensures choking-free operation.

3) Explosive or Flammable Chemicals –

Criticality

• Explosion or catching flames in the material because of two main reasons, one is the generation of static charges & other is excess heat generation in the system. Massive explosion along with life loss can happen if proper care is not taken.

Care Taken

• Special accessories can be provided to carry and ground the static charges generated in the system. Anti-static accessories can also be used. The sole purpose of all activities is to carry away any generated static charge which can become a catalyst for explosion or fire.
• Special detectors at mill feeding section avoids the entry of any undesired material impurity which can carry a static charge in the system.
• Cool nitrogen based closed loop system is also implemented when material is flammable or explosive. High pressure mills and other safety devices can be implemented in the system as per material properties.

4) Poisonous or Toxic Chemicals –

Criticality

• Dust and fumes of toxic or poisonous chemicals can be inhaled by industrial employees. It can cause a myriad of health problems that may normally take years to become apparent. Some chemicals can cause asthma or other diseases, as well as cancer. Many can harm the skin, and some can cause severe long-term harm to the lungs or other organs.

Care Taken

• Efficient and modern dust-free conveying solutions and clean air solutions with grinding solutions are used to avoid any losses due to exposure with Poisonous and toxic chemicals.

5) Abrasive Chemicals –

Criticality

• Abrasive chemicals are categorized into two main types – synthetic and natural abrasive chemicals. Some good examples of abrasive chemicals include cerium oxide, aluminum oxide, silica , boron carbide, iron oxide etc. They are used in applications where material removal from the surfaces is require. On the contrary, grinding tend to wear and tear of grinding system, internally. Hence, this results in low life of the system and addition of impurities in the final product.

Care Taken

• Conventional grinding mills can grind the abrasive and hard material up to 4 MOH scale. For material beyond this hardness, we need to go for material of construction of mills with special MS / CI alloys which have high penetration and abrasive resistance. Also, special grinding solutions with patented mechanisms are used.

6) Highly Reactive Chemicals –

Criticality

• Highly reactive chemicals tend to react with the material of construction of the grinding system. They corrode the system as well as get impure as a product . These properties are mostly present in oxides and hydroxides.

Care Taken

• Mild steel tend to corrode quicky. Comparatively, stainless steel of special grades have higher resistance to corrosion. Stainless steel, as a material of construction, can be used for the parts that are more prone to come in contact with the grinded reactive chemicals.
• In GMP grade requirement, the entire system is in Stainless steel. GMP grade system comes with all GMP design considerations and can be thoroughly washed with water.

Key Takeaways

All the above solutions are vital to ensure critical handling of the processes while grinding. With diligent care, we can enhance the grinding efficiency, improve material flowability, reduce water usage, and narrow the particle size distribution of the grinding materials.