10 Difficult Problems about Raw Grinding with Vertical Roller Mill Systems and their solutions

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To download the below  and all other Useful Books and calculations Excel sheets please click here 

To download the below  and all other Useful Books and calculations Excel sheets please click here 

10 Difficult Problems about Raw Grinding with Vertical Roller Mill Systems and their solutions

 

 

First : High vibrations

Potential causes:
Too many fines in mill feed
Material bed on grinding table not stable

Proposed solutions:
Increase feed size
Adjust crushers
Maybe eliminate a crusher

Expected results:
Less vibrations
Less fine fractions in mill feed
Lower crushing costs (energy, wear, maintenance)

Estimated costs:
Minimal

Implementation time:
Short-term

High amount of false air

 

Potential causes:
Defects on external seals

Proposed solutions:
Improve maintenance

Expected results:
Improved drying of mill product
Reduced specific power consumption (fans)

Estimated costs:
Minimal

Implementation time:
Short-term

Dynamic seal not working effectively

Potential causes:
Seal space too big
Possible damages on seal

Proposed solutions:
Improve maintenance (check status of seal more frequently)
Repair damages

Expected results:
Less coarse mill product
Reduced specific power consumption

Estimated costs:
Minimal

Implementation time:
Short-term

Mill exit temperature too low

Potential causes:
False air
Damper positions

Proposed solutions:
Reduce damper between conditioning tower and filter
Reduce damper of re-circulation air flow

Expected results:
Less humidity in mill product
Lower temperature in filter

Estimated costs:
Minimal

Implementation time:
Short-term

Roller pressure too low

Potential causes:
High vibrations
Pressure adjustment does not follow wear

Proposed solutions:
Train mill operators
Adjust pressure periodically

Expected results:
Increased feed rate and higher production
Reduced specific power consumption

Estimated costs:
Minimal

Implementation time:
Short-term

Air speed variations in mill

Potential causes:
Cone design
Inclination of nozzles

Proposed solutions:
Redesign cone
Adjust inclination of nozzles (35° to 60°)

Expected results:
More uniform speed increase
Less material falling through nozzle ring
Reduced specific power consumption

Estimated costs:
Minimal

Implementation time:Mid-term

Material distribution on grinding table not optimal

Potential causes:
Feed chute too short

Proposed solutions:
Prolong feed chute

Expected results:
More stable material bed
Less vibrations

Estimated costs:
Minimal

Implementation time:Mid-term

Grinding tools with high wear

Potential causes:
Recommendation of equipment supplier

Proposed solutions:
Investigate alternative (better) grinding tools

Expected results:
Prolonged lifetime of grinding tools
Reduced specific grinding costs

Estimated costs:
Medium

Implementation time:Mid-term

Manual operation

Potential causes:
Original installation not improved

Proposed solutions:
Investigate possible automation

Expected results:
More stable operation
Reduced specific costs of milling

Estimated costs:
High

Implementation time:Long-term

Material falling through nozzle ring

Potential causes:
Original installation not improved

Proposed solutions:
Install external material circulation

Expected results:
Less cleaning necessary
Environmental aspects improved

Estimated costs:
High

Implementation time:Long-term

 

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