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Beta Prototype Results

A 25 hp Hercules air-swept ring/roller mill, 3.5 MW equivalent, was retrofitted with a one ton per hour output magnetic separator to make the beta prototype MagMill at the pilot facilities of Bradley Pulverizer Company in Allentown, PA.  The unit shown in the photo processed ten tons each of raw Upper Freeport and Lower Kittanning coals from north central Pennsylvania. The prototype results illustrate the potential of the MagMill to improve the quality of the product that would be sent to the burner at a power plant.



 


Grade and recovery curves show trade-offs can be made between mineral reductions and Btu recovery for this coal. The symbols on the graph represent measured values for four different runs.

 

 


 

A summary of results obtained for one run processing Upper Freeport raw coal is given in the table. The 73% reduction in iron pyrite is significant. This impacts boiler operation by lessening iron which is a fluxing agent for boiler slag and by lowering iron sulfide to the lower boiler wall which leads to severe corrosion problems for those plants employing low NOX burners. The reduction in LbSO2/MBtu is enough to save a nominal 1,000 MW generating station $6 million per year in the cost of sulfur emission allowances after operating costs for the MagMill™ have been subtracted.

 

 

 Feed

 MagMill Product

 Reject

 % Reduction in Concentration

 Recovery %

Weight Percent

100

81.72

18.28

 

81.72

Btu Dry

12,135

13,528

5,908

 

91.1

Ash, wt%

19.78

11.9

55.04

39.85

 

Sulfur, wt%

2.68

1.43

8.29

46.71

 

Pyritic, wt%

1.43

0.39

6.09

72.76

 

Organic, wt%

1.25

1.04

2.18

16.67

 

#SO2/MBtu

4.42

2.11

28.06

52.2

 

 

 

Combustion Testing



Bench-top combustion testing at Brigham Young University in Provo, UT, shows that the MagMill product burns out fastest without loss of volatiles.

 

Petrographic evaluation shows that the product contains the greatest portion of reactive components of coal while inert fractions are rejected and do not go to the flame.  The inert fractions consist of noncombustible mineral fractions and relatively non-combustible carbonaceous components which otherwise would end up as unburned carbon in fly ash.