Solid Waste Solutions

 

Update 06/7/2017 - Utility Power Generation using Engineered Fuel


Studies continue on PENELEC’S Unit 3 (Homer City) fossil fuel generating station at Homer City, PA. to test the feasibility of utilizing municipal waste in an engineered fuel pellet to produce electricity.

The PennElec Boiler model employs a steady state Newton-Raphson algorithm with a Forward Euler algorithm for the Turbine and feedwater heaters moulded into an integrated unit that conserves mass and energy.


Fuel

A model fuel composition more representative of the Pennelec plant was selected as the base fuel case for ongoing municipal waste combustion evaluation.

The Boiler base case credit and loss summary contains the model fuel composition and Boiler efficiency data. Model mass and energy balance validation data is now detailed in the Powerpoint presentation 'Evaluating Green Projects' - Syn Fuel from Municipal Waste, currently REV 'O'      

A Hardcopy of base case calculated results (Heatsum.prt) is available for download for the model calculated initial case conditions here.  Hardcopies will be available for each distinctive model run when completed..


Case 4 Engr Fuel High Heating Value (HHV)

The High heating value for Case 4 is 12, 466 Btu/lb compared to 13,118 Btu/lb for the coal reference. Case 4 defines a new solid waste fuel composition that is a blend of municipal waste and shredded automobile tires, sans the steel belting. It was intentionally formulated to be on the high end of heat content.

Unfortunately, high hydrogen content of waste fuel is large compared to conventional fossil fuels. Municipal waste fuels can be readily blended to match the heat content of coal producing less emissions.

Deleted


Deleted.  Greater waste fuel combustion is precisely what is desired to rid municipalities of solid waste otherwise winding up in a landfil.  (All cases considered assume complete fuel combustion )


Note that fuel moisture includes the effect of humidity in the combustion air.


Case 4 Model Fuel Blend

Page One above contains the model fuel composition for Case 6 as determined by the Thermodynamic Approximation of Fuel Heat Content Table.

LATER

The waste Fuel composition is based on Table 1. Municipal Solid Waste (MSW) Heat Content and Biogenic/Non-Shares, 1989 - 2005 as noted in the Power Point presentation, Rev (N -1).  Enthalpies of combustion were calculated for the MSW components (carbon, hydrogen, etc) and verified against EPA heat content data. Engineered fuel composition was calculated as a mass fraction of both MSW and Shreded rubber tires. The Dulong equation and the thermodynamic heat content, (Btu/lb) were averaged to predict the High Heating Value (HHV) of the Fuel.  This value appears in the fuel summary on Page One of the Model 'Unit Credit and Loss Summary'.


Boiler

 

Predicted power generation based on Case 4 fuel is 656.1 MW.  Superheater spray runs quite a bit higher due to the 10.38% waste fuel hydrogen content.

Temperatures and pressures are equilvalent to the base case despite the lower carbon content. Unit operation for this case had to be modified to accomodate the fuel differences.  The Superheat and Reheat banks were allowed to slag up significantly (Kf = .82, .82 and Kf =.73, .78 respectively) for Case 4 in order to give better temperature control at the Throttle and Reheat turbine inlets. When higher carbon content is available in the waste fuel, increased sootblowing will restore the effective absorbtivity of the superheat and reheat boiler banks


Case 4 is typical of waste fuel combustion in utility power generation. It's high hydrogen temperature makes reheat temperature difficult to control. Deleted.  The unit was somewhat sluggish due to the over 7% fuel moisture content. Typically fuel would not be combusted with moisture contents much over 2% but it was necessary to demonstrate that higher waste fuel moisture content could be accomodated in a conventional utility boiler. 


Industrial fluidized bed boilers can accomodate higher fuel moisture contents than utility boilers and are well suited to burning solid municipal wastes including sewage sludge.

Unit Heatrate for Case 4 was 10,316 Btu/KWH versus 10,293 Btu/KWH for the 100% coal base case, the heatrate performance difference between coal and the waste fuel was less than a quarter percent of normal unit operation.


Model Material & Energy Balance

 


Case 4 Steam Conditions



The Pennsylvania Electric Homer City Unit 3 typically consumes approximately 1,600,000 tons of compliance coal per year.  The plant purchases approximately 75% of this coal from one supplier and that coal is blended at a coal blending facility owned by the supplier. The remainder of the coal needed for Unit 3 is obtained in the spot market. - http://www.getfilings.com/o0000912057-02-012778.html  Subsequent Unit 3 equipment improvements are not modeled and model architecture has been adjusted so fuel combustion operations are closer to Homer City’s original commissioning.

Be sure and ask the EPA and its climate modelers for the model validation data that justifys their global warming predictions before trusting in their conclusions.


Turbine:

 

The Pennelec Turbine is a GE 700 MW four valve unit operating in sliding pressure mode (99.9% open) with single state reheat.  The boiler is fired for temperature in all model case runs. The generator is Hydrogen cooled at 60 psi with Demineralized water heat exchange for stator cooling


Update 05/29/17: Turbine stage Effectiveness

 

Base case Turbine Output:   Case 4 First Stage pressure is 1891 psi and Turbine efficiency is 36.04%..

Effectiveness factors for each turbine stage have been determined based on the ratio of design to actual plant commissioning data. Turbine stage effectivesness remains constant whether the base or model plant conditions, they are:

HP: 0.95     IP1: 0.99    LP1: 1.0    LP2: 0.99     LP3: 1.00      LP4: 1.02            
          

Last Turbine Stage Moisture for Case 4 is calculated at 8.03%


Case 4 Results:

Mass Balance Correlation (page 5): Last State flow: 2838294/ 2847763 = 0.9967 compared to the base case of  0.9915, Energy balance Correlation was: 1.19 compared to the base case of 0.9809, significantly higher.


Cycle Eff, %: was 33.1% compared to the coal base of 33.2%  The loss in cycle efficiency is not particularly significant because the objective is to burn large quantities of waste fuel rather than conserving it.


Emissions:


Researchers accidently find industrial waste, orange peel material sucks mercury out of water

7584.6 tons
of waste were combusted in a 24 hour period greatly exceeding that of the coal reference case at nearly the same rate of power generation which is precisely what is desired to rid municipalities of accumulated solid waste.

Sulfur content of Case 4 fuel is 170.68 ppm to the reference base of 133.21 ppm, or based on composition:(.0247  - .0230) / .0230 x 100 = 7.39% increase in sulfur content before SO2 scrubbing is performed. Mercury emissions are essentially zero compared to our coal reference.

The real benefit in burning an engineered fuel is that both operating cost and certain emissions can be reduced.($0.34 per million BTUs for Case 4 versus $0.45 per million BTUs for our reference coal) at $55.00 per ton and a calculated $32.33 per ton of Case 4 solid waste.  Studies show that even if the cost of the engineered fuel was $38.42 per ton, the waste case would still produce savings at $0.40 per million BTU or about 4.7%.


Generation:




Case 4 produced 656.1 MW at 4492278 lbs/hr feedwater versus 656.8 MW at 4493358 lb/hr feedwater.   Adjusting to the same base 4493358 / 4492278 x 656.1 = 656.3  Error is (656.8 - 656.3)/ 656.8 *100 = 0.076%

Economics
 

Model electric revenue computations are based on $0.073 per Kilowatt hour.

Deleted.  Cost savings were considerable over coal alone while Unit operation was comparable to coal.  Case 4 provided thefollowing fuel savings at (0.02080 - .01557)/.02080 x 100 = 25.14%.  Work continues... This section will contain a generation data table on alternate fuels as tests progress.


CASE '0" 100% Coal Base reference
CASE 4 - Model Results Hardcopy


The table below is being revised to reflect the new base fuel composition and waste fuel test operating conditions.

      Notes:  Fuel Moisture content was 5% for this case.
                   Engineered fuel is essentially mercury free.