Reading Questions for Class 15: Practical Combustion & Gasification BYU: CH EN 733 U of U: CH EN 7960

1. Reading Questions for Class 15:Practical Combustion & GasificationBYU: CH EN 733U of U: CH EN 7960 Randy Pummill Cory Sennett Dave Wagner

2. Question 1:  Entrained flow discussion

3. Question 1:  Fluidized bed discussion

4. Question 1:  Fixed bed discussion

5. Question 2:   Postulate on the advantages and disadvantages of wall-fired entrained flow boilers versus tangentially-fired entrained flow boilers.

6. Question 3:   Please be prepared to discuss at length Figures 1.10, 1.12-1.13, 1.18, 1.20, 1.22, 1.26-1.27, 1.29-1.31. • 1.10 – 256 MW subcritical drum-type boiler for burning pulverized subbituminous coal. The jet burners are located at five elevations in the four corners for tangential firing. • 1.12-1.13 – (i) Distributed mixing burner concept (ii) Distributed mixing burner. The mixing burner with staging air inputs is a method to lower NOx formation and reduce other emissions as well. • 1.18 – Combustion Engineering IGCC repowering project: this figure is an overview of an IGCC facility with heat recovery, slag disposal, recirculation, and showing coal input to power output. • 1.20 – Black Dog bubbling AFBC Boiler • 1.22 – Tidd PFBC demonstration project: a pressurized, bubbling fluidized bed that operates at 1.2 MPa. Combustion air is supplied by the gas turbine compressor to ultimately generate about 16 MW of electricity. • 1.26-1.27 – (i) Traveling gate spreader stoker; coal is fed by mechanical feeders, throwing the coal over the grate (ii) Traveling gate overfeed stoker; coal is fed from a large hopper, slowly burned as it travels through the furnace • 1.29-1.31 – (i) Dry-ash Lurgi gasifier (ii) British Gas Corporation/Lurgi slagging gasifier (iii) Air-blown/integrated gasification combined-cycle project

7. Question 4:   Please discuss ash disposal. • Ash disposal in stokers occurs by sliding/brushing off the grate or by falling through; spreader stokers. • Ash can be sold as a base for concrete and/or roofing as long as the radiation is at low enough levels and the carbon is below a predetermined amount. • When fly ash is filtered out downstream of the furnace/boiler hot zone, it can be mixed with water and pumped out of the process. • Ash can build up in the hot zone or just downstream of it producing slag. This would have to removed by taking burner plates and the like off in order to chip/hammer the slag out of the boiler.

8. Question 5:   The BYU Heating Plant is currently burning coal in a spreader-stoker.  Dr. Baxter has tried to convince them to add biomass to cut down on fuel costs.  Please discuss the issues involved. • A few possible issues involved when co-firing biomass with coal to the spreader-stoker(SS) are: • Pre-processing may need to be done on the biomass to make it useable. • The SS is typically designed to use a narrow range of coals with certain fuel characteristics. Biomass is structurally different than coal which may affect the performance and operation of the SS. • Biomass has different ash characteristics which may affect performance and operation. • Biomass typically has a higher moisture content than coal which will affect combustion properties.