Permeabilities of coal-biomass mixtures for high pressure gasifier feeds

Open Access
Author:
Belvalkar, Rohan Anirrudha
Graduate Program:
Petroleum and Natural Gas Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 02, 2012
Committee Members:
  • Derek Elsworth, Thesis Advisor
  • Chris Marone, Thesis Advisor
  • Jonathan P Mathews, Thesis Advisor
Keywords:
  • permeability
  • porosity
  • kozeny-carmen
  • coal
  • biomass
  • gasifier
  • feed
  • particle size
  • stress
  • strain
  • isotropic
  • pulse decay
Abstract:
Complete measurements of permeability on coal-biomass mixtures as a potential feedstock to gasifiers to reduce net carbon emissions were performed. Permeability is measured under anticipated dry feed stress conditions to determine the potential for fugitive gas emissions from the gasifier into the feed hopper. Cylindrical samples of coal-biomass blends are housed within a triaxial apparatus capable of applying mean and deviatoric stresses and of concurrently measuring gas permeability. Evolution of strain, porosity and permeability under mean stresses of 3.5, 7 and 14 MPa was measured. Permeability is measured by pulse transmission testing using N2 and He as the saturant and assuming the validity of Darcy’s law. Porosity is measured by pressure pulse with He as saturant and assuming an ideal gas. Experiments are conducted on a range of coals and biomass blends at mixtures of 100 percent coal through 100 percent biomass. Measured permeabilities are in the range 10-13 to 10-16 m2 with the 100 percent biomass blends showing lower permeabilities than the coal biomass and 100 percent coal blends. Permeabilities change in loading and unloading and exhibit hysteresis. The data was fit to connect permeability with porosity using relations for porous media where permeability changes proportionally to the cube of the change in porosity. This model performs adequately since there is little size reduction in the granular mass due to the applied isotropic loading.