An experimental and modeling study of pressure effects on tar release by rapid pyrolysis of cellulose sheets in a screen heater
- Massachusetts Inst. of Tech., Cambridge, MA (United States)
Effects of total external pressure (vacuum [0.0001 atm], 1.3 and 69 atm of helium), on tar, char, and gas yields from rapid pyrolysis of 101-[mu]-m-thick cellulose sheets were measured in a screen heater reactor, using holding times of 0.2, or 5 s at final temperatures from 400 up to 1,100 C At a heating rate of 1,000 C/s, increasing pressure from 0.0001 to 1.3 atm at > 750 C or from 1.3 to 69 atm at > 650 C, decreased tar yields and increased gas production. Tar yields at 0.0001, 1.3, and 69 atm, at this heating rate, were well correlated for a wide range of temperatures, by mathematically modeling tar release rates in terms of the kinetics of tar generation by cellulose thermal decomposition, tar destruction by secondary reactions, and tar transport by pressure-cognizant mass transfer. The data and analysis imply that increasing pressure above vacuum, enhances tar holdup within the cellulose by slowing intrasubstrate diffusion of tar, and assists tar escape from the cellulose surface by augmenting free convection of surrounding gas. Related conclusions are that, at a 1,000 C/s heating rate, tar secondary reactions are significant within the fuel piece at pressures near and above 1 atm, and temperatures [>=] 650 C--750 C, and external to the fuel piece, including on the heater screen, at 0.0001 atm and [>=] 800 C.
- OSTI ID:
- 5591415
- Journal Information:
- Combustion and Flame; (United States), Vol. 95:1-2; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CELLULOSE
PYROLYSIS
TAR
CHEMICAL REACTION YIELD
CHARS
CHEMICAL REACTION KINETICS
FLASH HEATING
MATHEMATICAL MODELS
PRESSURE DEPENDENCE
PYROLYTIC GASES
WOOD FUELS
CARBOHYDRATES
CHEMICAL REACTIONS
DECOMPOSITION
ENERGY SOURCES
FLUIDS
FUELS
GASES
HEATING
KINETICS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
POLYSACCHARIDES
PYROLYSIS PRODUCTS
REACTION KINETICS
SACCHARIDES
THERMOCHEMICAL PROCESSES
YIELDS
090900* - Biomass Fuels- Processing- (1990-)