Pyrolysis Gas Composition Research Articles

Investigations in Combined Combustion of Biomass and Coal in Power Plant Technology

The possibility of a combined application of coal and biomass using two different co-combustion technologies has been investigated. A blending of pulverized biomass with coal showed a high burnout up to 20% thermal input of biomass for all particle sizes of the biofuels tested. CO emissions were generally lower than 150 mg/m3 (6% O2) and remain below 100 mg/m3 in the most cases. Reburn investigations with three pulverized biomasses resulted in NOx emissions of approximately 300 mg/m3 (6% O2). With pyrolysis gas as reburn fuel, minimum NOx emissions of 200 mg/m3 (100 ppm) at 6% O2 in the flue gas are possible. The main parameters are pyrolysis gas composition, stoichiometry, and residence time in the reduction zone. Best minimizing results have been achieved with pyrolysis gas produced at about 800 °C using coal as raw material; using biomass as feedstock, the influence of the pyrolysis temperature is only small. The nitrogen concentration, especially in the tar components of the pyrolysis gas, appears to ...

BoA and KoBra. Modern power-plant technology for brown coal

Coal topping gasification refers to a process that extracts the volatiles contained in coal into gas and tar rich in chemical structures in advance of gasification. The technology can be implemented in a reactor system coupling a fluidized bed pyrolyzer and a transport bed gasifier in which coal is first pyrolyzed in the fluidized bed before being forwarded into the transport bed for gasification. The present article is devoted to investigating the pyrolysis of lignite and bituminite in a fluidized bed reactor. The results showed that the highest tar yield appeared at 823 to 923 K for both coals. When coal ash from CFB boiler was used as the bed material, obvious decreases in the yields of tar and pyrolysis gas were observed. Pyrolysis in a reaction atmosphere simulating the pyrolysis gas composition of coal resulted in a higher production of tar. Under the conditions of using CFB boiler ash as the bed material and the simulated pyrolysis gas as the reaction atmosphere, the tar yields for pyrolytic topping in a fluidized bed reactor was about 11.4 wt.% for bituminite and 6.5 wt.% for lignite in dry ash-free coal base.

Biosludge incineration of FBSs: Behavior of ash particles

Coal topping gasification refers to a process that extracts the volatiles contained in coal into gas and tar rich in chemical structures in advance of gasification. The technology can be implemented in a reactor system coupling a fluidized bed pyrolyzer and a transport bed gasifier in which coal is first pyrolyzed in the fluidized bed before being forwarded into the transport bed for gasification. The present article is devoted to investigating the pyrolysis of lignite and bituminite in a fluidized bed reactor. The results showed that the highest tar yield appeared at 823 to 923 K for both coals. When coal ash from CFB boiler was used as the bed material, obvious decreases in the yields of tar and pyrolysis gas were observed. Pyrolysis in a reaction atmosphere simulating the pyrolysis gas composition of coal resulted in a higher production of tar. Under the conditions of using CFB boiler ash as the bed material and the simulated pyrolysis gas as the reaction atmosphere, the tar yields for pyrolytic topping in a fluidized bed reactor was about 11.4 wt.% for bituminite and 6.5 wt.% for lignite in dry ash-free coal base.

Behavior of sulfur during coal pyrolysis

Coal topping gasification refers to a process that extracts the volatiles contained in coal into gas and tar rich in chemical structures in advance of gasification. The technology can be implemented in a reactor system coupling a fluidized bed pyrolyzer and a transport bed gasifier in which coal is first pyrolyzed in the fluidized bed before being forwarded into the transport bed for gasification. The present article is devoted to investigating the pyrolysis of lignite and bituminite in a fluidized bed reactor. The results showed that the highest tar yield appeared at 823 to 923 K for both coals. When coal ash from CFB boiler was used as the bed material, obvious decreases in the yields of tar and pyrolysis gas were observed. Pyrolysis in a reaction atmosphere simulating the pyrolysis gas composition of coal resulted in a higher production of tar. Under the conditions of using CFB boiler ash as the bed material and the simulated pyrolysis gas as the reaction atmosphere, the tar yields for pyrolytic topping in a fluidized bed reactor was about 11.4 wt.% for bituminite and 6.5 wt.% for lignite in dry ash-free coal base.

A COAL PYROLYSIS REACTOR SYSTEM WITH FAST ON-LINE COMPOSITION ANALYSIS BY GAS CHROMATOGRAPHY

The development of a coal pyrolysis reactor and a novel gas chromatography method for fast on-line composition analysis of pyrolysis products are presented. The annular fluidized bed reactor system minimizes particle agglomeration during the pyrolysis of plastic coals and the new column switching technique significantly reduces the time required for measuring the composition of low-volatile pyrolysis gases on a conventional gas chromatograph. Data from representative pyrolysis runs are presented and discussed.

Changes associated with natural in situ weathering of a coking coal from southeastern British Columbia

A suite of naturally oxidized coals from a single coal seam from southeastern British Columbia was examined by means of pyrolysis gas chromatography together with ultimate and petrographic analysis. With increasing degree of oxidation (FSI decreasing from 7.5 to 0) a consistent decrease in fixed carbon and hydrogen and an increase in oxygen and moisture were found. Comparing the mildly oxidized coal (FSI 7.5 to 3) with the unweathered coal, there is very little detectable change in pyrolysis gas composition or chemistry. At more advanced stages of oxidation (FSI 3 to 0) the pyrolysis gas is markedly depleted in CO, CH4, C2H4 and C2H6 and correspondingly enriched in CO2. The carbon and hydrogen contents decrease and the oxygen content increases significantly. In the mildly oxidized coal, oxidation rinds develop on vitrinite particles, whereas in the more oxidized coal, microfissures and a darkish cast are evident.

Charring pyrolysis of wood in fires by laser simulation

Utilizing a 250 watt CO 2 -laser radiation source, wood pyrolysis at fire-level surface heat flux was investigated through the measurement of decomposition rates, solid temperatures and thermal properties, pyrolysis gas compositions and pressures, and crack formation. Heats of reaction calculated from these measurements show that at an incident heat flux of 0.76 cal/cm 2 -sec applied parallel to the wood grain direction, the pyrolysis layer (≈1cm thick) can be divided into three zones: (i) an endothermic primary decomposition zone at temperatures T <250°C, (ii) an exothermic partial char zone at 250°C< T <340°C, and (iii) an endothermic surface char zone at 340°C< T <520°C. The overall mass weighted effective heat of reaction is endothermic to the extent of −146 cal/g. At 2.0 cal/cm 2 -sec applied parallel or perpendicular to grain direction, pyrolysis reaction proceeds as a charring wave of ≈0.5 cm thickness advancing into the wood. The charring wave (250°C< T <450°C) is characterized by active overall exothermic reactions accompanied by rapid solid density change. In front of the wave is an endothermic primary decomposition zone, and behind the wave is an exothermic char layer ( T <800°C) of relatively constant density. The overall heat of reaction at the higher heat flux is exothermic, being greater for perpendicular heating (260–410 cal/g) than for parallel heating (25–94 cal/g). For parallel heating at both heat fluxes, macroscopic cracks (≈1mm wide) occur in the pyrolysis region, whereas for perpendicular heating no cracks are observed. Present results show that the wood pyrolysis process is dependent upon the external heating rate, the total time of heating, and the anisotropic properties of wood and char relative to the internal flow of heat and gas.

Influence of increasing pressure on pyrolysis of liquid hydrocarbons

1. The pyrolysis of n-hexane and straight-run naphtha has been studied at temperatures of 750–800°C, total pressures of 15–35 kgf/cm2, hydrocarbon partial pressures in the reaction mixture of 7–12 kgf/cm2, steam dilutions of 30–100% of the feedstock weight, and contact time approximately 1 sec. 2. It has been shown that a change in total pressure from 15 to 35 kgf/cm2 with a constant hydrocarbon partial pressure of 7 kgf/cm2 has far less influence on the pyrolysis gas composition than does a change in hydrocarbon partial pressure from 7 to 12 kgf/cm2 with a constant total pressure of 30 kgf/cm2. 3. It has been established that as the hydrocarbon partial pressure is increased from 7 to 12 kgf/cm2 and the temperature is increased from 750 to 800°C the concentrations of methane and ethane increase, and the concentrations of ethylene, propylene, and C4 decrease.

Nonequilibrium Flow and the Kinetics of Chemical Reactions in the Char Zone

Abstract In the temperature range of 500–2500°F, nonequilibrium flow analysis predicted only a small change in pyrolysis gas composition as the gases flow through the char zone. Essentially all of the reactions took place in the temperature range of 2000–2500°F. Comparing nonequilibrium flow with the two limiting cases, the energy absorbed in the char zone for frozen flow was two-thirds that of nonequilibrium flow, and equilibrium flow was about four times that of nonequilibrium flow at the 2500°F level.