Coal Gasification in CO₂ and Steam:  Development of a Steam Injection Facility for High-Pressure Wire-Mesh Reactors

Abstract

The development of a steam injection facility and a new control system for steam gasification experiments in a high-pressure wire-mesh reactor have been described. The design is based on preheating the steam path to prevent condensation during experiments. Steam is allowed to contact the coal sample only instants before the temperature of the sample is ramped. Results from experiments in helium, CO 2 , and steam at pressures up to 30 bar (1000 °C s -1 to 1,000 °C) have been compared for experiments extending to 60 s at peak temperature. The occurrence of a minimum in the conversion vs pressure diagrams, previously observed by numerous researchers, appears to be related to the reactivity of the gasifying agent and the holding time. The minimum, observed at shorter holding times in steam compared to CO 2 , appears related to the consumption of secondary char deposited during the pyrolysis stage. At 10 and 20 bar, the sample appears to be completely consumed in steam in about 60 s, while after 60 s in CO 2 , the process appeared to have reached completion at about 92% at 30 bar (∼80% at 10 bar), apparently due to deactivation of char by prolonged exposure to high temperatures. By contrast, chars withdrawn from a pilotplant gasifier fluidized with steam and air appear to be relatively unreactive. Larger particle sizes used in the pilot plant (d p < 3 mm vs 105-152 µm) tend to enhance tar repolymerization and longer exposures at high temperature, required for the consumption of these larger particles, appear to have reduced the reactivity of the pilot-plant chars.

Meteorite ablation products and their contribution to the atmospheres of terrestrial planets: An experimental study using pyrolysis-FTIR

“…However, carbonaceous dust ablating in the atmosphere of a terrestrial planet could be expected to experience a range of atmospheric compositions, from the current oxygen-nitrogen atmosphere of Earth to its previous oxygen-poor atmosphere, before the accumulation of oxygen around 2.4 Ga, or the carbon dioxide-rich martian atmosphere. Pyrolysis in the presence of reactive fluids is known to alter the nature of the pyrolysis products, as shown by hydrous pyrolysis and hydropyrolysis, in the presence of water and hydrogen, respectively (Sephton et al, 1999;Sephton et al, 2005), and by pyrolysis and gasification in steam and carbon dioxide (e.g., Messenbock et al, 1999;Jamil et al, 2004). The helium atmosphere used here is difficult to relate to the current oxygen-rich atmosphere of Earth, or its previous carbon dioxide-rich atmosphere.…”

Gasification Fundamentals

“…The extent of coal conversion can be measured by comparing the initial and final weights of the sample. Messenböck et al 47,48 measured coal pyrolysis yields at 1,000 o C in flowing helium as a function of pressure and hold time. These experiments were then repeated with steam or carbon dioxide instead of helium.…”

Experimental studies on gasification of the Shenmu coal char with CO2 at elevated pressures

“…The conversion of coal char was calculated from the recorded weight loss curves by using the relationship (1) Where W is the instantaneous char weight, W ∞ is the weight of ash and W 0 is the weight of initial char. The apparent reaction rate was defined as change rate of conversion a.…”

“…Heterogeneous reaction rate of char and CO 2 or steam usually controls the overall conversion process, which has been studied extensively for decades. High-pressure wire-mesh reactor (PWMR) [1], pressurized drop tube furnace (PDTF) [2,3] and pressurized thermo-gravimetric analyzer (PTGA) [4][5][6] were the most popular experimental apparatus for the gasification reaction study at high pressure. Liu and Niksa [7] have reviewed data from these apparatus.…”