Steam Gasification Rate Research Articles

各種石炭チャーのガス化反応に対するガス種および圧力の効果

各種石炭チャーのガス化反応に対するガス種および圧力の効果

Effects of coal carbonization conditions on rate of steam gasification of char

Effects of carbonization conditions on char reactivity in steam gasification were evaluated by a gravimetric method, using 12 coals varying widely in rank, type and source. The carbonization variables examined were 1. (1) heating rate (5–420K min −1) in steam atmosphere; 2. (2) gaseous atmosphere (N 2,H 2,H 2O andCO 2); 3. (3) incomplete devolatilization in N 2 (final temperature 200–800 °C); 4. (4) quenching of incompletely devolatilized char; and 5. (5) complete carbonization (900–1400 °C). The char reactivity to steam depended on the kind of coal but was almost independent of the carbonization conditions of heating rate, gaseous atmosphere and quenching at temperatures below ≈ 1000 ° C. Carbonization above 1100 °C reduced the char reactivity, for example by a factor of 7 to 10 at 1300 °C compared with 900–1000 °C, depending on the parent coal. The char deactivation brought about by increasing carbonization temperature could be correlated with a decrease in the micropore volume of the char, unless graphitization was significant.

脱灰した各種石炭のガス化反応性

Steam gasification rates of 17 kinds of demineralized coals were measured at 787°C by a rapid heating method to clarify the factor controlling the gasification reaction and to present a valid reactivity index. Upon the demineralization, the gasification rates of lower-rank coals (C<ca.80%) decreased largely, whereas those of higher-rank coals (C>ca.80%) changed little. The difference in the reactivity among the demineralized coals was very small, indicating that the intrinsic reactivity changes little with the coal rank. Thus the gasification of the lower-rank coals was found to be catalyzed by the coal minerals. Ca and Na in carboxylate salts were expected to act as effective catalysts for gasification. The pore structure such as surface area and micro pore volume could not be employed as a reactivity index especially for the lower-rank coals. The amount of oxygen trapped by the char, no, which was measured by the flash desorption technique, was expected to be a valid index of gasification reactivity, because no showed fairly good correlation with the gasification rate irrespective of the rank of coals.

Relation between the gasification rate of carbons supporting alkali metal salts and the amount of oxygen trapped by the metal

The amount of oxygen trapped by metal on the surface of carbon was measured by the flash desorption method by use of a Curie-point pyrolyser. The steam gasification rate of the carbon supporting several alkali metal salts was proportional to the amount of oxygen measured. Furthermore, the molar amount of oxygen trapped by metal on the carbon surface was found to equal the molar amount of metal supported. The F.T.-i.r. spectra indicated that the alkali metal ( M) traps oxygen in the form of an M O C bond. A mechanism for the catalytic gasification, consistent with these findings, was developed. The gasification rate equation based on this mechanism was found to fit the experimental data.

RELATION BETWEEN THE GASIFICATION RATE AND THE AMOUNT OF OXYGEN ON CARBON SURFACE DURING THE GASIFICATION OF A CARBON SUPPORTING SEVERAL ALKALINE METAL SALTS

Abstract The oxygen trapped by metal on the carbon surface was measured in terms of the so-called flash desorption method by use of a Curie-point pyrolyzer. The steam gasification rate of the carbon supporting several alkaline metal salts was found to be proportional to the amount of the oxygen measured by the method. Furthermore, the moles of the oxygen trapped by metal on the carbon surface were found to be equal to the moles of metal supported.

Comparison of steam gasification rates of various activated carbons by TGA method.

Thermogravimetric analysis was utilized to study kinetics of the activated carbon-steam reaction for five different carbons. The experimental results show that the heating rate of samples has very little effect on the values of the activation energy (E) and the reaction rate constant (K). The activation energy of gasification increases and passes through a maximum as the weight of a sample decreases, except for DARCO activated carbon. Initial rate of gasification increases with steam concentration for all the carbons. The calculated activation energies and initial reaction rate constants (k1073) were between 180 and 280kJ/mol, and 2.76 × 10-5 and 3.05 × 10-4s-1, respectively.

Steam gasification of German hard coal using alkaline catalysts: Effects of carbon burn-off and ash content

Laboratory-scale experiments were performed on chars from German hard coals with potassium carbonate addition. The steam gasification rate at 4 MPa and 700 °C as a function of the amount of catalyst added is described for a low-and high-ash char. From the burn-off behaviour the reaction order relative to carbon was determined. For the low-ash char a uniform reaction order was found but the high-ash char indicated a complex interaction of catalytic gasification, catalyst deactivation, and the development of the reacting surface.

Hydrogen from Coal Char in a Continuous Electrofluid Reactor

The production of a hydrogen-rich synthesis gas from coal char and steam has been demonstrated in a modified 12-in.-dia continuous fluid bed reactor with a three-phase ac power supply. Steam conversions and gasification rates were adequate at 1 atm and 1600 to 2000/sup 0/F. Operation of the reactor generally has been smooth with no serious difficulty in controlling electrical power but electrode problems still remain, including short electrode life, slag formation, and overheating.