00302 Catalytic gasification of biomass to produce hydrogen rich gas

03

Gaseous fuek (derived gaseous fuels)

observed mode of inhibition when quantities of hydrogen are limited, and reverse oxygen exchange dictates rate dependence on hydrogen at elevated pressures where the char surface is essentially saturated in hydrogen.

Derived gaseous fuels Advanced technological components enhance the performance of coal and oil gasification plants

99100299

Keller, H. J. et al. Proc. Annu. In?. Pittsburgh Coal Conf., 1997, 14, 25, 1222. This review describes the major components of an advanced plant concept for the gasification of coal or oil/residues. The guidelines for the developement of this plant concept have been operation, low production cost and environmental compatibility. The use of the components in existing gasification plants to enhance their performance is also discussed.

A paratus and procedure hydrogen and Por synthesis gas

99/00300

for

production

of

Noelscher, C. Ger. DE 19,636,068 (Cl. COlB3/36), 28 May 1998, Appl. 19,636,068, 5 Sep 1996; 8 pp. (In German) By endothermic partial oxidation and/or reforming in a reactor, an apparatus and procedure are disclosed for manufacture of HZ and/or synthesis gas from a feed gas (e.g. natural gas). The reforming reactor is integrated with a high-temperature fuel cell, but the devices have separate gas spaces. Energy necessary for the endothermic reaction is supplied from cooling of the high-temperature fuel cell. The gas pressure in the reactor is independent of the pressure in the fuel cell and the gas produced in the reforming reactor is withdrawn into a gas purification unit. 99lOO301

Behavior of fluidized-bed coal gasifier with inert

solid carrier

Luo, H. er al. Huagong Xuebao (Chin. Ed.), 1998, 49, (1). 111-115. (In Chinese) The simulation of a new fluidized-bed coal gasifier with separated combustion and gasification chambers and inert solid heat carrier is presented in this paper. The simulation shows that two-phase model proposed by Kunii and Levenspiel with a well-emulsion phase is suitable to describe the gasification for a laboratory fluidized bed.

Catalytic hydrogen rich gas

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gasification

of

biomass

to

produce

Rapagna, S. et al. Inl. .I. Hydrogen Energy, 1998, 23, (7), 551-557. In a bench scale plant consisting essentially of a fluidized bed gasifier and a secondary catalytic fixed bed reactor catalytic biomass steam gasification runs were performed. This secondary reactor employed alternatively two different steam reforming catalysts and calcined dolomite. The operating conditions in the gasifier were kept constant for all the runs. The influence of the operating conditions in the catalytic converter on the production of gases, especially HZ, was investigated over the temperature range of 660830”, for gas hourly space velocities (GHSV) in the range 9000-27,700 h-‘. About 2 m3 of dry gas (at ambient conditions) per kg of daf biomass were obtained by utilizing the fresh catalyst at the highest temperature level, with more than 60% by volume being hydrogen. The lowest tar residue was 0.45 g/kg of daf biomass, which increased slightly over the three hours gasification time. Substantial carbon deposition was observed, mainly on the catalyst layers contacting the inlet gas. On the basis of these results, a process configuration suitable for industrial applications is discussed.

Characterization of hydrogenation of aromatics in coal-derived middle distillate and 1-methylnaphthalene

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Machida, M. et al. Sekiyu Gakkaishi, 1998, 41, (4), 285-292. In the hydrogenation of a coal-derived middle distillate the effects of reaction temperature and partial pressure of hydrogen were examined over a Ni-MO/alumina catalyst. As the aromatics of naphthalene type were major components of the coal-derived middle distillate, hydrogenation of lmethylnaphthalene was also examined to quantity the conversion rate of the hydrogenation of aromatics. The hydrogenation proceeded via first-order reaction, with respect to both the content of 1-methylnaphthalene and the partial pressure of hydrogen. In conditions of temperature above 350°C and the hydrogen pressure around 4 MPa, not only rate of hydrogenation, but also thermodynamic limitation controlled the hydrogenation conversion of aromatics. At partial pressure of hydrogen around 12 MPa, up to the temperature of 400” the thermodynamic limitation of the hydrogenation of aromatics was effectively released.

Characterizing rate inhibition in steam/hydrogen gasification via analysis of adsorbed hydrogen

99lOO304

Lussier, M. G. et al. Carbon, 1998, 36, (9), 1361-1369. Hydrogen adsorbed onto Saran and coal char is conducted and analysed via post-gasification temperature programmed desorption to 1770 K to characterize hydrogen inhibition in steam gasification. Exposure of annealed, outgassed chars to H20/H2/Ar mixtures at 1120K and pressures to 3.1 MPa results in rapid adsorption of hydrogen on the char. Steam gasification rate simultaneously declines as a result of adsorbing hydrogen blocking a portion of reactive surface sites. Between 0.5 and 40% char conversion, adsorbed hydrogen concentration is constant at -2 x lo-’ mmol Hz mm2 at all conditions; steam gasification rate is also constant with conversion but depends strongly on hydrogen partial pressure through the reverse oxygen exchange pathway. Thus, dissociative adsorption is the

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Fuel and Energy Abstracts

January 1999

99lOO305

Circulating fluidized bed gasification

of a tire-

derived fuel Arena, U. and Cammarota, A. Proc. Inr. Conf. Fluid. Bed Combust., 1997, 14, (1). 433438. Operated with air and steam as oxidizers a market available tire-derived fuel (TDF) was continuously fed in a laboratory scale CFB gasifier. Silica sand was used as bed material. The riser and the recirculation column were maintained at 850°C by means of electric heaters driven by electronic controllers. The experiments were carried out at fixed values of solids mass flux (10 kglsm’) and superficial gas velocity in the primary (1.7 m/s) as well as in the secondary zone (2.7 m/s). The equivalence ratio and the H20/TDF d.a.f. ratio were varied between 0.3 and 0.6 and between 0.4 and 1.3, respectively. For each run, data from pressure electronic transducers, thermocouples and gas analysers were processed to evaluate riser axial profiles of pressure, temperature and gas concentration. Collecting, sieving and analysing solids hold-up in the riser allowed to estimate the amount of carbon

particles

and

their

size

distribution.

Coalbed methane underground coal gasification

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production

enhancement

by

Hettema, M. H. H. et al. Proc. Annu. Int. Piusburgh Coal Conf., 1997, 14, (13), 6-15. Studied is combined underground coal gasification and coal bed methane production using a single injection well. An axisymmetrical model is used to determine the effects induced by gasification, i.e. rubble formation and compaction and induced stress effects on overlying strata. The stress effects are subsequently related to changes in coal permeability.

Commercial steam reforming catalysts to improve biomass gasification with steam-oxygen mixtures. 2. Catalytic tar removal 99100307

Aznar, M. P. et al. Ind. Eng. Chemical Res., 1998, 37, (7), 2668-2680. In biomass gasification for hot gas cleanup and conditioning eight different commercial catalysts for steam reforming of naphthas and natural gas were tested. The catalysts were tested in a slip flow after a biomass gasifier of fluidized bed type at small pilot-plant scale (lo-20 kg of biomass/h). The gasifying agent used was steam-oxygen mixtures A guard bed containing a calcined dolomite was used to decrease the tar content in the gas at the inlet of the catalytic bed. Main variables studied were catalyst type, bed temperature, time-onstream and Hz0 + O2 to biomass feed ratio. All catalysts for reforming of naphthas showed to be very active and useful for tar removal and gas conditioning. 98% Tar removal was easily obtained with space velocities of 14,000 h-’ (n.c.). No catalyst deactivation was found in 48 h-onstream tests when the catalyst temperature was relatively high. Using a simple first-order kinetic model for the overall tar removal reaction, apparent energies of activation and preexponential factors were obtained for the most active catalysts.

Comparison of power generation integrated biomsss gasification

99100306

systems with

Roesch, C. and Kaltschmitt, M. DGMK Tagungsber., 1998, 9802, 209-216. (In German) A higher electrical efficiency could be achieved (22-37%) in combination with gas engines or gas turbines with biomass gasification plants as in comparison to biomass incineration with steam generation and steam turbine (15-18%). For combined heat and power generating plants with a performance up to 5 MW,, the use of gas motors had more advantages than the use of gas turbines. For plants with a performance of 3-20 MW,, power generation gas turbines with a preliminary biomass fluidized bed gasifier were the best available technology nowadays. The use of gas from biomass gasification in fuel cells had much promise, but nowadays the demand of the fuel cells on very pure gas make a lot of problems. The costs for combined power and heat generating plants with gas motors or gas turbines were assessed to be 4000-6000 DMRW,,. In conclusion the gasification of biomass followed by generation of electricity was seen as a promising technology for environmental and climate protection.

Comparison of various methods for the determination of the tar content in fuel gas from wood gasification

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Moersch, 0. et al. DGMK Tagungsber., 1998, 9802, 311-318. (In German) A differential FID method for a quasi-continuous measurement of the tar content of gas from biomass gasification is presented. Other methods from literature were compared to this method for time demand, accuracy and costs. A gravimetric method, a wet-chemical analysis, the solid-phase amino absorption method, and an online analysis with a process gas chromatograph are evaluated. The measurements were performed at a fluidized bed pyrolysis plant with wood as raw material and a pyrolysis temperature of 800”. The results obtained by each method are presented and discussed in brief for their advantages and disadvantages.