A study of cellulose gasification in a fluidized bed using a high-temperature solar furnace.

摘要

We have used a 4.2-meter solar furnace to study the gasification of cellulose with steam in a fluidized bed. The heating value of the high-temperature equilibrium products is about twenty percent higher than that of the reactants. The increase represents stored solar energy; and the product, synthesis gas, is valuable as a chemical feedstock or pipeline gas.; All experiments were performed at atmospheric pressure. Pure tabular alumina as well as crushed automotive exhaust was used as a bed material. Microcrystalline {dollar}alpha{dollar}-cellulose, entrained in argon, entered the fluidized bed just above the distributor. Steam was heated to the operating temperature in a 10 cm packed bed section below the fluidized bed. In all cases, the process ran with more steam than required to produce an equimolar mixture of carbon monoxide and hydrogen.; We used a quartz reactor between 1100 and 1430 K; a steel reactor at 1500 K and an Inconel reactor at 1600 K. Reactor inside diameter, nominally 5 cm, varied slightly; the bed height was adjusted to keep the gas residence time constant. Since steam reacted with the iron to form hydrogen, we measured the hydrogen production rate before and after our experiment with steam alone, and subtracted this amount from our results.; We did not achieve equilibrium mixtures in any of our experiments. The use of the catalyst improved our hydrogen yields, but even so we got higher than expected concentrations of carbon monoxide, methane and lighter hydrocarbons such as ethylene and acetylene.; For experiments performed without catalyst at 1300 K, we achieved a mixture (dry, argon-free) of 46 mole% CO, 30% H{dollar}sb2{dollar}, 14% CH{dollar}sb4{dollar}, 5% CO{dollar}sb2{dollar} and 5% C{dollar}sb2{dollar}H{dollar}sb4{dollar}. An equilibrium mixture at this temperature would have contained 39% CO, 30% H{dollar}sb2{dollar}, 7% CO{dollar}sb2{dollar} and no CH{dollar}sb4{dollar} or C{dollar}sb2{dollar}H{dollar}sb4{dollar}. With the catalyst, the CO and CH{dollar}sb4{dollar} decreased to 40% and 2% respectively, the H{dollar}sb2{dollar} increased to 47%, and CO{dollar}sb2{dollar} remained the same. No ethylene was formed. The hydrocarbon-rich mixtures we achieved are typical of results in rapid-pyrolysis processes, in which reactants are rapidly heated and products are quenched.