Experimental Study of Coal Topping Process in a Downer Reactor

Abstract

Experiments were carried out in a downer reactor integrated in a circulating fluidized bed combustor to examine the performance of the coal topping process. The effects of reaction temperature and coal particle size on the product distribution and their compositions were determined. The experimental results show that an increase in temperature will increase the yields of gas and liquid product, and the liquid yield decreases with the increase in coal particle size. The experiments exhibit an optimal condition for the liquid product. When the pyrolysis temperature is 660°C and coal particle size is less than 0.28 mm, the yield of light tar (hexanesoluble fraction) reaches 7.5 wt % (dry coal basis). The light tar is composed of acid groups (57.1 wt %), crude gasoline (aliphatics) (12.9 wt %), aromatics (21.4 wt %), and polar and basic groups (8.6 wt %). The experiments indicate that the coal topping process is a promising technology for partially converting coal into liquid fuels and fine chemicals.

Two fluid model using kinetic theory for modeling of one‐step hydrogen production gasifier

“…Figure 14 shows concentration profile of gas composition along the reactor height at the different operating pressures. At the operating pressure of 0.1 MPa, CO 2 is not absorbed well by CaO and Ca(OH) 2 . The effect of gas-water shift reaction is not significant.…”

“…The dissipation of fluctuating energy due to inelastic collision takes the form 2 , CaS, and Ash. The conservation equations for these chemical species can be represented but the N 2 for gas phase and Ash for solid phase, which are computed from the fact that the sum of all mass fractions is equal to one in the gas phase and solid phase, respectively.…”

“…Figure 16 shows the concentration profile of solid composition along the reactor height at the different operating pressures. In the experiment of single-step hydrogen production, Lin et al 42 drew a conclusion that the reaction rates decrease in the order CaO hydration [ coal pyrolysis [ CO 2 absorption by CaO or Ca(OH) 2 . The thermodynamic analysis results for the explanation of the experimental behaviors illustrated that CaO is first converted into Ca(OH) 2 at the reactor entrance.…”

“…Cycle (IGCC) have been believed to have the potential capability of hydrogen production for concentrating and sequestering CO 2 . 1 More attention has been paid to the process of hydrogen production from coal in a single step, [2][3][4] which combines the water gas shift reaction and reforming reactions with gasification in one reactor.…”

“…1 More attention has been paid to the process of hydrogen production from coal in a single step, [2][3][4] which combines the water gas shift reaction and reforming reactions with gasification in one reactor. This process can also be extended to biomass gasification and some excellent catalysts has been developed to accelerate a process of hydrogen and syngas production at very low temperature.…”