Syngas Production by Thermochemical Gasification of Carbonaceous Waste Materials in a 150 kW_th Packed-Bed Solar Reactor

Abstract

The solar thermochemical steam-based gasification of carbonaceous materials is investigated using concentrated solar energy as the source of the high-temperature process heat. Vis-à-vis conventional autothermal gasification, the solar-driven process delivers a higher syngas output of higher quality and lower CO2 intensity because no portion of the feedstock is combusted and its energy content is solar upgraded. The operation of a solar gasification pilot plant for a 150 kWth solar-radiative power input was experimentally demonstrated using a packed-bed solar reactor operated in batch mode. The experimentation was carried out in a solar tower. Six different carbonaceous waste feedstocks have been successfully processed: industrial sludge, fluff, tire chips, dried sewage sludge, low-rank coal, and sugar cane bagasse. The calorific value of the produced syngas was upgraded by a factor of up to 1.3. The solar-to-fuel energy-conversion efficiency, defined as the ratio of the heating value of the fuel produced to the solar and feedstock energy inputs, varied between 22 and 35%.

Assessing biomass steam gasification technologies using a multi-purpose model

“…Solar gasification experimental setups using various carbonaceous materials [13,14] showed that carbon dioxide concentration decreased as much as temperature in the solar reactor increased. In the cited studies, CO 2 was found to account for less than 1% at 1600K, while H 2 production was around 40%.…”

Design and demonstration of a prototype 1.5 kWth hybrid solar/autothermal steam gasifier

“…Prominent solar-driven gasifier designs that have been examined in literature have employed entrained flow [11,16,18], drop tubes [7,8,10], packed beds [15,19,20], and fluidized beds [12,[21][22][23][24][25][26][27][28]. Entrained-flow and drop-tube gasifiers generally have very short residence times while benefiting from enhanced heat and mass transfer.…”

Storage capacity assessment of liquid fuels production by solar gasification in a packed bed reactor using a dynamic process model

“…In comparison, with this reactor concept, the indirectly irradiated packed bed reactor, has been proven to be operationally robust at a scale of 150 kW th and could also feasibly operate in a pressurised environment (although this has not yet been experimentally demonstrated). However, in this system solar heat is transferred to the fuel bed via a SiC emitter plate [14][15][16][17][18][19], which makes the reactor less efficient than the solar vortex reactor where coal particles are directly irradiated [11,12]. Furthermore, because the packed bed reactor relies on solar energy alone to drive thermochemical reactions, it is far more susceptible to solar intermittency.…”

“…The indirectly irradiated, packed bed solar gasifier has been proven, at a scale of 150 kW th , to be operationally robust [14][15][16][17][18][19]. Concentrated solar thermal radiation is introduced into this reactor through a compound parabolic concentrator (CPC) at the top to irradiate a SiC-coated metal emitter plate (see Fig.…”

“…The emitter plate reaches temperatures of up to 1400 K after only one hour from the start of the solar day. However, the top of the fuel bed can take 2-3 h to reach steady-state temperatures [14,19]. As the temperature at the top of the bed rises, the fuel is dried, undergoes thermal decomposition (devolatilisation) to release volatile gases and is then slowly gasified at temperatures above 1000 K in the presence of steam.…”