Thermochemical Process Study on a Jet-Fluidized-Bed Gasifier Reaction System by an Equivalent Chemical Reactor Network

Abstract

To study the effects of operational parameters on gasifying characteristics in the jet-fluidized-bed reactor and illustrate the scaling relationships of jet-fluidized-bed coal gasifier in a scale-up process, we established an equivalent reactor network model for the gasifier using CHEMKIN 4.1 software. The model is based on hydrodynamic properties in the gasifier and knowledge of the burning zone and gasifying zone of the reactor. It involves two-phase flow between materials, heat and mass transfer, as well as the coal gasification process in the presence of mixed gases, most notably H 2 O, O 2 , N 2 , etc. The model was validated by comparing it to the experimental data of outlet gas compositions. To optimize characteristics of the jet-fluidized-bed coal gasifier, the influence of the oxygen feed rate into the center nozzle and the coal feed rate on the gasification process and gas composition were studied by the equivalent established reactor network. Within the calculation range, with the increase of the oxygen feed rate into the center nozzle, the jet region nearly doubled, the temperature increased by 306 K, carbon conversion efficiency rose from 68 to 97%; however, the temperature of the jetting region should be controlled within the coal ash-softening temperature, and in generated gases, the CO and H 2 contents had clearly changed. With the increase of the coal processing capacity, the jet region temperature decreased by 252 K, the gasifier overall temperature decreased, and carbon conversion reduced from 98 to 74%.

Influence of ash agglomerating fluidized bed reactor scale‐up on coal gasification characteristics

“…Based on hydrodynamics calculation of the previous AFB, the gasifier was divided into three parts, the jet zone, the annulus dense‐phase zone and the freeboard zone, and the combined equivalent reactor is illustrated in Figure a. In the jet zone, where the gas and solid are well mixed, a perfectly stirred reactor (PSR) is used to simulate this zone.…”

“…The computation process of energy conservation of each zone in the gasifier has been detailed in previous work . The heat loss caused by the sensible heat of ash ( Q ash ) is formulated as follows where m* (kg) represents the total amount of ash and Δ T (K) is the temperature change of ash.…”

“…The specific ash components, such as SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, SO 3 , MgO, and TiO 2 , are taken into account in the calculations reported elsewhere . The coal ash mass fraction in this article contains 43.09% SiO 2 , 29.83% Al 2 O 3 , 15.99% Fe 2 O 3 , 5.28%CaO, 0.80% MgO, 1.24% TiO 2 , 2.75% SO 3 , 0.78% K 2 O, 0.08% Na 2 O, and 0.09% P 2 O 5 .…”

Numerical analysis of gasification and emission characteristics of a two-stage entrained flow gasifier

“…The ROM description via RNM allows for detailed finite-rate chemical kinetics but with simplified flow representation in the gasification process. A number of ROM studies for coal gasification process have been reported [11][12][13][14][15][16][17][18][19][20][21][22]. For example, Monaghan et al have developed ROMs with multiple reactors to study entrained flow gasifiers, in which the reactors are constructed based on the zero axial velocity boundaries from CFD simulations [11,12].…”