•A numerical method was successfully applied to the heat transfer analysis of anti-wear beams.•The anti-wear beams would reduce heat transfer area and coefficient on the wall.•The sub solid flow formed between two beams was protected from the central axial flow.•The heat transfer at the middle of wall is stable when the operation parameters change.To install multi-stage anti-wear beams on waterwall is an effective method to protect against the erosion in a CFB boiler. However, it changes the gas–solid flow and heat transfer on the waterwall. For a clear understanding, this paper used a numerical method to analyze the effect of anti-wear beams on the wall heat transfer in a 330 MW CFB boiler. The gas–solid hydrodynamics in furnace was simulated based on the TFM and EMMS drag model, and the heat transfer characteristic was obtained by cluster renewal model. The results showed that the anti-wear beams would make the descending solid flow to be multi-staged with lower speed on waterwall. Not only the heat transfer area but also the heat transfer coefficient was decreased. Thus, the furnace heat absorption was reduced by about 5.5%, and the average temperature would rise by up to 30 °C after installing the beams. Moreover, the operation parameters have an effect on the wall heat transfer at the upper furnace, while minor effect on the middle and lower part. It can be explained by the protection of two adjacent anti-wear beams, which provide a relatively stable circumstance for solid descending flow and heat transfer.

To promote the effective utilization of different varieties of low-calorific gas mixtures in a porous media burner, combustion behaviors of three typical low-calorific gas mixtures in a two-layer porous burner are simulated with a two-energy and one-dimensional transient model. The equivalence ratio and inlet velocity are kept constant. A baseline simulation for the three mixtures is presented, and partial results are compared against the experimental measurement of axial temperatures and emission levels. A parametric study is conducted on the conductivity and convective coefficient of up- and downstream sections. The study shows that the upstream convective coefficient has more influence on temperature behaviors than that in the downstream. The solid conductivity effect on temperature behaviors is closely associated with the reaction zone location relative to the interface. CO emission behavior is found to be fairly sensitive to the change in upstream material properties. The results suggest that, for clean combustion of low-calorific gases in a two-layer burner, thermal conductivity of the upstream section should not be too large.

•An anti-wear mechanism of an anti-wear beam on the water wall was proposed for the first time.•Upward moving solids were observed and simulated in a certain area below an anti-wear beam.•An optimum beam width was suggested in the test rig for the least wear rate.Anti-wear beams installed on water walls of circulating fluidized bed (CFB) boilers are one of the most effective ways to protect against water-wall erosion. Beam effects from, for example, beam size and superficial gas velocity were investigated on gas–solid hydrodynamics in a CFB test rig using CFD simulations and experimental methods. The downward flow of the wall layer solids is observed to be disrupted by the beam but is then restored some distance further downstream. When falling solids from the wall layer hit the anti-wear beam, the velocity of the falling solids decreases rapidly. A fraction of the solids accumulates on the beam. Below the beams, the falling solids have reduced velocities but upward-moving solids were observed on the wall. The effect of the beam increases with width and superficial gas velocity. Wear occurs mainly above the beam and its variation with width is different above to below the beam. There is an optimum width that, when combined with beam height, results in less erosion.

The inclined flame front break in the filtration gas combustion of a lean methane (CH4)/air mixture during propagation downstream in an inert porous medium was investigated using a two-temperature and two-dimensional numerical model. The development of flame inclination was studied by focusing on the flame front break, which splits into two or three waves. The essence of the flame front instability and inclined flame front break mechanisms was discussed. The physical parameters, such as flame structure, gas temperature distributions, and effects of system properties on flame characteristics, were studied in detail. The results show that the flame front break easily takes place in higher Lewis number mixtures, higher inlet velocity, lower equivalence ratio, and larger heat loss regimes. Higher inlet velocity and lower equivalence ratios result in higher flame instability in the combustion process.

In this study, a porous inserted regenerative thermal oxidizer (PRTO) system was developed for a 125 kW industrial copper-melting furnace, due to its advantages of low NOx emissions and high radiant efficiency. Zirconium dioxide (ZrO2) ceramic foams were placed into the combustion zone of a regenerative thermal oxidizer (RTO). Different performance characteristics of the RTO and PRTO systems, including pressure drop, temperature distribution, emissions, and energy efficiency, were evaluated to study the effects of the porous inserts on non-premixed CH4 combustion. It was found that the PRTO system achieved a significant reduction in the NOx emission level and a fuel saving of approximately 30% compared to the RTO system. It is most suitable for a lean combustion process at an equivalence ratio <0.4 with NOx and CO emission levels within 0.002%–0.003% and 0.001%–0.002%, respectively.

Partial oxidation of methane in a unidirectional flow porous reactor is studied numerically. A number of partial oxidation mechanisms affecting H2 and CO yields are comparatively analyzed using kinetic modeling for a range of rich and ultrarich equivalence ratios, residence times, and preset reactor temperatures. Temperature profiles, hydrogen yields, and methane conversion ratios are predicted for various equivalence ratios using two-temperature filtration combustion model with selected detailed chemical mechanism. The simulation results show that the hydrogen yield has two obvious sections: the ignition section and stream reforming section. The hydrogen yield increases with temperature and equivalence ratio increase. The two-temperature model results show a good qualitative agreement with the experimental results especially for the maximum solid temperature and hydrogen production. The wave starts to propagate downstream at φ > 1.5. The maximum solid temperature decreases from 1760 K to 1665 K as the equivalence ratio increases from 1.5 to 3.0. The H2 yield is higher and methane conversion ratio is lower for high equivalence ratios, the thermal efficiency increases with the equivalence ratio increase. The H2 conversion ratio and H2 energy efficiency reach their maximum values at φ = 2.25, while CO conversion ratio and syngas energy efficiency reach maximum values at φ = 2.0. The results obtained for a unidirectional flow reactor are important for model validation and predictive modeling of a reciprocal flow reactor.

In large-scale circulating fluidized bed (CFB) boilers, it is common to use multiple cyclones in parallel for the capture of solids, assuming that gas–solid flow to be the same in the cyclones. This article presents a study investigating gas–solid flow through six parallel cyclones in a CFB cold test rig. The six cyclones were located asymmetrically on the left and right walls of the riser. Solid volume fraction and particle velocity profiles at the riser outlets and in the horizontal ducts were measured using a fiber optical probe. Cyclone pressure drop and solid circulating rate were measured for each individual cyclone. Measurements showed good agreement as to the non-uniform distribution of the gas–solid flow, which occurred mainly across the three cyclones on one side: the middle cyclones on both sides had higher particle velocities. Conversely, the solid volume fractions, solid fluxes and solid circulating rates of the middle cyclones were lower than those of the other four cyclones. The apparent reason for the flow non-uniformity among the cyclones is the significant flow non-uniformity at the riser outlets. Under typical operating conditions, the solid volume fractions at the riser outlets had a deviation of up to 26% whereas the solid circulating rates at the stand pipes, 7%. These results are consistent with most other studies in the literature.Graphical abstractCyclone layout and gas–solid flow measurements at riser outlets.Highlights► Six cyclones were located on the left and right walls of the riser in a CFB cold test rig. ► Measurements showed that the middle cyclone on each side had higher particle velocity, but lower solid volume fraction and solid circulating rate than other two cyclones, due mainly to the non-uniform gas–solid flow at the riser outlets.

Heat transfer of a furnace in a large-scale circulating fluidized bed (CFB) boiler was studied based on the analysis of available heat transfer coefficient data from typical industrial CFB boilers and measured data from a 12 MWe, a 50 MWe and a 135 MWe CFB boiler. The heat transfer of heat exchanger surfaces in a furnace, in a steam/water cooled cyclone, in an external heat exchanger and in the backpass was also reviewed. Empirical correlation of heat transfer coefficient was suggested after calculating the two key parameters, solids suspension density and furnace temperature. The correlation approach agrees well with the data from the large-scale CFB boilers.