Effect of Fe_(2)O_(3) on the Formation of Micro Glass Beads under Air Staged Combustion

The effect of Fe_(2)O_(3) on the formation of micro glass beads(MGBs)under air staged combustion was studied.The experimental temperature was 1450℃,and Hegang bituminous coal was used as the experimental object.X⁃ray diffractometer(XRD),ash fusion tester,viscosity formula and scanning electron microscopy(SEM)were used to analyze the fly ash.Nano Measurer 1.2 software was used to measure the diameter of MGBs.The results showed that with the increase of Fe_(2)O_(3) in Hegang coal,the glass phase in fly ash first increased and then decreased.When the amount of Fe_(2)O_(3) was 15%,the content of the glass phase was the highest,which was 51.26%.The ash melting point first decreased and then increased,while the viscosity gradually decreased and the particles gradually became spherical.With the increase of Fe_(2)O_(3),the proportion of MGBs with particle size less than 10μm increased gradually.From the above results,it can be concluded that the addition of Fe_(2)O_(3) is conducive to the formation of MGBs and the reduction of particle size.

Experimental research on inorganic solidified foam for sealing air leakage in coal mines

In order to efficiently seal air leakages and control spontaneous combustion of coal, solidified foam was developed by adding a certain compound additive to fly coal ash and cement as the main materials. It was prepared basing on the foaming characteristic through physical and mechanical system. We studied the effects of the different types of foaming agents, the mass ratio of cement to fly ash, and the mass ratio of solid to water and content of cellulose on the performance of solidified foam. The results show that when adding the composite protein, surfactant and cellulose foaming agents. The cement-fly ash ratio of 0.75:1, the water solid ratio as large as 2:1, and the solidified foam with high properties and density of only 516 kg/m 3 and compressive strength of up to 12.68 MPa were prepared. But the initial setting time, identity and compressive strength may be changed by varying the water solid ratio and/or the additives. We theoretically analyzed the influence mechanism of foam density, compressive strength and water solid ratio. The solidified foam is especially suitable for sealing surface leakage channels and filling the goaf with a wide application prospects.

Numerical Simulation of Combustion Characteristics in High Temperature Air Combustion Furnace

The influences of air preheating temperature, oxygen concentration, and fuel inlet temperature on flame properties, and NOx formation and emission in the furnace were studied with numerical simulation. The turbulence behavior was modeled using the standard k-ε model with wall function, and radiation was handled using discrete ordinate radiation model. The PDF （probability density function） /mixture fraction combustion model was used to simulate the propane combustion. Additionally, computations of NOx formation rates and NOx concentration were carried out using a post-processor on the basis of previously calculated velocities, turbulence, temperature, and chemical composition fields. The results showed that high temperature air combustion （HiTAC） is spread over a much larger volume than traditional combustion, flame volume increases with a reduction of oxygen concentration, and this trend is clearer if oxygen concentration in the preheated air is below 10%. The temperature profile becomes more uniform when oxygen concentration in preheated air decreases, especially at low oxygen levels. Increase in fuel inlet tempera- ture lessens the mixing of the fuel and air in primary combustion zone, creates more uniform distribution of reactants inside the flame, decreases the maximum temperature in furnace, and reduces NOx emission greatly.

NO_(x) and H_(2)S formation in the reductive zone of air-staged combustion of pulverized blended coals

Low NO_(x) combustion of blended coals is widely used in coal-fired boilers in China to control NO_(x) emission;thus,it is necessary to understand the formation mechanism of NO_(x) and H2S during the combustion of blended coals.This paper focused on the investigation of reductive gases in the formation of NO_(x) and H2S in the reductive zone of blended coals during combustion.Experiments with Zhundong(ZD)and Commercial(GE)coal and their blends with different mixing ratios were conducted in a drop tube furnace at 1200℃–1400℃with an excessive air ratio of 0.6–1.2.The coal conversion and formation characteristics of CO,H_(2)S,and NO_(x) in the fuelrich zone were carefully studied under different experimental conditions for different blend ratios.Blending ZD into GE was found to increase not only the coal conversion but also the concentrations of CO and H2S as NO reduction accelerated.Both the CO and H2S concentrations inblended coal combustion increase with an increase in the combustion temperature and a decrease in the excessive air ratio.Based on accumulated experimental data,one interesting finding was that NO and H2S from blended coal combustion were almost directly dependent on the CO concentration,and the CO concentration of the blended coal combustion depended on the single char gasification conversion.Thus,CO,NO_(x),and H2S formation characteristics from blended coal combustion can be well predicted by single char gasification kinetics.

Fluidized bed combustion of high water content alcohol extracted herb residue and the impacts of blending wasted activated coke

Combustion of herb residues(HRs)for heat recovery is a good way for their utilization,but there exists such a problem as high concentration NOx emission in flue gas.The alcohol extracted herb residue(AEHR),one special type of HRs,was chosen as the object and was subjected to immediate combustion in a fluidized bed reactor to investigate the characteristics of its resulting NOx emission.The results showed that,most of the NOx in the flue gas was produced from the char nitrogen(C-N);as the fuel water content increased,the NOx emission concentration exhibited a trend of first decreasing and then increasing;and a properly low combustion temperature inhibited the NOx emission upon the premise of ensuring full combustion.Air staging combustion was adopted to effectively control NOx:the NOx emission concentration in the flue gas was reduced to 296 mg⋅m􀀀3 and the NOx emission reduction rate reached 46.51%compared to conventional combustion.Co-combustion by blending wasted activated coke(WAC)into the AEHR helped both stabilize the combustion state and reduce further the NOx emission.When the blending ratio of WAC fell within a proper range of 20-30%,the NOx emission concentration in the flue gas was as low as 231.4 mg⋅m􀀀3.In addition to the dilution effect of the combustion flue gas of the blended WAC,the local reducing atmosphere caused by its incomplete combustion as well as its strong absorbability and catalytical effect was accountable for the further decrease of the NOx emission concentration.

Dome Combustion Hot Blast Stove for Huge Blast Furnace

In Shougang Jingtang 5 500m 3 huge blast furnace ( BF ) design , dome combustion hot blast stove ( DCHBS ) technology is developed.DCHBS process is optimized and integrated , and reasonable hot blast stove ( HBS ) technical parameters are determined.Mathematic model is established and adopted by computational fluid dynamics ( CFD ) .The transmission theory is studied for hot blast stove combustion and gas flow , and distribution results of HBS velocity field , CO density field and temperature field are achieved.Physical test model and hot trail unit are established , and the numeral calculation result is verified through test and investigation.3-D simulation design is adopted.HBS process flow and process layout are optimized and designed.Combustion air two-stage high temperature preheating technology is designed and developed.Two sets of small size DCHBSs are adopted to preheat the combustion air to 520-600℃.With the precondition of BF gas combustion , the hot blast stove dome temperature can exceed 1 420 ℃. According to DCHBS technical features , reasonable refractory structure is designed.Effective technical measures are adopted to prevent hot blast stove shell intercrystalline stress corrosion.Hot blast stove hot pipe and lining system are optimized and designed.After blowing in , the blast temperature keeps increasing , and the monthly average blast temperature reaches 1 300℃ when burning single BF gas.