Viscous sintering of coal ashes. 1. Relationships of sinter point and sinter strength to particle size and composition

Abstract

residence time on CH4 and C2H4 yields indicates that the cracking reactions of the volatiles (which generate more hydrocarbon gases) begin at an earlier stage during pyrolysis as pressure increases from 100 to 309 psig, consistent with both the weight loss and the tar yield decreasing more rapidly during the early stage of pyrolysis at 309 psig than at 100 psig.The apparent first-order rate constants for devolatilization were dependent on the extent of devolatilization and on the applied pressure. The devolatilization rate decreased significantly with increasing pressure. At each pressure, rate constants decreased as pyrolysis proceeded to greater extents of devolatilization. The first-order rate constants for swelling were similarly dependent on extent of swelling and applied pressure. Swelling rates reached a maximum at 100 psig and decreased as pressure was increased further. At each applied pressure, swelling rate constants decreased as swelling proceeded. The different effects of pressure on devolatilization rate and swelling rate provide evidence that two different mass-transfer mechanisms are operative, depending on applied pressure. At 100 psig or higher, the reduction in both devolatilization and swelling rates suggests that bubble transport was the main mass-transfer mechanism. At atmospheric pressure the devolatilization rate is higher but the swelling rate is lower than those observed at elevated pressures, indicating that a diffusional mechanism is predominant.Richard Hogg for assistance in using the optical image analysis system. Mohammad Fatemi developed the computer models of particle residence time and temperature used in this study, and Carl Martin and Ronald Wincek assisted in maintaining the high-pressure entrained-flow reactor system.

Application of the Mechanical and Pressure Drop Tests to Determine the Sintering Temperature of Coal and Biomass Ash

“…The interesting results of the ash deposits on tube strength in the convection section of pulverized coal-fired boilers were presented [22]. Based on the tested compressive strengths of sintered ash at three temperatures (750 °C, 850 °C, and 950 °C), it was found that the compressive strength was higher for higher temperatures and lower for larger ash particles.…”

“…That is originally applied in metallurgy [10]. The other interesting methods are thermal conductivity analysis [21], compressing strength analysis [22][23][24], electrical resistivity measurements [23], thermogravimetric analysis (TGA) [18,25], thermodynamic FactSage analysis [18], optical heating stage microscopy (OSHM) [26], pressure drop test [9,10,27,28], and other techniques presented in detail [29].…”

Thermal treatment of the fly ash from municipal solid waste incinerator with rotary kiln

“…The physical and chemical characteristics of the feeding materials, including components of ash, particle size and additives, etc., also affect the qualities of the sintering products [18,19]. There are some minor compounds like alkali metal, alkaline-earth metal, chloride and sulfate existed in fly ash, the partitions of different compounds influence the temperature of the sintering operation and the quality of products [20][21][22].…”

Ash Sintering Behavior of Lignite in Catalyzed Steam Gasification with Kaolin as Additive

“…It has been reported that K‐bearing aluminosilicate could react with other minerals to form the low temperature eutectics, which facilitated the formation of liquid phases. Those liquid phase could potentially act as a glue that bonded the ash particles together in a mechanism called the viscous flow sintering 10…”

“…Ash sintering is the bonding or welding of adjacent ash particles due to excess surface tension. It is triggered by the formation of viscous liquid phases on the ash particles′s surface 10. 11 The viscous liquid phases further lead to rearrangement and agglomeration of ash particles 12.…”