57 research outputs found
Synergistic effect on co-pyrolysis of capsicum stalks and coal
With the depletion of fossil fuel and the concern about environmental issues, the utilization of biomassĀ resources has attracted increasing worldwide interest. The pyrolysis behavior of capsicum stalks andĀ Baoji coal mixtures was investigated by TG-DSC. Results show that the thermal degradationĀ temperature range of capsicum stalks was 290 to 387Ā°C, while that of Baoji coal was 416 to 586Ā°C.Ā According to the comparison of experimental values and calculation results based on the algebraicĀ sum of the fraction of individual mixture samples, the synergistic effect was significant at temperatureĀ ranges of 314 to 369 and 431 to 578Ā°C. The synergistic effect could also be seen from the kinetic studiesĀ performed according to the Fried man Method. The rate of mass loss and k in the experiment is higherĀ than the calculated values in the range of 314 to 368Ā°C and that in the experiment is lower than theĀ calculated values in the range of 431 to 578Ā°C. Meanwhile, it was indicated that the pyrolysis process ofĀ capsicum stalks, Baoji coal and their mixtures could be described by one, two and four first orderĀ reactions, respectively.Keywords: Pyrolysis, capsicum stalks, mixing rate, kinetics, synergistic effec
Synergetic effect of sewage sludge and biomass co-pyrolysis: a combined study in thermogravimetric analyzer and a fixed bed reactor
The ash deposition mechanism in boilers burning Zhundong coal with high contents of sodium and calcium: A study from ash evaporating to condensing
Experimental study on preheating combustion characteristics and NOx emission of pulverized coal based on an entrained-flow gasifier
Pulverized coal preheating combustion technology has been proven to be a clean and efficient combustion technology. In view of the limited space and load-bearing capacity around the large coal-fired boiler, a novel technology and system with a compact entrained-flow gasifier to preheat pulverized coal is proposed for the first time. The preheating characteristics in the gasifier and the combustion characteristics of the preheated fuel in the down-fire combustor (DFC) are studied on the novel self-built preheating combustion test rig. The migration and transformation of coal nitrogen during the preheating combustion are investigated. The results show that the experiment system can operate continuously and steadily with small fluctuations in pressure and temperature. The temperature gradient in the gasifier is large, and the high temperature zone is located near the burner plane. The maximum temperature can reach 1 115 ā, while the outlet temperature of the gasifier decreases to 850 ā. The high temperature coal gas and char produced by the entrained-flow gasifier are provided to the DFC continuously and steadily. The volume fractions (dry basis) of CO, H2 and CH4 in high temperature coal gas are 13.15%, 8.72% and 0.78%, respectively. Compared to the raw coal, the size of the preheated char decreases. The 50% cut particle size of raw coal is 43 Ī¼m, while the preheated semi-coke is 24 Ī¼m. The specific surface area increases from 4.05 m2/g to 216.44 m2/g after preheating. At the same time, the pore volume of the char particles increases, and the combustion characteristics are improved. During the preheating process, 96.33% of volatile matter and 40.23% of fixed carbon are released into high temperature coal gas. Also, 69.74% of coal nitrogen is transformed in the gas phase, and 47.67% is converted into N2, the rest into NH3 and HCN. Stable combustion could be achieved with preheated fuels in the DFC with no ignition delay and a uniform temperature distribution. Most of the NH3 and HCN and the nitrogen released from char are converted into N2 in the main combustion zone. There is no NO generation in the main combustion zone. The CO and NOx emissions at the outlet of the DFC are 8.17 mg/Nm3 (6% O2) and 143.02 mg/Nm3 (6% O2), respectively. The combustion efficiency is 99.75%. After the pulverized coal is preheated by the new entrained-flow gasifier and burn in the DFC, only 4.69% of coal N is converted into NO
Coupling of cleaner production with a day-ahead electricity market : a hypothetical case study
Short Review on the Origin and Countermeasure of Biomass Slagging in Grate Furnace
Given the increasing demand for energy consumption, biomass has been more and more important as a new type of clean renewable energy source. Biomass direct firing is the most mature and promising utilization method to date, while it allows a timely solution to slagging problems. Alkali metal elements in the biomass fuel and the ash fusion behavior, as the two major origins contributing to slagging during biomass combustion, are analyzed in this paper. The slag presents various layered structures affected by the different compositions of ash particles. Besides, the high-temperature molten material which provides a supporting effect on the skeletal structure in biomass ash was proposed to evaluate the ash fusion characteristics. In addition, numerous solutions to biomass slagging, such as additives, fuel pretreatment and biomass co-firing, were also discussed
Water Wall Tubesā High Temperature Corrosion Root Cause Investigation: A 300 MW Level Boiler Case
High temperature corrosion poses a great threat to boiler water wall safe operation. To investigate the corrosion root cause, a 300 MW level boiler water wall high temperature H2S corrosion case was reported. The typical hydrogen sulfide H2S corrosion feature was large amounts of sulfur which could be found in the cut down sample tube corrosion layer, with a thickness of 482 Ī¼m. In addition, huge amounts of lead (Pb) could be found in the corrosion layer, which resulted from the lead sulfide (PbS) deposition when the high temperature flue gas condensed at the water wall tubes. Meanwhile, the sulfur in the corrosion layer was closely related to the H2S concentration in the water wall ambience. The related ambience test showed that the H2S could achieve up to 1000 ppm when the boiler was in operation, far larger than the suggested reference value of 100 ppm. Hence, the overlarge H2S concentration was a vital factor for the tube corrosion. To further investigate the reason why the H2S was kept in such high concentration in the boiler long term operation, and the reasons for the over-high sulfur content in the coal and the over-large diameter of the imaginary circle of primary air (DICPA), two factors were obtained. The peak sulfur content reached 2.5% and the suggested sulfur content was below 1%. The DICPA was so large (1580 mm) that the pulverized coal easily scoured the water wall tubes, which would boost the thinning process of the tubes. To relieve the high temperature corrosion, improve the coal qualities, decrease the DICPA, adjust the operation diameter and adopt a coating technology four measures were suggested
Water Wall Tubes’ High Temperature Corrosion Root Cause Investigation: A 300 MW Level Boiler Case
High temperature corrosion poses a great threat to boiler water wall safe operation. To investigate the corrosion root cause, a 300 MW level boiler water wall high temperature H2S corrosion case was reported. The typical hydrogen sulfide H2S corrosion feature was large amounts of sulfur which could be found in the cut down sample tube corrosion layer, with a thickness of 482 μm. In addition, huge amounts of lead (Pb) could be found in the corrosion layer, which resulted from the lead sulfide (PbS) deposition when the high temperature flue gas condensed at the water wall tubes. Meanwhile, the sulfur in the corrosion layer was closely related to the H2S concentration in the water wall ambience. The related ambience test showed that the H2S could achieve up to 1000 ppm when the boiler was in operation, far larger than the suggested reference value of 100 ppm. Hence, the overlarge H2S concentration was a vital factor for the tube corrosion. To further investigate the reason why the H2S was kept in such high concentration in the boiler long term operation, and the reasons for the over-high sulfur content in the coal and the over-large diameter of the imaginary circle of primary air (DICPA), two factors were obtained. The peak sulfur content reached 2.5% and the suggested sulfur content was below 1%. The DICPA was so large (1580 mm) that the pulverized coal easily scoured the water wall tubes, which would boost the thinning process of the tubes. To relieve the high temperature corrosion, improve the coal qualities, decrease the DICPA, adjust the operation diameter and adopt a coating technology four measures were suggested
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