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We intensively investigated the kinetic enhancement of dielectric-barrier-discharge (DBD) plasma on the pyrolysis and ignition of n-heptane, iso-octane, and n-decane fuels in a counterflow diffusion burner. The DBD plasma generated upstream from the fuel nozzle can contribute to low-temperature pyrolysis and high-temperature oxidation of pre-vaporized liquid fuels. Stable and short-lived intermediate species generated by plasma were measured by e x situ gas chromatography (GC) and in situ planar laser induced fluorescence (PLIF), respectively. GC results indicate that with plasma assistance approximately 2–3% of large hydrocarbons decompose at temperatures as low as 370 K and within 1 s. High-temperature oxidation experiments demonstrate that DBD can lower the ignition temperature of all three fuels with various global flow stretch rates. Experiments were compared with numerical analysis performed using the OPPDIF code that is formulated for the counterflow geometry. Finally, the discrete chemical explosive mode analysis (CEMA) elucidates the promotion of plasma-induced species, such as H 2 , C 2 H 4 , and OH radicals. [ABSTRACT FROM AUTHOR]

With the increasing use of low-grade lignite for energy production, ash related problems have received renewed attention due to their detrimental effects on power plant equipment. This study investigates the fuel effect on the ash deposition in a 25 kW self-sustained down-fired furnace, with practical implications to the efficient utilization of a sodium-rich Zhundong (ZD) lignite. The active fouling control methods include co-firing with Si/Al-dominated HAF-2 bituminous coal and pretreatment using water leaching. Both manipulation methods reduce the propensity to form ultrafine PM 0.2 particles and ash deposition for simulated furnace exit conditions compared with combustion of only ZD lignite. While the deposits formed by HAF-2 bituminous are prone to shed, blending with ZD lignite increases the ash collection efficiency and prevents massive deposit collapse. The morphology of the ZD ash deposits is characterized by a smooth shape with wide spreading angle, whereas those formed by the blended samples with ≥33 wt% bituminous coal have sharp and pointed shapes with smaller spreading angles. Deposits by samples with ≥67 wt% ZD lignite have an inner layer of micro-size particles. The local basic to acid ratio of the deposits gradually decreases from the inner to the outer layers. The apparent particle sticking probability due to the fuel effect derived from the experimental and theoretical results positively correlates with the yield of ultrafine PM 0.2 particles for the various coal samples. [ABSTRACT FROM AUTHOR]

The migration of K and Cl during biomass thermal utilization can cause serious ash-related problems. Pyrolysis experiments with KCl-loaded cellulose were conducted in a fixed-bed reactor to investigate the reaction of KCl with organic functional groups. The migration pathways of K and Cl were obtained based on the analysis of char samples after pyrolysis. Results showed that the amounts of generated K 2 CO 3 were negligible after pyrolysis at both temperature levels. After pyrolysis at 500 °C, char-Cl and char-K were generated, and the unreacted KCl existed in char as crystal particles. The released Cl amount increased first and then remained stable, whereas the Cl release ratio decreased monotonously with KCl content. Meanwhile, a small fraction of organic K was released. At 900 °C, almost all of the Cl (including KCl and char-Cl) was released, whereas a significant amount of char-K remained in char. Similar to the trend of O content, the amount of char-K increased first and then reached near-saturation with the increase in KCl content, indicating that char-K is associated with the char matrix via O. At 500 °C, during pyrolysis of cellulose with low KCl content, the formation of char-K and the release of Cl are the dominant migration pathways of K and Cl, respectively. With the increase in KCl content, unreacted KCl became the main existing form of K and Cl. The amounts of formed char-K and released Cl, as well as the formation ratio of char-Cl increased first and then reached saturation gradually. [ABSTRACT FROM AUTHOR]

CaO affects urea pyrolysis when coalescing with melting urea, which decreased the performance of urea-SNCR deNO x process. The influence of CaO on urea pyrolysis was studied with a thermogravimetric analyzer, a fixed bed reactor, and DRIFTS. The mechanism of CaO was also analyzed. Experimental results showed that CaO decreased the pyrolysis rate of urea, especially in the presence of O 2 . NH 3 production in urea pyrolysis was not influenced by CaO, whereas HNCO in the gaseous products disappeared and CO 2 production was increased remarkably. NO, N 2 O, and CO were also produced in the presence of O 2 . DRIFTS experiments showed that Ca(NCO) 2 and CaCN 2 were produced and the composition of the solid products varied with the atmosphere. Mechanism analysis showed that CaO initially reacted with melting urea and biuret to produce Ca(NCO) 2 and release NH 3 and H 2 O. Ca(NCO) 2 decomposed to CaCN 2 and CO 2 with increasing temperature, and CaCN 2 can exist stably in the absence of O 2 because of its high thermostability. In the presence of O 2 , Ca(NCO) 2 can be oxidized to N 2 O, CO 2 , and N 2 , whereas CaCN 2 can be oxidized to NO, CO, and N 2 . [ABSTRACT FROM AUTHOR]

This study examines how byproducts from thermal decomposition of sulfur fluoride (SF6) can be measured and applied to diagnose an overheating fault occurring in SF6 insulated equipment. Using a series of experiments performed on a SF6 thermal fault simulation system, the thermal decomposition characteristics of SF6 were obtained for temperatures below 400°C. Based on these results, the formation rate was extracted to indicate the progress of the thermal fault's development, and the characteristic component ratio was used to identify the type and severity of the thermal fault. The relationship of the fault temperature and the formation rate along with the correlation between the characteristic ratio and the fault temperature were studied. The results show that: the formation rate of the components effectively reflects the severity and development trend of the thermal fault; by integrating the IEC standard 60480‐2004, the obtained thermal fault maximum safe time (TMS) can accurately indicate the largest safe time when thermal fault happens; component characteristic ratios C(SO2)/C(SO2F2) and C(SO2F2+SOF4)/C(SOF2) can be used to evaluate whether the fault type is a thermal fault; and the thermal correlation ratio (TR) can be employed to recognize the temperature value from 300°C to 400°C. [ABSTRACT FROM AUTHOR]

Fast pyrolysis is one of the most economical and efficient technologies to convert biomass to bio-oil and valuable chemical products. Co-pyrolysis with hydrogen rich materials such as plastics over zeolite catalysts is one of the significant solutions to various problems of bio-oil such as high oxygen content, low heat value and high acid content. This paper studied pyrolysis of cellulose and polypropylene (PP) separately and co-pyrolysis of cellulose and PP over MCM-41 and Al-MCM-41. The pyrolysis over different heating rates (10 K/min, 20 K/min, 30 K/min) was studied by Thermogravimetry Analysis (TGA) and kinetic parameters were obtained by Coats-Redfern method and isoconversion method. TG and DTG data shows that the two catalysts advance the pyrolysis reaction of PP significantly and reduce its peak temperature of DTG curve from 458 °C to 341 °C. The activation energy of pyrolysis of PP also has a remarkable reduction over the two catalysts. Py-GC/MS method was used to obtain the product distribution of pyrolysis of cellulose and PP separately and co-pyrolysis of cellulose and PP over MCM-41 and Al-MCM-41 at constant temperature of 650 °C. Experiment results proved that co-pyrolysis with PP bring significant changes to the product distribution of cellulose. Oxygenated compounds such as furans are decreased, while yields of olefins and aromatics increase greatly. The yield of furans increases with the catalysis of MCM-41 as for the pyrolysis of cellulose and co-pyrolysis, while the yield of olefins and aromatics both experience significant growth over Al-MCM-41, which can be explained by the abundant acid centers in Al-MCM-41. [ABSTRACT FROM AUTHOR]

Pyrolysis and oxidation of heavy oil is the fundamental of in situ combustion process. Heavy oil from Xinjiang, China and its main components, saturates, aromatics and resins (SAR), were used as samples to study their pyrolysis and oxidation characteristics with a thermogravimetric analyzer (TGA) and a fixed-bed reactor. The DTG curves and the detected gas products differed between pyrolysis and oxidation of the heavy oil. Elemental analysis of pyrolysis and oxidation cokes indicates that low temperature oxidation (LTO) primarily accounted for the differences. Compared with independent pyrolysis and oxidation of saturates, aromatics and resins, they showed little interactions during co-pyrolysis, but significant interactions during co-oxidation. When saturates co-oxidized with aromatics or resins, both the beginning temperatures of LTO were increased, the DTG curve at high temperature oxidation (HTO) remained unchanged during co-oxidation with aromatics, while the DTG peaks at HTO changed from two into one during co-oxidation with resins. Co-oxidation of aromatics and resins showed similar effect at HTO. Oxygen-adding reactions of saturates, aromatics, and resins at low temperature promoted the polycondensation between intermediate products and altered the subsequent cracking reactions, which caused special characteristics during their co-oxidation. [ABSTRACT FROM AUTHOR]

With the increasing use of low-rank coal, the upgraded semi-char produced through low-temperature pyrolysis of lignite is one of promising alternatives towards the clean and high efficient utilization. The co-firing of these pyrolytic semi-chars with parent coals has received more attention. In this paper, a kind of semi-char, produced from Hulunbuir (HB) lignite under a pyrolysis temperature of 504 °C, was burned in a 25 kW self-sustained pulverized coal combustor. Different mass blending ratios of semi-char (0%, 40%, 60% and 100%) were used. The results indicate that the PM 0.1 yield from pure combustion of HB lignite is ∼1.6 times of that from semi-char. The PM 0.1 yields of the coal/char blends are much less than the linear summation of yields of two blending fuels without considering their interactions. As for coarser PM mode, the reductions still exist for both PM 0.1–1 and PM 1–10 particles. The different PM yields of pure combustion cases are attributed to less volatile mineral species and also less fragmentation degree of semi-chars during combustion. A mechanism is postulated for PM reduction during the combustion of coal blends. PM 0.1 amounts are decreased since the volatilized mineral species is considerably scavenged by the previously formed semi-char surfaces, as partly evidenced from a time scale analysis. The scavenged compounds then serve as “glue” to convert ash particles to larger agglomerates, which may result in the reduction of PM 0.1–10 yields. [ABSTRACT FROM AUTHOR]

The interactions between high density polyethylene (HDPE) and potato during their primary and secondary co-pyrolysis process were investigated by a thermogravimetric analyzer (TGA) and a tubular furnace. Kinetic analysis has shown that the devolatilization of potato was relatively faster compared to those of cellulosic materials, which has been ascribed to the multi-side-chain structure and lower polymerization degree of starch. The pyrolysis process of potato can be divided into three stages, and the main thermal degradation took place between 178 and 378 °C, while the HDPE decomposition occurred in a single stage in the temperature range of 380–517 °C. In the case of blends, the weight loss differences (Δ W ) between experimental and theoretical ones were less than ±8% in all cases, and the co-pyrolysis process of potato and HDPE can be described as two consecutive first order reactions, the apparent activation energies of blends were almost invariable, suggested that only physical step limitation was found in the primary co-pyrolysis process of potato and HDPE. On the contrary, the results of tubular furnace experiment showed that due to the relatively long gas resident time, the interaction occurred in the gas phase not only favored the formation of gaseous products, but also improved the bio-oil quality by significantly reducing the oxygen-to-carbon ratios (O/C) of the pyrolysis oil. [ABSTRACT FROM AUTHOR]

The interaction between flue gas and ash causes the redistribution of heavy metals and affect their emission characteristics. In this study, a double-layer fixed-bed reactor was used to investigate the effect of this interaction on Pb distribution at 800–1000 °C. Obvious gaseous Pb adsorption by ash just occurred in the case of high-Pb flue gas and less ash melting. In other cases, significant Pb release from ash occurred under the action of the high-temperature flue gas. The occurrences of Pb in ash was found to be thermally stable. Ash melting is the main reason for the Pb release. Gaseous Na in the combustion flue gas and reducing components in the pyrolysis flue gas promote the Pb release via promoting the ash melting. H 2 S and HCl in the pyrolysis flue gas also promote the Pb release by forming PbS and PbCl 2 , which are more volatile. [Display omitted] • The interaction between high-temperature flue gas and ash redistributes Pb. • Ash melting causes the significant release of Pb from ash at high temperatures. • Gaseous Na and reducing components in flue gas promote ash melting and Pb release. • H 2 S/HCl in flue gas also promotes Pb release by forming volatile PbS/PbCl 2. [ABSTRACT FROM AUTHOR]

Highlights: [•] High moisture content was conducive to the production of hydrogen rich fuel gas. [•] The steam involved in gasification and reforming reactions has a saturation value. [•] The toxic effect of tar decreased with the increase of moisture content. [•] The ejection of volatile matter was intensified by high moisture content. [Copyright &y& Elsevier]