Influence of different cover ratios on Gas-particle flow characteristics of a centrally-fuel-rich primary air burner: experiment and simulation

AbstractThe flow field for different cover ratios within a three-level conical ring concentrator of a centrally-fuel-rich swirl coal combustion burner has been studied both experimentally and numerically. A particle dynamics anemometer measurement system was employed in the study to measure velocity and particle volume flux after the outlet of third-level ring. And the numerical simulations were used to calculate the flow field in the conical ring region. In each cross-section, after the outlet of third-level ring, concentration ratio for each cover ratio is always larger than 2. With conical ring concentrator in the primary air tube, the coal concentration can be concentrated to a suitable range. In the cross-sections 0.5<x/D<4.0, as cover ratio increases, concentration ratio decreases and resistance coefficient increases

Particle sticking behavior near the throat of a low-NOx axial-swirl coal burner

The results of numerical simulations of particle sticking behavior near the throat of a low-NOx axial-swirl burner in a 600-MWe bituminous coal burned boiler are presented. A comparison of simulation results with measurements using a probe with hot-film sensors shows that the numerical model offers a reasonable description. Calculated results of slagging show that slag build-up is substantial near the throat of the designed burner and that the sticking-particle ratio is as much as 33.2%. Because central and primary air streams remain unchanged, the mass flux of the inner secondary air is 3.25 kg s-1 while that of the outer secondary air is 12.16 kg s-1; however, the sticking-particle ratio can still be lowered to as little as 9.6%. By adjusting the outer secondary air blade angle to 15°, the sticking-particle ratio can be further lowered to 8.73%.Swirl burner Numerical simulation Particle sticking behavior

Genome-Wide Identification of Differentially Expressed Genes Associated with the High Yielding of Oleoresin in Secondary Xylem of Masson Pine (Pinus massoniana Lamb) by Transcriptomic Analysis.

Masson pine is an important timber and resource for oleoresin in South China. Increasing yield of oleoresin in stems can raise economic benefits and enhance the resistance to bark beetles. However, the genetic mechanisms for regulating the yield of oleoresin were still unknown. Here, high-throughput sequencing technology was used to investigate the transcriptome and compare the gene expression profiles of high and low oleoresin-yielding genotypes. A total of 40,690,540 reads were obtained and assembled into 137,499 transcripts from the secondary xylem tissues. We identified 84,842 candidate unigenes based on sequence annotation using various databases and 96 unigenes were candidates for terpenoid backbone biosynthesis in pine. By comparing the expression profiles of high and low oleoresin-yielding genotypes, 649 differentially expressed genes (DEGs) were identified. GO enrichment analysis of DEGs revealed that multiple pathways were related to high yield of oleoresin. Nine candidate genes were validated by QPCR analysis. Among them, the candidate genes encoding geranylgeranyl diphosphate synthase (GGPS) and (-)-alpha/beta-pinene synthase were up-regulated in the high oleoresin-yielding genotype, while tricyclene synthase revealed lower expression level, which was in good agreement with the GC/MS result. In addition, DEG encoding ABC transporters, pathogenesis-related proteins (PR5 and PR9), phosphomethylpyrimidine synthase, non-specific lipid-transfer protein-like protein and ethylene responsive transcription factors (ERFs) were also confirmed to be critical for the biosynthesis of oleoresin. The next-generation sequencing strategy used in this study has proven to be a powerful means for analyzing transcriptome variation related to the yield of oleoresin in masson pine. The candidate genes encoding GGPS, (-)-alpha/beta-pinene, tricyclene synthase, ABC transporters, non-specific lipid-transfer protein-like protein, phosphomethylpyrimidine synthase, ERFs and pathogen responses may play important roles in regulating the yield of oleoresin. These DEGs are worthy of special attention in future studies

Quantitative RT-PCR validation of tag-mapped candidate genes associated with the yield of oleoresin.

<p>Relative expression levels of qRT-PCR calculated using Elongation factor 1-alpha as the internal control were shown in the right y-axis. Relative expression levels of DGE were shown in the left y-axis.</p

Biosynthetic pathway of terpenoids in <i>P</i>. <i>massoniana</i> (adapted from Zulak et al [22]).

<p>The number of unigenes homologous to gene families encoding these enzymes was provided in parentheses. The enzymes highlighted with red fonts showed that DEGs were detected in gene families encoding these enzymes. DXS: 1-deoxy-dxylulose-5-phosphate synthase; DXR: 1-deoxy-D-xylulose-5-phosphate reductoisomerase; MCT: 4-diphosphocytidyl-2Cmethyl-D-erythritol synthase; CMK: 4-diphosphocytidyl-2C–methyl-D-erythritol kinase; MECPS: 2C-methyl-D-erythritol 4-phosphate cytidylyltransferase; HDS: 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate synthase; HDR: 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase; AACT: acetoacetyl-CoA thiolase; HMGS: 3-hydroxy-3-methylglutaryl-CoA synthase; HMGR: 3-hydroxy-3-methylglutaryl-CoA reductase; MVK: mevalonate kinase; PMVK: phosphomevalonate kinase; MVD: mevalonate diphosphate decarboxylase; IPPI: isopentenyl-diphosphate isomerase; FPPS: farnesyl diphosphate synthase; GPPS: geranyl diphosphate synthase; SesquiTPS: Sesquiterpene synthase; MonoTPS: Monoterpene synthase; DiTPS: Diterpene synthase; CYP720B: Abietadienol/abietadienal oxidase PtAO.</p

Clustering and heatmap of key DEG related to the yield of oleoresin based on their expression levels.

<p>Three biological replicates were used for high-yielding genotype (H1, H2, H3) and low-yielding genotype (L1, L2, L3). Colored bars on the left of the heatmap mark the major distinct branches in the clustering tree grouping genes with similar expression pattern.</p

The average content and SD of oleoresin compounds and significant difference between 35 high and 35 low oleoresin-yielding masson pines using non-parametric Mann-Whitney test.

<p>* and ** show the significant difference at p value less than 0.05 and 0.01, respectively.</p><p>The average content and SD of oleoresin compounds and significant difference between 35 high and 35 low oleoresin-yielding masson pines using non-parametric Mann-Whitney test.</p