Characteristics of neonatal hypoxic-ischemic encephalopathy at high altitude and early results of therapeutic hypothermia.

BACKGROUND: Altitude hypoxia and limited socioeconomic conditions may result in distinctive features of neonatal hypoxic-ischemic encephalopathy (HIE). Therapeutic hypothermia (TH) has not been used at altitude. We examined characteristics of HIE and early outcomes of TH in 3 centers at two high altitudes, 2 at 2,261 m and 1 at 3,650 m. METHODS: The incidence of HIE at NICUs was noted. TH was conducted when personnel and devices were available in 2019~2020. Standard inclusion criteria were used, with the addition of admission age >6 hours and mild HIE. Demographic and clinical data included gestational age, gender, weight, Apgar score, ethnics, age on admission, age at TH and clinical degree of HIE. EEG was monitored for 96 hours during hypothermia and rewarming. MRI was performed before discharge. RESULTS: There was significant difference in ethnics, HIE degree, age at TH across 3 centers. The overall NICU incidence of HIE was 4.0%. Among 566 HIE patients, 114 (20.1%) received TH. 63 (55.3%) patients had moderate/severe HIE. Age at TH >6 hours occurred in 34 (29.8%) patients. EEG discharges showed seizures in 7~11% of patients, whereas spikes/sharp waves in 94~100%, delta brushes in 50~100%. After TH, MRI showed moderate to severe brain injury in 77% of patients, and correlated with center, demographic and clinical variables (Ps≤0.0003). Mortality was 5% during hospitalization and 11% after discharge until 1 year. CONCLUSIONS: At altitude, the incidence of HIE was high and brain injury was severe. TH was limited and often late >6 hours. EEG showed distinct patterns attributable to altitude hypoxia. TH was relatively safe. TRIAL REGISTRATION: The study was registered on February 23, 2019 in Chinese Clinical Trial Register (ChiCTR1900021481).

Genetic susceptibility to diabetic kidney disease is linked to promoter variants of XOR.

The lifetime risk of kidney disease in people with diabetes is 10-30%, implicating genetic predisposition in the cause of diabetic kidney disease (DKD). Here we identify an expression quantitative trait loci (QTLs) in the cis-acting regulatory region of the xanthine dehydrogenase, or xanthine oxidoreductase (Xor), a binding site for C/EBPß, to be associated with diabetes-induced podocyte loss in DKD in male mice. We examine mouse inbred strains that are susceptible (DBA/2J) and resistant (C57BL/6J) to DKD, as well as a panel of recombinant inbred BXD mice, to map QTLs. We also uncover promoter XOR orthologue variants in humans associated with high risk of DKD. We introduced the risk variant into the 5'-regulatory region of XOR in DKD-resistant mice, which resulted in increased Xor activity associated with podocyte depletion, albuminuria, oxidative stress and damage restricted to the glomerular endothelium, which increase further with type 1 diabetes, high-fat diet and ageing. Therefore, differential regulation of Xor contributes to phenotypic consequences with diabetes and ageing.

Cognitive Function Mainly Shaped by Socioeconomic Status Rather Than Chronic Hypoxia in Adolescents at High Altitude.

Yu, Linyang, Jinqing Feng, Chen Zhou, Xiaohan Zhu, Xiaobin Lou, Jian Yang, Haiying Qi, and Jia Li. Cognitive function mainly shaped by socioeconomic status rather than chronic hypoxia in adolescents at high altitude. High Alt Med Biol. 23:223-231, 2022. Background: The study evaluated cognitive function in relation to the changes in brain tissue oxygenation in three groups of high school students from different socioeconomic regions including Tibetans in Jiuzhi and Lhasa (both at 3,600 m), and Han in Beijing (44 m). Methods: Jiuzhi, Lhasa, and Beijing Group included 21 Tibetans, 24 Tibetans, and 23 Han, respectively. Wechsler Intelligence Scale was used for cognitive evaluation. Functional near infrared spectroscopy was used to measure the changes of oxygenated hemoglobin (oxy-Hb) during the cognitive assessment. Gross domestic product (GDP) was used to indicate the socioeconomic status. Results: All the cognitive scores were significantly lower in the two high altitude groups compared with the Beijing Group (p < 0.001). The scores in Jiuzhi Group were significantly lower compared with the Lhasa Group (p < 0.001). The changes in oxy-Hb in channels 6 and 15 in both high-altitude groups were significantly greater compared with the Beijing Group (p < 0.05), without significant difference between the two high-altitude groups. GDP was significantly correlated with all the scores (p < 0.001), but not altitude. Conclusions: Cognitive impairment occurs in adolescents at high altitude, being severer in Jiuzhi Group compared with the Lhasa Group. The lower performance in both high-altitude groups require greater brain activity over-compensated by cerebral oxygen delivery as indicated by the changes in oxy-Hb. The cognitive scores were significantly correlated with GDP rather than altitude. Cognitive function in adolescents at high altitude is not limited by chronic hypoxia, but mainly shaped by socioeconomic determinants.

Sleep Reactivity and Depressive Symptoms Among Chinese Female Student Nurses: A Longitudinal Mediation Analysis.

Previous cross-sectional studies have documented that sleep reactivity was associated with depressive symptoms, but the potential mechanisms underlying this relationship were understudied. Therefore, the present study with a longitudinal prospective design was to reveal the mediating roles of sleep disturbance and emotion regulation difficulties (ERD) between sleep reactivity and depressive symptoms. This study included 725 student nurses who were followed up periodically for 9 months, with an interval of three months. All participants completed questionnaires regarding sleep reactivity, sleep disturbance, ERD, and depressive symptoms. Adjusted analyses suggested that the direct effect of sleep reactivity on depressive symptoms was non-significant. The bootstrap procedure revealed two significant indirect effects: from sleep reactivity to depressive symptoms with sleep disturbance as a mediator and from sleep reactivity to depressive symptoms with sleep disturbance and ERD as sequential mediators. Therefore, sleep reactivity might be considered as an indicator of shiftwork adaptability in the evaluation of recruitment. Psychological interventions aimed at developing healthy sleep habits and emotion regulation skills may be helpful in decreasing the risk of depression.

Prevalences of and correlations between childhood trauma and depressive symptoms, anxiety symptoms, and suicidal behavior among institutionalized adolescents in Vietnam.

OBJECTIVES: We investigated the prevalence rates of childhood trauma, depressive symptoms, anxiety symptoms and suicidal behaviors among Vietnamese adolescents and compared the differences between institutionalized adolescents (IAs) and noninstitutionalized adolescents (NIAs). In addition, we examined the multidimensional associations between childhood trauma and psychopathology among IAs. METHODS: Five hundred forty-six participants were recruited into two groups (IAs and NIAs) matched by age, sex and grade. They completed a childhood trauma questionnaire, depression scale, anxiety scale, and 3 suicide-related questions. The chi-squared test and logistic regressions were performed. RESULTS: The prevalences of anxiety symptoms and suicide attempts among IAs was higher than that among NIAs (25.6 % vs 14.7 %, p = 0.001 and 8.1 vs 3.7, p = 0.03, respectively), while the prevalences of other psychopathologies did not differ significantly. In the IA group, high prevalences of victimization through physical abuse (22.3 %), emotional neglect (57.9 %), and physical neglect (72.9 %) were found, and 58.6 % of the participants had experienced more than one type of trauma. These figures were significantly higher in IAs than in NIAs. Depression and suicidal ideation were more strongly correlated with emotional abuse and neglect than other types of maltreatment, while anxiety, suicide planning and suicide attempts were more strongly correlated with physical abuse. IAs who experienced more than two categories of trauma or greater intensity of trauma were more susceptible to developing depression, anxiety, and suicidal behaviors. CONCLUSIONS: Childhood trauma was multidimensionally associated with adverse psychological outcomes. We suggest that various aspects of childhood trauma, as well as psychopathologies, must be routinely assessed.

Effects of Environmental Change on Travelers' Sleep Health: Identifying Risk and Protective Factors.

OBJECTIVE: The aim of this study is to predict the risk and protective factors for the differential effects of the environment on travelers' sleep health. METHODS: A sample of 505 travelers who stayed overnight in one of 28 hotels completed a sleep quality scale (SQS), a reduced scale of the Morningness/Eveningness questionnaire (rMEQ), and a hotel customer satisfaction questionnaire (H-SCI). RESULTS: Individuals who are of morning type (p = 0.002), have reduced sleep duration (p = 0.010), and have high sensitivity to the sleep environment (p = 0.000) are most affected by environmental change. Interestingly, business travelers are more affected by sleep disturbances than leisure travelers, travelers who are more satisfied with hotels are less likely to experience insomnia in a new sleep environment (p = 0.000), and insomniacs are more likely to recover from insomnia during a trip (p = 0.000). CONCLUSION: Environmental change has an inconsistent impact on the sleep health of different individuals. In a new sleep environment, the possible risk factors for sleep health include (1) being of morning type, (2) reduced sleep duration during trip, (3) sensitivity to the sleep environment, and (4) business stress, while a possible protective factor is satisfaction with the hotel. Possible factors aiding in recovery from home insomnia include (1) being of evening type and (2) higher satisfaction with the hotel.

Predictors of the initiation of shift work disorder among Chinese intern nurses: a prospective study.

AIM: Individual vulnerability to shift work disorder (SWD) varies. The aim of the present study was to verify the individual characteristics that predicted SWD onset by following Chinese intern nurses who at baseline had not worked rotating or night shifts. METHODS: A total of 706 Chinese first-year intern female nurses aged 16-24 years were recruited. At baseline (T0), they reported demographic characteristics, insomnia symptoms and excessive sleepiness, trait neuroticism, sleep reactivity, morningness, and circadian flexibility and languidity. At the three-month (T1) and six-month (T2) follow-up, the SWD status was determined based on significant sleep disturbance and/or excessive sleepiness in the context of working a rotating shift schedule. RESULTS AND CONCLUSIONS: The prevalence rates of SWD were 35.2% at T1 and 37.7% at T2. Two bivariate logistics regressions revealed that morningness (odds ratio [OR] = 1.31, 95% confidence interval [CI] = 1.09-1.58, T1; OR = 1.36, 95% CI = 1.12-1.65, T2), languidity (OR = 1.56, 95% CI = 1.28-1.90, T1), and sleep reactivity (OR = 1.29, 95% CI = 1.07-1.57, T1; OR = 1.31, 95% CI = 1.07-1.61, T2) predicted the onset of SWD, while flexibility (OR = 0.75, 95% CI = 0.62-0.90, T1) decreased the odds of SWD onset. By comparing nurses with SWD and nurses without SWD across all six months, morningness (OR = 1.58, 95% CI = 1.20-2.07), sleep reactivity (OR = 1.54, 95% CI = 1.16-2.04), languidity (OR = 1.70, 95% CI = 1.30-2.22), and flexibility (OR = 0.70, 95% CI = 0.54-0.90) showed significant effects on persistent SWD.

Newborn screening for congenital heart disease using echocardiography and follow-up at high altitude in China.

BACKGROUND: Pulse oximetry screening for critical congenital heart disease (CHD) is inapplicable to high altitude due to the variedly decreased arterial saturations and rare complex CHD. We examined the incidence and spectrum of CHD in newborns using echocardiography at high altitude and followed up their outcomes. METHODS: A total of 1337 babies were studied. Echocardiography was performed in 1002 asymptomatic newborns (3-5 days). In the same period, retrospectively studied 394 newborns (≤2 days) admitted to the NICU where echocardiograph was performed in 335. In both groups, follow-up was made at 1-3, 6 and 12-18 months. RESULTS: The incidence of CHD in asymptomatic newborns was 27.8%, consisting secundum atrial septal defect (ASD) [175 (62.7%)], patent ductus arteriosus (PDA) [61 (21.9%)], ventricular septal defect (VSD) [8 (2.9%)] and multiple defects [35 (12.6%)]. And 19.4% in NICU patients with similar spectrum, except for 2 with complex CHD who died before discharge. By 12-18 months of follow-up, 30% of CHD remained open. Thirteen patients developed mild to severe pulmonary arterial hypertension (PAH), and 2 of them died of heart failure. CONCLUSIONS: The incidence of CHD in newborns at high altitude is about 20 times higher than that at low altitude, consisting mostly of simple forms with left to right shunt, with rare complex CHD. By 12-18 months, the incidence of CHD is still about 10 times higher than that at low altitude. About 8% patients developed PAH or death. Follow-up must be reinforced in order to provide early intervention and prevent from PAH or death.

Glomerular Endothelial Mitochondrial Dysfunction Is Essential and Characteristic of Diabetic Kidney Disease Susceptibility.

The molecular signaling mechanisms between glomerular cell types during initiation/progression of diabetic kidney disease (DKD) remain poorly understood. We compared the early transcriptome profile between DKD-resistant C57BL/6J and DKD-susceptible DBA/2J (D2) glomeruli and demonstrated a significant downregulation of essential mitochondrial genes in glomeruli from diabetic D2 mice, but not in C57BL/6J, with comparable hyperglycemia. Diabetic D2 mice manifested increased mitochondrial DNA lesions (8-oxoguanine) exclusively localized to glomerular endothelial cells after 3 weeks of diabetes, and these accumulated over time in addition to increased urine secretion of 8-oxo-deoxyguanosine. Detailed assessment of glomerular capillaries from diabetic D2 mice demonstrated early signs of endothelial injury and loss of fenestrae. Glomerular endothelial mitochondrial dysfunction was associated with increased glomerular endothelin-1 receptor type A (Ednra) expression and increased circulating endothelin-1 (Edn1). Selective Ednra blockade or mitochondrial-targeted reactive oxygen species scavenging prevented mitochondrial oxidative stress of endothelial cells and ameliorated diabetes-induced endothelial injury, podocyte loss, albuminuria, and glomerulosclerosis. In human DKD, increased urine 8-oxo-deoxyguanosine was associated with rapid DKD progression, and biopsies from patients with DKD showed increased mitochondrial DNA damage associated with glomerular endothelial EDNRA expression. Our studies show that DKD susceptibility was linked to mitochondrial dysfunction, mediated largely by Edn1-Ednra in glomerular endothelial cells representing an early event in DKD progression, and suggest that cross talk between glomerular endothelial injury and podocytes leads to defects and depletion, albuminuria, and glomerulosclerosis.

[Comparison of echocardiographic parameters in healthy Chinese children born and living at high altitude or at sea-level].

OBJECTIVE: Chronic hypoxia at high altitude might result in cardiopulmonary adaptations including pulmonary arterial hypertension and cardiac remodeling. But little is known about the adaptive changes in healthy children born and living at high altitude. We compared the echocardiographic measurements between the healthy children living at 16 m (Shanghai, n = 220) and 3 700 m (Qinghai, total 257, Han children 117, Tibetan children 140). METHODS: Children's age ranged from 15 d to 14 years. Echocardiography measurements were performed, values of the left and right ventricular dimensions and wall thickness, systolic and diastolic function including cardiac output index (CI), as well as mean pulmonary arterial pressure (mPAP) were obtained. RESULTS: mPAP and right heart dimension, CI, right ventricular anterior wall thickness were significantly higher while ventricular systolic and diastolic function were significantly lower in 3 700 m group than in 16 m group (all P < 0.05). Left ventricular dimension was similar between the two groups. There were no differences on above measured parameters between the Han and Tibetan children from 3 700 m group (all P > 0.05). CONCLUSIONS: Children born and living at high altitude in China have significantly higher mPAP, dilated right heart and lower systolic and diastolic function of both ventricles and higher CI compared to children born and living at see-level. Above parameters were similar between the Han and the Tibetan childen born and living at high altitude. Present study provides reference values for the healthy children living at high altitude.

Anatomical and hemodynamic evaluations of the heart and pulmonary arterial pressure in healthy children residing at high altitude in China.

OBJECTIVES: Altitude-hypoxia induces pulmonary arterial hypertension and altered cardiac morphology and function, which is little known in healthy children at high altitude. We compared the cardiopulmonary measurements between the healthy children at 16 m and those at 3700 m in China and between the Hans and the Tibetans at 3700 m. METHODS: Echocardiography was assessed in 477 children (15 day-14 years) including 220 at 16 m and 257 at 3700 m. The dimensions and wall thickness of the left- and right-sided heart, systolic and diastolic functions including cardiac output index (CI) were measured using standard methods. Mean pulmonary arterial pressure (mPAP) was estimated by the Doppler waveforms in the main pulmonary artery. RESULTS: Compared to the 16 m-group, 3700 m-group had higher mPAP, increasing dilatation of the right heart, and slower decrease in right ventricular hypertrophy in 14 years (p < 0.05). The left heart morphology was not different (p > 0.20). Systolic and diastolic functions of both ventricles were significantly reduced, but CI was higher (p < 0.0001). There was no difference in any measurement between the Hans and the Tibetans (p > 0.05). CONCLUSIONS: Children living at high altitude in China have significantly higher mPAP, dilated right heart and slower regression of right ventricular hypertrophy in the first 14 years of life. Systolic and diastolic functions of both ventricles were reduced with a paradoxically higher CI. There was no significant difference in these features between the Hans and the Tibetans. These values provide references for the care of healthy children and the sick ones with cardiopulmonary diseases at high altitude.

Smad2-dependent downregulation of miR-30 is required for TGF-ß-induced apoptosis in podocytes.

Transforming growth factors beta (TGF-ß) are multi-functional cytokines capable of inducing apoptosis in epithelial cells, including glomerular podocytes. We and others have previously shown that podocyte-selective genetic deletion of the microRNA (miR)-processing enzyme, Dicer, caused glomerulosclerosis that was associated with podocyte apoptosis, and the miR-30 family was implicated in the process. Here, we report that apoptosis-associated genes were highly enriched among the predicted targets of miR-30 when compared with randomly selected miRs (26% vs. 4.5 ± 2.1%) or with the known TGF-ß-regulated miR-192 (6%), miR-216a (5.1%), and miR-217 (0%). miR-30 family members were abundantly expressed in podocytes in normal mice but were downregulated in albumin/TGF-ß transgenic mice with podocyte apoptosis and glomerulosclerosis. In vitro, TGF-ß downregulated miR-30s in wildtype and Smad3-deficient, but not Smad2- or Smad2/Smad3-deficient, podocytes. The TGF-ß-induced activation of caspase 3 and an increase in TUNEL-positive nuclei were significantly inhibited by the lentivirus-mediated overexpression of miR-30d, but not by a scrambled control miR, in podocytes. TGF-ß stimulated the phosphorylation of pro-apoptotic p53 in podocytes with lentiviral expression of a scrambled miR, but not in podocytes expressing miR-30d. In contrast, miR-30d had no effect on the phosphorylation of pro-apoptotic p38 MAP kinase induced by TGF-ß. Thus, we report that Smad2-dependent inhibition of miR-30s in podocytes is required for the activation of p53 and the induction of apoptosis by TGF-ß. These results demonstrate a novel functional role for miR-30 in podocyte survival and indicate that the loss of miR-30 survival signaling is a novel and specific mechanism of TGF-ß-induced podocyte apoptosis during glomerulosclerosis. We propose the therapeutic replacement of miR-30 as a novel strategy to prevent the podocyte apoptosis that is characteristic of progressive glomerular diseases.

Epithelial cell TGFß signaling induces acute tubular injury and interstitial inflammation.

TGFß signaling plays a central role in the development of acute and chronic kidney diseases. Previous in vivo studies involved systemic alteration of TGFß signaling, however, limiting conclusions about the direct role of TGFß in tubular cell injury. Here, we generated a double transgenic mouse that inducibly expresses a ligand-independent constitutively active TGFß receptor type 1 (TßR1) kinase specifically in tubular epithelial cells, with expression restricted by the Pax8 promoter. In this model, activation of TGFß signaling in the tubular epithelium alone was sufficient to cause AKI characterized by marked tubular cell apoptosis and necrosis, oxidative stress, dedifferentiation and regenerative cell proliferation, reduced renal function, and interstitial accumulation of inflammatory cells. This tubular injury was associated with mitochondrial-derived generation of reactive oxygen species (ROS), but cell damage and apoptosis were partially independent of mitochondrial-derived ROS. TßR1 signaling-induced tubular injury also associated with significant leukocyte infiltration consisting of F4/80(+) macrophages, CD11c(+) F4/80(+) dendritic cells, CD11c(+) F4/80(-) Ly6C(high) dendritic cells/monocytes, and T cells. Inhibition of mitochondrial-derived ROS significantly reduced accumulation of CD11c(+) F4/80(+) dendritic cells and T cells, suggesting a role for ROS in the activation and recruitment of the adaptive immune response to tubular injury. Taken together, these results suggest that TGFß signaling in the tubular epithelium alone is sufficient to cause acute tubular injury and inflammation; therefore, TGFß may be a mechanistic link between acute injury and chronic progression of kidney disease.

Characteristics and reactivity of rapidly hydrated sorbent for semidry flue gas desulfurization.

Semidry flue gas desulfurization with a rapidly hydrated sorbent was studied in a pilot-scale circulating fluidized bed (CFB) experimental facility. The desulfurization efficiency was measured for various operating parameters, including the sorbent recirculation rate and the water spray method. The experimental results show that the desulfurization efficiencies of the rapidly hydrated sorbent were 1.5-3.0 times higher than a commonly used industrial sorbent for calcium to sulfur molar ratios from 1.2 to 3.0, mainly due to the higher specific surface area and pore volume. The Ca(OH)2 content in the cyclone separator ash was about 2.9% for the rapidly hydrated sorbent and was about 0.1% for the commonly used industrial sorbent, due to the different adhesion between the fine Ca(OH)2 particles and the fly ash particles, and the low cyclone separation efficiency for the fine Ca(OH)2 particles that fell off the sorbent particles. Therefore the actual recirculation rates of the active sorbent with Ca(OH)2 particles were higher for the rapidly hydrated sorbent, which also contributed to the higher desulfurization efficiency. The high fly ash content in the rapidly hydrated sorbent resulted in good operating stability. The desulfurization efficiency with upstream water spray was 10-15% higher than that with downstream water spray.

Synthesis and properties of O-carboxymethyl chitosan/methoxy poly(ethylene glycol) graft copolymers.

O-carboxymethyl chitosan/methoxy poly(ethylene glycol) graft copolymers (OCMCS-g-MPEGs) with different degrees of substitution (DS) were synthesized by reductive N-alkylation of chitosan with poly(ethylene glycol) aldehyde. The properties of OCMCS-g-MPEGs, including the solubility, structure, hydrodynamic behaviors, isoelectric point (IEP) and interaction with water-soluble chitosan, were investigated. As a PEGylated polyampholyte, OCMCS-g-MPEGs can resolve in water over all pH range and the pH value at IEP (pH(IEP)) decreases when DS increases. The hydrodynamic behaviors of OCMCS-g-MPEGs in deionized H(2)O are markedly affected by DS and pH(IEP) in the experiment concentration range. The particle size of the complexes of OCMCS-g-MPEGs with water-soluble chitosan is strongly affected by the concentration of water-soluble chitosan and the pH value.

Investigation on the properties of methoxy poly(ethylene glycol)/chitosan graft co-polymers.

Methoxy poly(ethylene glycol)/chitosan graft co-polymers (CS-g-mPEGs) with different degrees of substitution were synthesized by reductive N-alkylation of chitosan with poly(ethylene glycol) aldehyde. The crystalline and thermal properties of CS-g-mPEGs were characterized by wide-angle X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetry (TG). The results indicate that CS-g-mPEG solids represent microphase separation morphology with mPEG crystal and CS domains coexistence and the introduction of PEG on CS improves the thermal decomposition. The hydrodynamic behavior of CS-g-mPEGs in aqueous solution and the influence of NaCl were investigated. The results indicate that the hydrodynamic behavior of CS-g-mPEGs in aqueous solution is significantly affected by the degree of substitution and the concentration of NaCl, which are quite different from that of CS. The results of this paper also certify that CS-g-mPEGs keep the property of complexation with a counter-ion, such as tripolyphosphate, to form nanoparticles through the electrostatic interaction.

Effect of near-wall air curtain on the wall deposition of droplets in a semidry flue gas desulfurization reactor.

The wall deposition of droplets is an important issue affecting the desulfurization efficiency and operating stability of semidry flue gas desulfurization (FGD) reactors. Various near-wall air velocities, near-wall air flow inlet heights, and spray characteristics were analyzed numerically to investigate their effect on the gas-liquid flow and droplet deposition characteristics. The analytical results show that the near-wall air curtain effectively reduces the wall deposition of droplets in the semidry FGD reactor. The droplet deposition ratio decreased rapidly with increasing near-wall air velocity due to the increased gas flow rates and the altered gas velocity distribution. The near-wall air flow inlet height had an optimum value due to the rapid decline of the near-wall air momentum along the reactor height. The optimum distance between the near-wall air inlet height and the droplet injection height was 1.2 times that of the droplet vertical movement distance before deposition based on the linear droplet movement. For commonly used spray characteristics in the semidry FGD process, i.e., droplet diameters of 50-150 microm, spray angles of 10-70 degrees and droplet initial velocities of 20-100 m/s, the droplet deposition ratio with the addition of the near-wall air curtain varied slightly with the droplet diameter and the spray angle but increased rapidly with the initial droplet velocity. Therefore, for the semidry FGD processes, the near-wall air curtain is an effective method to reduce the wall deposition of droplets for various droplet diameters and spray angles while the initial droplet velocity should be carefully controlled to reduce the wall deposition of droplets and improve the operating stability.

Effect of operating parameters and reactor structure on moderate temperature dry desulfurization.

A moderate temperature dry desulfurization process at 600-800 degrees C was studied in a pilot-scale circulating fluidized bed flue gas desulfurization (CFB-FGD) experimental facility. The desulfurization efficiency was investigated for various operating parameters, such as bed temperature, CO2 concentration, and solids concentration. In addition, structural improvements in key parts of the CFB-FGD system, i.e., the cyclone separator and the distributor, were made to improve the desulfurization efficiency and flow resistance. The experimental results show that the desulfurization efficiency increased rapidly with increasing temperature above 600 degrees C due to enhanced gas diffusion and the shift of the equilibrium for the carbonate reaction. The sorbent sulfated gradually after quick carbonation of the sorbent with a long particle residence time necessary to realize a high desulfurization ratio. A reduced solids concentration in the bed reduced the particle residence time and the desulfurization efficiency. A single-stage cyclone separator produced no improvement in the desulfurization efficiency compared with a two-stage cyclone separator. Compared with a wind cap distributor, a large hole distributor reduced the flow resistance which reduced the desulfurization efficiency due to the reduced bed pressure drop and worsened bed fluidization. The desulfurization efficiency can be improved by increasing the collection efficiency of fine particles to prolong their residence time and by improving the solids concentration distribution to increase the gas-solid contact surface area.

Effect of solids concentration distribution on the flue gas desulfurization process.

A dry flue gas desulfurization (FGD) process at 600-800 degrees C was studied in a pilot-scale circulating fluidized bed (CFB) experimental facility. Various fresh sorbent distribution types and internal structures were modeled numerically to investigate their effect on the gas-solid flow and sulfate reaction characteristics. Experimental results show that, after the fresh sorbent supply was stopped, the desulfurization efficiency declined rapidly even though the sorbent recirculation was maintained. Therefore, the fresh sorbent is the main contributor to the desulfurization process and the primary effect of the recirculated sorbent was to evenly distribute the fresh sorbent and to prolong the sorbent particle residence time. The numerical results demonstrate thatthe desulfurization efficiency varied greatly for the various fresh sorbent bottom injection methods. The desulfurization efficiency of the bottom-even injection method was 1.5 times that of the bottom two-sided injection method. Internal structures effectively improved the fresh sorbent solids concentration distribution and the desulfurization efficiency. Optimized internal structures increased the desulfurization efficiency of the bottom two-sided injection method by 46%, so that it was very close to that of the bottom-even injection method with only a 4.6% difference.