过氧化氢水溶液增湿Ca(OH)_2脱硫脱硝的实验研究

在小型喷雾气流反应脱硫脱硝实验台上研究了过氧化氢水溶液浓度以及各种因素(Ca/S摩尔比、Ca/N摩尔比、喷水量)对脱硫、脱硝效率的影响。结果表明,采用过氧化氢水溶液增湿Ca(OH)_2脱硫时,其脱硫效率随着过氧化氢水溶液浓度的增加而有较大的提高,提高幅度达15%～20%。单独脱硝和同时脱硫脱硝实验表明,采用过氧化氢水溶液增湿Ca(OH)_2脱硫效率有明显的提高,而过氧化氢溶液增湿Ca(OH)_2脱硝的效果并不明显,脱硝效率为5%左右。     

循环流化床锅炉燃烧福建无烟煤炉内脱硫对污染物排放和电除尘效率的影响

为测试和分析Ca/S摩尔比变化对燃烧福建无烟煤循环流化床锅炉炉内脱硫效果以及SO2、NOx等污染物排放和电除尘器效率的影响,在1台燃烧福建无烟煤75t/h循环流化床锅炉上进行炉内添加石灰石脱硫的工业热态试验。试验表明:(1)燃烧福建无烟煤循环流化床锅炉自脱硫效率较高,并且脱硫效率随着Ca/S摩尔比增大而呈"S"型曲线变化,在Ca/S摩尔比较低(<2.02)或较高(>2.82)时,脱硫效率随着Ca/S增加而迅速提高;当Ca/S摩尔比在一定范围内(2.02～2.82),脱硫效率缓慢提高;(2)炉内添加石灰石脱硫对NOx和CO排放的影响不明显,均随着Ca/S摩尔比增加而轻微上升;(3)飞灰含碳量随着Ca/S摩尔比增加而有所下降,但当Ca/S摩尔比达到较高值以后(本例Ca/S>2.02),飞灰含碳量不再明显变化,并有上升的趋势;(4)随着Ca/S摩尔比增加,飞灰比电阻增加,电除尘器进口、出口浓度同步增长,但除尘效率基本保持不变。     

钠法与钙法焦炉烟气旋转喷雾脱硫特性对比

在旋转喷雾脱硫(Spray Drying Absorber,SDA)实验台上对低含湿量、高烟温的模拟焦炉烟气进行了脱硫实验,研究高入口烟气温度、高绝热饱和温差条件下,Na_2CO_3和Ca(OH)_22种脱硫剂的脱硫特性.讨论了化学计量比、脱硫塔入口烟温、绝热饱和温差和脱硫塔内烟气温降对脱硫效率的影响.结果表明:随化学计量比的增大,Na_2CO_3脱硫效率增长速率比Ca(OH)_2脱硫效率增长速率更快,当2种脱硫剂与SO_2的化学计量比分别达到1.1和1.5时,脱硫效率趋于平缓;脱硫效率随绝热饱和温差的增大呈指数形式下降;在保持出口烟气温度不变条件下,提高入口烟气温度有利于提高脱硫效率;脱硫塔内烟气温降增大也有利于提高脱硫效率.     

CaO颗粒水合制备工艺的优化及其性能的CFBR实验研究

为了降低脱硫反应产物层的扩散阻力对于CaO颗粒脱硫反应的影响，提高脱硫反应速率和CFB-FGD工艺中的烟气脱硫率，必须降低CaO颗粒粒径。将分析纯CaO颗粒分别与去离子水和4种分散剂溶液进行水合反应并根据悬浮液分散度对脱硫剂制备工艺进行了必要的优化。对分析纯CaO颗粒与去离子水反应得到的Ca(OH)2颗粒悬浮液和分析纯CaO颗粒与0．006mole／l的(NaPO3)6溶液反应得到的Ca(OH)2颗粒悬浮液分别与飞灰混合、干燥、研磨得到的脱硫剂性能在自行设计制造的小型循环流化床热态实验台(CFBR)上进行了实验研究。实验结果表明：在600℃～800℃范围内，CFBR的烟气脱硫率达到最大值。提高Ca(OH)2悬浮液的分散度是降低CaO颗粒覆盖层厚度和提高脱硫剂在CFB-FGD工艺中的烟气脱硫率的有效方法之一。图3表5参9     

湿法烟气脱硫系统的脱汞性能研究

通过测量湿法烟气脱硫(WFGD)系统进出口烟气中汞的浓度,考察了采用NH3·H2O、NaOH、Na2CO3、Ca(OH)2、CaCO3等5种脱硫荆时系统的脱汞性能,并在脱硫液中添加KMnO4,Fenton试荆、K2S2O8/CuSO4、Na2S进行试验.结果发现:燃煤烟气中气态总汞主要成分是单质汞,二价汞所占比例不超过40%;常规WFGD系统能高效脱除烟气中的气态二价汞(Hg2+),脱除效率高达81. %～92.60%,而对气态总汞的脱除效率仅为13.27%～18.26%,经WFGD系统后单质汞略有增加;脱硫剂种类对脱汞效果影响不明显,提高液气比有利于提高WFGD系统的脱汞效率;KMnO4、Fenton试剂、K2SzO8/CuSO4和Na2S等添加剂均可提高脱汞效率,但不同添加剂的效果有所不同,其中Na:S效果最为显著,脱汞效率最高可达67%.     

燃烧福建无烟煤循环流化床锅炉炉内脱硫对SO2、NOx和CO等污染物排放的影响

在一台燃烧福建无烟煤75t/h循环流化床锅炉上进行炉内添加石灰石脱硫的工业热态试验,测试了Ca/S摩尔比变化对燃烧福建无烟煤循环流化床锅炉炉内脱硫效果以及SO2、NOx、CO等污染物排放的影响.试验表明:燃烧福建无烟煤循环流化床锅炉自脱硫效率较高,并且脱硫效率随着Ca/S摩尔比增大而呈"S"型曲线变化,在Ca/S摩尔比...     

循环流化床锅炉的燃烧脱硫试验研究

针对内蒙古1台75 t/h循环流化床锅炉进行了脱硫试验,根据现场数据分析了温度、粒度、升温速率及摩尔比等因素对循环流化床脱硫效率的影响.结果表明:在较小Ca/S摩尔比下,脱硫效率随时间增加呈上升趋势,随着Ca/S摩尔比增大,脱硫效率上升趋势减缓,且存在一个最佳的Ca/S摩尔比;加入石灰石脱硫时,需根据实际运行情况调节石灰石给料机的出力,以协调脱硫效率和锅炉效率之间的平衡.研究结果对循环流化床锅炉实际运行中SO2的排放和脱除具有预测作用.     

高钙煤灰增湿脱硫的热天平模拟实验

(上海交通大学 能源工程系) 摘要：采用热天平研究了低温(30°C～130℃)条件下湿高钙煤灰的脱硫特性，指出水是低温下高钙煤灰进行 脱硫反应的前提条件。探讨了水钙摩尔比(H2O/CaO)、温度、二氧化硫浓度和钙硫摩尔比(Ca/S)对煤灰脱硫 效率的影响。结果表明，随着H2O/CaO、二氧化硫浓度和Ca/S的增大，脱硫效率提高；随着温度的升高，脱硫 效率降低。     

影响固定床烟气脱硫因素的实验研究

以CaO粉末做吸收剂,通过固定床干法脱硫实验,分别研究了温度、进口浓度、Ca/S摩尔比、吸收剂粒径和停留时间等各因素对脱硫效率的影响,结果表明：当T= 825℃、Ca/S=2.82、粒径为75μm、进口浓度Cin=1783 mg/m3、tR=0.4 s时,脱硫效率可达89.6%,出口SO2浓度为185 mg/m3,低于国家标准规定的260 mg/m3.     

钙硫比对CFB锅炉炉内脱硫效率的影响研究

炉内脱硫效率影响因素诸多,其中Ca/S是影响循环流化床锅炉炉内脱硫效率的一个重要因素。通过对1060t/h亚临界循环流化床锅炉进行脱硫试验及其所得数据的分析可知:随Ca/S的增大,炉内脱硫效率也随之增大,当Ca/S小于3时,炉内脱硫效率随其增大变化幅度较大,当Ca/S大于3时,炉内脱硫效率随其增大变化幅度较小;同一Ca/S下,840℃时炉内脱硫效率最大,脱硫剂的反应速度最佳,床温低于或高于这一温度,脱硫效率均降低,且Ca/S为3时,脱硫效率便可达90%以上。不同床温下CFB锅炉炉内脱硫效率随Ca/S改变的变化趋势可为炉内脱硫脱硫剂投入量的多少以及锅炉最佳运行床温的控制提供一定的依据,具有重要的指导意义。     

Conversion of recycled sawdust into high HHV and low NOx emission bio-char pellets using lignin and calcium hydroxide blended binders

Spruce wood sawdust (S), as biomass waste, could be utilized as a renewable fuel, but it suffers from its bulky, low energy density, high volatiles content and NO_x emission. This study investigated the possibility of conversion S into bio-char pellets (SC-Ps) as renewable and CO₂-neutral bio-fuel. Sawdust derived bio-char (SC) was produced through pyrolysis, and subsequently compressed into SC-Ps bonded by lignin (L) and hardened by Ca(OH)₂, NaOH, CaCl₂, CaO. The combustion characteristics of S and SC, the physical properties of SC-Ps including abrasive resistances (ARs), impact resistance index (IRI) and compress strengthens (CS) were evaluated. Results showed that the high heat value (HHV) of SC increased by 95% and its NO_x emission decreased due to the release of N-containing volatiles. Among these hardeners, addition of 5% Ca(OH)₂–10% L reduced the disruptive force created by uptake moisture and played an effect of hydration on hardening the bonds. In addition, the catalysis of hydroxide promoted the polymer chain growing into three-dimensional cross-linking that strengthened the bonds. Thus, the mechanical strengths of the SC-Ps bonded by Ca(OH)₂/L were sufficient for directly transportation and being charged into the blast furnace.     

CFB-FGD 工艺中Ca(OH)2颗粒悬浮液最大分散度的实验研究

CFB-FGD工艺中的CaO颗粒粒径偏大，CaO转化率比较低．降低CaO颗粒粒径的途径之一是优化脱硫剂制备工艺．为此，研究了用5种不同制备工艺得到的Ca(OH)2颗粒悬浮液和悬浮液中Ca(OH)2颗粒的算术平均粒径．实验结果表明，采用0．006mol／L的六偏磷酸钠溶液与CaO水合反应得到的Ca(OH)2颗粒悬浮液的分散度增加了6．62倍，Ca(OH)2颗粒的算术平均粒径降低到了1053nm．这是一种简单、有效、经济的脱硫剂制备工艺．     

臭氧氧化结合化学吸收同时脱硫脱硝的研究

为深入研究和开发臭氧氧化结合化学吸收同时脱除多种污染物技术，阐明了石灰石吸收脱除臭氧氧化产物（SOx和NOx）的吸收反应机理，通过气液固平衡理论对石灰石浆液吸收SOx和NOx特性进行了分析研究。理论分析表明：烟气中CO2对SOx和NOx吸收的影响可以忽略，并给出浆液在吸收容量所能承受的最大气液比。当[CaCO3]=0．05mol／1时，临界点M=600-700；当[CaCO3]=0．1mol／1时，临界点M=1200～1300；当[CaCO3]=0．15mol／1时，临界点M=1900～2000。图4表1参9     

Biogas quality upgrade by simultaneous removal of CO2 and H2S in a packed column reactor

Biogas from anaerobic digestion of biological wastes is a renewable energy resource. It has been used to provide heat, shaft power and electricity. Typical biogas contains 50–65% methane (CH₄), 30–45% carbon dioxide (CO₂), moisture and traces of hydrogen sulphide (H₂S). Presence of CO₂ and H₂S in biogas affects engine performance adversely. Reducing CO₂ and H₂S content will significantly improve quality of biogas. In this work, a method for biogas scrubbing and CH₄ enrichment is presented. Chemical absorption of CO₂ and H₂S by aqueous solutions in a packed column was experimentally investigated. The aqueous solutions employed were sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)₂) and mono-ethanolamine (MEA). Liquid solvents were circulated through the column, contacting the biogas in countercurrent flow. Absorption characteristics were examined. Test results revealed that the aqueous solutions used were effective in reacting with CO₂ in biogas (over 90% removal efficiency), creating CH₄ enriched fuel. H₂S was removed to below the detection limit. Absorption capability was transient in nature. Saturation was reached in about 50 min for Ca(OH)₂, and 100 min for NaOH and MEA, respectively. With regular replacement or regeneration of used solutions, upgraded biogas can be maintained. This technique proved to be promising in upgrading biogas quality.     

基于脱硫产物化学组成的脱硫剂利用率研究

通过对取自5个不同电厂半干法脱硫装置的脱硫灰进行化学组成分析,发现半干法脱硫产物中存在很大比例的CaCO3,其质量份额与CaSO3相当,是造成半干法烟气脱硫工艺中脱硫剂利用率低的重要原因.针对SO2和CO2的竞争反应进行了试验,结果表明:确实存在SO2和CO2与Ca(OH)2反应的竞争,说明在脱硫反应过程中CO2的影响不可忽视,应该从强化脱硫反应、抑制CO2与脱硫剂反应入手,提高脱硫剂的利用率,以进行半干法脱硫技术的工艺改进.     

Evidence for H2S gas as an intermediate species in the reaction mechanism of trapping hydrogen by cobalt disulfide

Cobalt sulfide prepared by aqueous precipitation using Na₂S and a Co(II) salt is known to trap hydrogen at room temperature and low pressure. The importance of oxidation of the primary CoS precipitate with atmospheric oxygen with respect to its efficiency as a hydrogen absorber is demonstrated. This stage of oxidation produces a mixture of two solid phases: a partially crystallized cobalt hydroxide Co(OH)₂ and an amorphous cobalt sulfide CoS₂ with a Co(OH)₂/CoS₂ molar ratio of 1 as predicted by thermodynamics. This biphasic product is probably the basic cobalt sulfide CoSOH considered in older and even more recent work. This product traps molecular hydrogen with a H₂/Co molar ratio of 0.5 whereas unoxidized CoS precipitate traps almost no hydrogen (H₂/Co = 0.025). Moderate acidic treatment of the absorber at room temperature leads to the selective dissolution of Co(OH)₂. The remaining cobalt sulfide has CoS₂ stoichiometry and reacts with hydrogen to form H₂S gas and CoS. We showed that H₂S released is reactive toward bases: CoS or Na₂S were formed when H₂S reacted with Co(OH)₂ or NaOH, respectively. This proves that the hydrogen trapping reaction mechanism implies H₂S as an intermediate species.     

Hydrogen generation from polyethylene by milling and heating with Ca(OH)2 and Ni(OH)2

A process to produce hydrogen from polyethylene [–CH₂–]_n (PE) is developed by milling with Ca(OH)₂ and Ni(OH)₂ followed by heating the milled product. Characterizations by a set of analytical methods of X-ray diffraction (XRD), infrared spectroscopy (FT-IR), thermogravimetry–mass spectroscopy (TG/MS) and gas chromatography (GC) were performed on the milled and heated samples to monitor the process. It has been observed that addition of nickel hydroxide as well as increases in milling time and rotational speed of the mill is beneficial to the gas generation, mainly composed of H₂ and CH₄, CO, CO₂. Gaseous compositions from the milled samples vary depending on the added molar ratio of calcium hydroxide. H₂ emission occurs between 400 and 500 °C, and H₂ concentration of 95% is obtained from the mixture of PE/Ca(OH)₂/Ni(OH)₂ (C:Ca:Ni = 6:14:1) sample, and the concentrations of CO and CO₂ remain below 0.5%. The process offers a novel approach to treat waste plastic by transforming it into hydrogen.     

Alkaline treatment for detoxification of acetic acid-rich pyrolytic bio-oil for microalgae fermentation: Effects of alkaline species and the detoxification mechanisms

Bio-oil derived from Pyrolysis of lignocellulosic biomass contains appreciable amounts acetic acid, which can be used as substrate for growing microalgae Chlamydomonas reinhardtii. However, the toxic compounds in the bio-oil inhibit the cell growth. This work is to develop alkaline treatment methods to reduce the toxicity and improve fermentability of acetic acid rich bio-oil. When growing in raw bio-oil without any detoxification treatment, the algae can only tolerate up to 0.1 wt% of bio-oil. Treatment with KOH, NaOH and Ca(OH)₂ significantly reduced the toxicity and consequently improved the fermentability of bio-oil. The bio-oil tolerant level by microalgae depended on the alkali species used. Among the three alkali species, Ca(OH)₂ proved the most effective detoxification reagent. Inhibitory compounds such as furans, phenols, ketones, aldehydes, ethers, esters, alcohols were removed by Ca(OH)₂ treatment through precipitation. The detoxification mechanisms by the Ca(OH)₂ -based treatment were also explored. The synergistic effect of alkaline pH, high temperature, and presence of Ca²⁺ played an important role for the precipitation of those compounds, and the consequent detoxification. Collectively, the results shows alkali, particularly Ca(OH)₂-based, treatment is an effective for reducing the toxicity of the pyrolysis derived bio-oil as fermentative substrate for microalgae growth. The microalgae can tolerant Ca(OH) ₂-treated bio-oil up to 5.5 wt%, which was 55 times higher than algal tolerance level of untreated bio-oil.     

Dynamic simulation of CaO/Ca(OH)2 chemical heat pump systems

Using energy and exergy analyses, a dynamic simulation is carried out with a CaO/Ca(OH)₂ chemical heat pump system for heating and cooling applications. The system consists of hydration/dehydration reactor connected to condenser/evaporator with a control valve in between. During the dehydration process, heat is supplied at 700 K for dehydration of Ca(OH)₂ and steam is condensed at 293 K. During evaporation/hydration process, heat is supplied at 290 K for evaporation of water at 273 K and heat of hydration is supplied to a load at 353 K. Duration of one cycle takes about 12 hours. Two subsystems are used to provide for heating/cooling demands in a continuous manner. Using synthetic demands of a residential dwelling, various performance parameters have been calculated for a 24 hour period. The results showed that CaO/Ca(OH)₂ chemical heat pump system could satisfy heating and cooling demands of a typical dwelling. Its energy and exergy efficiencies were 58.7% and 61.6% for heating and 12.7% and 4.5% for cooling respectively.     

Direct gasification of dewatered sewage sludge in supercritical water. Part 1: Effects of alkali salts

In the present study, the catalytic effects of alkali salts [NaOH, KOH, K₂CO₃, Na₂CO₃ and Ca(OH)₂] on the direct gasification of dewatered sludge in supercritical water were investigated by using a high-pressure autoclave at a constant temperature of 450 °C and a residence time of 30 min. The hydrogen yield increased in the presence of the alkali salts, except for Ca(OH)₂. Specifically, the hydrogen yield increased from 0.68 to 3.45 mol/(kg OM) as the K₂CO₃ concentration increased from 0 to 8 wt%. Although Ca(OH)₂ did not significantly impact the catalytic effect on the hydrogen yield, it did impact the CO₂ yield. Generally, the addition of alkali salts did not affect the organic matter or total phenol concentrations in the liquid residue. Moreover, char formation was considerably suppressed by the alkaline catalyzed hydrolysis of the dewatered sludge [except in the case of Ca(OH)₂].