增湿活化脱硫试验研究

在热态脱硫试验台上进行了喷水活化和蒸汽活化脱硫试验,并研究了在不同钙硫比,饱和温距、SO2浓度和烟气速度下的脱硫性能,研究表明,与单纯的吸收剂喷射技术相比,蒸汽增湿活化和喷水增湿活化,都可以提高脱硫效率,但喷水活化效果比蒸汽活化效果好得多,而且脱硫效率随钙硫比增加,饱和温距、SO2浓度及烟气速度的降低而升高;在喷水增湿活脱硫中,脱硫剂浆滴的脱硫作用远远大于脱硫剂吸温脱硫作用。     

循环流化床烟气脱硫技术实验研究

提出一种干式烟气脱硫技术方案,并在４００￣８００℃的温度下进行了实验研究。为了提高脱硫效率和脱硫剂的利用率,还对在床内循环的脱硫剂进行了蒸汽处理。研究了烟气温度、Ｃａ／Ｓ、床内气流速度、床内固体物料浓度等参数对脱硫效率的影响,以及各参数之间的关系。研究发现温度对脱硫效率有明显的影响,近６００℃时最高。增加Ｃａ／Ｓ可以大幅度提高脱硫效率。此外,适当降低床内气体流速使床内的总物料量增加,可以提高脱硫效率。研究表明,蒸汽处理对脱硫效率的提高有明显效果,在本实验条件下,处理后的脱硫效率提高４２．１％。     

CO_2活化CaCO_3浆液对半干法烟气脱硫影响的实验研究

采用CO2气体对CaCO3脱硫剂浆液进行活化,以提高CaCO3与SO2的反应活性,从而使基于流态化的半干法烟气脱硫过程取得更高的效率。在高1．1m、内径12．5cm的流化床反应器中,以粒径为275μm、静止床高为98mm的粗砂作为流化介质,实验考察了活化时间、饱和接近度、钙硫比、脱硫荆粒径等因素对脱硫效率的影响。实验结果表明：钙硫比为1．2、饱和接近度为15～18℃、脱硫剂粒径为64μm时,经CO2气体活化后的CaCO3脱硫剂其脱硫效率可达92％,接近于相同条件下Ca（OH）2的脱硫效率。     

加压条件下石灰石同时煅烧和脱除H_2S的反应特性

基于石灰石等钙基脱硫剂在加压气化炉内可能同时发生煅烧和脱硫反应的事实,在Thermax 500型加压热重分析仪上进行了还原条件下石灰石的煅烧和脱硫过程同时进行的实验,主要研究了温度(800～900℃)和CO2分压(0～0.03,MPa)等因素的影响.结果表明:反应气体中无CO2时,石灰石煅烧和脱硫两个反应过程的影响程度与温度有关,800,℃比900,℃时更为明显;在CO2存在的条件下,石灰石的煅烧速率减缓,影响了后续脱硫过程的快速进行,而脱硫反应产物CaS的存在也严重抑制了煅烧过程的进行;在高CO2分压下,石灰石煅烧和脱硫过程之间的相互影响较大.     

钙基脱硫剂掺加粉煤灰在450_850_下的脱硫研究

在沉降炉上进行了掺加粉煤灰提高生石灰烟气脱硫率的实验。实验表明：生石灰掺加粉煤灰可以提高烟气脱硫率和脱硫剂的钙利用率。这种作用与反应温度有关,反应温度为５５０℃～７００℃时,效果最好。同时也研究了粉煤灰与生石灰掺混方式对气体脱硫率和脱硫剂的钙利用率的影响。     

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.     

钙基脱硫剂掺加粉煤类在450℃—850℃下的脱硫研究

在沉降炉上进行了掺加粉煤灰提高生石灰烟气脱硫率的实验。实验表明：生石灰掺加粉煤灰可以提高烟气脱硫率和脱硫剂的钙利用率。这种作用与反应温度有关,反应温度为５５０℃￣７００℃时,效果最好。同时也研究了粉煤灰与生石灰掺混方式对气体脱硫率和脱硫剂的钙利用率的影响。     

生石灰掺加粉煤灰脱硫性能研究

在沉降炉和热分析仪上进行的脱硫实验表明 :生石灰掺加粉煤灰可以提高烟气脱硫率和脱硫剂的钙利用率。这种作用与反应温度有关 ,反应温度为 550～ 70 0℃时 ,效果最好。同时也研究了粉煤灰与生石灰掺混方式对烟气脱硫率和脱硫剂的钙利用率的影响。     

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     

生石灰掺加粉灶灰脱硫性能研究

在沉降炉和热分析仪上进行的脱硫实验表明，生石灰掺加粉煤灰可以提高烟气脱硫率和脱硫剂的钙利用率，这种作用与反应温度有关，反应温度为５５０～７００℃时，效果最好，同时也研究了粉煤灰与生石灰掺混方式对烟气脱硫率和脱硫剂的钙利用率的影响。     

Sorbent enhanced hydrogen production from steam gasification of coal integrated with CO2 capture

In this work, CO₂ capture and H₂ production during the steam gasification of coal integrated with CO₂ capture sorbent were investigated using a horizontal fixed bed reactor at atmospheric pressure. Four different temperatures (650, 675, 700, and 750 °C) and three sorbent-to-carbon ratios ([Ca]/[C] = 0, 1, 2) were studied. In the absence of sorbent, the maximum molar fraction of H₂ (64.6%) and conversion of coal (71.3%) were exhibited at the highest temperature (750 °C). The experimental results verified that the presence of sorbent in the steam gasification of coal enhanced the molar fraction of H₂ to more than 80%, with almost all CO₂ was fixed into the sorbent structure, and carbon monoxide (CO) was converted to H₂ and CO₂ through the water gas shift reaction. The steam gasification of coal integrated with CO₂ capture largely depended on the reaction temperature and exhibited optimal conditions at 675 °C. The maximum molar fraction of H₂ (81.7%) and minimum CO₂ concentration (almost 0%) were obtained at 675 °C and a sorbent-to-carbon ratio of 2.     

A novel catalyst–sorbent system for an efficient H2 production with in-situ CO2 capture

This paper presents an experimental investigation for an improved process of sorption-enhanced steam reforming of methane in an admixture fixed bed reactor. A highly active Rh/Ce_αZr_1−αO₂ catalyst and K₂CO₃-promoted hydrotalcite are utilized as novel catalyst/sorbent materials for an efficient H₂ production with in situ CO₂ capture at low temperature (450–500 °C). The process performance is demonstrated in response to temperature (400–500 °C), pressure (1.5–6.0 bar), and steam/carbon ratio (3–6). Thus, direct production of high H₂ purity and fuel conversion >99% is achieved with low level of carbon oxides impurities (<100 ppm). A maximum enhancement of 162% in CH₄ conversion is obtained at a temperature of 450 °C and a pressure of 6 bar using a steam/carbon molar ratio of 4. The high catalyst activity of Rh yields an enhanced CH₄ conversion using much lower catalyst/sorbent bed composition and much smaller reactor size than Ni-based sorption enhanced processes at low temperature. The cyclic stability of the process is demonstrated over a series of 30 sorption/desorption cycles. The sorbent exhibited a stable performance in terms of the CO₂ working sorption capacity and the corresponding CH₄ conversion obtained in the sorption enhanced process. The process showed a good thermal stability in the temperature range of 400–500 °C. The effects of the sorbent regeneration time and the purge stream humidity on the achieved CH₄ conversion are also studied. Using steam purge is beneficial for high degree of CO₂ recovery from the sorbent.     

Thermodynamic analysis of hydrogen production via sorption-enhanced steam methane reforming in a new class of variable volume batch-membrane reactor

Combined reaction–separation processes are a widely explored method to produce hydrogen from endothermic steam reforming of hydrocarbon feedstock at a reduced reaction temperature and with fewer unit operation steps, both of which are key requirements for energy efficient, distributed hydrogen production. This work introduces a new class of variable volume batch reactors for production of hydrogen from catalytic steam reforming of methane that operates in a cycle similar to that of an internal combustion engine. It incorporates a CO₂ adsorbent and a selectively permeable hydrogen membrane for in situ removal of the two major products of the reversible steam methane reforming reaction. Thermodynamic analysis is employed to define an envelope of ideal reactor performance and to explore the tradeoff between thermal efficiency and hydrogen yield density with respect to critical operating parameters, including sorbent mass, steam to methane ratio and fraction of product gas recycled. Particular attention is paid to contrasting the variable volume batch-membrane reactor approach to a conventional fixed bed reaction–separation approach. The results indicates that the proposed reactor is a viable option for low temperature distributed production of hydrogen from methane, the primary component of natural gas feedstock, motivating a detailed study of reaction/adsorption kinetics and heat/mass transfer effects.     

Numerical study of heat transfer characteristics of semi-coke and steam in waste heat recovery steam generator for hydrogen production

With the steam obtained from the waste heat of high temperature semi-coke, the hydrogen production through gasification method is considered more commercially. The heat transfer of semi-coke bed and steam was investigated using an unsteady convection heat transfer three-dimensional model of semi-coke. The effects of particle size, steam flow and particle bed thickness on heat transfer characteristics were considered. The particle temperature calculated by three-dimensional model was in good agreement with the corresponding particle temperature of experiment. The heat transfer characteristics of single particle, the particle temperature, the amount of heat recovery and the heat flux were investigated. The results show that, in the first 10 min of the heat transfer of semi-coke bed and steam, the bottom particle temperature decreases rapidly, but the top particle temperature is almost unchanged. The heat transfer rate evolution of the single particle in different positions is revealed. The heat transfer rate evolution of the bottom particle is different from that of the middle particle and top particle, and the heat transfer rate evolution of middle particle is similar to that of the top particle. The particle size, the steam flow and the particle bed thickness have great influence on the heat transfer mechanism of semi-coke and steam, and the 7.5 kg/h is considered to be the best steam flow for heat recovery. The intrinsic heat transfer mechanism between semi-coke bed and steam was revealed.     

Hydrogen production from steam gasification of biomass: Influence of process parameters on hydrogen yield – A review

Steam gasification is considered one of the most effective and efficient techniques of generating hydrogen from biomass. Of all the thermochemical processes, steam gasification offers the highest stoichiometric yield of hydrogen. There are several factors which influence the yield of hydrogen in steam gasification. Some of the prominent factors are: biomass type, biomass feed particle size, reaction temperature, steam to biomass ratio, addition of catalyst, sorbent to biomass ratio. This review article focuses on the hydrogen production from biomass via steam gasification and the influence of process parameters on hydrogen yield.     

Enhanced coal gasification heated by unmixed combustion integrated with an hybrid system of SOFC/GT

For clean utilization of coal, enhanced gasification by in situ CO₂ capture has the advantage that hydrogen production efficiency is increased while no energy is required for CO₂ separation. The unmixed fuel process uses a sorbent material as CO₂ carrier and consists of three coupled reactors: a coal gasifier where CO₂ is captured generating a H₂-rich gas that can be utilized in fuel cells, a sorbent regenerator where CO₂ is released by sorbent calcination and it is ready for capture and a reactor to oxidize the oxygen transfer material which produces a high temperature/pressure vitiated air. This technology has the potential to eliminate the need for the air separation unit using an oxygen transfer material. Reactors' temperatures range from 750 °C to 1550 °C and the process operates at pressure around 7.0 bar. This paper presents a global thermodynamic model of the fuel processing concept for hydrogen production and CO₂ capture combined with fuel and residual heat usage. Hydrogen is directly fed to a solid oxide fuel cell and exhaust streams are used in a gas turbine expander and in a heat recovery steam generator. This paper analyzes the influence of steam to carbon ratio in gasifier and regeneration reactor, pressure of the system, temperature for oxygen transfer material oxidation, purge percentage in calciner, average sorbent activity and oxidant utilization in fuel cell. Electrical efficiency up to 73% is reached under optimal conditions and CO₂ capture efficiencies near 96% ensure a good performance for GHG's climate change mitigation targets.     

Sorption heat pipe—a new thermal control device for space and ground application

Sorption heat pipe (SHP) combines the enhanced heat and mass transfer in conventional heat pipes with sorption phenomena in the sorbent bed. SHP consists of a sorbent system (adsorber/desorber and evaporator) at one end and a condenser + evaporator at the other end. It can be used as a cooler/heater and be cooled and heated as a heat pipe. SHP is suggested for space and ground application, because it is insensitive to some “g” acceleration. This device can be composed of a loop heat pipe (LHP), or capillary pumped loop (CPL) and a solid sorption cooler. The most essential feature is that LHP and SHP have the same evaporator, but are working alternatively out of phase. SHP can be applied as a cryogenic cooler, or as a fluid storage canister. When it is used for cryogenic thermal control of a spacecraft on the orbit (cold plate for infrared observation of the earth, or space), or efficient electronic components cooling device (lased diode), it is considered as a cooler. When it is applied as a cryogenic storage system, it insures the low pressure of cryogenic fluid inside the sorbent material at room temperature.     

Hydrogen production from bio-oil aqueous fraction with in situ carbon dioxide capture

This paper presents the results of the investigation on steam reforming bio-oil aqueous fraction coupled with in situ carbon dioxide capture for hydrogen production. Experiments were carried out in a bench-scale fixed-bed reactor with calcined dolomite as the sorbent. The effects of temperature and water to bio-oil ratio on hydrogen production are reported. In the presence of calcined dolomite, maximum hydrogen yield of 75% was obtained among without sorbent, with CaO and with calcined dolomite at 600 °C, whereas hydrogen content was 83%, a little lower than that of 85% when CaO was used. Hydrogen content varies little at different water to bio-oil ratios and hydrogen yield was the greatest at the water to bio-oil ratio of 1:1. After regeneration of the sorbent, hydrogen content was back to the initial level but the hydrogen yield dropped.