可低温驱动的凝胶复合吸附剂的制备及吸/脱附性能研究

以丙烯酰胺单体、碳纳米管和无水氯化锂为原材料,通过原位聚合法制备了一种新型复合吸附剂,该吸附剂呈水凝胶形式。采用扫描电子显微镜和同步热分析仪对吸附剂进行表征,并用恒温恒湿箱测试了复合吸附剂的动态吸附/解附性能以及平衡吸附性能。研究表明,凝胶复合吸附剂在25℃和75%RH下,平衡吸附量高达1.75 g/g,是硅胶基复合吸附剂的2.5倍以上;并在45℃环境中解吸出70%的吸附水量;采用线性驱动力模型拟合计算了相同工况的动态吸附速率,与国内外其他复合吸附剂相比,本文吸附剂的吸附速率系数和吸附量均有很大提升。     

多盐复合吸附剂的非平衡吸附/解吸特性

以膨胀硫化石墨为基质,制备了新型氯化铵/氯化钙/氯化锰/膨胀硫化石墨复合吸附剂,并测试了其在非平衡条件下的吸附/解吸特性。在与3种单盐各自的Clapeyron反应平衡曲线的比较中发现,该多盐复合吸附剂同时具备这3种单盐的特性,却存在一定的差异。在非平衡条件下的吸附/解吸特性曲线测试过程中发现,该多盐复合吸附剂具备这3种金属氯化物各自的一些性质,却不存在金属氯化物-氨络合过程中普遍存在的吸附滞后现象。在实验的基础上计算和比较了使用不同吸附剂的单级间歇式吸附制冷循环的COP和SCP。结果证明多盐复合吸附剂的性能优于单盐吸附剂。     

Removal of SO2 from flue gas using a new semidry flue gas desulfurization process with a powder-particle spouted bed

A spouted bed of binary particle mixture was applied to a low temperature desulfurization process in order to develop a new type of semidry flue gas desulfurization (FGD) technology. We investigated the effects of operating parameters, such as type of SO₂ sorbent, diameter of SO₂ sorbent particles, apparent residence time of gas in the bed, approach to saturation temperature and Ca/S molar ratio, on SO₂ removal in a bench-scale powder-particle spouted bed. We also investigated the utilization rate of SO₂ sorbent and ways to enhance the efficiency of SO₂ removal and SO₂ sorbent utilization. The experimental results showed that SO₂ removal is significantly affected by the approach to saturation temperature and Ca/S molar ratio, and that a high SO₂ removal efficiency and effective sorbent utilization can be obtained under appropriate operating conditions. Thus, this new simple process of flue gas desulfurization is highly efficient and has little impact on the environment.     

Palladium/perovskite/zirconia catalytic premixed fiber burners for efficient and clean natural gas combustion

The present work was aimed at developing and testing – under realistic operating conditions on a specifically assembled pilot plant – a novel generation of catalytic premixed fiber burners for low-environmental-impact natural gas combustion. The adoption of a palladium-LaMnO₃-zirconia catalyst developed on purpose, where zirconia acts as a structural promoter and the noble metal/perovskite synergism is effectively exploited, led to enhanced performances with respect to non-catalyzed burners. In particular, lower CO and NO_x emissions were recorded over a wide field of operating conditions (basically excess of air with respect to the stoichiometric condition and nominal heat power).

Also, the effect of ageing and poisoning induced by sulfur compounds added as odorants in the natural gas network was studied, with promising indications as regards the burners durability: the overall performance, in terms of pollutant emissions, appeared to have slightly improved after prolonged exposure to SO₂ and high temperatures.     

Microwave-Assisted Extraction and Solid-Phase Separation of Quercetin from Solid Onion (Allium cepa L.)

The challenge of extraction of natural product in the twenty-first century is to achieve 100% selectivity of the desired product and develop renewable energy based processes. An object of the present work is to provide a method for producing specific bioactive compounds from agricultural products. A simple protocol was used to obtain the conditions of microwave-assisted extraction (MWAE) and ultrasound-assisted extraction (USAE). Total quercetin content under microwave irradiation for 150 sec at pH 6.25 (209 mg/ 100 gm F. wt). The effects of operating conditions, such as extraction time and pH on the extraction yield of quercetin were studied. Microwave-assisted ionic liquid-based silica sorbent (ILSis) was developed by a process involving surface chemical modification of commercial silica using a synthesized ionic liquid and characterized by FTIR. The obtained particles were successfully used as a special sorbent in a solid-phase separation process to isolate quercetin and its glycosides from solid onion. Different washing and elution solvents, such as water, water/methanol (v/v), and pure methanol were evaluated. Ionic liquid-based silica sorbent was compared with traditional C18 sorbent and it exhibited higher selectivity. The target compounds in solid onion containing quercetin and its glycosides were determined.     

Directly silica bonded analytical reagents: synthesis of 2-mercaptobenzothiazole–silica gel and its application as a new sorbent for preconcentration and determination of silver ion using solid-phase extraction method

A new and efficient method is described for the easy synthesis of directly bonded 2-mercaptobenzothiazole–silica gel. This new bonded analytical reagent is used as an effective sorbent for the solid-phase extraction of silver ion from aqueous solutions. Conditions for effective adsorption of trace levels of silver ion concentration are optimized with respect to different experimental parameters in column process. Sodium thiosulfate solution could efficiently elute the adsorbed silver ion from the surface of the sorbent which then was determined by atomic absorption spectroscopy (AAS). Common coexisting ions did not interfere with the separation and determination. The preconcentration factor is 300 (1 ml elution volume) for a 300 ml sample volume. The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be 343 μg of silver per gram of sorbent. The relative standard deviation under optimum conditions is 2.04% (n=7). Accuracy of the method was estimated by using test samples of natural water spiked with different amounts of silver ion. The method is simple and inexpensive.     

Feasibility study on pressure swing sorption for removing H2S from natural gas

The possibility of removing H₂S from natural gas by applying a pressure swing sorption (PSS) process was experimentally proven. The key technique of the PSS process relies on using a special type of sorbent where solid grains were coated by a layer of liquid. It was shown that the solubility of H₂S in the layer of liquid enlarged the concentration of H₂S at the solid surface and, hence enhanced the adsorption of H₂S on adsorbent. The solubility of H₂S is very sensitive to the partial pressure above the layer of liquid, therefore, the saturated sorbent could be easily regenerated by sweeping the bed of sorbent with nitrogen at ambient temperature and pressure. The sorption capacity as well as the coated sorbent was stable during the operation cycles of sorption/desorption. The new PSS technology of sweetening natural gas is advantageous over the prevailing technologies of today in that both savings of investment and energy cost could be expected.     

Reactive polymers, 50. The use of porous polymers in the sorption of tricyclic antidepressant in vitro

Three types of chemically different macroporous copolymers were investigated with respect to the possibility of their application as potential drug sorbents in blood detoxication and compared with activated charcoal which is used for this purpose in most cases. The measurements with a model drug solution were carried out in a dynamic arrangement under conditions resembling haemoperfusion. The effect of particle size of the sorbent on the rate of sorption and actual capacity of the column was detected and elucidated.     

Modelling the SO2-limestone reaction under periodically changing oxidizing/reducing conditions: the influence of cycle time on reaction rate

A simulation model is developed to analyse the dynamic behaviour of the SO₂-limestone reaction under periodically changing oxidizing/reducing conditions. Reference conditions assumed in the model are those typical of atmospheric fluidized-bed combustors operated with sorbent addition. The reaction network embodies limestone calcination, lime sulphation and sulphate reduction by carbon monoxide, relevant to periodic establishment of mildly reducing atmospheres around the sorbent particle. The model applies to the early conversion of particles and for short periods of time within the sulphation time.The influence of operating conditions on the rate of sulphur uptake by the sorbent is assessed, with particular emphasis on the effect of the cycle time of periodic shift between oxidizing and reducing conditions. Reaction regimes corresponding to the limiting cases of very short and very long cycle times are characterized. Analysis of model results is accomplished in the light of time-scales of circulation and periodic exposure to oxidizing/reducing conditions experienced by sorbent particles in fluidized-bed combustors.     

Nitrogen rejection from low quality natural gas by pressure swing adsorption experiments and simulation using dynamic adsorption isotherms

In order to remove N₂ from low quality natural gas, a mathematical model has been established by Aspen adsorption, using the CH₄-selective sorbent silicalite-1 pellets. The dynamic adsorption isotherm was first simulated by breakthrough simulation of a CH₄/N₂ mixture at different adsorption pressures and feed flow rates based on breakthrough experiments. The resulting simulated CH₄ dynamic adsorption amounts were very close to the experimental data at three different adsorption pressures (100, 200, and 300 kPa). Moreover, a single-bed, three-step pressure swing adsorption (PSA) experiment was performed, and the results were in good agreement with the simulated data, further corroborating the accuracy of the gas dynamic adsorption isotherm obtained by the simulation method. Finally, based on the simulated dynamic adsorption isotherm of CH₄ and N₂, a four-bed, eight-step PSA process has been designed, which enriched 75% (vol) CH₄ and 80% (vol) CH₄ to 95% (vol) and 99% (vol), and provided 99% (vol) recovery.     

Removal of sulfur compounds from utility pipelined synthetic natural gas using modified activated carbons

Synthetic natural gas (SNG), which is produced from petroleum and distributed via pipeline in Honolulu by The Gas Company, was analyzed using a gas chromatograph equipped with a sulfur chemiluminescence detector (GC/SCD). Hydrogen sulfide (H₂S), methyl mercaptan (MM), ethyl mercaptan (EM), dimethylsulfide (DMS), dimethyl disulfide (DMDS), tetrahydrothiophene (THT), ethyl disulfide (EDS), and one unidentified compound (UN1) were detected. Among these sulfur compounds, THT is added as an odorant and was present in the highest concentration.A commercial activated carbon (Calgon OLC plus 12X30) was modified by oxidation and impregnation methods and the resulting materials were evaluated for their ability to adsorb sulfur compounds present in SNG. The evaluation results indicate that all of the modification methods can improve the retention of individual sulfur compounds or the total sulfur capacity compared with the untreated virgin carbon. It is also found that activated carbons impregnated with metal impurities have different selectivity for sulfur compounds. Cu and Zn loaded carbons had the highest capacity for H₂S removal, Fe loaded carbon was more efficient for DMS removal (the most difficult S compound to remove), and carbon oxidized by HNO₃ was the best for THT removal.Based on these findings, a composite sorbent consisting of Cu loaded and Fe loaded carbons was designed and tested. The test results indicate that the composite sorbent had improved performance in the removal of individual sulfur compound. A linear programming model was used to design a composite sorbent optimized to minimize the required sorbent mass based on a 1-kW scale fuel cell system service target. Validation tests showed that the optimized sorbent required less of the individual modified carbon components than when they were individually used for the same sulfur removal target.     

紧急关断阀关断延迟对天然气管道泄漏过程的影响

准确判断泄漏速率对控制泄漏和计算应急区域范围非常关键,但现有天然气管道泄漏速率计算多在稳态的持续泄漏或紧急关断（ESD）阀同时关闭的动态泄漏假设下得到结果,与实际存在差别。本文结合管道过程,构建基于HYSYS的天然气集输管道泄漏等效模型,就ESD阀关断顺序和延迟对管道流量和泄漏速率的影响进行了模拟分析。结果表明,随着泄漏孔径的增加,管道内将出现逆流现象,管道ESD阀关断延迟顺序对小孔泄漏和大孔泄漏速率的控制存在明显不同的影响,对释放持续时间的影响较小。     

Removal of Copper (II) and Nickel (II) Ions from Aqueous Solutions by a Composite Chitosan Biosorbent

Abstract

A composite chitosan biosorbent (CCB) was prepared by coating chitosan on to ceramic alumina. The adsorption characteristics of the sorbent for copper and nickel ions were studied under batch equilibrium and dynamic flow conditions at pH 4.0. The equilibrium adsorption data were correlated with Langmuir, Freundlich, and Redlich‐Peterson models. The ultimate monolayer capacities, obtained from Langmuir isotherm, were 86.2 and 78.1 mg/g of chitosan for Cu(II) and Ni(II), respectively. In addition, dynamic column adsorption studies were conducted to obtain breakthrough curves. After the column was saturated with metal ions, it was regenerated with 0.1 M sodium hydroxide. The regenerated column was used for a second adsorption cycle.     

Investigation of the gypsum quality at three full-scale wet flue gas desulphurisation plants

In the present study the gypsum (CaSO₄·2H₂O) quality at three full-scale wet flue gas desulphurisation (FGD) plants and a pilot plant were examined and compared. Gypsum quality can be expressed in terms of moisture content (particle size and morphology dependent) and the concentration of residual limestone and other impurities. The particle size distributions (PSD) in the holding tanks of the investigated plants were similar, apart from a slightly higher fraction of small particles in the full-scale plants. These high levels of small particles could originate from nucleation, attrition or accumulation of fly ash and impurities from the sorbent. The crystal morphology obtained in the pilot plant was columnar with distinct crystal faces as opposed to the rounded shapes found at the full-scale plants. All the investigated full-scale plants consistently produced high quality gypsum (High purity, low moisture content and low impurity content). An episode concerning a sudden deterioration in the gypsum dewatering properties was furthermore investigated, and a change in crystal morphology, as well as an increased impurity content (aluminium, iron and fluoride), was detected.     

Reburning and burnout simulations of natural gas for heavy oil combustion

Reburning and burnout simulations were carried out through PLUG code of CHEMKIN-III using a reduced mechanism, in order to determine preliminary experimental parameters for achieving maximum NO_x reduction to implement the reburning technology for heavy oil combustion in pilot scale equipments in Brazil. Gas compositions at the entrance of the reburning zone were estimated by the AComb program. Simulations were performed for eight conditions in the usual range of operational parameters for natural gas reburning. The maximum NO reduction (ca. 50%) was reached with 10 and 17.5% of power via natural gas and 1.5 and 3.0% O₂ excess, respectively, at 1273 K. The model predicts 250 ppm of NO, 50 ppm of CO and air mass flows in the range of about 50-130 kg/h for burnout.     

Sorbent design for CO2 capture under different flue gas conditions

CO₂ capture by solid sorbents is a physisorption process in which the gas molecules are adsorbed in a different porosity range, depending on the temperature and pressure of the capture conditions. Accordingly, CO₂ capture capacities can be enhanced if the sorbent has a proper porosity development and a suitable pore size distribution. Thus, the main objective of this work is to maximize the CO₂ capture capacity at ambient temperature, elucidating which is the most suitable porosity that the adsorbent has to have as a function of the emission source conditions. In order to do so, different activated carbons have been selected and their CO₂ capture capacities have been measured. The obtained results show that for low CO₂ pressures (e.g., conditions similar to post-combustion processes) the sorbent should have the maximum possible volume of micropores smaller than 0.7 nm. However, the sorbent requires the maximum possible total micropore volume when the capture is performed at high pressures (e.g., conditions similar to oxy-combustion or pre-combustion processes). Finally, this study also analyzes the important influence that the sorbent density has on the CO₂ capture capacity, since the adsorbent will be confined in a bed with a restricted volume.     

Enhancement of CO2 capture and microstructure evolution of the spent calcium-based sorbent by the self-reactivation process

The effect of self-reactivation on the CO_2 capture capacity of the spent calcium based sorbent was investigated in a dual-fixed bed reactor.The sampled sorbents from the dual-fixed bed reactor were sent for XRD,SEM and N_2 adsorption analysis to explain the self-reactivation mechanism.The results show that the CaO in the spent sorbent discharged from the calciner absorbs the vapor in the air to form Ca(OH)_2 and further Ca(OH)_2·2 H_2 O under environmental conditions,during which process the CO_2 capture capacity of the spent sorbent can be self-reactivated.The microstructure of the spent sorbent is improved by the self-reactivation process,resulting in more porous microstructure,higher BET surface area and pore volume.Compared with the calcined spent sorbent that has experienced 20 cycles,the pore volume and BET surface area are increased by 6.69 times and 56.3% after self-reactivation when φ=170%.The improved microstructure makes it easier for the CO_2 diffusion and carbonation reaction in the sorbent.Therefore,the CO_2 capture capacity of the spent sorbent is enhanced by self-reactivation process.A self-reactivation process coupled with calcium looping process was proposed to reuse the discharged spent calcium based sorbent from the calciner.Higher average carbonation conversion and CO_2 capture efficiency can be achieved when self-reactivated spent sorbent is used as supplementary sorbent in the calciner rather than fresh CaCO_3 under the same conditions.     

Hydrierende Vergasung von Kohle – Neuere Betriebsergebnisse

Hydrogasification of coal – recent operational results . The Rheinische Braunkohlenwerke AG has built and has been operating a semi-technical pilot plant for hydrogasification of coal in a fluidized bed. The objective is to develop a coal gasification process with hydrogen for producing directly substitute natural gas. Between 1976 and 1981, the semitechnical pilot plant having a capacity of 100 kg C/h was operated for about 22,900 h under test conditions, more than 9,500 h of which were under gasification conditions. During this time, approximately 1,400 metric tons of dry coal were gasified. The longest coherent operational phase under gasification conditions was 748 h in which 86.4 metric tons of dry lignite were gasified. Carbon gasification rates up to 82% and methane contents in the dry raw gas (free of N₂) up to 48 vol.-% were obtained. A detailed evaluation of the test results provided information on the influence of additional parameters on the efficiency dates of the gasifier and a considerable refining of the results obtained previously. Moreover, several components were tested for which no operational experience had previously been gained; these were newly developed devices, e. g. the inclined tube for feeding coal into the fluidized bed. Within the framework of scale-up work to large-scale coal gasification plants, a pilot plant having a capacity of approximately 6 t C/h will be commissioned in late 1982.     

DYNAMIC SIMULATION OF A DISTILLATION COLUMN SEPARATING A MULTICOMPONENT MIXTURE

In this work, a dynamic model was developed to simulate the transient behaviour of a pilot scale, continuous, siagewise, 15 plate distillation column separating a mixture of ethanol, iso-propanol and isobutanol. The accuracy of the predictions was assessed by transient response data collected during experiments under step changes in reflux ratio, feed flow rate and feed composition.

Results demonstrated the feasibility of simulating multicomponent distillation under unsteady state conditions with fairly good success. Further improvements were suggested for a better accuracy     

Experimental and model investigation on the mass balance of a dry circulating fluidized bed for flue gas desulfurization system

A moderate temperature dry circulating fluidized bed flue gas desulfurization (CFB-FGD) process was developed using rapidly hydrated sorbent. This technique has the advantages of low cost, no water consumption, and a valuable dry product CaSO₄. To keep the system operation stable, a mass balance model, based on cell model considering flow state, particle abrasion, particle residence time, particle segregation and desulfurization processes, was built to predict the system state and optimize the operating condition. Experimental studies were conducted on a pilot-scale CFB-FGD system with rapidly hydrated sorbent made from CFB circulating ash and lime (circulating ash sorbent) or coal fly ash and lime (coal fly ash sorbent). Calculated results were compared with experimental results and the relative error was less than 10%. The results indicated that feed sorbent mass, feed sorbent size, superficial gas velocity, particle abrasion coefficient and cyclone efficiency had significant influence on the mass balance of CFB system. The circulating ash sorbent was better than the coal fly ash sorbent, for providing higher desulfurization efficiency and being better for the CFB-FGD system to achieve mass balance.