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Liu R.,Tianjin University | Qin Y.,Tianjin University | Li X.,Tianjin University | Liu L.,Chembrane Engineering and Technology Inc.
Frontiers of Chemical Science and Engineering | Year: 2012

Multiple-effect membrane distillation (MEMD) using a hollow fiber-based air-gap membrane distillation module was experimentally examined for concentrating dilute aqueous hydrochloric acid. The effects of the hot and cold feed-in temperatures, and the feed-in volumetric flow rates on the performance of the MEMD process were studied. The performance was evaluated using the performance ratio (PR), the average selectivity of water over HCl (β avg) and the permeation flux (N). Two types of porous fibers made from polypropylene were used to fabricate the MEMD modules. The experimental data indicated that hollow fibers with high porosity were preferred for the MEMD process. The PR, β avg and N all decreased as the feed concentration increased. When the feed concentration was below 12 wt-%, the PR was 6. 0-9.6 and β avg was 10-190. When the concentration of HCl reached 18 wt-%, the PR and β avg were about 4.4 and 2.3, respectively. However, β avg sharply decreased to around 1.0 when the feed was further concentrated. During an operational stability test that lasted for 30 days, the performance of the MEMD modules remained good. © 2012 Higher Education Press and Springer-Verlag Berlin Heidelberg. Source


Qin Y.,Chembrane Research and Engineering Inc. | Liu R.,Tianjin University | Li X.,Tianjin University | Liu L.,Chembrane Engineering and Technology Inc. | Zhang Y.,Chembrane Engineering and Technology Inc.
AIChE 2012 - 2012 AIChE Annual Meeting, Conference Proceedings | Year: 2012

It is well known that hydrochloric acid (HCl) is usually used as pickle liquor to remove surface oxide in a steel production industry. When pickling cannot be accomplished effectively and the quality of the treated metal surface deteriorates, the pickle liquor is discharged from the pickling tank, and the pickling tank is replenished with fresh acid solution. According to the data provided by the World Steel Association in 2011, the total world crude steel production was 1,490.1 million tonnes. And about 60 kg of spent pickle liquor was generated with the production of each ton of steel, and thus annual emission of spent pickle liquor was up to several million tons. As an example, 1000 ton of pickle liquor is being produced daily in a steel plant in north China, which contains 7% HCl and 15% FeCl2. The spent pickle liquor usually contains 2-8 wt% hydrochloric acid and is considered a hazardous waste. The spent pickle liquor from steel processes is usually neutralized with lime and disposed in a landfill, which results into the following problem: high-salinity wastewater and sludge volume, the remaining salt residue processing difficulties, and most importantly, the acid unrecoverable. Therefore, there is an urgent need to recover and enrich hydrochloric acid to achieve economical and ecological benefits. Since the 1960s, hydrochloric spent pickling liquor is often treated in a hydrochloric acid regeneration system such as ion-retardation, diffusion dialysis and electro-dialysis, which recovers some of the hydrochloric acid and ferric oxide. Nevertheless, these regeneration processes produce lots of dilute hydrochloric acid solution. Thus, there still needs a novel and efficient technology to concentrate the recovered dilute HCl solution for further use. In the last few years, numerous studies have been performed to test the application of membrane distillation for concentrating dilute HCl solution. However, the high thermal energy consumption of the traditional MD process is one of the biggest barriers in its industrialization. In the present study, multiple-effect membrane distillation (MEMD) based on AGMD module with function of internal heat recovery has been developed. This kind of MEMD process combines the advantages of MD process and conventional MSF process, avoids the disadvantages of MSF such as evacuation operation, and can provide a high PR value. The effects of feed-in concentration, cold feed-in temperature (Tc), hot feed-in temperature (Th) and feed-in volumetric flow rate (F) on the performance of MEMD process were studied. The permeation flux (N) and energy efficiency, performance ratio (PR), and the average selectivity of water over HCl (βavg) are the most important indicators for module performance evaluation. N indicates the productivity of this device; PR (performance ratio) is usually used to determine the thermal efficiency of evaporation-based process, which is defined as the amount of latent heat needed for evaporation of the produced water and the amount of heat provided to the system from an external energy source; βavg is represents the measure of the preferential transport of water. The results showed that MEMD process could be used successfully for concentrating dilute HCl solution with the advantage of energy saving. The experimental data indicated that all N, PR and βavg decreased with the increase of feed concentration. When the feed concentration was below 12 wt%, PR could achieve 6.0∼9.6, and βavg was about 10~190. As the concentration of HCl achieved 18 wt%, the values of PR and βavg were still about 4.4 and 2.3, respectively. However, βavg sharply decreased to a value around 1.0 when feed was further concentrated. It is also found that there exists trade-off phenomenon between N, PR and βavg under experimental ranges, that is, the maximum N will be obtained with high temperature Th, low temperature Tc and high flow rate F while the maximum PR is obtained with high temperatures Th and Tc, as well as low flow rate F. the lowest βavg will be obtained with low temperature Th, low temperature Tc and low flow rate F. During an operational stability test lasting for 30 days, the performance of MEMD modules was kept in good condition. Source


Yao K.,Tianjin University | Qin Y.,Chembrane Research and Engineering Inc. | Liu L.,Chembrane Engineering and Technology Inc. | Yuan Y.,Tianjin University | Liu D.,Chembrane Engineering and Technology Inc.
10AIChE - 2010 AIChE Annual Meeting, Conference Proceedings | Year: 2010

Bioethanol production is generally regarded as a promising alternative way to substitute the traditional petroleum-based liquid fuels. Lignocelluloses, which are abundant in nature and independent of the market for food and cattle feed, are preferable to conventional starch or sugar containing feedstocks as raw materials for large scale production. The reported concentration of fermentable sugars in the cellulosic hydrolysate prior to fermentation is relatively low because of some process restraints during hydrolysis to obtain high sugar yield. However, in order to decrease the size of footprint of the entire processing plant and also energy consumption in downstream separation/purification, the feed to fermentation requires high concentration of sugars. To resolve this contradiction, an economically efficient and well performed preconcentration unit is necessary to added between the hydrolysis and fermentation step. In the present study, multi-effect membrane distillation (MEMD), a new membrane based distillation process, has been developed, which combines the advantages of both membrane distillation (MD) and multistage flash (MSF) by equipping air gap membrane distillation (AGMD) with internal heat recovery. A novel separation device in the form of hollow fibers is fabricated to test its separation performance, which is identified as MEMD module. The water vapor flux (J) and energy efficiency in term of performance ratio (PR) and thermal efficiency (η) are the most important indicators for evaluation of module performance. J indicates the productivity of the membrane module; PR tells how much energy is recovered by internal configuration and η shows how much energy is lost due to conduction according to the second law of thermodynamics. Experiments were conducted using the dilute salt aqueous solution as a tracer to investigate the influences of operating variables including inlet temperatures of two sets of different fibers (Th:70-90°C and Tc: 25-45Å°C) and flow rate (F:16-48L/h) on these above three performance parameters. During the experiment, no leakage is detected and the distillate is of good quality which means the separation efficiency is almost 100%. It is found that the most important determinant parameter is flow rate and there exists trade-off phenomenon between flux (J) and energy efficiency (PR and η) under experimental ranges, that is, the maximum flux will be obtained with high temperature Th, low temperature Tc and high flow rate F while the maximum PR or η is obtained with high temperatures Th and Tc, as well as low flow rate F. Two kind of modules with different hollow fiber diameter and length (M1 and M2 fabricated in Chembrane, China) are also compared. Response surface method (RSM) is carried out to build an empirical quadratic model for prediction of the separation performance and optimization, which agrees well with the experimental results. In general, the typical measured water permeation flux in this study is around 2.0 - 9.0L/m2 h and the value of PR is 4 - 12 and the value of η is 0.80 - 0.95. Flux decline together with reduction of PR and the decrease of η were observed with the increased sugar concentration (up to about 500g/L) mainly because of its high viscosity and there existed slightly differences among three sugars (glucose, xylose and sucrose). But it should be noted that the performance of this new device is still appreciated even at higher concentration. This MEMD process was successfully applied in preconcentrating sucrose aqueous solution from 150g/L to 600g/L and also obtains 14-fold of initial concentration of model cellulosic hydrolysate (mixture of glucose and xylose aqueous solution) in a very efficient way. Source


Liu J.,Tianjin University of Technology | Qin Y.,Chembrane Engineering and Technology Inc. | Li P.,Tianjin University of Technology | Zhang K.,Tianjin University of Technology | And 2 more authors.
Journal of Chemical Technology and Biotechnology | Year: 2015

BACKGROUND: A major cost in acid-catalysed hydrolysis of biomass to fermentable sugars is the consumption of acid itself. In this study, a combined process was developed in which the acid and sugar in the hydrolysate were separated using an acid retardation process and then the dilute aqueous product streams were concentrated using a continuous-effect membrane distillation (CEMD) process, thus acid could be reused as catalyst. RESULTS: The recovery rate of sugar was as high as 94.3-99.2% while the recovery rate of sulfuric acid was 92.4-98.9%. The eluents were further concentrated using the CEMD process. When a solution of 2wt% sulfuric acid was concentrated to c. 40wt%, the maximum value of permeation flux (Jw) and gained output ratio (GOR) was 6.20Lm-2h-1 and 15.50, respectively. Meanwhile, the dilute aqueous sugar solution obtained from corn stover was concentrated 20-fold to a final concentration of c. 497.6gL-1 using the CEMD process with a final GOR of 5.5. CONCLUSION: The combination of acid retardation and CEMD is suitable for the production of sugar, further purification and concentration of eluents; the sugar solution can be used for fermentation and acid solution can be reused as catalyst. © 2015 Society of Chemical Industry. Source


Liu J.,Tianjin University | Qin Y.,Tianjin University | Qin Y.,Chembrane Engineering and Technology Inc. | Li P.,Tianjin University | And 3 more authors.
Journal of Chemical Technology and Biotechnology | Year: 2016

BACKGROUND: A major cost in acid-catalysed hydrolysis of biomass to fermentable sugars is the consumption of acid itself. In this study, a combined process was developed in which the acid and sugar in the hydrolysate were separated using an acid retardation process and then the dilute aqueous product streams were concentrated using a continuous-effect membrane distillation (CEMD) process, thus acid could be reused as catalyst. RESULTS: The recovery rate of sugar was as high as 94.3-99.2% while the recovery rate of sulfuric acid was 92.4-98.9%. The eluents were further concentrated using the CEMD process. When a solution of 2wt% sulfuric acid was concentrated to c. 40wt%, the maximum value of permeation flux (Jw) and gained output ratio (GOR) was 6.20Lm-2h-1 and 15.50, respectively. Meanwhile, the dilute aqueous sugar solution obtained from corn stover was concentrated 20-fold to a final concentration of c. 497.6gL-1 using the CEMD process with a final GOR of 5.5. CONCLUSION: The combination of acid retardation and CEMD is suitable for the production of sugar, further purification and concentration of eluents; the sugar solution can be used for fermentation and acid solution can be reused as catalyst. © 2015 Society of Chemical Industry © 2016 Society of Chemical Industry. Source

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