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Specialized Sessions:

 

1. Compact Heat Transfer Equipments for Advanced Energy Systems

 

Chair: Qiuwang Wang

School of Energy and Power Engineering

Xi'an Jiaotong University

Xi'an Shaanxi, 710049, P.R. China

Tel & Fax: +86-29-82663502

E-mail: wangqw@mail.xjtu.edu.cn

 

Objectives: Advanced power system is one of the key energy technologies to achieve energy savings and emission reduction. To improve its energy efficiency, it is necessary to utilize various kinds of high-performance heat transfer equipments, or compact heat exchangers. Compact heat exchangers (CHEs) having high heat transfer surface area to volume ratio or very high heat transfer coefficients in mini and micro passages are thus finding increasingly more and more applications not only in developing areas such as nanotechnology, fuel cells, microturbines etc., but also in traditional automotive, aerospace, electronics, HVAC, power, process, food, oil refining, environmental protection and chemical industries, to name but a few. In order to meet various special and tough requirements of various applications, various techniques are being adopted to enhance the heat transfer performance while maintaining a reasonable pressure drop for heat exchangers. Considerable attention is being paid in recent years to addressing the limitations of pressure, temperature, safety etc. in CHEs and their ranges of application are being broadened.

This specialized session includes, but is not limited to the following topics: innovative design of CHEs, heat transfer enhancement techniques for CHEs, multi-objective optimization methods for CHEs, CFD techniques for CHEs, etc.

 

(1) Numerical optimization of gas inlet structure for microturbine Recuperator

 

Linxiu Du, Dan Liao, Min Zeng, Qiuwang Wang

State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

Xi’an, Shaanxi, 710049, P.R. China

 

Abstract: The compact and efficient primary surface heat exchanger is often used as recuperator in microturbine regenerative cycle system. In the present study, the gas inlet of 100kW-microturbine recuperator is fixed with different kinds of inner guide plates and the flow performance in the inlet section is significantly affected by these plates. The hydrodynamic performance in the gas inlet section is simulated with three-dimensional method and the simulation results are presented by using pressure drop velocity uniformity. It is found that, when the guide plate number is four, the hydrodynamic performance in the gas inlet section is the best. It is also found that, the velocity uniformity in the inlet section with guide plates is greatly improved (up to 90%) while the pressure drop is almost the same to that in inlet section without guide plates, and the flow recirculation phenomena are also disappeared in such inlet section.

 

(2) Experimental investigations of pool boiling on horizontal surface sintered with metallic fiber  

 

J Y Huang, Z G Qu*, D G Li, Z G Xu, W. Q. Tao

State Key laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

Xi’an 710049, China

*Email: zgqu@mail.xjtu.edu.cn   

 

Abstract: In this paper, the pool boiling heat transfer performance of deionized water on horizontal surface sintered with copper metallic fiber of various geometries are experimentally investigated at atmospheric pressure. The sintered fiber has four kinds of porosity (0.6, 0.7, 0.8 and 0.9) and four kinds of fiber diameter (50, 80, 100 and 160 ) which are proposed to provide artificial nucleate site to improve heat transfer performance. The pool boiling curves are gained under the above geometry combinations and high speed camera is applied for photographing the local processes of bubble growth for different boiling surfaces. It is revealed that all the enhanced surfaces show a considerable enhancement of heat transfer compared to the smooth surface, the superheats at the incipience of nucleate boiling are reduced apparently. For the specimens with same porosity of the metallic fiber coating, the potential of the heat transfer enhancement increased with the decreasing of fiber diameter. However, the affect of porosity of the sintered metallic fiber on pool boiling performance has no uniform illustration and the performance depends more on pore diameter distribution even in the same pore density.

 

(3) The fin design for fin-tube surface with small-diameter tube and performance evaluation method  

 

Ju-Fang FAN, Zhi-Geng WU, Zhi-Guo QU, Ya-Ling HE, Wen-Quan TAO*

School of Energy & Power Engineering,Xi’an Jiaotong University, Xi’an 710049 , China

*Email: wqtao@mail.xjtu.edu.cn 

 

Abstract: Heat transfer enhancement technique provides a powerful tool to improve the thermal performance of heat exchanger, including the reduction of its size and saving energy for its operation. In order to save copper material of heat exchanger and reduce energy for its operation, a new fin cofiguration for small-diameter tube (4 mm and 5 mm) is required to replace the original fin with tubes of 7mm in inlet velocity range from 0.5m/s to 3.0m/s.

 

In the design of a new fin configuration, the designers are always faced with following two questions. First, how to evaluate the performance of an in-designing temporary structure or how to compare the performance among different design schemes? Although a lot of performance evaluation methods can be found in the literature, all of them are based on the important assumption that the heat transfer and friction factor correlations for the referenced fin are available and the reference dimension used for calculating the dimensionless characteristic number of enhanced surface is the same as that of the referenced one. For a temporary in-designing structure its geometric size and even shape are subjective to change, hence it is very difficult to meet the above assumptions; Second, how to obtain an optimum or near optimum combination for a selected structure? This is often conducted by numerical simulation in trial-and-error manner. This will leads to an enormous computational task.

 

In the present paper, for the first problem, based on some conventional assumptions we propose a very simple yet efficient performance comparison method. In this method no correlations are required, and only several discrete data are enough. For the second problem we adopt the orthogonal design method proposed by Taguchi to significantly reduce the number of computational cases yet we can still obtain nearly optimum combination of major geometric factors.

 

To illustrate the feasibility of the proposed approach, a new slotted fin with tubes of 4 mm is designed. The result shows that not only the heat transfer capability of the new fin configuration can satisfy the requirements for heat transfer rate of original louvered fin with tubes of 7mm, but also the saving of the copper tube materials is about 35%. At the same time, as the second example of the application of the proposed performance evaluation method, three designed fins configurations with tubes of 5 mm are compared, and the best design is obtained.

 

(4) Mixed salts fouling of plate heat exchanger during convective heat transfer  

 

Xu Zhi-ming, Huang Xing, GuoJin-sheng, Zhang Zhong-bin

Northeast China Dianli University, Jilin City of Jilin Province, China

Email: xuzm@mail.nedu.edu.cn

 

Abstract: In recent years, with the development of industry,science and technology, the world is confronting energy shortages and environmental degradation. The fouling problem has become increasingly highlighted for heat transfer enhancement in the petroleum industry, refrigeration engineering, power and nuclear energy industries. Fouling refers to the formation of unwanted deposit layers on heat transfer surfaces. Fouling deposition is one of most important and serious problems usually faced by transfer equipment during operation, since deposits of fouling on heat transfer surfaces create a barrier to heat transfer, increase pressure drop and promote corrosion of material. Then, it is a very important significance to reduce economical loss of fouling and increase the energy utilization efficiency.

 

Fouling is generally classified in six different categories-crystallization, particulate, reaction, corrosion, biological, and solidification. Out of all these types, crystallization fouling has the most detrimental effect on the industry around the world. At same time, crystallization fouling is composed largely of different varieties of salts, especially the calcium carbonate, calcium sulphate and calcium phosphate, which also are the main salts of recirculated cooling water. In this paper, the main purpose is to study the mechanism of mixed salts fouling at the same operation parameters such as solution inlet temperature and hydrodynamics of the system. Fouling of mixtures of calcium sulphate, calcium carbonate and calcium phosphate has been studied experimentally, and the mixed salts fouling curve varying with time was obtained. The effect of mixed salts component on fouling has been analyzed based on the experimental results. The results show that the fouling thermal resistance of two mixed salts solution reduce according to the order of Ca3(PO4)2/CaCO3, Ca3(PO4)2/CaSO4, CaCO3/CaSO4. However, the fouling thermal resistance of three salts mixed solution (Ca3(PO4)2/CaCO3/CaSO4) is between Ca3(PO4)2/CaCO3 and Ca3(PO4)2/CaSO4. Then, the fouling thermal resistance of mixed salts is not only depending on the supersaturation degree of solution component, but also depending on the salts species. We found that the Calcium Phosphate had an important effect on the fouling thermal resistance of mixed salts. The bigger concentration of the Calcium Phosphate in mixed solutions, the bigger fouling thermal resistance got. On the other hand, the Metallographic Microscope (MM) has been used to evaluate deposit characteristic, which will provide some proof of mixed salts fouling to further research.

 

(5) Comparative study of fin-and-tube heat exchangers with and without liquid-vapor separation in air conditioning systems  

 

Y. Chen1, N.Hua1, D. Wu2, X.F. Peng2

1Faculty of Material and Energy Engineering, Guangdong University of Technology, Guangzhou 510006, China

2Lab of Phase-change and Interfacial Transport Phenomena Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

 

Abstract: In present investigation, a new kind of compact heat exchangers as condensers was introduced to traditional air conditioning systems. The novel structure was composed of tube rows and a pair of manifolds at either end. The length of tube was short enough to make condensate always appear droplet and unsteady thin film state on the tube wall. As a result, condensation heat transfer coefficient was improved greatly. Moreover, a series of liquid-vapor separation devices called perforated plates were set in some ways on the manifolds, which made refrigerant condensate drain away from heat transfer tube automatically after every tube pass so that vapor with great vapor quality were left flowing continuously and contacted directly with cooled wall. Furthermore, different numbers of tube in each pass were optimized to keep mass flow approximate agreement during the whole condensation.

 

In this paper, the performances of systems used refrigerant R22 and two different fin-and-tube heat exchangers with and without manifolds were investigated experimentally in the different conditions. The two heat exchangers had the same tube length 490mm, external diameter Ø7mm, fin size and construction, which were to say, they had the same heat transfer area. The experiments were performed in a room with constant air temperature 20~45°C.

 

Effects of refrigerant charge and capillary tube length on the new air conditioning system were re-recognized and analyzed. The effects of the refrigerant mass flux and inlet air temperature were explored in detail in the two systems. The performance parameters such as condensing temperature, pressure drop between refrigerant inlet and outlet, power consumption were measured as mass flux was 0.139kg/s~0.149kg/s. The results indicated that the temperature variation with condensation was so limited that it could be regarded as isothermal process in the new condenser, in other words, the condensation process was close to thermodynamic equilibrium phase change. However, the refrigerant temperature fluctuated and descended as a whole tendency in the normal heat exchanger. The associated frictional pressure drop in the new condenser was relatively smaller 42.8%~68.4% than the normal one under present experimental conditions. The new heat exchangers presented better performances especially when the inlet air temperature was higher.

 

 

2. PEM Fuel Cells: High-Performance, High-Durability and Low-Cost Catalysts and Supports

 

Chair: Andy X. Sun

Department of Mechanical and Materials Engineering
The University of Western Ontario Canada
London, Ontario, Canada
Tel.: 519 661 2111, Ext 87759
Fax: 519 661 3020
E-mail: xsun@eng.uwo.ca

Website: http://www.eng.uwo.ca/people/asun/default.htm

 

Objectives: Fuel cells are non-polluting and efficient energy conversion devices that are expected to play a dominant role in energy solutions of the future. Cost and durability related to catalysts and catalyst supports are two major roadblocks that have to be overcome before proton exchange membrane fuel cell (PEMFC) system can become economically viable. This specialized session will focus on the synthesis and applications related to catalysts and catalyst supports, with emphasis on synthesis, characterization and design of new catalyst and electrode materials, but not limited to these.

 

(1) Advanced cathode nanocatalysts for PEM fuel cells

 

Zhongwei Chen

Dept. of Chemical Engineering, Waterloo Institute of Nanotechnology, Waterloo Institute for Sustainable Energy University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1

Email: zhwchen@uwaterloo.ca

 

Abstract: The polymer electrolyte membrane fuel cell (PEMFC) has been considered as an attractive and efficient power source for mobile and stationary applications. However, several performance and economic factors, such as limited lifetime, reliability, and cost, are presently hindering PEMFC commercialization. As present methods of limiting or eliminating platinum from the PEMFC cathode prove challenging, nonprecious catalysts for the oxygen reduction reaction (ORR) are becoming more attractive to the PEMFC technology. While many nonprecious metal catalysts exhibit both good oxygen reduction activity and respectable performance durability in alkaline and neutral media, virtually all precious-metal-free catalysts developed over the past several decades suffer from low activity and poor stability in the acidic environment of the PEMFC cathode. As a result, most of the effort invested to date in the development of nonprecious cathode catalysts has focused on enhancing the activity and durability of ORR active sites.

 

This talk will address the main challenges of the PEMFC electrocatalysts by focusing on the following two topics: (I). Precious metal electrocatalysts: novel cathode catalysts based on supportless Pt-Co nanowire and nanotubes that have remarkable durability and high catalytic activity has been developed. Due to their unique combination of dimensions at multiple length scales, the Pt alloy nanowires and nanotubes can provide high Pt surface area and have the potential to eliminate or alleviate most of the degradation pathways of the commercial carbon supported Pt catalyst and unsupported Pt black. (II) Non-precious metal electrocatalysts: mesoporous, high-surface-area and self-supported metal-Nx-C based catalysts were developed to enhance active site density of non-noble metal catalysts, capable of combining high oxygen-reduction activity with good performance durability.

 

(2) Different parameters governing the activity and stability of Fe/N/C-catalysts for the oxygen reduction in

      PEM fuel cells 

 

F. Jaouen, JP. Dodelet

Institut National de la Recherche Scientifique - Énergie, Matériaux et Télécommunications Varennes (QC) Canada

 

Abstract: Fe/N/C-catalysts for the cathode in proton-exchange-membrane fuel cells were recently shown to be competitive with Pt-based catalysts, on the basis of their activity. While further increasing their activity is desirable, the main challenge facing such catalysts is to combine high activity and good durability. Indeed, other but less active Fe/N/C-catalysts have shown interesting durability for up to 1,000 h of operation in fuel cell. To achieve combined high activity and good durability for such catalysts, it will be necessary to understand the structural parameters governing each of these characteristics. The presentation will review the parameters known to control on one hand the activity and on the other hand the durability, for Fe/N/C-catalysts synthesized at our laboratory.

 

(3) Development of one-dimensional nanomaterials for high-performance and low-cost fuel cell applications

 

Andy Sun1*, Mei Cai2, Siyu Ye3

1Department of Mechanical and Materials Engineering, University of Western Ontario

London, Ontario, N6A 5B9, Canada

2General Motors Research and Development Center Warren, MI 48090-9055, USA

3Ballard Power Systems Inc., 9000 Glenlyon Parkway, Burnaby, BC, Canada V5J 5J8

*Email: xsun@eng.uwo.ca

 

Abstract: Fuel cells are non-polluting and efficient energy conversion devices that are expected to play a dominant role in energy solutions of the future. The proton exchange membrane fuel cells (PEMFCs) still faces significant technology roadblocks that have to be overcome before it will become economically viable. A major impediment to the commercialization of PEMFCs is the high cost of materials and low stabilities. Current technology still suffers from low platinum utilization, limited mass transport capability, and limited electrochemical stability of commercially-used carbon black-based support in the electrode structure. Therefore, the optimization of electrode structure (including support for catalyst) is an important enabler in reducing the cost and performance gaps towards commercial viability. The key solution is to develop novel nanomaterials to lower the cost and increase stabilities to make fuel cells technically and economically competitive with today’s internal combustion engine. In collaboration with General Motors and Ballard Power Systems, our group at Western is synthesizing and using carbon nanotubes, nitrogen-doped CNTs (N-CNTs) and metal oxide nanowires as Pt catalyst supports for PEMFCs.

 

Carbon nanotubes (CNTs) are a class of new nanomaterials with unique structures and properties. While CNTs are grown on fuel cell backing (carbon paper or carbon cloth), the integrated network-like nanotube-based electrodes as electrocatalyst support are ideal materials for providing higher catalytic performance, high catalyst utilization, efficient mass transport, and a long operation life for fuel cells. Compared with pure CNTs, nitrogen-doped CNTs provide unique morphology, controlled electrical properties and strong interactions with deposited nanoparticles due to the presence of nitrogen.

 

Nanowires are a newer class of one-dimensional nanomaterials with a high aspect ratio. Nanowires have demonstrated superior electrical, optical, mechanical and thermal properties. The broader choice of various crystalline materials and doping other elements provide highly tunable properties (e.g., electrical) of nanowires. Similar to CNTs, it is expected that metal oxide nanowires (SnO2, WO3 and TiO2) are also good electrode materials for fuel cells.

 

In this talk, we will present the successful synthesis of N-doped CNTs and metal oxide nanowires on fuel cell backing (carbon paper) as support for Pt-based nanoparticles, and superior fuel cell performance over commercial fuel cell electrodes.

 

(4) Development of next generation catalyst layer for proton exchange membrane fuel cells

 

Madhu S. Saha

Queen’s - RMC Fuel Cell Research Centre 945 Princess St., Kingston, Ontario Canada, K7L 5L9

E-mail: Madhu.saha@queensu.ca  

 

Abstract: Proton Exchange Membrane Fuel Cells (PEMFCs) are considered to be a promising energy conversion device for transportation and portable consumer applications [1]. To make commercially viable PEMFCs technology for automotive applications, there are several challenges to be addressed. Among these factors, the cost of PEMFCs is one of the most critical limitations. Cost reducing can be realized through several approaches such as decrease in electrocatalyst loading and by achieving a more effective three-phase electrolyte–catalyst–gas phase boundary, thus leading to better catalyst utilization. Depending on the deposition methods used, the approach towards lowering noble metal loading can be classified into five broad categories: (i) thin film formation with carbon supported electrocatalysts, (ii) pulse electrodeposition of noble metals (Pt and Pt alloys), (iii) sputter deposition (iv) pulse laser deposition and (v) ion-beam deposition [3].

 

As the key component in PEMFC, the catalyst layer (CL) is the place where the electrochemical reactions take place and the electrical energy is produced, exhibiting a great influence on the total performance and durability. One of the important issues in PEMFC research is a reducing of noble metals content in electrodes, what dictating a need in preparation of thin (submicron range) catalyst layers. However, conventional techniques used for catalyst depositing onto membrane often fail to maintain layer uniformity at submicron thickness.

 

In this talk, I will demonstrate an improved catalyst deposition methodology based on a Piezo-electric printing technique that is able to produce a Pt electrode having (i) better utilization of the precious metal present on the electrode in PEMFCs and (ii) very low precious metal (Pt) loading.

 

[1]. R. Borup et al, Chem. Rev., 107 (2007) 3904.

[2]. H.A. Gasteiger, S.S. Kocha, B. Sompalli, F.T. Wagner, Appl. Catal. B-Environ., 56 (2005) 9.

[3]. M.S. Saha, A.F. Gull´a, R.J. Allen, S.Mukerjee, Electrochim. Acta, 51 (2006) 4680.

 

(5) Electrochemical Durability of Heat-treated and N-doped Carbon as catalyst supports for PEM fuel cells

 

Wei wan, Haifeng Lv, Shichun Mu* and Mu Pan

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing

Wuhan University of Technology, Wuhan 430070, China

*Email: msc@whut.edu.cn

 

Abstract: Carbon black is wildly used as catalyst supports in proton exchange membrane fuel cells (PEMFCs), however carbon supports appear a low resistance to electrochemical corrosion. In this paper, the heat treatment on carbon black (Vulcan XC-72) was carried out in ammonia gas. The effect of heating treatment (up to 1000 ℃) on resistances to electrochemical oxidation of the N-doped carbon black (HNC) was investigated. The structural of HNC was characterized by high resolution-transmission electron microscope (HRTEM) and Raman spectroscopic analyses. The surface oxidation of HNC was analyzed by cyclic voltammetry (CV). The resistance to electrochemical oxidation of carbon supports was investigated with potentiostatic oxidation up to 48h in 0.5 mol l-1 H2SO4 at a constant potential of 1.2 V vs RHE by simulating PEMFC environment. The increased oxidation in carbon black surfaces is visibly higher than that of the HNC after 48h oxidation test, exhibiting a higher resistance to electrochemical oxidation for the latter. The results show that the heat treated and N-doped carbon black has a great potential application in PEM Fuel cells.

 

(6) Single-crystal Pt nanowire-based 3D electrodes for PEM fuel cell applications 

 

Shuhui Sun1, Gaixia Zhang1, Ruying Li,1 Dongsheng Geng1, Yu Zhong1, Andy X. Sun1*, Mei Cai2

1Department of Mechanical and Materials Engineering, University of Western Ontario

London, Ontario, N6A 5B9, Canada

2General Motors Research and Development Center Warren, MI 48090-9055, USA

3Ballard Power Systems Inc., 9000 Glenlyon Parkway, Burnaby, BC, Canada V5J 5J8

*Email: xsun@eng.uwo.ca

 

Abstract: Pt is the key electrocatalyst in PEM fuel cells. Interestingly, it is well accepted that the catalytic activity of Pt depends highly on its morphology, and therefore the synthesis of Pt with specific nanostructure has become an area of considerable interest. However, most of previous studies focused on nanoparticles. Very recently, we have developed a simple method to synthesize single crystal Pt nanowires (4 nm in diameter), a new type of catalyst for fuel cells, which exhibit 3-times better specific activity than the state of the art commercial catalyst made of Pt nanoparticles [1,2].

 

Here, I will focus on our recent continued work on Pt nanowires for fuel cells. (i) PtNWs on Sn@CNT 3D electrode, which exhibit enhanced electrocatalytic performance in ORR, methanol oxidation, and CO tolerance [3]. (ii) Ultrathin single crystal Pt nanowires grown on N-doped CNTs [4]. The diameter of Pt NWs has been narrowed down to 2.5 nm and their growth process has been systematically studied. It is well known that the surface area increases with the diameter decrease of an individual nanowire, which in turn, has immediate effect on the surface-related applications. We are currently working on the electrochemical properties of ultrathin Pt NWs and the results will be present as well.

 

[1] Sun, S. H., Yang, D. Q., Villers, D., Zhang, G. X., Sacher, E., Dodelet. J. P. (2008) Adv. Mater., 20, 571-574.

[2] Sun, S. H., Jaouen, F., Dodelet, J. P. (2008) Adv. Mater., 20, 3900-3904.

[3] Sun, S. H., Zhang, G. X., Geng, D. S., Chen, Y. G., Li, R. Y., Cai, M., Banis, M., Sun, X. L. (2010) Chemistry- A European Journal. 16, 829-835. (Inside Cover)

[4] Sun, S. H., Zhang, G. X., Zhong, Y., Liu, H., Li, R. Y., Zhou, X. R., Sun, X. L. (2009) Chem. Commun. 45, 7048-7050

Figure 1 (a) SEM image of Pt NWs (4 nm in diameter); (b) PtNW-Sn@CNT 3D electrode; (C) TEM image of ultrathin single crystal Pt NWs (2.5 nm in diameter).

 

(7) Effect of pore size of the carbon porous supports on catalytic performance of DMFC at anode

 

An-Ya Lo1,2, Ningya Yu2, Shou-Heng Liu2, Cheng-Tzu Kuo3, Shang-Bin Liu2

1Department of Material Science and Engineering, National Chiao Tung University, Hsingchu 30010, Taiwan

2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan

3Department of Materials Science and Engineering, Mingdao University, Changhua 52345, Taiwan

 

Abstract: Carbon porous materials (CPMs) with pore size ranging from 2 to 50 nm have attracted considerable R&D attentions and practical applications in the past decade, particularly as catalyst support materials in direct methanol fuel cells (DMFCs) and proton exchange membrane fuel cell (PEMFC) [1]. However, the potential applications of microporous (< 2 nm) and macroporous (> 50 nm) carbons have been largely overlooked. We have developed a CVD process to fabricate CPMs with pore sizes ranging from micro-, meso-, to macroporous scales, which where replicated by using various porous silicas, such as zeolites, mesoporous silicas, and photonic crystals as the templates [2]. Upon incorporating the Pt catalyst, the supported Pt/CPMs were characterized by TEM, Raman and XPS spectroscopy, N2 adsorption/desorption isotherm, cyclic voltammetry, and competitive (CO vs. H2) chemisorption analyses. Compared to the commercial Pt/XC-72 with a similar Pt loading, the Pt/CPM electrodecatalysts exhibited superior activities during methanol oxidation reaction (MOR). This may be attributed to the presence of highly dispersed Pt nanoparticles with improved tolerance for CO-poisoning [2b]. In terms of the overall performances of DMFC at anode, it was found that Pt dispersed on the external surfaces were more effective than those incorporated within the pore channels of the CPM supports.

 

[1] (a) H. Chang, S. H. Joo and C. Pak, J Mater Chem 17, 3078–3088 (2007). (b) S. H. Joo, C. Pak, D. J. You, S.-A. Lee, H. I. Lee, J. M. Kim, H. Chang and D. Seung, Electrochimica Acta 52, 1618-1626 (2006).

[2] (a) A. Y. Lo, S. J. Huang, W. H. Chen, Y. R. Peng, C. T. Kuo and S. B. Liu, Thin Solid Films 498 (1-2), 193-197 (2006). (b) S. H. Liu, R. F. Lu, S. J. Huang, A. Y. Lo, S. H. Chien and S. B. Liu, Chem Commun (32), 3435-3437 (2006).

 

(8) Alternative electrocatalyst support for PEM fuel cell applications

 

Mei Cai

General Motors Research and Development Center Warren, MI 48090-9055, USA  

 

Abstract: The development of Proton exchange membrane (PEM) fuel cell/hydrogen propulsion technology has generated significant materials challenges for the scientific and engineering communities. PEM fuel cells currently suffer from inadequate reliability stemming from the corrosion of cathode and the accompanied loss of catalytic activity. Before mass‐produced fuel cell technology can be made practical, the oxidative instability of carbon, used as the catalyst support at the oxygen electrode, must be addressed. Developing alternate catalyst supports with better corrosion resistance is one of the methods being examined for prolonging the lifetime of the PEM fuel cells. Alternative non‐carbon substrates or composite substrates containing carbon and a refractory material such as titania or silica are potential alternatives to carbon supports. The refractory nature of the ceramic material can contribute to the corrosion resistance of the substrate whereas carbon or the dopant can provide the required electrical conductivity. In this talk, I will introduce several approaches and materials that have been evaluated in our lab as alternative fuel cell catalyst support for PEM fuel cell applications. The materials synthesis, physical and chemical properties analysis, as well as their electrochemical and durability performance will be presented in detail. The future research need in alternative catalyst supports will also be discussed.

 

(9) A novel catalytic system for improved oxygen reduction activity and durability at low Pt loading: the effect of carbon support activation

 

Anna Ignaszak1, Carolyn Teo1, Előd Gyenge1, Siyu Ye2

1Department of Chemical and Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, B.C., V6T 1Z3, Canada

2Ballard Power Systems, 9000 Glenlyon Parkway, Burnaby B.C., V5J 5J8, Canada   

 

Abstract: Significant progress on the technology development in polymer electrolyte membrane (PEM) fuel cell has been achieved in recent years. However, some challenges, particularly on cost reduction and durability improvement, still impede the wide spread applications of PEM fuel cells. In this presentation, a novel catalytic system for simultaneous improvements in oxygen reduction activity and durability will be reported. It is achieved through a simple-to-use method of carbon support surface activation method. Three types of carbon supports, Vulcan XC-72R, acetylene carbon black, and graphitized carbon, were investigated and compared with each other. Pt nanoparticles were synthesized by a modified polyol process and deposited with a loading of 0.1 mg cm-2 on activated carbon supports. The novel catalyst was remarkably beneficial with respect to the stability of the electrochemically active specific area (ECSA) and ORR electrocatalytic activity as revealed by accelerated durability testing using control samples without support activation (both commercial and in-house prepared). The oxygen mass transfer in the rotating porous catalyst is described by a combination of the Bonnecaze and Ahlberg models. The electrochemical results are supported by detailed surface analysis. The optimum catalyst composition will be discussed.

 

 

3. Advanced Biofuels

 

Chair: Dr. Chao Tan, PEng

Centre for Environmental Engineering Research & Education

University of Calgary

Tel.: 403 220 2698

Email: tanz@ucalgary.ca

Website: http://www.ucalgary.ca/~tanz

 

Objectives: To update the advances and to facilitate debate in advanced biofuels production and analysis. Authors and presenters are welcome to present state-of-the art review, latest research results, new developments, concepts, policies and other in advanced biofuels.

 

(1) Evolving biofuel and bioenergy opportunities in the Canadian context

 

Warren E. Mabee, Department of Geography, Queen's University, Mackintosh-Corry Hall, Room D201, Kingston, Ontario, Canada. K7L 3N6,  Phone:  (613) 533-6000, extension 77092, Email: warren.mabee@queensu.ca

 

Abstract: Options for biofuel production have typically been classified by the nature of technology employed and the feedstock under consideration.  A gradual progression from 'conventional' (1st-generation) to advanced or cellulosic biofuels (2nd-generation) has been anticipated for some time by both scientists and policymakers.  In this paper, we review the progress towards commercialization that has been achieved, and the changes in our expectations around emerging biofuel options.  We also consider the impact of new technologies (such as algal-based fuels and bioreactor design) that may factor in creating future biofuel opportunities.  Issues of competition between liquid biofuel production and net bioenergy potential of biomass feedstocks are addressed.  The relation between existing and emerging technology options and biofuel policy is explored, particularly in the Canadian context.

 

(2) Hydrogen production from wheat and flax straws pyrolysis using tubular reactor: a comparative study

 

Thilakavathi Mani, Pulikesi Murugan, and Nader Mahinpey

Department of Chemical and Petroleum Engineering, Schulich School of Engineering, The University of Calgary, Calgary, Canada, AB T2N 1N4

 

Abstract: Hydrogen is the most environmentally friendly fuel and expected to be the most prominent energy resource for the near future. Biomass has been considered as one of the most probable source for H2 production and is produced from effective thermochemical process such as pyrolysis and gasification. The objective of this work is to analyze product yields and the hydrogen production from different biomass pyrolysis such as wheat straw and flax straw using a tubular reactor at various pressures with constant temperature of 500ºC. As the pressure increases from 10 psi to 40 psi, flax straw pyrolysis yields more gas (45 %), whereas wheat straw pyrolysis favors bio-oil (37 %) production at higher pressures. The analysis of gaseous products from pyrolysis of flax straw shows that maximum hydrogen (33 %) obtained at 20 psi, however the production of hydrogen was sustained for 30 min at 30 psi and more than 120 min at 40 psi. This implies that flax straw has more tendencies to yield gas compared to other pyrolysis products such as bio-oil and char, especially for hydrogen production compared to wheat straw. This may be due to the presence of more fibrous substance in flax straw.

 

(3) Hydrothermal liquefaction of aquatic plants to bio-oil

 

Dong Zhou, Liang Zhang, Shicheng Zhang, Hongbo Fu, Jianmin Chen

Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China

zhangsc@fudan.edu.cn  jmchen@fudan.edu.cn

 

Abstract: Biomass has received increasing attention recent years for renewable fuels and chemicals due to environmental issues and energy crisis. Some of aquatic plants as biological invasion have been used as feedstocks for production of bio-oils. For the high moisture content of aquatic plants, hydrothermal liquefaction technique should be one of the best choices for conversing them to bio-oils. In present work, Enteromorpha prolifera and water hyacinth were selected as typical aquatic plants in seawater and freshwater. The experiments were carried out in a batch reactor at controlled temperatures under an initial pressure of 2.0 MPa N2. Effects of temperature, reaction time and catalyst on the liquefaction products yields were studied. Multiple measurements including elemental analysis, FTIR, GC-MS and 1H NMR were applied to analysis the liquid products. Bio-oil produced from Enteromorpha prolifera mainly contained fatty acids, esters and quite a few of heterocyclic compounds, while phenols and their derivatives were found the main compounds in bio-oils produced from water hyacinth. The aqueous phases obtained from two plants contain many organic acids such as the highest content of acetic acid and also some nitrogen-containing compounds, which indicates that they could be used to recover valuable chemicals or for agricultural purpose.

 

(4) The future of hydrothermal liquefaction of biomass to biooil

 

S. Yin, Z. Tan

Department of Mechanical & Manufacturing Engineering

Centre for Environmental Engineering Research & Education

University of Calgary, Alberta, Canada

tanz@ucalgary.ca

 

Abstract: Hydrothermal liquefaction (HTL) of inedible lignocellulosic biomass to biooil is of growing interest for it can handle wet feedstock without predrying. However, the HTL biooils are actually many carboxylic acids and aromatic chemicals dissolved in water, the reaction media, and require extensive separation processes. Our experimental studies showed that the compositions and structure of the so-called biooils extracted from the same batch of aqueous products are dependent on the organic solvents. These acidic and aromatic chemicals also create challenges to their transportation, storage and clean combustion. Our recent studies have shown that these problems could be solved by producing alkane biooils, and it is feasible both technically and economically, because of the voluntary separation of alkanes from water.

 

(5) Conversion of forest biomass to biochar for sequestration of carbon

 

Amit Kumar, Susanjib Sarkar

Sustainable Energy Research Laboratory, Department of Mechanical Engineering

University of Alberta, Edmonton, Canada T6X0A3

Amit.Kumar@ualberta.ca

 

Abstract: Charcoal produced from biomass is called biochar. This research work involved a conceptual techno-economic study to estimate the cost of production of forest biomass based charcoal in a centralized plant and its storage in a landfill to sequester carbon. The overall objective was to the estimate the abatement cost of carbon sequestration through landfilling of forest biomass based charcoal. The cost of production of biochar from whole forest biomass in western Canada ranges from $218 to $324 per tonne of biochar from a continuous process kiln and a batch process kiln, respectively. Similarly, the cost of production of charcoal from forest harvest residues (limbs and tops generated by logging operation) is about $154 per dry tonne of biochar. The abatement costs of carbon sequestration through biochar production pathway from whole forest biomass and forest harvest residues are $88 and $64 per tonne of CO2 sequestered.