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    Kinetic Study on a Commercial Amorphous Hydrocracking Catalyst by Weighted Lumping Strategy

    Sadighi, Sepehr, Ahmad, Arshad, Irandoukht, Akbar
    International Journal of Chemical Reactor Engineering, 2010, Vol.8(1) [Peer Reviewed Journal]
    Walter de Gruyter GmbH
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    Title: Kinetic Study on a Commercial Amorphous Hydrocracking Catalyst by Weighted Lumping Strategy
    Author: Sadighi, Sepehr; Ahmad, Arshad; Irandoukht, Akbar
    Publisher: De Gruyter
    Subject: Hydrocracking ; Vacuum Gas Oil ; Lump Kinetic Model ; Amorphous
    Description: Hydrocracking is an important upgrading process in the petroleum refinery, and it is generally used to process feedstocks ranging from vacuum gas oil (VGO) to vacuum residue. In this work, hydrocracking of VGO using a dual functional amorphous catalyst was carried out at a pilot scale unit under the following reaction conditions: liquid hourly space velocity (LHSV) from 1 to 1.5 hr-1 and reaction temperatures of 360-440°C at the constant pressure and hydrogen to oil, 156 bar and 1780 Nm3/m3, respectively. The effluent of the reactor was characterized to dry gas, naphtha, kerosene, diesel and unconverted VGO or residue. The pilot tests demonstrated that performing experiments beyond the temperature, recommended by catalyst vendor, lead the process to unstable hydrocracking. To describe the yield of hydrocracking products a five-lump discrete lumping approach with ten reactions was proposed. At first, the kinetic model contained twenty kinetic constants which were estimated by using the conventional objective function. The estimated parameters showed that the tendency of the catalyst to convert VGO to gas and naphtha was negligible whilst rate constants for hydrocracking of VGO to middle distillates were considerably high which was compatible with the nature of amorphous hydrocracking catalysts. After evaluating the magnitude of reaction rates and eliminating the ignorable constants, the network was reduced to six reactions in which only nine parameters were needed. The predictions indicated that the latter network could fit the yield of products more acceptable as if the average absolute deviation between experimental and calculated yields was descended from 16.25% to 12.6%. Then, to have a better prediction, a weighted objective function was used in which weight factors were calculated by a proposed weighted least square expression. The results confirmed that this approach could reduce average absolute deviation of model to 10.75%, and it created a fairly even distribution of deviation between hydrocracking products.
    Is part of: International Journal of Chemical Reactor Engineering, 2010, Vol.8(1)
    Identifier: 1542-6580 (E-ISSN); 10.2202/1542-6580.2193 (DOI)

    • Several versions

    4-Lump kinetic model for vacuum gas oil hydrocracker involving hydrogen consumption

    Sadighi, Sepehr, Ahmad, Arshad, Rashidzadeh, Mehdi
    Korean Journal of Chemical Engineering, 2010, Vol.27(4), pp.1099-1108 [Peer Reviewed Journal]

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    Comparison of Lumping Approaches to Predict the Product Yield in a Dual Bed VGO Hydrocracker

    Sadighi, Sepehr, Ahmad, Arshad, Shirvani, Mansoor
    International Journal of Chemical Reactor Engineering, 2012, Vol.9(1) [Peer Reviewed Journal]
    Walter de Gruyter GmbH
    Available
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    Title: Comparison of Lumping Approaches to Predict the Product Yield in a Dual Bed VGO Hydrocracker
    Author: Sadighi, Sepehr; Ahmad, Arshad; Shirvani, Mansoor
    Publisher: De Gruyter
    Subject: Hydrotreating ; Hydrocracking ; Lump Kinetic Model ; Hydrogen Consumption ; Dual Bed Hydrocracking Reactor
    Description: In this research, to predict the product yields of a pilot scale VGO hydrocracking reactor charged with mono functional hydrotreating and hydrocracking catalysts, two different four-lump models are developed. The first one, called combined bed model, is a simplex in which there is no boundary between hydrotreating and hydrocracking reactions through the reactor. The second one, called dual bed model, is a rigorous model in which hydrogen consumption and hydrotreating reactions are included. In this way, the reactor is subdivided into two different layers, so the effect of hydrotreating reactions on the hydrocracking section can be considered. Results show that the absolute average deviation (AAD%) of the yield prediction for the combined bed and the dual bed models are 8.23 percent and 5.87 percent, respectively. The main reason for the lower average deviation of the dual bed model is its higher accuracy to predict the yield of gas which is also the major advantage of this approach. However, the simplicity of the combined bed model can make it more applicable and attractive, especially when hydrogen consumption as well as sulfur, nitrogen and aromatic specifications of the feed and products are not accessible.
    Is part of: International Journal of Chemical Reactor Engineering, 2012, Vol.9(1)
    Identifier: 1542-6580 (E-ISSN); 10.1515/1542-6580.2519 (DOI)

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    Effect of Lump Partitioning on the Accuracy of a Commercial Vacuum Gas Oil Hydrocracking Model

    Sadighi, Sepehr, Ahmad, Arshad, Masoudian, Seyed Kamal
    International Journal of Chemical Reactor Engineering, 2012, Vol.10(1) [Peer Reviewed Journal]
    Walter de Gruyter GmbH
    Available
    More…
    Title: Effect of Lump Partitioning on the Accuracy of a Commercial Vacuum Gas Oil Hydrocracking Model
    Author: Sadighi, Sepehr; Ahmad, Arshad; Masoudian, Seyed Kamal
    Publisher: De Gruyter
    Subject: Hydrocracking ; Lump Kinetic Model ; Vacuum Gas Oil ; Partitioning ; Separation
    Description: In an industrial hydrocracking plant, except to the reactor, the separation section can affect the accuracy of the developed mathematical model. In this study, two combined-bed six and seven-lump kinetic models for the hydrocracking of vacuum gas oil in a real refinery are developed and their accuracies for the prediction of product yields are compared. In the six-lump model, the engaged components are selected according to the actual products of the plant, but the seven-lump one is included of lumps which are partitioned based on the specified initial and final boiling points.For both approaches, a complete kinetic network with the catalyst-decay functions is considered. It is found that over a 17-month period of operation from the start of run, the average absolute deviation (AAD%) of the six-lump and the seven-lump models for the yield prediction are 20.51% and 5.21%, respectively for all products. Additionally, the sum of residuals for the seven-lump model has been appreciably decreased in comparison to the six-lump one. Therefore, it is confirmed that partitioning of the products to the lumps with specific boiling points can acceptably decrease the deviation of the prediction. So it is conclusive that including the operation of the separation section in commercial models can effectively increase the accuracy of the model and smooth the prediction error.
    Is part of: International Journal of Chemical Reactor Engineering, 2012, Vol.10(1)
    Identifier: 1542-6580 (E-ISSN); 10.1515/1542-6580.2616 (DOI)

    • Several versions

    Vapor-liquid equilibrium of ethanol/ethyl acetate mixture in ultrasonic intensified environment

    Mahdi, Taha, Ahmad, Arshad, Ripin, Adnan, Nasef, Mohamed
    Korean Journal of Chemical Engineering, 2014, Vol.31(5), pp.875-880 [Peer Reviewed Journal]

    • Several versions

    Environmentally benign and highly regioselective ring opening of epoxides accelerated by ultrasound irradiation

    Nasef, Mohamed Mahmoud, Zakeri, Masoumeh, Asadi, Jahanbakhsh, Abouzari-Lotf, Ebrahim, Ahmad, Arshad, Malakooti, Reihaneh
    Green chemistry letters and reviews, 02 January 2016, Vol.9(1), pp.76-84 [Peer Reviewed Journal]

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    Thermogravimetric Analysis of Char Waste from the Air Gasification of Empty Fruit Bunch Briquette

    Nyakuma Bemgba Bevan, Mazangi Mojtaba, Johari Anwar, Ahmad Arshad, Tuan Abdullah Tuan Amran
    MATEC web of conferences, 01 July 2014, Vol.13, p.02004 [Peer Reviewed Journal]
    Directory of Open Access Journals (DOAJ)
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    Title: Thermogravimetric Analysis of Char Waste from the Air Gasification of Empty Fruit Bunch Briquette
    Author: Nyakuma Bemgba Bevan; Mazangi Mojtaba; Johari Anwar; Ahmad Arshad; Tuan Abdullah Tuan Amran
    Subject: Engineering
    Description: The thermal decomposition behavior of char waste produced from the air gasification of Empty Fruit Bunch (EFB) briquette was examined using thermogravimetric analysis (TGA). A comparison between the thermal decomposition behavior of char waste and EFB briquette is also presented. The results indicate that the char waste produced decreased from 22 % to 18 % with increasing temperature from 600 °C to 700 °C during gasification. This is due to the effect of high temperatures on the primary char decomposition reactions. It was observed that char degradation occurs in two steps; char degradation I & II with weight losses of 17 % and 32 % respectively. This showed that only ~ 50 % char was decomposed during thermal analysis, hence higher temperatures are required to ensure complete decomposition. The TGA curve for EFB briquette showed that complete thermal decomposition of EFB briquette occurs in four stages namely; drying, devolatization, reduction and char degradation. The most...
    Is part of: MATEC web of conferences, 01 July 2014, Vol.13, p.02004
    Identifier: 2261-236X (E-ISSN); 10.1051/matecconf/20141302004 (DOI)

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    An Empirical Study of Investigating Mobile Applications Development Challenges

    Ahmad, Arshad, Li, Kan, Feng, Chong, Asim, Syed Mohammad, Yousif, Abdallah, Ge, Shi
    IEEE access, 2018, Vol.6, pp.17711-17728 [Peer Reviewed Journal]
    IEEE Conference Publications, IEEE Journals & Magazines , IEEE Xplore, IEEE Journals & Magazines
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    Title: An Empirical Study of Investigating Mobile Applications Development Challenges
    Author: Ahmad, Arshad; Li, Kan; Feng, Chong; Asim, Syed Mohammad; Yousif, Abdallah; Ge, Shi
    Subject: Mobile Applications ; Application Programming Interfaces ; Mobile Communication ; Interviews ; Organizations ; Software Engineering ; Quality Assessment ; Mobile Application Development ; Mobile Apps Development ; Mobile Application Software Engineering ; Challenges and Barriers ; Empirical Study ; Engineering
    Description: Context: mobile application development is rapidly evolving with substantial economic and scientific interest. One of the primary reasons for mobile application development failure is the increasing number of mobile platforms; some organizations endorse mobile application development before understanding the associated development challenges of each target platform. Objective: the objective of this paper is to identify the challenges of native, web, and hybrid mobile applications, which can undermine the successful development of such applications. Method: we adopted a two-phase research approach: at first, the challenges were identified via a systematic literature review (SLR); and then, the identified challenges were validated through conducting interviews with practitioners. Results: through both research approaches, we identified nine challenges vital to the success of mobile application development and four additional challenges from interviews not reported in the literature....
    Is part of: IEEE access, 2018, Vol.6, pp.17711-17728
    Identifier: 2169-3536 (E-ISSN); 10.1109/ACCESS.2018.2818724 (DOI)

    • Several versions

    An Optimized Covalent Immobilization of Glucamine on Electrospun Nanofibrous Poly(vinylidene fluoride) Sheets Grafted with Oxirane Groups for Higher Boron Adsorption

    Nallappan, Madana, Nasef, Mohamed, Ting, Teo, Ahmad, Arshad
    Fibers and Polymers, 2018, Vol.19(8), pp.1694-1705

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    News Recommendation Systems - Accomplishments, Challenges & Future Directions

    Feng, Chong, Khan, Muzammil, Rahman, Arif Ur, Ahmad, Arshad
    IEEE access, 2020, Vol.8, pp.16702-16725 [Peer Reviewed Journal]
    IEEE Conference Publications, IEEE Journals & Magazines , IEEE Xplore, IEEE Journals & Magazines
    Available
    More…
    Title: News Recommendation Systems - Accomplishments, Challenges & Future Directions
    Author: Feng, Chong; Khan, Muzammil; Rahman, Arif Ur; Ahmad, Arshad
    Subject: Object Recognition ; Bibliographies ; Data Collection ; Quality Assessment ; Collaboration ; Computer Science ; Recommendations ; News Recommendations ; Literature Review ; Recommendation Techniques ; News Recommendation Overview ; Engineering ; Computer Science
    Description: News publishers have decreased disseminating news through conventional newspapers and have migrated to the use of digital means like websites and purpose-built mobile applications. It is observed that news recommendation systems can automatically process lengthy articles and identify similar articles for readers considering predefined criteria. The objectives of the current work are to identify and classify the challenges in news recommendation domain, to identify state-of-the-art approaches and classify on the application domain, to identify datasets used for evaluation and their sources, the evaluation approaches used and to highlight the challenges explicitly addressed. The literature is thoroughly studied over the time span of 2001-2019 and shortlisted 81 related studies, broadly classified into six categories and discussed. The analysis showed that 60% of news recommendation system adopted a hybrid approach, 66% studies little talk about datasets, and addresses a few challenges...
    Is part of: IEEE access, 2020, Vol.8, pp.16702-16725
    Identifier: 2169-3536 (E-ISSN); 10.1109/ACCESS.2020.2967792 (DOI)