Experimental And Kinetic Study On Co2 Catalytic Gasification Of Biomass Char Using Conventional And Microwave Heating

• Main Author: Amiri, Pooya Lahijani
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: T Technology; TJ181-210 Mechanical movements
• Online Access: http://eprints.usm.my/40699/1/Experimental_And_Kinetic_Study_On_Co2_Catalytic_Gasification_Of_Biomass_Char_Using_Conventional_And_Microwave_Heating.pdf; http://eprints.usm.my/40699/

Penyiasatan terhadap aspek asas proses penggasan telah menunjukan bahawa kadar penggasan arang, sebagai langkah menghadkan kadar semasa penggasan bahan karbon, memainkan peranan yang penting dalam prestasi keseluruhan penggasan. Projek ini menerokai kaedah untuk memudahkan penggasan CO2 arang dan meningkatkan kereaktifan arang semasa tindak balas penggasan. Dalam kerja ini, kulit buah kelapa sawit (OPS) dan tempurung pistachio (PNS) telah digunakan untuk menghasilkan arang untuk penggasan CO2. Ujikaji awal penggasan CO2 telah dijalankan pada keadaan isoterma dalam penganalisis Termogravimetri (TGA). Pengaruh pemangkin logam pada kereaktifan penggasan CO2 arang dikaji. Pemangkin yang digunakan adalah (a) jenis besi (FeCl3, Fe(NO3)3 dan Fe2(SO4)3) dicampur pada arang OPS, (b) logam nitrat (KNO3, NaNO3, Ca(NO3)2, Mg (NO3)2) dan Fe(NO3)3) dicampur pada arang PNS, dan (c) abu tandan kosong kelapa sawit (EFB-abu), sebagai pemangkin semula jadi yang kaya dengan kalium, dicampur pada arang OPS. Keputusan kajian penggasan bermangkin mendedahkan bahawa aktiviti pemangkin tertumpu ditumpukan kepada 5% berat Fe(NO3)3-OPS, 5% berat NaNO3-PNS dan 10% berat campuran EFB-abu dan arang OPS. Beberapa model kinetik termasuk model teras mengecut (SCM), model fungsi pengedaran normal (NDM), model liang rawak (RPM) dan model liang rawak terubahsuai (MRPM) telah digunakan untuk menggambarkan kadar tindakbalas penggasan dan tenaga pengaktifan di samping menentukan parameter kinetik yang lain. Keputusan daripada lengkung Arrhenius menunjukkan, tenaga pengaktifan untuk arang OPS dan PNS tanpa pemangkin yang diperoleh, masing-masing adalah 269 dan 206 kJ/mol. Tenaga pengaktifan Fe(NO3)3-OPS, NaNO3-PNS dan campuran EFB-abu dan arang OPS char masing-masing adalah 216, 152 dan 160 kJ/mol, menandakan kesan penggunaan pemangkin dalam meningkatkan kereaktifan arang. Berdasarkan kepada hasil eksperimen penggasan dalam TGA dan kajian kinetik, penggasan CO2 OPS menggunakan arang dan PNS telah dikaji menggunakan sinaran gelombang mikro. Sistem pemanasan gelombang mikro telah dibangunkan dengan mempertimbangkan pengaruh pelbagai parameter termasuk saiz zarah arang, suhu penggasan dan kadar aliran gas serta pemangkin terhadap perubahan CO2 dan evolusi CO. Pembuktian ciri-ciri utama sistem pemanasan gelombang mikro, telah dijalankan menggunakan eksperimen yang serupa pada keadaan tertentu di bawah relau pemanasan elektrik konvensional dan keputusan telah dibandingkan. Nilai tenaga pengaktifan untuk tindak balas penggasan gelombang mikro adalah jauh lebih daripada pemanasan konvensional. Nilai tenaga pengaktifan 36, 47, 74 dan 249 kJ/mol masing-masing diperolehi bagi penggasan gelombang mikro Fe(NO3)3-OPS, campuran EFB-abu dan OPS, arang OPS tulen dan penggasan terma arang OPS. Tenaga pengaktifan untuk gelombang mikro penggasan NaNO3-PNS dan arang PNS tulen yang diperoleh adalah masing masing 27 dan 47 kJ/mol, manakala untuk penggasan terma arang PNS, nilainya adalah 184 kJ/mol. Percubaan untuk meningkatkan kualiti gas campuran menyerupai gas pengeluar daripada penggasan udara dan stim menggunakan arang PNS berpemangkin telah dilakukan. Hasilnya, HHV gas simulasi penggasan udara meningkat daripada purata 6.4-8.0 MJ/m3 kepada 7.6-10.4 MJ/m3 dalam gas simulasi penggasan wap. ________________________________________________________________________________________________________________________ Investigations on the fundamental aspects of gasification process have shown that the char gasification rate, as the rate limiting step during the gasification of carbonaceous materials, plays an important role in overall gasification performance. The current project looks for routes to facilitate CO2 gasification of char and improve the char reactivity during the gasification reaction. In this work, oil palm shell (OPS) and pistachio nut shell (PNS) were used to prepare char for CO2 gasification. The preliminary CO2 gasification experiments were carried out under isothermal condition in a Thermogravimetric analyzer (TGA). The influence of metal catalysts on the CO2 gasification reactivity of chars were examined. The implemented catalysts were (a) iron species (FeCl3, Fe (NO3)3 and Fe2(SO4)3) loaded on OPS char, (b) metal nitrates (KNO3, NaNO3, Ca(NO3)2, Mg(NO3)2) and Fe (NO3)3) loaded on PNS char and (c) ash of palm empty fruit bunch (EFB-ash), as a natural catalyst rich in potassium, loaded on OPS char. The results of catalytic gasification studies revealed that the highest catalytic activities were devoted to 5 wt% Fe(NO3)3-OPS, 5 wt% NaNO3-PNS and 10 wt% EFB-ash loaded OPS char. Several kinetic models including shrinking core model (SCM), normal distribution function model (NDM), random pore model (RPM) and modified random pore model (MRPM) were used to describe the gasification reaction rate and the activation energy and other kinetic parameters were determined. From the Arrhenius curve fitting results, the activation energies of un-catalyzed OPS and PNS chars were obtained as 269 and 206 kJ/mol, respectively. The activation energies of Fe(NO3)3-OPS, NaNO3-PNS and EFB ash loaded OPS char were respectively 216, 152 and 160 kJ/mol, signifying the impact of the used catalysts on enhancing the char reactivity. Based on the outcomes of the gasification experiments in TGA and kinetic studies, CO2 gasification of OPS and PNS chars were investigated under microwave irradiation. A microwave heating system was developed and the influence of various parameters including the char particle size, gasification temperature and gas flow rate as well as catalyst loading on CO2 conversion and CO evolution was considered. To prove the salient features of microwave heating system, similar experiments at selected conditions were performed under conventional electric furnace heating and the results were compared. The calculated activation energies for microwave gasification reactions were impressively lower than conventional heating. The activation energies of 36, 47, 74 and 248 kJ/mol were obtained for microwave gasification of Fe(NO3)3-OPS, EFB-ash loaded OPS, pristine OPS char and thermal gasification of OPS char, respectively. The activation energies for microwave gasification of NaNO3-PNS and pristine PNS char were obtained as 27 and 47 kJ/mol respectively, while this value was 184 kJ/mol for thermal gasification of PNS char. It was also attempted to improve the quality of mix gases resembling the producer gas from air and steam gasification using catalyzed PNS char. As a result, the HHV of the gas simulating air gasification improved from an average of 6.4 to 8.0 MJ/m3 and from 7.6 to 10.4 MJ/m3 in the gas simulating steam gasification.