Sains Malaysiana 39(6)(2010): 981–987

Discharge Based Processing Systems for Nitric Oxide Remediation

(Sistem Pemprosesan Berasaskan Nyahcas untuk Pemulihan Nitrik Oksida)

S.A. Hashim & C.S. Wong*

Plasma Research Laboratory, Physics Department, Faculty of Science

University of Malaya, 50603 Kuala Lumpur, Malaysia

M.R. Abas

Department of Chemistry, Faculty of Science

University of Malaya, 50603 Kuala Lumpur, Malaysia

K.Z. Hj. Dahlan

Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor, Malaysia

Received: 21 October 2009 / Accepted: 4 March 2010

ABSTRACT

An electron beam (EB) flue gas test rig and a dielectric barrier discharge (DBD) reactor were tested for the removal of nitric oxide (NO) from gas stream in separate experiments. In both systems, energised electrons were used to produce radicals that reacted with the pollutants. The EB system was a laboratory scale test rig used to treat emission from a diesel run generator. At 1.0 MeV and 10 mA more than 90% NO removal from flue gases flowing at 120 Nm³/h can be achieved. For higher removal percentage, higher beam current was required. In a related effort, a table top, two tubes DBD reactor was used to process bottled gases containing 106 ppm NO. Total removal (>99%) was achieved when the inlet gas contained only NO and N₂. Additional SO₂ in the in let gas stream lowered the removal rate but was overcame by scaling up the system to 10 DBD tubes. The system was operated with input AC voltage of 35 kV peak to peak. In the EB treatment system, the amount of NO₂ increased at high beam current, showing that the NO was also oxidised in the process. Whereas in the DBD reactor, the amount of NO₂ remained insignificant throughout the process. This leads to the conclusion that the DBD reactor is capable of producing total removal of NO. This is highly desirable as post treatment will not be necessary.

Keywords: Dielectric barrier discharge; electron beam; nitric oxide

ABSTRAK

Kajian terhadap penghapusan nitrik oksida (NO) menggunakan teknik alur elektron (EB) dan nyahcas dielektrik berpenghadang telah dijalankan secara berasingan. Kedua-dua sistem ini menghasilkan elektron bertenaga tinggi untuk menghasilkan radikal yang bertindak balas dengan bahan pencemar. Sistem alur electron tersebut adalah binaan skala makmal yang digunakan untuk merawat gas tercemar yang terhasil daripada sebuah generator disel. Pada 1.0 MeV dan 10 mA, lebih 90% NO berupaya dinyahkan dari gas tercemar yang mengalir dengan kadar 120 Nm³/j. Arus bim yang lebih tinggi diperlukan untuk mencapai tahap penghapusan yang lebih tinggi. Dalam kajian lain yang berkaitan, sebuah reaktor 2 tiub DBD digunakan untuk memproses gas dari selinder yang mengandungi NO dengan kepekatan 106 ppm. Penghapusan sepenuhnya (>99%) telah dicapai apabila gas masukan mengandungi hanya NO dan N2. SO₂ tambahan pada gas masukan menyebabkan kadar pengenyahanan susut tetapi ini dapat diatasi dengan menambah bilangan tiub kepada 10. Sistem ini beroperasi pada voltan AC 35 kV puncak ke puncak. Bagi sistem menggunakan EB, didapati kepekatan gas nitrik dioksida (NO₂) meningkat pada arus bim tinggi, menandakan NO telah teroksida semasa proses berlaku. Di dalam sistem DBD bagaimanapun, kepekatan NO₂ tidak menunjukkan peningkatan yang ketara sepanjang proses. Ini menunjukkan bahawa sistem DBD tersebut mampu menyahkan NO secara menyeluruh tanpa keperluan rawatan susulan.

Kata kunci: Alur electron; nitrik oksida; nyahcas dielektrik berpenghadang

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*Corresponding author; email: cswong@um.edu.my