Chulalongkorn University Theses and Dissertations (Chula ETD)

Other Title (Parallel Title in Other Language of ETD)

การออกแบบเครื่องปฏิกรณ์โดยบูรณาการกระบวนการดูดซับและการออกซิเดชันด้วยแสงเพื่อการกำจัดสารประกอบอินทรีย์ระเหยง่าย (VOC) จากกระแสก๊าซที่ปนเปื้อนของสถานที่จัดเก็บในอุตสาหกรรมปิโตรเคมี

Year (A.D.)

2023

Document Type

Thesis

First Advisor

Pisut Painmanakul

Second Advisor

Kritchart Wongwailikhit

Faculty/College

Faculty of Engineering (คณะวิศวกรรมศาสตร์)

Department (if any)

Department of Environmental Engineering (ภาควิชาวิศวกรรมสิ่งแวดล้อม)

Degree Name

Doctor of Philosophy

Degree Level

Doctoral Degree

Degree Discipline

Environmental Engineering

DOI

10.58837/CHULA.THE.2023.998

Abstract

Even petrochemical industry plays an important role in meeting the global energy demand, it is also responsible for emitting significant amounts of Volatile Organic Compounds (VOCs), which pose serious environmental and health hazards. In this thesis, we propose an innovative approach to address this issue by designing a multifunctional reactor that integrates absorption and photocatalytic oxidation processes for the removal of VOC from polluted gas streams of storage facilities, during loading, discharging, and cleaning process. This research encompasses four scopes (i) Comparative study of gas-liquid contactors: Bubble Column Reactor (BCR) and internal-loop Airlift Reactor (IL-ALR). The relative effect of reactor’s configuration (i.e., gas diffuser type) and operating conditions (i.e., superficial gas velocity, additional solid media) on bubble hydrodynamic characteristic, liquid mixing behavior, and mass transfer performance were studied. The results of both reactor classes indicated that F-sand, the smallest orifice diffuser, showed the smallest air bubbles (3.14–4.90 mm) compared to other diffusers., followed by C-sand, which was larger about 22–28% on average than F-sand. IL-ALR exhibited a better ability to maintain smaller bubbles than BCR. Moreover, F-sand and C-sand diffusers showed a slower rising velocity through their smaller bubbles and the tiny bubble recirculation in ALR. Using F-sand in ALR, the rising velocity is about 1.60–2.58 dm/s, which is slower than that in BCR about 39–54%. KLa coefficient was estimated in every diffuser and reactor under the varying Vg. Up to 270% higher KLa value was achieved from the use of F-sand and C-sand compared to other types due to their smaller bubbles generated/maintained and longer bubble retention time through slower rising velocity. After adding 15% ring shape plastic media into the reactors with F-sand and C-sand diffusers, a better performance was achieved in terms of KLa coefficient (up to 39%) as well as gas hold-up and liquid mixing. Lastly, IL-ALR also had a larger portion of mixed flow pattern than BCR. This eventually promoted mass transfer by enhancing the mixed flow regime. (ii) Absorption process in IL-ALR gas-liquid contactor: the influencing of additional non-aqueous liquid phase, NAPs (i.e., oily waste, organic solvents, non-ionic surfactant, and mixed emulsion), and optimization of its volume fraction use, on the VOC absorption performance were analyzed in term of absorption ability, mass transfer rate, enhancement factor, and removal efficiency. The results indicated a substantial increase in VOC absorption capacity of selected NAPs compared to water (32.47 mg/L), with values of 46.97 mg/L, 50.45 mg/L, 59.02 mg/L, 79.24 mg/L, and 96.26 mg/L when 5% (v/v) of hydraulic oil, engine oil, silicone, paraffin, and PDMS was added, respectively. The significant variations of KLa in water (3.28 hr-1) and additional NAP/water mixtures, underscoring the negative influence on benzene mass transfer rate. No significant difference among various NAP absorbents, ranging from 1.86 hr-1 to 2.34 hr-1. Enhancement factor values were follows: Hydraulic oil (0.91) < Engine oil (1.03) < Silicone oil (1.30) < Paraffin (1.53) < PDMS (1.7). It is suggested that a 20% (v/v) of PDMS/water mixture provides an optimal VOC absorption efficiency up to 64%. Model predicting of KLa was proposed, showing a high correlation with experimental data. (iii) Photocatalytic Oxidation Process (PCO) for degradation of absorbed VOC in liquid absorbent and unabsorbed VOC in gas phase: Effect of catalyst configuration (i.e., commercial TiO2, coated TiO2 on surface of Raschig ring plastic media, and TiO2 based alumina ball), type of irradiation sources and its power input, photocatalyst dose, and media loading were examined in term of VOC degradation efficiency. 5TPcB-TiO2 photocatalyst class with 15% (v/v) loading, combined with the UVC-12W of irradiation source, resulted a highest VOC degradation efficiency in aqueous solution up to 70%, which was significantly superior to other conditions. Moreover, kinetic of benzene degradation in aqueous solution at different initial concentration of 10 – 150 mg/L were analyzed. Degradation efficiency distributes similar trend curve. Moreover, the degradation of unabsorbed VOC with low concentration were studied in an immobilized annular tube reactor at the optimal conditions (i.e., UVC and 5TPcB-TiO2 class). VOC concentration, gas retention time and photocatalyst recycle test were investigated in batch and continuous conditions. The result in batch operation suggests that 2 min of gas retention time is an optimum condition (less time and high efficiency) for the degradation efficiency. Moreover, VOC concentration is more important for maintaining high removal efficiencies in the designed photocatalytic reactor. The recycle test of selective photocatalyst was investigated for both liquid and gas experiments, it shows the remaining high efficiency and durability toward degraded VOC in both mediums aqueous and gas phases. (iv) A hybrid reactor prototype by integrating absorption and photocatalytic oxidation processes: This integrated design aims to provide a comprehensive and efficient solution for the removal of VOC from polluted gas streams in petrochemical storage facilities, ensuring compliance with environmental regulations and standards.

Other Abstract (Other language abstract of ETD)

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