investigation of fluid behavior in randomly packed columns ...core.ac.uk/download/pdf/ in the...

Click here to load reader

Post on 15-Jul-2020

0 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Scuola di Ingegneria

    Dipartimento di Ingegneria Civile e Industriale

    Master’s Degree in Chemical Engineering

    Investigation of fluid behavior in randomly packed

    columns using Computed Tomography

    Supervisors:

    Prof. Elisabetta Brunazzi

    Prof. Wolfgang Arlt

    Sebastian Schug, M. Sc.

    Prof. Roberto Mauri

    Candidate:

    Domenico Mangiaracina

    Academic year 2015/2016

  • i

  • ii

    Gran parte del progresso sta nella volontà del progredire.

    Seneca

    Il dizionario è l'unico posto dove successo viene prima di sudore.

    Vince Lombardi

  • iii

  • iv

    Abstract

    University of Pisa - Department of Civil and Industrial Engineering

    Master Thesis in Chemical Engineering

    Investigation of the fluid behavior in randomly packed columns using Computed Tomography

    Domenico Mangiaracina

    The qualitative investigation of the fluid behavior and the quantitative evaluation of

    widespread fluid dynamic parameters like liquid hold-up, wetted area and mass-transfer area

    in a randomly packed column are carried out using Computed Tomography CT, a totally non-

    invasive measuring technique. Despite the huge effort of different researchers, a lack of

    comprehension about the flow field within the packed bed still prevents the development of

    completely satisfying models, that are precisely able to predict these fluid dynamic

    parameters in order to achieve an economically optimized design of the column.

    In the present work, three commercial random packings (Raflux Ring, RMSR and RSR),

    belonging to different generations, are scanned in a 0.1 m diameter column in presence of two

    different systems: water / air and isopropanol /air. The latter is used for the first time in CT

    investigations despite the common industrial applications of these organic compounds. An

    algorithm, previously developed by Schug and Arlt. [1], is applied to compute the profile and

    the integral values of fluid dynamic parameters along the packed bed, highlighting the effect

    of the liquid load (ranged between 2 m3 / m2 h and 70 m3 / m2 h), the gas load (ranged

    between 0 Pa0.5 and 2 Pa0.5), the packing type.

    The main aims of the present work are summarized in two points: firstly, the investigation of

    the effect of the column’s re-packing and on the variance of the fluid dynamic parameters. The

    results show an extremely weak effect of the re-packing of the column, with deviation less

    than 4 % in terms of coefficient of variation for each fluid dynamic parameter. Secondly, these

    parameters are evaluated with an organic liquid (isopropanol) to assess the combined

    influence of significantly different physical properties like viscosity and surface tension. A

    better wettability of the packing and a higher mass-transfer area is recorded. Furthermore, a

    graphical qualitative evaluation of the liquid flow morphology and a successive classification

    of the present liquid structures (films and rivulets) are conducted.

  • v

  • vi

    Contents

    ABSTRACT ......................................................................................................................................................................... IV

    LIST OF FIGURES ................................................................................................................................................................ X

    LIST OF TABLES ........................................................................................................................................................... XVIII

    SYMBOLS .......................................................................................................................................................................... XX

    1. INTRODUCTION ................................................................................................................................................... 1

    1.1 OBJECTIVES AND AIMS ....................................................................................................................................... 1

    1.2 STRUCTURE OF THE THESIS ............................................................................................................................... 2

    2 LITERATURE REVIEW ......................................................................................................................................... 4

    2.1 PACKED COLUMNS .............................................................................................................................................. 4

    2.1.1 OPERATING PRINCIPLES AND PACKING TYPES .................................................................................... 4

    2.1.2 FLUID DYNAMIC PARAMETERS ............................................................................................................. 11

    2.1.2.1 Pressure drop estimation ....................................................................................................... 11

    2.1.2.2 Liquid hold-up ............................................................................................................................ 14

    2.1.2.3 Flow morphology....................................................................................................................... 17

    2.1.2.4 Wetted Area ................................................................................................................................. 19

    2.1.2.5 Mass-transfer Area .................................................................................................................... 19

    2.1.3 MASS-TRANSFER THEORIES AND PACKING HEIGHT DETERMINATION .......................................... 20

    2.1.3.1 Mass-transfer theories ............................................................................................................ 20

    2.1.3.2 Packing Height determination .............................................................................................. 22

    2.1.3.3 Experimental evaluation of wetted and mass-transfer area .................................... 24

    2.1.4 LIQUID MALDISTRIBUTION IN RANDOM PACKINGS ........................................................................... 26

    2.1.4.1 Effect on HETP ............................................................................................................................ 26

    2.1.4.2 Main causes .................................................................................................................................. 27

    2.1.4.3 Liquid maldistribution effects .............................................................................................. 28

    2.2 COMPUTED TOMOGRAPHY ............................................................................................................................... 30

    2.2.1 INTRODUCTION ....................................................................................................................................... 30

  • vii

    2.2.2 OPERATION PRINCIPLE .......................................................................................................................... 31

    2.2.3 X-RAYS - MATTER INTERACTION .......................................................................................................... 32

    2.2.4 HARDWARE: DESCRIPTION OF THE MAIN COMPONENTS .................................................................. 34

    2.2.4.1 Source of X-rays ......................................................................................................................... 35

    2.2.4.2 Detector ......................................................................................................................................... 36

    2.2.4.3 Gantry-System and Computer-System .............................................................................. 36

    2.2.5 IMAGES RECONSTRUCTION .................................................................................................................... 37

    2.3 PREVIOUS INVESTIGATIONS OF PACKED COLUMNS USING CT ...................................................................... 40

    3. MATERIALS AND METHODS ............................................................................................................................. 46

    3.1 EXPERIMENTAL SET-UP.................................................................................................................................... 46

    3.1.1 EXPERIMENTAL SET-UP DESCRIPTION ................................................................................................ 46

    3.1.2 SCANNED PACKING TYPES ..................................................................................................................... 47

    3.1.2.1 Raflux Ring ................................................................................................................................... 48

    3.1.2.2 RSMR (RVT Metal Saddle Ring) ........................................................................................... 48

    3.1.2.3 RSR (Raschig SuperRing) ....................................................................................................... 48

    3.1.3 CUSTOM-DESIGNED CT SYST

View more