| | SLO | ENG | Cookies and privacy

Bigger font | Smaller font

Show document

Title:Model zgorevanja trdnih odpadkov na rešetki
Authors:Rajh, Boštjan (Author)
Samec, Niko (Mentor) More about this mentor... New window
Hriberšek, Matjaž (Co-mentor)
Files:.pdf DOK_Rajh_Bostjan_2014.pdf (26,96 MB)
MD5: DA71AF6E1DA1C9D7B6A4651DF7AEF9CE
 
Language:Slovenian
Work type:Dissertation (m)
Typology:2.08 - Doctoral Dissertation
Organization:FS - Faculty of Mechanical Engineering
Abstract:V doktorskem delu je predstavljen model za zgorevanje trdnih odpadkov na rešetki. Modeliranje trdnih odpadkov na rešetki je sestavljeno iz dveh delov: modeliranje pretvorbe trdnega goriva v plinasto fazo na rešetki s pomočjo ustreznega ravnotežnega modela in numerična simulacija plinaste faze zgorevanja nad plastjo trdnega goriva s pomočjo računalniške dinamike tekočin (RDT). Oba dela sta med seboj neposredno povezana preko sestave sinteznega plina in sevalnega toplotnega toka. Predstavljen pristop modeliranja zahteva medsebojno izmenjavo podatkov med obema modeloma, dokler se podatki obeh modelov ne uskladijo oz. ni bistvene spremembe, t.j. med sinteznim plinom, ki zapušča plast trdnega goriva in sevalnim toplotnim tokom, ki prihaja na samo plast. Pretvorba trdnih odpadkov v plinasto fazo na rešetki je bila modelirana s pomočjo lastno razvitega empiričnega 1D ravnotežnega modela, ki temelji na vhodnih podatkih kot so: količina in sestava trdnih odpadkov, količina primarnega zraka, ki se dodatno pomeša še z recirkuliranimi dimnimi plini pod rešetko in sevalnim toplotnim tokom na vrhu plasti trdnega goriva. Ravnotežni model na podlagi vhodnih podatkov predvidi ustrezne robne pogoje na medfazni površini trdnega goriva in plinaste faze kot je sestava (O2, H2O, CO, volatili) temperatura in hitrost sinteznega plina vzdolž rešetke. Pridobljeni robni pogoji v okviru ravnotežnega modela predstavljajo vstopne robne pogoje za izvedbo simulacije plinaste faze zgorevanja. Numerična simulacija je bila narejena s pomočjo komercialnega paketa RDT ANSYS CFX z uporabo ustreznih numeričnih modelov zgorevanja. Z vidika validacije numeričnega modela je bila na različnih mestih znotraj kurišča narejena primerjava temperature z eksperimentalno pridobljenimi podatki. Narejena analiza s pomočjo RDT razkriva detajlno mešanje in karakteristike zgorevanja v realni kurilni napravi z rešetko in nudi možnost poiskati ustrezne rešitve na kakšen način jo optimizirati kot tudi kako izboljšati obratovanje takšnih naprav za energijsko izrabo odpadkov (EIO) z namenom doseganja boljšega izkoristka. Rezultati so pokazali, da neupoštevanje učinka vzgona lahko povzroči bistvene napake v numeričnih rezultatih. Izkazalo se je, da je v industriji mogoče uporabiti RDT kot osnovno orodje za optimizacijo takšnih objektov za EIO glede na številne kritične faktorje kot tudi, na kakšen način učinkovito optimizirati takšen sistem za namen boljšega obratovanja.
Keywords:Pretvorba trdnega goriva, trdni odpadki, modeliranje zgorevanja v plasti, ravnotežni model, kurilna naprava z rešetko, zgorevanje, računalniška dinamika tekočin (RDT)
Year of publishing:2014
Publisher:B. Rajh]
Source:[Maribor
UDC:662.61:628.474(043.3)
COBISS_ID:277251840 New window
NUK URN:URN:SI:UM:DK:PLVYYZO2
Views:1619
Downloads:205
Metadata:XML RDF-CHPDL DC-XML DC-RDF
Categories:KTFMB - FS
:
  
Average score:(0 votes)
Your score:Voting is allowed only for logged in users.
Share:AddThis
AddThis uses cookies that require your consent. Edit consent...

Hover the mouse pointer over a document title to show the abstract or click on the title to get all document metadata.

Secondary language

Language:English
Title:Waste combustion model on a grate
Abstract:In this work model for waste combustion on a grate is presented. Modeling of waste combustion in a grate-firing boiler consists of two parts: modeling of waste conversion in the fuel bed on the grate with suitable bed model and CFD simulation of gas phase combustion in the freeboard. These two processes are strongly coupled by the combustion gas leaving the fuel bed into the freeboard and the radiative heat flux emitted by the flame and furnace walls onto the fuel bed. The presented coupled modeling methodology needs to iteratively switch between the in-bed fuel conversion modeling and the freeboard CFD simulation, until there is no substantial change in either the combustion gas leaving the fuel bed or the radiative heat flux incident onto the fuel bed. The waste conversion in the fuel bed is modeled by own developed empirical 1D bed model, based on the feeding rate and composition of the waste, the flux of the primary air which is mixed with recirculated flue gases from beneath the grates and the incident radiative heat flux at the top of the fuel bed. The bed model provides profiles of temperature, species concentrations and velocity of the gas leaving the fuel bed into the freeboard, which serve as the grate inlet conditions for the freeboard CFD simulation. The 3D CFD simulation is done using commercial package ANSYS CFX with using suitable numerical models for gas phase combustion. As a validation effort, the temperature profiles at a number of ports in the furnace are measured and the experimental results are compared with the CFD predictions. The CFD analysis reveals the detailed mixing and combustion characteristics in the waste wood-fired furnace, pinpointing how to improve the design and operation in order to achieve better WtE efficiency. The results also show that neglecting buoyancy effects may lead to appreciable errors. It turned out it is possible to use CFD in industry as a basic design tool to optimize the WtE plant and their boiler design with respect to a large number of critical factors, as well as to shed lights on how to effectively optimize the grate-firing system for better performance.
Keywords:Solid fuel conversion, Solid Waste, Bed Combustion Modelling, Bed Model, Grate-fired burning device, Combustion, Computational Fluid Dynamics (CFD)


Comments

Leave comment

You have to log in to leave a comment.

Comments (0)
0 - 0 / 0
 
There are no comments!

Back
Logos of partners University of Maribor University of Ljubljana University of Primorska University of Nova Gorica