The use of Computational Fluid Dynamic modelling ( · PDF fileThe use of Computational Fluid Dynamic modelling (CFD) ... Scenario •Boundary types and ... PSV opening • Short transient

The use of Computational Fluid Dynamic modelling

(CFD) to optimise safety design in process plantsMarco Pontiggia1, Marco Gattuso2, Hulya Aras3, Giovanni Uguccioni1

(1) D’Appolonia S.p.A. – via Martiri di Cefalonia 2, 20097 – San Donato Milanese (MI) – Italy

(2) D'Appolonia S.p.A. - via Farabola Est 32, 55049 Viareggio (LU) – Italy

(3) D'Appolonia Müh. Tic. Ltd. Şti. Değirmen Sok. Nida Kule İş Merkezi No:18 Kat:9 Kozyatağı 34742 İstanbul-

Türkiye

[email protected]. International

Process Safety

Symposium and Exhibition

Summary

• Introduction

• CFD approach description

• Case #1 – Outdoor Toxic gas dispersion

• Case #2 – Indoor Toxic gas dispersion

• Case #3 – Flammable gas dispersion, mitigation design

• Conclusions


Process Safety


MumbaiAbu dhabi

Bucharest

Istanbul

Leuvren

Basra

Maputo

Washington DC

Cairo

Saint Petersburg

Beijing

Seoul

Rotterdam

Montevideo

Durban

D’Appolonia

2014 Project Countries

A Company belonging to the RINA Group of Italy providing

engineering and consultancy services to Clients worldwide,

through a network of Project offices and Local companies,

including Turkey (D’Appolonia Müh. Tic. Ltd in Istanbul)

Geosciences

Environment & Permitting

Health, Safety and Loss Prevention

Simulation & Modeling

Concept, Feasibility & Design

Project Management Consulting

Operation and Maintenance

Asset Integrity Management (AIM+)

D’Appolonia Main Services in the Process sector

D’Appolonia Process Safety services

LOSS PREVENTION – QRA - SAFETY CASES - SIL - HAZARDOUS AREAS

CLASSIFICATION - SAFETY CRITICAL ELEMENTS – FIRE PROTECTION STUDIES –

GAS & LIQUID DISPERSION SIMULATION - 3D CONSEQUENCE MODELING –

HUMAN FACTOR ANALYSES

HSE MANAGEMENT - EMERGENCY PLANNING - ACCIDENT INVESTIGATIONS -

HAZOP - HAZID - RELIABILITY STUDIES (RAM) - AVAILABILITY ANALYSES -

BUSINESS CONTINUITY - OCCUPATIONAL HEALTH - TRAINING – AUDITS

Introduction

General

The tool should besuitable for the widestrange of applications

Accurate

The tool should be ableto describe the

phenomena

Economic

The tool should be low time and resources

consuming

CFD Tools

• 3D modelling, • Full 3D meshing• Equivalent

porosity

• Wide application range

• Good accuracy even in geometrically complex environment

• Large computational time

Integral models

• Low resource consuming

• One dimensional modeling

• Roughness height for geometry representation

• Large overestimation of damage distances are possible


Process Safety


INTRODUCTION

CFD approach

• 3D model import or construction

• Mesh design

Geometry

• Hazardousmaterial

• Source termcharacterization

Scenario• Boundary types

and characterization

• Model tuning

Boundaries

• Most effectivemodel selection

• Convergencecriteria

Calculation• Post processing

tools

• Resultsinterpretation

Results

Open Issues• Lack of data• 3D format compatibility• Data corruption• Level of detail

New methodology• Easy-accessible data• Customizable level of

detail• Fast geometry building

Dose routine implementation

ProbitModified k-ε for

atmospheric turbulence


Process Safety


CHLORINE RELEASE

(IDLH = 10 PPM)

OPERATIVE CONDITIONS:

3 BARG, 50 °C

HOLE SIZE: 60 MM


Process Safety


CASE #1

CASE #1 - Problem


Process Safety


Simple analytical models for consequence assessment provide

very high danger distance s (approx 7 km to IDLH value, 10

ppm and approx 700 m to the 2,5% fatality probability.

Major and costly plant modifications could be required by

Authorities in charge of approving the plant safety report if

this danger distances were confirmed.

A more detailed and realistic modeling was required to

consider the effect on the gas dispersion of local terrain

condition.

CHLORINE RELEASE

(IDLH = 10 PPM)

OPERATIVE CONDITIONS: 3 BARG, 50 °C

HOLE SIZE: 60 MM

CASE #1 SET UP –

Geometry and Release

Earthwork (3m)

Wood (20m)

Plant (5-15m)

Release point

StepDuration

[s]Velocity

[m/s]Mass flowrate

[kg/s]

1 180 286 3.3

2 30 276 2.8

3 45 244 1.9

4 45 129 0.7

5 10 95 0.5


Process Safety


Case 1

GEOMETRY BUILDING

Shuttle Radar Topography Mission: 90 m resolution cartesian elevation map

Geo-referenced aerial photograph

TERRAIN OBSTACLES


Process Safety


• Wind speed 2 m/s,

Pasquill class F

• ASsM for atmospheric

profiles tuning

• North-West: minimum

slope, open field

• North: Increasing terrain

elevation, largest

obstacle downwind the

release

• South: Directed towards a

a valley, obstacles upwind

with respect to release

point

CASE #1 SET UP – Wind

Direction

North-West North

South


Process Safety


Strong recirculation

caused by plant

structures

Shifting in release point

(chlorine release takes

place from the building

wake)

Shifting in plume

direction due to terrain

slope

CASE #1 – Results

Wind to NW


Process Safety


Strong recirculation caused

by plant structures

Wood weakly influences

chlorine cloud at 10 ppm

Wood strongly influences

Probit values, since they

involves higher chlorine

concentrations

Terrain slope influences

chlorine plume direction

CASE #1– Results

Wind to N


Process Safety


CASE #1– Wind to N

Detail


Process Safety


Strong recirculation caused by plant

structures

Upwind obstacles (wood and terrain

slope) strongly enhance turbulence and

recirculation

The valley further increase chlorine

mixing with fresh air thus reducing IDLH

and Probit distances

CASE #1– Results

Wind to S


Process Safety


CASE #1 – Results

Wind direction

IDLHVulnerability

0.0035%Vulnerability

0.15%Vulnerability

2.5%

North-West 3480 721 472 309

North 2840 303 267 158

South 2110 289 186 103

AnalyticalModel

6615 1588 1023 646

Wind direction

IDLHVulnerability

(average)

North-West 47% 52%

North 57% 76%

South 68% 82%

Dam

age

dis

tan

ces

Red

uct

ion

in

dam

age

dis

tan

ces


Process Safety


CASE #1 - Conclusions


Process Safety


Authorities were satisfied that the reference accidental scenario

was not able to reach the huge distances predicted by analytical

models.

Realistic emergency plans could be developed.

Plant operation was granted.

CASE #2 - Problem


Process Safety


PSVs of a series of reactors inside a building discharge a

solution of Ammonia (NH3) inside a collection open drain

outside the building.

In case of a release, can ammonia recirculate inside the

building, causing danger to the operators inside?

Shall any design modification or specific operating procedure

be developed to ensure safety or personnel, and if so which

one?

CASE #2 – Description

1 3

2

• Ammonia release following a PSV opening

• Short transient (about 30 seconds)

• Three release points

• Effects of geometry heavilyinfluences release and dispersion

• Target is to identify potentialtoxic risk for people working in the facility

• Toxic effect calculated withprobit approach


Process Safety


CASE #2 – Geometry

detail

A B

C D


Process Safety


CASE #2 – Screenshots


Process Safety


Release Point 1

Release Point 3

CASE #2 – Release point 3


Process Safety


CASE #2 – Screenshots


Process Safety


Level 20 m

20 m

After 30 s

After 45 s

Release Point 1

Level 24 m

CASE #2 – Relase point 3


Process Safety




Process Safety


The three dimensional simulation of the release allowed to

assess the maximum NH3 concentration inside the building

(between 600 and 1200 ppm) and the time behaviour of the

NH3 cloud.

On the basis of these results, operating procedures for the

entrance of personnel at +20 and +24m levels were defined,

to ensure risk to personnel within safe limits.

Acceptability of the PSV and building arrangements was

therefore confirmed.

Case #3 - Description


Process Safety


For the project of an underground gas storage and

associated pipeline and compressor station in Italy, the

Authorities required to design a shelter around the filtering

and measuring station, to ensure protection to nearby

historical buildings and future industrial buildings in case of

natural gas accidental release from a leak.

The shelter needed not to be enclosed, and the optimum

design of wall height needed to be assessed.

Case #3 - Description

1.1 m

1.1 m

2.2 m 7.0 m Receiving traps

Case 1

Case 2

Wind Wind Wind Wind

• Flammable release fromlaunching trap potentiallyreaching nearby urban areas

• Two release directions

• Two design configurations

• Design mitigation (wall) toreduce damage distances

• Steady-state simulation


Process Safety


Case #3 - Geometry

Total height: 3m

Above ground: 3m

Total height: 3m

Above ground: 2m

Underground: 1m

A B


Process Safety


Case #3 - Results

South East

Ab

ove

gro

un

d

1m

be

low

gro

und

26 m

44 m 110 m

146 m

68 m

190 m


Process Safety


The three dimensional simulation of the

barrier effect allowed to design a

protection system sufficient to ensure

protection of the sensible targets

around.

On the basis of these results, the

Authorities granted building permit to

the plant.



Process Safety


CFD Modeling allows to analyze accidental

scenarios in a realistic and accurate way,

avoiding the risks of overdesigning

protection systems and overestimating

accident consequences.

The benefit of a CFD approach, from the

economic and authorization point of view,

are evident.

These tools require skills and competency

to be run, and the time and cost

associated can be significant. There use is

recommended whenever simpler analytical

tools can not provide the detail of results

required by the specific case

Conclusions


Process Safety


General

The tool shouldbe suitable for

the widest rangeof applications

Accurate

The tool shouldbe able to

describe the phenomena

Economic

The tool shouldbe low time

and resourcesconsuming

Thank you


Process Safety


Documents

The use of Computational Fluid Dynamic modelling ( · PDF fileThe use of Computational Fluid Dynamic modelling (CFD) ... Scenario •Boundary types and ... PSV opening • Short transient