The use of Computational Fluid Dynamic modelling (CFD) to optimise - - PowerPoint PPT Presentation

The use of Computational Fluid Dynamic modelling (CFD) to optimise safety design in process plants

Marco 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

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• II. International

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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

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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 be suitable for the widest range of applications

Accurate

The tool should be able to 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
• f damage distances

are possible giovanni.uguccioni@dappolonia.it

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INTRODUCTION CFD approach

• 3D model import
• r construction
• Mesh design

Geometry

• Hazardous

material

• Source term

characterization

Scenario

• Boundary types

and characterization

• Model tuning

Boundaries

• Most effective

model selection

• Convergence

criteria

Calculation

• Post processing

tools

• Results

interpretation

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 Probit Modified k-ε for atmospheric turbulence

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CHLORINE RELEASE (IDLH = 10 PPM) OPERATIVE CONDITIONS: 3 BARG, 50 °C HOLE SIZE: 60 MM

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CASE #1

CASE #1 - Problem

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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

Step Duration [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

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Case 1 GEOMETRY BUILDING

Shuttle Radar Topography Mission: 90 m resolution cartesian elevation map

Geo-referenced aerial photograph

TERRAIN OBSTACLES

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• Wind speed 2 m/s,

Pasquill class F

• ASsM for atmospheric

profiles tuning

• North-West: minimum

slope, open field

• North: Increasing terrain

elevation, largest

• bstacle 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

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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

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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

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CASE #1– Wind to N Detail

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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

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CASE #1 – Results

Wind direction IDLH Vulnerability 0.0035% Vulnerability 0.15% Vulnerability 2.5% North-West 3480 721 472 309 North 2840 303 267 158 South 2110 289 186 103 Analytical Model 6615 1588 1023 646 Wind direction IDLH Vulnerability (average) North-West 47% 52% North 57% 76% South 68% 82%

Damage distances Reduction in damage distances

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CASE #1 - Conclusions

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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

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PSVs of a series of reactors inside a building discharge a solution of Ammonia (NH3) inside a collection open drain

• utside 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

• ne?

CASE #2 – Description

1 3 2

• Ammonia release following a

PSV opening

• Short transient (about 30

seconds)

• Three release points
• Effects of geometry heavily

influences release and dispersion

• Target is to identify potential

toxic risk for people working in the facility

• Toxic effect calculated with

probit approach

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CASE #2 – Geometry detail

A B C D giovanni.uguccioni@dappolonia.it

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CASE #2 – Screenshots

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Release Point 1 Release Point 3

CASE #2 – Release point 3

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CASE #2 – Screenshots

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Level 20 m

20 m

After 30 s After 45 s Release Point 1 Level 24 m

CASE #2 – Relase point 3

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CASE #2 - Conclusions

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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

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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 from

launching trap potentially reaching nearby urban areas

• Two release directions
• Two design configurations
• Design mitigation (wall) to

reduce damage distances

• Steady-state simulation

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Case #3 - Geometry

Total height: 3m Above ground: 3m Total height: 3m Above ground: 2m Underground: 1m

A B

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Case #3 - Results

South East Above ground 1m below ground

26 m 44 m 110 m 146 m 68 m 190 m

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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.

CASE #3 - Conclusions

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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

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• II. International

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General

The tool should be suitable for the widest range

• f applications

Accurate

The tool should be able to describe the phenomena

Economic

The tool should be low time and resources consuming

Thank you

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