Dr Shaik M. Salim Nov 2015 Institute of Chemical and Engineering Sciences

Inspiring Creativity and Excellence in Science

Study of reactive chemical hazards

• Dust/aerosol/vapour explosion

• Safe process envelope, Advanced Reaction Onset Detection

• Process safety integration into emerging technologies (e.g. Batch-to-continuous)

Development of tools for risk and process safety evaluation • Safety tools (integrated

tools for process design/evaluation)

• LCI-IS (hybrid) • LCA-safety (hybrid) • Risk assessment

• Infusion of methodologies and technologies within ICES projects (α- and β-testing)

Human factors in safety •Safety perception •Behaviour-based safety •Human-systems interaction

Main Themes of Process Safety @ICES

• Safety capabilities within ICES currently consist of: – Process Safety – Chemical Hazard Characterisation – Risk Assessments and Evaluation – Occupational Safety & Health

A safety case is a document produced by the operator of a facility which: • Identifies the hazards and risks • Describes how the risks are controlled • Describes the safety management system in

place to ensure the controls are effectively and consistently applied.

Basic Process Control Systems

Non-safety Process alarms

Operator Intervention

PREVENTION Safety Critical Process Alarms

Safety Instrumented Systems

MITIGATION

Mechanical Mitigation Systems

Fire and Gas Systems

PLANT EMERGENCY RESPONSE

COMMUNITY EMERGENCY RESPONSE

Process Design

Protecting - Plant Employees Community Environment

Source: HSE, HID Regulatory Model, Safety Management in Major Hazard Industries

Bow-tie model of layers of protection Source: HSE, HID Regulatory Model, Safety Management in Major Hazard Industries

• Inadequate linking between major accident scenarios and the measures provided

• Incomplete arguments as to why an operator believes that all necessary measures (i.e. ALARP) have been taken to prevent or limit the consequences of a major accident.

• Inadequate information Ref: Britton, Trevor. IChemE Symposium Series, Vol. 149, 2003.

Qualitative Analysis (100% scenarios analysed)

Simplified Quantitative Analysis (10-20% of scenarios analysed)

Quantitative Analysis

(1% CPQRA)

Techniques

HAZOP, What-If/Checklist, FMEA

Quantified FMEA, F&EI, CEI

LOPA

Rough estimate with event tree

Event tree, Fault Tree, Human Reliability Analysis

•Saturday 9 July 1976 a bursting disc ruptured on a chemical reactor at the works of the Icmesa Chemical Company at Meda near Seveso •The start of the batch began at 16.00 on Friday 9 July. The batch process was interrupted prior to finishing the final step of removal of ethylene glycol by distillation, due to an Italian law requiring shutdown of plant operations over the weekend.

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•This batch was stopped by isolating the steam, and turning off the stirrer. •A runaway reaction occurred which led to the formation and release of tetrachlorodibenzodioxin (TCDD) •A white cloud drifted from the works and some TCDD settled downwind.

vent pipe

tetrachlorobenzene trichlorophenol tetrachlorodibenzodioxin(TCDD)

• the formation of small quantities of TCDD as a by-product is unavoidable. At a reaction temperature below 180°C the amount formed would be unlikely to exceed 1 ppm of TCP, but with prolonged heating in the temperature range 230±260°C it could increase a thousand-fold. The known decomposition exotherm starts at about 280°C

• There exists two (unknown) slow exotherms. One starts at about 185°C, the other starts at about 255°C

• The residual heat in the jacket then heated the upper layer of the mixture next to the wall to the critical temperature (ca. 180°C), starting a slow runaway decomposition, and after seven hours a rapid runaway reaction ensued when the temperature reached 230°C

• The relief valve eventually opened and 6 tonnes of material (1kg TCDD) were distributed over an area of 18 km2

3.5bar

12bar/188°C

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As we know, There are known knowns. There are things we know we know. We also know There are known unknowns. That is to say We know there are some things We do not know. But there are also unknown unknowns, The ones we don't know We don't know. — Donald Rumsfeld Feb. 12, 2002, Department of Defense news briefing

Known Knowns

Known Unknowns

Unknown Unknowns

The Unknown

It does makes sense…….REALLY!

• Our ultimate aim in SAFETY ASSESSMENT is to minimise the “unknown” hazards so that we do not get a nasty surprise in the form of an accident

Known Knowns

Known Unknowns

Unknown Unknowns

Hazards that have been identified

(usually handled via SOP, training, etc)

Generally known hazards that have yet to be identified (use

tools e.g. HAZOP. chemical hazard characterisation)

Unknown hazards that have not yet

been identified

Philosophically speaking it deals with “Epistemic modal logic” (reasoning about knowledge)

Dust/aerosol/vapour explosion

Hybrid dust-solvent explosions

Nanopowder explosions

Reactive Chemistry

Assessments of desired and Undesired Reactions

Inherently Safer Process

Process safety integration into emerging technologies (e.g. Batch-to-continuous: Reformatsky, Grignard)

Basis of Safety - Assessment

Investigating a possible basis of safety for scaling-up of an interesting/greener chemistry (diazonium intermediated C-H activation)

Thermal hazard assessment of a pharmaceutical API process

Investigation of unexpected polymeric material decomposition

Thermal hazard assessment of a specialty chemical process for local SME

Investigation of runaway reaction for local SME

Dr Shaik Mohamed Salim Institute of Chemical and Engineering Sciences

Process Science & Modelling Division shaik_salim@ices.a-star.edu.sg