Methanol Plant Safety Experiences in the last Twenty Years

Methanol Plant Safety

If it can go wrong – it will If something looks odd – it is Apparent safe systems can fail Issues include

• Metal dusting • Methanol or hydrogen fires • Intent changes • Methanation • “Safe Systems”

Where and what are the Hazards Reformer

H2, Fire & Heat

Converter Pressure,

temperature and H2

Distillation Flammable Inventory

Storage Flammable Inventory

Compression Pressure, H2

HPS, Machines

Before we even get started

South American Methanol Plant Welding plate to storage tank structure

• Should use butt weld – but initially tack weld • Wind broke weld – plate flew off • Killed welder

Working at height • Should be tied off • Workers found this inconvenient so did not • Fell 5 metre and died – two incidents

Hydrogen and Fires

S.E Asian Methanol Plant Feed-steam heater downstream of WHB Reformer effluent At 450-530°C, 19 bara Known metal dusting problem

• Ferrules in tubes failing • Channel and end refractory clad

Hydrogen and Fires

Hot summer day – operator on a bike Observed heat haze

Hydrogen and Fires

From ground to 6’ higher than normal Is this okay ?

No !

• Exchanger end thinned by metal dusting • Failed catastrophically due to internal pressure • Syn gas (70% dry H2) released • Caused fire • Closer to home – Gulf Coast Methanol Plant

Methanol Fires

Methanol is very flammable Product stored in large quantities

• Around 20,000-60,000 m³ • Or 300-900 TJ of energy • Or 80-240 ton of TNT

Methanol Fires

South American Methanol Plant Welding on a product storage tank Explosion and subsequent fire People killed Fire left to burn out Water used to cool adjacent tanks 20,000 m³ product destroyed (US$ 4m)

Road Tanker Fires

Intent Changes

Plant and equipment design for specific rate and duty

Do small and independent changes made to a plant affect design intent ?

Yes !

• SE Asian Methanol Plant – capacity 2,500 raised to 2,750 mtpd • Design intent change ?

Yes !

Intent Changes

Two relief valves (R size) at end of syn gas cooling train

Designed to relieve at 2,500 mtpd Discrete sizing – could handle 2,600 mtpd Change one to large S size – simple ?

No ! • Required stress analysis • Showed additional pipe support and structure required

Nickel Carbonyl

Formed when Ni exposed to CO, 40-240°C US OSHA limit 1ppb, at 1 bara need 100

ppm CO Colourless liquid – less dense than H2O High vapour pressure at ambient Forms black flame (Ni) Can lead to chemical pneumonitis &

pulmonary fibrosis and Death

Nickel Carbonyl A Gulf Coast Event

Plant shut down SOP followed Flare went black on restart – Stopped ! Found two levels in external LI Personnel exposed to Ni[CO]4 when

draining LI out Five hospitalised – one for many months CO import valve left open – CO to

reformer

Nickel Carbonyl Prevention

Test for low levels Purge till CO less than 10 ppm Use long line breathers et al if personnel

are to be potentially exposed Stringent decontamination Not just on methanol plants

Asian Converter Failure

1992 Asian converter failed “UA” higher than expected Bed inlet T raised 210 to 240 to 300°C

• Some bed T > vessel design T (335°C) On trip bed T > 450°C High water levels

Asian Converter Failure

Vessel failed 100 ton vessel moved 100 m Analysis indicated peak T of 600°C+ Methanol syn limited to ~330°C High water content indicated methanation Confirmed by high methane level SOP modifications

Inert Balls - Surely they can not cause Problems

Yes they can If they get into the wrong place !

Cooling Water Systems Are They Safe ?

CW systems run at low pressure • Around 2-3 bara

Only contains water • Plus low levels of chemicals

Surely this is low hazard and safe ?

No !

Cooling Water Line Failure

Cooling Water Line Failure

Cooling Water Line Failure

CW Lines Missing

1 m³ IBC

Cooling Water Line Failure What happened ?

Crude Cooler

HX-1

HX-2

T-1

Pump-1

Loop Catchpot

Cooling Tower

~ 80 Bar & 65°C 40°C

BurstingDiscsIsolated

Other Issues

Hydrogen embrittlement SCC What other production facilities on site ?

• Gulf Coast Plant – NH3, HCN ….. • European Plant – NH3, HCN, Amines …

CW and BFW chemicals (Cl2) Legionella in CW Towers

Other Issues

O2 line failure (Gulf Coast Plant) High box pressure (South American

Plants) Corrosion of loop air cooler header

(South American Plant) Secondary vessel failure *2 (Asian

Plant) Reformer burn downs – too many to

count

Summary

Many risks on methanol plants Even before start up Hydrogen will always fire Methanol fires are rare but dangerous Nickel carbonyl is a major hazard Methanation can occur in unexpected

places Apparent safe systems are hazardous

Confidential to JM