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Emission control in urea plants in normal operation and upset cases –why so many different solutions?Martina Schmitz – Athens, 20 – 23 February 2012

Emission control in urea plants20-23 Febr 2012Nitrogen + Syngas, M. Schmitz

Table of Content

1. Introduction

2. Emissions during normal operation

3. Emissions from tank vents and safety valves

4. Emergency releases

5. Case studies

6. Résumé

Emission Control in Urea PlantsTable of Content


Emissions during Normal OperationInternational Requirements for Ammonia Emissions

IFC – International Finance Corporation (World Bank Group)

Granulation Unit Prilling Unit

50 mg/Nm3 50 mg/Nm3

EFMA – European Fertilizer Manufacturer Association

Granulation Unit Prilling Unit Vents

50 mg/Nm3 50 mg/Nm3 4 kg/h

0.25 kg/t 0.5 kg/t 0.06 kg/t


1

Air from granulator

Steam condensate

Process water

LP Absorber

Atm Absorber

to Processcondensate

tank

Off gas from evaporation

UREA SYNTHESIS VENTS

UREA GRANULATION VENT

Granulator Scrubber

Bleed to evaporation

Processwater

Synthesis off-gas

Emissions during Normal OperationEmission Points

Total : 4 - 6 kg/h NH3 80 – 90 kg/h NH3


2

Granulator Scrubber

Weak urea solution

Air from granulator

AN- or AS-solution

Nitric or sulphuric acid

Process water

Emissions during Normal OperationAcidic Scrubbing in Granulation Plant

Acidic Part

Dust Part


Nitric acid + NH3 -> Ammonium nitrate (AN) solution

Sulphuric acid + NH3 -> Ammonium sulphate (AS) solution

Liquid Fertilizer AS crystals or pellets Incorporation in granules

Liquid Fertilizer UAN solution

Emissions during Normal OperationAcidic Scrubbing -> Purge Solution


1

Granulator Scrubber

Acidic part

Dust part

Solution TankAcid TankSolution purge

Emissions during Normal OperationAcidic Scrubbing in Granulation Plant - Requirements


3

Atm Absorber

LP Absorber

Acidic Scrubber

Nitric or sulphuric acid

AN- / AS-solution

Emissions during Normal OperationAcidic Scrubbing for Synthesis Vents


3

Atm Absorber

LP Absorber

Emissions during Normal OperationFlaring for Synthesis Vents

Supportgas

Flare

NOx

Nitrogen purge

Nitrogen purge


3

Atm Absorber

LP Absorber

Emissions during Normal OperationFlaring for Synthesis Vents - Consequences

Flare

NOx

NOx compared to NH3 has a negative environmental balance: Global warming potential Tropospheric ozone-forming potential Ozone-depletion

Supportgas

Nitrogen purge

Nitrogen purge


IFC – International Finance Corporation (World Bank Group)

This requirement only applies to 95 % of the time that the plant is operating

Granulation Unit Prilling Unit

50 mg/Nm3 50 mg/Nm3

EFMA – European Fertilizer Manufacturer Association

Connection of tank vents to the plant main stack or other safe location

Connection of ammonia pump safety relief valves to a flare

Emissions from Tank Vents and Safety ValvesInternational Requirements


Vents from tanks Vent stack Acidic scrubbing Flaring

Safety valves ammonia pump Flaring

Safety valves carbamate Avoidance of PSV (design)

Emissions from Tank Vents and Safety ValvesMitigating the Consequences


Emissions from Tank Vents and Safety ValvesMain Safety Valves in Urea Plant

Rectifyingcolumn

Reactor

NH3

CO2

Stripper

Pool Condenser

HP Scrubber

Presenter

Presentation Notes

In the rare case that the safety valves blow off on the reactor, a separator provided with water sprayers is installed. Special care has to be taken for the blow off lines in order to avoid any crystallisation risk. The separated liquid runs into the urea solution tank; the gases are ventet to a safe location. In case of rupture disc breakthrough gases and liquids are routed into a second dedicated separator, also provided with water sprayers header for decrease of ammonia emission and dilution of the liquid phase. The gases are directed via the stack to atmosphere, while liquids are collected in an additional dedicated tank. In the extremely rare case of tube rupture it has to be decided, where the tank content will be directed; either into the urea solution tank or into the ammonia water tank.


Rectifyingcolumn

Reactor

NH3

CO2

Stripper

Pool Condenser

PS

PS

PS

PS

PS

PS

Emissions from Tank Vents and Safety ValvesMain Safety Valves in Urea Plant

HP Scrubber

Presenter

Presentation Notes

In the rare case that the safety valves blow off on the reactor, a separator provided with water sprayers is installed. Special care has to be taken for the blow off lines in order to avoid any crystallisation risk. The separated liquid runs into the urea solution tank; the gases are ventet to a safe location. In case of rupture disc breakthrough gases and liquids are routed into a second dedicated separator, also provided with water sprayers header for decrease of ammonia emission and dilution of the liquid phase. The gases are directed via the stack to atmosphere, while liquids are collected in an additional dedicated tank. In the extremely rare case of tube rupture it has to be decided, where the tank content will be directed; either into the urea solution tank or into the ammonia water tank.


Vents from tanks Vent stack Acidic scrubbing Flaring

Safety valves ammonia pump Flaring

Safety valves carbamate Avoidance of PSV (design) Avoidance of blowing (pressure switches) Vent stack Flaring

Emissions from Tank Vents and Safety ValvesOverview Mitigating the Consequences


No international standards available, but neighbouring inhabitants? areas with frequent emissions?

local authority requirements or company policy limits

Event rare, but impact serious -> Risk evaluation

Emergency Release


Risk = Frequency x Consequence

Risk Ranking by

Risk Matrix LOPA (Layer Of Protection Analysis)

Emergency ReleaseRisk – Definition and Ranking


4

Stripper

Emergency Separator

Pool Condenser

HP Scrubber

Collection Tank

Emergency Release Tube Rupture - Separator System


4

Stripper

Pool Condenser

HP Scrubber

Collection Tank

Emergency Release Tube Rupture - Absorber System

Emergency Absorber

water


4

Stripper

Pool Condenser

HP Scrubber

Collection Tank

Emergency Release Tube Rupture - Flare System Emergency

Flare


3

Case Studies‚Zero Emission‘ Flaring System installed in Fertil Plant, Abu Dhabi

Supportgas

LP Absorber

Flare

N2

LP AbsorberProcess water

Processwater

NH3

Steam

Supportgas

Ammonia Flare

N2

Condensate

Collection tank

Tank vents

Atm AbsorberN2

Process water

VentFlare

Supportgas

Emergency Flare

Buffer tanksPSVs, RD

N2

Processwater

Processwater Process

water


3

Atm Absorber

LP Absorber

Acidic Scrubber

Nitric acid

AN solution

Case Studies Acidic Scrubbing installed in Yara Plant, The Netherlands

< 30 mg/Nm3


PRU-999 04/00

Case StudiesEmergency System installed in Yara Plant, The Netherlands

Emergency Absorber

Stripper

HP Scrubber

Urea Sol. Tank

Water Tank

AI

AI

Pool Condenser

AI

ConsumersTurbine

Vent


PRU-999 04/00

Case StudiesEmergency System installed in Safco 4 Plant, Saudi Arabia

Emergency Separator

Stripper

HP Scrubber

CollectionTank

Pool Condenser

water

ConsumersTurbine

Vent

Any questions?

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