Revamps for Ageing Methanol Plants

By Gerard B. Hawkins

Managing Director, CEO

Introduction

This presentation highlights some of the retrofits that can be applied to • Improve efficiency • Increase production

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Introduction

For older methanol plants, efficiency is worse than for a modern plant

To maximize profit must improve either • Plant efficiency • Plant production rate

This presentation highlights some of the retrofits that can be applied to improve efficiency or production

Plant Limitations

Need to address plant limitations, such as • Reformer pressure drop • Maximum tube wall temperature • Coil design temperatures in duct • Fan capacity • Compressor/Circulator limitations • High loop pressure drop • Low carbon efficiency

Basis for Study

Foster Wheeler furnace - 560 tubes Steam to carbon of 3.0

• No saturator Duct heat recovery is feed preheat and

steam raising 100 bar loop with no heat recovery 4 Bed ‘Quench Lozenge Converter’

Reformer Revamps Addition of Secondary

Either in parallel or in series • Parallel has less impact on the main

plant Main plant can run when secondary off line

Allows for optimization of Synthesis Gas composition

Can increase production rate by 23% Require an oxygen plant (10 mt/hr)

Addition of an ATR

Existing

Reformer

NG Preheater NG/Steam Preheater

MUG Cooler

Oxygen Preheater

Steam Drum

MP Boiler

Natural Gas Make Up Gas

Condensate

Addition of a Pre-Reformer

To obtain maximum benefit require reheat of effluent

Can achieve very high preheat and reheat temperature with latest generation of pre-reforming catalyst, which can be operated up to 540°C

Can recover more heat from duct and reduce furnace duty significantly • Must model effect on duct to ensure that existing

demands for heat are fulfilled (HP Steam Raising)

Addition of a Pre-Reformer

MP Steam

Existing Reformer

Natural Gas

Synthesis Gas

Pre-reformer

New Reheat Coil

Addition of Saturator

Recovers heat from loop into front end Maximizes quality and quantity Quantity depends on existing loop

equipment Can use refining column bottoms as

feed water Can feed fusel oil into circuit and

recycle carbon back into process For Base Case up to 40 mt/hr of

steam could be raised in the saturator

Addition of a Saturator

MP Steam

Existing Reformer

Natural Gas

Synthesis Gas

Heater

Saturator

Combustion Air Preheat

Allows for improvement in heat recovery from the duct

Most suitable for top fired furnaces but can be applied to side fired furnaces • Cost is higher due to complexity of ducting

Will reduce fluegas flow and therefore heat available in the duct - must model this carefully

Greater benefit than preheating the fuel gas

Effect of Combustion Air Preheat

600

700

800

900

1000

1100

1200

1300

0 200 400 600Combustion Air Preheat Temperature

NG F

uel R

ate

(km

ol/h

r)

1116

1118

1120

1122

1124

1126

1128

Flue

gas

Flow

(km

ol/h

r)

NG Fuel RateFluegas Flow

Reformer Retube

Can improve production rate by up to 18% • If additional feed gas available • If sufficient capacity on synthesis gas machine

Alternatively can increase exit temperature if exit headers allow • Reduces methane slip • Production rate increased by 3%

Also reduce pressure drop across primary reformer • This partially offsets increased pressure drop in other

front end equipment items

MUG Compressor Converter

Addition of a converter between stages of synthesis gas machine drops flowrate through the machine

Allows for • Reduction in power • Or increased throughput (+5.5%)

whilst maintaining machine power

Addition of Purge Converter

Can use either a Tube Cooled Converter or Steam Raising Converter

Can be single pass or multiple pass • Single pass is cheaper • Production increase of 2% • Multiple pass more expensive but

production increase is greater • Production increase of 3%

Best improvement occurs if more feed gas or CO2 addition is used in conjunction

Purge Converter

MUG

Flash Drum

Tube-cooled Converter

Cooler

Parallel Converter

Installing a parallel steam raising converter allows • Marginal production (1%) increases if no

addition synthesis gas is available • Large increases (4%) if additional

synthesis gas is available either from a front end rate increase or by CO2 addition

Especially beneficial if recycle gas rate is low • Loop pressure drop is decreased and

therefore a higher recycle flow can be achieved

Parallel Converter

MUG

Separator

New Interchanger

Crude

Purge New Steam Raising Converter

Replace Exiting Converter with Steam Raising Converter

Lower operating temperature of a steam raising converter equates to higher end of life activity

With a steam raising converter, all the gas is passed over all of the catalyst

Production rates are therefore higher - in this case 2.1%

If loop is less efficient then production increase will be greater

CO2 Addition to Reformer/Loop If local source of CO2 is available then can

be added to either reformer or the loop Addition to the reformer does mean

synthesis gas composition will be more carbon rich • Potential issues with metal dusting

downstream of the reformer in waste heat boiler

In either case, molecular weight of circulating gas is increased and circulation rate will be reduced • Often this effect is overlooked and in

reality predicted production rates will not be achieved

CO2 Addition to Reformer/Loop There is an optimum amount of CO2

that can be added As more CO2 is added then carbon

efficiency does drop But production steadily increases

• However, the reduction in recycle ratio can be so large that the production rate is reduced

• Effect is worse if recycle ratio is low to start with

CO2 addition to the reformer will produce more incremental methanol per ton of CO2

Effect of CO2 Addition

1250

1300

1350

1400

1450

1500

1550

0 200 400 600

CO2 Addition Rate (kmol/hr)

MeO

H P

rodu

ctio

n (m

tdp)

0

0.5

1

1.5

2

2.5

3

R R

atio Production

R Ratio

Other Options

AGHR in parallel/replacement of WHB H2 recovery when loop is operating below

stiochiometry Ammonia cooling of purge/letdown gases to

recover methanol Water washing of purge/letdown gases to

recover methanol CO2 recovery from fluegas Add CO rich gases Spike feed with higher hydrocarbons Add POx unit

Plant Revamp Methanol – Capacity Increases

What capacity increase is required ?

>15%

Front End Change SC ratio CA preheat Fuel preheat Increase exit temp

<5%

Front End Change catalyst Add pre-reformer

5-15%

Compression/Loop MUG Converter* Chill Syn Gas

Compression/Loop ARC converter* IMC converter* Purge converter* Parallel converter* Catchpot chiller

Front End Parallel secondary Re-tube

Compression/Loop CO2 addition

* - Additional synthesis gas will allow for much bigger increases in capacity

Plant Revamp Methanol – Efficiency Improvements

What efficiency improvement is required ?

>1 GJ/t

Front End Chill syngas MUG converter

<0.1 GJ/t

Front End Fuel gas preheat Saturator Pre-reformer

0.1-1 GJ/t Front End Combustion air preheat

Problems and Pitfalls Contractor and Contract

Must carefully select partners • Must have domain knowledge

Design and operations • Must have correct tools • Must be able to supply correct level of detail

for study Must select appropriate contract type

• LSTK or Reimbursable • Both have advantages and disadvantages

Problems and Pitfalls Modelling Capability

Must use correct tools Model the whole plant using a

flowsheeting package • Must include all unit operations • Must develop a robust base case • Must validate against plant data • Must understand deviations • Then develop the retrofit case

Problems and Pitfalls Retrofit Details

The customer and engineering contractor must determine • Precise scope for retrofit • Responsibilities • Key deliverables • A detailed and consistent design basis • Time scale and milestones • Review schedules

Summarize as Good Project Management

Problems and Pitfalls Design Basis

Engineering contractor must conduct on site visit • Must work with client • Collect representative plant data • Model and understand plant data • Discuss discrepancies and eliminate • Identify bottlenecks • Identify opportunities for improvement

These form the core of the design basis

Problems and Pitfalls HAZOPs and Commissioning

Must use systematic review method to highlight potential problems with retrofit • HAZOPs are a well proven system • Requires time and buy in from all parties • Results as good as quality of people !

Retrofit will change plant parameters • Must update PFDs and P&IDs • Must update operating instructions • Must take additional care during start up

What Can GBHE Catalysts Offer?

Detail catalyst unit operation models such as the industry leading VULCAN REFORMER SIMULATION program • Also models for other catalyst unit

operations Detail non-catalyst unit operation

models such as • Heat exchange programs • Finite Element Analysis • CFD modelling

One stop shop

What Can GBHE Catalysts Offer?

Domain Knowledge • Operations

Many staff have operations background

Troubleshooting clients plants • Design

Many staff have detailed engineering background

Engineers work on design daily Work with leading contractors on front end and detailed design issues

Catalysts

Consulting Services

Domain Knowledge

What Can GBHE Catalysts Offer?

Can supply any level of detail for retrofit

Scoping studies • Front End • What are the best options

Front End Engineering • Flowsheets and design of key components

Detailed Engineering • Design of all components of retrofit

A one stop shop for your revamp requirements

One Stop Shop Case Study Re-tube – Present Model

Plant Operator

Concept Engineer

Tube Supplier

Catalyst Vendor

Tube Installer

Catalyst Handler

No Communication

Detailed Engineer

One Stop Shop Case Study Re-tube – “One Stop Shop” Model

Plant Operator

GBHE Concept Engineer

Tube Supplier

Tube Installer

Catalyst Handler

Detailed Engineer

Seamless Minimum Cost

Maximum Benefit

Case Study How GBHE Catalysts Works

Strong position due to credibility from previous work

Uprate projects • Feasibility Process Uprate study on Naphtha 115%,

130% or 150% cases • FEEP (Front End Engineering Package, what would be

needed?)

115% FEEP adopted • Option evaluations and natural gas feed conversion

Followed by full Engineering Detail Design Also additional design work on Desulpurisation

Design Study

Conclusions

A number of retrofits have been presented that are suitable for application to methanol plants

They address all the key limitations that methanol plants typically suffer from

To take full benefit from some of these retrofits, others may also be required

GBHE Catalysts has all the right expertise and knowledge to develop and design retrofits