April 18, 2023 1

Training Program onBasic Process Engineering Practices

Module – 4A Design Basis

April 18, 2023 2

The Importance of Design Basis

FeasibilityStudy

BasicDesign

EngineeringConstruction

OperationMaintenance

RevampConcept

Concept

The design basis has tremendous impact on all aspects of a project-

Investment and Operating Cost Safety Operability Constructability Maintainability Profitability

The conceptual and feasibility stage help to set up the design basis.

April 18, 2023 3

The Impact of Initial Phase of Design Activities

The development of design basis is often ignored by the owner as well as the engineering consultant.

The conceptual and feasibility stage help to set up the design basis.

Every single line in a design basis should have thought and analysis behind it. A thorough study of key issues are needed to establish a proper design basis.

The graph in the next slide shows the impact of actions taken in early stages of project.

The best cost reduction exercise can be done at the design basis stage itself.

April 18, 2023 4

Concept, Design Basisand Basic Design

The Impact of Initial Phase of Design Activities

April 18, 2023 5

Check List on Important Process Design Basis

1. Project Description

i. Project Nameii. Ownershipiii. Brief Description

2. Plant Capacity Relatedi. Capacityii. Stream Factoriii. Turndown Ratio

3. Location and Site Datai. Location Mapii. Site Mapiii. Site Dataiv. Surrounding Detailsv. Access

4. Raw Material Source and Compositioni. Raw Material Sourceii. Transportation Modeiii. Raw Matl. Composition

5. Productsi. Product Slateii. Product Specificationiii. Product Destinationiv. Dispatch Mode

6. Battery Limit Relatedi. B/L Definitionii. B/L Temp. and Pr.

Raw Material & Products

Utilities

April 18, 2023 6

More on Capacity Related Parameters

Capacity is decided based on market survey and projection, which is part of feasibility study.

Capacity is defined in a number of ways depending on the type of project.

Oilfield- In oilfield it is described by oil production in BPD or MMTPA,

Gas Oil Ratio (e.g. SM3 gas per M3 oil) and water percent. Production profile over field life also is important capacity

parameter.

Refinery-

Crude Processing capacity in BPSD Product Slate

Petrochemical Plants- Often defined by product capacity

April 18, 2023 7

On-Stream Factor

On-Stream factor depends on-

Planned maintenance shutdown requirements. Unplanned shutdowns.

Normally in a complex process plant, 330 days a year is considered a good basis.

Some may require operation for a few months or even a few weeks a year.

But certain critical projects may call for 365 days a year. It is quite common in oil/gas production facilities.

On-Stream factor has influence on the process concept and costs of the project. Let us do an exercise.

April 18, 2023 8

On-Stream Factor - Exercise

A basic scheme for oil and gas production is given below. The owner wants 365 days a year operation. Present a process concept to meet the requirement.

OilDehydration

Pump

Compressor

Oil /LiquidPipeline

M

M

LPSeparator

WaterAtm.

Storage

HPSeparator

Well Fluid

Oil (Liquid)

Natural gas

Water

GasDehydrator

Water Treatment

Water dischargeOr re-injection

Gas toPipeline

April 18, 2023 9

Impact of Site Data on Process Design and Costs

Critical site data for process design are-

Contour diagram

Elevation

Maximum Design Ambient Temperature

Minimum Design Ambient Temperature

Ambient Pressure

Humidity

Wind Direction

Rainfall data

April 18, 2023 10

Case Study- How Contour Affects Cost

The scheme below had to be implemented….

In a hilly terrain like this…. Any advantage of the terrain?

20 M

OilDehydration

Pump

Compressor

Oil /LiquidPipeline

M

M

LPSeparator

(3 bar)

Water

Atm. Storage

600,000 M3

HPSeparator(15 bar)

Well Fluid

Oil (Liquid)

Natural gas

Water

GasDehydrator

Water Treatment

Water dischargeOr re-injection

Gas toPipeline

10 MMTPA

April 18, 2023 11

Case Study- Maximum Design Ambient Temp.

Metrological department gives temperature profile around the year for several years.

Designer should recommend Maximum Design Ambient temperature. In his case, it was too high affecting cooler cost.

TRAYS

PACKING

AirCooler

LPG Feed Propane

Butane

Propane Refrigerant Make-up Plant

Desert Location

Maximum Design Ambient Temp. taken as 50 0C

Required process temperature 55 0C

Turnkey skid mounted supply.

April 18, 2023 12

Importance of Wind Direction-1

Gas Processing Plant producing LPG out of natural gas Wind direction reported 75% times South East to North West Large Flare to be located 90 M away. Where shall you locate the flare stack?

PrevailingWind Direction

April 18, 2023 13

Importance of Wind Direction-2

Bhopal MIC leak was a major disaster. Thousand died or were affected. The operators could save themselves. They knew of prevailing

wind direction. Lesson? Location of a plant dealing with toxic chemical should

be such that there is no habitation in the prevailing wind direction. Also emergency response plan should be in place with involvement of community.

PrevailingWind DirectionLeaked MIC

Operators Escape

April 18, 2023 14

Raw Material and Product Specification

Processing scheme and operating conditions are dictated by product specification.

The plant needs to be designed with some flexibility on raw material and product specifications.

The flexibility need to be spelt out in the design basis. Example-

Range of natural gas composition for a gas processing plant.

Gasoline production facility in a refinery to produce to Indian spec as well as international spec.

April 18, 2023 15

Check List on Important Process Design Basis

1. Project Description

i. Project Nameii. Ownershipiii. Brief Description

2. Plant Capacity Relatedi. Capacityii. Stream Factoriii. Turndown Ratio

3. Location and Site Datai. Location Mapii. Site Mapiii. Site Dataiv. Surrounding Detailsv. Access

4. Raw Material Source and Compositioni. Raw Material Sourceii. Transportation Modeiii. Raw Matl. Composition

5. Productsi. Product Slateii. Product Specificationiii. Product Destinationiv. Dispatch Mode

6. Battery Limit Relatedi. B/L Definitionii. B/L Temp. and Pr.

Raw Material & Products

Utilities

April 18, 2023 16

Check List on Important Process Design Basis Contd..

7. Utility Related

a. Fuel b. Powerc. Steamd. Instrument and Plant Air Raw Water Specification Cooling Water Sea Water Process water

8. Storage and Handling

a. Raw Material Storage Criteriab. Raw Material Receiptc. Product Storage criteriad. Product Dispatche. Intermediate Product Storage

Criteriaf. Chemical Storage Criteriag. Yard Piping

April 18, 2023 17

Check List on Important Process Design Basis Contd..

10. Operation and Maintenance Related

a. Equipment Sparing Philosophyb. Instrumentation and Control Philosophyc. Safety Shutdown Systemsd. Operating Philosophy

9. HSE Related

a. Effluent Discharge Specificationsb. Flaring Philosophyc. Major Effluents Summaryd. Effluent Treatment Requirements

11. Buildings and Misc. Offsites

a. Office b. Maintenance Facilitiesc. Fire Fighting Facilitiesd. Entry Gatee. Control Room

April 18, 2023 18

Important Utility and Offsite Related Points

More than 50% of the investment in a process plant may go to utility and offsite facility.

Utilities contribute to a major share of the operating cost.

Often the client or external agency provides utilities and sets the utility specification.

Ideally for developing a basic design from scratch, as far as possible utility levels and specifications should be floating.

Some examples of key issues in setting utility design basis will be discussed here.

April 18, 2023 19

Cooling Water Recirculation System

Process Streams

T = 30oC

Cooling water supply header

Cooling water return header

T2 = 40oC

Cooling Tower

Cooling Water Pump

T1 = 30oC

April 18, 2023 20

Utility – Cooling Water System Contd.

T1 depends on temperature and humidity. Careful selection of ambient design temperature and humidity is necessary.

∆T (T1-T2) is normally kept around 10 0C in the design basis.

A careful study to set ∆T is necessary because-

• On one hand raising the temperature differential by 2 0C can reduce the circulation of water by 20% and corresponding saving in pump power and pipe size.

• On the other hand, chances of scaling on exchanger tubes go up at higher outlet temperatures.

• Exchanger size increases.

Process engineer and corrosion (water) specialist along with other disciplines can analyze the parameters to arrive at an economic design basis.

April 18, 2023 21

Optimization case on investment and operating cost.

In warm climate, consider air cooler followed by trim cooler.

In cold climate air cooler can be straight winner. In Canada, some process plants have air coolers only.

Availability of water source also can dictate choice.

Utility – Cooling Water vs. Air Cooler

April 18, 2023 22

Optimization between Fuel, Power and Steam is of great importance at today’s energy cost.

Combined cycle power generation and waste heat utilization are key issues.

Cooling Water vs. Air Cooler is also a key issue.

Keeping the utility parameters floating at design basis stages helps in evolving cost saving concepts.

Utility – Key Issue on Design Basis

April 18, 2023 23

Storage has a cost both in terms of investment and inventory cost.

Storage design basis is dictated by-

Internal operational requirements Downstream operators limitations Engineering limitations- what size of tanks? Tanker logistics – requiring operations research studies.

Storage could also be dictated by strategic reasons.

Keeping the utility parameters floating at design basis stages helps in evolving cost saving concepts.

Storage Design Basis

April 18, 2023 24

Unmanned remote operation totally changes instrumentation concept.

Unmanned concept is common in oil and gas production, pipelines, small plants in remote areas.

SCADA with telemetry tele-control concept is utilized in such cases.

Rotating machinery is avoided as far as possible.

For example, remote operated well platforms have solar power instead of generator for instrument power.

Example of Operating Philosophy

April 18, 2023 25

Manned operation in remote location-Simple rugged equipmentSimple instrumentation – consider pneumatic

Extent of automation

Sparing philosophy

Shift pattern

Example of Operating Philosophy Contd.

April 18, 2023 26

Summary and Conclusion

Design Basis affects the concept and cost of the process plant.

A number of key issues need to be studied to evolve an

economically optimum and safe design basis.