Involve…Innovate…Deliver

Rakesh Desai

Energetic Consulting Pvt. Limited

Energy Efficiency in Thermal Utilities in

Refinery

WHAT NEXT?

• The energy use is optimized by most of the refineries by co-generation and heat integration

• Heat integration aims at process to process heat transfer reducing demand of secondary energy i.e. steam, electricity, cooling water etc.

• Co-generation optimizes primary energy utilization by striking balance in various forms of secondary energy.

• Further optimization in energy is now possible through applications of improved availability of energy, Exergy maximization. Simply put, Exergy means the highest form of energy used to meet highest level of demand

WHAT NEXT?

• It is possible to achieve energy optimization by: • Integrating process and electricity generation • Upgrading low temperature energy for different

applications • Process interventions for substituting cooling

demand by secondary energy generation

Gas Turbine: Present Scenario

Gas Firing

2600 SCM

G

HRSG

Stack

Gas

Turbine

Furnace

35 Gcal/h

APH Fuel

4600 SCM

FD

Blower

ID

Blower

Stack

ID

Blower

Gas Firing

1445 SCM

8 MW

130°C

130°C

350°C

575°C

HP Steam

38 TPH

Gas Turbine: Proposed Scenario

Gas Firing

2600 SCM

G

HRSG

Gas Firing

2450 SCM Stack

Gas

Turbine

Furnace

35 Gcal/h

Gas Firing

2980 SCM

ID

Blower

Blower

8 MW

HP Steam

38 TPH

130°C

350°C

575°C

Gas Turbine: Summary

Details Unit Present

Scenario

Proposed

Scenario

Gas Firing SCM/ H 8645 8030

Power

Generation MW 8 8

HP Steam

Generation TPH 38 38

Blower Power kW 650 500

Process Intervention

• In one of the processes, high temperature fluid from reactor is cooled in series of heat exchangers and then by fin fan cooler near to ambient temperature

• In separator, hydrogen gas is separated and diesel + gases are sent to stripper for further separation

• Enroute to stripper, the fluid is preheated by hot stream from reactor

• The technology is changing and new technology of separation at high temperature is worked out by licensor

• Thus, instead of cooling the reactor stream to ambient temperature and reheating the stream, the stream is cooled to higher temperature.

• The energy used for reheating the steam is saved and it can be used for MP steam generation

M P Steam : Present Scenario

H 3

H 1

H 2

From

Reactor

400°C

Fin Fan

Cooler

Separator

H₂ Gas

To

Process

170°C

Stripper

Diesel +

Gas

40°C

270°C

280°C

125°C

160°C

130°C

220°C

M P Steam : Proposed Scenario

H 3

H 1

From

Reactor

400°C

Separator

H₂ Gas

To

Process

170°C

Stripper

Diesel +

Gas

Boiler Feed

Water

MP Steam

30 TPH @

17 kg/cm²

160°C

280°C

270°C 235°C

220°C

M P Steam : Summary

Details Unit Present

Scenario

Proposed

Scenario

∆T across H 1 Heat

Exchanger °C 60 60

∆T across H 2 Heat

Exchanger °C 90 -

∆T across H 3 Heat

Exchanger °C 90 60

MP Steam

Generation MT/h - 31

L P STEAM

POWER REFRIGERATION

(SJR / VAM) ORGANIC

RANKINE CYCLE

Usage of LP Steam

LP Steam for Power Generation

• LP superheated steam can be generated from any waste heat source of 200°C or equivalent

• The LP steam generated in heat exchanger is passed through turbine, specifically designed to generated power

LP Steam: Power Generation

Heat

Exchanger

Feed

Water

Cooling

Water

LP

Turbine

Condenser

Process

Fluid

5.5 kg/cm² (a)

180°C

10 Ton / h

G 1 MW

50°c

0.12 kg/cm² (a)

LP Steam for Refrigeration

• Exhaust steam is condensed and cooling water is used as condensing media. The condensing pressure is 0.1 kg/cm² (a)

• Normal cooling water inlet temperature is 32°C and outlet temperature is 40°C

• In such scenario, use of steam jet refrigeration (SJR) system shall enable reducing condensing pressure thereby increasing power generation from existing turbine

• Also, DM grade water shall be available which is require in refinery as make up water for boiler

• SJR shall use motive steam to generate low temperature cooling water which shall be circulated in condenser of turbine

• The motive steam and evaporated water shall be condensed in surface condenser which shall generate additional potable water

• LP steam generation will require 8 kg of steam per ton of refrigeration

WHR: Organic Rankine Cycle

• The low temperature energy can be captured from process and heat is transferred to fluid at constant pressure, vaporizing the fluid

• The fluid is expanded into turbine to generate electricity • The refrigerant cycle is closed loop system • All refrigerants / hydrocarbons (isobutane, pentane, propane)

can be used as working fluids in the cycle

WHR: Organic Rankine Cycle

Heat Exchanger

Heat Exchanger

G

Waste Heat

Inlet

100°C 400 m³/h

Waste Heat

Outlet

Cooling Water

Outlet Cooling

Water Inlet 700 m³/h

570 kW

WHR: Furnace

• Furnaces operate at very high temperature, typically between 900-1200°C

• To control tube wall temperature, higher air to fuel ratio is required resulting in higher %O₂

• It is possible to recirculate part of exhaust gas (from furnace exhaust) back to furnace as a diluting medium which allows controlling tube wall temperature at optimum %O₂

• This technology is particularly useful when furnaces are operating near to rated throughput condition. Possibilities of failure of fluid or cracking of fluid substantially increase when higher firing is done to increase throughput. This results in higher tube wall temperature

Furnace: WHR – Present System

Furnace: WHR – Proposed System

Preheated air 265 ⁰C

APH

Fuel Fired - 838 kg/h

Flue Gas - 350 ⁰C

From FD Fan (35 ⁰C)

To ID Fan -130 ⁰C

Furance7.5

Gcal/h

Recirculation gas - 10000 kg/h

Furnace: WHR Summary

Details Unit Present

Scenario

Proposed

Scenario

Fuel Firing Kg/h 1000 838

%O₂ % 10 3

Flue Gas Outlet

Temperature °C 130 130

Combustion Air Kg/h 25300 15300

Recirculation

Gas Kg/h - 10000

How to reach us

Energetic Consulting Pvt. Limited

TMA House, 2nd Floor,

Wagle Industrial Estate, Thane – 400 604

Phone: +9 1 22 2580 5126

Web: www.energy2profit.co.in

Email: mktg@ecpl.co.in

Thank You !