FR-Bottom Ash Handling System 20092010

BHAVANAPADU THERMAL POWER PROJECTSTAGE- I : 2x660 MW, ANDHRAPRADESH, INDIA

B 20.09.10 Revised as per ABIR Comments CKS MG SS

A 16.09.10 Preliminary Issue CKS MG SS

REV DATE DESCRIPTION PRPD CHKD APRD ECEPL

REVISION INDEX

BHAVANAPADU THERMAL POWER PROJECTSTAGE – I : 2x660MW, ANDHRAPRADESH, INDIA

DOCUMENT TITLE :

FEASIBILITY REPORT FOR BOTTOM ASH HANDLING SYSTEM

OWNER:

EAST COAST ENERGY PRIVATE LIMITEDHYDERABAD – INDIA

OWNER’S ENGINEER:

ENERGY INFRATECH PRIVATE LIMITEDTHERMAL POWER DIVISION, HYDERABAD - INDIA

BOP CONTRACTOR:

ABIR INFRASTRUCTURE PRIVATE LTDTHERMAL POWER DIVISION, HYDERABAD - INDIA

BOP CONSULTANT:

IDEA - PB CONSORTIUM

CHENNAI / BANGALORE - INDIA

FEASIBILITY REPORT FOR BOTTOM ASH HANDLING SYSTEMDOC.NO. AIPL-5310-M-1602-5016

Rev.: BPage 1 of 11


DOC.NO AIPL – 5310 – M – 1602– 5016 Page 1 of 11 Rev B

TABLE OF CONTENTS

1.0 INTRODUCTION 4

2.0 PROJECT BACKGROUND 4

3.0 SYSTEM DESCRIPTION 4

3.1 General 4

3.2 Jet Pump System 4

3.3 Scrapper Chain Conveying System 5

3.4 Source of Water 7

3.5 Cost Implications 9

4.0 Recommendation 9

APPENDIX

Appendix 1 Comparison of SCC System with Contract Requirements

LIST OF DRAWINGS

AIPL-5310-M-0102-5103 Flow Scheme – Bottom Ash Handling System (Jet Pump System)

AIPL-5310-M-0102-5113 Flow Scheme – Bottom Ash Handling System (SCC System)

AIPL-5310-M-0302-6033 Layout of SCC

AIPL-5310-G-0101-0001 General Layout Plan (Tentative Routing of Bottom Ash Conveyor)


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LIST OF ABBREVIATIONS

BA : Bottom Ash

BoP : Balance of Plant

DEC : DONGFANG Electric Corporation Ltd.

ECEPL : East Coast Energy Pvt. Ltd.

SCC : Scrapper Chain Conveyor


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1.0 INTRODUCTION

The purpose of this report is to check the feasibility of utilizing Scrapper Chain Conveyor (SCC) system for bottom ash removal in lieu of Jet Pump system.

The Contract specification calls for jet pump system for bottom ash removal and ash handling system DBR was accordingly submitted. However, in a meeting between the Owner and ABIR on 4th Sep. 2009, the Owner suggested Scrapper Chain Conveyor (SCC) system for bottom ash removal. This report examines the feasibility of incorporating an SCC system for the project.

2.0 PROJECT BACKGROUND

East Coast Energy Pvt. Ltd. (ECEPL) (Owner), proposes to install a 4x660 MW, Super Critical Thermal Power Plant based on a blend of imported coal and indigenous coal at Bhavanapadu, Srikakulam District of Andhra Pradesh, India about 175km away from Visakhapatnam sea port. This project is proposed to be implemented in two Phases i.e. Stage I – 2x660MW and Stage II - 2x660MW.

The Owner appointed NEC CONSORTIUM (ABIR & NAVAYUGA), as the EPC contractor for Balance of Plant and Civil Works for Stage I of the proposed power project. ABIR appointed IDEA-PB Consortium for carrying out the Engineering Consultancy and Project Management Services for Mechanical, Electrical and C&I work for the Balance of Plant.

3.0 SYSTEM DESCRIPTION

3.1 General

The following two types of Wet Bottom Ash Handling Systems are widely utilized in thermal power plants for bottom ash removal:-

Jet Pump System

Scrapper Chain Conveying System

3.2 Jet Pump System

The jet pump system consists of water impounded hopper (two ‘V’ legs or W-type), from where bottom ash passes through large gates (hydraulic Feed Gate) on to dual roll clinker grinders that grind clinkers to an appropriate size (maximum 25mm). The grinders then feed the ash to a hydraulic ejector (jet pump), which transfer the resultant ash-water slurry to an ash slurry sump located in the bottom ash slurry pump house. Make-up water and impulse water are supplied by Low Pressure (LP) and High Pressure (HP) water pumps. Operation of the jet pump requires high pressure impulse water that is supplied by the HP water pump.

The bottom ash handling system flow schematic (using jet pump system) is attached as Dwg. No. AIPL-5310-M-0102-5103.


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3.3 Scrapper Chain Conveying System

The SCC System receives hot ash, slag and clinkers falling from the boiler, through a transition chute to the water-filled trough. The transition chute provides an air-tight seal between the boiler and the scrapper chain conveyor. Ash is continuously conveyed up the conveyor incline for dewatering.

The bottom ash discharged onto the scrapper chain conveyor will be fed to clinker grinders where it is crushed to (-) 25mm size. The crushed bottom ash will be conveyed to the bottom ash silo by belt conveyors. A bottom ash silo having eight (8) hours storage capacity along with provision for water decantation is proposed for the each unit. Bottom ash collected in silo will be disposed to ash dyke by means of the belt conveyor and under emergency circumstances ash will be loaded on to truck for off-site disposal.

The bottom ash handling system flow schematic (using SCC system) is attached as Dwg. No. AIPL-5310-M-0102-5113.

Recirculation system:

Over flow water from trough of scrapper chain conveyor and seal trough over flow will be transferred to clarifier for supplying clear water to the Bottom ash system. This water will also be cooled in the recirculation system. Make up water (desalinated quality) will be added in the trough of scrapper chain conveyor.

Cooling arrangement for the SCC overflow water:-

Generally three options are available to cool the SCC overflow water:-

FRP Cooling tower

Plate type heat exchanger

Settling & surge tank

Normally settling & surge tank is required to clarify the contaminated ash water before it is cooled by the cooling tower or the heat exchanger. In the case of cooling tower additional auxiliary power will be required for operating the pumps and fans and make-up water will also be required to compensate for the blow down/evaporation losses. In the case of heat exchanger option secondary cooling water from the sea water will be required. In order to minimize water consumption, it is proposed to install a larger settling tank & surge tank, so that retention time will be more and cooling will be achieved by evaporation.

Layout and Routing of the belt conveyor

Belt conveyors are proposed to dispose the bottom ash from scrapper chain conveyor to bottom ash silo. In order to accommodate the bottom ash belt conveyor, IA/SA compressor house (No. 45) and Acid/Alkali Unloading Area & Neutralizaion Pit (No. 46) are shifted towards east side.


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The routing of the belt conveyor is shown in the enclosed drawing, Dwg. No. AIPL-5310-M-0302-6033.

The routing of the belt conveyor is tentative, which will require confirmation by DEC for any potential interference with the boiler equipment.

Bottom ash silo is proposed to be located at the location where hydrobin are envisaged, please refer to General Layout Plan, Dwg. No. AIPL-5310-G-0101-0001 enclosed in this report.

Pros and cons of the Jet Pump system compared to SCC system are as follows;

Pros Cons

Simple layout, occupies less space in BA area

Higher power consumption

Widely installed in Indian power plants More number of equipment and structures required

Higher installation cost

Water consumption high

To accommodate large volume of ash holdup, part of BA system with jet pump need to be located below ground.

Pros and cons of the SCC system compared to Jet Pump system are as follows;

Pros Cons

Less water consumption (about 10% less) Maintenance prone, hence standby SCC is required

Less power consumption (about 15 to 20% less)

Complex layout due to use of belt conveyors and belt feeders in the boiler area

Due to continuous operation, capacity of water recirculation system less.

Installation cost may be less

SCC located on the ground level and mounted on the rails


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3.4 Source of Water

The below tables summarizes the source of water required for handling ash.

Source of Water for AHS with Jet Pump

No.

Description Source Remarks

1. AHS Instrument Air Compressor cooling

DMCW or Desalinated CW

2. AHS Conveying Air Compressorcooling


3. AHS Vacuum Pump Desalinated water once through

Desalinated water will be used to cool/seal vacuum pump coolers, supplied from seal water pump. The discharge will be let into the Ash water sump and used in the AHS system.

4. Source of water for Jet pumps Desalinated water Supplied by HP Water Pumps

5. BA Hopper filling, BA Hopper Cooling and Seal Trough Make-up

Desalinated water Supplied by LP Water Pumps

6. Seal Water for Clinker Grinder, Sludge Pumps, BA Slurry Pumps

Desalinated water Supplied by Seal water pumps

7. For HCSD slurry preparation Desalinated water or Seawater

Seawater can be also used for HCSD slurry preparation. Sea water application will increase the cost of HCSD system by approximately 2 to 3 times.


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No.


8. Fly ash Conditioning Service water To be tapped off from service water network

Source of Water for AHS with Scrapper Chain Conveyor

No.


1. AHS Instrument Air Compressor cooling


2. AHS Conveying Air Compressor cooling


3. AHS Vacuum Pump Desalinated water once through

Desalinated water will be used to cool/seal vacuum pump coolers, supplied from seal water pump. The discharge will be let into the Ash water sump and used in the AHS system.

4. Economizer hopper flushing apparatus

Desalinated water

5. Make-up for seal trough and Scrapper Chain Conveyor

Desalinated water LP Pumps

6. Seal Water for Clinker Grinder Desalinated water Supplied by Seal water pumps

7 For HCSD slurry preparation Desalinated water or Seawater

Seawater can be also used for HCSD slurry preparation. Sea water application will increase the cost of HCSD system by approximately 2 to 3 times.


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No.


8. Fly ash Conditioning Service water To be tapped off from service water network

It shall be noted that, the water requirement for SCC system will be about 10% less than the Jet pump system.

3.5 Cost ImplicationsPreliminary discussion with the prospective vendors reveals that SCC system could be less expensive compared to the jet pump system in terms of capital cost.

4.0 Recommendation

Both Jet pump with hydro bin system and SCC described above are technically acceptable and both could be adopted depending upon the cost effectiveness. Also desalinated water requirement for scrapper conveyor system could be less compared to hydro bin system. Since SCC is prone to maintenance, a standby SCC is to be envisaged. The feasibility of scrapper conveying system will also depend to a large extent in the ability to route the belt conveyor between the boiler & the bottom ash silo. Preliminary assessment reveals that the routing can be accomplished as per enclosed drawings.

In view of the above, bottom ash handling system with scrapper conveyor system is recommended.


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Appendix 1Comparison of SCC System with Contract Requirements

Comparison with Contract RequirementsSl.No. Contract requirement Proposed system Remarks

Jet Pump System SCC System

1 Water impounded hopper Dry bottom ash hopper Make up water (Desalinated water) requirement likely to be less (by about 10%)

2 Jet pump Scrapper chain conveyor Jet pumps, ash slurry pumps, hydro bin system is not required

3 Clinker grinder Clinker grinder Bottom ash disposal will be semi wet4 Ash slurry pump Belt conveyor HP water is not required5 Hydro bin system Bottom ash silo

6 Power consumption Power consumption of SCC system will be approximately 15 to 20% less Power consumption will also be less


Rev.: APage 1 of 11

Documents

FR-Bottom Ash Handling System 20092010