Design of a boiler waste heat and water recovery system

Bvuchete Munyaradzi N0107413Z

Background

Aim

To design a boiler waste heat and water recovery system in order to optimize boiler

efficiency

Objectives

•To conduct an energy and water audit

•To design a boiler blow down system

•To design a closed loop condensate reticulation system

•To design an economizer

•To develop a PLC program for the monitoring and control of the boiler waste heat and water recovery system

NEED JUSTIFICATION

Eco-efficiency: max output from the non renewable fuel

Cleaner production & resource efficiency: waste minimization, environmental protection from pollution

Reduction in costs: coal cost, chemical cost, water cost, fuel cost

Reduce energy losses :blowdown ,condensate, flue gases

METHODOLOGY

1. Literature review

2. Data collection

3. Concept generation and Concept Selection

4. Modeling and Simulation

LITERATURE REVIEW

Heat exchangers Pumps Liquid level sensors Valves Programmable Logic Controllers Vessels and tanks

V-1

Heat exchanger

Circ

ulat

ing

pum

p

Flas

h ta

nk

Cold make upwater

Cold break tank

Boiler feed tank

ON/O

FF CONTRO

L

Multistage pum

p

drain

Blow

dow

n va

lve

boiler

Steam to plant

ConductivityprobeLevel

probe

advantages disadvantages

Occupies less space No blowdown water recovery

High thermal recovery efficiency Chemicals in water flushed to drain

Easy of maintenance No pollution control from flue gases

Concept 1

boiler

Boiler feed water tank

econ

omize

r

Flas

h ta

nk

Water holding tank

pump

Cold Makeup water tank

ReclaimedWater to

Other uses

Flue

gas

es

chimney

Blow

dow

n

Flash venting to the atmosphere

advantages disadvantages

Potential increase of boiler efficiency and a reduction of coal

usage by the boiler system

Potential of corrosion of economizer due to condensation of

flue gases (sulphur and nitrogen oxides which cause acidic

conditions)

Blowdown water recovered and reused Maintenance challenge of economizer due to clogging with

particles carried by the flue gases.

Significant heat energy recovered Flash steam and its energy wasted to to the atmosphere

Chemicals saved

Concept 2

Condensate from plant

Feed water tank fan

Stocker grate

Coal bunker

Cooling tower

drain

Flash

vess

el

Holding tank

Vent to the atmosphere

Condensate receiver

tank

Steam trap

Treated water from softeners

Screw conveyor

hot Flue gases

The boiler

advantages disadvantages

Potential increase in boiler efficiency and a reduction in coal

consumption

Maintenance challenges because of many moving elements

in the system

Condensate recovery result in reduction of boiler water usage

and reduction of chemicals used

Water wastage

Most significant amount of heat energy recovered Flash steam and its energy wasted

The induced fan consumes electricity

High temperature instability of the boiler feed water tank due

to the cold water being added in the tank

Concept 3

ColdBuffertank

Buffer tank 1

Feed water tank

Flash vessel

Heat exchanger

Condensate tank

Coal bunker

boiler

CondensateFrom washer

P1

P2

P3

P4

P6

V1

V2

V3V4

L3

L9

V5

L1

L2

L4

L5

L6

V6

L7

L8

C1

V7

V8

V9

WATER FROM SOFTERNERS

Cleaner production

Maximum heat and water recovered

Improved boiler efficiency

Reliable and non labour intensive

Expensive to implement

Concept 4

CONCEPT 4 CHOOSEN

QUESTIONS ??? AND COMMENTS

$$$? RECOVER waste heat ENERGY AND Recycle WATER???

Thank you!!!