Preparatory study Lot 7 Steam boilers · PDF fileRecovery System Part 2: Introduction to Steam boilers from an energygy p point of view i. Analysis of heat input and ouput ii

Preparatory studyPreparatory studyLot 7 Steam boilers

Task 4: Technologies

Assistant Professor Sotirios Karellas

National Technical University of Athens

PwC - ICCS - Fraunhofer ISI6th March 2014Preparatory study for Steam Boilers Ecodesign

Slide 1

Tasks’ structureTasks’ structure

Task 1:Scope

Task 2:Markets

Task 3:Users

Task 4:TechnologiesMarkets Users Technologies

T k 5 T k 6Task 5:Env. & Eco

Task 6:Design

Task 7:Scenarios

PwC – ICCS – Fraunhofer ISI6th March 2014Preparatory study for Steam Boilers Ecodesign

Slide 2

Task 4: TechnologiesTask 4: Technologies

Task 4 includes:Task 4 includes:Subtask 4.1: Technical product description

Subtask 4.2: Production, distribution and end-of-life

Subtask 4.3: Recommendations

Scope: Capacity building, definition of base case products for next tasks, data retrieval on material flows operational life cycle analysis of products and recommendation of product material flows, operational life cycle analysis of products and recommendation of product improvements on the scope of Ecodesign

The current presentation includes mainly Subtask 4.1:

P Th b i f i d i l b il• Part 1: The basic parts of an industrial steam boiler

• Part2: Introduction to Steam boilers from an energy point of view

• Part 3: Future development of Task 43 p 4


Slide 3

ContentsContents

Part 1: The basic parts of an industrial steam boileri S G i Si. Steam Generation System

ii. Steam Distribution System

iii. Steam End Use System

iv Recovery Systemiv. Recovery System

Part 2: Introduction to Steam boilers from an energy point of viewgy p

i. Analysis of heat input and ouputii. Primary heat losses categoriesiii H t b l i th b ti h biii. Heat balance in the combustion chamber

Part 3: Future development of Task 4Part 3: Future development of Task 4

i. Preliminary definition of base case boilers

ii. Data required for base cases


Slide 4

ii. Data required for base cases

The basic parts of an industrial steam boiler The basic parts of an industrial steam boiler

Steam Distribution System

Steam End Use System

Recovery systemy y

Steam Generation System


Slide 5

I Steam Generation SystemI. Steam Generation SystemSteam Generation System overview

Steam

Pressure Reduction Valve

*

Superheater*Steam Using Process

Reheater*

Circulatingpump

Boiler1

Economizer*

Warm feedwaterSteam trapFeedwater

treatment & pump

Blow ValveBurner

Air preheater*

Air

Cold Feedwater

Steam air preheater*

Blowdown

Flue gas

Cold Feedwater

1 incl control system safety accessories & interconnecting tubing

SteamCondensate/WaterFuel Air


Slide 6

incl. control system, safety accessories & interconnecting tubing* optional Flue gas

I Steam Generation System M t i d t i l b il I. Steam Generation SystemSteam Boilers

Heat source

• Natural gas

• Diesel oil

Most industrial boilers are “packaged” fire tube boilers

Advantages:• Small combustion space and high heat

Heat input

source• Biomass

• Waste heat

p grelease rate result in high evaporation rates• Large number of small diameter tubes leading to good convective heat transfer • Good combustion efficiency

Feedwater supply

Saturated steam

Boiler

y• 2 or more flue gas passes leat to ameliorated heat transfer efficiency

W t t b b il ( t k /h )Fire tube boilers (up to 12000 kg/hr)

Medium-low operating pressures

Water tube boilers (up to 120000 kg/hr)

Higher operating pressures


Slide 7

I Steam Generation System

Superheaters add additional energy to steam, resulting in a steam temperature that

I. Steam Generation SystemSuperheaters

p gy , g pexceeds the saturation temperature at a specific pressure, under which thesaturated steam exits the boiler.

Superheated steam Stack

Saturated steam

Superheater surface

Heat source


Slide 8


Economizers provide effective methods of increasing boiler efficiency byf i h h f h fl i i f d b f h i i f h

I. Steam Generation SystemEconomizers

transferring the heat of the flue gases to incoming feedwater before their exit of thesystem.

ChimneyFeedwater tank • The lowest temperature of the flue

i bj t t li it ti di Chimney

Economizer

F d t li

gases is subject to limitations regarding sulfur oxide and water (in non condensing economizers) condensation (200 and 121 oC respectively).

Feedwater line• It is possible to cool the flue gases from 200-300 oC down to even 65 oC in a modern fire tube boiler, increasing the thermal efficiency of the boiler up to 5%Boiler thermal efficiency of the boiler up to 5%

• Economizers are a standard design improvement for industrial steam boilers and are present in most modern productsand are present in most modern products


Slide 9

I Steam Generation SystemI. Steam Generation SystemAir preheaters

Combustion air preheaters transfer energyf h fl b k i h

Boiler control system

from the flue gases back into the system, tothe incoming combustion air. The efficiencybenefit is achieved through the utilization ofthe flue gas heat content. The efficiency

• Feedwater flow control Valve• Water Softener• Pretreatment(feedwater)equipment

D D i H dthe flue gas heat content. The efficiencybenefits are lower than in the case ofeconomizers.

• Deaerator, Deaerating Heater, andAtmospheric Deaerator (reduction of theoxygen content in water)• Feedwater PumpFeedwater Pump• Collecting/Storage Tank of thereturning condensate and preheatedwater


Slide 10


The combustion air system supplies the oxygen necessary for the combustion

I. Steam Generation SystemCombustion air and fuel system

The combustion air system supplies the oxygen necessary for the combustionreaction. To provide enough air for the amount of fuel used in industrial boilers,fans and dampers are typically required.

The fuel system includes all equipment used to provide fuel to generate the The fuel system includes all equipment used to provide fuel to generate the necessary heat such as Fuel Regulating Valve, Fuel Flow Meter, Burner

Boiler blowdown system The boiler blowdown system includes the valves and the controls for the continuous blowdown and bottom blowdown services necessary for


Slide 11

and bottom blowdown services necessary for cleaning the feedwater from impurities

II Steam Distribution SystemII. Steam Distribution SystemThe distribution system transports steam from the boiler to the various end uses. Although distribution systems may appear to be passive, in reality, these systems

• Piping

g y y pp p , y, yregulate the delivery of steam and respond to changing temperature and pressure requirements. Their main components include:

• Insulation

• Valves

• Steam Separators and accumulators (Removing water droplets before they reach end-Steam Separators and accumulators (Removing water droplets before they reach enduse equipment)

• Steam Traps

• Steam Meters

Steam accumulator

Steam Meters

Steam separatorp


Slide 12

III Steam End Use SystemSteam system end-use equipment transfers steam energy into other forms of useful energy.

In manufacturing industries steam end uses often directly support production making

III. Steam End Use System

In manufacturing industries, steam end uses often directly support production, making their performance and reliability essential to plant productivity. Steam end-use equipment is grouped into three basic categories:

• Key end-use equipment; • Conditioning and control equipment; • Additional equipment.

The end-use equipment of steam escapes the scope of the Ecodesign study and is not to be examined in depth. Namely, devices that are used for the utilization of the steam include:

• Condensers distillation towers • Condensers, distillation towers, dryers, evaporators• Heat exchangers, reboilers, reformers• Steam ejectors, stream injectors and strippers


Slide 13

IV Recovery SystemIV. Recovery SystemResponsible for collection and return of the condensate back to the generation part of the system. Condensate recovery provides thermal and water treatment

• Condensate Return Piping (transports condensate back to the boiler)

part of the system. Condensate recovery provides thermal and water treatment benefits. The main devices used for feedwater recovery are:

• Insulation

• Condensate Receiver Tanks (collect and store condensate)

• Condensate Pumps (move condensate from receiver tanks back to the boiler room)

• Flash Steam Vessels (allow the recovery of steam from condensate lines)Flash Steam Vessels (allow the recovery of steam from condensate lines)

• Condensate Meters (measure the flow rate of condensate in the return system)

• Filtration/Cleanup Equipment (remove contaminants from the system)


Slide 14

IV Recovery SystemIV. Recovery System

Condensate Receiver Tank and Pump CombinationPump Combination

Flash Steam Recovery VesselFlash Steam Recovery Vessel


Slide 15

Introduction to Steam boilers from an energy

Objectives Covers

Introduction to Steam boilers from an energy point of view Objectives-Covers• Energy conversion process understanding• Presentation of mass and energy balance• Definition of steam boiler thermal efficiency (direct

and indirect)• Explanation of heat losses categories

Water content in flue gas(1 10 %)

Unburnt fueld h Blowdown

Energy flow in steam boiler system

Dry flue gas(5-15%)

(1-10 %)and ash (1-5%)

Blowdown(1-5%)Shell (1%)

Heat input Steam boiler (100 %) boiler system Useful heat provided

to feed water (75-95%)

PwC - ICCS - Fraunhofer ISI Preparatory study for Steam Boilers Ecodesign Slide 16

I Analysis of heat input and ouputI. Analysis of heat input and ouput

Heat inputQin QB,ch QB,ph Qair

Heat input

Fuel chemical Total Fuel physical Combustion air + +

Steam boiler efficiency is a key evaluation parameter in steam boilers. Most

Fuel chemical energy

Total energy input

Fuel physical energy

Combustion air physical energy

= + +

Heat ouput

manufacturers of industrial steam boilers claim efficiencies of at least 85% (mostly 90%)

Quseful ms(hout hin)Useful heat delivered to the feedwater stream

Ql Heat losses Direct •Speed and ease of applyingQloss

Q Q Q QSteam boiler efficiency

expression •Fewer instruments for calculations

Indirect •Provides complete energy

Quseful

Qin

Qin Qloss

Qin

1QlossQin

Indirect expression balance

•Helps identify options for improvements•Difficult to measure-time

PwC - ICCS - Fraunhofer ISI

consuming

II Primary heat losses categories

• Stack Losses: related to dry “hot” flue gases coming out of the boiler,l l f h Th l h fl i h l

II. Primary heat losses categories

largest loss of the system. The lower the flue gas exit temperature, the lowertheir value.

• Blowdown Losses: related to blowdown process, important for thet t t lid l ft i th b il C b d d th hsystem to remove water solids left in the boiler. Can be decreased through

better water pretreatment and blowdown water heat recovery

• Unburned fuel losses: are caused by the incomplete combustion of thef th f l th t t th b ilmass of the fuel that enters the boiler.

• Condensate losses: moisture in flue gas due to water content of fuel,combustion air and hydrogen content of fuel carries a significant heat loadth t i j t d t th i tthat is rejected to the environment

• Convection and radiation "shell" losses: a part of the heat that isprovided to the boiler escapes to the environment through convection andradiation These losses can be avoided through improved insulationradiation. These losses can be avoided through improved insulation


Slide 18

III Heat balance in the combustion chamber

Combustion chamber is a major part of the steam boiler because it

III. Heat balance in the combustion chamber

greatly affects the efficiency of the conversion of the chemical energy of fuel to heat and its transfer to the working medium

Heat flow into the Heat transfer to the water

Heat towards combustion

chamber (fuel+air) =Heat transfer to the water

walls by radiation superheater economizer

and air preheater+Fuel consumptionFuel consumption

steam steam feedwaterfuel

m (h h )mη LHV

η LHVFuel consumption is directly influenced by the capacity of the boiler and its thermal efficiency.

Example combustion chamber in a liquid fuel watertube boiler


Slide 19

m3

Folie 19

m3 διόρθωση LHV στο κείμενοmpraim; 28.02.2014

Future development of Task 4 Future development of Task 4

I. Preliminary definition of base cases

From data gathered from manufacturers' brochures it is determined that there is a wide range of capacities of steam boilers. It is difficult to establish

ifi d t " t t ti " i t f it d specific products as "most representative" in terms of capacity and environmental impact

For the current study, based on US market data, four "base" case capacities were defined: 1, 7, 15 and 35 MWth

Next steps in definition of base cases:Next steps in definition of base cases:

• Retrieval of data on certain steam boilers of the aforementioned capacities


Slide 20

Future development of Task 4 Future development of Task 4

II. Data required for base case products MW MW MW MW1 MWth 7 MWth 15 MWth 35 MWth

Report on bills of materials (for manufacturing and assembly) by OEM

Material and volume flows of packaging materials

Transportation means and average distance for d li R i d d t i tdelivery

Additional heat and electricity consumption

Product service life

Required data input

End-of -Life behavior (i.e. recycled fraction)

Capacity factor

EfficiencyEfficiency

Building of case scenarios of environmentalassessment


Slide 21

Discussion QuestionsDiscussion-Questions

Thank you for your attention!Thank you for your attention!


Slide 22

Documents

Preparatory study Lot 7 Steam boilers · PDF fileRecovery System Part 2: Introduction to Steam boilers from an energygy p point of view i. Analysis of heat input and ouput ii