Energy consumption reduction in tissue drying methodology

Exclu do Energy consumption reduction in tissue drying methodology Author D Mainardi TO Italy Product Manager T ssue L nes PMT Italia A p S ...
Author: Easter Leonard
2 downloads 0 Views 6MB Size
Exclu do

Energy consumption reduction in tissue drying methodology

Author

D

Mainardi TO Italy

Product

Manager

T ssue

L nes

PMT Italia

A p S

Pinerolo

AbstraCt It is well known that drying tissue paper using high temperature and high drying rates is very inefficient process In order to reduce the cost of the tissue

plants

the

drying

many

attempts

to increase the efficiencies in this

For this purpose different state of the art

part of the process methodology for reducing energy

a

have been made in

costs

are

analyzed

from

the author

In betwwen these

methodologies a cogeneration system which feeds the mach nery and equipment reducing energy A similar system has been supplied by PMT Italia and started up with the aim of reducing thermal costs in a tissue plant Cogeneration or Combined Heat and Power CHP generation is the sequential use of the primary energy source to produce two forms of energy at the same time namely heat and Power The author analyzes and comments on the results from the recent example based on the experiente of the design installation up and running of a state of the art tissue machine fed with gases start coming from a brand new cogeneration plant supplied for this purpose is

a

good

Key

tool for

words tissue plant dryness cogeneration shoe press re nforced

or high n p

load

Yankee

D ryer

Palavra

Chave

Fabrica

de

Cilindro Papel Tissue Secagem gera Co ªo

Secador Yankee

refor ado Exclu do

1 INTRODUCTION the beg nn ng of 2006 PMT Italia t started up jointly Hayat w th Group n Izmit Turkey plant new for a the production of high quality bulky tissue to be converted and sold in the large demanding tissue areal of the Turkish region 1 The project has been developed as a greenfield mill in a 18 months span iointly time between th tw o e companies The plant that s cons dered one of the most modern in the nation includes a Crescent Former PMT Italia tissue machine for high quality tissue paper four unwind stations and one PMT Italia winding stat on for the production of multi layered types of tissue The plant also includes two PMT Italia stock preparation l nes w th the auxiliary systems necessary for the operation of the machine steam system high performance cogeneration hood lubrication system DCS etc The main technical

parameters are 000 converting 60 tpy

Production at

AD

Average daily production 180 tpd AD Max daiy production 230 tpd AD 200 mpm Design speed 2 Max speed 2 000 mpm 600 mpm Average speed 1 28 g Range of basis weights at reel 14 mZ The types of paper produced are mainly toilet tissue The

9

Exclu do

Exclu do

nas

Exclu do

ing

Exclu do

together

Exclu do

s

and kitchen towel

unique featurer of the Hayat plant is that the design of the machinery has been done in or o t r de optimize the production cycle the quality of the tissue produced and the energy savings factors

2 COGENERATION IN HAYAT TISSUE MILL

prying

tissue

as

purpose HAYAT

indicated

Yenikoy

The electr cal

and high dry ng is a very inefficient process In rates order dry ng process many attempts have been dope in the tissue plants For this cogeneration system has been designed for reduc ng thermal energy cost n

temperature us ng paper high

to reduce the cost of the a

The

as

q

Exclu do

canceuing

Exclu do

is

Exclu do

is

Tissue Plant

7percent and 66 3percent of energy nput is Hayat Yenikoy plant is 33 coming from the turbines These Ovaste gases having a sign ficant temperature about 500 C and at high flow rates can easily be used in a special design Yankee hood reduc ng and even their air systems depend ng on liminating the gas consumption n the production rates considered High temperature Ovaste gases are utilized to dry the tissue then to generate steam and cold water at a constant temperature levei Electrical equipment is needed to distribute the electricity or to produce it in parallel with the utility grid Hydraulic interconnections are needed to transport cold water or steam wherever it is required released

Exclu do

efficiency

n

residual heat in the Ovaste gases

in HAYAT Tissue Plant consists of six basic elements

cogeneration system Two 7 5MW gas

turbines natural gas fired

BRUNNSCHWEILER Yankee Hood Two steam boilers Four duct burners steam

two

reserve

burners for the hood

boilers ali to be used when the turbines

are

systems off

Absorption chillers New adapted control system in hood air circuits for operation of the hoods and the turbines The gas turbine is

designed

for cont nuous

operation

from

and two

the perfect

reserve

ntegration

burners for the

between the

idle to full load The turbines feature the

SoLoNO system that is a lean premix low emission combustion system for NOx control designed to achieve low NO and CO Selected turbine exhaust

necessities of mass gas flows and temperatures are suitable for the dry ng grades Full use of cogeneration gases is desired cogeneration gases flow calculated have minimum gas consumption in hood burners Fans burners hood boilers and chillers are designed according to the new air flows and temperatures As a comparison with tradit onal systems involving a conventional gas heated hood Ove can verify the ma n difference in the operation of a new system In fact Ove can see that the Ovaste energy flows delivered to the atmosphere re the n with reduced tissue dry ng and steam complete ntegration of the three processes Electricity generat on generat on which means that the total energetic efficiency of the system is improved We will quant fy this improvement with the actual efficiency parameters normally used in the next chapter Calculations various tissue

The ma n

advantages

of the system

are

Better gas energy

saving as no gas is consumed in the hood burners Minimum gas energy loss through ch mney because of use of residual cogeneration gases for dry ng and steam generat on

thermal energy from

3 CALCULATIONS The ma n

features of relevance to the case

under considerat on study

are

I

Exclu do 9

Yankee Diameter 5486 Yankee Yankee Yankee

Creping

mm

Paper Width 5600 mm Speed 2000 mpm Product on 7321 kg h Ratio 16

percent Weight 13 g m2 Energy Product on turbine efficiency

Reel Basis Electrical

7 33 percent

f

There

315 kW @ 15 C and 97 000 kg producing 7 hof Ovaste as in most countries the ratio between electricity unit in cost and thermal unit cost is very attractive for optimisat on About 3 kW of electrical energy can be h of Natural gas The rest of the energy will be util sed for the steam generation produced using 1 Nm3 and ch lled water production apart from the use of the Ovaste gases n the BRUNNSCHWEILER Yankee hoods Due to the electrical balance of the Hayat Site the generat on of electrical energy exceeds the requirements for the HAYAT Tissue plant n excess electrical energy will be For th s reaso used in a possible other HAYAT plant or can be sold to the grid Every tissue plant cogeneration system should be designed according to the r own necessities are

gases at

In this

two gas turbines and each

C 490

one

is

In the Turkish energy scenario

are designed to cover only around 78 of capacity what this means is that for an average production rate of the machine the gas consumption in the hoods is totally liminated The missing 20 thermal energy for the attainment of the maximum production capacity for high grammage tissue max drying capability in the machine will be supplied by the standby duct type burner in the hoods circuits For that case consumed Natural Gas amount is 2300 Nm3 h @ 15 C in every gas turbine h in every reserve hood burners always for maximum capacity See the following plus about 210 Nm3 graph case

Ovaste gases

the hood thermal energy

flowing from requirement

Total Natural gas consumed for both electrical and thermal energy

But

IN

In

on

Plant is 2300 Nm3 h x 2

210

the other hand in this way Ove

are

h Nm3

capable

4810

to sell

in the tissue

production

and

plant

h at full capacity in the tissue machine Nm3

an excess

of

electricity

to the net of

6 MW 3

COVENTIONAL MODE

the

case

conventional

of the

hood

typical

being

stopped

rec rculation

reduced flow in exhaust

consequently tine will be in

turbines in

operat on

Hood air circuits is not

in order to

enough

an

the Yankee Hood

mode

with

h gher standby

In this case the

produce required

amount of

additional externa air is

air

circuits

moisture

w ll

content

operate at

as

an

and

exhaust

burners installed in the exhaust air

steam but

as

the flow

given by

the

needed to compensate the missing flow in

the steam boilers In

this

h Nm3

case

the total natural gas

but no

So the energy

excess

electricity

consumed

is less

f

compared

is available to be used in the mil

cost balance in the two

capacity production

is summarized

n

exclu do

canceued

at maximum

IN COGENERATION MODE

Hayat 230 tpd

ed

the turbine exhaust

FOR FULL CAPACITY IN TISSUE MACHINE OF 230 TPD

other

exclu do

cases

conventional

the hereunder table

and

or

with the

cogeneration

mode

959

sold

cogeneration mode

for machine

full

FOR MAXIMUM PRODUCTION CAPACITY 230 TPD GOGENERATION HOOD Net production at reel

Prod uc ion

CONVENTIONAL

58 9

h ton

Net

production

HOOD

at reel

58 9

0 230 day ton anil cost

anil cost

32 0

Nm3 USD

HHV

80 10

Nm3 kWh

Natural HHV gas

Energy cosi

Gas

Electricity

80 kW hIN m3 10

cost

63 29

MWh USD

unlt cos when bu In

00 80

USDIMWh

unlt cost when bu

unir cost when

00 90

MWh USD

unir cost when

00 32

ton USD

ower

selling

unlt cost Steam

Latent heat at 8 bar Steam power

76 56

Gas

as

densit V

cost

ower

In

00 80 00 32

cost

Latent heat at 8 bar

USDIMWh

00 USD 90 MWh

selling

unlt

MWh USD

63 USD 29 MWh

ton USD

50 kJlkg 2029

Steam gower cost

steam

76 USD 56 MWh

3772 kc h

mc as

Turbines

Gas

steam

50 kJlkg 2029

cost

h ton

0 230 day ton

32 USD 0 Nm3

0 8 2 k INm3 4600 Nm3 h

as

Cost

1472 USD h

Natural gas 172 kg h 82 Nm3 0 kg

mgas Yankee

gas

denslty

hoods

V

210

as

Cost Total elect

ower

consumed

atlhe

Cost

67

lant

h USD

as

Cost Total elec

ower

consumed

at

0USD MWh

Cost

denslty V

0MW 11

unlt cost

786 kg h 82 kglN 0

mgas gas

h Nm3

lhe lant

unlt

0USD h

m3

959

h Nm3

307

h USD

0MW 10

cost

0 80 MWh USD

Cost

0 800 h USD

Electricit y Total Income

electricity produced at lhe plant electrlcity sold to lhe net

6 14

Excess of

Steam Steam

7 326 h USD 0ton 9 h

consumption

Cost

unlt cost

In lhe table paper

we can see

lhe reei of

on

In this table

we

produce

0

ton of paper at reel

a

that there is

Steam

unlt cost

h USD

5 126 ton USD

Cost to

0USD 19 tonof paper

have not considered lhe ncome

0 32 ton USD

Cost

produce

a

on

related to lhe

lhe reei Soa

excess

288

ton of paper at reel

net reduction in lhe energy cost consumed to

a

5 126 145 5

0toNh 9

consumption

0USDIton

Cost

Cost to

MW

6MW 3

Income

of steam

h USD

5 145 ton USD

produce

a

ton of

13 of reduction

produced

for

anc llary

equipment For 8000 noted

yr we h

that

equipment

no or

would have 19 0USD tonx

consideration

chilled water

of

lhe

58 ton 9 h x 8000

Income

related

to

lhe

456 USD 1 yr 160 h yrIt should be steam produced for ancillary

excess

has been mad

production

FOR A REDUCED CAPACITY IN TISSUE MACHINE TO 192 TPD

If

we now repeat lhe consumption required

same

comparison for a reduced capacity of 192 TPD and no additional burners we obtain lhe data summarized in lhe following table

gas

in hood

FOR A REDUCED PRODUCTION CAPACITY 192 TPD GOGENERATION H OOD Neproduction at

Production

reel

CONVENTIONAL HOOD

00 8

h ton

Net production at reel

00 8

0 192 day ton

N

a

t

anil cost

32 0

USDINm3

HHV

80 10

Nm3 kWh

ura l

gas

Gas

powercost

when cos uni E

ergy costa

Electricity

anil cost when

buying selling

anil cost Steam

Latent heat atØ bar eam powercost S mgas

Gas

gas

density

Turbines

Vgas Cost

N

tural gas mgas Yankee

gas

denslty

hoods

Total elect

Total olectricity Income

Income

Steam

Costa

consumption anil cost Cost

Cost to

produce

0 kg h 82 kgMm3 0

0 11

a

ton of papor at rcl

MW

mgas gas

density Vgas Cost

Total elec power consumed at thc

plane cost unl

0USD MWh

6 14

Stcam

powercost

MWh USD

ton 00 USD 32 2029 kJlkg stcam 5

76 56

MWh USD

82 kgMm3 0

produced alhe plan sold to tho net

Stoam

MWh USD

1472 USD h

0

Excess of clectricit

MWh USD

80 00 00 90

4600 Nm3 h

Cost lectricity

Latent hcatat8 bar

69 USD 29 MWh

h kg

0 USD h

cost

buying when selling cos anil cost

steam

0 Nm3 h

unlt

Nm9 kWh

anil

Cost

plant

Nm9 USD

80 10

MWh USD

00 32 2029 kJ 5 kg

3772

32 0

HHV

costwhen uni

ton USD

76 56

unir cost

Gas power cost

USDIMWh

Vgas

power consumed at lhe

Costa

69 USD 29 MWh

80 00 00 90

h ton

0 192 day ton

h USD

Cost

615 kglh kg Q82 Nm3 750 Nm3 h 240 USD h

1Q0

MW

0 80 MWh USD

0 800

h USD

MW

3MW 6

7 326 0 9

h USD h on

Steam

0USD ton

2 USD 143 ton

consumption unir cost

h 0 USD

Cost

Cost to

produce

a

ton of paper at reel

0 9 32 0

h ton ton USD

h 288 USD

0 166

ton USD

The reduction in the energy cost consumed to

2 ton 143 USD a 14 8 2 So

Jn

this table

have we

produce

one

ton of paper

on

the reei is

now

0 1

Exclu do

of reduction

Exclu do

not considered the incorre

tothe excess of related

steam

produced

for

ancillary

equipment

72 8

Exclu do Exclu do

For 8000

00 ton 8USD 2 x8 ton hx 800 0h yr 1 200 59It 4 yr USD should be noted that no consideration of the ncome related to the excess steam produced for ancillary equipment or chilled water production has been made

yr we h

would have

FFICIENCY COMPARISON

Exclu do

8

Exclu do

843

Exclu do 4

A

n

comparison effic ency

between the two different

Hereunder you find this kind of

drying approaches

could be

interesting

4

also in terms of

4 4 4

comparison

4 4 4

Energv efficiencv parameters CONVENTIONAL HOOD a 4 M r

hood evap

x

4 4

7171 kW

hfg

8

DRY NG M f

x

LHV

10526 kW

4 4 4

Enerav efficiencv Darameters COGENERATION HOOD b M r

hood x vap

hfgx hfg am Mst net Wx

DRY NG gOILER GENERATIONS

M

LHV

x r

7150 kW 2x7315 kW 2x6800 kW 74 3650 kW 2x22110 kW

Energv efficiencv parameters COGENERATION HOOD WITH CHILLERS c

vap x x M hood Msthfg t n Wx hfg 0ans r

g GEN DRYING AgS O CHILLER

M

x i fu

LHV

7150 kW 2x7315 kW 2x6800 kW 1x4650 kW 83

when

we use

only one chiller

3650 kW 2x22110 kW

hood x hfg Mevap Xhfg Qabs cam Ms net Wx r

DRY NG Ag gO GEN C H LLER S

M r

x

LHV

7150 kW 2x7315 kW 2x6800 kW 2x4650 kW 93

when

we use

two chillers

3650 kW 2x22110 kW

W here

vap hood evaporation kg M d h s of water evaporation at balance temperature nnet power produced by generator kW Wx am steam mass created in the boiler house kg Mst s Qabs Equivalent heat to chilled water kW

hfg enthalpy

kg kJ

5

quant ty to the conventional case s kg LHV gas low heat ng value i gas Mru

turbine

burners

cogeneration case

or

to

the hood

halves

kg kJ

COGENERATION FEATURES 4

pesired operation ofthe explained before as system cogeneration installations which

Parallel

are

is based

on

the

simplified

control

of

listed below

arrangement

to

simplify

controls and

enable easy

integration

between gas

turbines

and Yankee hoods Control of available pressure in the turbine exhaust Control of balance in the hoods Control of

supply temperature

Control of

0p

No

reason

in combustion fans

for moisture control

n

the exhaust from the Yankee hood

Bypass arrangement Control of pressure in Ovaste heat boiler

In the followinq

figure

a

schematic process

STEAM GENERATOR

diagram is shown

t

STEAM GENERATOR

RESERVE

RESERVE

BURNER

BURNER

1

EXHAUST FAN

Fig

1

Integration

of gas

exclu do 4

EXHAUST OFF

OFF

FAN

turbines Yankee hoods and Ovaste heat boilers for steam generation

6

q

SHOE PRESS SYSTEM FEATURES 5 As

already indicated before another implementation on the machine that might affect the energy consumpt on reduction s that the des gn has been prov ded in order to be easily retrofitted with shoe press technology For this reason the follow ng features have been appl ed to the press and YD sections The des gn of the felt run has been carried out with one press solution with the possibility to nstall the shoe press in a short shut down period The large diameter press has been supplied with no driven configuration The SPR can be re used for felt condit on ng in the shoe press configuration The YD prov ded PMT Italia sfully owned UK subs diary by PMT INDUSTRIES LIMITED has been supplied as h gh load dryer allowing to work up to 170 KN m nip The des gn of this solution allows to have versatility in the requirement for the t ssue manufacturer In fact a shoe press can be used aga nst the Yankee to increase post press dryness by ut lising h gher line loads than a conventional suction pressure roll in this way the energy consumpt on is reduced having h gher dryness at the hood inlet or by reducing the line load can reduce the loss in bulk associated with pressing as indicated in Fig 3 Erro V nculo In any atile to

case

w th

operate

nªo vÆlido

the introduction of the shoe press to with

But there must be

an

no

external line load of up to 170

loss n

drying capacity

as

t ssue machines the Yankee dryer needs to be m mas opposed to the conventional 90 kN kN

the Yankee may still be used with the conventional 90

m suction presser roll kN Th s

potential problems H gh external l ne loads create h gh fatigue stresses n the an acceptable leve the shell strength has to be ncreased However an increase in shell thickness the conventional way to increase shell strength reduces heat transfer flux and this results in less drying It also increases the possibility of shrinkage porosity reducing the tensile strength and quality of the casting Both these potential problems have to be addressed presents

some

shell to reduce the stresses to

1 Design 5

of

The heat transfer

h gh

load Yankee

problem through

was

compare the heat flux

condit ons model

the ribbed bore

is

plain h gher a

to show the distribution

producing

t ssue

Dryers

solved 40 years ago with the bore shell Th s

can

of heat flow

vs

a

ribbed

be illustrated

flux through

development

bore for the

by using a

FEA

section of

of the ribbed shell

same

a

pressure and l ne

Finite

Element

If

we

load

Analysis

Yankee shell when it is

HF1xX

HFlx

26m

260

2 38

239

298

zmm

9 1

iam

1a9

iam

119

iim

m sm

m sm

9 s9

m sm

9 29

9 29

F gure The model in

figure

3 Heat Flow

4 shows

a

through

section of

a

On the inside of the plain bore shell there is flow thus

a

Plain Bore Ribbed Bore Yankee Shell

plain Bore a layer of

shell

on

the left and

a

ribbed bore

condensate which acts

as

on

the

right

barrier to the heat

drying capacity The ribbed bore only has the layer at the bottom of the grooves with the rest of the rib in direct contact with the steam The heat flow pattern on the ribbed shell shows that most of the heat transfers from the side of the r b just above the condensate layer th s is because there s no condensate layer to insulate and restrict the heat transfer and there is less iron shell material to pass through than the rest of the rib On average the rib design has approximately 30 larger heat transfer than a corresponding pla n bore design with turbulator bars and approximately 50 larger heat transfer than a corresponding plain bore design w thout turbulator bars But with the increase in line loads further developments are needed For a high externa tine load the shell second moment of area needs to be increased to ma ntain acceptable shell stress leveis Th s can be done in two ways figure 5 insulating

i ii

reducing

the overall heat transfer and therefore

a

condensate

by increasing by increasing

the rib

he ght

or

the root thickness

Figure

4 Alternative

Design

Ribbed Bore Yankee Shells

The increased rib

height option has the disadvantages of a greater overall machining however it has the advantage of higher heat transfer

cost of

thickness and

HFixx

HFixx

00 430

08 439

2s 376

2s 376

50 322

59 322

75 268

7s 268

mm zis

mm 2is

Figure

5 Heat Flow

zs isi

2s isi

sm im7

sm im7

759 s3

7s0 s3

mmmm m

mmmm m

through

increased

Alternative

Design

Ribbed Bore Yankee Shells

The model

n figure 6 shows a section of the increased r b option on the left and the increased root option on the right As shown before most of the heat flows through the r b just above the condensate layer however in the case of the deep r b design the heat flow is larger because there is less metal between th s the

area

and the outs de

of the shell It should be noted that there

s

little

or no

heat flow

deep rib the add tional height of the rib provides strength only by ncreasing the second moment of area t is the reduction of root thickness that increases the heat flow The similarity of root thickness makes the deep rib design comparable in drying to a conventional low tine through

of the

top

load Yankee

2 Casting 5

of

high

load Yankee

The cast thickness of the shell for

casting quality

high

Dryers

load YD is

50 thicker than

a

conventional ribbed shell and

must be maintained

Over the last 50 years the

quality of PMT Ind castings has been improved dramatically Specially developed Class 60 shell material and optimised foundry practice ensure that Yankee dryers have the optimum strength conductivity and wear corrosion resistance character stics with m nimal var ation along the length of the shell As a result of these developments the Yankee castings have less surface defects less

through shell leaks radiographs which along Qual ty control assessment better

shell ultrason c

examination

are

part

of

a

r gorous

experiente and ongoing development PMT Ind now has another sophisticated gives an advantage over the predecessors the computer A recent investment in a state of the art casting software package now gives PMT Ind the chance to model a casting without the time and expense of making a casting This in conjunction with the acquired experiente has enabled us to predict the quality of a casting before any metal is poured Today

in addition to the

with 100

tool which

Figure

The

example shows a liquid The Hayat high

Example

section of load YD

November 2003 the first

3 5

6

deep

rib

PMT Italia shoe press

The PMT shoe presses

family

All the PMT solutions feature m up to range between 80 KN

an

was

of

Casting

Software

Modelling

Yankee Shell

18ft Yankee shell where the metal has frozen and where it is still the fourth

design

cast in this range of

Yankee shell

was

product by

PMT Ind On the 7th

0m cast 18ft diameter 6

long

design

varies from standard shoe press size to

patented SMARNIPTM solution edge relieving system and shoe tilting and can operate n a force line 170 KN m Shoe length s defined accord ng to the different shoe press

adoption Shoe presses main features

Machine direction

Long nip Possible

are

elongated nip

residence Time

high Press Impulse specific pressure peak intensity D specif c pressure development in M

Control of Gradual

Uniform Cross Machine

Nip propert es

10

Effect of shoe presses

on

tissue

grade

could be defined

Higher Bulk at same Dryness H gher Dryness at same Bulk Flex ble Nip no more crown issues poss bil ty

as

Or

Better adhesion of sheet Better moisture Better

Yankee

to

run

any

nip

dryer

profile

creping

The shoe press solution for easy retrofit in mach ne

on

a

new

proposed by PMT can be offered in three different ways for new machines machine prepared for l ke the case of Hayat and finally for major tissue

rebuilds

CONCLUSIONS 6

The authors have

presented with a practical case the innovation that can allow in a modern tissue consumptions costs For the total efficiency point of view cogeneration type drying is clearly the right choice and it opens a new field in the use of residual energies in the drying processes where very modest attempts jn this respect have been carried out in the past The main innovation of the Hayat project now a reality lies in the fact that no one ver undertaken an integration at this exten has Further considerations than could be done case by case adopting other different turbines design and plant

to reduce the energy

features Furthermore shoe press reliable

h gh

load YD s

Amendments

technology ava lable among PMT Italia tissue range products combined ght additional tool to implement energy consumption reduction

The author would

from Brunnschweiller

with

the r

Spa n

A S

like to thank

you the

Hayat Group management

and

to O

Lopez

for the contribution to the paper

Bibl ography D

1

s Article Mainardi Tissue World

reducition in tissue Energy consumption drying methodology Magazine July June 2007 by A Isiklar L Aydin D Mainardi and O Lopez Hayat

cogen cuts costs

2 O

2th APPITA

Lopez

A

23 2008 by D Mainardi G Gianlorenzi Conferente Rotorua New Zealand April 21 Emmanuel Energy consumption reduction in tissue drying methodology

exclu do

at

exclu do

n

exclu do

d

Suggest Documents