functional design specification (fds): waste ncv calculation · 6.4 , waste ncv (net calorific...

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www.hz-inova.com

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Project No.

P-3270

Project Name

Dublin Waste to Energy

AIC DocType Supplier HZI Document No. - Revision

12AAZ1

Customer Document No.

Functional Design Specification (FDS): WASTE NCV CALCULATION

2.0HAA

RevCreated

(Date, Initial)

Checked(Date, Initial)

Approved(Date, Initial)

Short description of change

1.0

0.0

18.05.2017Revision for first waste fire

HAA

18.05.2017

Haa

23.05.2017

Ebw

23.05.2017

18.11.2015Release for programming

ROR Smn

18.11.2015

Mra

18.11.2015

30.06.2015First Issue

Ror Rore

30.06.2015

Mra

30.06.2015

90057099 - 2.0HZIPDS

All rights reserved according to ISO 16016

12AAZ1 Waste Net Calorific Value Calculation

Title HZI Document No. - Revision Project Name Dublin

Functional Design Specification Waste Net Calorific Value

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Customer Document No. DocType PLD

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Table of Contents

1 General 4

1.1 System Description 4

1.2 Associated Documents 5

2 Operation Modes 6

2.1 Normal Operation 6

2.2 System Action in Case of Malfunction 6

3 Function Groups (FG) 7

4 Automatic Operations (AutoOp) 7

5 Closed Loop Controls 7

6 Calculations 8

6.1 Symbols and Indices 10

Symbols 10 6.1.1

Indices 10 6.1.2

6.2 Reference Condition 11

6.3 ��, � Waste Heat Input (Fuel Heat Input) 11

6.4 ��, � Waste NCV (Net Calorific Value of the Fuel) 12

6.5 �� Waste Throughput (Fuel Mass Flow) 12

Crane Weight Processing (M02-1) 12 6.5.1

Waste Throughput Calculation (L01-4) 14 6.5.2

6.6 Other Heat Credits 15

�� Heat Input Primary Air 15 6.6.1

� � Heat Input Secondary Air 16 6.6.2

�� Heat Input Process Air 16 6.6.3

�� Heat Input Steam Air Preheater 16 6.6.4

��ü Heat Input Water Vapors 16 6.6.5

� �� Heat Input SNCR Reactant 17 6.6.6

��, �� Heat Input Recirculated Flue Gas (Heat Input External Process Gas) 17 6.6.7

�� Power Credits 17 6.6.8

6.7 �� Useful Heat Output 18

�� Live Steam Heat Flow 18 6.7.1

�� Boiler Blowdown Heat Flow 19 6.7.2

��, � Extracted Steam Heat Flow, external use 19 6.7.3

�� Heat Flow for Air Preheater, from boiler drum 19 6.7.4

6.8 ��, �� Total Heat Loss 20

�� Flue Gas Loss 20 6.8.1




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�� Incomplete Combustion Loss 21 6.8.2

�� Bottom Ash Loss (Loss due to Enthalpy and Combustibles in Grate Ash) 21 6.8.3

�� Fly Ash Loss (Loss due to Enthalpy and Combustibles in Fly Ash) 22 6.8.4

� � Radiation Loss (Loss due to Radiation, Convection and Conduction) 23 6.8.5

� ü Grate Cooling Loss (Losses due to Cooling of Plant Parts) 23 6.8.6

7 Settings 24

8 Interlocks 24

9 Logic Diagram 24




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1 General

This document is a general, comprehensible explanation of the functions, sequences, interlocks, controls as well as the individual drives for the associated system.

1.1 System Description

System: Waste Net Calorific Value Calculation

AIC: 12AAZ1

The 3 hour and 8 hour average waste calorific values are calculated in the DCS using a heat balance.

The heat balance is based on the FDBR Guideline «Acceptance Testing of Waste Incineration Plants with Grate Firing Systems» (2013-03) [1].

Certain simplifications were made because their effect on the result is negligible.

Refer to chapter 6 for the detailed formulas along with further detailed specifications.

The results of the calorific value calculations are displayed on a designated DCS screen showing the load range diagram and the 3 hour and 8 hour average “operating points”.

The x-axis shows the average waste throughput in tons per hour, the y-axis the waste heat input in megawatt. In addition to the operating points the respective data is also displayed as numerical values.

Because the waste calorific value must be calculated using a heat balance the results can only represent the combustion conditions in the past – a conclusion from these values to the actual (or even future) waste calorific value is NOT permitted.

The measuring uncertainty of the calculated values is in the range of +/- 10%. This is mainly due to uncertainties of the waste weight measurement. The other measurements play a secondary role. Simplifications (deviations to FDBR) contribute to less than 1% in the calculated waste NCV.




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Figure 1: Load Range Diagram

1.2 Associated Documents

Combustion Diagram: 50031211

[1] FDBR-Guideline RL 7 Acceptance Testing of Waste Incineration Plants with Grate Firing Systems Edition 2013-03




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2 Operation Modes

Automatic mode or manual mode is selected in the DCS. All individual drives may be separately switched to «MANUAL». Interlocks and start releases defined for the individual drives remain active in manual mode.

2.1 Normal Operation

The calorific value calculation is activated only when the live steam flow has reached a minimum value of approximately 60% of the nominal live steam flow and when the burners are NOT in operation.

2.2 System Action in Case of Malfunction

When one of the burners is started the calorific value calculation is not active any more. The last calculated values are frozen and displayed on the DCS. A message is generated and displayed on the load range diagram screen. Once the burners are stopped, the NCV calculation resumes.




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3 Function Groups (FG)

n/a

4 Automatic Operations (AutoOp)

n/a

5 Closed Loop Controls

n/a




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6 Calculations

The next page shows the envelope used for the heat balance.

Please note that the air preheaters are OUTSIDE of the boundary allowing a simple and thus more precise measurement of the various heat flows for the balance.

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6.1 Symbols and Indices

Symbols 6.1.1

Symbol Quantity c specific heat capacity cp specific isobaric heat capacity Hu net calorific value (NCV) h specific enthalpy m weight m" mass flow rate Pm power credit p absolute pressure ps absolute saturation pressure Q" heat flow rate ρ density t time t temperature ts saturation temperature V" volume flow rate

Indices 6.1.2

Superscript Symbol Description % averaged value Subscript Symbol Description A Ash Ab Blowdown Water Aus Outlet B Fuel b Reference Value Brü Water Vapours CO Carbon Monoxide D Steam Ein Inlet FA Fly Ash FL Process Air G Flue Gas ges Total i Number, Type, Location Kond Condensate Kü Cooling Water L Air LV Air Preheating max Maximum




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N Available Heat; Rated Voltage n Standard Conditions PL Primary Air RA Bottom Ash Rezi Recirculated Flue Gas SL Secondary Air SNCR Selective Non-Catalytic Reduction Sp Feedwater St Radiation u Unburned Matter V Loss (Heat) Z Heat Input

6.2 Reference Condition

The reference temperature is used for enthalpy calculations of gases.

&' reference temperature 15.0 °C

The standard reference conditions for expressing gas volumes (described as Nm3) are: () standard pressure 1013.25 mbar &) standard temperature 0.0 °C

6.3 �" �,� Waste Heat Input (Fuel Heat Input)

The waste heat input is determined by the general heat balance equation of the steam generator: *"+,, = *". + *"0,123 − *"+ (L01/1) *"+,, waste heat input calculated value *"+ other heat credits refer to (L02/1) *". useful heat output refer to (L03/1) *"0,123 total heat loss refer to (L04/1)




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6.4 ��,� Waste NCV (Net Calorific Value of the Fuel)

Simplification according to [1]: Neglecting the sensible heat of the waste, the net calorific value of the waste is determined as follows:

56,, = *"+,,7" , (L01/3)

5"6,, waste NCV calculated value *"+,, waste heat input refer to (L01/1) 7" , waste throughput refer to (L01/4)

6.5 �" � Waste Throughput (Fuel Mass Flow)

This term is calculated from the waste cranes weight measurements according to HZI’s procedure explained in the following chapters. A simplified formula of HZI’s procedure is given below (for information only).

7" , = 1∆& : ; <,,=)

=>?: 7,,=

7" , waste throughput calculated value 7" ,,= crane grab weight (fuel weight) measurement <,,= FIFO stack factor per fuel weight acc. Logic Diagram ∆& observation period acc. Logic Diagram

Crane Weight Processing (M02-1) 6.5.1

The crane control system provides an analogue signal with the weight measured for each individual crane grab. Furthermore for every individual crane grab there is one binary signal per line. This signal indicates (when true), that the crane releases the waste into the feed hopper of the respective line. The logic then processes this weight and indicates to the crane control system by a 5 seconds pulse that the processing is terminated and that a new weight can be processed.




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Figure 3: Signal exchange with the crane control system

The signal exchange for a plant with two lines and two crane grabs is shown exemplarily in the following table: Crane control system to DCS DCS to crane control system

Binary Crane 1 Waste Released to

Hopper LINE 1

Binary Crane 1 Weight Recorded

LINE 1


Hopper LINE 1


LINE 1


Hopper LINE 2


LINE 2


Hopper LINE 2


LINE 2

Analogue Crane 1 Weight

Analogue Crane 2 Weight

Internally, the “Waste Released to Hopper” binary signal sets a flip flop; this flip flop freezes the analogue “Crane Weight” signal to its current value. The “Crane Weight” signal is written into two shift register arrays or FIFO stacks. One FIFO stack consists only of size one and it is used to detect, that the FIFO stacks have been shifted. The second FIFO stack is of size 30 and the “Crane Weight” signal is divided by 30 and written into this stack (only once). When the stacks have been shifted, the flip flop is reset and a 5 seconds pulse is sent to the crane control system. Stacks are shifted every 1 minute and it is absolutely necessary for them to shift synchronous.




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Waste Throughput Calculation (L01-4) 6.5.2

HZI calculates the average waste throughput using a special filter routine because the irregular charging of waste with a broad bandwidth of physical properties (density, water content, compressibility → resulting in different weight) may cause significant steps in the average waste flow signal. The impact of the most recently released weight is distributed over 30 minutes. See Figure 4 for details.

Figure 4: Crane Grab Weight Distribution over Time

The sum of all the entries in the 30 minutes register is copied into the 180 minute (3h) and 480 minute (8h) FIFO stacks every minute. The sum of all the entries in the 180 and 480 stacks are divided by 3 or 8 to give the 3h or 8h average waste throughput.




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6.6 " Other Heat Credits

*"+ = *"@A + *"BA + *"CA + *"A0 + *",Dü + *"B.EF + *"G,H6 + IJ (L02/1) *"+ other heat credits calculated value *"@A heat input primary air,

downstream of preheater refer to (L02/2)

*"BA heat input secondary air, downstream of preheater

refer to (L02/3)

*"CA heat input process air refer to (L02/4) *"A0 heat input steam air preheaters, external steam

refer to (L02/5)

*",Dü heat input water vapors refer to (L02/6) *"B.EF heat input SNCR reactant refer to (L02/7) *"G,H6 heat input external process gas refer to (L02/8) IJ power credits refer to (L02/9)

�" �� Heat Input Primary Air 6.6.1

*"@A = K"@A : ρA,) : MO̅,@A : P&@A − &'Q (L02/2) K"@A primary air volume flow 1 HLA10 CF901 ρA,) air density at standard condition, design

LPN 1.282

kg/Nm3

MO̅,@A average specific heat capacity primary air fluid property &@A primary air temperature, at envelope boundary

1 HLA10 CT002

&' reference temperature refer to chapter 6.3




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�" � Heat Input Secondary Air 6.6.2

*"BA = K"BA : ρA,) : MO̅,BA : P&BA − &'Q (L02/3) K"BA secondary air volume flow 1 HLA20 CF901 ρA,) air density at standard condition, design

LPN 1.282

kg/Nm3

MO̅,BA average specific heat capacity secondary air fluid property &BA secondary air temperature, at envelope boundary

1 HLA20 CT002


�" �� Heat Input Process Air 6.6.3

Simplification: primary air temperature before the primary air fan is used as the process air temperature at the envelope boundary.

*"CA = ρA,) : MO̅,CA : P&CA − &'Q : ; K"CA,=)

=>? (L02/4)

K"CA total process air volume flow K"CA,= burner cooling air flow, design 3400 Nm3/h

air flow through feed hopper, design 2400 Nm3/h

air flow of refractory lining system, design 0 Nm3/h

air flow for SNCR, design LPN 900 Nm3/h

various small air flows, design 0 Nm3/h ρA,) air density at standard condition, design LP N

1.282 kg/Nm3

MO̅,CA average specific heat capacity process air fluid property &CA process air temperature, at envelope boundary

1 HLA10 CT001


�" �� Heat Input Steam Air Preheater 6.6.4

This is the low pressure steam used for the air preheating. Since the air preheater is outside the envelope boundary the term must be set to zero. *"A0 = 0 (L02/5)

�" ��ü Heat Input Water Vapors 6.6.5




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This term refers to the vapors entering the system generated in the bottom ash extractor. Simplification: This term is considered to be negligible and therefore shall be set to zero since its contribution is less than 0.1% of the fuel heat input. *",Dü = 0 (L02/6)

�" �� Heat Input SNCR Reactant 6.6.6

Simplification: This term is considered to be negligible and therefore shall be set to zero since its contribution is less than 0.1% of the fuel heat input. *"B.EF = 0 (L02/7)

�" �,�� Heat Input Recirculated Flue Gas (Heat Input External 6.6.7Process Gas)

*"G,H6 = K"FCG : ρG,) : MO̅G,H6 : P&FCG − &'Q (L02/8) K"FCG recirculated flue gas volume flow 1 HNF10 CF901 ρG,) flue gas density at standard condition,

design LPN 1.270

kg/Nm3

MO̅G,H6 average specific heat capacity flue gas fluid property &FCG recirculated flue gas temperature, at envelope boundary

1 HNF10 CT001


�� Power Credits 6.6.8

This term includes the shaft power of the flue gas recirculation fan. Simplification: This term is considered to be negligible and therefor shall be set to zero since its contribution is less than 0.1% of the fuel heat input. IJ = 0 (L02/9)




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6.7 �" � Useful Heat Output

The useful heat output is the total heat transferred by the steam generator to the water / steam flows crossing the envelope boundary. Prerequisite is that the feedwater and spray water enthalpies are the same.

*". = *"S + *"T' + ; *"S,=)

=>?+ *"A0 (L03/1)

*". useful heat output calculated value *"S live steam heat flow refer to (C_03-1) *"T' boiler blowdown heat flow refer to (C_03-2) *"S,= extracted steam heat flow, external use

refer to (C_03-3)

*"A0 heat flow for air preheater, from boiler drum

refer to (C_03-4)

�" � Live Steam Heat Flow 6.7.1

*"S = 7" S : UVS − VBOW (L03/2) 7" S live steam mass flow 1 LBA10 CF901 VS live steam enthalpy,

at envelope boundary fluid property

(S: pressure 1 LBA10 CP001

&S: temperature 1 LBA10 CT901 VBO feedwater enthalpy, at envelope boundary

fluid property

(BO: pressure 0 LAB40 CP901

&BO: temperature 1 LAB40 CT001




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�" �� Boiler Blowdown Heat Flow 6.7.2

*"T' = 7" T' : UVT' − VBOW (L03/3) 7" T' blowdown mass flow, design LPN 0.373 t/h VT' blowdown enthalpy,

at envelope boundary fluid property

(X: saturation pressure 1 HAD10 CP004 VBO feedwater enthalpy, at envelope boundary

fluid property



�" �,� Extracted Steam Heat Flow, external use 6.7.3

There is no steam extraction for external use (other than steam extraction for air preheating) the term is set to zero. *"S,= = 0 (L03/4)

�" �� Heat Flow for Air Preheater, from boiler drum 6.7.4

*"A0 = 7" A0 : PVA0 − VB@Q (L03/5) 7" A0 saturated steam mass flow for air preheater,

from boiler drum 1 LBG30 CF901

VA0 saturated steam enthalpy, at envelope boundary

fluid property

(X: saturation pressure 1 HAD10 CP004 VBO feedwater enthalpy, at envelope boundary

fluid property






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6.8 �" �,�� Total Heat Loss

*"0,123 = *"G + *"EY + *"FT + *"CT + *"BZ + *"[ü (L04/1) *"0,123 total heat loss calculated value *"G flue gas loss,

downstream of steam generator refer to (L04/2)

*"EY incomplete combustion loss refer to (L04/3) *"FT bottom ash loss refer to (L04/4) *"CT fly ash loss refer to (L04/5) *"BZ radiation loss refer to (L04/6) *"[ü grate cooling loss refer to (L04/7)

�" � Flue Gas Loss 6.8.1

*"G = 7" G : MO̅G : P&G − &'Q (L04/2) 7" G flue gas mass flow,

downstream of steam generator refer to (L04/2-1)

MO̅G average specific heat capacity flue gas fluid property &G flue gas temperature, at envelope boundary

1 HBK50 CT001


7" G = \]K"@A + K"BA + ; K"CA,=)

=>?^ : <A_G + K"FCG` : ρG,) (L04/2-1)

K"@A primary air volume flow refer to (L02/2) K"BA secondary air volume flow refer to (L02/3) K"CA total process air volume flow refer to (L02/4) <A_G conversion factor, air to flue gas, design LPN

1.168

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K"FCG recirculated flue gas volume flow refer to (L02/8) ρG,) flue gas density at standard condition, design LPN

1.270 kg/Nm3




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�" �� Incomplete Combustion Loss 6.8.2

This term describes the losses by unburned combustibles in flue gas. Simplification: This term is considered to be negligible and therefor shall be set to zero since its contribution is less than 0.1% of the fuel heat input. *"EY = 0 (L04/3)

�" �� Bottom Ash Loss (Loss due to Enthalpy and Combustibles in 6.8.3Grate Ash)

Simplification: this term is considered proportional to the waste throughput. *"FT = 7" , : <FT (L04/4) 7" , waste throughput refer to (L01/4) <FT specific heat loss of bottom ash,

per fuel mass flow refer to (L04/4-1)

Herein <FT is obtained from:

<FT = 7" FT,a23=1)7" ,,a23=1) : b MF̅T : P&FT − &'Q + cFT : 56,6d (L04/4-1)

7" ,,a23=1) waste mass flow, design LPN 32.086 t/h 7" FT,a23=1) mass flow of dry bottom ash, design LPN 6.628 t/h MF̅T average specific heat bottom ash acc. [1]:

1.0 kJ/(kg*K) &FT temperature bottom ash, at the end of the grate

acc. [1]:

400 °C &' reference temperature refer to chapter 6.3 cFT unburned combustibles content of bottom, ash, determined as TOC, design

1.0 %

56,6 net calorific value of TOC acc. [1]:

33’000 kJ/kg




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�" �� Fly Ash Loss (Loss due to Enthalpy and Combustibles in Fly 6.8.4Ash)

Simplification: this term is considered proportional to the waste throughput. *"CT = 7" , : <CT (L04/5) 7" , waste throughput refer to (L01/4) <CT specific heat loss of fly ash,

per fuel mass flow refer to (L04/5-1)

Herein <CT is obtained from:

<CT = 7" CT,a23=1)7" ,,a23=1) : b MC̅T : P&CT − &'Q + cCT : 56,6d (L04/5-1)

7" ,,a23=1) fuel mass flow, design LPN 32.086 t/h 7" CT,a23=1) mass flow of dry fly ash, design LPN 0.642 t/h MC̅T average specific heat fly ash acc. [1]:

0.84 kJ/(kg K) &CT temperature fly ash, at envelope boundary

acc. [1]:

235 °C &' reference temperature refer to chapter 6.3 cCT unburned combustibles content of fly ash determined as TOC, design

1.0 %

56,6 net calorific value of TOC acc. [1]:

33’000 kJ/kg




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�" � Radiation Loss (Loss due to Radiation, Convection and 6.8.5Conduction)

Since it is not possible to measure this term, empirical values are to be used. In the calculation a constant value (taken from the design data sheet) is used for the radiation loss. *"BZ radiation loss, design 695 kW The following formula is for information only:

*"BZ = e : f *".,Jgh1000 ijkl.n (L04/6)

e empirical factor for waste fuel grate firing systems

acc. [1]:

30 kW

�" ü Grate Cooling Loss (Losses due to Cooling of Plant Parts) 6.8.6

The grate is air cooled or the cooling water circuit lies within the envelope boundary. *"[ü = 0 (L04/7)




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7 Settings

n/a

8 Interlocks

n/a

9 Logic Diagram