Component 129: lignite mill

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Component 129: lignite mill / pulverizer

Specifications

Line connections
1	Hot drying gas inlet 1
2	Outlet
3	Cooling drying gas inlet 2
4	Fuel inlet
5	Sealing air inlet
6	Air ingress inlet
7	Electric power inlet
8	Drying gas mixing specification
9	Specification TCLASS and MOUTGAS
10	Specification of the mill rotation speed

General User Input Values Results Characteristic lines Physics used Displays Example

General

Component 129 is intended for the thermodynamic balancing of a lignite coal mill (pulverizer) with coal grinding and drying process considered. It can be used for the modeling of a beater wheel mill.

The raw coal (specified at PIN 4) is grinded within the mill. The electric power (specified at PIN 6) is used to move the milling plant. The coal dust contacts the mixture of the hot (PIN 1) (normally flue gas) and the cool (PIN 3) drying gas (normally air) and is, therefore, dried (a certain fraction of water in coal evaporates). Finally, the mixture of dried and grinded coal, water steam and drying gas exits the component at PIN 2. In real mills / pulverizers the dust particles are classified by a classifier. The coarse particles are returned to further grinding building an internal circulation within the mill. This circulation is, however, neglected in the stationary computations of component 129. The exactly closed mass balance is presumed. I.e. the sum of all incoming mass flows is equal the mass flow at the outlet (PIN 2).

The mixing temperature of the drying gas 1 and 2 as well as the mass flow of that can be specified at the logical PIN 8.

The PIN 5 is used for the specification of the sealing air fraction penetrating into the component.

The air ingress into the component from the outside is introduced at PIN 6. The penetrating air fraction regarding to the overall gas mass flow at mill outlet can be specified in MIA. The value of MIATMIX corresponds to the penetrating air fraction relevant to the mixing temperature T8.

The component assumes that the raw coal water content corresponds to the value of XH2OB at PIN 4. It is therefore expected that the user specifies only solid material fractions at PIN 4 (no gas or liquid substances make sense). The specified residual water content (RXH2OB) is interpreted also as XH2OB fraction regarding to the solid phase composition at PIN 2 (not regarding to the overall composition at PIN 2!). Thereby the complete solid phase at PIN 2 is taken as a basis for the residual water content without distinguishing between the fine coal and e.g. the ash or unburnt carbon fractions coming with the drying gas into the mill.

Important. There is a deviation from the thermodynamic equilibrium state between the fine coal residual water content and the gas phase at the outlet of the real coal mill. The water in grains remains in the liquid phase although the temperature of gas is higher than the water saturation temperature. The classifier temperature TCLASS is therefore specified at the logical PIN 9. The gas phase at the outlet is assumed to be at T=TCLASS. The temperature of the mixture (gas and solid phase) at PIN 2 may therefore deviate (be less than) from TCLASS depending on the residual water content of the fine coal. The computed temperature T2 is only a theoretical temperature corresponding to the thermodynamic equilibrium state which can not be measured in the real coal mill. The temperature T2 should not be compared to any measured value (e.g. classifier temperature). TCLASS=T9 must be used instead. The classifier temperature computed from the energy balance is available as result value RTCLASS. The outlet temperature T2 corresponding to the desired classifier temperature is available as result value T2FTCL.

Note - Characteristic Lines Related to Nominal Temperature

For the component 129 there is a characteristic line CL_12, which refers to a nominal value of temperature. This is the characteristic line CL_12 for the residual water content of fine coal , which provides the ratio TCLASS / TCLASSN.

Unfortunately, such temperature ratios depend on the selected system of units. In contrast to other units where the conversion is effected only via a certain factor and therefore has no effects on the quotient, in the temperature conversion there is an additive offset whereby the value of the quotient changes.

There is the possibility to specify this characteristic line in other units (°F, K).

Users who prefer other unit systems for the temperature (eg ° F, K) must set the selected temperature unit in the new flag FTNI, because Ebsilon calculates internally with the temperature unit ° C.

Relative heat loss (DQLR) / Load-independent heat loss (QLA)

In the case of the component 129, a relative heat loss can be specified via the specification value DQLR.

In practice, however, the temperature conditions for the mill change only slightly with the load, so that a load-independent heat loss occurs. This can be specified via the specification value QLA. The flag FLOSS serves to define whether the relative or the absolute loss is to be used.

User input values

FFU	Mill ON/OFF Like in Parent Profile (Sub profile option only) Expression =0: OFF (If FFU=0, all inlet mass flows and enthalpies are expected to be specified, consequently, the values of FTMIX, FMOUTGAS, FCM and FCMEB are of no relevance) =1: ON
FMODE	Flag for calculation mode Design / Off-design Like in Parent Profile (Sub profile option only) Expression =0: global =1: local off-design (i.e. always off-design, even if global design mode was selected) =-1:local design
FDP12	Pressure build-up calculation (hot side) Like in Parent Profile (Sub profile option only) Expression =0: using DP12N and characteristic field 1 =1: P2 given from outside
DP12N	Pressure build-up (nominal)
FTMIX	Mixing temperature TMIX13 specification Like in Parent Profile (Sub profile option only) Expression =0: computed internally =1: externally at PIN 8
FMOUTGAS	Outlet gas mass flow specification MOUTGAS Like in Parent Profile (Sub profile option only) Expression =0: computed internally =1: externally at PIN 9
FCM	Specification gas mass flows Like in Parent Profile (Sub profile option only) Expression =1: MOUTGAS AND MIA specified, M1 AND M3 calculated =2: MOUTGAS AND M3 specified, M1 AND M6 calculated =3: MOUTGAS AND M6 specified, M1 AND M3 calculated =4: MOUTGAS AND M1 specified, M3 AND M6 calculated =5: M1, M3 AND M6 specified (not for FCMEB=0!)
FCMEB	Mass and energy balance treatment Like in Parent Profile (Sub profile option only) Expression =0: TCLASS given =1: All inlet conditions given, T2/TCLASS calculated
FQEL	Electric power specification Like in Parent Profile (Sub profile option only) Expression =0: Calculated by Q7N and Characteristic line Q7/Q7N=f(M4/M4N) =1: externally (PIN 7)
MQEL	Fraction of el. power converted to heat
MIA	Fraction of penetrating air on MOUTGAS
MIATMIX	Fraction of penetrating air relevant for TMIX136 (T8)
FLOSS	Specification of heat losses Like in Parent Profile (Sub profile option only) Expression =0: Specification by DQLR =1: Specification by QLA
DQLR	Heat loss (relative)
QLA	Heat loss (absolute)
FREV	Mill rotation speed specification Like in Parent Profile (Sub profile option only) Expression =0: from characteristic line REV/REVN=f(M4/M4N) =1: externally (PIN 10)
RXH2OBN	Residual water content of fine coal nominal
FTNI	Unit used for calculation of TCLASS/TCLASSN in CL_12 Like in Parent Profile (Sub profile option only) Expression =0: Celsius =1: Fahrenheit =2: Kelvin
MOUTGASN	Gas mass flow at outlet (nominal)
VOUTGASN	Gas volume flow at outlet (nominal)
TCLASSN	Classifier temperature (nominal)
M4N	Raw coal mass flow (nominal)
Q7N	Electric power (nominal)
REVN	Mill rotation speed (nominal)

The parameters marked in blue are reference parameters for off-design, which are calculated by Ebsilon in the design mode. The actual off-design values refer to these parameters in the equations used.

Allowed combinations of flags

	FCM	1	2	3	4	5
FCMEB
0		Yes (FTMIX=0)	Yes (FTMIX=0)	Yes (FTMIX=0)	Yes (FTMIX=0)	No
1		Yes (FTMIX=1)	Yes (FTMIX=1)	Yes (FTMIX=1)	Yes (FTMIX=1)	Yes (FTMIX=0)

Results

CWCB4	Computed minimal raw coal XH2OB value expected due to RXH2OB specification
CWCB4DIFF	Difference of CWCB4 to the spec. raw coal XH2OB value at PIN 4
DP12	Pressure build-up
DP12R	Reference pressure build-up
Q7CL	Electric power from characteristic line
RXH2OB	computed residual water content of fine coal
MOUTGAS	Outlet gas mass flow
MOUTGASCL	Outlet gas mass flow from characteristic line
VOUTGAS	Outlet gas volume flow
QLOSS	Heat losses
REVCL	Mill rotation speed from characteristic line
QT	Heat transferred from drying gas to coal
MOMON	Relative outlet gas mass flow
VOVON	Relative outlet gas volume flow
M4M4N	Relative fuel mass flow
TCTCN	Relative classifier temperature
REVREVN	Relative mill rotation speed
RTCLASS	Computed classifier temperature
T2FTCL	Thermodynamic equilibrium outlet temperature T2 for desired classifier temperature

Characteristic lines

Char. lines 1 to 10: Pressure build-up DP12/DP12N = f (VOUTGAS/VOUTGASN) for different REV/REVN

     X-Axis       1         VOUTGAS/VOUTGASN          1. point
                      2         VOUTGAS/VOUTGASN          2. point
                        .
                      N         VOUTGAS/VOUTGASN         last point

     Y-Axis       1          DP12/DP12N                        1. point
                      2          DP12/DP12N                       2. point
                      .
                      N         DP12/DP12N                        last point

Char. line 11: Electric power Q7/Q7N = f(M4/M4N)

     X-Axis     1        M4/M4N                                 1. point
                  2        M4/M4N                                 2. point
                    .
                  N        M4/M4N                                last point

     Y-axis      1        Q7/Q7N                                 1. point
                    2        Q7/Q7N                                2. point
                    .
                    N        Q7/Q7N                                 last point

Char. line 12: Water content of fine coal RXH2OB/RXH2OBN = f(TCLASS/TCLASSN)

     X-Axis     1        TCLASS/TCLASSN                   1. point
                  2        TCLASS/TCLASSN                   2. point
                    .
                  N        TCLASS/TCLASSN                  last point

     Y-axis      1        RXH2OB/RXH2OBN                1. point
                    2        RXH2OB/RXH2OBN               2. point
                    .
                    N        RXH2OB/RXH2OBN               last point

Char. line 13: Gas mass flow MOUTGAS/MOUTGASN = f(REV/REVN)

     X-Axis    1        REV/REVN                               1. point
                  2        REV/REVN                               2. point
                    .
                  N        REV/REVN                              last point

     Y-axis      1        MOUTGAS/MOUTGASN         1. point
                    2        MOUTGAS/MOUTGASN         2. point
                    .
                    N        MOUTGAS/MOUTGASN        last point

Char. line 14: Rotation speed REV/REVN = f(M4/M4N)

     X-Axis    1        M4/M4N                              1. point
                  2        M4/M4N                              2. point
                    .
                  N        M4/M4N                             last point

     Y-axis      1        REV/REVN                           1. point
                    2        REV/REVN                           2. point
                    .
                    N        REV/REVN                          last point

Physics used

Equations

FFU=1

MF2 - mass flow fine coal at outlet
MH2O2 - mass flow of water steam at outlet
QFM2 = Q((M1+M3+M5+M6), TCLASS) – heat of gas at outlet
HH2ODAMPF(TCLASS) - enthalpy water steam for T=TCLASS
HF2 = HCoal(P2,TVIRT, RXH2OB) – enthalpy fine coal with residual water content RXH2OB at TVIRT, P2
TVIRT - temperature at which the water in coal remains to be in the liquid phase at P2
COMP2 - composition at outlet 2

FMODE=0:
{
   If FDP12=0
        DP12 = DP12N
    If FDP12=-1
        DP12 = P1 – P2

    Q7CL = Q7N
    RXH2OB = RXH2OBN
    MOUTGASCL = MOUTGASN
    REVCL = REVN
}

FMODE=1:
{
    If FDP12 = 0
         DP12 = f(Char.lines 1-10)*DP12N
    If FDP12=-1
         DP12 = P1 – P2

    Q7CL = f(Char.line 11) * Q7N
    RXH2OB = f(Char.line 12) * RXH2OBN
    MOUTGASCL = f(Char.line 13) * MOUTGASN
    REVCL = f(Char.line 14) * REVN
}

P1 - P2 = DP12 (1)

If FMOUTGAS=0
MOUTGAS = MOUTGASCL
If FMOUTGAS=1
MOUTGAS = M9

If FTMIX = 1
TMIX136 = T8
HMIX136 = f(TMIX136) mixing enthalpy

All FMODE

    M2 = M1 + M3 + M4 + M5+M6                                               (2)
    M9 = MOUTGAS                                                                      (3)
    If FQEL=0
       QEL = Q7CL                                                                          (4)
    If FQEL=1
        QEL = Q7
    QGRIND = QEL*MQEL
    QLOSS = DQLOSS*(Q1+Q3+Q4+Q5+Q6+QGRIND)
    MMIX136 = M1+M3+ MIATMIX*M6
    HMIX136 = (M1*H1 + M3*H3 + MIATMIX*M6*H6) / MMIX136

If FCM = 1
    M6 = MIA*MOUTGAS                                                              (5)
    M1*H1 + M3*H3 = MMIX136*HMIX136- MIATMIX*M6*H6          (6)
    M1 + M3 = MMIX136 - MIATMIX*M6                                       (7)
If FCM = 2
    M1*H1 + MIATMIX*M6*H6 = MMIX136*HMIX136- M3*H3          (8)
    M1 + MIATMIX*M6 = MMIX136 - M6                                       (9)
If FCM = 3
    M1 and M3 computed from (6) and (7)
If FCM = 4
    M3*H3 + MIATMIX*M6*H6 = MMIX136*HMIX136- M1*H1         (10)
    M3 + MIATMIX*M6 = MMIX136 – M1                                      (11)

If FCMEB = 0
    QT = HF2*MF2 + MH2O2 * HH2ODAMPF(TCLASS)-Q4
    QMIX136 = QT – QGRIND – Q5 + QFM2 + QLOSS – (1-MIATMIX)*Q6
    HMIX136 = QMIX136 / MMIX136
    TCLASS = H8
    H2 = f(P2, TCLASS, TVIRT, COMP2)                                            (12)
    T2 = f(P2,H2,COMP2)
If FCMEB = 2
    H2 = (Q1+Q3+Q4+Q5+Q6+QGRIND-QLOSS) / M2                    (13)
    Composition at outlet without residual water content of fine coal:
    COMPVIRT = COMP2 – f(RXH2OB)
    corresponding enthalpy:
    H2VIRT = (Q1+Q3+Q4-QF2+Q5+Q6+QGRIND-QLOSS) / (M2-MF2)
    TCLASS = f(H2VIRT, P2, COMPVIRT)
    H9 = TCLASS                                                                           (14)

Component displays

Display option 1

Example

Click here >> Component 129 Demo << to load an example.

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