A General-Purpose Procedure For The Calculation of The Optimum Gas Velocity in Gas Exhaust Ducts of Stacks at Thermal Power Stations
A General-Purpose Procedure For The Calculation of The Optimum Gas Velocity in Gas Exhaust Ducts of Stacks at Thermal Power Stations
         Abstract—The regulations on stack designs at thermal power stations (TPS) has been analyzed. It is demon-
         strated that the applicable guidelines do not consider all the actual problems encountered in designing stacks
         for TPSs, such as optimization of the stack construction cost and its effective operation. The stack cost
         depends on its height and diameter, which, at a given connected capacity, are affected by the gas velocity in
         the stack channel. At present, the effective stack design procedures do not contain the notion of this econom-
         ically feasible, cost-effective index, and the stack diameter is selected based on the engineering-and-cost esti-
         mation calculation procedures, which have not been approved as mandatory standards. These procedures are
         supported by the planning-and-distribution model of the country’s economic development. The article
         announces a universal method developed by the authors for calculating the optimal flue gas velocity for any
         model of economic development irrespective of the trend in prices and expenditures for the production of
         goods and services. To calculate the optimal flue gas velocity, one should only input initial data valid at the
         present stage. The calculated results of the price factors' effect on the optimal flue gas velocity for single-flue
         and multiple-flue stacks are presented. Verification of the procedure against the initial data as of 1975 yields
         acceptable results.
         Keywords: stack, thermal power station, economics, computational method, optimal velocity, ecology, flue gas
         DOI: 10.1134/S0040601520030064
   The decree of the Government of the Russian Fed-                                     that, for stack operation with condensate formation,
eration [1], which approved the rules for determining                                   the gas velocity at the stack’s mouth should not exceed
the limit (maximum and minimum) capital costs for                                       18 m/s to prevent a large discharge of the condensate
the implementation of upgrading projects for thermal                                    into the atmosphere.
power station, indexation of these costs, and selection                                     According to [3], the minimum flue gas velocity at
of modernization projects, became effective in Febru-                                   the outlet of the stack mouth is recommended to be at
ary 2019. The scope of a TPS upgrading project may                                      least 4 m/s in summer or 7 m/s in winter to eliminate
also include the replacement (or construction) of a                                     the effect of blowout and envelopment of the stack top.
stack at a coal-fired power station. In this case, the                                  It is recommended to determine the maximum outlet
stack cost is comparable with the cost of the main                                      velocity from the condition of no positive static pres-
equipment. For power stations fired with solid fuel,                                    sure along the entire stack flue (except for stacks with
the average cost of stack construction exceeds 70% of                                   gas-tight exhaust flues or backpressure stacks). The
the average cost for complete boiler replacement, and                                   flue of a reinforced concrete stack should be designed
the percentage of the construction and erection can                                     in the form of a cylinder, truncated cone, or a combi-
be as high as 95%. The facilities and equipment with                                    nation of both (a truncated cone and a cylinder). The
a total capacity above 40 GW are to be upgraded                                         ratio of the height of the entire stack or its individual
between 2022 and 2031.                                                                  section to the outer diameter should not generally
   A code [2] was published in 2018 wherein a proce-                                    exceed 20/1. The slope of the generatrix of the stack
dure for the calculation of the critical parameter, i.e.,                               surface to the vertical should be taken to be a maxi-
flue gas velocity in the stack, is absent. It is only stated                            mum of 0.1.
                                                                                   157
158                                                      ZROICHIKOV et al.
    The stacks are the most expensive element of the                    The volume of the reinforced concrete shaft with
TPS auxiliaries. Hence, proper selection of their basic             lining is calculated by the formula from [8]
characteristics is essential to minimize capital and                                                                0.5
operating expenditures during construction and oper-                                                      Tg 
                                                                            Vr/c sh. l = 0.01 H
                                                                                               2.2    0.5 0.3
ation of TPSs. The basic parameter to be optimized is                                                    T  ,
                                                                                                     D0 K w.l.              (4)
                                                                                                          ref 
the flue gas velocity at the stack mouth. The conclu-
sions made in the study [4], performed in compliance                where H is the stack height, m; D0 is the stack mouth
with the planning-and-distribution model of the                     diameter, m; Kw.l. is the wind load factor for the stack
country economic development existing at that time,                 shaft to be taken depending on the wind region; Tg is
should be updated to account for the conditions of the              the flue gas temperature, K; and Tref = 423 K is the
present market economy in Russia.                                   flue gas temperature taken as the reference one.
    Over the last three decades, the cost indicators of                 According to the data given in Table 10.3 from [8],
goods (such as steel, concrete, and electricity) and ser-           the proportionality factor in formula (4) is taken as 0.01.
vices (such installation and commissioning of equip-                    The reinforced concrete price consists of the price of
ment) required for the construction of a stack have                 concrete and structural steel; at the current wholesale
grown considerably. In addition, taking into account                prices and the degree of reinforcement of 200 kg/m3, it
the time factor, the cost of capital has become variable.           is 11000 rubles/m3.
    The best option for an investment project should be                 As a first approximation, the stack height Н0, m, is
selected based on the criterion of lowest total dis-                calculated according to [9] by the formula
counted expenses. Therefore, the optimum gas veloc-
ity is that yielding the minimum total discounted cost                                         AM F
for the construction of the stack, Cd [5, 6], to be calcu-                           H0 =                ,                       (5)
                                                                                             cst 3 V ΔT
lated by the formula
                τ
                                                                    where A is the coefficient depending on the meteoro-
                (K                                −τ               logical conditions in the climatic region of interest;
        Cd =            inv   + Ex + Ex f ) (1 + E ) ,       (1)    М is the harmful emission rate, g/s; F is the coefficient
               τ= 0
                                                                    accounting for the deposition rate of a harmful sub-
where Kinv is the investments, Ex is the expenses                   stance in atmospheric air; for gaseous emissions, F = 1;
without depreciation, Exf is the financial expenses,                for ash, F = 2–3; сst is the concentration of harmful
τ is the design service life of the stack, and Е is the             impurities discharged from the stack at the human
discounting rate.                                                   being inhalation level, mg/m3; V is the flue gas volu-
    The stacks belong to Group 6 of the All-Russia Clas-            metric flowrate, m3/s; and ΔT is the difference in tem-
sifier of Fixed Assets [7] with a maximum service life of           perature between the flue gases and the ambient air, K.
15 years inclusive. Therefore, the design service life for              The stack height considering the emission parame-
the study of stack performance is taken to be τ = 15.               ters is calculated by the formula
    The discounting rate is calculated according to [6]
is calculated by the formula                                                           H = mH 0,                      (6)
                                 n                                  where m is determined depending on the complex
                         E=     E a ,
                                i =1
                                       i i                   (2)    k D03 using the data presented in [10]. For a single-
where Ei is the price of the ith captial, ai is the share of        flue stack, the coefficient k in the complex k D03 is
the ith capital in the total investments, and n is the              calculated by the expression
number of capital types in the total investments.                                                 2
    The most widely used stack type is a single-flue                                  k = 1621 V2    .                           (7)
stack with a clamped lining. Its load-bearing rein-                                           H 0 ΔT
forced concrete shaft with the lining is considered as                 The volumetric flowrate of flue gases, m3/s, dis-
one solid item. Therefore, the stack cost Kst is calcu-             charged from the stack mouth is calculated by the for-
lated by the expression                                             mula
                    К st = К sh. l + К found ,               (3)                              πD02
                                                                                         V =       w,                     (8)
where К sh. l = Vr/c sh. lPr/c sh. l + L sh. l is the cost of the                               4
shaft with lining (here, Vr/c.sh. l is the volume of the            where w is the flue gas velocity at the stack mouth, m/s.
shaft reinforced concrete with lining, m3; Pr./c sh. l is the          The flue gas velocity minimizing the total dis-
price of the construction material of the shaft with lin-           counted costs is optimal wopt.
ing, rubles/m3; Lsh.l is the labor cost for construction               The labor cost for the construction of the lined
of the shaft with lining, rubles; and Kfound is the foun-           reinforced concrete shaft is estimated based on the
dation cost, rubles).                                               man-day input (see Table 10.3 from [8]) taking into
account the volume of lined reinforced concrete shaft                   For single-flue conical stacks, the friction loss, Pa,
and the price of a man-day, Pm-d, rubles/day, by the                 can approximately be taken as
formula
                                                                                        Δhfr = 0.3hv.h0,                (16)
                 L sh.l = 3.6 Vr/c sh. lPm-d.                  (9)   where hv.h0 is the velocity head at the stack mouth, Pa
                                                                                                       2
   The foundation cost is estimated by                                                   hv.h0 = ρ g w ;                   (17)
                                                                                                     2
           К found = Vr/c foundPr/c found + L f ,            (10)    here,
where Vr/c. found is the reinforced concrete volume in
the stack foundation, m3; Pr/c. found is the price of rein-                          ρ g = 1.29 273  ,                     (18)
                                                                                               273 + tg
forced concrete in the stack foundation, rubles/m3;
and Lf is the labor cost for the construction of the                 is the flue gas density, kg/m3, and tg is the flue gas tem-
foundation, rubles.                                                  perature, °С.
    The reinforced concrete volume in the foundation                     The local resistances, Pa, are calculated by the
is calculated by the formula                                         formula
        Vr/c found = 0.004H 2.3D00.45K w0.2.l.K s0.25,        (11)                    Δhl.r = hv.h0   ζ ,                 (19)
where Ks is the coefficient accounting for the soil                  where    ζ is the sum of local resistance coefficients
                                                                     (for single-flue conical stacks,  ζ = 0). The coeffi-
quality.
    The dependence of the reinforced concrete vol-
ume on the diameter and height of a stack were taken                 cient of resistance of the flue gas duct connection to
from [11, 12]; the proportionality coefficient value of              the stack belongs to the local resistances of the flue gas
0.004 is the weighted average value according to                     duct.
Table 10.2 of [8]. With the foundation reinforcement                    The head loss with outlet velocity, Pa, is taken to be
level of 100 kg/m3, the reinforced concrete price is                 the velocity head hv.h0 at the stack mouth
7000 rubles/m3.                                                                         Δho.v = hv.h0.                     (20)
    The labor cost for foundation construction is esti-                 The stack effect, Pa, is calculated as
mated based man-day input according to Table 10.2
of [8] using the formula                                                           Δhst. eff = (ρa – ρg )gH ,              (21)
                 L f = 0.7Vr/c foundPm-d .                    (12)   where ρa is the air density,  kg/m3,
                                                                                                       and g is the gravity
                                                                     acceleration, m/s2. Air density is calculated by the
    In the considered options, the expenses E is calcu-              formula
lated as follows:
                                                                                      ρa = 1.29 273 ,                    (22)
                   Ex = nopμ2аepN g.t ,                       (13)                              273 + ta
where nop is the number of boiler operating hours (with              where ta is the air temperature, °С.
an average boiler downtime of 1 month, nop = 8000 h);                    The reference for the further analysis was the data
аep is the power generation cost (approximately аep =                in Fig. 1a, which shows the optimal flue gas velocities
1.5 rubles/(kW h)); μ is the installed capacity utiliza-             in a single-flue reinforced concrete stack based on the
tion factor (approximately μ = 0.75); and Ng.t is the                prices of 1975 [4].
power consumption for gas transportation through the                     The predictions for the construction of a stack by
stack, kW:                                                           one’s own funds at a constant cost of capital are shown
                               VΔ h ,
                               −3
                                                                     in Fig. 1b. The average man-day price was taken to be
                  N g.t = 10                           (14)          2000 rubles/man-day. The electricity price growth
                             ηd.f ηmot                               rate between 1975 and 2018 was much higher than the
where Δh is the pressure difference required for flue                construction material price increase rate in this
gas transportation, Pa; ηd.f is the efficiency of the draft          period. This fact affected the optimal gas velocities in
fan (to be taken as 0.7); and ηmot is the efficiency of the          the stacks. Nowadays, it is more profitable to use rela-
draft fan motor (to be taken as 0.98).                               tively cheap construction materials and try to reduce
   The pressure difference consists of the friction                  the cost of flue gas transportation, thereby decreasing
loss, Δhfr, the losses due to local resistances, Δhl.r, the          the optimal flue gas velocities.
head loss with outlet velocity, Δho.v, and the stack effect,             The predictions in Fig. 1c show the optimal flue
Δhst. eff:                                                           gas velocities in reinforced concrete stacks under the
                                                                     existing construction conditions using loan funds got
          Δh = Δhfr + Δhl.r + Δho.v + Δhst. eff .             (15)   at 10% annual interest considering an inflation of 5%.
                                     (а)                                                                      (b)
          wopt, m/s                                                            wopt, m/s
                                                                                                                    4
          44                                                                   16
                      3                               4
                              2                                                                                3
          36                             1                                     12                                           2
          28                                                                    8
                                                                                           1
          20                                                                    4
           800 1000 1200 1400 1600 1800 2000 2200 V, m3/s                       800        1000        1200        1400     1600 V, m3/s
                                     (c)                                                                      (d)
          wopt, m/s                                                            wopt, m/s
                                     4                                         30                      4
          25
                                                                               25
          20                  3                                                                    3
                                                  2                            20                                       2
          15
                                                                               15
          10                                                                   10
                          1                                                                    1
           5                                                                    5
           800        1000        1200       1400                  3
                                                          1600 V, m /s          800        1000        1200        1400      1600 V, m3/s
                                                                         4
                                             50
                                                             3
                                             40
                                                                                    2
                                             30
                                             20
                                                             1
                                             10
                                              800         1000    1200         1400     1600 V, m3/s
   Fig. 1. Dependence of the optimal f lue gas velocity at the single-flue reinforced concrete stack mouth on the flue gas volu-
   metric f lowrate. (a) As of 1975 [4]; (b) as of 2018 with the constant cost of capital, stack construction using one’s own
   resources, and Pm-d = 2000 rubles/day; (c) as of 2018 with the inflation and Pm-d = 2000 rubles/day; (d) as of 2018 with the
   inflation and for Pm-d = 3000 rubles/day; (e) as of 1975 with zero inflation and stack construction using one’s own resources; Н, m:
   1—120; 2—150; 3—180; 4—250.
The figure also shows that the inflation and the cost of                     half the optimal velocities specified in the database for
credit quite noticeably affect the optimal gas velocity.                     1975 (see Fig. 1a).
It increases by approximately 4 m/s for 120-m high                               To verify the developed procedure, Fig. 1e rep-
stacks, 5 m/s for 150- and 180-m high stacks, and 7 m/s                      resents the predictions for the prices for 1975, which
for 250-m high stacks.                                                       were as follows [4]: Pr/c. sh. l = 316.8 rubles/m3,
                                                                             Pr/c. found = 253.4 rubles/m3, Pman-day = 10 rubles/day,
    Under the same conditions, increasing the man-day                        аe.p = 0.005 rubles/(kW h). The data presented in
price by a factor of 1.5 rose the optimal gas velocity by                    Figs. 1a and 1d are nearly the same, especially for a
approximately 1.0 m/s for 120-m high stacks, 1.5 m/s                         180-m high stack.
for 150- and 180-m high stacks, and 2.5 m/s for 250-m                            Optimal velocities in a multiflue stack are further
high stacks (see Fig. 1d). However, these velocities are                     analyzed by an example of the most common four-
flue stacks, which are basically used at cogeneration              depends on the reinforced concrete volume and the
power stations (TETs). It is assumed that the average              man-day cost, by the formula
wall thickness of the flues is the same, and all the flues
are made of carbon steel with a corrosion allowance of                       L sh. found = 0.2 Vm-f foundPm-d .         (28)
14 mm. The flues are cylindrical along the entire                     The cost of the flues was calculated by the expression
height, and an increase in the metal volume in the
basement is taken into account in the average thickness                              К fl = PflVm + L fl,             (29)
of the flue walls. The minimum distance between the                where Pfl is the flue construction material price
wall of the flues is 1.2 m, and that between the outer wall        (which is approximately Pfl = 312 000 rubles/m3 for
of the flue and the inner wall of the reinforced concrete          steel); Vm is the volume of metal consumed for the
shaft in its upper part is 1.0 m. The cost of a multiflue          manufacture of all flues, m3; and Lfl is the labor cost
stack Km-f st is calculated by the formula                         for installation of all flues, rubles.
                                                                       The volume of metal for construction of all flues is
            К m-f st = К sh + К found + К fl,         (23)
where Ksh is the shaft cost (without lining in this case);                          Vm = π dfl H δN fl,              (30)
Kfound is the foundation cost; and Kfl is the cost of              where dfl is the flue inner diameter, m; δ is the flue
flues.                                                             wall thickness (for steel δ = 0.012–0.014 m); and Nc is
   The shaft cost is                                               the number of flues.
                 К sh = Vr/c shPr/c sh + L sh ,        (24)           The flue inner diameter was calculated by the for-
                                                                   mula
where Vr/c.sh is the volume of the shaft reinforced con-
                                                                                                 4Vfl
crete; Pr./c sh is the price of the construction material of                           dfl =           ,                 (31)
the shaft; and Lsh is the labor cost for construction of                                         π wfl
the shaft with lining.                                             where Vfl is the gas flowrate through one flue, m3/s;
   The reinforced concrete volume in the shaft is cal-             and wfl is the gas velocity in the flue, m/s.
culated by the formula                                                 According to [14], the labor cost for the installation
           Vr/c sh = 0.09H sh
                           1.75 0.6
                               Dsh K m-f w.l ,        (25)         of the flues, Lfl, rubles, is
where Hsh is the reinforced concrete shaft height (to be                             L fl = 60 VmPm-d .                  (32)
taken 5 m lower than the stack height); Dsh is the shaft                The predictions for the four-flue stacks with the
inner diameter at the stack outlet, m; and Km-f w.l is the         metal flues in a common reinforced concrete shaft in
wind load factor for the shaft of a multiflue stack (to be         the prices for 2018 are shown in Fig. 2.
taken according to Table 3 [13]).                                      Comparison of the data presented in Figs. 1b and 2a
   The price of reinforced concrete for a multiflue                demonstrates that the optimal velocity in the multiflue
stack was taken to be the same as the price for a single-          stack is higher than that in the single-flue stack. This
flue stack, i.e., 11000 rubles/m3.                                 difference is greater for relatively low stacks. The effect
   The labor costs for the construction of a rein-                 of volumetric flow rate and stack height for four-flue
forced concrete shaft in formula (24) are calculated               stacks is less pronounced than for single-flue stacks.
based on the number of expended man-days accord-                   This stems from the fact that the cost of multiflue
ing to Table 10.3 from [8], which depend on the vol-               stacks is considerably greater than the cost of single-
ume of reinforced concrete and the price of a working              flue stacks.
day, using the formula                                                 The predictions for the four-flue stacks with the
                 L sh = 2.9Vr/c shPm-d .                  (26)     metal flues in a common reinforced concrete shaft in
                                                                   the prices for 2018 with the inflation of 5% and the
    The cost of a multiflue stack foundation is calcu-             construction out of borrowed funds made at an inter-
lated by                                                           est rate of 10% per annum are shown in Fig. 2b. As is
                                                                   evident from the figure, the inflation and the interest
     К found = Vr/c sh. foundPr/c sh. found + L sh. found , (27)
                                                                   rate have a quite strong effect on the optimal velocity
where Vr/c. sh. found is the reinforced concrete volume in         of flue gases in four-flue stacks, which increases by
the foundation of a multiflue stack shaft, m3, to be cal-          approximately 5 m/s. The optimal gas velocities in
culated by formula (11); Pr/c. sh. found is the price of           250-m high four-flue (see Fig. 2b) and single-flue (see
material consumed in manufacturing the reinforced                  Fig. 1c) stacks are quite close. If the optimal gas veloc-
concrete foundation (to be taken the same as that for a            ities range from 19 to 27 m/s for single-flue stacks,
single-flue stack, i.e., 7000 rubles/m3); and Lsh. found is        then they range from 23 to 26 m/s for four-flue stacks.
the labor cost for construction of the shaft foundation.           For lower stacks, this difference increases.
   The labor cost for the construction of the multiflue                The effect of the man-day cost for installation
stack foundation was calculated from the number of                 activities on the optimal flue gas velocity can be
expended man-days according to Table 10.2 [8], which               revealed by comparing Figs. 2b and 2c. Increasing the
                                                (а)                                                                             (а)
wopt, m/s                                                                                    Кrat
                                                                                                                    3                     4
                                 4                                                           0.92
                                                      3
20
                                                                                             0.90
 15
             2                                  1                                                      1        2
 10
  800            1000            1200                 1400               1600      V, m3/s   0.88
                                                                                                800        1000         1200          1400      1600 V, m3/s
                                                (b)                                                                             (b)
wopt, m/s
                                                                                             Кrat                       3             4
                             4                             3
25
                                                                                             0.92
20
           2                 1
 15                                                                                          0.90
  800            1000            1200                 1400               1600      V, m3/s
                                                                                                      1
                                                (c)                                                                         2
wopt, m/s
                                                                                             0.88
                                                           3                   4                800        1000         1200          1400      1600 V, m3/s
25
                                                                                                Fig. 4. Dependence of the ratio of the cost of (a) single-
20                                                                                              flue or (b) four-flue stacks with the inflation considered to
                                 2                                                              the cost of the same stack estimated without inflation on
                                                                 1                              the flue gas volumetric flowrate; 1–4—see Fig. 1.
 15
  800            1000            1200                 1400               1600      V, m3/s
      Fig. 2. Dependence of the optimal flue gas velocity on the                             man-day cost by a factor of 1.5 raises the optimal
      flue gas volumetric flowrate in four-flue stacks with metal                            velocity by approximately 1 m/s.
      flues as of 2018. (a) With the constant cost of capital;
      (b) with the inflation and Pm-d = 2000 rubles/day; (c) with                               In spite of the fact that the diameters of flues and
      the inflation and Pm-d = 3000 rubles/day; 1–4—see Fig. 1.                              the shaft decrease, the cost of the stack increases by
                                                                                             11–12% irrespective of its height. This is explained by
                                                                                             the fact that the effect of increasing labor cost prevails
                                                                                             over a decrease in the price of the used construction
                                                (а)
                                                                                             materials.
Кrat                 1
                                                                                                 The comparison of Fig. 1d with Fig. 2c demon-
2.5                                              3                       2                   strates that the optimal gas velocities in 250-m high
                                                                                             single-flue and four-flue stacks are comparable. For
2.0                                                                                          lower stacks, a considerable difference is evident: the
                         4
                                                                                             optimal velocity is 20 m/s in four-flue stacks and 10 m/s
1.5                                                                                          in single-flue stacks.
  800                1000            1200                 1400               1600 V, m3/s
                                                (b)                                              Figure 3a shows the ratio of four-flue to single-flue
Кrat             1                                                                           stack cost Krat, which slightly depends on the flue gas
                                            3
                                                                                             volumetric flow but quite considerably on the stack
2.5                      2                                                                   height. This ratio is 2.6 for 120-m high stacks and 1.7
                                                                                             for 250-m high stacks.
2.0                                                                  4
                                                                                                 Figure 3b shows the ratio of four-flue to single-flue
1.5                                                                                          stack cost considering the effect of inflation. Compar-
  800                1000        1200                     1400            1600 V, m3/s       ison of Fig. 3b with Fig. 3a suggests that these values
                                                                                             have changed only slightly, but with the inflation taken
      Fig. 3. Dependence of the ratio of the cost of a four-flue                             into account the stack cost decreases with an increase
      stack with metal flues to the cost of a single-flue reinforced
      concrete stack, both designed for same parameters, in
                                                                                             in the optimal gas velocity. Comparison of Fig. 4a with
      prices for 2018 with (a) the constant cost of capital and                              Fig. 4b demonstrates a more pronounced effect of the
      (b) with inflation. 1–4—see Fig. 1.                                                    inflation on the cost for single-flue stacks.
Cd, Kst, million rubles                                                  We have developed the codes for calculating the
                                                        H, D0, m     optimal gas velocity for various stack types (single-flue
500
                                                                     stacks with a vented air clearance, three-flue stacks,
                                                                     etc.). Figure 5 represents the predicted optimal flue
                                                                     gas velocities in a 250-m high four-flue stack at a vol-
400                                                                  umetric flowrate of 1600 m3/s.
                                   4                                     The results of the aerodynamic calculation of the
                                                               200   distribution of positive static pressures pst along the
300                                                                  stack height performed by the procedure described
                                                                     in [15] with account taken for the slope of the stack
                 2                                                   generatrix, U, and the absolute roughness of the stack
                                                                     inner surface, Δ0, are shown in Fig. 6.
200                                                                      In the first case (see Fig. 6a), a negative pressure is
                1                                              100   observed along the entire stack height, which exceeds
                                                                     700 Pa at the stack bottom, and no limits are imposed
100                                                                  on the static pressures in the stack. In the second case
                                                                     (see Fig. 6b), a positive static pressure is built in the
                               3                                     top section of the stack. The codes have also been
                                                                     developed for calculating the optimal parameters of a
                                                               0     three-flue stack with flues having any diameter.
  0                    20               40         w, m/s
                                                                         Thus, the optimal flue gas velocity in exhaust flues
                                                                     in stacks of different designs can be calculated at dif-
  Fig. 5. Predicted optimal velocities of flue gases. 1—Cd;          ferent emission parameters considering the existing
  2—Кst; 3—D0; 4—Н.                                                  situation in the economics.
                                                                                        CONCLUSIONS
                             (а)
                                                        Н, m            (1) The developed mathematical model and the
                                                                     software package created on its basis have been veri-
                                                                     fied under the conditions of the planning and distribu-
                                                                     tion model of the country’s economic development.
                                                        200             (2) The procedure proposed by the authors for cal-
                                                                     culating the optimal flue gas velocity for any model of
                                                                     economic development is universal and does not
                                                                     depend on the trend of prices and costs for produc-
                                                        100
                                                                     tions goods and services. To calculate the optimal flue
                                                                     gas velocity, one should only input the initial informa-
                                                                     tion applicable at the present time.
                                                                        3. Application of the developed software code has
      рst, Pa   –600        –400       –200         0                yielded that the gas velocity adopted now in designing
                             (b)
                                                                     stacks are considerable overestimated.
                                                        Н, m
                                                                                         REFERENCES
                                                                     1. “On the selection of modernization projects for gener-
                                                        200             ating facilities of thermal power plants,” RF Govern-
                                                                        ment Decree No. 43 of January 25, 2019.
                                                                     2. SP 375.1325800.2017. Industrial Chimneys. Rules for
                                                                        Design (Izd. Standartov, Moscow, 2018).
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