Thermal load impact on steam parameters for cooling the shaft furnace.
Terziqi, Avni Kahriman ; Haxhiaj, Ahmet Bajram ; Kamberaj, Naim Sokol 等
1. INTRODUCTION
The cooling system by evaporation based on the level of the
temperature and the amount of heat released out of process. The proposed
outline for the furnace cooling as shown in Fig. 1, consist of part of
manifolds (TL1, TL2), from the part pipelines composite of the lower
cooling (FP), medium (FM) and on top (FS), from exonerative pipes (TSH1,
TSH2) and steam cylinder-separator (CS). In outline are including
connection pipes (TLDH1, TLDH2) and collectors (KO1, KO2). Manifolds,
connection and exonerative of outline are the diameter, length, height
and certain number ([d.sub.L1], [d.sub.L2], [d.sub.1], [d.sub.2],
[d.sub.SH1], [d.sub.SH2], [L.sub.L1] [L.sub.L2], [L.sub.SH1],
[L.sub.SH2], [H.sub.L1], [H.sub.N], [H.sub.FP], [H.sub.FM], [H.sub.FS],
[H.sub.SH1], [H.sub.SH2], [H.sub.KTH], [n.sub.L1], [n.sub.L2],
[n.sub.1], [n.sub.2], [n.sub.SH1], [n.sub.SH2]) as well as the
corresponding coefficient of hydraulic resistance [MATHEMATICAL
EXPRESSION NOT REPRODUCIBLE IN ASCII]. The impact of thermal loads,
thermal-physical parameters (p, [T.sub.N, [rho'],
[rho''], [rho], h', h", h, [c.sub.p], v, [mu],
[beta], a, [sigma], [lambda], [P,sub.r] [DELTA]h'/[DELTA]p) of
steam-water mixture, then geometric parameters and hydro mechanical of
communications of outlines circular in consumptions circular
([G.sub.o]), in speed of the circulation ([[omega].sub.o]) and mass
content of steam consumption ([x.sub.D]) is in interest to assess the
cooling system by evaporation in Trepca shaft furnace.
2. THERMAL LOAD IMPACT, ON DYPHASIC BRINGING OF OUTLINE
For practical calculations of heat transmission between gas and
cooling medium in the furnace coolant (FP, FM, FS), should be designate
the amount of heat per unit surface area according to the formula
(Michael & Howard, 2004) as the following:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1)
Where [[alpha].sub.G], [[alpha.sub.AU]--are coefficients of gas
heat transmission (Gordon, 1993) and steam- water composite (Sacadura,
1993) Who are determined by the following equation:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (2)
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (3)
Whereas [t.sub.G], [t.sub.AU]--is gases temperature in the lower
coolant level, and temperature of steam--water composite, [degree]C;
[[delta.sub.GA], [[delta.sub.M], [[delta.sub.K] then [[lambda.sub.GA],
[[lambda.sub.M] [[lambda.sub.M]--thickness and heat conductivity
coefficients for protective layer, coolant wall and calcium carbonates
layer in level of FP, FM and FS. Amount of heat transmitted to the unit
surfaces area of FP, FM and FS is determined according to equation:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (4)
Where are: [A.sub.P], [A.sub.M], [A.sub.s]--overall coolant
surfaces of the lower, medium and of the top level, [m.sup.2].
[FIGURE 1 OMITTED]
To determine the height from which come of the movement effort, it
is necessary to determinate the scission this begins the regime of steam
(Kutepov, M. 1983). This scission determined by the length of the
economizer part [l.sub.EK] as follows:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (5)
Where are: [h.sub.LSH]--water enthalpy incoming the manifolds,
kJ/kg; [q.sub.p]--heat density flux in the economizer scission,
kW/[m.sup.2]; d--Internal diameter of tube, m. Speed of circulation can
be determined by the gradual approximation method (equation 8). The
first designated the total coefficient of hydraulic resistance to water
line under the equation:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (6)
Where are: [Z.sub.L1], [Z.sub.L2], [Z.sub.EK]--overall coefficient
of hydraulic resistance in not heated manifolds with diameter dL1 and
[d.sub.L2] likewise in economizer part. The complex
[[SIGMA][DELTA].sub.ML] is determined by expression:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (7)
Where are: [[DELTA].sub.P.sub.PTF], [[DELTA].sub.P.sub.TSH],
[[DELTA].sub.P.sub.LL]--total loss of pressure in the hered of
half-pipes in the ranks of furnace coolants in manifold and in the part
of manifold (in up lift of composite above than free surfaces of liquid
in cylinder).
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (8)
Mass content of steam consumption at the exit of tubes herd of the
furnaces coolants determined by the following equation:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (9)
3. CALCULATIONS AND RESULTS
Incoming data (Agolli, 1985) for calculation are: [MATHEMATICAL
EXPRESSION NOT REPRODUCIBLE IN ASCII]. Calculations are done according
to the respective program.
[FIGURE 2 OMITTED]
Variables of the model, in this paper are calculated for several
levels of incoming values of thermal loads, meanwhile the presented
results above are obtained for average values of thermal loads:
[q.sub.P]=17653 W/[m.sup.2], [q.sub.M]=9655 W/[m.sup.2] and [q.sub.S]=
2669 W/[m.sup.2].For example, in fig. 2, fig. 3. and fig. 4. is shown
dependence [G.sub.o] = f ([Q.sub.F]), [[omega].sub.0] = f ([Q.sub.F])
and [x.sub.D] = f([Q.sub.F]), for a wider range of change of quantity of
heat (1/5, 1/2, 1, 2, 5, 10, 12, 15 and 20 x [Q.sub.F])
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
4. CONCLUSION
Dependence [G.sub.o] = f ([Q.sub.F]) and [[omega].sub.0] =
f([Q.sub.F]) is characterized with circulation consumption and speed low
circulation for small thermal loads.
By increasing of thermal loads we have consumption increase
([G.sub.o]) and circulations speed ([[omega].sub.0) up to a certain
level. In addition, with further increase of thermal loads appears
reduce of consumption ([G.sub.o]) and speed ([[omega].sub.0]) because
the other factors who act in the opposite direction affect on this.
By increasing the thermal load increases the content of steam
([x.sub.D]) in the outline, and moving effort where at once increases
the circulation consumption ([G.sub.o]) and on the other hand, increases
hydraulic resistance in upper parts outline, that have steam content.
For the average parameters of the work regime in the furnace, is
generated a considerable amount of steam in the furnaces coolant (FP,
FM, FS) as: [D.sub.AP] = 0.168 kg/s, [D.sub.AM] = 0.150 kg/s,
[D.sub.AS]' = 0.057 kg/s and [D.sub.AF]' = 0.375 kg/s.
5. REFERENCES
Agolli, F. (1985). Metallurgy of ferrous metals, Faculty of mining
and metallurgy, Mitrovice
Kutepov, M. & Sterman, S. (1983). Hydrodynamics and heat
transfer in the creation of steam, BBK 31. 31 K95 YDK 621.1.7, Moskva
Gordon, M. (1993). Thermal calculations of metallurgical furnaces,
Metallurgy, ISBN5-229-00711-7, Moskva
Michael, J. & Howard, N. (2004). Fundamentals of Engineering
Thermodynamics, John Wiley, ISBN 0-47127471-2, Hoboken
Sacadura, J. (1993). Knowledge for thermal transfer (Initiation aux
transferts thermiques, TEC&DOC, ISBN 2-85206-6181, Paris
