RU2001114C1 - Device for cooling metallurgical furnace walls - Google Patents

Abstract

Usage: the invention relates to metallurgy, in particular to cooling the walls of metallurgical furnaces, mainly blast furnaces The essence of the invention: a device for cooling the walls of a metallurgical shaft furnace contains vertically perimeter walls on the side of the inner surface of the casing in the thickness of the layer of heat-resistant concrete sections from water cooling pipes with transverse ribs, the input and output of each of which are oriented towards the casing. Moreover, the water cooling pipes are U-shaped and equipped with turbulators installed in their inner half The transverse ribs covering each water-cooling pipe are made in the form of plates that have different areas and are assembled in at least one package, in order to decrease the areas of these ribs from the central to the peripheral ribs, and the sizes and arrangement of elements designs are selected from the condition of ensuring acceptable temperature on the casing 3 sludge

Description

The invention relates to metallurgy, in particular to cooling the walls of metallurgical furnaces, mainly blast furnaces.

A device is known for cooling the wall of a metallurgical shaft furnace, in particular a blast furnace, and comprising sections located along the perimeter of the wall from water cooling pipes having U-obfmofofma installed on a building-element of the casing and built into the thickness of the layer of heat-resistant concrete, input and the output of each of which is oriented towards the building element of the casing.

A disadvantage of the known design of a device for cooling the wall of a metallurgical shaft furnace is the insufficient cooling efficiency of the furnace wall casing, since in this case it is not possible to obtain maximum heat dissipation at a given flow rate of the cooling agent.

The closest to the invention in technical essence and the achieved result is a device for cooling the wall of a metallurgical shaft furnace, containing vertically perimeter walls from the side of the inner casing, in the thickness of the layer of heat-resistant concrete sections from water pipes with transverse ribs, inlet and outlet each of which is oriented towards the casing. In order to increase the heat transfer efficiency in this device, the heat transfer surface is developed by finning.

A disadvantage of the device is the insufficient cooling efficiency of the furnace wall casing due to the absence of a direct relationship between the size and location of the water cooling pipes, as well as the size and location of the transverse ribs relative to the outer surface of the pipe, from the operating characteristics and thermal loads. This question can be solved by mathematical modeling to increase the cooling effect. In addition, in the design of this apparatus for cooling the wall of a metallurgical shaft furnace, cooling water is not used efficiently. The bulk of the water passes through the central part of the cross section of the water cooling pipe, not actively participating in heat transfer. Here, the water flow has a higher velocity than at the periphery of the cross section, where the wall effect of a decrease in velocity is affected. At the walls of the pipe there is an increase in water temperature, accompanied by the precipitation of salts of temporary hardness and

the formation on the walls of scale, disrupting heat transfer.

As a result, the durability of the lining of the furnace and the device for cooling the wall of the furnace itself are reduced.

The aim of the invention is to increase the cooling efficiency of the furnace wall casing and to reduce water consumption. The specified goal is achieved by the fact that in

the proposed device for cooling the wall of a metallurgical shaft furnace containing vertically perimeter walls from the side of the casing, in the thickness of the layer of heat-resistant concrete sections of water cooling pipes with transverse ribs, the inlet and outlet of each of which are oriented towards the casing, according to the invention water-cooled pipes are U-shaped

0 shape and equipped with turbulators installed in their inner cavity, the transverse ribs covering each water cooling pipe are made in the form of round plates, have different areas, are assembled in at least one package in order to decrease the areas of these ribs from the central to the peripheral ribs , elbow length and distance between inlet and outlet of water pipe

0 cooling, the distance between adjacent water cooling pipes along the longitudinal axis of the shaft furnace and in the transverse direction to it, as well as the height of the central transverse rib in each package

5 above the outer surface of the pipe and the layer of heat-resistant concrete from the outer surface of the pipe is selected from the condition:

t max t, f-r max t / „, 1 s - I о + (I Co I о) (Eo + mm

0+ Za Vl + S

 I 1

where Tcmax is the maximum temperature on the casing of the shaft furnace;

T0 is the ambient temperature;

Tsotakh - the maximum temperature on the casing of a shaft furnace without water cooling pipes;

a0, at, ay - regression coefficients;

p |, f) is the basis function

at (f 1,2- -;

3

2 24.86-40.67 -;

ABOUT

p3 3.83-6.54 Ј; S

0

5

(/)4

4.53-7.34 -;

ABOUT

10V-108

P

d -At

.91-1.5 b

AND

 (1-0.67) +

I, (.34

+ 0,) Amet

lbet -1

Re

CL

Peclet test;

dT)

when - I, when there is no turbulizer in the device;

IL

0.33

warmth

h

)

at I 0 0.023 A () ° 8- (M.

a // l

when the device has a turbulator. where d is the diameter of the water cooling pipe,

S is the distance between adjacent pipes in the transverse direction;

I is the distance between the inlet and outlet of the water cooling pipe;

L is the length of the elbow (bent portion) of the water cooling pipe;

d is the distance between adjacent pipes along the longitudinal axis of the shaft furnace;

Srtepl - heat capacity of the heat carrier;

G is the flow rate of the coolant through the water cooling pipe;

Atepl - thermal conductivity for the coolant;

Abeg - thermal conductivity of concrete;

I - viscosity of the coolant:

a - the height of the Central transverse ribs in each package above the outer surface of the pipe;

m is the height of the layer of heat-resistant concrete from the outer surface of the pipe;

Amet is the thermal conductivity of the material from which the transverse ribs are made.

Comparative analysis with the prototype shows that the claimed device is characterized in that the water cooling pipes are U-shaped and equipped with turbulators installed in their inner cavity, the transverse ribs covering each water cooling pipe are made in the form of round plates, have different areas collected in at least one package in order of decreasing areas of said ribs from central to peripheral ribs, the sizes and arrangement of structural elements of the device being selected from conditions.

Thus, the claimed device meets the criteria of the invention of novelty.

A comparison of the claimed solution with other 5 technical solutions shows that the use in technology for the intensification of the heat transfer process of silver pipes and turbulators is known. As a result of the analysis of well-known solutions, 10 it was found that the distinguishing feature

transverse ribs covering each water cooling pipe are made in the form of round plates, have different areas, are assembled at least

15, one packet, in order to decrease the area of these ribs from the central to the peripheral ribs, is not known. In addition, as a result of the analysis, it was found that the claimed device exhibits technical

20, a property that is not manifested in any of the known technical solutions containing distinctive features separately or in combination. A new technical property allows one to increase and optimize the specific heat from a unit volume. create a system of stabilization of temperature gradients by volume, which leads to an increase in the heat resistance of concrete lining. This allows us to conclude

30 according to the technical solution to the criterion, significant differences.

In FIG. 1 shows a section of a device for cooling a wall of a metallurgical shaft furnace, a general view,

35 longitudinally vertical section; in FIG. 2

a turbulator placed in a water cooling pipe; in FIG. 3 is a graph of the function of a (- + 1), which is a parabola,

passing through midpoints of the width of the cross section of the transverse ribs of the packet.

A device for cooling the wall of a metal, thallurgic shaft furnace is a section (not shown) located along the perimeter of the wall of the furnace. Each section (Fig. 1) includes at least two UCQ-shaped water-cooling tubes 1 mounted on a building element of the casing 2, input 3 and output

4 each of which is oriented towards the last. Built-in layer

5, the heat-resistant concrete of the water-cooling pipe 1 is provided with transverse ribs 6 located on their outer surface. Cross ribs b. welded to the water cooling pipe 1, cover the latter around its entire circumference and are assembled at least in

40

one packet 7 of the transverse ribs arranged in decreasing order from the central 8 to the periphery. In this case, the transverse ribs 6 in the packet 7 are contacted by end surfaces. Based on the technology of manufacturing ribs in this example, ribs 6 with a cross section made in the form of a rectangle consisting of two parts (not shown), or ribs b in the form of rings made, for example, from Art.20 can be used . A turbulator (Fig. 2) is installed in the inner cavity of each water-cooling pipe 1 (Fig. 2), for example, made in the form of a tape 9, which has petals at the edges of the slots 10 (not shown in Fig. 2), each of which is turned around its axis. Tape 9 is folded along a helical line.

Holes (not shown in the drawing) are cut out on the building element of the casing 2 for installing water-cooled pipes 1 with pre-welded fins 6, forming a single system.

A turbulator-ribbon 9 is installed in each water cooling pipe 1, which is fixed at the inlet 3 and outlet 4 of the pipe 1 by welding. Then, using formwork (not shown in the drawing), a layer 5 of heat-resistant concrete is applied according to the commonly used technology. Along the perimeter of the building element of the casing 2 of each section of the proposed device, a gap 11 is left in the form of a lining-free part of the casing for the possibility of welding joints between adjacent building elements and irreplaceable parts of the furnace shaft.

A cooled concrete structure is contemplated (Fig. 1). It is required to estimate the value of Tc as a function of S, I, h, g, Atepl, Abet. d, G, A met, a, m, To. Tw, i.e. to find

Tc f (S, I, h, Atepl D 6er, d, G, A met, a, t, To, Tw).

We will search for Tc in the form:

Tstax a0 + i ai pi,

where p 1 - some combination of parameters (Tcmax-max temperature on the casing).

Basic equations: thermal conductivity for concrete and casing

dlv (Agrad T) a, thermal conductivity for the coolant:

dlv (Q Cr UT) dlv (A rad T). Gr. conditions: at H, T Tw

f for the casing portion - A grad T - a (Tc-To),

 for the heat carrier section Т - Т0- at the inlet - - A grad Т 0 - at the outlet.

y-0

Let the determining parameters vary in the following ranges:

0 0.001-5 kg / s; d 3 m; I 0.3-2.2 m; h 0.07-0.3 m; g 0.05-0.15 m; S 0.05-0.15 m; A bet 0.1-1 W / mk

We introduce the assumptions: 1. The non-uniformity of the flow with respect to z does not affect Tstax:

2. The variability of thermophysical characteristics does not affect Txt, 0 These assumptions allow us to highlight for consideration a part of the structure with one cooling element.

We introduce the linear scale z0 S and write the dimensionless variables

  1; d-l; I l: h A:

Zo ZoZQZo

  G.S S.I 1T6PL

g -, E -, LO-A

Zqzo

We introduce the scale of the velocity Go and the scale 0 of thermal conductivity A o. We define the temperature as. Since S is always 1

I w I o

and, according to the assumptions, we write the basic equations in the form:

5

0

ABOUT

ir # I + #LAv v}

 §) (§ + Ts)

k3 EU2

or in dimensionless form: A-Ao (Tw-To), # 0, # 0,

 I-JL - 0 ZoEx2 du2

AND(

 V

Gpp. (J That)

Zo

Cquc

Oj | + vЈ)

W

40

AJTw-To), # 0h

J tTT dfy

w

., Э0, v 30 A, # 0 # & u dx v 3y cqUofo 2 + 2)

Zu cqUoZo -fa

We introduce Go qU0dz0 - the scale of the reduced flow rate.

0

THEN ° ° 1 °

Enter Peclet Re Number Re PR CqUpZo GoCqzo CpG AqdZoA dT

heat, / -

those. Pe

A 5 mash;

E0

A when there is no U-57 turbo

dx

E0 1, # 0

. # 0

2

+ (ChL 0.023 A (“3fe. (Tlcr:

0.33

- when there is a turbulator in the device.

Thus, the dimensionless equations are independent of 20.

Intervals of variation of dimensionless variables:

d 0.2-2.2; 1 3.3-44; h 0.46-6; Re - 00-U8; I bet 0.166-1.66; g 0.3-3.

We are looking for the initial response function in the regression equation

/ tlech

0 a0 + Ј aiti + Ј aijtitj,

6 & ah

i i

t is a factor that varies at two levels.

10

We construct an orthogonal plan and carry out a computational experiment

a (0) 3.6562

a (1) .59251

a (2) 1.6880

a (3) .3379020

a (4). 65365

a (5) -1.6872

a (6) 1.9393

a (7) 2.2820

a (8) -2050025

a (9) .43171

a (10) .32283

a (11) .63193E-02

a (12) .23070E-01

a (13), 36617E-0130

e (14) .39473E-01

a (15) .14321E-01

a (16) .43803E-01

a (17) .12479E-01

a (18) -98996E-0135

a (19) .71441E-C1

a (20) .75266E-02

a (21) .49462E-02

a (22) .18745E-04

a (23) .23546E-0240

a (24) .30053E-02

a (25) .25111E-02

a (26) .24625E-02

a (27) .27820E-02

a (28) .35486E-0245

a (29) -.29678E-02

a (30) .2826GE-02

a (31) .36125E-02

a (32) -.30317E-02

a (33) -.50761E-0250

a (34) .11209E-02

a (35) .73179E-02

a (36), 41815E-03

a (37) .36704E-03.

These are the regression coefficients for the equation 55

/ tpx37

JL a0 + Ј achr,

t / LOi - I

whether n dimensional form:

Tc ™ To + (Tsotakh-To) (a0 + 2 ai p i +

i 1

m

+ Е a i У1 Ю) i i

j i

Here, To is the ambient temperature, Tcomax is the maximum temperature on the casing of the shaft furnace without water cooling pipes.

R.-1.2-ZY.

/ B - 24.86-40.67 -,

rzf4

3.83-6.54 j 4.53-7.34

108-108

Staple D

-1.5

Db

d-Jat

em

1T6PL

l

 Dbet (1-0.67) Yamet - 0.67

(

Lbet

+ 0.33 t-5-)

m

a -1

Lmet

We define the function y a (1), the graph

which is a parabola passing through midpoints of the width of the cross section of the transverse ribs 6 of the packet 7, decreasing in height from the center to the periphery. This allows the heat to be regulated along the water cooling pipe parallel to the generatrix (Fig. 3). In FIG. 3 isoch2 the graph of the function y a (-y + 1) is shown,

the curve of which allows us to judge the smooth regulation of volumetric heat removal.

The device operates as follows.

The cooling medium (process water) enters the water cooling pipes 1. Heat is removed from the gas stream and charge materials, the cooling medium is heated and enters the external communications as pipes enter the mixture. The metal transverse ribs 6 are cooling fittings for the heat-resistant concrete 5, which can significantly reduce its wear. The presence of sections uniting several water cooling pipes 1 allows extremely narrowing the distance between the pipes, which will ensure reliable cooling of the furnace casing. The flow of the cooling medium moving along the pipe 1 interacts with the tape 9 and acquires a rotational movement around the axis of the pipe 1. At the same time, in the boundary layer this stream is additionally turbulized due to interaction with the petals (not shown in Fig. 2) located near the inner surface of the pipe 1. At the same time, the heat exchange of the flow with the pipe wall is intensified 1. The turbulator, swirling the flow of process water for better cooling, stirs up the sludge falling on the inner cavity of the pipe 1. The distilled part of the sludge is carried away Otok water.

The results of a model calculation for the selected conditions show that, compared with the prototype, the efficiency of the heat for the period of operation in the furnace of the proposed device increases by about 80-100%, which allows

DEVICE FOR COOLING A WALL OF A METALLURGICAL MINING FURNACE, containing sections vertically around the perimeter of the wall of the casing in the thickness of the layer of heat-resistant concrete sections from water-cooled pipes with transverse ribs, the inlet and outlet of each of which are oriented towards the casing, characterized in that the pipes water cooling are made U-shaped and equipped with turbulators installed in the internal cavity, and the transverse ribs are made in the form of plates having different areas and assembled by m at least one packet in order to decrease the area from the central to the peripheral ribs, the diameter d, the elbow length h and the distance I between the inlet and outlet of the water cooling pipe, the distance between adjacent water cooling pipes along the longitudinal axis of the shaft furnace and in the direction S transverse to it, as well as the height a of the central transverse rib in each packet above the outer surface of the pipe and the height m of the layer of heat-resistant concrete from the outer surface of the pipe is chosen from the condition

T ™ T0 + () (d0 + tm

+ 2 "1p1 +)

eleven .

where tst x - is the maximum temperature on the casing of the shaft furnace;

T0 is the ambient temperature;

Tc ™ ah - - maximum temperature at

0

5

0

5

0

5

0

5

within the same limits, reduce the consumption of the cooling medium. The use of the proposed device allows to increase the specific heat removal per unit volume, create a system of stabilization of temperature gradients by volume, increase the heat resistance of the concrete structure of the furnace, and also increase the campaign of the furnace by eliminating furnace repairs associated with replacing refrigerators, and increasing the productivity of the furnace by intensifying the process heat transfer.

The estimated economic effect of the proposed device is expressed in a sharp reduction in the cost of maintenance and repair of the furnace, since the overhaul mileage of the furnace is increased. (56) U.S. Patent No. 4,559,011, cl. C 21 87/10, 1985.

casing of a shaft furnace without water cooling pipes;

ao, ai, aj - regression coefficients;

p, p basis function

at 1 1.2-. , 86-40 ,,, 83-6.54., 53-7.34,

5-103-108-Re

, 91-1., Heat

7 -W - ° - ") + d" - ° -et

(jF + -34r-rr- +

 Bet 6CT + MST

+0.33

Re-Lmet

"/BEFORE

- Peclet criterion;

A () 0,023DMЈ

xdp

0.8 L-C ™

0.33

where Srepl is the heat capacity of the coolant;

G is the flow rate of the coolant through the water cooling pipe;

Atepl - thermal conductivity for the coolant;

Abet - thermal conductivity of concrete;

c - viscosity of the coolant;

Amet is the thermal conductivity of the material from which the transverse ribs are made.

Ј

FIG. {.