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Heat transfer analysis of blast furnace cast steel cooling stave
Z. Qian*, Z.-H. Du and L.-J. Wu
Cast steel blast furnace (BF) cooling staves are widely used in the Chinese steel industry. A heat transfer mathematical model of a BF cast steel cooling stave has been developed and verified by thermal state experiments. Calculation of a cooling stave working under steady state has been carried outbased on the model. Effects of two factors, thickness of scale on the cooling water pipes and gas clearance between the pipes and main body, which are difficult for experimental measurement but determined mathematically, on the temperature field of the stave body are discussed. The results indicate that much importance should be attached to the two factors during manufacturing of cooling stavesas they highly influence cooling capability of cooling stave and hence BF operation.
Keywords: Cooling stave, Thermal state experiment, Heat transfer, Gas clearance, Scale

List of symbols
a cp d h2 hwb hz1 hz2 Nu q R T T2 T0b T0d u x,y,z l(T) a d e l u r t thermal diffusivity, m2 s21 specific heat, J kg21 K21 diameter, m heat transfer coefficient between cool surface and atmosphere, W m22 K21heat transfer coefficient between cooling water and stave body, W m22 K21 heat transfer coefficient between stave body and gas flow, W m22 K21 heat transfer coefficient between stave body and ramming material, W m22 K21 Nusselt number heat flux, W m22 thermal resistance, m2 K W21 temperature, uC temperature of cool surface, uC temperature of stave body hot surface, uC temperature of rammingmaterial hot surface, uC water velocity, m s21 Cartesian coordinate thermal conductivity at temperature T, W m21 K21 heat convection coefficient, W m22 K21 thickness, m emissivity thermal conductivity, W m21 K21 kinematical viscosity, m2 s21 density, kg m23 time, s

c d e g i o p s w

coating layer ramming material equivalent gas flow or gas clearance inner outer water pipe scale waterIntroduction
The capability of cooling staves directly affects blast furnace (BF) campaign life and hence plant costs. Many researchers and manufacturers have attached much importance to the design and manufacture of cooling staves with excellent capability by using modern technology. In Japan and some other countries, copper staves are widely used and most of their researches are also focused on copperstaves.1–4 However, in China, cast steel BF cooling staves are widely used, especially in medium and small enterprises, because not only steel has good elongation, high tensile strength, high melting point, good thermal shock resistance and good thermal conductivity, but also the cost of cast steel staves is much lower than that of copper staves. Thus, in China, research on cast steel cooling stavesis very important. Hitherto, a lot of research work on BF cooling staves has been carried out1–16 and thermal analysis is usually adopted to study the effects of some parameters on the capability of staves. It is noted that quite a number of analyses5–9,13 are basically based on numerical computation and lack experimental validation. Sometimes experiments are difficult or impossible to analyse,for example, the air gap between the pipe and stave body. In the present paper, both numerical and experiment methods were adopted to study the effects of two factors, thickness of scale and thickness of air gap on the temperature field of cast steel BF cooling staves.

Subscripts
a atmosphere b stave body
Institute of Engineering Thermophysics, Shanghai Jiao Tong University, 200030, China*Corresponding author, email qian_zhong78@yahoo.com.cn

ß 2007 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 6 March 2006; accepted 12 June 2006 DOI 10.1179/174328107X165771

Ironmaking and Steelmaking

2007

VOL

34

NO

5

415

Qian et al.

Heat transfer analysis of blast furnace cast steel cooling stave

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