**1. Introduction**

CO2 emission is a global problem that affects many countries. Ironmaking processes contribute significantly to CO2 emission, and this is the case especially with blast furnace process, which produces more than 90% of the world's pig iron. The blast furnace is a chemical reactor involving counter-current flows of gas and solid [1–3]. Iron-bearing materials and coke are charged in turn at the top of the furnace. Hot air, enriched oxygen, and pulverized coal are blown into the furnace through the tuyeres. Iron-bearing materials are reduced by the reducing gas containing CO and H2, which are generated from the combustion of coke and coal in the cavity around the exit of a tuyere called the raceway [2–4]. The hot reducing gas flows upward, heats up the iron-bearing materials, and escapes from the top in the form of CO2, CO, H2, H2O and N2. Coke has several functions in a blast furnace: a fuel providing the heat for chemical reactions and for the melting of iron and slag; a reducing agent in itself and also providing gases for iron oxide reduction; and a permeable skeleton providing a passage for liquids and gases [5]. Therefore, it is very important for the efficiency of the blast furnace process and the quality of the hot metal. The carbon solution loss reaction of coke is a main means of coke gasification for the coke consumption in the upper part of the blast furnace. The strength and the size of the coke will deteriorate with the carbon solution loss reaction when the coke moves towards the lower zones of the blast furnace. This greatly affects the permeability of the bed and the efficiency of the process [1,5]. Therefore, the carbon solution loss of the coke should be restricted.

By conducting experiments under real blast furnace gas-temperature conditions, Babich et al. [6] found that the reaction rate of the coke close to the wall of the blast furnace was higher than that in the center of the furnace. By studying the reactivity of cokes charged in an experimental blast furnace, Lundgren et al. [7] found that the carbon solution loss reaction in the blast furnace was limited by the diffusion rate. Hilding et al. [5] found that the reactivity of coke increased when coke moved from the thermal reserve zone to the cohesive zone of the experimental blast furnace. Having investigated the transformation of mineral matters of cokes in the blast furnace, Gornostayev et al. [8] reported that this reduced coke reactivity by covering the pore wall. Loison et al. [9] stated that the carbon solution loss reaction occurred under a mixed regime in the thermal reserve zone of the blast furnace. When the temperature was raised, the chemical reaction rate increased exponentially and the diffusion rate was limited to the amount of CO2 gas. Sato et al. [10] stated that the coke pore structure modified the available carbon surface area for the carbon solution loss. Alkalies have catalytic effects on the solution loss reaction, and they can decrease the threshold temperature to approximately 760 ◦C [5,11,12]. Fe, CaO and MgO in coke ash are also shown to have a catalytic effect on solution loss [13,14]. However, the effects of different operational parameters on the carbon solution loss ratio are seldom studied. Physical experiments and mathematical modelling are common ways of investigating carbon solution loss. Several continuum models have been applied to improve practical operations of the ironmaking process especially in a blast furnace [15–19].

Therefore, in the present work, a three dimensional model of carbon solution loss of coke is established based on the actual production data of blast furnace B in Bayi Steel. The model is then used to analyze the effects of oxygen enrichment, coke oven gas injection and steel scrap charging on the carbon solution loss ratio of coke in the blast furnace. The research provides the theoretical reference and technical direction for Bayi Steel to control the carbon loss solution of coke.
