Coke burning chemical reaction

The chemical processes occurring inside the blast furnace can be stated to start basically from the hot air coming into contact with the white-hot coke. The coke burns to form carbon dioxide. This reaction generates a very large quantity of heat, and it is this heat which maintains the high temperature necessary for the reduction process. As the gas is... 

The chemical reaction for the intrinsic burning of slow coke is given by... 

Ash, as determined by the standard test method (ASTM D-3174), is the residue remaining after burning the coal and coke and differs in composition from the original inorganic constituents present in the coal. Incineration causes an expulsion of all water, the loss of carbon dioxide from carbonates, the conversion of iron pyrites into ferric oxide, and other chemical reactions. In addition, the ash, as determined by this test method, will differ in amount from ash produced in furnace operations and other firing systems because incineration conditions influence the chemistry and amount of the ash. 

The calculated influence of pore diffusion on the coke bum-off (Fig. 4) is also reflected by the measured carbon distribution over the particle cross section for catalyst samples, which were regenerated at different temperatures up to a defined bum-off degree of about 55%. Fig. 5 shows that a pronounced gradient of the carbon load over the particle cross section for a bum-off temperature of 530°C is developed. For a temperature of430°C no gradient is determined. The rate of the oxygen conversion is then so slow, that the diffusion in the pores has no influence and the coke is uniformly burned within the particle according to the (intrinsic) rate of the chemical reaction. Both results are consistent with the kinetic measurements und calculations (see Fig. 4). 

Where deactivation has occurred by steam damage or other irreversible chemical reactions the sieve must usually be replaced, but a coked sieve can sometimes be rejuvenated by controlled burn-off of the carbon deposits. This may sometimes be achieved directly without removing the sieve from the process vessel, but clearly the control of oxygen concentration during such a process is crucial, otherwise the temperature may rise to the point where irreversible structural damage occurs. Although such procedures are common industrial practice, very little information has been published. 

Regeneration of coked particles involves both chemical reaction and transport processes, since oxygen must be transported by external mass transfer and by pore diffusion to the internal coked surface. Pore diffusion strongly influences the effective rate of burn-off, at least for particle diameters and temperatures relevant for industrial (fixed bed) processes (>lmm, >400 °C). Consequently, radial gradients of the 02-concentration and, vdth proceeding burn-off also of the carbon content in a particle are established (Figure 6.9.9b). 

A description of the coke burn-off process in a single particle by well-known closed solutions like the homogeneous or shrinking core model (Sections 4.6.3.4 and 4.6.3.5) is only reasonable for the border cases of complete control by chemical reaction or by pore diffusion. 

What happens inside the blast furnace to recover the iron from its ore The actual chemical changes that occur are complex. A simplified explanation begins with the reaction of oxygen in hot air with coke, a form of carbon. Some of the coke burns to form carbon dioxide. 

Partial oxidation, which can be applied to a wide range of hydrocarbons but also to other carbonaceous materials such as oil, petroleum coke and coal, consists of burning the hydrocarbons or powdered coal with a preheated gas mixture of steam and oxygen using a burner inside a refractory-lined combustion chamber. The role of the steam is to moderate the combustion. The overall reaction scheme for the partial oxidation of a hydrocarbon having the empirical chemical formula S is ... 

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