Coke oven thermal balance
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When performing a heat balance on thermal equipment, the heat brought in by the input materials generally includes the sensible heat of the materials and their heat of combustion (chemical heat). For example, in coal-fired boilers, the heat brought into the system by the input material, coal, includes both its sensible heat and its heat of combustion. But why, when performing heat balance calculations for coke ovens, is only their sensible heat taken into account, while the heat of combustion is not?
If thermal equilibrium isn’t taken into account there, how can equilibrium be achieved?
After being loaded into the carbonization chamber, coking coal undergoes dry distillation rather than combustion. During this dry distillation process, there is a stage during which an exothermic reaction occurs; however, the reaction is too complex to allow for the heat effect to be taken into account in energy calculations. This is one of the reasons why experience plays such an important role in the field of coking!
When performing a heat balance on a coke oven, only its sensible heat is taken into account, and its heat of combustion is not considered? Who said that? Who told you? The heat of combustion accounts for 97% of the total heat – how dare you ignore that?
This post was last edited by wangshaobo on 2015-9-26 at 17:42. This is the heat balance calculation I’ve done (using blast furnace gas as the fuel); please take a look and point out any errors Thank you in advance! Thermal balance of the coke oven – Inlets and outlets. Sequence Number, Item, Heat in kJ, Percentage%. Sequence Number, Item, Heat in kJ, Percentage%. 1. Sensible heat of wet coal: 27,937 kJ, 1.0%. 1. Sensible heat carried away by coke: 105,043 kJ, 37.6%. 2. Sensible heat of gas: 19,556 kJ, 0.72%. Sensible and latent heat carried away by chemical products: 100,573 kJ, 3.6%. 3. Sensible heat of air: 16,762 kJ, 0.63%. Sensible and latent heat carried away by net gas flow: 413,467 kJ, 14.8%. 4. Heat of combustion of gas: 2,729,443 kJ, 97.74%. Sensible and latent heat carried away by water vapor: 446,992 kJ, 16.0%. 5. Heat carried away by exhaust gases: 502,866 kJ, 18.0%. 6. Heat lost from the surface of the furnace: 27,9370 kJ, 10.0%. Total: 27,936,981 kJ, 100.00%. Total: 27,936,981 kJ, 100.0%
The moderator immediately understood what my question was about! That’s exactly what I mean. I see that for gasification furnaces (unlike boilers which only involve combustion, gasification reactions also take place), the chemical heat (calorific value) generated by feeding in coal and producing substances such as tar is taken into consideration, but this isn’t the case for coke ovens. May I ask the moderator, where can I find relevant literature or knowledge (in journals or books)?
The theoretical development in the field of coke ovens is far behind practical application! I hope that in the future, with the development of certain technologies, the thermodynamic theory of coke ovens will also see significant progress
What I mean is this: in the thermal balance of a coke oven, there is no calorific value/chemical energy from coal, nor any calorific value/chemical energy from products such as tar and coke; whereas these are present in the thermal balance of coal gasifiers and coal boilers. I’m not sure why, when performing heat balance calculations for coke ovens, the heat of combustion/chemical energy of these substances isn’t taken into account; what’s the difference between them and other thermal equipment?
When coal enters the coke oven, it is heated in the absence of air (i.e., through carbonization); therefore, there is no heat of combustion from the coal, only physical heat.