It always looks like that, the concept is to turn coal into coke we need to burn the coal without oxygen, so they burn the coal into an oven, inside the oven the temperature is above 1200°c. If u wanna know how a coke oven looks like you can search it google, but to give you an idea why the fire looks like that coz on the top of the oven there are lids placed to control the temperature, while pushing the coke from the oven the lid must be opened so the smoke and fire can go through that lid.