Upgrading - Thermal Conversion (Coking)

Thermal Conversion or Coking involves breaking apart the long heavy hydrocarbon molecules using heat. Hydrocarbons have an interesting and very useful property. If they are subjected to high temperatures they will react and change their molecular structures. The higher the temperature, the faster these reactions will happen. This is sometimes called “Cracking” because large hydrocarbon molecules can be made to crack, or break down into smaller molecules. Coking is an intense thermal cracking process. It is particularly useful in upgrading bitumen into lighter, refineable hydrocarbons (naptha, kerosene distillates, and gas oils) and concentrates extra carbon into a material called coke. The coke is considered a byproduct of the coking process. Currently oil sands companies use two types of coking to upgrade bitumen: delayed coking and fluid coking.

Delayed coking is a process where bitumen is heated to 500°C (925°F), then pumped into one side of a doublesided coker. The bitumen cracks into two products: solid coke and gas vapour. It takes approximately 12 hours to fill one side with coke. When one coke drum is full the heated bitumen is diverted into the 2nd coker in the pair to continue the cracking process. A high-pressure water drill is used to cut out the solid coke from the first coking drum. The fluid coking process is similar except it is a continuous process. There is just one coking drum for fluid coking. The bitumen is heated to 500°C (925°F) but instead of pumping the bitumen it is sprayed in a fine mist around the entire height and circumference of the coker. The bitumen cracks into gas
vapour and coke. The coke is in a much finer powder-like form, which is then drained from the bottom.

The coke’s greatest value is as a fuel for coke furnaces, producing the heat needed for the hydro-cracking process. More coke is produced than is needed so it is stockpiled for future use.