Coker unit

The coker plant (Simplified coker or coker called ), a process plant of an oil refinery in the residues of different provenance are converted to lighter hydrocarbons. The long-chain hydrocarbons thermally (500 ° C) are cracked into shorter chains. In addition, substantial amounts of coke (carbon), which - depending on Kokertyp - sold as a product, or is gasified in the process in so-called low calorific gas. In comparison to other cracking processes Kokerprodukte have a higher proportion of unsaturated hydrocarbons. In all Kokeranlagen the separation of the product stream is carried in a subsequent rectification. Koker make the heavy oil production unnecessary. There are 3 different process variants: delayed coker, fluid coker and flexicoker

Delayed Coking

In the delayed coking the residual oil is first passed into the main fractionator of Koker / plant where it, inter alia, as washing medium for the product stream from the Kokstürmen - the actual reaction containers - used (heavy components from the active Koksturm are thus fed back into the process, recycled ). The residue of the rectification is then heated to about 500 ° C and then sprayed into the active coke drum, where it is converted to coke, liquid and gaseous hydrocarbons. In the other - inactive coke chamber - the petroleum coke is cured with steam and water or cooled and then cut out with a water jet (water pressure up to 350 bar). The petroleum coke, also called green coke, is used after drying as fuel in power plants or as an aggregate in the steel industry. Depending on the quality of the petroleum coke can be removed by calcination at 1200 ° C of the remaining volatile hydrocarbons, and then used for the production of an anode material for the aluminum and steel industry. The use is dependent on the quality parameters of the coke. Coke with high sulfur and metal content can not be used as anode material in the aluminum industry. In the steel industry, however, these requirements are not so high, so this coke here can still be used as anode material.

Fluid Coking

The fluid coking works similarly to the Fluid Catalytic Cracking. As a "catalyst" is used here as the fine powder produced / created coke. In the reactor, the use of the coke particles that form by a fluidized bed steam injection responding. The light products are drawn up, the coke dust runs into a so-called Coke Heater ( in FCC regenerator called ). Where the coke is partially combusted with air (so that the required process heat is generated ), a part is recycled to the reactor and a portion is pressed and sold after calcination. The advantage of this litigation is that - compared to the delayed coking - the dangerous cutting out the petroleum coke from the inactive Koksturm omitted. A fluid coker is however considerably more expensive and more complicated to handle.

Flexicoking

Flexicoking (Exxon patent) is an improved, but also more complicated version of the fluid coking. The coke is not burned in the heater, but heated by the hot exhaust gases ( low calorific synthesis gas) of a carburetor. The gasifier will use the excess coke in the fluid coking is discharged, is gasified by partial oxidation with air and steam injection. In this process only produces very small amounts of coke ( a small part must always be removed to remove the metals), but mainly atmospheric distillable hydrocarbons - and low calorific fuel gas. Sulfur can be from the main products through desulfurization ( hydrodesulfurization ) or removed by amine scrubbing.