Delayed Coking Process

Delayed Coking Process Description

Coking is a unit operation found in more complex refineries to convert tarry residual or ‘resid’ streams from vacuum and atmospheric distillation into value-added products and intermediates such as LPG, naphtha, diesel, light and heavy gas oils. Coking is often accomplished via a delayed coking unit that includes a furnace, two coking drums— one online and one in regeneration, and a fractionating column.

In the coking process in refinery, the flow is heated to coking temperature in the furnace, then fed to the online coking drum. Large volumes of steam are injected after the furnace to delay the coking reaction until the flow enters the coking drum, where the heavy oil is cracked to lighter hydrocarbons, and into coke that mostly deposits in the drum for removal during the regeneration cycle. The cracked hydrocarbons then head to the fractionator column for separation of the different streams, with the bottoms recycled back to the inlet for another pass through the coker.

In the fractionator, the remaining coke fines and initially injected steam exit the process in the fractionated products as particulate and water contamination. Depending on the product, removal of excess particulate and water is required to achieve final product quality, or to meet feedstock requirements for other unit operations, for example on kerosene or diesel streams feeding hydrotreaters.

Refinery Needs

Meet coker unit refinery production quotas
Ensure final product water and particulate standards are met on naphtha, diesel streams
Protect downstream units from production or reliability issues due to high solids or water levels in the coker fractionates

Production Challenge/Pall Solution

Challenge

Achieve daily coker unit production targets.

Solution

Meet coker production targets, product quality specifications and downstream unit protection by effective removal of particulate and free water contaminants that are driving fractionates out of specification.

Challenge

Consistently meet particulate and water specification on naphtha and diesel streams headed for final product blending.

Solution

For particulate control:

Solid particle contaminants in the delayed coker operations coker are mostly coke fines, some very fine that may not be adequately removed by nominal filters, or filter media without fixed pore sizes that may exhibit unloading, media migration, channeling or poor sealing.
A range of absolute and nominal rated filter elements is available to reliably reduce suspended solids to final product or intermediate solids specifications

Challenge

Ensure downstream reactor bed protection from delta P build or deactivation due to solids fouling or water contamination.

Solution

For liquids control:

Conventional glass fiber coalescers will disarm due to the high volume of surfactants in the fractionates—naturally occurring sulfur compounds, or additives such as corrosion inhibitors or well treating chemicals. Disarmed coalescers will let large volumes of free water downstream until the elements are changed out, producing high water content fractionate
Other separators such as mesh packs, chevrons, cyclones, sand beds or electrostatic precipitators will not provide effective removal of the fine droplet emulsion created by the surfactants, so that high levels of free water will be seen downstream
High efficiency AquaSep® EL coalescers operate without disarming and provide effective removal of the fine emulsions to as low as 15 ppmv free water, protecting final product quality and downstream processes such as hydrotreater beds.