Crude Distillation Unit: Decontamination of particles during cleaning

Challenge:
During an extensive shutdown of a crude distillation unit (CDU), the primary cleaning contractor for a large refinery asked United Rentals for containment equipment to support the project. Initially, only additional storage capacity to buffer the effluent following cleaning was required. Due to the involvement during an earlier phase of the project, United Rentals were able to partner with the cleaning contractor to review the scope of work and devise a joint approach for the decontamination of the CDU.

Solution: 
BakerCorp supported the full decontamination process with following 4 phases:

• Preparation phase: 12 Coil Tanks 70 m³ were installed to pre-heat the demineralised water. Once circulation of this water had started, a new batch was prepared simultaneously within the tanks. 
• Demineralisation phase: Two Mix Tanks 68 m³ were supplied to treat the preheated water with the required chemicals provided by the customer. Due to the agitation capabilities of the Mix Tanks, the chemicals were blended and circulation around the CDU could be started; decontamination of such unit requires multiple batches of water and recirculation. 
• Effluent storage phase: The used cleaning water was purged towards an onsite storage facility provided by 63 Lined Tanks 70 m³, and a new batch could then be used within the cleaning process. A Bag Filter System was used during change-outs to remove excess oil.
• Effluent treatment phase: The effluent from the temporary storage units was split into water and oil using an emulsion-splitter before being sent to Separator Tanks 70 m³ where the oil layer formed inside the tanks was extracted. Using a Bag Filter System equipped with oil adsorption bags, harmful components such as sediment and any remaining oil was removed which meant that the wastewater could be sent to the WWTP.

Benefits:
The preheating of liquids allowed for a quicker start of the actual cleaning process which reduced downtime of the CDU. By removing sediment and oils, the customer met its consent for directing wastewater to the WWTP quickly, thanks to the removal of major non-biodegradable components prior to discharge. As United Rentals were included in the total decontamination process, the customer was provided with a one stop shop for all the necessary equipment and a partner for process improvement that can result in reductions of downtime and costs for future projects.

Upon evaluation between the customer and United Rentals, it was discovered that by further treatment using a Lamella Filter Tanks, optimisation of the decontamination process and a reduction in the amount of wastewater could be achieved. By adding this treatment step, the cleaning water could be reused which meant less fresh water would be needed throughout the cleaning process, resulting in less downtime, significant cost savings and improved after-treatment.