Separation System & Energy Recovery

Crude Distillation Unit Optimization

The Crude Distillation Unit (CDU) is one of the most energy-intensive units of a refining process. A CDU consists of a distillation column, where the crude feed is separated into various components from lighter to heavier fractions before sending these fractions for further processing, and a preheat train and a furnace where the crude feed is heated up before entering the column. PIL's unique approach towards CDU optimization involves simultaneous optimization of the preheat train and the distillation columns, which gives us more opportunities for energy savings and yield improvement as compared to sequential optimization methods.

What Are the Major Issues with CDUs?

Very energy intensive

Very Energy Intensive

CDUs are highly energy intensive. The furnace alone consumes around $15 million a year to operate. If not carefully monitored, the column will consume additional energy that would exponentially increase the operating cost.

Usage of Various Grades of Feedstock

Change in crude feedstock is increasingly becoming common among refineries. Crude blends/low-quality crudes are currently being used to reduce the cost of feedstock. It is difficult to consistently produce high product yield with continuously varying feedstock, which leads to complex operation and loss of valuable feed and products.

Usage of various grades of feedstock:
System constraints and bottlenecks:

System Constraints and Bottlenecks

CDU operation often must deal with a few generic column constraints such as limiting furnace heating capacity, limiting top condenser and reboiler capacities, high vapor/liquid traffic across certain sections of the column, and cooling limitations across certain products draws. These limitations increase the complexity of operations and require expertise to overcome.

Throughput above Design Capacity

Several refineries choose to increase throughput above the design capacity of the column. This approach affects the separation of products leading to lower yields and may give rise to issues such as high-pressure drop and flooding across certain sections of trays respectively.

Throughput above design capacity

PIL's Offline Engineering Solutions

Our offline solutions are designed to propose operational guidelines to help our clients to maintain optimum operation even with crude feedstock variations and to overcome the unit constraints/bottlenecks. We also propose retrofit modifications to the preheat train and the column to help our clients to achieve higher energy recovery, higher furnace coil inlet temperature and better product separation in the column.

  • No Investment required (excluding consulting cost)
  • Low to medium investment required

Operational optimization: The following key operational parameters are adjusted to bring savings (typically between 3-5% per year of current operating cost) without any investment:

  • Preheat train exchanger flowrates (i.e. bypasses, split ratios)
  • Furnace loading
  • Condenser and reboiler settings
  • Other column operational parameters (i.e. stripping steam flow rates, pump-around flow rates)

Retrofit optimization: The following changes are done to your system set up to bring savings (typically between 5-15% per year of current operating cost) with low to medium CAPEX:

  • Repiping, resequencing or adding area to existing heat exchangers
  • Adding new heat exchanger
  • Replacing pumps and column internals