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APC - Prime-D

Specific Application for Prime-D

The Prime-D advanced control package combines Axens Horizon' latest generation multivariable controller MVAC, in association with on line inferential reactor model and feed switch technology; it is designed to maximize the benefits from Prime-D process at the lowest operating cost.

As process licensor, catalyst manufacturer and advanced control technology supplier, Axens Horizon combines all the necessary expertise for successful Prime-D APC projects.

A six-step control strategy is implemented

  • precise control of sulfur in ultra low sulfur products
  • adjustment of hydrogen make-up for optimal H2/HC ratio in the 2 reactor beds
  • control of reactor bed outlet temperatures
  • catalyst deactivation monitoring
  • throuput maximization (under catalyst run length and unit constraints)
  • if 2 feed available, maximization of lowest value feed

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Feed switch technology

  • for a new feed, determination of new MV targets, using the reactor model
  • rapid ramping to new targets, with constraint protection and sulfur control

Precise sulfur control

  • the Prime-D control package uses Axens Horizon' on-line ULSD reactor models to estimate the sulfur content of the product at the reactor outlet.
  • this technology allows precise sulfur control and fast feed switchover, even when the downstream sulfur on-line analyzer has a measurement lag in the order of 2 hours.
  • static gains of APC models are updated on-line, for better control


  • Sulfur on spec without give-away
  • Minimization of feed switch time
  • Catalyst run length maximization
  • Reduction of hydrogen make up
  • Minimization of energy consumption
  • Increased throughput (if feed available)

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