(103d) Hydrotreater Optimization by Direct Online Control of the Accumulated Product Tank Sulphur

Syncrude is one of the largest producers of crude oil from Canada's oil sands. The bitumen extracted from oil sands is processed in the upgrading section to produce value-added sweet crude oil. Hydrotreater units are used at the tail end of the upgrading section for Sulphur and Nitrogen treatment (and upgrading) of freshly distilled and re-run Heavy Gas Oil (HGO), Light Gas Oil (LGO) and Naphtha to produce marketable synthetic crude oil. Treated HGO product is sent to the storage tanks from where it is drawn down to the pipeline. Honeywell’s multivariable predictive controllers are implemented on the HGO Hydrotreaters to control and maximize the rundown sulphur to the target.

Tank sulphur indication and control aids in running closer to the sulphur specification leading to substantial benefits by reducing over-treating requirement, reduced hydrogen consumption and extended catalyst run-length. This paper will present a method used by Syncrude for online indication and control of the Tank sulphur. The selected method uses the product analyzer readings to calculate the accumulated product tank sulphur and make correction to the hydro-treating reactor operation for online control of the Tank sulphur concentration.

In the present application, an online calculation has been implemented for predicting the current and future sulphur concentration in the HGO tank based on the Hydrotreater rundown flow and sulphur readings. A feedback control scheme has been implemented for controlling the accumulated product tank sulphur concentration by manipulating the hydrotreater rundown sulphur target in the linear multivariable controller. This paper will discuss some of the design and implementation issues.