Case Study: Designing China's biggest hydrocracker

Designing and bringing online China’s largest capacity hydrocracker was a highly challenging project on an enormous scale. Not only was the hydrocracker at CNOOC’s grassroots Huizhou refinery approaching the known technical boundaries, it also had to process an extremely difficult feedstock.

Nevertheless, Shell Global Solutions licensed hydrocracking technology and the specially developed Criterion catalysts met all the performance guarantees when the 80,000-bbl/d hydrocracker in Guangzhou Province started up in 2009.  

The $3 billion refinery uses leading-edge processing and environmental protection technology, and supplies more than 7 Mt of premium gasoline, kerosene and diesel, and over 4 Mt of other petrochemical products to the thriving local markets of Guangdong Province and South China.

The facility is the largest single-train refinery in China and, to utilise the Peng Lai crude oil that CNOOC extracts from the Bohai Sea, it is the first plant in the world specially designed to process 100% heavy, high-acid, naphthenic crude oil. 

Processing such a distinctive crude places special demands on many aspects of the overall design of the refinery. The high acidity of the Peng Lai crude could potentially lead to corrosion problems in the crude unit and also in the downstream hydroprocessing units if not carefully managed. In addition to the corrosion aspect, highly naphthenic crudes can be characterised by poor distillate properties such as low kerosene smoke points, low diesel cetane index and high diesel density, which places especially high demands on the catalysts used in all of the hydroprocessing units.

Selecting the optimal combination of catalysts and process conditions for the hydrocracker was, therefore, a critical factor for achieving the target distillate properties and managing corrosion in a cost-effective design.

CNOOC worked closely with Shell Global Solutions and Criterion. Together, they configured special catalysts for the hydrocracker, which is currently China's largest in terms of single-unit capacity. The catalysts are optimised for the design feed of VGO and HCGO; the desired product slate; and the process technology.

The hydrocracking unit has two parallel reaction section trains, each with one reactor. Shell Global Solutions designed the reactors to the exact specifications supplied by CNOOC, to help ensure that the reactors could be manufactured in China. Each reactor has six catalyst beds containing all of the required grading, demetallisation, pretreating and cracking catalysts.

Because the hydrocracking catalysts are fundamental to the refinery's performance and its ability to meet China's increasingly stringent fuel specifications, the results of a 36-h test run, which was conducted after five months of operation and was designed to assess the unit's performance, were especially significant. Key product quality data are shown in Table 1.

Following the test run, Wu Qing, Director of Planning & Investment Management, CNOOC Oil & Petrochemicals Co., Ltd, Huizhou refinery said, "The catalyst is performing excellently and the design indicators have been achieved. We are benefiting from high yields of middle distillates with minimal light ends, and hydrowax production is meeting our target."

According to Wu, the yield of middle distillates has exceeded the design value and the main product properties are meeting or exceeding design values.

"CNOOC are extremely satisfied with the operational data and catalyst performance during the first cycle," added Wu. "Based on this proven performance, we have requested that Criterion supply the catalysts for the second cycle."

Ed Daniels, Executive Vice President, Shell Projects & Technology, says, "The co-operation amongst the CNOOC management, operations and project teams, the local design institute and Shell Global Solutions formed the basis for a successful start-up and meeting the guarantees for the largest hydrocracker unit in China."