About Nihonkai Oil Company, Ltd.
Nihonkai Oil Company, Ltd. (Nihonkai Oil) was established in 1967 and is affiliated with Nippon Oil Corporation, Japan's largest oil corporation. Nihonkai Oil has its headquarters in Toyama, a port city on the Sea of Japan that is 400 km northwest of Tokyo. The company's Toyama refinery processes 60,000 barrels of crude oil per day into propane, butane, naphtha, gasoline, kerosene, gas oil, heavy oil, and other fuels, and it sells these products as a representative supplier throughout Japan's Hokuriku region.

Reasons for Selecting Yokogawa
To come out ahead in today's highly competitive petroleum product marketplace, Nihonkai Oil is focused on improving the productivity and efficiency of its refinery operations. Nihonkai Oil is in the process of migrating from its existing CENTUM-V and CENTUM-XL systems to the CENTUM CS 3000. As an initial phase of this process the company installed the CENTUM CS 3000 operator console for use with its legacy systems. To make fuller use of the capabilities of the CENTUM CS 3000, the company also decided to replace existing process control software running on another computer with Yokogawa's Advanced Process Control (APC) software.

The Challenge and the Solution
The Toyama refinery needs to stabilize the quality of the products coming from its atmospheric distillation tower and to minimize the amount of steam consumed by its depropanizer. To stabilize quality, each product’s distillation point has to be kept within specified upper and lower limits. To minimize reboiler steam consumption in the depropanizer, the propane quality has to be kept as close as possible to a specified lower limit. 

Applications such as the above are highly complex, with numerous interactive variables that must be estimated and optimized in real time. As a solution, Nihonkai Oil has turned to Yokogawa's APC software. Exasmoc, a multi-variable predictive controller, and Exarqe, a quality estimator, are in use in at refineries and petrochemical plants worldwide and are renowned for their ability to optimize plant productivity and efficiency. Nihonkai Oil has deployed two Exasmoc packages for this refinery's atmospheric distillation and depropanizer towers and a single Exarqe package for the depropanizer tower.

 

Details of this Project
This was a fast-track project requiring the full-time assignment of one engineer. This person spent six months in total on this project engaged in the following processes:

-   Site research and design: 1 month
-   Engineering: 4 months
-   Field testing: 1 month

Yokogawa worked closely with Nihonkai Oil through the course of this project and provided a comprehensive range of services beginning with the onsite inspection and APC design and proceeding through to response testing, interface design, DCS connection testing, and plant commissioning.

 

Results
The Exasmoc and Exarqe packages installed at the atmospheric distillation tower maintained product quality between set upper and lower limits, and the Exasmoc package installed at the depropanizer kept product quality at the specified lower limit. As a result, Nihonkai Oil was able to stabilize its product quality and reduce steam consumption. In quantitative terms, the standard deviation for the kerosene 95% distillation point was reduced 50% and reboiler steam consumption in the depropanizer was reduced 10%. 

 

Expectations for Yokogawa
Nihonkai Oil and Yokogawa are highly satisfied with the successful outcome of this project and wish to continue building on the good relationship that they have established. The company looks forward to seeing progress being made in Yokogawa's development of an auto-correcting process modeling system and in development of a simpler version of its advanced process control system.