Jul-2015

Implementing real time optimisation technology

Modelling implementation of real time optimisation and its potential for increased profitability in refining processes

Hamid GANJI, Saeid SHOKRI, Mahdi AHMADI MARVAST, Sorood ZAHEDI ABGHARI and BEHROUZ NONAHAL
Research Institute of Petroleum Industry

Article Summary

In this article, implementing real time optimisation (RTO) technology in the oil and gas industries is categorised worldwide, its potential execution is investigated, and the rate of profitability offered is obtained as far as possible. The processes that contained the highest level of RTO implementation included FCC, distillation, olefins production, utilities, hydrocracking, alkylation, catalytic conversion and polymerisation. By studying the oil and gas industries in Iran and comparing them to similar foreign industries, the potential for implementing RTO technology is investigated.

By using the rate of reported profitability for the selected processes and considering the capacity of domestic units, the rate of profitability for these processes is calculated. It was found that, by implementing RTO technology, the potential annual profit was around $114 million for distillation, catalytic reforming, FCC, hydrotreating, hydrocracking, gas refining, olefin and sulphur recovery units in Iran.

Also it is evident that, from the economic point of view, the order of priority for implementing RTO is: gas refining, distillation, FCC, hydrotreating, olefin production, catalytic reforming, hydrocracking, and sulphur recovery.

Optimising production
In the last two decades, due to the increasing cost of energy and raw materials, tough environmental measures, safety issues and worldwide competition, considerable changes in optimising production and quality in the chemical industries have taken place. These changes have been made in the design of processes and operating conditions to reduce costs and meet the requirements of existing process limitations. The performance of a process may be influenced by factors such as atmospheric conditions and reduced catalyst activity.

Developing smart processes to react appropriately to modifications by eliminating human interference as much as possible is receiving careful attention. Smart processes provide better operating conditions and should receive more attention.

RTO is one of the most widely used technologies to optimise a chemical process online. By using RTO technology, the operating conditions of processes for certain periods are calculated and optimised. In fact, RTO systems control the mechanisms of closed loop processes to maintain automatically the operating conditions of the process nearest to optimised conditions. By applying RTO, continuous assessment of the system and maintaining the operating conditions of the process can be achieved.

Nowadays, advances in network communications technology and the enhanced power of computing has made RTO state of the art in many industries. RTO offers greater opportunities to chemical engineers and technologists to achieve their processing objectives. In a RTO system, a high performance control system must be used as the infrastructure employing complex and accurate models of the processes as well as economic data to determine the optimised operating conditions. These control systems mainly include control algorithms and calculation platforms. RTO takes place in the management layer of the integrated production structure of the system and acts as a bridge between unit planning (medium term planning) and the control system (short term planning).

In the hierarchy of process control, disturbances with high frequencies may be controlled by using process controllers at the RTO level. Variations in optimised operating conditions are chased due to changes at low frequencies. An RTO system determines the permissible values of variations and implements them via control systems without operator interference.

Optimisation can be carried out at two different stages of a project’s lifespan. The first stage consists of selection of the size and appropriate location of the equipment; the second stage includes continuous optimisation and online profitability control (operational/economic) of the existing unit. RTO may be implemented in a variety of processes but has higher potential in the oil and gas industries because of the complexity of their processes and the number of variables that influence decision making. For this reason, different projects have been carried out worldwide that have resulted in high profitability and fast return on capital deployed. This article investigates the implementation of RTO as well as calculating the rate of profitability of selected units in the oil and gas industries.

RTO technology worldwide
By studying databases, documents and available references,1,2 a wide-ranging investigation of implementation of RTO throughout the world was carried out. The statistical reports included the profit incurred by implementing RTO technology and the software used to facilitate this.

Reports indicate that 133 cases of RTO technology have been implemented in the world’s oil and gas industries. Based on this information, the units that gained most by implementing RTO technology were considered to be the best potential candidates (see Table 1).

Using the information gathered, the rate of profitability through implementation of RTO technology in the processes listed in Table 1 was categorised. In order to compare profitabilities, it was decided to compare the rate of profitability with respect to inlet feed or finished products of the units separately. Table 2 compares the rate of profitability of different processes by unit feed or final products. As can be seen, the rate of profitability through implementation of RTO technology for catalytic reforming, crude distillation, olefin production, FCC, gas refining, isomerisation and sulphur recovery is $0.03-0.50 per barrel of feed.

Implementation of RTO
With regards to the rate of 
profitability obtained by implementing RTO technology within the processes shown in Table 2 and with respect to the capacity of domestic units, the rate of increased profitability was calculated. As  Table 2 shows, these units are for refining, petrochemical and gas processes. Figure 1 compares the rate of profitability for the listed units. As Figure 1 shows, for units where RTO technology is implemented, gas refining enjoys most of the profitability, followed by distillation units in oil refineries. It should be noted that some of the processing units do not exist in all nine of Iran’s oil refineries, for instance catalytic conversion, hydrogen purification and FCC units only exist in two oil refineries. Looking at the relative rate of profitability for various units, a comparison should be made for a typical unit with a mean value of feed. For example, a distillation unit with a capacity of 201 667 b/d and a catalytic conversion unit with a capacity of 20444 b/d were considered. By using this technique, the rate of profitability was obtained and is shown in Figure 2. From an economic point of view, the priority for implementation of RTO technology in selected processes is: gas refining, distillation, FCC, hydrotreating, olefin production, catalytic reforming, hydrocracking and sulphur recovery.

Case study
Since the rate of profitability with RTO technology is not reported for integrated processing units in an oil refinery in the resources available, it was decided to compare the total profit of RTO implementation in all units of an oil refinery with that of a gas refinery. It was assumed that an oil refinery’s processes consisted of distillation, catalytic reforming, hydrocracking, hydrotreating and FCC. Figure 3 compares the profitability of RTO implementation in oil and gas refineries. It can be seen that RTO technology yields higher profitability for an oil refinery. This is because oil refineries have more added values in their products and, by implementing RTO technology, the profitability rises accordingly. Also, oil refineries have units such as catalytic reforming and hydrocracking units which produce final products with high added values.