Hydrogen (H2) demand in the refining sector will continue to increase due to the trend of processing heavier and sourer crude oil. Additionally, more stringent regulations on refinery products, such as tighter sulfur and aromatics specifications, will drive H2 consumption. Another influencing factor is the replacement of older facilities to achieve greater efficiency and reliability. The H2 demand may be initially small (110 million standard cubic feet per day [MMscfd]) or mid-size (1120 MMscfd). These requirements are likely to evolve as the project is developed. Therefore, it is necessary to have flexibility in developing the project, and it is important to consider different options in terms of incremental H2 supply.
There are two basic configurations for a steam methane reformer (SMR) design: can and box. Each design has its pros and cons and range of applicability, as discussed below.
A can reformer consists of a cylindrical, up-fired furnace that houses the catalytic reformer. Fig. 1 shows a picture of a typical H2 plant based on a can configuration. A cylindrical geometry for the reformer furnace provides excellent heat transfer characteristics. Furthermore, it is the most cost-effective design for relatively small H2 requirements, taking manufacturability and transportation into account. These plants are standardized in design and modular in construction, with relatively short field construction schedules. The capacity of a single can reformer can range from 0.2 MMscfd to over 8.0 MMscfd of H2. Capacity can be doubled with a dual can design. The following plant configurations are available to meet specific project requirements:
In a high-export steam configuration, heat recovery from both flue gas and process gas streams is maximized to generate steam. There is no combustion air preheat. Typically, the amount of export steam is ~100 lb per 1,000 scf of H2 produced. This configuration is attractive when low-cost fuel gas is available.
In low-energy units, combustion air and reformer feed temperatures are optimized to minimize energy consumption. Energy consumption can be as low as 400 British thermal units (Btu) per scf of H2 produced.1
High-efficiency units can be designed as a combination of the two cases presented above.
| Fig. 1. Hydrogen plant with a can reformer. |
A firebox reformer consists of a compact firebox with vertical, top-supported catalyst tubes arranged in multiple parallel rows. The furnace can be customized, prefabricated and field-erected. The compact design is reliable, efficient and easy to maintain. These plants are suitable for 10 MMscfd to over 120 MMscfd of H2, with the option to combine several trains for increased capacity.
Box reformer plants can also be designed for either low operating cost or low-capital, maximum-steam production. These configurations will result in different project-specific waste-heat recovery concepts. The integration of refinery offgas as feed or fuel can be considered to further improve efficiency. A picture of a typical box reformer is shown in Fig. 2.
| Fig. 2. Hydrogen plant with a box reformer. |
Typical operating performances of can and box reformers are presented in Table 1. In this example, the box reformer capacity is six times larger than that of the can reformer. However, it can be seen that a box reformer is more efficient due to the higher degree of heat integration.
A key consideration for selecting whether the reformer configuration should be can or box is the H2 production capacity. However, there is a certain gray area that permits the use of either a can or box reformer (Fig. 3). In such situations, it is necessary to take a close look at the associated steam production and possible future expansion plans. A detailed economic assessment must be carried out, taking into account capital and operating costs and the required plant flexibility. Project schedule, transportation limitations and general site conditions are other important factors to be considered. The ability to simulate, side-by-side, the various configurations and options by combining different technologies or process steps is the key to finding the best overall solution.
| Fig. 3. Can and box reformer capacities overlap. |
Selecting a hydrogen plant requires an in-depth assessment of capital and operating costs for both a can and box reformer. Ideally, it is important to engage a company that designs, owns and operates H2 plants based on in-house technology for a range of plant sizes. Such a company has the ability to evaluate the entire gamut of possibilities for H2 production. The ideal technology supplier is one that also owns and operates large industrial gas processing plants. At the Linde Group, experience from operating plants is fed back to the engineering group for continuous improvement of performance and reliability, ensuring the best plant design and overall solution for a given set of circumstances. HP
1 Based on low heating value
|The authors |
||Wolfgang Schoerner is the business unit director for hydrogen and synthesis gas plants in North America with Linde Engineering. Prior to this role, he performed engineering and project management roles for Linde in Germany. He holds a diploma in process engineering from the Technical University of Munich. |
||Goutam Shahani is the business development manager with Linde Engineering. He has over 25 years of experience in industrial gases for the energy, refining and chemical industries. He holds a BS degree in chemical engineering from the University of Bombay, an MS degree in chemical engineering from the Illinois Institute of Technology, and an MBA degree from Lehigh University. |
||Nick Musich is the head of the proposals and process engineering department for Hydro-Chem in Holly Springs, Georgia. He has 15 years of industrial experience, and worked for Mobil Oil and Siemens before joining Hydro-Chem. He has a BS degree in chemical engineering from Georgia Tech and an MBA degree from Kennesaw State University.|