Rehan Afzal and Keith J. DeCarlo, Ph.D., Blasch Precision Ceramics, USA, exposit on the use of modified ceramics designed to withstand high temperatures while reducing costs and improving performance.
Hydrocarbon engineering processes involve high temperatures (up to 1000°C for some applications) and require reliable products to mitigate failure and increase industrial efficiency. Due to the high heat and corrosive environments, ceramics are often chosen for hydrocarbon processing due to having excellent corrosion, thermal shock, and creep resistance; all at high temperatures. The choice of ceramic is dependent on the specific application, however, the most frequently used ceramic materials include fireclay, alumina, mullite, and silicon carbide.
As the demand for reduced costs and improved performance rises in hydrocarbon processes, it is crucial for ceramic manufacturers to continue to develop innovative materials and products that provide the required benefits.
Functional self-supporting structural ceramic systems
Large structural systems are typically required for commercial hydrocarbon engineering processes which necessitate time-sensitive labour to assemble. These structural systems are the powerhouse behind the processes and can be several tens of feet tall, requiring many skilled labourers to shape and mortar ceramic bricks together into complex systems. Of the many hydrocarbon processes, the Claus sulfur recovery units (SRUs), and steam methane reformers (SMRs) are two examples of units that are exceptionally large in size and require highly laborious brick and mortar setups.
Due to the high temperatures required for the many hydrocarbon processing applications, the bricks and the mortar experience thermal expansion, inducing a strain within the mortar joints. Typically, the mortar is not resilient enough to withstand the stress and as a result, cracks begin to form and compromise the mortar. The compromised mortar will eventually result in the ceramic structure either completely or partially collapsing, ultimately reducing system efficiency or preventing it from working altogether.
To improve the robustness of ceramic products used in complex systems, Blasch Precision Ceramics (BPC) has developed block-type products that include precast interlocking features with no mortar required for both SRUs and SMRs. These interlocking features ensure that each block mechanically interacts with one another and provides support throughout the entire application process without introducing strain from the thermal expansion mismatch between bricks and mortar. Furthermore, BPC has engineered the interlocking features with precise gapping that seals at application temperature.
The specific products BPC has developed for use in SRUs include the HexWallTM and VectorWallTM (Figure 1 left and Figure 1 right, respectively). Both the HexWall and VectorWall products are hexagonal ceramic blocks with interlocking features that are inherently stable and structurally supported. Furthermore, both products allow for flow control within an SRU which enhances the chemical interactions through increasing turbulence and resonance time of the inlet streams (i.e. mixing). The VectorWall further promotes mixing of the inlet reactant streams through the ability to directly control the reactant flow path, thus achieving increased SRU efficiency.
A similar system of interlocking bricks has been developed for SMR tunnels. Similar to SRU systems, SMR tunnel walls are built using ceramic bricks which are mortared together. Additionally, the SMR tunnel walls are structured in a way that creates passages through the tunnel wall to allow for thermal homogeneity, further increasing stress concentration in the wall structure. Thus, the thermal cycling and pressure differential present in normal use cause mortar failure resulting in partial or full collapse of the tunnels and/or a phenomenon in which the tunnel wall displaces creating curvature called snaking. Once a tunnel wall is defected, the efficiency of the SMR measurably decreases. Furthermore, due to the complex nature of tunnel design, lengthy skilled labour is required to build these tunnels. Depending on the size of the reformer, it can take up to four weeks or longer to build a complete set of tunnels.
In order to decrease the amount of skilled labour and time required to build tunnels while also minimising maintenance downtime and reducing mechanical strain in the system, BPC developed the StaBloxTM flue gas reformer tunnels system. This system is composed of precast interlocking ceramic blocks that are roughly six times larger than traditional ceramic bricks, which helps to reduce needed brick quantities, while also weighing less than 50 lbs. The interlocking features mechanically secure the blocks to one another. These blocks are custom-designed for each reformer and include engineered gaps at the interlocking features, similar to the HexWall and VectorWall products, which fully seal when the application temperature is reached (Figures 2A and 2B). Furthermore, holes that are cast directly into the StaBlox product in a circular shape are used for the homogenisation of temperature in the SMR system, this design minimises stress intensity at these openings and maximises thermal homogeneity.
Both the SRU and SMR self-supporting structural ceramic systems are specifically designed and engineered to reduce the amount of labour and materials required. The developed self-supporting structures allow for the reduction of skilled labour while also improving the robustness of the product, allowing for advancements in the production process.