Process intensification and process scale-up: Gaps and opportunities

Process intensification (PI) has gained traction in modern chemical engineering and process technology with its potential for drastic improvements in equipment size, efficiency and carbon footprint. Technologies that exert greater control of process fluid dynamics, heat and mass transfer, and reaction kinetics offer the ability to achieve step changes in performance over conventional technology. Process intensification has already found commercial success exploiting these phenomena in niche separations and reactions, prominently in the area of specialty chemicals and products. In large-scale industrial processes such as refining and commodity chemicals, effective process scale-up is required to capture economies of scale for large production volumes. The current paradigm for rapid scale-up uses small-scale studies to decouple the relevant process physics and use models to integrate these physical effects for confident commercial design. Translating this paradigm presents challenges and opportunities for process intensification to address. The complex and closely-coupled physics in PI technologies (e.g., dynamic absorption) require deeper understanding than conventional technologies in order to scale up with confidence. This physical coupling may require larger process demonstration testing that significantly increases development time and cost relative to conventional technologies. This paper will present an assessment of the unique challenges for scale-up of PI technologies addressing both the technical complexity of scale-up as well as the applicability for large-scale commodity processes. Where scale limitations of current PI technologies exist, it highlights tradeoffs between scale-up and “number-up” approaches to commercial design. The authors will present examples to illustrate these opportunities, including commodity processing areas where new PI solutions are still needed (e.g., solids handling, bio-processes)

Increased Span Length for the MGS Long-Span Guardrail System Part III: Failure Analysis

The objective of this research study was to review and analyze the system failure observed during crash testing of an increased span length for the MGS long-span guardrail system in test no. MGSLS-2. Test no. MGSLS-2 was a full-scale crash test conducted on the MGS long-span guardrail with a span length of 311⁄4 ft (9.5 m). This test utilized universal breakaway steel posts (UBSPs) adjacent to the long span in lieu of the controlled release terminal (CRT) wood posts used in previous long span systems. An engineering analysis was undertaken to review the downstream end anchorage failure observed in test no. MGSLS-2. The analysis also compared critical aspects of the barrier performance with previous full-scale crash tests that had similar features or increased anchor loading. The results of this analysis and conclusions regarding potential causes of the anchor failure suggested that there was no identifiable root cause for anchor failure, but the pocketing and deflection suggest that the barrier system may have been pushed near its limits. It was noted that certain factors may have contributed to the anchor failure, including increased span length, location of the impact point, differences in the breakaway post behavior adjacent to the unsupported span, and natural variation in wood strength. Following the analysis, several potential design modifications were noted for improving the barrier system and reducing the potential for end anchorage failure. However, it was noted that further analysis of these potential improvements, selection of a preferred design, and evaluation of the revised barrier system through full-scale crash tests will be required to fully evaluate the system to MASH TL-3 criteria

Development of MASH TL-3 Transition Between Guardrail and Portable Concrete Barriers

Often, road construction causes the need to create a work zone. In these scenarios, portable concrete barriers (PCBs) are typically installed to shield workers and equipment from errant vehicles as well as prevent motorists from striking other roadside hazards. For an existing W-beam guardrail system installed adjacent to the roadway and near the work zone, guardrail sections are removed in order to place the portable concrete barrier system. The focus of this research study was to develop a proper stiffness transition between W-beam guardrail and portable concrete barrier systems. This research effort was accomplished through development and refinement of design concepts using computer simulation with LS-DYNA. Several design concepts were simulated, and design metrics were used to evaluate and refine each concept. These concepts were then analyzed and ranked based on feasibility, likelihood of success, and ease of installation. The rankings were presented to the Technical Advisory Committee (TAC) for selection of a preferred design alternative. Next, a Critical Impact Point (CIP) study was conducted, while additional analyses were performed to determine the critical attachment location and a reduced installation length for the portable concrete barriers. Finally, an additional simulation effort was conducted in order to evaluate the safety performance of the transition system under reverse-direction impact scenarios as well as to select the CIP. Recommendations were also provided for conducting a Phase II study and evaluating the nested Midwest Guardrail System (MGS) configuration using three Test Level 3 (TL-3) full-scale crash tests according to the criteria provided in the Manual for Assessing Safety Hardware, as published by the American Association of Safety Highway and Transportation Officials (AASHTO)

Transition of Temporary Concrete Barrier

The objective of this research was to design a transition from temporary concrete barriers to a permanent concrete barrier for median applications. The researchers at Midwest Roadside Safety Facility utilized a combination of free-standing and tied-down Kansas temporary concrete barriers and a dual-nested thrie beam for the transition to the single-slope permanent barrier as well as a transition cap. Two full-scale vehicle crash tests were performed on the system. Evaluation of the approach transition required testing at two Critical Impact Point (CIP) locations. The first tests was performed using a half-ton pickup truck that impacted the temporary barriers 1,432 mm upstream from the permanent barrier, at a speed and angle of 100.7 km/h and 24.7 degrees, respectively. The second crash test was also performed using a half-ton truck that impacted the temporary barriers 16.6 m upstream from the permanent barrier, at a speed and angle of 100.1 km/h and 26.2 degrees, respectively. Both tests were conducted and reported in accordance with requirements specified in the Manual for Assessing Safety Hardware (MASH) and were determined to be acceptable according to the Test Level 3 (TL-3) evaluation criteria

Racetrack SAFER barrier on temporary concrete barriers

Previously, the Steel and Foam Energy Reduction (SAFER) barrier system was successfully developed and crash tested for use in high-speed racetrack applications for the purpose of reducing the severity of racecar crashes into permanent, rigid, concrete containment walls. The SAFER barrier has been implemented at all high-speed oval race tracks that host events from NASCAR’s top three race series and IRL’s top series. However, there are a number of racetrack facilities in the United States that use temporary concrete barriers as a portion of the track layout during races. These barriers are typically used on race tracks to shield openings or protect portions of the infield. Some of these temporary barrier installations are in areas where current safety guidance would recommend treatment with the SAFER barrier. Thus, a system was successfully designed, tested, and evaluated for a system targeted towards the most pressing need in the US motorsports industry, a system for spanning openings between rigid concrete parapets on the inner walls of various race tracks

MGS Dynamic Deflections and Working Widths at Lower Speeds

The Midwest Guardrail System (MGS) has been full-scale crash tested in many configurations, including installations adjacent to slopes, with different types of wood posts, with and without blockouts, for culvert and bridge applications, and at high flare rates. Although the performance of the MGS and the dynamic deflection and working width of the barrier have been examined, little is known about the dynamic deflection and working width of the MGS when impacted at lower speeds. The MGS is a relatively low-cost barrier, and the Test Level 3 (TL-3) version could be installed for TL-2 and TL-1 applications. The barrier is expected to capture or redirect errant vehicles impacting at speeds less than or equal to those used for crash testing according to TL-3of the Manual for Assessing Safety Hardware (MASH). Accurate dynamic deflections and working widths of the MGS when impacted at lower speeds are critical for the safe placement of guardrail to reduce the likelihood of vehicle impact with a shielded hazard in the Zone of Intrusion (ZOI) for use on level terrain and in combination with curbs. LS-DYNA computer simulation models of a 2007 Chevrolet Silverado impacting both a tangent MGS and MGS in combination with a curb at a 6-ft 3-in. (1.9-m) post spacing (i.e., standard post spacing) were calibrated against previous crash tests. Then, the model was simulated with two lower speeds and at five impact locations with a conservative soil model to determine the maximum dynamic deflection and working width of the system at TL-1 and TL-2 impact conditions of MASH