DEVELOPMENT OF A MECHANISM AND PROCESS TO CONTINUOUSLY PRODUCE SPHERICAL, TORREFIED BIOMASS PELLETS

A recently developed novel biomass fuel pellet, the Q’ Pellet, offers significant improvements over conventional white pellets, with characteristics comparable to those of coal. The Q’ Pellet was initially created at bench scale using a proprietary die and punch design, in which the biomass was torrefied in-situ¬ and then compressed. To bring the benefits of the Q’ Pellet to a commercial level, it must be capable of being produced in a continuous process at a competitive cost. A prototype machine was previously constructed in a first effort to assess continuous processing of the Q’ Pellet. The prototype torrefied biomass in a separate, ex-situ reactor and transported it into a rotary compression stage. Upon evaluation, parts of the prototype were found to be unsuccessful and required a redesign of the material transport method as well as the compression mechanism. A process was developed in which material was torrefied ex-situ and extruded in a pre-compression stage. The extruded biomass overcame multiple handling issues that had been experienced with un-densified biomass, facilitating efficient material transport. Biomass was extruded directly into a novel re-designed pelletizing die, which incorporated a removable cap, ejection pin and a die spring to accommodate a repeatable continuous process. Although after several uses the die required manual intervention due to minor design and manufacturing quality limitations, the system clearly demonstrated the capability of producing the Q’ Pellet in a continuous process. Q’ Pellets produced by the pre-compression method and pelletized in the re-designed die had an average dry basis gross calorific value of 22.04 MJ/kg, pellet durability index of 99.86% and dried to 6.2% of its initial mass following 24 hours submerged in water. This compares well with literature results of 21.29 MJ/kg, 100% pellet durability index and <5% mass increase in a water submersion test. These results indicate that the methods developed herein are capable of producing Q’ Pellets in a continuous process with fuel properties competitive with coal.

Polymer Process Partitioning: Extruding Plastic Pipe

When plastic pipe is solidified, it proceeds through a long cooling chamber. Inside this chamber, inside the hollow extrudate, the plastic is molten, and this inner surface solidifies last. Sag, the flow due to the self-weight of the molten plastic, then happens in this cooling chamber, and sometimes, thickened regions (called knuckles) arise in the lower quadrants, especially of large diameter thickwalled pipes. To compensate for sag, engineers normally shift the die centerpiece downward. This thesis focuses on the consequences of this decentering. Specifically, when the molten polymer is viscoelastic, as is normally the case, a downward lateral force is exerted on the mandrel. Die eccentricity also affects the downstream axial force on the mandrel. These forces govern how rigidly the mandrel must be attached (normally, on a spider die). We attack this flow problem in eccentric cylindrical coordinates, using the Oldroyd 8-constant constitutive model framework. Specifically, we revise the method of Jones (1964), called polymer process partitioning. We estimate both axial and lateral forces. We develop a corresponding map to help plastics engineers predict the extrudate shape, including extrudate knuckles. From the mass balance over the postdie region, we then predict the shape of the extrudate entering the cooling chamber. We further include expressions for the stresses in the extruded polymer melt. We include detailed dimensional worked examples to show process engineers how to use our results to design pipe dies, and especially to suppress extrudate knuckling.

EXAMINING HOW SAME-GENDER AND MIXED-GENDER COUPLES NAVIGATE SEXUAL ISSUES IN THEIR RELATIONSHIPS

Sexual scripts—the definitions and expectations that individuals hold for sexual interactions—are thought to play an important role in the maintenance of sexual well-being. Sexual scripts can be rigid or flexible, and they can be concordant or discordant between members of a couple. Sex therapists support sexual script flexibility for maintaining sexual and relationship satisfaction when couples are navigating sexual issues. However, empirical research examining the role of sexual script flexibility and the degree of script concordance/discordance in couples’ sexual well-being has been limited, due in part to the limited measures available. Furthermore, within the existing research, there has been an unfortunate tendency to exclude individuals in same-gender relationships – perpetuating the long-standing knowledge gap in the literature on positive sexuality in diverse relationships. To address these gaps in the literature, we conducted a series of online studies that recruited individuals in diverse relationships. A measure of individual sexual script flexibility in response to sexual issues was developed (Chapter 2); in addition, the structure of an existing measure assessing couple sexual scripts in response to a sexual issue was evaluated (Chapter 3). Chapter 4 examined how individuals in diverse relationships compared on measures of individual sexual script flexibility and on couple sexual scripts. Findings suggest that there are more similarities than differences across diverse couples. Chapter 5 explored how flexibility in an individual’s approach to sexual issues relates to sexual well-being, specifically by assessing sexual communication and partner responses as mediators. Results suggest that individual sexual script flexibility relates to sexual well-being through reciprocal partner processes. Collectively, this research program suggests that more similarities than differences exist between individuals in same- and mixed-gender relationships, and that partners are important to consider in the relationship between individual sexual script flexibility and sexual well-being. These findings have implications for sex and couple therapy; these results emphasize the importance of interventions that target both members of the couple, and further our understanding of sexuality in same- and mixed-gender relationships.