Improving supercritical water gasification of sludge by oil palm empty fruit bunch addition: Promotion of syngas production and heavy metal stabilization

The co-gasification of sewage sludge and palm oil empty fruit bunch (EFB) in supercritical water (SCW) was conducted at 400℃ with a pressure of over 25 MPa. This study aimed to investigate the influence of EFB addition on the syngas production and its composition. The heavy metal distribution and the leaching potential of the solid residue were also assessed. The results showed that syngas yield significantly increased with the addition of EFB into the feedstock. The cold gas efficiency (CGE) and carbon efficiency (CE) of co-gasification were higher than those of individual gasification. The actual syngas production from co-gasification of sludge and EFB was 45% higher than the theoretical total volume. The results indicated that the addition of EFB to sludge had the synergetic promotion effect on syngas production from sludge and EFB in supercritical water. This enhancement might be due to the dissolution of alkali metals from EFB and the adjustment of organic ratio. In addition, higher percentage of heavy metals were deposited and stabilized in the solid residue after SCWG. The leaching concentration of heavy metals from the solid residues was decreased to a level below the standard limit which enables it to be safely disposed of in landfill. In conclusion, the EFB addition has been proved to promote syngas production, as well as, stabilize the heavy metal in solid residues during co-SCWG.     

A parallel coextrusion technique for simultaneous measurements of radial die swell and velocity profiles of a polymer melt in a capillary rheometer

This article proposes a new experimental technique to simultaneously measure radial die swell and velocity profiles of polystyrene melt flowing in the capillary die of a constant shear rate rheometer. The proposed technique was based on parallel coextrusion of colored melt‐layers into uncolored melt‐stream from the barrel into and out of the capillary die. The size (thickness) ratio of the generated melt layers flowing in and out of the die was monitored to produce the extrudate swell ratio for any given radial position across the die diameter. The radial velocity profiles of the melt were measured by introducing relatively light and small particles into the melt layers, and the times taken for the particles to travel for a given distance were measured. The proposed experimental technique was found to be both very simple and useful for the simultaneous and accurate measurement of radial die swell and velocity profiles of highly viscous fluids in an extrusion process. The variations in radial die swell profiles were explained in terms of changes in melt velocity, shear rate, and residence time at radial positions across the die. The radial die swell and velocity profiles for PS melt determined experimentally in this work were accurate to 92.2% and 90.8%, respectively. The overall die swell ratio of the melt ranged from 1.25 to 1.38. The overall die swell ratio was found to increase with increasing piston speed (shear rate). The radial extrudate swell profiles could not be reasoned by the shear rate change, but were closely linked with the development of the velocity profiles of the melt in the die. The die swell ratio was high at the center (～1.9) and low (～0.9) near the die wall. The die swell ratio at the center of the die reduced slightly as the piston speed was increased. Polym. Eng. Sci. 44:1960–1969, 2004. © 2004 Society of Plastics Engineers.     

Use of paraffin impregnated lightweight aggregates to improve thermal properties of concrete panels

In this study, the effect of aggregates impregnated with phase change material (paraffin type) on properties of concrete is investigated. The experimental series consists of two stages. The first stage is to investigate the techniques used to impregnate phase changed material (paraffin type) into lightweight aggregates and the properties of aggregates with paraffin inside (PLA). Two impregnation techniques are introduced, (1) heat only and (2) heat and pressure (autoclaving). Using the obtained results, the aggregate with the highest level of impregnation in the shortest time is selected to use in the concrete production process of the next stage. In the second stage, the properties of concrete mixed with non-paraffin and paraffin impregnated lightweight aggregates (PLA) at different proportions are investigated. The experimental series include density and absorption, compressive strength, thermal storage (and insulation) and sound transmission loss. Results in aggregate level show the increase in specific gravity and the decrease in absorption with paraffin inserted into aggregates. In concrete form, the density, compressive strength and sound insulation are found to increase with the PLA replacement ratio. The sound transmission loss, on the other hand, becomes less efficient with increasing PLA replacement ratio.     

Experimental studies on radial extrudate swell and velocity profiles of flowing PS melt in an electro‐magnetized die of an extrusion rheometer

This article investigates the radial extrudate swell and velocity profiles of polystyrene melt in a capillary die of a constant shear‐rate extrusion rheometer, using a parallel coextrusion technique. An electro‐magnetized capillary die was used to monitor the changes in the radial extrudate swell profiles of the melt, which is relatively novel in polymer processing. The magnetic flux density applied to the capillary die was varied in a parallel direction to the melt flow, and all tests were performed under the critical condition at which sharkskin and melt fracture did not occur in the normal die. The experimental results suggest that the overall extrudate swell for all shear rates increased with increasing magnetic flux density to a maximum value and then decreased at higher densities. The maximum swelling peak of the melt appeared to shift to higher magnetic flux density, and the value of the maximum swell decreased with increasing wall shear rate and die temperature. The effect of magnetic torque on the extrudate swell ratio of PS melt was more pronounced when extruding the melt at low shear rates and low die temperatures. For radial extrudate swell and velocity profiles, the radial swell ratio for a given shear rate decreased with increasing r/R position. There were two regions where the changes in the extrudate swell ratio across the die diameter were obvious with changing magnetic torque and shear rate, one around the duct center and the other around r/R of 0.65–0.85. The changes in the extrudate swell profiles across the die diameter were associated with, and can be explained using, the melt velocity profiles generated during the flow. In summary, the changes in the overall extrudate swell ratio of PS melt in a capillary die were influenced more by the swelling of the melt around the center of the die. Polym. Eng. Sci. 44:2298–2307, 2004. © 2004 Society of Plastics Engineers.     

Melt strength,local velocity,and elongational viscosity profiles of low‐density polyethylene filaments affected by the die design and process conditions

An experimental arrangement to simultaneously measure the melt strength, velocity profiles, and elongational viscosity profiles across the cross section of a molten filament that emerged from either a circular or slit die for low‐density polyethylene (LDPE) under nonisothermal and isothermal conditions is proposed. The proposed experimental rig was based on a parallel coextrusion technique of colored LDPE melt layers into an uncolored melt flowing from the barrel into and out of a die to form a continuous filament before they were pulled down by mechanical rollers until the filament failed. The experimental rig was also equipped with a high‐speed data‐logging system and a personal computer for real‐time measurements. The results suggest that the draw‐down forces changed continuously with changing roller speed, and the velocity profiles of the melt were not uniform across the LDPE filament during the stretching of the melt. Greater draw‐down forces and local melt velocities were obtained in the slit die or under the nonisothermal condition. The draw‐down forces and velocity profiles in both dies were affected by the volumetric flow rates from the extruder and the roller speeds used, with the effect being more pronounced for the circular die. The elongational viscosity profiles of the LDPE filament were not uniform across the filament cross section and corresponded well to the obtained velocity profiles. The elongational viscosities of the LDPE filament were relatively higher when the filament was extruded and stretched in the circular die and under the nonisothermal condition. The changes in the elongational viscosity profiles were more sensitive to changes in the volumetric flow rate and roller speed in the circular die. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermodynamic study on the integrated supercritical water gasification with reforming process for hydrogen production: Effects of operating parameters

In this paper, a conceptual process design of the integrated supercritical water gasification (SCWG) and reforming process for enhancing H₂ production has been developed. The influence of several operating parameters including SCWG temperature, SCWG pressure, reforming temperature, reforming pressure and feed concentration on the syngas composition and process efficiency was investigated. In addition, the thermodynamic equilibrium calculations have been carried out based on Gibbs free energy minimization by using Aspen Plus. The results showed that the higher H₂ production could be obtained at higher SCWG temperature, the H₂ concentration increased from 5.40% at 400 °C to 38.95% at 600 °C. The lower feed concentration was found to be favorable for achieving hydrogen-rich gas. However, pressure of SCWG had insignificant effect on the syngas composition. The addition of reformer to the SCWG system enhanced H₂ yield by converting high methane content in the syngas into H₂. The modified SCWG enhanced the productivity of syngas to 151.12 kg/100kg_feed compared to 120.61 kg/100kg_feed of the conventional SCWG system. Furthermore, H₂ yield and system efficiency increased significantly from 1.81 kg/100kg_feed and 9.18% to 8.91 kg/100kg_feed, and 45.09%, respectively, after the modification.     

Rheological properties,flow visualization and extrudate swell of NR compound by rotating‐die rheometer

An experimental apparatus coupled with a rotating die system was especially designed and manufactured to study the rheological properties, flow patterns and swelling behavior of natural rubber (NR) compound for different shear rates and die rotating speeds at a test temperature of 110°C, the results being compared with those by the static capillary die. It was found that NR compound used exhibited psuedoplastic non‐Newtonian behavior. The rotation of the capillary die could reduce the extrusion load. The wall shear stress for any given shear rates increased with increasing die rotating speed. The fluctuation of the entrance pressure drop increased with increasing die rotating speed. The flow pattern development in the rotating‐die rheometer was different from that observed in the static die. The flow patterns in the rotating die were clearly unstable and contained two flow components which included axial flow along the barrel and circumferential flow at the die entrance. The size and shape of the axial and circumferential flows were more dependent on the piston displacement. It was found that the swelling ratio of the NR compound decreased with increasing die rotating speed. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

A novel capillary rheometer for measurement of flow properties of polymer melts

This paper introduces a novel type of capillary rheometer, with respect to its design and operation, for investigating flow properties of a polymer melt. The constructed capillary rheometer is fitted into a standard tensile testing machine such that the mode of extrusion could be altered. The equipment features the possibility of moving either the piston or the barrel, the latter being novel in design. In addition, this work presents a novel pressure sensor for determining the pressure drop along the die in the capillary rheometer. It is found that the constructed capillary rheometer, coupled with the novel pressure sensor, is a useful device to monitor the flow properties of the polymer melt. The preliminary results show that the flow properties are dependent not only on the test condition used, but also on the mode of operation. Received: 21 May 1999 / Reviewed and accepted: 31 May 1999     

A die rotating system for moderations of extrusion load and pressure drop profiles for molten PP and wood/polypropylene composites in extrusion processes

A die‐rotating system was proposed in this work for moderations of extrusion forces and entrance pressure drop for molten polypropylene (PP) and wood/polypropylene (WPP) composites in a capillary rheometer and a single screw extruder. The effects of processing conditions and wood loading in PP were of our interests. The extrusion force and entrance pressure drop with and without the die rotating system were monitored in real‐time. This was the first time that the die‐rotating system was used for processing of highly viscous wood/polymer composite materials. It was found that the flow properties of the molten PP and WPP composites obeyed pseudoplastic non‐Newtonian behavior. The behavior was more obvious at wood contents of above 6 wt % and in the capillary rheometer. The rotation of the die could moderate the extrusion load by 60% and entrance pressure drop by 20% in the capillary rheometer, and the entrance pressure drop by 30% in the single screw extruder, especially at the conditions where the viscosities of the WPP and the extrusion rate were high. Greater fluctuations in entrance pressure drop caused by die rotation were observed in the single screw extruder. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120:1006–1016, 2011     

Mechanical strengths of molten and solidified LLDPE/LDPE blends and wood/LDPE composites under tensile deformation

The mechanical strengths of neat low‐density polyethylene (LDPE), a blend of LDPE with linear low‐density polyethylene (LLDPE), and a composite of LDPE with wood flour (wood/LDPE) were investigated in molten and solidified states under tensile deformation. The results are discussed in terms of the effects of LLDPE and wood contents, roller speed, and volumetric flow rate. In LLDPE/LDPE blends, incorporating LLDPE from 0 to 30 wt% into LDPE caused a slight increase in drawdown force, a larger fluctuation in drawdown force, and a reduction of maximum roller speed to failure. The mechanical properties of the solidified LLDPE/LDPE corresponded to those of the molten LLDPE/LDPE with regard to the effect of LLDPE content. For wood/LDPE composites, increasing the wood flour content in molten LDPE caused considerable reductions in drawdown time and maximum roller speed to failure. The drawdown force increased with increasing wood flour up to 10 wt% before it decreased at the wood loading of 20 wt%. A number of voids and pores on the extrudate surfaces became obvious for the composites with 20 wt% of wood content. Increasing wood content enhanced the tensile modulus for the solidified LDPE but decreased its tensile strength. Unlike those of LLDPE/LDPE blends, the changes in tensile modulus and strength of solidified wood/LDPE composites with wood content did not correspond to those of the molten composites. In all cases, the drawdown force increased with increasing roller speed. The effect of volumetric flow rate from the extruder on the mechanical strengths of the solidified blends was more pronounced than on those of the molten ones. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers