Exergy Footprint Assessment of Cotton Textile Recycling to Polyethylene

Circular economy implementations tend to decrease the human pressure on the environment, but not all produce footprint reductions. That observation brings the need for tools for the evaluation of recycling processes. Based on the Exergy Footprint concept, the presented work formulates a procedure for its application to industrial chemical recycling processes. It illustrates its application in the example of cotton waste recycling. This includes the evaluation of the entire process chain of polyethylene synthesis by recycling cotton waste. The chemical recycling stages are identified and used to construct the entire flowsheet that eliminates the cotton waste and its footprints at the expense of additional exergy input. The exergy performance of the process is evaluated. The identified exergy assets and liabilities are 138 MJ/kg ethylene and 153 MJ/kg ethylene, reducing the Exergy Footprint by 75% and the greenhouse gas footprint by 43% compared to the linear pattern of polyethylene production. The exergy requirements for producing raw cotton constitute a large fraction of the liabilities, while the polyethylene degradation provides the main asset in the reduction of the Exergy Footprint.

FACILITY LAYOUT REDESIGN USING SYSTEMATIC LAYOUT PLANNING METHOD IN PT. PILAR KEKAR PLASINDO

Good equipment and product design are meaningless if there is no good layout planning. Problems owned by PT. Pilar Kekar Plasindo occurs in the production of small polyethylene. This is because small polyethylene production has large material total transfer distance. Small polyethylene problems include the distance between stations, cross-movement, backtracking, and the broken machine that is still placed in the production section. These conditions make the material handling costs and distance large. Therefore, this research aims to produce a layout design of production facilities that can minimize the distance and cost of material movement. The method used in this study is Systematic Layout Planning (SLP). Three alternative designs were compared, and the second proposed facility layout was chosen because it can reduce the total cost of material transfer by 68.3% and reduce the distance of material transfer by 59.6% from the initial facility layout.

Selective Hydrogenation of Acetylene to Ethylene Over Nanosized Gold and Palladium Supported Catalysts

Ethylene, the main raw material for polyethylene production, is a by-product produced by thermally decomposing naphtha and it contains a small amount of acetylene. The acetylene reacts as a permanent catalyst poison for the ethylene polymerization catalyst. In this study, we wanted to improve the acetylene conversion and the ethylene selectivity by selective hydrogenation of acetylene for removing acetylene contained in ethylene. Catalyst was prepared by loading nanosized gold (Au) and palladium (Pd) particles on support (Al2O3, TiO2). Deposition order Au and Pd particles was changed. The activity of the catalyst was investigated using a flow-typed fixed bed reactor under atmospheric pressure. Au and Pd particles deposited on TiO2 were oxidized to Au2O3 and PdO due to strong metal support interaction (SMSI). It was considered that the Au/Pd/Al2O3 catalyst was more active than the Pd/Au/Al2O3 catalyst due to the formation of the interface between Au particles and Pd particles (or support). But Pd/Au/Al2O3 catalyst is considered to have poor activity because Pd particles cover part of the interface between Au and the support. Au/Pd/Al2O3 catalyst showed the best catalytic activity, and acetylene conversion and ethylene selectivity were 100% and about 80% at 40 °C, respectively.

CFD MODELING OF POLYETHYLENE GAS PHASE FLUIDIZED BED REACTOR WITH INTERNAL CHILLER

Polyethylene production in a gas phase fluidized bed reactor is exposed to unstable temperature behavior, and if not controlled properly the temperature oscillation can cause polymer melting and potential plant shutdown (Ghasem, 1999). Accordingly, the present work improves the previous simple mathematical model by the CFD modelling that addresses the prediction of ethylene concentration and temperature profile in entire reactor of the fluidized bed reactor employed for polyethylene production. The CFD model considers gas phase molecular diffusion in the axial and radial directions. Results revealed that the size of the internal heat exchanger mainly the exchanger heat transfer interface area has strong impact on the temperature contour inside the reactor. Ethylene feed rate and ethylene concentration, catalyst feed rate effect the temperature profile inside the reactor considerably. The increase in ethylene concentration and catalyst feed rate strongly influences the fluidized bed temperature. As ethylene concentration increases reactor temperature increases. Proper temperature control inside the polyethylene gas phase is essential fluidized reactor to maintain the reactor temperature below polymer melting point and hence long term operation of fluidized bed reactor without reactor shutdown and temperature excursion above the polymer melting point.

Investigation of Hydrogen Storage Characteristics of MgH2 Based Materials with Addition of Ni and Activated Carbon

Magnesium-based materials are promising as hydrogen storage media due to their high theoretical hydrogen absorption capacity, abundance and low price. The subject of this study are the hydrogen sorption characteristics of the composites 80 wt % MgH2-15 wt % Ni-5 wt % activated carbon (synthesized from polyolefin wax, a waste product of polyethylene production at low pressure which will be denoted further in the text as POW) and 90 wt % MgH2-5 wt % Ni-5 wt % POW, prepared by ball milling under argon atmosphere. Structure, phase and surface composition of the samples before and after hydrogenation are determined by XRD and TEM. The maximum absorption capacity value of the composites at a temperature 573 K and after 60 min. of hydrogenation are 5.3 wt % H2 for the material with higher Ni content and 5.5 wt % H2 for the other sample. The presence of both additives—nickel and activated carbon derived from POW—has a positive impact on hydrogenation kinetics and the capacity achieved. The results from TEM characterization, e.g., the polycrystalline SAED (selected area electron diffraction) show the presence of graphite, Mg and monoclinic Mg2NiH4.

Mechanistic study of the competitiveness between branched and linear polyethylene production on N-arylcyano-β-diketiminate nickel hydride

This paper provides a guide to identify and understand the mechanistic origin of the catalytic activity and selectivity in the production of linear and branched polyethylene through a nickel hydride catalyst.