Chemical stability of a filled polymer composite in ammonia production

Abstract

The problem of selection of materials for the manufacture of contact devices of heatand mass-transfer units used in ammonia plants is very relevant. Such devices are made of carbon steel, stainless steels, ceramic materials, and, experimentally, unfilled pol~-propylene. Devices made of these materials have significant drawbacks: those made of carbon steel break down rapidly because of its low corrosion resistance; those made of steel 12KhlSNIOT (in the form of Raschig rings or GIAP (State Scientific-Research and Design Institute of the Nitrogen Industry and Organic Synthesis) packing elements) are expensive (scarce nickel is consumed), and, in addition, they exert an unfavorable effect on the composition of the working solution; those made of ceramics are leached by the working solutions and fracture because of brittleness (fouling of the packing by the leaching products is possible); and those made of unfilled polypropylene are insufficiently heat-resistant and melt in contact with the working solutions. Now a material, Komponor RR03-4-0, has been developed which is a highly filled polymer composite from polypropylene, having a set of physicomechanical properties satisfying the operating conditions of packings in ammonia production. The material is obtained by activation filling; it has a density exceeding the density of the utilized working solutions, good technologicalproperties (making it possible to convert the material to products on standard molding equipment), economy, and higher rigidity and heat resistance than the starting polymer.In this paper, we investigated the chemical stability of the material Komponor RR03-4-0 in ammonia-production media and monitored the serviceability of experimental products made of it obtained on serially manufactured molding equipment.In ammonia production, one of two working solutions is used to remove COa from converted gas: a Karsol solution, 25-28% K2CO 3 potash, 1.9% C2H~(OH) 2 diethanolamine, and 0.4% V20 s vanadium pentoxide, or an aqueous solution containing 20% monoethanolamine (MEA). Such solutions were also used in a test of specimens and products at 120~ with an autoclave pressure of 0.5 MPa and a test duration of 600 h. After holding of specimens in the form of standard paddles in the working solutions under the mentioned conditions, we obtained the data given in Table i. We detected no changes by microscopic investigation of the appearance of the specimens and their cross sections.Experimental products made of Komponor, Pall rings 50 mm in diameter and 50 nun in height, were obtained by injection molding on a standard molding machine. The fabricated products had half the technological shrinkage (1-1.5%) of similar products made of unfilled polypropylene. To reproduce the service conditions of the most loaded elements located in the lower part of a 6-mm-high packing bed, the experimental products were additionally loaded with a constant compressive force of 20 N per element.After holding of the products in glycerol at 120~ for I00 h under the mentioned loading,...