Comparison of plate and packed contact devices in column vessels

Abstract

11Contact devices for mass-exchange processes in packed and plate columns are investigated. A comparative analysis is made of contact devices (sieve plate, irregular packed, and regular structured packings) for the purpose of selecting equipment optimal for a blow-through column used to produce weak nitric acid.Selection of optimal contact devices is a critical problem in the development of new, and modernization of existing vessels for mass-exchange processes. Many mass-exchange processes (absorption, desorption, distillation, etc.) are carried out in column vessels with plate, packed, or film contact devices (regular structured packings).The hydrodynamic situation in packed columns (PC) with irregular packings (IP) is characterized by disordered movement of flows over time and in cross sections over the height of the vessel, and longitudinal displacement, as well as displacement as liquid flows move toward the walls of the column. Owing to the indicated characteristic features of a PC, its operating efficiency decreases with increasing diameter. Figure 1 shows packed elements of one type of IP for PC. In PC fitted with structured packings (SP), the flow of liquid through the SP is predominately film in nature, and the movement of both liquid, and also gas flows is ordered over the height of the column and in the cross section of the vessel (in providing uniformity of the flow introduced to the packed layers). In PC with SP, displacement of liquid toward the walls of the column is eliminated by creating discontinuities in the liquid film and its redistribution at the joints between packing bundles, which are turned 90°relative to one another. PC with SP (for example, the Sulzer Chemtech Co. [1], Fig. 2) have low hydraulic resistance and high mass-exchange characteristics.The movement of flows in plate columns (PLC) is clearly organized both within the limits of a single plate, and also on the plates over the height of the column. Since channel formation, by-passing, and longitudinal displacement do not occur on the plates, the separation efficiency in PLC, as calculated per unit height of the effective zone of the vessel, is higher than in PC, and is less dependent on scale factor, since sectioned plates are normally used in large-diameter columns. Figure 3 shows a schematic diagram of a sectional sieve (zero-gradient [2]) plate 2600 mm in diameter. For a uniform distribution of flows, this design of plate ensures a scale-transition factor close to unity with increasing diameter of the PLC [2].Analysis of PC and PLC indicated the following: 1. As compared with PLC, PC have a low hydraulic resistance, as calculated per unit height of transfer, since the plates operate in a submerged regime, and the gas passing through the column must overcome a resistance equal to the total pressure of the liquid columns on all plates. The hydraulic resistances of PLC and PC with SP differ particularly significantly. The low

Features of fluid film falling on the corrugated surface of structured packings with perforations

“…1) have lower pressure drop compared with trays and random packings at the same efficiency [3,4]. However, structured packings are very sensitive to the uniformity of liquid distribu tions over the cross section of a packed column in comparison with random packings.…”

Hardware and Process Optimization of Production Unit for Concentrating Isopropyl Benzene Hydroperoxide in the Course of Phenol Production By cumene Process

“…Operating region for single-stage IPB HP production (at P resid.top = 3 mm Hg) World leading companies in research and development of regular packing are SULZER, NORTON and GLITSCH. Top Russian companies include FGUP RSC "Applied Chemistry" (GIPH packing), "Kedr", "Peton" and "Ingehim"[5][6][7][8][9]. The GIPH packing has the best product output per unit of volume (up to 10 kg/(m 3 ·s)).…”