Recovery of vinyl chloride from by‐streams of polyvinyl chloride production by TPSA in a multitubular adsorber

Abstract

This work aims at developing an efficient and feasible adsorption‐based separation process for the separation of vinyl chloride and nitrogen, on activated carbon, by employing a multitubular packed bed geometry, with adsorbent material inside the tubes. Using this geometry, a 2‐dimensional mathematical model of a temperature pressure swing adsorption process was used to developed a 6‐step three multitubular adsorbers system capable of separating and purifying an industrial scale gas stream of a 40:60% (v/v) vinyl chloride/nitrogen mixture into a 95% (v/v) vinyl chloride stream and a nitrogen stream with a vinyl chloride limit concentration of 8 ppm (w/w). The process reported energy consumption of 4.88 × 106 J/kgVCM and recovery capacity of 24.35 kgVCM/(m3unit h). The multitubular geometry enabled the use of lower adsorbent loads, shorter cycle times, and lower regeneration temperatures. An equivalent 1‐dimensional model has also shown to satisfactorily estimate the performance of the current equipment.

Vinyl Chloride Recovery in a Multitubular Adsorber on Maxsorb Carbon

“…In the present work, the proposed fixed bed mathematical model will be used to simulate and predict the dynamic behavior of the adsorbent packed bed within the tube side of the MTA system. As shown by Carmo et al, 13 an equivalent 1dimensional (axial direction, 1D) mathematical model can accurately predict the packed bed's internal thermal behavior by approximating the radial (2-dimensional model) thermal behavior by a lumped contribution. Using a derivation proposed by Froment, 23 the thermal transport in the radial direction can be estimated by the theoretical sum of the wall and bulk radial diffusion resistances.…”

“…As previously described by Carmo et al, 13 the fixed bed mathematical model used in this work is composed of a set of mass, thermal, and momentum balances. The mass transfer will be considered solely between the gas and the solid phase, while energy transfer will be considered between the gas phase, solid phase, column wall, and the shell side heat exchange fluid.…”

“…All of the assumptions, models, and balances used in the present mathematical model have already been fully described in the literature. 7,13,24 Industrial & Engineering Chemistry Research 2.5. Multitubular Temperature Pressure Swing Adsorption Model.…”

“…Although equilibrium isotherms with high adsorption enthalpy are advantageous for gas capture processes, the high energy requirements necessary for the desorption of the more heavily adsorbed species make pressure swing separation systems ineffective, limiting the available processes to temperature swing types. 7 A previous work has already been performed to overcome this drawback, 13 which resulted in applying a multitubular adsorber (MTA) geometry to a typical temperature pressure swing adsorption cycle. This design allowed for the use of more lenient regeneration conditions; it led to a substantial reduction in the required adsorbent inventory and a respective increase in productivity compared to a standard fixed-bed TPSA system.…”

“…The use of a higher-performance adsorbent material should also improve the performance of the separation process developed in the previous works. A multitubular temperature and pressure swing adsorption (MT-TPSA) cycle was designed for VCM and N 2 recovery, using an equivalent 13 1-dimensional mathematical model. The developed VCM recovery system must be capable of producing two different product streams, that is, a 40/60% (v/v) VCM/ N 2 gas mixture with a feed flow rate of 180 Nm 3 /h.…”