The UCT distillation unit is equipped with two stainless steel distillation columns – one with an inner diameter of 300 mm and another with an inner diameter of 150 mm. The maximum height of the packed bed is approximately 2.7 m. The unit is outfitted with a water-cooled plate condenser and an electrically heated kettle-type reboiler with a maximum output of 210 kW. Vapor from the reboiler is introduced into the column through a chimney type distributor with eighteen chimneys evenly distributed across the column’s base cross-section.

the subcooled condensate is collected in the reflux head and pumped by the reflux pump through a preheater into the liquid distributor. The preheater heats up the condensate to the temperature in the column head with a tolerance +/- 1°C. The pipe-type liquid distributor with 97 nozzles (1 373 drip points/m²)*1, with an inner diameter of 2.0 mm ensures uniform initial liquid distribution. The reflux pump is controlled by PI regulation based on the level in the reflux head. The reflux flow is measured upstream (AI) the preheater with a Coriolis flowmeter with an accuracy of 0.1 % of the flow rate. The total pressure is measured at the top of the column. During “atmospheric distillation”, the pressure is maintained by keeping the gas filled space of the condenser open to the atmosphere. In other cases, the pressure is controlled by the simultaneous introduction of nitrogen and its removal via vacuum pump from the space downstream of (AI) the condenser.

A 3 cm layer of EPDM foam provides thermal insulation. The column heat loss along the packed bed was estimated at 0.6 kW during operation at atmospheric pressure.

The 36 flanges are positioned along the column for installing sampling devices or thermometers. Samples of the vapor and liquid phases, taken directly from the packed bed, are collected using specialized sampling devices, as illustrated in Fig. X. The Sputnik Plus device (left) consists of two PTFE cups: one oriented downward to collect the liquid phase and another oriented upward to collect the vapor phase. The Sputnik 3Plus device (right) consists of three pairs of such cups. Both sampling devices are fixed in the packed bed by four stainless steel rods at their front. A PTFE disk is mounted at the end of each sampling device to prevent the tubes that drain samples from being dislodged.

Vapor samples from the space below and above the packed bed are collected in cooled glass syringes, where the vapor fully condenses to yield approximately 4 ml of liquid. To prevent liquid from the column from contaminating the vapor sample, the needles used for vapor sampling are protected by sharply cut PTFE tubing.

All samples are analyzed by refractometry, with an accuracy better than 0.1 mol%.

The pressure drop across the packed bed is measured using a differential pressure meter connected to the column via 4 mm inner diameter tubes. The connection ports are in the same height as/ vertically aligned with (AI) the top and bottom vapor sampling points. The top connection port of the differential pressure meter is located above the liquid distributor, but the pressure drop across the liquid distributor was found insignificant. A low flow rate of nitrogen is maintained through the 4 mm tubes to prevent vapor from the column from entering and condensing in the tubes. In post-processing, the measured pressure drop is corrected for unequal tube lengths and the pressure drop caused by the nitrogen flow is subtracted. Additionally, the hydrostatic contribution to the measured pressure drop is subtracted to account for the density difference between the nitrogen in the tubes and the vapor phase in the column.

*1) 100 nozzles (1415 m−2) v článcích

Packed bed

The packed bed consists of vendor-supplied structured or random packing. The structured packing elements  are manufactured to the column’s internal diameter. Newly delivered  packing elements are thoroughly cleaned before use. Some structured packing elements may be drilled perpendicular to their sheets to allow the insertion of sampling devices into the bed.

Structured packing elements are stacked vertically in the column, with each element rotated 90° relative to the one below it. Random packing elements are introduced in the column through 100 mm inner-diameter tube, enabling their discharge to be directed for uniform distribution across the column cross-section.A grid with a 30 x 30 mm mesh size, topped with a single layer of NexRing 1.2, serves as the support for random packing packed bed.

For Mellapak Plus 252.Y packing, which has a lower geometrical surface area, elements were fitted with two additional wall-wipers made from 0.1 mm thick stainless steel sheet, supplementing the original wall-wipers made from metal gauze (see Fig. X). The additional wall-wipers improved the hydrodynamics of the phases within the packed bed, resulting in more homogeneous composition of phases across the column’s cross-section. by suppression of the (possibly inhomogenous) wall-flow. their effect on overall separation efficiency was found reasonably low/, with a difference in HETPs of approximately 3 %.

The distances between the packed bed, the vapor and liquid distributors, and the top and bottom vapor sampling points for Mellapak Plus 452.Y, Mellapak Plus 252.Y, and NeXRing 0.7 packings are provided in Tab. X.

Distance / Packing	M452.Y	M252.Y	NXR 0.7
Packed bed – L distributor (cm)	5	5	4
Packed bed – G distributor (cm)	52	51	57
Packed bed – top vapor SP (cm)	28	25	22
Packed bed – bottom vapor SP (cm)	7	6	7
High of packed bed (m)	2.54	2.58	2.54

 

Popsat navrtání a odkaz na Čmelíková 2020 jak to ovlivní chování lože, extra-wall wipery na M252.Y, proč byly aplikovány a jestli se při jejich aplikaci změnila separační účinnost.

Testing procedure

Before charging the column with the test mixture, it is dried by evacuation. Any leaks are identified by monitoring changes in the total pressure within the pressurized column. The reboiler is filled with 180 l of the test mixture, composed of analytical-grade constituents. The batch composition is designed to produce a symmetric composition profile along the packed bed, with a 50% composition at the bed’s midpoint (e.g. distillation range from 90 % to 10 % of the volatile component).

Liquid from the reboiler is pumped through the reflux pipeline to the column, and trial liquid-phase samples are collected from the packed bed. These samples must be free of non-condensable gases. Vapor‑phase sampling points are inspected to ensure they do not draw in any liquid phase.

At the start of real testing, the reboiler is set to a constant power level, approximately 80% of the estimated packing capacity. After the packing is thoroughly wetted, the reboiler power is adjusted to the required value. The facility start-up takes approximately four hours to allow the column to properly heat up and reach operating temperature (AI). The reflux is preheated by a 42 kW electrical preheater to within 1 °C of the column head temperature before entering the column.

/ Once the column reaches steady-state conditions (AI), typically 90 minutes after the last operator adjustment, all process data and samples are collected. Stability of the top temperature and reflux flow rate are used as indicators of steady-state conditions.* Samples are taken simultaneously over a 15-minute period, cooled, and analyzed immediately. Process data corresponding to each sample set are recorded as averages over the 10-minute interval preceding the start of sampling.

* Steady-state conditions are indicated by stable top temperature and reflux flow rate.

 

 

 

 

The packed bed of Mellapak Plus 252.Y. H = 2.58 m Ilustrativní – ještě zkontroluji a přeložím	The packed bed of NeXRing 0.7. H = 2.54 m Ilustrativní – ještě zkontroluji