Columns and process towers

Columns and process towers — definition: Static equipment for chemical separation, absorption, distillation or extraction in which liquid and/or gas streams are passed countercurrently through a packed or structured bed. Columns fall under PED 2014/68/EU (pressure vessel), ATEX 2014/34/EU (zone 1/2 gas/vapour), EN 13445 (unfired pressure vessels) and GMP Annex 1 (2022) for pharmaceutical API isolation columns (chromatography, crystallisation). Materials: 316L stainless steel, Hastelloy C-276, titanium — per EN 10204 3.1 inspection certificate.

Key points — columns and process towers

• Standards: PED 2014/68/EU, ATEX 2014/34/EU zone 1/21, EN 13445, ASME Section VIII Div. 1, GMP Annex 1 (2022), EN 10204 3.1
• Types: distillation column (tray/packed), absorption column (Raschig rings, structured packing Sulzer MellapakPlus), stripper, chromatography column (pharma API), wash column
• Pressure/temperature: MAWP 1–160 bar, temp. –196°C to +400°C; SIL level (IEC 61511) determines safety fittings (PSV, burst disc, SIL 2/3)
• HECHT link: vacuum and pressure transport to/from columns, endless liner SBK for HPAPI column discharge (OEB 4–5), ProClean Conveyor for powder-fed columns
• ROI: a correctly designed process column improves separation efficiency +15–25% (theoretical plates, HETP), lowers energy use –10–20% via optimised reflux ratio

Process columns are at the heart of chemical and pharmaceutical separation processes. Discover how HECHT's bulk handling systems interface with columns, our pharma process solutions and plan a process trial at our Test & Trial Centre in Pörnbach.

Columns and process towers are designed for separating, purifying and treating liquid and gas streams within industrial processes. Through controlled mass transfer between phases, these systems enable efficient distillation, absorption, stripping and rectification.

These installations form a critical part of processes where product purity, yield and process control are paramount.

FAQ — Columns and process towers

Which materials are used for process towers in the chemical industry?

Material selection guide for process towers: 316L stainless steel (general corrosive, T <400°C, P <160 bar); Hastelloy C-276 (strongly acidic/oxidising media, HCl, H₂SO₄, FeCl₃); titanium (seawater, oxidising acids, wet chlorine gas); fibreglass-reinforced resin (GRP, T <120°C, hydrochloric acid wash columns). Material selection per NACE MR0103 (process chemistry), EN 10204 3.1 inspection certificate. HECHT supplies process towers in all common alloys with ATEX and PED documentation.

How is a process column sized for optimal separation efficiency?

Sizing follows: (1) mass balance per component (McCabe-Thiele or rigorous simulation in Aspen Plus); (2) determination of theoretical plates (N) and HETP (height equivalent to a theoretical plate, 0.2–0.8 m for structured packing); (3) column diameter via flooding calculation (Souders-Brown, 70–80% flooding); (4) auxiliary equipment: reboiler (thermosiphon/kettle), condenser, reflux drum; (5) hydraulic pressure drop calculation. HECHT's engineering team performs these calculations as part of the basic engineering package.

Which PED category applies to a process column and what are the inspection requirements?

PED 2014/68/EU categorises pressure vessels based on PS×V (bar×litre) and fluid group (hazardous = Group 1, non-hazardous = Group 2). From Cat. III/IV, a Notified Body (NoBo) is mandatory for design and production inspection. Periodic inspection per applicable pressure equipment regulations: external inspection 1×/year, internal inspection 1×/5 years (or RBI-based justification). HECHT supplies CE-documented process columns with a test report (EN 13445-5 hydraulic pressure test at 1.3× MAWP).

• High efficiency: optimal separation and purification
• Flexibility: suitable for diverse processes and industries
• Scalability: from pilot installation to large-scale production
• Reliability: robust and proven technology
• Process control: precise control of temperature, pressure and flows
• Sustainability: potential for energy integration and material recovery

Frequently asked questions about columns and process towers