Installation, Operation & Maintenance | DAIER Chemical Separation Standard

Engineering Reference for Process Engineers

 

Section 9: Installation and Commissioning

46. Q: What are the correct procedures for installing random packing?A: (1) Ensure column is clean and level. (2) Install support plate and bottom distributor. (3) Pour packing gently to avoid breakage (for ceramic) or nesting (for plastic). Do not dump from height >1 m. (4) Level the bed surface. (5) Install bed limiter and top distributor.

47. Q: How is structured packing installed?A: (1) Modules are stacked in layers with 90° rotation between layers. (2) Ensure modules are tightly fitted to column wall – use sealing strips to prevent bypass. (3) Align corrugation orientation as specified. (4) Install each layer with proper orientation. (5) Secure bed limiter.

48. Q: What is the importance of packing bed leveling?A: An uneven bed causes maldistribution – liquid channels to low spots, gas bypasses high spots. Efficiency can drop by 30-50%. Leveling is done by manually smoothing the surface or using a leveling grid.

49. Q: How is column pre-commissioning done?A: (1) Water flush to remove debris. (2) Air-water test to check distributor operation. (3) Pressure test (if specified). (4) Visual inspection of internals. (5) Calibrate instruments.

50. Q: What safety precautions are needed during installation?A: Confined space entry procedures. Proper ventilation when handling plastic or ceramic packing (dust). Use of appropriate personal protective equipment (gloves, dust mask, safety glasses). Lifting equipment for heavy modules.

Section 10: Operation and Performance Monitoring

51. Q: What are the key operating parameters to monitor?A: (1) Pressure drop across bed – indicator of flooding or fouling. (2) Temperature profile – detects maldistribution. (3) Flow rates (liquid and vapor). (4) Composition analysis – calculates efficiency. (5) Differential pressure across distributors.

52. Q: How is column efficiency monitored during operation?A: Efficiency is calculated from actual separation vs. theoretical stages. For distillation: take samples of overhead and bottoms, calculate actual stages, compare to design. For absorption: measure outlet gas concentration, calculate NTU achieved.

53. Q: What is gamma ray scanning and when is it used?A: Gamma ray scanning is a non-destructive technique to diagnose column internal conditions. It can detect flooding, channeling, packing damage, distributor malfunction, and bed height changes. Used when performance drops unexpectedly.

54. Q: How to detect flooding during operation?A: Signs of flooding: sudden increase in pressure drop, rapid decrease in separation efficiency, liquid carryover in overhead, erratic temperature profile. Flooding occurs when gas velocity exceeds ~80% of flooding point.

55. Q: What causes maldistribution and how is it identified?A: Causes: poor initial distribution, distributor plugging, bed settlement, wall flow. Identification: temperature profile asymmetry, lower-than-expected efficiency, gamma scan showing uneven density. Correction: clean distributor, repack or level bed.

Section 11: Maintenance, Cleaning, and Replacement

56. Q: How often should tower packing be inspected?A: During planned turnarounds (typically every 2-5 years). For corrosive service or frequent fouling, more frequent inspection. Inspection includes visual check, pressure drop trend analysis, and sample extraction for condition assessment.

57. Q: Can tower packing be cleaned and reused?A: Yes, if not deformed, corroded, or permanently fouled. Cleaning methods: water washing (for soluble fouling), solvent washing (for organic deposits), steam cleaning (for light fouling), mechanical tumbling (for metal packing). Plastic packing may absorb chemicals and should be replaced if degraded.

58. Q: What are the criteria for replacing packing?A: (1) Physical damage: broken rings, crushed modules (>10% damage). (2) Corrosion: wall thickness reduction >30% or visible pitting. (3) Fouling: permanent plugging that cannot be cleaned. (4) Performance drop: pressure drop increase >50% or efficiency drop >30% from baseline.

59. Q: How to clean fouled structured packing?A: For organic fouling: soak in solvent, then high-pressure water jet ( < 50 bar to avoid damage). For biological fouling: chlorinated water soak. For scale: acid wash (dilute HCl or citric acid), followed by neutralization and rinsing. Wire mesh packing is delicate – use low-pressure water only.

60. Q: What is the typical service life of tower packing?A: Non-corrosive service: 10-20 years. Mildly corrosive: 5-10 years. Highly corrosive (e.g., chlorides at high temperature): 2-5 years. Plastic packing in UV-exposed or high-temperature service: 3-7 years. Ceramic packing in acid service: 10-20+ years if thermal cycling is avoided.

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