structured packing vs trays
While good distributor design, water testing, and inspection can eliminate most maldistribution issues, it only takes a few small details that fall through the cracks to turn success into failure. Thorough removal of residual liquid, wash water, air, or process gas trapped in structured packings at startup and shutdown is more difficult than with trays. FLEXERAMIC® Ceramic Structured Packing Our geometrically arranged corrugated sheets provide greater resistance to fouling than random packing, while our design provides high capacity, higher efficiency and lower pressure drop than any random packing and most trays that are available today. Washing and purging. If the tower internals malfunction, the distillation tower will follow suit and the entire chemical process will suffer. MellapakPlus™ is the latest generation of structured packing. Structured packings are usually less troublesome than trays in such services. In tray towers, changing tray spacing gives similar results, but is more difficult to do. (3) Bubble cap tray, the traditional type of tray, extremely expensive, but it has its applications. The original packed towers used Raschig rings, hollow ceramic cylinders, typically 1 in outer diameter (OD), 0.75 in inner diameter (ID), and 1 in long.A state-of-the-art packing is called structured packing.This material is made of thin sheets of crimped or corrugated metal, with small holes, fastened together with thin bars. Trays vs. Random Packings The following factors generally favor trays compared to random packings, but not compared to structured packings. 3. Random packings are usually more troublesome than trays in services prone to process surges (e.g., those caused by slugs of water entering a hot oil tower, relief valve lifting, compressor surges, or instability of liquid seal loops). Packing fires. Structured packing efficiency is about 1.5 times that of trays or random packing. Eng. In packed towers, every complexity requires additional distribution and/or liquid collection equipment. Structured packings are usually less troublesome than trays in such services. Distillation towers are essential to the chemical process industries (CPI), so it is imperative that they are properly designed and operated. The loss of capacity of structured packing is greatest in this range. The performance of the Column in relation to the process requirements (dew point) is determined by carefully selecting the following parameters: (a) Height of packing (or # of trays) (b) Packing or Tray Design (c) Glycol Concentration When the gas is moved by a fan through the tower, or when the tower is in the suction of a compressor, the smaller packing pressure drop is often a controlling consideration. (The other 2 devices are structured packing and trays.) Better separation efficiency. equipped with trays or random packings, have been revamped with Mellapak in orderto improve yield or purity or to in-crease . Capacity and Efficiency Comparison Kister et al. Ser. Structured Packing. Structured packed columns are shorter than trayed columns. Flexibility. structured packing has been successfully utilized in a variety of high liquid rate,high pressure systems besides the usual applications in vacuum and atmospheric processes normally reserved for structured packing. Experience indicates that use of structured packings has capacity/ efficiency disadvantages in the higher-pressure (higher-flow-parameter) region. (Page 1) When it comes to distillation trays and packing, chemical processors require the same criteria they seek from all equipment in this tight economy — technology that will reduce energy use and boost throughput without costly facility expansion. Structured packing can be manufactured from corrugated sheets of perforated embossed metal, plastic (including PTFE), or wire gauze. Not all trays are fouling-resistant. 3. Support plate: Support plates for random packing units are often multi-beam units, set on a continuous ring. Columns with diameter less than 1 m (3 ft) are difficult to access from inside to install and maintain the trays. The capacity of structured packings tends to rapidly fall off at high liquid rates. Ceramic and plastic packings are cheap and effective. However, it’s advantages counter this. High capacity 2. The thin sheets of structured packing (typically 0.1 mm) poorly dissipate heat away from hot spots. Our units are configured for easy onsite installation. The pressure drop advantage is invaluable in vacuum column revamps, can be translated to a capacity gain, an energy gain, a separation improvement, or various combinations of these benefits. Eng., July 2007. Trays require internal access for scheduled maintenance. Structured packing towers offer more surface area and have a lower pressure drop than packed towers do. The separation loss can often be regained by retrofitting with smaller packings in sections of the tower that are not highly loaded. Packing Lili Lyddon December 12, 2006. FLEXIPAC ® structured packing is used for large crimp sizes where the addition of high-capacity features has little effect and for the replacement of standard structured packings where an exact duplicate is required. 5. In the loaded sections of the tower, larger packings can overcome capacity bottlenecks at the expense of loss in separation. Cost high 4. Unless very expensive distributors are used, packed tower turndown is usually limited by distributor turndown. 2. Either option is expensive. operations where trayed towers are used. Packing is also preferred for columns where pressure drop and possible foam formation are important considerations. Solids tend to accumulate in packing voids.