Tower Trays Of Various Types & Designs

 

Tray columns have wide range of application in process industry meant for separation purposes, utilizing pressure and temperature differential to segregate varied products from feed stream. In tray columns, weir holds a different liquid level of each tray, vapor coming from lower tray must overcome liquid head to move up column. On the tray, vapor and liquid are contacted, and then above the tray, they’re separated, performing well in highly liquid and vapor loading. At low flow parameters, trays’ capacity and efficacy tend to reduce, having high pressure drop than packing. However, Mass Transfer Tray tower have traditionally played an instrumental role in thermal fractionation for longer period of time. To meet increasing demand for reliability and high-performance rating, Finepac, leader in Mass Transfer & Separation Technology, has come up with an extensive portfolio of mass transfer Tray tower tailormade to meet process requirements catering to specific applications. Sieve trays, bubble cap trays and cartridge Tray tower encompass the portfolio of conventional Tray tower or tower trays offering by Finepac including special kind of Tray tower you may request.

Pointers to look for when it comes to using Tray Tower:

·         Trays have corner capacity problems in heavy framing service.

·         Tray tower has higher pressure drop than structured packing column.

·         Tray tower is highly-resistant to corrosion.

·         Trays generally have more entrainment than packing leading to loss of column efficiency.

Excessive vapor and liquid maldistribution on Tray tower results in loss of column efficiency

Below are types and designs of varied kinds of Tray tower:

Sieve Trays-These type of Tray tower or tower trays are generally considered as reliable, low-cost mass transfer solutions. These are basically used in applications where high downturn is not necessary. Sieve tray is perforated plate with holes punched into plate, usually having holes of 3/16 inch to 1 inch in diameter, standard size being ½ inch with perforation punched downward, with vapor coming out of holes for giving a multi-orifice effect. Vapor velocity keeps liquid from flowing through holes. Vapor flow through tray deck and contact with liquid is regulated by number and size of perforations on Tray tower. Sieve tray has relatively higher entrainment as compared to valve tray at same vapor velocity, and can be widely used in almost all services.

Bubble Cap Trays-These kind of Tray tower or tower tray is one of the most widely used equilibrium-stage plates, provided with inverted bubble caps having vertical slots fixed over cylindrical risers. Vapor travels upwards through riser and diffuses through bubble caps. These are best suited for low liquid loads, having wide array of turndown ratio without weeping. To put it simply, bubble cap tray tower is perforated flat plate having riser over holes covered with cap, equipped with slots enabling passage of vapor to be mixed with liquid flowing across tray giving rise to bubble formation where mass transfer occurs. Each bubble cap tray is provided with one or more downcomers in which liquid flowing across tray is conducted to tray below. Bubble cap Tray tower can operate at low vapor and liquid flow rates, functioning well in high turndown applications, with cap size creating hydraulic gradient across deck with high vapor side pressure drop. Bubble cap tray is the costliest of all Tray tower.

Dual Flow Trays-Dual-flow tray is sieve tray without downcomer, vapors moving up to tray above through hole, whilst liquid travels down in same hole-unlike sieve tray, resulting in mal-distribution of vapor/liquid and low efficiency. Dual flow tray is designed in keeping with optimum open area on tray for eliminating stagnation and promoting back missing that makes them suited to tackle highly fouling and corrosive services. This Tray tower is apt for fractionation of polymerizable compounds owing to more bubbling area, having greater capacity than other tray types. It’s the least expensive Tray tower, easier on installation and maintenance, performing best in operating region of 60-80% of flood, increasing efficiency with vapor rate.

Floating Valve Trays-Floating Valve Tray tower uses moveable disc almost closing off completely at low vapor rate thereby reducing tray open area. Upon lifting, vapor rate and open area increases for vapor flow between valve disc and tray deck. These trays are either round or rectangular floating valves with or without a caging structure. Valves are floating owing to vapor flow from underneath, maintaining near constant pressure drop with respect to variation in vapor flow rate. Due to this characteristic, valve trays sustain higher tray efficiency, and are generally used in applications involving high turndown ratio. Valve trays can operate over wide range of flow rates having higher separation efficiency and large flexibility. Floating valve trays are provided with either moving round valves or unique rectangular shaped valves.

Rectangular Valve:

·         Specialized rectangular valves

·         No liquid flow under valves

·         Excellent turndown ratio

·         Very good efficiency & capacity profile

 

Round Valve:

·         Available in wide array of specifications

·         Good efficiency characteristics

·         Exhibit low pressure drop

Owing to their price and flexibility, valve trays are being replaced by bubble-cap trays with minimum capacity of approximately 60%-dry pressure drop of valve tray being lower than bubble cap as valve doesn’t require chimney for vapor depending on valve weight.

Fixed Valve Trays-This kind of tray has valves in bridge-like construction extruded from tray deck, enabling increased stiffness to tray deck. These valves provide large vapor passages, functioning at low pressure drops with high capacities, exhibiting excellent fouling resistance characteristic. Fixed valve Tray tower with V-shaped grids combine attributes of sieve holes and float valves. These valves provide large vapor passages, operating at low pressure drops with high capacities. Rectangular valves extruded from tray decks are oriented parallel to liquid flow.

Characteristics of Fixed Valve Trays:

·         Large opening size provided for improved fouling resistance

·         Easy-to-clean-less downtime

·         Durable construction for long tray life

·         Liquid push strong enough to help flush out solid material downstream

·         Lateral vapor release through

·         No protrusions below tray deck

Advantages of Fixed Valve Trays:

·         Less entrainment owing to lateral vapor release

·         Excellent fouling resistance

·         No wear on account of number of moving parts

·         High efficiency over wide range through improved vapor-liquid contact

 

Cartridge Trays-This kind of tray is generally used in small diameter where physically installing Tray tower is not a feasible option. Cartridge trays are assembled in bundled ensuring easy and fast installation. They are used in column diameters ranging from 300mm to 1m, equipped with all types of tray decks and downcomers.

Get a complete range of mass transfer products at Finepac Structures-a prominent name to reckon with in the industrial arena, started wayback in 1993. Finepac offers solutions for all your separation applications, reveling in the fact of having an impressive portfolio constituting state-of-the-art products for distillation, absorption, phase separation, stripping, evaporation & liquid extraction applications like structured packing, random packing, high performance Tray tower, grid packing and column internals, etc. We believe in delivering you the best!