You are currently viewing: Literature



Improve separation in your column by increasing the number of trays

Refiners often face revamp challenges when trying to improve separation within an existing column. Improving diesel recovery from gas oil, splitting benzene precursors from naphtha reformer charge, or simply minimizing product overlaps after capacity creep can all be difficult when limited by a fi xed existing tower height. For these cases, revamp solutions that increase the number of theoretical stages by adding trays to an existing column or a section of a column pay large dividends.

Improving Separation by Increasing Tray Count
One direct way to increase efficiency within a column section is to simply increase the number of trays. In a revamp with a fixed section height and column diameter, stage count can be increased by reducing tray spacing and installing a larger number of high capacity trays

High capacity trays address both liquid and vapor tray capacity requirements within the column’s physical limits. Sulzer VGPlusTM trays incorporate the use of high capacity valves with an optimized layout, high performance downcomer technology, and additional features like froth promoters that improve distribution across the tray. With conventional trays, the froth height and jet fl ood constraints may require additional spacing. VGPlus trays have larger capacity than conventional trays and can be installed at tray spacings as low as 14”.

Mechanical Aspects to the Re-Tray Design
Shutdown time constraints often prohibit revamp modifications such as welding to the column shell. Commonly, existing column support rings and downcomer bolting bar configurations do not match with the geometries required for the new trays. Additionally, the new, smaller tray spacings require new tray rings at elevations where no rings currently exist. In these cases, new ring segments or full 360° expansion rings are used to provide support for new trays. New ring segments can be supported off existing rings. Expansion support rings are expanded out to press tightly against the column wall and supported from below or above with support rods welded to existing attachments. Sulzer also uses envelope downcomers to allow the installation of trays on expansion rings or in positions where no downcomer was previously located.

The column cutaway figure illustrates a revamp where additional trays are added. Envelope downcomers, new support ring segments, and support struts are utilized to avoid welding to the column shell. Existing supports are shown in red – these previously welded attachments are utilized as the base for the new supports.

Other High Capacity Technology
Many conventional tray designs can be upgraded by replacing trays with structured packing or installing high capacity trays like Sulzer VGPlus on smaller tray spacings. Sulzer can also provide specialized trays that can be installed at tray spacing as low as 12”, like Shell HiFiTM multiple downcomer trays. These can also be excellent potential solutions to increasing stages in a fixed column elevation.

Other Literature

Tray designs for extreme fouling applications

Today refiners experience a lot of problems with processing of opportunity or heavy crudes. Such crudes have very high sulfur content and require the addition of amine scavengers before desalting. These amines decompose in the heater and create ammonium chlorides in the presence of water in the top of ...


Anti-fouling trays maximize coker main fractionator profitability

The Coker Main Fractionator is systematically subjected to harsh operating conditions that can lead to deteriorating efficiency and performance due to coking and fouling. Poor reliability results in loss of profitable coking margins for the refinery. The main fractionator vapor feed from the coke drum ...


Improve separation in your column by increasing the number of trays

Refiners often face revamp challenges when trying to improve separation within an existing column. Improving diesel recovery from gas oil, splitting benzene precursors from naphtha reformer charge, or simply minimizing product overlaps after capacity creep can all be difficult when limited by a fi xed ...


Gain 5-10% efficiency with this simple 4-pass tray revamp

The design of 4-pass trays can be complex. It not only requires a close evaluation of the mechanical design but also the process response to that design at various flow rates. The balancing of the fluid flows across the tray can have a substantial effect on the tray performance, namely efficiency.


Proper design of mass transfer internals in the FCC flue gas scrubber can help reduce PM emissions

The EPA’s New Source Performance Standards (40 C.F.R. §60.100-1-0, subpart Ja) regulates refinery particulate emissions, including the discharge of catalyst fines from the FCCU flue gas scrubber stack. Because refiners have traditionally correlated particulate matter (PM) emissions with FCCU ...


Improve fouling resistance in your wastewater benzene stripper

Benzene stripper columns, built so that refineries can meet the National Emissions Standards for Hazardous Air Pollutants (NESHAP), operate with several unique conditions – low vapor rates, high liquid loads, and a high tendency toward fouling make designing well-balanced, effective internals difficult.


Important tray design features that improve column operating reliability

How often does Maintenance personnel open a column during a shutdown and find tray panels fallen without any obvious damage? How about tray valves stuck in the bottoms pump suction? While the initial reaction may be to blame faulty installation where the hardware was not properly tightened, the answer ...


Green design practices: focus on efficiency

Green design is more than recycling scrap materials or calculating carbon footprints. It minimizes negative environmental impact through skillful design and operating practices to produce efficient, better-functioning processes. Because green practices reduce resource requirements, in many cases, they ...


4 simple ways to convert turnarounds into profitable tower upgrade opportunities

With planned outages commonly occurring at intervals of 2-5 years, a refinery turnaround is a prime opportunity to replace column and separator internals with the newest available technology. Planning for an outage with a “replacement-in-kind” strategy will address lost performance from refinery ...


Maximizing light cycle oil recovery in the FCC main fractionator

Refiners operating FCCU's have adjusted their operating strategies to maximize light cycle oil production to meet the increased demand for automotive diesel. Catalyst formulations and reactor conditions can alter yields, but the refinery cannot take full advantage of the increased LCO recovery without ...