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Quotes - Engineering - SalesApplications
Condensers Sorted
by the Job They Do
Nobody buys a condenser for its own sake. It is bought to hold a vacuum, to send clean condensate back to a boiler, to put reflux back on a column, to recover a solvent that is worth money, or to keep a vent stream inside a permit. Those jobs decide the design far more than the exchanger type does, which is why this section of the site is arranged by application rather than by construction.
The three sections below each open into the specific duties inside them. Every duty page states the vapor source, what is being recovered or protected, the operating pressure the condenser sees, the noncondensable load to expect, and the exchanger arrangements normally selected for it, and each ends with the information an engineer needs to quote it.
If your duty is not named on these pages, it is still a duty we size every week. Send the vapor, the rate, the pressure and the coolant, and an engineer will tell you where it fits.
Request a QuoteRequest a QuoteNobody buys a condenser for its own sake. It is bought to hold a vacuum, to send clean condensate back to a boiler, to put reflux back on a column, to recover a solvent that is worth money, or to keep a vent stream inside a permit.
Those jobs decide the design far more than the exchanger type does.
What Each Section Covers
The three sections are cut by what the vapor is and what happens to the condensate afterwards. Steam is a single pure component with a known curve. Distillation vapor is a mixture whose composition changes as it condenses. Recovery duty is usually a dilute vapor in a large flow of noncondensable gas, which is the hardest case of the three.
Steam Systems
- Clean and pure steam condensing for sanitary and pharmaceutical plants
- Condensate recovery from exhaust, flash and utility steam
- Feedwater and makeup water preheating with recovered heat
- Condensate quality, drainage and stall are the recurring problems
Distillation & Separation
- Total and partial overhead condensers on batch and continuous columns
- Fractionation, side-draw and product condensers
- Reflux and knock-back condensers mounted on columns, stills and reactors
- The condenser is part of the separation, so vapor-liquid equilibrium matters
Recovery & Emissions
- Solvent and VOC recovery from dryers, reactors, vents and vacuum systems
- Waste and off-gas condensing ahead of flare, scrubber or reuse
- Hazardous, corrosive and flammable vapor recovery
- Pre-condensers that shrink the load on carbon beds, oxidizers and scrubbers
Steam Systems
Steam is the easy vapor and the unforgiving system. The condensing curve is a single temperature, so the thermal calculation is short; what goes wrong is everything around it. Condensate that cannot drain floods tubes and takes surface out of service, a trap sized on the wrong load stalls the exchanger under turndown, and air that enters through vents and vacuum breakers blankets the cold end. Clean steam adds drainability, surface finish and materials to the list, because the condensate is often the product or touches it. Condensate recovery and feedwater heating are where the money is: every pound of condensate returned hot is water, chemicals and fuel not bought again.
Distillation & Separation
On a column the condenser is a process element, not a utility. A total condenser sets the reflux temperature; a partial condenser or dephlegmator does part of the separation itself, and the split between what condenses and what carries on as vapor depends on the surface temperature the coolant can hold. Distillation and fractionation condensers are rated on the real condensing curve of the overhead mixture, not on a single latent heat. Knock-back condensers mount vertically on the vessel so condensate runs back against the rising vapor, which means flooding margin has to be checked, not assumed.
Recovery & Emissions
Recovery duty is the hard case. The vapor of interest is often a few percent of a gas stream that is mostly air or nitrogen, so the gas film controls heat transfer and the condenser has to be arranged so the noncondensable gas sweeps continuously to a vent instead of collecting at the cold end. Solvent recovery and VOC recovery are usually staged, with the last stage on chilled water or brine, because the amount left in the gas is set by its dew point at the coldest surface. Waste gas, hazardous vapor and emissions abatement pre-condensers exist to make the downstream device smaller: a carbon bed, an oxidizer or a scrubber that receives a cooler, drier, leaner stream is a smaller and cheaper one.
What the Application Changes
Application decides orientation (vertical for anything that has to drain back or stay hygienic, horizontal for the largest surface in the least headroom), which side the vapor goes on (shell side for large volumes and vacuum, tube side for hygienic and high-pressure duty), how the noncondensables are vented, what the condensate has to look like when it leaves, and which coolant is worth paying for. Two duties with the same heat load can end up as completely different exchangers for those reasons alone, and the pages in this section are written to make that visible before a quotation is requested.
What Every Duty Page Tells You
Each application page is written the same way so pages can be compared.
- The vapor source and what it contains, including noncondensables
- What is being recovered, protected or held to a setpoint
- The operating pressure: vacuum, atmospheric or pressurized
- Coolant choices and the approach each one buys
- The exchanger arrangements normally selected, and why
- The data needed to quote it
Have This Ready When You Call
A selection comes together quickly once the duty is stated; six figures settle most of it.
- Vapor rate (lb/hr or kg/hr) and composition
- Operating pressure and the condensing temperature or setpoint
- Coolant type, flow available and inlet temperature
- Allowable vapor-side pressure drop
- Materials or hygiene class required
- Orientation, mounting and space constraints
Before you pick a duty page
Pick the page named for your vapor source, then confirm that the condensate destination it describes is also yours; if it is not, the neighboring page in the same section is usually the better fit. A brewery kettle vent, for example, is mostly water vapor and looks like steam on a heat balance, but it belongs with recovery duty when the plant wants the aromatics back or has an odor permit to meet. A solvent reaction with a condenser on the reactor head sits under distillation even though no column is involved, because the liquid returns to the vessel. When a stream straddles two sections, read both and quote from the one with the tighter outlet condition, since that is the condition that sets the surface.
A steam condenser is a vapor condenser with the easiest possible vapor, one component condensing at one temperature with a coefficient high enough that surface is cheap. Put 2,000 lb/hr of 15 psig steam into a shell and it releases about 1.9 million BTU/hr at a steady 250 F, so tower water rising from 85 F to 115 F has a wide driving force from inlet to outlet. Give the same 1.9 million BTU/hr to a solvent vapor diluted with nitrogen and the condensing temperature slides downward as the lighter material comes out, the gas film takes over near the outlet, and the surface can double or triple. Ask for the condensing curve, not a single temperature, whenever the vapor is anything other than steam.
Choose water cooling when the condensing temperature must sit within about 20 F of your coolant supply, and air cooling when the vapor condenses 40 F or more above the hottest summer dry-bulb temperature on site. Tower water at 85 F on a July afternoon can hold a 110 F condensing temperature on a modest bundle, while an air cooler designed for a 100 F ambient needs the vapor at 140 F or hotter before the tube bank stays reasonable. Atmospheric steam at 212 F or a hot solvent overhead at 180 F are good air-cooled candidates; a vacuum still condensing at 120 F is not. Count fan horsepower in the comparison, and remember that an air cooler is weakest on the afternoon the plant is pushing hardest.
Work out the duty in BTU/hr, then divide it by the overall coefficient times the log-mean temperature difference, and expect the answer to move more with those last two numbers than with the first. Take 1,000 lb/hr of atmospheric steam: at roughly 970 BTU/lb the duty is 970,000 BTU/hr, and against tower water warming from 85 F to 105 F the log-mean difference is about 117 F. With a clean-steam coefficient near 200 BTU/hr-ft2-F that is only about 40 ft2 of tube.
Now condense the same 970,000 BTU/hr as a lean solvent in nitrogen, where the coefficient may fall to 40 and the usable difference to 40 F, and the answer is about 600 ft2. The surface grew fifteenfold while the heat load never changed. That is why a quote needs the composition and pressure, not just the rate.
A noncondensable gas sets a floor on what leaves the condenser as vapor, because the gas is still saturated at the temperature of the coldest surface it touched, no matter how much tube is behind it. Air leaving at 100 F carries about 6.5 percent water vapor by volume; the same air chilled to 60 F carries under 2 percent, so for a moisture knock-out the outlet temperature does more than the area. The gas also has a tell in the plant: condensate comes out cold while vapor keeps escaping, and the coolant return runs below its rated temperature because the surface is blanketed, not fouled. Put the vent nozzle where the gas collects, state the gas rate on the datasheet in lb/hr rather than as a note, and have the cold end rated with gas-phase mass transfer included.
