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Quotes - Engineering - SalesCoffee plants
A caustic heater for coffee oil and tannin film
Coffee extraction, concentrate and ready-to-drink lines foul with a soil that behaves more like a baked-on oil than a food residue. Coffee oils carried out of the extractor oxidize and polymerize on warm stainless into a brown varnish, tannins bind to it, and fine grounds that escaped the screens lodge in the film. Left a few cycles, the varnish is hard enough to blunt a scraper. The caustic step that removes it is the hottest and strongest on a beverage site: 2–3% sodium hydroxide at 170–175°F, often with a wetting agent, for 30–45 minutes.
Brew water in most coffee plants is hard, and the extractors run hot, so carbonate scale sits under the oil film. A nitric or phosphoric step at about 1% and 130–140°F follows the caustic a few times a week. Rinse and sanitize water is pushed to 180–185°F on ready-to-drink lines.
Coffee plants are tank-recirculation plants. A 1,000-gallon caustic tank taken from 70°F to 175°F in 30 minutes is about 1.75 MBtu/h, and the heater has to do that while the same varnish that coats the extractor builds on its own solution side. That is why many coffee plants ask for a heater they can brush rather than one they have to pull.
Coffee varnish on the heater tubes comes off with a brush
On a coffee circuit the solution side of the heater fouls with the same oil film as the extractor. A straight-tube heater with removable heads lets the plant brush the tubes in place in 30 minutes, without pulling a bundle or breaking the steam connections.
The circuit: 175°F, 2–3% caustic, hard water underneath
Coffee oil varnish does not swell or dissolve at the 140–150°F a soft drink plant uses. It softens above about 165°F in strong caustic and comes off as a sheet rather than a solution, so the return carries flakes of film and fine grounds back to the tank. Plants push to 175°F because every 18°F less roughly doubles the contact time, and a 45-minute caustic step is already the longest part of the cycle.
The hardness underneath is why the acid step runs more often than in a juice plant. Calcium carbonate from brew water deposits at the hot end of the extractor and on the heater, and caustic alone will not lift it. Phosphoric at 1% keeps the gaskets happy; where the plant runs nitric hot, the heater's solution-side head gasket needs FKM rather than EPDM.
The heater: straight tube, brushable, 316L on the solution side
Our recommendation for most coffee circuits is a straight-tube shell-and-tube with removable heads, steam on the shell side and caustic through the tubes, so the plant can open both heads and brush the varnish off the tube bores without pulling a bundle. Tubes, heads and tubesheets are 316L, and the tubes are 3/4-inch or 1-inch so a standard brush passes through them.
Where sanitation prefers to pull and soak rather than brush, the U-tube removable bundle with steam inside the tubes is the alternative, and the varnish comes off in the plant's own caustic tank. Either way we size for 1.75 MBtu/h at the 30-minute heat-up with a fouling allowance of 0.001–0.002 on the coffee side, and steam at 125 psig gives 353°F in the shell and a 178°F approach to the 175°F target.
What to send for a coffee plant heater
Tell us how the plant wants to clean the heater as well as the line, because that decides straight tube or U-tube before any surface area is calculated. Then the usual duty figures follow.
- Brush in place or pull and soak: your preference
- Caustic tank gallons and the heat-up time the schedule allows
- Caustic strength and target temperature on the extraction circuit
- Acid used, concentration and frequency
- Steam pressure at the heater
- Hardness of the brew water, or a recent water analysis
- Connection type and any finish requirement on the loop
Call and talk it through with an engineer: 1-805-484-2992
Coffee plant questions
Because coffee varnish is a brushing soil. It comes off a tube bore with a nylon brush and a bucket of hot caustic in a few minutes, and a straight-tube heater with both heads off gives you a clear line of sight through every tube. A U-bundle has to be pulled and soaked to clean the same film. Both work; the straight tube is less downtime for this particular soil.
Yes. 316L is comfortable at that concentration and temperature indefinitely, and the solution-side gaskets are EPDM, which is rated well above 175°F and is unaffected by caustic. The steam side is separate and sees only steam and condensate. What wears a coffee heater is the acid step, not the caustic, and that is a gasket choice we make at the quote.
The oil does not care what temperature it was extracted at. Cold brew leaves the same lipid film on tanks, filters and lines, and it polymerizes in air just as readily. Plants that wash cold brew equipment at 140°F find the film thickens week by week until a hand clean is needed. The CIP heater for a cold brew circuit is sized the same as for hot extraction.
About 1.75 MBtu/h to reach 175°F from 70°F in 30 minutes, which condenses roughly 1,800 lb/h of steam while the tank heats. Give the tank 60 minutes and the heater drops to about 900,000 Btu/h. The boiler has to supply the figure at the heater inlet, not at the header, so tell us the pressure you actually see at the CIP room.
Fine grounds settle in the tank and in the low points of the shell or heads rather than on the hot surface, so heat transfer holds up, but they do collect where the solution slows. A strainer ahead of the heater and a drain on the solution-side head let the plant flush them out at the end of the cycle. On a straight-tube unit they wash out when the heads are opened for brushing.
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