1-805-484-2992
Quotes - Engineering - SalesTomato paste
Heating the caustic for a multiple-effect tomato evaporator
A tomato paste concentrator is a multiple-effect evaporator, and during the campaign it runs around the clock with a CIP wash every 12–24 hours because the product fouls the first effect faster than any other food. The soil is scorched tomato solids, pectin and fiber on the heating tubes, with a hard mineral scale beneath: calcium oxalate and calcium citrate from the fruit, carbonate from the water. Fruit acidity does the tubes no harm, but it leaves the scale the caustic cannot touch, so the acid step on a tomato evaporator is an every-wash step, not a weekly one.
The volumes are large. A concentrator CIP set holds 4,000–5,000 gallons of caustic because the effects, vapor bodies and condensers are washed together through 6-inch lines at 200 gpm or more. Sodium hydroxide runs at 2% and 170–175°F; nitric at 1–1.5% and 140–150°F follows, hot and frequent, which puts the elastomer question front and center.
Bringing a 5,000-gallon tank from 70°F to 175°F in 60 minutes is about 4.4 MBtu/h. Then the season ends. The heater that ran every day in September sits drained and cold until the following July, and it has to come back without a pitted shell or a seized head bolt.
Hot nitric every wash puts FKM on a tomato heater's head gasket
At 1–1.5% nitric and 150°F, run once a shift for 90 days, EPDM hardens within a season. FKM on the solution-side head gasket holds through the campaign and through the idle months, so the heater opens the next July without a leak.
The circuit: 2% caustic at 175°F, nitric at 150°F, 200 gpm
The concentrator wash is a two-chemical cycle every time. Caustic at 2% and 170–175°F circulates for 30–45 minutes to lift the scorched solids and pectin from the first-effect tubes; an intermediate rinse follows; then nitric at 1–1.5% and 140–150°F runs for 15–20 minutes to dissolve the oxalate and citrate scale that the caustic exposed. Skipping the acid for a few washes shows up as evaporator capacity falling off by the end of the week.
Flow is set by the evaporator's own tube count and the 6-inch CIP header, and 200 gpm is a common figure for a mid-sized line. The return comes back at 150–160°F, which is heat worth recovering against the next day's makeup water on a plate exchanger, and worth recovering most in a plant that pays for 125 psig steam.
The heater: 316L U-tube, drainable, built for a season on and a season off
We recommend a U-tube shell-and-tube with steam inside the tubes and caustic on the shell side, sized for about 4.4 MBtu/h with a fouling allowance of 0.001–0.002 on the solution side for pectin and carbonate. Steam at 125 psig condenses at 353°F, which keeps the bundle compact for the duty. Shell, bundle and heads are 316L; the head gasket is FKM for the nitric step. The shell carries a low-point drain so the heater empties completely at the end of the campaign, and we recommend the plant leave it open rather than full.
Bundle removability matters twice here: during the 90-day campaign to clear pectin, and before shutdown so the shell can be inspected and dried. Leave clearance equal to the bundle length on the head end of the skid when the evaporator CIP set is laid out.
What to send for a concentrator heater
A tomato evaporator quote is about scale and schedule. Give us these and we will size the bundle for the campaign, specify the gasket for the nitric step, and tell the boiler house what the start-up will draw.
- Caustic tank gallons and the heat-up time between washes
- Caustic and nitric concentrations and their wash temperatures
- CIP header size and the flow through the effects in gpm
- Steam pressure at the evaporator CIP set
- Return temperture, if you want a recovery exchanger quoted alongside
- Length of the campaign and how the heater is stored off-season
Call and talk it through with an engineer: 1-805-484-2992
Tomato paste questions
Because tomato scale is oxalate and citrate, which precipitate on the hot first-effect tubes faster than milkstone forms in a pasteurizer. Caustic lifts the organic layer and leaves the mineral exposed; without acid the next run scorches onto that rough base and evaporator capacity drops within days. The heater sees the same acid, so its solution-side gasket is specified for nitric from the start.
Yes. Both are 316L duties, and a heater sized for the caustic heat-up has surface to spare for the acid, which runs cooler and shorter. The only component that cares which chemical is in the shell is the head gasket, and FKM covers both. The control valve has to turn down for the acid step, so tell us both set points.
Nothing, if it is drained and left dry. The risk is a shell left full of dilute caustic or rinse water that concentrates by evaporation over nine months, or a head bolted tight on a gasket that was already hard. A low-point drain, a bundle pulled and inspected at shutdown, and a fresh gasket set at start-up are the whole program. Chloride-free water for the last rinse helps.
Against the evaporator itself, no. The first effect alone condenses far more steam than the CIP heater, so the boiler house is used to the load. What matters is the pressure at the heater inlet during start-up, when the evaporator may also be pulling hard. We size the bundle for the pressure you actually have at the CIP set, and 125 psig there gives a compact heater.
Related
Applications
Sauce Cooking Kettle CIP
A jacketed kettle soaks up the first ten minutes of hot caustic as cold steel. Sizing a kettle circuit heater for 3% caustic, two spray devices and a cold wall.
+ Learn More
Applications
Vegetable Blanching Line CIP
On a blancher the hot rinse, not the caustic, sizes the heater. A steam-to-water shell-and-tube for 50 gpm at 185°F, with field grit kept off the tubes.
+ Learn More
Applications
Kettle & Sauce Lines
Burnt-on starch and fat need caustic at the top of the range for most of an hour. Sizing a kettle-line tank heater that holds 175°F while the soil fights back.
+ Learn More
