Pumps for Sugar-Ethanol Mills: Technical Selection Guide by Pumping Point

1. The thirteen pumping points of a sugar-ethanol mill

From the pumping standpoint, a sugar-ethanol mill is not a plant — it is a collection of coupled processes, each with its own characteristic fluid.

There is no "mill pump": this guide organizes the services into thirteen points — mixed juice (the cane juice leaving extraction), clarified juice, clarifier mud, syrup, massecuite, A/B molasses, final molasses, fermentation must, de-yeasted wine, vinasse, hydrous ethanol, anhydrous ethanol and, where present, the thermal oil circuit. Imbibition water, cooling water, condensate and boiler feed follow the criteria of the hot water and power plant guides.

Each point has different temperature, viscosity, pH, and solids content — and requires a different selection decision.

The table summarizes, for each point, the nature of the fluid, the data that must be measured at the mill and the indicated FB series. It gives no numerical ranges: temperature, viscosity and pH vary with feedstock, process and time of harvest, and selection uses the values measured at your plant.

2. The five most critical mill applications

Not all pumps weigh the same when they fail. Some stop the distillery or the sugar factory; others have an installed standby or a buffer tank. Rank each point by the consequence of a stoppage at your mill — lost production, environmental risk, fire risk — and concentrate detailed specification and spare parts on those points.

Five services tend to combine two or more aggressive factors at once: high temperature, solids abrasion, corrosion, small NPSH available or high viscosity.

• 1. Vinasse at the distillation outlet — it leaves the column base hot, close to its boiling point at column pressure, and NPSH available depends almost only on the liquid height above the pump and on suction losses. It is acidic, with dissolved and suspended solids; the material comes from the analysis (chlorides, pH, temperature) and from the mill’s corrosion history.
• 2. Final molasses — very high viscosity, which drops with temperature; the service is positive displacement (FBEI or FBE). Insulated and heated lines and heating on the pump body (chamber on the FBE, jacket on the FBEI) keep the fluid from cooling in the clearances.
• 3. Massecuite — crystals suspended in viscous molasses. Because solids are present, speed, clearances and bushings are defined by FB during selection (FBE manual, item 2.3), with Brix, crystal content and temperature data.
• 4. Ethanol close to its boiling point (column base, reflux, condensate) — little NPSH margin and a flammable fluid. It requires NPSH checked at the real point, sealing defined with the seal manufacturer and electrical equipment certified for the zone.
• 5. Clarifier mud — flocculated solids and soil, abrasive and prone to settling. The FBCN manual asks for FB consultation for suspended solids and provides the S3 arrangement (flushing with clean external liquid) for abrasive particles.

3. Pump for molasses and final blackstrap: the viscosity curve that defines the technology

Molasses and blackstrap are concentrated sugar solutions with impurities. Viscosity rises with Brix and falls sharply with temperature, and the same mill can see very different values over the harvest. The specification therefore needs viscosity measured in the laboratory at the real line temperatures — including start-up and after stoppages —, not a generic table from another process.

Viscosity is one selection criterion alongside flow, pressure, solids and temperature. ANSI/HI 9.6.7 addresses centrifugal performance corrections for Newtonian liquids; the method’s limits are not an automatic rule for switching technologies. The FBE 2026 catalogue matrix relates viscosity, speed and models: at 50,000–100,000 SSU, for example, it lists 300–150 rpm only for 3″, 4″, 5″ and 6″. FBEI publishes 140,000 cP as an independent series maximum; crystals require specific assessment and do not automatically make a gear pump suitable.

At installation: short suction of generous diameter, with NPSH available calculated with the real viscosity — suction pressure drop grows sharply with viscosity —; insulated and heated lines; and heating on the pump body when the fluid can cool in the clearances: heating chamber on the FBE (CA execution) or jacket on the FBEI, whose limits in manual MAN001-10 are steam up to 185 °C and thermal fluid up to 232 °C, both up to 10 bar.

4. Vinasse: chemistry, temperature and suction

Vinasse is the residue of wine distillation. It leaves the column base hot, close to its boiling point at column pressure, and goes to cooling, tanks and field distribution. In the State of São Paulo, storage, transport and soil application follow CETESB Technical Standard P4.231, which requires waterproofed storage tanks and master or primary channels (items 5.2 and 5.5) and a Vinasse Application Plan prepared or updated every year (item 5.7); the pumped flow follows from that plan.

It is acidic and carries dissolved and suspended solids; chloride and potassium contents vary with the feedstock (juice, molasses or a blend) and with the process. Temperature, pH, chlorides and solids must come from the analysis of the mill’s own vinasse.

The FBCN manual documents cast-iron, WCB carbon-steel and CF8M stainless-steel casings. Compare vinasse composition and temperature with corrosion data and plant inspections. An index such as PREN helps compare alloys but does not prove performance in this stream. If documented options are unsuitable, confirm the feasibility of another construction before specifying it; duplex alloys and coatings must not be promised as catalogue options.

NPSH: with saturated liquid at the column base, NPSH available comes down to the liquid height above the pump minus suction losses. Check the margin over the NPSH required from the model curve at maximum flow and keep the suction short and free of restrictions.

Failure modes to monitor: localized corrosion in unsuitable material, erosion-corrosion where velocity is high, seal damage from thermal shock at start-up, and shaft and bearing overload during prolonged operation away from BEP. Recording these events per pump is what allows the specification to be corrected in the next harvest.

5. Hydrous versus anhydrous ethanol: what changes in the pump

Hydrous and anhydrous ethanol have their own quality specifications, set by ANP Resolution No. 907/2022, and differ mainly in water content. For the pump, however, what changes most is the position of the service: column-base, reflux and condensate pumps handle liquid close to its boiling point; storage and dispatch pumps handle cooled product. The hydraulics can be the same, but not the NPSH margin.

Pure ethanol boils at about 78 °C at atmospheric pressure (351.5 K, NIST Chemistry WebBook average). For comparison, at 35 °C the vapor pressure of pure ethanol is about 13.8 kPa, close to 14% of the standard atmosphere (101.325 kPa), per the Antoine equation published by NIST (Ambrose and Sprake data, 1970). With saturated liquid in the suction vessel, vapor pressure equals vessel pressure, and NPSH available comes down to the liquid column above the pump minus suction losses.

NPSH required belongs to the model curve, not to the product: what is checked is the margin between available and required at the real point and at maximum flow.

For ethanol, the seal manufacturer should define faces, elastomers, arrangement and auxiliary system from actual conditions and the emissions criterion. If the project adopts API 682 plans, identify the plan and scope in the enquiry. FBCN allows a mechanical seal selected for the duty. The FBE manual describes magnetic coupling as an option to confirm; this neither approves FBE for every ethanol viscosity nor guarantees no leakage under all conditions.

Hazardous area: zone extent comes from the project area classification study (ABNT NBR IEC 60079-10-1), not from a fixed radius. Motor, panel and instruments installed in the zone need mandatory Inmetro Ex certification (Inmetro Ordinance 115/2022). When specified, FB quotes the set with an Ex motor that the motor manufacturer supplies with that certification and a coupling guard in non-sparking material, an option provided in the series manuals.

6. The harvest reality and maintenance planning

A 240-day campaign operating 24 hours a day totals 5,760 theoretical operating hours. Actual hours depend on each mill’s crushing schedule and downtime. Plan the maintenance window around that actual operating regime.

The practical goal is to get through the harvest without unplanned intervention at critical points. That depends on three decisions the mill controls: operating point close to BEP on centrifugal pumps (and flow, pressure and speed within the table on gear pumps), correct material and sealing for each fluid, and preventive maintenance in the off-season.

There is no reference MTBF valid for every mill, and FB does not publish such a figure. The reliable indicator is the mill’s own history: record hours and failures per pump, define which failures are counted and the observation period, and use the result to decide overhauls, material changes and spare-parts stock.

In the off-season, the overhaul scope comes from the condition found and from the series manual: disassembly, clearance measurement (impeller and wear rings on centrifugal pumps; gears and bushings on gear pumps), replacement of seals, bearings and gaskets when indicated, alignment and, when contracted, bench performance testing.

7. Material matrix by pumping point

Material selection follows no single rule: each point combines different chemical composition, temperature and abrasion, and the answer is a combination of casing, impeller or gears, sealing and elastomers.

The table presents documented materials and the data needed to assess each stream. A different construction can enter the order only after FB confirms feasibility, materials, limits and availability.

8. Why four FB Bombas series serve a single mill

In a mill, the variety of fluids means no single technology serves every point: standardizing everything on one series takes pumps outside their field of application.

The choice between series follows verifiable criteria: viscosity at pumping temperature, presence of solids, service temperature and pressure, and the documented limit of each series.

The FBCN (back pull-out normalized centrifugal; manual MTEC-03/00 states mechanical construction per ASME B73.1) covers low-viscosity liquids — juice, must, wine, vinasse, ethanol and water —, with general data of up to 2,200 m³/h, 135 m and 260 °C, not simultaneous. The FBE (external gear, 12 sizes from 1/8″ to 6″ in MTEC-01/01) covers syrup and molasses, with speed chosen by viscosity.

The FBEI (internal gear with gear reducer) is published with independent maximums of 136 m³/h, 14 bar differential, 140,000 cP and 340 °C. The FBOT only comes in where the mill has a thermal oil circuit, with a 350 °C series limit.