1. The Kraft process: architecture and pumping points
The Kraft process separates wood fibres by chemical cooking and recovers the reagents in its own cycle. To organise pump selection, distinguish the fibreline, chemical recovery, the paper machine and utilities. A market-pulp mill may not have an integrated paper machine.
White liquor supplies the alkaline cooking chemistry, including sodium hydroxide and sodium sulphide. Digester and transfer conditions differ: temperature, pressure and concentration must come from the plant balance and specification, without a single range applied to every point.
After cooking, washing separates the fibres from the black liquor. Recovery concentrates that liquor and uses its energy content; the green liquor and recausticising cycle regenerates white liquor. These fundamentals, described by Valmet, help identify streams that should not receive the same pump selection.
For each stream, record dissolved and suspended solids separately. For stock, give consistency, fibre type and entrained gas; for liquor, add viscosity at startup and operating temperatures. White water and effluent also need characterisation, because they are not automatically equivalent to clean water.
At FB Bombas, three manuals list paper and pulp among their applications. The manuals for the FBCN normalized centrifugal pump (MTEC-03/00, p.1) and the FBME multistage centrifugal pump (MTEC-08/01, p.1) describe series developed for clean or turbid liquids; the manual for the FBE external gear pump (MTEC-01/01, p.1) describes a series developed for viscous fluids.
The 2026 FBE catalog (p.3) places pulp and paper among the markets that make wide use of the various types of gear pumps manufactured by FB. Naming the industry does not approve a stream: all three manuals require consulting FB when the fluid carries suspended solids (item 2.3 of each).
The published operating data are series maxima, which do not occur at the same time. The FBCN ranges from DN 25 to 300 mm, with flow up to 2,200 m³/h, total head up to 135 m, temperature up to 260 °C and speed up to 3,500 rpm. The FBME ranges from DN 80 to 150, with up to 400 m³/h, 300 m, 140 °C and 3,500 rpm.
On the FBE, the maximum viscosity in Table 2 of the manual increases with size, from 2,500 SSU at 1/8″ to 1/4″ up to 100,000 SSU from 3″ to 6″, and speed drops from 1,750 down to 150 rpm, with a pulley or gear reducer. The actual point for each stream comes from the curve or table of the configuration.
| Arrangement | Sealing | Fluid indicated in the manual | Temperature |
|---|---|---|---|
| ST (packing) | Lubrication by the pumped fluid, internal sealing | Standard arrangement, for clean and non-aggressive fluids | Up to 160 °C |
| S1 (packing) | Sealing with clean liquid from an external source | Toxic, aggressive or malodorous fluids; suction from a tank under vacuum or below atmospheric pressure | Up to 105 °C |
| S2 (packing) | Lubrication and sealing with liquid from an external source | Solid particles or small fibres in suspension | Up to 105 °C |
| S3 (packing) | Flushing with clean liquid from an external source | Abrasive particles in suspension or a tendency to crystallise | Up to 105 °C |
| S (mechanical seal) | Mechanical seal | According to the needs of the application and the request | Not set in item 10 |
Note
In the external-source arrangements (S1, S2 and S3), the FBCN manual states that a cooling chamber cannot be used. With a mechanical seal, the arrangement follows line S, and the configuration, support plan and auxiliary fluid are defined with the seal supplier for the actual stream.
2. White liquor pump: alkalinity, material and sealing
Identify the alkali concentration, sulphidity, temperature, residual solids and cleaning condition of the white liquor. The line after filtration must not be confused with lime mud suspension or with the green liquor circuit. The pump position in the process is part of the specification.
The FBCN manual lists cast iron, WCB and CF8M constructions, but it does not approve CF8M for every white liquor or document duplex 2205 as standard. The corrosion assessment must consider the actual concentration and temperature, as well as every wetted component.
The impeller material also limits speed. Item 6 of the FBCN manual sets the maximum peripheral speed by material: cast iron up to 40 m/s, nodular iron and carbon steel up to 60 m/s and stainless steels up to 80 m/s.
When the corrosion assessment leads to a stainless steel impeller, Table 4 requires the efficiency shown on the curves to be reduced according to the impeller passage width: 3 points up to 12 mm, 2 points from 12 to 15 mm and no reduction above 15 mm. Compare proposals using that corrected efficiency.
Sealing must account for deposits, shutdown conditions, pressure and auxiliary-fluid compatibility. If there is a dual arrangement, the seal supplier must define materials, support plan, pressure and monitoring. Do not adopt Plan 53B/54, a water barrier or an elastomer just because the fluid is called white liquor.
With packing, item 10 of the FBCN manual selects the arrangement by fluid condition, not by stream name. S3, with flushing by clean liquid from an external source, is indicated for fluids with abrasive particles in suspension or a tendency to crystallise; S1, with sealing by clean liquid from an external source, for toxic, aggressive or malodorous fluids. Both go up to 105 °C and do not allow a cooling chamber.
With a mechanical seal, line S of the same item applies, and the arrangement is defined with the seal supplier.
3. Black liquor pump: high viscosity, abrasion and chemical recovery
Black liquor from washing goes through evaporation before energy recovery. Its concentration changes along the plant; therefore, provide the measured solids content and the temperature at the pump. A weak or strong classification does not replace fluid analysis.
Viscosity, density, crystals and gas can vary with operating conditions. Use samples and process data to calculate losses, power and suction, including startup and shutdown. Do not assign a fixed 500–2,000 cP range or an impeller life in months to every concentrated liquor.
The FBCN manual (MTEC-03/00) does not tie 1,750, 1,450 or 1,150 rpm to black-liquor solids bands; for fluids with suspended solids, item 2.3 says to consult FB. Nor should it be presumed that the FBE or FBEI accepts crystals and abrasives because it pumps viscous fluids. Construction, corrected curve where applicable, sealing and compatibility must be confirmed for the stream.
The FBE manual (MTEC-01/01, item 2.3, p.6) sets the same rule: a fluid with suspended solids requires consulting FB. When the stream is a viscous fluid without abrasive solids, FBE selection starts from Table 2 of the manual, by viscosity at pumping temperature and by size, with speed reduced by a pulley or gear reducer.
The FBE has no impeller and no rolling bearing: the shafts turn in bushing bearings, and the heating chamber, a series accessory, is available from 1.1/2″ to 6″.
Warning
There is no documentary basis to promise FBCN for black liquor above 65% solids. Provide composition, rheology, temperature and installation to assess the appropriate technology before selecting a series.
4. Pulp stock: consistency and centrifugal pump limits
Consistency gives the proportion of dry fibres in the suspension, but on its own it does not describe hydraulic behaviour. Fibre type and length, entrained gas, temperature and stock condition also affect pumping.
In medium-consistency stock, entrained gas can impair inlet flow and pumping capacity. Some designs use a turbulence generator to fluidise the suspension and a dedicated gas-removal circuit. Selection must confirm these features for the stock conditions; their consistency ranges cannot be transferred to FBCN.
For retrofit, send the curve and drawing of the existing pump, the impeller type, the suction condition and the fluid history. The replacement must demonstrate that it meets the same scenarios, including variations in consistency and tank level.
The FBCN manual does not establish a universal fibre-consistency limit or document a construction for 6% pulp. Assessment must confirm solids passage, fibre behaviour and available construction before proposing a model for stock. Also provide entrained air, temperature and variation between operating duties.
For filtrates and water with small fibres in suspension, item 10 of the FBCN manual indicates the S2 seal chamber arrangement, with lubrication and sealing by liquid from an external source, up to 105 °C. It is a sealing indication, not a consistency limit: item 2.3 still requires consulting FB for fluids with suspended solids, and the impeller passage, curve and suction must be checked for the stream.
| Stream | Fluid data | Hydraulic verification | Suitability criterion |
|---|---|---|---|
| White water and filtrates | Fibres, solids, chemistry and temperature | Curve, passage and suction | Confirm construction for the liquid |
| Stock after washing | Consistency, fibre and gas | Hydraulics suited to suspension | No published universal FBCN limit |
| Stock in towers and preparation | Consistency and feed variation | Inlet, fluidisation and degassing | Assess specific technology |
| Sludge and fibrous rejects | Solids, contaminants and rheology | Passage, blockage risk and power | Do not assume clean-water pump suitability |
5. Bleaching: chemistry changes by stage
Bleaching includes stages with different reagents and conditions. Identify the pump stream rather than treating the whole plant as one chemical duty.
ECF does not use elemental chlorine and may use chlorine dioxide; TCF avoids chlorinated reagents. Sequences and chemistry vary by project, as the systems described by Valmet show. Record the stage, reagents, concentration and carryover between stages.
Assess temperature, pH, chlorides, oxidants and solids together. PREN is a preliminary alloy comparison, not proof of resistance in the actual bath; Outokumpu explicitly describes this limitation.
The FBCN manual does not document duplex 2205, superduplex 2507 or 254 SMO as standard constructions for bleaching. Special materials and sealing need specific confirmation. Plan 53B, barrier fluid or elastomer is not fixed for every ECF stage.
On FB’s side, the FBCN manual documents casings in cast iron, A216 WCB carbon steel and A743 CF8M stainless steel (Figures 1 and 2, p.6). An alloy outside that list is a special construction, which depends on confirmation of availability and feasibility before the proposal.
With packing, the S1 arrangement of item 10, with sealing by clean liquid from an external source, is the one indicated for aggressive fluids, up to 105 °C; with a mechanical seal, line S applies, with the arrangement defined by the seal supplier for the chemistry of the stage.
6. Paper machine: white water, showers and drying
White water, filtrates and showers have different requirements for solids, pressure and stability. For each point, send the water quality, flow, head and nozzle requirements. The FBCN publishes a general limit of 135 m; it is not presented as a multistage line for any high-pressure shower.
When a shower or another machine point requires head beyond the FBCN range, the FB series is the FBME multistage centrifugal pump: DN 80 to 150, up to 400 m³/h, 300 m, 140 °C and 3,500 rpm (manual MTEC-08/01, p.1), maxima that do not occur at the same time. The impellers are radial and closed, mounted in diffusers (item 2.2), and item 2.3 requires consulting FB for fluid with suspended solids.
Therefore, the quality and filtration of the shower water go into the enquiry together with the flow and the pressure at the nozzles.
The return of trim and paper breaks, known as broke, must be assessed as a fibrous suspension. Provide consistency, disintegration, contaminants and suction; being below 4% does not establish automatic approval.
Do not assume thermal oil in every modern machine: Voith describes steam-heated dryer cylinders and condensate systems. Assess FBOT only where a compatible heat-transfer-fluid loop exists. Its 350 °C series limit does not establish energy savings over steam or a paper machine’s flow requirement.
7. Brazilian pulp and paper market: context and quotation
In March 2026, Ibá reported Brazilian pulp production of 29.4 million tonnes and exports of 20.7 million in 2025. These are annual sector figures, not installed capacity or FB Bombas market share.
The scale of the industry does not remove the differences between mills. The stream map, the duty points and the maintenance conditions are the basis for comparing pumps and preparing a technical proposal.
Chemical recovery connects the mill to power generation through the use of black liquor. Its water, condensate and oil auxiliaries must be specified separately from the stock circuits; also consult the power-plant page when the project includes cogeneration.
The FBCN, FBME and FBE are manufactured in Cabreúva, São Paulo, where FB has CNC machining, assembly and a performance test bench conforming to ANSI/HI 14.6, the test standard for rotodynamic pumps such as the FBCN and FBME. A certified curve and FAT are included when they are part of the contracted scope.
To obtain a quotation from FB Bombas, send the fluid data, normal and contingency operation, the existing installation, the required materials and the procurement documents. The proposal must confirm configuration and scope before attributing suitability for liquors, fibres or bleaching. Delivery time and support need confirmation for the supply.