02 BOPs / Woods D.R 2008 rules-of-thumb-in-Engineering-practice (epdf.tips)

6.16 PFTR: Packing 241

x Area of Application

Phases: gas–liquid, liquid–liquid, gas–liquid and solid (bio). Intermediate reaction rates. High capacity, high conversion in both gas and liquid phases. Intensive dispersion of gas in liquid. Large number of plates gives plug flow. Some flexibility in varying liquid holdup; and exchange heat via coils on plates. d+ = 40–100; 0.6 I Ha I 3.

Gas–liquid: Residence time, short. Use for very fast reactions, all reaction is in the liquid film and is mass transfer controlled. Gas–liquid surface area max. observed area 800 m2/m3 with the usual range 200–500 m2/m3 or slightly higher than a bubble column. Target species Henry’s law constant I 107 kPa/mol fraction; feed gas concentration I 1 vol %. Not for foaming. Limited in handling corrosive or particulates. Some flexibility in varying the gas/liquid volumetric flowrates. Related topic about surface area Section 1.6.1.

Liquid–liquid: can operate as gravity flow or with fluid pulsed operation. For pulsed operation: surface area 75–3000 m2/m3. Related topics: solvent extraction, Section 4.10, direct contact heat exchange, Section 3.6 and size reduction, Section 8.3.

x Guidelines

General characteristics, Section 1.6.1.

Gas–liquid: liquid holdup = 0.15 with some flexibility in that the liquid holdup can be adjusted by the weir height; typical liquid mass transfer coefficient = kLa = 0.01–0.05 1/s; kL = 1.5 q 10–4 –4.5 q 10–4 m/s; for gas phase kG = 0.02– 0.2 m/s sieve tray; power 0.01–2 kW/m3 and usually 0.01 to 0.2 kW/m3. superficial gas velocity, 0.75 to 1.5 m/s for atmospheric pressure; 0.2 m/s for pressure operation and 2.5 m/s for high vacuum; holdup I 0.8.

Gas–liquid–solid (bio): Power: 3 kW/m3; OTR: 2.8 g/s m3; mixing time: 300 s; gas content: 50 %; maximum volume 1000 m3.

Liquid–liquid: Sieve tray holes 3–8 mm with a smaller diameter as the surface tension increases; spacing between the holes 3 to 4 times the diameter of the holes to prevent coalescence soon after the drops are formed. For pulsed operation: superficial velocities 2 q 10–3–0.02 m/s.

x Good Practice

See Section 4.2.

6.16

PFTR: Packing

The general characteristics of gas–liquid contacting are described in Section 1.6.1. Other operations that use this type of contactor include gas absorption, Section 4.8, gas desorption/stripping, Section 4.9; gas–liquid separations, Section 5.1; turbulent bed contactor (TCA, TVA) contactor, Section 5.2, distillation, Section 4.2, reactive distillation, Section 6.35 and direct contact heat exchange Sections 3.8 and 3.9. Porosity 0.6–0.95 depending on the packing. (Contrast with trickle bed

242 6 Reactors

with solid catalyst “packing”, Section 6.17.) The liquid Peclet number is 0.1 to 0.5; the gaseous Peclet number is 1 to 5.

x Area of Application

Phases: gas–liquid, liquid–liquid, gas–liquid biosolids. Very fast reactions, essentially plug flow for both G and L. High capacity, high conversion in both gas and liquid phases. Difficult to control temperature, adiabatic. Conversion is often limited by equilibrium. Design like an absorber, Section 4.8. Dimensionless Hatta number, 0.3 I Ha I 0.6 and d+ = 10–100.

Gas–liquid: Use for very fast reactions, all reaction is in the liquid film and is mass transfer controlled. Gas resistance important with very soluble gases.

Surface area gas–liquid per volume of reactor: 50–250 m2/m3 volume reactor; surface area gas–liquid per volume of liquid phase: 1000–1600 m2/m3 liquid phase. Cocurrent over packed: surface area 400–3000 m2/m3. Target species Henry’s law constant I 107 kPa/mol fraction; feed gas concentration I 1 vol %; vulnerable to plugging. Low pressure drop, cannot handle solids, can handle foaming by operating in the cocurrent upflow bubble region. Little flexibility in varying the gas/liquid volumetric flowrates because of flooding. OK for corrosive. Liquid–liquid: Surface area 7–75 m2/m3. Sensitive to contamination. Related topics solvent extraction, Section 4.10 , direct contact heat exchange, Section 3.6 and size reduction, Section 8.3.

Gas–liquid biosolids: Gravity and rotating:

Gravity: Trickling filter reactor (carbon removal): the gas–liquid surface area 45–115 m2/m3; the solid surface area = 0.55–10.6 m2/m3; the biofilm area = 200 m2/m3. Holdup volume fraction solids = 0.55–0.7. Mass transfer: for gas– liquid kLa = 0.01–0.8 1/s; for liquid–solid, kLa = 0.06 1/s. Standard rate loading: 1.3–4.2 kg BOD5/s m3. High rate loading: 4.2–21 kg BOD5/s m3.

(carbon oxidation/nitrification combo): plastic media: loading I 4 kg BOD5/s m3. Biofilter: (carbon removal) organic loading: 20–50 kg BOD5/s m3.

Rotating: rotating biological contactor:, RBC: (carbon oxidation): loading 0.250 g BOD5/L; capacity 20–5000 L/s; (nitrification): loading 10–20 mg NH3–N/L.

x Guidelines

General characteristics, Section 1.6.1.

Gas–liquid: Liquid holdup per total reactor volume: volume fraction liquid 0.05– 0.15; Superficial velocities: select for loading on packing that are 0.5–0.7 times flooding conditions; Backmix: for short column heights = 0.2–0.3 m, significant backmixing can occur with Peclet for the liquid = 0.4–2; Peclet for the gas = 4–20. For short columns, double design height to account for backmixing. Bulk/film volume ratio, d+ = 10–100. Superficial gas velocity, 0.75 to 1.5 m/s for atmospheric pressure; 0.2 m/s for pressure operation and 2.5 m/s for high vacuum; holdup I 0.95; energy 0.01 to 0.2 kW/m3; kLa = 0.005 to 0.02 1/s; packing i 6 mm; catalyst i 3 mm. Column diameter/packing diameter i 8 and prefer i 30 to prevent liquid channeling. Redistributors every 3 to 4.5 m. Higher mass transfer coefficient, kLa = 0.15 1/s. for cocurrent upflow in the bubble regime.

6.16 PFTR: Packing 243

Packing: (see Section 1.6.1) plastic packings have effective surface area = 1⁄2 corresponding value for ceramic if fluids are polar. OK for nonpolar; metal stainless steel are less wetted than ceramic but better than plastic. Preferred packings include unglazed ceramic, intalox 2–3.8 cm but i 5 cm the interfacial area is too small and I 2 cm the capacity is reduced because of flooding. Other recommended packings include Pall rings, mini-rings, sulzer, multinit and Tellerettes. Liquid–liquid: Superficial velocity of continuous phase = 30 to 50 % of flooding. Backmixing less than in spray column or tray columns. The walls and packing must be preferentially wetted by the continuous phase. Packing size = 0.5–1 cm. Superficial velocities 0.001–0.02 m/s. Prefer diameter I 0.6 m; superficial velocity about 5.5 L/s m2; 2.5 cm Pall rings. Redistribute the dispersed phase every 1.5–2 m.

Gas–liquid biosolid: Gravity:

Packed column: Power: 0.5 kW/m3; OTR: 0.14 g/s m3; gas content: 85 %; maximum volume 100 m3.

Trickling filter reactor: Gas holdup 0.46–0.94; (carbon oxidation):

standard rate: liquid superficial velocity 0.01–0.04 L/s m2, depth 1.8–3 m; recycle ratio 0;

high rate: liquid superficial velocity 0.1–0.4 L/s m2, depth 0.9–2.4 m; recycle ratio 1/1–4/1.

(carbon oxidation/nitrification combo): liquid superficial velocity = 0.095– 0.18 L/s m2. 6 m depth, recirculation ratio 1:1.

(nitrification): liquid superficial velocity = 0.3–1.3 L/s m2.

Biofilter reactor: media depth 1.5–6.5 m, usually 4 m; liquid recycle ratio 0.4; liquid loading: 2.3 L/s m2.

Rotating: RBC: (carbon oxidation) Liquid residence time I 1 h; 3–3.6 m diameter; 40 % submerged; 1–2 rpm; bio layer 2–4 mm thick. Liquid loading 0.0005– 0.004 L/s m2; temperature i 13 hC; module 10 000 m2; power typically = 3.5 kW. (nitrification): liquid loading 0.0004–0.0025 L/s m2; temperature i 13 hC.

x Good Practice

For fast reactions, change in the flow regime has dramatic effects on performance. Prevent foaming. Liquid distributor design is very important. Carefully plan the liquid redistribution along the walls for columns I 2–3 m diameter. For these small columns place redistributors at distances = 8–10 times the column diameter. The critical surface tension of the solid packing should be greater than the surface tension of the liquid to ensure that the liquid film remains intact in a packed contactor.

x Trouble Shooting

Trickling filter: “Plugged: interstitial voids become filled with biological growth”: packing too small/packing of variable diameter/organic to liquid loading i design. “Ice formation on top filter surface”: liquid maldistribution/feed liquid temperature too low/air temperature too cold. “Odors”: loss of aerobic conditions/accumulation of sludge and biological growth/lack of chlorine in influent/high organic

244 6 Reactors

loadings in feed especially from milk processing and canneries. [Foaming]*: see generic causes Section 1.12.

Gas–liquid–solid packed column bio reactor: Carryover”: [ foaming]*.

[Foaming]*: liquid downflow velocity through the foam is too low and generic causes of [ foaming]*, Section 1.12.

See trouble shooting: STR, Section 6.27 for more on trouble shooting aerobic bioreactors.

6.17

PFTR: Trickle Bed

Gas liquid flow cocurrently down through a packed bed of catalyst. Porosity 0.38–0.42. (Contrast with packing described in Section 6.16.)

x Area of Application

Phases: GLcS

Gas liquid catalytic solid: Use for very fast reactions, all reaction is in the liquid film and is mass transfer controlled. Ha i 3 and d+ = 2–10.

x Guidelines

Gas-liquid with solid catalyst: Catalyst particle diameter 1–5 mm. Operate close to the boundary between two phase (trickle) and pulse flow. Figure 6.8 illustrates, the flow regimes for nonfoaming systems.

Figure 6.8 Flow regimes in trickle flow.

6.17 PFTR: Trickle Bed 245

Superficial liquid velocity 0.005 I vLo I 9 mm/s (although some operate in the range 0.8–25 L/s m 2 or mm/s). The velocity should be reduced if liquid tends to foam.

Superficial gas velocity i 0.010 m/s.

Holdup volume fraction liquid 0.05–0.25. Static liquid holdup is constant for low Eotvos number, Eo I 4 (Eo = density liquid q gravitational constant q particle diameter squared/liquid–gas surface tension). Liquid holdup increases with Eo for Eo i 4. Dynamic liquid holdup increases with liquid flowrate but is independent of gas flowrate.

The liquid axial backmixing is negligible if the height/particle diameter i 150. Holdup volume fraction catalyst 0.6–0.7.

Holdup volume fraction gas 0.2–0.35. Surface area solid 1000–2000 m2/m3. Surface area gas–liquid 100–3500 m2/m3. Power input 1–100 kW/m3.

Catalyst activity: variable but often reduced because of mass transfer limitation. Plug flow is favorable.

Catalyst selectivity: often reduced because of mass transfer limitation; plug flow is favorable.

Catalyst stability: should have stability because of difficulty in replacing. Heat exchange is challenging so we usually work adiabatically.

x Good Practice

Ensure operation in the correct flow regime. The effectiveness of the solid catalyst and of the gas–liquid mass transfer decrease if solid catalyst is not wet. For good wetting of the solid keep the surface tension of the solid i surface tension of the liquid. Prevent foaming. The efficiency depends on the skill in initially distributing the gas and the liquid. Use liquid distribution plate similar to design used for packed towers. The liquid distribution plate should have at least 50 holes/ m2 of catalyst bed.

x Trouble Shooting1)

For trickle bed reactors with specific applications to hydrotreating.

“Low conversion”: feed composition change/wrong catalyst for feed/sample error/ flowrate error/feedrate higher but reactor temperature not increased/temperature profile wrong/thermocouple fault/controller fault/feed bypassing reactor through leak in heat exchanger/[channeling]*/[catalyst]*/[ foaming]*/For hydrotreating: [hydrogen starvation]*/catalyst not presulfided/[incomplete presulfiding of catalyst]*. “Sudden loss of activity of catalyst”: heat exchanger leak/change in feed composition/For hydrotreating: [hydrogen starvation]*

1)Based on Koros, R.M., Engineering Aspects of Trickle Bed Reactors, pp. 579 to 630 in “Chemical Reactor Design and Technology” H. de Lasa, ed, Martinus Nijhoff Publishers,

1986 and M.D. Edgar, D.A. Johnson, J.T. Pistorius, T. Varadi , Trouble Shooting Made Easy, Hydrocarbon Process., May 1984, p. 65.

246 6 Reactors

“Dp across the catalyst bed i design”; [channeling]*/cracked hydrocarbon feed stored without effective nitrogen blanket/solids in feed/corrosion products from upstream operations/bypass on feed filter open/feed distributor fault/top catalyst support tray has holes that are too small/bottom catalyst bed support tray holes are too large/pugged or partially plugged outlet/crush strength of catalyst exceeded and fines plug bed/excessive recycle compressor surge causing breakdown of top layer of catalyst.

For hydrotreating: “Rapid breakthrough of H2S during catalyst sulfiding”: [channeling]* “Nonuniform bed temperatures across the diameter during sulfiding”: [channeling]*

“Color i specifications”: composition change in feed/catalyst aged.

[Catalyst]*: regeneration failed to remove carbon from catalyst/excessive regeneration temperature i 540 hC causing sintering, i 760 hC molybdenum sublimation, i 820 hC reduction in crush strength and change in alumina/poisons in feed/aged catalyst.

[Channeling]*: nonuniform catalyst bed density/low superficial flowrate I 1.4 kg/s m2/off set, tilted or faulty feed distributor/thermal shock to upstream pipes or equipment causes scale to dislodge and buildup on bed/internal vessel obstructions such as thermowells or supports.

[Foaming]*: residence time insufficient/designed for a vertical vessel but a horizontal vessel installed/liquid downflow velocity through the foam is too low/operating in the wrong flow regime and generic cause, Section 1.12.

[Hydrogen starvation]*: change in feed composition without corresponding change in hydrogen/leaks/dissolution of hydrogen in liquid product/lower concentration of hydrogen in treat gas/flowrate of treat gas I expected because of recycle compressor fault.

[Incomplete presulfiding of catalyst]*: contact with hydrogen at high temperature for too long a time/maximum temperature of 150–175 hC exceeded/use of cracked feed/excessive addition of presulfiding agents.

[Rapid coking of catalyst]*: [hydrogen starvation]*/temperatures too high. [Hydrogen starvation]*: change in feed composition without corresponding change in hydrogen/leaks/dissolution of hydrogen in liquid product/lower concentration of hydrogen in treat gas/flowrate of treat gas I expected because of recycle compressor fault.

[Incomplete presulfiding of catalyst]*: contact with hydrogen at high temperature for too long a time/maximum temperature of 150–175 hC exceeded/use of cracked feed/excessive addition of presulfiding agents.

[Rapid coking of catalyst]*: [hydrogen starvation]*/temperatures too high.

6.18

PFTR: Monolithic

Related topics: static mixer in tube, Section 6.6, and trickle bed, Section 6.17.

6.19 PFTR: Thin Film 247

x Area of Application

Phases: Gas with solid catalyst; liquid with solid catalyst; gas–liquid with solid catalyst. Use when mass transfer affects selectivity or reactivity. Perhaps not for highly exothermic reactions because of the limitation in radial heat transfer unless cross flow is used.

x Guidelines

Prefer because of intensification with 1.4–4 times the surface/volume. Possible to install in pipelines. See Section 3.3 Cubic/monolithic.

6.19

PFTR: Thin Film

Related topics evaporation: Section 4.1 for gravity and agitated falling films.

x Area of Application

Phases: Gas–liquid, liquid–liquid, GL solid bio. Absorption with fast and very exothermic reaction in viscous liquid or very endothermic reaction that produces volatiles whose desorption is desired.

Gas–liquid: Residence time 3–600 s; reaction rate: mass transfer controlled, fast absorption and highly exothermic reactions, very exothermic reactions in viscous liquids or highly endothermic reactions producing a volatile compound whose desorption is desirable to shift the equilibrium or prevent side reactions; volume 1–80 L; capacity 0.02–5 kg/s. Gravity falling film or agitated falling film for viscous fluids. For gravity film: Liquid residence time: 5–100 s; surface area gas–li- quid per volume of reactor: 3–100 m2/m3 volume reactor; surface area gas–liquid per volume of liquid phase: 300–600 m2/m3 liquid phase; film surface area per unit 0.1–100 m2/unit; viscosity I 1500 mPa s. For agitated film: Liquid residence time: 5–600 s; film surface area gas–liquid per total reactor 0.1–25 m2/unit reactor; viscosity: I 2 000 000 mPa s. Hatta i 3; d+ = 10–200.

Liquid–liquid: Surface area 5–120 m2/m3. Related topics: solvent extraction, Section 4.10, heat exchange, Sections 3.3 and 3.6 and size reduction, Section 8.3.

x Guidelines

Gas–liquid: gravity falling film: Holdup: liquid holdup per total reactor volume: volume fraction liquid 0.01–0.15; liquid holdup per total reactor volume: 0.0002–0.5 m3; liquid loading: 0.06–1.1 L/s m of length. Energy for a falling film = energy as packed tower.

Gas–liquid: agitated thin film: Holdup: liquid holdup per total reactor volume: 0.0002–0.2 m3; Liquid loading: 0.06–1.25 L/s m of length. Backmixing: liquid plug flow or as a series of at least 5 backmix stages; energy needed 1 kW/m2 film surface. Mass transfer controlled reactions.

Liquid–liquid: gravity wetted wall; superficial velocities 2 q 10–5–8 q 10–4 m/s.

248 6 Reactors

Gas–liquid–biosolids: trickling continuous film, vertical vessel with liquid pumped from the bottom to top to be distributed onto wetted walls; compressed gas is introduced at the bottom and some may be recycled from top back to bottom inlet. Power: 1.5 kW/m3; OTR: 0.8 g/s. m3; gas content: 90 %; maximum volume 500 m3. Floating roller, horizontal wetted roller brings liquid in contact with air. Power: 0.1 kW/m3; OTR: 0.05 g/s m3; gas content: 0.1 %; maximum volume 1 m3.

x Good Practice

See Section 4.1.

6.20

PFTR: Scraped Surface Reactor

A scraped surface device can process a thin viscous film. Here the focus is on its use as a reactor. Elsewhere are described its use to condition foodstuffs, Section 3.3, as a vertical device for evaporation, Section 4.1 and as a crystallizer, Section 4.6.

x Area of Application

Especially for viscous feed. OK for foaming, for fouling, crystal formation and suspended solids. Viscosities i 2000 mPa s.

x Guidelines

Relative to agitated film, retention time of 1:1 and volume 1:1. Overall heat transfer coefficient for sulfonation, U = 0.8–2.2 kW/m2 hC; for polymerization, U = 1–2.8 kW/m2 hC. decreasing with increasing viscosity.

6.21

PFTR: Multiple Hearth

x Area of Application

Phases: Gas plus reactant solid. Regeneration of adsorbents, catalysts, incineration of sludges, reduction of ores and roasting of some solids. Capacity about 0.01–10 kg/s; solid particle diameter 0.2–20 mm. Temperatures for incineration in the range 790–980 hC.

x Guidelines

Solid residence time, 5000–30 000 s; usually 15 000–18 000. Hot combustion gas flows over the solids. Solids loading 1.25 to 2 g/s m2 of single hearth or 2 to 20 g/s m2 of total hearth.

–activated carbon regeneration: 2 g/s m2 of single effective hearth; 2.7–

5.4g/s m2 of total effective hearth.

–bauxite adsorbent, regeneration: 8–16 g/s m2 of total effective hearth.

–bone char, adsorbent, regeneration: 20–35 g/s m2 of total effective hearth.

6.22 PFTR: Traveling Grate 249

–calcination of kaolin for pigment: 4–6.5 g/s m2 of total effective hearth.

–charcoal from wood: 2.5–5.2 g/s m2 of total effective hearth.

–foundry sand reclamation: 20–35 g/s m2 of total effective hearth.

–lime sludge recalcination: 2–3.5 g/s m2 of total effective hearth.

–pyrites roasting: 1.25–2.5 g/s m2 of single effective hearth.

–iron ore reduction to direct reduced iron (DRI): 15 g DRI/s m2 of total effective hearth.

–sludge incineration: 1.8 g/s m2 of single effective hearth; 9–18 g/s m2 of total

effective hearth.

The effective hearth area is 42–62 % of nominal area calculated from the overall OD with the higher % referring to larger diameter hearths. For fast reactions, bulk phase film diffusion may control and pore diffusion may control if the solid diameter i 1.5 mm.

The heat load is 150–250 kW/m3 with the usual design capacity about 7 MW. Incineration: heat release from combustion 150–250 kW/m3.

Reactors: solids residence time 4–5 h. For direct reduced iron, bed height of pellets, 2.0–2.5 cm; flame temperature 1300–1350 hC with flame composition CO/CO2 = i 2/1. A new variation for DRI is the paired straight hearth furnaces patented by Lu and Huang. For DRI, bed height of pellets, 12 cm; flame temperature 1600 hC and fully oxidized. The loading is 35 g DRI/s m2 of total effective hearth.

6.22

PFTR: Traveling Grate

x Area of Application

Phases: Gas plus reactant solid. Feed solid particle diameter 8–30 mm. For sintering: product diameter 80–150 mm; product crush strength i 104 kPa. Capacity 1 to 300 kg/s.

x Guidelines

Solid residence time, 2500–20 000 s; gas residence time, I 1 s. Processing gas flows through the bed.

Sintering: Capacity 0.015–0.04 kg/s m2. For fast reactions, bulk phase film diffusion may control and pore diffusion may control if the solid diameter i 1.5 mm. Windbox 1.1–1.2 Nm3/s m2 grate; discharge air 0.65 Nm3/s m2 grate at 50 m2 to 0.35 Nm3/s m2 grate at 200 m2.

Induration: Temperature depends on basicity: basic 1180–1250 hC; acid then it is a little lower temperature. The pellet layer is about 25 cm high but the bottom 5 cm is material that has already been fired. This protects the grate and improves the uniformity of heating. The flame is above, the gas flows down through the pellets and then later it flows up through the hot pellets to preheat the air. Usually use natural gas. Feed: pellets bound together by a water bridge containing 1 % bentonite. Induration is basically drying a pellet.

Incineration: temperature 1000 hC; solid residence 1200–2700 s.

2506 Reactors

6.23

PFTR: Rotary Kiln

Related topics drying, Section 5.6.

x Area of Application

Temperature 520 to 1700 hC; atmospheric pressure; Particle diameter 7 mm– 20 mm; solid residence time 2000 –35 000 s. Phases: Gas plus reactant solid. Relatively large solids capacity 3 to 300 kg/s with the usual being 15–300 kg/s; solid particle diameter 7 mm–20 mm. Sinter product: product diameter 80–150 mm; product crush strength i 104 kPa.

x Guidelines

Solid residence time, 2500–20 000 s; gas residence time, I 1 s; 820–1600oC; heat load 250–400 kW/m3 with the usual design capacity about 18.5 MW. Incineration: Volumetric loading 5 % solids; temperatures 820–1600 hC; heat release from combustion 260–415 kW/m3; gas velocity 4.5–6 m/s; solids residence time 1–2 h; gas residence time 2–4 s. L/D 3.4–4/1.

Sintering: 0.012 kg/s m3 volume. For fast reactions, bulk phase film diffusion may control and pore diffusion may control if the solid diameter i 1.5 mm. Reaction: Volumetric solids loading 3–12 %; heat usage: 25–60 kW/m3 of kiln volume; solids capacity, g/s m3 kiln volume; dry cement, 4–12; wet cement, 3–8.5; limestone calcination, 5–9.5; dolomite calcination, 4.5–6.5; alumina, 5.5–8.3; barium sulfide, 4–9.5; inorganic pigments, 2–20; iron pyrites roasting, 3–4; ore roasting, 3–7. The heat transfer is a function of the thickness of the layer of solids. For ore roasting: currently only small sized units are used with temperatures I 1000 hC. In larger sized units, the fines tend to coat and build up on the inside of the kiln. For the reduction of iron ore (SL/RN) process, feed is lump iron ore or pellet and special coals. For ore reduction the energy efficiency is relatively low. Further complications include a layer of solids that build up inside the drum.

x Good Practice

As incinerators: operate at –2 to –8 kPa g to provide slight vacuum.

6.24

PFTR, Shaft Furnace

(Thanks to W-K. Lu and G. Irons for their input.)

x Area of Application

Phases: Gas plus reacting solid. Solid particle diameter 8–300 mm. Capacity 0.2–1 kg/s. Can operate as a shaft furnace where the product is a solid, the furnace has countercurrent gas–solid flow and the blast furnace where the product is hot metal liquid; the furnace has countercurrent gas liquid solid flow. Blast fur-