ARBOK-Scrubber (cement kiln dust → potash fertilizers, salts, metal concentrates)

Overview

Potassium is not destroyed in a cement kiln — it volatilises at ~1,000 °C, condenses in the preheater and circulates until rings and buildups stop the kiln. The chlorine bypass removes it as dust, and that dust — the richest in K and Cl on the plant, and the most loaded with Pb, Cd, Tl — cannot return to the kiln and is landfilled. World CKD generation is 15–20% of cement mass (up to 700 mln t/yr at the upper estimate); USA ~13 mln t/yr with ~80% of the unreturnable surplus stockpiled or landfilled (3.3 mln t from 110 plants in 38 states by the regulator's count). The fine KCl aerosol that fabric filters miss leaves the stack as PM2.5.

ARBOK-Scrubber captures the dust in water instead of on fabric, then processes brine and slurry in the ARBOK vacuum module at ~1 kPa and ambient temperature: water back at up to 99.98%, residue dry at 10–15% moisture and dechlorinated (returns to kiln or to cement/road-base/liming use), brine split fractionally into KCl (MOP), K₂SO₄ (SOP), NaCl and a controlled Tl/Pb/Cd concentrate. No membranes, reagents or consumables; no second sludge; no wastewater.

Applications

Feedstock: chlorine bypass dust (primary — 10–30% Cl, high K/Na, Pb/Cd/Tl enriched); main-baghouse CKD surplus (secondary — 2–6% K₂O); quench/scrubber water of either.

Outputs: KCl (MOP); K₂SO₄ (SOP); NaCl technical; heavy-metal concentrate (Tl, Pb, Cd; As, Cr minor); dechlorinated limestone-clinker residue, dry 10–15% moisture; recycled water.

Residue outlets: back to kiln as raw meal; mineral addition to cement ≤5%; soil/road-base stabilisation; liming of acid soils, neutralisation of acid effluents.

Users: integrated cement plants with bypass; plants under particulate emission quotas; potash-importing agricultural economies.

Scale: 20-ft container module, 200 m³/day water; parallel modules per dust tonnage.

Operating Principle

1. Bypass gas (after quench) and, optionally, main-filter dust are contacted with water in a wet scrubber . Soluble salts → brine; insoluble CaCO₃, free lime (→ Ca(OH)₂), clinker minerals → slurry. Stack emits vapour, not PM2.5.
2. Brine and slurry enter the sealed deep-vacuum chamber (~1 kPa). No heat supplied, no temperature set-point; process temperature = incoming stream = ambient.
3. Water evaporates at low pressure, is condensed and returned to the scrubber (closed loop, up to 99.98%).
4. Solids leave dry (10–15% moisture). Dissolved load crystallises fractionally along the train: KCl, K₂SO₄, NaCl in sequence; heavy metals (Tl, Pb, Cd) report to the final mother-liquor fraction as a separate concentrate — same principle as the antimony/manganese/Zr-Hf tracks.
5. No membranes, reagents, consumables; indifferent to feed composition.

Key Parameters

Platform: ~1 kPa, ambient temperature; 0.72 kWh/m³ net (SGS-certified platform figure); water return up to 99.98%; residue moisture 10–15% (Michael, 2026-09-07); module 200 m³/day, 20-ft container; service life 15–20 years.

Reference kiln: 4,000 t/day clinker (~1.5 mln t cement/yr) → ~30 t/day bypass dust, ~10,000 t/yr.

Reference yield (estimate): ~2,000 t/yr KCl + ~1,000 t/yr K₂SO₄ + ~500 t/yr NaCl + metal concentrate.

Incumbent benchmark: Chinese plant, 4,000 t/day kiln — water wash, CO₂ carbonation for Pb, triple-effect steam evaporator on waste-heat steam, 6 t/day KCl at 90% purity; separate chemical shop, lead sludge, open water balance.

Prices (Sep 2026): MOP $310–400/t; SOP $575–770/t; NaCl technical ~$60/t EXW; Pb ~$1,900/t; Cd ~$3,000/t; Tl metal $9,300/kg (world market ~10 t/yr — concentrate credit only); As₂O₃ ~$1,500/t; Cr metal ~$10,000/t.

Architecture and Components

Wet scrubber / venturi quench on the bypass duct (and optionally main-filter dust slurry tank) → slurry/brine transfer → ARBOK vacuum separation module (chamber, condenser, dry-solids discharge, fractional salt collection, heavy-fraction take-off) → condensate return line to scrubber → residue conveyor to raw-meal silo or product bay. 20-ft container on hard standing beside the kiln; SCADA/PLC.

Advantages

Technical: captures submicron KCl aerosol that fabric misses; no fouling/blinding/poisoning; one pass, no second sludge; residue dechlorinated and returnable to kiln.

Economic: 4 cost lines (raw-material loss, landfill, kiln downtime, quota fees) become 3 revenue lines; ~$3 mln/yr per 4,000 t/day kiln (see §12).

Environmental: no PM2.5 chloride emission; no landfill; closed water loop; ~28 t CO₂/yr per module on grid vs 200–400 t for classical treatment.

Strategic: domestic potash at existing plants in 100%-importing countries; Hormuz-independent.

Integrations

Retrofits on any kiln with a chlorine bypass; compatible with alternative-fuel kilns (higher Cl → richer dust). Plant waste heat not required; may be converted to electricity for the module (separate optimisation). Related: ARBOK-VC (Vacuum Cracking) · Arbok Zero-Organic-Waste (AZOW) · Arbok-Potassium · ARBOK-Antimony (heavy-fraction principle) · ARBOK-PV (dust taken into liquid at source) · ARBOK-DeSulph.

Deployment & Operation

Container on the bypass circuit; BOOM or per-tonne/per-m³ fee. Continuous, automated, one operator per shift shared with plant. Commissioning set by site dust assay (K, Cl, SO₄, Pb, Cd, Tl, Rb), which fixes the fraction sequence and the residue outlet.

TRL

Platform TRL 9. Cement-dust application: TRL 3–4 (resource case and process concept; no wetted bypass-dust stream processed yet). First site assay pending.

Market Potential

World: 4.2 bln t cement/yr; 1,553 integrated + 620 grinding plants outside China, >3,000 kiln sites with China. CKD up to 700 mln t/yr; at 3% K₂O ≈ 21 mln t K₂O ≈ 33 mln t KCl-eq/yr ≈ 50% of world potash consumption (~70 mln t KCl/yr). Resource figure, not recovery forecast.

USA: 12.9 mln t CKD/yr → up to 600,000 t KCl-eq/yr ≈ 10% of imports; landfill spend ≈ $200 mln/yr (3.3 mln t × ~$60/t).

India: 470 mln t cement → >3 mln t KCl-eq/yr, ≈ entire potash import; imports 100% of potash; $32 bln/yr fertilizer subsidy.

Trigger: Hormuz closed 28 Feb 2026; ~1/3 of seaborne fertilizer trade; urea $400→$850, DAP $580→$770, MOP +12% in 2026.

Typical Project Economics

Reference kiln 4,000 t/day, 10,000 t/yr bypass dust:

• KCl 2,000 t × $360 = $0.72 mln
• K₂SO₄ 1,000 t × $600 = $0.6 mln
• Metal concentrates + NaCl ≈ $0.2–0.3 mln
• Avoided landfill/haulage 10,000 t hazardous ≈ $0.8 mln
• 1 avoided kiln stop for ring cleaning ≈ $0.5 mln

Total ≈ $3 mln/yr per kiln. Payback 5–7 years.

Risk Factors

No wetted bypass-dust stream processed yet; yields are composition-based estimates. 700 mln t CKD is the upper literature estimate (older surplus estimate 30 mln t); US 12.9 mln t figure dates from the 1990s. K₂SO₄ share per site varies with fuel sulphur. Thallium market ~10 t/yr — revenue must not be quoted at metal price. High-pH, hot chloride slurry — materials and Pb behaviour. Cement plants in arid regions: water loop must be demonstrably closed. US/Brazil potash import shares (>90%, >95%) from general knowledge, not verified this session.

Related Technologies

ARBOK-VC (Vacuum Cracking) · Arbok Zero-Organic-Waste (AZOW) · Arbok-Potassium · ARBOK-PV · ARBOK-Antimony · ARBOK-Manganese · ARBOK-DeSulph · ARBOK-SULPHUR