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Recovery Island

Recovery Boiler

Kraft Recovery Boilers — Turnkey Solution by Rajshree India

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Rajshree Group supplies complete Recovery Boiler systems for kraft pulp mills. The recovery boiler simultaneously burns heavy black liquor to recover inorganic chemicals (green liquor) and generate high-pressure steam for power generation.

PROVEN TRACK RECORD

Our 2021 project in Baroda, Gujarat included a multi-effect evaporator and recovery boiler that raised plant efficiency by 30%. Since 2003, Rajshree Group has delivered 22+ pulp and paper projects across three continents — India, Africa and the Middle East — totalling over 2,000 TPD of installed capacity.

Product Overview

It is the heart of the chemical recovery cycle, enabling mills to be self-sufficient in energy and chemicals.

Kraft recovery boiler supplied by Rajshree Group for a pulp mill
Recovery boiler for kraft chemical recovery

Key Features

  • Black liquor firing system with high-capacity guns
  • Composite floor and lower furnace design

Applications

  • Chemical recovery in kraft mills
  • Steam and power generation
  • Green liquor for causticising
  • Reduced sulphur (RS) gas handling
  • Mill energy self-sufficiency

Our Turnkey Project Process

1
Consultation & Feasibility
We understand your requirements, site conditions, and budget to prepare a detailed feasibility report.
2
Engineering & Design
Complete process design, P&IDs, civil layout, electrical single lines, and equipment specifications.
3
Manufacturing & Supply
In-house and vendor-sourced equipment manufactured, quality-inspected, and dispatched on schedule.
4
Installation & Commissioning
Our engineers supervise erection, electrical, instrumentation, and commission the plant to design parameters.
5
Training & After-Sales Support
Hands-on operator training, performance guarantee trial, and ongoing technical support for the life of the plant.

Technical Specifications

Capacity500 – 5000 MT DS/day
Steam Pressure45 – 120 bar
Steam Temperature380 – 520°C
Steam Generation3.5 – 4.5 kg steam/kg DS
Smelt DissolvingGreen liquor 120–140 g/L TTA
ESP Efficiency> 99.7%
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Tell us your capacity requirement and we'll send a detailed technical and commercial proposal within 48 hours.

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Contact Our Experts

📞+91 87996 27889 📞+1 (219) 256-9887 ✉️sales@rajshreeent.com
📍🏢 Head Office: 60, Swapnil-2 Industrial Park, Kuha, Ahmedabad - 382433, Gujarat, India |
📍 Branch Office: 1913 Gunbarrel Road, Suite 105 Chattanooga, TN 37421, USA |
📍 Branch Office: D7, Varsity Chateau, Uniport Road Aluu, Port Harcourt, Rivers State, Nigeria |

Why Choose Rajshree?

  • 20+ years industry experience
  • 22+ successful projects delivered
  • Serving India, Africa & Middle East
  • Complete turnkey — single point responsibility
  • After-sales support and spare parts
  • Competitive pricing and financing options

Recovery Boiler: The Heart of Kraft Mill Energy and Chemical Recycling

The kraft recovery boiler is arguably the most critical single piece of equipment in a kraft pulp mill. It serves three functions simultaneously: combusting the organic content of concentrated black liquor to generate high-pressure steam; reducing the inorganic sodium and sulphur compounds to a molten smelt for recycling to white liquor; and managing the mill's energy balance by generating the steam that powers the turbogenerator and all process heating loads. No other industrial boiler combines energy generation with chemical recovery in this way.

Rajshree Group designs and supplies recovery boilers sized from 100 to 1,500 tonnes of dry solids per day (TDS/day) — corresponding to kraft mills of 30 to 400 TPD pulp capacity. Our boiler designs use membrane wall construction, multiple air levels (primary, secondary, tertiary) for staged combustion, and combustion air optimisation systems that maximise carbon burnout while maintaining a stable reducing zone for effective sulphate reduction in the char bed.

Rajshree's recovery boilers generate steam at pressures of 40–80 bar and temperatures of 420–490°C — parameters that support efficient backpressure turbine operation for on-site power generation. Mills with Rajshree recovery boilers report average steam yields of 3.8–4.2 tonnes of steam per tonne of dry solids fired — meeting or exceeding benchmark performance for boilers in the same size class.

🔥 Safety-Critical Design

Rajshree's recovery boilers are designed in full compliance with BLRBAC (Black Liquor Recovery Boiler Advisory Committee) safety standards — the global gold standard for recovery boiler safety. All water-leak detection, emergency shutdown, and smelt-water explosion prevention systems are hardwired safety interlocks independent of DCS/PLC status.

Frequently Asked Questions

A recovery boiler burns concentrated black liquor (the spent cooking chemicals dissolved in lignin from the digester) to simultaneously recover sodium and sulphur chemicals and generate high-pressure steam. Without a recovery boiler, kraft pulp mills must purchase replacement chemicals at very high cost, making them economically unviable. The recovery boiler enables chemical closure and energy self-sufficiency.
Rajshree's recovery boilers achieve sodium recovery efficiency of 95–97% and sulphur recovery of 92–95%. This means only 3–5% make-up chemicals are needed to replace unavoidable losses. The smelt from the boiler (Na₂CO₃ + Na₂S) dissolves in water to form green liquor, which is causticised back to white liquor (NaOH + Na₂S) for reuse in the digester.
Rajshree's recovery boilers generate high-pressure steam at 40–60 bar, 400–450°C, from 50 TPD to 300 TPD black liquor solids firing. Steam generation is approximately 3.5–4.5 kg steam per kg of black liquor solids fired. This steam drives a back-pressure turbine to generate 2–8 MW of electricity and provides exhaust steam for all mill process heating needs.
The primary risk is a smelt-water explosion caused by water contacting molten smelt. Rajshree's designs incorporate: automatic boiler shutdown if water leaks are detected, smelt spout heating to prevent solidification and blockage, emergency boiler flushout procedures, and smelt dissolving tank with explosion relief. All safety systems are fail-safe and interlocked.
Yes. For soda-process mills (NaOH only, no sulphide), Rajshree supplies a soda recovery furnace, which operates at lower temperatures than a kraft recovery boiler and without the sulphur recovery requirement. The soda furnace generates Na₂CO₃ smelt, which is causticised to NaOH for reuse. It also generates steam for the mill, reducing purchased energy costs.

Countries We Serve

Rajshree Group supplies and installs our Recovery Boiler — and complete pulp & paper mill machinery — for mills across India, Africa and the Middle East, with sea-freight delivery, on-site erection, commissioning and after-sales support in every market we serve.

IndiaNigeriaKenyaGhanaSouth AfricaEgyptTanzaniaUgandaSaudi ArabiaUAE

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