Boilers and Furnaces (industrial boiler)

A boiler is a closed pressure vessel in which water is heated by burning a fuel — biogas, biomass, coal, oil or electricity — to produce steam or hot water. The steam or hot water then transfers heat through pipes to a process: digester heating, drying, sterilisation, or power generation through a steam turbine. In biogas plants, the boiler's role is to maintain the digester at mesophilic (35-40°C) or thermophilic (50-55°C) temperature year-round, and in tyre pyrolysis or rubber processing it supplies process steam at 8-10 bar.

Two construction families dominate Indian industrial practice. Fire-tube boilers route hot combustion gases through tubes immersed in a water-filled shell; they are simple, cheap, and well-suited to steam loads below 25 TPH and pressures up to 17 bar. Water-tube boilers reverse the arrangement, with water inside the tubes and flames on the outside; they handle higher pressures (up to 100+ bar) and capacities, suiting CHP applications and pyrolysis steam loops.

Indian operation is governed by the Indian Boilers Act, 1923 and the IBR (Indian Boiler Regulations), which require statutory inspection, a registered operator certificate, an annual fitness certificate, and pressure-safety-valve testing. Vessels above 25 litres at over 1 bar are notifiable. Efficiency targets under PAT (Perform, Achieve and Trade) for industrial boilers are typically 80-85% on net calorific value; biogas-fired packaged boilers in CBG plants run at 82-88% because the fuel is clean and burns completely.

Operational trade-offs centre on fuel choice and load matching. Burning raw biogas saves the cost of upgrading but means the boiler ingests up to 200-500 ppm H₂S, which forms sulphuric acid in flue-gas condensate and corrodes economiser tubes — life drops from 15 years to 5-7 years without flue-gas treatment. Sizing too large for the typical load forces frequent cycling, raising fuel-per-tonne-steam by 10-15%. Most CBG installations therefore use a small auxiliary biogas boiler for digester heating alongside CHP recovery, rather than a single oversized unit.