Plants making cement, brick, glass, dry mixes and precast concrete share two heat problems. Products need warm gauging water, steam curing, mould drying and closely held dryer air, while kilns and furnaces send out flue gas at 350–600°C that is usually lost through the stack. The same boiler house can supply the first duty and recover the second.
What building materials plants ask of heat
Heat here is a process parameter, not a comfort item. Steam curing of concrete products, drying of moulds and green ware, warm gauging water and heating of aggregate hoppers and bitumen stores all have to stay within limits, because drift shows in the product as cracking, distortion or low strength.
Load swings with the season and the shift pattern. A dry mix plant draws far more in winter, a ceramics dryer works to a programmed curve rather than a flat set point, and a precast works needs curing steam in the morning and little later in the day. Plant is selected for a wide modulating range.
- Steam curing
- Saturated steam for curing chambers and moulds, with pressure held while several chambers cycle.
- Mass preparation
- Clay, bitumen and viscous components warmed evenly, with no local overheating.
- Dryer air
- Large air volumes at stable temperature, clean of combustion products where surfaces must stay unmarked.
- Winter continuity
- Gauging water, hoppers and pipe runs kept above freezing so the line never stops.
- Recovered heat
- Kiln and furnace gas at 350–600°C used for drying, air preheating and site heating.
Recovering heat from kilns and furnaces
Cement and glass works are among the most energy-intensive plants in industry, and much of that energy leaves in the flue gas. A waste heat boiler behind a rotary kiln or a melting furnace turns the flow into steam or hot water for raw material drying, batch preheating, combustion air heating and buildings.
The gas itself is the difficulty: dusty, abrasive and carrying alkali and sulphur compounds. PHOENIX and ECHO recovery boilers are laid out for this service, with gas velocities chosen against tube erosion, tube spacing set for dust build-up and cleaning systems selected from the gas composition. Wall temperatures keep acid condensation out of the tail surfaces at part load and during kiln starts and stops.
Equipment for this sector
Most sites end up with two or three circuits, and they are simpler to operate when boilers, components and controls come from one range.
Thermal oil for clay, bitumen and viscous media
MAGMA to 10 MW and CRUX to 10 MW work in liquid phase at effectively atmospheric pressure with carrier temperature up to 300°C, so the usual 200–300°C duty for clay preparation and bitumen storage sits well inside the range. Pressureless operation rules out water hammer, and surfaces are sized for high oil velocity so the fluid does not coke. EXPAND and STORE carry expansion and drain volume.
Steam and hot water
TOR and TRIPASS supply curing chambers, water heaters and workshop circuits to 0.7 and 15 bar; RAPID and PILLAR start in minutes for shift-based curing; HERO covers higher pressure in compact form. CORE, SLIM, CORE DUO, TRINITY, BASE and MEGA cover heating and gauging water to 50 MW, and ROOK or WARD house the same plant outdoors.
Air heaters for dryers
ZEPHYR, KENO, LUMO and ROCK deliver up to 1500 kW of hot air. In the indirect design the air passes over an exchanger and never meets combustion products, which keeps soot off unfired ware before glazing; the direct design suits brick dryers where contact is acceptable. Control is close enough to run programmed drying curves by clay type.
Carriers, outputs and operating limits
These are platform limits of the series; the working point follows from your curing, drying and heating balance.
- Steam
- 0.6–154 MW, up to 45 bar, saturated for curing or superheated to 450°C.
- Hot water
- Up to 50 MW and 16 bar, flow to 115°C, for gauging water, hoppers and buildings.
- Thermal oil
- Up to 10 MW with carrier to 300°C, covering the 200–300°C band for clay and bitumen.
- Hot air
- Up to 1500 kW, direct or indirect, for dryer chambers, drums and workshops.
- Waste heat
- Up to 30 MW from gas at up to 600°C, as steam to 25 bar or as hot water.
What keeps the plant in service
Dust and abrasion decide the life of recovery surfaces, so cleaning systems are specified with the boiler rather than added later, and heavy particles drop into hoppers before they can wear the tube bundle. On the water side, DEGAS deaerates feed water, BUFFER returns condensate and DRY handles blowdown, with dosing set from a water analysis.
Modular delivery matters on a running site: recovery boilers and boiler rooms arrive in a high state of works completion, which shortens the tie-in window. CONTROL panels run burner, feed and safety chains with modulating output, while Digital Twin telemetry flags drift in efficiency, flue gas temperature or water quality before it becomes a fault. BOOST and ECO economisers recover the last flue gas heat.
How we work through a project
We begin with your process data and the flue gas you already have, since recovery often changes the size of the fired plant you need.
- Input data
- Curing, drying and heating loads with their seasonal profile, kiln gas flow and temperature, fuels and layout.
- Selection
- Fired and recovery plant compared together on capital and running cost, with the schematic agreed with your engineers.
- Design and manufacture
- Boiler, duct and skid drawings with documentation to EN 12952 or EN 12953 and PED 2014/68/EU.
- Works testing
- Hydraulic tests, control loop checks and functional trials under ISO 9001 before dispatch.
- Commissioning
- Tie-in planning around your kiln stop, burner tuning, safety chain proving and operator training.