Drying dominates papermaking energy use — and even small gains before the dryer produce outsized steam savings. Shoe presses, impulse drying, and superheated steam are emerging as the pivotal levers.
Drying is the heaviest energy sink in papermaking, soaking up the majority of the web’s water and driving 60–80% of steam (heat) use and 70–80% of total mill energy into pulping and drying (researchgate.net) (researchgate.net).
In Indonesia, audits likewise found that 70–80% of total mill energy (mostly steam) is consumed in pulping and drying (researchgate.net). Older tissue machines, for instance, often burn through 5.2–7.4 GJ per AD ton (ADt; air‑dry tonne) of product in the dryer (mdpi.com).
Scale that to the U.S. and the tab is stark: a government/industry study estimated about 400 million GJ per year (≈$1.5 billion) is spent on drying by U.S. paper mills (pulpandpapercanada.com). That is why APPTI (America’s Agenda 2020) set an aggressive target: reach 65% solids (the dry content of the web; the remainder is water) entering the dryer, versus today’s typical ~45–55% after pressing (pulpandpapercanada.com).
Drying energy baseline and targets
Modern mills commonly exit the press at roughly 45–55% solids (pulpandpapercanada.com). The physics are unforgiving: every extra percentage point of press dryness cuts dryer steam use by about 4–5% (mdpi.com).
APPTI’s 65%‑solids goal matters because moving the typical ~50% up even a few points at over 10,000 mills globally could slash CO₂ emissions by millions of tonnes (pulpandpapercanada.com) (mdpi.com).
Press‑section dewatering gains
Because the dryer must evaporate what the press leaves behind, optimizing mechanical dewatering is the first line of attack. Extended‑nip (shoe) presses — a press design with prolonged web–press contact — or additional press nips are proven routes to higher solids. Replacing a conventional press with a shoe press can cut drying energy by 2–15% (≈10–15% is typical for tissue grades) (iipinetwork.org).
Kramer et al. report about a 15% dryer savings in a tissue line with an X‑Nip™ shoe press (iipinetwork.org). The capital runs on the order of $38 per ton of paper capacity, with roughly $2.24 per ton added O&M (iipinetwork.org).
Multiple press nips, vacuum‑assisted pressing, tight felts and moulds, and felt‑condition monitoring (to prevent rewetting) likewise push solids higher; achieving 60%+ out of the press is widely viewed as “low‑hanging fruit” (pulpandpapercanada.com) (mdpi.com).
Impulse drying (high‑intensity contact)
Impulse (or “steam/steam” or contact) drying presses the web against a very hot roll or platen for a short time to flash‑evaporate moisture. Bench and pilot work suggests it can replace a large fraction of cylinder drying, with some estimates claiming 50–75% steam savings — though accompanied by higher electricity use for heating elements and drives (iipinetwork.org).
More grounded analyses report roughly 18–20% less drying steam (≈2.1 GJ per ton of paper) when an impulse stage is added (iipinetwork.org). By raising press solids 5–10 percentage points via impulse drying, studies show heat consumption drops by about 0.44–0.90 GJ per ton (iipinetwork.org).
Given typical drying energies of 10–15 GJ per ton, impulse drying can cut 2–3 GJ per ton of steam, with a few hundred kWh per ton more electricity (iipinetwork.org). The trade‑offs are complexity and cost — the technology is largely at demonstration scale — but the fuel savings are material.
Superheated‑steam drying (airless operation)
Superheated‑steam (near‑100% steam atmosphere) drying recirculates evaporated water as vapor, nearly eliminating convective heat losses and condenser duty. Numerous studies (e.g., Van Deventer et al.) have shown significantly lower energy use versus conventional cylinder drying (mdpi.com).
Pilot and some commercial systems report roughly a 15–30% reduction in steam consumption relative to a hood/cylinder dryer when using superheated steam recycling; the MDPI energy‑efficiency review notes that switching entirely to superheated‑steam drying produces “significant improvement” in dryer efficiency (mdpi.com).
It is especially useful for grades like tissue or specialty papers with open web structure, or where ultra‑high dryness is needed, and some emerging systems combine superheated steam with impingement or infrared to further cut energy (mdpi.com). Implementation requires airtight hoods and condensate handling; fewer exhaust losses and reuse of latent heat drive the efficiency gains (mdpi.com).
Conventional dryer optimizations
Fundamentals still matter. Maintaining steam traps, insulation, oven seals, and managing blow‑through steam prevents waste. Thermocompressors or mechanical vapor recompression (MVR; mechanically boosting low‑pressure vapor back to dryer pressure) of exit steam can save 10–15% of fuel. Heat recovered from dryer exhaust air (e.g., via heat exchangers or micro‑nozzles) can preheat makeup air. Tighter process controls — optimal hood ventilation and staged steam levels — further tune performance.
Utilities housekeeping on the water/steam side typically accompanies such work. Feedwater quality management can include demineralizers in the boiler house. Precise chemical addition in utilities and water systems often relies on a dosing pump. Clean condensate return to the boiler cycle can be supported by a condensate polisher.
In Indonesia and elsewhere, stacking these measures helps mills meet energy‑use regulations (for example, ≤40 GJ per ton for integrated pulp–paper; prod.iea.org). Case in point: Tangerang mills that installed MVR and better deaerators report 15–25% lower steam use in drying, saving several GJ per ton (researchgate.net) (pulpandpapercanada.com).
What the numbers add up to
Raising press dryness and capturing waste heat are the headline plays. Even a 1–2% increase in press solids can slash boiler fuel; extended‑nip presses are proven in the field. Beyond that, advanced dryers promise deeper cuts: impulse drying is capable of 2.0+ GJ per ton steam savings (iipinetwork.org), while superheated‑steam systems have shown “significant” gains, often around 20% or more depending on configuration (mdpi.com).
Industry goals and benchmarks underscore the opportunity — including APPTI’s 65%‑solids target (pulpandpapercanada.com) and policy limits such as ≤40 GJ per ton for integrated pulp–paper (prod.iea.org). With drying still consuming 5.2–7.4 GJ per ADt in many older tissue machines (mdpi.com) and typical drying energies of 10–15 GJ per ton in many contexts, even fractional improvements deliver large absolute savings at mill scale.
Methodology and sources
These data‑driven insights draw on industry benchmarks and studies: Indonesian energy audits reporting ~70–80% of mill energy as thermal (mostly drying) (researchgate.net); industry guides summarizing shoe‑press savings (iipinetwork.org); case studies quantifying press versus dryer impacts (pulpandpapercanada.com) (mdpi.com); and peer‑reviewed analyses of impulse and steam‑dryer performance (iipinetwork.org) (mdpi.com). The U.S. drying spend estimate (~400 million GJ/yr; ≈$1.5 billion) comes from a government/industry study (pulpandpapercanada.com).
