Fire Protection For Paper And Pulp Plants

There is a sense in some markets that the paper and pulp industry will decline owing to the digital technologies with which people interact every day. While this might be considered logical, the reality is entirely different. The paper and pulp industry has experienced steady growth and will continue to do so in 2021.

Production of paper increased by more than 450% in the last decades. The demand for paperboard in the world is expected to grow significantly, driven by e-commerce and big retailers increasing their presence in the online sales universe. This sustained growth in production capacity and paper consumption presents several fire risks to companies. It exposes communities that develop around paper mills to the impact of disasters caused by these fire risks.

Fire Risks In The Paper And Pulp Industry

Paper and cardboard are combustible, but this is not the only fire risk found in these types of industries. Raw materials and finished goods storage are sensitive to fire. The paper-making process includes several stages where fires can occur due to hot surfaces or poor ventilation. The most relevant fire risks on a paper plant are:

Storage Areas: As mentioned before, paper and cardboard are combustible. Solid paper blocks and reels have hard surfaces that don’t ignite easily, but usually, these reels can suffer minor damages or have loose sheets that significantly increase the fire risk.

When paper reels are stacked in columns, gaps in the centre can act as chimneys, and when fires start in the bottom of the stack, this chimney effect will accelerate smoke and hot air spread, increasing vertical and horizontal flame spread.

Wood And Bale Storage Fire Risks

Raw materials for the papermaking process can have two primary sources, forestry products (mainly wood) or recycled cardboard and paper. Wood storage presents several challenges, mainly due to wood chips that are highly combustible and, in some cases, even explosive.

Bale storage also presents a high fire risk, as loose materials are always present. Fire in the baled paper is difficult to extinguish and generates heavy smoke. In many recycling facilities, these paper bales are stored outdoors, where paper or rags soaked in flammable liquids embedded between the paper sheets can ignite, resulting in fast-spreading fire.

Chemicals, Flammable Liquids And Gases

It is also possible to find different types of chemicals, flammable liquids, and gases used in the papermaking process. These materials have fire-related risks that need to be taken into consideration.

Production Areas: In pulp factories, there are several long-distance conveyors that transport wood and wood chips. These conveyors constitute a fire risk, and the most probable causes of fire are bearing damage, overheating the conveyor and igniting chips in the environment.

IR Dryers, A Common Source Of Fire

After the wood has been transported, chipped and digested, the papermaking process becomes exceptionally humid due to the large amounts of hot water and steam needed. As soon as the pulp fibre sheet starts to dry, the hot surfaces in contact with the paper sheets can be a source of ignition. IR dryers used in the process are also a common source of fire in the paper industry.

When the sheet of paper is formed, close contact with reels and bearings moving fast can create static electricity that could ignite loose paper or airborne particles. Problems like these are likely to be more extensive in tissue mills. Paper dust is generated in certain parts of the process, especially where paper shits are slit or cut.

Poorly Insulated Steam Pipes Lead To Fire

Poorly insulated steam pipes can ignite paper dust or even their insulation materials. Besides, paper dust gathers in the ventilation grills of machinery, causing overheating and igniting as well.

The heated oil is used in several parts of the process as well, and if a malfunction occurs on the Hot Oil Roll systems, leaks might occur, exposing hot surfaces to this oil and causing ignitions. A paper mill has hydraulically operated machinery, where leaks or sprays might ignite as well.

Service Areas: As in many other manufacturing facilities, fire can find several service areas. Electrical and network equipment rooms have an inherent fire risk due to damaged wires or equipment, overheating or short circuits in high voltage circuits. Transformer and generator areas entail fire risks as well.

High Fire Risk For Boiler Rooms

Hot water and steam are vital components of the papermaking process. For this reason, paper plants use high capacity boilers that flammable liquids or gases can power. We can consider high fire risk for boiler rooms.

Flammable gas distribution systems can be ignition sources in case of leaks or damaged pipes or valves. In addition to the fire risks mentioned in these areas, many maintenance operations can also pose a fire risk, mainly when hot works are being performed.

Sparks caused by welding or using specific tools can ignite paper sheets or dust in the air. Poor housekeeping and buildup of paper dust, for example, increases the risk associated with maintenance and construction works.

Prevention, The First Line Of Defense

According to the Health and Safety Executive from the United Kingdom, 60% of fires on paper mills are caused by machine faults and poor housekeeping.

The first line of defence to avoid fire risks in paper plants is prevention. As mentioned before, a high number of fires in these types of facilities occur because of poor housekeeping and machine malfunction. The key is to identify the risks and possible ignition sources and apply measures to minimise them.

As in many industries, fire protection has two main components: Passive and Active protection.

Passive Fire Protection Measures

Passive measures include fire-rated walls, ceilings, and floors in the most critical areas. Plant Operators should physically separate chemical storage areas from other dangerous areas; if this is not possible, then the walls separating areas should be fire-rated, and operators must store materials in a way that minimises the risk of fire spread by radiation or conduction.

Proper compartmentalisation and intumescent protection of structural elements should be part of the package as well. Passive measures include adequate ventilation and smoke control. As mentioned before, paper dust is a significant fire risk, which is why ventilation and cleaning of hoods over the paper machine is essential to minimise the possibility of ignition.

Fire resisting construction should be designed with the following goals in mind:

Protection of escape routes
Form compartments to contain fires that might occur
Separate areas of higher fire risk
Protect load-bearing and structural members to minimise the risk of collapse

Sprinkler Systems, Gas Extinguishing Systems And Hose Reels

Active fire protection includes sprinkler systems, gas extinguishing systems and hose reels to support fire brigades. Operators should protect finished goods stored indoors with sprinkler systems, and the same should be considered for chemical storage areas and certain raw materials.

Paper bales ideally should be protected by sprinklers that are suitably designed to cope with the height and located, in all cases, 3 meters above the level of bales stacked vertically (which should not exceed 5 meters height).

Spark Detectors In Hoods, Pipes And Ventilation Systems

Dangerous sparks could be generated in several parts of the papermaking process, which is why spark detectors must be installed in hoods, pipes, and ventilation systems. Engineers can use water spray and Co2 methods to protect machinery against these risks.

Means to fight fires, like extinguishers and hose reels, should be provided to support fire brigades. Engineers should adequately identify all the elements, and all personnel should be trained and made aware of the location of such devices.

Importance Of Fire Alarms

Fire alarms are required in all paper mills, and fire alarm call points should be provided in all locations, according to international guidelines, such as NFPA 72 or EN54. The spread of flames and smoke in paper, wood and chemical storage might become extremely fast. For this reason, early detection is critical. Engineers might apply many technologies in the different areas of a paper plant.

Nevertheless, dusty or humid areas where regular heat or smoke detectors might fail under certain circumstances. For these areas, primarily located outdoors, innovative state-of-the-art detection solutions might be applied, like Video Fire Detection (VFD).

NFPA 72 Standard For Flame And Smoke Detection

NFPA 72 provides guidelines to implement this technology for flame and smoke detection, opening attractive alternatives for designers and fire protection engineers. Many EHS managers and fire protection professionals selected VFD because it is the only fire detection solution that effectively covered their needs.

Many engineers specialised in fire protection for paper plants explained that they tested linear heat detection, aspiration smoke detection, IR/UV detectors and even beams, but none of these technologies performed as they needed on the dirtiest or more humid areas.

Video Fire Detection (VFD) Solutions

Outdoor storage areas are often unprotected because deploying flame or heat detection in large open spaces can be costly and mostly ineffective. VFD solutions can detect smoke and flames in outdoor conditions, allowing the monitoring and protection of wood and paper bales in large areas.

Fire detection and alarm systems should be designed with the following goals:

Minimise the risk of fires, including the use of fire detection technology in areas where standard detection technologies cannot be implemented or are not practical.
Minimise the risk of flame and smoke spread with state-of-the-art detection algorithms that guarantee fast and effective detection. Also, reliable algorithms minimise the possibility of nuance or unwanted alarms.
In case of a fire, fast detection gives occupants a life-saving time to reach a place of safety before the flames and smoke have spread to dangerous levels.

Global production of paper and pulp reached 490 million tons in 2020, with many industries and markets depending on the paper and pulp supply chain. That is why innovative ways to protect this supply chain are essential to sustain the paper market growth in the future.