Reducing the risks generated by combustible dust in tobacco and food production
24.02.2020

Dust from organic material - sugar, flour, grains, spices, and wood, for example - are as combustible as metal dust. Minimizing the risks of a severe or even fatal explosion requires awareness - both from management and operators - as well as the use of equipment that can adequately capture the dust and then remove it from the production process.

Organic dust is frequently encountered in food production and ignites easily

Almost any kind of organic dust can explode if the moisture content is sufficiently low. Seemingly harmless and the agricultural ingredients used for broth, potato flour, and similar products are no exception. Many industrial food processing plants add major amounts of spices, flavors, and starch to their products, often releasing clouds of dust from bags and other containers used in the process. Mixing these substances with relatively moist products (such as fresh fruits or minced meat) eliminates the risk of an explosion, but until this happens, the dust can ignite and cause major damage if it comes into contact with an overheated motor or even a cigarette butt.

Fine and dry dust can quickly appear and accumulate in large amounts

Even moist and thus safe materials can explode when finely ground and exposed to low humidity.

Nederman recently delivered a FlexFilter EX system to a tobacco company in Sweden whose products are made from moist tobacco dust. Since the powder usually contains a relatively high percentage of moisture, it was not initially considered potentially explosive. However, manufacturing and packaging processes involve some degree of spillage. Once spilled in the open air, tobacco powder will quickly become drier, often losing more than 90% of its moisture content in less than half an hour.

This significantly dried substance was removed approximately once every hour through a high-vacuum dust filtration system. Unfortunately, the system operated at such a high speed that the particles became even finer as they passed through the pipes, resulting in substantial amounts of fine, combustible dust accumulating in the system's pipes and the dust container. Moreover, the rubber cloth filter that was used at the time to collect the particles regularly burst and had to be replaced at least twice a year.

The finer the dust, the higher the risk of combustion

As the dust travels through a pipe or duct, static electricity is accumulated. If too much dust accumulates in the filter and also inside the pipe over time, it can result in a major explosion.

A test was conducted in which the tobacco manufacturer's main product was processed into a very fine dust and then sent to a company for analysis. At the test facility of the respective company, the dust was ignited to measure its KST value. This value indicates the maximum rate of pressure rise in bar and makes it possible to estimate the anticipated behavior of the dust, particularly the likelihood and strength of an explosion. 

The measured KST value of the tobacco dust was approximately 70, which is higher than dust  from wood or rice, for example. However, it is noteworthy that flour and sugar have KST values of approximately 150.

Installing a FlexFilter with a release panel and a one-way valve helps minimize the impact of an organic dust explosion

Following the risk assessment and the conclusion that the tobacco dust generated during the production process poses a workplace hazard, the company decided to install a FlexFilter EX system. While this equipment cannot prevent the dust from exploding, it evacuates the flame and hot air that will be created in such an event. An evacuation tunnel will absorb the fire and control it through a one-way valve. Subsequently, the filter will need to be replaced, and the cause of the explosion will need to be investigated in detail, but production is likely to resume within 24 hours. The suction system also collects excess tobacco powder and filters it for safe and easy storage.

Without the necessary equipment to handle these types of dust explosions, damage to personnel, panels, and machines can be significant and may cause production to be halted for an extended period.

A few key factors for preventing combustible dust

In many ways, the greatest danger of combustible dust is simply ignoring the risks it presents. Fortunately, awareness of the issue is increasing, even though this awareness varies considerably between companies, industries, and geographic regions. More and more companies include it as a potential risk factor in workplace safety assessments concerning the products they manufacture and the amounts of dust generated by production.

Implementing industrial cleaning procedures is an essential aspect of this effort, as it helps ensure a sanitary and safe environment for workers, equipment, and products alike. Installing appropriate extraction arms, extraction hoods, and other types of ventilation necessary for the process means that dust will not be able to settle or spread to a significant extent, preventing explosions and human exposure to fumes and other hazardous particles.

Besides awareness, the use of appropriate cleaning equipment and procedures, the complexity of the production system itself is a factor that should be considered when building a new section or factory. A system that is intuitive and relatively easy to use will likely lead to fewer damages, errors, and maintenance activities.