Condensation problem

In particular in the cold season, there are often queries regarding apparent damp in our products. This reference should contribute to being able to conducting an objective debate.

Euroquarz dries its products to a drying degree of 0.15 weight/%. This means that one tonne (1,000 kg) of our products contains about 1,5 kg of water (surface damp sticking to the sand grain). In a bag of 25 kg, this is about 38 g..

From our drying plant, the dried products are conveyed at a temperature of 50 °C into our silo plant and then bagged, if applicable. The water quantity remaining in the product (0.15%) is, sticking to the product, evenly distributed in the entire bag or silo.

 

When – in particular in the cold season – the products are loaded as bagged goods into unheated warehouses or loosely in silo trucks and transported over long distances through extremely cold environments, the following happens:

the cold outdoor temperature results in the dew point (see physical background) in the outside area of the bag or silo being first fallen below of, meaning that water condenses here. The relatively higher temperatures in the product middle mean that the water that is still there evaporates and condensates outwards.

 

Due to this process, nearly the entire remaining water shifts to the outer areas and condensates there – i.e. exists there in liquid form only. A bag of 25 kg therefore contains a quantity of up to 38 g of water distributed on the inside of the film (approx. two shot glasses). For this reason, the bag acts as if the product contained in it were wet. Considered over the entire bag, the remaining dampness is nevertheless only 0.15 M-%.

 

With a loose delivery of, for instance, 26 tonnes, the effect becomes even clearer: in the silo lorry nearly 40 litres (= 40 kg) of water can be found in the outer area of the products, although the remaining dampness – considered in respect of the entire load – is only a maximum of 0.15 weight/%. When sample taking is not performed in a representative way (see notes on sample taking), receipt control may result in dampness measurement values, which result in queries. .

 

If a sample is taken from the middle of the delivery, no or small residue dampness can be found there. By mixing or blowing into standing silos, the products are harmonised.

 

Whether the water in the outer area may result in issues in the production of our customers depends on the individual case. If a production risk is given, it is nevertheless often not possible to provide the customer with a replacement delivery without such condensation occurrence, as long as the temperature conditions have not changed, as the physical connection - also for a new delivery - cannot be avoided.

Physical background:

Water can occur in the 3 different aggregate states of solid, liquid and gaseous. Below 0 °C water is, as a rule, solid and above 100 °C it is gaseous.

But at temperatures between 0 and 100 °C gaseous water exists in the air. The warmer the air, the more water it can absorb.

Temperatur    

max. water

  quantity
0    °C4g/m³
20   °C15g/m³
40   °C49g/m³
60   °C152g/m³
80   °C546g/m³

 

As can be seen from the table, air can absorb a maximum of 152 g of water vapour in one m³ at a temperature of 60 °C. But if this air contains, for instance, only 100 g of water vapour (absolute quantity in g), this is only 70% of the maximum absorption capacity – relative humidity is 70 %.

Figure 1: Absorption capacity at 60 °C

The maximum possible quantity of water vapour decreases the coler it gets. The absolute quantity of water vapour remains the same, this results in relative humidity being exactly 100% at a certain temperature.

Figure 2: Dew point

If the temperature drops further, the air can absorb less water than water vapour already exists - the water condenses. This point is also called the dew point. If the temperature continues to drop, ever more water condenses.

 

 

Figure 3: Condensing after exceeding the dew point