During the production of zinc oxides, a large amount of heat is generated in the process of oxidizing zinc vapor to zinc oxide. In order to find a judicious use to this energy, Norzinco has implemented an energy recovery process in its plant. It has been established with a neighboring silvicultural company, specialized in the production of firewood notably for households. Four years of works were required before the system was commissioned in 2014. In this way, Norzinco can valorize previously untapped heat, while its partner increases its drying capacity at a lowest cost and without using more natural resources.
A majority of the heat energy produced by Nozinco’s process is absorbed in a stream of hot air and zinc oxide. In the production filters the powdery zinc oxide is separated from the hot air.
This hot air is not simply blown into the environment, but it is directed into an air-air heat exchanger. In this heat exchanger, cold drying air is heated up to around 110 °C. An adjustable fan blows the drying air from the heat exchanger through an isolated pipe into big containers filled with firewood or wood chips. The drying air enters the containers at the bottom and flows through the wood filled containers. The hot air absorbs the humidity from the wood and later on leaves the containers at the top. Different sensors are continuously measuring the temperatures in the containers, the flow rate of the drying air and the amount of heat to guarantee constant drying conditions.
This technique tremendously speeds up the drying of the wood and makes it possible to produce best quality firewood in a very short time. Due to this process it only takes 3-4 days to produce firewood instead of the 2-3 years it needs to get dry firewood, when it is stored outdoors.