Grain and rapeseed dryers
Grain dryers are one of the production range that the company J4 s.r.o. offers. Nowadays we produce the grain dryer, type NS8000 that is intended for hygienic harmless drying of the products coming into the food-stuff market.
Indirect heated grain dryer of type NS
Dryer is an all-metal three-layer jacketed body that is closed with the engine room from the front and with the fans on the face from the backside.
Three-jacket body is modular and it influences with its length (6,8,10 and 12 m) directly the performance of the dryer. These three jackets define four spaces. The first jacket forms the boundary of the heating area, in which the combustion products from the natural gas circulate. This heating system works in negative pressure and it is hermetically sealed from the second space (the space between the first and the second jacket), which is the space of the heat exchanger, where the flowing air takes over the heat and it is distributed to vent holes of the second jacket. Through this it enters the third space (space between the second and the third jacket), it is the space of dried product. The third jacket is the stainless steel sieve enabling the leaving of air into the ambient space, then into the fourth space in order. Drying runs continuously. The performance of the dryer is given by the type of the dryer (the length of the body), drying temperature and the requested percentage of moisture removal.
Commodities for drying
Product for drying should be loose and non-sticky mass. Grain dryer is mainly intended for drying grain, corn and rapeseed. The temperature in the dryer heating system ranges according to the type of dried product and the size of the temperature gradient from 160 to 360 °C. This temperature ensures the transfer of heat into the second space where the drying air is heated and where it enter the active space through the vent holes.
Temperature and course of drying
The drying temperature again depends on the type of dried product and the temperature gradient of the exchanger. It ranges from 40 to 120°C. NS 8000 dryer capacity is 12.8 m3. The dryer is equipped with an upper feeding screw, which fills the dryer and refills the decreasing dried product. The product falls down through the third space, in the right and left strand, which is completely surrounded by the source of heat. The product is being flown around by the drying air and then it gravitates slowly to the intercepting flaps in the bottom part of the dryer.
The flaps gradually, in regular intervals, empty the product into the lower unloading screw, which then continually moves the product to the conveyor passage and to the container. The dryer’s operation is controlled by a programmable automatic device. With this device we select the temperature, the hold-up duration and thus we directly influence the dryer’s performance. The dryer’s operational safety is ensured by a doubled security system. Control of the combustion process is in compliance with European standards.
The filling opening with the dimensions 273 x 273 mm is positioned at the height of 6150 mm. The unloading opening has the same dimensions and is positioned at 1250 mm height. The hold-up duration for the product in the dryer is optional from 40 minutes up to three hours. The dryer’s ground plan takes up 2.6 x 12.45 m and the required free surrounding space for manipulation must be a minimum of 1.5 m.
The dryer burdens the surroundings with natural gas combustion (max. 1400 m3/hr. – combustion in the Weishaupt G3 burner with decreased NOx). The leaving velocity from the chimneys does not exceed 3.5 m/s. Furthermore, the surroundings are loaded with water vapour in the amount of ca. 500 kg/hr, which the dryer extracts from the dried product. The leaving velocity from the slots of the outer jacketing does not exceed 0.04 m/s. The noise level does not exceed 85 dB at the attendance site. The dryer is not a source of vibrations. With regard to energy, the dryer demands a max. of 120 m3/hr of natural gas (2 kPa), and the consumption of electrical energy is 36 kW.
To control the flaps, 0.5 MPa – 5m3/hr of compressed air is necessary. The entire dryer operates in a very economical energy regime given by its construction, as the source of heat is completely surrounded by the product being dried. In this case, the transfer of heat from the source to the exchanger is zero. All heat of the source with the exception of chimney losses must go through the dried product. Chimney loss (ca. 25%) is an inevitable tax for the hygienic “correctness” of the indirect NS 8000 type dryer.