Due to the fact that almost all the energy in the exhaust air is being transported back into fresh air, this system uses only half the thermal energy conventional systems use. Late 2013 the Latvian sawmilling company Saldus MR had two Model 1003 dryers installed and with these produces nearly 100,000 m3 lumber per year.
Saldus MR, a sawmill located in eastern Latvia, last year processed 450,000 fm logs into 225,000 m3 lumber. Mainly thin Fir & Pine logs, with 10-20 cm. in top diameter. Only 3 years ago, this company’s processing of saw logs was at not even one quarter of today’s value (105,000 fm). With the massive rise in production, made possible by a new saw line (see Holzkurier issue 7/13 pg. 20-21), the existing drying capacities were no longer sufficient. The company decided on two parallel energy saving Continuous kilns, model 1003, by Muehlboeck. Together these dry nearly 100,000 m3 lumber per year.
The Energy Saving Principle
Unlike traditional drying systems, where thermal energy that has been brought in, is ventilated out with the exhaust air, Heat Recovery system 1003 transports the energy in the waste air back into the fresh air for a different drying zone. This ‘free’ heated air is used for pre-drying” explains Maris Melngavis of Tirgus Tilts-Systems, Muehlboeck’s Latvian representative. The three drying zones are pre-, main- and post-drying. About half the moisture is being dried out in the first zone. Main- and post-drying zones pull the remaining water from the wood. The ventilation out of main- and post-drying zones flows through heat exchangers. Subsequently the water that was previously removed from the wood condensates, due to which a large amount of the energy input is recovered. The dehumidified air is circulated back into the kiln. For pre-drying only thermal energy from this Heat Recovery is being used. The air for the pre-dryer is being pulled from the finished dry wood at the end, thus absorbing its remaining heat. The air then flows through the mechanical room under the roof, where the complete heating equipment is located, and where the available heat is absorbed. “This way insulation loss is prevented and energy use in comparison to traditional systems is cut in half” Melngavis elucidates.
Through thick & thin
At Saldus the two parallel arranged kilns are being used for different lumber thicknesses. “In one we mainly dry lumber with a 35 mm. thickness, and in the other one boards thinner than 30 mm. to usually 18% final moisture” one of the kiln managers at Saldus tells us. In particular he likes the high level of automation of the new drying kilns, as well as the user friendly visualization. Especially for the Continuous kiln Muehlboeck developed a new control system. Key features of this software are the intuitive operation, as well as the clear and lucid graphics in conjunction with a comprehensive display of all the important information.
General Service Provider
Aside from the manufacturing of the Continuous kilns in Eberschwang, Muehlboeck provided the Latvian company an extensive package of services. Together with Tirgus Tilts-Systems, Muehlboeck took on the design and complete project planning, the foundation, heating pipe installation, programming of the controls, and the installation and start-up, as well as follow-up and optimization of the kilns. For Saldus MR’s Managing Director Gatis Zommers the benefits of the new drying installation besides the energy savings, are the space saving way of building, the fast drying and the high level of automation. ‘Our space availability is very limited and with traditional kilns we would have had difficulty implementing the increase of 100,000 m3 drying capacity’ Zommers clarifies. Due to the high level of automation the company is also saving on labor. Why Saldus MR has chosen for the Muehlboeck products is easy to see: ’We have already several Muehlboeck drying kilns in operation and are completely satisfied with those. The good quality of its competent service, and the proper price quality ratio of the Austrian company, made this decision easy for us’ Zommers summarizes. Saldus MR currently dries only 2/3 of its sawmill production. Even with the limited space availability the Managing Director is planning on raising this level and with it the value of the company. He is already talking to Muehlboeck again.
Holzkurier 19/2015, Günther Jauk