The hot mill is the main equipment for the production of medium density fiberboard, and it is also the most energy-consuming equipment in the production process of MDF. It consumes both heat and electricity. MDF production is originally a high-energy-consuming industry, and nearly half of its energy consumption in production is occurring in the hot-grinding section. Therefore, how to save energy and save energy in the hot grinding section is particularly important. At the macro level, it is in line with China's current economic sustainable development war, and by 2020 the GDP will quadruple from 2000, while energy consumption will only double. At the micro level, it enables enterprises to reduce energy consumption, save costs, and improve the competitiveness of their own products. In the increasingly fierce market of MDF, enterprises can continue to survive and develop.
The author will analyze how to save energy in the hot grinding section from the following aspects:
l Establish energy-saving awareness during equipment selection or equipment transformation
1.1 Pay attention to the power factor of the heat grinding motor
Generally, the heat mill motor of MDF has a large power. For example, the power of a hot mill motor with an annual output of 80,000 m3 of MDF board is about 3 000 kW, while the power factor of domestic three-phase asynchronous motor is generally not high, generally o. 8~o. Between 8, it makes a lot of electric energy useless work. Therefore, in the equipment selection process, the equipment manufacturer is required to perform capacitance compensation on the power of the hot-grinding motor, so that the power factor reaches o. 9 to 0.92. If the equipment manufacturer does not have a capacitor compensator, the MDF manufacturer can also be equipped with a matching capacitor compensator during the equipment retrofit process to increase its power factor. The investment is not large, and the total investment can be recovered in three months.
1.2 carefully select the motor power of the mill
According to the production and production of MDF, the production process, and the tree species to be produced, it is necessary to determine the motor with a large power of the hot mill, so as to prevent the phenomenon of the big horse-drawn car.
1.3 The equipment configuration in front of the hot mill should be perfected
In the production of MDF, a large amount of mud sand and iron filings will inevitably be mixed into the wood chips. If these mud sands and iron chips enter the mill together with the wood chips, the grinding blades of the heat mill will be damaged. In order to ensure the quality of the ground fiber, the operator has to reduce the gap between the grinding motor and the plate, thereby increasing the cutting resistance of the mill, increasing the power consumption of the mill, and wasting a lot of electrical energy. Therefore, an effective iron removal device must be installed in front of the hot mill, and a wood chip washing device is provided to remove iron filings and mud sand from the wood chips.
1.4 equipped with a set of fiber sorting devices after the dryer
If the fiber drying machine is equipped with a fiber sorting device, the fiber stalks and the like in the fiber can be removed, which can improve the appearance quality of the MDF, and can avoid the small moving plate in order to reduce the coarse fiber stalk. The power consumption caused by the gap increases, thereby saving energy.
2 Establish energy-saving ideas in the process control process
2.1 Reasonably set the thickness of the hot ground fiber
In general, MDF is only a semi-finished product, and it is generally subjected to surface processing before final use. Therefore, under the premise of meeting the surface quality of MDF, the finer the finer fiber is required, the better. Amplifying the gap between the hot-grinding motorized disk and the platen reduces the frictional resistance between the two, thereby greatly reducing the power consumption of the heat mill.
2.2 Develop a reasonable hot grinding cooking process
According to the different species, the steam pressure of the cooking cylinder and the cooking time of the chips are adjusted reasonably. If the wood chips are not cooked enough, the chips are not easily rubbed, and the chips consume too much electricity during the grinding process. If the wood chips are cooked too much and consume too much steam heat, and the fibers are deep in color, affecting the quality of the MDF. Therefore, the development of reasonable cooking pressure and time parameters can also reduce the energy consumption of the hot mill.
2.3 Control the looseness ratio of the wood chips and the uniformity of the size of the wood chips
Different types of wood chips and different sizes of wood chips make the wood chips steamed and unsteamed during the cooking process. In order to ensure fiber quality, either the cooking time is long or the gap between the fixed plates is reduced. This is bound to consume too much energy.
3 Saving energy in production operations
3.1 to ensure the cleanliness of the wood chips
Improve the cleanliness of the wood chips, clean the iron scraps on the iron remover in time, and effectively prevent mud and sand from mixing into the wood chips, thus ensuring that the grinding blades of the mill are not easily damaged. If the grinding piece is slightly damaged, the coarse fiber stalk content in the ground fiber will increase. At this time, in order to reduce the coarse fiber stalk, the operator often reduces the gap between the moving plates, resulting in an increase in the resistance of the grinding chip. Large, mill power consumption increases.
3.2 Adjustment of cooking time
In the actual production process, various situations often occur, such as changes in wood sheet species, changes in loose mix ratio, and changes in product specifications. At this time, the operator must correctly and reasonably adjust the hot mill. Cooking time. If you encounter an increase in hardwood, properly extend the cooking time of the chips, that is, increase the level of the wood chips in the cooking tank; if you encounter an increase in the output of the product, in order to ensure that the cooking time is constant, the wood chips of the cooking cylinder should be appropriately adjusted. Level.
3.3 Correct and reasonable adjustment of the grinding maneuver, the gap between the plates
If the gap between the fixed plates is too large, the wood chips are too much between the plates, and some of the chips cannot be fully ground, making the fiber state unstable and prone to excessive fiber stalks, which reduces the power of the mill. Consumption, but makes the MDF affect the appearance quality of the product due to excessive coarse fiber. The gap between the moving plate and the fixed plate is too small. At this time, the fiber state of the product is fine, and the appearance quality of the product is good. However, since the gap between the moving plates is small, the grinding resistance is increased to increase the power consumption of the mill. .
3.4 Replace the new grinding disc in time
The grinding disc is a consumable part on the hot mill. It is equivalent to the tool on the machine tool. When the tool is sharp, it saves energy and saves power. When the tool is blunt, it is not easy to cut, which affects the grinding quality and wastes energy. The fiber quality can also meet the quality requirements of the product, but the power consumption per unit product increases rapidly, and it should be considered to replace the new grinding piece. Generally, the new grinding disc should be replaced when the electric energy consumed per lm dry fiber reaches 120kwÂ·h. When replacing a new grinding disc, the grinding disc of the appropriate model size should be replaced according to the fiber yield and the change of the wood species.
3.5 Adjust the opening of the discharge valve according to the change of fiber output
If the opening of the discharge valve is too large, a large amount of steam is discharged from the grinding chamber to the drying pipe, and these saturated steam containing a large amount of heat has no effect on the drying of the fiber, and is finally discharged into the atmosphere. Therefore, when the fiber yield is lowered, the opening degree of the discharge valve is adjusted accordingly.
4 equipment maintenance and maintenance of the heat mill power consumption is also very obvious
4.1 timely repair and replacement of the wood mesh screen
The effect of the wood chip sieve is to remove the oversized wood chips and fine wood chips in the wood chips, so that the sieved wood chips are evenly sized. If the screen of the wood mesh screen is damaged, the oversized wood chips will enter the mill. Because the large wood chips are not steamed and softened under the same cooking conditions, they are not easily ground into qualified fibers. In the fiber, the fiber stalk is increased. In order to ensure the quality of the fiber, the operator generally reduces the gap of the moving plate, which will inevitably increase the power consumption of the heat mill.
4.2 Timely replacement of the grinding wheel of the mill
The function of the material wheel is to uniformly transport the wood chips conveyed from the belt spiral to the grinding disc to the grinding zone of the grinding disc. If the fingers of the dial wheel are worn out seriously, the amount of wood chips conveyed to the grinding zone of the grinding disc is uneven and unstable, and the time is long and small. When the transported wood chips are small, the moving and fixed plates are touched, and the electric energy consumption of the mill is increased. When the wood chips are sent too much, excessive coarse fiber stalks are generated. At this time, the operator often adjusts the grinding plate of the fixed plate. The gap increases the power consumption of the mill. Therefore, the wear condition of the material should be checked frequently. If it is serious, the new material should be replaced in time.
4.3 Regularly check the end face runout of the grinding motorized disk and the parallelism of the moving and fixed plates, and make appropriate adjustments.
The end face runout of the grinding motor disk is generally not allowed to exceed 0.1 mm, and the parallelism error between the moving plate and the fixed plate is not allowed to exceed o. 05mm. If the end face of the moving plate is out of tolerance, the gap of the moving plate on the entire disk surface is large, some areas are small, the gap is small, the cutting resistance is large, the power consumption of the mill is increased; when the gap is large, the coarse fiber is ground. In order to ensure the fiber quality, the operator often reduces the grinding gap of the moving plate, which further increases the energy consumption of the mill.
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