Energy saving in paper making process

lk1In the process of paper making, most of the energy saving is related to improving the energy efficiency of the drying process and the utilization of the waste heat. In general, pulp and paper energy costs accounted for about 10% to 35% of the cost of production; consumption of vacuum consumption accounted for 15% of paper electric power consumption to 18%, most of the vacuum energy is supplied to the vacuum roller, suction tank and vacuum suction tank; drying is the highest part of energy consumption in the production of paper. The key factor to reduce the energy consumption is to increase the dry degree of paper after press.

(1)

Optimization of wet part dehydration: the energy consumption of the 1kg water is 5 times of the 1kg water in the forming part, and the energy consumption of the drying part is 25 times of the 1kg water. Therefore, from the point of view of energy saving, it should be strengthened in the shape of the Ministry, the Ministry of press and the optimization of the drying part of the distribution.
(2)

Control of the drying dew point: the gas cap determines the heat exchange efficiency, and the heat efficiency is affected by the fan. To strengthen the measurement and control of the dew point state in the air hood of paper machine, to optimize the heat exchange efficiency of the drying process and to save energy. At the same time, optimize the gas cap control, can provide better drying quality, more uniform product quality.
(3)

Paper machine vacuum system optimization: each machine has a vacuum pump and vacuum system, paper machine vacuum system consumption of power and power consumption of paper machine. Therefore, by strengthening the paper machine each part of the vacuum pumping and the vacuum degree and other optimized configuration, can be in the same amount of dehydration, saving more energy.
(4)

Chemical mixing and energy saving: in the most close to the flow of slurry tank flash mixed wet chemicals, high efficiency, low energy consumption. The traditional hybrid system in head box feed pipe with chemicals, long time delay. With the aid of the flash mixing time of the slurry tank pipe into the slurry jet stream, the distance is shortened, the distance is close, the energy saving effect is good, and the mixing is uniform.
(5)

Vacuum energy saving of the water suction tank: the vacuum degree of the vacuum suction tank is lower than that of the vacuum roller, but it needs to be driven to overcome the sliding friction and the energy consumption is consumed. Compared with the traditional gap cover plate, the new special open cover vacuum chamber can significantly improve the dewatering performance and reduce the unit energy consumption of the corresponding position. The reason lies in the high efficiency area of holes, and the vacuum in the cover of more stable; in addition, the opening of the special surface morphology can improve the thickness of water film are scraped from forming the inner surface of the network, so the paper wet minimum. At the end of forming, by changing the position of the high vacuum suction tank, mounted directly on the arc in vacuum roll, can reduce the friction caused by net vacuum, can be part of the final paper in the network terminal consumes too much energy and wet back to a minimum. Compared with the traditional vacuum chamber, the vacuum chamber can significantly reduce the energy consumption of the forming part.

 

(6)

Vacuum roller energy-saving technology: Most of the vacuum roller energy consumption and vacuum consumption, the vacuum roller used in forming the amount of vacuum required for all the vacuum amount of about 1/2, vacuum energy consumption will be with the machine speed and vacuum Degrees increase. Mainly due to the vacuum roll rotation, the shell of the gap needs to be continuous evacuation of the reason, need to evacuate about 2/3 of the air. Vacuum roller shell on the linear drilling to minimize the re-wet, no tapered hole, through the couch after the dryness of paper increased by 1% to 2%; in the same vacuum, the linear hole shell air The volume is reduced and vacuum flow is reduced by approximately 10%. The large surface area of the vacuum opening increases the energy consumption of the vacuum roll. Typically, about 60% of the open area is tapered, primarily to improve the drainage capacity of the dewatering process.

(7)

Energy consumption and energy saving technology in the press section: For every 1% increase in the dryness of the press section, the paper machine speed can be increased by about 50m / min. The shoe press usually increases the dryness by about 6%, ie, the shoe press increases the maximum speed by about 300 m / min. However, before replacing the shoe press and speeding up the paper machine, it is necessary to update the transmission equipment, improve the dewatering capacity of the forming section, and improve the running performance of the drying section. One of the main advantages of miniature shoe presses is that the existing press structure is less variable, reducing the amount of work and downtime, without the need to update the crane. In the press with a full-width jet device on the paper machine, the transverse moisture difference can generally be reduced by 80% or more, after the press drying paper increased by 2.5% to 3.0%. The dryness of the paper is higher after pressing, which reduces the steam consumption of the drying section; and the running performance is improved and the energy is saved by reducing the number of paper breaks.
(8)

Energy-saving drying technology: Developed by the US National Laboratory of multi-channel dryer, compared to the traditional dryer capacity can be increased by 50%, compared with equipped with a turbo-bar dryer capacity can be increased by about 20%. Conventional dryer with condensed water, as heat transfer obstacles. The new multichannel dryer has a relatively small passageway near the inner surface of the dryer, which improves heat transfer efficiency by significantly reducing the thickness of the condensate layer and increasing the surface temperature of the dryer. The technical transformation, the cost is only 20% of the new dryer. Stainless steel Yankee dryer with the same size steam drum of the same quality of traditional iron Yanke compared to the heat transfer coefficient and evaporation capacity increased by 25% to 30%. The drying capacity can be increased by 10% ~ 15% in the whole drying process. The efficiency of the dryer is greatly improved because the stainless steel material reduces the total quality of the dryer and reduces the thermal inertia and heat transfer resistance. In addition, the required drive energy is lower and easier to install. At the same time, because the stainless steel material can absorb a series of problems caused by cast iron dryer heat and pressure shock, and thus more secure.
(9)

Energy-saving effect of frequency conversion technology: Intermittent pulper through the motor frequency transformation, the use of basically the same process, running time, comprehensive energy-saving rate of about 25%. The pump frequency control is an effective energy-saving technology, energy-saving efficiency is high, almost because of design redundancy and the amount of waste and energy savings all the savings. In the conventional valve control, such as the motor speed constant, the excess energy to flow control valve baffle energy loss; and frequency control, which according to process requirements to automatically adjust the pump speed, the basic no extra loss of energy . Water ring vacuum pump is a positive displacement pump, which is characterized by pumping volume and speed is proportional to the working point of shaft power and its speed is proportional to the power of 1.7. That is, when the water ring vacuum pump is determined, can adjust the speed to adjust the pumping capacity. If the inverter can be used in 0.5 ~ 100Hz can be adjusted within the characteristics of continuous speed, you can 2 times the motor rated speed range to adjust the pumping capacity. Compressor air compressor energy loss is the main mechanical losses, the loss of compressed air waste, air compressor operating loss of air load, compressed air flow losses and other losses. When the air compressor output pressure is greater than a certain value, some paper companies or automatically open the unloading valve, the asynchronous motor idling, a serious waste of energy, or downtime. Motor start frequently, stop, affect the life of the motor, and air compressor frequency starting current, the impact on the power grid, motor bearing wear, maintenance of large equipment. Frequency conversion technology can solve the above problems.

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