9 measures of energy-saving for paper machines that you should know
April 6, 2023
The energy conservation and consumption reduction of enterprises is a crucial segment. However, if you cannot find good energy-saving and consumption reduction measures at the moment, how can you not make people anxious! Is there any way to solve your troubles? Let's take a look together.
Nine measures of energy-saving for paper machines
- Optimization of paper machine vacuum system
Each paper machine has vacuum pumps and vacuum systems. The power consumption of the vacuum system of the paper machine is equivalent to the power consumed by the drive paper machine. Therefore, by strengthening the optimization configuration of vacuum pumping demand and vacuum degree of various parts of the paper machine, a significant amount of energy can be saved under the same total dehydration amount.
- Chemical mixing energy-saving
Mixing wet end chemicals closest to the headbox results in high mixing efficiency and low energy consumption. The traditional mixing system involves adding chemicals to the material pipe of the headbox, resulting in a long delay time.With the help of the main pipe of the headbox, the mixing time of the slurry injection flow is significantly shortened, the distance is short, the energy-saving effect is good, and the mixing is even.
- Vacuum energy-saving of suction tank
The vacuum degree of the suction tank is lower than that of the vacuum roller, but it needs transmission to overcome the sliding friction and consume the transmission energy. Compared with traditional gap cover plates, the new special perforated cover plate vacuum box can significantly improve the dehydration performance at corresponding positions and reduce unit energy consumption.
The reason for the higher efficiency lies in the large opening area and the more stable vacuum degree on the entire cover plate; In addition, the special surface morphology of this opening can significantly improve the thickness of the water film scraped from the inner surface of the formed mesh, thus minimizing the moisture regain of the paper web.At the end of the forming part, by changing the position of the high vacuum water suction tank and directly installing it under the paper guiding roller, the arc vacuum zone can reduce the sliding friction force caused by the vacuum pumping of the wire part, and can control the excessive energy consumption and moisture regain of the paper at the last end of the wire part to a minimum. Compared with traditional vacuum boxes, curved cover vacuum boxes can significantly reduce the energy consumption of the forming part.
- Energy consumption and energy-saving technology of the press section
Generally, for every 1% increase in the dryness of the press section of the paper web, the speed of the paper machine can be increased by about 50m/min. Shoe press can usually increase dryness by about 6%, which means that shoe press can increase the maximum speed by about 300 m/min.However, before switching to shoe press or increasing the speed of the paper machine, it is necessary to update the transmission equipment, improve the dehydration capacity of the forming section, and improve the operational performance of the drying section.
One of the main advantages of micro shoe press is that it allows for minimal modifications to the existing press structure, reduces renovation workload and downtime, and eliminates the need to update the crane. On a paper machine equipped with a full width steam spraying device in the pressing section, the lateral moisture difference can generally be reduced by more than 80%, and the dryness of the paper web increases by 2 5%～3.0%. After pressing, the paper web has a higher dryness, reducing the steam consumption in the drying section; Moreover, by reducing the number of paper breaks, the operational performance is improved and energy is saved.
- Energy saving drying technology
The multi-channel drying cylinder developed by the National Laboratory of the United States can increase production capacity by 50% compared to traditional drying cylinders, and can increase production capacity by about 20% compared to drying cylinders equipped with turbulence rods. Traditional drying cylinders contain condensed water, which becomes a heat transfer barrier.
The new multi-channel drying cylinder is equipped with relatively small channels near the inner surface of the drying cylinder, which significantly reduces the thickness of the condensate layer and increases the surface temperature of the drying cylinder, thereby improving heat exchange efficiency.
During this technological transformation, the required cost is only 20% of the newly installed drying cylinder. Compared with traditional cast iron Yankee dryers of the same size and steam pressure, stainless steel Yankee dryers have a 25% to 30% increase in heat transfer coefficient and evaporation capacity. During the entire drying process, the drying capacity can be increased by an average of 10% to 15%;
Due to the stainless steel material reducing the total mass of the drying cylinder, as well as reducing thermal inertia and heat transfer resistance, the efficiency of the drying cylinder is greatly improved. In addition, the required transmission energy is lower and easy to install. At the same time, due to the stainless steel material being able to absorb the heat and pressure impact that cause a series of problems in the cast iron drying cylinder, the safety is higher.
- The energy-saving effect of frequency conversion technology
After the intermittent pulp crusher is modified with motor frequency conversion, it adopts a basically consistent process flow and operating time, with a comprehensive energy-saving rate of about 25%. The variable frequency speed regulation of the slurry pump is an effective energy-saving and consumption reducing technology, with high energy-saving efficiency, which can almost save all the electrical energy wasted due to design redundancy and changes in dosage.
In conventional valve control, if the motor speed remains constant, excess electrical energy is lost through the energy of the flow control valve baffle; And variable frequency control, which automatically adjusts the speed of the slurry pump according to process requirements, has almost no excess energy loss.
- Wet end dehydration optimization
The energy consumption for removing 1kg of water from the pressing section is usually five times that of the forming section; The energy consumption for removing 1kg of water from the drying section is 25 times that of the forming section. Therefore, from the perspective of energy conservation, it is necessary to strengthen the optimized allocation of dehydration in the forming section, pressing section, and drying section.
- Control of drying dew point
The dew point of water vapor in the hood determines the heat exchange efficiency, which is also affected by the ventilation fan. Strengthening the measurement and control of dew point status inside the paper machine hood, optimizing the heat exchange efficiency of the drying process, is beneficial for energy conservation. Meanwhile, optimizing hood control can provide better drying quality and more uniform product quality.
- Vacuum roller energy saving technology
Most of the energy consumption of vacuum rollers is related to vacuum consumption. The amount of vacuum used by the vacuum roller accounts for about half of the total vacuum required for the forming part. The energy consumption of vacuum will increase with the increase of the operating speed and vacuum degree of the paper machine. Mainly due to the continuous evacuation of the gaps in the shell of the vacuum roller during rotation, approximately 2/3 of the air needs to be evacuated.
The linear drilling on the vacuum roller shell minimizes moisture regain. Without the use of conical holes, the dryness of the paper web after passing through the couch roller increases by 1% to 2%; Under the same vacuum degree, the air volume of the straight hole shell is smaller, and the vacuum flow rate decreases by about 10%. The large surface area of the conical hole vacuum opening will increase the energy consumption of the vacuum roller. Usually, about 60% of the opening area is conical expansion, mainly to improve the drainage capacity of the dehydration process.
Conclusion
The development of the paper industry requires significant energy consumption. In order to achieve green development, it is necessary to optimize the technology and structure of paper machines on the existing basis, implement various energy-saving and consumption reduction measures, and ensure effective control of production energy consumption without affecting production efficiency.