What is the vacuum system of the paper machine

In the auxiliary system of the paper machine, the energy consumption of the vacuum system accounts for 30% to 40% of the whole system, and some are even higher.

Problems faced by vacuum system

In the auxiliary system of the paper machine, the vacuum system occupies an extremely important position in terms of energy consumption and equipment investment.

The speed and quantitative range of modern paper machines are getting wider and wider, and the paper types are also changing with market changes. The vacuum system faces severe challenges:

(1) The vacuum system must work finely to adapt to changes in paper ration and vehicle speed;

(2) The vacuum system must be adapted to the different stages of use of the paper machine forming wire and felt;

The vacuum system must provide optimized water and electricity consumption, saving energy.

Comparison of two vacuum systems

Water ring vacuum pump vacuum system

The principle of water ring vacuum pump will not be repeated here, and many materials have been introduced. The paper machine vacuum system is shown in Figure 1. In the actual design process, some other vacuum systems are also derived from this, but the basic core has not changed, mainly including steam-water separator, water-ring vacuum pump, vacuum pump water-ring water system ( Vacuum pump water collection tank, self-priming tank, cooling tower and other equipment).

Inverter turbine vacuum system

The working principle of the turbo vacuum pump: the steam-water mixture from each vacuum suction point of the paper machine enters a special steam-water separator, the liquid and the lost fine fibers are extracted by the pump installed at the lower part of the gas-water separator, and the gas enters the turbo-type vacuum pump after passing through the filter . With the rotation of the impeller of the turbo vacuum pump, the gas enters the hole in the middle of the impeller, and is accelerated and pressurized by the radial rotation of the impeller. The turbo vacuum pump is generally used in combination with a multi-stage turbo vacuum pump and two single-stage turbo vacuum pumps to meet the vacuum requirements of different suction points of the paper machine.

The total installed capacity of the turbine vacuum pump is 1315kW, and the total installed capacity of the water ring vacuum pump is 1830kW. The turbine vacuum pump system saves about 28% of the installed capacity. The main reason is that the turbo vacuum pump has an ultra-high efficiency of 80%, while the traditional water ring vacuum pump is only 40% to 50%, or even lower.

In the operation stage of the paper machine, due to the flexible use of the turbo vacuum pump, especially when producing low-quantity products, the energy-saving effect will be more obvious. On the other hand, the turbine vacuum pump system has no water ring vacuum pump water ring water system, which further saves the power consumption of the circulating water pump and cooling tower. The total water ring water system in this project is 67.5kW.

water consumption comparison

The water ring water circulation of the water ring vacuum pump is used, only considering the power consumption, not the water replenishment; before the renovation of this project, the water ring vacuum pumps were all belt-driven, the packing and sealing water was about 40 L·min-1, and the cooling water of the turbine vacuum pump lubricating oil station totaled 30~40 L·min-1, in the vacuum system of a large paper machine, the water ring vacuum pump is generally driven by a coupling, and it also needs lubricating oil cooling water. The turbine vacuum pump has the advantage of saving water.

Equipment layout and construction costs

In the design of conventional paper machine workshops, the wet end drive side is usually arranged with a flow system and a vacuum system, with dense pipelines, many equipment, and limited space, especially for paper machines that use compound presses, the wet end drive side has a further space.

The steps are compressed, the equipment layout is very compact, there are many pipe elbows, and the pressure drop loss is large. The turbo vacuum pump system adopts a multi-process design to reduce the length of the pipeline, and the number of equipment is 50% less than that of the water ring vacuum pump.

Or more, the layout is flexible, it can be arranged on the first floor or on the second floor, which greatly reduces the space occupied by the vacuum system.

(1) Only the area of the pump room is considered here, and the area of the pre-separator of the water ring vacuum pump system is not considered. The original area of the water ring vacuum pump is 6.5 m×36 m, and the area of the turbine vacuum pump is only 6.5 m×18 m. m, saving 50% of floor space.

(2) There is no water ring water system in the turbo vacuum pump system, and the water ring water collection pool of the water ring vacuum pump system is not required. Only the equipment foundation of the turbo vacuum pump and the steam-water separator is designed and constructed, which is about 90% less than that of the water ring vacuum pump system. Civil construction costs.

heat recovery

Due to the low grade of the water ring vacuum pump exhaust, there is basically no value for recycling, and most of them are directly emptied; while the exhaust temperature of the turbine vacuum pump is high (about 140 ℃), and the moisture content is low, which can be used for heating wet

The air supply from the ceiling can also be used to heat the air hood, and the electric energy can be converted into heat energy to improve the utilization efficiency of electric energy, so as to achieve the purpose of saving energy and reducing consumption.

The turbine vacuum system has the characteristics of saving water, electricity and land.

During the renovation process of the project, some business owners doubted its actual use effect, and suggested that the press section should use a turbine first, because the dehydration of the press section is far less than that of the wire section. For a long time, the water ring vacuum pump has matured

Reliability is the choice of vacuum system for papermaking. However, in the face of the national strategy of vigorously promoting energy saving and emission reduction, enterprises must also make changes. The price and maintenance cost of turbo vacuum pumps make many enterprises look forward to it.