Roots vacuum pump dewatering process in paper mill

Through the application of vacuum pump, the cost of papermaking is effectively reduced and the quality of paper is improved. Today, EVP vacuum pump manufacturers will tell you about the application and selection of Roots vacuum pump in the paper industry. In the process of pulp and paper technology, the method of vacuum dehydration can be applied to the dehydration process. Using roots vacuum pump is a common method of paper dehydration. So let’s take a look at the application of Roots vacuum pump in dehydration process.

Roots vacuum pump is also known as mechanical booster pump. It is a positive displacement vacuum pump. A gas cooler is installed under the exhaust port of Roots vacuum pump. Part of the cooled gas returns to the pump cavity through the pipe to cool the rotor, so that the compression heat is balanced, so this kind of pump can directly exhaust the atmosphere.

Because there is no working medium in the pump cavity, this kind of pump also belongs to dry pump. In order to meet the requirements of different limit vacuum degree, this kind of pump can be used in series. Generally, an air-cooled direct discharge atmospheric Roots pump is added in front of it, and the limit vacuum reached is one order of magnitude higher than that of the previous pump. This kind of air-cooled direct exhaust roots pump and unit has been tested in aerospace space simulation, petroleum field, chemical industry field, plastic field, pesticide field and turbine rotor dynamic balance device for a long time.

Generally speaking, the standard air extraction rate in paper production line is certain, but in order to reduce energy consumption and production cost, the selection of vacuum pump is particularly important. For paper industry, roots vacuum pump is usually used instead of water ring vacuum pump. Therefore, comparing the economic benefits of Roots vacuum pump and water ring vacuum pump is the primary problem of paper-making manufacturers, of course, this will also involve the selection of Roots vacuum pump.


Roots vacuum pump concept and selection

The function of Roots vacuum pump is to remove gas molecules from the vacuum chamber, reduce the gas pressure in the vacuum chamber, and make it reach the maximum required vacuum degree. Generally speaking, there is a large range from atmosphere to extremely high vacuum. So far, no vacuum system can cover this range. Therefore, in order to meet the requirements of process index, working efficiency and equipment working life of different products, different vacuum system configuration needs to be selected for different vacuum sections.

In order to achieve the best configuration, the following points should be considered when selecting the vacuum system:

1、 Types of extracted gas and air volume

Check and determine the type and volume of air extraction required by the process. Because if the kind of pumped gas reacts with the liquid in the pump, the roots vacuum pump system will be polluted. At the same time, it is necessary to determine the appropriate exhaust time and the amount of gas produced in the process of extraction.

2、 Vacuum degree

The vacuum degree determines the structure of the product. There are two readings of gauge pressure and absolute pressure.

Absolute pressure means that the reading is absolute, that is, the closer the reading is to ‘0’, the higher the vacuum. But on the contrary, the closer the gauge pressure is to 760mmh, the higher the vacuum degree is. If the absolute pressure (limit vacuum) you require is close to ‘0’, then only the vacuum pump can meet this demand, but if the demand is close to 1bar (atmospheric pressure), then you can choose Roots fan or centrifugal fan to meet this demand.

3、 Determine the working roots vacuum range

The degree of vacuum required for each process must be determined. Because each process has its suitable vacuum range, we should carefully study and determine what kind of vacuum is suitable for this process.

4、 Vacuum volume inspection

Determine the time required to achieve the required vacuum, the flow resistance of the vacuum pipe, and leakage. After the required vacuum degree is reached, the air extraction rate required to maintain vacuum under certain process requirements is considered.

5、 Determine the limit vacuum

On the basis of determining the vacuum degree required by the process, check the limit vacuum degree of Roots vacuum pump system, because the limit vacuum degree of the system determines the best working vacuum degree of the system. Generally speaking, the limiting vacuum degree of the system is 20% lower than the working vacuum degree of the system, and 50% lower than the limiting vacuum degree of the previous stage pump.

Of course, the above formula is only the theoretical calculation result, and there are several variables not taken into account, such as pipeline flow resistance, leakage, flow resistance of filter, temperature of extracted gas, etc. In fact, the safety factor should also be taken into account.

Vacuum pump is widely used in papermaking industry. The application of Roots vacuum pump in dehydration process has good performance. If you want to know more about roots vacuum pump, please contact us at any time.

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