Recently, the "low temperature and low pressure" technology is quietly popular in the domestic paperboard industry. The maturity of this technology will bring another technological revolution to the productivity of domestic paperboard enterprises. At present, some domestic cardboard enterprises act as pioneers and dare to try, and take the lead in applying "low temperature and low pressure" technology in daily production. So, what exactly is "low temperature and low pressure" technology? In addition, in the production of cardboard, how much steam pressure should be configured to meet the "low pressure" technology?

Status: The domestic application of low temperature and low pressure technology is not optimistic

Some industry experts have visited several domestic cardboard companies that have successfully used "low temperature and low pressure" technology, but it is obvious that the actual application of "low temperature and low pressure" technology is not optimistic, such as tile line design and actual production conditions are not optimistic, resulting in product The quality is also inconsistent. In addition, it was also found that when the tile line runs for a period of time, the steam pressure must return to the previous high pressure to produce.

Compared with Europe and the United States, there may be three major problems in my country's low temperature and low pressure technology

The expert visited a number of cardboard companies in developed European countries on low temperature and low pressure technology. Through exchanges and learning, I have a basic understanding of the high and new technologies currently mastered by foreign cardboard enterprises, and there is still a deviation from the concept of "low temperature and low pressure" proposed by domestic cardboard enterprises in my country, which is debatable. To this end, the author shares the following experience with colleagues in the industry:

Control the temperature of each layer of paper and cardboard, and control the temperature of low and high textures

Domestic high-speed tile lines generally use the "anti-bending system" program. By detecting and controlling the temperature of the cardboard at each key point of the tile line, it ensures that the temperature of the cardboard after exiting the drive wheel is controlled within a reasonable range, so that the cardboard is flat and not easily deformed. Therefore, we need to control the temperature of each layer of paper and cardboard, and control the temperature of low texture and high texture.

It is reminded here that the heat requirements of three-layer and five-layer cardboard are different. If a uniform "low pressure" value is used to produce cardboard, the heat supplied by the tile line cannot meet the heat demand of cardboard production.

The steam pressure of each part is not a uniform "low pressure" value

The author looks at the steam pressure situation of each part of the tile line provided by foreign countries, and finds that the distribution of its steam pressure is also focused. For example, for a tile line with a width of 2500mm and a vehicle speed of 350m/min, the steam pressure of the main steam pipeline is 14kgf/cm². The pressure distribution is roughly as follows:

(1) High quantitative cardboard, double-sided machine hot plate pressure 10-12 kgf/ cm². Corrugated stick pressure 8 kgf/cm². Preheating cylinder 4-6 kgf/cm

(2) Low quantitative cardboard, double-sided machine hot plate pressure 6-8 kgf/ cm². Corrugated stick pressure 6 kgf/cm². Preheating cylinder 2-4 kgf/cm

From the pressure distribution table, we can see that the amount of steam supply pressure is also different depending on the ration of cardboard. Therefore, in the production process of tile line, the steam pressure of each part is not a uniform "low pressure" value. Especially for the tile line parts that require "high pressure", "high pressure" production is still required. Only in this way can the efficient production of tile lines and the quality of cardboard be ensured.

Don't blindly follow foreign experience

To a certain extent, for a high-speed tile line with a speed of 300m/min, such a steam pressure supply is indeed a "low pressure" for us, but we can't follow it blindly.

The author analyzes the main reasons as follows:
<1> The tile rollers and double-sided machine hot plates equipped with foreign high-speed tile lines are all peripheral heating types. Compared with our domestic cavity-type heating vessels, their thermal efficiency is high and the temperature conversion is fast, which we cannot imitate.

<2>In order to meet the heating temperature of cardboard, each heating container of foreign tile line has implemented automatic adjustment of steam pressure. At the same time, a lot of arc heaters are installed in key parts for heat compensation, which is easy to ignore.

<3> The adhesive process and raw materials used in foreign cardboard factories are also quite different from ours. They use wheat starch, and the gelatinization temperature is generally controlled at about 53 degrees Celsius, while we generally use corn flour or tapioca flour, and the gelatinization temperature is between 56-60 degrees Celsius.