Press felts cleaning in a paper machine

Chemical press felt cleaning in the press section

The batt-fibers act as a type of filter and retain impurities from the production process. This is unavoidable, but such soiling can lead to a variety of problems. In most cases, these relate to a loss of paper quality. Sheet stealing is another negative side effect: Press dewatering can deteriorate, which leads to an upward trend in the number of sheet breaks. Increased vacuum in the suction rolls and boxes leads to higher energy consumption and felt wear. Should these problems become acute, the only solution is a felt change. The resultant additional shut downs naturally result in production losses. Today, chemical press felt cleaning is indispensable for paper makers.

Energy saving in paper making process

In 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.

The Manufacturing Process Of Paper Machine Clothing

What is paper machine clothing?

Paper machine clothing are used in the whole paper making process to help to make paper, including forming, pressing, drying process.

Forming:

A sheet of paper begins in the forming section, and in this section, a mixture of 99% water and 1% cellulose fiber is introduced evenly across a forming fabric. Thereby the polyester forming fabric acts as both a sheet conveyor and a dewatering device.

Pressing:

In this section, additional water is mechanically removed from the newly formed sheet and the sheet is carried continuously by a large press fabric between two rolls, where our press felt acts as a sheet conveyor and a press filter belt.

Drying:

In the dryer section, the paper sheet travels around large diameter heated cylinders, where the balance of the water is removed by evaporation. Polyester dryer fabrics hold the sheet tightly in contact with the cylinders through the dryer section.

Paper Making dryer clothes or dryer screen

The dryer clothes or dryer screen or felt has a significant function in the dryer part. Synthetic dryer cloth or fabric is also recognized as conveyor belts.

When paper web exceed press section of a paper machine, it contains more than half of its weight is water. Most of this water of the paper web should be removed in the dryer section of the paper machine to ensure 4%-6% of final water content. The drying section is one of the most energy consuming parts (about 60%) of the paper machine. Consequently the role of dryer clothes or screen is absolutely enormous.

Function of dryer screen:
The dryer cloth presses the paper web against the surface of steam-heated drying cylinders. Therefore the temperature of the paper web increases and water is evaporated into and through a porous dryer screen. Moreover dryer clothes assist to support the paper web to shift from one cylinder to another cylinder. Dryer screen controlled paper web shrinkage.

Paper making wire cloth or forming fabric

Wire cloth or forming fabric is a very important for a paper machine in a paper mill. In general formation of paper depends on wire cloth and refining of paper pulp. Paper machine wire cloth (forming fabric) made from polyester or poly-amide mono-filaments. To shape an uninterrupted belt, it is made by endless of a seam. During woven of wire cloth, filaments are composed of paper machine direction and paper machine cross direction. The filaments of paper machine direction or lengthwise are called warp. One the other hand the filaments of paper machine cross direction are called weft or Shute or filling. The construction of wire cloth depends on some weaving variables such as pattern, mesh, yarn, diameter, degree of crimping etc. Mesh is very important for a wire cloth (forming fabric). Water drainage and retain of fibers are depends on it.

According to the category, wire cloth (synthetic forming fabric) can be divided into single layer wire cloth, 1.5 layer wire cloth, double layer wire cloth, two and a half layer wire cloth, triple layer wire cloth and 3.5 layer wire cloth. In accordance with weaving, wire cloth (forming fabric) can be divided into 2-shed, 4-shed, 5-shed, 7-shed, 8-shed, 16-shed, 24-shed etc. A paper machine wire cloth has two surfaces. One is the forming surface or top surface and another is the wearing surface or underside surface.

Depending on paper machine and various paper grades wire cloth also difference. The uses of double layer wire cloth (forming fabric) is increasing day by day. 

Source: pulppapermill.com

FORMING FABRIC CLEANING

Modern paper machine clothing is manufactured with a specific set of design and quality specifications for each paper machine’s performance requirements. Such specifications, i.e. surface characteristics, open area, void volume, permeability, smoothness, etc. are engineered to achieve specific goals in the papermaking process. The need to implement an effective PMC cleaning program has become increasingly crucial in recent years. This change is primarily due to increasing levels of recycled furnish, faster machine speeds and accompanying technology, elevated sheet quality requirements, and the desire for longer fabric life. Forming fabrics must be kept free of contaminants in order to maintain surface characteristics, adequate open area, and to prevent sheet marking.