Integrated mills

For various reasons, including financial ones, the United States was slower than Japan and Europe to install continuous slab casters for the production of sheet. Electric melters cast billets continuously from about 1975 onward. Casting was done cmdely at first but the sophistication increased rapidly, culminating in the operation of a thin-slab caster at one of Nucor s plants. This opened up another avenue of attack on sheet markets, once the province of integrated mills. 

FIGURE 21.3 Simplified flow diagram of an integrated mill. (Taken fromU.S. EPA, Profile of the Pulp and Paper Industry, 2nd ed., report EPA/310-R-02-002, U.S. EPA, Washington, November 2002.)... 

The major sources of pollutant releases in pulp and paper manufacture occur at the pulping and bleaching stages, respectively. As such, nonintegrated mills (i.e., those mills without pulping facilities on site) are not significant environmental concerns when compared to integrated mills or pulp mills. 

Figure 16.24. Air-lift dryer with an integral mill...

One of the problems seen when sizing with rosin at pseudo-nentraT pH is the loss of sizing from the natural rosins in unbleached pulp, especially in integrated mills. This natural rosin can often contribute positively at pH 4.5-5.0, but as it is not modified in any way it loses its effectiveness at higher pH. 

The solution to the problem of soluble trash is fairly simple, especially with an 694 integrated mill. Careful control of the washing of the pulp will reduce the soluble 695 trash to reasonable levels and obviously reduce the problem. For non-integrated 696 mills, control of pulp quahty is important but pulp pre-treatment with cationic 697 polymer or ATC is often employed as a pulper additive. 698... 

Direct or Mill. A vertically integrated mill prints its own greige (uncolored, prepared for print) fabric for wholesale to textile cut, make, trim (CMT) product manufacturer. 

A much improved ORC-process can be obtained with heat recovery steam (HR-steam) from the TMP-steam reboilers. An integrated mill with a TMP-plant combined with a paper machine is taken here as an example. Paper grade is newsprint with a basis weight of 40 g absolute dry web/m. With a machine speed of 1700 m/min and a sheet width of 10 m the production of paper is 12.3 kg/s air-dry paper with 92 % dry solids. The paper... 

Conventional heat recovery from paper machine exhaust air streams can be designed optimally with respect to the climate at the mill location and the type of drying process involved. Different heat pump types can be applied, for example absorption heat transformers, to elevate the stream temperatures above the temperature of the excess heat. In an integrated mill with impingement drying the eventual excess low-pressure steam from the TMP-heat recovery, before or after the reboilers, can be utilised in an organic Rankine cycle for production of electrical power. The next step is to study the design and economic aspects of different types of ORC-plants. 

The objective of fiber stock preparation systems is to modify the different ingoing raw materials in such a way that the finished stock finally supplied to the paper machine suits the requirements of the paper machine and of the quality demands put on the produced paper or board. The raw stocks used are the various types of virgin pulps as well as recovered paper grades. They are available in the form of bales, loose material or, in the case of integrated mills, as suspensions. The finished stock is a suspension of defined quality as far as the mixture and characteristics of the fibers, additives, and impurities are concerned. This quality essentially determines paper machine runnability and is the basis for the final paper and board quality. 

---