Pulp and Paper Industry Electrical Developments R. R. B A K E R

A S S O C I A T E A I E E

EL E C T R I C A L D E V E L O P M E N T S have contributed materially to the efficient operation of pulp and paper

mills throughout the United States. This can be appre-ciated readily when consideration is given to the extensive use of power throughout the industry. In the year 1947, the industry required some 14 billion kilowatt-hours to produce 21 million tons of paper.

To obtain high quant i ty production it has been necessary to mechanize the industry. Mechanization has been carried to a point where each productive worker utilizes some 15 horsepower in power-driven equipment in pro-ducing some 800 pounds of paper per day. This is 2.3 times the national average of 6.5 horsepower per worker.

The paper industry, unlike other industries, generates the major portion of its total power requirements, actually 70 per cent as compared to a national average of only 30 per cent. The extensive use of process steam required in cooking pulp and drying paper together with the de-velopment of the modern bleeder-type turbine unit and the high pressure and temperature boiler plants permit developing a large portion of the total energy requirements as a by-product of the process steam.

Power is distributed at generator voltage, usually 2,300 volts, to the various load centers where it either is applied directly to the large motors or where it is transformed to lower voltage for application to the smaller motors. The industry has taken advantage of dry-type transformers suitable for indoor location for this service. In power

Digest of paper 48-115, "Electrical Developments in the Pulp and Paper Industry," recommended by the AIEE general industry applications committee and approved by the AIEE technical program committee for presentation at the AIEE summer general meeting, Mexico, Federal District, Mexico, June 21-25, 1948. Scheduled for publication in AIEE TRANSACTIONS, volume 67, 1948. R. R. Baker is paper mill application engineer in the industry engineering department of Westinghouse Electric Corporation, East Pittsburgh, Pa.

Figure 1. Two 7,500-kw bleeder turbines (operating at 550 pounds per square inch) in the power plant of a large kraft pulp and paper mill where full use is made of by-product power

generation

distribution metal-clad switchgear affords the advantages of factory built and assembled equipment with all com-ponent parts properly co-ordinated. Such equipment is available with either air-break or oil-break switches and its use results in minimum operating costs. Control centers for both high- and low-voltage mill motors are being applied extensively in the modern mills. Such equipment has the advantage of factory built and as-sembled equipment with a co-ordinated design resulting in low operating cost.

In the utilization of electric power full advantage has been taken of the recent developments in both electronic and rotating regulators. Electronic regulators have been developed for use with sectional paper machine drive which provide the extreme sensitivity required for accurate control together with the inherent feature of electronic circuits which results in a maintained accuracy of per-formance without other than routine maintenance.

The Rototrol, a form of rotating regulator as supplied by one manufacturer, provides an accurate regulating device which has been applied to control numerous func-tions in the paper mill, materially improving the operating performance.

Drives also have been developed to meet the special requirements of new process equipment. Many of these drives are fully automatic and a minimum amount of supervision is required in their operation. With these drives automatic regulators accurately maintain quality control of production.

In the pulp and paper industry the efficient generation and distribution of electric power together with its effective use have contributed materially to a high-quality low-cost product meeting the demands of an ever expanding market

Figure 2. A 1,500-horsepower 277-rpm synchronous motor built for direct connecting to full-log chipper

Both the electrical design and heavy mechanical construction of the motor contribute to low-cost high-quality chip production

SEPTEMBER 1948 Baker—Pulp and Paper Industry Electrical Developments 883