Paper Machine Influence on Industrial Energy System

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May 20 1 0,Volume 4,No.5(Serial No.30) Journal of Energy and Power Engineering.ISSN 1 934-8975.USA 辩kI!IHtN ̄ 

Paper Machine Influence on Industrial Energy System 

A.Hazi and G.Hazi Department ofPower Engineering,“Vasile Alecsandri”University ofBacau,157,Marasesti Street,Bacau 6001 15,Romania 

Received:January 6,2010/Accepted:February 9.2010/Published:May 3 I,2010 Abstract:In this paper,the influence oflow power factor on electricity system and the influence ofpaper breaking on heat system are presented.For that,a mathematical model and a case study for a paper mill are realised.The electric mathematical model is based on the 

relations of energy losses in cables and in transformers as a function of power factor.The thermal mathematical model includes 

characteristic energy and efficiency of boiler depending on its load.Characteristic ofefficiency is modeled by a quadratic dependence 

between foeI consumption and steam flow.In the case,study were estimated to reduce energy Iosses for factor neutral f0.921 against 

real power factor(O.75)for the electrical scheme ofa paper machine.Analytical expression ofthe boiler characteristic and variation of 

boiler efficiency depending on its load were estimated.too. 

Key words:Power factor,energy losses,efficiency of boiler,energy system,paper machine 1.1ntr0ducti0n The papermaking process is the most energy intensive and consumes,about 45%oftotal energy use. Energy use reduction can provide cost savings,often with low capital investment. The main energy forms that are needed in the production process are electricity,steam,water and natural gas[1】. Flow of reactive power adversely affects operation of distribution network from two important reasons: (1)Increasing active power losses due to increasing absolute values of currents. (2)S ignificant increase of voltage fall in the network Paper machine has a large number of asynchronous engines that operate with low power factor,especially when they work with low load.The power factor is low and electricity losses on the cables and on the transformers are high.Increasing the power factor CaB be done by installing capacitor batteries,which generme reactive power required by the consumer or by j udicious choice of asynchronous engines rated in the 

Corresponding author:A.Hazi,Ph.D.,professor,research fileds:thermal installations,energy generation,electrical substation and energy efficiency.E—mail:ahazi58@yahoo.corn. 

sense approach and rated engine.If power factor is maintained at neutral value,energy saving can be realized. Some installations that consume heat have a constant regime and another have a variable regime imposed by technological process.Regime of technological installations determines regime ofthermal power plant. Drying is the highest energy consumer,requiring large amounts of heat(steam)to evaporate water from paper or paperboard.In the machine,operating appears paper breaking when steam consumption of the dryer cylinders is cutting down automatically.Load of the steam boilers must be reduced correspondingIy.But, these breaks are often repeated and determine a variable regime of the steam boilers,and its efficiency decrease.Thus.more fueI is consumed for steam generation. 

2.Energy Supply System of Paper Machine Electrical energy is used to drive the paper machine, pumps,ventilating fans,etc.on medium voltage or on low voltage. The steam is used on different locations in the paper making process.The steam flow in the paper mill is Paper Machine Influence on Industrial Energy System coming from the combine heat power(CHP)plant oil low pressure.The CHP plant delivers electrical energy, too.When the CHP plant produces too little electrical energy,the difference will be brought from the public grid on high voltage.Transformers on 1 1 0/6 kV and on 6/0.4 kV are used usually.The diagram of the energy flow is presented in Fig.1. 

3.The Mathematical Model To study paper machine influence on power system, a mathematical model is developed. Induction motors are used to drive pumps and fans of water and air circuits of the paper machine.This leads to a low power factor.To highlight the influence of machine operation with a low power factor on power system,we calculate energy losses in cables and transformers depending on power factor. Maximum apparent power,S(cos ̄p)in kVA,is a function of power factor[21: S(cos )=P・COS [kVA】 (1) Where,P is the maximum active power during T,in kW;T during analysis,in h/year;cosq)is a power factor. Maximum current,l(cosq ̄),is: