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By: Chuck Wells and Don Harroll

Purpose:

The purpose of this paper is to presentfor implementation throughout aapplications presented: Generic Energy Management Module, Motor Condition Monitoring Module, Transformer Condition Monitor Module, CEMS module, a

Executive Summary In accordance with Energy Management savings applications definedModules, below is the list of energy reduction applications

• Assist in module design approach for setting up anprovide rapid energy consumption awareness.

• Assist in module design approach using PI’sMills and Kilns (One MDB object)

• Assist in module design for development of system.

• Assist in module design for transformer condition monitoring and alerting

• Assist in module design for CO control system for Kilns

• Assist in module design for CEMS system

• Assist in running parallel projects to get value

• Implement Batch tags for each cement type for use in tracking quality

• Reading energy data from this example plant’s

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Chuck Wells and Don Harroll

purpose of this paper is to present several energy management and emissioimplementation throughout a Cement Producer’s enterprise. There are five

: Generic Energy Management Module, Motor Condition Monitoring Module, Transformer Condition Monitor Module, CEMS module, and Kiln Combustion Control.

Summary:

ance with Energy Management savings applications defined by using OSIsoft PI Modules, below is the list of energy reduction applications.

module design approach for setting up an energy management infrastructure to provide rapid energy consumption awareness.

module design approach using PI’s ACE based Energy Management System for Mills and Kilns (One MDB object)

for development of electric drive motor condition maintenance

for transformer condition monitoring and alerting

for CO control system for Kilns

for CEMS system data analysis and reporting

projects to get value as soon as possible

lement Batch tags for each cement type for use in tracking quality performance.

Reading energy data from this example plant’s ION OPC server

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ons related systems suitable basis energy savings PI

: Generic Energy Management Module, Motor Condition Monitoring Module, nd Kiln Combustion Control.

by using OSIsoft PI

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performance.

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Introduction Large amounts of electricity and fuel are required for cement manufacturing. Five percent of worldwide Green House Gases are from Cement Manufacturing; hence, there is an opportunity to reduce both energy consumption and green house gas emissions. We review each task below, and recommend specific action plans utilizing various PI modules.

Energy Infrastructure One of the key success factors in energy management is the implementation of a consistent database infrastructure across the enterprise. This includes tag naming conventions that make it easy for data users to find and create visualizations of energy consumption data. We find that companies using this approach reap large energy savings simply by making energy and power information available to a wide range of internal users. Our example is already taking this approach using the ION system. We suggest that these data along with other plant energy data be consolidated in a corporate PI server and made available via web browser. The data displayed include both electrical energy and fuel consumption on a plant by plant basis as well as a single metric for each plant in terms of energy consumed per tonne of each product produced. This basic metric will highlight low performing plants and help identify specific areas where improvements will be cost effective. As outlined in the sections below, energy metrics will be computed in a consistent unit system, specifically the SI (International System of Units). One method to accelerate the visualization of energy consumption was to create a set of standard PI ProcessBook and DataLink views of the raw power data. The most common view is a daily trend of power consumption. This often shows simple excess usage of power such as early startup or late shutdown of unnecessary equipment including lighting and air conditioning.

Energy Management Module (Major energy consuming processes)

The example company produces at least 20 million tonnes of clinker based products per year. The electrical energy consumed in cement production is approximately 110 kWh/tonne, and around 40% of this energy is consumed for clinker grinding. About 95 percent of the electric power is for grinding raw and finished product. This means the electric power consumption is about 2,090,000,000 kWh or at a cost of $.05/kWh a total of $104.5 million per year in electric power. We believe that focusing on monitoring and then reducing the electric energy consumption associated with clinker grinding should be the first priority. The next area is in grinding of raw material. About 32 percent of the electricity is consumed in grinding limestone, followed by about 21 percent in blending and cooling. All plant processes consuming electric power will be reviewed.

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The next process is the Kiln combustion control system itself that includes both fossil fuel consumption and electric power. We recommend that all three processes be monitored in real time using a single MDB data structure and a single ACE program. This will reduce software lifecycles costs and creates a common method of benchmarking variations among all of the groups cement production plants. The first step is to simply identify all energy tags associated with the process and trend these in module referenced ProcessBook displays. This provides instant visibility of the power consumption. Another action is to optimize conventional cement clinker grinding circuits and in the last decade significant progress has been achieved. The increasing demand for “finer cement” products, and the need for reduction in energy consumption and green house gas emissions, reinforces the need for grinding optimization.

Grinding:

� Clinker grinding

Clinker grinding is the most energy intensive process in the manufacture of cement. We will focus on the Clinker grinding module in detail, but the analysis applies all grinding operations. A typical ball mill is driven by about 1500 horsepower motors and is rated at 30STPH. The vertical mills occupy less space and typically consume less power as shown in Table 1. Estimated ball mill operating costs per day: 42.4 kWh/t * $0.05/kWh * 30 t/h *24 h/d = $1526/day electricity costs per mill.

Check: 1500 hp *0.7456 kw/hp * 24h * $0.05/kWh = $1342/day electricity cost for 1500 motor, so the remaining power is expended for the air fans.

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A Grinding Module has been developed and re-used throughout all facilities. The first application is for clinker grinding, since this is the most energy intensive process in the plant. This module preferentially measure input and output flow of both material and energy. The energy contribution is provided in three forms: (a) electrical power, (b) heat and (c) combined energy converted to a common unit such as Joules. There are two forms of energy involved with grinding that can also be combined into a single common metric:

• Heat

• Electric power

• Combined energy A heat balance can be written around the grinding operation. This includes latent heat associated with the inbound cooled clinker, the frictional heat created in the process, losses due to convection, radiation and conduction, and the heat leaving the process in the finished product. Basic measurements suggested include:

• Material inflow rate

• Inflow temperature

• Material outflow rate

• Airflow rates for the classifiers

• Outflow temperature

• Outflow product quality (lab data, particle size distribution, chemistry etc.)

• Real power to all electric motors in the grinding circuit

• Reactive power to all electric motors in the grinding circuit

• Power factor for the positive sequence and each phase

• Zero sequence voltage, current, phase angles. Suggested Energy Performance Indicators (EPI):

• Latent heat/MT

• Energy/MT

• Power/MT

• Total energy/MT

• Torque/MT burden Computation of torque

ω

τP

9549=

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P is power in kW, ω is rotational speed (RPM),τ is torque in Joules (Nm or J) The torque should be trended as well as the estimated burden in the mill. Then a new energy metric could be computed by normalizing torque by the mill burden. Thus the units would be J/kg... Alarms definitions for:

• Deviations above or below each of the metrics outlined above.

• Specifically, we recommend sending SMS alerts to key supervisory personnel in the mill when certain ranges of power quality are exceeded. For example

• Power factor

• Low voltage

• High voltage

• Zero sequence alarms For each grade of cement manufactured, the EPIs should be constant. If the plant makes more than one grade of cement we suggest setting up Batch events for this. This will help establish the nominal values for the performance metrics associated with each grade. Specifically, the amount of energy expended per ton of a specific product should have a constant mean value with a Gaussian random variation about the mean. The SQC charts tests this hypothesis and shows the results graphically. A sample chart is shown below:

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This shows a range chart, showing the distribution of difference between the maximum and minimum values between successive samples A moving average chart is shown below:

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This chart shows the moving average SQC chart. And the following chart is a moving x-bar chart.

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In each of these cases, SQC alarms are emitted when limits are exceeded. The alarms are shown below:

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A typical combined Energy Performance Index display might look as shown below:

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. We also recommend adding spectral analyses to the grinding module This is a function offered as a PI interface. It will compute the Fourier Transform of the “torque” on each mill. This is to show the effects of circulating loads in the grinding circuit. An example of a typical analysis is shown in the Figure below:

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The bar chart for example shows significant build up of energy at 0.093 Hz (5.58 cycles per minute)

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This shows that the energy peak has moved from 0.093 to 0.107 (6.42 cycles per minute).

Fuel consumption (Kiln Combustion Control)

The cost of coal for firing cement kilns is a major component in the overall manufacturing cost of cement: typically 0.1 ton coal/MT clinker with total CO2 emissions of 0.7 MT per ton of clinker. For this example:

� “The total volume was approximately 20 million metric tons —including more than 17 million metric tons of cementitious materials”

� Plus reduction in fuel costs of one percent – 0.1 ton coal/tonne clinker = 1.7 million tonnes

• Savings = 170,000 tonnes per year at $25/tonne • = $4.25 million per year fuel savings

This suggests a major program to improve fuel utilization (combustion).

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� Combustion improvement

One method of improving fuel utilization is to burn the coal at the optimal ratio of fuel to air. The basic principal is to gradually reduce the combustion air until the CO in the exhaust rapidly increases. At this point, one would add just a small amount of air to keep the combustion process safe. A typical example of the phenomena is shown in the following figure. Notice that as the excess oxygen is reduced the production rate also increases. At certain point, the exhaust gas contains too much combustible material and becomes unsafe. In order to implement such a system, additional instrumentation is required. These include gas velocity profile, concentration of O2 and CO. It is difficult to keep such instrumentation reliable and available in such a hot dirty environment. However, we believe that the technology recently demonstrated by TVA in large coal fired boiler applies directly to Kiln control systems. These systems, developed by EPRI and demonstrated at several TVA plants, clearly show that the measurements can be reliable and used for closed loop control. We suggest instrumentation be added to a Kiln system and that these sensors be connected to a PI system. It is also suggested that CO2 be measured at the same point. The use of this measurement is discussed below. Basically need the following:

• Gas mass flow measurement (multipoint array)

• CO from short coupled extractive system

• CO2 from short coupled extractive system OSIsoft owns a pending patent on CO control of combustion processes. This technology may be useful for any cement producer. The measurements are difficult, but based on the EPRI results; we suggest

producers implement a prototype and when successful, then deployment is to the remaining plants. To do this the following information is needed:

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• Gas velocity profile across the duct

• Temperature profile across the duct

• O2 profile across the duct

• CO2 profile across the duct.

• Dust loading across the duct. Based on this information, we can determine if the EPRI measurement system will suffice for Kilns.

� Carbon credits

Cement manufacturers generate 5 percent of all greenhouse gases world wide. Sixty percent of the CO2 emitted is from the calcining process and nothing can be done to reduce this except perhaps sequestration, which will be expensive and is unproven. However the remaining 40 percent can be used as the basis for voluntary carbon emission reductions. (VER)

� 0.7 tonnes CO2 per MT (40 percent due to fuel) � = 4.76 million tonnes due to fuel � One percent savings

– = 476,000 MT per year � Price of Carbon CER = $20 EU

– = $9.52 million $EU per year earnings The example enterprise can earn nearly $10 million per year by improving the combustion of coal in Kilns. This income stream is available for 21 years after initial approval by the United Nations.

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Transformer Condition Monitoring

� Power quality

Most power disturbances come from within a facility itself, such as large loads turning on simultaneously, improper wiring and grounding practices; however disturbances can also come from the transmission grid. Monitoring of incoming power can be used to: • Evaluate incoming electric supply and distribution throughout the facility to determine if power quality disturbances or variations are impacting, or have the potential to impact, facility operations and/or manufacturing processes • Provide a baseline for establishing predictive maintenance activities and avoiding interruptions of critical business activities • Optimization of power mitigation equipment using a reliability- or condition-based monitoring approach. Power parameters can be correlated with process performance and output to locate production defects caused by poor power quality. • Reduction of energy costs by comparing actual energy usage versus the bills from the Utility company. Electric motors are sensitive to power quality problems such as unbalance and harmonics, and can produce sags for other equipment on the circuit. When a motor is first energized, a large inrush of current results, typically 6-10 times the normal steady state current running levels. This large current change results in a significant voltage drop across the source wiring impedance and the resulting sag leaves less voltage remaining for the loads connected to the same circuit. Power monitoring systems are used to observe these inrush conditions associated with start-up, as well as to provide critical information on voltage irregularities, one of the factors attributed to motor failures. Incoming power quality can have a direct impact on motor performance. For example, under-voltage and over-voltage conditions can cause rapid heating in the windings, shortening their life. Transients can trigger failures in the winding insulation, while harmonics from nearby equipment can contribute to overheating of the windings. Unbalanced voltage conditions between phases will result in increased current flow and overheated windings as well.

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Power monitors are used to baseline incoming power, identify any conditions that might contribute to motor failure, trend parameters that could lead to long-term degradation, and provide data to reduce energy consumption.

� Specific measurements

Install power monitoring equipment on both the high and the low side of the incoming transformer (substation). The data will be continually analyzed by a PI Module and associated Module referenced display. This display will include:

• Positive Sequence Voltage Flicker

• Positive Sequence Current Flicker

• Zero sequence voltage and current

• Negative sequence voltage and current

• Voltage and Current each phase

• Power factor each phase

• Real, Reactive and apparent power in each phase and in the sequences

• First 50 harmonics in each phase voltage

• First 50 harmonics in each phase current

• Addition performance metrics as provided by the power monitoring equipment. The display will contain the following types of objects:

• Trends of voltages (PS, NS, ZS, and A,B,C phases)

• SQC on voltages

• SQC on power factor

• X-Y plots of phase angles (real and imaginary components)

• X-Y plots of real and reactive power

• Flicker trends on current and voltages

• Flicker alarms

• Voltage Alarms.

• Power duration curves (percent of time power consumed > x) The SQC functions will be performed on the server side, with the display of information in PI ProcessBook. These displays may be converted to ERP display view or RtWebParts for use across the enterprise on thin client devices (laptop, desktop, or mobile devices). Additionally, the system will compute the complex impedance between the primary and the secondary coils. This is done using the complex voltage and current signals from the PMUs measuring power quality.

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Continuous Emission Monitoring System: CEMS Pi can also be used as a common CEMS reporting system across the enterprise. This is possible using PI MDB and ACE modules. PI will provide real-time traditional measurements from the stack that can include: gas velocity and pollutant concentrations including SO2, CO2, NOX, particulates (PM10 and PM2.5), moisture and temperature. Some weather data may also be available. The CEMS module would hold many different variables that are traditionally required by the Air Quality Boards. These typically include moving averages of concentrations of emitted gases, mass flows of pollutants, hourly and daily statistics, etc. These will be configured by changing values of the parametric properties of the module.

Motor Condition Monitoring The PI FFT module is used to monitor the condition of large electric motors. This will compute the FFT in real time and alarm on abnormal spectral features. The primary variable would be watts or MJ/tonne. More than likely the mass flow of material being moved by the primary drive motor may not be available, so the motor watts or amperage would be the variable used as input to the FFT. The spectrum is stored as well as its key features such as peak locations, heights, widths, and the areas under the spectral curve. The condition of the motor will be determined by the shape of the spectrum of the power draw of the motor. The sampling rate for watts should be at least once per second.

Conclusions: It is possible to for each plant to pursue the following tasks in parallel with adequate resources using the afore mentioned PI modules:

• Provide the development of an ACE based Energy Management System for Mills and Kilns (One MDB object)

This energy application includes the design of a single MDB class object that contains a full

complement of alias and properties such that a single ACE program would compute a consistent set of energy metrics independent of the process.

• Provide the development of Electric Drive motor condition maintenance system. This project includes the design of a single MDB class object that contains a full complement

of alias and properties such that a single ACE program will compute a consistent set of energy metrics independent of the process. The project will include computing FFT is either power or current flow to the key motors.

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• Provide PI data for transformer condition monitoring and alerting This project includes the design of a single MDB class object that contains a full complement

of alias and properties such that a single ACE program could compute a consistent set of energy metrics independent of the process. Two power quality meters will be used to compute the complex impedance across the coils and alarm on abnormal conditions.

• OSIsoft can provide application guidance for CO control system for Kilns This project includes the design of a single MDB class object that contains a full complement

of alias and properties such that a single ACE program would compute a consistent set of energy metrics independent of the process. This will include computation and sending set point change signals to the DCS

• PI will provide for monitored data and reporting for all CEMS systems This project includes the design of a single MDB class object that contains a full complement

of alias and properties such that a single ACE program could compute a consistent set of energy metrics independent of the process. This will include interfaces to the CEMS system installed in the stacks and a general purpose calculating engine for emission reports.

• Implement Batch tags for each cement type run for use in tracking grade performance. These will be added to track cement types.

• Investigate reading energy data from this example plant’s ION OPC server This is done to collect energy data in the PI servers. The bottom line is OSIsoft’s PI System has a host of modules that are being utilized for significant energy savings. With over 14,000 installations of the PI System globally, there are numerous industries using it specifically to reduce energy costs, implement condition based maintenance and emission reduction.