Flue gases content measurement after electrostatic precipitators

Transcription

1 Flue gases content measurement after electrostatic precipitators LUCICA ANGHELESCU LUMINITA, POPESCU MIHAI CRUCERU Department of Automatic, Energy and Environment University Constantin Brancusi of Targu Jiu No.30 Eroilor St., Targu-Jiu, ROMANIA Abstract: One of the most important problems of the modern age is the air pollution. To reduce pollution must perform emission measurements, namely measurements of particulate emissions discharged to cart smog. This measurement is performed using special equipment called opacimeter measuring dust content of flue gases by electrostatic precipitators. Key-Words: particulate emissions, electrostatic precipitators, particle concentrations, flue gas. 1. Introduction Measurements of particulate exhaust emissions from the chimney of the boiler no. 3 from CE Rovinari include two aspects: - continuous measurements carried out by means of special devices known opacimeter measuring the dust content in the flue gas by electrostatic precipitators; - measured by the performance tests. Rovinari lignite composition is as follows: C i = carbon content of 23,15%, hydrogen content: H i = 2.17%, sulfur content of fuel: Sc i = 0.93%, oxygen content: O i = 9.36%; nitrogen content: N i = 0.6% total moisture: WTI = 43.78%, ash: Ai = 20.01%). 2.Continuous measurement content by electrostatic precipitator To measure the dust by electrostatic precipitators particle analyzer is used SC600. The analyzer is designed to accurately monitor and record the particulate emissions. SC600 provides facilities for monitoring range and is able to perform calculations; all functions are accessed and operated by means of control keys. The device can be calibrated to display the emissions of particulate mass concentrations (mg/m3). SC600 analyzer contains three main components: - the transmission unit; - receiver unit; - control unit. SC600 processor uses advanced technology in addition to the measured particle concentration can generate alarms when limit values are exceeded allowable emissions. The name comes from opacimeter measurement principle: SC600 uses the principle of optical scintillation by monitoring changes in light received from a beam transmitted through the flue gases. This variation is due to the opacity of the flue gas (particulate matter in the flue gas being monitored). This method is effective because measurements are not affected by dirt on the lens unit. The response unit is therefore directly related to the concentration of particulates in the exhaust gas. The system can be configured on a single measurement channel and to the four measurement channels. For channel is used extension module. Figure 1.a is shown configured on a single channel system and figure 1.b 4 channel configured system. Transmission and reception unit are mounted on one side and the other side of the track that is made monitor emissions of particles, so that the light beam emitted by the transmission unit to reach the receiver unit (see Figure 2). Transmission and reception unit are mounted by means of flanges. The transmitter is positioned by means of an alignment unit for the adjustment of the beam direction thereof. Both units are equipped with instrument air purge fittings. In Figure 2, the notations have the following meanings: 1. flange 2. air purge fitting 3. intermediate body (incorporating purge air diffuser) 4. housing 5. cable gland ISBN:

2 The control unit (Figure 3) contains the microprocessor and memory circuit for storing the measured values. Operation of the system is achieved by means of menus that are displayed in textual or graphical display. Sizes are accessed and selected by using the arrow keys and menu. A liquid crystal display and two menu keys provide reading alphanumeric data acquired. I added two LEDs (green for voltage presence and red alarms). Menu keys are typically used to access menus saved. Menu buttons below the screen and choose from within a screen controls that appear at the bottom of the image in two boxes corresponding to these keys. The most common use of the button on the right (but not exclusive) is in connection with the selection function (SELECT). The most common use of the button to the left (but not exclusive) is in connection with the position of abandonment (QUIT). SC600 has four arrow keys (+), (-), L (left = left), R (Right = right). These keys are used for framing options menu or to change values of some parameters. Depending on the function selected, the instrument setting values can be changed by selecting the user with a complete set of letters, numbers and characters. At any time, pressing LEVEL will be able to view the particulate emissions. The control unit can be connected to a PC via a serial port. Figure 3 notations have the following meanings: - display - arrow keys - right menu button - left Menu key - emission display key level - alarm LED (red) - led power supply (green). The expansion module is a device that interfaces of optical signals from the measuring channels 2, 3 and 4 to the control unit. Comes with ma isolated outputs per channel and auxiliary inputs on each channel. The module is constructed to be mounted at one meter away from the control unit. Particle analyzer SC600 has two software packages for advanced data analysis: - EPA REPORTER package that allows downloading and analysis. It facilitates the graphical or textual reports over a period of time; - PREDICT package that allows detailed analysis of the performance of electrostatic precipitators. This gives an assessment tool lifetime to a stop for maintenance. In Figure 4 application screen is presented PREDICT. Measuring signals are transmitted particle concentration and continuous emission monitoring system to basket whose screen is shown in Figure 5. You can view the content of particles ("dust") currently, the average half-hourly or daily average. Also, continuous emission monitoring system to basket (CEMS) may issue reports emissions (printing of tables with daily averages or monthly averages). 2. Determination of pubescent on performance tests Determination of particle concentrations in the flue gas was performed by gravimetric method. Sampling was performed using a device manufactured by SICK GRAVIMAT SHC502 Germany. It allows determination of particle concentrations in the range mg/m3, with isokinetic sampling samples from the flue gas. The design and construction ensures equipment: - automatic control of the amount of flue gas removed in order to ensure the equality between the speed of extraction times and speed of the combustion gas discharge channels (automatic maintenance of isokinetic); - accurately measure the amount of gas extracted by using a differential pressure sensor mbar ± 0.2% of the sample located in the sample head. - high precision sampling and integrity through special construction dust collectors; - automatic correction of the position deviation of the probe caused by the sampling probe to the actual direction of flow of the flue gases (the wellhead is provided with differential pressure sensors for the measurement of the actual sampling to the direction of flow of the exhaust gases). Combustion-gas analysis measuring section for determining the concentration of O 2 (O 2 to the correction reference 6%) was performed by using portable analyzer with electrochemical sensor TESTO 350 XL. - Weighing dust collectors, both before and after sampling is carried out (after drying) with a precision laboratory analytical balance, manufactured by Sartorius Werke of Germany. - After weighing and data entry software GRAVIMAT specialized equipment SHC ISBN:

3 502 automatically calculates the concentration of dust. SHC 502 GRAVIMAT equipment complies with ISO 9096 and in addition to the European Norm EN , time required for the determination of low concentrations of particulates from the flue gases (below 50 mg/nm 3 ). Section measuring and sampling method were chosen so that the samples obtained are representative. To this end, before making measurements and the arrangements of the measuring points have been chosen and were determined: - as the positive section of the measurements; - the number and distribution of measuring points in the cross section; - the number and duration of samples. Conclusions This section has been chosen as a straight portion of the flue gas channel, having constant diameter, the velocity distribution and the dust concentration in the uniform section and the gas flow vortex or not the reversal of the direction of flow. The results of the measurements carried out are shown in Table 1. References: [1] Racoceanu, C., CăpăŃînă, C., Emissions of power stations, House Publishing MatrixRom, Bucureşti, [2] Racoceanu, C., Environmental impact of power plants, House Publishing Focus, Petroşani, [3] Diaconu, B.M., Thermoelectric Plants, SITECH House Publishing, Craiova, [4] ICPET-ECO, Creating stand and investigations to determine the process parameters to reduce dust emissions, 2007 [5] Government Decision 541 of 17 May 2003 establishing measures for the limitation of emissions of certain pollutants from large combustion plants [6] Reduce air pollution by improving filtering performance of electrostatic precipitators, Polytechnic University of Bucharest. Contract: UPB - CNCSIS , Project Manager: S.l. dr.ing. Laurentiu Marius Dumitran [7] User of de-dusting system (electrostatic precipitators) from CE Rovinari [8] User particle analyzer SC600- CE Rovinari [9] Handbook cyclones (electrostatic precipitators) from CE Rovinari Figure 1.a SC600 system structure configured on a single channel ISBN:

4 Figure 1.b SC600 system structure configured on four channels Figure 2. Transmission and reception units ISBN:

5 Figure 3. The control unit Figure 4. PREDICT application screen ISBN:

6 Figure 5. Display continuous emission monitoring system No. crt. 1. Table 1: Results of the measurements for determining the concentration of dust Parameter Gas temperature in the channel Suction pressure VG Unit Sample No MW Electrostatic precipitator no. 1 Electrostatic precipitator no. 2 Sample Sample Sample Sample Sample Sample No. 2 No. 3 No. 2 No. 3 No.4 No MW 223 MW 325 MW 325 MW MW MW Sample No MW 0 C 132,3 123,2 123,6 127,0 131,0 129,5 132,1 130,0 2. mm H 2 O O 2 % 8,84 10,40 11,05 12,00 8,34 10,35 10,24 12,10 4. Gas velocity in the channel m/s 17,96 17,68 17,40 26,33 18,95 17,61 15,86 26,25 5. Gas flow m 3 /h channel Nm 3 /h Dust mg/nm 3 concentration 6% O 2 25,86 21,72 19,48 24,35 23,65 22,19 21,31 22,87 ISBN: