Kessel

ZFR2. Auxiliary boilerPrinciple of a 3-pass double flame tube/smoke tube boiler The boiler is a shell boiler. Contrary to a water tube boiler the water is outside the tubes. The hot flue gases are inside the smoke tubes. On the flue gas side the boiler contains 3 passes: • a furnace (flame tube) as 1st pass • 2 tube banks as 2nd and 3rd pass. The boiler is equipped with 2 burners. The flue gas passes for both burners are separated completely until the boiler outlet. Connection from 1st to 2nd pass is an internal, water-cooled reversing chamber. Connection from 2nd to 3rd pass is the external front reversing chamber with a door for access to the smoke tubes. Thermotechnology1 TT/SLI5-ASU | 07.04.2015 | © Bosch Industriekessel GmbH 2015. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Principle of a 3-pass double flame tube/smoke tube boiler Front view: two tube banks 2nd pass two tube banks 3rd pass two tube banks 1st pass Thermotechnology2 TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR2. Auxiliary boilerPrinciple of a 3-pass double flame tube/smoke tube boiler inspection openingSide view: at the steam side steam dryer ECO finned tube bundle (option) flue gas collection chamber inspection door flame inspection eye, inspection opening at the water side Thermotechnology3 TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR2. Auxiliary boilerPrinciple of a 3-pass double flame tube/smoke tube boilerTop view: wet back reversing reversing chamber chamber water tubewith thermal dividing wall insulation ECO finned tube bundle (option) waste gas dividing wall Thermotechnology4 TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR2. Auxiliary boilerPrinciple of a 3-pass double flame tube/smoke tube boiler Thermotechnology 5 TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops Level control: Purpose: The boiler is filled not completely with water. The boiler volume is devided in a • steam area • water area The water level has to be kept strictly in a small range between • low water level (approx. 100 mm above highest heated surfaces) • high water level (approx. 190 mm above low level) Thermotechnology6 TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR2. Auxiliary boilerMain equipment and control loops Level control: The boilers are equipped with a continuously measuring level electrode. The current level in the boiler is transferred as 4-20 mA-signal = 0-100% to the boiler control LBC. Note: 0-100 % depends on the visible level in the sight glass. - 100 % means approx. 2 cm below upper end of sight glass, not completely full boiler - 0 % means approx. 1 cm above lower end of sight glass, not empty boiler Adjustment 0-100% is done during commissioning! Thermotechnology 7 TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR2. Auxiliary boilerMain equipment and control loops Level control: Depending on the measured level in the boiler the feed water control valves are controlled: Feed water control valvefrom feed to the boilerpump pump recirculation toThermotechnology feed water tank8 TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR2. Auxiliary boilerMain equipment and control loops Level control:An electric actuator adjusts a perforated cone and regulates the feed- water flow rate. Another smaller perforated cone opens the flow to recirculation when the main cone falls below a minimum lift. The mass flow through the pump is almost constant, while the flow is divided into flow to boiler and recirculation. So the minimum flow rate through the pump is always available.Factory setting for level set point: 60 %Only one feed pump is in operation, one is spare. Change over between both feed pump is done manually on the boiler control panel or automatically in case of a disturbance. Thermotechnology9 TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR2. Auxiliary boilerMain equipment and control loopsProtection against high and low water:It has to be ensured properly, that heating surfaces in the boiler do not emerge from the water => high danger of serious damages!So each boiler is equipped with 2 independent working low water limiting electrodes. If one of both respond due to low water, the firing is shut-off immediately and interlocked.Possible reasons for low water level:• Feed pump disturbance• Empty feed water tank (dry run protection)• Faulty feed water control valve• Strainer in feed water line is soiled• Insufficient water quality (high alcalinity or high conductivity, oil, grease)• ...10 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops Protection against high and low water: If high water in the boiler is detected (pre-set at 98%) the feed pumps are stopped and the feed water control valve closed. When the water level falls, the feed pump operation is released again. The boiler is not shut- down! Possible reasons for high water level: • Feed pump disturbance, pump does not stop • Faulty feed water control valve • Steam extraction from boiler too high • Insufficient water quality (high alcalinity or high conductivity, oil, grease) For details about operation at the panel see instructions - G311 - Level control - G326 - Feed pump control11 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR The level sight glass is installed on the right side.2. Auxiliary boilerMain equipment and control loops The level measuring equipment: Electrodes are installed in 2 special mounting sockets on the left side of the boiler.12 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR3. Auxiliary boilerMain equipment and control loops Pressure control: The boiler is equipped with a continuously measuring pressure 4- transmitter. The current pressure in the boiler is transferred as 20 mA-signal = 0-100 % to the boiler control. 100 % corresponds with the set pressure of the boiler safety valve, in this case 18 bar-g. Depending on the measuring signal the burner load is controlled continuously to maintain a medium operation pressure PM. Factory setting for pressure set point PM: 14,9 bar-g13 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3. Auxiliary boiler Main equipment and control loops Pressure control: The burner operates continuously between 2 set points: - Burner ON: 75 % of PM = 13,5 bar-g - Burner OFF: 91 % of PM = 16,4 bar-g Set points for Burner ON/OFF are related to the mean working pressure PM and are changed together with this.14 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR3. Auxiliary boilerMain equipment and control loops Hot stand-by: The boiler can be switched from normal operation to hot stand-by condition. In hot stand-by condition the boiler is kept warm and under pressure by the burner. The burner operates only at low load. The set points in hot stand-by are: - Burner ON: PM/2 - Burner OFF = normal burner OFF15 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3. Auxiliary boiler Main equipment and control loops Protection against overpressure: The boiler is equipped with a pressure monitor. If the pressure monitor responds due to high pressure the firing is shut-down and interlocked. The set point is pre-set to 95% = 17,1 bar-g. The setting is done mechanically at the pressure monitor, so it changes not, when PM is changed! To avoid undesirable disturbances the range for setting PM by the operating personnel is limited to max. 86 %. Second equipment for overpressure protection are safety valves mounted to the boiler top. The set pressure is 100 % = 18 bar.16 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops Protection against overpressure: Possible reasons for high boiler pressure alarm: • Wrong setting of pressure monitor (95 %) • Operating pressure PM too high • Rapid shut-off of steam valves in the plant => burners can not be shut-down fast enough. For details about operation at the panel see instruction - G338 - Performance regulation17 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops The pressure measuring Pressure gauge equipment is installed on Pressure transmitter the manostat pipe on the Pressure monitor water level sight glass. Manostat pipe18 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops Desalting control: During boiler operation the salt content and with this the electrical conductivity in the boiler water raises due to densification. A high conductivity may lead to priming of the boiler water. Level control can be incorrect. For this the boilers are equipped with a conductivity electrode. The current conductivity of the boiler water is transferred as 4-20 mA- signal to the boiler control. Depending on the signal, the desalting control valve is opened and closed.19 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops Desalting control: The desalting control valve has 3 positions OPEN, MIDDLE, CLOSED. Medium conductivity: CM Valve is in middle position Lower conductivity: CU Valve is closed Higher conductivity: CO Valve is open For demineralised water CM is set to approx. 150 µS/cm. CU and CH are related to CM and are changed together with this value. Pre-setting: CU = 0,9 * CM = 135 µS/cm CO = 1,2 * CM = 180 µS/cm Alarm: CH = 1,4 * CM = 210 µS/cm20 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops Desalting control: Possible reasons for high desalting rate or conductivity alarm: • Insufficient water quality • Irruption of impurities in the condensate system • Desalting shut-off valve is closed • Wrong settings of limit switches at the control valve For details about operation at the panel see instruction - G350 - Desalting control21 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR2. Auxiliary boilerMain equipment and control loops Equipment for desalting control: The electrode is installed in a sleeve socket on the left side of the boiler. The desalting control valve is installed after an angle shut-off valve22 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops Blow-down control: During boiler operation solids accumulate at the boiler bottom. To remove these solids the boilers are equipped with a quick-action blow-down valve. The blow-down valve is operated time-controlled. After a period TP the valve opens for a time TI. The pre-setting is: TP = 8 hours TI = 3 seconds If there are water hammers during blow-down process the reason is a water pocket in the blow-down line.23 Thermotechnology TT/SLI5-ASU | 07.04.2015 | © Bosch Industriekessel GmbH 2015. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3-way solenoid valve 2. Auxiliary boiler Main equipment and control loops Equipment for blow-down control: The blow down valve is installed at the rear end of the boiler. It is operated pneumatically with instrument air by a 3-way solenoid valve. For details about operation at the panel see instruction - G351 - Blow-down control Blow down valve24 Thermotechnology TT/SLI5-ASU | 07.04.2015 | © Bosch Industriekessel GmbH 2015. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 2. Auxiliary boiler Main equipment and control loops Safety chain: For boiler protection critical operation states lead to an immediate shut-down of the firing and interlocking of the control: • Low boiler water level • High boiler pressure • High boiler water conductivity (delayed by 30 seconds) as requirement of unattended operation for 72 hours • Oil leakage below the burner • High superheated steam temperature The safety chain can only be unlocked locally at the panel!25 Thermotechnology TT/SLI5-ASU | 07.04.2015 | © Bosch Industriekessel GmbH 2015. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR3. SuperheaterPrinciple of a superheater on the front reversing chamber The superheaters are mounted on the top of the front reversing chamber of the boiler. For each flue gas pass there is a separated superheater module. Hot flue gases come from 2nd boiler pass and flow through the tube bundle, in which the saturated steam is superheated. Finally the flue gases leave the boiler via the 3rd pass. The superheated steam temperature is controlled by means of a flue gas regulating flap in the front reversing chamber. This regulates the quantity of flue gases, that flow through the superheater tube bundle.26 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR3. SuperheaterPrinciple of a superheater on the front reversing chamber 2 separate superheater steam modules dryer superheater tube bundle flue gas control flap27 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3. Superheater Principle of a superheater on the front reversing chamber28 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3. Superheater Main equipment and control loops Temperature control: The superheater is designed for • steam capacity: 2 x 20 t/h • set point steam temperature TSHM: 260°C from part load 50 % • steam pressure: 14 bar-g after superheater Without control above part load of 50 % the superheated steam temperature would be > 260°C. By means of the flue gas flap a part of the flue gases are lead directly from 2nd to the 3rd pass, so a constant steam temeperature is maintained.29 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3. Superheater Main equipment and control loopsTemperaturecontrol:30 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3. Superheater Main equipment and control loops Temperature control: The superheater is equipped with • 1 temperature transmitter Pt100. The signal is transferred as 4-20 mA to the boiler control and displayed in the panel. Depending on the signal the flue gas control flap is adjusted. If the upper set point for pre-warning TSHO (25 K above TSHM = 285 °C) is reached, the burner load is reduced to low load. • 1 local thermometer • 1 safety temperature monitor. If the monitor responds due to high steam temperature, the firing is shut off and interlocked (part of safety chain). Set point for temperature monitor is approx. 50 K above normal steam temperature, here approx. 310°C.31 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3. Superheater Main equipment and control loops Temperature control: Possible reasons for high steam temperature alarm: • Flue gas control flaps blocked or disturbance of actuator • Boiler heating surfaces are soiled • Wrong setting of switching points Possible reasons if steam temperature is not reached: • Insufficient water quality (to much water in saturated steam) • Superheater tubing dirty • Flue gas control flaps blocked or disturbance of actuator • Wrong setting of switching points For details about operation at the panel see instruction - G341 - Superheated steam temperature control32 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.

ZFR 3. Superheater Main equipment and control loops Additional superheater equipment: Each superheater module is equipped with • a safety valve for protection against overpressure • a start-up valve: During boiler start up the start-up valves prevent that saturated steam gets into the system. They are opened as long as the steam temperature is not high enough (set point adjustable in the boiler control panel). The motorized main steam valves are closed then. When the set temperature is reached the main steam valves are opened and the start-up valves are closed automatically.33 Thermotechnology TT/SLI5-ASU | 09.08.2012 | © Bosch Industriekessel GmbH 2012. Alle Rechte vorbehalten, auch bzgl. jeder Verfügung, Verwertung, Reproduktion, Bearbeitung, Weitergabe sowie für den Fall von Schutzrechtsanmeldungen.