NO319297B1

NO319297B1 - Procedure for hot leaching of lime

Info

Publication number: NO319297B1
Application number: NO19980435A
Authority: NO
Inventors: Poju R Stephansen
Original assignee: Poju R Stephansen
Priority date: 1998-02-02
Filing date: 1998-02-02
Publication date: 2005-07-11
Also published as: NO980435L; NO980435D0

Description

Foreliggende oppfinnelse vedrører en fremgangsmåte for satsvis lesking av brent kalk for produksjon av kalkslurry med større finhetsgrad og forlenget sedimenteringstid. The present invention relates to a method for batchwise slaking of quicklime for the production of lime slurry with a greater degree of fineness and extended sedimentation time.

Kalkleskere av ulike typer, hvorav de fleste er bestemt for kontinuerlig drift, har lenge vært anvendt industrielt. Som eksempler kan nevnes "W+T" - og "BJF"-leskere. Lime slakers of various types, most of which are intended for continuous operation, have long been used industrially. Examples include "W+T" and "BJF" readers.

US-patentsøknad 4547349 omhandler en anordning for ikke-satsvis, kontinuerlig kalklesking. US patent application 4,547,349 relates to a device for non-batch, continuous descaling.

I UK-patentsøknad GB 2048107A er det vist og beskrevet en kalklesker, likeledes for ikke-satsvis kontinuerlig drift. In UK patent application GB 2048107A a lime slaker is shown and described, likewise for non-batch continuous operation.

EU-patentsøknad 0510675A3 omhandler en kalklesker for ikke-satsvis kontinuerlig drift. EU patent application 0510675A3 concerns a lime crusher for non-batch continuous operation.

CA patentsøknad 1212825 omhandler en regulert prosess for satsvis fremstilling av lesket kalk. CA patent application 1212825 deals with a regulated process for the batch production of slaked lime.

Kalkleskere som drives kontinuerlig, har til felles at de er vanskelig å kontrollere, meget vedlikeholdskrevende, lite egnet for datastyrt drift, og kostbar i fremstilling. Lime slakers that are operated continuously have in common that they are difficult to control, very maintenance-intensive, not suitable for computer-controlled operation, and expensive to manufacture.

I NO-patentsøknad P933084, tidligere inngitt av P.R. Stephansen, er det beskrevet en fremgangsmåte for satsvis lesking, såkalt "batch-lesking", av brent kalk, også i relativt små mengder i forhold til lekserens volum, hvorved det oppnås et sluttprodukt med relativt lav kalkkonsentrasjon. In NO patent application P933084, previously filed by P.R. Stephansen, a method is described for batch slaking, so-called "batch slaking", of quicklime, also in relatively small quantities in relation to the volume of the slaker, whereby a final product with a relatively low lime concentration is obtained.

Foreliggende oppfinnelsen kjennetegnes ved den karakteriserende del av krav 1. The present invention is characterized by the characterizing part of claim 1.

Alternative foretrukne utførelsesformer av oppfinnelsen kjennetegnes ved underkravene av hovedkravet. Alternative preferred embodiments of the invention are characterized by the sub-claims of the main claim.

Ved utøving av den nye fremgangsmåte ifølge oppfinnelsen for batchvis varmlesking av brent kalk, anvendes en kalkleskeranordning som vist og detaljert beskrevet i nevnte NO-patentsøknad P933084, hvortil det henvises. When practicing the new method according to the invention for batchwise hot slaking of burnt lime, a lime slaking device is used as shown and described in detail in the aforementioned NO patent application P933084, to which reference is made.

En foretrukket kalkleskeranordning, som er skjematisk vist i figur 1, omfatter i hovedtrekk en kalklesker 2 med effektivt volum 1200 I (vektskalaområde 0 - 1400 kg), med sylindrisk overdel 53 og konisk underdel 54, montert på tre veieceller 7 for satsvis veiing av vann og kalk, og med en omrører 16 med et spesialkonstruert blandeorgan og drivmotor 18, rotasjonsovervåker 20 samt en vanndysedreven kombinert støvavsuger/overløpsinnretning/baffel 15 som tilføres vann gjennom en rørledning med ventil 17, mens leskeren 2 mottar vann gjennom en rørledning med ventiler 8 og 9. Leskerlokket 4 er forbundet med et spesialkonstruert vannutstrøm-ningsforhindrende spjeld som også atskiller den våte og den tørre kalksone. Leskeren står i forbindelse med en kalksilo 1, f.eks. av volum 50 m<3>, og med en nivåmåler samt et filter 52 med drivmotor 51 for mekanisk rensing. Siloen rommer 50 tonn brent kalk, for eksempel av volumvekt 1.1 (vektskalaområde 0-50 tonn), og er utstyrt med veieceller for vektavlesing. Veiecellenes forsterker avgir et 4-20mA signal til PLS. Siloen er også forsynt med to luftaktivatorer som startes og følger en fast syklus, dersom doseringstiden for skruetransportøren overskrides. A preferred lime crusher device, which is schematically shown in Figure 1, mainly comprises a lime crusher 2 with an effective volume of 1200 I (weight scale range 0 - 1400 kg), with a cylindrical upper part 53 and a conical lower part 54, mounted on three weighing cells 7 for batch weighing of water and lime, and with a stirrer 16 with a specially designed mixing device and drive motor 18, rotation monitor 20 as well as a water nozzle-driven combined dust extractor/overflow device/baffle 15 which is supplied with water through a pipeline with valve 17, while the laser 2 receives water through a pipeline with valves 8 and 9. The desiccant lid 4 is connected to a specially constructed damper preventing water outflow which also separates the wet and the dry lime zone. The desiccant is connected to a lime silo 1, e.g. of volume 50 m<3>, and with a level gauge and a filter 52 with drive motor 51 for mechanical cleaning. The silo holds 50 tonnes of quicklime, for example of volume weight 1.1 (weight scale range 0-50 tonnes), and is equipped with weighing cells for weight reading. The weighing cell's amplifier emits a 4-20mA signal to the PLC. The silo is also equipped with two air activators which are started and follow a fixed cycle, if the dosing time for the screw conveyor is exceeded.

Gjennom et innblåsningsrør fylles siloen med kalk fra f. eks. en tankbil. Vektmengden i siloen angis fra et skap ved silopåfyllingsstedet. Ved oppnådd 95%-vektmengde (AH) avgis alarm i form av lyd/lyssignal som varsel om at påfyllingen må avbrytes. Lydalarmen kan avstilles fra skapet og/eller automatisk av PLS for eksempel etter tre minutter. Ved 100%-vekt (AHH) stenges en hylseventil automatisk og kalkinnblåsingen opphører. Mens ventilen er stengt, vil en rød varsellampe i skapet indikere at silofylling ikke kan foregå. Hylseventilen kan styres manuelt fra panel i kontrollsentral. Through a blow-in pipe, the silo is filled with lime from e.g. a tanker. The amount of weight in the silo is entered from a cabinet at the silo filling point. When 95% by weight (AH) is reached, an alarm is emitted in the form of a sound/light signal as a warning that the filling must be interrupted. The sound alarm can be silenced from the cabinet and/or automatically by the PLC, for example after three minutes. At 100% weight (AHH), a sleeve valve closes automatically and the lime injection ceases. While the valve is closed, a red warning light in the cabinet will indicate that silo filling cannot take place. The sleeve valve can be controlled manually from a panel in the control center.

Veieceller montert på siloen avgir et alarm- og et trippesignal: Weighing cells mounted on the silo emit an alarm and a trip signal:

- ved > AH. Operatør varsles om høyt nivå i silo. - at > AH. The operator is notified of a high level in the silo.

- ved > AHH. Operatør varsles og stenger hylseventil. - by > AHH. The operator is notified and closes the sleeve valve.

Filtermotor foretrekkes utstyrt med sikkerhetsbryter og servicevender (auto/man.). Filter motor preferably equipped with safety switch and service switch (auto/manual).

Etter avsluttet kalkifylling i siloen startes filtermotor 51 manuelt fra lokalt skap. Fra skapet avgis signal til ytre PLS som starter filtermotoren og overvåker motorens driftstilstand. Filtermotoren 51 stopper automatisk etter tre minutter. After filling the silo with lime, filter motor 51 is started manually from the local cabinet. A signal is sent from the cabinet to the external PLC which starts the filter motor and monitors the motor's operating condition. The filter motor 51 stops automatically after three minutes.

Eksempel Example

1. Startknapp i lokalt skap aktiviseres 1. Start button in local cabinet is activated

2. Filtermotor 51 starter og driftslys i skapet tennes 2. Filter motor 51 starts and the operating light in the cabinet lights up

3. Filtermotor stopper etter ca. tre minutter 3. Filter motor stops after approx. three minutes

Med skruetransportøren 6 overføres kalk fra siloen 1 til leskeren 2 med spjeldventilene 11 og 12 i åpen stilling. Leskingen innledes ved at første sats leskes manuelt. Kalktilberedningen foregår deretter automatisk, hvorved leskeren 2 ifylles fortynningsvann i forutvalgt vektmengde. Leskeren tømmes deretter til en forutvalgt gjenblivende mengde, hvori den neste kalksats skal leskes. With the screw conveyor 6, lime is transferred from the silo 1 to the licker 2 with the butterfly valves 11 and 12 in the open position. The reading begins with the first batch being read manually. The lime preparation then takes place automatically, whereby the slaker 2 is filled with dilution water in a pre-selected amount by weight. The slaker is then emptied to a pre-selected remaining quantity, in which the next batch of lime is to be slaked.

Kalkleskingstemperaturen bestemmes av forholdet mellom gjenværende antall kilo kalkslurry i leskeren (EVL) og antall kilo tilsatt kalk (EVH), eller de valgte instil-lingspunkter på veiecellene 7. Antallet kilo vann som er valgt i det siste inn-stillingspunkt (EVHH) er bestemmende for konsentrasjonen av ferdiglesket kalk. The lime slaking temperature is determined by the ratio between the remaining number of kilograms of lime slurry in the slaker (EVL) and the number of kilograms of added lime (EVH), or the selected setting points on the weighing cells 7. The number of kilograms of water selected in the last setting point (EVHH) is decisive for the concentration of ready-slaked lime.

Veiecellene 7 genererer fire arbeidskontakter for bruk i sekvensen: The load cells 7 generate four working contacts for use in the sequence:

Ferdigberedt kalk uttømmes til lagertank 3 gjennom ventil 22 ved hjelp av en motor. Motoren foretrekkes utstyrt med sikkerhetsbryter og servicevender. Finished lime is emptied into storage tank 3 through valve 22 with the help of a motor. The motor is preferably equipped with a safety switch and service reverser.

Ved start ifylles 300 kg vann manuelt i leskeren 2 etterfulgt av 100 kg CaO under omrøring. Når blandingen har nådd en temperatur av 85 °C, registrert av et temperaturmålerelement, kan automatisk drift innkobles og vann tilsettes til en blandingsvekt av 1000 kg, hvilket gir en 10%-slurry av temperatur ca. 32 °C . Gjennom ventilen 22 tømmes leskeren til en gjenstående vektmengde av eksempelvis 240 kg. Deretter innledes 30 sekunders pause, for tilbakerenning fra for eksempel pumpen. Det er viktig at styresystemet kan registrere satsens reelle verdi og tarere til 0 kg, hvilket er nødvendig fordi treghet i systemet kan medføre risiko for at mer eller mindre kjemikalie enn forutsatt tilsettes i leskeren. At the start, 300 kg of water is manually filled into the laser 2, followed by 100 kg of CaO while stirring. When the mixture has reached a temperature of 85 °C, registered by a temperature measuring element, automatic operation can be engaged and water added to a mixture weight of 1000 kg, which gives a 10% slurry of temperature approx. 32 °C. Through the valve 22, the hopper is emptied to a remaining weight amount of, for example, 240 kg. A 30-second break is then introduced, for backflow from, for example, the pump. It is important that the control system can register the real value of the batch and tare to 0 kg, which is necessary because inertia in the system can entail the risk of more or less chemical than expected being added to the digester.

Ved automatisk styring, når vektmengden i leskeren 2 er under 240 kg eller ny beregnet verdi grunnet temperaturreguleringen, og når 30-sekunders pause er utløpt, skal leskeprosessen starte dersom den ikke allerede er i gang, og ventilen 22 skal være stengt. With automatic control, when the amount of weight in the cooler 2 is below 240 kg or a new calculated value due to the temperature regulation, and when the 30-second break has expired, the cooling process must start if it is not already underway, and valve 22 must be closed.

Spjeldventil 12 i leskerlokket mottar åpningssignal og bekreftes i åpen stilling fra grensebryter, åpningssignal avgis til ventil 17, og støvavsuger 15 igangsettes. Etter fem sekunders tidsforsinkelse åpnes spjeldventil 11 ved utløpsenden av skruetransportøren 6 og bekreftes åpen fra grensebryter. En rotasjonsovervåker kontrollerer at omrøreren er i gang, og alarm avgis dersom dette ikke er tilfellet eller hvis ventilen ikke åpnes etter kommando. Hvis omrører stopper, skal ventil 9 åpnes og leskeren fylles fullstendig med vann og prosessen avbrytes. Butterfly valve 12 in the reader lid receives an opening signal and is confirmed in the open position from the limit switch, an opening signal is sent to valve 17, and dust extractor 15 is started. After a five-second time delay, butterfly valve 11 is opened at the outlet end of the screw conveyor 6 and is confirmed open from the limit switch. A rotation monitor checks that the stirrer is running, and an alarm is issued if this is not the case or if the valve does not open on command. If the stirrer stops, valve 9 must be opened and the hopper filled completely with water and the process interrupted.

Skruetransportøren 6 startes fem sekunder etter at en grensebryter har bekreftet ventil 11 i åpen stilling, og igangsetter tidsur for normal doseringstid, f. eks. 120 sekunder. Hvis tiden overskrides, skal luftstimulatorene åpnes og lukkes i en bestemt syklus (åpen ca. 0,5 sek. for hvert 30. sekund) med start i pausedelen og begrenset til 180 sekunder, hvoretter syklusen avbrytes og alarm avgis. The screw conveyor 6 is started five seconds after a limit switch has confirmed valve 11 in the open position, and starts a timer for normal dosing time, e.g. 120 seconds. If the time is exceeded, the air stimulators shall be opened and closed in a specific cycle (open approx. 0.5 sec. for every 30 seconds) starting in the pause part and limited to 180 seconds, after which the cycle is interrupted and the alarm is sounded.

Skruetransportøren 6 holdes i gang til den ønskede kalkmengde (60kg) er innveid. 1 sekund etter at transportøren har stoppet stenges spjeldventil 11.10 sekunder etter at ventilen er bekreftet stengt, åpnes en magnetventil i 3 sek. for luft til utløpsvibrator. Spjeldventil 12 stenges i 30 sek. etter at spjeldventil 11 er bekreftet stengt, og en grensebryter kontrollerer at ventilen er lukket. Alarm avgis dersom ventilen ikke lukkes etter kommando. 20 sekunder etter at ventil 12 er stengt, avgis stengesignal til ventil 17 og støvavsugeren 15 stoppes. Etter at skruetransportøren er stoppet, påbegynnes jus-terbar lesketid, for eksempel 10 minutter. Den valgte lesketid og forløpet av denne bør indikeres for operatør. The screw conveyor 6 is kept running until the desired amount of lime (60kg) has been weighed. 1 second after the conveyor has stopped, the butterfly valve is closed 11.10 seconds after the valve has been confirmed closed, a solenoid valve is opened for 3 seconds. for air to outlet vibrator. Butterfly valve 12 is closed for 30 sec. after butterfly valve 11 has been confirmed closed, and a limit switch checks that the valve is closed. An alarm is emitted if the valve does not close on command. 20 seconds after valve 12 is closed, a closing signal is sent to valve 17 and the dust extractor 15 is stopped. After the screw conveyor has been stopped, adjustable cooling time begins, for example 10 minutes. The selected cooling time and its course should be indicated to the operator.

Når lesketiden er utløpt, tilføres vann gjennom ventil 8 og gjennom spyledysene 24 i 15 sekunder. Deretter tilføres 600 kg fortynningsvann gjennom ventil 9, hvilket gir en 10%-kalkslurry av temperatur 32 °C. Ved en feil i tilsatt kalkmengde over +2% justeres mengden av fortynningsvann. When the cooling time has expired, water is supplied through valve 8 and through the flushing nozzles 24 for 15 seconds. Then 600 kg of dilution water is supplied through valve 9, which gives a 10% lime slurry at a temperature of 32 °C. If there is an error in the amount of added lime above +2%, the amount of dilution water is adjusted.

Temperaturen i leskeren overvåkes av et temperaturmålingselement. Hvis det under leskeprosessen ikke oppnås temperatur av 83 °C, uttømmes 10 kg mer av den ferdige slurry, hvorved EVL minsker til 230 kg eller motsatt hvis temperaturen blir for høy (87°C) til 250 kg. The temperature in the cooler is monitored by a temperature measuring element. If a temperature of 83 °C is not reached during the liquefaction process, 10 kg more of the finished slurry is discharged, thereby reducing EVL to 230 kg or vice versa if the temperature becomes too high (87 °C) to 250 kg.

Hvis temperaturen under leskeprosessen overstiger 96 °C, åpnes også ventil 8, leskeren vannfylles til fullt nivå EVHH, prosessen avbrytes og alarm avgis, uten at omrøreren stoppes. If the temperature during the liquefaction process exceeds 96 °C, valve 8 is also opened, the liquefier is filled with water to full level EVHH, the process is interrupted and an alarm is issued, without stopping the agitator.

For tilberedning, som tidligere beskrevet, av en 10%-kalkslurry er det ønskelig å tilsette 60 kg CaO og 600 kg vann. Totalnivået vil variere avhengig av temperaturreguleringen. Den ferdige kalkslurrys konsentrasjonsgrad er bestemmende for temperaturen av slurryen hvori kalken tilsettes for neste lesking. Hvis det ønskes en kalkslurry av høyere konsentrasjongrad, bør leskingen foregå ved høyere starttempera-tur. Hvis det ønskes en lavere konsentrajonsgrad, bør slurryen fortynnes utenfor leskeren, eksempelvis i rørledningen til lagertanken, eller det kan tilsettes tilmålte vann-mengder i lagertanken samtidig med at leskeren, fra full vekt i mindre satser, for eksempel fire, tilsetter proporsjonale kalkslurrymengder i lagertanken. For the preparation, as previously described, of a 10% lime slurry, it is desirable to add 60 kg of CaO and 600 kg of water. The total level will vary depending on the temperature control. The finished lime slurry's degree of concentration determines the temperature of the slurry into which the lime is added for the next leaching. If a lime slurry of a higher degree of concentration is desired, the slaking should take place at a higher starting temperature. If a lower degree of concentration is desired, the slurry should be diluted outside the crusher, for example in the pipeline to the storage tank, or measured amounts of water can be added to the storage tank at the same time that the crusher, from full weight in smaller batches, for example four, adds proportional quantities of lime slurry to the storage tank .

Etter utløpt lesketid kontrolleres nivået i lagertanken, og når dette er redusert til EVLL, åpnes ventil 22 og satsen uttømmes i lagertanken. After the cooling time has expired, the level in the storage tank is checked, and when this has been reduced to EVLL, valve 22 is opened and the batch is emptied into the storage tank.

Ferdig kalkslurry lagres midlertidig i lagertankene 3 som er utstyrt med en nivåmåler i form av trykktransmitter samt omrører(e). Nivåsignalet genererer to arbeidskontakter for bruk i sekvensen samt to signaler for alarm ved hhv. lavt og høyt nivå og ett signal for start av pumper. Finished lime slurry is temporarily stored in the storage tanks 3, which are equipped with a level gauge in the form of a pressure transmitter and agitator(s). The level signal generates two working contacts for use in the sequence as well as two signals for alarm when low and high level and one signal for starting pumps.

Omrøreren skal drives kontinuerlig og overvåkes av PLS. Alarm avgis i tillegg av stopp. The stirrer must be operated continuously and monitored by the PLC. Alarm is issued in addition to stopping.

Ved dosering av slurry til forbruket benyttes en eller flere pumper. Pumpene er anordnet "standby" for hverandre og er manuelt omstillbare. Pumpenes pakkbokser tilføres sperrevann gjennom magnetventiler, og har innebygde strømningsbryterefor avføring av vann. Hvis sperrevann uteblir mer enn tre minutter etter start avgis alarm og pumpene stopper. Det samme vil inntreffe dersom sperrevann uteblir i tre minutter under drift. Videre er hver pumpe utstyrt med en strømningsvakt og en trykkføler som er innmontert i røret på pumpenes trykkside. Hvis disse ikke registrerer vannmengde og trykk etter 15 sekunder, avgis alarm. Hvis vannmengde og trykk uteblir i ytterligere 15 sekunder, stopper pumpene. For måling av slurrymengde fra lagertank til sandfilter anvendes flowmeter. Denne måler sender et 4-20 mA-signal tilbake tii frek-vensomformer(e). Bunnfall uttømmes fra lagertanken gjennom en manuelt betjent bunnventil. When dosing slurry for consumption, one or more pumps are used. The pumps are arranged "standby" for each other and can be manually adjusted. The pumps' packing boxes are supplied with barrier water through solenoid valves, and have built-in flow switches for discharging water. If there is no barrier water more than three minutes after starting, an alarm is sounded and the pumps stop. The same will occur if there is no barrier water for three minutes during operation. Furthermore, each pump is equipped with a flow monitor and a pressure sensor which is installed in the pipe on the pump's pressure side. If these do not register water quantity and pressure after 15 seconds, an alarm is issued. If there is no water flow and pressure for another 15 seconds, the pumps stop. A flowmeter is used to measure the quantity of slurry from the storage tank to the sand filter. This meter sends a 4-20 mA signal back to the frequency converter(s). Sediment is discharged from the storage tank through a manually operated bottom valve.

Claims

1. Procedure for batch-wise slaking of quicklime, for the production of lime slurry with a greater degree of fineness and extended sedimentation time, characterized in that it comprises the following process steps: a. emptying of pre-slaked and diluted lime slurry from a slaker (2), until there is a predetermined amount of slurry weight remaining, which is used for mixing with the next batch; b. automatic engagement of a control system for automatic operation after the desired leaching temperature of the first batch has been achieved, which adds dilution water and then burnt lime in a predetermined amount by weight in subsequent stages; c. automatic regulation of the leaching temperature in the next slurry batch, where the ratio between water and lime is adjusted if the desired leaching temperature was not reached in the previous batch, and where the digester (2) is completely filled with water, so that leaching is interrupted if the given maximum temperature is exceeded; d. automatic recording of the loader's remaining slurry weight amount after a run-in break of predetermined length, and subsequent taring of the load cell unit (7) to 0 kg, before the next loading.

2. Method for batch hot slaking of quicklime according to claim 1, characterized in that the ratio of lime/water during slaking is increased if the slaking temperature was too low, and in that the ratio of lime/water is reduced if the slaking temperature was too high.

3. Method for batch hot slaking of quicklime according to claim 2, characterized in that the adjustment of the quantity ratio takes place by adjusting the amount of remaining, fully slaked and diluted lime slurry, so that the weight of the remaining lime slurry is reduced if the slaking temperature was too low, and increased if the slaking temperature was too high, while the amount of lime added in the next batch is kept constant.

4. Method for batch hot slaking of burnt lime according to claim 2, characterized in that the adjustment of the quantity ratio takes place by keeping the amount of remaining, fully slaked and diluted lime slurry fixed, while the amount of added lime is changed, so that the amount of added lime is reduced if the slaking temperature was too high , and increased if the leaching temperature was too low.

5. Method for batch hot slaking of quicklime according to claim 2, characterized in that the adjustment of the quantity ratio takes place by keeping the amount of remaining, finished slaked and diluted lime slurry, as well as the amount of added lime fixed, while a varying amount of water is added before slaking, as that the amount of added water is increased if the leaching temperature was too high, and decreased if the leaching temperature was too low.