WO2019050415A1 - Système et méthode de récupération d'énergie - Google Patents

Système et méthode de récupération d'énergie Download PDF

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Publication number
WO2019050415A1
WO2019050415A1 PCT/NZ2018/050119 NZ2018050119W WO2019050415A1 WO 2019050415 A1 WO2019050415 A1 WO 2019050415A1 NZ 2018050119 W NZ2018050119 W NZ 2018050119W WO 2019050415 A1 WO2019050415 A1 WO 2019050415A1
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WIPO (PCT)
Prior art keywords
steam
slurry
flash tank
pipe
flash
Prior art date
Application number
PCT/NZ2018/050119
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English (en)
Inventor
Curtis Allen MARSH
Original Assignee
CFD Design and Engineering Limited
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Filing date
Publication date
Priority claimed from AU2017903642A external-priority patent/AU2017903642A0/en
Application filed by CFD Design and Engineering Limited filed Critical CFD Design and Engineering Limited
Publication of WO2019050415A1 publication Critical patent/WO2019050415A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C01F7/062—Digestion
    • C01F7/064—Apparatus for digestion, e.g. digestor vessels or heat exchangers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/06—Flash distillation
    • B01D3/065—Multiple-effect flash distillation (more than two traps)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/42—Regulation; Control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0006—Controlling or regulating processes
    • B01J19/0013—Controlling the temperature of the process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0006—Controlling or regulating processes
    • B01J19/0033—Optimalisation processes, i.e. processes with adaptive control systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/24—Stationary reactors without moving elements inside
    • B01J19/245—Stationary reactors without moving elements inside placed in series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00051—Controlling the temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00162—Controlling or regulating processes controlling the pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J2219/0873—Materials to be treated
    • B01J2219/0881—Two or more materials
    • B01J2219/089—Liquid-solid
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Definitions

  • the invention relates to an energy recovery system, particularly for use in the extraction of alumina from bauxite.
  • the invention is further suited to any process seeking to reduce the pressure and/or temperature of an abrasive slurry.
  • One such example is the high pressure acid leach process used in the nickel industry.
  • alumina from bauxite involves dissolving ground bauxite in a sodium hydroxide solution (caustic liquor) within a digestion vessel. Temperature and pressure are applied within the digestion vessel to dissolve the bauxite. The resulting slurry is flash-cooled to atmospheric boiling point by flowing through a series of flash tanks that operate at successively lower pressures. Flash steam generated in the flash tanks is utilised to preheat the incoming caustic liquor prior to its introduction to the digestion vessel. Unstable flash steam temperatures can cause inefficient heat transfer from the flash steam to the caustic liquor and reduce the efficiency of the overall process.
  • an energy recovery system comprises: a first flash tank having a first slurry inlet adapted to receive a slurry into the first flash tank, a first slurry outlet adapted to discharge the slurry from the first flash tank, and a first steam outlet adapted to discharge flash steam from the first flash tank; a second flash tank having a second slurry inlet adapted to receive the slurry discharged from the first flash tank; a first slurry pipe connecting the first slurry outlet and the second slurry inlet; a first steam pipe connecting the first steam outlet with a first heat exchanger; a first steam diversion pipe connected to the first steam pipe, the first steam diversion pipe adapted to divert at least part of the flash steam discharged from the first steam outlet away from the first heat exchanger; and a control valve on the first steam diversion pipe operable to control a flow of steam diverted through the first steam diversion pipe.
  • control valve is connected to a pressure sensor adapted to measure a pressure within the first flash tank.
  • control valve is adapted, on the pressure sensor detecting a drop in pressure within the first flash tank, to decrease the flow of steam through the first steam diversion pipe.
  • control valve is adapted, on the pressure sensor detecting an increase in pressure within the first flash tank, to increase the flow of steam through the first steam diversion pipe.
  • control valve is adapted to increase and/or decrease the flow of steam through the first steam diversion pipe when the pressure sensor detects a pressure outside a target pressure range to restore the pressure to within the target pressure range.
  • control valve is connected to a level sensor adapted to measure a level of slurry within the first flash tank.
  • control valve is adapted, on the level sensor detecting an increase in slurry level within the first flash tank, to decrease the flow of steam through the first steam diversion pipe.
  • control valve is adapted, on the level sensor detecting a decrease in slurry level within the first flash tank, to increase the flow of steam through the first steam diversion pipe.
  • control valve is adapted to increase and/or decrease the flow of steam through the first steam diversion pipe, on the slurry level sensor detecting a slurry level outside a target slurry level range, to restore the slurry level to within the target slurry level range.
  • control valve is connected to the pressure sensor and the level sensor.
  • the first steam diversion pipe connects the first steam pipe and the first slurry pipe, the first steam diversion pipe adapted to introduce at least part of the flash steam discharged from the first steam outlet into the slurry discharged from the first flash tank; and the control valve on the first steam diversion pipe is operable to control the flow of steam introduced into the slurry discharged from the first flash tank.
  • the first slurry pipe is fitted with an orifice plate positioned intermediate the first slurry outlet and the second slurry inlet, the first steam diversion pipe connected at a first end to the first steam pipe and connected at a second end to the first slurry pipe at a point intermediate the orifice plate and the second slurry inlet.
  • the first steam diversion pipe connects the first steam pipe and the second flash tank, the first steam diversion pipe adapted to introduce at least part of the flash steam discharged from the first steam outlet directly into the second flash tank; and the control valve on the first steam diversion pipe is operable to control the flow of steam introduced directly into the second flash tank.
  • the energy recovery system further comprises: a second slurry outlet adapted to discharge the slurry from the second flash tank; a second steam outlet adapted to discharge flash steam from the second flash tank; and a second steam pipe connecting the second steam outlet with a second heat exchanger.
  • the first steam diversion pipe connects the first steam pipe and the second steam pipe, the first steam diversion pipe adapted to introduce at least part of the flash steam discharged from the first steam outlet into a flow of steam discharged from the second flash tank; and the control valve on the first steam diversion pipe is operable to control the flow of steam introduced into the flow of steam discharged from the second flash tank.
  • the first steam diversion pipe connects the first steam pipe and an export pipe, the first steam diversion pipe adapted to introduce at least part of the flash steam discharged from the first steam outlet into one or more of a water evaporator or other auxiliary use.
  • the energy recovery system further comprises: a third flash tank having a third slurry inlet adapted to receive the slurry discharged from the first flash tank or the second flash tank, and a third steam outlet adapted to discharge flash steam from the third flash tank; a second slurry pipe connecting the second slurry outlet and the third slurry inlet; a third steam pipe connecting the third steam outlet with a third heat exchanger; a slurry bypass pipe connecting the first slurry outlet and the third slurry inlet; at least one slurry bypass valve in communication with the slurry bypass pipe and the first slurry pipe, the at least one slurry bypass valve adapted to selectively divert the slurry from the first flash tank into either the second flash tank or the third flash tank; a tank bypass
  • the second flash tank is downstream of the first flash tank.
  • the second flash tank operates at lower pressure and temperature than the first flash tank.
  • the third flash tank is downstream of the second flash tank. The third flash tank operates at lower pressure and temperature than the second flash tank.
  • the energy recovery system comprises further steam diversion pipes/valves and slurry bypass pipes/valves to enable steam to be diverted into one or more subsequent flash tanks, or to one or more pipes associated with a subsequent flash tank.
  • the tank bypass valve is adapted to selectively divert at least part of the flash steam discharged from the first steam outlet into the second flash tank or the third flash tank.
  • tank bypass pipe is connected to the third flash tank via the second slurry pipe.
  • tank bypass pipe is directly connected to the third flash tank.
  • tank bypass pipe connects the first steam diversion pipe and the third steam pipe.
  • tank bypass valve is adapted to selectively divert at least part of the flash steam discharged from the first steam outlet into the flow of steam discharged from the second flash tank or the flow of steam discharged from the third flash tank.
  • a method of recovering energy comprises: providing a first flash tank, the first flash tank having a first slurry inlet adapted to receive a slurry into the first flash tank, a first slurry outlet adapted to discharge the slurry from the first flash tank, and a first steam outlet adapted to discharge flash steam from the first flash tank; providing a second flash tank, the second flash tank having a second slurry inlet adapted to receive the slurry discharged from the first flash tank; providing a first slurry pipe connecting the first slurry outlet and the second slurry inlet; providing a first steam pipe connecting the first steam outlet with a first heat exchanger; providing a first steam diversion pipe connected to the first steam pipe, the first steam diversion pipe adapted to divert at least part of the flash steam discharged from the first steam outlet away from the first heat exchanger; and providing a control valve on the first steam diversion pipe operable to control a flow of steam diverted through the first steam diversion pipe.
  • the method comprises providing a pressure sensor adapted to measure a pressure within the first flash tank, the control valve connected to the pressure sensor.
  • the control valve is adapted, on the pressure sensor detecting a drop in pressure within the first flash tank, to decrease the flow of steam through the first steam diversion pipe.
  • control valve is adapted, on the pressure sensor detecting an increase in pressure within the first flash tank, to increase the flow of steam through the first steam diversion pipe.
  • control valve is adapted to increase and/or decrease the flow of steam through the first steam diversion pipe when the pressure sensor detects a pressure outside a target pressure range to restore the pressure to within the target pressure range.
  • the method comprises providing a level sensor adapted to measure a level of slurry within the first flash tank, the control valve connected to the level sensor.
  • control valve is adapted, on the level sensor detecting an increase in slurry level within the first flash tank, to decrease the flow of steam through the first steam diversion pipe. In an embodiment the control valve is adapted, on the level sensor detecting a decrease in slurry level within the first flash tank, to increase the flow of steam through the first steam diversion pipe.
  • control valve is adapted to increase and/or decrease the flow of steam through the first steam diversion pipe, on the slurry level sensor detecting a slurry level outside a target slurry level range, to restore the slurry level to within the target slurry level range.
  • control valve is connected to the pressure sensor and the level sensor.
  • first steam diversion pipe connects the first steam pipe and the first slurry pipe, the first steam diversion pipe adapted to introduce at least part of the flash steam discharged from the first steam outlet into the slurry discharged from the first flash tank; and the control valve on the first steam diversion pipe is operable to control the flow of steam introduced into the slurry discharged from the first flash tank.
  • the first slurry pipe is fitted with an orifice plate positioned intermediate the first slurry outlet and the second slurry inlet, the method comprising connecting the first steam diversion pipe at a first end to the first steam pipe; and connecting the first steam diversion pipe at a second end to the first slurry pipe at a point intermediate the orifice plate and the second slurry inlet.
  • the first steam diversion pipe connects the first steam pipe and the second flash tank, the first steam diversion pipe adapted to introduce at least part of the flash steam discharged from the first steam outlet directly into the second flash tank; and the control valve on the first steam diversion pipe is operable to control the flow of steam introduced directly into the second flash tank.
  • the method of recovering energy further comprises: providing a second slurry outlet adapted to discharge the slurry from the second flash tank;
  • the first steam diversion pipe connects the first steam pipe and the second steam pipe, the first steam diversion pipe adapted to introduce at least part of the flash steam discharged from the first steam outlet into a flow of steam discharged from the second flash tank; and the control valve on the first steam diversion pipe is operable to control the flow of steam introduced into the flow of steam discharged from the second flash tank.
  • the first steam diversion pipe connects the first steam pipe and an export pipe, the first steam diversion pipe adapted to introduce at least part of the flash steam discharged from the first steam outlet into one or more of a water evaporator or other auxiliary use.
  • a refining system comprises at least one flash tank having an energy recovery system according to the first aspect.
  • the refining system further comprises at least one flash tank having a control valve on its associated slurry line.
  • the invention in one aspect comprises several steps.
  • the relation of one or more of such steps with respect to each of the others, the apparatus embodying features of construction, and combinations of elements and arrangement of parts that are adapted to affect such steps, are all exemplified in the following detailed disclosure.
  • This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features.
  • '(s)' following a noun means the plural and/or singular forms of the noun.
  • the term 'and/or' means 'and' or 'or' or both. It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5, and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed.
  • Figure 1 shows an example of a prior art energy recovery system.
  • Figure 2 shows an example of an energy recovery system in accordance with the first aspect of the invention.
  • Figure 3 shows an embodiment of the energy recovery system of figure 2 that enables a flash tank to be optionally bypassed.
  • FIG. 4 shows an example of an energy recovery system in accordance with the third aspect of the invention.
  • Figure 5 shows an embodiment of the energy recovery system of figure 4 that enables a flash tank to be optionally bypassed.
  • FIG. 1 shows an example of a prior art energy recovery system 100 within a digestion flash train.
  • the system 100 is particularly suited to the extraction of alumina from bauxite.
  • a digestion vessel 102 receives ground bauxite and a solution of sodium hydroxide (caustic liquor). By applying steam and pressure within the digestion vessel 102, the bauxite dissolves. The alumina released from the bauxite as it dissolves reacts with the sodium hydroxide to form sodium aluminate. The remaining solids form a waste product known in the industry as 'red mud'.
  • the material within the digestion vessel 102 typically comprises a suspension of silicates, iron oxides and titanium oxides. The slurry is flash-cooled to atmospheric boiling point by flowing through a series of flash tanks that operate at successively lower pressures.
  • 'flash tank' as used in the specification means a pressure vessel. It is common in the industry to refer to an unpressurised 'tank' and a pressurised 'vessel'. However it is also common to refer to a pressurised 'flash tank'.
  • One such flash tank is shown as a first flash tank 104.
  • the tank 104 has a slurry inlet 106 adapted to receive the slurry discharged from the digestion vessel 102 through a slurry pipe 108.
  • a control valve 110 referred to as a back pressure control valve, is fitted to slurry pipe 108.
  • the slurry pipe 108 further includes an orifice plate 112 to reduce the differential pressure across the control valve 110.
  • the tank 104 has a slurry outlet 114 that is adapted to discharge the slurry from tank 104 into a slurry pipe 116.
  • Slurry pipe 116 is fitted with an orifice plate 118 to reduce the pressure between flash tank 104 and flash tank 130.
  • Some slurry pipes, particularly downstream slurry pipes that operate at lower temperatures and pressures, may have control valves instead of orifice plates.
  • Slurry pipe control valves may not be practical for high temperature/pressure flash tanks because valves that are able to withstand the required temperature and pressure are very expensive, and the harsh conditions can lead to high maintenance cost and reliability issues.
  • Flash steam is generated within slurry pipe 108 and/or flash tank 104.
  • the tank 104 includes a steam outlet 120 adapted to discharge the flash steam into a steam pipe 122.
  • a heat exchanger 124 is connected to the steam pipe 122.
  • heat exchangers include shell and tube heat exchangers and/or direct steam injection heaters.
  • the heat exchanger 124 is adapted to preheat caustic liquor and/or slurry entering the digestion vessel 102 through pipe 126. Condensate from the heat exchangers, indicated for example at 128 is used for boiler feed water and/or for washing waste mud.
  • a second flash tank 130 has a slurry inlet 132 adapted to receive the slurry discharged from flash tank 104.
  • the slurry pipe 116 connects slurry outlet 114 of flash tank 104 to slurry inlet 132 of flash tank 130.
  • Flash tank 130 has a slurry outlet 134 that is adapted to discharge the slurry from tank 130 into a slurry pipe 136.
  • the slurry pipe is connected to a further flash tank.
  • the flash tanks are arranged so as to create a series of flash tanks that operate at successively lower pressures.
  • flash tank 130 operates at a lower pressure than flash tank 104.
  • the orifice plate 118 ensures that there is sufficient differential pressure between flash tank 104 and flash tank 130.
  • Flash steam is generated within slurry pipe 116 and/or flash tank 130 in the same way as in slurry pipe 108 and/or flash tank 104.
  • Flash tank 130 includes a steam outlet 138 adapted to discharge the flash steam into a steam pipe toward a heat exchanger in the same manner as for flash tank 104.
  • the pressure drop through the slurry pipe 116 from flash tank 104 to flash tank 130 is a function of the mass flow of slurry and steam. As the steam fraction in the slurry pipe 116 increases, the volumetric flow increases which in turn increases the pressure drop. With an increasing pressure drop there is also an increasing amount of steam evolved from the slurry.
  • the performance of the heat exchangers determines the amount of steam condensed at each flash tank stage. This in turn affects the steam balance for each flash tank and the amount of steam exiting the flash tank with the slurry.
  • the heat exchanger performance also changes with flash tank pressures, spent liquor temperature feeding the heat exchanger, and the condition of the heater tubes.
  • the changing heat exchanger performance has the potential to alter the steam balance existing within the flash tank.
  • the amount of steam present in the slurry therefore changes, which in turn alters the pressure drop, which then changes the steam temperatures and heat exchanger performance. All of these effects are linked, which has the potential to produce a process cascade that is highly variable.
  • a small change in the process conditions results in a large change in pressures along the flash tank train as the system finds a new equilibrium. Determining a single fixed orifice plate 118 for slurry pipe 116 to suit the complete range of process conditions is very difficult.
  • the principal compromise involves accepting high steam flow rates through the slurry piping. High steam flow rates can increase the maintenance requirement for the slurry pipe 116.
  • FIG. 2 shows an example of an energy recovery system 200 that is intended to address some of the disadvantages of the prior art system shown above in figure 1.
  • the system 200 includes a digestion vessel 202, a first flash tank 204, and a second flash tank 230 that are similar to tanks 102, 104 and 130 respectively from figure 1.
  • the first flash tank 204 has a slurry inlet 206 adapted to receive the slurry discharged from the digestion vessel 202 through a slurry pipe 208.
  • a slurry outlet 210 is adapted to discharge slurry from tank 204 to a slurry pipe 212.
  • a steam outlet 214 is adapted to discharge flash steam into a steam pipe 216 connected to a heat exchanger 224 in the same manner as flash tank 104 from figure 1.
  • the second flash tank 230 has a slurry inlet 232 adapted to receive the slurry discharged from flash tank 204.
  • the slurry pipe 212 connects slurry outlet 210 of flash tank 204 to slurry inlet 232 of flash tank 230.
  • flash tank 230 is connected to a further flash tank adapted to receive slurry discharged from flash tank 230.
  • slurry pipe 208 and slurry pipe 212 are fitted with orifice plates 240 and 242 respectively.
  • the orifice plates are intended to ensure that there is a sufficient pressure drop between flash tanks to provide the required pressure at each stage.
  • the overall sizing of the orifice plates is chosen to provide an even pressure distribution through the system. The actual size chosen will depend on the piping layout of an individual plant.
  • a steam diversion pipe 250 is connected to steam pipe 216.
  • the steam diversion pipe 250 is adapted to divert at least part of the flash steam within the steam pipe 216.
  • a control valve 252 is fitted to steam diversion pipe 250.
  • the control valve 252 is connected to a sensor 254.
  • the senor 254 is a pressure sensor adapted to measure a pressure within the flash tank.
  • the senor 254 is a level sensor adapted to measure a level of slurry within the flash tank. In an embodiment the sensor 254 comprises a pressure sensor and a level sensor.
  • the steam diversion pipe 250 is adapted to divert at least part of the flash steam discharged from the steam outlet 214 away from the heat exchanger 224.
  • the steam diversion pipe 250 is adapted to introduce at least part of the flash steam discharged from the steam outlet 214 of the flash tank 204 into the slurry discharged from the first flash tank 204.
  • the steam diversion pipe 250 in one embodiment is connected at a first end to the steam pipe 216 and is connected at a second end to the slurry pipe 212.
  • the steam diversion pipe 250 for example is connected to the slurry pipe 212 at a point in the slurry pipe 212 between the orifice plate 242 and the slurry inlet 232.
  • the steam diversion pipe 250 is adapted to introduce at least part of the flash steam directly into flash tank 230 in addition to, or as an alternative to, introducing the flash steam into slurry pipe 212.
  • the control valve 252 on the steam diversion pipe 250 is operable to control the flow of steam introduced directly into the second flash tank 230.
  • the steam diversion pipe 250 connects the steam pipe 216 and an export pipe, the steam diversion pipe 250 adapted to introduce at least part of the flash steam discharged from the steam outlet 214 into another part of the plant.
  • flash steam could be introduced into a water evaporator or other auxiliary use.
  • the control valve 252 in an embodiment is adapted to control steam flow through the slurry pipe 212.
  • the control valve 252 closes to decrease a flow of steam through the first steam diversion pipe 250 and to increase the steam flow through the slurry pipe 212 via the outlet 210.
  • the control valve 252 opens to increase a flow of steam through the first steam diversion pipe 250 and to decrease the steam flow through the slurry pipe 212.
  • the control valve 252 closes to decrease a flow of steam through the first steam diversion pipe 250 and to increase the steam flow through the slurry pipe 212 via the outlet 210.
  • the control valve 252 opens to increase a flow of steam through the first steam diversion pipe 250 and to decrease the steam flow through the slurry pipe 212.
  • control valve 252 is adapted to increase and/or decrease a flow of steam through the steam diversion pipe 250 when the sensor 254 detects a pressure in flash tank 204 that is outside a target range to restore the pressure to within the target range.
  • control valve 252 is adapted to increase and/or decrease a flow of steam through the steam diversion pipe 250 when the sensor 254 detects a slurry level in flash tank 204 that is outside a target range to restore the slurry level to within the target range.
  • the control valve 252 has the potential to control a pressure drop between flash tank 204 and flash tank 230 without the use of a control valve in the slurry pipe 212.
  • the addition of the steam pipe 250 with control valve 252 between flash tank 204 and flash tank 230 has the potential to balance the steam for each of flash tanks 204 and 230 so that when the steam demand reduces in flash tank 204, the excess steam can be directed to the downstream flash tank 230.
  • the energy can be recovered by the heat exchanger associated to the flash tank 230.
  • Flash tank pressure and slurry level are inversely related. Diverting steam from the steam outlet 214 reduces the pressure in the first flash tank 204 and causes the slurry level in the first flash tank 204 to increase. This reduces the steam fraction within the slurry pipe 212 and reduces the pressure drop between the first flash tank 204 and the second flash tank 230.
  • Slurry level is also related to the size of the orifice plates.
  • the orifice plates should be sized so that at the highest slurry flow rate, the pressure drop across the orifice plate is sufficient to generate a slurry level in the flash tank that the slurry is discharged from.
  • orifice plate 242 should be sized so that at the highest slurry flow rate the pressure drop across orifice plate 242 generates a slurry level in flash tank 204.
  • a higher slurry level in the first flash tank 204 increases the static head in the first flash tank 204 and increases the pressure at outlet 210, increasing the pressure drop between the first flash tank 204 and the second flash tank 230.
  • a slurry level will not necessarily be present in a flash tank, depending on the
  • control valve 252 as required to maintain the steam balance/pressure drop within a range of a pressure setpoint.
  • flash tank 230 is fitted with a steam diversion pipe, control valve and pressure sensor similar to steam diversion pipe 250, control valve 252 and pressure sensor 254 respectively.
  • at least some of the flash tanks are fitted with similar steam pipes.
  • the flash tanks closest to the digestion vessel 202 are each fitted with steam pipes.
  • Figure 3 shows an embodiment of an energy recovery system 200 that enables flash tank 230 to be optionally bypassed, for example so that the system can continue to operate if flash tank 230 is taken offline.
  • the second flask tank 230 has a slurry outlet 234 adapted to discharge the slurry from the second flash tank 230, and a steam outlet 238 adapted to discharge flash steam from the second flash tank 230.
  • a third flash tank 260 is similar to the first flash tank 204 and the second flash tank 230.
  • the third flash tank 260 has a slurry inlet 262 adapted to receive the slurry discharged from the first flash tank 204 or the second flash tank 230.
  • the third flash tank 260 is fitted with a steam diversion pipe, control valve and pressure sensor similar to steam diversion pipe 250, control valve 252 and pressure sensor 254 respectively.
  • flash tank 260 is connected to a further flash tank adapted to receive slurry discharged from flash tank 260.
  • a slurry pipe 236 connects slurry outlet 234 of the second flash tank 230 to a slurry inlet 262 of the third flash tank 260.
  • a slurry bypass pipe 276 connects the slurry outlet 210 of the first flash tank 204 and the slurry inlet 262 of the third flash tank 260.
  • At least one slurry bypass valve 278 is in communication with the slurry bypass pipe 276 and the slurry pipe 212 of the first flash tank 204.
  • the at least one slurry bypass valve 278 is adapted to selectively divert the slurry from the first flash tank 204 into either the second flash tank 230 or the third flash tank 260.
  • a tank bypass pipe 264 is in communication with the steam outlet 214 of the first flash tank 204.
  • the tank bypass pipe 264 is adapted to divert at least part of the flash steam discharged from the steam outlet 214 away from the heat exchanger 224.
  • the tank bypass pipe 264 connects the steam diversion pipe 250 with the third flash tank 260 via the slurry pipe 236 that discharges slurry to the third flash tank 260.
  • the tank bypass pipe 264 is directly connected to the third flash tank 260.
  • At least one tank bypass valve 266 is in communication with the tank bypass pipe 264 and the steam diversion pipe 250, to selectively divert at least part of the flash steam discharged from the steam outlet 214 of the first flash tank 204 into the tank bypass pipe 264 or the steam diversion pipe 250.
  • the at least one tank bypass valve 266 is adapted to selectively divert at least part of the flash steam discharged from the first steam outlet 214 into the second flash tank 230 or the third flash tank 260.
  • a control valve 252 is operable to control the flow of steam diverted into the tank bypass pipe 264 or the steam diversion pipe 250 from the first flash tank 204.
  • the tank bypass pipe 264 and the slurry bypass pipe 276 allow the energy recovery system to operate if a flash tank is removed from the system, for example for maintenance purposes.
  • the energy recovery system 200 comprises further steam diversion pipes/valves and slurry bypass pipes/valves to enable steam to be diverted into one or more subsequent flash tanks, or to one or more pipes associated with a subsequent flash tank.
  • at least some of the steam diversion pipes are fitted with similar flash tank bypass pipes and tank bypass valves.
  • Figure 4 shows another embodiment of an energy recovery system 300.
  • the energy recovery system 300 has similar features and functions to those described above in relation to the energy recovery system 200, except as described below.
  • the steam diversion pipe 350 of energy recovery system 300 diverts steam to a steam pipe 356 of the second flash tank 330.
  • Like numbers are used to indicate like parts with the addition of 100.
  • the steam pipe 356 connects the steam outlet 338 of the second flash tank 330 with a heat exchanger 368.
  • Steam diversion pipe 350 connects the steam pipe 316 of the first flash tank 304 and the steam pipe 356 of the second flash tank 330.
  • steam diversion pipe 350 is adapted to divert at least part of the flash steam within the steam pipe 316 away from the heat exchanger 324. Instead of introducing at least part of the flash steam discharged from the steam outlet 214 of the first flash tank 204 into the slurry discharged from the first flash tank 204, the steam diversion pipe 350 is adapted to introduce at least part of the flash steam discharged from the steam outlet 314 of the first flash tank 304 into the flow of steam discharged from the steam outlet 338 of the second flash tank 330.
  • a control valve 352 is fitted to steam diversion pipe 350.
  • the control valve 352 is connected to a sensor 354.
  • the control valve 352 is operable to control the flow of steam introduced in the flow of steam discharged from the second flash tank 330.
  • This embodiment has the potential to be easier to retrofit than the embodiment of figures 2 and 3. It may be useful where heat loss through the pipes cause the steam in the steam pipe 356 to be near saturation temperature when it reaches heat exchanger 368. Where this is not the case, the embodiment of figure 2 may lead to greater system efficiencies.
  • FIG. 5 shows an embodiment of an energy recovery system 300 that enables flash tank 330 to be optionally bypassed, for example so that the system can continue to operate if flash tank 330 is taken offline.
  • This embodiment has similar features and functions to those described above in relation to the tank bypass embodiment of figure 3 above, except as described below.
  • the tank bypass pipe 364 connects the steam diversion pipe 350 with a steam pipe 372 of the third flash tank 360.
  • Like numbers are used to indicate like parts with the addition of 100.
  • Third flash tank 360 has a steam outlet 370 adapted to discharge flash steam from the third flash tank 360.
  • a steam pipe 372 connects the steam outlet 370 with a third heat exchanger 374.
  • a slurry bypass pipe 376 connects the slurry outlet 310 of the first flash tank 304 and the slurry inlet 362 of the third flash tank 360.
  • At least one slurry bypass valve 378 is in communication with the slurry bypass pipe 376 and the slurry pipe 312 of the first flash tank 304. At least one slurry bypass valve 378 is adapted to selectively divert the slurry from the first flash tank 304 into either the second flash tank 330 or the third flash tank 360.
  • a tank bypass pipe 364 is in communication with the steam outlet 314 of the first flash tank 304. The tank bypass pipe 364 is adapted to divert at least part of the flash steam discharged from the steam outlet 314 away from the heat exchanger 324. In the embodiment shown, the tank bypass pipe 364 connects the steam diversion pipe 350 with the steam pipe 372 of the third flash tank 360. At least one tank bypass valve 366 is in communication with the tank bypass pipe 364 and the steam diversion pipe 350, to selectively divert at least part of the flash steam discharged from the first steam outlet 314 into the tank bypass pipe 364 or the steam diversion pipe 350.
  • At least one tank bypass valve 366 is adapted to selectively divert at least part of the flash steam discharged from the first steam outlet 314 into the flow of steam discharged from the second flash tank 330 or the flow of steam discharged from the third flash tank 360.
  • a control valve 352 is operable to control the flow of steam diverted into the tank bypass pipe 364 or the steam diversion pipe 350 from the first flash tank 304. Similar to the embodiment of figure 3 above, the tank bypass pipe 364 and the slurry bypass pipe 376 allow the energy recovery system to operate if a flash tank is removed from the system, for example for maintenance purposes.
  • the energy recovery system 300 comprises further steam diversion pipes/valves and slurry bypass pipes/valves to enable steam to be diverted into one or more subsequent flash tanks, or to one or more pipes associated with a subsequent flash tank.
  • at least some of the steam diversion pipes are fitted with similar flash tank bypass pipes and tank bypass valves.
  • a refining system can comprise a combination of the energy recovery system 200 (figures 2 and 3) and the energy recovery system 300 (figures 4 and 5) associated with different flash tanks. An appropriate combination of embodiments may be selected to generate the highest efficiencies depending on system parameters.
  • the refining system further comprises at least one flash tank having a control valve on its associated slurry line.
  • the techniques described above are adapted to maintain a level within a flash tank. For example, when the level in the flash tank falls, the excess steam can be fed to a downstream flash tank thereby restoring the level.
  • the flash tank pressure will fluctuate with the overall slurry flow rate. In this scenario, a reduction in slurry flow will reduce the pressure drop between the flash tanks and ultimately reduce the pressure and temperature of the first high-pressure flash tank. The pressure of the highest pressure flash tank ultimately determines how much energy can be recovered from the slurry, therefore a drop in flash tank pressure is not always desirable.
  • a flash tank is operated with little or no level. The system is then controlled by setting a pressure of the flash tank and adjusting the steam control valve to maintain this set point. As the pressure of the flash tank falls, the steam valve closes thereby forcing more steam through the slurry piping and/or steam piping. With an increased steam fraction in the slurry the pressure drop between the flash tanks will increase and the pressure of the flash tank will be maintained.
  • the cascade of heater performance-steam balance-slurry/steam flow-flash tank pressures-heat exchanger performance is interrupted which produces a more stable system.
  • the process range that the orifice plates need to be sized for is much smaller. This has the potential to make the design process easier and greatly reduces the amount of steam that passes through the slurry piping.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Nutrition Science (AREA)
  • General Health & Medical Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)

Abstract

Un aspect de l'invention concerne un système de récupération d'énergie (200). Le système comprend un premier réservoir de détente (204) ayant une première entrée de suspension (206) conçue pour recevoir une suspension dans le premier réservoir de détente (204), une première sortie de suspension (210) conçue pour évacuer la suspension du premier réservoir de détente (204), et une première sortie de vapeur (214) conçue pour évacuer la vapeur de détente du premier réservoir de détente (204) ; et un second réservoir de détente (230) ayant une seconde entrée de suspension (232) conçue pour recevoir la suspension évacuée du premier réservoir de détente (204). Un premier tuyau de suspension (212) relie la première sortie de suspension (210) et la seconde entrée de suspension (232). Un premier tuyau de vapeur (216) relie la première sortie de vapeur (214) à un premier échangeur de chaleur (224). Un premier tuyau de dérivation de vapeur (240) est relié au premier tuyau de vapeur (216), le premier tuyau de dérivation de vapeur (240) étant conçu pour dévier au moins une partie de la vapeur de détente évacuée de la première sortie de vapeur (214) à l'opposé du premier échangeur de chaleur (224). Une vanne de régulation (252) sur le premier tuyau de dérivation de vapeur (240) peut fonctionner pour contrôler un écoulement de vapeur dévié à travers le premier tuyau de dérivation de vapeur (240).
PCT/NZ2018/050119 2017-09-08 2018-09-04 Système et méthode de récupération d'énergie WO2019050415A1 (fr)

Applications Claiming Priority (4)

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AU2017903642A AU2017903642A0 (en) 2017-09-08 Energy recovery system and method
AU2017903642 2017-09-08
AU2017904829 2017-11-30
AU2017904829A AU2017904829A0 (en) 2017-11-30 Energy recovery system and method

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