Supercritical water oxidation reactor and process

Abstract

The present invention relates to supercritical water oxidation reactor adapted to contain inside the reactor an aqueous fluid below and above its supercritical state, said fluid comprising organic and/or inorganic material and a method of controlling such a reactor.

Claims

1. A supercritical water oxidation reactor (1) adapted to contain inside the reactor (1) an aqueous fluid below and above its supercritical state, said fluid comprising organic and/or inorganic material, wherein the reactor (1) comprising: a reactor body (2) in the form of an elongate tubular element arranged, during use, with its longitudinal extension parallel to or substantially parallel to gravity, the reactor body (2) being closed at its upper and lower ends thereby defining a cavity (3) inside the reactor body (2); a residue output connection (4) having an inlet (5) arranged at a first vertical height (h.sub.1) inside the cavity (3) and having an outlet (6) arranged outside the reactor body (2), said residue output connection (4) extends from its inlet (5) downwardly towards the lower of the reactor; a distillate output connection (7) having an inlet (8) arranged at a second vertical height (h.sub.2) inside cavity (3) being higher than the first vertical height (h.sub.1) and having an outlet (9) arranged outside the reactor body (2), said distillate output connection (7) extends from its inlet (8) downwardly towards the lower end of the reactor; an aqueous fluid inlet connection (10) arranged at the lower end of the reactor body for inletting into the cavity (3) the aqueous fluid to be brought into and above its supercritical state, a plurality of individual controllable thermal elements (11), at least some of the plurality of thermal elements (11) are arranged below the first height (h.sub.1) in the reactor body (2) and/or inside the cavity (3) and being adapted to provide an individually controllable heat flux into/out from the cavity (3) so as to impose a vertical temperature profile on the fluid inside the cavity (3), and a plurality of temperature sensors (14) arranged to measure a fluid temperature, or a temperature of the reactor body, at a plurality of different vertical positions, including a position above and a position below the first vertical height (h.sub.1) and/or a salt concentration sensor (15) arranged to measure the salt concentration in the fluid flowing through the residue output connection (4).

2. A supercritical water oxidation reactor according to claim 1, wherein at least the thermal element(s) (11) arranged below the first vertical height (h.sub.1) is(are) configured to provide sufficient heat to fuel or to cool the process.

3. A supercritical water oxidation reactor according to claim 1, wherein the thermal element(s) (11) is(are) configured for and/or used for cooling only at and/or below the first vertical height (h.sub.1).

4. A super critical water oxidation reactor according to claim 1, wherein the plurality of individually controllable thermal elements (11) comprises at least some thermal elements (11) arranged above the first vertical height (h.sub.1).

5. A supercritical water oxidation reactor according to claim 1, wherein the plurality of thermal elements (11) are arranged vertically side-by-side, optionally with a vertical distance between each element (11), at the wall or in the reactor body.

6. A supercritical water oxidation reactor according to claim 1, wherein one or more of the plurality of thermal elements (11) are arranged vertically side-by-side, optionally with a vertical distance between each element (11), inside the cavity (3).

7. A supercritical water oxidation reactor according to claim 1, wherein a number of the thermal elements (11) are adapted to provide a heat flux into the cavity (3) and the remaining thermal elements (11) are adapted to provide a heat flux out from the cavity (3).

8. A supercritical water oxidation reactor according to claim 1, wherein each thermal element (11) fully encircles the reactor body (2) along a horizontal perimeter of the reactor body (2).

9. A supercritical water oxidation reactor according to claim 1, wherein one or more, or all, of the thermal elements (11) are electrical heating elements and/or electrical cooling elements and/or are Peltier elements and/or are tubular heat exchangers configured for receiving a heating/cooling fluid.

10. A supercritical water oxidation reactor according to claim 1, wherein the reactor further comprising a catalyst (13) arranged above the first vertical height, said catalyst enhancing the oxidation process(es) in the reactor.

11. A supercritical water oxidation reactor according to claim 1, wherein the catalyst (13) is arranged in front of and/or below the inlet (8) of the distillate output connection (7).

12. A supercritical water oxidation reactor according to claim 1, wherein the reactor further comprising a salt filter (16) for filtering salt, if any, from the fluid leaving the reactor through the distillate output connection (7).

13. A supercritical water oxidation reactor according to claim 12, wherein the salt filter (16) is arranged in front of and/or below the inlet (8) of the distillate output connection (7).

14. A supercritical water oxidation reactor according to claim 12, wherein the salt filter comprising a catalyst arranged in the salt filter to provide contact with the fluid leaving the reactor through the distillate output connection (7).

15. A supercritical water oxidation reactor according to claim 12, wherein the salt filter is in the form of or comprising a screen, a cyclone, a moving bed filter or catalysts enhancing oxidation processes so as to speed-up of the oxidation processes taking place in the reactor.

16. A supercritical water oxidation reactor according to claim 1, further comprising an oxidation fluid input connection (12) arranged at the lower end of the rector body for inputting into the cavity (3) an oxidant.

17. A supercritical water oxidation reactor according to claim 1, wherein the inlet (5) of the residue output connection (4) is arranged vertically moveable inside the cavity (3).

18. A supercritical water oxidation reactor according to claim 1, wherein the residue output connection (4) is configured to provide a flow path of a distance being longer than the first height so as to enhance heat exchange between the fluid flowing internally in the residue output connection and the fluid surrounding the residue output connection said residue output connection (4) being preferably coiled along a least a part of the residue output connection.

19. A supercritical water oxidation reactor according to claim 1, wherein the distillate output connection (7) is configured to provide a flow path of a distance being longer than the second height so as to enhance heat exchange between the fluid flowing internally in the distillate output connection and the fluid surrounding the distillate output connection said distillate output connection (7) being preferably coiled along a least a part of the distillate output connection.

20. A supercritical water oxidation reactor according to claim 1, further comprising an inner liner (18) forming an inner cavity (20) being open at an upper end thereof and comprising the aqueous fluid inlet connection (10) at the lower end of the inner cavity (20), said inner liner (18) is provided with dimensions providing a horizontal distance (.sub.1) between an inner surface of the reactor body (2) and an outer surface of the inner liner (18) thereby defining a space there-between and the reactor further comprising a further distillate outlet connection (17) in fluid communication with said defined space.

21. A supercritical water oxidation reactor according to claim 20, wherein said inner liner (18) is provided with dimensions providing a distance vertical (.sub.2) between the bottom of the reactor body (2) and a bottom of the inner liner (18) thereby defining a space there-between, said space being in fluid communication with the further distillate outlet connection (17).

22. A supercritical water oxidation reactor according to claim 20, wherein residue output connection (4) is arranged inside the inner liner (18).

23. A supercritical water oxidation reactor according to claim 20, wherein distillate output connection (7) is arranged inside the inner liner (18).

24. A super critical water oxidation reactor according to claim 23, wherein the distillate output connection (7) comprising a coiled section encircling at least a section of the residue output connection (4).

25. A supercritical water oxidation reactor according to claim 20, wherein the inner liner (18) has a upper rim (21), which upper rim (21) is arranged at or below the same vertical height (h.sub.2) as the inlet (8) of distillate output connection.

26. A supercritical water oxidation reactor according to claim 20, wherein a salt filter (16) and/or a catalyst (13) is(are) be arranged at the upper end of the inner liner (18), said catalyst being selected from the group catalysts enhancing the oxidation process(es) in the reactor.

27. A supercritical water oxidation reactor according to claim 1, wherein the reactor body comprising a reactor liner (19) forming at least a part of the reactor body (2) being in contact with the fluid inside the supercritical water oxidation reactor and is made from a material being resistant to chemical corrosion.

28. A supercritical water oxidation process for treating an aqueous fluid comprising organic and/or inorganic material the process comprising feeding the fluid into a reactor according to claim 1, and controlling the heat flux through the reactor body by use of the thermal elements (11) to obtain a vertical reference temperature profile in the reactor (1).

29. A supercritical water oxidation process according to claim 28, wherein the controlling of the heat flux through the reactor body includes: determining the temperatures by use of the temperature sensors (14); comparing the determined temperatures to the reference temperature profile, and at each position where a thermal element (11) is located increase the heat content in fluid in the reactor at the specific location, if the temperature determined is lower than the reference temperature at the specific position, or decrease the heat content in the fluid in the reactor at the specific location, if the temperature determined is higher than the reference temperature at the specific position and/or adjusting the flow of organics into the reactor.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The present invention and in particular preferred embodiments thereof will now be described in greater details with reference to the accompanying figures. The figures show ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

(2) FIG. 1 schematically illustrates in a cross sectional view a reactor according to a first embodiment of the invention,

(3) FIG. 2 schematically illustrates in a cross sectional view a reactor according to a second embodiment of the invention in which the reactor further comprising a catalyst (and/or mechanical filter for trapping inorganic salt),

(4) FIG. 3 is a schematically illustration of a control method according to a preferred embodiment of the invention,

(5) FIG. 4 schematically illustrates in a cross sectional view a reactor according to a further embodiment of the invention,

(6) FIG. 5 schematically illustrates in a cross sectional view a reactor according to a further embodiment of the invention,

(7) FIG. 6 schematically illustrates in a cross section view a reactor according to a further embodiment of the invention,

(8) FIG. 7 schematically illustrates in a cross sectional view a further embodiment, wherein a salt filter and/or a catalyst is(are) arranged at the upper end of the inner liner shown in FIG. 6.

DETAILED DESCRIPTION OF AN EMBODIMENT

(9) Reference is made to FIG. 1 illustrating schematically a supercritical water oxidation reactor 1 according to a preferred embodiment. The reactor 1 is illustrated as a cross sectional view and the reactor is typically in the form an elongate tubular element, such as a cylinder, extending in vertical direction, during use. The reactor is adapted to contain inside the reactor 1 an aqueous fluid below and above its supercritical state. Thus, as the supercritical state of the fluid is accompanied by a relatively high pressure and temperature, the reactor 1 is adapted by a suitable selection of material and thickness of the material so that the reactor can withstand the pressure and temperature.

(10) The fluid typically comprising organic and/or inorganic material and, as disclosed herein, the reactor 1 is for providing a supercritical water treatment and/or supercritical water gasification of the fluid typically in manner where e.g. salt(s) precipitate when the fluid enters into a super critical phase. It is noted, that during operation, there will typically be a flow of fluid from the sub-critical phase to the supercritical phase as will be disclosed in further details below.

(11) Accordingly, the reactor 1 of FIG. 1 comprises a reactor body 2 in the form of an elongate tubular element arranged, during use, with its longitudinal extension parallel to or substantially parallel to gravity, the reactor body 2 being closed at its upper and lower ends thereby defining a cavity 3 inside the reactor body 2.

(12) The reactor 1 has a residue outlet connection 4 having an inlet 5 arranged at a first vertical height h.sub.1 inside the cavity 3 and having an outlet 6 arranged outside the reactor body 2. The reactor 1 also has a distillate output connection 7 having an inlet 8 arranged at a second vertical height h.sub.2 inside cavity 3 being higher than the first vertical height h.sub.1 and having an outlet 9 arranged outside the reactor body 2. It is noted that the terms inlet and outlet refer to the preferred flow direction through the connections of the reactor during use.

(13) As illustrated in the FIG. 1 (and in FIGS. 2-6) the residue output connection 4 extends from its inlet 5 downwardly towards the lower end of the reactor. Similarly, the distillate output connection 7 extends from its inlet 8 downwardly towards the lower end of the reactor. This provides a flow where feed enters into the reactor 1 at the lower end of the reactor 1 (through aqueous fluid inlet 10) and flows upwardly towards the upper end of the reactor 1. Residue is produced below (and at the salt mirror) which flow downwardly through the residue output connection 4. Distillate is present above the salt mirror and flows downwardly through the distillate output connection 7.

(14) Further, liquid to be treated is to be fed into the reactor and to this, an aqueous fluid inlet connection 10 is arranged at the lower end, such as at the bottom of the rector body for inletting into the cavity 3 the aqueous fluid to be brought into and above its supercritical state. In the embodiment shown, the inlet connection 10 is shown at the side of reactor, however, the inlet connection 10 may also be arranged at the bottom of the reactor 1.

(15) As presented in the above, an aim of the invention is to be able to control the temperature in at least a part of the vertical extension of the reactor, typically in a region above and below the inlet 5 of the residue outlet connection 4, and in order to do this, the reactor 1 comprises a plurality of individually controllable thermal elements 11 arranged below the first vertical height h.sub.1. In FIG. 1, thermal elements 11 are arranged along the full length of the reactor, which is considered within the scope of the present invention.

(16) In certain preferred embodiments, the thermal elements 11 are arranged only below the first vertical height and are used for heating and/or cooling the fluid below the first vertical height. Thus, in such embodiments, at least the thermal element(s) 11 arranged below the first vertical height h.sub.1 is(are) configured to provide sufficient heat to fuel or cool the process. By fuel or heat the process is preferably meant that no further heat exchange in needed in order to keep the process running.

(17) In still further embodiments, the thermal element(s) 11 is(are) configured for and/or used for cooling only at and/or below the first vertical height h.sub.1.

(18) As presented in the figures, the reactor 1 may further comprise a plurality of individually controllable thermal elements (11) arranged above the first vertical height h.sub.1. The thermal elements 11 may be configured to provide a heat flux into and/or out from the reactor as presented below.

(19) The thermal elements 11 are typically of a type allowing both addition of heat to the reactor and extraction of heat from the reactor. While the thermal elements 11 may be arranged at different location of the reactor 1, such as at or in the reactor body 2 and/or inside the cavity 3, it is generally preferred to provide such elements 11 on the outer wall of the reactor body. This has inter alia the advantage that they are arranged away from the harsh environment inside the cavity 3 and easily accessible for e.g. servicing. The thermal element 11 are configured to provide an individually controllable heat flux into/out from the cavity 3 so as to impose a vertical temperature profile on the fluid inside the cavity 3.

(20) While the thermal element 11 can add heat to or extract heat from the fluid inside the cavity 3 individually, the amount of heat extracted or added are typically based on measurement of the temperature of the fluid inside the cavity 3, typically independently of each other.

(21) The temperature measurements are carried out by use of a plurality of temperature sensors 14 arranged to measure a fluid temperature at a given height of the reactor. The temperature sensors 14 should typically at least be arranged to measure the temperature in a region above and below the inlet 5 of the residue outlet connection 4. In many instances, it is more practical to arrange the temperature sensors 14 on the outside of the reactor body 2 (as illustrated in FIG. 1) and in such cases, the temperatures measured may deviate slightly from the temperature of the fluid inside the reactor 1 due to a temperature gradient though the wall of the reactor body. However, it has been found that this difference may either be neglected or encountered for by use of e.g. the heat conductivity of the reactor wall which is often well known. Thus, as illustrated in FIG. 1, it is preferred to determine the temperature of the reactor body 2, at a plurality of different vertical positions, including a position above and a position below the first vertical height h.sub.1. Although, temperature sensors 14 are illustrated in the figures herein to be applied along the full height of the reactor 1, it may be sufficient to have only temperature sensors 14 in a region above and below the first height h.sub.1. One or more temperature sensor 14 may also be arranged at the top of the reactor 1

(22) That the temperature is determined above and below the first vertical height h.sub.1 follows from the aim of controlling the position of the so-called salt mirror to be above the inlet of the residue outlet connection 5. As will be disclosed further e.g. with respect to FIG. 3, the position of the salt mirror is recognizable in a vertical temperature profile as a part of the profile where:

(23) $\frac{\mathrm{dT}}{\mathrm{dh}}<o$
where o is a small number, T is the temperature and h is the height from the bottom

(24) Or said in another manner, the change in temperature with height is smaller than changes in temperature above and below the salt mirror. The salt mirror will also typically occur close to the critical temperature of water 374 C.

(25) It is noted that although the fluid is moving around inside the cavity 3 of the reactor, the temperature of the fluid is considered to be equal along each horizontal cross section through the cavity 3. That this may be considered as an approximation can be seen e.g. in FIG. 3 where the salt mirror has a vertical extension of a substantive size, defining a zone where the fluid goes from sub-critical to super critical phase, which is due to the motion of the fluid inside the zone of reactor cavity 3.

(26) As an alternative to, or in combination with the temperature sensors 14, the reactor 1 may comprise a salt concentration sensor 15 arranged to measure the salt concentration in the fluid flowing through the residue output connection 4. This salt concentration sensor 15 may be used to determine whether the salt mirror is above or below the inlet 5 of the residue outlet connection 4 as if the salt mirror is above the inlet 5, salt will precipitate above the inlet 5 and find its way to the salt concentration sensor 15, whereas if the salt mirror is located below the inlet 5, salt will precipitate below the inlet 5 and at least a less amounts of salt or no salt at all will find its way to the salt concentration sensor 15. As a moving upwardly or downwardly of a salt mirror can be effected by changing the heat content in the fluid (e.g. by considering change in specific heat content as Q=C*T, where specific refers to per mass unit) below or above the salt mirror, this can be used as a control mechanism by increasing the heat in fluid below the inlet 5 by use of the thermal elements 11.

(27) It is noted that it generally preferred, that at least the thermal element(s) 11 arranged below the first vertical height h.sub.1 is(are) configured to provide sufficient heat to fuel the process.

(28) In the preferred embodiment shown in FIG. 1, the one or more of the plurality of thermal elements 11 are arranged vertically side-by-side preferably with a vertical distance between each element 11, at the wall. The thermal elements 11 may also be arranged in the reactor body 2. Alternatively, or in combination with the above, the one or more of the plurality of thermal elements 11 are arranged vertically side-by-side, preferably with a vertical distance between each element 11, inside the cavity 3. The number of thermal elements 11 used is often based on a requirements as to which degrees a control is aimed at; to this, if a high degree of control is the aim, a relatively higher number of elements 11 are used with less space in between than if a less degree of control is aimed at.

(29) The temperature of the fluid inside the reactor is, in general, determined by four contributions, namely: heat produced by reaction(s) in the fluid heat used by the reaction(s) in the fluid heat extracted from the fluid to the outside, and heat added to the fluid from the outside.

(30) As all thesein total fourways, the temperature of the fluid can be altered, there is preferably a need for both providing a heat flux into the cavity and for providing a heat flux out from the cavity to control the temperature inside the cavity 3. In order to achieve this, the reactor 1 shown in FIG. 1 may have a number of the thermal elements 11 which are adapted to provide a heat flux into the cavity 3 and the remaining thermal elements 11 are adapted to provide a heat flux out from the cavity 3. It is noted, that depending of the type of thermal elements 11, a thermal element 11 which may provide selectively both a heat flux into and a heat flux out from the cavity can be used. The thermal elements 11 used are typically identical from a mode of operation point of view (heat flux in or out) but may differ from each other from a capacity point of view (watts per element).

(31) It is often preferred to have a as constant as possible temperature along horizontal cross sections of the reactor and in such cases, each thermal element 11 preferably fully encircles the reactor body 2 along a horizontal perimeter of the reactor body 2. This means that along a horizontal perimeter of the reactor body 2, there are preferably no open areas not covered by the thermal element 11. Similarly, if the thermal elements 11 are arranged in the reactor body and/or inside the reactor, the thermal elements also encircles along a horizontal perimeter of the reactor body 2. However, thermal elements 11 may also be applied so as to cover a horizontal and vertical section of the reactor only.

(32) One or more, such as all, of the thermal elements 11 may be selected from: electrical heating elements, electrical cooling elements, Peltier elements tubular heat exchangers configured for receiving a heating/cooling fluid.

(33) It has been found in connection with the present invention that a catalytic material present in the supercritical region may have an advantageous effect in processing water with contaminants. Thus, a reactor according to the present invention may preferably further comprising a catalyst 13 arranged above the first vertical height, said catalyst being selected from catalysts enhancing oxidation processes so as to speed-up of the oxidation processes taking place in the reactor.

(34) In the embodiment shown in FIG. 2, the catalyst 13 is arranged in front of and/or below the inlet 8 of the distillate output connection 7 in a manner so that fluid leaving the reactor through inlet 8 comes into contact with the catalyst 13. The catalyst is typically a heterogeneous catalyst, e.g. in the form of pellets or a porous structure providing a flow path past the catalyst towards the inlet 8. Alternatively, or in combination thereto, the catalyst may be applied to surfaces of a flow structure e.g. a filter (as disclosed below).

(35) Although the invention aims at providing a salt-free distillate, some salt may be present in the distillate. Other salts may bond to organic matter and is released in the upper part of the reactor after oxidation. Such salts may need to be filter off in order to avoid clogging of the distillate output connection 7.

(36) In other situations, the salt mirror is temporarily above the inlet 8 of the distillate output connection 7 resulting in that salt precipitate above the inlet 8. To prevent salt from entering into the distillate output connection 7, a salt filter 16 may be arranged at the inlet 8 of the distillate output connection 7. Thus, a reactor may preferably further comprise a salt filter 16 for filtering salt, if any, from the fluid leaving the reactor through the distillate output connection 7. As illustrated in FIG. 2, the salt filter 16 may be arranged in front of and/or below the inlet 8 of the distillate output connection 7.

(37) As the salt filter 16 provides a flow path into the distillate output connection 7, the salt filter may advantageously comprise a catalyst arranged in the filter 16 to provide contact with the fluid leaving the reactor 1 through the distillate output connection 7, for instance the surface(s) of the filter 16 may be coated at least partly with or made at least partly from a catalytic material.

(38) The salt filter may for example be in the form of or comprising a screen, a cyclone, a moving bed filter, a plate filter or combinations thereof.

(39) The filters 16 may be cleaned from salts by lowering the temperature in the reactor in the region of the salt filter to sub-critical condition so as to dissolve the salts in the fluid, or the salt filter may be cleaned mechanically e.g. by scraping, shaking or the like or by back-flushing the filter.

(40) Some of process which suitable can be carried out by the present invention may require an addition of oxygen (or other fluids) and to this the reactor 1 may further comprise an oxidation fluid input connection 12, preferably arranged at the lower end of the rector body for inputting into the cavity 3 an oxidant (see e.g. FIGS. 1 and 2). If other fluids than oxygen is to be fed into the reactor, the oxidation fluid input connection 12 can serve this purpose. The oxidant may be a gas of a liquid comprising or consisting essentially of oxygen. It is noted that due to the elevated pressure inside the reactor, it may be needed to pump the oxidant into the cavity 3 which pumping and/or infeed may or may not result in phase change of the oxidant.

(41) The aqueous fluid inlet connection 10 and the oxidation fluid inlet connection 12 may instead of being shown in the figures as two separate inlets being provided as a single inlet and the two fluid (feed and oxidation fluid or other fluids) may be mixed outside the reactor 1; this may e.g. be accomplished by a T-pipe where the two fluids are fed into and mixed and fed from the T-pipe into the reactor 1.

(42) It has further been found that although the position of the salt mirror can be altered by use of the thermal element 11, it can be beneficial to be able to move the position of the inlet 5 of the residue output connection. To this, the reactor may be equipped with the inlet 5 of the residue output connection 4 being arranged vertically moveable inside the cavity 3. This may be provided e.g. by the residue output connection 5 has a telescopic part inside the cavity 3 and/or the with the output connection 5 being slideable arranged in vertical direction in the reactor 1.

(43) Reference is made to FIG. 3 introducing inter alia a reference temperature profile and a measured temperature profile. Such temperature profiles represents respectively a reference temperature profile or the actual temperature profile of the fluid inside the reactor as a function of the height (where zero height is the bottom of the reactor 1). The reference temperature can be seen as an temperature profile aimed at during use of the reactor and is used in a comparison with actual measured temperature to determine on control measures to be taken if deviations exists between the measured and reference temperatures. Differences between reference temperatures and measured temperatures are used to decide whether the temperature is to be increased or lowered at a given height in order to achieve a match between reference temperature profile and measured temperature profile. A threshold may be introduced in the sense that a difference should be above a certain threshold before changes are imposed e.g. in order to avoid instabilities in the control. As disclosed above, the heat flux is controlled by the thermal elements 11 and the temperatures are determined by the temperature sensors 14.

(44) Accordingly, in a process for treating an aqueous fluid comprising organic and/or inorganic material, such as waste water or industrial waste water in general, the process comprising feeding the fluid into a reactor as disclosed herein, and controlling the heat flux through the reactor body 2 by use of the thermal elements (11) to obtain a horizontal reference temperature profile in the reactor (1).

(45) The controlling of the heat flux through the reactor body typically includes: determining the temperatures by use of the temperature sensors 14; comparing the determined temperatures to the reference temperature profile, and at each position where a thermal element 11 is located increase the heat content in fluid in the reactor at the specific location, if the temperature determined is lower than the reference temperature at the specific position, or decrease the heat content in the fluid in the reactor at the specific location, if the temperature determined is higher than the reference temperature at the specific position and/or adjusting the flow of organics into the reactor.

(46) The adjustment of the flow of organics into the reactor typically refers to that the amount of organic material that is introduced into the reactor per time unit is adjusted. As the process taken place in the reactor are mainly exothermic a fuel is the organic material, a change in the amount of fuel available will have an influence in the temperature inside the reactor.

(47) The specific heat content (per mass unit) may be approximated by Q=C(TT.sub.0) where Q is the heat content, C is the specific heat capacity T is the temperature and T.sub.o is a zero point e.g. 0 Kelvin.

(48) As illustrated in FIG. 3, upper right figure, the measured temperature profile is shown together with the reference temperature profile and discrepancies are identified since: the reference temperatures are higher than the measured temperatures below the salt mirror, and the measured temperatures are higher than the reference temperatures above salt mirror.

(49) The actual state of operation of the reactor is indicated as supplying heat and extracting heat respectively above and below the point where the two temperature profiles cross each other.

(50) FIG. 3 lower part illustrates two different control situations. To the right in FIG. 3, a situation as illustrated in FIG. 3 upper right figures is show. As illustrated, the control involves cooling of the fluid above the crossing of the two temperature profiles and heating below that point. In implementing these measures, it may be necessary to take into account whether the process taking place inside the reactor at a given position is exothermic or not and where an exothermic process takes place, as e.g. heating of an exothermic process may be accomplished by lowering extraction of heat from the fluid. In FIG. 3 lower part to the left, the opposite situation is shown together with the measures to be taken according to preferred embodiments of the invention.

(51) In some situations, it may be practical to apply changes based on the result of one or more previous heat flux changes imposed. This could for instance be implemented by considered the time wise derivative of the difference between reference and measured temperature and if the changes growth in time, then the applied change in heat flux is inadequate and should be changed with opposite change, e.g. if

(52) $\frac{T_{t+t}-T_t}{t}>0\mathrm{and}{H}_{t+t}-H_t>0\mathrm{then}{H}_{2t}<H_t$
where
T=T.sup.RT.sup.M

(53) T is the temperature, superscript R refers to reference temperature profiled, M refers to measured temperature profiled, H is the heat flux and t is time.

(54) Reference is made to FIG. 4 schematically illustrates in a cross section view a reactor according to a further embodiment of the invention. Compared with the embodiment, the residue output connection 4 has been shaped so as to increase heat transfer between the fluid flowing internally in the residue output connection and the fluid flowing outside the residue output connection 4. In the embodiment shown in FIG. 4, the increase of heat transfer has been provided by shaping the residue output connection 4 as a coil which provides a relatively larger surface to transfer heat through as well as providing a flow pattern providing a higher transfer coefficient (h).

(55) Although not disclosed, the distillate output connection may alsoor alternatively to increasing the heat transfer of the residue output connectionbe shaped to increase heat transfer, e.g. by shaping the distillate output connection as a coil similarly to the illustrated coil of the residue output connection.

(56) Thus, the reactor of FIG. 4 resides inter alia in that the residue output connection 4 is configured to provide a flow path of a distance being longer than the first height, so as to enhance heat exchange between the fluid flowing internally in the residue output connection and the fluid surrounding the residue output connection, which is provided in a preferred embodiment by the residue output connection 4 is coiled along a least a part of the residue output connection.

(57) Further, the distillate output connection 7 may further or alternatively be configured to provide a flow path of a distance being longer than the second height, so as to enhance heat exchange between the fluid flowing internally in the distillate output connection and the fluid surrounding the distillate output connection, which may be provided by the distillate output connection 7 is coiled along a least a part of the distillate output connection. This is illustrated in FIG. 5 illustrating an embodiment in which both the residual output connection 4 as well as the distillate output connection is coiled. It is noted that the coiled regions may differ from what is disclosed in FIGS. 4 and 5.

(58) Reference is made to FIG. 6 schematically and in cross sectional view illustrates a further embodiment of a super critical water oxidation reactor 1 (SCWO-reactor 1). In the illustration depicted in FIG. 6, the thermal elements 11 as well as the temperature sensors 14 (not illustrated) are arranged as disclosed e.g. in relation to FIGS. 1, 2, 4 and 5.

(59) In the embodiment shown in FIG. 6, SCWO-reactor 1 comprises an inner liner 18 forming an inner cavity 20 being open at the upper end and comprising the aqueous fluid inlet connection 10 at the lower end of the inner cavity. As illustrated the aqueous fluid inlet connection 10 extends from the outside the SCWO-reactor 1 and to the interior of the inner cavity 20.

(60) The inner liner 18 is made from a fluid impermeable material such as metal, and as illustrated the inner liner 18 is provided with dimensions providing a horizontal distance .sub.1 between the inner surface of the reactor body 2 and the outer surface of the inner liner 18 defining a space there between as well as a vertical distance .sub.2 between the bottom of the reactor body 2 and the bottom of the inner liner 18 defining a space there between. As will become apparent from the following disclosure, these distances provides flow passages inside the SCWO-reactor 1. It is noted that the vertical distance .sub.2 may be zero, meaning the inner liner 18 extend to and abut the bottom of the reactor body 2, or the bottom of the inner liner 18 is constituted by the inner bottom surface of the reactor body 2; in later case, it may be preferred to provide a fluid sealing between the inner line 2 and the inner bottom surface of the reactor body 2. When the vertical distance .sub.2 is zero, the outgoing distillate will flow around the tubular gap between the liners 18 and 19 (wall of reactor body if no line 19 is provided) and communicate with the further distillate outlet 17.

(61) In FIG. 6, a reactor liner 19 is also illustrated. This reactor liner 19 forms at least a part of the reactor body 2 of SCWO-reactor being in contact with the fluid inside the reactor and is preferably made from a material being resistant to chemical corrosion

(62) The position of the critical point (salt mirror position) above which the fluid is super critical and below which the fluid is sub critical is also illustrated in FIG. 6.

(63) The residue output connection 4 is arranged inside the inner liner 18 and the inlet of the residue output connection 5 is arranged at a vertical height h.sub.1 that is below the position of the critical point during normal operation.

(64) The distillate output connection 7 is also arranged inside the inner liner 18 although with its inlet 8 of the residue output connection 7 arranged at the vertical height h.sub.2, that is above the position of the critical point during normal operation. In the embodiment shown in FIG. 6, the distillate output connection 7 comprising a coiled section encircling the residue output connection 4 and acting as a heat exchanger heating the aqueous fluid entering into the inner cavity 20 formed by the inner liner 18. At the bottom of the SCWO-reactor 1, the coiled section of the distillate output connection proceed into a straight section extending to the outside of the SCWO-reactor 1 and forming the outlet 9 of the distillate output connection 7.

(65) As also illustrated in FIG. 6, the upper rim 21 of the inner liner 18 is arranged at the same vertical height h.sub.2 as the inlet 8 of distillate output connection 7, although the height at which the upper rim 21 may be offset, typically downward to a position above the position at which the fluid is critical. That is, the upper rim 21 is positioned to be in supercritical zone.

(66) During normal operation, the aqueous liquid is fed into the reactor 1 through the aqueous fluid inlet connection 10 and enters thereby into the inner cavity 20 formed by the inner liner 18. The aqueous fluid is heated (or cooled) by the thermal elements 11 and/or by the fluid flowing downwardly inside the distillate output connection 7. As described herein, the aqueous fluid is heated so that the fluid becomes critical at a vertical position above h.sub.1 and below h.sub.2 thereby produces a residue flowing into the residue output connection 4. The distillate (produced by the fluid becomes super critical) moves upwardly in the super critical region. The distillate has two flow paths out of the SCWO-reactor 1 namely through the distillate output connection 7, and through the space defined between the inner liner 18 and the wall liner 19 (provided by the distance .sub.1) as well as the space below the inner liner 18 and the bottom of the reactor (provided by the distance .sub.2) forming a flow path towards a further distillate outlet 17.

(67) It is noted that the fluid flowing in the space between the inner liner 18 and the wall liner 19 will also exchange heat with the fluid inside the inner liner 18, and the heat exchange rate may be controlled e.g. by controlling the mass flow in said space. Further, since the flow in the space between the inner liner 18 and the wall line 19 is highly controllable (e.g. by regulating the flow out of the further distillate outlet 17 by a valve mechanism), this flow may be controlled in accordance with specific needs and/or applications.

(68) By equipping the SCWO-reactor 1 with an inner liner 18, the fluid contacting the reactor wall, e.g. the wall liner 19, may be restricted to distillate being less corrosive than the residue. This has the advantage that the reactor body 2 can be made with the aim to withstand the pressure inside the reactor, and the inner liner 18 can be designed to withstand corrosion (or other material degradation processes). Further, the inner liner 18 can be replaced without the need for replacing parts of the reactor body 2, whereby the inner liner 18 can be made as a replaceable insert. Further, in case the salt mirror becomes located below the inlet 5 of the residue output connection 4, the salt being released will be kept inside the inner cavity, thereby not contacting the wall of the reactor body 2.

(69) Since the inner liner 18 introduces a space in between the inner liner 18 and the wall of the reactor body, it may be necessary to pump pure water into the space for flushing purposes, which flushing will typically be performed with a flow going from bottom towards the top of the SCWO-reactor 1. In such cases, the further distillate outlet 17 can be used as an inlet for the flushing liquid, and/or a separate inlet dedicated for introducing the flushing liquid can be arranged in the reactor 1.

(70) As disclosed in connection with FIG. 2, the embodiment shown in FIG. 6 may also comprise a salt filter 16, which may be arranged in front of and/or below the inlet 8 of the distillate output connection 7. The salt filter 13 may for example be in the form of or comprising a screen, a cyclone, a moving bed filter, a plate filter or combinations thereof.

(71) As also illustrated in connection with FIG. 2, a catalyst 13 may arranged in front of and/or below the inlet 8 of the distillate output connection 7 in the embodiment of FIG. 6 in a manner so that fluid leaving the reactor through inlet 8 comes into contact with the catalyst 13. The catalyst is typically a heterogeneous catalyst, e.g. in the form of pellets or a porous structure providing a flow path past the catalyst towards the inlet 8. Alternatively, or in combination thereto, the catalyst may be applied to surfaces of a flow structure e.g. a filter. The catalyst being selected from the group catalysts enhancing the oxidation process(es) in the reactor.

(72) In a further embodiment, the salt filter 16 and/or the catalyst 13 may be arranged at the upper end of the inner liner 18. This is schematically illustrated in FIG. 7 in which an upper section of the inner liner 18 is depicted. As illustrated in FIG. 7 the upper rim 21 is in such embodiments preferably formed by an upper rim of the salt filter 13 and/or catalyst 16. It may be preferred to offset the upper rim 21 downwardly relatively to the inlet 8 of the distillate output connection 7 by a distance .sub.3 which distance is preferably selected so that the upper rim 21 is located in the super critical zone.

(73) In addition, the embodiment shown in FIG. 6 may also comprise an oxidation fluid input connection 12 (not illustrated) arranged as illustrated e.g. in connection with FIG. 2. A Salt concentration sensor 15 may also be arranged to measure the salt concentration in the residue (as disclosed herein).

(74) Further, in the embodiments disclosed herein, typically only a single output connection (7, 4) is disclosed, however, a number of such output connections may be arranged, typically in parallel, in the SCWO-reactor.

Example

(75) The following example illustrates the treatment of landfill leachate by a reactor of the present invention. Prior to the treatment, the leachate was pre-treated with a mechanical filter and an ion exchanger, and then concentrated using reverse osmosis (RO). The composition of the resulting concentrated leachate is shown in Table 1.

(76) The concentrated leachate from the RO unit was pressurised to 250 bar and fed to the reactor simultaneously with pressurised air, where the organic compounds and ammonium were oxidized while the inorganic salts and heavy metals were separated as a concentrated salt residue (concentrate). The reactor comprised a heat exchanger consisting of a helically coiled tube in the lower region of the reaction zone, a linear tube in the intermediate zone, a helically coiled tube in the upper zone and a linear tube in the top zone. Reactor retention times were about 30-60 seconds.

(77) The compositions of the distillate and the concentrate are also shown in Table 1. The COD value of the outgoing distillate was reduced 99.8%, while the ammonium content was reduced 99.999% compared to the ingoing concentrated leachate.

(78) Almost all of the inorganic salts in the leachate were concentrated and extracted from the reactor. Depending on the composition of the inlet leachate, this concentrate can be mixed into the final product stream or destroyed at a waste treatment plant. The ammonium-N content in the concentrate can, if necessary, be further reduced from 120 mg/L to 30 mg/L by adding chemicals to the process.

(79) TABLE-US-00001 TABLE 1 Concentrated Distillate, Concentrate, leachate from RO SCWO SCWO Volume (L) 200 180 20 COD (mg/L) 5600 9 260 TOC (mg/L) 1300 3 Na NH4 + N (mg/L) 1900 0 120 pH 8 6 7 dH 1 <1 6.5 Conductivity (mS/cm) 40 0.4 ~250

LIST OF REFERENCE SYMBOLS USED

(80) 1 supercritical water oxidation reactor 2 a reactor body 3 cavity 3 inside the reactor body 2 4 residue output connection 4 5 inlet of residue output connection 4 6 outlet of residue output connection 7 distillate output connection 8 inlet of distillate output connection 9 outlet of distillate output connection 10 aqueous fluid inlet connection 11 thermal element 12 oxidation fluid input connection 13 catalyst (and/or filter element) 14 temperature sensor 15 salt concentration sensor 16 salt filter 17 further distillate outlet 18 inner liner 19 reactor liner 20 inner cavity 21 upper rim

(81) Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms comprising or comprises do not exclude other possible elements or steps. Also, the mentioning of references such as a or an etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.