A process and plant

Abstract

The present disclosure relates to a process and plant for treating an aqueous feed stream including material to produce a distillate and a concentrate. The process and plant includes multiple evaporators and condensers in which each evaporator operates a lower temperature than the previous evaporator. In addition, heat energy from the distillate of the previous condenser is transferred to a feed of the subsequent evaporator, thereby enhancing usage of available heat energy.

Description

A PROCESS AND PLANTRELATED APPLICATION

[0001] The present application claims priority to Australian provisional application number 2023903913 filed 4 December 2024 entitled A PROCESS AND PLANT, and in the name of CLEAN TEQ PTY LTD. The full contents of the specification of provisional application is hereby incorporated into the present specification.FIELD

[0002] The present disclosure relates to a process and plant for treating an aqueous feed stream including material to produce a distillate and a concentrate.BACKGROUND

[0003] The demand for water that can be used in industrial processes, normally referred to as process water, has been increasing for some time. In addition, there is a need to concentrate industrial waste streams, such as saline streams, to reduce the volume of these streams which has the benefit of reducing the cost of disposing of these streams. In the past techniques such as reverse osmosis, which uses membranes to concentrate saline streams and recover process water and a concentrated waste stream have been used. However, membranes used in reverse osmosis are generally only suitable when feed concentrations range from low to moderate. When the feed concentrations are high, evaporation techniques such as vacuum distillation and mechanical vapor recompression (MVR) have been used. However, these existing techniques have several shortcomings such as low energy efficiency, limited robustness, and are prone to fouling and scale build up in equipment items, particularly heat exchangers.

[0004] The present disclosure relates to an alternative process and plant.SUMMARY

[0005] The present disclosure relates to a process of treating an aqueous feed stream including material to produce an aqueous distillate and an aqueous concentrate, the process includes: a first evaporating step in which a first warm feed stream contacts a first cool gas stream to volatilize water and provide a warm humidified first gas stream and a first concentrate; a first condensing step in which the warm humidified first gas contacts a first cool distillate stream to condense water from the warm humidified first gas and provide a first distillate (product) and the first cool gas stream that contacts the first warm feed stream in the first evaporating step; a first heat transfer step in which heat is transferred from at least a portion of the first distillate to a second feed stream to provide a second warm feed stream; and a second evaporating step in which the second warm feed stream contacts a second cool gas stream to volatilize water from the second warm feed stream and provide a warm humidified second gas stream and a second concentrate.

[0006] That is to say, the temperature of the first warm feed stream will be higher than the temperature of the first cool gas stream. Likewise, the first warm feed stream is hotter than the second warm feed stream.

[0007] The aqueous concentrate includes at least parts of the first and second concentrate, and the aqueous distillate includes at least a part of the first distillate.

[0008] The present disclosure relates to a process of treating an aqueous feed stream including material to produce an aqueous distillate and an aqueous concentrate, the process includes: a first evaporating step in which a first warm aqueous feed stream contacts a cool gas stream to volatilize water and provide a warm humidified first gas stream and a first concentrate, wherein the first evaporating step includes the first feed stream and the first cool gas stream flowing in counter current; and a first condensing step in which the warm humidified first gas contacts a first cool distillate stream to condense water from the warm humidified first gas and provide a distillate and the first cool gas stream that is supplied to the first evaporating step, wherein the first warm humidified gas stream and the first cool distillate stream flowing in counter current.

[0009] The process described in the paragraph above may include a first heat transfer step in which heat is transferred from at least a portion of the distillate to a second aqueous feed stream.

[0010] The first warm gas stream and the first cool gas stream recycle between the evaporation step and the condensing step as outlined above.

[0011] The term "material" and variations thereof including plurals, is used throughout this specification to embrace salts, such as carbonates, nitrates, sulphates, sulphites, silicates, chlorides, fluorides, bromides, iodides, amines, organic materials such as proteins, and other materials such as polyolefins, waxes, and so forth. The conjugate for the salts mentioned above may be any suitable pair. Examples of salts include NaCI, NajSCU, (NF hSCU, KCI, Li2SO4, CaSO4, CaCOs, and MgSO4. The distillate may be substantially free of the material, whereas the concentrate may include the material and, indeed, a more concentrated form of the material compared to the feed. Moreover, the concentrate will include the material in solution, but may or may not include a portion of the material as a solid in suspension.

[0012] The term "stream" as used herein embraces both continuous streams, discontinuous streams, or discrete samples. For example, the term "stream" embraces flows during start-up of a process, during continuous operation which may or may not require steady state, fluctuations, purges and so forth.

[0013] The first heat transfer step may include heat being transferred from the at least a portion of the distillate to the second feed stream, thereby cooling at least a portion of the first distillate to provide the first cool distillate stream, and in which at least part of the cool distillate stream contacts the warm humidified first gas in the first condensing step.

[0014] The process may include heating a first feed stream to a first temperature to provide the first warm stream, and the first heat transfer step may include heating the second warm feed stream to a second temperature that is less than the first temperature of the first warm feed stream.

[0015] The process may include controlling the temperature of at least one of: a) the first warm feed stream and / or b) the second warm feed stream, so that the temperature of the first warm feed stream is greater than the temperature of the second warm feed stream.

[0016] The process may include controlling the temperature of the first feed stream and the second feed stream so that there is temperature differential of at least 10°C, and suitably a differential in the range of 5 to 30°C, and suitably approximately 20°C. The temperature of the first feed stream being greater than the temperature of the second feed stream.

[0017] The process may include a second condensing step in which the warm humidified second gas stream contacts a second cool distillate stream to condense water from the second gas stream and providing a second distillate and the second cool gas stream that is supplied to the second evaporating step.

[0018] The process may include a second heat transfer step which may include operating a heat pump to transfer heat from at least a portion of the second distillate to either any one or a combination of the first feed stream and / or the second feed stream to provide the first warm feed stream and / or the second warm feed stream respectively.

[0019] In one example, the process may include a second heat transfer step in which heat is transferred between a portion of the second distillate and a third feed stream.

[0020] The first and second feed streams may originate from a single source and as such contain the same types of material. Similarly, the first, second and third feed stream may originate from a single source and as such contain the same types of material.

[0021] The process may include adding air to the cool second gas stream supplied to the second evaporation step. The air may be ambient air.

[0022] The process may include venting at least a portion of the warm humidified second gas stream from the process.

[0023] The process may include controlling the rate at which air is added to the cooled second gas stream to control the temperature of the second cooled gas stream supplied to the second evaporating step. This allows the temperature differential between the second warm feed stream and the cooled second gas stream to be controlled.

[0024] As the rate at which air is added to the cooled second gas stream will affect the temperature the cooled second gas stream, this will also impact on the temperature required for the second feed stream, which in turn, effects the temperature of the first cooled distillate.

[0025] That is to say, the first heat transfer step can be controlled based on factors including the rate at which air is added to the cooled second gas stream.

[0026] For instance, controlling the rate of air added to the second cooled gas stream will impact on the return rate of the second concentrate.

[0027] The process may include controlling the nett discharge of the second concentrate from the second evaporating step based on factors including the rate of air being added to the second cooled gas stream.

[0028] The process may include a third evaporating step in which the third feed stream contacts an ambient air stream to volatilize water from the third feed stream and provide a humidified air stream and a third concentrate. The humidified air stream may be vented to atmosphere.

[0029] The process may include controlling the rate at which the ambient air is supplied to the third evaporating step to control the temperature differential between the third warm feed stream and the ambient air stream.

[0030] It will be appreciated that during start-up of the process, the temperatures of the first and second warm humidified gas streams, the first and second cool gas streams, the first and second concentrate streams, and the first and second distillate streams, may not be at operating temperature. However, after the process has been operating for a period of time, which may or maynot necessary be steady state operation, there will be temperature differences between the streams to drive mass transfer of water from the feed stream to ultimately produce the distillate.

[0031] The temperature of the first warm feed stream may be greater than the temperature of the first cool gas stream. Similarly, the temperature of the second warm feed stream may be greater than the temperature of the second gas stream.

[0032] The temperature of the first cool distillate stream returned to the first condensation step may be less than the temperature of the warm humidified first gas stream fed to the first condensation step.

[0033] The temperature of the second cool distillate stream returned to the second condensation step may be less than the temperature of the warm humidified first gas stream fed to the first condensation step.

[0034] The temperature of the first distillate may be greater than the temperature of the feed stream. In other words, the first distillate may then be used to heat a portion of the feed stream that is used as the second warm feed stream.

[0035] The temperature of the first warm feed stream may be greater than the temperature of the second warm feed stream. The process may include controlling the temperature of the first warm feed stream and the second warm feed stream. For instance, the first warm feed stream may have a temperature differential of at least 10°C, and suitably a differential in the range of 5 to 30°C greater than the temperature of the second warm feed stream, and suitably a temperature of approximately 20°C greater than the temperature of the second warm feed stream.

[0036] The temperature of the second warm feed stream may be greater than the temperature of the third warm feed stream. The process may include controlling the temperature of the second warm feed stream and the third warm feed stream For instance, the first warm feed stream may have a temperature differential of at least 10°C, and suitably a differential in the range of 5 to 30°C greater than the temperature of the second warm feed stream, and suitably a temperature of approximately 20°C greater than the temperature of the second warm feed stream.

[0037] The process may include heating the first warm feed stream in a preliminary heating step. For example, prior to being supplied to the evaporating step.

[0038] The process may include controlling the heat transfer rate of the preliminary heating step, and in turn the temperature of the first warm feed stream, based on factors including flow rate of the first feed stream.

[0039] The process may include controlling the rate at which heat is transferred to the first feed stream, and in turn the temperature of the warm first feed stream, based on factors including flow rate of the first distillate (product).

[0040] For example, the flow rate of the first feed stream may be a set flow rate that is determined by upstream parameters.

[0041] For example, this may include adjusting the heating load of the heat pump when the flow rate of the first feed stream is set. Similarly, this may include adjusting the heating load of the heat pump when the flow rate of the second and / or third feed streams is substantially constant.

[0042] In another example, the situation when the first feed stream, and the other feed streams (if present) are heated using a heating fluid such as steam, the rate flow rate of the heating fluid may be adjusted to adjust the heat transfer rate to the respective feed stream(s).

[0043] The process may include returning at least a portion of the first concentrate to the first evaporation step.

[0044] The process may include heating the portion of the first concentrate returned to the first evaporation step.

[0045] In the situation where the concentrate includes solids, the process may include separating the first concentrate of the first evaporating step into a first slurry phase and a first liquid phase, and returning at least a portion of the first liquid phase, hereinafter called a return first liquid phase, to the first evaporating step.

[0046] The process may include heating the return liquid phase returned to the first evaporation step.

[0047] The process may include controlling the flow rate of the portion of the concentrate or the first liquid phase returned to the first evaporation step based on factors including available heat in the preliminary heating step. Moreover, the process may include controlling heat loss from the process by controlling the flow rate of the concentrate or the liquid phase returned to the first evaporating step. In other words, thereby in part controlling the temperature of the first evaporating step. In the situation when the concentrate includes solids, the process may include controlling the flow rate of the first slurry phase as a factor in controlling the temperature of the first evaporating step.

[0048] One possible reason for returning at least a portion of the return first liquid phase is to assist in maintaining a saturation level of material in the water in the first evaporating step. For instance, the first evaporating step may be carried out in a first evaporator and the bottom section of the first evaporator may have a pool of the concentrate in which crystals provide a site for further crystallization of material such as salts.

[0049] The first slurry phase may be discharged, and optionally treated in downstream processes.

[0050] The step of separating the first concentrate into the slurry phase and the liquid phase may include feeding the first concentrate into a separation unit and discharging the first slurry phase and the first liquid phase from the separator.

[0051] Examples of suitable separation units include any one or a combination of: hydrocyclone separator, a settling pond, settling tank, a centrifuge, and a filter and so forth.

[0052] The portion of the returned first liquid that is returned to the first evaporating step may be heated with the first feed stream in the preliminary heating step.

[0053] In the situation where the concentrate includes dissolved materials, the process may include a crystallization step to precipitate some materials from the solution.

[0054] The process may include returning at least a portion of the second concentrate to the second evaporation step.

[0055] The process may include heating the portion of the second concentrate returned to the second evaporation step.

[0056] The process may include separating the second concentrate into a second slurry phase and a second liquid phase, and returning at least a portion of the second liquid phase, hereinafter called a return second liquid phase, to the second evaporating step.

[0057] The process may include heating the return second liquid phase returned to the second evaporation step.

[0058] The process may include controlling the flow rate of the portion of the second concentrate or the second liquid phase returned to the second evaporation step based on factors including available heat in the first heating step. Moreover, the process may include controlling heat loss from the process by adjusting the flow rate of the concentrate or the liquid phase returned to the second evaporating step. In other words, thereby in part controlling the temperature of the second evaporating step. In the situation when the concentrate includes solid, the process may include controlling the flow rate of the second slurry phase as a factor in controlling the temperature of the second evaporating step.

[0059] One possible reason for returning at least a portion of the second liquid phase is to assist in maintaining a saturation level of materials in the water in the second evaporating step. For instance, the second evaporating step may be carried out in a second evaporator and the bottom section of the second evaporator may have a pool of the concentrate in which crystals provide a site for further crystallization of materials such as salts.

[0060] The second slurry phase may be discharged, and optionally treated in downstream processes.

[0061] The step of separating the second concentrate into the second slurry phase and the second liquid phase may include feeding the second concentrate into a second separation unit. Examples of suitable second separation units include any one or a combination of: hydrocyclone separator, a settling pond, settling tank, a centrifuge, and a filter and so forth.

[0062] The step of separating the second concentrate into the second slurry phase and the second liquid phase may include treating the second concentrate in a settling pond.

[0063] The portion of the returned second liquid phase returned to the second evaporating step may be heated with the first feed stream.

[0064] In the situation in which the process includes the third evaporating step, the process may include a third separating step in which the third concentrate is separated into a third slurry and a third liquid stream. The third liquid stream may be added to the third feed stream. This may have the possible benefit of assisting in maintaining a concentration level of the materials in the third evaporating step.

[0065] The first evaporating step may include the first feed stream and the first cool gas stream flowing in counter current. That this, the first feed stream may be supplied to an upper portion of a first evaporating column and the first cool gas supplied to a lower portion of the first evaporating column, and the first warm humidified gas stream may be discharged from the upper portion of the first evaporating column and the first concentrate discharged from a lower portion of the evaporating column.

[0066] The first condensing step may include the first warm humidified gas stream and the cool distillate stream flowing in counter current. That is, the first warm humidified gas stream may be supplied to a lower portion of the first condensing column and the cool distillate stream supplied toan upper portion of the first condensing column, and the first cool gas stream discharged from the upper portion of the first condensing column and the distillate discharged from the lower portion.

[0067] The second evaporating step may include the second feed stream and the second cool gas stream flowing in counter current. That is, the second feed stream may be supplied to an upper portion of a second evaporating column and the second cool gas supplied to a lower portion of the second evaporating column, and the second warm humidified gas stream may be discharged from the upper portion of the second evaporating column and the second concentrate discharged from a lower portion of the evaporating column.

[0068] The second condensing step may include the second warm humidified gas stream and the second cool distillate stream flowing in counter current. That is, the second warm humidified gas stream may be supplied to a lower portion of the second condensing column and the second cool distillate stream supplied to an upper portion of the second condensing column, and the second cool gas stream discharged from the upper portion of the second condensing column and the second distillate discharged from the lower portion.

[0069] The process may include controlling the flow rate of the first concentrate stream discharged from the first evaporating step to control a recovery factor of the first evaporating step and condensing step, being a ratio (such as volume ratio) of the first distillate product to the first feed warm stream. In the situation where the first concentrate stream is a slurry and the process includes a separating step to separate the first concentrate into a first liquid phase and a first slurry phase, the process may include controlling the flow rate of the first slurry phase discharged from the process to control a recovery factor of the first evaporating step and condensing step, being a ratio (such as volume ratio) of the first distillate product to the first feed warm stream.

[0070] Similarly, the process may include controlling the flow rate of the second concentrate stream discharged from the second evaporating step to control a recovery factor of the second evaporating step and condensing step, being a ratio of the second distillate product to the second warm feed stream. In the situation where the second concentrate stream is a slurry and the process includes a separating step to separate the second concentrate into a second liquid phase and a second slurry phase, the process may include controlling the flow rate of the second slurry phase discharged from the process to control a recovery factor of the second evaporating step and condensing step, being a ratio (such as volume ratio) of the second distillate product to the second feed warm stream. Furthermore, the process may include controlling the flow rate of the third concentrate stream discharged from the third evaporating step to control a recovery factor of the third evaporating step and condensing step, being a ratio of the third distillate product to the third warm feed stream. In the situation where the third concentrate stream is a slurry and the process includes a separating step to separate the third concentrate into a third liquid phase and a third slurry phase, the process may include controlling the flow rate of the third slurry phase discharged from the process to control a recovery factor of the third evaporating step and condensing step, being a ratio (such as volume ratio) of the third distillate product to the third feed warm stream.

[0071] The total dissolved solids (TDS) of the material in the feed stream may range up to 800 g / L, and suitably up to 700 g / L, and more suitably up to 600 g / L, and even more suitably up to 500g / L, and preferably up to 400 g / L. In one example, the TDS of the feed stream may be in the range of 10 to 400 g / L. These ranges do not include suspended material in the feed stream.

[0072] By way of example, the feed stream may include any one or a combination of the following salts: NaCI, NajSC , (NF hSCU, KCI, IJ2SO4, CaSCU, CaCOs, MgSC or other combinations of the component ions. The feed could be below, or at, saturation for one or more of the ion combinations.

[0073] The present disclosure also relates to a plant for treating an aqueous feed stream including material to produce an aqueous distillate and an aqueous concentrate, the plant includes: a first evaporator in which a first warm feed stream contacts a first cool gas stream to volatilize water and provide a first humidified gas stream and a first concentrate; a first condenser in which the humidified first gas contacts a first cool distillate stream to condense water from the first humidified gas and provide a distillate and the first cool gas stream that contacts the first warm feed stream in the first evaporating step; a first heat exchanger for transferring heat from at least a portion of the distillate to a second warm feed stream; and a second evaporator in which the second warm feed stream contacts a second cooler gas stream to volatilize water from the second warm feed stream and provide a second humidified second gas stream and a second concentrate.

[0074] The aqueous concentrate may include at least parts of the first and second concentrate, and the aqueous distillate includes at least a part of the first distillate.

[0075] The plant may include a preliminary heat exchanger for heating the first warm feed stream.

[0076] The plant may include a second condenser in which the second humidified gas stream contacts a second cool distillate to provide a second distillate and the second cool gas stream.

[0077] The plant may include a third evaporator in which a third warm feed stream contacts an ambient air stream to volatilize water from the third warm feed stream and provide a third concentrate.

[0078] The plant may include a second heat exchanger for transferring heat to the third warm feed stream from at least a portion of the second distillate stream which provides the cool second distillate stream.

[0079] The plant may include any one or a combination of: i) a first separation unit for separating the first concentrate into a first slurry phase and a first liquid phase so that at least a portion of the first liquid phase can be returned to the first feed stream; ii) a second separation unit for separating the second concentrate into a second slurry phase and a second liquid phase so that at least a portion of the second liquid phase can be returned to the second feed stream; iii) a third separation unit for separating the third concentrate into a third slurry phase and a third liquid phase so that at least a portion of the third liquid phase can be returned to the second feed stream.

[0080] The plant may include a heat pump for transferring heat energy from at least a portion of the second distillate stream to the first warm feed stream.

[0081] The heat pump may also be used to transfer heat energy from at least a portion of the second and / or third distillate stream to the first and / or second warm feed streams.

[0082] The plant may also include one or more flow generators for driving the flow of the first humidified gas stream and the first cool gas stream.

[0083] The plant may also include one or more flow generators for driving the flow of the second warm humidified gas stream and the second cool gas stream.

[0084] The plant may also include a controller for the control of the flow and / or temperature of the streams described herein. For example, the controller may control any one or a combination of:A) the temperature of i) the first warm feed stream and / or ii) the second warm feed stream, so that the temperature of the first warm feed stream is greater than the temperature of the second warm feed stream,B) the temperature of the first warm feed stream and the second warm feed stream so that there is a temperature differential of at least 10°C, and suitably a differential in the range of 5 to 30°C, and suitably approximately 20°C,C) the temperature of the warm first feed stream, based on factors including flow rate of the first distillate (product),D) the flow rate of the first concentrate stream discharged from the first evaporating step to control a recovery factor of the first evaporator and condenser, being a ratio (such as volume ratio) of the first distillate product to the first feed warm stream.E) the flow rate of the portion of the concentrate or the first liquid phase returned to the first evaporator based on factors including available heat in the preliminary heat exchanger,F) the flow rate of the first slurry phase discharged from the process to control a recovery factor of the first evaporator and condenser, being a ratio (such as volume ratio) of the first distillate product to the first feed warm stream,G) the flow rate of the second concentrate stream discharged from the second evaporator to control a recovery factor of the second evaporator and condenser, being a ratio of the second distillate product to the second warm feed stream,H) the flow rate of the second slurry phase discharged from the process to control a recovery factor of the second evaporator and condenser, being a ratio (such as volume ratio) of the second distillate product to the second feed warm stream,I) the flow rate of the portion of the second concentrate or the second liquid phase returned to the second evaporator based on factors including available heat in the first heat exchanger.J) the flow rate of the third concentrate stream discharged from the third evaporating step to control a recovery factor of the third evaporating step and condensing step, being a ratio of the third distillate product to the third warm feed stream,K) the flow rate of the third slurry phase discharged from the process to control a recovery factor of the third evaporating step and condensing step, being a ratio (such as volume ratio) of the third distillate product to the third feed warm stream.

[0085] The plant may include any one or a combination of the features of the process described herein. Similarly, the process may include any one or a combination of the features of the plant described herein.

[0086] The present invention relates to a process of treating a feed stream including an aqueous solution and materials to produce a distillate and a concentrate, the process includes: heating a first feed stream to a first temperature;supplying the first feed stream and a cold first gas stream to a first evaporating step operating at a first temperature (range) in which water volatilizes from the first feed stream and saturates the first gas stream; discharging a water saturated gas stream (at a first / warm / hot temperature) and a first concentrate from the first evaporating step; supplying the water saturated gas stream (and a cool liquid stream) to a first condensing step in which water is condensed from the water saturated gas stream to produce the distillate; discharging a cool gas stream from the first condensing step which is used as the first gas stream; transferring heat from the at least a portion of the distillate to a second feed stream, thereby cooling at least a portion of the distillate to provide a cool distillate, and heating the second feed stream to a second temperature that is less than the first temperature of the first feed stream; using the cool distillate to provide at least part of the cool liquid stream that is supplied to the first condensing step to facilitate condensation of the distillate; supplying the second feed stream and a second gas stream to a second evaporating step in which water volatilizes to form further concentrate.

[0087] The present disclosure relates to a process of treating a feed stream including an aqueous solution and materials to produce a distillate and a concentrate, the process includes: heating a first feed stream to a first temperature; a first evaporating step in which water is volatilized from the first feed stream and contacts a (cool) gas stream to provide a warm humidified first gas stream and a first liquid concentrate; a first condensing step in which water is condensed from the warm humidified first gas by contacting a cool distillate / water stream to provide the distillate and a cool gas stream that is supplied to the first evaporating step; transferring heat from the at least a portion of the distillate to a second feed stream, thereby cooling at least portion of the distillate to provide a cool distillate stream, and heating a second feed stream to a second temperature that is less than the first temperature of the first feed stream; using the cool distillate to provide at least part of the cool liquid stream that contacts the warm saturated first gas in the first condensing step; and a second evaporating step in which water is volatilized from the second feed stream and saturates a second cooler gas stream to provide, a warmer saturated second gas stream and a second liquid concentrate.

[0088] The present disclosure relates to a process of treating a feed stream including an aqueous solution and materials to produce a distillate and a concentrate, the process includes: heating (a first portion of) the feed stream to provide a first feed stream at a first temperature;supplying the first feed stream and a cold first gas stream to a first evaporation step in which water volatilizes from the first feed stream and humidifies the first gas stream; discharging a humidified gas stream (at a first / warm / hot temperature) and a first concentrate from the first evaporating step; supplying the water saturated gas stream (and a cool liquid stream) to a first condensing step in which water is condensed from the water saturated gas stream to produce the distillate (including a first distillate); discharging a cool gas stream from the first condensing step which is used as the first gas stream; transferring heat from the at least a portion of the distillate to a second portion of the second feed stream, thereby cooling at least portion of the distillate to provide a cool distillate; and heating a second feed stream to at least part of the second temperature of the second feed stream; recycling the cool distillate to the first condensation step to facilitate condensation in the first condensation step; supplying the second feed stream and a second gas stream to a lower (second) temperature evaporation step in which water volatilizes to form further concentrate.DESCRIPTION OF THE DRAWINGS

[0089] These and other features, aspects, and advantages of the present disclosure are described with reference to the drawings of certain embodiments, which are intended to schematically illustrate certain embodiments and not to limit the disclosure. The drawings may be summarized as follows.

[0090] Figure 1 is a flow diagram illustrating a process and plant according to a preferred embodiment for treating a feed stream including an aqueous solution and materials to produce a distillate and a concentrate. The embodiment includes heating a first portion of the feed stream to a first temperature using a heat pump and heating a second portion of the feed stream to a second temperature using indirect heat exchange between the feed stream and the distillate of two condensers.

[0091] Figure 2 is a flow diagram illustrating a process and plant according to an alternative example for treating a feed stream including an aqueous solution and materials to produce a distillate and a concentrate. The embodiment includes heating the first portion of the feed stream to a first temperature using a heat source and heating a second portion of the feed stream to a second temperature using indirect heat exchange between the second portion of the feed stream and the distillate of two condensers.DETAILED DESCRIPTION

[0092] Embodiments will now be described in the following text which includes reference numerals that correspond to features illustrated in the accompanying Figures. Although certain examples are described herein, those skilled in the art will appreciate that the disclosure extends beyond the specifically disclosed examples and / or uses and obvious modifications and equivalents thereof.Thus, it is intended that the scope of this disclosure should not be limited by any particular examples described herein.

[0093] This specification refers to quoted temperatures or temperature ranges that relate to temperatures during continuous operation of the process 56 and plant 57 unless stated otherwise. Continuous operation of the process 56 and plant 57 may occur irrespective of whether the process56 and plant 57 is, or is not, operating at steady state. Other temperatures or temperature ranges described herein may relate to temperatures during start-up procedures of the process 56 and plant57 when stated.

[0094] An embodiment relates to a process 56 and plant 57 for treating a feed stream 9 including an aqueous solution and materials, and produces a concentrate including the materials which may be a more concentrated form of the concentrates, and a distillate.

[0095] With reference to Figures 1 and 2, the embodiments includes splitting an aqueous feed stream 9 into a first and second feed streams 20a and 21a, and heating the first feed stream 20a to a first high temperature, ranging for example, from a temperature ranging from 60°C to the boiling point, or just below the boiling point and suitably ranging from 70 to 90°C, and ideally approximately 80°C in a preliminary feed heat exchanger 34 to provide a first warm feed stream 20b. As will be described further, the second feed stream 21a is also heated in a first heating step 29 to provide a second warm feed stream 21b. It will be appreciated that the boiling point of the first and second feed streams 20a and 21a may be above 100°C on account of the dissolved materials, including salts and so forth, in the first feed stream 20a, and a second feed stream 21a. The feed stream 9 may be split equally or unequally between the first and second feed stream 20a and 21a.

[0096] After the preliminary feed heat exchanger 34, the first warm feed stream 20b is supplied to a first evaporating step 10 in which the first warm feed stream 20b directly contacts a first cool gas stream 32 which transfers heat to the first cool gas 32 and volatilizes water from the first warm feed stream 20b to provide a warm humidified first gas stream 31 and a first concentrate 23. That is to say, heat is directly transferred from the first warm feed stream 20b to the first cool gas stream 32 which is also humidified to provide the warm humidified first gas stream 31. As can be seen, the first warm feed stream 20b is supplied to an upper portion of a first evaporator column 11 in which the first evaporating step 10 is carried out, and the first cool gas stream 32 is supplied to a lower portion of the first evaporator column 11 such that the first warm feed stream 20b flows downwardly in the first evaporator column 11 and the first cool gas stream 32 flows upwardly in counter current. The warm humidified first gas stream 31 is discharged from an upper portion of the first evaporator column 11 and the first concentrate 23 is discharged from a bottom portion of the evaporator column 11.

[0097] The embodiments also include a first condensing step 12 in which the warm humidified first gas 31 contacts a first cool distillate stream 33 to condense distillate including water from the warm humidified first gas stream 31. In addition to the distillate condensing from the warm humidified first gas 31, heat is also directly transferred from the warm humidified first gas 31 to the first cool distillate 33, providing the first cool gas stream 32. As can be seen in Figures 1 and 2, the warm humidified first gas 31 is supplied to a lower portion of the first condenser column 13 and flows upwardly in the column 13, and the first cool distillate 33 is supplied to an upper portion of the first condenser column 13 and flows in counter current. The first cool gas stream 32 is discharged from the upper portion of the first condenser column 13 and the distillate 24a is discharged from a lower portion of the column 13. The first cool gas stream 32 is supplied to the first evaporating step 10.

[0098] The warm humidified gas stream 31 and the first cool gas stream 32 circulate in a loop between the first evaporating step 10 in which water vapour is loaded due to the higher temperature of the evaporating step 10 provided by the temperature of the first feed stream 20b, and the first condensing step 12 in which water vapour is condensed from the warm humidified first gas stream 31 on contacting a lower temperature of the first cool distillate stream 33.

[0099] As can be seen, the embodiments also include a first heat transfer step 29 in which at least a portion of the first distillate 24a, referred to as the first return distillate 62, is cooled to provide the first cool distillate stream 33 that is supplied to the upper portion of the condenser column 13 for contacting with the warm humidified gas stream 31. In other words, heat energy from the first return distillate 62 is transferred to at least a portion of the second feed stream 21a in the first heat transfer step 29, which provides a first cool distillate 33 and heats the second feed stream 21a to provide the second warm feed stream 21b which is supplied to a second evaporating step 14. Another portion of the first distillate 24a, referred as the first discharge distillate 24b is discharged from the process 56 and plant 57.

[0100] In order to provide adequate temperature driving forces for heat and mass transfer, ideally the first warm feed stream 20b and the second warm feed stream 21b have a temperature differential in the range of 10 to 30°C, and suitably approximately 20°C.

[0101] The process 56 also includes a second evaporating step 14 in which the second warm feed stream 21b is contacted with a second cool gas 46 which volatizes water from the second feed warm stream 21b and heats the second cool gas 46 to provide a warm humidified second gas 45 and a second concentrate 37. That is to say, heat is directly transferred from the second warm feed stream 21b to the second cool gas stream 46 which is also humidified to the provide the warm humidified second gas 45. As can be seen, the second warm feed stream 21b is supplied to an upper portion of a second evaporator column 15 in which the second evaporating step 14 is carried out, and the second cool gas stream 46 is supplied to a lower portion of the second evaporator column 15 such that the second warm feed stream 21b flows downwardly in the second evaporator column 15 and the second cool gas stream 46 flows upwardly in counter current.

[0102] If required, ambient air 66 can be added to the second cool gas stream 46 and / or the second evaporation step 14 / evaporator 15. The ambient air 66 could have a lower humidity than the second cool gas stream 46 discharged from the second condenser column 17, thereby potentially increasing the amount of the water vapour that can be volatilized from the warm humidified second feed stream 45. To prevent over pressurization of second evaporator column 15 and the second condenser column 17, a side stream 64 of the warm humidified second stream 45 may be purged from second evaporator step 14 and / or from the warm humidified second gas stream 45.

[0103] The rate at which the ambient air 66 is added to the cooled second gas stream 46 may be controlled to control the temperature of the second cooled gas stream 46 supplied to the second evaporating step 14. This allows the temperature differential between the second warm feed stream 21b and the cooled second gas stream 46 to be controlled. As the rate at which ambient air 66 is added to the cooled second gas stream 46 will affect the temperature the cooled second gas stream 46, this will also impact on the temperature required for the second warm feed stream 21b, which in turn, effects the temperature of the first cooled distillate 33. That is to say, the first heat transfer step 29 can be controlled based on the rate at which ambient air 66 is added to the cooled second gas stream 46 and / or the second evaporation step 14 / evaporator 15. For instance, controlling the rate of ambient air 66 is added to the second cooled gas stream 46 will impact on the return rate of the second concentrate 37. In order to provide adequate temperature driving forces for heat and mass transfer, ideally the second warm feed stream 21b and the third warm feed stream 22b (see Figure 2, not shown in Figure 1) will have a temperature differential in the range of 10 to 30°C, and suitably approximately 20°C.

[0104] The second warm humidified gas stream 45 is discharged from an upper portion of the second evaporator column 15 and the second concentrate 37 is discharged from a bottom portion of the evaporator column 15.

[0105] The embodiments also include a second condensing step 16 in which the warm humidified second gas 45 contacts a second cool distillate stream 47 to produce a second condensed distillate38a including water from the warm humidified second gas stream 45. The condensed distillate may be split to include a second return distillate 47, and second discharge distillate 38b. In addition to the condensing water from the warm humidified second gas 45, heat is also directly transferred from the warm humidified second gas 45 to the second cool distillate 47, providing the second cool gas 46. As can be seen in Figures 1 and 2, the warm humidified second gas 45 is supplied to a lower portion of the second condenser column 17 and flows upwardly in the column 17, and the second cool distillate 47 is supplied to an upper portion of the condenser column 17 and flows in counter current. The second cool gas stream 46 is discharged from the upper portion of the second condenser column 17 and the second distillate 38a is discharged from a lower portion of the column 17. The second cool gas stream 46 is supplied to the second evaporating step 14.

[0106] With reference to Figure 1, the second cool distillate 47 is cooled by a second heat transfer step 43 in which heat is transferred from either one or a combination of the second return distillate 47 and a portion of the first discharge distillate 24b. The second heat transfer step may be provided by means of a heat pump 35. The heat pump 35 generates a hot heat transfer fluid 36a which is used to transfer heat to the first feed stream 20a to generate the first warm feed stream 20b and a cooled heat transfer fluid 36b which is returned to the heat pump 35. The heat pump 35 may comprise a refrigerant that cycles between compression and expansion stages (not shown), including use of a compressor to assist in compression of the refrigerant. In the case of the embodiment shown in Figure 1, the heat pump 35 may transfer heat from the refrigerant to a heat transfer fluid 36a, 36b which in turn is used to transfer heat to the first feed stream 20a. A potential benefit this provides is that the first warm feed stream 20b is less likely to be contaminated with refrigerant in the event of leakage of the refrigerant from the heat pump 35. Another potential benefit is that the heat pump 35 does not need to be made of corrosive resistant materials because the heat pump 35 has no direct contact with the streams 20a and 47.

[0107] In an alternative embodiment, not shown in the Figures, the heat transfer fluid 36a, 36b can be omitted, and the first feed stream 20a passes through one side of the heat pump 35 to receive heat from the refrigerant. It will also be appreciated that the heat pump 35 may be substituted with some other heat source or hot medium, such as process water or steam.

[0108] With reference to Figures 1 and 2, the process 56 and plant 57 also includes a first separating step 25 that separates the first concentrate 23 discharged from the first evaporating step 10, into a first slurry 26a and a first liquid phase 27. The first separating step 25 allows at least part of the first liquid phase 27 to be returned to the first evaporating step 10. For example, the first liquid phase 27 may be mixed with the first feed stream 20a. A portion of the first slurry phase 26a, referred to as first return slurry 26c may also be returned directly to the first evaporating step 10. The first slurry 26c may be supplied into the first evaporating step 10 to assist in maintaining a saturation concentration of at least some of the materials in the pool. Supplying the first slurry 26c back into the evaporating step 10 / evaporator 11 can assists in providing crystallization sites for the materials. Another portion of the first slurry phase 26a, referred as first discharge slurry 26b, can be discharged from the process 56 and plant 57. The first separating step 25 may be carried out using any suitable technique including a first hydrocyclone 28, settling ponds and so forth.

[0109] The process 56 and plant 57 may include controlling the flow rate of the first concentrate 23 or the first discharge slurry 26b that is discharged from the first evaporating step 10 as a factor in controlling the operating temperature of the first evaporating step 10. The rate at which the first concentrate 23 or the first discharge slurry 26b is discharged from the process 56 and plant 57 may be one factor that can influence the operating temperature of the first evaporating step 10, and the reason why this occurs is that the flow rate of the first concentrate 23 or the first discharge slurry 26b results in heat loss for the evaporating step 10. For instance, reducing the flow rate of the first discharge slurry 26b being discharged from the first evaporating step 10, can have the effect of maintaining or increasing the temperature in the first evaporating step 10, at least temporarily.Similarly, the process 56 may also include controlling the flow rate of the second concentrate 37 or the second slurry stream 40a that is discharged from the second evaporating step 14 to control the operating temperature of the second evaporating step 14. The flow rate of the first discharge slurry stream 26b may be controlled so that either one or a combination of: i) a constant flow rate, ii) a variable flow rate, or iii) a flow rate in batches such that there is intermittent flow. One of the benefits this provides is that the process can be more easily controlled in response to changes in ambient temperature conditions, such as differences between winter and summer temperatures, or between night and daytime temperatures whilst maintaining a desired recovery factor.

[0110] The process 56 and plant 57 may include controlling the temperature of the first evaporating step 10 by controlling operation of the heat pump 35, including the flow rate and temperature of the heat transfer fluid 36.

[0111] The process 56 and plant 57 also includes a second separating step 39 that separates the second concentrate 37 into a second slurry 40a and a second liquid phase 41, in which at least part of the second liquid phase 41 may be returned to the second evaporating step 14. For example, by being mixed with the second feed stream 21a. In addition, a portion of the second slurry 40a, referred as the second return slurry 40c, may be returned to the second evaporating step 14 and, in particular, to a pool of the second concentrate 37 in the second evaporating step 14 to assist in maintaining saturation concentration of at least some of the materials in the pool. This assists in providing crystallization sites for the materials. Another portion of the second slurry 40a, referred to the second discharge slurry 40b, can be discharged from the process 56 and plant 57. The second separating step 39 may be carried out using any suitable technique including a second hydrocyclone 42, settling ponds, settling tanks, centrifuge separators, filters and so forth.

[0112] The process 56 and plant 57 may also include controlling the flow rate of the second concentrate 37 or the first discharge slurry 40b that is discharged from the second evaporating step 14 as a factor in controlling the operating temperature of the second evaporating step 14. The rate at which the second concentrate 37 or the second discharge slurry 40b is discharged from the process 56 and plant 57 may be one factor that can influence the operating temperature of the second evaporating step 14, and the reason why this occurs is that the flow rate of the second concentrate 37 or the second discharge slurry 40b results in heat loss for the second evaporating step 14. For instance, reducing the flow rate of the second discharge slurry 40b being discharged from the second evaporating step 14, can have the effect of maintaining or increasing the temperature in the second evaporating step 14, at least temporarily. Similarly, the process 56 and plant 57 may also include controlling the flow rate of the second concentrate 37 or the second discharge slurry 40b that is discharged from the second evaporating step 14 to control the operating temperature of the second evaporating step 14. The flow rate of the second discharge slurry 40b may be controlled so that either one or a combination of: i) a constant flow rate, ii) a variable flow rate, or iii) a flow rate in batches such that there is intermittent flow. One of the benefits this provides is that the process can be more easily controlled in response to changes in ambient temperature conditions, such as differences between winter and summer temperatures, or between night and daytime temperatures whilst maintaining a desired recovery factor.

[0113] The performance of the process 56 may be assessed against a recovery factor, which can be defined as a ratio of the volume of the distillate product to the volume of the first warm feed stream 20b. The process 56 may include controlling the recovery factor by controlling the flow rate of the concentrate stream 23, including the rate of the slurry stream 26b discharged from the process 56. For example, the process 56 may include controlling the recovery factor of the first evaporating step 10 and condensing step 12, being a ratio of the first discharge distillate 24b to the feed stream 20a by controlling the flow rate of the first discharge slurry 26b discharged from the first evaporating step 10. It will be appreciated that if there are little or no precipitates, the first discharge slurry 26b will contain little or no precipitates, and the concentrate stream 23 may be divided into the returnstream 27 and the first slurry discharge 26b even though it contains little or no precipitates. Similarly, the process 56 may include controlling the recovery factor of the second evaporating step 14 and condensing step 16, being a ratio of the second discharge distillate 38bto the second warm feed stream 21a by controlling the flow rate of the second concentrate 37, including the second slurry stream 40b discharged from the second evaporating step 14 of the process 56. It will be appreciated that the second slurry stream 40b may not be present when there is little or no precipitates.

[0114] The recovery factor will be dependent on the composition of the feed streams 20a, 21a, and if present, feed stream 22a. As mentioned herein, the feed streams 20a, 21a and 22a, may come from a single source or from multiple sources. As such, the concentration of the materials in the feed streams 20a, 21a and 23a may be the same or different. The recovery factor will also depend on objectives regarding volume of waste and the concentration of materials in the first and second concentrate stream 23 and 37. In the situation in which the feed streams 20a and 21a includes NaCI and NajSCU, the output of the process and in particular, the recovery factor of the first evaporating and condensing steps 10 and 12 can be controlled by controlling the flow rate of the concentrate stream 23, and the first discharge slurry 26b. At a low recovery factor, the flow of the concentrate stream 23, and the first discharge slurry 26b, can be increased so no crystals and low concentrations of NajSC salts will be produced in the first discharge distillate 24b. At a medium or slightly higher recovery factor, the flow of the concentrate stream 23, and the first discharge slurry 26b, can be reduced compared to the lower recovery factor, and the first discharge distillate 24b will contain some NajSC salts. At higher recovery factors, both NaCI and NajSCU salts will be present in the first discharge distillate stream 24b. This could change when the salts in the first and second feeds stream 20a and 21a occur in different ratios. Other factors including scaling elements, such as Ca, Mg, Si, Fe among others, may also limit the recovery factor.

[0115] The materials of the (first, second and third) feed streams 20a, 21a, 22a may include a total dissolved solids (TDS) of the feed streams 20a, 21a and 22a in the range of 10 to 800 g / L and suitably in the range of 1 to 400 g / L. By way of example, the feed streams 20a, 21a and 22a may include any one or a combination of the following salts: NaCI, NajSCU, (NF hSCU, KCI, LijSCU, CaSCU, MgSCU and CaCOs or other combinations of the component ions. Moreover, the feed streams 20a, 21a and 22a may include any one or a combination of the materials, including salts and organic materials according to the definition of the word "material" provided herein. The feed could be below, or at saturation. The first and second slurry streams 26a and 40a may include precipitates of these salts.

[0116] The process 56 and the plant 57 shown in Figures 1 and 2 both include the first evaporating step 10, the first condensing step 12, the second evaporating step 14, the second condensing step 16, and the first heat transfer step 34. In addition, Figures 1 and 2 also include the first and second separation steps 25 and 39 for separating the first and second concentrates 23 and 37 into first and second slurry streams 26a and 40a, and first and second liquid phases 27 and 41.

[0117] One of the differences between the process 56 and plant 57 in Figures 1 and 2 is that, in the case of Figure 2, a third evaporation step 50 is provided for cooling the second discharge distillate 63 instead of a heat pump 35, as shown in Figure 1. Specifically, the process 56 and plant 57 in Figure 2 includes a second heat transfer step 43 in which heat energy is transferred from the second discharge distillate 63 to a third feed stream 22a to provide a third warm feed stream 22b. The third feed stream 22b may be heated to a temperature greater than ambient air temperature. For example, to a temperature in the range of 35 to 45°C, and suitably to a temperature of approximately 40°C.

[0118] The third warm feed stream 22b is then supplied to the third evaporating step 50 where it is contacted with a gas stream, suitably ambient air, to volatilize water from the third warm feed stream 22b and produce a third concentrate 59. A stream of humidified air can be vented toatmosphere. As can be seen, the third warm feed stream 22b is supplied to the upper portion of a third evaporating column 51 and flows downwardly therein, and the ambient air is supplied to a lower portion of the third evaporating step 50 and flows upwardly in counter current.

[0119] Although not shown in Figure 2, this embodiment could also include a third condensing step, in which a cool gas and a warm humidified gas are conveyed between in the same manner as the first evaporating and condensing steps 10 and 12, and the second evaporating and condensing steps 15 and 16.

[0120] A third separating step 60 also separates the third concentrate 59 into a third slurry stream 54a and a third liquid stream 55 by means of third hydrocyclone 61. The third liquid stream 55 can be directly supplied back into the third evaporating step 50, or mixed with the third feed stream 22a for heating in the second heat transfer step 43.

[0121] Although not shown in Figure 2, it is possible that a heat pump may be used to transfer heat from any one of the streams in the process, such as the first feed stream 20a.

[0122] The gas streams 31 and 32 of the first evaporating and condensing steps 10 and 12, and gas streams 45 and 46 of the second evaporating and condensing steps 15 and 16 may comprise any suitable gas, such as oxygen, nitrogen, argon or other inert gases. In one example, the gas streams 31, 32, 46 and 46 may comprise air.

[0123] Figures 1 and 2 illustrate the first and second feed streams 20a and 21b as originating from the same source. However, it will be appreciated that this need not be the case, and that the first and second feed stream 20a and 21a may be supplied from different sources, and may therefore have different starting temperatures and / or may include materials at different concentrations. Figure 2 includes a third feed stream 22a that is illustrated as originating from the same source as the first and second feed streams 20a and 21a. However, it will be appreciated that anyone or a combination of the first, second and third streams 20a, 21a, and 22a in Figure 2 may originate from the two or more sources, and may comprise the same or different temperatures, and may comprise the same or different concentrations of the materials.

[0124] Although not shown in Figures 1 and 2, the process 56 may include controlling pressure in the evaporating steps 10, 14 and / or the condensing steps 12, 16. Controlling pressure may be achieved by venting to atmosphere either: warm humidified gas streams 31, 45 formed in the evaporating steps 10, 14, or cool gas 32, 46 formed in the condensing steps 12, 16. This may be achieved by opening valves that vent to atmosphere, or rupturing bursting disks. Controlling pressure may also include operating fans or blowers 48 and 49 in the streams to generate pressure and flow in the warm humidified gas streams 31 and 45 and the cool gas streams 32 and 46. In any event, the evaporating steps 10, 14 in Figures 1 and 2, evaporating step 50 in Figure 2 and the condensing steps 12 and 16 in Figures 1 and 2, may be carried out at, or close to, atmospheric pressure.

[0125] The plant 57 illustrated in Figure 1 includes first and second evaporator columns 11 and 15, and first and second condenser columns 13 and 17. The first warm feed stream 20b is supplied to an upper region of the first evaporation column 11 and a cool first gas stream 32 is supplied to a lower region of the first evaporation column 11. Similarly, the second warm feed stream 21b is supplied to an upper region of the second evaporator column 15 and the second cool gas 46 is supplied to an upper region of the second evaporation column 17. The warm humidified first gas 31 stream having a higher percentage weight of water vapour is discharged from upper sections of the first and second evaporation columns 11 and 15 and supplied to lower region of the condenser columns 13 and 17, and the second cool gas stream 46 having a lower percentage of water vapour is discharged from the upper region of the second condenser column 17 and conveyed to the lower region of the second evaporator column 15 as mentioned. The first and second distillates 24a and 38a are formedin the first and second condenser columns 13 and 17 and split into a product distillate 65 including discharge distillate 24b and 38b and a the first and second return distillate streams 62 and 63. The plant includes a first heat exchanger 30 for transferring heat from a return portion of the distillate which provides the cool distillate 33, and the second feed stream 21b. The cool distillate stream 33 being fed to the upper portion of the first condenser column 13 to cool and condense the distillate from the warm humidified first gas stream 31. The cool distillate stream 47 being fed to the upper portion of the second condenser column 17 to cool and condense the distillate from the warm humidified second gas stream 45. The second distillate 38a of the second condenser column 17 is also split into a second discharge (product) distillate 38b and a second return distillate 47. The plant 57 also includes a heat pump 35 comprising a refrigerant to transfer heat from the second return portion to a heat carrying medium, namely heat transfer fluid 36, which removes heat from cool distillate 47. The heat transfer fluid 36a is supplied to a preliminary feed heat exchanger 34 so that the heat transfer fluid 36a heats the first feed stream 20a.

[0126] A controller, not shown in Figure 1, may control the temperature of the first feed stream 20a. For instance, the controller may adjust or control any one or a combination of the following; i) the work performed by the heat pump 35 and in turn the temperature of the heat transfer fluid 36a supplied to the preliminary feed heat exchanger 34, ii) the flow rate of the heat transfer fluid 36a through the preliminary feed heat exchanger 34, iii) the flow rate of the first feed stream 20a through the preliminary feed heat exchanger 34, and iv) the surface area of the preliminary feed heat exchanger 34 being utilized such as opening and closing valves that allow the heating medium to flow through parts of the preliminary feed heat exchanger 34.

[0127] In addition, the controller may control the temperature of the second feed stream 21b supplied to the second evaporation step 14. For instance, the controller may adjust or control i) the flow rate of the return distillate 33 supplied to the first condenser column 13, and / or ii) the flow rate of the second feed stream 21a. Similarly, in the case of Figure 2, the controller may also control the temperature of the third warm feed stream 22b by controlling the relative flow rates of the third stream 22b and the cool distillate stream 47 being returned to the condensing step 16.

[0128] The first and second evaporation columns 11 and 15 also include a sump that is located below inlets for the first and second cool gas streams 32 and 46 that are fed to the first and second evaporation columns 11 and 15. The first and second concentrate 23 and 37 pools in the sump of the first and second evaporation columns 11 and 15 and the first and second concentrate streams 23 and 37 may be conveyed through separators including hydrocyclones 28 and 42 which separates the concentrates 23 and 37 into first and second slurries 26a and 40a, and first and second liquid phases 27 and 41 . As can be seen, a portion of, or all of, the liquid phases 27 and 41 can be recycled back to the respective evaporator column 11 and 15, for instance by being mixed with the respective first and second feed streams 20a and 21a respectively. Although not shown, the returning liquid phases 27 and 41 can be fed directly to the sump of the first and second evaporation columns 11 and 15. A portion of the slurry streams 26a and 40a, namely return slurry 26c and 40c may be returned to the sump of the respective first and second evaporator columns 11 and 15 at levels below inlets of the first and second cool gas stream32 and 46. Figure 2 includes an additional evaporation column 51 also having a sump and a separator including hydrocyclone 61 that receives concentrate 59 discharged from the evaporation column 51. The hydrocyclone 61 separates the concentrate 59 into a third slurry 54a and a third liquid phase 55. A portion of, or all of, the liquid phase 55 can be recycled back to the evaporator column 51, for instance by being mixed with the third feed stream 22a. Similarly, a portion of the slurry 54a, namely third return slurry 54c may be returned to the sump of the third evaporator columns 51 at levels below the inlet at which ambient air is supplied to the column 51. In the event that the concentrates 23, 37 and 59 do not include solids, it will be appreciated that the first, second and third separation step 25, 39 and 60 can be omitted.

[0129] The separation steps 25, 39 and 60, and indeed the separators 28, 42 and 61 can be performed using any suitable separation equipment item such as a hydrocyclone separator, a settling pond, a settling tank, a centrifuge, a filter and so forth. In addition, it is also possible that one or more of the separation steps 25, 39 and 60, may be carried out in a sump, that acts as a settling reservoir, that forms part of the respective first, second and third evaporation columns 11, 15 and 51. For instance, although not illustrated in Figures 1 and 2, the evaporation columns 12, 14 and 60 may include a sump having multiple outlets for discharging various stream. One of the outlets can be used for discharging the slurry streams 26b, 40b and 54b, and optionally, another outlet can be used for discharging a liquid stream which may be combined with the respective feed stream 20a or 21a.

[0130] As can been seen, warm fans 48 may be provided in ducting that conveys the first and second warm humidified gas streams 31 and 45 from the first and second evaporators columns 11 and 15 to the first and second condensers 13 and 17. Similarly, cold fans 49 may be provided in the ducting that conveys the first and second cool gas streams from the first and second condensers 13 and 17 to the first and second evaporators columns 11 and 15. Operation of the fans 48 and 49 may be controlled by a controller, not shown, to adjust the flow rate of the first and second warm humidified gas streams 31 and 45 and, in turn, the temperature of these streams 31 and 45.

[0131] The plant 57 shown in Figure 2, is essentially the same as the plant 57 shown in Figure 1, except for the heat pump 35 in Figure 1 being substituted with a third evaporation column 51 and a second heat exchanger 44 for transferring heat from a second return distillate stream 63 to a third feed stream 22a. The second return distillate stream 63 is cooled to provide the second cooled distillate stream 47 that is fed to the upper portion of the second condenser column 17 and a third feed stream 22b is fed to an upper portion of the third evaporation column 51. Ambient air is also fed to a lower portion of the evaporation column 51 by an air blower and a third concentrate 59 is discharged from a lower portion of the evaporation column 51 and humidified air is discharged from an upper portion of the evaporation column 51. The third concentrate 59 passes through a third hydrocyclone 61 and produces a third slurry stream 54a and a third liquid phase 55. The third liquid phase 55 may be fed to the third evaporator column 51 and is suitably mixed with the third feed stream 22a. A portion of the third slurry 54a, namely a third return slurry 54c may be returned to the third evaporator column 51 and suitably to a sump of the third evaporator column 51 between the entry point of ambient air in to the third evaporation column 51. Another portion of the third slurry 54a may be discharged from the process, namely a third discharge slurry 54b.

[0132] The plant in Figure 2 may also include a preliminary feed heat exchanger 34 for transferring heat from a heat source, such as hot water, low pressure steam, and so forth. Although preliminary feed heat exchanger 34 in Figure 2 is arranged to provide heat to the first feed stream 20a, it will be appreciated that the preliminary feed heat exchanger 34 can be arranged to provide heat to any one of combination of the first, second, and third feed streams 20a, 21a and 22a.

[0133] Although not shown in detail in Figures 1 and 2, it will be appreciated that the process 56 may include anti-blocking steps for preventing blockages or removing blockages. The anti-blockage steps may include injecting wash water into pipework in which the process 56 is carried out. The plant 57 may include injection nozzles for injecting wash water to mobilize the solid material within pipework and / or equipment items. Injecting nozzles may be arranged in the plant 57 at desired locations to mobilize the solid material.

[0134] Table 1 below comprises mass flows and temperatures for the main streams of the process 56 and plant 57 shown in Figure 1 according to process simulations. The data provided in Table 1 are based on feed stream 9 having a nominal flow rate of 1000 kg / h and a 90% recovery, i.e. producing 900 kg / hr of distillate, namely distillate stream 65, and slurry streams 26a and 40a being 100 kg / hr of concentrated brine. Feed stream 9 contains NaCI at a concentration of 60 g / L. The mass flowsare expressed as true flow rate for liquid streams in kg / hr and moist air flow rate for gas / vapour streams in kg / ma.hr. The feed stream 9 was equally divided between the first feed stream 21a and the second feed stream 22a. Other assumptions include: i) The heat content of feed stream 9 and distillate stream 65 was disregarded, ii) The impact of the amount of liquid that is evaporated in the evaporating steps 10 and 14 and condensed in the condensing steps 12 and 16 will have a neglibile impact on the heat balance and represent about 2% of the the fluid flow in the evaporating and condensing steps. It effect has therefore not been taken into account, iii) Heat loss due to release of hot concentrate is disregarded, iv) Air temperatures are presented as dewpoint. V) No ambient air is added to the second cool gas 46 supplied to the second evaporator, which means no addition additional cooling was provided.Table 1 - example Temperature and Mass flows for Figure 1.

[0135] Part of the overall efficiency derived by the process 56 and plant 57 is that part of the heat energy used to heat the first feed stream 20a passes to the warm humidified first gas stream 31, which transfers part of this heat to the distillate 24a, and in turn, part of the heat in the distillate 24a is transferred to the second feed stream 21a via the first heat exchanger step 29 and the first heat exchanger 30. In summary, a portion of the heat energy supplied to the first warm feed stream 20bis in turn transferred to the second warm feed stream 21b at a lower temperature level. On other words, at least part of the available heat energy is utilized twice in separate evaporation steps 10 and 14 by initially heating the first warm feed stream 20b and utilizing heat of the distillate that is volatized from the first feed stream 20b and then condensed to thereafter heat the second warm feed stream 21b at a lower temperature. In addition, distillate 24a from evaporating step 12 transfers heat energy to the second feed 21a thereby producing the first warm feed 21 and cool distillate 33 which cools the warm humidified first gas 31, thus producing the first cool gas 32.

[0136] One possible benefit of the present disclosure is that the materials of the feed stream 9 are concentrated in the first concentrate 23 and the second concentrate 37, so that these concentrates can be more easily handled in downstream waste treatment. The concentration of materials of the first, second and third feed streams 20a, 21a and 22a may be substantially the same.

[0137] Another possible benefit of the present disclosure is that the first and second discharge distillate streams 24b and 38b can be used for various uses, including use as a process water. However, those skilled in the art will appreciate that the first and second distillate may include volatile constituents other than just water from the feed stream. Therefore, depending on the makeup of the feed water, without further processing, the distillate may or may not be suitable for human consumption or other uses.

[0138] Another possible benefit is that by the process and plant operating at atmospheric or close to atmospheric pressure, equipment items such as piping, the evaporator columns 11, 15 and 51 and the condenser columns 13 and 17 can be constructed from non-metallic materials, including polymeric, plastic, PVC, and so forth. In addition, the relatively low temperatures of the evaporation steps 10, 14 and 50 means that the plant can be constructed of polymeric materials. Where indirect heat transfer is required, such as in heat exchangers 30, 44 and 34, heat conducting material including metal may of course still be used. Similarly, valves and other fittings may or may not be constructed of metal.

[0139] The invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, however, it will be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Also, the various embodiments described above may be implemented in conjunction with other embodiments, for example, aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.Reference Numeral Table

Claims

CLAIMS1. A process of treating an aqueous feed stream including material to produce an aqueous distillate and an aqueous concentrate, the process includes: a first evaporating step in which a first warm feed stream contacts a first cool gas stream to volatilize water and provide a warm humidified first gas stream and a first concentrate; a first condensing step in which the warm humidified first gas contacts a first cool distillate stream to condense water from the warm humidified first gas and provide a first distillate and the first cool gas stream that contacts the first warm feed stream in the first evaporating step; a first heat transfer step in which heat is transferred from at least a portion of the first distillate to a second feed stream to provide a second warm feed stream; and a second evaporating step in which the second warm feed stream contacts a second cool gas stream to volatilize water from the second warm feed stream and provide a warm humidified second gas stream and a second concentrate; wherein the aqueous concentrate includes at least parts of the first and second concentrate, and the aqueous distillate includes at least part of the first distillate.

2. The process according to claim 1, wherein the first warm feed stream is hotter than the second warm feed stream.

3. The process according to claim 1 or 2, wherein the first heat transfer step includes heat being transferred from the at least a portion of the first distillate to the second feed stream, thereby cooling at least a portion of the first distillate to provide the first cool distillate stream, and in which at least part of the first cool distillate stream contacts the warm humidified first gas in the first condensing step.

4. The process according to any one of the preceding claims, wherein the process includes controlling the temperature of at least one of: a) the first warm feed stream and / or b) the second warm feed stream, so that the temperature of the first warm feed stream is greater than the temperature of the second warm feed stream.

5. The process according to any one of the preceding claims, wherein the process includes heating a first warm feed stream to a first temperature to provide the first warm feed stream, and the first heat transfer step includes heating the second warm feed stream to a second temperature that is less than the first temperature of the first warm feed stream.

6. The process according to any one of the preceding claims, wherein the process includes controlling the temperature of the first warm feed stream and the second warm feed stream so that there is a temperature differential of at least 10°C, and suitably a differential in the range of 5 to 30°C, and suitably approximately 20°C.

7. The process according to any one of the preceding claims, wherein the process includes a second condensing step in which the warm humidified second gas stream contacts a second cool distillate stream to condense water from the second gas stream and providing a second distillate and the second cool gas stream that is supplied to the second evaporating step.

8. The process according to any one of the preceding claims, wherein the process includes a second heat transfer step which includes operating a heat pump to transfer heat from at least a portion of the second distillate to either any one or a combination of the first feed stream and / or the second feed stream to provide the first warm feed stream and / or the second warm feed stream respectively.

9. The process according to any one of the preceding claims, wherein the first and second feed streams originate from a single source and as such contain the same types of material.

10. The process according to any one of the preceding claims, wherein the process includes a second heat transfer step in which heat is transferred between a portion of the second distillate and a third feed stream to provide a third warm feed stream.

11. The process according to claim 10, wherein the process includes controlling the temperature of the second warm feed stream and the third warm feed stream so that the second warm feed is hotter than the third warm feed stream, and there is a temperature differential of at least 10°C, and suitably a differential in the range of 5 to 30°C, and suitably approximately 20°C.

12. The process according to claims 10 or 11, wherein the first, second and third feed stream originate from a single source and as such contain the same types of material.

13. The process according to any one of the preceding claims, wherein the process includes adding air to the cool second gas stream supplied to the second evaporation step.

14. The process according to claim 13, wherein the process includes venting at least a portion of the warm humidified second gas stream from the process.

15. . The process according to claim 13 or 14, wherein the process includes controlling the rate at which air is added to the cooled second gas stream to control the temperature of the second cooled gas stream supplied to the second evaporating step.

16. The process according to any one of claims 13 to 15, wherein the first heat transfer step can be controlled based on factors including the rate at which air is added to the cooled second gas stream.

17. The process according to any one of claims 13 to 16, wherein the process includes controlling the nett discharge of the second concentrate from the second evaporating step based on factors including the rate of air being added to the second cooled gas stream.

18. The process according to any one of the preceding claims, wherein the process includes a third evaporating step in which a third warm feed stream contacts an ambient air stream to volatilize water from the third feed stream and provide a third concentrate.

19. The process according to any one of the preceding claims, wherein the temperature of the first warm feed stream is greater than the temperature of the first cool gas stream.

20. The process according to any one of the preceding claims, wherein the temperature of the second warm feed stream is greater than the temperature of the second gas stream.

21. The process according to claim 3, wherein the temperature of the first cool distillate stream returned to the first condensation step is less than the temperature of the warm humidified first gas stream fed to the first condensation step.

22. The process according to claim 7 , wherein the temperature of the second cool distillate stream returned to the second condensation step is less than the temperature of the warm humidified first gas stream fed to the first condensation step.

23. The process according to any one of the preceding claims, wherein the first distillate is used to heat a portion of the feed stream that is used as the second warm feed stream.

24. The process according to any one of the preceding claims, wherein the process includes heating the first warm feed stream in a preliminary heating step prior to being supplied to the evaporating step.

25. The process according to 23 or 24, wherein the process includes controlling the temperature of the first warm feed stream, based on factors including flow rate of the first distillate (product).

26. The process according to any one of the preceding claims, wherein the process includes returning at least a portion of the first concentrate to the first evaporation step.

27. The process according to any one of the preceding claims, wherein the process includes controlling the flow rate of the first concentrate stream discharged from the first evaporating step to control a recovery factor of the first evaporating step and condensing step, being a ratio (such as volume ratio) of the first distillate product to the first warm feed stream.

28. The process according to claim 26 or 27, wherein the process includes heating the portion of the first concentrate returned to the first evaporation step.

29. The process according to any one of the preceding claims, wherein the process includes separating the first concentrate of the first evaporating step into a first slurry phase and a first liquid phase, and returning at least a portion of the first liquid phase, hereinafter called a return first liquid phase, to the first evaporating step.

30. The process according to claim 29, including heating the return first liquid phase returned to the first evaporation step.

31. The process according to claim 27 or 28, including controlling the flow rate of the portion of the concentrate or the first liquid phase returned to the first evaporation step based on factors including available heat in the preliminary heating step.

32. The process according to any one of claims 27 to 29, wherein the step of separating the first concentrate into the slurry phase and the liquid phase includes feeding the first concentrate into a separating unit and discharging the first slurry phase and the first liquid phase from the separator.

33. The process according to any one of claims 29 to 32, wherein the process includes controlling the flow rate of the first slurry phase discharged from the process to control a recovery factor of thefirst evaporating step and condensing step, being a ratio (such as volume ratio) of the first distillate product to the first feed warm stream.

34. The process according to any one of claims 22 to 32 when appended to claim 24, wherein the portion of the returned first liquid that is returned to the first evaporating step is heated with the first feed stream in the preliminary heating step.

35. The process according to any one of the preceding claims, wherein the process includes returning at least a portion of the second concentrate to the second evaporation step.

36. The process according to any one of the preceding claims, wherein the process includes controlling the flow rate of the second concentrate stream discharged from the second evaporating step to control a recovery factor of the second evaporating step and condensing step, being a ratio of the second distillate product to the second warm feed stream.

37. The process according to claim 35 or 36, wherein the process includes heating the portion of the second concentrate returned to the second evaporation step.

38. The process according to any one of the preceding claims, wherein the process includes separating the second concentrate into a second slurry phase and a second liquid phase, and returning at least a portion of the second liquid phase, hereinafter called a return second liquid phase, to the second evaporating step.

39. The process according to claim 38, wherein the process includes controlling the flow rate of the second slurry phase discharged from the process to control a recovery factor of the second evaporating step and condensing step, being a ratio (such as volume ratio) of the second distillate product to the second feed warm stream.

40. The process according to claim 38 or 39, wherein the process includes heating the return second liquid phase returned to the second evaporation step.

41. The process according to claim 38, wherein the process includes controlling the flow rate of the portion of the second concentrate or the second liquid phase returned to the second evaporation step based on factors including available heat in the first heating step.

42. The process according to any one of claims 38 to 41, wherein the step of separating the second concentrate into the second slurry phase and the second liquid phase may include feeding the second concentrate into a second separation unit.

43. The process according to any one of claims 38 to 42, wherein the portion of the returned second liquid phase returned to the second evaporating step is heated with the second warm feed stream in the first heating step.

44. The process according to claim 43, wherein the process includes controlling the flow rate of the third concentrate stream discharged from the third evaporating step to control a recovery factor of the third evaporating step and condensing step, being a ratio of the third distillate product to the third warm feed stream.

45. The process according to any one of the preceding claims when appended to claim 17, wherein the process includes a third separating step in which the third concentrate is separated into a third slurry and a third liquid stream.

46. The process according to claim 45, wherein the process includes controlling the flow rate of the third slurry phase discharged from the process to control a recovery factor of the third evaporating step and condensing step, being a ratio (such as volume ratio) of the third distillate product to the third feed warm stream.

47. The process according to any one of the preceding claims, wherein the first evaporating step includes the first warm feed stream and the first cool gas stream flowing in counter current.

48. The process according to any one of the preceding claims, wherein the first condensing step includes the first warm humidified gas stream and the cool distillate stream flowing in counter current.

49. The process according to any one of the preceding claims, wherein the second evaporating step includes the second warm feed stream and the second cool gas stream flowing in counter current.

50. The process according to any one of the preceding claims, wherein the second condensing step includes the second warm humidified gas stream and the second cool distillate stream flowing in counter current.

51. The process according to any one of the preceding claims, wherein the material of the feed stream has a total dissolved solids (TDS) ranging up to 800 g / L, and suitably up to 700 g / L, and more suitably up to 600 g / L, and even more suitably up to 500g / L, and preferably up to 400 g / L, in one example, the TDS of the feed stream may be in the range of 50 to 400 g / L.

52. The process according to any one of the preceding claims, wherein the material of the feed stream includes any one or a combination of the following salts: NaCI, NajSC , (NL hSCU, KCI, LiaSC , CaSCU, CaCOs, MgSCU, or other combinations of the component ions.

53. A plant that carries out the process according to any one of claims 1 to 52 for treating an aqueous feed stream including materials to produce an aqueous distillate and an aqueous concentrate.

54. A plant for treating an aqueous feed stream including material to produce an aqueous distillate and an aqueous concentrate, the plant includes: a first evaporator in which a first warm feed stream contacts a first cool gas stream to volatilize water and provide a warm humidified first gas stream and a first concentrate; a first condenser in which the warm humidified first gas contacts a first cool distillate stream to condense water from the warm humidified first gas and provide a distillate and the first cool gas stream that contacts the first warm feed stream in the first evaporating step; a first heat exchanger for transferring heat from at least a portion of the distillate to provide a second warm feed stream; and a second evaporator in which the second warm feed stream contacts a second cooler gas stream to volatilize water from the second warm feed stream and provide a second humidified gas stream and a second concentrate, wherein the aqueous concentrate includes at least parts of the first and second concentrate, and the aqueous distillate includes at least a part of the first distillate.

55. The plant according to claim 54, wherein the plant includes a preliminary heat exchanger for 1heating the first feed stream.

56. The plant according to claim 54 or 55, wherein the plant includes a second condenser in which the second humidified gas stream contacts a second cool distillate to provide a second distillate and the second cool gas stream.

57. The plant according to any one of claims 54 to 56, wherein the plant includes a third evaporator in which a third warm feed stream contacts an ambient air stream to volatilize water from a third warm feed stream and provide a third concentrate.

58. The plant according to claim 57 when appended to claim 56, wherein the plant includes a second heat exchanger for transferring heat to the third warm feed stream from at least a portion of the second distillate stream which provides the second cool distillate stream.

59. The plant according to any one of claims 54 to 58, wherein the plant includes any one or a combination of: i) a first separation unit for separating the first concentrate into a first slurry phase and a first liquid phase so that at least a portion of the first liquid phase can be returned to the first evaporator; and ii) a second separation unit for separating the second concentrate into a second slurry phase and a second liquid phase so that at least a portion of the second liquid phase can be returned to the second evaporator.

60. The plant according to claim 57 or 58, wherein the plant includes a third separation unit for separating the third concentrate into a third slurry phase and a third liquid phase so that at least a portion of the third liquid phase can be returned to the third evaporator.

61. The plant according to any one of claims 54 to 60, wherein the plant includes a heat pump for transferring heat energy from at least a portion of the second distillate stream to the first warm feed stream.

62. The plant according to claim 61, wherein the heat pump can be used to transfer heat energy from at least a portion of the second and / or third distillate stream to the first and / or second warm feed streams.

63. The plant according to any one of claims 54 to 62, wherein the plant includes one or more flow generators for driving the flow of the first humidified gas stream and the first cool gas stream.

64. The plant according to any one of claims 54 to 63, wherein the plant includes one or more flow generators for driving the flow of the second warm humidified gas stream and the second cool gas stream.

65. The plant according to any one of claims 47 to 64, wherein the plant includes a controller that controls any one or a combination of: a) the temperature of i) the first warm feed stream and / or ii) the second warm feed stream, so that the temperature of the first warm feed stream is greater than the temperature of the second warm feed stream, b) the temperature of the first warm feed stream and the second warm feed stream so that there is a temperature differential of at least 10°C, and suitably a differential in the range of 5 to 30°C, and suitably approximately 20°C, c) the temperature of the warm first feed stream, based on factors including flow rate of the first distillate (product),d) the flow rate of the first concentrate stream discharged from the first evaporating step to control a recovery factor of the first evaporator and condenser, being a ratio (such as volume ratio) of the first distillate product to the first feed warm stream.

66. The plant according to claim 59, wherein the plant includes a controller that controls any one or a combination of: e) the flow rate of the portion of the concentrate or the first liquid phase returned to the first evaporator based on factors including available heat in the preliminary heat exchanger, f) the flow rate of the first slurry phase discharged from the process to control a recovery factor of the first evaporator and condenser, being a ratio (such as volume ratio) of the first distillate product to the first feed warm stream, g) the flow rate of the second concentrate stream discharged from the second evaporator to control a recovery factor of the second evaporator and condenser, being a ratio of the second distillate product to the second warm feed stream, h) the flow rate of the second slurry phase discharged from the process to control a recovery factor of the second evaporator and condenser, being a ratio (such as volume ratio) of the second distillate product to the second feed warm stream, i) the flow rate of the portion of the second concentrate or the second liquid phase returned to the second evaporator based on factors including available heat in the first heat exchanger.

67. The plant according to claim 60, wherein the plant includes a controller that controls any one or a combination of: j) the flow rate of the third concentrate stream discharged from the third evaporating step to control a recovery factor of the third evaporating step and condensing step, being a ratio of the third distillate product to the third warm feed stream, k) the flow rate of the third slurry phase discharged from the process to control a recovery factor of the third evaporating step and condensing step, being a ratio (such as volume ratio) of the third distillate product to the third feed warm stream.

68. A process of treating an aqueous feed stream including material to produce an aqueous distillate and an aqueous concentrate, the process includes: a first evaporating step in which a first warm aqueous feed stream contacts a cool gas stream to volatilize water and provide a warm humidified first gas stream and a first concentrate, wherein the first evaporating step includes the first feed stream and the first cool gas stream flowing in counter current; and a first condensing step in which the warm humidified first gas contacts a first cool distillate stream to condense water from the warm humidified first gas and provide a distillate and the first cool gas stream that is supplied to the first evaporating step, wherein the first warm humidified gas stream and the first cool distillate stream flowing in counter current.

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