WO2023249632A1

WO2023249632A1 - Volatile material concentrators

Info

Publication number: WO2023249632A1
Application number: PCT/US2022/034721
Authority: WO
Inventors: Assaf PINES; Doron Schlumm; Mark Sandler
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2022-06-23
Filing date: 2022-06-23
Publication date: 2023-12-28

Abstract

In an example, an apparatus includes a heating module, a concentrator comprising a first portion and a second portion and a recovery module. In some examples the heating module is to output gas through the second portion of the concentrator to increase a concentration of volatile material in the gas. The recovery module may receive the gas which has passed through the second portion of the concentrator, recover volatile material from the received gas and output gas through the first portion of the concentrator to decrease a concentration of volatile material of the gas.

Description

VOLATILE MATERIAL CONCENTRATORS

BACKGROUND

[0001] Volatile materials are substances which may readily vaporise. Such materials may be useful in processes, such as industrial processes or printing. However there may be health and environmental concerns associated with their release into the environment or other locations. Therefore, there may be efforts to reduce the concentration of volatile materials in gasses which are exhausted from such processes.

BRIEF DESCRIPTION OF DRAWINGS

[0002] Non-limiting examples will now be described with reference to the accompanying drawings, in which:

[0003] Figure 1 is a simplified schematic drawing of an example apparatus;

[0004] Figure 2 is a simplified schematic drawing of an example apparatus;

[0005] Figure 3 is a simplified schematic drawing of an example concentrator;

[0006] Figure 4 is a flowchart of an example of a method for recovering volatile material from a gas;

[0007] Figure 5 is a flowchart of another example of a method for recovering volatile material from a gas; and

[0008] Figures 6 and 7 are simplified schematic drawings of an example printing apparatus.

DETAILED DESCRIPTION

[0009] Volatile materials are materials which have a high volatility, wherein volatility is a property of a material which describes how readily the material vaporizes. A substance with high volatility may vaporize, boil or evaporate at, or near, room temperature and pressure, or at temperatures of processes in which it is used. Volatile materials have many uses in industrial processes, for example as solvents. They may also be used in substances such as paints, inks or varnishes. For example, a colorant such as a dye or pigment may be mixed with a volatile material which acts as a solvent. When the mixture is deposited on a surface, such as a substrate (for example paper, card, plastic, or the like) the volatile material may evaporate (i.e. vaporize) leaving the colored pigment or dye on the surface. Volatile materials are therefore often used in printing processes as a solvent.

[0010] Volatile materials include volatile organic compounds (VOCs), which are organic chemicals which have a low boiling point at standard atmospheric pressure and near room temperature (i.e. a high vapour pressure). A VOC may be defined as an organic compound having a boiling point less than or equal to 250°C at standard atmospheric pressure. Examples of VOCs include isoparaffinic fluids such as Isopar (e.g. Isopar L, Isopar H, Isopar M), hexane or Isopropyl alcohol (IPA).

[0011] Volatile materials, such as VOCs, may be dangerous to human health or may harm the environment. Therefore, emission of VOCs may be regulated or controlled. Processes which use volatile materials may therefore employ filtering to remove volatile materials from gasses which are exhausted from the process or exchanged between an environment of the process and its surroundings (e.g. an interior of an apparatus carrying out the process and a room the apparatus is located in).

[0012] In some examples, volatile materials may be captured and disposed of, while in other examples the captured material may be reused or recycled. Volatile materials may condense at low temperatures, therefore some processes may reduce the volatile material concentration of their exhaust gasses by cooling the exhaust gas causing the volatile materials therein to condense to a liquid which may then be collected. The collected liquid may be recycled, reused or safely disposed of. This reduces harm caused by emission of the volatile material and can also reduce costs associated with the process when the material is reused or recycled. Furthermore it may be more convenient for a user or operator because supplies of the volatile material and filter materials may be replenished or replaced less frequently if the volatile material and filter materials can be reused.

[0013] The exhaust gases may be cooled using an apparatus such as a heat exchanger to reduce the temperature of the exhaust gas. However, a heat exchanger (e.g. connected to a site chiller) may be unable to reduce the volatile material concentration below a certain level. This level may be determined by the operating temperature of the heat exchanger. For example, a heat exchanger which operates at 10°C may be able to reduce the exhaust concentration of an example volatile material of Isopar L to approximately 200ppm. It may not be practically possible to operate heat exchangers at significantly lower temperatures because at lower temperatures ice may form on cooling fins of the heat exchanger causing loss of efficiency. Ice formation may be removed by use of a defrosting cycle, however this may also lead to a reduction in efficiency.

[0014] Figure 1 shows an example of apparatus 100, which may be used for recovering volatile material from a filter material. As used herein, a filter material may comprise a porous material through which a fluid may permeate while trapping a material which is intended to be removed from the fluid. For example the fluid may comprise a gas, the gas may comprise mainly air and may be from a process such as a printing process and the material intended to be removed may be a volatile material such as VOCs.

[0015] In some examples, the apparatus 100 may be a printing apparatus or may be associated with a printing apparatus. For example, the apparatus 100 may be an apparatus for processing gas from a printing process. As used herein printing may refer to depositing agents (e.g. inks, colorants) on a substrate or generating three dimensional objects using additive manufacturing.

[0016] A concentrator may comprise a filter material which may be used to capture (e.g. adsorb or absorb) and release (e.g. desorb) volatile material from a gas to reduce and increase the concentration of volatile materials in streams of gas passed through the concentrator, thereby concentrating volatile material in one stream of gas while reducing the concentration of volatile material in another stream of gas. As the quantity of volatile material captured by the filter material increases, the ability of the filter material to capture more volatile material may reduce as the filter material becomes saturated with volatile material. When the ability to capture volatile material drops below a certain level, the filter material may be considered “full”, “used” or “saturated”. To continue to efficiently reduce volatile material concentration in a gas, the filter material may be replaced or regenerated. Replacement of filter material may be inconvenient for a user or operator of an apparatus and when filter material is replaced the used volatile material captured by the used filter material may not be recovered, for example the filter material or the volatile material therein may be incinerated. In some cases, when a filter material is replaced, the type of volatile material adsorbed by the filter material may not be identifiable to the entity processing the filter material and so recovery and reuse of the volatile material may not be practical, resulting in incineration being used as a practical means for processing used filter materials and/or captured volatile materials. The apparatus 100 allows the filter material to be regenerated so that the filter material may be reused and the volatile material captured by the filter material can be recovered for recycling or reuse. As used herein, filter material includes material which may be used to capture volatile material, such as adsorbing material (i.e. adhesion to a surface of the filter material) or absorbing material (i.e. entering the bulk of the filter material).

[0017] The volatile material adsorbed by the filter material may be a VOC, such as Isopar (e.g. Isopar L).

[0018] The apparatus 100 comprises a heating module 102, a concentrator 104 and a recovery module 110, wherein the concentrator 104 comprises a first portion 106 and a second portion 108. Figure 1 shows the concentrator 104 in a first position, in which the recovery module 110 outputs gas through the first portion 106 of the concentrator 104 and the heating module 102 outputs gas through the second portion 108 of the concentrator 104. However, in some examples the concentrator 104 may be moveable between a number of positions. In some examples, in operation of the apparatus the concentrator 104 may be moved substantially continuously such that the concentrator 104 moves through various positions in addition to the first position. Such further positions are described in further detail below. In some examples, moving the concentrator 104 may comprise rotating the concentrator 104, although in principle the position may be changed by sliding or the like.

[0019] In use of the apparatus 100, the heating module 102 outputs gas through the second portion 108 of the concentrator 104. The second portion 108 of the concentrator 104 may be a “used” portion of the concentrator 104 i.e. it may have been used to adsorb volatile material from a gas and therefore contains adsorbed volatile material. Passing gas therethrough may act to increase a concentration of volatile material in the gas, as volatile material may be released (e.g. by evaporation or vaporization) from the second portion 108 as the gas passes therethrough. The heating module 102 may supply heated gas 112 with a first volatile material concentration to the second portion 108 of the concentrator 104. The heating module 102 may comprise any suitable type of heating apparatus for heating the gas, for example the heating module may comprise an electrical heater, such as a resistive heater. For example, the heating module 102 may comprise a resistive heating element located in a gas stream (i.e. within a duct or pipe through which a gas flows). In some examples, the heating carried out by the heating module 102 may, at least in part, be part of another process, for example a process of drying a printing fluid on a substrate may include heating the printing fluid. In some examples the heated gas 112 may be heated to at least 100°C or a temperature of approximately 180°C. In some examples the temperature of the heated gas is less than the autoignition temperature of the volatile material. For example, the autoignition temperature of Isopar L may be 220°C. Therefore, when the volatile material is Isopar L, the temperature of the heated air may be less than 200°C (for example approximately 180°C) to ensure the Isopar L does not ignite.

[0020] In use of the apparatus 100, the recovery module 110 is to receive the gas 114 which has passed through the second portion 108 of the concentrator 104. The gas 114 which has passed through the second portion 108 of the concentrator 104 may have a second volatile material concentration, wherein the second volatile material concentration is higher than the first volatile material concentration.

[0021] Use of the apparatus 100 may therefore cause the second portion 108 of the concentrator 104 to be regenerated by reducing the quantity of volatile material in the concentrator 104. The heated gas 112 is supplied to the second portion 108 of the concentrator 104 at a temperature which causes the volatile material to evaporate or vaporize, thereby increasing the concentration of volatile material in the gas 114 output from the second portion 108 of the concentrator 104 relative to the heated gas 112 input to the second portion 108 of the concentrator 104. A relatively small flow rate (compared with total flow rate of gas through the concentrator 104) of heated gas 112 to the second portion 108 of the concentrator 104 may also contribute to increasing the concentration of volatile material in the gas 114 output from the second portion 108 of the concentrator 104 relative to the heated gas 112 input to the second portion 108 of the concentrator 104. This also results in a reduction of the quantity of volatile material in the second portion 108 of the concentrator 104, thereby regenerating the second portion 108 of the concentrator 104 to allow it to be used again in a filtering role to remove volatile material from a gas. Regeneration of the second portion 108 of the concentrator 104 may reduce waste and costs associated with disposing of and replacing filter materials because it allows each portion of the concentrator 104 to be regenerated and reused.

[0022] In use of the apparatus 100 the recovery module 110 is to recover volatile material from the received gas 114 which has passed through the second portion 108 of the concentrator 104. The gas 114 which has passed through the second portion 108 of the concentrator 104 has an increased concentration of volatile material due to the evaporation or vaporization of volatile material from the second portion 108 of the concentrator 104. The recovery module 110 may use any suitable means to recover the volatile material from the gas 114 which has passed through the second portion 108 of the concentrator 104, for example it may cool the gas 114 and/or increase the pressure of the gas 114 to cause condensation of the volatile material. Condensed volatile material may then be collected. The collected volatile material may be recycled or reused in a process within the apparatus 100 or in a different process. In some examples the gas 114 which has passed through the second portion 108 of the concentrator 104 may be provided directly to the recovery module 110 without participating in any other substantial process. However, in some examples the gas 114 which has passed through the second portion 108 of the concentrator 104 may be used in another process within the apparatus 100, for example the gas 114 may be useful due to its high temperature and therefore may be used in a process which uses hot gas or elevated temperatures.

[0023] In use of the apparatus 100, the recovery module 110 outputs gas 116 through the first portion 106 of the concentrator 104 to decrease a concentration of volatile material of the gas. For example, the first portion 106 of the concentrator 104 may capture volatile material from a portion of the gas 116 output from the recovery module 110. The gas may then be exhausted from the apparatus 100 after passing through the first portion 106 of the concentrator 104. In some examples the gas may be heated prior to being exhausted from the apparatus to avoid cooling the environment around the apparatus 200 where the gas has been cooled therein and/or to remove heat from the interior of the apparatus 100, thereby cooling the apparatus 100, as described in greater detail below.

[0024] The first portion 106 and the second portion 108 of the concentrator 104 may be substantially the same in terms of their construction (i.e. materials, structure, etc.). Indeed, they may comprise different zones of a substantially continuous concentrator. In some examples at least one of the first portion 106 of the concentrator 104 and the second portion 108 of the concentrator 104 comprise a silica gel, activated carbon, a zeolite or any other material suitable for capturing (e.g. adsorbing or absorbing) volatile material form the gas.

[0025] The concentrator 104 may be any suitable shape, such as rectangular, square, polygonal or the like. In particular examples, it may for example be cylindrical with gas passing through the portions of the concentrator 104 in a direction parallel to axis of the cylinder. The concentrator 104 may comprise a number of distinct segments, each comprising a filter material. The segments may be formed by a number of walls extending radially within the concentrator 104 from the centre of the concentrator 104 to the circumference of the concentrator 104 and parallel to the axis of the concentrator 104. The walls may be impermeable to gas, and therefore they cause the gas to flow substantially axially within the concentrator. The walls may also allow the different segments of the concentrator 104 to simultaneously perform different roles, for example a portion of the concentrator 104 may be used to actively capture volatile material from a gas, while other portions of the concentrator 104 are being regenerated or performing other roles without these different processes interfering with each other. The walls may be evenly spaced to provide segments with an equal volume of filter material.

[0026] The first portion 106 of the concentrator 104 receives gas 116 output from the recovery module 110 and captures remaining volatile material from said gas 116 (after treatment by the recovery module 110) to reduce the concentration of volatile material in the gas 116, for example by adsorbing the volatile material. Gas may be exhausted from the first portion 106 of the concentrator 104 after it has passed through the concentrator 104. The concentration of VOC in the gas exhausted from the first portion 106 of the concentrator 104 may be lower than, and in some examples significantly lower than, the concentration of VOCs in the gas 116 received by the concentrator 104. For example, the gas 116 received by the first portion 106 of the concentrator 104 (i.e. gas 116 output by the recovery module 110) may have a volatile material concentration of approximately 200ppm (parts per million) whereas the gas exhausted by the first portion 106 of the concentrator 104 may have a volatile material concentration of less than 10ppm.

[0027] When the concentration of volatile material exhausted from the first portion 106 of the concentrator 104 is low, it may safely be exhausted from the apparatus, for example into a room in which the apparatus is located or into the environment. [0028] As described above, in some examples the concentrator 104 may be movable between a number of positions and in some examples the concentrator may comprise a number of distinct segments. In an illustrative example the concentrator 104 is a cylindrical concentrator and comprises a plurality, for example 12, segments, which are referred to herein as segment 1 , segment 2, and so on up to segment 12 (labelled in a clockwise direction). Segments 1 to 8 may contain the first portion 106 of the concentrator 104 and when the concentrator 104 is in the first position segments 1 to 8 may receive gas 116 output from the recovery module 110. Segments 9 to 12 may comprise the second portion 108 of the concentrator 104 and while the concentrator 104 is in the first position segments 9 to 12 may receive gas from the heating module 102. During operation of the apparatus 100, the concentrator 104 may be moved within the apparatus. In this example the concentrator 104 is rotated continuously in an anticlockwise direction. When the concentrator 104 has performed 1 /12^th of a full anticlockwise rotation, segments 2 to 9 receive gas 116 output from the recovery module 110 and segments 10, 11 , 12 and 1 receive gas from the heating module 102. When the concentrator 104 has performed further 1/12^th of a full anticlockwise rotation, segments 3 to 10 receive gas 116 output from the recovery module 110 and segments 11 , 12, 1 and 2 receive gas from the heating module 102. The concentrator 104 may continuously rotate such that each of the segments spends a portion of time receiving gas from the recovery module 110, during which it actively captures volatile material from the gas and spends another portion of time receiving gas from the heating module 102 during which it is being regenerated, until a complete rotation is performed and the cycle begins again. In this way the concentrator 104 can substantially continuously capture volatile material from the gas received from the recovery module 110 while increasing the concentration of gas 114 input to the recovery module 110.

[0029] The gas 112, 114, 116 may be routed within the apparatus via any suitable ducting. In the example wherein the concentrator 104 comprises a number of segments, the gas may be supplied to the segments via funnels (i.e. ducting with increasing cross sectional area along its length). In the example wherein the concentrator 104 comprises 12 segments, a first funnel may provide segments 1 to 8 with gas 116 from the recovery module 110 when the concentrator 104 is in the first position and a second funnel may provide gas 112 from the heating module 102 to segments 9 to 12 when the concentrator 104 is in the first position. As the concentrator 104 rotates the funnels may provide gas to different segments of the concentrator 104. The apparatus 100 may also include blowers, fans or the like to cause the gas to move through the ducting and the other components of the apparatus described herein.

[0030] Figure 2 shows an example of an apparatus 200. The apparatus 200 may be an example of the apparatus 100 described with respect to Figure 1.

[0031] The arrows in Figure 2 indicate routing of gas within the apparatus 200. Relative volumes of gas may be indicated by the thickness of the arrows i.e. a thicker arrow may indicate a greater volume of gas than a thinner arrow. In practical examples, the gas may be routed within pipes or ducting.

[0032] The apparatus 200 comprises a heating module 202, a concentrator 204 and a heat exchanger 210 which may correspond to the heating module 102, the concentrator 104 and recovery module 110 of Figure 1 , respectively. The concentrator 204 includes the first portion 106 and the second portion 108 as described with respect to concentrator 104 of Figure 1 , and further includes a third portion 206, which is described in further detail below. The apparatus 200 further includes an actuator 208, which is also described in more detail below.

[0033] Figure 2 shows the apparatus 200 with the concentrator 204 in a first position. In this example, with the concentrator 204 in the first position, the first portion 106 of the concentrator 204 is actively capturing volatile material e.g. it is adsorbing volatile material and the second portion 108 of the concentrator 204 is being regenerated i.e. the quantity of volatile material in the second portion 108 of the concentrator 204 is being reduced, or is ‘desorbing’.

[0034] As described in relation to Figure 1 , the heating module 202 heats gas to an elevated temperature. With the concentrator 204 in the first position the heated gas from the heating module 202 is provided to the second portion 108 of the concentrator 204. The heated gas causes volatile material in the second portion 108 of the concentrator 204 to evaporate causing the second portion 108 concentrator 204 to release captured volatile material into the gas. The second portion 108 of the concentrator 204 therefore outputs gas with an increased volatile material concentration to the heat exchanger 210. In some examples the output gas 114 from the second portion 108 of the concentrator 204 may be cooled before entering the heat exchanger 210 (for example by a second heat exchanger, as described in further detail below). [0035] In this example, the apparatus 200 comprises an actuator 208 to move the concentrator which can move the first portion 106 and the second portion 108 of the concentrator 204 within the apparatus 200. For example, the actuator 208 may reposition the concentrator 204 from a first position, as illustrated in Figure 2, to be in a second position. The actuator may cause the concentrator 204 to move substantially continuously. For example, in which the roles of the first portion 106 and the second portion 108 may be periodically cycled as the concentrator 204 moves. For example, the concentrator 204 may move from the first position to a second position in which heated gas from the heating module 202 may be provided to the first portion 106 of the concentrator 204 to regenerate the first portion 106 of the concentrator while the second portion 108 of the concentrator 204 is actively capturing volatile material in gas output from the heat exchanger 210. The actuator 208 may continue to cause the concentrator 204 to move, thereby cycling between the first and second positions.

[0036] In some examples the actuator 208 may comprise a motor, such as an electric motor. Such a motor may cause the concentrator 204 to rotate such that the positions of the first portion 106 and second portion 108 change. In other examples the actuator 208 may comprise a motor or a linear actuator which causes the concentrator 204 move linearly or in an arc to change the positions of the first portion 106 and the second portion 108 of the concentrator 204.

[0037] In some examples the actuator 208 is to rotate the concentrator 204. For example, the concentrator 204 may be a substantially cylindrical shape and the actuator may be a motor which causes the concentrator 204 to rotate about an axis of the concentrator 204. In an example the concentrator 204 may have a diameter of approximately 0.3m and a thickness of approximately 0.4m.

[0038] In this example, the recovery module is a heat exchanger 210 and recovers liquid volatile material by reducing the temperature of the gas causing the volatile material to condense. A heat exchanger 210 may be an apparatus which transfers heat between two fluids. In this example, the heat exchanger 210 is used to transfer heat away from the gas, causing it to be cooled thereby reducing the temperature of the gas. However, in other examples any other suitable means for cooling the gas may be used, such as refrigeration.

[0039] In this example, the gas which has passed through the second portion 108 of the concentrator 204 has an increased temperature and an increased volatile material concentration relative to the gas input to the heating module 202. The heat exchanger 210 may also, as shown in this example, have a further gas input 212. In some examples, the gas received at the gas input 212 may be gas extracted from an apparatus which releases VOCs, such as a printing apparatus. Gas which has passed through the second portion 108 of the concentrator 204 and the gas input 212 may be mixed prior to entering the heat exchanger 210 or mixed within the heat exchanger 210. Due to the high volatile material concentration of the gas which has passed through the second portion 108 of concentrator 204, the overall volatile material concentration of gas input to the heat exchanger 210 is increased relative to the concentration of volatile material input at the gas input 212. The heat exchanger 210 is therefore able to more efficiently recover volatile material than a heat exchanger which does not have a high concentration of volatile material in its input gas. The efficiency of the heat exchanger 210 may be defined as

wherein the volatile material concentration of the output gas is determined by the operational temperature of the heat exchanger 210. Therefore, the efficiency increases as the volatile material concentration of the input gas increases because the volatile material concentration of the output gas is substantially constant. Therefore, in some examples, the concentration of VOCs in gas emitted by a process such as a printing process may initially be increased by the addition of gas recovered from the second portion 108 of the concentrator 204, before being reduced by the heat exchanger 210 to increase the efficiency of recovery of VOCs.

[0040] The condensed volatile material may be collected and recycled or reused. For example, the volatile material may be reused in a process within the apparatus 200, or a process associated with the apparatus 200. For example, in examples wherein the apparatus 200 is a printing apparatus or an apparatus associated with a printing process, the recovered volatile material may be reused in the printing process. In some examples the collected volatile material may undergo some additional processing before it can be reused.

[0041] In this example, with the concentrator 204 in the first position, a portion of the gas output from the heat exchanger 210 is supplied to the heating module 202 to be heated prior to being output through the second portion 108 of the concentrator 104 to form heated gas with the first volatile material concentration. As the heat exchanger 210 reduces the concentration of volatile material in the gas output therefrom, this gas which is input to the heating module 202 has a relatively low concentration of volatile material (e.g. approximately 200ppm). Therefore, the heated gas which is provided to the second portion 108 of the concentrator 204 also has a relatively low concentration of volatile material (e.g. approximately 200ppm). This gas with a relatively low volatile material concentration and relatively high temperature causes a volatile material captured in the second portion 108 of the concentrator 204 to evaporate at a relatively high rate, thereby increasing the efficiency of regeneration of the second portion 108 of the concentrator 204 for reuse. However, in other examples, the gas flow may be provided from some other source.

[0042] In this example, the concentrator 204 further comprises a third portion 206. The portion of gas output from the heat exchanger 210 is to pass through the third portion 206 prior to being supplied to the heating module 202. The portion of gas output from the heat exchanger 210 has a relatively low temperature, for example approximately 10°C. Therefore, passing this gas through the third portion 206 of the concentrator 204 may cool this portion of the concentrator 204. Moreover, this further reduces the concentration of volatile material supplied to the heating module, which may further increase the efficiency of regeneration of the second portion 108 of the concentrator 204 as described above.

[0043] The actuator 208 may move the concentrator 204 from a first position to a second position and from a second position to a third position, wherein in the first position the first portion 106 is to capture volatile material in gas output from the heat exchanger 210, in the second position the first portion 106 is to release captured volatile material into gas received from the heating module 202 and in the third position the first portion 106 is to be cooled by gas received from the heat exchanger 210. Therefore, when in the first position, as shown in Figure 2, the third portion 206 of the concentrator 204 contains a low quantity of volatile material because it was recently regenerated by passing heated air through it. However, this means that the third portion 206 of the concentrator 204 would have been relatively hot. Therefore, cool air is passed through the third portion 206 of the concentrator 204 to cool this portion of the concentrator 204 before the concentrator 204 is further moved (e.g. rotated) and the third portion 206 is used to actively capture volatile material. Cooling a portion of the concentrator 204 after it has been regenerated and prior to active use to capture volatile material from a gas may increase the efficiency at which the portion of the concentrator 204 can capture the volatile material. [0044] The first portion 106, second portion 108 and the third portion 206 of the concentrator 204 may be substantially the same in terms of their construction (i.e. materials, dimensions, shape, etc.). Indeed, they may comprise different zones of a substantially continuous filter material. In some examples each portion of the concentrator 204 comprises a silica gel, activated carbon or a zeolite.

[0045] As the concentration of volatile material exhausted from the first portion 106 of the concentrator 204 is low when the concentrator 204 is in the first position, it may safely be exhausted from the apparatus 200, for example into a room in which the apparatus is located or into the environment. However, the temperature of this gas may be relatively low because it has passed through the heat exchanger 210 which may use low temperatures (e.g. approximately 10°C) to recover volatile material. Therefore, the exhaust gas may pass through a second heat exchanger, referred to as an ‘economiser’, before being vented from the apparatus 200 to the room or environment. Such a second heat exchanger may use the cool exhaust gas to reduce the temperature of the gas input to the heat exchanger 210 to further increase efficiency of recovery of volatile material. The gas input to the heat exchanger 210 may be from an industrial process and therefore may have a relatively high temperature, for example in the range 100°C to 200°C. The gas from the process may be cooled by the economiser to a temperature of 30°C to 40°C prior to being input to the heat exchanger 210 which may further cool the gas to approximately 10°C. The exhaust gas may have a temperature of approximately 10°C prior to passing through the second heat exchanger (i.e. the economiser), which may heat the exhaust gas, for example to room temperature (i.e. around 20°C to 25°C). Therefore, the exhaust gas 220 may be vented from the economiser of the apparatus 200 to a room without adversely affecting the temperature in the room and without releasing gas with a harmful concentration of volatile material.

[0046] In some examples the apparatus 200 may further comprise a controller. The controller may control the actuator 208 to cause the concentrator 204 to move as described above. The controller may be implemented, at least in part, by processing circuitry executing machine readable instructions.

[0047] As described with respect to Figure 1 , the heating module 202 may heat the gas to a temperature of at least 100°C, for example 180°C. In some examples the temperature of the heated gas may be less than the autoignition temperature of the VOC under consideration. For example, for Isopar L which may have an autoignition temperature of 220°C, the temperature may be less than 220°C or less than 200°C.

[0048] Figure 2 depicts gas from the second portion 108 of the concentrator 204 being input to the heat exchanger 210. In some examples this gas is used in a process in the apparatus 200 prior to being input to the heat exchanger 210. This gas has been heated and therefore may be useful for a process which uses heated air. For example, as described in further detail in relation to Figure 7, the apparatus 200 may be a printing apparatus and the heated gas may be used in an air knife. In other examples, the heated gas may be used to warm gas to be output to the environment in the economiser.

[0049] A blower, a fan or a vacuum pump or the like may then be used to direct or suck gas which has been jetted by an air knife to be input into the heat exchanger 210. The blower, fan or vacuum pump may also direct or suck gas which was not jetted from the air knife into the input of the heat exchanger. This additional gas may be from a process associated with the apparatus 200, for example the gas may be associated with a printing process, for example from the interior of a printing apparatus.

[0050] Figure 3 is an example of a concentrator 300 which may be used in the apparatus 100, 200 described in relation to Figures 1 and 2. In this example, the concentrator 300 is a cylinder and comprises a first sector 302, a second sector 304 and a third sector 306. In this example, the concentrator 300 rotates clockwise as indicated by arrow 308. An actuator, such as a motor, may cause the concentrator 300 to move, however, it is not shown in this figure for simplicity. The concentrator 300 is shown in the first position and when the concentrator 300 rotates it moves from the first position to the second position, from the second position to the third position and from the third position back to the first position.

[0051] In this example, in the first position the recovery module (e.g. heat exchanger 210) outputs gas through the first sector 302 of the concentrator 300 and the heating module 202 outputs gas through a second sector 304 of the concentrator 300. The first sector 302 comprises the first portion 106 of the concentrator 300 and the second sector 304 comprises the second portion 108 of the concentrator 300, wherein the first and second portions 106, 108 are described in relation to Figures 1 and 2. In other words, the first portion 106 is located within at least part of the first sector 302, and in some examples is a sub-portion thereof, and the second portion 108 is located within at least part of the second sector 304, and in some examples is all or a sub-portion thereof. [0052] In this example the first sector 302 is larger than the second sector 304. Therefore, the rate of flow of gas through the first sector 302 of the concentrator 300 may be greater than the rate of flow of gas through the second sector.

[0053] In this example the concentrator 300 further comprises a third sector 306, which may comprise the third portion 206 described in relation to Figure 2. In other words, the third portion 206 is located within at least part of the third sector 306, and in some examples is all or a sub-portion thereof. In this example the first sector 302 is larger than the third sector 306. Therefore, the rate of flow of gas through the first sector 302 of the concentrator 300 may be greater than the rate of flow of gas through the third sector 306. The second sector 304 may be substantially the same size as the third sector 306, and the rate of gas flowing through the second sector 304 may be the same as the rate of gas flowing through the third sector 306. The first sector 302 may comprise approximately 3/4 of the volume of the concentrator 300, and each of the second sector 304 and the third sector 306 may comprise 1/8 of the volume of the concentrator 300. In some examples, the third sector 306 may be smaller than the second sector 304, for example when less cooling is intended.

[0054] As the concentrator 300 rotates, the concentrator 300 is initially in the first position in which the first portion 106 of the concentrator 300 captures volatile material in gas 310 output from the heat exchanger 210, then the concentrator 300 rotates to a second position in which the first portion 106 releases captured volatile material into gas 312 received from the heating module 202, then the concentrator 300 rotates to a third position in which it is cooled by gas 314 received from the heat exchanger 210 before returning to the first position. Therefore, the concentrator 300 may simultaneously be actively filtering volatile material from a gas 310, while a different portion of the concentrator 300 is being regenerated with heated gas 312 and another portion of the concentrator 300 is being cooled by cool gas 314.

[0055] The concentrator 300 may rotate at a substantially constant rate, for example at a rate in the range of 5 seconds to 2 minutes per rotation. The rate of rotation may be selected based on the dimensions of the concentrator 300, for example a thicker concentrator may be capable of capturing more volatile material and may desorb the volatile material at a slower rate and therefore may rotate at a slower rate than a thinner concentrator. Other factors affecting the selected rotation speed are concentrator material, concentrator dimensions, compaction or density of the concentrator material, and the concentration of volatile material in the gas.

[0056] As indicated by the thickness of the arrows in Figure 3, when the concentrator 300 is in the first position the flow rate of gas through the first sector 302 of concentrator 300 may be greater than the flow rate of gas through the heating module 202, second sector 304 and third sector 306 of the concentrator 300. Therefore, a relatively small portion of the gas 314 output from the heat exchanger 210 is used to regenerate the concentrator 300 and the bulk of the gas 310 is directed through the first sector 302 of the concentrator 300 which is actively capturing volatile material.

[0057] The regeneration process may be operated efficiently with a relatively low flow rate, for example the ratio of flow rate of gas through the first sector 302 to the flow rate of gas through the second sector 304 may be 10:3. For example, the flow rate of gas through the heat exchanger may be approximately 100 litres per second (l/s) resulting in approximately 23 l/s of gas through the third sector 306, heating module 202 and second sector 304, and 77 l/s through the first sector 302 of the concentrator 300. However, the flow rates may vary depending on size and desorption efficiency of the concentrator 300 and sectors thereof, which may depend on gas temperature and mechanical configuration of the concentrator 300. The output of the heat exchanger 210 may be split and flow to the second sector 304 of the concentrator 300 (via the heating module 202 and third sector 306 of the concentrator 300) and to the first sector 302 of the concentrator 300. In the first position a greater volume of gas may flow to the first sector 302 of the concentrator 300 than the second or third sectors 304, 306, for example the flow rate of gas through the first sector 302 may be 3 to 10 times greater than the flow rate through the second and third sectors 304, 306.

[0058] In this example, in the first position, the first sector 302 of the concentrator 300 (which comprises, in at least part thereof, the first portion 106 of the concentrator 104 discussed in Figures 1 and 2) actively removes volatile material from a gas. At the same time, the second sector 304 of the concentrator 300 (which comprises, in at least part thereof, the second portion 108 of the concentrator 104 discussed in Figures 1 and 2) is being regenerated i.e. volatile material which has been captured (e.g. adsorbed) by the second sector 304 of the concentrator 300 is being removed. Also at the same time, the third sector 306 (which comprises, in at least part thereof, the third portion 206 of the concentrator 204 discussed in Figure 2) is being cooled by gas 314 from the heat exchanger 210.

[0059] The concentrator 300 may rotate so that a portion of the concentrator 300 in the first sector 302 travels to a position where heated gas is supplied thereto to regenerate that portion of the concentrator 300. The concentrator 300 may then be further rotated so that cooled gas is supplied to the same portion of the concentrator 300 prior to being further rotated so that it can again actively capture volatile material from a gas. This allows one part of the concentrator 300 to be actively capturing volatile material from a gas while another part of the concentrator 300 is being regenerated, and another part of the concentrator 300 is being cooled, allowing substantially continuous filtration of volatile material from a gas. Furthermore, this means the concentrator 300 may be reused without replacement and the volatile material captured by the concentrator 300 may be efficiently recovered for recycling or reuse. While in this example, a single concentrator 300 is described, in other examples there may be additional concentrators, for example working in parallel or series.

[0060] As described in relation to Figure 1 , the concentrator 300 may be physically divided into a number of individual, physically distinct segments. For example, a number of radial or diametric solid walls may separate the filter material into the distinct segments. In an example the concentrator 300 is divided into 10 or more segments. The solid walls between segments prevent gas travelling between segments within the concentrator 300 i.e. the gas can travel substantially parallel to the axis of the concentrator 300 but not circumferentially within the concentrator 300. Therefore, a portion of the concentrator 300 may be used to actively capture volatile material from a gas, while other portions of the concentrator 300 are being regenerated or cooled without these different processes interfering with each other.

[0061] In an example, the concentrator 300 may comprise 12 segments, referred to as segments 1 to 12. In this example, the first sector 302 of the concentrator 300 may comprise segments 1 to 8, the second sector 304 may comprise segments 9 and 10 and the third sector 306 may comprise segments 11 and 12. When the concentrator 300 is in the first position segments 1 to 8 may receive gas 310 output from the heat exchanger 210, segments 9 and 10 may receive gas 312 from the heating module 202 and segments 11 and 12 may receive gas 314 from the heat exchanger 210. When the concentrator 300 has performed 1 /12^th of a full clockwise rotation, segments 12 and 1 to 7 receive gas 310 output from the heat exchanger 210, segments 8 and 9 may receive gas 312 from the heating module 202 and segments 10 and 11 may receive gas 314 from the heat exchanger 210. When the concentrator 300 has performed further 1 /12^th of a full rotation segments 11 , 12 and 1 to 6 receive gas 310 output from the heat exchanger 210, segments 7 and 8 may receive gas 312 from the heating module 202 and segments 9 and 10 may receive gas 314 from the heat exchanger 210. The concentrator 300 may continuously rotate such that each of the segments spends a portion of time performing each role (i.e. actively capturing, regenerating and cooling).

[0062] Figure 4 is an example of a method, which may comprise a method for recovering volatile material from a gas. The gas may be a gas associated with an industrial process such as a printing process, for example it may be a gas extracted from an interior of a printing apparatus.

[0063] The method comprises, in block 402, passing a first stream of gas comprising a volatile material through a first portion of a concentrator to decrease a concentration of volatile material in the first stream of gas. As the first stream of gas passes through the first portion of the concentrator, volatile material in the first stream of gas may be captured by the concentrator thereby increasing the quantity of volatile material in the first portion of the concentrator and decreasing the concentration of volatile material in the first stream of gas after it has passed through the concentrator. The first stream of gas may correspond to the gas 116 output from the recovery module through the first portion of the concentrator described in Figures 1 and 2 or the gas 310 output from the heat exchanger through the first sector of the concentrator described in Figure 3.

[0064] The method comprises, in block 404, heating a second stream of gas. The second stream of gas may be heated using a heating module as described in relation to Figures 1 to 3. The gas to be heated may undergo some processing prior to being heated, for example it may undergo a process to reduce the concentration of volatile material in the gas. For example, the concentration of volatile material in the gas to be heated may be reduced by a recovery module or heat exchanger as described in relation to Figures 1 to 3.

[0065] The method comprises, in block 406, providing the heated second stream of gas to a second portion of a concentrator containing a captured (e.g. absorbed or adsorbed) volatile material to decrease a quantity of volatile material in the second portion of the concentrator and increase a concentration of volatile material in the heated second stream of gas.

[0066] The second portion of the concentrator may have been used to absorb or adsorb volatile material from a gas and has become loaded, or saturated, with the volatile material. Therefore, the second portion of the concentrator may have captured a significant quantity of volatile material. Passing the heated gas through the second portion of the concentrator may cause the volatile material in the second portion of the concentrator to evaporate, vaporise, or otherwise be released, thereby reducing the quantity of volatile material in the second portion of the concentrator. The heated gas may be passed through the second portion of the concentrator until the quantity of volatile material in the second portion of the concentrator has reduced to a low enough level such that the second portion of the concentrator may be reused to capture volatile material from a gas again, thereby regenerating the second portion of the concentrator for reuse. The concentrator may correspond to the concentrator 104 described in relation to Figure 1 , the concentrator 204 described in relation to Figure 2 or the concentrator 300 described in relation to Figure 3.

[0067] The method comprises, in block 408, providing the second stream of gas, after passing through the second portion of the concentrator, to a recovery apparatus to recover volatile material from the gas. The recovery apparatus may be any apparatus suitable for recovering volatile material from a gas. For example, the recovery apparatus may cool and/or compress the gas to cause the volatile material to condense. The recovery apparatus may be a recovery module as described in relation to Figure 1 and/or a heat exchanger as described in relation to Figures 2 or 3.

[0068] Figure 5 provides an example of the method of Figure 4. As discussed in greater detail below, blocks 502, 506, 508 and 510 may provide an example of the method of blocks 402 to 408 described in relation to Figure 4.

[0069] Block 502 comprises passing a first stream of gas comprising a volatile material through a first portion of a concentrator to decrease a concentration of volatile material in the first stream of gas, and may correspond to block 402 of Figure 4.

[0070] For example the first stream of gas may comprise output gas of a recovery apparatus, and may be passed through the first portion of the concentrator as described in relation to Figures 1 to 3. The first portion of the concentrator is to capture (e.g. absorb or adsorb) volatile material in gasses which pass through it. For example, the gas output from the recovery apparatus may comprise approximately 200ppm volatile material and the same gas after passing through the first portion of the concentrator may comprise less than 10ppm.

[0071] After the gas has passed through the first portion of the concentrator it may be exhausted to a surrounding environment. In some examples, the gas may be heated prior to being exhausted. For example, the gas may pass through a heat exchanger (i.e. an economiser) prior to being exhausted to increase the temperature of the gas. This heat exchanger may also be used to decrease the temperature of gas which is provided to the recovery apparatus. This heat exchanger may therefore increase the efficiency of the recovery apparatus by pre-cooling the gas provided thereto. This heat exchanger may also raise the temperature of the exhausted gas so that it is close, or closer, to that of the environment (e.g. to room temperature).

[0072] Block 504 comprises, passing a second stream of gas through a third portion of the concentrator. The second stream of gas may be part of the steam of gas output from a recovery apparatus. The second stream of gas may be relatively cool and therefore passing the second stream of gas through the third portion of the concentrator may cool the third portion of the concentrator.

[0073] Block 506 comprises heating the second stream of gas and may correspond to block 404 of Figure 4. Block 508 comprises providing the heated second stream of gas to a second portion of a concentrator containing a captured (e.g. absorbed or adsorbed) volatile material to decrease a quantity of volatile material in the second portion of the concentrator and increase a concentration of volatile material in the heated second stream of gas, and may correspond to block 406 of Figure 4. Block 510 comprises providing the second stream of gas, after passing through the second portion of the concentrator, to a recovery apparatus to recover volatile material from the gas and may correspond to block 408 of Figure 4.

[0074] Block 512 comprises providing gas from an industrial process to the recovery apparatus to recover volatile material from the gas from the industrial process, wherein the heated gas has higher volatile material concentration than the gas from the industrial process. The gas from the industrial process may be mixed with the heated gas prior to the recovery of volatile material. The industrial process may be a process which uses volatile material, such as VOCs, for example a printing process. Therefore, the gas from the industrial process may have an elevated concentration of volatile material. [0075] The mixed gases may be provided to the recovery apparatus to recover volatile material from the gas from the industrial process. In this example the heated gas has higher volatile material concentration than the gas from the industrial process. Therefore, the higher concentration of volatile material in the heated gas causes the overall concentration of volatile material input to the recovery apparatus to be increased. The recovery apparatus may be able to operate more efficiently when the gas input to the recovery apparatus comprises a higher concentration of volatile material. Therefore, by using the heated second stream of gas which has been used to reduce the quantity of volatile material in the concentrator during regeneration of the second portion of the concentrator as an input to the recovery apparatus, the overall efficiency of recovery of the volatile material by the recovery apparatus may be increased. The method therefore provides a means for regenerating filter materials while they are being used to capture volatile material and also results in increased recovery of volatile material by the recovery apparatus.

[0076] Block 514 comprises repositioning the concentrator, in this example by rotation. The rotation may be a partial rotation (i.e. less than a complete 360° rotation) or the concentrator may be rotated substantially continuously. The concentrator may be rotated, for example, using an actuator such as a motor. As described in relation to blocks 516 and 518 the roles performed by each of the portions may change due to the repositioning of the concentrator.

[0077] The concentrator may be rotated substantially continuously, such that each portion of the concentrator cycles through each of the roles described herein. For example, when the concentrator has completed a partial rotation block 516 comprises passing the first stream of gas through the second portion of the concentrator and block 516 comprises providing the heated second stream of gas to the first portion of the concentrator. Therefore, after the partial rotation of the concentrator, the second portion of the concentrator may capture volatile material from the first stream of gas and the first portion of the concentrator may be regenerated by the second stream of gas.

[0078] Similarly, as the concentrator is rotated each of the first, second and third portions of the concentrator may cycle through each of the roles, for example initially the first portion may be actively capturing volatile material, the second portion may be regenerating and the third portion may be cooling. After a first partial rotation the first portion may be cooling, the second portion may be actively capturing volatile material and the third portion may be regenerating. Similarly after a second partial rotation the first portion may be regenerating, the second portion may be cooling and the third portion may be actively capturing volatile material. A further partial rotation may cause the portions to return to their initial roles. There may be other partial rotational states of the concentrator. In this way the concentrator may be used continuously to capture volatile material from a gas, without becoming saturated and while allowing volatile material captured by the concentrator to be recovered for reuse or recycling.

[0079] Figure 6 is an example printing apparatus 600. For example, the printing apparatus 600 may be a Liquid Electrophotographic (LEP) printer, laser printer, inkjet printer or additive manufacturing apparatus (e.g. a 3D printer). The printing apparatus 600 may be an example of the apparatus described in relation to Figures 1 , 2 or 3 and may carry out the methods described in Figures 4 or 5.

[0080] The printing apparatus 600 comprises a concentrator 602 comprising a first portion 604 and a second portion 606, and a recovery module 608. The concentrator 602 may correspond to any of the concentrators 104, 204, 300 described in relation to Figures 1 to 3.

[0081] The printing apparatus 600 may also comprise printing apparatus components such as print head(s), at least one print agent supply, and the like. Where the print apparatus is a ‘two dimensional’ printer, it may for example comprise a LEP printer, a laser printer, an inkjet printer or the like, and may comprise a print head, substrate handling system, sources of print agents, inks or toner, and the like. Where the printer is a ‘three dimensional’ printer, it may comprise, or be associated with, a print bed, a fabrication chamber, a print head, at least one energy source, a source of build material, or the like.

[0082] In use of the printing apparatus 600, the first portion 604 of the concentrator 602 captures volatile material to reduce a volatile material concentration of a gas 610 and the second portion 606 of the concentrator 602 releases the captured volatile material to increase a volatile material concentration of gas 612 to be provided to the recovery module. Therefore, the concentration of volatile material in the gas 614 output from the first portion 604 of the concentrator 602 is lower than the concentration of volatile material in the gas 610 input to the first portion 604 of the concentrator 602 and the concentration of volatile material in the gas 616 output from the second portion 606 of the concentrator 602 is higher than the concentration of gas 612 input to the second portion 606 of the concentrator 602.

[0083] In use of the printing apparatus 600, the recovery module 608 is to recover volatile material from gas 618 received from a printing operation and gas 616 received from the second portion 606 of the concentrator 602. The recovery module 608 may correspond to the recovery module 110 of Figure 1 or the heat exchanger 210 of Figures 2 or 3. The recovery module 608 may cool and/or compress the gas 616, 618 to cause the volatile material in the gas 616, 618 to condense. The volatile material may then be collected, reused or recycled.

[0084] The second portion 606 of the concentrator 602 may have been used to capture volatile material from a gas. Therefore, in this example the second portion 606 of the concentrator 602 contains a captured (e.g. absorbed or adsorbed) volatile material. In use of the printing apparatus 600 the captured volatile material may be released from the second portion 606 of the concentrator 602 to increase volatile material concentration of the gas 616, 618 provided to the recovery module 608.

[0085] In use of the printing apparatus 600, the first portion 604 of the concentrator 602 may capture (e.g. absorb or adsorb) volatile material to reduce volatile material concentration of a gas 610 received from a printing operation. Printing operations may use volatile materials which evaporate during or after the printing operation. The gas associated with the printing operation (e.g. from the interior of the printing apparatus) may therefore have elevated concentrations of volatile material. If this gas was vented out of the printing apparatus 600 without further treatment it may be harmful to the environment or people in the vicinity of the printing apparatus. Therefore, the first portion 604 of the concentrator 602 may reduce the volatile material concentration of the gas to a safe level.

[0086] The printing apparatus 600 may further comprise the components described in relation to Figures 1 to 3. For example, the recovery module 608 may provide gas to the second portion 606 of the concentrator 602 via a third portion of the concentrator 602 and a heater. The gas may be provided to the third portion of the concentrator 602 to cool the third portion of the concentrator 602. Gas which has passed through the first portion 604 of the concentrator 602 may be exhausted from the apparatus 600.

[0087] The printing apparatus 600 is shown with the concentrator 602 in a first position, wherein the first portion 604 of the concentrator 602 is actively capturing volatile material from a gas 610 and the second portion 606 of the concentrator 602 is being regenerated (i.e. the amount of captured volatile material therein is being reduced). The printing apparatus 600 may further comprise an actuator (for example a motor), wherein the actuator may cause the concentrator 602 to change position, such that the roles of the first portion 604 and second portion 606 of the concentrator 602 are switched. For example, the actuator may cause the concentrator 602 to rotate as described in relation to Figure 3.

[0088] Figure 7 is an example printing apparatus 700, which may be an example of the printing apparatus 600 of Figure 6. The printing apparatus 700 comprises the concentrator 602 and the recovery module 608 described in relation to Figure 6.

[0089] In use of the printing apparatus 700, the gas 616 provided to the recovery module 608 passes through the second portion 606 of the concentrator 602 and is subsequently used in a printing process prior to being provided to the recovery module 608. In some examples the gas 612 entering the second portion 606 of the concentrator 602 is heated, for example by a heating module as described in relation to Figures 1 to 3. The elevated temperature of this gas may be utilised in a process within the printing apparatus.

[0090] In this example the printing process comprises using the gas in an air knife 702. The air knife 702 may comprise a constriction, such as small orifices or a narrow slot, through which the gas passes. The constriction causes an increase in the velocity of the gas, which may be jetted for use in a process. For example, when the apparatus 700 is a printing apparatus 700, the gas jetted from the air knife 702 may be directed towards print agent which has been deposited on a substrate to increase the rate at which the agent dries, or it may be used to remove dust or debris from a substrate prior to printing. The air knife 702 may direct gas towards a surface to break a boundary layer of gas at the surface, thereby increasing the rate of evaporation of a fluid from the surface. In other examples, an air knife may be used to clean a printing surface of a print apparatus, for example a photoconductive imaging plate on which an image may be formed prior to being applied to a substrate.

[0091] The gas jetted by the air knife may be received by an inlet 704 to the recovery module 608. A blower, fan, vacuum pump or the like may be used to direct or suck gas jetted from the air knife 702 to the inlet 704. [0092] In some examples at least one of the first portion 604, second portion 606 or third portion of the concentrator 602 comprises silica (e.g. a silica gel), activated carbon or a zeolite. In some examples, a concentrator which comprises silica gel may adsorb up to 11 % of its weight in VOCs. In some examples the apparatus 600 may further comprise a controller. The controller may be implemented, at least in part, by processing circuitry executing machine readable instructions.

[0093] Examples in the present disclosure can be provided as methods, systems or machine readable instructions, such as any combination of software, hardware, firmware or the like. Such machine readable instructions may be included on a computer readable storage medium (including but not limited to disc storage, CD-ROM, optical storage, etc.) having computer readable program codes therein or thereon.

[0094] The present disclosure is described with reference to flow charts and/or block diagrams of the method, devices and systems according to examples of the present disclosure. Although the flow diagrams described above show a specific order of execution, the order of execution may differ from that which is depicted. Blocks described in relation to one flow chart may be combined with those of another flow chart. It shall be understood that each block in the flow charts and/or block diagrams, as well as combinations of the blocks in the flow charts and/or block diagrams can be realized by machine readable instructions.

[0095] The machine readable instructions may, for example, be executed by a general purpose computer, a special purpose computer, an embedded processor or processors of other programmable data processing devices to realize the functions described in the description and diagrams. In particular, a processor or processing apparatus may execute the machine readable instructions. Thus functional modules of the apparatus and devices may be implemented by a processor executing machine readable instructions stored in a memory, or a processor operating in accordance with instructions embedded in logic circuitry. The term ‘processor’ is to be interpreted broadly to include a CPU, processing unit, ASIC, logic unit, or programmable gate array etc. The methods and functional modules may all be performed by a single processor or divided amongst several processors.

[0096] Such machine readable instructions may also be stored in a computer readable storage that can guide the computer or other programmable data processing devices to operate in a specific mode. [0097] Such machine readable instructions may also be loaded onto a computer or other programmable data processing devices, so that the computer or other programmable data processing devices perform a series of operations to produce computer-implemented processing, thus the instructions executed on the computer or other programmable devices realize functions specified by block(s) in the flow charts and/or block diagrams.

[0098] Further, the teachings herein may be implemented in the form of a computer software product, the computer software product being stored in a storage medium and comprising a plurality of instructions for making a computer device implement the methods recited in the examples of the present disclosure.

[0099] While the method, apparatus and related aspects have been described with reference to certain examples, various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the present disclosure. It is intended, therefore, that the method, apparatus and related aspects be limited only by the scope of the following claims and their equivalents. It should be noted that the above- mentioned examples illustrate rather than limit what is described herein, and that those skilled in the art will be able to design many alternative implementations without departing from the scope of the appended claims.

[00100] The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims.

[00101] The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.

Claims

1. An apparatus comprising: a heating module; a concentrator comprising a first portion and a second portion; and a recovery module; wherein: the heating module is to output gas through the second portion of the concentrator to increase a concentration of volatile material in the gas; and the recovery module is to: receive the gas which has passed through the second portion of the concentrator; recover volatile material from the received gas; and output gas through the first portion of the concentrator to decrease a concentration of volatile material of the gas.

2. An apparatus as claimed in claim 1 wherein the recovery module is a heat exchanger and recovers liquid volatile material by reducing the temperature of the gas causing the volatile material to condense.

3. An apparatus as claimed in claim 1 , further comprising: an actuator to move the concentrator to reposition the first portion and the second portion of the concentrator within the apparatus.

4. An apparatus as claimed in claim 3, wherein the actuator is to rotate the concentrator.

5. An apparatus as claimed in claim 3, wherein the actuator is to move the concentrator from a first position to a second position and from the second position to a third position, wherein: in the first position the first portion is to capture volatile material in gas output from the recovery module; in the second position the first portion is to release captured volatile material into gas received from the heating module; and in the third position the first portion is to be cooled by gas received from the recovery module.

6. An apparatus as claimed in claim 1 wherein a portion of the gas output from the recovery module is supplied to the heating module to be heated prior to being output through the second portion of the concentrator.

7. An apparatus as claimed in claim 6, wherein the concentrator further comprises a third portion, and wherein the portion of gas output from the recovery module is to pass through the third portion prior to being supplied to the heating module.

8. An apparatus as claimed in claim 1 wherein the recovery module outputs gas through a first sector of the concentrator comprising the first portion and the heating module outputs gas through a second sector of the concentrator comprising the second portion of the concentrator, and wherein the first sector is larger than the second sector.

9. A method comprising: passing a first stream of gas comprising a volatile material through a first portion of a concentrator to decrease a concentration of volatile material in the first stream of gas; heating a second stream of gas; providing the heated second stream of gas to a second portion of a concentrator containing a captured volatile material to decrease a quantity of volatile material in the second portion of the concentrator and increase a concentration of volatile material in the heated second stream of gas; and providing the second stream of gas, after passing through the second portion of the concentrator, to a recovery apparatus to recover volatile material from the gas.

10. A method as claimed in claim 9 further comprising: providing gas from an industrial process to the recovery apparatus to recover volatile material from the gas from the industrial process, wherein the heated gas has higher volatile material concentration than the gas from the industrial process; and mixing the gas from the industrial process with the heated gas prior to the recovery of volatile material.

11. A method as claimed in claim 9, further comprising: prior to heating, passing the second stream of gas through a third portion of the concentrator.

12. A method as claimed in claim 9, further comprising: rotating the concentrator; and after rotating the concentrator: passing the first stream of gas through the second portion of the concentrator; and providing the heated second stream of gas to the first portion of the concentrator.

13. A printing apparatus comprising: a recovery module; and a concentrator comprising: a first portion to capture volatile material to reduce a volatile material concentration of a gas; and a second portion to release the captured volatile material to increase a volatile material concentration of a gas to be provided to the recovery module; wherein the recovery module is to recover volatile material from a gas received from a printing operation and the second portion of the concentrator.

14. A printing apparatus as claimed in claim 13 wherein the gas provided to the recovery module passes through the second portion of the concentrator and is subsequently used in a printing process, prior to being provided to the recovery module.

15. A printing apparatus as claimed in claim 13 wherein the concentrator comprises: a silica gel; activated carbon; or a zeolite.