Patent Publication Number: US-2010125159-A1

Title: Moving Bed Hydrocarbon Conversion Process

Description:
FIELD OF THE INVENTION 
     This invention generally relates to the art of solid particle transport. More specifically, the invention relates to hydrocarbon conversion processes including a reaction zone, a regeneration zone, and a particle transfer zone where catalyst moves through the zones. 
     BACKGROUND OF THE INVENTION 
     There are many chemical processes where it is necessary to bring into contact a fluid and a solid particulate matter, such as adsorbents and catalysts. Frequently, chemical reactions as well as physical phenomena occur for a predetermined period of time in the contact zone, e.g. a reaction or adsorption zone. In many of these processes, the particles are transported between two or more particle containing vessels. The particles may be transported for a variety of reasons depending on the process. For example, particles may be transported from one contacting vessel or zone into another contacting zone in order to take advantage of different process conditions to improve product yields and/or purity. In another example, particles may be transported from a reaction zone into a regeneration zone in order to rejuvenate the particles, and after rejuvenation, the particles may be transported back to the reaction zone. The particles may be introduced to and withdrawn from the vessels or zones in a continuous or semi-continuous manner sufficient to maintain the desired contacting process continuously. 
     The vessels between which the catalyst is transported are not necessarily adjacent. The outlet of the source vessel from which the catalyst is transported may be a significant distance horizontally and/or vertically from the inlet of the destination vessel to which the catalyst is transported. Pneumatic conveying through a conduit is a well known and commonly used method of transferring catalyst over vertical and horizontal distances. One characteristic of pneumatic conveying is that because of the pressure difference across the conduit between the source and destination, the destination pressure must be less than the source pressure to account for the pressure drop across the pneumatic conveying system. However, process conditions may require the destination vessel to operate at a higher pressure than this value (source pressure minus pneumatic conveying system pressure drop). Examples include circulating particles between two zones maintained at different pressures; and transferring particles from one vessel to another where both vessels are maintained at the same pressure. Under such conditions, a pneumatic conveying system alone is insufficient to transfer the particles. 
     A lock hopper is commonly used to transfer particles from a lower pressure zone to a higher pressure zone. The use of lock hoppers in conjunction with pneumatic conveying is also well known in the art to transfer particles between vessels or zones that are maintained at different pressures. First, a lock hopper transfers particles from the upper, low pressure source zone to a middle zone, and then to a lower, high pressure zone. A pneumatic conveying system then transfers the particles from the high pressure zone to the destination zone. Although the destination zone has a pressure less than that of the high pressure zone, the destination zone pressure may be greater than that of the low pressure source. In the art, the term “lock hopper” has been used to designate the combination of the upper, middle, and lower zones, and “lock hopper” has been used to designate only the middle zone. 
     In one example, the flow of particles from an upper vessel into the middle zone and out of the middle zone into a lower zone is controlled by valves located in the conduits or transfer pipes that connect the zones. The valves may be double block-and-bleed ball valves. Thus, a batch of particles may be transferred to the middle zone through the upper valve or valves when the lower valve or valves are closed. The middle zone may then be isolated by closing the upper valve(s). Various conduits may be connected to the isolated volume to introduce or remove the fluid phase, usually gas, or change the pressure inside the middle zone. For example, a regenerated catalyst may enter the vessel, be purged with nitrogen to remove oxygen, and pressured with hydrogen before being transferred to the reactor which is at a higher pressure than the regenerated catalyst. After catalyst exits the middle zone, the middle zone can be purged with nitrogen to remove the hydrogen before filling again with catalyst. 
     U.S. Pat. No. 4,576,712 discloses a method and apparatus for maintaining a substantially continuous gas flow through particulate solids in two zones. The solids are moved from a low pressure zone to a high pressure zone by means of a valveless lock hopper system. Maintenance of gas flow while simultaneously transferring particles between zones is accomplished without the use of moving equipment such as valves. 
     U.S. Pat. No. 4,872,969 discloses a method and apparatus for controlling the transfer of particles between zones of different pressure using particle collection and particle transfer conduits. The solids are moved from a low pressure zone to a high pressure zone by means of a valveless lock hopper system that vents all of the gas from the collection zones through the particle collection conduits. The venting of gas is accomplished by varying the size of the transfer conduits between zones. 
     As is known in the art, physical characteristics of the particles and basic process information such as the operating pressure in the upper and lower zones and the acceptable range of gas flow rates are initial design information. Processes are designed from this basic information and standard particle and gas engineering principles to routinely provide stable operating units. Surprisingly, it has been found that a particular unit will operate predominantly in a stable manner but experience sporadic upsets. These upsets involving a sudden surge of particles from one zone to another, which may reverse the particle flow, have been unpredictable with respect to which unit will be affected, and which particle transfer cycle will experience an upset in an affected unit. These upsets occur despite conformance to the same design methods. Such upsets interrupt the consistent flow of particles and can physically damage the particles as well as the equipment. 
     Consequently, there is desire to eliminate these sporadic upsets in order to minimize damage to the equipment and particles and ensure the consistent flow of particles. The consistent flow or transfer of particles involves a series of steps which are repeated in a cyclic manner to transfer the particles in batches. Although it remains unpredictable whether an upset will occur during any particular cycle in an apparatus, we have discovered that the upsets usually occur during the middle zone depressurization step or the middle zone empty step. Our invention provides an improved method and apparatus that eliminates all or many of these sporadic upsets without negatively impacting the vast majority of operating units or cycles that do not experience upsets. 
     SUMMARY OF THE INVENTION 
     The invention is a moving bed hydrocarbon conversion process wherein catalyst particles are transferred from a regeneration zone to a reaction zone through a particle transfer apparatus. The catalyst moves from an upper zone of the particle transfer apparatus through a middle zone to a lower zone where the zones are connected by valveless conduits. The lower zone pressure is higher than the upper zone pressure. A container within the lower zone is in particle communication a valveless conduit. The transfer of particles from the upper zone to the container within lower zone is controlled by varying the pressure of the middle zone and the flow rates of gas passing upwards through the valveless conduits. The container retains at least a portion of the particles before they are passed through a container outlet to the volume of the lower zone outside the container. 
     In a broad embodiment, the invention is a moving bed hydrocarbon conversion process comprising: contacting a catalyst moving downward through a reaction zone with a hydrocarbon feed; withdrawing the catalyst from the reaction zone; conveying the catalyst to a regeneration zone wherein the catalyst moves downward through the regeneration zone; withdrawing the catalyst from the regeneration zone and passing the catalyst downward to an upper zone of a particle transfer apparatus; introducing a first gas stream into the lower zone of the particle transfer apparatus; transferring the catalyst downward from the upper zone to the middle zone of the particle transfer apparatus through an upper valveless conduit, and transferring gas from the lower zone upward through a lower valveless conduit into the middle zone; increasing the middle zone pressure; transferring the catalyst downward from the middle zone, through the lower valveless conduit to a container within the lower zone, and transferring gas from the middle zone upward through the upper valveless conduit into the upper zone; decreasing the middle zone pressure; transferring the catalyst from the container to a volume of the lower zone outside the container; and conveying the catalyst from the lower zone of the particle transfer apparatus to the reaction zone; wherein the lower zone pressure is greater than the upper zone pressure. 
     In another broad embodiment, the invention is an apparatus comprising: an upper zone; a middle zone; a lower zone; a container located within the lower zone, the container comprising an inlet and an outlet; an upper valveless conduit extending from the upper zone to the middle zone; a lower valveless conduit extending from the middle zone to the lower zone, the lower valveless conduit providing particle communication to the container; a gas inlet conduit providing fluid communication to the lower zone; and a first gas conduit in fluid communication with the middle zone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representative view depicting the zones of the apparatus in different vessels and an embodiment of the container in the lower zone. 
         FIG. 2  is a representative view depicting a particular arrangement of gas conduits used in an embodiment of the invention. 
         FIG. 3  illustrates another embodiment of the gas conduits encompassed by the invention and shows the zones of the apparatus within a single vessel. 
         FIGS. 4A-4D  and  5  illustrate various configurations of the lower valveless conduit and container that are encompassed by the invention. 
     
    
    
     The Figures are intended to be illustrative of the invention and are not intended to limit the scope of the invention as set forth in the claims. The drawings are simplified diagrams showing exemplary embodiments helpful for an understanding of the invention. Details well known in the art, such as cone deflectors, control valves, instrumentation, and similar hardware which are non-essential to an understanding of the invention may not be shown. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention may be used to transfer solid particulate matter from an upper zone, through a middle zone, to a lower zone where the lower zone pressure is greater than the upper zone pressure. The invention transfers particles without using moving equipment such as valves to block the particle flow path. Generally, particles received in an upper zone are transferred through an upper valveless standpipe or transfer conduit to a middle zone. A lower valveless standpipe or transfer conduit is used to transfer the particles from the middle zone to a container located within a lower zone. Thus the zones, valveless conduits, and container may be in particle communication and the valveless conduits may provide particle communication. 
     The invention can be used within and/or between a variety of process units to transfer particles, such as catalyst and adsorbents. The upper zone of the invention may receive particles from a separate process zone and the lower zone may deliver the particles to another separate process zone. For example, an associated process unit may include a separate vessel that operates as a reaction zone which provides catalyst particles to the upper zone, and the lower zone may deliver catalyst to a separate process vessel such as a feed hopper of a pneumatic conveying apparatus which in turn delivers the catalyst to the top of another reactor. In another embodiment, the invention may be arranged so that the upper zone and/or the lower zone are integrated with a process unit such that one or more process steps, or portions thereof, occurs within the upper and/or lower zones or the vessel(s) which contain the upper and/or lower zones. For example, the upper zone may be the lower portion of a reduction zone vessel or the entire reduction zone vessel of a process unit and/or the lower zone may be the upper portion of a surge vessel or the entire surge vessel of a process unit. The surge vessel in turn may introduce the particles into other zones of the same or a different process unit. 
     The invention may communicate with or the invention may comprise a portion of a process unit which provides for changing the fluid that contacts the particles. For example, the process unit may involve contacting catalyst with a gas containing hydrocarbons and/or hydrogen in a reaction zone and removing carbon deposits from the catalyst using a gas containing oxygen in a regeneration zone. As the catalyst is transferred between the reaction and regeneration zones, care must be taken to prevent mixing of the hydrocarbon/hydrogen atmosphere and the oxygen atmosphere. Examples of hydrocarbon conversion processes that may employ the invention include: alkylation, hydrorefining, hydrocracking, dehydrogenation, hydrogenation, hydrotreating, isomerization, dehydroisomerization, dehydrocyclization, and steam reforming. One widely practiced hydrocarbon conversion process that may employ the invention is catalytic reforming using particles of catalyst. Exemplary reaction and regeneration zones are disclosed in, e.g., U.S. Pat. No. 5,858,210. 
     The upper, middle, and lower zones of the invention may be separate vessels or portions of separate vessels that are connected by valveless transfer conduits. In other embodiments, two or more of the upper, middle, and lower zones may be contained within a single vessel and separated by dividers within the vessel. The upper, middle, and lower zones of the invention may also provide one or more functions or process steps of an associated process unit. In an embodiment, the upper, middle, and lower zones may be aligned sufficiently vertically to allow catalyst to flow, at least in part, by gravity from at least one vessel at a higher elevation to at least one vessel at a lower elevation. 
     Flow of the particles into and out of the middle zone may be controlled by regulating the pressure of the middle zone, the flow rate of gas through each valveless particle transfer conduit, and the gas flow path. The same basic method steps may be accomplished by various configurations of gas and particle conduits to introduce, vent, and change the flow path of the gas used to control particle transfers. U.S. Pat. No. 4,576,712 and U.S. Pat. No. 4,872,969 disclose different methods and apparatus to control particle transfer and are hereby incorporated by reference in their entirety. The invention may use the same basic method steps and is not limited to any particular configuration of the gas flow path and conduits. Existing configurations and control schemes can be readily adapted to employ the invention. 
     The method of transferring particles from upper zone  10  to lower zone  30  may be accomplished without blocking the particle transfer path with moving equipment such as valves by repeating the following four step cycle: 1) a fill or load step wherein particles are transferred from the upper zone to the middle zone; 2) a pressurization step wherein the middle zone pressure is increased; 3) an empty step wherein particles are transferred from the middle zone to the container within the lower zone; and 4) a depressurization step wherein the middle zone pressure is decreased. The steps may overlap. For example, transfer of particles may begin while the middle zone pressure continues to increase or decrease and the middle zone pressure may begin to increase or decrease while particles continue to transfer. 
     A single cycle results in the transfer of one batch of particles from the upper zone to the lower zone. The time required to complete one cycle, i.e. the cycle time, will depend on a variety of factors including: the properties of the particles; the batch size, or amount of particles transferred per cycle; and the times needed to change the pressure of the middle zone. The invention is not limited by the cycle time. In an embodiment, the cycle time may be about 50 seconds. In another embodiment, the cycle time may be less than about 10 minutes, and the cycle time may be between about 2 minutes and about 4 minutes. A controller such as process control computers and programmable controllers may be used to regulate the cycle. The controller may receive various inputs, e.g. signals from particle level sensors, pressure gauges or indicators, differential pressure sensors, and timers such as for an individual step and/or the overall cycle. The controller may also send signals for example to open, close, and adjust valves to control the flow pattern and rate of various gas steams. Such a controller and related signals are not shown in the figures as they are not essential to the invention and are well known to the skilled artisan. 
     Broad embodiments of the invention will now be described with reference to  FIG. 1 . In step 1 of the method, particles are transferred from upper zone  10  to middle zone  20  through upper valveless conduit  40 . The upper and middle zones are at approximately the same pressure during step 1. Gas ascending through upper valveless conduit  40 , if any, is insufficient to retain the particles in conduit  40 . During step 1, gas may enter lower zone  30  through gas inlet conduit  11 . Gas may also enter lower zone  30  from an associated process zone, not shown. Valve  12  may regulate the quantity of gas flowing into lower zone  30 ; this flow rate may be varied independently of the invention by means, not shown, for controlling the pressure of lower zone  30 . The gas is selected to be compatible with the particles being transferred and may be the same gas as used in the associated process unit. Nitrogen, hydrogen, and air are non-limiting examples of gas that may be used. 
     During step 1, gas flows upward from lower zone  30  through lower valveless conduit  50  at a sufficient rate to retain the particles in conduit  50  thus causing middle zone  20  to fill with particles. Various configurations of the gas flow path may be used. For example, a portion of the gas entering middle zone  20  from lower valveless conduit  50  may flow through gas conduit  15  to upper zone  10  as shown in  FIG. 2 . In other embodiments not illustrated, a portion of the gas may flow through gas conduit  15  to another destination or simply be vented. In the embodiment illustrated in  FIG. 3 , which depicts the three zones of the apparatus in one vessel, upper valveless conduit  40  has a larger diameter than lower valveless conduit  50  so that all gas entering middle zone  20  may flow through upper valveless conduit  40  at a flux which is insufficient to retain the catalyst therein. 
     Upper  40  and/or lower  50  valveless particle transfer conduits may have a restriction, that is, a smaller cross-sectional area for particle flow than the balance of the respective conduit. The cross-sectional areas of the restrictions if present and the balance of the conduit may be any regular or irregular shape including a circle, oval, square, rectangle, and triangle. The cross-sectional area shape of a conduit may be the same or it may differ over its length and may be the same or different in the upper  40  and lower  50  valveless conduits. The cross-sectional area of a restriction and the balance of the conduit may have different shapes or the same shape. The restriction may be located in a lower portion of the conduit, that is, in the lower ⅓ of the respective conduit&#39;s height. The restrictions may be created in a wide variety of ways including crimping the conduit, using an insert, and forming the conduit with the restriction. Restrictions may be located proximate an outlet in the lowermost end of the conduit. In an embodiment, the conduit, or a portion thereof is tapered toward the outlet to form the restriction at the outlet. The type, cross-sectional area shape, and/or location of restrictions in upper 40 and lower 50 valveless conduits may be the same, or they may differ. 
     Step 1 ends when middle zone  20  is filled to its operating capacity with particles. As shown in  FIG. 1 , upper valveless conduit  40  may extend into middle zone  20  to define its operating capacity. That is, particles stop flowing into the middle zone when particles in the middle zone accumulate to reach upper valveless conduit outlet  45 . Thus, there may be a continuous mass of particles from a lower portion of upper zone  10  through upper valveless conduit  40 , middle zone  20 , and lower valveless conduit  50 . In another embodiment, the operating capacity of middle zone  20  is predetermined and an optional upper level sensor, not shown, is used to detect when particles rise to this preset level. In such an embodiment, particles need not reach upper valveless conduit outlet  45  and upper valveless conduit  40  need not extend past the shell of middle zone  20 . In other embodiments, the operating capacity of middle zone  20  may be determined by a preset time interval. Use of an adjustable timing interval or high level set point enables the size of each particle batch to be varied from cycle to cycle. The particle levels and/or time increments may be measured and a signal sent to a controller to initiate step 2 when the middle zone has been filled. Thus, particles may continue to flow into middle zone  20  for a time after step 2 begins if the particles are below upper valveless conduit outlet  45  at the end of step 1. In other embodiments, the particle flow may be stopped at this point in the cycle and the apparatus may be held with middle zone  20  filled to its operating capacity until it is desired to continue the particle transfer cycle. This portion of the cycle may also be known as a separate hold or ready step. For example, in the embodiment of  FIG. 2 , valve  16  is closed to force all the gas upwards through both valveless conduits thereby stopping particles from flowing out of both the upper and middle zones. Similarly, in the embodiment of  FIG. 3 , valve  14  can be opened in addition to valve  12  to accomplish the same effect. 
     In step 2 of the cycle, the pressure within middle zone  20  is increased. The middle zone pressure may be increased to stop the transfer of particles from the upper zone. In an embodiment, the middle zone pressure is increased to equilibrate with the higher pressure in lower zone  30 . This may be accomplished by introducing gas into middle zone  20  through gas conduit  13 . Gas to gas conduit  13  may be supplied from a variety of sources including, but not limited to: gas inlet conduit  11 , lower zone  30 , and separate supply sources such as facility headers and other zones in the associated or other process units. In the embodiment illustrated in  FIG. 2 , valve  14  is opened and valve  16  is closed to pressurize middle zone  20 . In the embodiment shown in  FIG. 3 , middle zone  20  is pressurized by opening valve  14  and closing valve  12 . There is no need to change the gas flow path as the cycle moves from step 2 to step 3. However, as explained above there are numerous ways of routing the gas flow path to control the desired particle movement. Thus, the invention encompasses changing the gas flow path between and/or within steps 2 and 3 to equilibrate the middle and lower zone pressures and retain particles within upper valveless conduit  40 . 
     Step 3 may be referred to as the empty step of the cycle. As the pressures in the middle and lower zones equalize, particles begin to flow from middle zone  20  through lower valveless conduit  50  to container  60  which is located within lower zone  30 . During step 3, gas flows upward through upper valveless conduit  40  at a sufficient rate to prevent the transfer of particles from upper zone  10  into middle zone  20 . The level of particles in middle zone  20  falls as particles flow out of lower valveless conduit  50 . A minimum particle level in middle zone  20  may be used to decrease the length requirement of lower valveless conduit  50 . This may be accomplished in various ways such as using a preset time interval for the transfer, measuring the amount of particles that have entered lower zone  30 , and measuring the level of particles remaining in middle zone  20 . For example, low level sensor  25  may detect the absence of particles at the low level set point and send a signal to a controller to begin depressurizing or venting the middle zone, step 4. Multiple inputs may be used to manage the particle transfer cycle steps. In an embodiment, the length of step 3 may be controlled by a timer with low level sensor  25  being used initiate step 4 early if the particles fall below the minimum level set point. 
     In step 4, the depressurization step, the pressure in middle zone  20  may be decreased to equilibrate the middle and upper zone pressures. In another embodiment, the middle zone pressure may be decreased to stop the transfer of particles from the middle zone. This may be accomplished for example by re-establishing the gas flows that were used in step 1. Thus, in the embodiment of  FIG. 2  valve  14  may be closed and valve  16  opened so that the gas flux upward in lower valveless conduit  50  is sufficient to retain particles therein while sufficient gas flows through gas conduit  15  to equalize the pressure between the upper and middle zones. In other embodiments not illustrated, a portion of the gas may flow through gas conduit  15  to another destination or simply be vented. In the embodiment illustrated in  FIG. 3 , valve  14  is closed and valve  12  is opened to re-establish the gas flow path of step 1 of that embodiment. 
     When the pressure of middle zone  20  is decreased in step 4 to equilibrate with upper zone  10  and increased in step 2 to equilibrate with lower zone  30  it is understood that the pressures in the two zones, superior and inferior, being equilibrated may or may not be the same. For example, pressure differences may exist, if there is some gas flow between the two equilibrated zones, or if they are being controlled independently. Also, there is no requirement that the inferior zone be at the same or lower pressure than the superior zone of the two zones being equilibrated. That is, particles may transfer from either superior zone to the respective inferior zone even though the pressure of the inferior zone is higher than the pressure of the superior zone. The gas flow paths described for the embodiments of  FIGS. 2 and 3  show that the invention may provide for the continuous flow of gas to each of the upper, middle, and lower zones throughout a cycle. Further, the embodiment of  FIG. 2  provides an uninterrupted flow of gas from the lower zone through the middle zone and into the upper zone throughout the cycle. In other embodiments not illustrated, various gas conduits may be used to control the middle zone pressure and the gas flow rates through the upper and lower valveless particle transfer conduits to regulate the particle movement as herein described. 
     It is understood that the step numbers used herein are arbitrary and a transfer cycle may be considered to begin with any step and each step is employed at least once during a cycle. The invention encompasses various orders of the steps and some steps may be repeated in the course of transferring a single batch of particles from the upper zone to the lower zone. For example, the transfer of particles in steps 1 and/or 3 may be interrupted by employing steps 2 and 4 multiple times during a transfer cycle. Thus, in an embodiment, the order of steps may be 1—transfer particles from the upper zone to the middle zone; 2—increase the middle zone pressure to stop the transfer of particles; 4—decrease the middle zone pressure to equilibrate the middle and upper zone pressures; 1—transfer particles from the upper zone to the middle zone; 2—increase the middle zone pressure to equilibrate the middle and lower zone pressures; 3—transfer particles from the middle zone to the container within the lower zone; and 4—decrease the middle zone pressure to equilibrate the middle and upper zone pressures. In another embodiment the order of steps may be 1, 2, 4, 1, 2, 3, 4, 2, 3, and 4. Other steps such as purging the middle zone may be included in a transfer cycle. 
     Returning to the discussion of step 3. Container  60  is located within lower zone  30  to receive particles emerging from lower valveless conduit  50 . Container  60  may be spaced apart from the inside surface of the lower zone and secured via one or more support elements  67 . For example, the container may be suspended such as by wires or rods  67 ′ in  FIG. 2 ; fastened to or supported by relatively horizontal rails or beams  67 ″ in  FIG. 3 ; or located on a stand secured to a lower portion of the zone. Such supports which are known in the art may be used in any combination to locate the container  60  relative to the lower valveless conduit  50  as described herein. These support elements may in turn be secured to any inside surface of the lower zone or any other internal structures within the lower zone including lower valveless conduit  50 . The container and support elements may be of the same or different material of construction suitable for the process conditions. In an embodiment, the support is of the same material of construction as that of the lower zone inside surface. 
     In the embodiments of  FIGS. 1-3 , container  60  is located below and spaced vertically apart from outlet  55  of the lower valveless conduit  50 . Thus, particles may emerge or be discharged from outlet  55  of lower valveless conduit  50  and then pass to container  60  through inlet  62 . The container is an open top cylindrical form with a solid bottom plate and outlet  65  located in a lower portion of the sidewall. Particles pass from container  60  through outlet  65  to the volume of lower zone  30  outside the container. In an embodiment, particles passing from container  60  through outlet  65  fall freely to a lower portion of lower zone  30 . That is, the container may be located above and spaced apart from accumulated particles in lower zone  30 . Lower valveless conduit  50  preferably extends into lower zone  30  as shown in  FIG. 1 , though this extension into lower zone  30  is not required. 
       FIGS. 4A-4D  illustrate a few non-limiting configurations of the lower valveless transfer conduit  50  and the container  60  which are encompassed by the invention. Although the configurations differ, the same reference numerals are used to identify the corresponding elements in each Figure. The support element(s) are not illustrated in these views as they are not necessary for an understanding of the configurations. In an embodiment, the surfaces of the container are imperforate. In another embodiment, all or a portion of the surfaces may have uniform or non-uniform perforations. As used herein, “perforations” includes holes, gaps, slots, other openings, and combinations thereof which are sufficiently small to retain the particles while allowing gas to pass through the surface. 
     In the embodiment of  FIG. 4A , container  60  has a square form the bottom surface of which is tapered towards outlet  65  located the lowermost portion of the container. Inlet  62  may be in the uppermost surface of the container, and the inlet permits the entry of particles where lower valveless conduit  50  extends through the inlet to discharge particles directly into the volume of the container. As shown in  FIG. 4B , lower valveless conduit  50  need not extend into lower zone  30  and more than one such conduit may be used. Container inlet  62  may comprise multiple openings in the uppermost surface  63  of the container which is positioned to receive the particles. Container outlet  65  may comprise multiple openings in the lowermost surface of the container. There is no requirement that the number of conduits, inlet openings, and outlet openings be the same.  FIG. 4C  shows container  60  may be in the form of a funnel. The container surface or sidewall may also be a support element for the container by being extended and attached to the inside surface of the lower zone. The uppermost surface  63  of the container may be the top edge of a surface wall or sidewall of the container. As illustrated, the lower valveless conduit  50  may extend to the inlet of container  60  such that the lower valveless conduit and the container are not spaced vertically apart. As shown, a container may be asymmetrical.  FIG. 4D  shows that container inlet  62  is not required to be in the uppermost surface of the container. This embodiment also shows that the lower valveless conduit  50  need not be strictly vertical, but may be angled relative to true vertical. Also, a conduit may be tapered along its entire length or a portion thereof towards outlet  55 . These non-vertical and tapering embodiments may also be used in upper conduit  40 . Lower conduit  50  may be connected to container inlet  62 . These conduit configurations may be used independently. When outlet  65  comprises multiple openings, the openings may be configured differently, e.g. be in different locations and have different sizes and shapes size. The container outlet has a cross-sectional area equal to the sum of the cross-sectional areas of each outlet opening. The cross-sectional area of the container inlet is determined in the same manner. Likewise, multiple inlet openings and conduits may be configured differently. 
     In an embodiment, container  60  has a top surface which is above an imaginary, horizontal plane that bisects the height of the container and a bottom surface which is below this imaginary plane. The container&#39;s height is the vertical distance between the uppermost and lowermost points of the container&#39;s surfaces. Container inlet  62  may be located in the top surface of the container. In an embodiment, the inlet is located in the uppermost portion of the top surface, i.e., the uppermost surface of the container. Container outlet  65  may be located in the bottom surface of the container. Particles are discharged or transferred from the container through the outlet into the volume of the lower zone outside the container. In an embodiment, the container outlet is located in the lowermost portion of the bottom surface, i.e., the lowermost surface of the container. When a container outlet is located in a particular surface, it is only necessary for one opening of the outlet to be in that surface. Other outlet openings, if any, may be located in the same surface or elsewhere. The same is true for the container inlet. 
     Container  60  may be fabricated in any shape sufficient to retain at least a portion of the particles discharged by lower valveless conduit  50  during step 3. Particles accumulate within container  60  during step 3 and reach a level to contact the lower valveless transfer conduit outlet  55 . That is, container  60  and lower valveless conduit  50  are configured to form a continuous mass of particles between middle zone  20  and container  60  through lower valveless conduit  50  during a portion of the particle transfer cycle. The particle transfer rate from the middle zone may vary during step 3. For example, the continuous mass of particles may be formed during step 3 when the particle transfer rate from conduit  50  into the container is greater than the particle transfer rate from the container through outlet  65  to the lower zone volume outside the container. The particles may then continue to transfer from the middle zone to the container moving as a continuous mass, limited by the particle transfer rate out of the container. The level of particles retained by the container may then fall below conduit outlet  55  as the particle transfer rate from conduit  50  decreases. Similar to the transition to step 2 pressurization, particle transfer to the container may continue during a portion of step 4, depressurization. Also, particle transfer from the container to the volume of the lower zone outside the container may continue during at least a portion of step 4. 
     Container outlet  65  may be sized and configured to control the particle transfer rate from container  60  to the volume of lower zone  30  outside the container. For example, outlet  65  may comprise multiple openings of various shapes and cross-sectional areas arranged at different locations, such as various heights in the container surface. In an embodiment, the cross-sectional area, A 2 , of container outlet  65  is less than the minimum cross-sectional area of the lower valveless conduit  50 . The particle transfer rate from the container through outlet  65  may be less than the particle transfer rate from the lower valveless conduit to the container. As shown in  FIG. 5 , the cross-sectional area, A 2 , of outlet  65 , being the sum of the cross-sectional areas of the outlet openings, may be less than the cross-sectional area, A 1 , of lower valveless conduit outlet  55 . In an embodiment, container inlet  62  has a cross-sectional area, A 3 , which is greater than the cross-sectional area, A 1 , of lower valveless conduit outlet  55 .  FIG. 5  illustrates that tapering of a valveless conduit towards the outlet does not require an extensive distance along the conduit. 
     The size of the container may be related to the batch size of particles transferred from the middle zone during a cycle of the method, i.e. the middle zone operating capacity less the volume of particles remaining in the middle zone when step 4 is initiated. The container may be smaller than the volume of a single batch of particles. For example, particles may flow out of the container as it is being filled and particles may form a mound above the container. The container may be larger than the particle batch volume such as when the lower valveless conduit extends into the container. As the particle batch size may vary, the minimum container volume may be related to the minimum particle batch size. The upper limit of the container volume is constrained by the design of the lower zone including the lower zone volume and the volume of particles to be maintained within the lower zone. In an embodiment, the volume of the container is at least about 30% of the minimum particle batch volume. The container volume may be at least about 60% of the minimum particle batch volume, and in another embodiment, the container volume is at least about the same as the minimum particle batch volume. 
     By regulating the particle transfer rates to and from container  60 , the formation and continued existence of the continuous mass of particles from the middle zone to the container may be controlled. In an embodiment, this continuous mass of particles may exist for a portion of step 3. In another embodiment, the continuous mass of particles may exist for a portion of step 4; and the level of particles retained by container  60  may fall below the level of conduit outlet  55  before the beginning of step 1. Thus, particles may transfer from the container to the volume of lower zone  30  outside the container during step 4. In yet another embodiment, container  60  and outlet  65  are configured to essentially empty the container of particles before the subsequent step 3 begins such as by locating outlet  65  in the lowermost surface of container  60 . That is, particles may occupy less than about 10% of the container volume when step 3 begins; and in an embodiment, particles occupy less than about 5% of the container volume at this time. Particles may occupy less than about 3% of the container volume when step 3 begins. 
     In an embodiment, particles may form a mound which contacts lower valveless conduit outlet  55 . The mound may be wholly within container  60  or it may extend above container inlet  62  to reach conduit outlet  55 . That is, the volume of particles retained by the container may be greater than the volume of the container. If particles mound above the container inlet, particles may fall or slide down the mound into the volume of the lower zone outside the container without passing through the container volume. Lower valveless conduit  50  provides particle communication to container  60 ; and lower valveless conduit  50  and container  60  may be in particle communication even if the lower valveless conduit and container are not connected. Container  60  and lower valveless conduit  50  may be spaced apart by a distance D. In an embodiment, the vertical distance, D, separating container inlet  62  and lower valveless conduit outlet  55  is less than about 1.15*R*tan θ, where R is the effective radius of the cross-sectional area, A 3 , of the container inlet  62  and θ is the angle of repose of the particles. In another embodiment, D may be less about 1.07*R*tan θ; and D may be less than about R*tan θ. The effective radius of the cross-sectional area of the container inlet is the radius of a circle having the same cross-sectional area of the container inlet. The angle of repose of the particles is a well known property of particles that is determined by depositing the particles on a horizontal surface with negligible velocity to form a pile. The angle formed between the slope of the pile and the horizontal surface is the angle of repose. See Andrew W. Jenike, Storage and Flow of Solids, Bulletin No. 123 of the Utah Engineering Experiment Station Sixth Printing (revised), March, 1970, University of Utah. 
     During the particle transfer cycle, the inventory in upper zone  10  may be continuously and/or intermittently replenished with particles such as from an associated or integrated process zone and/or as added from a fresh particle feed hopper. Likewise, particles delivered to lower zone  30  may be withdrawn from or pass out of the lower zone continuously and/or intermittently. It is preferred that an inventory or surge volume of particles be maintained in both the upper and lower zones throughout the particle transfer cycle. As previously described, upper zone  10  may also provide one or more functions of an associated or integrated process unit including regeneration zones. Non-limiting examples include: a particle feed hopper, a reaction zone, an atmosphere purge zone, another catalyst transfer zone, a reduction zone, and an elutriation zone. The internal pressure of upper zone  10  may be independently controlled by means well known in the art. For example, upper zone  10  may be in fluid communication with a process zone so that the upper zone pressure depends upon and varies with the pressure in that process zone. The upper zone pressure is not critical and may be atmospheric, sub-atmospheric, or super atmospheric. 
     Lower zone  30  may be a holding vessel, or surge zone from which the particles are transferred by other means such as pneumatic conveying. In other embodiments, lower zone  30  may provide one or more functions of an associated or integrated process unit including regeneration zones. Non-limiting examples include: a particle feed hopper, a reaction zone, an atmosphere purge zone, another catalyst transfer zone, a reduction zone, and an elutriation zone. The internal pressure of lower zone  30  may be independently controlled by means well known in the art. For example, lower zone  30  may be in fluid communication with a process zone so that the lower zone pressure depends upon and varies with the pressure in that process zone. In an embodiment, the upper zone pressure may be higher than the lower zone pressure for a portion of the transfer cycle. In another embodiment, lower zone  30  may be maintained at a higher pressure than upper zone  10 . For example, upper zone  10  may be maintained at a nominal pressure of 34 kPa (g) and permitted to vary within a range from about 14 to about 55 kPa (g) while the nominal pressure of lower zone  30  may be 241 kPa (g) within a range from about 207 to about 276 kPa (g). In another embodiment, upper zone  10  may be maintained at a nominal pressure of 241 kPa (g) and permitted to vary within a range from about 172 to about 310 kPa (g) while the pressure of lower zone  30  may be within a range from about 345 to about 2068 kPa (g). Thus, the differential pressure between the lower zone  30  and upper zone  10  might range from about 35 to about 1896 kPa. However, this invention may be used when the pressure differential between zones is as little as about 0.7 kPa and in excess of 2000 kPa. Middle zone  20  serves as an intermediate zone, and its nominal pressure is adjusted to regulate the flow of the particles. 
     The apparatus of the invention may be used as a solids flow control device for an entire process, since the flow rate of particles from the upper zone to the lower zone can be varied, as discussed above. The upper, middle, and lower zones may contain other non illustrated apparatus known in the art such as baffles, screens, and deflector cones which may be used to facilitate particle flow and/or direct the particles or the gas through a zone in a desired manner. The components of the present invention may be fabricated from suitable materials of construction, such as metals, plastics, polymers, and composites known to the skilled artisan for compatibility with the particles, and operating conditions, e.g. gas, temperature, and pressure. The size, shape, and density of the particles is only limited by the size of the equipment and the type and flow rates of the gas or gases used. In an embodiment, the particles are spheroidal and have a diameter from about 0.7 mm to about 6.5 mm. In another embodiment, the particles have a diameter from about 1.5 mm to about 3 mm. The particles may be catalysts an example of which is disclosed in U.S. Pat. No. 6,034,018. 
     As previously noted, particle transfer apparatus of the prior art may be adapted to incorporate the invention. Likewise, standard engineering principles especially those related to the flow of solids and gases and known design methods may be used in this invention. In addition to the teachings herein, the design considerations and methodology described in U.S. Pat. No. 4,576,712 and U.S. Pat. No. 4,872,969 may be used to practice this invention. For example, the pressure in the upper and lower zones, the minimum and maximum gas flow rates upwards through the zones and the valveless conduits, and the required particle transfer rate are design factors that are often fixed by the associated process unit. The length of the particle column inside the valveless conduit, the height of particles in the zone above the valveless conduit, and the diameter of the conduit may be balanced so that changing the pressures and gas flow paths as described herein controls whether particles will flow down through or be retained within the conduit. The design method includes limiting the gas flow rates and pressure differentials to avoid fluidizing particles within the zones and to prevent particles from being suddenly forced up or down the valveless conduits. It is well known to those skilled in the art in design of solids flow systems to conduct experiments to determine flow characteristics of the particular solid involved. 
     Thus, it is known that the internal pressures of the upper and lower zones, the minimum and maximum gas flow rates, the identities of the gas and the particles, and the required range of particle transfer rates, may be used to determine various parameters of the invention. These parameters include: the normal minimum and maximum volumes occupied by the particles in the zones, the particle heights required in the zones above the transfer conduits, the diameter of the transfer conduits, and the lengths of the transfer conduits. These and other parameters such as the gas conduit size and arrangement may characterize a particular embodiment encompassed by the invention. 
     In an embodiment, a hydrocarbon feed is contacted with catalyst particles moving downward through a hydrocarbon conversion process reaction zone. The catalyst is withdrawn from the reactor and conveyed upwards to a top portion of a regeneration zone. The catalyst passes downward through the regeneration zone undergoing one or more treatment steps. The catalyst is withdrawn from the regeneration zone and passed downward to an upper zone of a particle transfer apparatus. The upper zone pressure may be less than the reaction zone pressure. The particle transfer apparatus transfers the catalyst from the upper zone to a container within the lower zone and from the container to the volume of the lower zone outside the container as described above. The catalyst, now at a higher pressure, may be conveyed upwards to a top or upper portion of the reaction zone by a known pneumatic transport system such as described in U.S. Pat. No. 5,716,516 and U.S. Pat. No. 5,338,440. 
     Moving bed systems and processes which employ them are well known in the art. See for example U.S. Pat. No. 3,725,249 and U.S. Pat. No. 3,692,496. The reaction zone is oriented substantially vertically (i.e. sufficiently vertical for catalyst to flow downward at least in part by gravity) and may be divided into multiple reactors or sub zones, for example, to manage the heat of reaction. The reaction zone may consist of a single vertical stack of one or more sub zones, or the reaction zone may be split into two or more vertical stacks to manage structural height limitations. A stack may comprise more than one vessel. It is also important to note that the reactants may be contacted with the catalyst bed in either an upward, downward, or radial flow fashion with the latter being preferred. In addition, the hydrocarbon feed may be in the vapor phase when contacting with the catalyst bed. That is, the catalyst moves gradually downward in the reaction and regeneration zones as a non-fluidized, dense phase or compact bed that is withdrawn from the bottom or lower portion of the reaction and regeneration zones and is replenished by adding catalyst to the top portion of these zones. The catalyst withdrawn from the reaction zone is lifted to the top of the regeneration zone by equipment known in the art including mechanical devices such as screw or bucket conveyors or star valves. Preferably, the catalyst is lifted by a pneumatic transport system. 
     In the reaction zone, the catalyst may deactivate over time by one or more mechanisms including deposition of carbonaceous material or coke upon the catalyst, sintering or agglomeration of catalyst metals, loss of catalytic promoters such as halogens, and exposure to the reaction atmosphere at reaction temperatures up to 760° C. and pressures ranging from about 0 to about 6,900 kPa(g). As used herein, “reaction temperature” means the weighted average inlet temperature (WAIT), which is the average of the inlet temperature to the first bed of catalyst contacted with the feed and each subsequent bed of catalyst following a heating or cooling stage to manage the heat of reaction weighted by the quantity of catalyst in the corresponding reactor. Frequently, the reaction conditions include the presence of hydrogen that may be introduced separately or combined with the hydrocarbon feed. Hydrocarbon products from the reactor are often cooled and separated into vapor and liquid streams such as in a flash drum or vapor/liquid separator. All or a portion of the vapor stream, containing hydrogen may be recycled to the reaction zone while the liquid stream may be sent to storage, blended with other streams or processed further. 
     The regeneration zone is designed and operated to restore or rejuvenate the catalyst performance and may include multiple zones and/or treatment steps. Non-limiting examples include a burn or combustion zone, a halogenation zone, a drying zone, and a cooling zone. The regeneration zone may include other known zones such as an elutriation zone and a disengaging zone. The regeneration zone may comprise one or more vessels which are substantially vertically aligned in one or more stacks. Additional regeneration zone details are available in the art such as U.S. Pat. No. 6,034,018. The regeneration zone may operate at a pressure ranging generally from about 0 to about 6900 kPa(g) and a temperature from about 370° C. to about 538° C. Often, the regeneration zone includes an atmosphere containing oxygen in contrast to the reaction zone hydrocarbon/hydrogen atmosphere. Thus, separation of the reactor and regenerator atmospheres may be important to prevent undesirable side reactions. Various known elements such as nitrogen seals or bubbles, isolation valves, and pressure differentials to maintain desired purges and gas flows may be used to prevent the hydrogen and oxygen atmospheres from mixing. 
     The catalyst being withdrawn from the reaction zone may be purged with hydrogen to keep excess hydrocarbons in the reaction product stream. In an embodiment, the reaction zone atmosphere such as hydrogen and/or remaining hydrocarbon gas surrounding the catalyst is purged with nitrogen before the catalyst enters the oxygen containing atmosphere. Oxygen may be introduced to the regenerator vessel, or oxygen may be added upstream of the regenerator, for example, in a disengaging vessel or isolation valves of the regeneration zone. This change from the reaction zone atmosphere to an inert or nitrogen atmosphere may be conducted before or after the catalyst is lifted or conveyed from the bottom of the reaction zone to the top of the regeneration zone. Likewise, the change from the regeneration zone oxygen atmosphere may be accomplished by a nitrogen purge followed by introduction of a reaction zone gas or reducing gas, such as hydrogen. This atmosphere change is usually completed below the regeneration zone before the catalyst enters the upper zone of the particle transfer zone or apparatus. However, this atmosphere change may be accomplished within the particle transfer apparatus or after the catalyst exits the particle transfer apparatus, before or after the catalyst is lifted to the top of the reactor zone. Low pressure differentials ranging for example from about 2 to about 14 kPa may be sufficient to maintain proper nitrogen purges or flows to keep the regeneration and reaction zone atmospheres separated. Catalyst may be purged with nitrogen in a conduit or the catalyst may enter a nitrogen containing vessel as it moves through the process. 
     The catalyst may also undergo a reduction step. If needed, the reduction step is normally performed after the catalyst leaves the regenerator vessel when the catalyst is under a reducing gas or reaction zone gas atmosphere. In an embodiment, the reduction step occurs in the upper zone of the particle transfer apparatus. In another embodiment, the reduction step occurs in a reduction zone located atop the reactor in the reaction zone. Typical reduction conditions include an atmosphere comprising hydrogen, a temperature ranging from about 315° C. to about 540° C., and a super atmospheric pressure. 
     In an embodiment, the hydrocarbon conversion process is a reforming process which is well known in the petroleum refining and petrochemical industries. In brief, the reforming feed comprises a petroleum fraction known as naphtha which may have an initial boiling point from about 40° C. to about 120° C. and an end boiling point from about 145° C. to about 218° C. In an embodiment, the naphtha has an initial boiling point from about 65° C. to about 104° C. and an end boiling point from about 150° C. to about 195° C. The naphtha feed may be a straight run petroleum fraction and/or obtained as a product from one or more petroleum and petrochemical processes such as hydrocracking, hydrotreating, FCC, coking, stream cracking, and any other process which produces a hydrocarbon product in the naphtha boiling range. A number of different reactions may occur in a reforming process including the dehydrogenation of cyclohexanes and dehydroisomerization of alkylcyclopentanes to yield aromatics, dehydrogenation of paraffins to yield olefins, dehydrocyclization of paraffins and olefins to yield aromatics, isomerization of paraffins, isomerization of alkylcycloparaffins to yield cyclohexanes, isomerization of substituted aromatics, and hydrocracking of paraffins. As a result, reforming is an overall endothermic process and it is common to use more than one reaction zone to allow reheating of the reactants in order to obtain the desired performance. 
     Reforming conditions may include reaction temperatures from about 425° C. to about 580° C., preferably from about 450° C. to about 560° C.; a pressure from about 240 kpa(g) to about 4830 kPa(g), preferably from about 310 kPa(g) to about 1380 kPa(g); and a liquid hourly space velocity (LHSV), defined as liquid volume of fresh feed per volume of catalyst per hour, from about 0.2 to about 10 hr −1 . The reforming reaction is carried out in the presence of sufficient hydrogen to provide a hydrogen/hydrocarbon mole ratio from about 0.5:1 to about 10:1. A reforming catalyst typically comprises one or more noble metals (e.g., platinum, iridium, rhodium, and palladium), a halogen component, and a porous carrier or support, such as an alumina. Exemplary catalysts are disclosed in U.S. Pat. No. 6,034,018. The regeneration zone pressure may range from about 0 kPa(g) to about 345 kPa(g). In an embodiment, the regeneration zone pressure ranges from about 0 kpa(g) to about 103 kPa(g), and in another embodiment from about from about 172 kpa(g) to about 310 kPa(g). 
     The hydrocarbon conversion process may be a dehydrocyclodimerization process wherein the feed comprises C 2  to C 6  aliphatic hydrocarbons which are converted to aromatics. Preferred feed components include C 3  and C 4  hydrocarbons such as isobutane, normal butane, isobutene, normal butene, propane and propylene. Diluents, e.g. nitrogen, helium, argon, and neon may also be included in the feed stream. Dehydrocyclodimerization operating conditions may include a reaction temperature from about 350° C. to about 650° C.; a pressure from about 0 kPa(g) to about 2068 kPa(g); and a liquid hourly space velocity from about 0.2 to about 5 hr −1 . Preferred process conditions include a reaction temperature from about 400° C. to about 600° C.; a pressure from about 0 kPa(g) to about 1034 kPa(g); and a liquid hourly space velocity of from 0.5 to 3.0 hr −1 . It is understood that, as the average carbon number of the feed increases, a reaction temperature in the lower end of the reaction temperature range is required for optimum performance and conversely, as the average carbon number of the feed decreases, the higher the required reaction temperature. Details of the dehydrocyclodimerization process are found for example in U.S. Pat. No. 4,654,455 and U.S. Pat. No. 4,746,763. 
     The dehydrocyclodimerization catalyst may be a dual functional catalyst containing acidic and dehydrogenation components. The acidic function is usually provided by a zeolite which promotes the oligomerization and aromatization reactions, while a non-noble metal component promotes the dehydrogenation function. Exemplary zeolites include ZSM-5, ZSM-8, ZSM-11, ZSM-12, and ZSM-35. One specific example of a catalyst disclosed in U.S. Pat. No. 4,746,763 consists of a ZSM-5 type zeolite, gallium and a phosphorus containing alumina as a binder. Multiple reactors or reaction zones may be used to manage the heat of reaction as described above for the reforming process. The dehydrocyclodimerization process regeneration zone pressure may range from about 0 kpa(g) to about 103 kPa(g). In a particular embodiment, the regeneration conditions may include a step comprising exposing the catalyst to liquid water or water vapor as detailed in U.S. Pat. No. 6,657,096. 
     In an embodiment, the hydrocarbon conversion process is a dehydrogenation process for the production of olefins from a feed comprising a paraffin. The feed may comprise C 2  to C 30  paraffinic hydrocarbons and in a preferred embodiment comprises C 2  to C 5  paraffins. General dehydrogenation process conditions include a pressure from about 0 kPa(g) to about 3500 kPa(g); a reaction temperature from about 480° C. to about 760° C.; a liquid hourly space velocity from about 1 to about 10 hr −1 ; and a hydrogen/hydrocarbon mole ratio from about 0.1:1 to about 10:1. Dehydrogenation conditions for C 4  to C 5  paraffin feeds may include a pressure from about 0 kPa(g) to about 500 kPa(g); a reaction temperature from about 540° C. to about 705° C.; a hydrogen/hydrocarbon mole ratio from about 0.1:1 to about 2:1; and an LHSV of less than 4. Additional details of dehydrogenation processes and catalyst may be found for example in U.S. Pat. No. 4,430,517 and U.S. Pat. No. 6,969,496. 
     Generally, the dehydrogenation catalyst comprises a platinum group component, an optional alkali metal component, and a porous inorganic carrier material. The catalyst may also contain promoter metals and a halogen component which improve the performance of the catalyst. In an embodiment, the porous carrier material is a refractory inorganic oxide. The porous carrier material may be an alumina with theta alumina being a preferred material. The platinum group includes palladium, rhodium, ruthenium, osmium and iridium and generally comprises from about 0.01 wt % to about 2 wt % of the final catalyst with the use of platinum being preferred. Potassium and lithium are preferred alkali metal components comprising from about 0.1 wt % to about 5 wt % of the final catalyst. The preferred promoter metal is tin in an amount such that the atomic ratio of tin to platinum is between about 1:1 and about 6:1. A more detailed description of the preparation of the carrier material and the addition of the platinum component and the tin component to the carrier material may be obtained by reference to U.S. Pat. No. 3,745,112. Again, multiple reactors or reaction zones may be used to manage the heat of reaction as described above for the reforming process. The dehydrogenation process regeneration zone pressure may range from about 0 kpa(g) to about 103 kPa(g).