Patent Application
20140004610
The present invention generally relates to processes and apparatuses for converting a feedstock, and more particularly relates to processes and apparatuses that intermittently measure process conditions through instrument taps and purge the instrument taps.
The conversion of biomass feedstock into bio-oil, i.e., a renewable liquid fuel derived from biological sources, has become a valuable process for producing an alternative fuel source. Biomass feedstock includes, but is not limited to, lignin, plant parts, fruits, vegetables, plant processing waste, wood chips, chaff, grains, grasses, corn and corn husks, weeds, aquatic plants, hay, recycled and non-recycled paper and paper products, and any cellulose-containing biological material or material of biological origin. Typically, the biomass feedstock is ground into particles and delivered to a conversion reactor. In the conversion reactor, the biomass feedstock can be converted to bio-oil through catalytic or thermal processes. For both catalytic and thermal conversion processes, the biomass particles may be transported through the conversion reactor by a carrier gas. Further, the biomass particles may be contacted with solid catalyst particles or with solid heat transfer medium particles. The carrier gas, biomass particles, solid catalyst particles and/or solid heat transfer medium particles form a fluidized solid stream.
As the biomass is converted during the catalytic or thermal process, process conditions may vary and are typically monitored. In fact, process conditions in a conversion reactor are generally monitored continuously. Specifically, instrument taps in the reactor are opened and are in fluid communication with measuring instruments. The measuring instruments may include pressure, differential pressure, temperature, level measurement instruments, and the like. During processing, the solid catalyst particles, the solid heat transfer medium particles, or the biomass itself can enter into the instrument taps and become lodged in or otherwise obstruct the measuring instruments. Therefore, it is desirable to reduce or prevent lodging of particles in or obstruction of the measuring instruments or taps.
Generally, a purge gas is used to reduce or prevent lodging of particles in or obstruction of the measuring instrument. It is typical that the purge gas be continuously flowed to the instrument tap. However, the purge gas is commonly air, and the introduction of additional oxygen through instrument taps reduces the yield of bio-oil from the biomass feedstock proportionally to the amount of oxygen added. Therefore, a reduction of the amount of oxygen delivered to the conversion reactor through instrument tap purges would improve the conversion process yield.
Accordingly, it is desirable to provide processes and apparatuses for converting a feedstock with improved yield. Further, it is desirable to provide processes and apparatuses for converting a feedstock which reduces ingress of oxygen. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
Processes and apparatuses for converting a feedstock are provided. In accordance with an exemplary embodiment, a process of converting biomass includes flowing the biomass and a gas through a process unit. A default value is provided for a frequency of measuring a process condition in the process unit. The process condition is measured according to the frequency to obtain process condition measurements. The process condition measurements are evaluated to assess the stability of the process condition. Then, it is determined whether to change the default value depending on the stability of the process condition.
In accordance with another exemplary embodiment, a process for monitoring a fluidized solid stream includes contacting a gas with solids to form the fluidized solid stream. The process intermittently opens fluid communication with the stream through a tap at a first frequency. Further, the method includes measuring a process condition at the tap to obtain measured process conditions and simultaneously purging solids from the tap while fluid communication with the fluidized solid stream is open.
In accordance with another exemplary embodiment, an apparatus for converting a feedstock to bio-oil includes a conversion reactor for receiving the feedstock. The conversion reactor includes a reaction zone adapted to convert the feedstock to bio-oil. A tap is connected to the reaction zone and a monitoring instrument configured for measuring a condition in the reaction zone is fluidly connected to the tap by a conduit. The apparatus includes a valve connected to the conduit between the measuring instrument and the tap for selectively opening and closing fluid communication therebetween. Further, a gas source is connected to the conduit between the valve and the measuring instrument for purging the tap of solids. The apparatus further includes a controller electronically connected to the measuring instrument and the valve. The controller is configured to intermittently open the valve to obtain a condition measurement and to simultaneously purge the tap of solids.
Embodiments of processes and apparatuses for converting a feedstock will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the processes and apparatuses for converting a feedstock. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background or brief summary, or in the following detailed description.
It is contemplated herein that the conversion of a feedstock can be improved under conditions in which oxygen levels are controlled. Specifically, the processes and apparatuses for converting feedstocks described herein can be used to limit the volume of oxygen introduced to a process unit, such as a conversion reactor or any chamber or conduit through which a fluidized solid stream flows. In many conventional processes, oxygen continuously enters process units through instrument taps purged with air. The processes and apparatuses for converting feedstocks described herein reduce the introduction of oxygen through the instrument taps by only intermittently taking measurements through, and simultaneously purging, the instrument taps. Further, the processes and apparatuses for converting feedstocks described herein monitor the measurements taken and, based on the monitored measurements, determine a frequency for future measurements and purges.
In accordance with the various embodiments herein,
Exemplary process unit 20 is outfitted with an instrument tap 40 at location 42 and an instrument tap 40 at location 44. While two instrument taps 40 are shown in the exemplary process unit 20, more (or fewer) instrument taps 40 may be provided in other locations as desired. Typically, each instrument tap 40 defines an inner channel having a one-inch (2.54 cm) or two-inch (5.08 cm) diameter in fluid communication with the process unit 20. Further, the inner channel of each instrument tap 40 is in fluid communication with a conduit 46 that is connected to a measuring instrument 50. As a result, the measuring instrument 50 is in fluid communication with the process unit 20 at location 42 and location 44 through the conduits 46 and taps 40.
An exemplary conduit 46 has a ¾-inch (1.905 cm) diameter and includes a reducing flange (not shown) connecting the conduit 46 to the respective tap 40. Further, connection between the conduit 46 and the measuring instrument 50 is, for example, performed with a two-inch (5.08 cm) diameter opening, and the conduit 46 may include a reducer (not shown) to accommodate the diameter change. Depending on the apparatus 10 and the desired processing, the measuring instrument 50 may be a pressure, differential pressure, temperature, level measurement, or other measurement device or sensor. As shown in
While the embodiment illustrated in
As shown, the apparatus 10 includes a purge gas header 54 which supplies a purge gas, identified by arrows 56, to the conduits 46. Typically, the purge gas 56 is supplied to the conduits 46 at a constant pressure through a conduit 58. In an exemplary embodiment, the purge gas 56 is air and is supplied at a pressure of about 50 psig (3.447 bar) to about 100 psig (6.895 bar) and the conduit 58 has a ¾-inch (1.905 cm) diameter. During flow from the purge gas header 54, the purge gas 56 passes through a strainer to remove any particulates and through a flow regulator, such as an orifice plate with sixteenth-inch (0.15875 cm) diameter orifice, before passing into the conduit 46. To purge the instrument tap 40 at location 42 and the instrument tap 40 at location 44, the purge gas 56 is urged through conduits 58 and conduits 46. As the purge gas 56 flows, it dislodges and removes any solid particles that may accumulate in the conduits 46 or the instrument taps 40 and carries the particles into the process unit 12, i.e., the purge gas 56 purges the instrument taps 40 and conduits 46.
During conventional processing, purge gas is continuously flowed through instrument taps while measurements are obtained by measuring instruments. However, as the purge gas is typically air, it adds additional, and often undesirable, amounts of oxygen to the process unit. The additional oxygen can inhibit economical processing of the feedstock and result in a yield reduction for the product oil. Therefore, to reduce the amount of oxygen added to the process unit 12, the exemplary apparatus 10 provides for reducing the amount of purge gas 56 added to the process unit 12. Specifically, the apparatus 10 provides for non-continuous purges of the instrument taps 40 and conduits 46 with the purge gas 56. Accordingly, the apparatus 10 provides for non-continuous process condition measurement with the measuring instrument 50.
To provide for non-continuous purging and non-continuous process condition measurement, the apparatus 10 includes valves 60 located on the conduits 46 to close and open fluid flow therethrough. Valves 60 may be actuated block valves that operate with binary off/on signals. During operation, valves 60 are in a closed configuration unless opened by a signal. Typically, the valves 60 move to an opened configuration for a purge/measurement period duration upon receiving an open signal. Then, the valves 60 automatically return to the closed configuration, blocking flow of the purge gas to the process unit 20 and interrupting fluid communication between the process unit 20 and the measuring instrument 50.
Apparatus 10 further includes a controller 64 electronically connected to the measuring instrument 50 and to valves 60. The controller 64 utilizes a software algorithm to monitor the measurements, or measured process conditions, obtained by the measuring instrument 50. Based on the monitored measurements over time, the controller 64 identifies process variability or process trend and determines a measurement schedule or frequency, i.e., how often measurements in the process unit 12 should be taken in order to maintain sufficient process control. In typical processing, the measured process conditions are used to determine whether processing changes are needed, such as changes to flow rates, temperatures, pressures, etc. When process variability is volatile, more frequent measurements are needed to ensure proper processing changes are being made. On the other hand, when the process trend is relatively steady, the measurement frequency may be reduced. In either situation, the controller 64 sends the open signal to the valves 60 according to the measurement frequency. In response, the valves 60 move to the opened configuration, the measuring instrument 50 measures the process condition at location 40 and at location 42, and the purge gas 56 flows through and purges the conduits 46 and instrument taps 40. At all other times, the valves remain closed and no unnecessary air, and hence oxygen, is delivered to reactor 20.
Referring now to
Each measuring instrument 50 of
The exemplary apparatus 10 includes valves 60 located on the conduits 46 to close and open fluid flow therethrough. Valves 60 may be actuated block valves that operate with binary off/on signals. During operation, valves 60 are in a closed configuration unless opened by a signal. Typically, the valves 60 move to an opened configuration for a selected purge/measurement period duration upon receiving an open signal. While the valves 60 are open, the measuring instruments 50 may obtain or record a measurement of a process condition while purge gas 56 purge the conduits 46 and instrument taps 40. Then, the valves 60 automatically return to the closed configuration, blocking flow of the purge gas the process unit 20 and fluid communication between the process unit 20 and the measuring instrument 50.
Apparatus 10 further includes a controller 64 electronically connected to the measuring instruments 50 and to valves 60. As described above, the controller 64 utilizes an algorithm to monitor the measurements, or measured process conditions, obtained by the measuring instruments 50, identifies process variability or process trend, and determines a measurement schedule or frequency. The controller 64 then sends the open signal to the valves 60 according to the measurement frequency. In response, the valves 60 move to the opened configuration, the measuring instrument 50 measures the process condition at location 40 and at location 42, and the purge gas 56 flows through and purges the conduits 46 and instrument taps 40.
Referring to
As shown, each measurement/purge unit 72 is electronically connected to a controller 64. As described above, the controller 64 monitors the measured process conditions obtained by the measuring instruments, sets a measurement frequency based on the measured process conditions, and selectively opens the valves according to the measurement frequency that it sets. The controller 64 can dynamically modify the measurement frequency in real-time upon receiving new measurements from the measuring instruments. As the controller 64 is electronically connected to measurement/purge units 72 at locations throughout the apparatus 10, the controller 64 can universally monitor process conditions throughout the apparatus 10. Further, because different locations in the apparatus 10 may operate under different regimes, such as for example, level control, flow control, or pressure control, the controller 64 may set measurement frequencies that vary between the measurement/purge units 72 and, hence, locations within the apparatus 10.
In view of the apparatuses in
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the processes without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.
