Roasting system with clean emissions and high thermal efficiency

Abstract

A bean roasting system includes a roasting chamber, a blower, a variable diverter and a controller. The roasting chamber, the blower and the variable diverter each is disposed at least partially within a recirculating gas flow path. The blower is configured to provide a flow stream of gas through the recirculating gas flow path. The variable diverter is configured to split the gas flow path into at least two flow paths including a treated flow path and a bypass flow path. The treated flow path includes a series arrangement of a gas heater and a catalytic converter. The variable diverter is configured to control a percentage of a flow stream of gas that is diverted into the bypass flow path. The controller is configured to activate different predetermined operating modes for the bean roasting system by controlling a state of the variable diverter and a state of the heater.

Description

FIELD OF THE DISCLOSURE

The present disclosure pertains to the roasting of food products, particularly to beans, and more particularly to coffee beans. Yet more particularly the present disclosure describes a roasting system that has improved gas or air handling to improve both emissions and energy efficiency of the roaster in a compact size.

BACKGROUND

Food roasting machines are in wide use. One particularly common roasting machine is utilized to prepare coffee beans to be either packaged or ground and brewed. The roasting process consumes considerable energy and, without some emissions treatment, emits noxious gases. To reduce the emissions, various solutions have been employed such as those that utilize high temperature incineration of the output stream along with costly filtration. The incineration adds to the energy consumption and complexity of the roasting system. In addition, the practice of incineration also often involves installation of costly ventilation systems, which some buildings are unable to accommodate. There is an ongoing need to find better designs that reduce energy consumption and provide a clean output.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram schematic of an example roasting system.

FIG. 2 is an electrical block diagram of an example roasting system.

FIG. 3 is a flowchart representing an example sequence of operation for a roasting system.

FIG. 4 is a graphical representation of an example of a roasting profile including graphs of temperature (solid) and humidity (dashed) versus time.

FIG. 5 is a flowchart representing a process that can take place during a roasting operation.

FIG. 6 is a flowchart depicting an example method by which a controller modulates temperatures for catalytic converter and roasting chamber for a given operating mode, according to an embodiment.

SUMMARY

In one embodiment, a bean roasting system includes a roasting chamber, a blower, a variable diverter and a controller. The roasting chamber is disposed at least partially within a recirculating gas flow path. The blower is disposed at least partially within a recirculating gas flow path. The blower is configured to provide a flow stream of gas through the recirculating gas flow path. The variable diverter is disposed at least partially within a recirculating gas flow path. The variable diverter is configured to split the gas flow path into at least two flow paths including a treated flow path and a bypass flow path. The treated flow path includes a series arrangement of a gas heater and a catalytic converter. The variable diverter is configured to control a percentage of a flow stream of gas that is diverted into the bypass flow path. The controller is configured to activate a plurality of different predetermined operating modes for the bean roasting system by controlling a state of the variable diverter and a state of the heater.

In one implementation, the bean roasting system includes a cyclonic separator that is disposed at least partially within the recirculating gas flow path, and that receives the flow stream from the roasting chamber and delivers the flow stream to the diverter. The cyclonic separator removes fragments and/or particles of debris from the flow stream and delivers them to a container or receptacle.

In another implementation the two flow paths recombine at a fluid junction before entering the gas inlet of the roasting chamber. In one implementation, the blower is a main blower located downstream of the junction and upstream of the inlet of the roasting chamber. In another implementation the fluid junction is defined by a mixing chamber.

In yet another implementation the bypass percentage is a dominant factor in determining a relative magnitude or ratio of a temperature in the roasting chamber as compared to the a temperature in the catalytic converter. As the bypass percentage increases, the roasting chamber temperature decreases in relation to the catalytic converter temperature. The catalytic converter temperature can be maintained at an optimum or predefined temperature for catalysis. An optimal catalysis temperature can be, for example, within a range of 500 to 1000 degrees Fahrenheit or about 800 degrees Fahrenheit. The variable diverter setting in combination with airflow and heater power are used to modulate the roasting chamber temperature for different operating modes of the roasting system while controlling and/or maintaining the catalytic converter temperature (e.g., within a desired temperature range or as close as possible to optimal).

In a further implementation the plurality of different predetermined operating modes are in part defined by a temperature in the roasting chamber. The plurality of different predetermined operating modes can include a preheat operating mode, a bean drying mode, a temperature recovery ramp mode, and a roast development mode, to name some examples.

In another embodiment, a bean roasting system includes a roasting chamber, a blower, a variable diverter, a catalytic converter, a heater, a fluidic junction and a controller. The roasting chamber has a gas inlet and a gas outlet fluidically coupled to the gas inlet by a recirculating gas flow path. The blower is disposed at least partially within the recirculating gas flow path and configured to establish a flow stream of gas through the recirculating gas flow path. The variable diverter is disposed at least partially within the recirculating gas flow path and configured to split the recirculating gas flow path into at least two gas flow path segments including a treated gas flow path segment and bypass gas flow path segment. The variable diverter is configured to control a percentage of the flow stream of gas that is diverted to the bypass gas flow path segment. The catalytic converter is disposed at least partially within the treated gas flow path segment. The heater is in series with the catalytic converter and disposed at least partially within the treated gas flow path segment. The fluidic junction recombines at which the at least two gas flow path segments before the flow stream of gas reaches the gas inlet of the roasting chamber. The controller is configured to control a state of the variable diverter and a state of the heater to provide closed loop temperature control of both the catalytic converter and the roasting chamber such that an increase in the percentage of the flow stream of gas that is diverted to the bypass gas flow path segment reduces a temperature in the roasting chamber relative to a temperature of the catalytic converter.

In one implementation the blower is disposed between the fluid junction and the gas inlet of the roasting chamber.

In another implementation a mixing chamber defines the fluid junction.

In yet another implementation the controller is configured to define and activate a plurality of different operating modes that are defined at least in part upon a temperature of the roasting chamber, the controller activating the different operating modes by controlling at least the states of the main blower, the variable diverter, and the heater.

In another embodiment, a bean roasting system includes a roasting chamber a humidity sensor and a controller. The roasting chamber and the humidity sensor are each disposed at least partially within a recirculating gas flow path. The roasting chamber includes a gas inlet and a gas outlet. The humidity sensor is disposed within the roasting chamber or in the recirculating gas flow path proximate to the gas outlet. During a roasting operation the controller analyzes a signal from the humidity sensor to identify characteristics of the roast. In response to roast characteristics, the controller can then take a further action in response to the identification. In a first implementation, the further action includes adjusting parameters of the roasting operation such as duration, heat input, and/or airflow. In a second implementation, the controller sends a message to a mobile device of a person responsible for the roasting operation. The message can be provided to a user through a user interface that allows the person to elect to change the roasting operation based upon the detection of the humidity peak. Further implementations can include automatically adjusting the roasting operation and sending wirelessly a message.

DETAILED DESCRIPTION

FIG. 1 is a block diagram schematic of roasting system 2, according to an embodiment. Roasting system 2 includes a roasting chamber 4 having a gas outlet 6 and a gas inlet 8. A gas conduit 10, in combination with other relevant components discussed below, defines a recirculating gas flow path (referenced herein interchangeably as gas conduit 10 or recirculating gas flow path 10) and is coupled to and includes the roasting chamber 4. The recirculating gas flow path 10 performs a number of functions including removing debris and noxious gases from the roasting process and regulating a temperature of the roasting chamber 4. The roasting system 2 also includes a bean hopper 12 for a loading unroasted beans before they are inputted to the roasting chamber 4. Between the bean hopper 12 and the roasting chamber 4 is a load valve 14 for releasing the beans from the hopper 12 into the roasting chamber 4. An unload valve 16 is for releasing the beans to a bean cooling system (not shown).

During operation of the roasting system 2 a flow stream 18 of gas is established in the recirculating gas flow path 10 from the gas outlet 6 to the gas inlet 8 of the roasting chamber 4. After leaving the gas outlet 6 the flow stream 18 passes to a cyclonic separator 20, which removes debris from the gas flow stream 18 that is collected below the cyclonic separator 20.

The flow stream 18 then passes to a variable diverter 22. Variable diverter 22 splits the gas flow path 10 into at least two flow path segments including a treated flow path segment 24 and a bypass flow segment 26. The variable diverter 22 controls a “bypass percentage,” which is a percentage of the flow stream 18 that is diverted into the bypass flow segment 26. The bypass percentage can be varied between zero percent to 100 percent of the mass flow of the flow stream 18. When the bypass percentage is zero then all of the mass flow of the flow stream 18 is flowing through the treated flow path segment 24. When the bypass percentage is X, then 100−X percent of the mass flow of the flow stream is passing through the treated flow segment 24 and X percent of the mass flow of the flow stream 18 is passing through the bypass flow segment 26. When the bypass percentage is 100, then all of the mass flow of the flow stream 18 is passing through the bypass flow segment 26.

The treated flow segment 24 includes a heater 28 and a catalytic converter 30 in a fluidic series. In the embodiment shown in FIG. 1, the heater 28 is the main heater 28 for the catalytic converter 30 and the roasting chamber 4. The catalytic converter 30 has an operating temperature (referred to as a catalyst temperature T_CT) that is used for catalysis. A catalyst temperature T_CT is typically in a range of 500 to 1000 degrees Fahrenheit. On the other hand, the roasting chamber 4 has a roasting chamber temperature T_RC that can vary between 150 and 500 degrees Fahrenheit depending upon a desired roasting process and a step within the process.

The bypass flow segment 26 is coupled to a mixing chamber 32 (also referred to herein as a junction 32). The mixing chamber 32 (junction 32) defines the point at which the separated or split flow paths recombine into one flow path. Between the junction 32 and the gas inlet 8 of the roasting chamber 4 is a main blower 34.

Coupled to the bypass flow segment 26 is an inlet component 36 to allow ambient air to enter the recirculating gas flow path 10. The inlet component 36 includes an inlet control valve and inlet blower coupled in series to allow and force ambient air into the recirculating gas flow path 10. Coupled to the mixing chamber 32 is a outlet component 38 to release gas from the recirculating gas flow path 10 to the ambient environment. The outlet component 38 includes an outlet control valve, a condenser, and a filter in series.

The roasting system 2 employs various sensors 40 including temperature sensors T. These sensors 40 are utilized to enable a closed loop control of various processes within the roasting system 2.

In alternative embodiments the bypass flow segment can include an auxiliary heating and/or cooling temperature modulator 44. In another alternative embodiment the main blower 34 can be located at other locations in the recirculating gas flow path 10 or multiple blowers can be employed. In yet another alternative embodiment, the inlet component 36 may be integrated into the mixing chamber, and the outlet component 38 may be moved to a point in the fluid flow path that is immediately after the catalytic converter.

FIG. 2 is an electrical block diagram of the roasting system 2 of FIG. 1. Some reference numbers in FIG. 2 correspond to reference numbers in FIG. 1. Roasting system 2 includes a controller 42 that receives signals from sensors 40 and provides control signals to various components including valves 14 and 16, variable diverter 22, main heater 28, main blower 34, inlet component 36, outlet component 38, and optionally an auxiliary temperature modulator 44 (providing heating and/or cooling).

Controller 40 includes a processor 46 coupled to an information storage device 48. The information storage device 48 includes a non-transient or non-volatile storage device storing software that, when executed by processor 46, controls the various components of roasting system 2 and provides functions for which the controller 42 is configured. The controller 42 can be a located at one location or distributed among multiple locations in roasting system 2. For example, controller 42 can be disposed within a housing (not shown) of roasting system 2 and/or a housing of an appropriate component of roasting system 22 such as a housing of the variable diverter 22. The controller can be electrically and/or wirelessly linked to the various components of roasting system 2.

The controller 42 is configured to define and activate a plurality of different predetermined or predefined operating modes. Each operating mode can define a step or process in a sequence of steps and processes that are executed during the operation of the roasting system 2. An example sequence will be described with respect to FIG. 3.

A particular operating mode can be defined, for example, in part by a time duration and a state of various components of the roasting system 2. States that are directly controlled are those of components that receive direct control signals from the controller 42. Examples of directly controlled states include the bypass percentage of the variable diverter 22, an output power of the main heater 28, an airflow rate of the main blower 34, and a control of the inlet and outlet components 36 and 38 respectively. An optional example would be control of auxiliary temperature modulator 44.

States that are indirectly determined are those states that are a consequence of those states that are directly determined. These include a temperature of the roasting chamber 4 and an internal temperature of the catalytic converter 30. These temperatures are determined (and thereby indirectly controlled) through the control of the main heater 28, the main blower 34, and the variable diverter 22.

Controller 42 reads signals or data from sensors 40 indicative of various temperatures within the roasting system 2. These signals or data may be indicative of a temperature of the roasting chamber 4, the catalytic converter 30, or various portions of the recirculating flow path 10. The controller 42 then modulates the directly controlled states to maintain desired temperature set points.

FIG. 3 is a flowchart representing an example sequence of operation 50 for the roasting system 2. Each step of the operational sequence is based upon a predetermined operating mode an indicator for which is stored in controller 42. For each of these steps the controller 42 controls various components as discussed with respect to FIG. 2.

Step 52 represents an initial state of the roasting system 2 after it has been off long enough to equilibrate with an ambient environment. The heater power is zero, meaning that no power is being sent to main heater 28. The main blower 34 is off. As a result the catalytic converter 30 temperature and the roasting chamber 4 temperatures are both at ambient temperature which can be about 70 degrees Fahrenheit.

Step 54 represents a pre-heat mode for the roasting system 2. This operational mode can have a time duration of about 30 minutes. During this mode the power delivered to the main heater 28 is in a “high” state. In one implementation the power delivered to main heater 28 is more than 75 percent or even 100 percent of the maximum power level that is used for the main heater 28. The main blower 34 is operated in a “high” state. In one particular implementation the main blower 34 is operated with a flow rate of 200 cubic feet per minute, and the bypass percentage starts out at a low value or less than 10 percent or even zero and then ramps up to bypass percentage of more than 50 percent, more than 75 percent or about 85 to 90 percent. In another implementation, the bypass percentage is kept at a low value throughout preheat, and the blower speed is decreased as the system heats up in order to reduce the delivery energy to various parts of the system. In this case, the heater temperature remains high, but the energy drawn and outputted by the heater is lower due to the decrease in energy transport. During the pre-heat mode the temperature of the catalytic converter 30 ramps up from ambient temperature to an effective catalytic temperature in a range of 500 to 1000 degrees Fahrenheit. In one implementation the catalytic temperature is about 800 degrees Fahrenheit. The roast chamber 4 temperature also ramps up to a temperature range to begin the roasting process. In one embodiment this temperature is in a range of 300 to 400 degrees Fahrenheit or about 350 degrees Fahrenheit.

Step 56 represents a standby mode that has an indeterminate duration. During this operational mode the power delivered to the main heater 28 is in a “low” state. In one implementation the power delivered to heater 28 is less than 50 percent in a range of about 5 to 15 percent of the maximum power level that is used for the main heater. This low main heater 28 power is all that is used to maintain the catalytic converter 30 temperature and the roasting chamber 4 temperature. In one implementation, the main blower is operated in a “low” state. In one implementation the main blower is operated with a flow rate of 100 cubic feet per minute (CFM). In this case, the bypass percentage is more than 50 percent, more than 75 percent, or in a range of about 85 to 90 percent. In another implementation, the main blower operates at an output less than 100 cubic feet per minute (CFM), and the speed is modulated to control the energy distribution throughout the system. In this case, the bypass percentage is kept low, around 0-10 percent. In all cases, catalytic converter 30 temperature is in a range of 500 to 1000 degrees Fahrenheit or about 800 degrees Fahrenheit. The roasting chamber 4 temperature is in a range of 300 to 400 degrees Fahrenheit or about 350 degrees Fahrenheit.

Step 58 represents an operational mode in which the valve 14 is opened to load beans from the hopper 12 to the roasting chamber 4. The component states for step 58 are the same as those of step 57 except that the main blower is operated in a “high” state. In one implementation the main blower 34 is operated with a flow rate of 200 cubic feet per minute.

Steps 60, 62, and 64 represent a complete cycle for bean roasting. During these steps the main blower 34 is operated in a “high” state which can be 200 cubic feet per minute. The combined time duration for steps 60, 62, and 64 is about 10-15 minutes.

Step 60 is an operational mode for drying the beans, which can last about 1-3 minutes. The main heater 28 is operated with a “low” power level, which can be in a range of 10 to 20 percent of maximum power. The bypass percentage is in a range of 50 to 90 percent or about 71 percent. The catalyst temperature in a range of 500 to 1000 degrees Fahrenheit or about 800 degrees Fahrenheit. The roast chamber 4 temperature is in a range of about 170 to 180 degrees Fahrenheit or about 175 degrees Fahrenheit.

Step 62 is a “recovery ramp” mode during which the roasting chamber temperature is increased to a roasting development temperature. The “recovery ramp” mode can have a duration of about 3-6 minutes. The main heater 28 is operated with a “high” power level which can be in a range of 75 to 100 percent of maximum power. The bypass percentage is in a range of zero to 10 percent so that some gas having a higher temperature from the main heater 28 is directed to the roasting chamber 4. As a result, the roasting chamber temperature increases to a roasting development temperature, which can be about 390 degrees Fahrenheit. During step 62 the catalyst temperature may fall to about 650 degrees Fahrenheit.

Step 64 is a roasting development mode during which the temperature of the roasting chamber 4 is increased. The roasting development mode has a duration of about 3 minutes. The main heater 28 is operated with a “low” power that can be 20 to 30 percent of maximum power. The bypass percentage is in a range of 50 to 100 percent or about 76 percent. The bypass percentage can be increased while the heater input is decreased during this mode. The roasting chamber 4 temperature increases from about 390 degrees Fahrenheit to about 460 degrees Fahrenheit. The catalyst temperature increases from about 650 degrees Fahrenheit to about 750 degrees Fahrenheit. Also as part of this mode, the inlet 36 and outlet 38 components are operated to allow a one to five percent gas exchange with the ambient air environment.

During step 66 the valve 16 is opened to drop the roasted beans into a cooling chamber. During step 68 the beans are cooled and the system states are returned to those of the standby mode of step 56 after a preheating operation.

As a note, the specific states described above with respect to FIG. 3 can vary depending on a desired “roasting profile.” In particular, the roasting chamber 4 temperature states are a function of such a roasting profile. Thus, the described sequence 50 can have variations in terms of component states and the temperatures indicated with respect to FIG. 3 are examples for a particular roasting profile or set of roasting profiles.

Referring to FIG. 1, the sensors 40 can include humidity (designated H) and oxygen (designated O₂) sensors. The controller 42 can use information from these sensors to track progress of the roasting steps 60-64 (of FIG. 3). As a unique example, the controller 42 can infer information about the roast process by analyzing the humidity versus time of gas that is exiting the outlet 6 of the roasting chamber 4.

A milestone event during roasting steps 60-64 is a “first crack” of the beans. Once this begins, the remaining time and temperature of the roasting profile can be more accurately determined. The added time and temperature is dependent on the type of roast (e.g., light roast versus full French roast).

FIG. 4 is a graph of an example of temperature and humidity versus time. The dashed line represents the humidity versus time curve; the solid line represents the humidity temperature versus time curve. The values in this graph are generated using sensors 40 that are placed at or proximate to the outlet 6 of the roasting chamber 4. As shown, a relatively sharp peak in the graph of humidity versus time corresponds to the “first crack” milestone of the roasting development step 64. This peak in the humidity curve can be a factor in deciding subsequent steps in the roasting process.

FIG. 5 is a flowchart depicting an example roasting process 70. Roasting process 70 can be similar to and/or preformed in conjunction with the roasting steps 60-64 except that it incorporates additional operations. According to step 72, the humidity is monitored by the H sensor 40 at the outlet 6 of roasting chamber 4. As part of step 72, the controller 42 analyzes the graph of humidity versus time (or an equivalent such as a look-up table stored in memory, an equation presenting the humidity-time curve) to identify rapid changes in a magnitude of the slope and a localized maximum.

According to step 74, a humidity peak is identified. This corresponds to the “first crack” of the beans. This identification of the humidity peak indicates a certain progress of the roasting process 70.

According to step 76, a response or action is activated in response to the identification of the first crack milestone. This can take any number of forms.

In one implementation the roast development duration is automatically adjusted based upon the milestone identification and a desired roast type. In this implementation parameters such as the heater power, airflow, and/or bypass percentages can also be adjusted.

In another implementation an alert can be automatically sent to a person who is responsible for the roasting operation. For example, this can be a message wirelessly sent to a mobile device that is utilized by the person. The message can provide an option for the person to adjust the roast profile based upon the timing of the milestone.

FIG. 6 is a flowchart depicting an example method 80 by which the controller 42 modulates temperatures for the catalytic converter 30 and the roasting chamber 4 for a given operating mode. As discussed above, the catalytic converter 30 temperature T_CT can be maintained at an optimum temperature for catalysis that tends not to change as a function of an operating mode of the roasting system 2. On the other hand, the roast chamber 4 temperature T_RC is a function of the operating mode.

According to step 82 the method 80 begins with a receipt of operating parameters for an operating mode including a specified roast chamber setting T_RC. The method 80 then includes two independent temperature control loops that can be executed concurrently. An example catalytic converter 30 temperature T_CT control loop is depicted by steps 84 to 88. An example roasting chamber 4 temperature control loop is depicted by steps 90 to 94.

According to step 84 a temperature T_CT of the catalytic converter 30 is monitored. As part of step 84, the controller 42 receives temperature T_CT data for the catalytic converter 30 from a temperature sensor 40 that is within or proximate to or receiving air exiting from the catalytic converter 30.

According to step 86 a determination is made as to whether the temperature T_CT of the catalytic converter 30 is within a specified range. This specified temperature range is within an overall temperature range of for example 500 to 1000 degrees Fahrenheit. In one implementation the specified temperature range is narrower and centered around a temperature of about for example 800 degrees Fahrenheit. If the temperature T_CT of the catalytic converter 30 deviates from the specified range, then the method 80 proceeds to step 88. According to step 88 a power delivered to the main heater 28 is adjusted to counteract the temperature deviation determined in step 86. As part of step 88 the controller 42 sends a control signal to adjust a power input to the heater 28. Then steps 84 and 86 are repeated. When according to step 86 the temperature T_CT of the catalytic converter 30 is within the specified range, the loop proceeds to step 84 to continue monitoring the temperature T_CT of the catalytic converter 30.

According to step 90 a temperature T_RC of the roasting chamber 4 is monitored. As part of step 90, the controller 42 receives temperature T_RC data for the roasting chamber 4 from a temperature sensor 40 that is either within or proximate to or receiving air exiting from roasting chamber 4.

According to step 92 a determination is made as to whether the temperature T_RC of the roasting chamber 4 is within a specified range. This specified range is based upon the specified roast chamber temperature setting T_RC for the current operating mode from step 82. If the temperature T_RC of the roasting chamber 4 deviates from the specified range, then the method 80 proceeds to step 94.

According to step 94, the variable diverter 22 is adjusted to counteract the deviation. As part of step 94 the controller 42 sends a control signal to the variable diverter 22. In response to the control signal, the variable diverter 22 increases or decreases the bypass percentage. For example, if the temperature is too high then the bypass percentage will be increased. Then steps 90 and 92 are repeated. When according to step 92 the temperature T_RC of the roasting chamber 4 is within the specified range, the loop proceeds to step 90 to continue monitoring the temperature T_RC of the roasting chamber 4.

The two temperature control loops for the catalytic converter 30 and the roasting chamber 4 continue independently of each other from the perspective of a control system operation. However, they do have an indirect dependency. When the heater 28 is adjusted according to step 88 this will impact the temperature T_RC of the roasting chamber 4. Then the control loop for the roasting chamber 4 will most likely need to respond.

The specific embodiments and applications thereof described above are for illustrative purposes only and do not preclude modifications and variations encompassed by the scope of the following claims.

Claims

1. A bean roasting system, comprising: a roasting chamber coupled to a recirculating gas flow path;a blower coupled to the recirculating gas flow path, the blower configured to provide a flow stream of gas through the recirculating gas flow path;a variable diverter coupled to the recirculating gas flow path, the variable diverter configured to split the gas flow path into at least two flow paths including a treated flow path and a bypass flow path, the treated flow path including a series arrangement of a gas heater and a catalytic converter, the variable diverter configured to control a percentage of a flow stream of gas that is diverted into the bypass flow path; anda controller configured to activate a plurality of different predetermined operating modes for the bean roasting system by controlling a state of the variable diverter and a state of the heater, gas flows out of the roasting chamber through the variable diverter and through the treated flow path and bypass flow path before returning to the roasting chamber along the recirculating flow path, the variable diverter is configured such that (1) the percentage of the flow stream of gas that is diverted into the bypass flow path controls a temperature in the roasting chamber as compared to a temperature in the catalytic converter, and (2) the temperature in the roasting chamber decreases relative to the temperature in the catalytic converter as the percentage of the flow stream of gas that is diverted into the bypass flow path is increased.

2. The bean roasting system of claim 1, further comprising a cyclonic separator coupled to the recirculating gas flow path and configured to remove fragments of material from the flow stream of gas before the flow stream of gas enters the variable diverter.

3. The bean roasting system of claim 1, wherein the at least two flow paths recombine at a fluid junction before entering the roasting chamber.

4. The bean roasting system of claim 3, wherein the blower is disposed downstream of the fluid junction within the recirculating gas flow path and before the roasting chamber.

5. The bean roasting system of claim 3, further comprising a mixing chamber that defines the fluid junction.

6. A bean roasting system, comprising: a plurality of components at least partly defining a recirculating gas flow path;a roasting chamber coupled to the recirculating gas flow path;a blower coupled to the recirculating gas flow path, the blower configured to provide a flow stream of gas through the recirculating gas flow path;a variable diverter coupled to the recirculating gas flow path, the variable diverter configured to split the gas flow path into at least two flow paths including a treated flow path and a bypass flow path, the treated flow path including a series arrangement of a gas heater and a catalytic converter, the variable diverter configured to control a percentage of a flow stream of gas that is diverted into the bypass flow path; anda controller configured to activate a plurality of different predetermined operating modes for the bean roasting system by controlling a state of the variable diverter and a state of the heater, gas flows along the recirculating gas flow path out of the roasting chamber through the variable diverter and through the treated flow path and bypass flow path before returning to the roasting chamber, the plurality of different predetermined operating modes are partly defined by a temperature in the catalytic converter and a temperature in the roasting chamber.

7. The bean roasting system of claim of claim 6, wherein at least one of the operating modes from the plurality of different predetermined operating modes is also defined by an exchange of ambient air with the recirculating gas flow path.

8. The bean roasting system of claim 6, wherein the plurality of different predetermined operating modes include a preheating operating mode during which the temperature of the catalytic converter and the temperature of the roasting chamber are increased to enable a bean roasting operation, the preheating operating mode includes a variable diverter setting that dynamically increases the diversion of air to the bypass flow path during the preheating operating mode.

9. The bean roasting system of claim of claim 6, wherein the plurality of different predetermined operating modes include a bean drying mode defined by a heater state of less than 30 percent of the maximum output of the heater and a variable diverter state in which the variable diverter diverts more than 50 percent of the gas flow to the bypass flow path.

10. The bean roasting system of claim of claim 9, wherein the plurality of different predetermined operating modes include a recovery ramp mode following the bean drying mode during which a heater power is increased relative to the drying mode and the variable diverter diverts less than 30 percent of the gas flow to the bypass flow path.

11. The bean roasting system of claim 10, wherein the plurality of different predetermined operating modes includes a roast development mode in which the heater power is reduced relative to the recovery ramp mode and the variable diverter diverts more than 50 percent of the gas flow path to the bypass flow path.

12. A bean roasting system, comprising: a roasting chamber having a gas inlet and a gas outlet fluidically coupled to the gas inlet by a recirculating gas flow path;a blower coupled to the recirculating gas flow path and configured to establish a flow stream of gas through the recirculating gas flow path;a variable diverter coupled to the recirculating gas flow path and configured to split the recirculating gas flow path into at least two gas flow path segments including a treated gas flow path segment and bypass gas flow path segment, the variable diverter configured to control a percentage of the flow stream of gas that is diverted to the bypass gas flow path segment;a catalytic converter coupled to the treated gas flow path segment;a heater in series with the catalytic converter and coupled to within the treated gas flow path segment, the blower, the variable diverter, and the treated and bypass flow paths segments define portions of the recirculating gas flow path between the gas inlet and gas outlet of the roasting chamber;a fluidic junction at which the at least two gas flow path segments are recombined before the flow stream of gas reaches the gas inlet of the roasting chamber; anda controller configured to control a state of the variable diverter and a state of the heater to provide closed loop temperature control of both the catalytic converter and the roasting chamber such that an increase in the percentage of the flow stream of gas that is diverted to the bypass gas flow path segment reduces a temperature in the roasting chamber relative to a temperature of the catalytic converter, the controller is configured to define and activate a plurality of different operating modes that are defined at least in part upon a temperature of the roasting chamber and a temperature of the catalytic converter, the controller configured to activate the different operating modes by controlling at least the states of the blower, the variable diverter, and the heater.

13. The bean roasting system of claim of claim 12, wherein the blower is coupled to the recirculating gas flow path downstream from the fluid junction and upstream from the gas inlet of the roasting chamber.

14. The bean roasting system of claim of claim 12, further comprising a mixing chamber that defines the fluidic junction.