Gas-fired coffee roasters commonly heat a drum with a burner and shape the roasting temperature profile by changing burner input. Some small and medium-sized machines use bottled liquefied petroleum gas (LPG).
Flowmethod has worked with coffee-roaster manufacturers to introduce gas mass flow controllers into the gaseous LPG supply stage, providing a defined quantity of fuel to the burner.
Why control fuel delivery by flow?
Users of bottled LPG may notice changes in flame behavior. LPG is typically a propane/butane mixture; composition can vary with the supply and operating conditions. Pressure and vaporized composition can also change as a cylinder is used, and a new cylinder may behave differently.
A pressure gauge and manual valve setting give indirect information about fuel delivery. Stable pressure does not by itself establish a constant mass of fuel reaching the burner each second. Operators may need repeated adjustments to maintain a similar roasting curve across batches.
A settable and repeatable fuel-flow reference
In this application, an MFC measures gas flow and regulates it against a command. It replaces an unrecorded manual adjustment with a flow target that can be set, repeated and logged, within the instrument's specified conditions.
This gives the equipment manufacturer one defined input to coordinate with burner design and temperature control. It can support more reproducible operation, but a flow setpoint is not a complete measure of burner heat input if fuel composition and calorific value change.
Keep the complete system in view
LPG must be appropriately vaporized and pressure-regulated so that the approved gas phase, not liquid carryover, enters the flow controller. The roaster manufacturer is responsible for designing the fuel piping, burner, flame safeguards and required gas-safety functions for the applicable installation. Flowmethod supplies the specified gas-flow measurement and regulation part of that system.
An MFC does not remove gas-source composition variations, nor does its regulating valve replace an independent safety shutoff. Overall roasting performance also depends on the burner, thermal process and control logic; it should not be attributed to the flow instrument alone.
Selection and technical support
Flowmethod configures products for the customer's gas, calibration range and interface requirements. A roaster manufacturer should provide the fuel composition, normal and maximum flow, inlet/outlet pressures and intended integration method so the engineer can confirm a suitable arrangement.
Use the required pressure monitoring, leak checks, safe gas-handling and installation procedures, and maintain piping and fittings as specified for the complete combustion system.
This application extends gas-flow control into coffee-roasting equipment. The objective is a better-defined and reproducible fuel-supply stage, designed together with the equipment manufacturer for the actual process.
For selection, installation or technical enquiries, contact Flowmethod: Mr. Dou, +86 180 3818 3381; doufeijin@hotmail.com. See Contact for the full contact list.