Low pressure continuous dense phase convey system using a non-critical air control system
View Patent ↗An air control system for a low pressure continuous dense phase convey system employs a non-critical air flow control system that allows for a supply pressure to be only incrementally larger than a convey pressure. The convey system has an inlet for introduction of pressurized air into the system and an airlock associated with a feedpoint for introduction of particulate into the system. A first pressure sensor is positioned immediately downstream of an air source to measure the supply pressure, and a second pressure transducer is positioned proximate an airlock to measure the convey pressure. The non-critical air flow control system is dependent on the supply and convey pressures and a position of a control valve, such as a sonic nozzle. The difference between the convey pressure and the supply pressure is less than 10% of the supply pressure.
1. A method of conveying particulate through a convey system employing a non-critical air flow control system, the method comprising the steps of:
positioning an air source upstream of an inlet of the convey system;
positioning a control valve downstream of the air source and immediately upstream of the inlet;
positioning a first pressure transducer downstream of the air source and upstream of the control valve for sensing of a supply pressure produced by the air source;
positioning a second pressure transducer proximate a feedpoint of particulate into the convey system for sensing a convey pressure of the convey system;
employing a controller having a processor and a memory to receive first and second signals respectively representing the first and second sensed pressure signals; and
employing the controller to process the first and second pressure signals and to control a position of the control valve to obtain a desired rate of air flow according to the following equation:
Q
n
c
=
Q
(
critical
)
x
*
(
P
1
-
P
2
P
1
)
y
,
wherein the rate of air flow is a function of supply pressure P 1 , convey pressure P 2 , and the control valve position.
2. The method of claim 1 , wherein a ratio of the supply pressure P 1 to the convey pressure P 2 is less than 1.25:1, such that the rate of air flow through the control valve is non-critical.
3. The method of claim 2 , wherein a ratio of the supply pressure P 1 to the convey pressure P 2 is less than 1.1:1.
4. The method of claim 2 , wherein the supply pressure P 1 varies during the conveying operation by less than ±1%, and the supply pressure P 1 is not held constant.
5. The method of claim 2 , wherein a difference in the convey pressure P 2 and the supply pressure P 1 is 1-2 psi.
6. The method of claim 1 , wherein the rate of air flow is determined based on a desired convey velocity for the particulate, a size of the convey line, and a calculated air leakage through the airlock.