LOW PRESSURE CONTINUOUS DENSE PHASE CONVEY SYSTEM USING A NON-CRITICAL AIR CONTROL SYSTEM

• US 20110268510A1
• Filed: 05/02/2011
• Published: 11/03/2011
• Est. Priority Date: 05/03/2010
• Status: Active Grant

• Current Assignee: Schenck Process LLC (Schenck Process Holding GmbH)
• Original Assignee: MAC Equipment, Inc. (Schenck Process Holding GmbH)
• Inventors: Thorn, Jonathan
• Granted Patent: US 8,747,029 B2
• Time in Patent Office: Days
• US Class Current: 406/30
• CPC Class Codes: B65G 53/66 Use of indicator or control devices, e.g. for controlling gas pressure, for controlling proportions of material and gas, for indicating or preventing jamming of material controlling the flow of coal firing systems C21B5/003
• CPC Class Codes: G05D 7/0688 by combined action on throttling means and flow sources G05D7/0694 takes precedence

Abstract

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.

Claims

1. A low pressure continuous dense phase convey system having an inlet for introduction of pressurized air into the system and an airlock associated with a feedpoint for introduction of particulate into the system, said pressurized air flowing through the system from an upstream position and to a downstream position, said system comprising:

an air source for supplying pressurized air into the convey system, said air source being positioned upstream of the inlet;

a control valve positioned downstream of the air source and upstream of the inlet, said control valve operable to selectively adjust the rate of air flow received from the air source;

a first pressure transducer for sensing a supply pressure, P1, produced by the air source, said first pressure transducer positioned downstream of the air source and upstream of the control valve;

a second pressure transducer for sensing a convey pressure, P2, said second pressure transducer positioned downstream of the inlet and proximate the airlock,

said supply pressure P1 being greater than said convey pressure P2 during conveying operation;

a convey line for receipt and conveying of said particulate therethrough; and

a controller operable to receive first and second signals respectively corresponding to the sensed air pressures for the first and second pressure transducers, said controller operable to selectively control the air source to produce the supply pressure P1 and to control the positioning of the control valve,

wherein a ratio of the convey pressure P2 to the supply pressure P1 is greater than or equal to 90%, such that the rate of air flow through the control valve is non-critical.

2. The convey system of claim 1, wherein the rate of air flow is a function of P1, P2, and the control valve position according to the following equation:

3. The convey system of claim 1, wherein a ratio of the supply pressure P1 to the convey pressure P2 is less than 1.25:

1, such that the rate of air flow through the control valve is non-critical.

4. The convey system of claim 3, wherein a ratio of the supply pressure P1 to the convey pressure P2 is less than 1.1:

1.

5. The convey system of claim 2, wherein the supply pressure P1 varies during the conveying operation by less than ±

1%, and the supply pressure P1 is not held constant.

6. The convey system of claim 1, wherein a difference in the convey pressure P2 and the supply pressure P1 is 1-2 psi.

7. The convey system 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.

8. A method of employing a non-critical air flow control system in a low pressure continuous dense phase convey system having an air source for supplying pressurized air into a convey line of the convey system, an inlet for introduction of pressurized air into the system, and an airlock associated with a feedpoint for introduction of particulate into the system, said pressurized air flowing through the system from an upstream position and to a downstream position, said control valve interposed between said air source and said inlet, said method comprising the steps of:

determining a desired rate of air flow for the convey system based on a volume of particulate to be conveyed, a desired convey velocity, a length of the convey line, and a calculated air leakage through the airlock;

determining a range of operating values for a supply pressure P1 produced by the air source and a convey pressure P2 proximate the airlock;

coupling the control valve with a flow meter to measure a rate of air flow exiting the control valve;

iteratively measuring the rate of air flow for each of the operating values in the determined range;

calculating a best fit error of a predicted air flow versus the measured air flow;

minimizing the error by adjusting the constants x and y in a non-critical rate of air flow equation;

9. The method of claim 8, wherein a ratio of the supply pressure P1 to the convey pressure P2 is less than 1.25:

1, such that the rate of air flow through the control valve is non-critical.

10. The method of claim 9, wherein a ratio of the supply pressure P1 to the convey pressure P2 is less than 1.1:

1.

11. The method of claim 8, wherein the supply pressure P1 varies during the conveying operation by less than ±

1%, and the supply pressure P1 is not held constant.

12. The method of claim 8, wherein a difference in the convey pressure P2 and the supply pressure P1 is 1-2 psi.

13. 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;

14. The method of claim 13, wherein a ratio of the supply pressure P1 to the convey pressure P2 is less than 1.25:

1, such that the rate of air flow through the control valve is non-critical.

15. The method of claim 14, wherein a ratio of the supply pressure P1 to the convey pressure P2 is less than 1.1:

1.

16. The method of claim 14, wherein the supply pressure P1 varies during the conveying operation by less than ±

1%, and the supply pressure P1 is not held constant.

17. The method of claim 14, wherein a difference in the convey pressure P2 and the supply pressure P1 is 1-2 psi.

18. The method of claim 13, 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.