Controlling refrigeration compression systems

Patent metadata

Field	Value
Publication number	US-9696074-B2
Application number	US-201414147325-A
Country	US
Kind code	B2
Filing date	Jan 3, 2014
Priority date	Jan 3, 2014
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A refrigerant compression system and method for controlling a refrigerant compression system are described. In some aspects, the refrigerant compression system includes a compressor system having a plurality of compression stages, a plurality of quench valves, a first suction temperature control circuit associated with a first quench valve, a second suction temperature control circuit associated a second quench valve, and a discharge temperature control circuit associated with a plurality of the quench valves. Quench valve settings are determined based on evaluation of one or more outputs from the suction temperature control circuits and the discharge temperature control circuit.

First claim

The invention claimed is:

1. A refrigerant compression system comprising:
a compressor system having a plurality of compression stages;
a first suction temperature control circuit associated with a first quench valve operable to provide an adjustable flow of quench fluid into a first compression stage, the first suction temperature control circuit operable to:
identify a first temperature setpoint and an inlet temperature of the first compression stage; and
determine a first quench flow demand of a quench fluid flow that is injected through the first quench valve into the first compression stage based on the first temperature setpoint and the inlet temperature of the first compression stage;

a second suction temperature control circuit associated with a second quench valve operable to provide an adjustable flow of quench fluid into a second compression stage, the second suction temperature control circuit operable to:
identify a second temperature setpoint and an inlet temperature of the second compression stage; and
determine a second quench flow demand of a quench fluid flow that is injected through the second quench valve into the second compression stage based on the second temperature setpoint and the inlet temperature of the second compression stage;

a discharge temperature control circuit for controlling a discharge temperature at an outlet of the plurality of compression stages, the discharge temperature control circuit operable to:
receive information regarding the discharge temperature at the outlet of the plurality of compression stages and a discharge temperature setpoint; and
determine a third quench flow demand of the quench fluid flow that is injected through the first quench valve into the first compression stage and a fourth quench flow demand of the quench fluid flow that is injected through the second quench valve into the second compression stage such that the discharge temperature at the outlet of the plurality of compression stages is maintained at or below the discharge temperature setpoint; and

a first quench valve controller associated with the first quench valve, the first quench valve controller operable to:
receive the first quench flow demand determined by the first suction temperature control circuit;
receive the third quench flow demand determined by the discharge temperature control circuit; and
determine a valve position demand of the first quench valve based on the first quench flow demand and the third quench flow demand; and

a second quench valve controller associated with the second quench valve, the second quench valve controller operable to:
receive the second quench flow demand determined by the second suction temperature control circuit;
receive the fourth quench flow demand determined by the discharge temperature control circuit; and
determine a valve position demand of the second quench valve based on the second quench flow demand and the fourth quench flow demand.

2. The refrigerant compression system of claim 1 , wherein
the first suction temperature control circuit is operable to:
receive information regarding a first inlet pressure at the first compression stage; and
determine, dynamically, the first temperature setpoint according to a first dew temperature curve based on the first inlet pressure at the first compression stage; and
the second suction temperature control circuit is operable to:
receive information regarding a second inlet pressure at the second compression stage; and
determine, dynamically, the second temperature setpoint according to a second dew temperature curve based on the second inlet pressure at the second compression stage.

3. The refrigerant compression system of claim 2 , wherein
the first suction temperature control circuit is operable to receive a first temperature setpoint margin; and wherein the first temperature setpoint is determined according to the first dew temperature curve based on the first inlet pressure at the first compression stage and the first temperature setpoint margin; and
the second suction temperature control circuit is operable to receive a second temperature setpoint margin; and wherein the second temperature setpoint is determined according to the second dew temperature curve based on the second inlet pressure at the second compression stage and the second temperature setpoint margin.

4. The refrigerant compression system of claim 1 , further comprising:
a first anti-surge valve operable to provide a first recycle fluid flow injected through the first anti-surge valve into the first compression stage;
a second anti-surge valve operable to provide a second recycle fluid flow injected through the second anti-surge valve into the second compression stage; and

wherein the discharge temperature control circuit is operable to:
determine the third quench flow demand based on the first recycle fluid flow injected through the first anti-surge valve into the first compression stage; and
determine the fourth quench flow demand based on the second recycle fluid flow injected through the second anti-surge valve into the second compression stage.

5. The refrigerant compression system of claim 4 , wherein the discharge temperature control circuit comprises a discharge temperature sub-controller operable to:
receive the information regarding the discharge temperature at the outlet of the plurality of compression stages and the discharge temperature setpoint; and
determine a fifth quench flow demand based on the discharge temperature at the outlet of the plurality of compression stages and the discharge temperature setpoint; and
wherein the discharge temperature control circuit is operable to:
compute a first ratio of the first recycle fluid flow injected into the first compression stage to a maximum recycle fluid flow among recycle fluid flows injected into the plurality of compression stages;
determine the third quench flow demand of the first compression stage based on a product of the fifth quench flow demand and the first ratio;
compute a second ratio of the second recycle fluid flow injected into the second compression stage to the maximum recycle fluid flow among recycle fluid flows injected into the plurality of compression stages; and

determine the fourth quench flow demand of the second compression stage based on a product of the fifth quench flow demand and the second ratio.

6. The refrigerant compression system of claim 1 , wherein the discharge temperature control circuit is operable to:
receive a first fudge factor and a second fudge factor;
determine the third quench flow demand of the quench fluid flow based on the first fudge factor; and
determine the fourth quench flow demand based on the second fudge factor.

7. The refrigerant compression system of claim 1 , wherein
the first quench valve controller is operable to:
compare the first quench flow demand determined by the first suction temperature control circuit and the third quench flow demand determined by the discharge temperature control circuit; and

determine the valve position demand of the first quench valve based on a larger quench flow demand as between the first quench flow demand and the third quench flow demand; and
the second quench valve controller is operable to:
compare the second quench flow demand determined by the second suction temperature control circuit and the fourth quench flow demand determined by the discharge temperature control circuit; and
determine the valve position demand of the second quench valve based on a larger quench flow demand as between the second quench flow demand and the fourth quench flow demand.

8. A control method for a refrigeration compression system, the refrigeration compression s

Assignees

• Woodward Inc

Inventors

• Ceccarelli Nicola
• Monge Jean Philippe
• Benim Alex

Classifications

• F25B49/022

  Compressor control arrangements · CPC title

• F25B2700/21151

  at the suction side of the compressor · CPC title

• F25B2700/21152

  at the discharge side of the compressor · CPC title

• F25B2500/08

  Exceeding a certain temperature value in a refrigeration component or cycle · CPC title

• F25B1/10 Primary

  with multi-stage compression (with cascade operation F25B7/00) · CPC title