US20150322959A1

US20150322959A1 - Turbo machine and method for the operation thereof

Info

Publication number: US20150322959A1
Application number: US14/422,392
Authority: US
Inventors: Ludger Alfes
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2012-09-06
Filing date: 2013-07-25
Publication date: 2015-11-12
Also published as: CN104603467B; RU2015112106A; IN2015DN00715A; EP2864643A1; RU2623323C2; CN104603467A; WO2014037149A1

Abstract

A turbo machine, particularly a turbo compressor, including at least one rotor, which extends along an axis, at least one gas seal, which uses a seal gas to seal a gap between the rotor and a stator of the turbo machine, and a processing module, which processes process fluid taken from the high-pressure position at a tapping into seal gas, which seal gas is fed to the gas seal is provided. To reduce the investment costs for processing the seal gas for the gas seal, a control valve is provided in a first pipe of the turbo machine, the turbo machine has a control unit and a sensor in a second pipe for the seal gas between the processing module and the gas seal, and the control unit is designed such that the control valve controls the pressure or the mass flow or the volume flow measured by the sensor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT Application No. PCT/EP2013/065685, having a filing date of Jul. 25, 2013, based on DE 102012215823.5 having a filing date of Sep. 6, 2012, the entire contents of which are hereby incorporated by reference.

FIELD OF TECHNOLOGY

The following relates to a turbomachine, in particular a turbocompressor, comprising at least one rotor which extends along an axis, comprising at least one axial high-pressure position, at least one axial low-pressure position, wherein, when the turbomachine is in operation, the pressure of a process fluid is higher at the high-pressure position than at the low-pressure position, at least one gas seal which seals, by means of seal gas, a gap between the rotor and a stator of the turbomachine, a preparation module which prepares process fluid, extracted from the high-pressure position at an extraction point, to give seal gas, which seal gas is supplied to the gas seal. The following further relates to a method for operating the turbomachine.

BACKGROUND

Turbomachines, in particular turbocompressors for combustible and/or toxic gases, are frequently sealed with dry gas seals, in particular dry gas seals. The seal gas for these gas seals is generally extracted from the pressure connection of the compressor, prepared, reduced in pressure and supplied to the gas seals. In the case of very high-pressure compressors with dry gas seals, it is difficult to acquire components for the function preparation (liquid separation, filtering, heating, pressure control). Furthermore, these components are very expensive.
Proceeding from the turbomachine mentioned in the introduction, embodiments of the invention reduce the investment cost for the preparation of the seal gas for the gas seal.

SUMMARY

Indications of direction, such as axial, radial, tangential or circumferential direction, always refer unless otherwise stated to the axis of the rotor of the turbomachine.
The preparation module comprises a substantial part of the seal gas preparation from the process fluid to the seal gas. This includes at least the liquid separation or the filtering or the heating or the pressure control of the seal gas. By virtue of the arrangement, according to embodiments of the invention, of the preparation downstream of the control valve, the components of the preparation module can be configured for a lower pressure and are, for that reason at least, more cost-effective. In the case of particularly high compressor pressures, it is thus possible to eliminate acquisition problems for these components of the preparation module and to avoid special production runs therefor. This results in lower costs, a greater choice of suppliers and shorter supply times. An additional positive effect is that the risk potential is significantly reduced on account of the lower pressure in the preparation module, which plays an important role in the case of combustible or toxic gases and also with respect to costs.
Particularly expedient is the use of embodiments of the invention for a compressor, in particular a high-pressure compressor for pressures above 100 bar.
Particularly expediently, the sensor measures either the pressure behind the preparation module or a pressure difference across a throttle, such that the mass flow rate or volume flow rate of seal gas toward the gas seal is reliably controlled. Expediently, downstream of the control valve is a discharge line at a lower pressure, which can for example be shut off by a safety valve if, as a consequence of the pressure control or pressure difference control malfunctioning, the possibly toxic or combustible process fluid in the line downstream of the control valve exceeds the maximum permitted pressure and thereby risks escaping into the surroundings of the turbomachine. This low pressure can for example be the discharge line leading to a flare where the process fluid if combustible is flared off
Particularly expediently, the control unit comprises a pressure difference transmitter which controls a pressure difference, between the pressure of the extraction point of the process fluid and the pressure of the seal gas downstream of the preparation module, to a setpoint value. This setpoint value can be a setpoint value which is predefined instantaneously by a superordinate controller and which is dependent on the current operating conditions of the turbomachine.
The turbomachine preferably has a balancing piston, i.e. a gradation in the rotor R which ensures, by means of a shaft seal, that the pressures acting on the two sides of the gradation balance or reduce as far as possible the thrust of the turbomachine in rated operation. Furthermore, the chamber of the balancing piston is connected to the suction side of the turbomachine and thus the sealing pressures of the gas seals on the suction side and the pressure side are near identical. The pressure in the chamber of the balancing piston is only slightly higher, owing to the flow losses, than the pressure on the suction side and is therefore used as impulse pressure for the control. The process fluid extracted for seal gas via the extraction point at the high-pressure position can preferably be extracted at the pressure connection of the turbomachine in the region of this balancing piston and, according to embodiments of the invention, be supplied to the preparation module via the control valve. The invention is described in more detail below with reference to an exemplary embodiment and with reference to a drawing.

BRIEF DESCRIPTION

Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:
FIG. 1 shows a schematic flow diagram representation of the turbomachine or method.

DETAILED DESCRIPTION

FIG. 1 shows a schematic representation of the turbomachine TM or method according to embodiments of the invention as a flow diagram. The turbomachine TM in the exemplary embodiment is designed as a turbocompressor CO with a rotor R which extends along an axis X. Along the axis X, the turbocompressor CO has a high-pressure position HPS and a low-pressure position LPS at which, during operation, a process fluid PF in the flow path of the turbomachine TM is, respectively, at a higher or a lower pressure. A gap GP (not shown in more detail) between the stator CAS and the rotor R of the turbomachine TM is sealed on both sides of the turbomachine by means of gas seals DGS. The turbomachine TM, or the stator CAS which is formed as a casing, has an inlet INL and an outlet OTL, wherein a process fluid PF enters the turbomachine for compression through the inlet INL and is conveyed to the outlet OTL where it leaves the turbomachine at a higher pressure. An extraction point EX for the process fluid PF is provided at the outlet OTL, which process fluid PF is guided from this axial high-pressure position HPS to a control valve CV by means of a line PIP1 of the turbomachine TM. At the control valve CV, the pressure of the process fluid PF is lowered and the process fluid is supplied to a preparation module SGM for preparing the process fluid PF to give seal gas SG. From the preparation module SGM, the seal gas SG is supplied to the gas seals DGS by means of a second pipe PIP2. A control unit CU controls the position of the control valve CV such that the extraction pressure is lowered sufficiently that the desired seal gas pressure SG prevails at the gas seals DGS. To that end, the control unit CU has a pressure difference transmitter DPT which, as sensor SEN, compares the pressure downstream of the preparation module SGM with the pressure at a balancing piston BP of the turbomachine TM and, as a function thereof, controls the pressure of the seal gas SG upstream of the gas seals DGS by driving the control valve CV. Orifice plates TH, at which a pressure difference drops, are provided in the second line PIP2 and the respective supply to the gas seals DGS. The pressure of the seal gas SG is preferably set by means of the control valve CV such that the pressure drop across the orifice plates TH and across the chamber of the balancing piston BP becomes constant at a certain setpoint value.
In the event of the control valve CV malfunctioning, the situation of the control valve CV being fully open can arise. As a result, much more process fluid PF would flow in the direction of the preparation module SGM and the orifice plates TH and thus, on account of the resistance profile of the preparation module SGM and of the orifice plates TH, substantially increase the pressure upstream of the gas seals DGS, which can lead to the design pressure being exceeded. In order to guard against this malfunction, a safety valve SV, which opens at a start-to-leak pressure, is provided downstream of the control valve CV. The start-to-leak pressure is slightly above the maximum operational pressure downstream of the control valve CV. The components of the pipes PIP1, PIP2, the preparation module SGM, the control valve CV and the orifice plates TH are as a minimum configured for this start-to-leak pressure of the safety valve SV.
Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.
For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements. The mention of a “unit” or a “module” does not preclude the use of more than one unit or module.

Claims

1. A turbomachine comprising

at least one rotor that extends along an axis;

at least one axial high-pressure position along a flow path of a process fluid through the turbomachine;

at least one axial low-pressure position along the flow path of the process fluid through the turbomachine, wherein, when the turbomachine is in operation, a pressure of the process fluid is higher at the at least one axial high-pressure position than at the at least one axial low-pressure position;

at least one gas seal which seals, by means of a seal gas, a gap between the at least one rotor and a stator of the turbomachine;

a preparation module that prepares the process fluid, extracted from the at least one axial high-pressure position at an extraction point, to give the seal gas, the seal gas being supplied to the at least one gas seal wherein a control valve is provided in a first line of the turbomachine that guides the process fluid from the at least one axial high-pressure position to the preparation module; and

a control unit that drives the control valve;

wherein the turbomachine has, in a second line for the seal gas between the preparation module and the at least one gas seal, a sensor that determines at least one of a pressure, a mass flow rate, and a volume flow rate of the seal gas between the preparation module and the at least one gas seal;

wherein the control unit is designed such that the control valve controls at least one of the pressure, the mass flow rate, and the volume flow rate measured by the sensor.

2. The turbomachine as claimed in claim 1, wherein the turbomachine is a compressor.

3. The turbomachine as claimed in claim 1, wherein the sensor is designed as a pressure difference measurement and measures the pressure difference between a position at a balancing piston of the turbomachine and a seal gas pressure downstream of the preparation module and forwards the pressure difference value to the control unit.

4. The turbomachine as claimed in claim 3, wherein the control unit controls the pressure difference, measured by the sensor, to a setpoint value by means of the control valve.

5. A method for operating a turbomachine as claimed in claim 1, wherein the process fluid is extracted at the extraction point at the at least one axial high-pressure position along the flow path through the turbomachine;

the extracted process fluid is supplied to the preparation module;

the preparation module prepares the extracted process fluid to give the seal gas by liquid separation, filtering, heating and/or pressure matching;

the seal gas is supplied to the at least one gas seal of the turbomachine, wherein the at least one axial low-pressure position along the flow path of the process fluid through the turbomachine is provided, wherein, when the turbomachine is in operation, the pressure of the process fluid is higher at the at least one axial high-pressure position than at the at least one axial low-pressure position, wherein in the first line of the turbomachine which guides the process fluid from the high-pressure position to the preparation module, the process fluid is throttled by means of the control valve;

the control unit of the turbomachine drives the control valve;

the seal gas is guided from the preparation module to the at least one gas seal by means of the second line;

at least one of the pressure the mass flow rate, and the volume flow rate in the second line is determined using a sensor; and

by driving the control valve, the control unit controls at least one of the pressure, the mass flow rate, and the volume flow rate measured by the sensor.