RU2572656C2 - Steam system - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: set of inventions relates to the steam system to be used in production of olefins. The steam system comprises low-pressure feed water degasifier (16). Its working pressure first level (P1) is higher than barometric pressure P1>1 bar. The working pressure of the system low-pressure steam line (22) features the second pressure level (P2). Note here that the second pressure level is higher than the first one P2>P1. The steam system comprises also high-pressure steam line (38) with working pressure featuring the third pressure level P3. Note here that the third pressure level is higher than the second one P3>P2. Claimed system comprises between the high pressure steam line (38) and the degasifier (16) at least one steam turbine (40) to expand the steam of the high pressure steam line (38) from (P3) to (P1).

EFFECT: higher power use efficiency subject to pressure differences, lower power consumption.

11 cl, 2 dwg

Description

The invention relates to a steam system, in particular to a steam system for use in plants for the production of olefins.

In a plant for the production of olefins, the latter (or alkenes, in particular ethylene or propylene) are obtained in a reaction furnace from saturated hydrocarbons. In such installations for heating / incandescent / evaporation or cooling of process streams, a plurality of heat exchangers are provided. Steam systems are well established as a favorable network for using the residual heat generated in the process.

A fragment of a conventional steam system in a very simplified form is depicted in figure 2. Through the feed pipe 10, the demineralized and condensation water of the steam system is supplied and heated in two heaters 12 and 14 before this feed water enters the degasser 16. In this degasser 16, the feed water continues to be heated to boiling point and is distilled off with steam to remove dissolved gases in this water, for example, in particular oxygen. Feed water degassed in this way is pumped 18 through a pipe 20 from a degasser 16 to a steam generator (not shown).

In addition, the steam system comprises a low pressure steam line 22 with an operating pressure of, for example, 6.5 bar and an operating temperature of, for example, 240 ° C., connected to the aforementioned steam generator via control valves and / or turbines. Water vapor in this low pressure steam line 22 is supplied to one or more process consumers 24. Condensation water generated by the process consumers 24 is supplied to a condensate collector 26, from which it is discharged through a pipe 30 through a pump 28. The condensation water generated in the first heater 12 is also supplied to this condensate collector 26.

The second heater 14, the degasser 16 and the condensate collector 26 need a coolant, which also uses steam from the steam system. Since these components 14, 16, 26 are operated with steam with an operating pressure of only about 1.5 bar, the pressure level of water vapor in the low pressure steam pipe 22 has to be reduced from about 6.5 bar to a pressure level of about 1.5 bar. To this end, in the respective connecting pipes between the low pressure steam pipe 22 and the components 14, 16, 26, several valves 32, 34, 36 are usually provided in which the water vapor is vented to a desired lower pressure level.

In addition, the steam system comprises a high pressure steam line (not shown in FIG. 2) with a working pressure of, for example, about 45 bar. Several turbines are usually included between this high pressure steam line and the low pressure steam line, for example, for pumps expanding the steam from a pressure level of about 45 bar to a pressure level of about 6.5 bar. Then the steam, expanded to a pressure level of about 6.5 bar, is usually supplied to process consumers or continues to be vented through valves 32-36. In addition, the steam of the low pressure steam line is usually communicated with external sources / receivers.

An object of the present invention is to provide an improved steam system.

This problem is solved using a steam system with the features of paragraph 1 of the claims. Preferred and improved embodiments are the subject of the dependent claims.

The steam system according to the invention comprises a low-pressure degasser for degassing feed water, wherein the operating pressure of the low-pressure degasser at a first pressure level is higher than atmospheric pressure; a low pressure steam line, the working pressure of which is at the second pressure level, the second pressure level being higher than the first pressure level, and a high pressure steam line, whose working pressure is at the third pressure level, the third pressure level being higher than the second pressure level. In addition, at least one steam turbine is provided between the high pressure steam line and the low pressure degasser to bleed the steam from the high pressure steam line from the third pressure level to the first pressure level.

While in the conventional steam system of FIG. 2, several steam turbines are provided for bleeding steam from a third pressure level in a high pressure steam line to a second pressure level in a low pressure steam line, at least one steam is installed and made in the steam system according to the invention turbine for direct expansion of steam from a third pressure level in a high pressure steam line to a first pressure level. As a result of a greater pressure drop between the third and first pressure levels compared to the difference between the third and second pressure levels and, consequently, as a result of less back pressure of the steam turbine (steam turbines), the steam in the steam system can be used more efficiently, and the quantity steam can thus be saved and / or more energy can be released in steam turbines, which can be used for other purposes. Thus, the energy efficiency of the steam system, depending on the magnitude of the pressure drop, can be increased more or less explicitly.

An advantage of the present invention is that steam turbines, already existing in the steam system and used to drive units or machines, are installed in the steam system according to the invention at a lower back pressure, namely at the first pressure level instead of the higher second level, due to which steam turbines consume less energy.

By “degasser” is meant any device that is suitable for removing dissolved gases from the feed water. The gases to be removed include, in particular, oxygen and nitrogen. Various technical means are known for degassing liquids; the degassing process is preferably carried out by supplying gas for heating and evaporation of the feed water. This steam supply in the steam system according to the invention is due to water vapor, vented to the first pressure level, which condenses.

The concept of "feed water" in this regard includes any type of liquid that may find application in the installation as a process stream. Preferably, demineralized water degassed in a degasser before steam production is used as feed water.

"Technological consumer" in the sense of the invention is any device or device to which water vapor from a steam system is supplied as an energy carrier. Preferably, a process consumer may interact with another medium in the form of heat exchange between water vapor and another medium. Preferably, the interaction between the water vapor and the medium, depending on the type of installation in which the steam system is used, can also be direct when the water vapor, for example, is mixed or mixed with another process stream. Preferably, in the process consumer, the energy contained in the steam stream can be converted to another type of energy, such as in turbines.

In this regard, the term “high pressure steam line” should be understood to mean a conductive system for water vapor at a third pressure level. Through the high pressure steam pipeline, water vapor at the third pressure level can be distributed among different components (here, in particular, to technological consumers and steam turbines). Similarly, the term "low pressure steam line" in this regard should generally be understood as a conductive system for water vapor at a second pressure level for distribution to different components of water vapor located at a second pressure level. Both the high pressure steam line and the low pressure steam line usually communicate with external sources / receivers. In this case, the pressure levels of the steam lines are essentially set by these external connections.

A “steam turbine” in this regard is any kind of device that is suitable for converting the difference in vapor enthalpies between two pressure levels into kinetic energy, for example, into rotational energy. This kinetic energy in this case can be driven, for example, by any unit connected to a steam turbine. When energy is converted, water vapor expands, for example, from a higher third pressure level to a lower second pressure level. "At least one" steam turbine means one, or two or more turbines. In the case of two or more turbines, they are preferably connected in parallel, however, they can also be connected in series.

In one preferred embodiment of the invention, at least one process consumer is provided, operated with a working pressure of a first pressure level. In this case, this at least one process consumer is also connected to at least one steam turbine. However, in this embodiment, the process consumers, which with conventional steam systems are supplied from a high or low pressure steam line, can also dispense steam with a lower working pressure and receive water vapor from a steam turbine. Thus, the throughput and productivity of the steam turbine can be further improved, which leads to a further increase in the energy efficiency of the steam system.

Preferably, at least one process consumer, operated with a working pressure of a first pressure level, is also connected to a low pressure steam turbine, preferably through a valve device, which pares the steam from the second pressure level to the first pressure level. Thus, it is possible to ensure that technological consumers, regardless of the amount of steam supplied by the steam turbines, are always supplied with sufficient water vapor. In other words, the need of technological consumers for water vapor, which for some reason cannot be provided by steam turbines with a sufficient amount of water vapor at the first pressure level, is covered by water vapor from the low pressure steam pipeline. In this case, the steam system is preferably made in such a way that the amount of steam vented by the valve device from the second pressure level to the first pressure level is minimized in the normal mode.

In another preferred embodiment, the at least one steam turbine drives an assembly selected from current generators, pumps, compressors and blowers. Thus, it is clearly possible to reduce the energy demand of the entire installation, in particular, the current requirement of the installation to provide the installation with drive energy supplied from the outside. In principle, using the at least one steam turbine of the steam system according to the invention, it is also possible to completely cover the installation demand for drive energy. Preferably, using a turbine (s) used, a current generator can be driven to power various components, for example, olefin production plants.

In yet another preferred embodiment of the invention, at least one heat exchanger is provided for pre-heating the feed water, operated by steam with a working pressure of a first pressure level. In this case, at least one heat exchanger is also preferably connected to at least one steam turbine.

In another preferred embodiment of the invention, at least one condensate collector is provided which is operated with a working pressure of a first pressure level. In this case, at least one condensate collector for heating with a steam turbine a steam expanded to a first pressure level is preferably also connected to at least one steam turbine. Thus, the condensate collector is also a “technological consumer” of the steam system. The condensate collector preferably serves to collect steam condensate downstream of at least one process consumer and / or other process consumers.

In one preferred embodiment of the invention, at least one steam turbine is provided that vents steam from a high pressure steam line from a third pressure level to a pressure level even lower than the first pressure level, preferably to or below ambient pressure. Then this even more expanded steam can be used for at least one heat exchanger for preheating feed water and / or for at least one condensate collector for collecting steam condensate and / or for heating other consumers. Thus, the water vapor in the steam system or the energy contained therein can be used even more efficiently.

In another preferred embodiment of the invention, the low pressure degasser, at least one process consumer, at least one heat exchanger and / or at least one condensate collector are connected via a low pressure steam line, the working pressure of which is at the first pressure level of at least with one steam turbine.

Preferably, the first pressure level is about 1.2 bar, more preferably about 1.3 bar, and a maximum of about 2.0 bar, more preferably a maximum of about 1.75 bar. In another preferred embodiment, the first pressure level is about 1.5 bar.

Preferably, the second pressure level is about 2.0 bar, more preferably about 4.0 bar, even more preferably about 5.0 bar. Preferably, the second pressure level is a maximum of about 12 bar, more preferably a maximum of about 10 bar, even more preferably a maximum of about 8.0 bar. In another preferred embodiment, the second pressure level is about 6.5 bar.

Preferably, the third pressure level is about 15 bar, more preferably about 25 bar, even more preferably about 35 bar. Preferably, the second pressure level is a maximum of about 100 bar, more preferably a maximum of about 75 bar, even more preferably a maximum of about 60 bar. In one preferred embodiment, the second pressure level is about 45 bar.

It goes without saying that the steam system according to the invention may contain other components, as well as other steam lines with different pressure levels.

The above-described steam system according to the present invention can be particularly advantageously used in an olefin production plant. Other preferred uses of the steam system according to the invention are in the petrochemicals, petroleum and chemical industries.

The above, as well as other features, advantages and applications of the invention will become clearer from the following description of one of the preferred examples of the steam system with reference to the accompanying drawings, of which

figure 1 depicts a schematic partial section of a steam system according to an exemplary embodiment of the present invention, and

figure 2 is a schematic partial section of a conventional steam system.

Figure 1 shows a partial section of a steam system, which can be used in the installation for the production of olefins. In this case, the same or corresponding components are denoted by the same reference numbers as in the conventional steam system of FIG. 2.

Demineralized and condensation water from the steam system (collectively referred to as feed water) at a temperature of about 70 ° C is supplied to the steam system through the feed pipe 10 with a capacity of, for example, up to 1000 t / h. After pre-heating in the heaters 12 and 14, the feed water continues to be heated in the low-pressure degasser 16 to the boiling point and is distilled off with steam from the steam system for its degassing, i.e. liberation from gases dissolved in it, such as oxygen and nitrogen. The use of demineralized and degassed water, in particular, serves to protect the components, in particular, from corrosion.

Steam is supplied to the second heater 14 and to the low pressure degasser 16 as a heat carrier for heating the feed water from the steam system, and the working steam pressure in both devices is at the first pressure level P1, for example, 1.5 bar, slightly exceeding atmospheric pressure .

Degassed feed water from the degasser 16 by means of a pump 18 through a pipe 20 is supplied to a steam generator not shown. In this steam generator, demineralized and degassed feed water is converted to superheated steam.

Superheated water vapor with a working pressure of the second pressure level P2 of about 6.5 bar and with a working temperature of about 240 ° C. enters the low pressure steam turbine 22. This low pressure steam turbine 22 distributes water vapor, among other things, between process consumers 24 operated by steam with a working pressure of a maximum of about 6.5 bar. In the case of these process consumers 24, it is mainly a question of heat exchangers. In the example of FIG. 1, water vapor with a pressure level P2 is supplied to process consumers 24 of the order of 25 t / h.

Condensation water generated in process consumers / from process consumers 24 is supplied to a condensate collector 26. Condensation water generated at the first heater 12 is also supplied to this condensate collector 26. Finally, from the condensate collector 26, the condensation water is again fed back to the system via a pipe 30, for example, through a feed pipe 10.

Water condensate from the steam system is also supplied to the condensate collector 26 as a coolant, the working pressure of the steam being at the first pressure level P1 of the order of 1.5 bar. Water vapor from the condensate collector 26 is fed further to the first heater 12 to heat the feed water therein in the feed water conduit 10.

In addition, steam superheated in the steam generator, with a working pressure at the third pressure level P3 of about 45 bar and at a working temperature of about 400 ° C., enters the high pressure steam turbine 38. This high pressure steam turbine 38 supplies superheated steam with several parallel-connected steam turbines 40. In these steam turbines 40, water vapor expands from a third pressure level P3 of about 45 bar to a first pressure level P1 of about 1.5 bar.

In this case, the vapor enthalpy difference corresponding to this pressure difference of about 43.5 bar is converted into kinetic energy, preferably into rotation energy. Then, with the help of this kinetic energy, one / one or several (not shown) units or machines, for example pumps, compressors, blowers, etc., connected to steam turbines 40 are driven. Even a current generator can be driven, which can at least to partially cover the installation’s demand for electricity, so that the installation’s need for external drive energy can be substantially reduced.

The downstream steam turbines 40 are connected to a low pressure steam turbine 42, the operating pressure of which is at a first pressure level of about 1.5 bar. This low pressure steam turbine 42 distributes water vapor among the components described above, the working pressure of which is at a first pressure level in steam. This is, in particular, about the low pressure degasser 16, as well as the second heater 14 and condensate collector 26.

If the installation for the production of olefins also has technological consumers 24 operated with steam with a working pressure of the order of a maximum of 1.5 bar, then these technological consumers 24 can also be supplied with water vapor from the low pressure steam line 42. In this example of FIG. 1, up to about 25 t / hr of water vapor of the first pressure level P1 are supplied to process consumers 24 via the lowest pressure steam line 42.

Since the need for water vapor of the first pressure level P1 cannot always be covered by steam turbines 40, the lowest pressure steam turbine 42 is also connected to the low pressure steam turbine 22, the working pressure of which is at the second pressure level P2, with P3 > P2> P1. In this case, balancing the steam demand is preferably carried out by means of a control valve between the low pressure steam pipe 22 and the lowest pressure steam pipe 42. In this case, the amount of steam vented by the control valve 44 from the second pressure level P2 to the first pressure level P1 is preferably minimized in the normal mode.

In addition, balancing the entire steam system is carried out by regulating the production of steam.

Due to the use of steam turbines 40 a significant pressure difference between the third and first pressure levels, the required amount of steam in the steam system can be reduced or more energy can be converted in steam turbines 40. Thus, the energy efficiency of the steam system and, therefore, the entire plant for the production of olefins can be significantly increased.

In the example of FIG. 1, using steam turbines 40, 86 t / h of water vapor are vented, for example, from a third pressure level of about 45 bar not to a second pressure level P2 of about 6.5 bar, but to a first pressure level P1 of about 1.5 bar. If for steam turbines 40 we assume the same degree of efficiency, for example 60%, then they will need about 48 t / h less water vapor.

In addition, in the exemplary embodiment of FIG. 1, approximately 50 t / h of water vapor are supplied as an example to technological consumers 24, while other components, i.e. A total of 61 t / h of water vapor are supplied to the degasser 16, heater 14 and condensate collector 26 from the lowest pressure steam line 42.

In the above described embodiment, low pressure degasser 16, second heater 14 and condensate collector 26 are respectively supplied with water vapor of the first pressure level P1 of the order of 1.5 bar. If you go to increase the complexity of the steam system, water vapor can be used even more efficiently, for which water vapor for preheating demineralized feed water expands to an even lower pressure level, and the overpressure P1 is used only for the low pressure degasser 16 that needs it .

Claims (11)

1. A steam system including a low-pressure degasser (16) for degassing feed water, the working pressure of which is at the first level (P1) of pressure above atmospheric pressure P1> 1 bar, the low pressure steam line (22), whose working pressure is at the second level (P2) pressure, the second pressure level being higher than the first pressure level P2> P1, and the high pressure steam line (38), the working pressure of which is at the third pressure level (P3), the third pressure level being higher than the second pressure level P3> P2, different those that at least one steam turbine (40) is installed between the high pressure steam pipe (38) and the low pressure degasser (16) to expand the steam from the high pressure steam pipe (38) from the third pressure level (P3) to the first pressure level (P1) . 2. The steam system according to claim 1, characterized in that it contains at least one process consumer (24), operated with a working pressure of the first pressure level (P1) and connected to at least one steam turbine (40). 3. The steam system according to claim 2, characterized in that at least one process consumer (24), operated with a working pressure of the first pressure level (P1), is connected to a low pressure steam line (22). 4. The steam system according to claim 3, characterized in that at least one process consumer (24), operated with a working pressure of the first pressure level (P1), is connected to the low pressure steam pipe (22) via a valve device (44). 5. A steam system according to any one of claims 1 to 4, characterized in that at least one steam turbine (40) is designed to drive an unit selected from the group including a current generator, pump, compressor and blower. 6. A steam system according to any one of claims 1 to 4, characterized in that it comprises at least one steam turbine expanding the steam from the high pressure steam pipe (38) from a third pressure level (P3) to an ambient pressure level or lower. 7. A steam system according to claim 1, characterized in that it comprises at least one heat exchanger (12, 14) for pre-heating the feed water, operated with a working pressure of the first pressure level (P1) and connected to at least one steam turbine (40). 8. A steam system according to claim 1 or 7, characterized in that it comprises at least one condensate collector (26), operated with a working pressure of a first pressure level (P1) and connected to at least one steam turbine (40). 9. A steam system according to any one of claims 1 to 3, 7, characterized in that the low-pressure degasser (16), at least one process consumer (24), at least one heat exchanger (12, 14) and / or at least one condensate collector (26) is connected to at least one steam turbine (40) by means of a steam line (42) of the lowest pressure, the working pressure of which is at the first pressure level (P1). 10. A steam system according to claim 8, characterized in that the low-pressure degasser (16), at least one process consumer (24), at least one heat exchanger (12, 14) and / or at least one collector (26 ) condensate using the steam line (42) of the lowest pressure, the working pressure of which is at the first pressure level (P1), connected to at least one steam turbine (40). 11. Installation for the production of olefins containing a steam system according to any one of claims 1 to 10.

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