CN100434852C - Method for condensing steam drained by steam turbine into water - Google Patents

Abstract

The present invention discloses a method for condensing steam discharged by a steam turbine into water, which is characterized in that the method comprises the following step: a condenser is formed by four expansible nozzles and a condensing water tank, wherein the four expansible nozzles are connected up and down in a mode of contraction, expansion, contraction and expansion; a heat exchanger is respectively arranged in the three lower nozzles arranged in a mode of expansion, contraction and expansion; the condenser is composed of a main cooling section and a secondary cooling section; the ratio between the sectional area of the outlet of the first nozzle and the sectional area of a steam inlet is 0.3; the discharged steam of which the discharge pressure of the steam turbine in a power plant is from 4.5KPa to 5.5KPa and the discharge speed is 95-100m/s is introduced into the inlet of the condenser; the heat exchanger arranged at the cooling section can cool 1/3-1/2 of the steam from an accelerating section. The method of the present invention can greatly save the heat exchanging area and the cooling water, and simultaneously, the operation is reliable and stable.

Description

A kind of method of condensing steam drained by steam turbine into water

Technical field

The present invention relates to the method that a kind of steam that utilizes the stream-liquid two-phase flow shock wave that steam turbine is discharged condenses into water.

Background technology

The steam of in power plant steam turbine being discharged condenses into water, the vacuum in vacuum plant is kept turbine discharge cylinder and condenser, and the make-up water of condensate water recovery as boiler.Finish with a kind of plant condenser.But the method that condenses into water with the steam that present plant condenser is discharged steam turbine is, cooling water is walked in managing, and steam condenses outside pipe, and steam is to condense waiting to depress.This method has following shortcoming, and (1) bulky heat exchange efficiency is low; (2) it is very big influenced by incoagulable gas; (3) fouling and corrosion problems are arranged; (4) need the big water gaging of consumption.

Summary of the invention

The objective of the invention is provides a kind of steam that utilizes the stream-liquid two-phase flow shock wave that steam turbine is discharged to condense into the method for water in order to overcome the shortcoming that used condenser is discharged steam turbine in the existing power plant steam condenses into the method for water.

Technical scheme of the present invention is: a kind of method of condensing steam drained by steam turbine into water is characterized in that method step is:

1, sets up to connect up and down with condensate tank and constitute a condenser by contracting noz(zle), divergent nozzle, contracting noz(zle), these four nozzles of divergent nozzle, be equipped with heat exchanger respectively in divergent nozzle below, contracting noz(zle), these three nozzles of divergent nozzle, condenser is made up of main cooling section, inferior cooling section, and the ratio of the sectional area that makes the 1st contracting noz(zle) exit and the sectional area at steam inlet place is 0.3;

2, be 4.5-5.5KPa with the power plant steam turbine pressure at expulsion, velocity of exhaust is that the steam discharge of 95-100m/s is introduced the condenser inlet;

3, the heat exchanger in main cooling section setting makes the next cold 1/3-1/2 of falling of steam of the 1st contracting noz(zle).

Operation principle of the present invention is:

Because is the power plant steam turbine pressure at expulsion 4.5-5.5KPa, velocity of exhaust is that the steam discharge of 95-100m/s is incorporated into by four scaling type nozzles and constitutes, comprise the condenser inlet that main cooling section and time cooling section are formed, steam in the main cooling section 1/3-1/2 that is cooled, make part steam condense, will reduce at place, the 2nd jet area pressure like this, form certain vacuum, under this vacuum pressure effect, make steam at the 1st nozzle, can quicken in the passage of the 2nd nozzle, enhancing along with the intensity of main cooling section cooling, the 1st nozzle, the flow velocity of water vapour vapour-liquid two-phase can improve constantly in the passage of the 2nd nozzle, finally reach velocity of sound, reach supersonic speed at place, the 2nd jet area then at place, the 1st jet area.At this moment shrink the back through the 3rd nozzle and produce the stream-liquid two-phase flow shock wave at place, the 3rd jet area.Vapor stream has been improved pressure by violent compression behind the shock wave, thereby shortens vapour pressure into water.At this moment saturation temperature and saturation pressure all raise.Inferior cooling section is responsible for that steam is compressed into the heat that water discharges and is taken away.Can save heat exchange area and cooling water in a large number with the method for the invention, its operation simultaneously is also reliable and stable.

Description of drawings

Fig. 1 is the used condenser structure principle chart of this method.

The specific embodiment:

By shown in Figure 1, a kind of method of condensing steam drained by steam turbine into water is characterized in, method step is:

1, foundation is by the a-b contracting noz(zle), the b-c divergent nozzle, the c-d contracting noz(zle), these four nozzles of d-e divergent nozzle connect up and down with condensate tank and constitute a condenser, at the b-c divergent nozzle, the c-d contracting noz(zle), be equipped with heat exchanger 1 respectively in these 3 nozzles of d-e divergent nozzle, 2,3, condenser is by main cooling section f-g, inferior cooling section d-e forms, described main cooling section f-g is made of the part of b-c divergent nozzle and the part of c-d contracting noz(zle), inferior cooling section d-e is made of the d-e divergent nozzle, and the ratio of the sectional area A2 that makes a-b contracting noz(zle) outlet b place and the sectional area A1 at steam inlet a place is 0.3;

2, be 4.5-5.5KPa with the power plant steam turbine pressure at expulsion, velocity of exhaust is that the steam discharge of 95-100m/s is introduced the condenser inlet;

3, the heat exchanger in main cooling section setting makes the next steam of a-b contracting noz(zle) cool away 1/3-1.

For characteristics of the present invention are described, this method is done following analysis:

Basic energy spectrometer

When this device can (about 100m/s) with the inlet velocity of steam and cool off the kinetic energy that is produced and be used, make it change the pressure energy into, and utilize this part pressure to compress to make steam be transformed into water to steam, and present conventional condenser this part can all be wasted, in theory about 100m/s, the quality steam quality is that 90% water vapour two phase flow kinetic energy all is converted into pressure condensing pressure is increased approximately $500\mathrm{Kpa}(P=\frac{1}{2}{\mathrm{\ρ}}_m{u}_m^2)$ This will improve condensation efficiency greatly.

Efficiency analysis

By shown in Figure 1, A ₁Be the sectional area at steam inlet a place, A ₂For the sectional area at accelerating sections outlet b place, when the water vapour two-phase flow velocity at steam inlet a place is the 100m/s left and right sides,

Be 0.3 o'clock, cross section b place vapor stream promptly can reach local velocity of sound, and c place in cross section promptly can reach supersonic speed.The amount of cooling water of main cooling section f-g will satisfy the pressure reduction that this operating mode is provided, and this pressure reduction is local resistance and the on-way resistance that is used for overcoming from cross section a to cross section c.Theory analysis shows, can satisfy above-mentioned condition as long as make incoming flow steam cool away 1/3～1/2 at f-g master's cooling section.At this moment be the supersonic speed stream-liquid two-phase flow at cross section c place, behind cross section d place shock wave, water vapour two phase flow pressure will be brought up to the pressure at 1.5～2 times a place, steam inlet cross section at least, and its saturation temperature improves about 7～12 ℃.This is favourable to condensing of steam aspect two, and higher pressure can make part steam be compressed into water on the one hand; The raising of saturation temperature can make heat transfer temperature difference increase on the other hand, improves the heat transfer efficiency of time cooling section.

The characteristic of the energy-conservation and economical with materials of following surface analysis this method:

(1) at main cooling section f-g, owing to only cooled off 1/3～1/2 of incoming flow steam flow, so heat exchange area is certainly less than 1/3～1/2, and reason is that do not condense when beginning to cool down liquid film or the liquid film that condenses of steam is thinner.

(2) at inferior cooling section, owing to improved adiabatic condensation temperature, so heat transfer temperature difference increases, conservative estimation can reach heat transfer temperature difference can increase 7～12 ℃, this is compared with the condenser of routine and can reduce time cooling section heat exchange area about 50%, simultaneously because the raising of saturation pressure also can shorten the part vapour pressure into water.

(3) water (water the water vapour two phase flow) that flows into from main cooling section f-g has lower temperature (saturation temperature is low), liberated heat when steam condenses also can absorb shock wave after by the shock wave of cross section d after (saturation temperature is higher herein, exceeds about 7～12 ℃ than cross section d place).This effect can further reduce heat exchange area herein.

(4) owing to adiabatic condensation temperature behind the shock wave is higher, therefore the heat that absorbs from economizer also can reduce.

From top two, only material is one, and the present invention can save 25%～30%, 300MW generating set of condenser heat exchange area at least, its condensing is thought highly of about 400 tons, utilize the present invention only 1 condenser of material just can save more than 100 ton of heat exchange material (being generally copper or stainless steel).

Because the raising of heat exchange efficiency, corresponding circulating water flow also can reduce, and estimates to reduce at least about 25%, and this is energy-conservation beneficial to circulation, can reduce as the circulating water pipe caliber, and water circulating pump can reduce etc.

Service behaviour is analyzed

Owing to reach velocity of sound at throat's b place vapor stream, so its flow and pressure are definite value, the variation of downstream, b cross section parameter can not passed to the upstream, and this will make the duty of condenser highly stable.This device can adopt at present the type of cooling of condenser usually in the type of cooling of main cooling section f-g and time cooling section g-e.

Above said content only is the basic explanation of the present invention under conceiving, and according to any equivalent transformation that technical scheme of the present invention is done, all should belong to protection scope of the present invention.

Claims (1)

1, a kind of method of condensing steam drained by steam turbine into water is characterized in, method step is:

(1) sets up by the a-b contracting noz(zle), the b-c divergent nozzle, the c-d contracting noz(zle), these four nozzles of d-e divergent nozzle connect the condenser that constitutes with condensate tank up and down, at the b-c divergent nozzle, the c-d contracting noz(zle), be equipped with heat exchanger (1 respectively in 3 nozzles of d-e divergent nozzle, 2,3), condenser is by main cooling section (f-g), inferior cooling section (d-e) is formed, described main cooling section (f-g) is made of the part of b-c divergent nozzle and the part of c-d contracting noz(zle), inferior cooling section (d-e) is made of the d-e divergent nozzle, and to make the ratio of the sectional area A1 that sectional area A2 that a-b contracting noz(zle) outlet (b) locates and steam inlet (a) locate be 0.3;

(2) be 4.5-5.5KPa with the power plant steam turbine pressure at expulsion, velocity of exhaust is that the steam discharge of 95-100m/s is introduced the condenser inlet;

(3) heat exchanger in main cooling section setting makes the next steam of a-b contracting noz(zle) cool away 1/3-1/2.

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