CN1730915A - Exhaust steam heat energy utilization apparatus for large-scale direct air cooling unit for thermal power generation - Google Patents

Abstract

The exhaust heat energy utilizing device for directly air cooling large thermal power generating units includes air conveying channel, heat exchanger set in the end ports of the air conveying channel, steam turbine exhaust port connected to the heat exchanger, air inlet set in the heat exchanger, expansion tower connected to the air conveying channel, turbine configured to the bottom outlet of the expansion tower, power generator connected to the turbine and air outlet set in the top of the expansion tower. The expansion tower has height of 250-1500 m and diameter of 40.2-63.5. The present invention utilizes the afterheat the air cooling sets exhaust to reach the aims of utilizing energy source and protecting environment. The present invention can increase power generating amount of 3.09-7.94 %.

Description

The device that large electric power plant Direct Air-cooled Unit exhaust steam heat energy utilizes

Technical field

The present invention relates to heat energy and electric energy switch technology, the device that particularly a kind of large electric power plant Direct Air-cooled Unit exhaust steam heat energy utilizes.

Background technique

Steam turbine exhaust steam cooling is the important constituent element of thermal power plant's power generation process: how cooling off exhaust steam and reclaim working medium, how to manufacture and design the effective heat exchange device, how to utilize low steam heat release of sampling, is one of key problem that is related to thermal power plant's safety and economic operation.In today of energy shortage, shortage of water resources, address this problem extremely urgent.

The conventional method of thermal power plant's cooling steam is clammy mode: steam turbine exhaust steam and cooling water are not in contact with heat exchange in the cooling tower mutually, form condensed water and recycle, and the cooling water after the heat exchange forms moisture discharge in atmosphere.The advantage of clammy mode is: the coefficient of heat transfer of water is very big, and cooling effect is good, and steam turbine discharges the exhaust steam temperature near atmospheric temperature, the efficiency of thermal cycle value of reaching capacity, and the heat of exhaust steam does not almost have value; Its significant disadvantages is to expend a large amount of cooling waters.Northern China has the abundant in coal resource, but the water resources famine, so the thought of traditional planning construction thermal power plant " fixed with water " has seriously hindered the development of electric power stations near coal-mines.

In order to reduce the consumption of water resources in the thermal power generation, Air cooling technique is developed.Air cooling technique utilizes the cooling working medium of air as the steam turbine exhaust steam, and is corresponding with clammy mode, is called dry and cold mode again.Air cooling system is divided into direct air cooling mode and indirect air cooling mode, mainly contains following three kinds:

1, direct air cooling system

Direct air cooling system is meant that the steam discharge of steam turbine directly cools off with air, and required cooling air is supplied by the mechanical ventilation mode usually, and cooling air and exhaust steam are not in contact with heat exchange in the heat exchanger mutually.The steam turbine steam discharge is delivered in the air condenser by thick blow-off line, and the axial flow cooling blower makes air flow through the radiator outer surface, and steam discharge is condensed into water, and water of condensation is in the heat regenerative system through the pumped back steam turbine.Direct air cooling system is general and the high back pressure steam turbine is supporting.

2, Hai Leshi indirect air cooling system

In the Hai Leshi indirect air cooling system, highly purified neutral cooling water enters directly that condenser mixes with turbine discharge and with its condensation, the cooling water overwhelming majority after being heated is delivered to the air cooling tower radiator by cooling water circulating pump, through with the cross-ventilation heat exchange after by the pressure regulation water turbine cooling water is delivered to jet condenser again and enters next circulation, few part of the recirculated cooling water that is heated is delivered to Steam Turbine Regenerative System after the polishing unit that condenses is handled.This system can be supporting with middle back pressure turbine.

3, Harmon formula indirect air cooling system

This system grows up on Hai Leshi indirect air cooling system basis.It is made up of surface condenser and air cooling tower, and is similar with the humid-cool system of routine, just replaces clammy tower with air cooling tower, locates salt solution and replaces circulating water, and Enclosed Type Circulating Cooling Water System replaces the open type recirculating cooling water system.Harmon formula indirect air cooling system need not be applied to large-scale unit to the cooling water precision processing.

Air cooling system has obvious effects for reducing cooling-water consumption.But the cooling capacity of air is far below water, drives air cooling system and expends a large amount of station services, and make that the exhaust temperature of steam turbine is higher, and is high 20～30 ℃ when clammy approximately.From the thermodynamic cycle angle, this part heat energy still has certain value, moreover large electric power plant set waste-heat discharge amount is very big, for example, the waste heat discharge power of 600MW unit is about 900MW, and the no one pays close attention to the recycling of this part heat all the time, directly is discharged in the atmosphere usually, both cause energy huge waste, again environment had been caused serious thermo-pollution.

Summary of the invention

Defective and deficiency at above-mentioned prior art exists the objective of the invention is to, the device that provides a kind of large electric power plant Direct Air-cooled Unit exhaust steam heat energy to utilize, and the used heat that utilizes Air-cooled Unit to discharge reaches the purpose of utilizing the energy and protection environment.

Technical solution of the present invention is achieved in that and the present invention includes air delivery passage, the port of air delivery passage is provided with heat exchanger, connect the turbine discharge outlet on the heat exchanger, heat exchanger is provided with air intlet, air delivery passage connects expanding tower, the bottom inlet place configuration turbine of expanding tower, turbine connects and is connected with generator, and the expanding tower top is provided with air outlet slit.

Air intlet is shaped as gradual shrinkage, and air intlet is arranged on heat exchanger or even layout the, perhaps density inequality.

Air outlet slit is the rotatable gradual shrinkage mouth of pipe.

Described expanding tower height is 250～1500m, and diameter is 40.2～63.5m.

The expanding tower construction material is high thermal resistance, conventional structural material: reinforcing bar, cement and concrete.The import of heat exchanger ambient air is a gradual shrinkage, and quantity is some, and as 8, inlet can evenly distribute, also can according to the locality all the year round the wind direction result arrange: the more time for the direction of facining the wind on the air intlets of arranging more, leeward direction is arranged less.The direction import of facining the wind is opened, and leeward direction is closed.But the air outlet slit on expanding tower top is the rotation of gradual shrinkage box haul, and air is discharged from the leeward direction of expanding tower.

Hot air after the heat exchange of the present invention is introduced expanding tower by pipeline, can save the air driven blower fan, under the natural ventilation condition, air velocity is lower, cooling effect is more than the forced ventilation weak effect, in order to reach same air cooling effect, the heat exchange area under the natural ventilation condition will increase greatly.Driving power of fan under the forced ventilation condition is very big, so power consumption is very big." pull out force " that the present invention utilizes expanding tower that heated air is produced is used for replacing the driving of blower fan, need not blower fan under the natural ventilation condition, also just do not need consumption of electric power just can reach cooling effect under the forced ventilation condition.

Hot air after the heat exchange of the present invention rises with certain speed in expanding tower, can generate electricity, realization used heat utilizes, expanding tower acts on except substituting blower fan " pull out force " of hot air, can also make thermal air current promote the turbine power generation of expanding tower ingress with the speed of 10～25m/s, this makes and causes that never a large amount of tow taste heats that people pay attention to have obtained utilization under the clammy and air cooling mode.Though the present invention utilizes used heat efficient very low, theoretical utilization ratio has only 0.85～5.08%, because the waste heat discharge amount that exhaust steam is carried is very huge, so total revenue still is appreciable.For example, the 600MW generatine set heat efficiency is about 40%, and discharging used heat power is about 900MW, adopt the present invention, saving blower fan power consumption and electricity amount summation is 18.55～47.64MW, accounts for 3.09～7.94% of total generated energy, and the Spring Festival holidays are economized standard coal 11500.0～29430.1t.

The open direction of facining the wind of the present invention, the air intlet of closing leeward direction are gradual shrinkage, can utilize the low latitude wind energy more, improve the initial velocity of air, the forced heat exchanging effect.Arrange rotary gradual shrinkage air outlet slit on the expanding tower top, air outlet slit direction box haul changes and rotates, and air flows to the back pressure district of expanding tower along wind direction, has reduced the air outlet slit resistance, thereby has utilized high altitude wind energy.The utilization of low latitude high altitude wind energy has been equivalent to improve the height of expanding tower, thereby has improved the utilization ratio of used heat.

Expanding tower is built by the common building material of high thermal resistance, high temperature air after being heated flows therein, expanding tower is equivalent to a high temperature heat source, can be in environment heat discharge, be discharged into the high-altitude at the most, avoid air cooling and the clammy problem that all thermal power plant's surrounding environment is caused thermo-pollution, improved the quality of air.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 (a) is a shell-and-tube heat exchanger structural representation of the present invention;

Fig. 2 (b) is the air intlet structural representation;

Fig. 3 is an air circulation route schematic representation of the present invention;

Fig. 4 is air theoretical circulation thermomechanics temperature entropy of the present invention (brief note is T-S) figure;

Fig. 5 is air actual cycle thermomechanics temperature entropy T-S figure of the present invention.

Embodiment

Fig. 1 is the device that a kind of large electric power plant Direct Air-cooled Unit of the present invention exhaust steam heat energy utilizes.The port of air delivery passage 6 is provided with heat exchanger 3, connect turbine discharge outlet 1 on the heat exchanger 3, heat exchanger 3 is provided with air intlet 5, air delivery passage 6 connects expanding tower 7, the bottom inlet place configuration turbine 8 of expanding tower 7, turbine 8 is connected with generator 9, and expanding tower 7 tops are provided with air outlet slit 10.

Exhaust steam in steam turbine is discharged by air outlet slit 1, enters the air that shell-and-tube heat exchanger 3 and air intlet 5 enter through exhaust steam conveyance conduit 2 and carries out not contact heat-exchanging.Exhaust steam exhaust steam after the heat release in heat exchanger 3 becomes condensed water, and exhaust steam is condensed into water and discharges through condensing water conduit 4, recycles.The air density of being heated diminishes, and forms to have the air stream that certain speed rises, and sends into expanding tower 7 through hot air transfer passage 6.Air part kinetic energy is used for replacing the driving blower fan, make and himself flow through heat exchanger 3, another part kinetic energy is used to promote to be placed on turbine 8 rotations at expanding tower 7 bottom inlet places, and turbine 8 drives generators 9 generatings, realizes the utilization that low grade heat energy is carried in the steam turbine exhaust steam.The remaining kinetic energy of hot air after the acting is used for driving from rising in expanding tower, and last air is discharged to the upper atmosphere from rotatable air outlet slit 10 and goes.

Fig. 2 (a) is the structural representation of shell-and-tube heat exchanger (b).Single arrow is an air-flow direction among the figure, and double-head arrow is the exhaust steam in steam turbine flow direction. wherein a is the heat exchanger layout plan, and b is gradual shrinkage air intlet 5 schematic representation.Air enters from the air intlet 5 that is arranged in heat exchanger surface, and the air intlet of being arranged 5 can arrange evenly that as 2 in each direction, the four sides amounts to 8, also can arrange import according to the long-term wind direction in locality, and the direction of facining the wind arranges that leeward direction is arranged less more.During system works, the window of the direction of facining the wind is opened, and the window of leeward direction is closed, and the permission air of direction down with the wind enters heat exchanger, improves the initial velocity of air with this, improves the heat exchange effect of air.

Fig. 3 is an air circulation route schematic representation.For the convenience of system's thermodynamic analysis, respectively each position of air is defined as: IV before te and the air outlet slit 10 after III, the turbine 8 before air outlet slit 10 back I, high-altitude I ', air intlet 5 II of place, the turbine 8.The air whole motion process as shown by arrows.II-III is air and an exhaust steam heat transfer process in the heat exchanger, and heated air forms air stream, and the turbine that promotes the te place rotates acting; Te-IV is for the air uphill process in expanding tower after doing work, at IV place effusion expanding tower; IV-I and I-I ' are altitude air advection process; I-II is an altitude air decline process.

Fig. 4 is air theoretical circulation thermomechanics T-S figure.II-III is air and an exhaust steam heat transfer process in the heat exchanger, and the isobaric heat absorption temperature raises; III-te is that thermal air current promotes turbine rotation adiabatic process, realizes the used heat utilization; The te-IV air is the adiabatic expansion uphill process in expanding tower.Do not consider every actual loss.

Fig. 5 is air actual cycle thermomechanics temperature entropy T-S figure.Actual cycle comprises three kinds of losses: turbine loss, kinetic energy rejection and expanding tower loss.Have only the concrete numerical value of determining every loss in the practical application, could accurately calculate the utilization ratio of system heat energy.

With regard to the thermodynamic system process of air, derive as follows below to theoretical utilization ratio.

The generating efficiency of system:

Wherein, the heat power P that in heat exchanger, absorbs of air _AbsorbSize is:

P _absorb＝mc _p(T ₃-T ₂)＝mc _pΔT ₂₃。(2)

In the formula, m is a MAF, c _pBe the pressurization by compressed air specific heat capacity, T is temperature everywhere, and subscript is represented particular location, sees Fig. 4, is designated as the even numbers word table down and shows corresponding process variable (down with).

By the second law of thermodynamics as can be known, in the III-IV process, only some merit can be used for driving turbine and rotate generating, and remaining energy is used for driving air and rises at chimney, and chimney height is Δ z:

P _3-4＝mc _p(T ₃-T ₄)， (3)

P _3te-4＝mc _p(T _3te-T ₄)＝mgΔz； (4)

Adiabatic decline process:

$-\frac{\mathrm{dT}}{\mathrm{dz}}=\frac{g}{c_p};...\left(5\right)$

H is identical with the I-II process for te-IV process enthalpy drop Δ:

Δh＝gΔz＝c _p(T ₂-T ₁′)， (6)

Output work P _AbsorbFor:

P _absorb＝mc _p(T ₃-T ₄)-mc _p(T ₂-T ₁′)， (7)

Wushu (2), (6) and (7), isentropic process ratio c=T ₂/ T ₁=T ₃/ T ₄, whole substitution formulas (1) can get system's ideal efficiency:

$\mathrm{\&eta;}=1-\frac{1}{c}=\frac{\mathrm{g\&Delta;z}}{{\mathrm{<figure-callout\; id="2"\; label="c\; p\; T"\; filenames="A20051004308800132.png"\; state="\{\{state\}\}">c</figure-callout>}}_p{T}_{}{}_2}....\left(8\right)$

Sample calculation analysis

Be that example is calculated with 600MW thermoelectricity Air-cooled Unit below.

Known conditions ^[1]:

(1) design heat dissipating capacity Q=900MW, ambient temperature T ₂=288K, year working time t=5000h;

(2) establish air heat exchange temperature rise Δ T=25K, the air temperature T after the heat exchange ₂'=313K, a standard atmosphere is depressed C _p=1005J/ (kgK), hot air density p=1.13kg/m ³

Calculation procedure:

(1) calculate hot air flowrate v:

Q＝ρVC _pΔt， (9)

Then:

V＝Q/(ρC _pΔt)。(10)

(2) calculate the chimney inside diameter D: suppose that the hot air flow velocity is respectively v in the chimney,

By

$V=\frac{\mathrm{\&pi;}}{4}{D}^{2}v,...\left(11\right)$

:

$D=\sqrt{\frac{4V}{\mathrm{\&pi;v}}}....\left(12\right)$

(3) calculate output power P:

Suppose that chimney height is Δ z, calculate corresponding theoretical efficiency η by formula (8) _t

If electromechanical efficiency: η _Wt=0.8, air stream linear loss: η _y=0.05.

(4) actual availability of efficient:

η＝η _tη _wt(1-η _y)。(13)

(5) actual power power:

P＝Qη。(14)

(6) chimney substitutes the station service that blower fan is saved:

Axial flow cooling blower fan number: n=48 platform, every power: P _f=270kW, fan efficiency η _f=55%, then total blower fan consumed power: P _Fj=48 * 0.27=12.9MW;

As long as " pull out force " effect that chimney produces air reaches the action effect of the actual driving power of blower fan, just can save blower fan:

Qη _t(1-η _y)＞Pη _f， (15)

Then Δ z＞245.1m just can save blower fan as long as chimney height surpasses 245.1m.Simultaneously, unnecessary aerodynamic energy can be used for generating electricity.

(7) energy conservation altogether:

Compare with conventional Air-cooled Unit, save power altogether:

P _z=P+P _Fj, (16) account for the ratio of generated output:

Annual save power:

E＝P _zt。(18)

Calculating resulting structures size and economic analysis above gathers as follows:

Table 1 chimney size

	Correspondingly-sized
					Air velocity v (m/s) chimney diameter D (m)	10 63.5	15 51.9	20 44.9	25 40.2

Table 2 economic analysis

Project	Every corresponding relation
								Chimney height Δ z (m)	250	400	600	800	1000	1200	1500
Theoretical efficiency η t (%)	0.85	1.35	2.03	2.71	3.39	4.06	5.08
								Practical efficiency η (%)	0.65	1.03	1.54	2.06	2.58	3.09	3.86
Blower fan power consumption P fj(MW)	12.9	12.9	12.9	12.9	12.9	12.9	12.9
								Generated output P (MW)	5.85	9.27	13.86	18.54	23.22	27.81	34.74
Save total output P (MW)	18.55	22.17	26.76	31.44	36.12	40.71	47.64
								Account for generated output (%)	3.09	3.70	4.46	5.24	6.02	6.79	7.94
The Spring Festival holidays are economized electric weight E (* 10 8kW·h/a)	0.93	1.10	1.39	1.57	1.81	2.04	2.38
								Spring Festival holidays province-norm coal m (t)	11500.0	13602.2	17188.2	19414.0	22381.7	25225.8	29430.1

The conclusion that draws by table:

Device of the present invention both can not consume cooling water, directly cooled off steam turbine discharging exhaust steam with air, can save the blower fan that drives cooling air again, had saved blower fan cost and station service, can also generate electricity, and had protected environment simultaneously.Utilize the thermodynamic cycle principle analysis to reach a conclusion: the low taste heat energy theoretical efficiency that system's generating is utilized is directly proportional with chimney height.When chimney height is designed to 250～1500m, utilization efficiency of heat energy 0.85～5.08%, for the 600MW unit, Spring Festival holidays province-norm coal 11500.0～29430.1t.

Though the utilization of this power generation system energy is very low, thermal source itself belongs to discarded heat, and normal conditions all are directly to be discharged in the atmosphere, have both caused energy dissipation, again environment are caused thermo-pollution.Supply angle from the energy does not have cost, therefore can not only weigh the quality of system by the heat energy utilization rate, can comprehensively weigh the quality of systematic function by cost, income and the environmental protection many-side of system.

Claims (4)

1. the device that utilizes of a large electric power plant Direct Air-cooled Unit exhaust steam heat energy, comprise, air delivery passage (6), its port are provided with heat exchanger (3), it is characterized in that, heat exchanger (3) is gone up and is connected turbine discharge outlet (1), heat exchanger (3) is provided with air intlet (5), and air delivery passage (6) connects expanding tower (7), the bottom inlet place configuration turbine (8) of expanding tower (7), turbine (8) is connected with generator (9), and expanding tower (7) top is provided with air outlet slit (10).

2. the device that a kind of large electric power plant Direct Air-cooled Unit exhaust steam heat energy according to claim 1 utilizes, it is characterized in that, air intlet (5) is shaped as gradual shrinkage, and air intlet (5) is gone up or evenly arranged at heat exchanger (3), or the uneven layout of density.

3. according to the device of claim 1 or 3 described a kind of large electric power plant Direct Air-cooled Unit exhaust steam heat energies utilizations, it is characterized in that air outlet slit (10) is the rotatable gradual shrinkage mouth of pipe.

4. the device that a kind of large electric power plant Direct Air-cooled Unit exhaust steam heat energy according to claim 1 utilizes is characterized in that described expanding tower (7) highly is 250～1500m, and diameter is 40.2～63.5m.

Images