The circulating-water in thermal power plant system
Technical field
The present invention relates to the circulating-water in thermal power plant system, particularly circulating water quality detects control system.
Background technology
Recirculated water is long-term used in generating plant, chemical plant and a lot of heat transmission equipment, and the water yield is huge, and financial cost is high.Recirculated cooling water is because heat radiation evaporation, makes that various mineral matters are constantly concentrated increase with ion concentration in the water, and separates out and be deposited on the heating surface; Make heat interchanger heat conductivility variation; Heat exchange efficiency reduces, and energy consumption increases, and can cause line clogging, discharge to diminish when serious and produces underdeposit corrosion.In the circulating cooling system, heat interchanger and pipeline be mostly by made, and salinity, dissolved oxygen DO etc. contact and can make metal produce galvanic corrosion in metal material and the water.Water saving has become a lot of enterprises of a kind of puzzlement serious problems with the contradiction of fouling of heat exchanger corrosion.
Comprise with recirculated water corrosive attack and the closely-related parameter of fouled condition: saturation index (Is), index of stability (S) and scaling index (PSI).
1, saturation index (Is)
When dissolves carbonate reaches capacity state in water, there is following transient equilibrium relation:
Ca(HCO
3)
2=Ca
2++2HCO
3- (1-1)
HCO
3-=H
++CO
3- (1-2)
CaCO
3=Ca
2++CO
3 2- (1-3)
Bright lattice rel in 1936 has proposed the notion of saturation pH value and saturation index according to above-mentioned equilibrium relation, in water, whether can separate out incrustation scale to judge lime carbonate, and proposes to control separating out of incrustation scale to add the pre-service that acid adds alkali.
Can find out from reaction equation (1-2) with (1-3), add alkali like Xiang Shuizhong, then H
+Be neutralized, the pH value of water raises, and reaction equation (1-2) carries out to right-hand, and reaction equation (1-3) carries out to left, and lime carbonate is prone to separate out.If lime carbonate is state of saturation in the water, then reaction equation (1-1), (1-2), (1-3) are in equilibrium state, and calcium bicarbonate does not resolve into lime carbonate, and lime carbonate can not continue dissolving yet.This moment, the pH value of water was called this water saturation pH value, represented with PHs.Bright lattice rel has been derived the formula that calculates PHs, and judges separating out of incrustation scale with the difference of actual pH value and PHs value.This difference is called saturation index (also claiming bright lattice rel index), representes with Is.
When Is>0, calcium carbonate scale can be separated out, and this water belongs to fouling type water;
When Is<0, the calcium carbonate scale layer that then was attached to originally on the heat-transfer area can be dissolved, carbon steel exposed in water corroded, and this water belongs to corrosion type water;
When Is=0, lime carbonate is not promptly separated out, and original calcium carbonate scale layer can be not dissolved yet, and this water belongs to stable type water.
2 index of stability (S)
Nineteen forty-six thunder now Nasdaq index go out, false judgment often appears in saturation index when prediction water quality character.At some in particular cases, though its saturation value be on the occasion of, aqueous corrosion property is very strong.
Thunder is contained on the basis of a large amount of experiments now, has proposed to replace saturation index prediction water quality performance with 2PHs-PH.And be called index of stability to the difference of 2PHS-PH.
3 scaling indexs (PSI)
Pa Kelazi in 1979 thinks corrosion and the fouling tendency that basicity more can reaction cycle water than the practical measurement pH value of water.After a hundreds of circulation had been done to study, he thought that the practical measurement pH value with water in the index of stability changes more practical in production of equilibrated ph value (PHeq) into, and equilibrated ph value and basicity can be calculated by following formula:
PHeq=1.465lg (M basicity)+4.54
The total alkalinity of recirculated water in M basicity-system (in lime carbonate, unit is mg/L)
And propose:
PSI=2PHs-PHeq>6 corrosion
PSI=2PHs-PHeq=6 is stable
PSI=2PHs-PHeq<6 foulings
Above-mentioned three kinds of judge index to fouling corrosion; Though all be the theory that grows up on bright lattice rel basis; They are main with bright lattice rel index, and index of stability and scaling index are auxilliary, but they have a very big weakness; That calculates very numerous and diverse exactly, is unfavorable for the instantaneous control that exercises supervision.
Conventional circulation generally includes water charging system, circulating water pool, water circulating pump, condenser, cooling tower, control device, blowoff valve and charge pump etc.Circulating water pool, water circulating pump, condenser, cooling tower link to each other through pipeline successively, constitute cooling system.Water charging system mainly is the quantity of circulating water according to default, timely replenishment cycles water, the capacity of maintenance circulating water pool.Control device is connected with charge pump with blowoff valve, controls its opening and closing, adds corrosion inhibiting and descaling agent, sewage effluent to circulating water pool.
The prior art circulation is that the determination data with supplementing water carries out approximate treatment; Control with 70%~80% of corrosion inhibiting and descaling agent scale inhibition ability; Most of at home industries in the general tradition comparatively all of circulating water treatment, all adopt blowdown manually or timer blowdown according to each analytical test result at present, daily in service owing to produce to load and change; Same cooling water quality also can change thereupon; The variation of monitoring water quality promptly and accurately will bring fouling or etching problem to system, thereby influence ordinary production if fail in the case.In other words, if discovery variation water quality early, that petty increase analysis frequency that just needs; Adopt the timer blowdown to set according to initial calculated value often; Blowdown is put once setting, generally can not change, and when water quality changes, can not monitor equally.In sum, the low level management of blowdown can cause that circulation blowdown flow rate deficiency causes system's fouling, and the excessive meeting of blowdown causes the increase of waste, manual work and the operating cost of water resource.
Summary of the invention
Technical matters to be solved by this invention is directed against the shortcoming that the prior art circulation causes system's fouling and water resource waste easily exactly, and a kind of circulating-water in thermal power plant system based on computer distributed control system (DCS) is provided.
The present invention solve the technical problem, and the technical scheme of employing is the circulating-water in thermal power plant system; Comprise circulating water pool, water circulating pump, condenser, cooling tower, control device, blowoff valve and charge pump, said circulating water pool, water circulating pump, condenser, cooling tower link to each other through pipeline successively, and said control device is connected with charge pump with blowoff valve; Control its opening and closing; It is characterized in that said control device comprises DCS system, recirculated water detection system, blowoff valve controller and charge pump controller, said DCS system is connected with the charge pump controller with the blowoff valve controller; Go out the recirculated water index of discrimination according to input data and detection data computation; And according to said recirculated water index of discrimination driving blowoff valve controller and charge pump controller, respectively blowoff valve and charge pump are controlled, add medicine and/or sewage effluent to circulating water pool; Said recirculated water detection system is made up of temperature-detecting device, total hardness pick-up unit, total alkalinity pick-up unit, pH value pick-up unit and conductivity pick-up unit; Said recirculated water detection system detects Circulating Water Parameters in real time, and input DCS system, and said conductivity pick-up unit is arranged in the circulating water line; Gather in real time the recirculated water conductivity data, said DCS system sets the blowdown point according to the recirculated water conductivity data.
Concrete, said recirculated water index of discrimination comprises saturation index, index of stability, scaling index.
Concrete, said medicine comprises corrosion inhibiting and descaling agent and/or saline and alkaline spreading agent.
Concrete, said DCS system has computer system to constitute.
The invention has the beneficial effects as follows; Only need to gather less data (being generally 5 groups of data); Just can find the optimization control parameter and the blowdown set point of water quality easily, online conductivity pick-up unit can monitor the variation of water quality automatically, just can change the blowdown set point in time through the DCS system; Change the size (, need not make any setting and change usually) of blowdown flow rate giving under the situation of water quality stabilizing.The present invention can accomplish the accurate control of recirculated water blowdown, can avoid the fouling corrosion of circulation, can reasonably carry out blowdown control again, practices thrift great amount of water resources.Do several simple conventional analysis chemical examinations (doing 1~2 time in per 12 hours) in service daily needs and follow the tracks of judgement, thereby reduce manually-operated, reduce operating cost, bring distinct economic, really reach the effect of energy-saving and emission-reduction to enterprise as water quality.
Description of drawings
Fig. 1 is a structural representation of the present invention;
Fig. 2 is the control device structural representation.
Embodiment
Below in conjunction with accompanying drawing and embodiment, describe technical scheme of the present invention in detail.
Circulation of the present invention is through gathering the recirculated water analysis data, and some data need be through manually input, and some data can detect (like TDS) automatically.Control device carries out corresponding calculated according to these data, obtains the recirculated water index of discrimination, comprises saturation index Is, index of stability S, scaling index PSI.And correspondence goes out the best blowdown point (reference electrode conductance parameter is set) of system.The DCS system is sent to charge pump controller and blowoff valve controller with steering order; And the online conductivity of foundation contrasts the determination data of recirculated water and the setting range of blowdown optimum set point; Automatically the start and stop of being controlled the blowdown solenoid valve by controller reach best reasonable blowdown, thereby reach the purpose of water-saving and emission-reducing.
Embodiment
This routine circulating-water in thermal power plant system, as shown in Figure 1, comprise circulating water pool, water circulating pump, condenser, cooling tower, control device, blowoff valve and charge pump.Circulating water pool, water circulating pump, condenser, cooling tower link to each other through pipeline successively, constitute circulating cooling system, and the water charging system among the figure is used for when the water level of circulating water pool is lower than setting value owing to blowdown and evaporation, replenishing.This routine control device is as shown in Figure 2, comprises DCS system, recirculated water detection system, blowoff valve controller and charge pump controller.The recirculated water detection system is made up of temperature-detecting device, total hardness pick-up unit, total alkalinity pick-up unit, pH value pick-up unit and conductivity pick-up unit among the figure, and these pick-up units detect circulating water temperature, total hardness, total alkalinity and pH value parameter in real time.The means of passing through that these supplemental characteristics have input to the DCS system, and what have then can gather automatically, is monitored in real time by the DCS system.Particularly the conductivity pick-up unit is arranged in the circulating water line, gathers the recirculated water conductivity data in real time, and the DCS system sets the blowdown point according to the recirculated water conductivity data, and through blowoff valve controller control sewage discharge.The DCS system is also according to circulating water temperature, total hardness, total alkalinity, conductivity and pH value; Computation cycles water index of discrimination; Comprise saturation index, index of stability, scaling index, and the recirculated water controlled variable of calculated value and setting is compared, in time add corrosion inhibiting and descaling agent and/or saline and alkaline spreading agent through the charge pump controller; Recirculated water saturation index, index of stability, scaling index are controlled at setting range; Can not produce fouling and corrosion, adding medicine and sewage effluent that again can not be too much, thus reach the purpose of water-saving consumption-reduction.This routine DCS system adopts computer system to constitute, and has operation interface intuitively, is convenient to carry out man-machine interaction.
Comparison with the regular circulation water system
Because the change that analysis data of itself and blowdown are provided with a little is untimely, just set the blowdown point at last, owing to carrying out accurately or in time controlling and cause following harm:
Being set to 10 with the blowdown point is example, and blowdown point fluctuates up and down acutely, has been up to 24, and at this moment rate of water make-up has reduced, but the ion in the water increases substantially, and equipment scaling trend increases, and the safe operation of equipment is caused very big harm.During the fluctuation downwards of blowdown point, minimumly reached 3.5, the water ions content is low, and scaling tendency reduces, but blowdown flow rate can significantly increase, and rate of water make-up also can significantly increase, and adds the production cost of large enterprises, causes economic loss.
Circulation of the present invention adopts the DCS system to control in real time, and water quality is fluctuation in a narrow margin around blowdown point 10; Upwards fluctuation is no more than 12; Downward fluctuation can not be lower than 8, in fouling and economical operation, has found optimum, and blowdown is provided with a little and effective control device owing to and analyzing, calculate, changing; Avoided the above-mentioned two kinds of harm in the conventional control better, safety and production and economical operation have had better guarantee.