CN1837088A - Gas distribution adjustment method for blast aeration system - Google Patents

Abstract

Disclosed is an air distribution adjustment method for blower aeration systems, wherein the aeration amount needed by each aeration tanks is employed for the accurate aeration by means of integrally adjusting air blower and flow regulating valve, and the objective of energy conservation can also be met.

Description

Gas distribution adjustment method for blast aeration system

Technical field

The present invention relates to the gas distribution adjustment method of blast aeration system in the sewage disposal.

Background technology

Usually adopt in the technology of biological treatment in municipal sewage treatment at present, the bottom blast aeration is the aeration mode of using always.Aeration is the topmost energy consumption link of Sewage Plant, accounts for the 50-80% of total power consumption.Along with the improvement of control mode and the development of power-saving technology, accurately aeration becomes the importance of Sewage Plant reducing energy consumption, has obvious energy-saving effect.So-called accurately aeration is meant the actual needs air feed according to the Sewage Plant biological reaction tank.Can guarantee the stable of biological treatment environment like this, on the one hand; On the other hand, make the aeration rate in the system be unlikely to excessive and cause waste again.

Yet, only know that the required aeration rate of system is not enough.In order to realize accurate aeration, also need to comprise the aerating pipelines system distribution accurately of gas blower and other parts, to reach the purpose of accurate aeration.

Summary of the invention

The purpose of this invention is to provide a kind of method that the blast aeration system that adopts in the sewage disposal is regulated, accurate aeration is become may and reach purpose of energy saving.

Blast aeration system control method according to the present invention is characterised in that, the aeration rate required according to each aeration tank realized accurate aeration by regulating described gas blower and flow control valve integratedly, reaches energy-conservation purpose simultaneously.And, the feature of this blast aeration system also is to regulate by this way described gas blower, promptly, the static pressure that gas blower provides should be equal to or slightly greater than the various pressure-losseses that exist in the system, and these pressure-losseses comprise the linear loss of working medium, the pressure-losses of each valve, the top hole pressure loss at aeration head place.The top hole pressure loss at described aeration head place is meant that aeration head place gas can carry out the required minimum pressure of aeration.The feature of this control method also is and will be arranged to full gate corresponding to the valve of the arm of pressure-losses maximum in all arms, flow-aperture performance according to the valve that is adopted, on the basis of the required flow of each arm except the arm of pressure-losses maximum, set the aperture of other each valve.

Description of drawings

Fig. 1 is that wherein piping system is tree-shaped distribution according to the synoptic diagram of the suitable blast aeration system of gas distribution adjustment method for blast aeration system of the present invention.

Fig. 2 A and Fig. 2 B are respectively the synoptic diagram of the another kind of blast aeration system that is suitable for according to gas distribution adjustment method for blast aeration system of the present invention, and wherein piping system distributes in the form of a ring.

Embodiment

Fig. 1 is that wherein blast aeration system comprises at least one gas blower 1 according to the synoptic diagram of the suitable blast aeration system of blast aeration system control method of the present invention.Here the quantity and the mode of connection thereof that are to be noted that gas blower in the diagram only are examples.Aeration house steward 3 is connected gas blower 1 in the system with aeration arm 4 in the aeration tank 8.In the suitable blast aeration system of gas distribution adjustment method of the present invention, the distributing style of aeration house steward 3 and aeration arm 4 can have multiple, is not limited to situation shown in Figure 1.Show two kinds of synoptic diagram of the piping systems of layout in the form of a ring respectively at Fig. 2 A and Fig. 2 B.Setting pressure transmitter 2 on aeration house steward 3, the pressure distribution in 2 pairs of systems of this pressure unit detects, thus taking place to warn when unusual at pressure is convenient to timely adjusting.Flow control valve 5 and under meter 6 are set on each aeration arm 4.Each 8 bottom, aeration arm 4 terminal aeration tanks also is provided with some aeration heads 9.Here it should be noted that the quantity and the mode of connection thereof of aeration head only is example among the figure.8 limits, aeration tank are provided with liquidometer 7, and these liquidometers 7 are used for measuring the liquid level degree of depth of aeration tank 8, and this degree of depth can be used to calculate the top hole pressure loss of aeration head 9.Like this, gas blower 1 is worked under certain pressure and power, via aeration house steward 3 air of aequum is distributed to each aeration arm 4, finally discharge from aeration head 9, thereby to the sewage treatment process oxygen supply in the aeration tank 8.The effect that flow control valve of installing on each aeration arm 45 and under meter 6 have played the air flow quantity in each aeration arm 4 of accurate control.And then, for further conserve energy, each aeration arm 4 can be designed to the non-constant section pipeline of longshore current to cross-sectional expansion.Like this, working medium is when pipeline flows, and its speed reduces.The ideal situation is, in the time guaranteeing normal aeration, promptly at the aeration head place, the static pressure of working medium is a bit larger tham the ambient pressure at aeration head place, and the speed of working medium is reduced to and approaches 0.When other condition was identical, this design situation can drop to minimum with the pressure-losses of system.

In order to make this system's energy steady running, also reach energy-conservation purpose simultaneously, at first should determine the aeration rate that each aeration tank is required.In the application number of applicant is 2005100287229 patent application, aeration rate required when being controlled at the DO concentration in the aeration tank in the less fluctuation range has been described.Here, introduce this patent application as a reference in full.So just can determine the air flow quantity of gas blower.On this basis, in order to determine the operating power of gas blower, also should determine the pressure that total system is required.The required pressure of total system can calculate from the pressure-losses of each link of system.Below will be elaborated to this.

The pressure-losses of blast aeration system mainly comprises: the pressure-losses of the pressure-losses of pipeline, the pressure-losses of valve and aeration head etc.Owing to as working medium, in calculating, can not consider the elevation change of pipeline with air.Below putting up with these aspects is described.At first, the loss of pressure head expression formula of pipeline is as follows:

$p_{\mathrm{ti}}=\frac{{\mathrm{\λ}}_i}{4R_{s_i}}\frac{{\mathrm{\ρv}}_i^2}{2}{l}_i,---\left(1\right)$

P in the formula (1) _TiBe the loss of pressure head that i section pipeline is caused, ρ is ducted density of air, and v _iBe average flow velocity, R _SiHydraulic radius for pipeline; l _iBe the length of pipeline, the straight tube that can be equal to certain-length according to the pressure-losses that engineering experience produces structures such as ducted elbow, threeway, connecting joint, reducing X-over, damper hole takes in.Coefficient of frictional resistance λ _iRelevant with factors such as flow characteristics and inner-walls of duct roughness, provide by following formula,

$\frac{1}{\sqrt{{\mathrm{\λ}}_i}}=-2\lg (\frac{K_i}{3.71D_i}+\frac{2.51}{R_{e_i}\sqrt{{\mathrm{\λ}}_i}}),$

Wherein, K _iBe the average absolute roughness of i inner surface of pipeline, R _EiBe Reynolds number, D _iBe equivalent diameter.This experimental formula is an implicit formula, need find the solution by the method for iteration.On the basis of the pressure-losses of calculating each pipeline i,, can calculate the pressure-losses that causes of all pipelines according to the pipeline distribution situation:

p _t＝p _t(r ₁，F ₁；r ₂，F ₂；…；r _i，F _i) _i＝1，N (2)

Wherein, r _i, F _iBe respectively resistance coefficient and the flow of pipeline i, N is the number of pipeline.By formula (2) as can be seen, under pipeline fixed situation, the crushing and the flow of pipeline have functional relation.

Next, analyze the loss of pressure head of flow control valve, it can be expressed as

$p_{\mathrm{vi}}=K_i\frac{F_i^2}{2g}$

P in the formula _ViBe i the loss of pressure head that valve caused; K _iBe the pressure loss factor of i valve, the pressure loss factor value of the valve of different sorts, type, specification and structure is different, K _iChange along with the difference of aperture; F _iBe the flow of i valve of flowing through, g is a universal gravity constant.So total valve loss of pressure head is:

p _v＝p _v(K ₁，F ₁；K ₂，F ₂；…K _i，F _i)/2g (3)

P in the formula _vBe the loss of pressure head that all valves cause, under the situation that valve is determined, the total head loss is the function of aperture and flow.Aperture φ=(φ ₁, φ ₂... φ _N), corresponding flow is F=(F ₁, F ₂... F _N).For the general valve that adopts in the engineering, its pressure-losses and its aperture become the funtcional relationship of monotone decreasing substantially, the aperture that is valve is big more, the pressure-losses by valve is more little, and this characteristic provides certain thinking for how to select the aperture of valve in having the aerating system pipeline of a plurality of valves and arm.

Then, consider the loss of pressure head of aeration head.If i aeration head is h apart from the height of aeration tank liquid level _i, then the pressure-losses of this aeration head is

p _ji＝ρ _wgh _i

ρ in the formula _wBe density of liquid in the aeration tank.For guaranteeing that all aeration heads all can aeration, total aeration head loss of pressure head is taken as the maximum value of all aeration head pressure-losseses, promptly

$p_j=\underset{i}{\mathrm{Max}}\left({\mathrm{\ρ}}_{w}g{h}_i\right).---\left(4\right)$

On the basis of above analysis, can determine the operation conditions of gas blower quantitatively.At first, gas blower should be able to provide air flow quantity required in the treatment process, i.e. the flow of gas blower $F\&GreaterEqual;\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{F}_i.$ Next considers formula (2), (3) and (4), and the static pressure that gas blower provides should be able to overcome the various pressure-losseses in the system, comprises the linear loss of working medium, the pressure-losses of each valve, the pressure-losses at aeration head place, i.e. the static pressure p of gas blower _SFShould satisfy: p _SF〉=p _i+ p _v+ p _jAccording to aforementioned two constraint conditions, can determine the function and the working order of gas blower about gas blower flow and pressure.Particularly, the shaft power of gas blower is $p_{\mathrm{sh}}=\frac{[\mathrm{\&delta;}{p}_{\mathrm{sF}}+\mathrm{\&rho;}\frac{{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="A20061002589100091.png,A20061002589100102.png"\; state="\{\{state\}\}">v</figure-callout>}}^2}{2}]F}{{\mathrm{\&eta;}}_{\mathrm{in}}{\mathrm{\&eta;}}_{\mathrm{me}}},$ Wherein $\mathrm{\&delta;}=1-\frac{p_{\mathrm{sF}2}-{\mathrm{<figure-callout\; id="1"\; label="p\; sF"\; filenames="A20061002589100091.png,A20061002589100102.png"\; state="\{\{state\}\}">p</figure-callout>}}_{\mathrm{sF}}}{2\mathrm{<figure-callout\; id="1"\; label="k\; p\; sF"\; filenames="A20061002589100091.png,A20061002589100102.png"\; state="\{\{state\}\}">k</figure-callout>}{p}_{\mathrm{sF}}{1}_{}},$

And p _SF2, p _SF1Be respectively the outlet static pressure and the import static pressure of gas blower, k=1.4 is the compressibility coefficient, at blower fan total head (be between the export and import of blower fan total head poor) p _TFDuring＞2500Pa, need take into account this compressibility coefficient, otherwise get δ=1; p _SFBe fan static pressure, promptly the total head of blower fan deducts the dynamic pressure in exit; ρ is a density of air, and v is the speed of blower export place gas, and $F=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{F}_i$ Be total air flow quantity; η _InBe the internal efficiency of gas blower, value 0.82 in calculating, η _MeBe the mechanical efficiency of gas blower, value 0.98 in calculating.On the basis of determining blower shaft power, can determine the power p=kp of the motor of blower _Sh, wherein safety coefficient can be taken as k=1.15.In above calculating, suppose that blower inlet place air velocity is 0, its static pressure is a normal atmosphere, and total system steady running.But in actual motion, the running status of gas blower is positioned within its performance envelope curve.Undoubtedly, when the various disturbance that taking into account system may occur, the actual motion state of gas blower should be away from the border of this performance envelope curve, and this system that makes has better anti-jamming capability.In addition, gas blower is in operation, if when the flow of output and the flow in pressure and the tubing system and pressure do not match, may produce the phenomenon of flutter.About flutter mechanism that produces and the method for eliminating flutter, can be with reference to pertinent literature.

In this system, the variation of each valve opening might cause the variation of other valve flow and the pressure-losses.Concerning any one valve, both can under big pressure (pressure behind the gas blower) and less valve opening situation, obtain, also can under less pressure and larger opening situation, obtain the flow that certain is determined.Big aperture obviously is more excellent operating point, because the pressure-losses that big aperture causes is little, and need not gas blower bigger pressure output is provided, and under the situation that flow is determined, lower pressure output means that the air blast function works under lower power.

For the aerating system of a plurality of arms and valve is arranged, supposing at certain each arm of specific time slot request provides aeration according to one group of specific flow, in order to realize this group flow, certainly exists the combination of the aperture of many group valves.Similarly, system both can work under the combination of bigger pressure and less one group of valve opening, also can work under less pressure and bigger one group of valve opening combination.Less pressure and the combination of bigger aperture are more excellent operating points, and its pressure-losses is less, and the power output of gas blower is lower, just can reach purpose of energy saving.

In addition, should will be arranged to full gate corresponding to the valve of the arm of pressure-losses maximum in all arms.Adjust the aperture of all the other each valves according to the flow-aperture curve of valve then, to obtain the required flow of each arm.The benefit of this practice is under the set situation of flow and piping system, can make the loss of total pressure minimum that all valves cause.Like this on the basis of required accurate aeration rate, the performance perameter and the operation conditions of gas blower have been determined in energy-conservation mode, and determined the aperture of each valve in the mode of economy, and realized the one of blast aeration system is regulated, reached accurate aeration and purpose of energy saving.

Those skilled in that art be it is evident that, under the situation that does not depart from the spirit or scope of the present invention, can implement the present invention in other specific mode.Therefore, example and embodiment should be considered to be exemplary and not restrictive, and the invention is not restricted to details given here, but can improve in the scope and spirit of claims.

Claims (5)

1. a gas distribution adjustment method for blast aeration system is characterized in that, the aeration rate required according to each aeration tank realized accurate aeration by regulating gas blower and flow control valve integratedly, reaches purpose of energy saving simultaneously.

2. gas distribution adjustment method for blast aeration system according to claim 1, it is characterized in that, regulate described gas blower by this way, promptly, the static pressure that described gas blower provides should be equal to or slightly greater than the various pressure-losseses that exist in the system, and these pressure-losseses comprise the linear loss of working medium, the pressure-losses of each valve, the pressure-losses at aeration head place.

3. gas distribution adjustment method for blast aeration system according to claim 2 is characterized in that, the pressure-losses at described aeration head place is meant that described aeration head place gas can carry out the required minimum pressure of aeration.

4. gas distribution adjustment method for blast aeration system according to claim 1 is characterized in that, will be arranged to full gate corresponding to the valve of the arm of pressure-losses maximum in all arms.

5. gas distribution adjustment method for blast aeration system according to claim 1, it is characterized in that, according to the flow one aperture performance of the valve that is adopted, on the basis of the required flow of each arm except the arm of pressure-losses maximum, set the aperture of other each valve.

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