CN104250034B - A kind of whole process rolling reverse osmosis seawater desalination system operation optimization method - Google Patents

Abstract

The invention discloses a kind of whole process rolling reverse osmosis seawater desalination system operation optimization method.The method is according to the reverse osmosis mechanism of seawater desalination system and the structure of whole flow process, the mode using exact mechanism establishes full-range reverse osmosis controlling the water circulation and the accurate model of water-retention process, model uses differential algebraic equations to describe, and product water process and water supply process are linked up, utilizes the cushioning effect of cistern and the stepped change of electricity price to reduce overall operation expense.The optimal problem that the differential algebra form brought to solve Accurate Model describes, uses simultaneous solution technology to solve optimal problem.The present invention has considered the multiple variable element influence factor of seawater desalination system, set up the whole process systematic procedure model of variable element, by the operation optimization of simultaneous Optimization Solution technical research seawater desalination system, try hard to reduce seawater desalination system operating cost further.

Description

A kind of whole process rolling reverse osmosis seawater desalination system operation optimization method

Technical field

The invention belongs to the process field of water, waste water, sewage or mud, be specifically related to by optimizing rolling reverse osmosis sea water Desalination system operation makes system operate on most economical operating point so that the average daily operating cost of system is minimum.

Background technology

Desalination technology is one of maximally efficient method alleviating fresh water crisis.This technology is broadly divided into two classes: steam Evaporate method and hyperfiltration.The way of distillation is primarily used to large-scale desalinization and processes upper and that heat energy is abundant place.Reverse osmosis membrane The applicable surface wide due to it and efficient salt rejection rate are widely used.

Reverse osmosis is with semipermeable membrane by solution different for two kinds of concentration separately.Solvent in the solution that concentration is low passes through automatically Semipermeable membrane permeates to the solution that concentration is high, finally reaches Osmotic balance state, and forms a pressure differential, and this pressure differential is referred to as oozing Pressure thoroughly.If apply the pressure more than osmotic pressure in concentrated solution side, the solvent in concentrated solution then permeates to weak solution side, direction In opposite direction with former infiltration, this process is known as reverse osmosis.Sea water is applied the high pressure higher than reverse osmotic pressure so that sea water In moisture separated by semipermeable membrane, thus the technology obtaining fresh water is Reverse-osmosis Seawater Desalination Technology.Basis at present Reverse osmosis material structure form is different, and Reverse-osmosis Seawater Desalination Technology is divided into rolling embrane method and doughnut reverse osmosis technology.Closely Nian Lai, along with low cost, the development of equipment with high desalinization membrane technology and the progress of high efficiency energy retracting device, rolling embrane method reverse osmosis sea Water desalination technology becomes desalination technology that is most popular and that pay close attention to.Since the 1950's, every cubic metre of desalination water Production cost is reduced to close to 0.5 dollar of level from tens dollars.But energy consumption cost is the main operating cost producing water process, Therefore, system operation cost is affected the biggest by energy prices.

For reducing system operation cost, the method reducing system energy consumption further by system optimized operation and energy management Receive highest attention.But existing research mainly considers system design optimization, operation optimization is related on the low side, to existing The various service conditions of seawater desalination system dynamically change and uncertain consideration deficiency.And for actual seawater desalination system, Ocean temperature or salt content the most constantly fluctuates；Electricity rates also have the biggest time difference opposite sex；And In order to avoid complexity and the difficulty solved of modeling, describe aspect at model in the past and typically use simple lumped-parameter method to enter Line description, although simple still precision is low, and the accuracy of optimum results is not enough.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, it is proposed that a kind of whole process rolling reverse osmosis seawater desalination system operation is excellent Change method.The method, according to the reverse osmosis mechanism of seawater desalination system and the structure of whole flow process, uses the side of exact mechanism Formula establishes full-range reverse osmosis controlling the water circulation and the accurate model of water-retention process, and model uses differential algebraic equations to describe, and Product water process and water supply process are linked up, utilizes the cushioning effect of cistern and the stepped change of electricity price to reduce total gymnastics Make expense.The optimal problem that the differential algebra form brought to solve Accurate Model describes, uses simultaneous solution technology to excellent Change proposition to solve.The present invention is conducive to the enforcement of system on-line optimization technology, has extraordinary Energy-saving Perspective.The present invention Consider the multiple variable element influence factor of seawater desalination system, set up the whole process systematic procedure model of variable element, By the operation optimization of simultaneous Optimization Solution technical research seawater desalination system, try hard to reduce seawater desalination system further and run Cost.

The present invention comprises the following steps:

Step 1: set up rolling reverse osmosis seawater desalting controlling the water circulation process model.

The basic procedure of rolling reverse osmosis seawater desalination system is as shown in Figure 1.According to reverse osmosis process mechanism and quality, Law of conservation of energy, rolling embrane method reverse osmosis process model can use below equation to be described.

Q_p=Q_f-Q_r (1)

Q_fC_f=Q_rC_r+Q_pC_sp (2)

$Q_p=n_{\mathrm{PV}}{n}_{l}W\underset{0}{\overset{L}{\∫}}{J}_v\mathrm{dz}---\left(3\right)$

Jv=A_w(P_f-P_d-P_p-Δπ) (4)

Js=B_s(C_m-C_p) (5)

P_b=P_f-P_d (6)

Δ P=(P_b-P_p) (7)

$A_w=A_{\mathrm{wo}}\exp ({\mathrm{\α}}_1\frac{T-273}{273}-{\mathrm{\α}}_2(P_f-P_d))---\left(8\right)$

$B_s=B_{s0}\exp \left({\mathrm{\β}}_1\frac{T-273}{273}\right)---\left(9\right)$

Δ π=RT (C_m-C_p) (10)

$\mathrm{\φ}=\frac{C_m-C_p}{C_b-C_p}=\exp \left(\frac{\mathrm{Jv}}{k_c}\right)---\left(11\right)$

$\mathrm{Sh}=\frac{k_c{d}_e}{D_{\mathrm{AB}}}=0.065{\mathrm{Re}}^{0.875}{\mathrm{Sc}}^{0.25}---\left(12\right)$

Re=ρ Vd_e/μ (13)

Sc=μ/(ρ D_AB) (14)

Js=Jv*C_p (15)

λ=6.23K_λRe^-0.3 (16)

$D_{\mathrm{AB}}=6.73\×{10}^{-6}\·\exp (0.1546\×{10}^{-3}{C}_b-\frac{2513}{273+T})---\left(17\right)$

$\mathrm{\ρ}=498.4M+\sqrt{{248400M}^2+{752.4\mathrm{MC}}_b},M=1.0069-2.757\×{10}^{-4}T---\left(18\right)$

$\mathrm{\μ}=1.234\×{10}^{-6}\·\exp (0.00212C_b+\frac{1965}{273.15+T})---\left(19\right)$

$\frac{\mathrm{dV}}{\mathrm{dz}}=-\frac{2\mathrm{Jv}}{h_{\mathrm{sp}}}---\left(20\right)$

$\frac{{\mathrm{dP}}_d}{\mathrm{dz}}=-\mathrm{\λ}\frac{\mathrm{\ρ}}{d_e}\frac{V^2}{2}---\left(21\right)$

$\frac{{\mathrm{dC}}_b}{\mathrm{dz}}=\frac{2\mathrm{Jv}}{h_{\mathrm{sp}}V}(C_b-C_p)---\left(22\right)$

R_ec=Q_p/Q_f (23)

SEC=(P_fQ_f/η_HP-P_rQ_rη_PX)/Q_p (24)

Sp=C_p/C_f× 100% (25)

Ry=(1-C_p/C_f) × 100% (26)

In above equation: Q_f、Q_p、Q_rRepresent sea water feed rate, infiltration discharge and strong brine flow, C respectively_f、C_p、C_r Represent charging salinity, the salinity of infiltration water and strong brine salinity, n respectively_lRepresent the blade quantity of RO film, n_PVRepresent pressure The number of force container, W represents RO film width, and L represents the length of RO passage, J_vRepresent solvent flux, J_sRepresent Solute flux, A_w Represent film coefficient of permeability, A_w0Represent the intrinsic coefficient of permeability of film, B_sFilm saturating salt coefficient, B_s0Film intrinsic salt coefficient, P_bRepresent charging The pressure of passage maritime interior waters, P_dRepresent the pressure loss along RO passage, P_pRepresent that the pressure of infiltration water side (is generally defaulted as ring Border pressure), Δ P represents feed water and the pressure differential of infiltration water in passage, and T represents sea water feeding temperature, α₁, α₂, β₁Represent respectively Continuative transport parameter, Δ π represents that osmotic pressure, R represent gas law constant, C_mRepresent the salinity of the feed side on film surface, φ Represent concentration polarization parameter, C_bRepresenting the salt concentration of sea-water along feeding-passage, Sh represents sherwood number, k_cRepresent mass tranfer coefficient, table Show D_ABRepresent dynamic viscosity, d_eRepresenting feed spacer passage hydraulic diameter, Re represents that Reynolds number, Sc represent that Schmidt number, ρ represent The density of infiltration water, μ represents that apparent viscosity, λ represent coefficient of friction, K_λRepresenting empirical parameter, V represents charging axially stream in passage Speed, h_spRepresent the height of feed spacer passage, R_ecRepresenting Water Sproading rate, SEC representation unit produces water consumption, η_HPRepresent high-pressure pump Mechanical output, η_PXRepresenting the organic efficiency of energy recycle device, Ry represents that salt rejection rate, Sp are that salt leads to coefficient.

Model above has taken into full account temperature, pressure and the sea water salinity change impact on reverse osmosis process, model There is the good suitability.In order to ensure the accuracy of model, equation gives physical parameter along with temperature, salinity change And situation about changing.

Step 2. sets up cistern dynamic process model

The importation of cistern is to come from the infiltration water that reverse osmosis controlling the water circulation process (RO process) obtains, and output unit is divided into The fresh water of supply user, because the last handling processes such as pH value regulation are the least on the impact of whole water-retention process, can ignore at this. Therefore, the dynamic process model of cistern is represented by:

$\frac{{\mathrm{dH}}_t}{\mathrm{dt}}=(Q_p-Q_{\mathrm{out}})/S_t---\left(27\right)$

$\frac{{\mathrm{dC}}_{t,\mathrm{out}}}{\mathrm{dt}}=\frac{Q_p}{S_t{H}_t}(C_{\mathrm{sp}}-C_{t,\mathrm{out}})---\left(28\right)$

Here, t express time, S_tAnd H_tRepresent area and the water level of cistern, Q respectively_pFor infiltration discharge, Q_outFor with Family water requirement, C_t,outFor the fresh water salinity of output to user, C_spSalinity for the per-meate side that reverse osmosis controlling the water circulation process obtains (C_pFor C_spValue at modular terminal), for guaranteeing that system operates safety, cistern water level must is fulfilled for H_t,lo<H_t<H_t,up。Q_pWith C_spValue obtained by reverse osmosis process model.

Step 3. sets up system operating cost model

According to rolling reverse osmosis seawater desalting process flow and real process feature, system operating cost (operational cost, OC) specifically includes that 1) .RO process operation energy consumption cost (OC_EN), predominantly high-pressure pump, booster pump And the energy consumption of energy-recuperation system.2). seawater taking system and early stage preprocessing process energy consumption cost (OC_IP).3). chemistry adds Add the expense (OC of agent_CH), predominantly acid adding, add the expense of the aspect such as antisludging agent and flocculant.4). reverse osmosis membrane renewal cost (OC_ME).According to design and ruuning situation, the year turnover rate generally according to about 15-20% calculates.5). upkeep cost (OC_MN)。 Comprise the upkeep cost of whole system such as film, high-pressure pump, motor etc..6). labour cost (OC_LB)。

The operating cost of sea water water intaking and pretreatment system mainly includes chemical addition agent expense and seawater taking system With early stage preprocessing process energy consumption cost.According to operating experience, the expense of chemical addition agent is represented by:

OC_CH=F_UCHQ_f=0.0225Q_f (29)

Seawater taking system is expressed as with early stage preprocessing process energy consumption cost:

${\mathrm{OC}}_{\mathrm{IP}}=\frac{P_{\mathrm{in}}\&CenterDot;Q_f\&CenterDot;P_{\mathrm{elc}}}{{\mathrm{\&eta;}}_{\mathrm{IP}}}\&times;\mathrm{PLF}---\left(30\right)$

Here, P_inRepresent the outlet pressure of water pump.Q_fRepresenting feed rate, PLF represents load factor, P_elcRepresent electricity Power price, η_IPRepresent the efficiency of sea water water pump.

For RO process unit, operating cost mainly include high-pressure pump and booster pump energy consumption cost, film renewal cost and The energy consumption cost that energy recycle device is saved.High-pressure pump energy consumption cost is expressed as:

${\mathrm{OC}}_{\mathrm{HP}}=\frac{(P_f-P_0)Q_f}{{\mathrm{\&eta;}}_{\mathrm{HP}}{\mathrm{\&eta;}}_{\mathrm{VFD}}}\&times;P_{\mathrm{elc}}---\left(31\right)$

P_fRepresent high pressure pump outlet pressure, P₀Represent high pressure pump inlet pressure, η_HPRepresent the mechanical efficiency of high-pressure pump, η_VFD Representing the efficiency of converter, its value changes along with frequency change.

The energy consumption cost that energy recycle device is saved is expressed as:

OC_PX=Q_r·(P_r-P_a)·η_PX·P_elc (32)

Q_rRepresent the flow of concentrated solution, P_rRepresent the pressure head of concentrated solution, P_aRepresent strong brine from energy recycle device out time The pressure waited, η_PXRepresent the efficiency of pressure exchanger.The energy consumption cost of booster pump is then expressed as:

OC_BP=Q₂·(P_f-P_s)/η_BP·P_elc (33)

Here, Q₂Represent the flow by high-pressure pump, P_sRepresent the seawater pressure after energy regenerating, η_BPRepresent booster pump Mechanical efficiency.

So energy consumption of reverse osmosis controlling the water circulation process is represented by:

OC_EN=OC_HP-OC_PX+OC_BP (34)

Reverse osmosis membrane renewal cost is represented by:

OC_ME=Pri_ME×MOD×ζ_re/365 (35)

Here Pri_MERepresenting the price of single membrane module, MOD represents the number of membrane module, ξ_reRepresent the year of membrane module more Change rate.

The upkeep cost of system is relevant with practical operation situation and system investments situation, can be expressed as under normal circumstances Routine operation expense is multiplied by the proportionality coefficient of a 3%-5%, as follows:

OC_MN=OC^Nom×Coe_MN (36)

Here OC^NomThe routine operation expense of expression system, Coe_MNRepresent proportionality coefficient.Labour cost is then according to workman's Wage and number determine, typically constitute from the 8%-15% of routine operation expense, are represented by:

OC_LB=OC^Nom×Coe_LB (37)

Here Coe_LBRepresent the proportionality coefficient of system convention operating cost shared by labour cost.

Step 4. is according to model above and the target of reduction system operating cost, constructing system operation optimization proposition.

In order to reduce the running cost of system, it is required that the operating cost of system is minimum.Because either water supply load Or electricity rates or ocean temperature, all have the approximation characteristic with a day as cycle, therefore to optimize conveniently, with one day The minimum target of operating cost carry out the operation optimization of system.In view of facility constraints and electricity rates situation of change, with 1 Hour regulate performance variable (its feed rate Q for unit_fWith feed pressure P_f).Therefore, the object function of optimization can represent For:

$\underset{Q_f,P_f,H_t,T}{\min }\underset{0}{\overset{24}{\&Integral;}}({\mathrm{OC}}_{\mathrm{IP}}+{\mathrm{OC}}_{\mathrm{EN}}+{\mathrm{OC}}_{\mathrm{ME}}+{\mathrm{OC}}_{\mathrm{MN}}+{\mathrm{OC}}_{\mathrm{LB}}+{\mathrm{OC}}_{\mathrm{CH}})\mathrm{dt}---\left(38a\right)$

In order to solve the operating cost of each several part in object function, meet water supply quality and want summation device security constraint, excellent The constraint equation changing proposition is represented by following form:

Equality constraint equation:

Reverse osmosis process model (eqn. (1)-(26)) (38b)

Cistern dynamic process model (eqn. (27)-(28)) (38c)

Operating cost model (eqn. (29)-(37)) (38d)

Inequality constraints:

Water quality retrains: C_t,out≤C_wq,limit (38e)

Antiscale retrains: C_r≤C_r,limit (38f)

Concentration polarization restriction on the parameters: φ≤1.2 (38g)

Equipment pressure confines: P_f,lo≤P_f≤P_f,up (38h)

RO module flow rate retrains: V_f,lo≤V_f≤V_f,up (38i)

Cistern restriction of water level H_t,lo<H_t<H_t,up (38j)

Boundary condition:

H_t(0)-H_t(24)=0 (38k)

Initial and end condition:

Z=0, V=V_f=Q_f/(n_lWh_sp)；P_b=P_f；C_b=C_f；

Z=L, V=V_r=Q_r/(n_lWh_sp)；Z=L, P_b=P_r；C_b=C_r (38l)

Wherein C_wq,limitRepresent water supply salinity limit value, C_r,limitRepresent the strong brine salinity limit that reverse osmosis process produces Value, P_f,lo、V_f,loAnd H_t,loRepresent the lower limit of relevant parameter, P respectively_f,up、V_f,upAnd H_t,upRepresent the upper limit of relevant parameter respectively. H_t(0) water level at the 0th hour, H are represented_t(24) water level at the 24th hour is represented.

The operation optimization proposition formed is solved by step 5..

The optimal problem being made up of formula (38a)-(38l) had both comprised strong nonlinearity algebraic equation, comprised again the differential equation, for Solve conveniently, use finite element collocation method to be formed by its most discrete non-linear algebraic equation that turns to, form formula (39) and represent Nonlinear optimal problem.Then use large-scale nonlinear solver that it is optimized to solve, it is thus achieved that optimal objective function Value and the optimal value of performance variable.With the performance variable optimal value that obtains as setting value, autocontrol method is used to strain mutually Amount controls at setting value, then the operation optimization of feasible system.Here the finite element collocation method used is conventional method, greatly Scale nonlinear optimization solver is the solver based on sequential quadratic programming algorithm or interior-point algohnhm.Mentioned here automatically Control method both can be regulatory PID control method, it is also possible to be advanced control method.

$\left.\begin{array}{c}\underset{x\&Element;R^n}{\min }f\left(x\right)\\ g\left(x\right)=0\\ x^L\&le;x\&le;x^U\end{array}\right\}---\left(39\right)$

The beneficial effects of the present invention is: the present invention considers charging ocean temperature, salinity etc. to reverse osmosis produced water Impact, establishes strict each several part model accurately, the adaptability of model and accuracy high；The present invention is by controlling the water circulation process and water supply Combine processes gets up to consider, equal diversity when utilizing water-holding capacity and the electricity rates of cistern, it is possible to obtain the most energy-conservation Effect；The Optimization Solution strategy that the present invention uses is conducive to the on-line implement of operation optimization, can preferably analyze whole process Internal state change and operating cost composition.

Accompanying drawing explanation

Fig. 1 is the basic procedure schematic diagram of reverse osmosis seawater desalination system；

Fig. 2 is RO cistern dynamic schematic diagram；

Fig. 3 is water supply planning chart；

Fig. 4 is electricity rates figure；

Pressure changing before and after Fig. 5 a optimization；

Changes in flow rate situation before and after Fig. 5 b optimization；

Fresh water salinity situation of change before and after Fig. 5 c optimization；

Cistern liquid level situation of change before and after Fig. 5 d optimization；

Fig. 6 a pressure operation curve；

Fig. 6 b flow operating curve；

Fig. 6 c response rate change curve.

Detailed description of the invention

Below in conjunction with accompanying drawing, the invention will be further described.

The inventive method comprises the following steps:

Step 1: set up rolling reverse osmosis seawater desalting controlling the water circulation process model.

The basic procedure of rolling reverse osmosis seawater desalination system is as shown in Figure 1.According to reverse osmosis process mechanism and quality, Law of conservation of energy, rolling embrane method reverse osmosis process model can use below equation to be described.

Q_p=Q_f-Q_r (1)

Q_fC_f=Q_rC_r+Q_pC_sp (2)

$Q_p=n_{\mathrm{PV}}{n}_{l}W\underset{0}{\overset{L}{\&Integral;}}{J}_v\mathrm{dz}---\left(3\right)$

Jv=A_w(P_f-P_d-P_p-Δπ) (4)

Js=B_s(C_m-C_p) (5)

P_b=P_f-P_d (6)

Δ P=(P_b-P_p) (7)

$A_w=A_{\mathrm{wo}}\exp ({\mathrm{\&alpha;}}_1\frac{T-273}{273}-{\mathrm{\&alpha;}}_2(P_f-P_d))---\left(8\right)$

$B_s=B_{s0}\exp \left({\mathrm{\&beta;}}_1\frac{T-273}{273}\right)---\left(9\right)$

Δ π=RT (C_m-C_p) (10)

$\mathrm{\&phi;}=\frac{C_m-C_p}{C_b-C_p}=\exp \left(\frac{\mathrm{jv}}{k_c}\right)---\left(11\right)$

$\mathrm{Sh}=\frac{k_c{d}_e}{D_{\mathrm{AB}}}=0.065{\mathrm{Re}}^{0.875}{\mathrm{Sc}}^{0.25}---\left(12\right)$

Re=ρ Vd_e/μ (13)

Sc=μ/(ρ D_AB) (14)

Js=Jv*C_p (15)

λ=6.23K_λRe^-0.3 (16)

$D_{\mathrm{AB}}=6.73\&times;{10}^{-6}\&CenterDot;\exp (0.1546\&times;{10}^{-3}{C}_b-\frac{2513}{273+T})---\left(17\right)$

$\mathrm{\&rho;}=498.4M+\sqrt{{248400M}^2+{752.4\mathrm{MC}}_b},M=1.0069-2.757\&times;{10}^{-4}T---\left(18\right)$

$\mathrm{\&mu;}=1.234\&times;{10}^{-6}\&CenterDot;\exp (0.00212C_b+\frac{1965}{273.15+T})---\left(19\right)$

$\frac{\mathrm{dV}}{\mathrm{dz}}=-\frac{2\mathrm{Jv}}{h_{\mathrm{sp}}}---\left(20\right)$

$\frac{{\mathrm{dP}}_d}{\mathrm{dz}}=-\mathrm{\&lambda;}\frac{\mathrm{\&rho;}}{d_e}\frac{V^2}{2}---\left(21\right)$

$\frac{{\mathrm{dC}}_b}{\mathrm{dz}}=\frac{2\mathrm{Jv}}{h_{\mathrm{sp}}V}(C_b-C_p)---\left(22\right)$

R_ec=Q_p/Q_f (23)

SEC=(P_fQ_f/η_HP-P_rQ_rη_PX)/Q_p (24)

Sp=C_p/C_f× 100% (25)

Ry=(1-C_p/C_f) × 100% (26)

In above equation: Q_f、Q_p、Q_rRepresent sea water feed rate, reverse osmosis water flow and strong brine flow, C respectively_f、C_p、 C_rRepresent charging salinity, the salinity of reverse osmosis water and strong brine salinity, n respectively_lRepresent the blade quantity of RO film, n_PVTable Showing the number of pressure vessel, W represents RO film width, and L represents the length of RO passage, J_vRepresent solvent flux, J_sRepresent that solute leads to Amount, A_wRepresent film coefficient of permeability, A_w0Represent the intrinsic coefficient of permeability of film, B_sFilm saturating salt coefficient, B_s0Film intrinsic salt coefficient, P_bRepresent The pressure of feeding-passage maritime interior waters, P_dRepresent the pressure loss along RO passage, P_pRepresent that infiltration water lateral pressure (is generally defaulted as Ambient pressure), Δ P represents feed water and the pressure differential of infiltration water in passage, and T represents sea water feeding temperature, α₁, α₂, β₁Table respectively Show that continuative transport parameter, Δ π represent that osmotic pressure, R represent gas law constant, C_mRepresent the salinity of the feed side on film surface, φ represents concentration polarization parameter, C_bRepresenting along feeding-passage concentration of seawater, Sh represents sherwood number, k_cRepresent mass tranfer coefficient, represent D_ABRepresent dynamic viscosity, d_eRepresenting feed spacer passage hydraulic diameter, Re represents that Reynolds number, Sc represent that Schmidt number, ρ represent and ooze Permeable density, μ represents that apparent viscosity, λ represent coefficient of friction, K_λRepresenting empirical parameter, V represents charging axially stream in passage Speed, h_spRepresent the height of feed spacer passage, R_ecRepresenting Water Sproading rate, SEC representation unit produces water consumption, η_HPRepresent high-pressure pump Mechanical output, η_PXRepresenting the organic efficiency of energy recycle device, Ry represents that salt rejection rate, Sp are that salt leads to coefficient.

Model above has taken into full account temperature, pressure and the sea water salinity change impact on reverse osmosis process, model There is the good suitability.In order to ensure the accuracy of model, equation gives physical parameter along with temperature, salinity change And situation about changing.

Step 2. sets up cistern dynamic process model

The importation of cistern is to come from the infiltration water that reverse osmosis controlling the water circulation process obtains, and output unit is divided into supply user Fresh water (the most as shown in Figure 2) because the last handling processes such as pH value regulation are the least on the impact of whole water-retention process, can at this To ignore.Therefore, the dynamic process model of cistern is represented by:

$\frac{{\mathrm{dH}}_t}{\mathrm{dt}}=(Q_p-Q_{\mathrm{out}})/S_t---\left(27\right)$

$\frac{{\mathrm{dC}}_{t,\mathrm{out}}}{\mathrm{dt}}=\frac{Q_p}{S_t{H}_t}(C_{\mathrm{sp}}-C_{t,\mathrm{out}})---\left(28\right)$

Here t express time, here, S_tAnd H_tRepresent area and the water level of cistern, Q respectively_pFor reverse osmosis water flow, Q_outFor user's water requirement, C_t,outFor the fresh water salinity of output to user, C_spObtain permeating water for reverse osmosis controlling the water circulation process Salinity, for guaranteeing that system operates safety, cistern water level must is fulfilled for H_t,lo<H_t<H_t,up。Q_pAnd C_spValue pass through reverse osmosis Process model obtains.

Step 3. sets up system operating cost model

According to the rolling reverse osmosis seawater desalting process flow shown in Fig. 1 and real process feature, system operating cost (operational cost, OC) specifically includes that 1) .RO process operation energy consumption cost (OC_EN), predominantly high-pressure pump, booster pump And the energy consumption of energy-recuperation system.2). seawater taking system and early stage preprocessing process energy consumption cost (OC_IP).3). chemistry adds Add the expense (OC of agent_CH), predominantly acid adding, add the expense of the aspect such as antisludging agent and flocculant.4). reverse osmosis membrane renewal cost (OC_ME).According to design and ruuning situation, the year turnover rate generally according to about 15-20% calculates.5). upkeep cost (OC_MN)。 Comprise the upkeep cost of whole system such as film, high-pressure pump, motor etc..6). labour cost (OC_LB)。

The operating cost of sea water water intaking and pretreatment system mainly includes chemical addition agent expense and seawater taking system With early stage preprocessing process energy consumption cost.According to operating experience, the expense of chemical addition agent is represented by:

OC_CH=F_UCHQ_f=0.0225Q_f (29)

Seawater taking system is expressed as with early stage preprocessing process energy consumption cost:

${\mathrm{OC}}_{\mathrm{IP}}=\frac{P_{\mathrm{in}}\&CenterDot;Q_f\&CenterDot;P_{\mathrm{elc}}}{{\mathrm{\&eta;}}_{\mathrm{IP}}}\&times;\mathrm{PLF}---\left(30\right)$

Here, P_inRepresent the outlet pressure of water pump.Q_fRepresenting feed rate, PLF represents load factor, P_elcRepresent electricity Power price, η_IPRepresent the efficiency of sea water water pump.

For RO process unit, operating cost mainly include high-pressure pump and booster pump energy consumption cost, film renewal cost and The energy consumption cost that energy recycle device is saved.High-pressure pump energy consumption cost is expressed as:

${\mathrm{OC}}_{\mathrm{HP}}=\frac{(P_f-P_0)Q_f}{{\mathrm{\&eta;}}_{\mathrm{HP}}{\mathrm{\&eta;}}_{\mathrm{VFD}}}\&times;P_{\mathrm{elc}}---\left(31\right)$

P_fRepresent high pressure pump outlet pressure, P₀Represent high pressure pump inlet pressure, η_HPRepresent the mechanical efficiency of high-pressure pump, η_VFD Representing the efficiency of converter, its value changes along with frequency change.

The energy consumption cost that energy recycle device is saved is expressed as:

OC_PX=Q_r·(P_r-P_a)·η_PX·P_elc (32)

Q_rRepresent the flow of concentrated solution, P_rRepresent the pressure head of concentrated solution, P_aRepresent strong brine from energy recycle device out time The pressure waited, η_PXRepresent the efficiency of pressure exchanger.The energy consumption cost of booster pump is then expressed as:

OC_BP=Q₂·(P_f-P_s)/η_BP·P_elc (33)

Here, Q₂Represent the flow by high-pressure pump, P_sRepresent the seawater pressure after energy regenerating, η_BPRepresent booster pump Mechanical efficiency.

So energy consumption of reverse osmosis controlling the water circulation process is represented by:

OC_EN=OC_HP-OC_PX+OC_BP (34)

Reverse osmosis membrane renewal cost is represented by:

OC_ME=Pri_ME×MOD×ζ_re/365 (35)

Here Pri_MERepresenting the price of single membrane module, MOD represents the number of membrane module, ξ_reRepresent the year of membrane module more Change rate.

The upkeep cost of system is relevant with practical operation situation and system investments situation, can be expressed as under normal circumstances Routine operation expense is multiplied by the proportionality coefficient of a 3%-5%, as follows:

OC_MN=OC^Nom×Coe_MN (36)

Here OC^NomThe routine operation expense of expression system, Coe_MNRepresent proportionality coefficient.Labour cost is then according to workman's Wage and number determine, typically constitute from the 8%-15% of routine operation expense, are represented by:

OC_LB=OC^Nom×Coe_LB (37)

Here Coe_LBRepresent the proportionality coefficient of system convention operating cost shared by labour cost.

Step 4. is according to model above and the target of reduction system operating cost, constructing system operation optimization proposition.

In order to reduce the running cost of system, it is required that the operating cost of system is minimum.Because either water supply load Or electricity rates or ocean temperature, all have the approximation characteristic with a day as cycle, therefore to optimize conveniently, with one day The minimum target of operating cost carry out the operation optimization of system.In view of facility constraints and electricity rates situation of change, with 1 Hour regulate performance variable (its feed rate Q for unit_fWith feed pressure P_f).Therefore, the object function of optimization can represent For:

$\underset{Q_f,P_f,H_t,T}{\min }\underset{0}{\overset{24}{\&Integral;}}({\mathrm{OC}}_{\mathrm{IP}}+{\mathrm{OC}}_{\mathrm{EN}}+{\mathrm{OC}}_{\mathrm{ME}}+{\mathrm{OC}}_{\mathrm{MN}}+{\mathrm{OC}}_{\mathrm{LB}}+{\mathrm{OC}}_{\mathrm{CH}})\mathrm{dt}---\left(38a\right)$

In order to solve the operating cost of each several part in object function, meet water supply quality and want summation device security constraint, excellent The constraint equation changing proposition is represented by following form:

Equality constraint equation:

Reverse osmosis process model (eqn. (1)-(26)) (38b)

Cistern dynamic process model (eqn. (27)-(28)) (38c)

Operating cost model (eqn. (29)-(37)) (38d)

Inequality constraints:

Water quality retrains: C_t,out≤C_wq,limit (38e)

Antiscale retrains: C_r≤C_r,limit (38f)

Concentration polarization restriction on the parameters: φ≤1.2 (38g)

Equipment pressure confines: P_f,lo≤P_f≤P_f,up (38h)

RO module flow rate retrains: V_f,lo≤V_f≤V_f,up (38i)

Cistern restriction of water level H_t,lo<H_t<H_t,up (38j)

Boundary condition:

H_t(0)-H_t(24)=0 (38k)

Initial and end condition:

Z=0, V=V_f=Q_f/(n_lWh_sp)；P_b=P_f；C_b=C_f；

Z=L, V=V_r=Q_r/(n_lWh_sp)；Z=L, P_b=P_r；C_b=C_r (38l)

Wherein C_wq,limitRepresent water supply salinity limit value, C_r,limitRepresent the strong brine salinity limit that reverse osmosis process produces Value, P_f,lo、V_f,loAnd H_t,loRepresent the lower limit of relevant parameter, P respectively_f,up、V_f,upAnd H_t,upRepresent the upper limit of relevant parameter respectively. H_t(0) water level at the 0th hour, H are represented_t(24) water level at the 24th hour is represented.

The operation optimization proposition formed is solved by step 5..

The optimal problem being made up of formula (38a)-(38l) had both comprised strong nonlinearity algebraic equation, comprised again the differential equation, for Solve conveniently, use finite element collocation method to be formed by its most discrete non-linear algebraic equation that turns to, form formula (39) and represent Nonlinear optimal problem.Then use large-scale nonlinear solver that it is optimized to solve, it is thus achieved that optimal objective function Value and the optimal value of performance variable.With the performance variable optimal value that obtains as setting value, autocontrol method is used to strain mutually Amount controls at setting value, then the operation optimization of feasible system.Here the finite element collocation method used is conventional method, greatly Scale nonlinear optimization solver is the solver based on sequential quadratic programming algorithm or interior-point algohnhm.Mentioned here automatically Control method both can be regulatory PID control method, it is also possible to be advanced control method.

$\left.\begin{array}{c}\underset{x\&Element;R^n}{\min }f\left(x\right)\\ g\left(x\right)=0\\ x^L\&le;x\&le;x^U\end{array}\right\}---\left(39\right)$

It is embodied as describing to the present invention below in conjunction with embodiment:

The present invention carries out case study to certain rolling reverse osmosis seawater desalination system.This system uses first-stage reverse osmosis stream Journey, and use PX energy recycle device.Membrane module uses Tao Shi SW30HR series.7 membrane modules of series connection in each pressure vessel, 90 groups of pressure vessels compose in parallel reverse osmosis produced water unit.Cistern is as producing water and the temporary location of water supply, after water quality Process and realize producing water and the buffering of water supply.The design parameter of system is as shown in table 1, supplies water plan as shown in Figure 3.For solving This optimal problem, uses 40 finite elements and 3 Radau collocation points to carry out discrete the reverse osmosis module differential equation.To water-retention The dynamic differential equation of process uses 24 finite elements and 3 Radau collocation points to carry out discrete, the most discrete precision than Higher, discrete rear optimal problem information is as shown in table 2.To the optimal problem after discretization, use under GMAS24.0 platform based on The large-scale nonlinear solver IPOPT of interior-point algohnhm is optimized and solves.

Table 1 system feeding condition and cistern parameter information

Feed conditions	Numerical value
		Input concentration (kg/m3)	30
Feeding temperature (DEG C)	20
		Feed pressure (Bar)	59
Charging PH	5-8
		Cistern parameter	Numerical value
Liquid level area St (m2)	150
		The liquid level upper limit (m)	15
Liquid level lower limit (m)	2
		Initial concentration (kg/m3)	0.430
Initial liquid height (m)	4

Model information after table 2 discretization

Model Condition	Numerical value
		Total variable	70901
Equality constraint	70853
		Inequality constraints	25
Jacobi non-zero points	246408
		Hessian non-zero points	104450
Film finite element number	40
		Collocation point	3
Timing departure number	24
		Collocation point	3

For guaranteeing the effectiveness of model, use this model that the response rate and salt rejection rate index are calculated, result of calculation Comparing with real data and ROSA9.0 the data obtained, result is as shown in table 3.As can be seen from Table 3, this model result tool There is higher accuracy.

Table 3 model data and real data, ROSA9.0 calculate data and compare

Type	The response rate (%)	Salt rejection rate (%)
			Real data	41.6	99.37
ROSA9.0 data	42.7	99.58
			Model data	42.1	99.52

Below, the present invention will be analyzed in terms of scheme 1 fixing charging parameter, scheme 2 variations in temperature two.Set system System charging and service condition are as follows: sea water feeding temperature is 20 DEG C；Charging salinity is 30kg/m³；Water supply plan such as Fig. 3 shows, uses Electricity price lattice such as Fig. 4 shows.In the case optimal problem is solved, and optimum results is compared with routine operation result Relatively.Here routine operation is defined as CaseA, this behaviour is optimized and is defined as Case B.

Case A does not carry out operation optimization, fixing operation pressure and flow, uses on off control to meet the upper and lower boundary treaty of water level Bundle and final constraint so that total aquifer yield is equal to water requirement.

In Case B cistern liquid level circle adjustable, reduced by regulation operation pressure, feed rate and cistern liquid level Total expense cost.

For scheme 1, of substantially equal during in order to ensure the liquid level in the moment when 24 with initial value, use and shut down strategy, and set Fixed its operates pressure P in running_fFor 64.4bar, operate flow Q_fFor 1125m³/h.Based on Case A and the meter of Case B Calculate results contrast and be shown in Table 4 and Fig. 5 a to Fig. 5 d.

Overall expenses and composition situation before and after table 4 optimization

It can be seen from the table, total operation expense is 2.781 ten thousand yuan of every days before optimization, and the most only RO process energy consumption just accounts for 58.1%, add water intaking and preprocessing part, then total energy consumption proportion is 64.8%；And the renewal cost of membrane module is the lowest In 10%, the most in the highest flight.By the optimization to model, total operating cost can be reduced to 2.039 ten thousand yuan of every days, becomes this section Province's rate is more than 26%.Wherein the energy consumption of RO module is reduced to 0.9943 ten thousand yuan from 1.6146 ten thousand yuan, is to cause cost to be greatly reduced Principal element.

In accompanying drawing 5,5a is the pressure changing before and after optimizing, and 5b is the changes in flow rate situation before and after optimizing, and 5c is for producing The situation of change of water salinity, 5d is then the liquid level situation of change of cistern.Compared to routine operation, optimize operation in operation pressure Power is the most relatively low with on operation flow, and when the electricity rates shown in Fig. 4 are higher, its flow and pressure reduce bigger.Often Rule operation completes overall water supply requirement before latter two hour, uses and shuts down strategy so that its flow and pressure are zero.

For scheme 2, the present invention, according to actual temperature change, analyzes sea water feeding temperature behaviour between 16～32 DEG C Make optimization situation.Here high-pressure pump mechanical efficiency is set as 0.85, and energy recycle device organic efficiency is set as 0.9.The most excellent Change and the results are shown in Table shown in 5.

Optimum Operation expense and composition situation (DEG C) thereof under the different sea water feeding temperature of table 5

Project	16	18	20	22	24	26	28	30	32
										OCIP	0.1373	0.1357	0.1362	0.1371	0.1335	0.1295	0.1259	0.1281	0.1267
OCEN	1.3426	1.1322	0.9943	0.9277	0.9236	1.001	0.9466	0.9392	0.9395
										OCCH	0.2676	0.2656	0.2636	0.2628	0.2601	0.2591	0.2573	0.2558	0.2545
OCME	0.2170	0.2170	0.2170	0.2170	0.2170	0.2170	0.2170	0.2170	0.2170
										OCLB	0.3200	0.3200	0.3200	0.3200	0.3200	0.3200	0.3200	0.3200	0.3200
OCMN	0.1080	0.1080	0.1080	0.1080	0.1080	0.1080	0.1080	0.1080	0.1080

OC

2.392

2.178

2.039

1.973

1.962

2.035

1.978

1.968

1.966

As can be seen from Table 5, temperature has material impact to running cost.Product water cost when 16 DEG C is higher than 32 DEG C 0.426 ten thousand yuan of every days because manually, safeguard and film renewal cost fix, the cost of raising essentially consists in energy consumption cost aspect.This The rising being because temperature contributes to increasing the penetrating power of water, can obtain and more permeate water under same operation pressure. As can also be seen from Table 5, total when temperature is more than 24 DEG C operating cost has fluctuated, this is because the raising of temperature also makes Salinity penetrating power improves, and in order to meet water quality requirement, needs to adjust operation pressure and other parameters, and this makes energy consumption cost occur one Fixed repeatedly.

Owing to sea water feeding temperature is not only very big along with seasonal variations in real process, within one day, also there is bigger ripple Dynamic, as shown in following formula (40a) and (40b).Here the operation optimization in the case of constant temperature and alternating temperature is analyzed for.Analysis is divided into Summer constant temperature STC, alternating temperature STV in summer, constant temperature WTC in winter and tetra-kinds of situations of alternating temperature WTV in winter.Optimum behaviour in the case of these four The results are shown in Table shown in 6 as Cost Optimization, corresponding optimum manipulation variable curve and performance curve such as Fig. 6 a of desalinization, figure Shown in 6b and Fig. 6 c.As seen from Table 6, the Optimum Operation expense when 15 DEG C is much higher than the Optimum Operation when 22 DEG C Expense.Optimum results under summer alternating temperature operating mode, significantly better than constant temperature operating mode, illustrate to change according to operational factor to be optimized Operation can obtain more preferable effect.

$T=4.0\exp \left(\frac{{(t-15.5)}^2}{-18.403}\right)+22---\left(40a\right)$

$T=7.0\exp \left(\frac{{(t-15.5)}^2}{-20.403}\right)+15---\left(40b\right)$

From pressure operation curve (Fig. 6 a), operation pressure is much higher than summer operation pressure in the winter time, and the behaviour in winter Making flow (Fig. 6 b) and increase ratio than summer the most not quite, after variations in temperature is described, preferential regulation pressure is more suitable.In response rate side Face (Fig. 6 c), relatively low first 8 hours of electricity price, the response rate of summer condition was higher than winter；And in electricity price relatively High time interval, although the response rate is greatly lowered, but the response rate of winter condition is higher than summer；This situation Occur relevant with the dual restriction of membrane module water-yielding capacity in winter and energy consumption.

Optimum Operation expense under table 6 different temperatures parameter

Project	Temperature (DEG C)	Optimum Operation expense (ten thousand yuan)
			STC	T=22	2.1031
STV	Equation (40a)	2.0819
			WTC	T=15	2.8212
WTV	Equation (40b)	2.5084

Instance analysis shows: 1., compared with the operation of conventional reverse osmosis seawater desalination system, operation optimization in this paper can System overall operation cost is greatly lowered.Becoming often occurs in actual reverse osmosis seawater desalination system operational factor such as temperature Dynamic, it is bigger on the impact of Optimum Operation cost and correlation performance parameters；Optimize operation and can effectively reduce operating cost, it is achieved Water quality and the safe operation of equipment.Optimum results in the case of temperature wide variation again shows that, the system that the present invention is given Model and solution strategies have the good suitability and robustness.

Claims (1)

1. a whole process rolling reverse osmosis seawater desalination system operation optimization method, it is characterised in that the method includes following step Rapid:

Step 1: set up rolling reverse osmosis seawater desalting controlling the water circulation process model；

According to reverse osmosis process mechanism and quality, law of conservation of energy, rolling embrane method reverse osmosis process model can use with Lower equation is described；

Q_p=Q_f-Q_r (1)

Q_fC_f=Q_rC_r+Q_pC_sp (2)

$Q_p=n_{PV}{n}_{l}W\underset{0}{\overset{L}{\&Integral;}}{J}_{v}dz---\left(3\right)$

Jv=A_w(P_f-P_d-P_p-Δπ) (4)

Js=B_s(C_m-C_p) (5)

P_b=P_f-P_d (6)

Δ P=(P_b-P_p) (7)

$A_w=A_{wo}\exp ({\mathrm{\&alpha;}}_1\frac{T-273}{273}-{\mathrm{\&alpha;}}_2(P_f-P_d\left)\right)---\left(8\right)$

$B_s=B_{s0}\exp \left({\mathrm{\&beta;}}_1\frac{T-273}{273}\right)---\left(9\right)$

Δ π=RT (C_m-C_p) (10)

$\mathrm{\&phi;}=\frac{C_m-C_p}{C_b-C_p}=\exp \left(\frac{Jv}{k_c}\right)---\left(11\right)$

$Sh=\frac{k_c{d}_e}{D_{AB}}=0.065{\mathrm{Re}}^{0.875}{\mathrm{Sc}}^{0.25}---\left(12\right)$

Re=ρ Vd_e/μ (13)

Sc=μ/(ρ D_AB) (14)

Js=Jv*C_p (15)

λ=6.23K_λRe^-0.3 (16)

$D_{AB}=6.73\&times;{10}^{-6}\&CenterDot;\exp (0.1546\&times;{10}^{-3}{C}_b-\frac{2513}{273+T})---\left(17\right)$

$\mathrm{\&rho;}=498.4M+\sqrt{248400M^2+752.4{\mathrm{MC}}_b},M=1.0069-2.757\&times;{10}^{-4}T---\left(18\right)$

$\mathrm{\&mu;}=1.234\&times;{10}^{-6}\&CenterDot;\exp (0.00212C_b+\frac{1965}{273.15+T})---\left(19\right)$

$\frac{dV}{dz}=-\frac{2Jv}{h_{sp}}---\left(20\right)$

$\frac{{\mathrm{dP}}_d}{dz}=-\mathrm{\&lambda;}\frac{\mathrm{\&rho;}}{d_e}\frac{V^2}{2}---\left(21\right)$

$\frac{{\mathrm{dC}}_b}{dz}=\frac{2Jv}{h_{sp}V}(C_b-C_p)---\left(22\right)$

R_ec=Q_p/Q_f (23)

SEC=(P_fQ_f/η_HP-P_rQ_rη_PX)/Q_p (24)

Sp=C_p/C_f× 100% (25)

Ry=(1-C_p/C_f) × 100% (26)

In above equation: Q_f、Q_p、Q_rRepresent sea water feed rate, infiltration discharge and strong brine flow, C respectively_f、C_p、C_rRespectively Represent charging salinity, the salinity of infiltration water and strong brine salinity, n_lRepresent the blade quantity of RO film, n_PVRepresent that pressure holds The number of device, W represents RO film width, and L represents the length of RO passage, J_vRepresent solvent flux, J_sRepresent Solute flux, A_wRepresent Film coefficient of permeability, A_w0Represent the intrinsic coefficient of permeability of film_,B_sFilm saturating salt coefficient, B_s0Film intrinsic salt coefficient, P_bRepresent feeding-passage The pressure of maritime interior waters, P_dRepresent the pressure loss along RO passage, P_pRepresenting the pressure of infiltration water side, Δ P represents charging in passage Water and the pressure differential of infiltration water, T represents sea water feeding temperature, α₁, α₂, β₁Representing continuative transport parameter respectively, Δ π represents infiltration Pressure, R represents gas law constant, C_mRepresenting the salinity of the feed side on film surface, φ represents concentration polarization parameter, C_bRepresent edge The salt concentration of sea-water of feeding-passage, Sh represents sherwood number, k_cRepresent mass tranfer coefficient, D_ABRepresent dynamic viscosity, d_eRepresent charging Washer channel hydraulic diameter, Re represents that Reynolds number, Sc represent that Schmidt number, ρ represent the density of infiltration water, and μ represents apparent viscosity, λ represents coefficient of friction, K_λRepresenting empirical parameter, V represents charging axial flow velocity in passage, h_spRepresent the height of feed spacer passage Degree, R_ecRepresenting Water Sproading rate, SEC representation unit produces water consumption, η_HPRepresent the mechanical output of high-pressure pump, η_PXRepresent energy regenerating The organic efficiency of device, Ry represents that salt rejection rate, Sp are that salt leads to coefficient；

Step 2. sets up cistern dynamic process model

The importation of cistern is to come from the infiltration water that reverse osmosis controlling the water circulation process obtains, output unit be divided into supply user light Water, the dynamic process model of cistern is represented by:

$\frac{{\mathrm{dH}}_t}{dt}=(Q_p-Q_{out})/S_t---\left(27\right)$

$\frac{{\mathrm{dC}}_{t,out}}{dt}=\frac{Q_p}{S_t{H}_t}(C_{sp}-C_{t,out})---\left(28\right)$

Here, t express time, S_tAnd H_tRepresent area and the water level of cistern, Q respectively_pFor infiltration discharge, Q_outNeed for user The water yield, C_t,outFor the fresh water salinity of output to user, C_spFor the salinity of the per-meate side that reverse osmosis controlling the water circulation process obtains, for Guaranteeing that system operates safety, cistern water level must is fulfilled for H_t,lo<H_t<H_t,up；

Step 3. sets up system operating cost model

System operating cost specifically includes that RO process operation energy consumption cost OC_EN, seawater taking system and early stage preprocessing process energy Consumption cost OC_IP, expense OC of chemical addition agent_CH, reverse osmosis membrane renewal cost OC_ME, upkeep cost OC_MN, labour cost OC_LB；

The expense of chemical addition agent is represented by:

OC_CH=F_UCHQ_f=0.0225Q_f (29)

Seawater taking system is expressed as with early stage preprocessing process energy consumption cost:

${\mathrm{OC}}_{IP}=\frac{P_{in}\&CenterDot;Q_f\&CenterDot;P_{elc}}{{\mathrm{\&eta;}}_{IP}}\&times;PLF---\left(30\right)$

Here, P_inRepresent the outlet pressure of water pump；Q_fRepresenting feed rate, PLF represents load factor, P_elcRepresent electric power valency Lattice, η_IPRepresent the efficiency of sea water water pump；

For RO process unit, operating cost mainly includes high-pressure pump and booster pump energy consumption cost, film renewal cost and energy The energy consumption cost that retracting device is saved；High-pressure pump energy consumption cost is expressed as:

${\mathrm{OC}}_{HP}=\frac{(P_f-P_0)Q_f}{{\mathrm{\&eta;}}_{HP}{\mathrm{\&eta;}}_{VFD}}\&times;P_{elc}---\left(31\right)$

P_fRepresent high pressure pump outlet pressure, P₀Represent high pressure pump inlet pressure, η_HPRepresent the mechanical efficiency of high-pressure pump, η_VFDRepresent and become Frequently the efficiency of device, its value changes along with frequency change；

The energy consumption cost that energy recycle device is saved is expressed as:

OC_PX=Q_r·(P_r-P_a)·η_PX·P_elc (32)

Q_rRepresent the flow of concentrated solution, P_rRepresent the pressure head of concentrated solution, P_aRepresent strong brine from energy recycle device out time Pressure, η_PXRepresent the efficiency of pressure exchanger；The energy consumption cost of booster pump is then expressed as:

OC_BP=Q₂·(P_f-P_s)/η_BP·P_elc (33)

Here, Q₂Represent the flow by high-pressure pump, P_sRepresent the seawater pressure after energy regenerating, η_BPRepresent the machinery of booster pump Efficiency；

So energy consumption of reverse osmosis controlling the water circulation process is represented by:

OC_EN=OC_HP-OC_PX+OC_BP (34)

Reverse osmosis membrane renewal cost is represented by:

OC_ME=Pri_ME×MOD×ζ_re/365 (35)

Here Pri_MERepresenting the price of single membrane module, MOD represents the number of membrane module, ξ_reRepresent the year turnover rate of membrane module；

The upkeep cost of system is relevant with practical operation situation and system investments situation, is expressed as routine operation expense and is multiplied by one The proportionality coefficient of 3%-5%, as follows:

OC_MN=OC^Nom×Coe_MN (36)

Here OC^NomThe routine operation expense of expression system, Coe_MNRepresent proportionality coefficient；Labour cost is then according to the wage of workman Determine with number, account for the 8%-15% of routine operation expense, be represented by:

OC_LB=OC^Nom×Coe_LB (37)

Here Coe_LBRepresent the proportionality coefficient of system convention operating cost shared by labour cost；

Step 4. is according to model above and the target of reduction system operating cost, constructing system operation optimization proposition；

The operation optimization of system is carried out with the minimum target of the operating cost of a day；Change in view of facility constraints and electricity rates Situation, regulated performance variable in units of 1 hour, its feed rate Q_fWith feed pressure P_f；Therefore, the target letter of optimization Number can be expressed as:

$\underset{Q_f,P_f,H_t,T}{Min}\underset{0}{\overset{24}{\&Integral;}}({\mathrm{OC}}_{IP}+{\mathrm{OC}}_{EN}+{\mathrm{OC}}_{ME}+{\mathrm{OC}}_{MN}+{\mathrm{OC}}_{LB}+{\mathrm{OC}}_{CH})dt---\left(38a\right)$

In order to solve the operating cost of each several part in object function, meet water supply quality and want summation device security constraint, optimize life The constraint equation of topic is represented by following form:

Equality constraint equation:

Reverse osmosis process model (eqn. (1)-(26)) (38b)

Cistern dynamic process model (eqn. (27)-(28)) (38c)

Operating cost model (eqn. (29)-(37)) (38d)

Inequality constraints:

Water quality retrains: C_t,out≤C_wq,limit (38e)

Antiscale retrains: C_r≤C_r,limit (38f)

Concentration polarization restriction on the parameters: φ≤1.2 (38g)

Equipment pressure confines: P_f,lo≤P_f≤P_f,up (38h)

RO module flow rate retrains: V_f,lo≤V_f≤V_f,up (38i)

Cistern restriction of water level H_t,lo＜ H_t＜ H_t,up (38j)

Boundary condition:

H_t(0)-H_t(24)=0 (38k)

Initial and end condition:

Z=0, V=V_f=Q_f/(n_lWh_sp)；P_b=P_f；C_b=C_f；

Z=L, V=V_r=Q_r/(n_lWh_sp)；Z=L, P_b=P_r；C_b=C_r (38l)

Wherein C_wq,limitRepresent water supply salinity limit value, C_r,limitRepresent the strong brine salinity limit value that reverse osmosis process produces, P_f,lo、V_f,loAnd H_t,loRepresent the lower limit of relevant parameter, P respectively_f,up、V_f,upAnd H_t,upRepresent the upper limit of relevant parameter respectively；H_t (0) water level at the 0th hour, H are represented_t(24) water level at the 24th hour is represented；

The operation optimization proposition formed is solved by step 5.；

The optimal problem being made up of formula (38a)-(38l) had both comprised strong nonlinearity algebraic equation, comprised again the differential equation, for solving Convenient, use finite element collocation method to be formed by its most discrete non-linear algebraic equation that turns to, form that formula (39) represents is non- Linear optimization problem；Then use GMAS24.0 large-scale nonlinear solver IPOPT that it is optimized to solve, it is thus achieved that optimum Target function value and the optimal value of performance variable；With the performance variable optimal value that obtains as setting value, use autocontrol method Relevant variable is controlled at setting value, then the operation optimization of feasible system；

$\left.\begin{array}{c}\underset{x\&Element;R^n}{\min }f\left(x\right)\\ g\left(x\right)=0\\ x^L\&le;x\&le;x^U\end{array}\right\}---\left(39\right).$