CN113655824A - Wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method - Google Patents
Wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method Download PDFInfo
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Abstract
The invention relates to the technical field of waste gas purification by a semi-liquid phase method, and discloses a wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method, which is used for controlling the pH value of spraying slurry in a slurry circulation loop during desulphurization by adopting a gypsum method, solving the influence of each manipulated variable in a desulphurization device on the desulphurization effect and the operation cost by a fractional analytical factor design, and then solving the combination of the manipulated variables which enables the operation cost of the whole desulphurization device to be the lowest on the premise of meeting the desulphurization effect by using an optimization algorithm, thereby realizing the red line pressing operation of the whole desulphurization device and ensuring the lowest operation cost; in the invention, the closed-loop replacement method is adopted to ensure that the frequency of the variable-frequency circulating pump is as low as possible, thereby leaving the SO at the outlet of the desulfurization deviceXThe residual amount of the SO in the flue gas can be adjusted quickly after the content fluctuatesXAfter the load is lifted, the frequency of the variable frequency pump is quickly adjusted by lifting.
Description
Technical Field
The invention relates to the technical field of waste gas purification by a semi-liquid phase method, in particular to a wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method.
Background
The lime/limestone slurry is used as an absorbent for wet desulphurization, and is a main method for flue gas desulphurization in the existing coal-fired power plants.
In the existing desulfurization device, part of slurry which is contacted with flue gas is mixed with new slurry and then pumped back to an absorption tower by a circulating pump for spraying, so that the liquid-gas ratio is improved and an absorbent is fully utilized. The absorption tower is divided into two sections by a collecting bowl, each section is provided with a set of slurry circulation loop, in the two slurry circulation loops, the pH value of slurry sprayed in a lower circulation mode is lower SO as to facilitate calcium sulfite oxidation and gypsum crystallization, and the pH value of slurry sprayed in an upper circulation mode is higher SO as to fully absorb SOXSince the residence time of the upper circulation is short, it is also necessary to equip the upper circulation with an oxidation tower (also called AFT tower) to extend the oxidation time of the slurry in the upper circulation.
However, since the combustion condition of the boiler is constantly fluctuating, the SO of the flue gas entering the desulfurizerXThe load is constantly changing. To adapt to SOXLoad changes require adjustment of the flow rate of the slurry sprayed in the slurry circulation loop (also known as the spray volume to adjust the liquid-to-gas ratio), and adjustment of the slurry supply flow rate (slurry supply flow rate is a term in the industry that refers to the flow rate of new slurry, and changing the slurry supply flow rate can be used to adjust the pH of the sprayed slurry).
At present, the two flows are relatively coarsely regulated, the flow of the spraying slurry is regulated by changing the starting number and frequency of the circulating pumps according to experience of operators, the flow of the slurry supply is regulated by a PID controller, the given value in the PID controller is the set value of the pH value of the spraying slurry, the controlled object is the actual pH value of the spraying slurry, and the manipulated variable is the opening degree of a slurry supply valve of new slurry. The value of the given value in the PID controller is manually given by an operator in the DCS according to the smoke condition.
The two adjusting modes have different characteristics, and the flue gas SO at the outlet of the absorption tower can be immediately reduced after the spraying amount is increasedXBut has little influence on the desulfurization capability of the desulfurization device itself; the desulfurization capacity of the desulfurization device can be directly improved after the flow of the slurry supply is improved, but the flue gas SO at the outlet of the absorption tower is subjected toXThe effect of concentration is more delayed.
Since both flow adjustments can change the desulfurization capacity of the desulfurization unit, and both are connected in a million ways before. After the coupling control is involved, how to reduce the energy consumption and the material consumption on the premise of ensuring the desulfurization effect becomes more complex, at present, no method for optimizing the coupling control exists, and operators adjust the slurry supply flow and the spraying amount according to experience, so that the slurry supply flow and the spraying amount are always seriously beyond the actual requirement.
Disclosure of Invention
The invention provides a wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method.
The technical problem to be solved is that: in the existing wet desulphurization device, an optimized coupling control method is not available, and operators adjust the slurry supply flow and the spraying amount according to experience, so that the slurry supply flow and the spraying amount both seriously exceed the actual requirements.
In order to solve the technical problems, the invention adopts the following technical scheme: a wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method is used for minimizing the operation cost of a desulphurization device on the premise of ensuring the desulphurization effect when desulphurization is carried out by adopting a gypsum method, and comprises the following steps:
the method comprises the following steps: carrying out a fractional factorial design to obtain the flue gas SO of each manipulated variable at the outlet of the absorption tower of the desulfurization deviceXInfluence on concentration, influence on electricity consumption and influence on material consumption;
step two: establishing an optimization model of a slurry circulation loop in a desulfurization device, and constructing an economic objective function with uniform dimension based on the output of the model; obtaining an algorithm of a target function, and recording the algorithm as an optimization algorithm; recording the starting and stopping states of each circulating pump as pump states; parameters reflecting the running state of the desulfurization device under the current pump state are recorded as optimization variables;
step three: in the current pump state, the optimization algorithm traverses the conditions of the optimization variable combinations in all slurry circulation loops, the optimization variable combination with the optimal economy is found out, and the set values in all controllers of the desulfurization device are adjusted according to the optimization variable combination with the optimal economy, so that closed-loop optimization is realized.
Further, in the second step, the optimization algorithm is a genetic algorithm or a particle swarm algorithm, and a penalty factor in the optimization algorithm is the over-removed SOXThe objective function being the rejection of SO that should be removed but not removedXThe amount of (a) is greater than 0.
Further, in the second step, the constraint condition in the optimization algorithm includes the pH value adjustment range of the slurry sprayed in each slurry circulation loop, and the optimization variable is the pH value of the slurry sprayed in each slurry circulation loop.
Further, the desulfurization device is a single-tower double-circulation device and comprises an upper circulation loop and a lower circulation loop; the circulating pump of the lower circulation comprises a plurality of power frequency pumps and an on-stream variable frequency pump, and the circulating pump of the upper circulation comprises a plurality of power frequency pumps; the constraints also include a frequency range in which the circulation pump is adjustable.
Further, in the third step, the pH value of the sprayed slurry in the lower circulation is close to the upper limit of the pH value adjusting range in the lower circulation; meanwhile, on the premise of meeting the desulfurization effect, when the starting number of the power frequency pumps is minimum and the frequency of the variable frequency pump is close to the lower limit of the frequency regulation range of the variable frequency pump, the operating cost is minimized.
Further, the frequency of the variable frequency pump is used for absorbing the flue gas SO at the outlet of the towerXAnd in the third step, closed-loop optimization is realized by adopting a closed-loop displacement method, which comprises the following specific steps:
flue gas SO at outlet of absorption towerXUnder the condition that the concentration is stable and not exceeds the standard, if the frequency of the variable frequency pump does not reach the lowest and the pH value of the lower-cycle spraying slurry does not reach the upper limit of the adjusting range, gradually increasing the pH value of the lower-cycle spraying slurry, and then under the condition that the SO concentration is stable and not exceeds the standardXUnder the action of concentration feedback control, changeThe frequency of the frequency pump is gradually reduced, and the replacement from the pH value to the frequency is completed until the frequency of the frequency conversion pump is lowest or the pH value of the lower circulating spraying slurry is highest.
Further, the optimization method further comprises the fourth step of: if the frequency of the variable frequency pump of the lower circulation reaches the highest value and the pH value of the lower circulation spraying slurry reaches the highest value, the flue gas SO at the outlet of the absorption towerXAnd if the concentration still has an ascending trend, starting a power frequency pump in the lower circulation or the upper circulation, and then adopting the closed-loop replacement method to enable the frequency of the variable frequency pump to be the lowest or enable the pH value of the lower circulation spraying slurry to be the highest.
Further, in the first step, an orthogonal test method is adopted for carrying out the design of the analytical factorization.
Further, in step one, the orthogonal test is performed as follows:
spraying slurry pH value orthogonal test, and if a plurality of slurry circulation loops exist, respectively testing each slurry circulation loop;
spraying a slurry flow orthogonal test, and if a plurality of slurry circulation loops exist, respectively testing each slurry circulation loop;
and (4) performing orthogonal test on the load working condition of the unit.
Further, in the first step, a model equation of the influence of each operation variable is fitted by adopting a method of European crown linear interpolation.
Compared with the prior art, the wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method has the following beneficial effects:
according to the invention, the influence of each manipulated variable in the desulfurization device on the desulfurization effect and the operation cost is solved through a fractional factorial design, and then the set value of the controller with the lowest operation cost of the whole desulfurization device is combined on the premise of solving the requirement of the desulfurization effect by using an optimization algorithm, so that the red line pressing operation of the whole desulfurization device is realized, and the operation cost is lowest;
in the invention, the frequency of the variable frequency pump is as low as possible by adopting a closed-loop replacement method, SO that the SO at the outlet of the desulfurization device is reservedXThe residual amount of the SO in the flue gas can be adjusted quickly after the content fluctuatesXAfter the load is lifted, the frequency of the variable frequency pump is liftedThe spraying amount is rapidly increased (the power frequency pump is started slowly, and the frequency conversion of the frequency conversion pump is very fast) SO that the outlet SO of the desulfurization deviceXThe content is rapidly reduced; the variable frequency pump reserves a large adjusting space, and the requirement for adjustment can be met by adopting a single variable frequency pump, so that the number of the variable frequency pumps with lower efficiency is reduced, the energy efficiency is improved, and the difficulty in control is reduced;
in the invention, the pH value of the spraying slurry of the lower circulation is set close to the upper limit of the adjusting range during stable operation and is a stable value, and the desulfurization by-product with stable quality can be obtained when the pH value is stable.
Drawings
FIG. 1 is a flow chart of the present invention for finding an objective function;
FIG. 2 is a schematic view of two slurry circulation circuits using the single-tower double-circulation desulfurization apparatus of the present invention, in which a blast line and a slurry withdrawal line are omitted;
wherein, the method comprises the steps of 1-an absorption tower, 11-a collection bowl, 2-an oxidation tower, 3-a circulating pump, 4-a fresh slurry pipe and 5-a spraying slurry pipe.
Detailed Description
In the invention, all the expressions of 'the amount of XX' can be carried out by adopting various expressions such as volume, mass, amount of substances and the like, and only the dimension in the calculation process is required to be ensured to be correct. Similarly, the "XX flow rate" can be expressed in various ways such as a volume flow rate, a mass flow rate, and a mass flow rate; the concentration of XX can be expressed in various ways such as volume fraction, mass concentration, and quantity concentration of substances, and only the correct dimension is ensured in the calculation process.
In this embodiment, all "XX amounts" are mass, all "XX flow rates" are mass flow rates, and all "XX concentrations" are mass concentrations. SO (SO)XWith SO2To count the remaining types of SOXNeglected.
A wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method is used for minimizing the operation cost of a desulphurization device on the premise of ensuring the desulphurization effect when desulphurization is carried out by adopting a gypsum method, and comprises the following steps:
the method comprises the following steps:carrying out a fractional factorial design to obtain the flue gas SO of the outlet of the absorption tower 1 of the desulphurization device by each manipulated variableXInfluence on concentration, influence on electricity consumption and influence on material consumption; the manipulated variable refers to adjusting means such as slurry supply flow and the like;
as shown in fig. 1, step two: establishing an optimization model of a slurry circulation loop in a desulfurization device, and constructing an economic objective function with uniform dimension based on the output of the model; obtaining an algorithm of a target function, and recording the algorithm as an optimization algorithm; the start-stop state of each circulating pump 3 is recorded as a pump state; parameters reflecting the running state of the desulfurization device under the current pump state are recorded as optimization variables;
the start-stop state of each circulating pump 3, which circulating pumps 3 start and which circulating pumps 3 close, reflects the change in the hardware of the desulfurization device, and the hardware of the desulfurization device needs to be determined first, and then the running state of the desulfurization device can be compared.
The optimization variables are not considered only considering parameters related to the desulfurization capability of the desulfurization apparatus, such as the flow rate and pH of the slurry sprayed in each slurry circulation circuit, and parameters unrelated to the temperature and the like. In this example, the optimization variable is the pH of the slurry sprayed in each slurry circulation loop. In the invention, for the best economy, the desulfurization device is operated in red line, namely the flue gas SO at the outlet of the absorption tower 1XThe concentration is stabilized around the upper concentration limit of the allowable discharge by means of a predictive controller, on the premise that when the pH value of the slurry sprayed in each slurry circulation circuit is determined, the flow rate of the slurry sprayed in each slurry circulation circuit is also determined.
Step three: in the current pump state, the optimization algorithm traverses the conditions of the optimization variable combinations in all slurry circulation loops, the optimization variable combination with the optimal economy is found out, and the set values in all controllers of the desulfurization device are adjusted according to the optimization variable combination with the optimal economy, so that closed-loop optimization is realized.
In the second step, the optimization algorithm is a genetic algorithm or a particle swarm algorithm, and the genetic algorithm is selected in the embodiment; punishment factor in the optimization algorithm is over-removed SOXOf the objective function, the overruling condition of the objective function being to be removedUnremoved SOXThe amount of (a) is greater than 0. The overruling condition here means that the SO at the outlet of the desulfurization unit cannot be made by the objective function onceXThe concentration of (A) is up to standard, and SO which is to be removed but not removed existsXThe objective function is directly dropped and re-optimized. SO to be removedXThe amount of (2) is defined as the flue gas SO at the inlet of the desulfurization unitXConcentration minus outlet flue gas SOXMultiplying the standard concentration by the volume of the flue gas; over-removing refers to the flue gas SO at the outlet of the absorption tower 1XIs lower than designed and does not require the removal of SOXIs removed.
In the second step, the constraint conditions in the optimization algorithm include the pH adjustment range of the slurry sprayed in each slurry circulation loop, that is, when the pH of the slurry sprayed should be adjusted, the pH should be kept within the range, which is an artificially specified range, and the actual adjustment capability is not limited thereto.
As shown in fig. 2, the desulfurization apparatus in this embodiment is a typical single-tower double-circulation device.
The absorption tower 1 is divided into two sections by the collecting bowl 11, so that two slurry circulation loops of upper circulation and lower circulation exist in the device, and the flue gas passes through the absorption tower 1 from bottom to top. The upper cycle is equipped with an oxidation column 2. The new slurry in the new slurry pipe 4 and the slurry extracted from the absorption tower 1 are mixed and then pumped back to the absorption tower 1 along the spraying slurry pipe 5 by the circulating pump 3. The circulating pump 3 in the lower circulation comprises two power frequency pumps and a frequency conversion pump in operation, and the two circulating pumps 3 in the upper circulation are both power frequency pumps. The constraints therefore also include the frequency range in which the circulation pump 3 can be adjusted. Is in operation, i.e. is always put into operation.
In this embodiment, the lower circulation includes two power frequency pumps and a variable frequency pump, and the upper circulation includes two power frequency pumps, should have two circulating pumps 3 at least in the lower circulation in the operation, and the variable frequency pump is normally open, consequently, in this embodiment, the pump state has following six:
1. and (3) circulating: 2 circulating pumps run and comprise 1 power frequency pump and 1 variable frequency pump; and (3) upper circulation: 0 power frequency pump runs;
2. and (3) circulating: 2 circulating pumps run and comprise 1 power frequency pump and 1 variable frequency pump; and (3) upper circulation: 1, operating a power frequency pump;
3. and (3) circulating: 2 circulating pumps run and comprise 1 power frequency pump and 1 variable frequency pump; and (3) upper circulation: 2, operating the power frequency pumps;
4. and (3) circulating: 3 circulating pumps run and comprise 2 power frequency pumps and 1 variable frequency pump; and (3) upper circulation: 0 power frequency pump runs;
5. and (3) circulating: 3 circulating pumps run and comprise 2 power frequency pumps and 1 variable frequency pump; and (3) upper circulation: 1, operating a power frequency pump;
6. and (3) circulating: 3 circulating pumps run and comprise 2 power frequency pumps and 1 variable frequency pump; and (3) upper circulation: and 2 power frequency pumps run.
The pump states are given as operating instructions, and if a certain pump state can meet the flue gas load handling requirements, the pump state is marked green, and if the flue gas load handling requirements cannot be met, the pump state is marked red. And when the colors are marked, economic indexes under each combination mode are provided, and whether the operating personnel need to be further switched to a more economic pump state is prompted and guided.
In the third step, the pH value of the sprayed slurry in the lower circulation is close to the upper limit of the pH value adjusting range in the lower circulation; meanwhile, on the premise of meeting the desulfurization effect, when the starting number of the power frequency pumps is minimum and the frequency of the variable frequency pump is close to the lower limit of the frequency regulation range of the variable frequency pump, the operating cost is minimized. Here the pH of the slurry sprayed in the upper cycle has little effect and so the pH of the slurry sprayed in the lower cycle is mainly adjusted.
The frequency of the variable frequency pump is used for absorbing the flue gas SO at the outlet of the tower 1XAnd in the third step, closed-loop optimization is realized by adopting a closed-loop displacement method, which comprises the following specific steps:
flue gas SO at outlet of absorption tower 1XUnder the condition that the concentration is stable and not exceeds the standard, if the frequency of the variable frequency pump does not reach the lowest and the pH value of the lower-cycle spraying slurry does not reach the upper limit of the adjusting range, gradually increasing the pH value of the lower-cycle spraying slurry, and then under the condition that the SO concentration is stable and not exceeds the standardXUnder the action of concentration feedback control, the frequency of the variable frequency pump is gradually reduced to finish the replacement from the pH value to the frequency until the frequency of the variable frequency pump is the lowest or the slurry is sprayed in a lower circulation mannerThe pH value of the solution is the highest.
Because the closed-loop replacement of the spraying slurry pH value-frequency of the variable frequency pump exists, when the frequency of the variable frequency pump reaches the upper limit, but the lower circulating spraying slurry pH value does not reach the upper limit of the adjusting range, the flue gas SO at the outlet of the absorption tower 1 can be adjusted by adjusting the lower circulating spraying slurry pH valueXAnd (4) concentration.
If the frequency of the variable frequency pump of the lower circulation reaches the highest value and the pH value of the spraying slurry of the lower circulation reaches the highest value at the same time, the flue gas SO at the outlet of the absorption tower 1XThe concentration still has an ascending trend, which indicates that the load of the currently input equipment is full, a power frequency pump in the lower circulation or the upper circulation is automatically started, and then the closed-loop replacement method is adopted to ensure that the frequency of the variable frequency pump is the lowest or the pH value of the lower circulation spraying slurry is the highest. Note that the line frequency pump with the least power should be preferentially started here. And when additionally starting the power frequency pump, the lower circulation spraying slurry pH value can be set to be a value higher than the upper limit of the current lower circulation spraying slurry pH value adjusting range, in the embodiment, the upper limit of the lower circulation spraying slurry pH value adjusting range is 5.2, but when additionally starting the power frequency pump, the upper limit adjustment can be carried out by adopting a mode of switching to manual adjustment, and the lower circulation spraying slurry pH value is adjusted to 5.5, SO that the adjusting sensitivity can be improved, and SO (SO) is prevented from being generated when starting the power frequency pumpXThe concentration exceeds the standard for a long time. After the pump is started, the SO is dischargedXIf the concentration is rapidly reduced, the pH value of the circulating spraying slurry is gradually reduced to 5.4, and after the pH value of the lower circulating spraying slurry is stable, the frequency conversion frequency is gradually reduced to the lowest possible frequency. To be exported SOXAfter the concentration is stable, performing pH value-frequency conversion replacement, and keeping the pH value of the high-spraying slurry and the frequency of the low-frequency conversion pump to operate.
Considering that disturbance factors received by the desulfurization process are very many, the occurrence mechanism of the desulfurization process is not clear under different flue gas temperatures, flue gas flow rates, sulfur dioxide concentrations, oxygen contents and slurry atomization degrees, and the process parameters detected by local measuring points are difficult to describe the real conditions inside the absorption tower 1 and the oxidation tower 2, so that the development of the dual-cycle optimization process of the desulfurization absorption tower 1 by establishing an accurate mechanism model is very difficult. In the first step, an orthogonal test method is adopted for carrying out the design of a fractional factorization.
In step one, the orthogonal test is performed as follows:
spraying slurry pH value orthogonal test, and if a plurality of slurry circulation loops exist, respectively testing each slurry circulation loop;
spraying a slurry flow orthogonal test, and if a plurality of slurry circulation loops exist, respectively testing each slurry circulation loop;
and (4) performing orthogonal test on the load working condition of the unit.
The whole orthogonal test process does not comprise about 6 hours for adjusting the working condition, and the test process relates to the following steps:
1. performing an orthogonal test on the pH value of the upper-circulation spraying slurry, wherein the pH value is divided into three sections in an adjustable range, namely a low value, a middle value and a high value;
2. performing an orthogonal test on the flow of the upper-circulation spraying slurry, wherein a pump starting process test is adopted to prevent a red line from crossing;
3. the pH value of the lower circulation spraying slurry in the orthogonal test is divided into three sections in the adjustable range of the pH value, namely a low value, a middle value and a high value;
4. in the orthogonal test of the lower circulation spraying slurry flow, in order to prevent red line crossing, only the variable frequency circulating pump 3 is tested, the frequency is divided into three sections, and the frequency is low value-middle value-high value;
5. orthogonal tests of unit load working conditions are tested under 50%, 75% and 95% working conditions, and test results are corrected according to flue gas flow, flue gas temperature, oxygen content and the like under different load working conditions.
Taking a 95% load condition test as an example, the detailed test steps are as follows:
1. preparation before testing
Adjusting the load of the unit to 95% load working condition, removing AGC, switching the steam turbine main control to manual operation, switching the boiler main control to manual operation, and keeping the boiler combustion stable and the flue gas load stable; the frequency of the variable frequency pump is switched manually, the lower circulating new slurry supply valve is switched manually, the upper circulating new slurry supply valve is switched manually, the stable operation of the gypsum slurry discharging and dehydrating process is kept, and the stability of a desulfurization system is kept;
2. top circulation slurry circulating pump 3 test
Manually starting one-stage circulating slurryA circulating pump 3 for recording SO at the outlet of the absorption tower 1XAnd recording the power consumption condition of each pump and the increase condition of the upper circulation slurry supply flow rate according to the concentration change condition.
Manually stopping an upper circulating slurry circulating pump 3, and recording the SO at the outlet of the absorption tower 1XAnd recording the power consumption condition of each pump and the increase condition of the upper circulation slurry supply flow rate according to the concentration change condition.
3. Upper cycle spray slurry pH test
Manually opening a new slurry supply valve with large upper circulation, adjusting the pH value from a low value to an intermediate value, and recording the SO at the outlet of the absorption tower 1XAnd recording the power consumption condition of each pump and the increase condition of the upper circulation slurry supply flow rate according to the concentration change condition.
Continuously and manually opening a new slurry supply valve which circulates upwards, adjusting the pH value from the middle value to the high value, and recording the SO at the outlet of the absorption tower 1XAnd recording the power consumption condition of each pump and the increase condition of the upper circulation slurry supply flow rate according to the concentration change condition.
And manually restoring the upper-circulating new slurry supply valve to restore the pH value of the upper-circulating spraying slurry to a low value.
4. Bottom circulation slurry circulating pump 3 test
Manually increasing the frequency of the lower circulating slurry variable frequency pump to an intermediate value, and recording the SO at the outlet of the absorption tower 1XAnd recording the power consumption condition of each pump according to the concentration change condition, and increasing the circulating slurry supply flow rate.
Manually increasing the frequency of the lower circulating slurry variable frequency pump to a high value again, and recording the SO at the outlet of the absorption tower 1XAnd recording the power consumption condition of each pump according to the concentration change condition, and increasing the circulating slurry supply flow rate.
And manually restoring the frequency of the lower circulating slurry variable frequency pump to a low value.
5. Lower circulation slurry pH test
Manually opening a new slurry supply valve which circulates at the top and the bottom, adjusting the pH value from a low value to an intermediate value, and recording the SO at the outlet of the absorption tower 1XAnd recording the power consumption condition of each pump according to the concentration change condition, and increasing the circulating slurry supply flow rate.
Continuously and manually opening a new slurry supply valve which circulates up and down to adjust the pH value from the middle value to the high value,record absorption tower 1 outlet SOXAnd recording the power consumption condition of each pump according to the concentration change condition, and increasing the circulating slurry supply flow rate.
And manually restoring a new slurry supply valve of the lower circulation to restore the pH value of the lower circulation spraying slurry to a low value.
6. Recovery site
Recovering the automatic control of the desulfurization system, recovering the automatic control of the steam engine main control and the boiler main control, and putting into AGC.
Looking up the historical curve, evaluating and obtaining the SO removal of each adjustable meansXThe contribution capacity of the power generation device and the generated electricity consumption and material consumption conditions.
Note that: industrial frequency pump for removing SOXThe contribution capacity and the generated electricity consumption and material consumption conditions are calibrated by adopting the test result of the variable frequency pump.
The test procedures for the 50% load condition and the 75% load condition are similar and will not be described herein. The tests do not need to be combined with each other, and because the test working conditions are limited, in practical application, the model needs to be fitted in a mode of European crown linear interpolation.
If the fresh slurry in the apparatus includes a powder silo slurry in addition to fresh limestone slurry and the powder silo slurry and fresh limestone slurry do not share a new slurry supply valve, then the new slurry supply valves on the fresh limestone slurry and the powder silo slurry can be orthogonally tested, respectively.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (10)
1. The utility model provides a wet flue gas desulfurization sprays volume and sprays thick liquid pH value coupling control optimization method for when adopting the gypsum method to carry out the desulfurization make desulphurization unit working costs minimizing under the prerequisite of guaranteeing desulfurization effect, its characterized in that: the method comprises the following steps:
the method comprises the following steps: carrying out a fractional factorial design to obtain the flue gas SO of each manipulated variable at the outlet of an absorption tower (1) of the desulfurization deviceXInfluence on concentration, influence on electricity consumption and influence on material consumption;
step two: establishing an optimization model of a slurry circulation loop in a desulfurization device, and constructing an economic objective function with uniform dimension based on the output of the model; obtaining an algorithm of a target function, and recording the algorithm as an optimization algorithm; the starting and stopping states of each circulating pump (3) are recorded as pump states; parameters reflecting the running state of the desulfurization device under the current pump state are recorded as optimization variables;
step three: in the current pump state, the optimization algorithm traverses the conditions of the optimization variable combinations in all slurry circulation loops, the optimization variable combination with the optimal economy is found out, and the set values in all controllers of the desulfurization device are adjusted according to the optimization variable combination with the optimal economy, so that closed-loop optimization is realized.
2. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 1, characterized in that: in the second step, the optimization algorithm is a genetic algorithm or a particle swarm algorithm, and a penalty factor in the optimization algorithm is the over-removed SOXThe objective function being the rejection of SO that should be removed but not removedXThe amount of (a) is greater than 0.
3. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 2, characterized in that: in the second step, the constraint conditions in the optimization algorithm comprise the pH value adjusting range of the slurry sprayed in each slurry circulation loop, and the optimization variable is the pH value of the slurry sprayed in each slurry circulation loop.
4. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 3, characterized in that: the desulfurization device is a single-tower double-circulation device and comprises an upper circulation loop and a lower circulation loop; the circulating pump (3) of the lower circulation comprises a plurality of power frequency pumps and an on-going variable frequency pump, and the circulating pump (3) of the upper circulation comprises a plurality of power frequency pumps; the constraints also include a frequency range in which the circulation pump (3) is adjustable.
5. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 4, characterized in that: in the third step, the pH value of the sprayed slurry in the lower circulation is close to the upper limit of the pH value adjusting range in the lower circulation; meanwhile, on the premise of meeting the desulfurization effect, when the starting number of the power frequency pumps is minimum and the frequency of the variable frequency pump is close to the lower limit of the frequency regulation range of the variable frequency pump, the operating cost is minimized.
6. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 5, characterized in that: the frequency of the variable frequency pump is the flue gas SO at the outlet of the absorption tower (1)XAnd in the third step, closed-loop optimization is realized by adopting a closed-loop displacement method, which comprises the following specific steps:
flue gas SO at outlet of absorption tower (1)XUnder the condition that the concentration is stable and not exceeds the standard, if the frequency of the variable frequency pump does not reach the lowest and the pH value of the lower-cycle spraying slurry does not reach the upper limit of the adjusting range, gradually increasing the pH value of the lower-cycle spraying slurry, and then under the condition that the SO concentration is stable and not exceeds the standardXUnder the action of concentration feedback control, the frequency of the variable frequency pump is gradually reduced, and the replacement from the pH value to the frequency is completed until the frequency of the variable frequency pump is lowest or the pH value of the lower circulating spraying slurry is highest.
7. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 6, characterized in that: further comprising the steps of:
step four: if the frequency of the variable frequency pump of the lower circulation reaches the highest value and the pH value of the lower circulation spraying slurry reaches the highest value at the same time, the flue gas SO at the outlet of the absorption tower (1)XIf the concentration still has a rising trend, starting a power frequency pump in the lower circulation or the upper circulation, and then adopting the closed-loop replacement method to ensure that the frequency of the variable frequency pump is the lowest or the pH value of the lower circulation spraying slurry is the highest。
8. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 1, characterized in that: in the first step, an orthogonal test method is adopted for carrying out the design of a fractional factorization.
9. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 8, characterized in that: in step one, the orthogonal test is performed as follows:
spraying slurry pH value orthogonal test, and if a plurality of slurry circulation loops exist, respectively testing each slurry circulation loop;
spraying a slurry flow orthogonal test, and if a plurality of slurry circulation loops exist, respectively testing each slurry circulation loop;
and (4) performing orthogonal test on the load working condition of the unit.
10. The wet desulphurization spraying amount and spraying slurry pH value coupling control optimization method according to claim 8, characterized in that: in the first step, a model equation of the influence of each operation variable is fitted by adopting a method of European crown linear interpolation.
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