CN113019086B - Precise feeding method of desulfurization synergist - Google Patents

Precise feeding method of desulfurization synergist Download PDF

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CN113019086B
CN113019086B CN202110224934.3A CN202110224934A CN113019086B CN 113019086 B CN113019086 B CN 113019086B CN 202110224934 A CN202110224934 A CN 202110224934A CN 113019086 B CN113019086 B CN 113019086B
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synergist
concentration
desulfurization
slurry circulating
flue gas
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CN113019086A (en
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陈彪
雷石宜
王洁
秦刚华
冯向东
吴贤豪
王维平
黄斐鹏
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Zhejiang Energy Group Research Institute Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/80—Semi-solid phase processes, i.e. by using slurries
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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Abstract

The invention relates to a precise adding method of a desulfurization synergist, which comprises the following steps: step 1, firstly, performing a synergist adding characteristic test on a unit desulfurization system, and making a synergist adding characteristic curve; and 2, comparing the economical efficiency of the added synergist and the added slurry circulating pump, and determining the concentration of the equivalent synergist. The invention has the beneficial effects that: the invention overcomes the defects that the existing desulphurization synergist feeding principle standard, the adding time, the adding amount and the like are not referred to and are controlled by experience, can realize timely and quantitative feeding of the desulphurization synergist, and ensure that the SO at the outlet is discharged2The concentration is operated close to the emission limit value, and the economical efficiency of the desulfurization system is controlled at a limit economic level. The invention can control the whole process outlet SO2The concentration line pressing operation effectively reduces the over-standard instantaneous value, reduces the adjustment workload of operators on duty, and does not need additional reconstruction investment.

Description

Precise feeding method of desulfurization synergist
Technical Field
The invention belongs to the technical field of adding of desulfurization synergists, and particularly relates to a precise adding method of a desulfurization synergist.
Background
The coal-fired power generation is the most main thermal power generation mode in China at present, and the coal-fired flue gas is desulfurized by a limestone-gypsum wet method, so that the coal-fired power generation has the main advantages of mature technology, strong adaptability of coal load and deep desulfurization potential. At present, after ultralow emission transformation, a desulfurization system is mature in structural design and performance optimization, and the desulfurization efficiency can reach a higher level, but a desulfurization slurry circulating pump is still the main power consumption equipment of the desulfurization system, the power consumption of the desulfurization slurry circulating pump accounts for 65-76% of the power consumption of the whole desulfurization system, and the power consumption under certain working conditions is higher.
In order to control the energy consumption of a desulfurization system, the optimal operation of a slurry circulating pump is generally realized by seeking an optimal slurry circulating pump combination mode in operation experience under different working conditions at present. The optimized operation method has the major disadvantages that:
1. the liquid-gas ratio of the desulfurization reaction cannot be continuously adjusted by the feeding and withdrawing of the slurry circulating pump, and the deviation between the actually operated liquid-gas ratio and the optimal liquid-gas ratio is large;
2. the start and stop of the slurry circulating pump can generate large fluctuation on the pH value of the slurry in the absorption tower, and is not beneficial to the stable reaction in the absorption tower and the scaling prevention requirement of a system;
3. under the working condition of rapid fluctuation of unit load, the adjustment time for switching the combination mode of the slurry circulating pump is long, and automatic control is difficult to realize.
And some units adopt a high-pressure high-power slurry circulating pump variable-frequency speed regulation device, so that the liquid-gas ratio of the desulfurization reaction can be continuously controlled within a certain range, and the aim of saving energy is fulfilled. But the spraying layer blocks slurry accumulation, the high-power frequency converter has insufficient use reliability, large initial investment and the like, so that the scheme is not applied on a large scale all the time.
The desulfurization synergist is also a desulfurization efficiency-improving idea which is generally applied at present, and is mainly characterized in that the whole process is applicable by performing resistance reduction and efficiency improvement aiming at the slurry mass transfer process, the use cost is low, the desulfurization synergist is used both flexibly and conveniently, and no negative influence is caused on a desulfurization system. At present, the synergist can be automatically added through a metering pump, but the adding time and the adding amount can be controlled only through the experience of operators on duty, SO that the desulfurization outlet SO is always caused by excessive addition of the synergist2Too low concentration or delayed addition of sulfur results in SO at the desulfurization outlet2And the instantaneous value of the concentration exceeds the standard.
In view of the defects that the existing desulphurization synergist adding principle standard, adding time, adding amount and the like are not referenced and are controlled by experience, how to accurately add the desulphurization synergist is still a technical problem, and the deep energy-saving and consumption-reducing work of a desulphurization system is greatly limited.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a precise adding method of a desulfurization synergist.
The precise adding method of the desulfurization synergist comprises the following steps:
step 1, firstly, performing a synergist adding characteristic test on a unit desulfurization system, and making a synergist adding characteristic curve;
step 2, comparing the economical efficiency of the added synergist and the added slurry circulating pump, and determining the concentration of the equivalent synergist;
step 3, desulfurizing the clean flue gas SO2The concentration is a control principle, and the desulfurized clean flue gas SO is used under the condition of meeting the unit load fluctuation allowance2Controlling the concentration at a target value, and making a limit economic operation mode curve of the synergist in the whole process;
step 3.1, under the combined operation working condition of N slurry circulating pumps, desulfurizing clean flue gas SO2Horizontally drawing a straight line in a coordinate system where a synergist adding characteristic curve is located for the concentration target value; after the straight line is intersected with the synergist adding characteristic curve corresponding to the equivalent synergist concentration, the number of the slurry circulating pumps in combined operation is switched to be N +1 (if the operation of two slurry circulating pumps is changed into three operation);
step 3.2, readjusting the concentration of the desulfurization synergist to ensure that the desulfurization clean flue gas SO2After the concentration reaches the target value, continuing to remove the SO from the clean flue gas2Horizontally drawing a straight line in a coordinate system where a synergist adding characteristic curve is located according to the concentration target value, switching the number of slurry circulating pumps which are operated in a combined mode to be N +2 after the straight line is intersected with the synergist adding characteristic curve corresponding to the equivalent synergist concentration, and assigning the N +2 to the N; the concentration of the synergist is adjusted again to ensure that the flue gas SO is desulfurized and purified2The concentration is a target value;
step 3.3, repeating the step 3.1 to the step 3.2 until the value of N reaches the upper limit;
step 3.3, combining all horizontal straight lines drawn from the step 3.1 to the step 3.3 to form a limit economic operation mode curve; the curve of the ultimate economic operation mode is the raw flue gas SO2Concentration, different circulating pump combination forms and different desulfurization synergistsA concentration pre-judging curve, and the ultimate desulfurization economy can be obtained by operating according to the curve;
step 4, according to the original SO of the desulfurization inlet in the limit economic operation curve2The concentration of the desulfurization synergist is determined, and the desulfurization synergist is supplemented regularly by combining the comprehensive degradation rate of the synergist in the tower;
step 4.1, combining the efflux consumption Q of the synergist1And chemical degradation amount Q of synergist2Determining the supplement amount of the desulfurization synergist to be Q1+Q2(ii) a The mass concentration of the prepared desulfurization synergist is CFeeding material(50% -70% can be taken), the feeding quantity of the synergist automatic metering pump is set to be QFeeding materialIn kg/h, then:
Qfeeding material＝(Q1+Q2)/CFeeding material
In the above formula, QFeeding materialAutomatic metering of the feed quantity, Q, for the synergist1Consumption of synergist by efflux, Q2Is the chemical degradation amount of the synergist; cFeeding materialThe mass concentration of the prepared desulfurization synergist is adopted;
step 4.2, increasing the adjustment amount of the concentration of the desulfurization synergist on the basis of the target value when the load suddenly increases, and reducing the adjustment amount of the concentration of the desulfurization synergist on the basis of the target value when the load decreases so as to adapt to the operation requirement of the unit; in addition, the learning capacity of the system can be expanded, and when the desulfurization efficiency is reduced due to the abnormality of system equipment, the obtained big data under the balanced state is utilized to further update the synergist adding characteristic curve and give an alarm prompt.
Preferably, step 1 specifically comprises the following steps:
step 1.1, determining a combined operation mode of a slurry circulating pump;
step 1.2, determining the concentration of the desulfurization synergist;
step 1.3, establishing a plane rectangular coordinate system, and desulfurizing the original flue gas SO of the inlet2The concentration is taken as the abscissa, and the desulfurized clean flue gas SO is taken as2Concentration as ordinate;
step 1.4, the different desulfurization inlet raw flue gas measured under the working conditionSO2Concentration (e.g., 1000 mg/m)3～1800mg/m3) The corresponding desulfurization clean flue gas SO within the pH value of 5.2-5.6 (a certain value is fixed as 5.3) of the desulfurization slurry2The concentrations are connected into a line and used as a synergist adding characteristic curve under the working condition;
step 1.5, under the combined operation mode of the slurry circulating pumps corresponding to the step 1.1, resetting the concentration of the desulfurization synergist to be a concentration value with a fixed quantity, and dividing the obtained characteristic curve for adding the synergist with the fixed quantity into a group;
step 1.6, adding a plurality of combined operation modes of the slurry circulating pump except the combined operation mode of the slurry circulating pump selected in the step 1.1, and returning to execute the step 1.2 to the step 1.5 after adopting one combined operation mode of the plurality of combined operation modes of the slurry circulating pump; all synergist adding characteristic curves in the plane rectangular coordinate system are obtained to jointly form a desulfurization synergist adding characteristic curve after all slurry circulating pump combined operation modes are adopted; the more characteristic curves obtained by the test, the more accurate the obtained economic operation control mode.
Preferably, step 2 specifically comprises the following steps:
step 2.1, calculating the cost of adding the synergist:
F1＝Fsynergist×(Q1+Q2)
In the above formula, F1The unit is Yuan/h for adding the synergist; the F synergist is synergist unit price, and the unit is yuan/kg; q1The unit is kg/h for the outward discharge consumption of the synergist; q2The unit is kg/h for chemical degradation amount of the synergist;
Q1＝2.125×Qflue gas×COriginal SO2×10-6/η1×CSynergist×10-6
In the above formula, Q1The unit is kg/h for the outward discharge consumption of the synergist; 2.125 is CaSO4And SO2136/64; qFlue gasIs the flow rate of the exhaust smoke of the unit in Nm3/h；COriginal SO2For desulfurizing the imported raw flue gas SO2Concentration in mg/Nm3；η1Is the solid content of the gypsum slurry; cSynergistThe concentration of the desulfurization synergist is expressed in ppm;
Q2＝Csynergist×α×η2/24
In the above formula, Q2The unit is kg/h for chemical degradation amount of the synergist; cSynergistThe concentration of the desulfurization synergist is expressed in ppm; alpha is the holding amount of the synergist in the tower and the concentration conversion coefficient of the desulfurization synergist, and the unit is kg/ppm; eta2The daily degradation consumption rate of the desulfurization synergist (determined according to the degradation performance of the synergist and can be obtained by tests); wherein: α ═ π × D2/4×H×ρ×10-6
In the above formula, alpha is the holding amount of the synergist in the tower and the concentration conversion coefficient of the desulfurization synergist, and the unit is kg/ppm; d is the diameter of the desulfurizing tower and is m; h is the slurry liquid level in the desulfurizing tower and the unit is m; rho is the density of the desulfurized slurry in kg/m3；
Step 2.2, calculating the cost of the slurry circulating pump:
F2＝F3+F4
in the above formula, F2In order to increase the cost of a slurry circulating pump, the unit is Yuan/h; f3The operation cost of a single slurry circulating pump is unit/h; f4The unit of the cost generated by increasing the electric quantity of the induced draft fan after increasing the input is yuan/h;
F3＝P×Felectricity price
In the above formula, P is the operating electric power of a slurry circulating pump, FPrice of electricityThe unit is yuan/kwh for supplying power price;
F4＝Qflue gas*PResistance block/3600/1000/η3/η4*FPrice of electricity
In the above formula, PResistance deviceThe smoke resistance increased after the slurry circulating pump is put into use is expressed in Pa, eta3For inducing internal efficiency of the fan, eta4The mechanical efficiency of the induced draft fan is improved; fPrice of electricityThe unit is yuan/kwh for supplying power price; qFlue gasIs the flow rate of the exhaust smoke of the unit in Nm3/h；
Step 2.3, if the cost of adding the synergist is equivalent to that of adding a slurry circulating pump of one slurry circulating pump, the corresponding concentration C of the desulfurization synergist is determinedSynergistThe equivalent synergist concentration is set.
Preferably, the combined operation mode of the slurry circulating pumps in the step 1.1 and the step 1.6 comprises the following steps: two slurry circulating pumps are combined to operate, three slurry circulating pumps are combined to operate, and four slurry circulating pumps are combined to operate.
Preferably, the desulfurization synergist concentrations in step 1.2 include: 0ppm, 100ppm, 200ppm, 300ppm, 400ppm and 500 ppm.
Preferably, the desulfurization synergist concentration is reset to another three to five values in step 1.5, and the resulting three to five synergist addition characteristic curves are divided into one group.
Preferably, the clean flue gas SO is desulfurized in the step 32The target concentration was 35mg/m3；35mg/m3The higher the control is, the better the economical efficiency is, so the target value can be 35mg/m3(the emission balance is the clean flue gas SO of desulfurization2The target value of the concentration and the pH value of the desulfurization slurry are controlled together).
Preferably, N in the steps 3.1 to 3.3 is the number of slurry circulating pumps which are operated in combination, and N is more than or equal to 2 and less than or equal to 4.
Preferably, the pH of the desulfurized slurry in step 1.4 assumes a fixed value of 5.3.
The invention has the beneficial effects that: the invention overcomes the defects that the existing desulphurization synergist feeding principle standard, the adding time, the adding amount and the like are not referred to and are controlled by experience, can realize timely and quantitative feeding of the desulphurization synergist, and ensure that the SO at the outlet is discharged2The concentration is operated close to the emission limit value, and the economical efficiency of the desulfurization system is controlled at a limit economic level. The invention can control the whole process outlet SO2The concentration line pressing operation effectively reduces the exceeding of an instantaneous value, reduces the adjustment workload of operators on duty, and does not need additional transformation investment.
Drawings
FIG. 1 is a graph of synergist addition characteristics;
FIG. 2 is a graph of the ultimate economic operation of a synergist;
FIG. 3 is a flow chart of a precise desulfurization synergist feeding method.
Detailed Description
The present invention will be further described with reference to the following examples. The following examples are set forth merely to aid in the understanding of the invention. It should be noted that, for a person skilled in the art, several modifications can be made to the invention without departing from the principle of the invention, and these modifications and modifications also fall within the protection scope of the claims of the present invention.
According to the addition characteristic curve of the synergist and the concentration of the equivalent synergist, the method makes a limit economic operation mode curve of the synergist in the whole process. Obtaining the specific circulating pump combination and the raw flue gas SO according to the curve2Under the concentration, the required synergist concentration is obtained, and the synergist metering pump is automatically controlled to quantitatively supply the desulfurization synergist. The condition of excessive or insufficient synergist can not occur, and the ultimate economic operation of the whole desulfurization process is realized.
As an example, as shown in FIG. 3, a precise dosing method of desulfurization synergist comprises the following steps:
step 1, firstly, performing a synergist adding characteristic test on a unit desulfurization system, and making a synergist adding characteristic curve as shown in figure 1;
step 1.1, determining a combined operation mode of a slurry circulating pump;
step 1.2, determining the concentration of the desulfurization synergist;
step 1.3, establishing a plane rectangular coordinate system, and desulfurizing the original flue gas SO of the inlet2The concentration is taken as the abscissa, and the desulfurized clean flue gas SO is taken as2Concentration as ordinate;
step 1.4, measuring different desulfurization inlet raw flue gas SO under the working condition2Concentration (e.g., 1000 mg/m)3～1800mg/m3) The corresponding desulfurization clean flue gas SO within the pH value of 5.2-5.6 (a certain value is fixed as 5.3) of the desulfurization slurry2The concentrations are connected into a line and used as a synergist adding characteristic curve under the working condition;
step 1.5, under the slurry circulating pump combination operation mode corresponding to the step 1.1, resetting the concentration of the desulfurization synergist to be a concentration value with a fixed quantity, and dividing the obtained characteristic curve for adding the synergist with the fixed quantity into a group;
step 1.6, adding a plurality of combined operation modes of the slurry circulating pump except the combined operation mode of the slurry circulating pump selected in the step 1.1, and returning to execute the step 1.2 to the step 1.5 after adopting one combined operation mode of the plurality of combined operation modes of the slurry circulating pump; all synergist adding characteristic curves in the plane rectangular coordinate system are obtained to jointly form a desulfurization synergist adding characteristic curve after all slurry circulating pump combined operation modes are adopted; the more characteristic curves obtained by the test are, the more accurate the obtained economic operation control mode is;
step 2, comparing the economical efficiency of the added synergist and the added slurry circulating pump, and determining the concentration of the equivalent synergist;
step 2.1, calculating the cost of adding the synergist:
F1＝Fsynergist×(Q1+Q2)
In the above formula, F1The unit is Yuan/h for adding the synergist; the F synergist is synergist unit price, and the unit is yuan/kg; q1The unit is kg/h for the outward discharge consumption of the synergist; q2The unit is kg/h for chemical degradation amount of the synergist;
Q1＝2.125×Qflue gas×COriginal SO2×10-6/η1×CSynergist×10-6
In the above formula, Q1The unit is kg/h for the outward discharge consumption of the synergist; 2.125 is CaSO4And SO2136/64; qFlue gasIs the flow rate of the exhaust smoke of the unit in Nm3/h；COriginal SO2For desulfurizing the imported raw flue gas SO2Concentration in mg/Nm3；η1Is the solid content of the gypsum slurry; cSynergistThe concentration of the desulfurization synergist is expressed in ppm;
Q2＝Csynergist×α×η2/24
In the above formula，Q2The unit is kg/h for chemical degradation amount of the synergist; cSynergistThe concentration of the desulfurization synergist is expressed in ppm; alpha is the holding amount of the synergist in the tower and the concentration conversion coefficient of the desulfurization synergist, and the unit is kg/ppm; eta2The daily degradation consumption rate of the desulfurization synergist (determined according to the degradation performance of the synergist and can be obtained by tests); wherein: α ═ π × D2/4×H×ρ×10-6
In the above formula, alpha is the holding amount of the synergist in the tower and the concentration conversion coefficient of the desulfurization synergist, and the unit is kg/ppm; d is the diameter of the desulfurizing tower and is expressed in m; h is the slurry liquid level in the desulfurizing tower and the unit is m; rho is the density of the desulfurized slurry in kg/m3；
Step 2.2, calculating the cost of the slurry circulating pump:
F2＝F3+F4
in the above formula, F2In order to increase the cost of a slurry circulating pump, the unit is yuan/h; f3The operation cost of a single slurry circulating pump is unit/h; f4The unit of the cost generated by increasing the electric quantity of the induced draft fan after increasing the input is yuan/h;
F3＝P×Fprice of electricity
In the above formula, P is the operating electric power of a slurry circulating pump, FPrice of electricityThe unit is yuan/kwh for supplying power price;
F4＝Qflue gas*PResistance device/3600/1000/η3/η4*FPrice of electricity
In the above formula, PResistance deviceThe smoke resistance increased after the slurry circulating pump is put into use is expressed in Pa, eta3For inducing internal efficiency of the fan, eta4The mechanical efficiency of the induced draft fan is improved; fPrice of electricityThe unit is yuan/kwh for supplying power price; qFlue gasIs the flow rate of the exhaust smoke of the unit in Nm3/h；
Step 2.3, if the cost of adding the synergist is equivalent to that of adding a slurry circulating pump of one slurry circulating pump, the corresponding concentration C of the desulfurization synergist is determinedSynergistSetting the equivalent synergist concentration;
step 3, toDesulfurization clean flue gas SO2The concentration is a control principle, and the desulfurized clean flue gas SO is used under the condition of meeting the unit load fluctuation allowance2Controlling the concentration at a target value, and making a curve of the limit economic operation mode of the synergist in the whole process as shown in figure 2;
step 3.1, under the combined operation condition of N slurry circulating pumps, desulfurizing clean flue gas SO2Horizontally drawing a straight line in a coordinate system where the synergist adding characteristic curve is located for the concentration target value; after the straight line is intersected with the synergist adding characteristic curve corresponding to the equivalent synergist concentration, the number of the slurry circulating pumps in combined operation is switched to be N +1 (if the operation of two slurry circulating pumps is changed into three operation);
step 3.2, readjusting the concentration of the desulfurization synergist to ensure that the desulfurization clean flue gas SO2After the concentration reaches the target value, continuing to remove the SO from the clean flue gas2Horizontally drawing a straight line in a coordinate system where a synergist adding characteristic curve is located according to the concentration target value, switching the number of slurry circulating pumps which are operated in a combined mode to be N +2 after the straight line is intersected with the synergist adding characteristic curve corresponding to the equivalent synergist concentration, and assigning the N +2 to the N; the concentration of the synergist is adjusted again to ensure that the flue gas SO is desulfurized and purified2The concentration is a target value;
step 3.3, repeating the step 3.1 to the step 3.2 until the value of N reaches the upper limit;
step 3.3, combining all horizontal straight lines drawn from the step 3.1 to the step 3.3 to form a limit economic operation mode curve; the curve of the ultimate economic operation mode is the raw flue gas SO2The concentration, different circulating pump combination forms and different desulfurization synergist concentration pre-judging curves are operated according to the curves to obtain the ultimate desulfurization economy;
step 4, according to the original SO of the desulfurization inlet in the limit economic operation curve2The concentration of the desulfurization synergist is determined, and the desulfurization synergist is supplemented regularly by combining the comprehensive degradation rate of the synergist in the tower;
step 4.1, combining the efflux consumption Q of the synergist1And chemical degradation amount Q of synergist2Determining the supplement amount of the desulfurization synergist to be Q1+Q2(ii) a The prepared desulfurization synergist is preparedIn a quantitative concentration of CFeeding material(50% -70% can be taken), the feeding quantity of the synergist automatic metering pump is set to be QFeeding materialIn kg/h, then:
Qfeeding material＝(Q1+Q2)/CFeeding material
In the above formula, QFeeding materialAutomatic metering of the feed quantity, Q, for the synergist1For the efflux consumption of synergist, Q2Is the chemical degradation amount of the synergist; cFeeding materialThe mass concentration of the prepared desulfurization synergist is adopted;
step 4.2, increasing the adjustment quantity of the concentration of the desulfurization synergist on the basis of the target value when the load is suddenly increased, and reducing the adjustment quantity of the concentration of the desulfurization synergist on the basis of the target value when the load is reduced so as to adapt to the operation requirement of the unit; in addition, the learning capacity of the system can be expanded, and when the desulfurization efficiency is reduced due to the abnormality of system equipment, the obtained big data under the balanced state is utilized to further update the synergist adding characteristic curve and give an alarm prompt.
A certain boiler is a 500-ton steam extraction back pressure type coal-fired heat supply generating set. The boiler is an open-air arrangement boiler with high temperature and high pressure, natural circulation, single steam pocket, n-shaped arrangement, single furnace chamber four-corner tangential combustion, balanced ventilation, solid-state slag discharge, water spray temperature reduction and all-steel framework suspension structure. The maximum continuous evaporation capacity of the boiler is 500t/h, and the minimum stable combustion load is 200 t/h. The diameter of the desulfurization absorption tower is 8.2m, the operating liquid level is 8.5m, and the parameters of the slurry circulating pump are as follows in the following table 1:
TABLE 1 slurry circulating pump parameter table
Index (I) 3A slurry circulating pump 3B slurry circulating pump 3C slurry circulating pump 3D slurry circulating pump
Lift m 18 20 22 24
Flow rate m3/h 2900 2900 2900 2900
Rated current A 32.1 32.1 35.2 39.1
First, desulfurization synergist addition characteristic curve
The test conditions are as follows: the flow rate of the main steam is 496.6t/h, the pH control range is 5.29-5.34, the concentration of S02 in the raw flue gas is 1100-1750 mg/m3, the density of the absorption tower is 1119-1128 kg/m3, the liquid level of the absorption tower is 7.22-7.4 m, the inlet temperature of FGD is 99.8-102.2 ℃, and the density of limestone slurry is 1235-1248.6 kg/m 3. Test data are obtained according to the step 1, and a desulfurization synergist addition characteristic curve under different pump combination modes and typical desulfurization synergist concentrations is drawn as shown in a graph 1;
secondly, calculating the concentration of the equivalent synergist
1. According to the power of 280kw of a single circulating pump and the power price of 0.4 yuan/kwh, the electricity fee F per hour3Is 112 yuan; according to the flue gas flow rate of 543886m3The resistance of a single circulating pump is 400Pa, and the calculation in the step 2 shows that the fan increases the electricity charge F per hour4Comprises the following steps:
543886 400/3600/1000/0.85/0.98 0.4 ═ 29.02 yuan, adding one slurry circulating pump increases the cost F2112+29.02 ═ 141.02 yuan/h; wherein 0.85 and 0.98 are respectively the internal efficiency and the mechanical efficiency of the induced draft fan; 3600 is a unit conversion factor of hour to second; 1000 is the unit scaling factor for w to kw;
2. at a concentration of 400ppm synergist, the cost F of synergist supplementation is calculated according to step 21Comprises the following steps:
19.8*(2.125*543886*1630*10-6/0.2*400*10-6+400 × 0.5 × 0.4/24) ═ 140.6 yuan/h, where 19.8 is the synergist unit price 19.8 yuan/kg, 2.125 is CaSO4And SO2Molar mass ratio of (2), flue gas flow measuring 543886m31630 is the raw flue gas SO2Concentration 1630mg/Nm30.2 is the solid content of the desulfurization slurry, 400ppm is the concentration of the synergist in the tower, 0.5 is the conversion coefficient of the holding amount of the synergist in the tower and the concentration of the synergist, 0.4 is taken as the degradation rate of the synergist per day, and 24 is the conversion of the daily degradation amount to hours.
When the cost of the circulating pump is compared with the cost of the supplementary synergist at 400ppm, the cost is 141.02 yuan/h and 140.6 yuan/h respectively, and the cost are equivalent, so the concentration of the equivalent synergist is 400 ppm.
Thirdly, limit economic operation curve of synergist in whole process
Control of clean flue gas SO by adjusting synergist2The concentration is 35mg/m3When the concentration reaches 400ppm, the slurry circulating pump control mode is adjusted from two-pump operation to three-pump operation, and then the synergist is continuously adjusted to control the clean flue gas SO2The concentration is 35mg/m at the target value3. A black line in the curve was obtained (in this example, the black line was 35 mg/m)3Horizontal straight line, at 400ppm, the operation mode is changed from two circulating pumps +400ppm synergist to three circulating pumps +0 ppm. ) The curve is the maximum economic operating curve of the synergist. Looking up the curve can obtain the original SO of the flue gas under the current working condition2The concentration corresponds to the target value of the concentration of the synergist.
Specific desulfurization operationThe method comprises the following steps: in the raw flue gas SO2The concentration is from 800mg/m3To 1600mg/m3Automatically tracking and adding chemicals by using a synergist metering pump, keeping the two absorption tower slurry circulating pumps running and keeping the concentration of the synergist of the slurry in the absorption tower at a target value (a line segment of a square line, 400ppm, and a black line intersection point); raw flue gas SO2The concentration exceeds 1600mg/m3Then, the curve jumps to three absorption tower slurry circulating pumps to operate, the concentration of the synergist can be adjusted to 0ppm and the synergist follows the original SO of the flue gas2The concentration rises over 1750mg/m3Then, the administration of the synergist was started gradually in accordance with the target value (line segment at the intersection of the circular line and the black line).
Fourthly, quantitatively supplementing the synergist according to the target value of the concentration of the synergist
When the target concentration value is X ppm according to the calculation formula, the synergist supplement amount tracked by the synergist metering pump is Y kg/h, and the synergist supplement amount comprises the following components: the efflux consumption of the synergist and the chemical degradation amount of the synergist. The calculation according to step 2 has the following relationship: y ═ Q1+Q2)/CFeeding material＝(136/64*543886*1630*10-6/0.2*X*10-6+ X0.5X 0.4/24)/0.5 ═ 0.0355X, where the daily synergist degradation rate was taken to be 0.4, original SO2The concentration is 1630mg/m3Measuring 543886m of flue gas flow3136, 64 are CaSO respectively4And SO2The ratio of the two molar masses of the components is 2.125, 0.2 is the solid content of the taken desulfurization slurry, 0.5 is the holding amount of the synergist in the tower and the conversion coefficient of the concentration of the synergist, and 24 is the time for converting the daily degradation amount into hours; the synergist holding amount and synergist concentration conversion coefficient alpha ═ pi × 8.2 × 8.2/4 × 8.5 × 1130 × 10 in the tower-6The slurry density p is 1130kg/m at 0.5kg/ppm3Original SO2The concentration is 1630mg/m3Measuring 543886m of flue gas flow3H, formulation synergist feed concentration CFeeding materialTaking 50 percent. The synergist is added according to the tracked synergist supplement amount, SO that the SO at the desulfurization outlet can be controlled2The concentration is close to 35mg/m3The ultimate economic mode of operation. For example, when the concentration of the slurry synergist is controlled to be 400ppm, the synergist is required to be added in an amount Y of 0.0355X 400 of 14.2 kg/h.

Claims (9)

1. A precise adding method of a desulfurization synergist is characterized by comprising the following steps:
step 1, firstly, performing a synergist adding characteristic test on a unit desulfurization system, and making a synergist adding characteristic curve;
step 2, comparing the economical efficiency of the added synergist and the added slurry circulating pump, and determining the concentration of the equivalent synergist;
step 3, desulfurizing the clean flue gas SO2The concentration is a control principle, and the desulfurized clean flue gas SO is used under the condition of meeting the unit load fluctuation allowance2Controlling the concentration at a target value, and making a limit economic operation mode curve of the synergist in the whole process;
step 3.1, under the combined operation condition of N slurry circulating pumps, desulfurizing clean flue gas SO2Horizontally drawing a straight line in a coordinate system where a synergist adding characteristic curve is located for the concentration target value; after the straight line is intersected with the synergist adding characteristic curve corresponding to the equivalent synergist concentration, the number of the slurry circulating pumps which are switched to operate in a combined mode is N + 1;
step 3.2, readjusting the concentration of the desulfurization synergist to ensure that the desulfurization clean flue gas SO2After the concentration reaches the target value, continuing to remove the SO from the clean flue gas2Horizontally drawing a straight line in a coordinate system where a synergist adding characteristic curve is located according to the concentration target value, switching the number of slurry circulating pumps which are operated in a combined mode to be N +2 after the straight line is intersected with the synergist adding characteristic curve corresponding to the equivalent synergist concentration, and assigning the N +2 to the N; the concentration of the synergist is adjusted again to ensure that the flue gas SO is desulfurized and purified2The concentration is a target value;
step 3.3, repeating the step 3.1 to the step 3.2 until the value of N reaches the upper limit;
step 3.3, combining all horizontal straight lines drawn from the step 3.1 to the step 3.3 to form a limit economic operation mode curve;
step 4, according to the original SO of the desulfurization inlet in the limit economic operation curve2Supplementing the desulfurization synergist at fixed time according to the concentration of the desulfurization synergist determined by the concentration;
step 4.1, combining the efflux consumption Q of the synergist1And synergistsChemical degradation amount Q2Determining the supplement amount of the desulfurization synergist to be Q1+Q2(ii) a The mass concentration of the prepared desulfurization synergist is CFeeding materialSetting the feeding quantity of the synergist automatic metering pump to be QFeeding materialIn kg/h, then:
Qfeeding material＝(Q1+Q2)/CFeeding material
In the above formula, QFeeding materialAutomatic metering of the feed quantity, Q, for the synergist1For the efflux consumption of synergist, Q2Is the chemical degradation amount of the synergist; cFeeding materialThe mass concentration of the prepared desulfurization synergist is adopted;
step 4.2, increasing the adjustment quantity of the concentration of the desulfurization synergist on the basis of the target value when the load is suddenly increased, and reducing the adjustment quantity of the concentration of the desulfurization synergist on the basis of the target value when the load is reduced; when the desulfurization efficiency is reduced due to the abnormality of system equipment, the obtained big data information in the equilibrium state is utilized to further update the synergist adding characteristic curve and give an alarm prompt.
2. The method for precisely adding the desulfurization synergist according to claim 1, wherein the step 1 specifically comprises the following steps:
step 1.1, determining a combined operation mode of a slurry circulating pump;
step 1.2, determining the concentration of the desulfurization synergist;
step 1.3, establishing a plane rectangular coordinate system, and desulfurizing the imported raw flue gas SO2The concentration is taken as the abscissa, and the desulfurized clean flue gas SO is taken as the ordinate2Concentration as ordinate;
step 1.4, measuring different desulfurization inlet raw flue gas SO under the working condition2The concentration of the clean flue gas SO is within 5.2-5.6 of the pH value of the desulfurized slurry2The concentrations are connected into a line and used as a synergist adding characteristic curve under the working condition;
step 1.5, under the slurry circulating pump combination operation mode corresponding to the step 1.1, resetting the concentration of the desulfurization synergist to be a concentration value with a fixed quantity, and dividing the obtained characteristic curve for adding the synergist with the fixed quantity into a group;
step 1.6, adding a plurality of combined operation modes of the slurry circulating pump except the combined operation mode of the slurry circulating pump selected in the step 1.1, and returning to execute the step 1.2 to the step 1.5 after adopting one combined operation mode of the plurality of combined operation modes of the slurry circulating pump; and (4) all the synergist adding characteristic curves in the plane rectangular coordinate system obtained after all the slurry circulating pumps are adopted to form a desulfurization synergist adding characteristic curve.
3. The method for precisely adding the desulfurization synergist according to claim 1, wherein the step 2 specifically comprises the following steps:
step 2.1, calculating the cost of adding the synergist:
F1＝Fsynergist×(Q1+Q2)
In the above formula, F1The unit is Yuan/h for adding the synergist; the F synergist is synergist unit price, and the unit is yuan/kg; q1The unit is kg/h for the outward discharge consumption of the synergist; q2The unit is kg/h for chemical degradation amount of the synergist;
Q1＝2.125×Qflue gas×COriginal SO2×10-6/η1×CSynergist×10-6
In the above formula, Q1The unit is kg/h for the outward discharge consumption of the synergist; 2.125 is CaSO4And SO2136/64; qFlue gasIs the flow rate of the exhaust smoke of the unit in Nm3/h；COriginal SO2For desulfurizing the imported raw flue gas SO2Concentration in mg/Nm3；η1Is the solid content of the gypsum slurry; cSynergistThe concentration of the desulfurization synergist is expressed in ppm;
Q2＝Csynergist×α×η2/24
In the above formula, Q2The unit is kg/h for chemical degradation amount of the synergist; cSynergistThe concentration of the desulfurization synergist is expressed in ppm; alpha is the holding amount of the synergist in the tower and the concentration of the desulfurization synergistDegree conversion coefficient, unit is kg/ppm; eta2The daily degradation consumption rate of the desulfurization synergist; wherein:
α＝π×D2/4×H×ρ×10-6
in the above formula, alpha is the holding amount of the synergist in the tower and the concentration conversion coefficient of the desulfurization synergist, and the unit is kg/ppm; d is the diameter of the desulfurizing tower and is m; h is the slurry liquid level in the desulfurizing tower and the unit is m; rho is the density of the desulfurized slurry in kg/m3；
Step 2.2, calculating the cost of the slurry circulating pump:
F2＝F3+F4
in the above formula, F2In order to increase the cost of a slurry circulating pump, the unit is Yuan/h; f3The operation cost of a single slurry circulating pump is unit/h; f4The unit of the cost generated by increasing the electric quantity of the induced draft fan after increasing the input is yuan/h;
F3＝P×Fprice of electricity
In the above formula, P is the operating electric power of a slurry circulating pump, FPrice of electricityThe unit is yuan/kwh for supplying power price;
F4＝Qflue gas*PResistance device/3600/1000/η3/η4*FPrice of electricity
In the above formula, PResistance deviceThe smoke resistance increased after the slurry circulating pump is put into use is expressed in Pa, eta3For inducing internal efficiency of the fan, eta4The mechanical efficiency of the induced draft fan is improved; fPrice of electricityThe unit is yuan/kwh for supplying power price; qFlue gasIs the flow rate of the exhaust smoke of the unit in Nm3/h；
Step 2.3, if the cost of adding the synergist is equivalent to that of adding a slurry circulating pump of one slurry circulating pump, the corresponding concentration C of the desulfurization synergist is determinedSynergistThe equivalent synergist concentration is set.
4. The method for precisely dosing a desulfurization synergist according to claim 2, wherein the combined operation of the slurry circulation pump in step 1.1 and step 1.6 comprises: two slurry circulating pumps are combined to operate, three slurry circulating pumps are combined to operate, and four slurry circulating pumps are combined to operate.
5. The method for the precise dosing of desulfurization potentiators of claim 2, wherein the concentration of desulfurization potentiators in step 1.2 comprises: 0ppm, 100ppm, 200ppm, 300ppm, 400ppm and 500 ppm.
6. The method for accurately adding the desulfurization synergist according to claim 2, characterized in that: in step 1.5, the concentration of the desulfurization synergist is reset to three to five values, and the obtained three to five synergist addition characteristic curves are divided into a group.
7. The method for accurately adding the desulfurization synergist according to claim 1, characterized in that: desulfurizing and purifying the flue gas SO in the step 32The target concentration was 35mg/m3。
8. The method for the precise dosing of desulfurization potentiators of claim 1, characterized in that: n in the steps from 3.1 to 3.3 is the number of the slurry circulating pumps which are operated in a combined mode, and N is more than or equal to 2 and less than or equal to 4.
9. The method for the precise dosing of desulfurization potentiators of claim 2, characterized in that: the pH value of the desulfurization slurry in the step 1.4 is set to be 5.3.
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