CN112710487B - Method for evaluating influence of desulfurization wastewater drying system on thermal efficiency of boiler - Google Patents
Method for evaluating influence of desulfurization wastewater drying system on thermal efficiency of boiler Download PDFInfo
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Abstract
The invention discloses a method for evaluating the influence of a desulfurization wastewater drying system on the thermal efficiency of a boiler, which can accurately calculate the exhaust gas temperature of the boiler through the weighting of the amount of exhaust gas, further obtain the more accurate thermal efficiency of the boiler after the desulfurization wastewater drying system is put into operation, effectively solve the problem that the influence of the exhaust gas of a bypass air preheater on the thermal efficiency of the boiler cannot be evaluated by taking the outlet of the air preheater as a boundary condition in the calculation of the thermal efficiency of the boiler, and be used for guiding the modification of a subsequent desulfurization wastewater drying system.
Description
The technical field is as follows:
the invention belongs to the technical field of boiler analysis of coal-fired power stations, and particularly relates to an evaluation method for influence of a desulfurization wastewater drying system on thermal efficiency of a boiler.
Background art:
limestone-gypsum wet desulphurization technology is widely applied to SO in flue gas of coal-fired power station boilers due to high desulphurization efficiency and relatively mature technology 2 Removing and treating. However, the desulfurization technology can generate a large amount of desulfurization wastewater, the wastewater is acidic, the components are complex, the salt content is high, the corrosivity is strong, and the direct discharge can seriously harm the surrounding environment and the human health, so that the power plant carries out various treatment methods on the desulfurization wastewater in order to realize the zero discharge of the desulfurization wastewater. Wherein, the evaporation concentration crystallization process is a mode of waste water end treatment and has wider application.
In the evaporative concentration crystallization process, part of flue gas is directly extracted from an inlet of an air preheater by part of power plants and is directly introduced into an evaporative crystallizer, and evaporative crystallization treatment of desulfurization wastewater is realized through reasonable system parameter design; and finally, feeding the mixed gas of the water vapor and the flue gas into a downstream flue of an outlet of the air preheater, thereby realizing the clean treatment of the desulfurization wastewater. The heat source for drying the waste water in the process is used for supplying the middle-high temperature flue gas to the front of the inlet of the air preheater, and the dried flue gas is supplied to the downstream flue of the outlet of the air preheater, so that the clean treatment of the desulfurization waste water can be realized. The main influence of the evaporative crystallization desulfurization wastewater of the bypass flue of the air preheater on the operation of the unit is as follows:
1. the adoption of the bypass flue gas of the air preheater for drying the desulfurization wastewater can reduce the flow of the flue gas entering the air preheater, influence the temperature of hot primary air and secondary air and further influence the combustion in the furnace;
2. the desulfurization wastewater sprayed into the flue is evaporated to cause the increase of the flow rate of flue gas, the output of a draught fan under the same load is increased, and the power consumption is increased;
3. the water content in the flue gas after the air preheater is increased, so that the water supplement amount of a desulfurization system can be reduced;
4. the exhaust gas temperature of the air preheater is influenced, and the thermal efficiency of the boiler is influenced. Because the bypass flue gas amount is less (less than 3% of the total flue gas amount), the evaporation desulfurization waste water amount is less (about 6t/h of the evaporation waste water amount of a 600MW unit at most), the influence on combustion in the boiler, the power consumption of a fan, the desulfurization water supplement is less, and the measurement is difficult, so that the influence on the heat loss of the boiler flue gas is only considered.
According to national standard or ASME standard, in the calculation of boiler thermal efficiency, the heat loss takes an outlet of an air preheater as a boundary condition, in the process, part of flue gas bypasses the air preheater, the calculation of the boiler thermal efficiency can not be calculated according to a conventional calculation mode, and as for how to evaluate the influence of evaporative crystallization desulfurization waste water of a bypass flue of the air preheater on the boiler thermal efficiency, patents or documents rarely report that the heat absorbed by waste water evaporation is the heat lost by the flue gas bypass air preheater, the statement is wrong in nature, and the heat absorbed by waste water evaporation is less than or equal to the heat lost by the flue gas bypass air preheater, so that a method for evaluating the influence of evaporative crystallization desulfurization waste water of the bypass flue of the air preheater on the boiler thermal efficiency needs to be provided.
The invention content is as follows:
in order to solve the technical problems in the prior art, the invention provides a method for evaluating the influence of a desulfurization wastewater drying system on the thermal efficiency of a boiler.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a method for evaluating the influence of a desulfurization wastewater drying system on the thermal efficiency of a boiler comprises the following specific steps:
1) The desulfurization wastewater drying system is not put into operation to carry out a benchmark test, test data corresponding to test load is obtained after the unit is in a stable operation state, the heat loss of exhaust smoke of the boiler, the incomplete combustion loss of gas, the incomplete combustion heat loss of solid, the heat dissipation loss of the boiler and other heat losses in the benchmark test are calculated, and further the heat efficiency of the boiler in the benchmark test is calculated;
2) The desulfurization wastewater drying system is put into operation to carry out comparison test, test data corresponding to test load is obtained after the unit operation state is stable, the heat loss of exhaust smoke of the boiler, the loss of gas which is not completely combusted, the heat loss of solid which is not completely combusted, the heat dissipation loss of the boiler and other heat losses in the comparison test are calculated, and then the heat efficiency of the boiler in the comparison test is calculated;
3) And comparing the boiler thermal efficiency in the benchmark test with the boiler thermal efficiency in the comparison test to obtain the influence of the desulfurization wastewater drying system on the boiler thermal efficiency.
Preferably, the test data in step 1) and step 2) both comprise boiler flue gas temperature.
Preferably, the boiler exhaust gas temperature in the test data in the step 2) is obtained by weighted calculation according to the flue gas volume of the circulating air preheater and the flue gas volume of the inlet of the desulfurization wastewater drying system according to the outlet flue gas temperature of the air preheater and the inlet flue gas temperature of the inlet of the desulfurization wastewater drying system.
Preferably, the outlet flue gas temperature of the air preheater and the inlet flue gas temperature of the desulfurization wastewater drying system are measured by thermocouples.
Preferably, the inlet flue gas volume of the desulfurization wastewater drying system is calculated according to the following steps:
first, a theoretical air amount V required for complete combustion of 1kg of fuel is calculated 0 ；
Secondly, the air preheater inlet excess air coefficient alpha is calculated, and the actual air quantity V required by 1kg of fuel when the fuel is completely combusted is calculated k ；
Thirdly, calculating the theoretical smoke generated when 1kg of fuel is completely combusted
Fourthly, calculating the actual smoke volume V generated when 1kg of fuel is completely combusted y ；
Fifthly, calculating heat Q absorbed by the evaporation of the waste water according to the enthalpy difference between the water vapor inlet and the water vapor outlet Waste water ；
Sixthly, according to the conservation of energy, obtaining the heat Q used by the bypass flue gas for evaporating and crystallizing the desulfurization wastewater Flue gas ；
And seventhly, calculating the inlet flue gas quantity of the desulfurization wastewater drying system according to the enthalpy value of each component of the flue gas or the average constant pressure specific heat of each component of the flue gas.
Preferably, the theoretical air amount V required for complete combustion of the 1kg fuel 0 The calculation method is as follows:
V 0 ＝0.0889R ar +0.265H ar -0.0333O ar (1)
in the formula: v 0 Theoretical air quantity m required for complete combustion of 1kg of fuel 3 /kg；H ar To receive hydrogen,%; o is ar To receive oxygen,%; r ar For three atoms received,%;
actual air volume V required for complete combustion of the 1kg fuel k The calculation method is as follows:
V k ＝αV 0 (2)
in the formula: v k The actual air amount m required for complete combustion of 1kg of fuel 3 Per kg; alpha is the excess air coefficient of the inlet of the air preheater;
theoretical amount of smoke generated when 1kg of fuel is completely combusted
The calculation method is as follows:
in the formula:
is the theoretical amount of smoke, m, produced when 1kg of fuel is completely combusted 3 /kg；/>
Is CO in theoretical smoke amount generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
Is SO in theoretical smoke generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
Is the volume of three-atom gas m in the theoretical smoke gas generated when 1kg of fuel is completely combusted 3 /kg；/>
N in theoretical smoke generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
H is the theoretical amount of smoke generated when 1kg of fuel is completely combusted 2 Volume of O, m 3 /kg；N ar Percent for radical nitrogen; m ar To receive base water,%;
preferably, the actual smoke amount V generated when the 1kg fuel is completely combusted y The calculation method is as follows:
in the formula: v y Is the actual smoke amount m generated when 1kg of fuel is completely combusted 3 /kg；
N in the actual smoke amount generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
H in the actual amount of flue gas generated when 1kg of fuel is completely combusted 2 Volume of O, m 3 /kg；/>
Is O in the actual smoke amount generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；
Heat Q absorbed by evaporation of said waste water Waste water The calculation method is as follows:
in the formula:
is the enthalpy of the steam inlet, kJ/m 3 ；/>
Is the enthalpy of the water vapor outlet, kJ/m 3 ；q Waste water Is the flow rate of desulfurization waste water, kg/h, m Water (W) Is the mass ratio of water in the desulfurization wastewater,%;
heat Q for evaporating, crystallizing and desulfurizing waste water by bypass flue gas Flue gas The calculation method is as follows:
according to the conservation of energy:
Q waste water ＝Q Flue gas (13)
Preferably, the inlet flue gas volume q of the desulfurization waste water drying system Flue gas The calculation method is as follows:
the enthalpy value of each component of the smoke is calculated to obtain:
Q flue gas ＝q Flue gas [(cθ 2 ) Flue gas -(cθ 1 ) Flue gas ] (14)
In the formula: (c θ) 2 ) Flue gas Is the enthalpy of the flue gas at the inlet of the bypass flue gas, kJ/m 3 ；(cθ 1 ) Flue gas Is the enthalpy of the flue gas at the bypass flue gas outlet, kJ/m 3 ；
Is the three-atom enthalpy of the bypass flue gas, kJ/m 3 ；/>
For by-pass flue gas CO 2 Enthalpy, kJ/m 3 ；(cθ) Flue gas Is the enthalpy of bypass flue gas, kJ/m 3 ；/>
Is the N2 enthalpy of bypass flue gas, kJ/m 3 ；/>
Is the enthalpy of water vapor of bypass flue gas, kJ/m 3 (ii) a The enthalpy values are obtained by inquiring an enthalpy thermometer;
preferably, the inlet flue gas volume q of the desulfurization waste water drying system Cigarette with heating means The gas determination method comprises the following steps:
the average constant pressure specific heat of each component of the flue gas is calculated to obtain:
in the formula: q Dry flue gas Heat lost to dry flue gas;
heat lost to water vapor;
in the formula: q. q of Flue gas The flue gas quantity m at the inlet of a desulfurization waste water drying system 3 /h；
Is the average constant pressure specific heat of the water vapor, kJ/(m 3 ·) K) ；T 2 Flue gas inlet temperature, deg.C; t is 1 The temperature of the flue gas outlet is DEG C;
in the formula: c. C p, dry flue gas The dry flue gas average specific constant pressure heat capacity is kJ/(m < 3 >. K);
CO 2 +O 2 +N 2 ＝100 (21)
in the formula: CO2 2 、O 2 、N 2 Are each CO 2 、O 2 、N 2 The volume ratio of the dry flue gas;
are each CO 2 ，O 2 ，N 2 Has an average specific constant heat capacity of kJ/(m) 3 ·K)；
Preferably, the calculation formula of the boiler exhaust gas temperature is as follows:
V general (1) ＝V y M Coal (coal) (22)
In the formula: v General assembly Actual total flue gas amount; m Coal (coal) T/h is total coal amount; t is Row board Is the temperature of the boiler exhaust smoke; t is Into The inlet flue gas temperature of the desulfurization waste water drying system; t is Go out Is the temperature of the flue gas at the outlet of the air preheater.
Compared with the prior art, the invention has the following beneficial effects:
according to the method for evaluating the influence of the desulfurization wastewater drying system on the thermal efficiency of the boiler, the exhaust gas temperature of the boiler can be accurately calculated through the weighting of the amount of the exhaust gas, so that the more accurate thermal efficiency of the boiler after the desulfurization wastewater drying system is put into operation can be obtained, the problem that the influence of the exhaust gas of a bypass air preheater on the thermal efficiency of the boiler cannot be evaluated by taking the outlet of the air preheater as a boundary condition in the calculation of the thermal efficiency of the boiler is effectively solved, and the method is used for guiding the subsequent modification of the desulfurization wastewater drying system.
The specific implementation mode is as follows:
the first embodiment is as follows:
in order to make the objects, technical solutions and novel points of the present invention more clearly illustrated, the present invention is further described in detail with reference to examples. It should be understood that the description herein of specific embodiments is intended to be illustrative only and is not intended to be limiting. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The method for evaluating the influence of the desulfurization wastewater drying system on the thermal efficiency of the boiler comprises the following specific steps:
1) The desulfurization wastewater drying system is not put into operation to carry out a benchmark test, test data corresponding to test load is obtained after the unit is in a stable operation state, the heat loss of exhaust smoke of the boiler, the incomplete combustion loss of gas, the incomplete combustion heat loss of solid, the heat dissipation loss of the boiler and other heat losses in the benchmark test are calculated, and further the heat efficiency of the boiler in the benchmark test is calculated; the test data in the reference test comprise the exhaust gas temperature of the boiler, the element analysis result and the industrial analysis result of the test coal quality, the combustible content analysis result of the fly ash, the combustible content analysis result of the slag, the inlet and outlet flue gas temperature of the air preheater, the inlet and outlet flue gas oxygen content of the air preheater and the carbon monoxide content.
2) The desulfurization wastewater drying system is put into operation to carry out comparison test, comparison test data corresponding to test load is obtained after the unit operation state is stable, the heat loss of exhaust smoke of the boiler, the incomplete combustion loss of gas, the incomplete combustion heat loss of solid, the heat dissipation loss of the boiler and other heat losses in the comparison test are calculated, and further the heat efficiency of the boiler in the comparison test is calculated; the test data in the comparison test comprise the exhaust gas temperature of the boiler, the element analysis result and the industrial analysis result of the test coal quality, the combustible content analysis result of the fly ash, the combustible content analysis result of the slag, the inlet and outlet flue gas temperature of the air preheater, the inlet and outlet flue gas oxygen content of the air preheater and the carbon monoxide content.
3) And comparing the boiler thermal efficiency in the benchmark test with the boiler thermal efficiency in the comparison test to obtain the influence of the desulfurization wastewater drying system on the boiler thermal efficiency.
Example two:
the further design of this embodiment lies in: in the embodiment, the boiler exhaust gas temperature in the step 2 comparison test data is obtained by weighted calculation according to the air preheater outlet flue gas temperature and the desulfurization wastewater drying system inlet flue gas temperature and according to the circulating air preheater flue gas amount and the desulfurization wastewater drying system inlet flue gas amount.
Wherein, the temperature of the flue gas at the outlet of the air preheater and the temperature of the flue gas at the inlet of the desulfurization waste water drying system are measured by thermocouples;
the inlet flue gas volume of the desulfurization wastewater drying system is calculated according to the following steps:
first, from the results of the elemental analysis of the test coal quality, the theoretical air amount V required for complete combustion of 1kg of fuel was calculated 0 ；
Secondly, measuring the oxygen content of the inlet flue gas of the air preheater by adopting a test method, calculating the excess air coefficient alpha of the inlet of the air preheater, and calculating the actual air volume V required by 1kg of fuel when the fuel is completely combusted k ；
Thirdly, according to the results of the elemental analysis and the industrial analysis of the test coal quality and the theoretical air volume V required for complete combustion of the 1kg fuel 0 Calculating the theoretical smoke quantity generated when 1kg of fuel is completely combusted
Fourthly, according to the element analysis result and the industrial analysis result of the test coal quality, the inlet excess air coefficient alpha of the air preheater and the theoretical air quantity V required by 1kg of fuel when the fuel is completely combusted 0 Calculating the actual smoke volume V generated when 1kg of fuel is completely combusted y ；
Fifthly, calculating the heat Q absorbed by the evaporation of the waste water according to the enthalpy difference between the water vapor inlet and the water vapor outlet Waste water ；
Sixthly, according to energy conservation, the heat absorbed by the waste water is equal to the heat released by the flue gas, and the heat Q used by the bypass flue gas for evaporating and crystallizing the desulfurization waste water is obtained Flue gas
And seventhly, calculating the inlet flue gas quantity of the desulfurization wastewater drying system according to the enthalpy value of each component of the flue gas or the average constant pressure specific heat of each component of the flue gas.
The theoretical air amount V required for complete combustion of the above-mentioned 1kg fuel 0 The determination method comprises the following steps:
V 0 ＝0.0889(C ar +0.375S ar )+0.265H ar -0.0333O ar (1)
since the complete combustion reaction of C with S can be written as the general formula: r + O2= RO2, so the above formula can also be written:
V 0 ＝0.0889R ar +0.265H ar -0.0333O ar (2)
in the formula: v 0 Theoretical air quantity m required for complete combustion of 1kg of fuel 3 /kg；C ar Percent as received base carbon; s ar To receive basal sulfur,%; h ar To receive hydrogen,%; o is ar To receive oxo oxygen,%; r is ar For three atoms received,%;
the actual air amount V required for complete combustion of the above-mentioned 1kg fuel k The determination method comprises the following steps:
V k ＝αV 0 (3)
in the formula: v k Is the actual amount of air, m, required for complete combustion of 1kg of fuel 3 Per kg; alpha is the excess air coefficient of the inlet of the air preheater;
theoretical amount of smoke generated when 1kg of fuel is completely combusted
The determination method comprises the following steps:
in the formula:
is the theoretical amount of smoke, m, produced when 1kg of fuel is completely combusted 3 /kg；/>
Is the volume of CO2 m in the theoretical smoke generated when 1kg of fuel is completely combusted 3 /kg；/>
Is SO in theoretical smoke generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
Is the volume of three-atom gas m in the theoretical smoke gas generated when 1kg of fuel is completely combusted 3 /kg；/>
N in the theoretical smoke generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
H is the theoretical amount of smoke generated when 1kg of fuel is completely combusted 2 Volume of O, m 3 /kg；N ar Percent to receive basic nitrogen; m ar To receive basal water,%;
actual amount of flue gas V generated when 1kg of fuel is completely combusted y The determination method comprises the following steps:
in the formula: v y Is the actual smoke amount m generated when 1kg of fuel is completely combusted 3 /kg；
N in the actual smoke amount generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
H in the actual amount of flue gas generated when 1kg of fuel is completely combusted 2 Volume of O, m 3 /kg；/>
Is O in the actual smoke amount generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；
Heat Q absorbed by evaporating the above waste water Waste water The determination method comprises the following steps:
in the formula:
is the inlet enthalpy of water vapor, kJ/m 3 ；/>
Is the enthalpy of the water vapor outlet, kJ/m 3 ；q Waste water Is the flow rate of desulfurization waste water, kg/h, m Water (I) Is the mass ratio of water in the desulfurization wastewater;
the bypass flue gas is used for evaporating heat Q used by the crystallized desulfurization wastewater Flue gas The determination method comprises the following steps:
according to the conservation of energy:
Q waste water ＝Q Flue gas (22)
The inlet flue gas amount q of the desulfurization wastewater drying system Cigarette with heating means The gas is calculated by any one of the following two methods:
the enthalpy value of each component of the smoke is calculated to obtain:
Q flue gas ＝q Flue gas [(cθ 2 ) Flue gas -(cθ 1 ) Flue gas ] (15)
Due to the fact that
Therefore take out>
In the formula: (c θ) 2 ) Flue gas Is the enthalpy of the flue gas at the inlet of the bypass flue gas, kJ/m 3 ；(cθ 1 ) Flue gas Is the enthalpy of the flue gas at the bypass flue gas outlet, kJ/m 3 ；
Is the three-atom enthalpy of bypass flue gas, kJ/m 3 ；/>
For by-pass flue gas CO 2 Enthalpy, kJ/m 3 ；(cθ) Flue gas Is the enthalpy of bypass flue gas, kJ/m 3 ；/>
Is bypass flue gas N2 enthalpy, kJ/m 3 ；/>
Is the enthalpy of the bypass flue gas water vapor, kJ/m 3 (ii) a The enthalpy values are obtained by inquiring an enthalpy thermometer;
and (II) calculating the average constant pressure specific heat of each component of the flue gas to obtain:
in the formula: q Dry flue gas Heat lost to dry flue gas;
heat lost to water vapor;
in the formula: q. q of Flue gas M3/h is the flue gas volume at the inlet of the desulfurization wastewater drying system;
is the average constant pressure specific heat of the water vapor, kJ/(m 3. Degree K) ；T 2 Flue gas inlet temperature, deg.C; t is 1 The temperature of the flue gas outlet, DEG C；
In the formula: c. C p, dry flue gas The dry flue gas average specific constant pressure heat capacity is kJ/(m < 3 >. K);
CO 2 +O 2 +N 2 ＝100 (21)
in the formula: CO2 2 、O 2 、N 2 Are each CO 2 、O 2 、N 2 The volume ratio of the dry flue gas;
are each CO 2 ，O 2 ，N 2 Has an average specific constant heat capacity of kJ/(m) 3 ·K)；
The calculation formula of the boiler exhaust gas temperature is as follows:
according to the calculated actual smoke amount V generated when 1kg of fuel is completely combusted y And total coal amount M Coal (coal) (obtained by DCS system) and calculating the actual total flue gas volume V General assembly Namely:
V general assembly ＝V y M Coal (coal) (23)
Final boiler exhaust gas temperature T Row board The determination is as follows:
in the formula: v General assembly The actual total smoke amount is obtained; m is a group of Coal (coal) T/h is total coal amount; t is a unit of Row board Is the temperature of the boiler exhaust smoke; t is Into The inlet flue gas temperature of the desulfurization waste water drying system; t is Go out Is the temperature of the flue gas at the outlet of the air preheater.
The application example is as follows:
the evaluation method in the embodiment is implemented on a 600MW supercritical unit boiler, the model of the 600MW supercritical unit boiler is HG-1950/25.4-YM3, the boiler is arranged in a II shape, a single hearth, double flues at the tail part, a full steel frame, a suspension structure, a burner front wall and a burner rear wall, opposite combustion and a three-bin rotary air preheater.
The test working condition selects a 580MW load working condition, the temperature of the desulfurization wastewater to be evaporated is 30 ℃, the evaporated steam and the flue gas are mixed and sent to a downstream flue of an outlet of an air preheater, the temperature of the flue gas is 120 ℃, the flow of the wastewater to be evaporated is 1t/h and 6t/h, the exhaust temperature of the desulfurization wastewater drying system is 140.8 ℃ when the desulfurization wastewater drying system is not put into operation, the thermal efficiency of a boiler is 93.52%, and the coal quality data of the test working conditions are shown in the following table:
| serial number | Name (R) | (symbol) | Unit of | Test coal species |
| 1 | Test coal quality (carbon) | C ar | ％ | 52.71 |
| 2 | Test coal quality (Hydrogen) | H ar | ％ | 3.23 |
| 3 | Test coal quality (nitrogen) | N ar | ％ | 0.90 |
| 4 | Test coal quality (oxygen) | O ar | ％ | 9.61 |
| 5 | Test coal quality (Sulfur) | S ar | ％ | 0.58 |
| 6 | Test coal quality (Ash) | A ar | ％ | 19.83 |
| 7 | Test coal quality (moisture) | M t | ％ | 13.14 |
| 8 | Volatile matter (air-dry basis) | V d | ％ | 28.17 |
| 9 | Test coal quality (Low calorific value) | Q net,ar | kJ/kg | 19836 |
The main data of the desulfurization waste water drying system when it is put into operation are shown in the following table.
The calculation shows that when the waste water flow of 1t/h is evaporated, the boiler thermal efficiency is reduced by about 0.02 percentage point, and when the waste water flow of 6t/h is evaporated, the boiler thermal efficiency is reduced by about 0.08 percentage point.
Claims (8)
1. A method for evaluating the influence of a desulfurization wastewater drying system on the thermal efficiency of a boiler is characterized by comprising the following steps: the method comprises the following specific steps:
1) The desulfurization waste water drying system is not put into operation to carry out a benchmark test, test data corresponding to test load is obtained after the unit is in a stable operation state, the heat loss of exhaust smoke of the boiler, the heat loss of incomplete combustion of gas, the heat loss of incomplete combustion of solid, the heat dissipation loss of the boiler and other heat losses in the benchmark test are calculated, and further the heat efficiency of the boiler in the benchmark test is calculated; wherein the test data obtained in the reference experiment comprises the exhaust gas temperature of the boiler;
2) The desulfurization wastewater drying system is put into operation to carry out comparison test, test data corresponding to test load is obtained after the unit operation state is stable, the heat loss of exhaust smoke of the boiler, the heat loss of gas incomplete combustion, the heat loss of solid incomplete combustion, the heat dissipation loss of the boiler and other heat losses in the comparison test are calculated, and then the heat efficiency of the boiler in the comparison test is calculated; the test data obtained in the comparison test comprise boiler exhaust gas temperature, and the boiler exhaust gas temperature is obtained by weighted calculation according to the air preheater outlet flue gas temperature and the desulfurization wastewater drying system inlet flue gas temperature and according to the circulating air preheater flue gas amount and the desulfurization wastewater drying system inlet flue gas amount;
3) And comparing the boiler thermal efficiency in the benchmark test with the boiler thermal efficiency in the comparison test to obtain the influence of the desulfurization wastewater drying system on the boiler thermal efficiency.
2. The method for evaluating influence of a desulfurization waste water drying system on thermal efficiency of a boiler according to claim 1, characterized in that: and the outlet flue gas temperature of the air preheater and the inlet flue gas temperature of the desulfurization wastewater drying system are measured by thermocouples.
3. The method for evaluating influence of a desulfurization waste water drying system on thermal efficiency of a boiler according to claim 1, characterized in that: the inlet flue gas volume of the desulfurization wastewater drying system is calculated according to the following steps:
first, a theoretical air amount V required for complete combustion of 1kg of fuel is calculated 0 ；
Secondly, the air preheater inlet excess air coefficient alpha is calculated, and the actual air quantity V required by 1kg of fuel when the fuel is completely combusted is calculated k ；
Thirdly, calculating the theoretical smoke generated when 1kg of fuel is completely combusted
Fourth, complete combustion of 1kg of fuel is calculatedActual amount of flue gas V produced y ；
Fifthly, calculating the heat Q absorbed by the evaporation of the waste water according to the enthalpy difference between the water vapor inlet and the water vapor outlet Waste water ；
Sixthly, according to the conservation of energy, obtaining the heat Q used by the bypass flue gas for evaporating and crystallizing the desulfurization wastewater Flue gas ；
And seventhly, calculating the inlet flue gas quantity of the desulfurization wastewater drying system according to the enthalpy value of each component of the flue gas or the average constant pressure specific heat of each component of the flue gas.
4. The method for evaluating influence of a desulfurization waste water drying system on thermal efficiency of a boiler according to claim 3, characterized in that: theoretical air quantity V required for complete combustion of the 1kg fuel 0 The calculation method is as follows:
V 0 ＝0.0889R ar +0.265H ar -0.0333O ar (1)
in the formula: v 0 Theoretical air quantity m required for complete combustion of 1kg of fuel 3 /kg；H ar To receive hydrogen,%; o is ar To receive oxo oxygen,%; r ar For three atoms received,%;
actual air volume V required for complete combustion of the 1kg fuel k The calculation method is as follows:
V k ＝αV 0 (2)
in the formula: v k Is the actual amount of air, m, required for complete combustion of 1kg of fuel 3 Per kg; alpha is the excess air coefficient of the inlet of the air preheater;
theoretical amount of smoke generated when 1kg of fuel is completely combusted
The calculation method is as follows: />
In the formula:
is the theoretical amount of smoke, m, produced when 1kg of fuel is completely combusted 3 /kg；/>
Is CO in theoretical smoke generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
Is SO in theoretical smoke generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
Is the volume of three-atom gas m in the theoretical smoke gas generated when 1kg of fuel is completely combusted 3 /kg；
N in theoretical smoke generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
H is the theoretical amount of smoke generated when 1kg of fuel is completely combusted 2 Volume of O, m 3 /kg；N ar Percent for radical nitrogen; m ar To receive the base water,%.
5. The method for evaluating influence of a desulfurization waste water drying system on thermal efficiency of a boiler according to claim 4, wherein: the actual smoke volume V generated when the 1kg fuel is completely combusted y The calculation method is as follows:
in the formula: v y Is the actual smoke amount m generated when 1kg of fuel is completely combusted 3 /kg；
N in the actual smoke amount generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；/>
H in the actual amount of flue gas generated when 1kg of fuel is completely combusted 2 Volume of O, m 3 /kg；/>
Is O in the actual smoke amount generated when 1kg of fuel is completely combusted 2 Volume, m 3 /kg；
Heat Q absorbed by evaporation of said waste water Waste water The calculation method is as follows:
in the formula: (c θ) 1 ) H2O Is the enthalpy of the steam inlet, kJ/m 3 ；
Is the enthalpy of the water vapor outlet, kJ/m 3 ；q Waste water Is the flow rate of desulfurization waste water, kg/h, m Water (W) Is the mass ratio of water in the desulfurization wastewater,%;
heat Q for evaporating, crystallizing and desulfurizing waste water by bypass flue gas Flue gas The calculation method is as follows:
according to the conservation of energy:
Q waste water ＝Q Flue gas (13)。
6. The method for evaluating influence of a desulfurization waste water drying system on thermal efficiency of a boiler according to claim 5, wherein: the inlet flue gas amount q of the desulfurization wastewater drying system Cigarette with heating means The gas calculation method is as follows:
the enthalpy value of each component of the smoke is calculated to obtain:
Q flue gas ＝q Flue gas [(cθ 2 ) Flue gas -(cθ 1 ) Flue gas ] (14)
In the formula: (c θ) 2 ) Flue gas Is the enthalpy of the flue gas at the inlet of the bypass flue gas, kJ/m 3 ；(cθ 1 ) Flue gas Is the enthalpy of the flue gas at the bypass flue gas outlet, kJ/m 3 ；
Is the three-atom enthalpy of the bypass flue gas, kJ/m 3 ；/>
For by-pass flue gas CO 2 Enthalpy, kJ/m 3 ；(cθ) Flue gas Is the enthalpy of bypass flue gas, kJ/m 3 ；/>
For bypass flue gas N 2 Enthalpy, kJ/m 3 ；/>
Is the enthalpy of the bypass flue gas water vapor, kJ/m 3 (ii) a The enthalpy values are obtained by inquiring an enthalpy thermometer.
7. The method for evaluating influence of a desulfurization waste water drying system on thermal efficiency of a boiler according to claim 5, wherein: the inlet flue gas amount q of the desulfurization wastewater drying system Flue gas The determination method comprises the following steps:
the average constant pressure specific heat of each component of the flue gas is calculated to obtain:
in the formula: q Dry flue gas Heat lost to dry flue gas;
heat lost to water vapor;
in the formula: q. q.s Flue gas The flue gas quantity m at the inlet of a desulfurization waste water drying system 3 /h；
The average constant pressure specific heat of the steam is kJ/(m < 3 >. K); t is 2 Flue gas inlet temperature, deg.C; t is 1 The temperature of the flue gas outlet is DEG C;
in the formula: c. C p, dry flue gas The dry flue gas average specific constant pressure heat capacity is kJ/(m < 3 >. K);
CO 2 +O 2 +N 2 ＝100 (21)
in the formula: CO2 2 、O 2 、N 2 Are each CO 2 、O 2 、N 2 The volume ratio of the dry flue gas;
are each CO 2 ，O 2 ，N 2 Has an average specific constant heat capacity of kJ/(m) 3 ·K)。
8. The method for evaluating influence of a desulfurization waste water drying system on thermal efficiency of a boiler according to claim 6 or 7, wherein: the calculation formula of the boiler exhaust gas temperature is as follows:
V general assembly ＝V y M Coal (coal) (22)
In the formula: v General (1) The actual total smoke amount is obtained; m Coal (coal) T/h is total coal amount; t is Row board Is the temperature of the boiler exhaust smoke; t is Go into The inlet flue gas temperature of the desulfurization waste water drying system; t is a unit of Go out Is the temperature of the flue gas at the outlet of the air preheater.
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