A desulfurization optimization method for CFB boilers with variable coal types

Abstract

The present invention discloses an optimization method for desulfurization with variable coal types in a CFB boiler, which includes the following steps: classifying the coal types purchased by the power plant according to the converted sulfur content on an as-received basis; obtaining the limestone consumption in the furnace, the boiler efficiency, and the actual input heat of the boiler to characterize the actual coal input heat of the boiler; conducting an off-furnace desulfurization test simultaneously with the boiler efficiency test, collecting the concentrations of O2 and SO2 in the clean flue gas and the raw flue gas, taking samples of off-furnace limestone and gypsum for chemical analysis, calculating the off-furnace limestone consumption, and recording the power consumption of the desulfurization equipment during the test; calculating the coal combustion cost, the in-furnace limestone cost, the off-furnace limestone cost, and the power consumption cost of the desulfurization equipment, and then adding up the various costs to obtain the comprehensive operation cost; comparing the comprehensive operation costs of different coal types and selecting the coal type with higher operating economy for the CFB boiler. The optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention can guide the power plant to purchase and blend coal types and improve the operating economy of the CFB boiler.

Description

Technical Field

[0001] The present invention belongs to the field of energy conservation and emission reduction of power station boilers, and particularly relates to a desulfurization optimization method for CFB boilers with variable coal types. Background Art

[0002] CFB (circulating fluidized bed) boilers have been widely used due to their advantages such as wide fuel adaptability, high combustion efficiency, and excellent environmental protection performance. Since the release of the ultra-low emission standards, the in-furnace desulfurization of CFB boilers can no longer meet the requirements of ultra-low SO2 emissions, and it is necessary to add an out-of-furnace desulfurization device to further purify the flue gas at the tail. How to reasonably allocate the desulfurization shares inside and outside the furnace to reduce the boiler operation cost has once become the main research topic of relevant experts and scholars. In recent years, the coal market has been in short supply and high prices. Purchasing a large amount of low-quality coal with low prices has become the primary solution for power plants to reduce operating costs. However, low-quality coal usually has high sulfur content, high ash content, and low calorific value, and the economic efficiency of boiler operation often increases instead of decreasing, which is counterproductive. Summary of the Invention

[0003] To solve the technical problems existing in the prior art, the purpose of the present invention is to provide a desulfurization optimization method for CFB boilers with variable coal types.

[0004] To achieve the above purpose and reach the above technical effects, the technical solution adopted by the present invention is as follows:

[0005] A desulfurization optimization method for CFB boilers with variable coal types includes the following steps:

[0006] Classify the coal types purchased by the power plant into low-sulfur coal, medium-sulfur coal, and high-sulfur coal according to the sulfur content on an as-received basis converted to a dry basis;

[0007] Conduct boiler efficiency tests and out-of-furnace desulfurization tests for different coal types to obtain various economic indicators of the boiler, including the in-furnace limestone consumption, boiler efficiency, actual input heat of the boiler, out-of-furnace limestone consumption, and power consumption of the desulfurization equipment during the test period;

[0008] Calculate the coal combustion cost, in-furnace limestone cost, out-of-furnace limestone cost, and power consumption cost of the desulfurization equipment for different coal types, and add up the various costs to obtain the comprehensive operation cost;

[0009] Compare the comprehensive operation costs of different coal types, and select and match the coal type with higher economic efficiency for CFB boiler operation.

[0010] In a desulfurization optimization method for CFB boilers with variable coal types provided by the present invention, the sulfur content on an as-received basis converted to a dry basis S ar,zs is calculated according to the following formula:

[0011]

[0012] where Sar,zs is the converted sulfur content of the as-received coal, i.e., the as-received sulfur content corresponding to 1000 kcal / kg calorific value of the coal, with the unit of %; S ar is the as-received sulfur content of the coal, with the unit of %; Q net,ar is the lower calorific value of the as-received coal, with the unit of kcal / kg;

[0013] The converted sulfur content of the low-sulfur coal is not greater than 0.2%; the converted sulfur content of the medium-sulfur coal ranges from 0.2% to 0.5%, excluding 0.2%; the converted sulfur content of the high-sulfur coal is greater than 0.5%.

[0014] In an optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention, the in-furnace limestone consumption is obtained by the following steps:

[0015] Carry out a calibration test on the output of the limestone feeder by the weighing method to obtain the output m of the limestone feeder ln and the opening x of the feeder i of the fitting curve f(x i ). According to the opening of the feeder, the in-furnace limestone consumption m ln = f(x i ).

[0016] In an optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention, the steps of carrying out a calibration test on the output of the limestone feeder by the weighing method include:

[0017] When the openings x i of the feeder are 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% respectively, weigh the limestone powder amount per unit time using a calibrated platform scale to obtain the output of the limestone feeder at each opening, and fit the relationship curve m ln between the output of the limestone feeder and the opening x i m ln = f(x i ).

[0018] In an optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention, the steps of carrying out a boiler efficiency test for different coal types include:

[0019] Under typical load conditions, carry out a boiler efficiency test for different coal types by the inverse balance method to obtain the boiler efficiency, and calculate the actual input heat of the boiler by the direct balance method to represent the actual coal input heat of the boiler.

[0020] In an optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention, the boiler efficiency is calculated according to the following formula:

[0021] η gl,i = 100 - (q2 + q3 + q4 + q5 + q6 + q7 + q oth - q ex )

[0022] where η gl,i is the boiler efficiency corresponding to coal type i, in %; q2 is the heat loss due to flue gas, in %; q3 is the heat loss due to incomplete combustion of gas, in %; q4 is the heat loss due to incomplete combustion of solid, in %; q5 is the heat loss due to boiler heat dissipation, in %; q6 is the sensible heat loss of ash slag, in %; q7 is the heat loss due to desulfurization, in %; q oth is other heat loss, in %; q ex is the percentage of external heat to the lower calorific value of fuel, in %.

[0023] In an optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention, the actual input heat of the boiler and the actual coal input heat of the boiler are calculated according to the following formulas respectively:

[0024]

[0025]

[0026] Q sc,i = D zq × h zq - D gs × h gs + D zr × h zr - D lzr × h lzr - D gj × h gj - D zj × h zj

[0027] where Q sr,i is the actual input heat of the boiler corresponding to coal type i, in 10 3 kJ / h; B sj,i is the actual coal input heat of the boiler corresponding to coal type i, in 10 3 kcal / h; Q sc,i is the actual output heat of the boiler corresponding to coal type i, in 10 3 kJ / h; D zq is the main steam flow rate, in t / h; h zq is the main steam enthalpy value, in kJ / kg; D gs is the final feed water flow rate, in t / h; h gs is the final feed water enthalpy value, in kJ / kg; D zris the reheater steam flow rate, with the unit of t / h; h zr is the enthalpy value of reheater steam, with the unit of kJ / kg; D lzr is the cold reheater steam flow rate, with the unit of t / h; h lzr is the enthalpy value of cold reheater steam, with the unit of kJ / kg; D gj is the desuperheating water flow rate of superheater, with the unit of t / h; h gj is the enthalpy value of desuperheating water of superheater, with the unit of kJ / kg; D zj is the desuperheating water flow rate of reheater, with the unit of t / h; h zj is the enthalpy value of desuperheating water of reheater, with the unit of kJ / kg.

[0028] In an optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention, the off - furnace desulfurization test is carried out synchronously with the boiler efficiency test. The steps for the off - furnace desulfurization test for different coal types include:

[0029] Collect the concentrations of O2 and SO2 in the clean flue gas and the raw flue gas, take samples of off - furnace limestone and gypsum for chemical analysis, and calculate the off - furnace limestone consumption m lw,i and record the power consumption W of the desulfurization equipment during the test lw,i which is obtained by statistically recording the electricity meters of each equipment in the electrical switch room.

[0030] In an optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention, the off - furnace limestone consumption is calculated according to the following formula:

[0031]

[0032]

[0033] where m lw,i is the off - furnace limestone consumption corresponding to coal type i, t / h; V RG,i is the volume flow rate of the raw flue gas, standard dry, 6% O2, with the unit of m 3 / h; is the concentration of SO2 in the raw flue gas, standard dry, 6% O2, with the unit of mg / m 3 ; is the concentration of SO2 in the clean flue gas, standard dry, 6% O2, with the unit of mg / m 3 ; is the molar mass of CaCO3, 100.09 kg / mol; is the molar mass of SO2, 64.06 kg / mol; F R,i is the purity of limestone, with the unit of %; S t,i is the calcium - sulfur molar ratio; is the mass content of CaCO3 in gypsum, with the unit of %; is the mass content of CaSO4·2H2O in gypsum, with the unit of %; is the mass content of CaSO3·0.5H2O in gypsum, with the unit of %; is the molar mass of CaSO4·2H2O, 172.18 kg / mol; is the molar mass of CaSO3·0.5H2O, 129.15 kg / mol.

[0034] In an optimization method for desulfurization with variable coal types in a CFB boiler provided by the present invention, the steps of calculating the coal combustion cost, in-furnace limestone cost, out-of-furnace limestone cost, and desulfurization equipment power consumption cost for different coal types, and adding up the various costs to obtain the comprehensive operation cost include:

[0035] According to the coal combustion unit price R m,i , in-furnace limestone unit price R ln , out-of-furnace limestone unit price R lw , and desulfurization equipment electricity price R tl , calculate the coal combustion cost C m,i , in-furnace limestone cost C ln,i , out-of-furnace limestone cost C lw,i , and desulfurization equipment power consumption cost C tl,i for different coal types respectively, and add up the various costs to obtain the comprehensive operation cost C zh,i ;

[0036] The comprehensive operation cost C zh,i is calculated according to the following formula:

[0037]

[0038] C m,i = R m,i × B sj,i

[0039] C ln,i = R ln × m ln,i

[0040] C lw,i = R lw × m lw,i

[0041]

[0042] Among them, C zh,i is the comprehensive operation cost corresponding to coal type i, with the unit of yuan / MWh; C m,i is the coal combustion cost of coal type i, with the unit of yuan / h; C ln,i$C_{limestone - in - furnace}^i$ is the cost of limestone in the furnace corresponding to coal type $i$, with the unit of yuan / h; $C$ lw,i $C_{limestone - out - furnace}^i$ is the cost of limestone outside the furnace corresponding to coal type $i$, with the unit of yuan / h; $C$ tl,i $P_{electricity - consumption - out - furnace}^i$ is the electricity cost of the desulfurization equipment outside the furnace corresponding to coal type $i$, with the unit of yuan / MWh; $P$ e $P_{active - power}$ is the active power of the generator set, with the unit of MW; $R$ m,i The unit price of coal for coal type $i$ is in yuan / 10 3 kcal; $R$ ln $R_{limestone - in - furnace}$ is the unit price of limestone in the furnace, with the unit of yuan / t; $R$ lw $R_{limestone - out - furnace}$ is the unit price of limestone outside the furnace, with the unit of yuan / t; $R$ tl $W_{electricity - price - out - furnace}$ is the electricity price of the desulfurization equipment outside the furnace, with the unit of yuan / kWh; $W$ lw,i $m_{total - electricity - consumption - out - furnace}$ is the total power consumption of the desulfurization equipment outside the furnace, with the unit of kW; $m$ In，i $m_{limestone - in - furnace}^i$ is the consumption of limestone in the furnace corresponding to coal type $i$.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] The present invention discloses an optimization method for desulfurization with variable coal types in a CFB boiler, which includes the following steps: First, introduce the received - base converted sulfur content, classify the coal types purchased by the power plant into low - sulfur coal, medium - sulfur coal, and high - sulfur coal. Conduct boiler efficiency tests and out - of - furnace desulfurization tests for coal types under different received - base converted sulfur contents to obtain various economic indicators of the boiler, including boiler efficiency, actual input heat of the boiler, in - furnace desulfurization limestone consumption, out - of - furnace desulfurization limestone consumption, out - of - furnace desulfurization equipment power consumption, etc. Combine the unit price of coal, the unit price of in - furnace desulfurization limestone, the unit price of out - of - furnace desulfurization limestone, and the electricity price of the desulfurization equipment to calculate the comprehensive operation costs of each coal type respectively. Finally, select and match the coal type with higher operation economy for the CFB boiler. The present invention comprehensively considers the changes in boiler economic indicators from the source of coal procurement, guides the power plant to reasonably purchase and blend coal types with higher operation economy, so as to achieve the purpose of reducing operation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is the flow chart of the present invention;

[0046] Figure 2 is the relationship curve between the output of the limestone feeder and the feeder opening degree of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0047] The following is a detailed description of the present invention, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0048] A brief overview of one or more aspects is given below to provide a basic understanding of these aspects. This overview is not an exhaustive survey of all contemplated aspects and is neither intended to identify key or decisive elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to a more detailed description given later.

[0049] As Figure 1-2 shown, a desulfurization optimization method for a CFB boiler with variable coal types includes the following steps:

[0050] S1. Classify the coal types purchased by the power plant into low-sulfur coal, medium-sulfur coal, and high-sulfur coal according to the received-base converted sulfur content S ar,zs where the received-base converted sulfur content S ar,zs is calculated according to the following formula:

[0051]

[0052] where S ar,zs is the received-base converted sulfur content of the coal, that is, the received-base sulfur content corresponding to 1000 kcal / kg calorific value of the coal, with the unit of %; S ar is the received-base sulfur content of the coal, with the unit of %; Q net,ar is the received-base lower calorific value of the coal, with the unit of kcal / kg;

[0053] The received-base converted sulfur content of low-sulfur coal is not greater than 0.2%, the received-base converted sulfur content of medium-sulfur coal is 0.2% - 0.5% (excluding 0.2%), and the received-base converted sulfur content of high-sulfur coal is greater than 0.5%.

[0054] S2. Conduct a calibration test on the output of the limestone feeder using the weighing method to obtain the fitting curve of the output of the limestone feeder and the feeder opening. The limestone consumption in the furnace can be obtained according to the feeder opening

[0055] Specifically, when the feeder opening x i is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% respectively, weigh the limestone powder amount per unit time using a calibrated platform scale to obtain the output of the limestone feeder at each opening, and fit the relationship curve f(x i ) between the output of the limestone feeder and the feeder opening x i . The limestone consumption m ln in the furnace can be obtained according to the feeder opening, m i = f(x i ), where x ln is the feeder opening, with the unit of %; m

[0056] S3. Under typical load conditions, the boiler efficiency test is carried out for different coal types using the inverse balance method to obtain the boiler efficiency η gl,i , and the actual input heat Q of the boiler is calculated using the direct balance method sr,i to characterize the actual coal input heat B of the boiler sj,i ;

[0057] S4. Synchronously with step S3, the flue gas desulfurization test outside the furnace is carried out. The concentrations of O2 and SO2 in the clean flue gas and the original flue gas are collected. The limestone samples outside the furnace and the gypsum samples are taken for chemical analysis. The consumption m of limestone outside the furnace is calculated from the calcium-sulfur molar ratio and the SO2 removal amount lw,i , and the power consumption W of the desulfurization equipment during the test is recorded lw,i ;

[0058] S5. According to the unit price R of coal m,i , the unit price R of limestone in the furnace ln , the unit price R of limestone outside the furnace lw , and the electricity price R of the desulfurization equipment tl , the coal combustion costs C of different coal types m,i , the limestone costs C in the furnace ln,i , the limestone costs C outside the furnace lw,i and the electricity costs C for the desulfurization equipment tl,i are calculated respectively. The sum of each cost gives the comprehensive operation cost C zh,i ;

[0059] S6. Compare the comprehensive operation costs of different coal types and select the coal type with higher operation economy for the CFB boiler by optimization

[0060] In step S3, under typical load conditions, the boiler efficiency η obtained for different coal types using the inverse balance method gl,i is calculated according to the following formula:

[0061] η gl,i = 100 - (q2 + q3 + q4 + q5 + q6 + q7 + q oth - q ex )

[0062] where η gl,i is the boiler efficiency corresponding to coal type i, in %; q2 is the heat loss due to flue gas, in %; q3 is the heat loss due to incomplete combustion of gas, in %; q4 is the heat loss due to incomplete combustion of solid, in %; q5 is the heat loss due to boiler heat dissipation, in %; q6 is the sensible heat loss of ash and slag, in %; q7 is the heat loss due to desulfurization, in %; q oth is other heat loss, in %; q ex is the percentage of external heat to the lower calorific value of fuel, in %;

[0063] The actual input heat Q of the boiler obtained by the positive balance method for different coal types sr,i and the actual coal input heat B of the boiler sj,i are calculated according to the following formula:

[0064]

[0065]

[0066] Q sc,i = D zq × h zq - D gs × h gs + D zr × h zr - D lzr × h lzr - D gj × h gj - D zj × h zj

[0067] where B sj,i is the actual coal input heat of the boiler corresponding to coal type i, with the unit of 10 3 kcal / h; Q sr,i is the actual input heat of the boiler corresponding to coal type i, with the unit of 10 3 kJ / h; Q sc,i is the actual output heat of the boiler corresponding to coal type i, with the unit of 10 3 kJ / h; D zq is the main steam flow rate, with the unit of t / h; h zq is the main steam enthalpy value, with the unit of kJ / kg; D gs is the final feed water flow rate, with the unit of t / h; h gs is the final feed water enthalpy value, with the unit of kJ / kg; D zr is the hot reheat steam flow rate, with the unit of t / h; h zr is the hot reheat steam enthalpy value, with the unit of kJ / kg; D lzr is the cold reheat steam flow rate, with the unit of t / h; h lzr is the cold reheat steam enthalpy value, with the unit of kJ / kg; D gj is the superheater desuperheating water flow rate, with the unit of t / h; h gj is the superheater desuperheating water enthalpy value, with the unit of kJ / kg; D zj is the reheater desuperheating water flow rate, with the unit of t / h; h zj is the reheater desuperheating water enthalpy value, with the unit of kJ / kg.

[0068] In step S4, the out-of-furnace limestone consumption m for different coal typeslw,i Calculated according to the following formula:

[0069]

[0070]

[0071] Wherein, m lw,i is the limestone consumption outside the furnace corresponding to coal type i, t / h; V RG,i is the volume flow rate of the original flue gas (standard dry, 6% O2), with the unit of m 3 / h; is the SO2 concentration in the original flue gas (standard dry, 6% O2), with the unit of mg / m 3 ; is the SO2 concentration in the clean flue gas (standard dry, 6% O2), with the unit of mg / m 3 ; is the molar mass of CaCO3, 100.09 kg / mol; is the molar mass of SO2, 64.06 kg / mol; F R,i is the purity of limestone, with the unit of %; S t,i is the calcium-sulfur molar ratio; is the mass content of CaCO3 in gypsum, with the unit of %; is the mass content of CaSO4·2H2O in gypsum, with the unit of %; is the mass content of CaSO3·0.5H2O in gypsum, with the unit of %; is the molar mass of CaSO4·2H2O, 172.18 kg / mol; is the molar mass of CaSO3·0.5H2O, 129.15 kg / mol.

[0072] The total power consumption W of the desulfurization equipment in step S4 lw,i can be obtained by counting the electricity meters of each equipment in the electrical switch room. The main power-consuming equipment includes slurry circulation pumps, oxidation blowers, vacuum pumps, etc.

[0073] In step S5, the comprehensive operation cost C of different coal types zh,i is calculated according to the following formula:

[0074]

[0075] C m,i = R m,i × B sj,i

[0076] C ln,i = R ln × m ln,i

[0077] C lw,i = R lw × m lw,i

[0078]

[0079] Among them, C zh,i is the comprehensive operating cost corresponding to coal type i, with the unit of yuan / MWh; C m,i is the coal combustion cost of coal type i, with the unit of yuan / h; C ln,i is the in-furnace limestone cost corresponding to coal type i, with the unit of yuan / h; C lw,i is the out-of-furnace limestone cost corresponding to coal type i, with the unit of yuan / h; C tl,i is the electricity consumption cost of the out-of-furnace desulfurization equipment corresponding to coal type i, with the unit of yuan / MWh; P e is the active power of the generator set, with the unit of MW; R m,i is the unit price of coal combustion for coal type i, with the unit of yuan / 10 3 kcal; R ln is the unit price of in-furnace limestone, with the unit of yuan / t; R lw is the unit price of out-of-furnace limestone, with the unit of yuan / t; R tl is the electricity price of the out-of-furnace desulfurization equipment, with the unit of yuan / kWh; W lw,i is the total power consumption of the out-of-furnace desulfurization equipment, with the unit of kW; m In，i is the consumption of in-furnace limestone corresponding to coal type i.

[0080] Example 1

[0081] Taking a 150MW CFB (Circulating Fluidized Bed) boiler in a certain power plant as an example, a desulfurization optimization test with variable coal types was carried out. The test was carried out at a load of about 135MW, and 5 coal types with different received-base converted sulfur contents (T-01 low-sulfur coal, T-02 medium-sulfur coal, T-03 medium-sulfur coal, T-04 high-sulfur coal, T-05 high-sulfur coal) were selected. Boiler efficiency tests, in-furnace limestone consumption tests, out-of-furnace desulfurization tests, etc. were carried out respectively. The results of the desulfurization optimization test with variable coal types for the 150MW CFB boiler of this power plant are shown in Table 1 below.

[0082] Table 1

[0083]

[0084]

[0085]

[0086] Figure 2Relationship curve between the output of the limestone feeder in Example 1 and the feeder opening. Among them, the relationship curve between the output of the No. 1 limestone feeder and the feeder opening is expressed as f(x i ) = 0.1616x - 0.0687, R 2 = 0.9984; the relationship curve between the output of the No. 2 limestone feeder and the feeder opening is expressed as f(x i ) = 0.1682x + 0.1178, R 2 = 0.9978; according to the feeder opening, the in-furnace limestone consumption m ln corresponding to the No. 1 and No. 2 limestone feeders can be obtained, where m i = f(x i ), where x ln is the feeder opening, with the unit of %; m

[0087] is the in-furnace limestone consumption, with the unit of t / h. Finally, the in-furnace limestone consumptions of the No. 1 and No. 2 at different openings are added to obtain the in-furnace limestone consumption.

[0087] It can be seen from Table 1 that at a load of 135 MW, when the received-base converted sulfur content in the coal is 0.16%, 0.29%, 0.39%, 0.53% and 0.58% respectively, the in-furnace limestone consumptions are 4.06 t / h, 9.25 t / h, 22.15 t / h, 25.25 t / h, 28.11 t / h respectively, the SO2 concentration in the original flue gas at the boiler outlet (standard dry, 6% O2) is 2094.6 mg / m 3 , 2887.0 mg / m 3 , 2859.1 mg / m 3 , 2253.7 mg / m 3 and 2097.8 mg / m 3 respectively, the boiler efficiencies are 89.04%, 88.60%, 86.70%, 84.38% and 84.06% respectively, the coal combustion costs are 271.16 yuan / MWh, 265.34 yuan / MWh, 250.55 yuan / MWh, 254.38 yuan / MWh and 273.24 yuan / MWh respectively. After considering the in-furnace and out-of-furnace limestone costs and the power consumption cost of the desulfurization equipment, the comprehensive operating costs of each coal type are 278.58 yuan / MWh, 276.38 yuan / MWh, 269.90 yuan / MWh, 274.43 yuan / MWh and 294.90 yuan / MWh respectively.

[0088] The coal combustion costs of medium-sulfur coal and high-sulfur coal are lower than those of low-sulfur coal, but considering the limestone cost and desulfurization power consumption, there is no obvious advantage in the comprehensive operating cost compared with burning low-sulfur coal. In order to improve the boiler efficiency, reduce the coal consumption of the unit, and reduce the limestone consumption, it is recommended to control the received-base converted sulfur content S ar,zs in the coal entering the furnace not to be higher than 0.4%. Calculated by 4000 kcal / kg, the received-base converted sulfur content Sar Not higher than 1.6%; During daily operation, control the SO2 concentration of the raw flue gas at the boiler outlet at about 3000 mg / m 3 and, on the premise of ensuring that the SO2 emission concentration of the clean flue gas meets the standard, appropriately increase the share of off-boiler desulfurization.

[0089] For the parts or structures not specifically described in the present invention, existing technologies or existing products can be adopted, and no further elaboration will be made here.

[0090] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0091] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A desulfurization optimization method for CFB boilers with variable coal types, characterized in that, It includes the following steps: Classify the coal types purchased by the power plant into low-sulfur coal, medium-sulfur coal, and high-sulfur coal according to the sulfur content on an as-received basis; Conduct boiler efficiency tests and off-boiler desulfurization tests for different coal types to obtain various economic indicators of the boiler, including the in-furnace limestone consumption, boiler efficiency, actual input heat of the boiler, off-furnace limestone consumption, and power consumption of the desulfurization equipment during the test period; Calculate the coal combustion cost, in-furnace limestone cost, off-furnace limestone cost, and power consumption cost of the desulfurization equipment for different coal types, and add up the various costs to obtain the comprehensive operation cost; Compare the comprehensive operation costs of different coal types, and select the coal type with higher operating economy for the CFB boiler by optimization; The in-furnace limestone consumption is obtained by the following steps: The weighing method is used to carry out the calibration test of the limestone feeder output, and the output m of the limestone feeder is obtained ln and the opening x of the feeder i of the fitting curve f(x i ). According to the opening of the feeder, the consumption m of limestone in the furnace can be obtained ln = f(x i ); The steps for conducting boiler efficiency tests for different coal types include: Under typical load conditions, conduct boiler efficiency tests for different coal types using the inverse balance method to obtain the boiler efficiency, and calculate the actual input heat of the boiler using the direct balance method to represent the actual coal combustion input heat of the boiler; The off-boiler desulfurization test is carried out synchronously with the boiler efficiency test. The steps for conducting off-boiler desulfurization tests for different coal types include: Collect the concentrations of O2 and SO2 in the clean flue gas and the raw flue gas, take samples of limestone outside the furnace and gypsum samples for chemical analysis, and calculate the consumption m of limestone outside the furnace from the calcium-sulfur molar ratio and the SO2 removal amount lw,i , and record the power consumption W of the desulfurization equipment during the test lw,i , which is obtained by counting the electricity meters of each equipment in the electrical switch room 2. The desulfurization optimization method for CFB boilers with variable coal types according to claim 1, wherein The as-received basis converted sulfur content S ar,zs is calculated according to the following formula: Among them, S ar,zs is the converted sulfur content on the as-received basis of coal, that is, the sulfur content on the as-received basis corresponding to 1000 kcal / kg calorific value of coal, with the unit of %; S ar is the sulfur content on the as-received basis of coal, with the unit of %; Q net,ar is the lower calorific value on the as-received basis of coal, with the unit of kcal / kg; The converted sulfur content of the low-sulfur coal is not more than 0.2%; the converted sulfur content of the medium-sulfur coal ranges from 0.2% to 0.5%, excluding 0.2%; the converted sulfur content of the high-sulfur coal is greater than 0.5%.

3. The desulfurization optimization method for CFB boilers with variable coal types according to claim 1, characterized in that, The steps for calibrating the output of the limestone feeder using the weighing method include: At the opening x of the feeder i When they are 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% respectively, use a calibrated platform scale to weigh the amount of limestone powder per unit time, obtain the output of the limestone feeder at each opening, and fit the output m of the limestone feeder ln And the opening x of the feeder i The relationship curve m ln = f(x i ).

4. A desulfurization optimization method for a CFB boiler with variable coal types according to claim 1, characterized in that The boiler efficiency is calculated according to the following formula: η gl,i = 100 - (q2 + q3 + q4 + q5 + q6 + q7 + q oth - q ex ) Among them, η gl,i is the boiler efficiency corresponding to coal type i, in %; q2 is the heat loss due to flue gas, in %; q3 is the heat loss due to incomplete combustion of gas, in %; q4 is the heat loss due to incomplete combustion of solid, in %; q5 is the heat loss due to boiler heat dissipation, in %; q6 is the sensible heat loss of ash and slag, in %; q7 is the heat loss due to desulfurization, in %; q oth is other heat loss, in %; q ex is the percentage of the external heat to the lower calorific value of the fuel, in %.

5. A desulfurization optimization method for CFB boilers with variable coal types according to claim 1, characterized in that, The actual input heat of the boiler and the actual coal combustion input heat of the boiler are calculated according to the following formulas respectively: Q sc,i = D zq × h zq - D gs × h gs + D zr × h zr - D lzr × h lzr - D gj × h gj - D zj × h zj Among them, Q sr,i is the actual input heat of the boiler corresponding to coal type i, with the unit of 10 3 kJ / h; B sj,i is the actual coal input heat of the boiler corresponding to coal type i, with the unit of 10 3 kcal / h; Q sc,i is the actual output heat of the boiler corresponding to coal type i, with the unit of 10 3 kJ / h; D zq is the main steam flow rate, with the unit of t / h; h zq is the main steam enthalpy value, with the unit of kJ / kg; D gs is the final feed water flow rate, with the unit of t / h; h gs is the final feed water enthalpy value, with the unit of kJ / kg; D zr is the hot reheat steam flow rate, with the unit of t / h; h zr is the hot reheat steam enthalpy value, with the unit of kJ / kg; D lzr is the cold reheat steam flow rate, with the unit of t / h; h lzr is the cold reheat steam enthalpy value, with the unit of kJ / kg; D gj is the superheater desuperheating water flow rate, with the unit of t / h; h gj is the superheater desuperheating water enthalpy value, with the unit of kJ / kg; D zj is the reheater desuperheating water flow rate, with the unit of t / h; h zj is the reheater desuperheating water enthalpy value, with the unit of kJ / kg.

6. A desulfurization optimization method for a CFB boiler with variable coal types according to claim 1, characterized in that, The off-furnace limestone consumption is calculated according to the following formula: where m lw,i is the limestone consumption outside the furnace corresponding to coal type i, t / h; V RG,i is the volume flow rate of the original flue gas, standard dry, 6% O2, with the unit of m 3 / h; is the SO2 concentration in the original flue gas, standard dry, 6% O2, with the unit of mg / m 3 ; is the SO2 concentration in the clean flue gas, standard dry, 6% O2, with the unit of mg / m 3 ; is the molar mass of CaCO3, 100.09 kg / mol; is the molar mass of SO2, 64.06 kg / mol; F R,i is the purity of limestone, with the unit of %; S t,i is the calcium-sulfur molar ratio; is the mass content of CaCO3 in gypsum, with the unit of %; is the mass content of CaSO4·2H2O in gypsum, with the unit of %; is the mass content of CaSO3·0.5H2O in gypsum, with the unit of %; is the molar mass of CaSO4·2H2O, 172.18 kg / mol; is the molar mass of CaSO3·0.5H2O, 129.15 kg / mol.

7. A method for optimizing desulfurization of a CFB boiler with variable coal types according to claim 1, characterized in that, The steps for calculating the coal combustion cost, in-furnace limestone cost, off-furnace limestone cost, and power consumption cost of the desulfurization equipment for different coal types, and adding up the various costs to obtain the comprehensive operation cost include: According to the unit price of coal R m,i , the unit price of in-furnace limestone R ln , the unit price of out-of-furnace limestone R lw , the electricity price of desulfurization equipment R tl , calculate the coal combustion cost C m,i , the in-furnace limestone cost C ln,i , the out-of-furnace limestone cost C lw,i and the electricity cost of desulfurization equipment C tl,i for different coal types respectively. Add up the various costs to obtain the comprehensive operation cost C zh,i ; The comprehensive operating cost C zh,i is calculated according to the following formula: C m,i = R m,i × B sj,i C ln,i = R ln × m ln,i C lw,i = R lw × m lw,i Among them, C zh,i is the comprehensive operating cost corresponding to coal type i, with the unit of yuan / MWh; C m,i is the coal combustion cost of coal type i, with the unit of yuan / h; C ln,i is the in-furnace limestone cost corresponding to coal type i, with the unit of yuan / h; C lw,i is the out-of-furnace limestone cost corresponding to coal type i, with the unit of yuan / h; C tl,i is the electricity consumption cost of the out-of-furnace desulfurization equipment corresponding to coal type i, with the unit of yuan / MWh; P e is the active power of the generator set, with the unit of MW; R m,i is the unit price of coal combustion for coal type i, with the unit of yuan / 10 3 kcal; R ln is the unit price of in-furnace limestone, with the unit of yuan / t; R lw is the unit price of out-of-furnace limestone, with the unit of yuan / t; R tl is the electricity price of the out-of-furnace desulfurization equipment, with the unit of yuan / kWh; W lw,i is the total power consumption of the out-of-furnace desulfurization equipment, with the unit of kW; m ln，i is the consumption of in-furnace limestone corresponding to coal type i.

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