An economic performance evaluation method applied to a mixed combustion sludge boiler system

Abstract

This invention provides an economic performance evaluation method for sludge co-firing boiler systems, which can accurately evaluate the impact of sludge co-firing on the boiler's economic indicators. The method includes the following steps: conducting at least two sets of comparative tests on the sludge co-firing boiler system, each set of comparative tests including operation under both sludge-free and sludge-coated conditions, and recording the test parameters respectively. The operating order of the two sets of comparative tests is reversed. The power consumption for sludge treatment at the plant is calculated using a formula. The output of the sludge co-firing boiler system is calculated using a formula. The boiler efficiency is calculated using a formula. The online CEMS correction coefficient for the sludge co-firing boiler system is obtained using a formula. Subsequently, the pollutant emission data during the comparative tests are corrected using the correction coefficient k.

Description

Technical Field

[0001] This invention relates to the field of performance evaluation technology, specifically to an economic performance evaluation method for sludge co-firing boiler systems. Background Technology

[0002] By the end of 2021, China's installed power generation capacity reached 2.38 billion kilowatts, with coal-fired power units accounting for approximately 1.11 billion kilowatts. With rapid urbanization, the amount of sludge produced by urban wastewater treatment plants is increasing daily. To fully leverage the role of existing coal-fired power units in reducing, rendering harmless, recycling, and disposing of urban sludge on a large scale, and to maximize their positive role in local environmental protection, the number of coal-fired power plants co-firing sludge has been gradually increasing in recent years. Coal-fired power plants can obtain sludge disposal subsidies by disposing of sludge, while also fulfilling their social environmental responsibilities—a win-win situation for the government, enterprises, and society. For coal-fired power plants, besides sludge disposal fees (mainly influenced by market supply and demand), the impact of co-firing sludge on the boiler's economic viability is a key concern.

[0003] After the sludge co-firing system is retrofitted into a coal-fired power plant boiler, it is objectively necessary to conduct an assessment and evaluation of the system's operation to evaluate its performance indicators and provide decision-making basis for power plant technicians. However, there is currently a lack of assessment and evaluation methods for the sludge co-firing system. Therefore, it is necessary to develop a simple and easy-to-implement evaluation method to comprehensively evaluate the main economic performance indicators of coal-fired boilers after sludge co-firing. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an economic performance evaluation method for sludge co-firing boiler systems, which can accurately evaluate the impact of sludge co-firing on the boiler's economic indicators.

[0005] The technical solution is as follows: an economic performance evaluation method for sludge co-firing boiler systems, characterized in that the method includes the following steps:

[0006] At least two sets of comparative tests were repeated on the sludge-fired boiler system. Each set of comparative tests included operation under both sludge-free and sludge-fired conditions, and the test parameters were recorded separately. The order of operation was reversed during the two sets of comparative tests.

[0007] The power consumption for treating sludge at the plant was calculated using the formula.

[0008] The output of the sludge-coated boiler system is obtained from the calculation formula.

[0009] Boiler efficiency is obtained from the calculation formula.

[0010] The online CEMS correction coefficient for the sludge-coated boiler system is obtained based on the calculation formula. The pollutant emission data from the comparative experiment were then corrected using a correction factor k, i.e., C1 = k × C dcs1 ;

[0011] Wherein, ΔP is the power consumption for sludge treatment at the plant, in kWh / t;

[0012] Δr1 represents the difference in plant power consumption between the start-up and shutdown of the sludge-coated boiler system in the first comparative experiment, in kWh;

[0013] Δr2 represents the difference in plant power consumption between the start-up and shutdown of the sludge-coated boiler system in the second comparative experiment, in kWh.

[0014] Δt1 represents the sludge co-firing time in the first comparative experiment (h); Δt2 represents the sludge co-firing time in the second comparative experiment (h).

[0015] w1 represents the amount of sludge fed into the sludge chamber in the first comparative experiment, in tons; w2 represents the amount of sludge fed into the sludge chamber in the second comparative experiment, in tons.

[0016] w represents the output of the sludge-co-firing boiler system, in t / d; w1 represents the total weight of sludge fed into the silo during the test, in t; Δt represents the test time for sludge co-firing, in h;

[0017] Δη1 represents the efficiency difference of the boilers in the first group of comparative tests, in %; Δη2 represents the efficiency difference of the boilers in the second group of comparative tests, in %;

[0018] C grid0 For comparison of pollutant concentrations measured using the grid method during the period; C dcs0 The DCS dial values ​​of pollutants during the comparison period;

[0019] C1 is the pollutant correction value during the test; C dcs1 The DCS dial value for pollutants during the test.

[0020] Furthermore, the method also includes preparatory work before the experiment, specifically including the following steps:

[0021] S1.1 Before conducting the test, check that the sludge silo level display of the sludge co-firing boiler system is normal, and then put the sludge co-firing boiler system into operation to burn the sludge silo to the low level l1 to ensure that the sludge can enter the silo normally during the test.

[0022] S1.2. The boiler in the sludge co-firing boiler system is blew soot, and then the sludge silo is fed.

[0023] S1.3 Adjust the load of the sludge-coated boiler system to 100% of its rated load;

[0024] Furthermore, after completing the preparatory work, two sets of comparative tests were repeated on the sludge co-firing boiler system, specifically including the following steps:

[0025] S2.1 First, conduct a test without sludge co-firing and record the unit parameters of the sludge co-firing boiler system during this test period, which lasts for 2 to 3 hours.

[0026] S2.2 After the test without sludge co-firing is completed, the boiler air preheater is blew soot once;

[0027] S2.3 After the air preheater soot blowing is completed, a sludge co-firing test is conducted. The sludge co-firing boiler system is started and kept at maximum output. The combustion operation mode is kept the same as the non-sludge co-firing test until the sludge bin level drops to the low material level l1. The unit parameters of the sludge co-firing boiler system during this test are recorded. The test time is 2h to 3h. The first group of comparative tests ends here.

[0028] S2.4 After the first set of comparative tests, repeatable tests were conducted at different time periods. First, a sludge co-firing test was conducted, that is, step S2.3 was repeated. After the test, the boiler air preheater was soot blown once. After the soot blowing was completed, a test without sludge co-firing was prepared, that is, step 2.1 was repeated. The second set of comparative tests was then completed.

[0029] Furthermore, during sludge co-firing, the coal quality parameters and sludge parameters obtained during the sludge co-firing test were used to calculate the corresponding calorific value and elemental composition of the fuel entering the furnace, i.e.

[0030]

[0031]

[0032] Q fix =w c Q c +w w Q w

[0033] γ fix =w c γ c +w w γ w

[0034] Among them, w c The percentage of coal by mass in the total fuel is the sum of coal and sludge.

[0035] w w The percentage of sludge by total fuel mass;

[0036] f cThe coal flow rate into the furnace, in t / h, is obtained from DCS data acquisition.

[0037] F w The sludge flow rate into the furnace, t / h, is calculated by dividing the output of the sludge-co-fired boiler system by the operating time.

[0038] Q fix The total weighted calorific value of the fuel is expressed in kJ / kg.

[0039] Q c The net calorific value of coal is measured in kJ / kg.

[0040] Q w The lower heating value of the sludge is given as received, in kJ / kg;

[0041] γ fix The total fuel weighted elemental composition, %;

[0042] γ c The basic elemental composition of coal, %;

[0043] γ w The basic elemental composition of the sludge, %;

[0044] Furthermore, pollutant emission data were obtained through grid testing and then compared with the online CEMS table of the sludge-fired boiler system to obtain the online CEMS correction coefficient k of the sludge-fired boiler system; pollutants included SO2, NOx, and particulate matter concentration.

[0045] Furthermore, the sludge co-firing boiler system includes a sludge silo, sludge drying equipment, a boiler, a denitrification reactor, an air preheater, an electrostatic precipitator, a fan, a desulfurization tower, and a chimney. The outlet of the sludge silo is connected to the inlet of the sludge drying equipment, and the outlet of the sludge drying equipment is connected to the inlet of the boiler. The flue gas outlet of the boiler is connected to the inlet of the denitrification reactor, and after passing through the air preheater, it is connected to the electrostatic precipitator. The flue gas outlet of the boiler is also connected to the air inlet of the sludge drying equipment. The bottom of the boiler has an outlet for discharging slag. The outlet of the electrostatic precipitator is connected in sequence to the fan, the desulfurization tower, and the chimney, so the treated flue gas pollutants are discharged into the atmosphere through the chimney.

[0046] The beneficial effects of this invention are that by conducting at least two sets of comparative tests on the addition and removal of sludge in a sludge-fired boiler system, the power consumption for sludge treatment at the plant, the output of the sludge-fired boiler system, the boiler efficiency, and the boiler pollutant emission values ​​after the system is put into operation can be determined. Through the determined performance indicators, the impact of sludge co-firing on the economic indicators of the boiler can be accurately evaluated, thereby providing a basis for decision-making for power plant technicians. Attached Figure Description

[0047] Figure 1 This is a structural block diagram of the sludge co-firing boiler system in this invention. Detailed Implementation

[0048] like Figure 1 As shown, this invention provides an economic performance evaluation method for a sludge co-firing boiler system. The sludge co-firing boiler system includes a sludge silo 1, a sludge drying equipment 2, a boiler 3, a denitrification reactor 4, an air preheater 5, an electrostatic precipitator 6, a fan 7, a desulfurization tower 8, and a chimney 9. The outlet of the sludge silo 1 is connected to the inlet of the sludge drying equipment 2, and the sludge outlet of the sludge drying equipment 2 is connected to the inlet of the boiler 3. The flue gas outlet of the boiler 3 is connected to the inlet of the denitrification reactor 4, and then connects to the electrostatic precipitator 6 via the flue gas outlet of the air preheater 5. The flue gas outlet of the boiler 3 is also connected to the air inlet of the sludge drying equipment 2. Primary and secondary air enter the bottom of the air preheater 5. The bottom of the boiler 3 has an outlet for discharging slag. The outlet of the electrostatic precipitator 6 is sequentially connected to the fan 7, the desulfurization tower 8, and the chimney 9, so the treated flue gas pollutants are discharged into the atmosphere through the chimney 9.

[0049] The method includes the following steps:

[0050] At least two sets of comparative tests were repeated on the sludge-fired boiler system. Each set of comparative tests included operation under conditions without sludge (also known as blank test) and operation under conditions with sludge, and the test parameters were recorded separately. The order of operation under conditions was reversed during the two sets of comparative tests.

[0051] Specifically:

[0052] The preparation work before the comparative experiment includes the following steps:

[0053] S1.1 On the first day, before conducting the test, check that the sludge silo level display of the sludge co-firing boiler system is normal. Then, put the sludge co-firing boiler system into operation and burn the sludge silo to the low level l1 to ensure that the sludge for the test on the second day can be put into the silo normally.

[0054] S1.2. Perform soot blowing on the boiler in the sludge co-firing boiler system, prepare coal for the next day's silo, test the coal quality to keep it as stable as possible, then the sludge truck enters the plant for weighing, the sludge silo begins to be fed, and the sludge truck number entering the silo is recorded.

[0055] S1.3 Adjust the load of the sludge-fired boiler system to 100% of the rated load;

[0056] After completing the preparation work, two sets of comparative tests were repeated on the sludge co-firing boiler system, specifically including the following steps:

[0057] S2.1 First, conduct a test without co-firing sludge and record the unit parameters of the boiler system with co-firing sludge during this test period. The test time is 2 hours. The unit parameters include plant power, boiler flue gas temperature, flue gas oxygen content and carbon monoxide content. Collect coal, ash and slag samples and record the air preheater inlet air temperature, atmospheric temperature, atmospheric humidity, atmospheric pressure and coal feed rate.

[0058] S2.2 After the test without sludge co-firing is completed, the boiler air preheater is blew soot once in preparation for the test with sludge co-firing.

[0059] S2.3 After the air preheater soot blowing is completed, a sludge co-firing test is carried out. The sludge co-firing boiler system is started and kept at maximum output. The combustion operation mode is kept the same as the non-sludge co-firing test until the sludge bin level drops to the low material level l1. The unit parameters of the sludge co-firing boiler system during this test are recorded. The test time is 2 hours. The first group of comparative tests ends here.

[0060] S2.4 After the first set of comparative tests, repeatability tests were conducted on the third day. First, a sludge co-firing test was conducted, i.e., step S2.3 was repeated. After the test, the boiler air preheater was soot blown once. After the soot blowing was completed, a test without sludge co-firing was prepared, i.e., step 2.1 was repeated. The second set of comparative tests was then completed.

[0061] By implementing air preheater soot blowing measures during the two daily test periods and arranging the test periods in reverse order over two days, the interference caused by ash accumulation on the heated surface can be effectively reduced in boiler flue gas temperature. Furthermore, during the tests, both the blank test and the sludge-blended control test must maintain stable coal quality, stable combustion mode, and stable total air volume entering the boiler to minimize the impact of changes in coal quality and combustion mode on boiler efficiency. The same coal quality parameters are used in both the blank test and the sludge-blended control test.

[0062] The following are the specific performance indicators for boilers after co-firing sludge:

[0063] (1) The power consumption ΔP for sludge treatment in the plant is obtained according to the calculation formula. The power consumption ΔP for sludge treatment in the plant represents the impact of co-fired sludge on the plant's power consumption.

[0064] The average of the two-day repeatability comparison test results was taken as the final result.

[0065] Wherein, ΔP is the power consumption for sludge treatment at the plant, in kWh / t;

[0066] Δr1 represents the difference in plant power consumption between the start-up and shutdown of the sludge-coated boiler system in the first comparative experiment, in kWh;

[0067] Δr2 represents the difference in plant power consumption between the start-up and shutdown of the sludge-coated boiler system in the second comparative experiment, in kWh.

[0068] Δt1 represents the sludge co-firing time in the first comparative experiment, in hours.

[0069] Δt2 represents the sludge co-firing time in the second comparative experiment, in hours.

[0070] w1 represents the amount of sludge fed into the sludge chamber in the first comparative experiment, in tons;

[0071] w2 represents the amount of sludge fed into the silo in the second comparative experiment, in tons;

[0072] (2) The output w of the sludge co-firing boiler system is obtained according to the calculation formula. The output w of the sludge co-firing boiler system directly affects the amount of sludge disposal fee.

[0073] The average output of the sludge co-firing boiler system from the two-day repeatable comparative test was taken as the final result. The daily output of the sludge co-firing boiler system was measured by weighing on a weighbridge. The sludge silo level was kept consistent before and after co-firing, and it was assumed that all the sludge entering the silo that day was co-fired. This was to avoid the correction of sludge level deviation caused by the difference in sludge silo level before and after co-firing, thus avoiding the introduction of new errors. The co-firing operation time was converted to one day.

[0074] The output (24 hours) of the sludge co-firing boiler system is calculated using the following formula:

[0075] Where w represents the output of the sludge-coated boiler system, in t / d;

[0076] w1 represents the total weight of mud deposited during the test, in tons;

[0077] Δt is the test time for co-firing sludge, in hours;

[0078] (3) The boiler efficiency Δη is obtained according to the calculation formula. The boiler efficiency Δη represents the influence of sludge co-firing on the boiler efficiency. The average value of the 2-day repeatable comparison test is taken as the final result, i.e.

[0079] Wherein, Δη1 is the boiler efficiency difference in the first group of comparative tests, in %;

[0080] Δη2 represents the difference in boiler efficiency in the second comparative test group, expressed as a percentage.

[0081] The boiler efficiency in the blank test and the sludge co-firing test was obtained by back-balancing calculation according to GB10184-2015, as illustrated below:

[0082] η = 100 - q² - q³ - q⁴ - q⁵ - q⁶ - q oth +q ex (A-1)

[0083] In the formula:

[0084] η—Boiler efficiency during the test, %;

[0085] q2—Smoke exhaust heat loss, %;

[0086] q3 — Heat loss due to incomplete combustion of gas, %;

[0087] q4 — Heat loss due to incomplete combustion of solids, %;

[0088] q5—Boiler heat loss, % (based on design value);

[0089] q6—Physical sensible heat loss from ash and slag, %;

[0090] q oth Other heat losses, including heat loss from coal and stone emissions, are not considered in this case.

[0091] q ex —Percentage of external heat to lower heating value of fuel, %. ex Consider the physical heat carried by the air and fuel entering the system.

[0092] The boiler efficiency reference temperature during the test was 25℃. The ash balance ratio in the boiler efficiency calculation during the test was: fly ash:

[0093] 90%; Slag: 10%.

[0094] After sludge is co-burned, it generally affects the heat loss of flue gas, the heat loss of incomplete combustion of gas, and the heat loss of incomplete combustion of solids, while the heat loss of other items remains almost unchanged.

[0095]

[0096]

[0097]

[0098]

[0099]

[0100] Q2 = Q 2fgd +Q 2wvfg (A-8)

[0101] Q 2fgd =V fgd ×C pfgd ×(t fglv -t re (A-9)

[0102] V fgd =V fgdth +(α-1)×V adth (A-10)

[0103] V fgdth =(1.8658C b +0.6989S ar +79V adth +0.8N ar ) / 100 (A-11)

[0104] V adth =0.0888C b +0.0333S ar +0.2647H ar -0.0334O ar (A-12)

[0105]

[0106]

[0107]

[0108]

[0109] Q 2wvfg =V wvfg ×C pw ×(t fglv -t re ) (A-17)

[0110]

[0111] Q4=3.3727A ar ×w cm (A-18)

[0112]

[0113] Q ex =Q f +Q ad +Q wv (A-20)

[0114] Q f =c f ×(t f -t re ) (A-21)

[0115]

[0116] Qwv =1.293αV adth ×h a ×1.501×(t am -t re (A-23)

[0117] In the formula:

[0118] Q2—Heat carried away by the exhaust, kJ / kg;

[0119] Q3—Heat loss due to incomplete combustion of gas, kJ / kg;

[0120] Q4——Heat loss due to incomplete combustion of solids, kJ / kg;

[0121] Q6—Physical heat loss of ash and slag, kJ / kg;

[0122] Q ex —Total external heat, kJ / kg;

[0123] Q 2fgd —Heat carried away by dry flue gas, kJ / kg;

[0124] Q 2wvfg —The sensible heat of water vapor in flue gas, kJ / kg;

[0125] V fgd —Actual dry flue gas volume generated, m 3 / kg;

[0126] C pfgd —Specific heat of dry flue gas, 1.37 kJ / (m³) 3 .K);

[0127] t fglv —Smoke exhaust temperature, °C;

[0128] t re —Base temperature, 25℃;

[0129] V fgdth —Theoretical dry flue gas volume, m 3 / kg;

[0130] α — Excess air coefficient;

[0131] V adth —Theoretical dry air volume, m 3 / kg;

[0132] C b —Actual carbon burned, kg / kg;

[0133] C ar H arO ar H ar S ar W ar A ar —The carbon, hydrogen, oxygen, nitrogen, sulfur, moisture, and ash content in the fuel, in percent;

[0134] —Oxygen content in exhaust smoke, %;

[0135] —Carbon monoxide content in flue gas, %;

[0136] w cm —Average combustible content in ash, %;

[0137] w cs —Combustible content of slag, %;

[0138] w cas —Combustible content of fly ash, %;

[0139] h a —Air humidity, kg / kg, take 0.01;

[0140] C s —Specific heat of slag, kJ / (kg.K), taken as 1.11;

[0141] c pd —Specific heat of fly ash, kJ / (kg.K), taken as 0.78;

[0142] c f —Specific heat of coal, kJ / (kg.K), taken as 1.60;

[0143] q ap — Primary air volume, t / h;

[0144] q as —Secondary air volume, t / h;

[0145] q m —Fuel input to the furnace, t / h;

[0146] t ap —Air preheater inlet primary air temperature, °C;

[0147] t as —Air preheater inlet secondary air temperature, °C;

[0148] Q f —Physical heat from the fuel entering the furnace, kJ / kg;

[0149] Q ad —Physical heat generated by the dry air entering the furnace, kJ / kg;

[0150] Q wv —The heat carried by water vapor in the air entering the furnace, kJ / kg;

[0151] t am —The average air temperature at the air preheater inlet can be calculated by weighting the primary air temperature and the secondary air temperature, in °C.

[0152] Right now:

[0153] (4) Pollutant emissions meet the standards. Emissions are a mandatory environmental protection indicator. Before the test, the online CEMS meter should be checked and calibrated to ensure that the display is normal.

[0154] Boiler pollutant emissions are environmental control indicators. During the experiment, pollutant emissions (SO2, NOx, and particulate matter concentration) at the chimney inlet were measured using a grid method. These emissions were then compared with the online CEMS data of a sludge-fired boiler system during the same period to obtain the correction coefficient k for the online CEMS of the sludge-fired boiler system.

[0155] Subsequently, the pollutant emission data from the blank test and the sludge co-firing test were corrected according to the correction factor k, i.e., C1 = k × C dcs1 ;

[0156] Among them, C grid0 The comparison was based on the actual pollutant concentration (6% O2) measured using the grid method during the period.

[0157] C dcs0 The DCS dial value of the pollutants during the comparison period (6% O2);

[0158] C1 is the pollutant correction value during the test;

[0159] C dcs1 The DCS dial value for pollutants during the test.

[0160] The comparison period corresponds to the on-site measurement time period, which is generally about 2 hours.

[0161] The test period is usually quite long, generally around 4 hours, or even longer.

[0162] When co-firing sludge, the coal quality parameters and sludge parameters during the co-firing test are used to calculate the corresponding calorific value and elemental composition of the fuel entering the furnace, i.e.

[0163]

[0164]

[0165] Q fix =wc Q c +w w Q w

[0166] γ fix =w c γ c +w w γ w

[0167] Among them, w c The percentage of coal by mass in the total fuel is the sum of coal and sludge.

[0168] w w The percentage of sludge by total fuel mass;

[0169] F c The coal flow rate into the furnace, in t / h, is obtained from DCS data acquisition.

[0170] F w The sludge flow rate into the furnace, t / h, is calculated by dividing the output of the sludge-coated boiler system by the operating time.

[0171] Q fix The total weighted calorific value of the fuel is expressed in kJ / kg.

[0172] Q c The net calorific value of coal is measured in kJ / kg.

[0173] Q w The lower heating value of the sludge is given as received, in kJ / kg;

[0174] γ fix The total fuel weighted elemental composition, %;

[0175] γ c The basic elemental composition of coal, %;

[0176] γ w The basic elemental composition of the sludge is %.

[0177] By determining the performance indicators of the boiler after co-firing sludge, power plant technicians can evaluate the boiler sludge co-firing system based on these indicators and make corresponding decisions.

[0178] This invention takes the retrofitting of a sludge-fired boiler system in a 660MW unit of a certain plant as an example, and provides a detailed description through the following table:

[0179] Table 1 Output of Sludge-Co-firing Boiler System

[0180]

[0181]

[0182] In Table 1, the sludge silo level was 500mm before the test, 1450mm after feeding under test condition T-02, and 500mm after the sludge co-firing test. It is assumed that the sludge co-firing during the test period is the same as the sludge fed into the silo, meaning that 38.44t of sludge was processed within 4.78h, which translates to a daily processing capacity of 192.9t / d. Similarly, the output of the sludge co-firing system under test condition T-03 was 171.3t / d. The average output of the sludge co-firing boiler system under both conditions T-02 and T-03 was 182.1t / d. Power plant technicians can then make decisions regarding sludge disposal costs and corresponding measures based on these values.

[0183] Table 2 Results of Power Consumption for Sludge Treatment in the Plant

[0184]

[0185]

[0186] In Table 2, during the T-02 test condition, the hourly plant power consumption was 24065.5 kWh. After the sludge system was shut down, the hourly plant power consumption was 23624.4 kWh, resulting in a difference of 441.1 kWh per hour. The sludge co-firing system operated for 4.78 hours, corresponding to an additional 2110.3 kWh of plant power consumption. The amount of sludge processed was 38.44 t, and the sludge system power consumption was 54.9 kWh / t. Similarly, the sludge system power consumption during the T-03 test condition was 51.1 kWh / t. The average power consumption for sludge processing during the T-02 and T-03 test conditions (based on the difference in plant power consumption) was 53.0 kWh / t. Based on these values, power plant technicians can make decisions regarding changes in unit coal consumption, the impact of sludge co-firing on plant power consumption, and corresponding measures.

[0187] Table 3 Boiler efficiency test results

[0188]

[0189]

[0190]

[0191]

[0192]

[0193]

[0194] In Table 3, test condition T-01 was a blank test (system without sludge co-firing), with a boiler efficiency of 93.52%. Test condition T-02, after co-firing sludge, had a boiler efficiency of 93.42%, showing a decrease of 0.10 percentage points in boiler efficiency. Test condition T-03, after co-firing sludge, had a boiler efficiency of 93.67%. Test condition T-04, also a blank test, had a boiler efficiency of 93.81%, showing a decrease of 0.14 percentage points in boiler efficiency. The average boiler efficiency for the two sets of comparative tests was 0.12 percentage points. Power plant technicians can use these values ​​to make decisions regarding changes in unit coal consumption, the impact of sludge co-firing on boiler efficiency, and corresponding measures.

[0195] Table 4 Pollutant Emission Test at Chimney Inlet

[0196]

[0197] In Table 4, the measured values ​​were first compared with the DCS dial values ​​using the grid method to obtain correction coefficients for SO2, NOx, and particulate matter dial values. The pollutant emission data for the blank test and the sludge co-firing test were then corrected using the pollutant correction coefficients.

[0198] In Tables 1 to 4, T-01 represents the blank test in the first group of comparative tests, which meets national environmental protection requirements;

[0199] T-02 represents the sludge co-firing test in the first group of comparative tests, which meets national environmental protection requirements;

[0200] T-03 represents the sludge co-firing test in the second group of comparative tests, which meets national environmental protection requirements;

[0201] T-04 represents the blank test in the second group of comparative tests, which meets national environmental protection requirements.

[0202] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An economic performance evaluation method for a sludge co-firing boiler system, characterized in that: The method includes the following steps: At least two sets of comparative tests were repeated on the sludge-fired boiler system. Each set of comparative tests included operation under both sludge-free and sludge-fired conditions, and the test parameters were recorded separately. The order of operation was reversed during the two sets of comparative tests. The power consumption for treating sludge at the plant was calculated using the formula. The output of the sludge-coated boiler system is obtained from the calculation formula. Boiler efficiency is obtained from the calculation formula. The online CEMS correction coefficient for the sludge-coated boiler system is obtained based on the calculation formula. The pollutant emission data from the comparative experiment were then corrected using a correction factor k, i.e., C1 = k × C dcs1 ; Wherein, ΔP is the power consumption for sludge treatment at the plant, in kWh / t; Δr1 represents the difference in plant power consumption between the start-up and shutdown of the sludge-coated boiler system in the first comparative experiment, in kWh; Δr2 represents the difference in plant power consumption between the start-up and shutdown of the sludge-coated boiler system in the second comparative experiment, in kWh. Δt1 represents the sludge co-firing time in the first comparative experiment (h); Δt2 represents the sludge co-firing time in the second comparative experiment (h). w1 represents the amount of sludge fed into the sludge chamber in the first comparative experiment, in tons; w2 represents the amount of sludge fed into the sludge chamber in the second comparative experiment, in tons. w represents the output of the sludge-co-firing boiler system, in t / d; w1 represents the total weight of sludge fed into the silo during the test, in t; Δt represents the test time for sludge co-firing, in h; Δη1 represents the efficiency difference of the boilers in the first group of comparative tests, in %; Δη2 represents the efficiency difference of the boilers in the second group of comparative tests, in %; C grid0 For comparison of pollutant concentrations measured using the grid method during the period; C dccs0 The DCS dial values ​​of pollutants during the comparison period; C1 is the pollutant correction value during the test; C dcs1 The DCS dial value for pollutants during the test.

2. The economic performance evaluation method for a sludge co-firing boiler system according to claim 1, characterized in that: The sludge co-firing boiler system includes a sludge silo, sludge drying equipment, a boiler, a denitrification reactor, an air preheater, an electrostatic precipitator, a fan, a desulfurization tower, and a chimney. The outlet of the sludge silo is connected to the inlet of the sludge drying equipment, and the outlet of the sludge drying equipment is connected to the inlet of the boiler. The flue gas outlet of the boiler is connected to the inlet of the denitrification reactor, and after passing through the air preheater, it is connected to the electrostatic precipitator. The flue gas outlet of the boiler is also connected to the air inlet of the sludge drying equipment. The bottom of the boiler has an outlet for discharging slag. The outlet of the electrostatic precipitator is connected in sequence to the fan, the desulfurization tower, and the chimney, so the treated flue gas pollutants are discharged into the atmosphere through the chimney.

3. The economic performance evaluation method for a sludge-co-firing boiler system according to claim 1, characterized in that: The method also includes preparatory work before the experiment, specifically including the following steps: S1.1 Before conducting the test, check that the sludge silo level display of the sludge co-firing boiler system is normal, and then put the sludge co-firing boiler system into operation to burn the sludge silo to the low level l1 to ensure that the sludge can enter the silo normally during the test. S1.

2. The boiler in the sludge co-firing boiler system is blew soot, and then the sludge silo is fed. S1.3 Adjust the load of the sludge-fired boiler system to 100% of the rated load.

4. The economic performance evaluation method for a sludge co-firing boiler system according to claim 3, characterized in that: After completing the preparation work, two sets of comparative tests were repeated on the sludge co-firing boiler system, specifically including the following steps: S2.1 First, conduct a test without sludge co-firing and record the unit parameters of the sludge co-firing boiler system during this test period, which lasts for 2 to 3 hours. S2.2 After the test without sludge co-firing is completed, the boiler air preheater is blew soot once; S2.3 After the air preheater soot blowing is completed, a sludge co-firing test is conducted. The sludge co-firing boiler system is started and kept at maximum output. The combustion operation mode is kept the same as the non-sludge co-firing test until the sludge bin level drops to the low material level l1. The unit parameters of the sludge co-firing boiler system during this test are recorded. The test time is 2h to 3h. The first group of comparative tests ends here. S2.4 After the first set of comparative tests, repeatable tests were conducted at different time periods. First, a sludge co-firing test was conducted, i.e., step S2.3 was repeated. After the test, the boiler air preheater was soot blown once. After the soot blowing was completed, a test without sludge co-firing was prepared, i.e., step 2.1 was repeated. The second set of comparative tests was then completed.

5. The economic performance evaluation method for a sludge co-firing boiler system according to claim 1, characterized in that: When co-firing sludge, the coal quality parameters and sludge parameters during the co-firing test are used to calculate the corresponding calorific value and elemental composition of the fuel entering the furnace, i.e. Q fix =w c Q c +w w Q w c fix =w c c c +w w c w Among them, w c The percentage of coal by mass in the total fuel is the sum of coal and sludge. w w The percentage of sludge by total fuel mass; F c The coal flow rate into the furnace, in t / h, is obtained from DCS data acquisition. F w The sludge flow rate into the furnace, t / h, is calculated by dividing the output of the sludge-co-fired boiler system by the operating time. Q fix The total weighted calorific value of the fuel is expressed in kJ / kg. Q c The net calorific value of coal is measured in kJ / kg. Q w The lower heating value of the sludge is given as received, in kJ / kg; γ fix The total fuel weighted elemental composition, %; γ c The basic elemental composition of coal, %; γ w The basic elemental composition of the sludge is %.

6. The economic performance evaluation method for a sludge-co-firing boiler system according to claim 1, characterized in that: Pollutant emission data were obtained through grid testing and then compared with the online CEMS table of the sludge-fired boiler system to obtain the online CEMS correction coefficient k of the sludge-fired boiler system; pollutants included SO2, NOx, and particulate matter concentration.

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