A method and system for on-line evaluation of the dust conveying capacity of a single dust hopper of a boiler dust collector

Abstract

The present application relates to a kind of on-line evaluation method of single dust hopper dust conveying capacity of boiler dust collector, comprising the following steps: measuring the volume flow of compressed air, pressure, temperature;According to the volume flow of compressed air, pressure, temperature, the mass flow of compressed air is calculated;Measure the falling dust temperature;After compressed air and dust mixing, measure the dust gas mixing temperature;According to dust gas mixing temperature, falling dust temperature, the dust conveying capacity of each dust hopper is calculated.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of boiler dust collector single hopper dust conveying amount online evaluation method and system, belong to the field of boiler dust removal. BACKGROUND

[0002] The fly ash of large coal-fired boiler is mostly transported by pneumatic conveying, compared with wet conveying, its advantage is that fly ash can be recycled. The dust conveying capacity of the dust conveying system is related to the coal quality and the running state of the boiler and dust remover. At present, the dust conveying system obtains the dust amount by installing dust amount measuring device, such as material level meter. However, various material level meters have low measurement accuracy, and the material level meter is expensive and has high maintenance cost, so only a few dust conveying systems will be installed at some positions. Therefore, a dust amount measurement method with lower cost is needed.

[0003] Patent CN102981480A "Dust conveying control method and control system" discloses the calculation of relevant parameters of dust conveying process; the relevant parameters calculated are used to calculate the dust accumulation amount in the hopper; the conveying process of the bin pump or bin pump group is controlled according to the calculated dust accumulation amount in the hopper. In this method, the coal composition is used to calculate the dust amount entering the hopper, which is the total dust amount, and the dust conveying amount of a single hopper cannot be calculated. Usually, there are several hoppers in each electric field or each dust conveying row, and the dust conveying amount of each hopper is not necessarily the same. The dust conveying amount of the hopper is related to whether the hopper works normally, and has monitoring needs, but there is no corresponding single hopper dust conveying amount detection method at present. There was a vicious accident of dust remover collapse caused by hopper dust accumulation in China. SUMMARY

[0004] In order to overcome the problems in the prior art, the present application designs an online evaluation method and system for the dust conveying amount of a single hopper of a boiler dust remover, temperature meters are installed at upstream and downstream positions of each bin pump, the dust conveying amount of each hopper is calculated according to the temperature change before and after material mixing and the specific heat relationship, which is inexpensive and reliable, has low maintenance cost, can determine the dust conveying amount of each hopper online and in real time, and has higher accuracy than material level meter.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0006] Technical scheme one

[0007] An online evaluation method for the dust conveying amount of a single hopper of a boiler dust remover, comprising the following steps:

[0008] Measuring the volume flow, pressure and temperature of compressed air;

[0009] Calculating the mass flow of compressed air according to the volume flow, pressure and temperature of compressed air;

[0010] Measuring the temperature of the falling ash; measuring the temperature of the ash-air mixture after the compressed air and the ash are mixed;

[0011] According to the temperature of the ash-air mixture and the temperature of the falling ash, the ash conveying amount of each ash bucket is calculated.

[0012] Further, the mass flow rate of the compressed air in the calculation main pipe is calculated, which is expressed by the formula as follows:

[0013]

[0014] In the formula, is the mass flow rate of the compressed air, kg / s; ρ0 is the standard air density, kg / m 3 ; is the measured volume flow rate of the compressed air, m 3 / s; p is the measured pressure of the compressed air, Pa; p0 is the standard air pressure, Pa; t0 is the standard air temperature, ℃; and t is the measured temperature of the compressed air, ℃.

[0015] Further, the ash conveying amount of each ash bucket is calculated, which is expressed by the formula as follows:

[0016]

[0017] In the formula, is the ash conveying amount of the nth ash bucket, kg / s; is the mass flow rate of the compressed air, kg / s; c is the ratio of the specific heat of air to the specific heat of ash; is the ash conveying amount of the ith ash bucket, kg / s; t n is the temperature of the ash-air mixture corresponding to the nth ash bucket, ℃; t an is the temperature of the falling ash corresponding to the nth ash bucket, ℃.

[0018] Further, the measured temperature value is corrected, which is expressed by the formula as follows:

[0019] ts n = (t a -t b )ke -k(n-1)Δτ Δτ+ts n-1

[0020] In the formula, n is the nth sampling time; ts n is the nth sampling value of the thermometer, ℃; ts n-1 is the (n-1)th sampling value of the thermometer, ℃; t a is the temperature of the falling ash corresponding to the ith ash bucket, ℃; t b is the temperature of the compressed air before being mixed with the falling ash corresponding to the ith ash bucket, ℃; k is a coefficient; and ΔA is the calculation sampling interval, s.

[0021] Further, it also comprises:

[0022] The calibration coefficient is calculated, and the formula is:

[0023]

[0024] In the formula, g is the calibration coefficient; A i is the calculated value of the ash discharge amount of the i-th ash bucket in a conveying period, kg, t is the conveying period, s; Q is the measured value of the total ash amount, kg; n is the number of ash buckets;

[0025] According to the calibration coefficient, the calculated ash amount is optimized.

[0026] Technical solution two

[0027] An online evaluation system for the ash conveying amount of a single ash bucket of a boiler dust collector, comprising:

[0028] A measurement unit for measuring the compressed air volume flow, compressed air pressure, compressed air temperature, falling ash temperature, and ash-air mixture temperature of the mixture of compressed air and ash;

[0029] A calculation unit for calculating the mass flow of compressed air according to the volume flow, pressure, and temperature of compressed air, and calculating the ash conveying amount of each ash bucket according to the ash-air mixture temperature and falling ash temperature.

[0030] Further, the mass flow of compressed air in the calculation main pipe is calculated, and the formula is:

[0031]

[0032] In the formula, is the mass flow of compressed air, kg / s; ρ0 is the standard air density, kg / m 3 ; is the measured compressed air volume flow, m 3 / s; p is the measured compressed air pressure, Pa; p0 is the standard air pressure, Pa; t0 is the standard air temperature, ℃; t is the measured compressed air temperature, ℃.

[0033] Further, the ash conveying amount of each ash bucket is calculated, and the formula is:

[0034]

[0035] In the formula, is the ash conveying amount of the n-th ash bucket, kg / s; is the mass flow of compressed air, kg / s; c is the ratio of air specific heat to ash specific heat; Q is the ash conveying amount of the i-th ash hopper, kg / s; t n T is the ash gas mixed temperature corresponding to the n-th ash hopper, ℃; t an T is the falling ash temperature corresponding to the n-th ash hopper, ℃.

[0036] Further, the calculation unit is also used for correcting the measured temperature value, which is expressed by the formula as follows:

[0037] ts n = (t a -t b )ke -k(n-1)Δτ Δτ+ts n-1

[0038] In the formula, n is the n-th sampling time; ts n is the n-th sampling value of the thermometer, ℃; ts n-1 is the (n-1)-th sampling value of the thermometer, ℃; t s is the temperature of the falling ash corresponding to the i-th ash hopper, ℃; t b is the temperature of the compressed air before mixing with the falling ash corresponding to the i-th ash hopper, ℃; k is a coefficient; Δτ is the calculation sampling interval, s.

[0039] Further, the calculation unit is also used for performing the following steps:

[0040] The calibration coefficient is calculated, which is expressed by the formula as follows:

[0041]

[0042] In the formula, g is the calibration coefficient; A i is the calculated value of the ash discharging amount of the i-th ash hopper in one ash conveying period,

[0043] kg; t is the ash conveying period, s; Q is the total ash amount measured value, kg; n is the number of ash hoppers;

[0044] According to the calibration coefficient, the calculated ash amount is optimized.

[0045] Compared with the prior art, the present application has the following characteristics and beneficial effects:

[0046] The present application installs thermometers at the upstream and downstream positions of each bin pump, calculates the ash conveying amount of each ash hopper according to the temperature change before and after the material mixing and the specific heat relationship, is inexpensive and reliable, has low maintenance cost, can determine the ash conveying amount of each ash hopper online and in real time, and has higher accuracy than the material level meter. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is the flow chart of the present application;

[0048] Figure 2This is a schematic diagram of the ash conveying system of a boiler dust collector;

[0049] Figure 3 , 4 This is a diagram showing the installation of a thermometer.

[0050] In the diagram: 1. Thermocouple; 2. Mounting bracket. Detailed Implementation

[0051] The present invention will now be described in more detail with reference to the embodiments.

[0052] Example 1

[0053] like Figure 1 , 2 As shown, an online evaluation system for the ash conveying capacity of a single ash hopper in a boiler dust collector includes: an ash conveying air source, several ash hoppers and several silo pumps, an ash silo, ash conveying pipelines, a measurement unit, and a calculation unit. The ash conveying pipelines include a main pipe and several branch pipes extending from it. The main pipe is connected to the ash conveying air source, and each branch pipe is connected to the ash discharge pipe of the silo pump. Compressed air enters the branch pipes from the ash conveying air source, and ash material enters the branch pipes via the ash hoppers and the ash discharge pipes of the silo pumps. The ash material is then conveyed to the ash silo by the compressed air in the branch pipes. In actual operation, the branch pipes convey ash alternately (no simultaneous ash conveying), typically one pipe per electric field.

[0054] The measuring unit is used to measure the volumetric flow rate of compressed air, compressed air pressure, compressed air temperature, ash discharge temperature, and the ash-air mixing temperature of compressed air and ash material. Specifically, it includes: a flow meter, a thermometer, and a pressure gauge on the main pipe; a thermometer on the ash discharge pipe of the silo pump for measuring the ash discharge temperature; and a valve on the branch line, with a thermometer downstream of its connection to the ash discharge pipe of the silo pump for measuring the ash-air mixing temperature.

[0055] The calculation unit is used to calculate the mass flow rate of compressed air based on the volumetric flow rate, pressure, and temperature of the compressed air; and to calculate the ash conveying capacity of each ash hopper based on the ash-air mixing temperature and the ash falling temperature.

[0056] This embodiment requires a thermometer that measures the ash temperature and ash-gas mixing temperature with a rapid response capability and can be replaced during operation. Therefore, the thermometer adopts... Figure 3 The installation method shown is as follows: A base is installed on the pipe, and a fine-sheathed thermocouple (0.5-2mm in diameter) is fixed inside the pipe to form a measuring probe. The head of the sheathed thermocouple is exposed at the measuring end and bent into a [shape]. Figure 4 The shape shown is "L".

[0057] Example 2

[0058] Calculate the ash conveying capacity of each branch, including the following steps:

[0059] Measure the volumetric flow rate, pressure, and temperature of compressed air in the main pipe;

[0060] The mass flow rate of compressed air in the main pipe is calculated by the formula:

[0061]

[0062] wherein, is the mass flow rate of compressed air, kg / s; p0 is the standard air density, kg / m 3 ; is the measured volume flow rate of compressed air, m 3 / s; p is the measured pressure of compressed air, Pa (absolute pressure); p0 is the standard air pressure, Pa (absolute pressure); t o is the measured temperature of compressed air, °C.

[0063] The mixed temperature of ash and air and the temperature of falling ash are measured.

[0064] The ash conveying rate of each ash hopper is calculated by the formula:

[0065]

[0066] wherein, is the ash conveying rate of the nth ash hopper, kg / s; is the mass flow rate of compressed air, kg / s; c is the ratio of air specific heat to ash specific heat; is the ash conveying rate of the ith ash hopper, kg / s; t n is the mixed temperature of ash and air corresponding to the nth ash hopper, °C; t sn is the temperature of falling ash corresponding to the nth ash hopper, °C.

[0067] For example, the ash rates of the first, second and third ash hoppers are calculated as follows:

[0068]

[0069]

[0070]

[0071] wherein, is the ash conveying rate of the first ash hopper, kg / s; t1 is the mixed temperature of ash and air corresponding to the first ash hopper, °C; t a1 is the temperature of falling ash corresponding to the first ash hopper, °C; is the ash conveying rate of the second ash hopper, kg / s; t2 is the mixed temperature of ash and air corresponding to the second ash hopper, °C; t a2 is the temperature of falling ash corresponding to the second ash hopper, °C; is the ash conveying amount of the third ash bin, kg / s; t3 is the ash gas mixed temperature corresponding to the third ash bin, ℃; t a3 is the ash falling temperature corresponding to the third ash bin, ℃.

[0072] Example Three

[0073] Since all the thermometers are contact type, there is a lag in measuring the ash gas mixed temperature and the ash falling temperature. An empirical formula is constructed to correct the response lag of the measured temperature, which is expressed as:

[0074] ts n = (t a -t b )ke -k(n-1)Δτ Δτ+ts n-1

[0075] In the formula, n is the nth sampling time; ts n is the nth sampling value of the thermometer, ℃; ts n-1 is the (n-1)th sampling value of the thermometer, ℃; t s is the ash falling temperature, ℃; t b is the air temperature upstream of the ash falling pipe of the bin pump corresponding to the ash bin, ℃ (for the first ash bin, t b is the temperature of the compressed air after entering the branch but before mixing with the ash; for the nth ash bin, t b is the temperature of the compressed air in the branch between the downstream of the ash falling pipe of the bin pump corresponding to the (n-1)th ash bin and the upstream of the ash falling pipe of the bin pump corresponding to the nth ash bin); k is a coefficient for correcting the temperature; Δτ is the calculation sampling interval, s. Among them, the values of t a , t b and multiple sampling values of the thermometer are obtained through experiments, which are substituted into the above formula to solve the value of k, and the average value is taken after multiple calculations.

[0076] Example Four

[0077] Further, the calculated ash amount is calibrated:

[0078] Empty the ash bin and perform an ash conveying; after the ash conveying is completed, the ash discharge amount of each ash bin is calculated and the ash entering the ash bin is weighed to obtain the total ash amount; the calibration coefficient is calculated using the total ash amount, which is expressed as:

[0079]

[0080] In the formula, g is the calibration coefficient; A i is the calculated value of the ash discharge amount of the ith ash bin in one ash conveying period,

[0081] kg, t is the ash conveying period, s; Q is the measured value of the total ash amount, kg; n is the number of ash bins.

[0082] Or, using the same ash conveying branch for multiple times of ash conveying; after the ash conveying is finished, weighing the ash entering the ash storage to obtain the total ash amount; using the total ash amount to calculate the calibration coefficient, expressed as a formula:

[0083]

[0084] In the formula, g is the calibration coefficient; A ij is the calculated value of the ash discharge amount of the ith ash bucket for the jth time of ash conveying; n is the number of ash buckets; m is the number of times of ash conveying; Q is the total ash amount of the m times of ash conveying, kg.

[0085] According to the calibration coefficient, the calculated ash amount is optimized, expressed as a formula:

[0086] a n = gA n

[0087] In the formula, g is the calibration coefficient; A n is the ash conveying amount of the nth ash bucket, kg.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should analyze and can modify or equivalently replace the technical solutions of the present application without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for on-line evaluation of the individual hopper dust delivery of a boiler dust collector, characterized by, The method comprises the following steps: measuring the volume flow, pressure and temperature of the compressed air; calculating the mass flow of the compressed air according to the volume flow, pressure and temperature of the compressed air; measuring the ash drop temperature; measuring the ash-air mixture temperature after the compressed air and the ash are mixed; calculating the ash conveying amount of each ash bucket according to the ash-air mixture temperature and the ash drop temperature; wherein the mass flow of the compressed air in the main pipe is calculated and expressed by the formula: wherein is the compressed air mass flow, kg / s; is the standard air density, kg / m 3 ; is the measured compressed air volume flow, m 3 / s; is the measured compressed air pressure, Pa; is the standard air pressure, Pa; is the standard air temperature, °C; is the measured compressed air temperature, °C; wherein the ash conveying amount of each ash bucket is calculated and expressed by the formula: wherein, is the conveying amount of the nth ash bin, kg / s; is the compressed air mass flow, kg / s; is the ratio of air specific heat and ash specific heat; is the conveying amount of the ith ash bin, kg / s; is the ash-air mixture temperature corresponding to the nth ash bin, ℃; is the falling ash temperature corresponding to the nth ash bin, ℃.

2. The method according to claim 1, wherein the method is characterized by, further comprising correcting the measured temperature value, which is expressed by the formula: In the formula, n is the nth sampling time; is the nth sampling value of the thermometer, ℃; is the n-1th sampling value of the thermometer, ℃; is the temperature of the falling ash corresponding to the ith ash bucket, ℃; is the temperature of the compressed air before mixing with the falling ash corresponding to the ith ash bucket, ℃; is a coefficient; is the calculation sampling interval, s.

3. The method according to claim 1, wherein the method is characterized by: further comprising: calculating the calibration coefficient, which is expressed by the formula: wherein g is a calibration factor; is the calculated value of the amount of ash discharged from the i-th ash chute in one ash conveying cycle; is the measured value of the total amount of ash, kg; and n is the number of ash chutes. optimizing the calculated ash amount according to the calibration coefficient.

4. An on-line system for evaluating the dust conveying capacity of a single hopper of a boiler dust collector, characterized by The method comprises: a measuring unit for measuring the volume flow of the compressed air, the pressure of the compressed air, the temperature of the compressed air, the ash drop temperature and the ash-air mixture temperature after the compressed air and the ash are mixed; a calculating unit for calculating the mass flow of the compressed air according to the volume flow, the pressure and the temperature of the compressed air; and for calculating the ash conveying amount of each ash bucket according to the ash-air mixture temperature and the ash drop temperature; wherein the mass flow of the compressed air in the main pipe is calculated and expressed by the formula: wherein is the compressed air mass flow, kg / s; is the standard air density, kg / m 3 ; is the measured compressed air volume flow, m 3 / s; is the measured compressed air pressure, Pa; is the standard air pressure, Pa; is the standard air temperature, °C; is the measured compressed air temperature, °C; wherein the ash conveying amount of each ash bucket is calculated and expressed by the formula: wherein, is the conveying amount of the nth ash bin, kg / s; is the compressed air mass flow, kg / s; is the ratio of air specific heat and ash specific heat; is the conveying amount of the ith ash bin, kg / s; is the ash-air mixture temperature corresponding to the nth ash bin, ℃; is the falling ash temperature corresponding to the nth ash bin, ℃.

5. The system for on-line evaluation of the amount of dust delivered by a single dust hopper of a boiler dust collector according to claim 4, characterized in that, the calculating unit is further used for correcting the measured temperature value, which is expressed by the formula: In the formula, n is the nth sampling time; is the nth sampling value of the thermometer, ℃; is the n-1th sampling value of the thermometer, ℃; is the temperature of the falling ash corresponding to the ith ash bucket, ℃; is the temperature of the compressed air before mixing with the falling ash corresponding to the ith ash bucket, ℃; is a coefficient; is the calculation sampling interval, s.

6. The system for on-line evaluation of the amount of dust delivered by a single dust hopper of a boiler dust collector according to claim 4, characterized in that, the calculating unit is further used for performing the following steps: calculating the calibration coefficient, which is expressed by the formula: where g is a calibration factor; is the calculated value of the amount of ash discharged from the i-th ash hopper during one ash conveying cycle, kg; is the measured value of the total amount of ash, kg; and n is the number of ash hoppers.​ optimizing the calculated ash amount according to the calibration coefficient.

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