Biomass powder hot air feeding blending combustion system and blending combustion method

Abstract

The invention discloses a biomass powder hot air feeding blending combustion system which comprises a stock bin, a belt conveyor, a drying machine, a boiler, a combustor, an air pre-heater and a dust remover, the air outlet end of the boiler communicates with the air pre-heater, and the smoke outlet end of the air pre-heater communicates with the dust remover; the dust remover is communicated with a smoke exhaust pipeline structure; the air pre-heater assembly is communicated with a secondary air pipeline structure; the air inlet end of the drying machine is provided with an induced draft fan and a smoke exhaust pipeline structure controlled by a valve in a communicating mode, the secondary air pipeline structure is communicated to the air inlet end of the induced draft fan, and the induced draft fan pumps feeding hot air formed by secondary air and dedusted smoke into the drying machine to dry materials. The invention further discloses a blending combustion method based on the blending combustion system, and the blending combustion method comprises the steps of conveying biomass materials and controlling and conveying secondary air and dedusted flue gas, so that controlled blending combustion is realized. Through the technical scheme disclosed by the invention, the blending combustion efficiency of the biomass is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass blending and burning, and in particular relates to a biomass powder hot air powder conveying and blending and burning system and a blending and burning method. Background Art

[0002] Biomass is a "zero-carbon emission" renewable energy source and a potential alternative to fossil fuels. Biomass energy has good diversified development advantages. It can not only provide heat and electricity for household life and industrial applications, but also serve as the main source of transportation fuel.

[0003] In recent years, global gasification changes have continued to intensify, and the task of carbon emission reduction is arduous. The biofuel market with good carbon reduction properties has ushered in a demand boom, among which the coupling of coal-fired power generation units with biomass combustion has become an important technical means.

[0004] Based on this, there are many public reports on the technology of using biomass as a blending fuel in the prior art. For example, the Chinese patent publication number is: CN109386838 A, which discloses a biomass blending system and process. Specifically, the biomass blending system includes a biomass preparation system, a biomass metering system, a biomass conveying system, a control room and a boiler, wherein the discharge port of the biomass preparation system is connected to the feed port of the biomass conveying system, and the discharge port of the biomass conveying system is connected to the feed port of the boiler; the biomass metering system is arranged on a belt, which is used to weigh and measure the biomass powder and analyze the calorific value online, and transmit the measured data to the control room. In the combustion system disclosed in the patent, because the entire system is independent of the boiler fuel system, the biomass has a lower ignition point and can be put into use in advance during ignition, which can save ignition fuel and enhance the boiler load regulation characteristics; at the same time, the blending system is independently set, and the original unit can operate normally whether the system is put into use or not.

[0005] However, most of the biomass combustion systems disclosed in the prior art have the following technical defects:

[0006] 1. Due to the positive pressure pneumatic conveying method, the biomass crushed material is fed into the pneumatic conveying pipeline by a rotary feeder and the positive pressure pneumatic conveying is realized by the Roots blower, which makes the process complicated;

[0007] 2. The rotary feeder is prone to backflow and difficulty in feeding. The biomass crushed material fibers are easy to entangle the rotary feeder rotor, causing jamming;

[0008] 3. At the same time, due to the use of cold air to deliver powder, the exhaust gas temperature increases significantly and the boiler thermal efficiency decreases significantly. Some patents consider hot air to deliver powder, but there are no technical measures to prevent the spontaneous combustion of biomass transportation and accumulated powder. Summary of the invention

[0009] Based on the above background, the object of the present invention is to provide a biomass powder hot air powder conveying and co-combustion system.

[0010] To achieve the above objectives, the present invention adopts the following technical solutions:

[0011] A biomass powder hot air powder delivery and combustion system, comprising a silo, a belt conveyor, a dryer, a boiler, a burner, an air preheater, and a dust collector. The belt conveyor is arranged at the discharge end of the silo, and the dryer is arranged at the discharge end of the belt conveyor.

[0012] The discharge end of the dryer is connected to a passing fan, and the discharge end of the passing fan is connected to a boiler;

[0013] A burner is installed in the boiler, and the feed fan delivers the material to the burner position;

[0014] The gas outlet end of the boiler is connected to the air preheater, and the flue gas outlet end of the air preheater is connected to the dust collector; the dust collector is connected to a smoke exhaust pipe structure;

[0015] The air preheater is connected to a secondary air duct structure;

[0016] The air inlet end of the dryer is connected to an induced draft fan, the exhaust pipe structure and the secondary air pipe structure are connected to the air inlet end of the induced draft fan, and the induced draft fan pumps the hot air formed by the secondary air and the dust-removed smoke into the dryer to dry the material;

[0017] The biomass powder hot air powder delivery and combustion system also includes a first valve and a second valve for controlling a secondary air duct structure and a smoke exhaust duct structure.

[0018] Preferably, the silo is an underground silo;

[0019] A spiral pushing structure is installed at the discharge port of the silo, and the spiral pushing structure is used to assist in unloading the biomass onto the belt conveyor.

[0020] Preferably, the air inlet end of the induced draft fan is equipped with a hot air feeding duct;

[0021] The secondary air duct structure and the smoke exhaust duct structure are respectively connected to the feeding hot air duct.

[0022] Preferably, the secondary air duct structure includes a secondary air inlet pipe connected to the air preheater, the air outlet end of the air preheater is connected to a secondary air outlet pipe, and the secondary air outlet pipe is connected to the air inlet end of the boiler;

[0023] The secondary air outlet pipe is connected to a first branch pipe, and the first branch pipe is connected to a hot air feeding pipe.

[0024] Preferably, the smoke exhaust pipe structure includes a first smoke exhaust pipe connected to the smoke exhaust end of the boiler;

[0025] The smoke outlet end of the first smoke outlet pipe is connected to the smoke inlet end of the air preheater, the smoke outlet end of the air preheater is connected to the second smoke outlet pipe, and the second smoke outlet pipe is connected to the smoke inlet end of the dust collector;

[0026] The dust collector is connected to a fume exhaust pipe, and the fume exhaust pipe is connected to a feeding hot air pipe through a second branch pipe.

[0027] Preferably, a first valve is installed on the first branch pipe, and a second valve is installed on the second branch pipe.

[0028] Preferably, a weighing sensor is installed on the belt to weigh the biomass.

[0029] Preferably, the desiccant is a drum dryer.

[0030] The present invention also discloses a biomass powder hot air powder feeding and burning method based on the above biomass powder burning system, comprising the following steps:

[0031] (1) Feeding: After the biomass material is fed through the silo, it is transported to the dryer through a belt conveyor;

[0032] The induced draft fan pumps the hot air formed by the secondary air and the dust-removed flue gas into the dryer to dry the material;

[0033] After the material is dried, it is pumped into the boiler through the feed fan and mixed with the burner;

[0034] (2) Blending control:

[0035] 2.1 The hot secondary air temperature at the outlet of the air preheater is measured as T1, the flue gas temperature at the outlet of the dust collector is measured as T2, the flue gas oxygen measurement point is marked as O2,2, the flue gas CO measurement point is marked as CO2, and the hot secondary air oxygen measurement value is O 2,1 , the CO content measurement value is CO1;

[0036] 2.2 Add hot secondary air and flue gas flow measurement points after dust removal, and the measured values ​​are Q1 and Q2 respectively. The opening of the first valve and the second valve are controlled by the mixed hot air temperature and oxygen content. The specific control method is as follows:

[0037] The mixed hot air temperature is recorded as T, the oxygen content is recorded as O2, and the CO content is recorded as CO. In order to ensure that the biomass does not spontaneously combust, the hot air temperature, oxygen content, and CO content are set as T. p , O 2, p、CO p ;

[0038] Measure the specific heat capacity of hot secondary air and flue gas after dust removal, which are c1 and c2 respectively, and measure the amount of biomass powder entering the furnace, which is Qs, in kg / s;

[0039] The mixed hot air flow is measured as Q, and the material passing fan is frequency-controlled to effectively adjust the conveying gas-solid ratio, that is, adjust Q to control the minimum flow without blockage, which is a known quantity in the calculation. From the conservation of matter and energy, the following correlation is obtained:

[0040] Q1+Q2=Q;

[0041] Q1*O 2,1 +Q2*O 2,2 =Q*O2;

[0042] Q1*CO1+Q2*CO2=Q*CO;

[0043] c1*Q1*(T1-T)=c2*Q2*(T-T2);

[0044] The calculations show that:

[0045] O2=(Q1*(O 2,1 -O 2,2 )+Q*O 2,2 ) / Q;

[0046] When O2 is higher than the set value O 2,p Then reduce Q1 and adjust it by closing the first valve or opening the second valve;

[0047] CO=(Q*CO1+Q2*(CO2-CO1)) / Q;

[0048] When CO is higher than the set value CO p Then reduce Q2 and adjust it by closing the second valve or opening the first valve;

[0049] T=(Q1*(c1*T1-c2*T2)+c2*T2*Q) / (Q1*(c1-c2)+c2*Q);

[0050] When T is higher than the set value Tp, Q1 is reduced by closing the first valve or opening the second valve.

[0051] Preferably, in step (2), 2,1 =21%; the mixed hot air temperature is recorded as T, the oxygen content is recorded as O2, and the CO content is recorded as CO. In order to ensure that the biomass does not spontaneously combust, the mixed hot air temperature is not higher than 200°C, the oxygen content is controlled not higher than 10%; the CO content is controlled not higher than 0.02%.

[0052] The present invention has the following beneficial effects:

[0053] 1. In the technical solution disclosed in the present invention, the biomass crushing material is directly transported, the process is simple, and it is energy-saving and efficient.

[0054] 2. Use hot secondary air and dust collector outlet flue gas mixed with hot air to dry biomass crushed materials. Calculate the temperature and oxygen content of the mixed flue gas by measuring the temperature and oxygen content of the two-branch working fluids, control the temperature and oxygen content of the mixed hot air, and avoid the accumulation of biomass powder and the spontaneous combustion during transportation.

[0055] 3. The technical solution disclosed in the present invention has a simple process, is energy-saving and reliable, and effectively avoids the problems of sticking and clogging that are prone to occur in positive pressure pneumatic conveying systems;

[0056] 4. The use of hot air powder delivery can avoid the problem of increased exhaust gas temperature and reduced boiler thermal efficiency caused by cold air powder delivery. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0058] Figure 1 Schematic diagram of the overall structure of the embodiment of the present invention.

[0059] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0062] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0063] Example 1 Biomass powder hot air powder delivery and combustion system

[0064] like Figure 1 As shown, a biomass powder hot air powder conveying and incineration system includes a silo 1 (the silo 1 is an underground silo 1. In order to facilitate unloading and prevent the biomass crushed material from arching and difficulty in unloading, a spiral pushing structure 10 is installed at the discharge port of the silo 1 according to the existing discharge method. The spiral pushing structure 10 is used to assist the unloading of biomass onto the belt conveyor 2. Specifically, the spiral pushing structure 10 includes a spiral pushing blade and a motor installed on the spiral pushing blade. During the working process, the spiral pushing blade is used to assist the unloading of materials in the same way as the structure and principle of the existing spiral pushing device).

[0065] At the same time, the biomass powder hot air powder conveying and combustion system also includes a belt conveyor 2, a dryer 3, a boiler 6, a burner 7, an air preheater 8, and a dust collector 9. The belt conveyor 2 is arranged at the discharge end of the silo 1 (according to the existing weighing method, a weighing sensor is installed on the belt conveyor 2 to realize the weighing of the biomass fed to the belt conveyor 2), and the dryer 3 is arranged at the discharge end of the belt conveyor 2 (the desiccant is a drum dryer 3).

[0066] Specifically, the discharge end of the dryer 3 is connected to the feed fan 5 (according to the existing method, a frequency converter is installed in the feed fan 5 to facilitate the adjustment of the fan output), and the discharge end of the feed fan 5 is connected to the boiler 6. Specifically, a burner 7 is installed in the boiler 6, and the feed fan 5 delivers the material to the burner 7 (that is, the discharge end of the feed fan 5 is connected to the burner 7 through a pipeline installation). In addition, pneumatic and manual gates and temperature measuring points can be installed on the pipeline according to the existing method, and a video monitoring system can be installed on the biomass burner 7 to monitor and prevent accidents caused by positive pressure or backfire in the furnace, and close the gate when the system is disabled or in an accident state to isolate the biomass blending system.

[0067] The gas outlet end of the boiler 6 is connected to the air preheater 8, and the flue gas outlet end of the air preheater 8 is connected to the dust collector 9; the dust collector 9 is connected to a smoke exhaust duct structure; the air preheater 8 is equipped with a secondary air duct structure, and the secondary air duct structure is connected to the boiler 6.

[0068] Through the secondary air duct structure and the smoke exhaust duct structure, the secondary air is mixed with the high-temperature dust-removed smoke to form hot mixed air for the dryer 3 to dry the material.

[0069] At the same time, the air inlet end of the dryer 3 is equipped with an induced draft fan 4 (the hot mixed air is introduced into the dryer 3 through the induced draft fan 4), and the smoke exhaust duct structure and the secondary air duct structure are connected to the air inlet end of the induced draft fan 4. The induced draft fan 4 pumps the feeding hot air formed by the secondary air and the dust-removed smoke into the dryer 3 to dry the material.

[0070] At the same time, the biomass powder hot air powder delivery and combustion system also includes a first valve 11 and a second valve 12 for controlling the secondary air duct structure and the smoke exhaust duct structure. The first valve 11 and the second valve 12 are used to control the amount of hot air / smoke extracted.

[0071] At the same time, the air inlet end of the induced draft fan 4 is equipped with a feeding hot air duct; the secondary air duct structure and the smoke exhaust duct structure are respectively connected to the feeding hot air duct 106.

[0072] Example 2 Biomass powder hot air powder delivery and combustion system

[0073] like Figure 1 As shown, based on the structure of Example 1, this embodiment specifically discloses the specific structure of the secondary air duct structure and the smoke exhaust duct structure in the co-firing system and the connection relationship between the various components.

[0074] Specifically, the secondary air duct structure includes a secondary air inlet pipe 104 connected to the air preheater 8, the air outlet end of the air preheater 8 is connected to a secondary air outlet pipe 102, and the secondary air outlet pipe 102 is connected to the air inlet end of the boiler 6; the secondary air outlet pipe 102 is connected to a first branch pipe 103, and the first branch pipe 103 is connected to the feeding hot air duct 106.

[0075] At the same time, the smoke exhaust pipe structure includes a first smoke outlet pipe 101 connected to the smoke outlet end of the boiler 6; the smoke outlet end of the first smoke outlet pipe 101 is connected to the smoke inlet end of the air preheater 8, the smoke outlet end of the air preheater 8 is connected to a second smoke outlet pipe 108, and the second smoke outlet pipe 108 is connected to the smoke inlet end of the dust collector 9; the dust collector 9 is connected to a smoke exhaust pipe 105, and the smoke exhaust pipe 105 is connected to the feeding hot air pipe 106 through a second branch pipe 107.

[0076] The first branch pipe 103 is installed with a first valve 11 , and the second branch pipe 107 is installed with a second valve 12 .

[0077] During the working process, the biomass material is fed through the silo 1 and then transported to the dryer 3 through the belt conveyor 2; the induced draft fan 4 pumps the feeding hot air formed by the secondary air and the dust-removed flue gas into the dryer 3 to dry the material.

[0078] After the material is dried, it is pumped into the boiler 6 through the feed fan 5 and mixed with the burner 7. In this process, the feeding hot air (the flow rate and temperature of the mixed air) is controlled by controlling the first valve 11 and the second valve 12.

[0079] Example 3 Blending method

[0080] like Figure 1 As shown, this embodiment is based on a biomass powder hot air powder delivery and combustion system, and discloses a combustion method based on the system, including the following steps:

[0081] (1) Feeding: After the biomass material is fed through the silo 1, it is transported to the dryer 3 through the belt conveyor 2;

[0082] The induced draft fan 4 pumps the hot air formed by the secondary air and the dust-removed flue gas to the dryer 3 to dry the material;

[0083] After the material is dried, it is pumped into the boiler 6 through the feed fan 5 and mixed with the burner 7;

[0084] (2) Blending control:

[0085] 2.1 Measure the hot secondary air temperature at the outlet of air preheater 8 as T1, measure the flue gas temperature at the outlet of dust collector 9 as T2, and mark the flue gas oxygen measurement point as O 2,2 , the flue gas CO measurement point is marked as CO2, and the hot secondary air oxygen measurement value is O 2,1 , the CO content measurement value is CO1 (the actual measured value is about 0). Specifically, the hot secondary air oxygen content measurement value is: 2,1 =21%; the mixed hot air temperature is recorded as T, the oxygen content is recorded as O2, and the CO content is recorded as CO to ensure that the biomass does not spontaneously combust. Specifically, the mixed hot air temperature is not higher than 200°C, the oxygen content is controlled not higher than 10%; the CO content is controlled not higher than 0.02%.

[0086] 2.2 Add hot secondary air and flue gas flow measurement points after dust removal, and the measured values ​​are Q1 and Q2 respectively. The opening of the first valve 11 and the second valve 12 are controlled by the mixed hot air temperature and oxygen content. The specific control method is as follows:

[0087] The mixed hot air temperature is recorded as T, the oxygen content is recorded as O2, and the CO content is recorded as CO. In order to ensure that the biomass does not spontaneously combust, the hot air temperature, oxygen content, and CO content are set as T. p , O 2, p、CO p ;

[0088] The specific heat capacities of hot secondary air and flue gas after dust removal are measured as c1 and c2 (in J / (kg·℃)), and the amount of biomass powder entering the furnace is measured as Qs, in kg / s;

[0089] The mixed hot air flow is measured as Q, and the feed fan 5 is frequency-controlled to effectively adjust the conveying gas-solid ratio, that is, adjust Q to control the minimum flow without blockage, which is a known quantity in the calculation. From the conservation of matter and energy, the following correlation is obtained:

[0090] Q1+Q2=Q;

[0091] Q1*O 2,1 +Q2*O 2,2 =Q*O2;

[0092] Q1*CO1+Q2*CO2=Q*CO;

[0093] c1*Q1*(T1-T)=c2*Q2*(T-T2);

[0094] The calculations show that:

[0095] O2=(Q1*(O 2,1 -O 2,2 )+Q*O 2,2 ) / Q;

[0096] When O2 is higher than the set value O 2,p Then Q1 is reduced, and the adjustment is made by closing the first valve 11 or opening the second valve 12; in this way, the adjustment in the first case is achieved.

[0097] CO=(Q*CO1+Q2*(CO2-CO1)) / Q;

[0098] When CO is higher than the set value CO p Then Q2 is reduced by closing the second valve 12 or opening the first valve 11 to adjust; in this way, the adjustment in the second situation is achieved.

[0099] T=(Q1*(c1*T1-c2*T2)+c2*T2*Q) / (Q1*(c1-c2)+c2*Q);

[0100] When T is higher than the set value Tp, Q1 is reduced by closing the first valve 11 or opening the second valve 12 to adjust the third situation.

[0101] Through the above-mentioned measurement formula and adjustment method, the entire system can be adjusted in an adjustable manner during the blending process.

[0102] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A biomass powder hot air powder delivery and combustion system, characterized in that: It includes a silo, a belt conveyor, a dryer, a boiler, a burner, an air preheater, and a dust collector. The belt conveyor is arranged at the discharge end of the silo, and the dryer is arranged at the discharge end of the belt conveyor. The discharge end of the dryer is connected to a passing fan, and the discharge end of the passing fan is connected to a boiler; A burner is installed in the boiler, and the feed fan delivers the material to the burner position; The gas outlet end of the boiler is connected to the air preheater, and the flue gas outlet end of the air preheater is connected to the dust collector; The dust collector is connected to a smoke exhaust duct structure; The air preheater is connected to a secondary air duct structure; The air inlet end of the dryer is connected to an induced draft fan, the exhaust pipe structure and the secondary air pipe structure are connected to the air inlet end of the induced draft fan, and the induced draft fan pumps the hot air formed by the secondary air and the dust-removed smoke into the dryer to dry the material; The biomass powder hot air powder delivery and combustion system also includes a valve structure for controlling a secondary air duct structure and a smoke exhaust duct structure.

2. The biomass powder hot air powder conveying and burning system according to claim 1 is characterized in that: The silo is an underground silo; A spiral pushing structure is installed at the discharge port of the silo, and the spiral pushing structure is used to assist in unloading the biomass onto the belt conveyor.

3. The biomass powder hot air powder conveying and burning system according to claim 1 is characterized in that: The air inlet end of the induced draft fan is connected with a hot air feeding duct; The secondary air duct structure and the smoke exhaust duct structure are respectively connected to the feeding hot air duct.

4. The biomass powder hot air powder conveying and burning system according to claim 3 is characterized in that: The secondary air duct structure includes a secondary air inlet pipe connected to the air preheater, the air outlet end of the air preheater is connected to a secondary air outlet pipe, and the secondary air outlet pipe is connected to the air inlet end of the boiler; The secondary air outlet pipe is connected to a first branch pipe, and the first branch pipe is connected to a hot air feeding pipe.

5. The biomass powder hot air powder conveying and combustion system according to claim 4 is characterized in that: The smoke exhaust pipe structure comprises a first smoke outlet pipe connected to the smoke outlet end of the boiler; The smoke outlet end of the first smoke outlet pipe is connected to the smoke inlet end of the air preheater, the smoke outlet end of the air preheater is connected to the second smoke outlet pipe, and the second smoke outlet pipe is connected to the smoke inlet end of the dust collector; The dust collector is connected to a fume exhaust pipe, and the fume exhaust pipe is connected to a feeding hot air pipe through a second branch pipe.

6. The biomass powder hot air powder conveying and burning system according to claim 5 is characterized in that: The valve structure includes a first valve installed on the first branch pipe, and the valve structure also includes a second valve installed on the second branch pipe.

7. The biomass powder hot air powder conveying and combustion system according to claim 1 is characterized in that: A weighing sensor is installed on the belt to weigh the weight of the biomass.

8. The biomass powder hot air powder conveying and burning system according to claim 1 is characterized in that: The dryer is a drum dryer.

9. A biomass powder hot air powder feeding and burning method using the biomass powder hot air powder feeding and burning system according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Feeding: After the biomass material is fed through the silo, it is transported to the dryer through a belt conveyor; The induced draft fan pumps the hot air formed by the secondary air and the dust-removed flue gas into the dryer to dry the material; After the material is dried, it is pumped into the boiler through the feed fan and mixed with the burner; (2) Blending control: The hot secondary air temperature at the outlet of the air preheater is measured as T1, the flue gas temperature at the outlet of the dust collector is measured as T2, and the flue gas oxygen measurement point is marked as O 2,2 , the flue gas CO measurement point is marked as CO2, and the hot secondary air oxygen measurement value is O 2,1 , the CO content measurement value is CO1; Add hot secondary air and flue gas flow measurement points after dust removal, and the measured values ​​are Q1 and Q2 respectively. The opening of the first valve and the second valve are controlled by the mixed hot air temperature and oxygen content. The specific control method is as follows: The mixed hot air temperature is recorded as T, the oxygen content is recorded as O2, and the CO content is recorded as CO. In order to ensure that the biomass does not spontaneously combust, the hot air temperature, oxygen content, and CO content are set as T. p , O 2, p、CO p ; Measure the specific heat capacity of hot secondary air and flue gas after dust removal, c1 and c2 respectively, and measure the amount of biomass powder entering the furnace, Qs; The mixed hot air flow is measured as Q, and the material passing fan is frequency-controlled to effectively adjust the conveying gas-solid ratio, that is, adjust Q to control it at the minimum flow without blockage. According to the conservation of matter and energy, the following correlation is obtained: Q1+Q2=Q; Q1*O 2,1 +Q2*O 2,2 Q*O2; Q1*CO1+Q2*CO2=Q*CO; c1*Q1*(T1-T)=c2*Q2*(T-T2); The calculations show that: O2=(Q1*(O 2,1 -O 2,2 )+Q*O 2,2 ) / Q; When O2 is higher than the set value O 2,p Then reduce Q1 and adjust it by closing the first valve or opening the second valve; CO=(Q*CO1+Q2*(CO2-CO1)) / Q; When CO is higher than the set value CO p Then reduce Q2 and adjust it by closing the second valve or opening the first valve; T=(Q1*(c1*T1-c2*T2)+c2*T2*Q) / (Q1*(c1-c2)+c2*Q); When T is higher than the set value Tp, Q1 is reduced by closing the first valve or opening the second valve.

10. The blending method according to claim 9, characterized in that: In the step (2), 2,1 =21%; the mixed hot air temperature is recorded as T, the oxygen content is recorded as O2, and the CO content is recorded as CO. In order to ensure that the biomass does not spontaneously combust, the mixed hot air temperature is not higher than 200°C, the oxygen content is controlled not higher than 10%; the CO content is controlled not higher than 0.02%.

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