A method for controlling oxidation air in a wet dual-tower desulfurization system

Abstract

This invention provides a method for controlling the oxidation air in a wet dual-tower desulfurization system. The dual-tower desulfurization system includes a primary tower, a secondary tower, a primary tower oxidation fan, and a secondary tower oxidation fan. After the dual-tower desulfurization system starts working, air is supplied to the primary tower through the primary tower oxidation fan, and air is supplied to the secondary tower through the secondary tower oxidation fan. When (primary tower raw flue gas flow rate × connecting flue gas SO2 concentration / 1000) < (primary tower full-load raw flue gas design flow rate × secondary tower inlet design SO2 concentration / 1000 × a), the primary and secondary oxidation air connecting valve is opened, and the secondary tower switching valve is closed. When (primary tower raw flue gas flow rate × connecting flue gas SO2 / 1000) > (primary tower full-load raw flue gas design flow rate × secondary tower inlet design SO2 concentration / 1000 × b), the primary and secondary oxidation air connecting valve is closed, and the secondary tower switching valve is opened. This invention solves the problems of poor airflow adjustment flexibility and high energy consumption in the oxidation air system used in existing dual-tower desulfurization technologies.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flue gas desulfurization technology, in particular, especially relates to a wet double-tower desulfurization system oxidation air control method. BACKGROUND

[0002] In the wet desulfurization flue gas desulfurization double-tower operation process, the primary tower and the secondary tower are respectively provided with independent oxidation air systems, which supply the primary desulfurization absorption tower and the secondary desulfurization absorption tower respectively. This traditional process control process is relatively rough, and the oxidation degree of the desulfurization slurry cannot be accurately controlled, so the phenomena of over-oxidation or under-oxidation often occur, which brings a series of problems to the power plant, such as the decline of gypsum quality, the increase of desulfurization system energy consumption, the easy scaling of equipment, etc., which is not conducive to the normal operation of the desulfurization system and causes huge economic losses.

[0003] The existing process uses an oxidation air system, which has the problems of poor flexibility of air volume regulation and high operation energy consumption. The operation mode is basically to supplement the slurry pool in the tower with the designed maximum oxidation air volume, and the slurry is often in an over-oxidation state, resulting in high operation energy consumption of the oxidation air system. At the same time, due to the excessive air supplement into the absorption tower slurry pool, the foaming phenomenon of the absorption tower slurry pool tends to be serious, and the dissolved oxygen in the tower slurry is increased, which intensifies the corrosion risk of equipment and pipelines. SUMMARY

[0004] In view of the above-mentioned technical problems of poor flexibility of air volume regulation and high operation energy consumption of the oxidation air system used in the existing double-tower desulfurization technology, a wet double-tower desulfurization system oxidation air control method is provided.

[0005] The technical means adopted by the present application are as follows:

[0006] A wet double-tower desulfurization system oxidation air control method, the double-tower desulfurization system comprising a primary tower, a secondary tower, a primary tower oxidation air fan and a secondary tower oxidation air fan; the primary tower and the secondary tower are connected in communication through a connecting flue; the primary tower oxidation air fan is connected to the primary tower through a primary tower oxidation air pipe; the secondary tower oxidation air fan is connected to the secondary tower through a secondary tower oxidation air pipe, and is also connected to the primary tower through a connecting pipeline; the connecting pipeline is provided with a secondary oxidation air connecting valve, and the secondary tower oxidation air pipe is provided with a secondary tower on-off valve;

[0007] After the double-tower desulfurization system starts to work, air is supplied to the primary tower by the primary tower oxidation air fan; air is supplied to the secondary tower by the secondary tower oxidation air fan, the secondary tower on-off valve is opened, and the secondary oxidation air connecting valve is closed;

[0008] When (primary tower original flue gas flow × connection flue SO2 concentration / 1000) < (primary tower full load original flue gas design flow × secondary tower inlet design SO2 concentration / 1000 × a), the secondary tower oxidation fan is switched to supply air to the primary tower, air supply to the secondary tower is stopped, the primary-secondary oxidation air connection valve is opened, and the secondary tower switch valve is closed; the value range of a is 0.3-0.42.

[0009] When (primary tower original flue gas flow × connection flue SO2 / 1000) > (primary tower full load original flue gas design flow × secondary tower inlet design SO2 concentration / 1000 × b), the secondary tower oxidation fan is switched to supply air to the secondary tower, air supply to the primary tower is stopped, the primary-secondary oxidation air connection valve is closed, and the secondary tower switch valve is opened; the value range of b is 0.45-0.52.

[0010] Further, the primary tower is provided with a gypsum slurry sulfite on-line automatic analyzer for real-time monitoring of the sulfite content in gypsum in the primary tower.

[0011] Further, the primary tower oxidation fan comprises oxidation fan A and oxidation fan B, the secondary tower oxidation fan comprises oxidation fan C, and the power of the oxidation fan C < the power of the oxidation fan A < the power of the oxidation fan B.

[0012] Further, the oxidation fan A and the oxidation fan B adopt Roots blowers, and the oxidation fan C adopts a centrifugal fan; the primary tower oxidation fan comprises two oxidation fan A, namely oxidation fan A1 and oxidation fan A2; the secondary tower oxidation fan comprises two oxidation fan C, namely oxidation fan C1 and oxidation fan C2.

[0013] When the secondary tower oxidation fan is switched to supply air to the primary tower and air supply to the secondary tower is stopped:

[0014] If the primary tower is in a low load condition, the primary tower is supplied with air by starting the oxidation fan C1 or the oxidation fan C2;

[0015] or the primary tower is supplied with air by starting the oxidation fan A1 or the oxidation fan A2 + the oxidation fan C1 or the oxidation fan C2 in combination;

[0016] If the primary tower is in a medium-high load condition, the primary tower is supplied with air by starting the oxidation fan A1 + the oxidation fan A2 + the oxidation fan C1 or the oxidation fan C2 in combination.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] The oxidation air control method for a wet dual-tower desulfurization system provided by this invention uses the primary tower as the main oxidation zone and the secondary tower as the high-efficiency absorption zone. The oxidation air volume required by the primary tower is much greater than that of the secondary tower. By using the oxidation air control method provided by this invention, the operation mode of the oxidation fans is optimized, which can reduce the frequent start-stop of the high-power fans in the primary tower. By controlling and switching the operation of the low-power oxidation fans in the secondary tower to replace the high-power oxidation fans in the primary tower to supply air to the primary tower, the purpose of energy saving and optimization is achieved.

[0019] Based on the above reasons, this invention can be widely promoted in fields such as flue gas desulfurization. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the dual-tower desulfurization system described in this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] like Figure 1 As shown, this invention provides a method for controlling the oxidation air in a wet dual-tower desulfurization system. The dual-tower desulfurization system includes a primary tower, a secondary tower, a primary tower oxidation fan, and a secondary tower oxidation fan. The primary tower and the secondary tower are connected via a connecting flue. The primary tower oxidation fan is connected to the primary tower via a primary tower oxidation air duct. The secondary tower oxidation fan is connected to the secondary tower via a secondary tower oxidation air duct and simultaneously connected to the primary tower via a connecting pipeline. The connecting pipeline is equipped with a secondary oxidation air connecting valve, and the secondary tower oxidation air duct is equipped with a secondary tower on / off valve.

[0025] After the double-tower desulfurization system is started, the first-stage tower oxidation fan supplies air to the first-stage tower, and the second-stage tower oxidation fan supplies air to the second-stage tower, the second-stage tower switch valve is opened, and the first-second-stage oxidation air communication valve is closed.

[0026] When (first-stage tower raw flue gas flow rate x communication flue SO2 concentration / 1000) < (first-stage tower full-load raw flue gas design flow rate x second-stage tower inlet design SO2 concentration / 1000 x a), the second-stage tower oxidation fan is switched to supply air to the first-stage tower, air supply to the second-stage tower is stopped, the first-second-stage oxidation air communication valve is opened, and the second-stage tower switch valve is closed; the value range of a is 0.3-0.42.

[0027] When (first-stage tower raw flue gas flow rate x communication flue SO2 / 1000) > (first-stage tower full-load raw flue gas design flow rate x second-stage tower inlet design SO2 concentration / 1000 x b), the second-stage tower oxidation fan is switched to supply air to the second-stage tower, air supply to the first-stage tower is stopped, the first-second-stage oxidation air communication valve is closed, and the second-stage tower switch valve is opened; the value range of b is 0.45-0.52.

[0028] The first-stage tower full-load raw flue gas design flow rate and the second-stage tower inlet design SO2 concentration are design values of the double-tower desulfurization system, the first-stage tower full-load raw flue gas design flow rate represents a designed raw flue gas flow rate capable of being treated when the first-stage tower is full load, and the second-stage tower inlet design SO2 concentration represents a designed SO2 concentration at the second-stage tower inlet.

[0029] Further, the first-second-stage oxidation air communication valve comprises a pneumatic valve and a manual valve.

[0030] Further, in actual production, the specific values of a and b can be adjusted according to long-term gypsum generation of the double-tower desulfurization system and the content of sulfite in the gypsum in the first-stage tower in different thermal power plants, and the best value for energy saving effect is selected.

[0031] Preferably, the value of a is 0.4, and the value of b is 0.5.

[0032] Further, the first-stage tower is provided with a gypsum slurry sulfite on-line automatic analyzer for real-time monitoring of the content of sulfite in the gypsum in the first-stage tower.

[0033] Further, the first-stage tower oxidation fan comprises oxidation fan A and oxidation fan B, the second-stage tower oxidation fan comprises oxidation fan C, and the power of the oxidation fan C < the power of the oxidation fan A < the power of the oxidation fan B.

[0034] Further, the oxidation fan A and the oxidation fan B adopt Roots blower, the oxidation fan C adopts centrifugal fan; the oxidation fan of the first stage tower includes two oxidation fan A, which are oxidation fan A1 and oxidation fan A2 respectively; the oxidation fan of the second stage tower includes two oxidation fan C, which are oxidation fan C1 and oxidation fan C2 respectively;

[0035] When the oxidation fan of the second stage tower is switched to supply air to the first stage tower and stop supplying air to the second stage tower:

[0036] If the first stage tower is in a low load condition (low sulfur content) of less than 300 kW, the oxidation fan C1 or the oxidation fan C2 is started to supply air to the first stage tower;

[0037] Or the oxidation fan A1 or the oxidation fan A2+ the oxidation fan C1 or the oxidation fan C2 is started to supply air to the first stage tower. In this way, in the low load condition, the oxidation fan B or the oxidation fan A1+ the oxidation fan A2 can be replaced to supply air to the first stage tower, thereby avoiding frequent start and stop of high-power fan, meeting the efficient and energy-saving operation of oxidation air in low load condition. The specific scheme can be determined according to the rated air volume of the oxidation fan A and the oxidation fan C and the actual oxidation air volume required by the first stage tower.

[0038] If the first stage tower is in a medium-high load condition (medium-high sulfur content) of 300-600 MW, the oxidation fan A1+ the oxidation fan A2+ the oxidation fan C1 or the oxidation fan C2 is started to supply air to the first stage tower. In this way, in the medium-high load condition, the oxidation fan A1 or the oxidation fan A2+ the oxidation fan B can be replaced to supply air to the first stage tower, thereby avoiding frequent start and stop of high-power fan, meeting the efficient and energy-saving operation of oxidation air in medium-high load condition.

[0039] Further, the oxidation fan A is a Roots blower with motor power of 315 kW, head of 107160 Pa and rated air volume of 6641 Nm 3 / h; the oxidation fan B is a Roots blower with motor power of 560 kW, head of 109000 Pa and rated air volume of 12360 Nm 3 / h; the oxidation fan C is a centrifugal fan with motor power of 160 kW, head of 98000 Pa and rated air volume of 4150 Nm 3 / h.

[0040] The double-tower desulfurization system uses the first tower as a main oxidation zone and the second tower as a high-efficiency absorption zone, and the oxidation air volume required by the first tower is much larger than that of the second tower; the oxidation air control method provided by the application optimizes the operation mode of the oxidation air fan, can reduce the frequent start and stop of the high-power fan of the first tower, and can supply air to the first tower by controlling the switching of the low-power oxidation air fan of the second tower to replace the high-power oxidation air fan of the first tower, so that the purpose of energy saving and optimization is achieved.

[0041] The oxidation air control method is applied to the No. 3 desulfurization system of Huaneng Qinbei Power Plant, and the oxidation air power consumption rate is reduced by about 10% compared with the previous year, and 400,000 KW.h of electricity is saved per year.

[0042] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A method for controlling the oxidation air in a wet dual-tower desulfurization system, characterized in that, The double-tower desulfurization system comprises a primary tower, a secondary tower, a primary tower oxidation fan and a secondary tower oxidation fan; the primary tower and the secondary tower are communicated through a connecting flue; the primary tower oxidation fan is connected to the primary tower through a primary tower oxidation air pipe; the secondary tower oxidation fan is connected to the secondary tower through a secondary tower oxidation air pipe and to the primary tower through a connecting pipeline; the connecting pipeline is provided with a secondary oxidation air connecting valve, and the secondary tower oxidation air pipe is provided with a secondary tower switch valve; After the double-tower desulfurization system is started, the primary tower oxidation fan supplies air to the primary tower, and the secondary tower oxidation fan supplies air to the secondary tower, the secondary tower switch valve is opened, and the secondary oxidation air connecting valve is closed; When (primary tower original flue gas flow × connecting flue SO2 concentration / 1000) < (primary tower full load original flue gas design flow × secondary tower inlet design SO2 concentration / 1000 × a), the secondary tower oxidation fan is switched to supply air to the primary tower, air supply to the secondary tower is stopped, the secondary oxidation air connecting valve is opened, and the secondary tower switch valve is closed; the value range of a is 0.3-0.42; When (primary tower original flue gas flow × connecting flue SO2 / 1000) > (primary tower full load original flue gas design flow × secondary tower inlet design SO2 concentration / 1000 × b), the secondary tower oxidation fan is switched to supply air to the secondary tower, air supply to the primary tower is stopped, the secondary oxidation air connecting valve is closed, and the secondary tower switch valve is opened; the value range of b is 0.45-0.52; The primary tower oxidation fan comprises oxidation fan A and oxidation fan B, and the secondary tower oxidation fan comprises oxidation fan C, and the power of the oxidation fan C < the power of the oxidation fan A < the power of the oxidation fan B.

2. The method for controlling oxidation air in a wet dual-tower desulfurization system according to claim 1, characterized in that, The primary tower is provided with a gypsum slurry sulfite on-line automatic analyzer for real-time monitoring of the sulfite content in gypsum in the primary tower.

3. The method for controlling oxidation air in a wet dual-tower desulfurization system according to claim 1, characterized in that, The oxidation fan A and the oxidation fan B adopt Roots blowers, and the oxidation fan C adopts a centrifugal fan; the primary tower oxidation fan comprises two oxidation fan A, namely oxidation fan A1 and oxidation fan A2; the secondary tower oxidation fan comprises two oxidation fan C, namely oxidation fan C1 and oxidation fan C2; When the secondary tower oxidation fan is switched to supply air to the primary tower and air supply to the secondary tower is stopped: If the primary tower is in a low load condition, the primary tower is supplied with air by starting the oxidation fan C1 or the oxidation fan C2; or the primary tower is supplied with air by starting the oxidation fan A1 or the combination of the oxidation fan A2 and the oxidation fan C1 or the oxidation fan C2; If the primary tower is in a medium-high load condition, the primary tower is supplied with air by starting the combination of the oxidation fan A1, the oxidation fan A2 and the oxidation fan C1 or the oxidation fan C2.

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