A treatment method for improving the quality of gypsum slurry in an absorption tower of a coal-fired power plant

Abstract

The application provides a treatment method for improving the quality of gypsum slurry in an absorption tower of a coal-fired power plant, which adopts a standby absorption tower or an accident slurry tank to treat slurry in a running tower which is poured into the standby absorption tower or the accident slurry tank, wherein the slurry in the running absorption tower with high running density or with a little decrease in slurry quality is poured into the standby absorption tower or the accident slurry tank. The application can improve the quality of the slurry and efficiently consume the deteriorated slurry.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of desulfurization, in particular, especially relates to a treatment method for improving the quality of gypsum slurry in an absorption tower of a coal-fired power plant. BACKGROUND

[0002] Wet desulfurization accounts for more than 92% of flue gas desulfurization processes and is widely used in the power, steel and other industries. Due to the fluctuation of sulfur content in coal, excessive dust in raw flue gas, insufficient gypsum generation time, limited wastewater discharge and other factors, it is easy to cause the deterioration of slurry quality in the desulfurization system, and replacement of slurry is the most effective means to improve the quality of slurry in a short time. However, how to safely and efficiently consume the poor quality slurry replaced and the slurry discharged when the absorption tower is emptied has been one of the difficulties in the flue gas desulfurization industry for a long time.

[0003] Usually, the slurry in the accident slurry tank is directly transported to the running absorption tower for consumption. Such consumption means can cause all solids, ions and fine dust in the slurry to enter the running absorption tower, which not only causes the slurry quality of the running absorption tower to decrease, but also has the risk of reducing the desulfurization efficiency and exceeding the environmental protection standard. Therefore, it leads to low consumption efficiency of the accident slurry, which seriously restricts the safe and stable operation of the desulfurization system.

[0004] With the vigorous development of new energy in recent years, the power generation hours and power generation of thermal power generating units have decreased year by year, and some coal-fired units have been converted to standby state and have been idle for a long time. At present, there is no effective method for using standby absorption towers. SUMMARY

[0005] In view of the above technical problems, a treatment method for improving the quality of gypsum slurry in an absorption tower of a coal-fired power plant is provided. The present application mainly prolongs the residence time of the slurry by using a standby absorption tower or an accident slurry tank to improve the quality of the slurry and efficiently consume the poor quality slurry.

[0006] The technical means adopted by the present application are as follows:

[0007] A treatment method for improving the quality of gypsum slurry in an absorption tower of a coal-fired power plant, which uses a standby absorption tower or an accident slurry tank to process the running tower slurry transported into it, wherein the slurry in the running absorption tower with high running density or with slightly decreased slurry quality is transported into the standby absorption tower or the accident slurry tank.

[0008] Further, the standby absorption tower is the absorption tower of a shutdown unit in the desulfurization system, and the unit absorption tower is in standby state; the structure of the standby absorption tower is the same as that of the running absorption tower.

[0009] Further, the accident slurry tank is provided with an aeration device, a gypsum discharge pump and a pipeline from the gypsum discharge pump to a gypsum cyclone station.

[0010] Further, the processing method specifically comprises the following steps:

[0011] Step one, part of the slurry in the absorption tower with high running density or deteriorated slurry quality is transported to the standby absorption tower or the accident slurry tank through the connecting pipeline;

[0012] Step two, the running absorption tower after transportation is fully watered to reduce the supersaturation of the slurry in the running absorption tower, and the running absorption tower is operated in a tower blanking mode to increase the slurry residence time in the tower, promote the generation and growth of gypsum crystals, and then the running absorption tower is dehydrated to improve the slurry quality of the running absorption tower and improve the distribution efficiency of the gypsum cyclone station;

[0013] Step three, after the slurry in the standby absorption tower or the accident slurry tank is tower-blanked for more than 8 hours, the dehydration system is put into operation; the gypsum generated in the dehydration process falls into the gypsum warehouse, and the filtrate water is consumed to the running absorption tower;

[0014] Step four, after the above process is completed, steps one to three are repeated to continuously improve the slurry quality of the running absorption tower.

[0015] Further, in step two, the time of the running absorption tower in the tower blanking mode is greater than 2 hours.

[0016] Further, the deteriorated slurry is transported to the standby absorption tower or the accident slurry tank for dehydration, and when the dehydration slurry phenomenon occurs, a proper proportion of good-quality slurry can be mixed and then dehydrated.

[0017] Further, in the processing process, when the standby absorption tower exists in the desulfurization system, the slurry quality is improved through the standby absorption tower, and when there is no standby absorption tower available in the desulfurization system, the accident slurry tank replaces the function of the standby absorption tower.

[0018] Further, after the standby absorption tower completes the improvement of the slurry quality or before the standby absorption tower is put into operation, the branches of the oxidation air system of the standby absorption tower are flushed to prevent the oxidation air pipe from being blocked, and an appropriate amount of clean water is injected into the standby absorption tower, and then the slurry in the tower is reduced to a low liquid level through dehydration to achieve the purpose of keeping the standby absorption tower in a good standby state.

[0019] Further, during the operation of the standby absorption tower, the agitator in the standby absorption tower is ensured to be started to keep the particles in the slurry in the tower in a suspended state, and whether the oxidation air system is put into operation is determined according to the sulfite concentration of the slurry poured into the standby absorption tower.

[0020] Further, the PH value of the slurry in the standby absorption tower is the same as the PH value of the slurry discharged from the running absorption tower; and the sulfite concentration of the slurry in the standby absorption tower is the same as the sulfite concentration of the slurry discharged from the running absorption tower.

[0021] The slurry in the running absorption tower is transported to the standby absorption tower through the connection pipeline system, the tower is allowed to stand for a proper time, and then the standby absorption tower is dewatered according to the water balance in the whole desulfurization system and the quality of the slurry in the running absorption tower, so as to achieve the following two operation adjustment targets: (1) a certain amount of slurry is transported from the running absorption tower, a proper amount of clean water is added, the tower is allowed to stand for a period of time under the premise of reducing the supersaturation of the slurry, so as to reduce the enrichment of fine dust in the tower and the content of small particle size gypsum, improve the gypsum formation environment in the tower, promote the formation of large particle size gypsum, and enhance the working distribution efficiency of the gypsum cyclone station; (2) the slurry transported to the standby absorption tower is allowed to stand for a period of time, under the condition of constant temperature and proper PH, the calcium sulfite is continuously oxidized into calcium sulfate dihydrate, and the small particle size gypsum is secondarily crystallized and grown up, and the gypsum is discharged through the gypsum discharge pump of the standby absorption tower, so as to increase the discharge amount of gypsum, fine dust and ions in the whole desulfurization system.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] 1. The treatment method for improving the quality of gypsum slurry in the absorption tower of the coal-fired power plant provided by the present application prolongs the residence time of the slurry in the running absorption tower through the standby absorption tower or the accident slurry tank, so as to improve the quality of the slurry and efficiently consume the deteriorated slurry.

[0024] 2. The treatment method for improving the quality of gypsum slurry in the absorption tower of the coal-fired power plant provided by the present application can effectively weaken the influence of the poor quality slurry on the quality of the slurry of the running unit when the poor quality slurry is consumed by the standby absorption tower or the accident slurry tank, and greatly improves the operability of the disposal of the poor quality slurry.

[0025] 3. The treatment method for improving the quality of gypsum slurry in the absorption tower of the coal-fired power plant provided by the present application has obvious improvement effect on the slurry with high sulfite content and small particle size gypsum when the deteriorated slurry is consumed by the standby absorption tower or the accident slurry tank, but the dewatering effect is not obvious for the deteriorated slurry caused by excessive slurry supply and high dust content in the original flue gas, and a part of good quality slurry needs to be mixed into the standby absorption tower for dewatering.

[0026] 4. The treatment method for improving the quality of gypsum slurry in the absorption tower of the coal-fired power plant provided by the present application uses the idle absorption tower for slurry treatment, does not need equipment investment, realizes the improvement of the quality of the slurry and the consumption of the accident slurry through the optimization of the operation mode, is economical and practical, safe and reliable, and high in working efficiency, provides a new method and a new idea for the desulfurization system of the coal-fired power plant with standby tower in the current thermal power system, and is worth promoting.

[0027] 5. The coal-fired power plant absorption tower slurry quality improvement method provided by the present application,

[0028] Based on the above reasons, the present application can be widely popularized in the field of slurry treatment. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0030] Figure 1 The present application is a flowchart.

[0031] In the figure: 1, standby absorption tower; 2, running absorption tower; 3, emergency slurry tank. DETAILED DESCRIPTION

[0032] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. The description of the at least one exemplary embodiment is actually only illustrative, not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0034] It should be noted that the terms used herein are only for describing specific embodiments, not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form, and in addition, it should be understood that when the terms "comprise" and / or "include" are used in the specification, it means that there is a feature, step, operation, device, component and / or combination thereof.

[0035] The relative arrangement of parts and steps, numerical expressions, and values set forth in the examples herein are not intended to limit the scope of the application unless specifically stated otherwise. It is to be understood that the various portions shown in the drawings are not drawn to scale and that, for the sake of convenience and clarity, not all of the routine features of the apparatus are shown in detailed drawings. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail but are intended to be understood as a part of the specification when appropriate. In all examples shown and discussed herein, any specific values are to be interpreted as merely exemplary and not as a limitation. Thus, other examples of exemplary embodiments can have different values. It is to be noted that like reference numerals and letters refer to like items in the several views of the drawings, and, once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0036] The technical problem to be solved by the present application is to provide a treatment method for improving the quality of gypsum slurry in a coal-fired power plant absorption tower, which can judge the quality of the slurry in the current unit under construction, and prolong the slurry residence time by using a standby absorption tower, so as to improve the quality of the slurry and efficiently consume poor quality slurry.

[0037] In the operation process of the coal-fired power plant unit, the desulfurization absorption tower system causes the quality of the slurry to decrease due to insufficient slurry residence time and insufficient slurry oxidation, and in the case that the absorption tower of the unit under operation is used for slurry adjustment for a long time and the effect is slow. The quality of the slurry can be improved by using the standby absorption tower for slurry quality adjustment. This method can shorten the adjustment period of the slurry quality, improve the slurry quality, and reduce the problem of the decrease of the desulfurization treatment capacity of the unit under operation caused by poor slurry quality.

[0038] Once the diameter and liquid holdup height of the absorption tower are determined, the residence time of the gypsum slurry in the tower is also basically determined. In order to ensure good gypsum crystallization, the selection and capacity expansion space of the gypsum cyclone station are very small. The present application uses the standby absorption tower, fully utilizes the shutdown absorption tower without changing the existing desulfurization process and without equipment investment. Through operation mode optimization, not only the dehydration channel is increased and the gypsum crystallization time of part of the slurry is prolonged, but also the gypsum generation environment of the running absorption tower is effectively improved, and the consumption of poor quality slurry is greatly promoted. The present application strongly promotes the development of energy saving and consumption reduction of the desulfurization system and the work of maintaining the quality of the slurry.

[0039] When there is a shutdown unit in the coal-fired power plant and the absorption tower of the unit is in standby state (the liquid level of the absorption tower meets the starting condition of the agitator and the agitator has been started, and the slurry in the absorption tower can be in a good suspended state), it can be used as a standby absorption tower.

[0040] The present application uses a standby absorption tower 1 or an accident slurry tank 3 to treat the operating tower slurry poured into it, wherein the slurry in the operating absorption tower 2 with high operating density or with a certain degree of slurry quality deterioration is poured into the standby absorption tower or the accident slurry tank. As shown in the flow chart of Figure 1 The present application adds an aeration device and a gypsum discharge pump to the accident slurry tank after modification, and a pipeline to the gypsum cyclone station. In actual use, when the desulfurization system has a standby absorption tower, the slurry quality is improved through the standby absorption tower, and when the system does not have a standby absorption tower available, the standby absorption tower function is replaced by the modification of the accident slurry tank. It should be noted that the original absorption tower (standby absorption tower) has an oxidation air system and a gypsum discharge system by default. The accident slurry tank has the same function as the standby absorption tower. Like the standby absorption tower, the accident slurry tank after modification can fully assume the function of the standby absorption tower.

[0041] The present application uses a standby absorption tower of a coal-fired power plant to improve the slurry quality of the absorption tower, and the method specifically includes the following steps:

[0042] First step: part of the slurry in the operating absorption tower with high operating density or with a certain degree of slurry quality deterioration is poured into the standby absorption tower through a connecting pipeline.

[0043] Second step: the operating absorption tower after pouring is fully watered to reduce the supersaturation of the slurry in the operating absorption tower, and the operating absorption tower is operated in a stagnant state (for more than 2 hours), so as to increase the residence time of the slurry in the tower and promote the generation and growth of gypsum crystals. After the stagnant operation is completed, the operating absorption tower is dehydrated to improve the slurry quality of the operating absorption tower and improve the distribution efficiency of the gypsum cyclone station.

[0044] Third step: after the slurry in the standby absorption tower is stagnant for more than 8 hours, it is put into the dehydration system. The gypsum generated during the dehydration process falls into the gypsum storage, and the filtrate water is consumed into the operating absorption tower.

[0045] Fourth step: after completing the above process, the above steps should be repeated to continuously improve the slurry quality of the operating absorption tower.

[0046] It should be noted that the deteriorated slurry is poured into the standby absorption tower for dehydration, and when the dehydration slurry phenomenon occurs, a proper proportion of good quality slurry can be mixed and then dehydrated.

[0047] During the use of the standby absorption tower, the following components should be operated:

[0048] a, agitator (to keep the particles in the slurry in a suspended state).

[0049] b, gypsum discharge system (including gypsum discharge pump, gypsum discharge pump to gypsum cyclone station pipeline, and gypsum cyclone station).

[0050] c. The communication pipeline between each absorption tower (the running absorption tower slurry is transported to the standby absorption tower).

[0051] d. Oxidation air system (according to the sulfite concentration of the slurry poured into the standby absorption tower, it is determined whether it needs to be put in).

[0052] The application is a kind of wet flue gas desulfurization system standby absorption tower usage method in thermal power plant, including the following processes:

[0053] Through the public pipeline system, the running absorption tower slurry is transported to the standby absorption tower. After the tower is soaked for a proper time, according to the evaporation capacity and slurry quality of the running absorption tower, the dehydration method not only consumes the slurry transported into the standby absorption tower, but also achieves the following two operation goals: (1) A certain amount of quality deteriorated slurry is transported out of the running absorption tower, and then a proper amount of clean water is added, and the tower is operated for a period of time to reduce the enrichment of fine dust in the tower and reduce the content of small particle size gypsum, promote the generation of large particle size gypsum, and make the gypsum cyclone station work in the high efficiency area; (2) The quality deteriorated slurry and the quality good slurry are mixed in the standby absorption tower according to a certain proportion, and then left for a period of time. Under the conditions of low temperature and appropriate PH, calcium sulfite continues to be oxidized into calcium sulfate dihydrate, and small particle size gypsum is crystallized and grown again. The gypsum is discharged through the standby absorption tower gypsum discharge pump, and the discharge amount of gypsum, fine dust and ions in the whole desulfurization system is increased.

[0054] From the mechanism and external factors of gypsum crystallization, there are mainly the following six aspects:

[0055] 1. Suitable slurry supersaturation (reduce the slurry supersaturation in the standby absorption tower).

[0056] 2. Sufficient slurry residence time in the tower (the slurry in the standby absorption tower can meet the longer slurry residence time, which is beneficial to the secondary crystallization and growth of gypsum).

[0057] 3. Suitable pH value (the pH value of the slurry in the standby absorption tower is the same as that of the slurry poured out of the running absorption tower, and there is no situation that the PH value rises due to the change of the working condition of the running absorption tower which causes the increase of slurry supply).

[0058] 4. Sufficient oxidation air (the sulfite concentration of the slurry in the standby absorption tower is the same as that of the slurry poured out of the running absorption tower. When the sulfite concentration in the slurry of the running absorption tower is too high due to the failure of the oxidation air system or other reasons, the slurry can be naturally oxidized or forcibly oxidized by the oxidation air system of the standby absorption tower to ensure that the sulfite concentration of the slurry in the standby absorption tower is within the qualified range).

[0059] 5. Moderate disturbance of slurry (too many start-up of slurry circulating pumps can cause the generated gypsum crystals to be destroyed. Moderate disturbance of slurry is achieved by the stirrer, and there is no phenomenon of the grown gypsum crystals being destroyed due to too many start-up of circulating pumps).

[0060] 6. Other factors that are not conducive to gypsum generation: excessive slurry supply, high original flue gas dust, high ion concentration in the tower (the slurry in the standby absorption tower can effectively reduce the phenomenon of poor gypsum crystallization caused by excessive slurry supply, high original flue gas dust, and high ion concentration in the tower, compared with the slurry in the running absorption tower).

[0061] In view of the above gypsum generation mechanism, the standby absorption tower of the present application can meet most of the above conditions for favorable gypsum generation, so using the standby absorption tower for dewatering can effectively promote the generation of part of the slurry gypsum, and improve the quality of the slurry in the running absorption tower.

[0062] Compared with the running absorption tower, the standby absorption tower of the present application does not undertake the task of treating sulfur dioxide and dust in flue gas, but is only used to improve the gypsum crystallization effect and increase the discharge amount of gypsum, dust, ions, etc. in the entire desulfurization system, so as to improve the quality of the slurry in the entire desulfurization system.

[0063] After the standby absorption tower completes the improvement of the quality of the slurry, or before the standby absorption tower needs to be put into operation, the branches of the oxidation air system of the standby absorption tower should be flushed to prevent the oxidation air pipe from being blocked, and an appropriate amount of clean water should be injected into the standby absorption tower, and then the slurry in the tower is lowered to a low liquid level by dewatering, so as to achieve the purpose of the standby absorption tower being in a good standby state.

[0064] For coal-fired power plants with a standby unit that has existed for a long time, without changing the process flow of the desulfurization system, the slurry in the running absorption tower is transferred to the standby absorption tower, and the slurry tank and oxidation system of the standby absorption tower are used for deep oxidation of the slurry in the absorption tower and secondary crystallization of gypsum crystals. According to the water balance of the entire desulfurization system, dewatering is carried out, which not only achieves the purpose of improving the quality of the slurry in the running absorption tower, but also achieves the purpose of efficient discharge of the slurry gypsum in the standby absorption tower. After the slurry in the standby absorption tower is dewatered, the filtrate water enters the running absorption tower.

[0065] During the use of the standby absorption tower for half a year, the slurry density of each running absorption tower decreased significantly, and the quality of the gypsum was good, with a purity of more than 85%. Not only was the quality of the desulfurization slurry well maintained, but also the effective consumption of accident slurry greatly promoted the smooth development of the maintenance work. Without equipment investment, the existing system is used to effectively improve the quality of the slurry and promote the consumption of accident slurry, ensuring the smooth development of the maintenance work.

[0066] The method is suitable for local conditions, makes full use of idle absorption tower, and provides a method for effectively improving slurry quality and consuming accident slurry.

[0067] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application, but not limited to them; although the present 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 present application.

Claims

1. A method for improving the quality of gypsum slurry from an absorber tower in a coal-fired power plant, characterized in that, The slurry from the operating tower that is transferred to its interior is treated using a standby absorption tower (1) or an emergency slurry tank (3). Specifically, the slurry from the operating absorption tower (2) with a high operating density or a decrease in slurry quality is transferred to the standby absorption tower (1) or the emergency slurry tank (3). The processing method specifically includes the following steps: Step 1: Transfer part of the slurry in the absorber with high operating density or reduced slurry quality to the standby absorber (1) or emergency slurry tank (3) through the connecting pipeline. Step 2: After the transfer, the operating absorption tower (2) is fully replenished with water to reduce the supersaturation of the slurry in the operating absorption tower (2), and the operating absorption tower (2) is shut down to increase the residence time of the slurry in the tower and promote the formation and growth of gypsum crystals; after the shut-down operation is completed, the operating absorption tower (2) is dehydrated to improve the slurry quality of the operating absorption tower (2) and improve the distribution efficiency of the gypsum hydrocyclone station. Step 3: After the slurry in the standby absorption tower (1) or the emergency slurry tank (3) has been sealed for more than 8 hours, it is put into the dewatering system; the gypsum produced during the dewatering process falls into the gypsum storage, and the filtrate water is consumed in the operating absorption tower (2). Step 4: After completing one of the above processes, repeat steps 1 to 3 to continuously improve the slurry quality of the operating absorption tower (2); In step two, the operating time of the absorption tower (2) is greater than 2 hours.

2. The method for improving the quality of gypsum slurry in the absorption tower of a coal-fired power plant according to claim 1, characterized in that, The standby absorption tower (1) is the absorption tower of the shut-down unit in the desulfurization system, and the absorption tower of the unit is in standby status; the structure of the standby absorption tower (1) is the same as that of the operating absorption tower (2).

3. The method for improving the quality of gypsum slurry in the absorption tower of a coal-fired power plant according to claim 1, characterized in that, The accident slurry tank (3) is equipped with an aeration device, a gypsum discharge pump, and a pipeline from the gypsum discharge pump to the gypsum cyclone station.

4. The method for improving the quality of gypsum slurry in the absorption tower of a coal-fired power plant according to claim 1, characterized in that, The deteriorated slurry is transferred to the standby absorption tower (1) or the emergency slurry tank (3) for dewatering. When the dewatered slurry becomes rotten, an appropriate proportion of high-quality slurry is added, and the mixture is then dewatered.

5. The method for improving the quality of gypsum slurry in the absorption tower of a coal-fired power plant according to claim 1, characterized in that, During the process, when there is a backup absorption tower (1) in the desulfurization system, the slurry quality is improved by the backup absorption tower (1). When there is no backup absorption tower (1) available in the desulfurization system, the backup absorption tower (1) function is replaced by the emergency slurry tank (3).

6. The method for improving the quality of gypsum slurry in the absorption tower of a coal-fired power plant according to claim 1, characterized in that, After the standby absorption tower (1) completes the work of improving the slurry quality, or before the standby absorption tower (1) needs to be put into operation, the branch pipes of the oxidation air system of the standby absorption tower (1) are flushed to prevent the oxidation air pipes from being blocked; an appropriate amount of clean water is injected into the standby absorption tower (1), and then the slurry in the tower is reduced to a low liquid level by dehydration, so as to achieve the purpose of the standby absorption tower (1) being in a good standby state.

7. The method for improving the quality of gypsum slurry in the absorption tower of a coal-fired power plant according to claim 1, characterized in that, During the operation of the standby absorption tower (1), ensure that the agitator inside the standby absorption tower (1) has been started to keep the particulate matter in the slurry inside the tower in a suspended state; determine whether to put the oxidation air system into the slurry according to the sulfite concentration of the slurry poured into the standby absorption tower (1).

8. The method for improving the quality of gypsum slurry in the absorption tower of a coal-fired power plant according to claim 1, characterized in that, The pH value of the slurry in the standby absorption tower (1) is the same as the pH value of the slurry in the operating absorption tower (2) when it is poured out; the sulfite concentration of the slurry in the standby absorption tower (1) is the same as the sulfite concentration of the slurry in the operating absorption tower (2) when it is poured out.

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