A method and system for adsorption and drying treatment of precipitated coal ash from citric acid chemical cleaning wastewater

Abstract

The present invention discloses a method and system for adsorption drying treatment of precipitated coal ash of citric acid chemical cleaning waste liquid, and belongs to the technical field of chemical cleaning waste liquid treatment. The treatment method is as follows: the citric acid chemical cleaning waste liquid is distilled, concentrated and cooled to obtain a concentrated solution, which is then transferred to a liquid storage tank; the concentrated solution is stirred and mixed with the ethanol solvent in the liquid storage tank to obtain a mixed solution, and the substances insoluble in ethanol in the mixed solution are precipitated and filtered to obtain solid matter and mother liquor; the solid matter is dried to obtain solid waste; the mother liquor is subjected to graded distillation and fly ash is added for adsorption to obtain distilled ethanol, distilled water and distillation residue; the distillation residue is combined with the solid waste to complete the adsorption drying treatment of precipitated coal ash. The above treatment method has high drying efficiency for citric acid chemical cleaning waste liquid and good solid form, and avoids the risk of damaging the scraper of the drying equipment due to stickiness when the citric acid chemical cleaning waste liquid is directly dried.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical cleaning waste liquid treatment, and particularly relates to a method and system for adsorbing and drying precipitated coal ash from citric acid chemical cleaning waste liquid. Background Art

[0002] Citric acid is widely used as a pickling medium during industrial equipment maintenance to remove dirt, rust, and other deposits from surfaces. However, the wastewater generated after pickling presents a significant treatment challenge. This wastewater primarily consists of residual citric acid, complexes formed with metal ions such as iron, copper, and magnesium, and stripped chromium oxides. Its acidity and complexity make its treatment particularly critical.

[0003] The basic principles of the citric acid wastewater concentration process are similar to those of other organic acid chemical cleaning wastewaters, but there are significant differences in the details of the treatment process. In particular, the conversion of the wastewater concentrate to a solid state often results in the formation of a viscous, gel-like or paste-like substance. These substances have strong adhesive properties and easily adhere to equipment surfaces, causing significant inconvenience in subsequent cleanup.

[0004] To handle these concentrated waste liquids, scraper-type or rake-type drying equipment is commonly used in industry. These devices, while drying the waste liquid after distillation and concentration, scrape and collect the dried material using a scraper or rake. However, citric acid cleaning waste liquid contains a variety of components that are difficult to solidify or easily adhere to, such as residual citric acid, ammonium citrate, sodium citrate, and high-boiling organic polymer corrosion inhibitors. These substances are difficult to fully solidify during the drying process and easily form cohesive solids, which in turn cause severe wear and tear and breakage of the scraper and rake of the drying equipment, affecting the normal operation of the equipment and even posing a threat to the personal safety of on-site workers.

[0005] Therefore, for the treatment of citric acid cleaning waste liquid, more sophisticated and professional measures need to be taken to ensure that the waste liquid is treated safely and effectively, while also ensuring the normal operation of industrial equipment and the personal safety of workers. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method and system for the adsorption and drying treatment of precipitated coal ash of citric acid chemical cleaning waste liquid. The above-mentioned treatment method has high drying efficiency and good solid form for citric acid chemical cleaning waste liquid, and avoids the risk of damaging the scraper of the drying equipment due to stickiness when the citric acid chemical cleaning waste liquid is directly dried.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for treating precipitated coal ash of citric acid chemical cleaning waste liquid by adsorption and drying, comprising the following steps:

[0009] The citric acid chemical cleaning waste liquid is distilled, concentrated and cooled to obtain a concentrated liquid, which is then transferred to a liquid storage tank;

[0010] The concentrated solution is stirred and mixed with the ethanol solvent in the liquid storage tank to obtain a mixed solution, and the ethanol-insoluble substances in the mixed solution are precipitated and then filtered to obtain a solid substance and a mother liquor;

[0011] The solid matter is dried to obtain solid waste; the mother liquor is subjected to graded distillation while adding fly ash for adsorption to obtain distilled ethanol, distilled water and distillation residue;

[0012] The distillation residue is combined with solid waste to complete the adsorption and drying treatment of the precipitated coal ash.

[0013] In one embodiment, the volume of the concentrated liquid is 1 to 5 cubic meters; the water content of the concentrated liquid is 30% to 50%; and the cooling temperature is 0 to 50°C.

[0014] In one embodiment, the volume ratio of the ethanol solvent to the concentrated solution is (1-5):1.

[0015] In one embodiment, the ethanol solvent in the liquid storage tank is cooled at a temperature of 0 to 50°C.

[0016] In one embodiment, the ethanol-insoluble substances in the mixed solution include but are not limited to ferric citrate, ammonium ferric citrate and ammonium citrate.

[0017] In one embodiment, the precipitation time is 5 to 30 minutes; the fractional distillation includes sequential distillation processes of ethanol and water, wherein the temperature of the ethanol distillation is 75 to 85°C, and the temperature of the distilled water is 95 to 100°C.

[0018] In one embodiment, the volume ratio of the fly ash to the mother liquor is (1-3):10.

[0019] In one embodiment, the distillation residue is high-boiling-point oily organic matter and a small amount of ethanol-soluble substances in the citric acid chemical cleaning waste liquid adsorbed on the fly ash.

[0020] The present invention also provides a precipitated fly ash adsorption and drying treatment system for citric acid chemical cleaning waste liquid, comprising a distillation and concentration device, the outlet of the distillation and concentration device being connected to the inlet of a condenser, the outlet of the condenser being connected to the inlet of a liquid storage tank, an agitator and a liquid level gauge being provided inside the liquid storage tank, the liquid storage tank containing an ethanol solvent, the outlet of the liquid storage tank being connected to the inlet of a filtering device, the liquid outlet of the filtering device being connected to the inlet of a graded distillation device, the solid outlet of the filtering device being connected to the inlet of a drying device, and the graded distillation device being provided with a fly ash addition port, a distilled ethanol outlet, a distilled water outlet, and a distillation residue outlet.

[0021] In one embodiment, the liquid storage tank includes a first liquid storage tank and a second liquid storage tank connected in sequence; wherein the first liquid storage tank is provided with a liquid level gauge and a delivery pump, and the second liquid storage tank is provided with an agitator;

[0022] The delivery pipe between the outlet of the first liquid storage tank and the inlet of the second liquid storage tank is adapted to the volume of the concentrated liquid in the first liquid storage tank.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a method for treating citric acid chemical cleaning waste liquid by precipitation and fly ash adsorption and drying, which mainly treats citric acid cleaning waste liquid containing a variety of components that are difficult to solidify by organic solvent precipitation and fly ash adsorption. Through the organic solvent precipitation method, complexes of iron and organic components such as ammonium ferric citrate in the waste liquid can be quickly precipitated to form solid substances that are easy to dry. This not only improves the drying efficiency, but also the obtained solid waste has a good morphology, avoiding the damage of the equipment scraper by sticky wall during direct drying. The addition of fly ash not only effectively absorbs the high-boiling point oily organic waste residue in the mother liquor, making it loose and easy to handle, but also the solid waste ash residue after adsorption can be poured into the coal yard for mixed combustion, thereby realizing the rapid and harmless treatment of citric acid chemical cleaning waste liquid, and has high practicality and environmental value.

[0025] The present invention also provides a fly ash adsorption drying treatment system for citric acid chemical cleaning wastewater. This system utilizes a distillation and concentration unit and a condenser to effectively concentrate the wastewater, reducing processing volume and improving subsequent processing efficiency. A stirrer within the liquid storage tank ensures thorough mixing of the concentrate with the ethanol solvent, facilitating the precipitation of insoluble matter. A filtration unit separates solid matter from the mother liquor, facilitating subsequent drying and distillation processing. A graded distillation unit utilizes the adsorption properties of fly ash to remove high-boiling-point oily organic waste residue from the mother liquor, while simultaneously recovering ethanol and water resources, achieving resource utilization. The reuse of ethanol solvent reduces chemical consumption, lowers processing costs, and minimizes the generation of chemical waste. The addition of fly ash not only improves distillation efficiency but also allows for the reuse of solid waste ash, reducing environmental impact. The recyclable materials in the system, such as distilled ethanol and distilled water, provide an effective approach for energy conservation, emission reduction, and resource recycling. Through this system, harmful substances in citric acid chemical cleaning wastewater are effectively removed, meeting environmental emission standards. After treatment, solid waste and distillation residue can be used as blending materials in coal yards, achieving harmless disposal and resource utilization of waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the present invention's method for treating precipitated coal ash by adsorption and drying of citric acid chemical cleaning wastewater;

[0027] Figure 2 This is a schematic diagram of the weight gain of citric acid solid waste with a water content of 30% within 192 hours of the present invention;

[0028] Figure 3 This is a schematic diagram of the weight gain of citric acid solid waste with a water content of 50% within 192 hours of the present invention;

[0029] Figure 4 The figure is a schematic diagram of the adsorption and drying treatment system for precipitated coal ash of citric acid chemical cleaning waste liquid of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0032] The present invention is described in further detail below with reference to the accompanying drawings:

[0033] The present invention provides a method for treating precipitated coal ash of citric acid chemical cleaning waste liquid by adsorption and drying, comprising the following steps:

[0034] The citric acid chemical cleaning waste liquid is distilled, concentrated and cooled to obtain a concentrated liquid, which is then transferred to a liquid storage tank; the citric acid chemical cleaning waste liquid concentrate is pumped from the distillation and concentration equipment to a condenser for cooling to reduce the solubility of the components;

[0035] The concentrated solution is stirred and mixed with the ethanol solvent in the liquid storage tank to obtain a mixed solution, and the ethanol-insoluble substances in the mixed solution are precipitated and filtered to obtain a solid substance and a mother liquor; the volume ratio of the ethanol solvent to the concentrated solution is (1-5):1; wherein the ethanol-insoluble substances in the mixed solution include but are not limited to ferric citrate, ammonium ferric citrate, and ammonium citrate;

[0036] The solid matter is dried to obtain solid waste; the mother liquor is subjected to graded distillation and fly ash is added for adsorption to obtain distilled ethanol, distilled water and distillation residue; the volume ratio of fly ash to mother liquor is (1-3):10; the distillation residue is high-boiling point oily organic matter in the citric acid chemical cleaning waste liquid adsorbed on the fly ash and a small amount of ethanol-soluble material;

[0037] The distillation residue is combined with solid waste to complete the adsorption and drying treatment of the precipitated coal ash.

[0038] In the above-mentioned precipitation process (precipitation process), after the concentrated citric acid waste liquid is quickly added to the transparent anhydrous ethanol solvent, the solution will quickly turn from black to white, and at the same time, a large amount of black precipitates will be produced in the lower layer. Extracting these black precipitates separately can reveal their easy-to-dry characteristics, and their main components are complexes of iron and organic components such as ammonium ferric citrate.

[0039] The organic solvent precipitation method used in the aforementioned citric acid chemical cleaning wastewater precipitation and fly ash adsorption drying treatment method involves using a poor solvent to reduce the solubility of the desired extracted substance or impurities in the solution, thereby forming an amorphous solid precipitate. When the citric acid chemical cleaning wastewater is rapidly added to ethanol, the following changes occur in the wastewater components: citric acid gradually reacts in the ethanol to form triethyl citrate (boiling point 294°C), while substances such as ammonium citrate, ferric citrate, and ammonium ferric citrate, which are highly soluble in water but poorly soluble in ethanol, quickly precipitate, thus achieving separation. These solids form quickly during the drying process and do not damage the equipment's scrapers. Furthermore, the fly ash adsorption method involves adding fly ash to the mother liquor and distilling it. The high-boiling-point, oily organic waste residue in the mother liquor is adsorbed on the fly ash, causing it to become loose and easier to handle. Fly ash is fine ash captured from the flue gas after coal combustion and has a certain degree of adsorption.

[0040] In one embodiment, the volume of the concentrate is 1 to 5 cubic meters; the water content of the concentrate is 30% to 50%; and the cooling temperature is 0 to 50°C. The ethanol solvent in the storage tank also needs to be cooled at a temperature of 0 to 50°C. The precipitation time is 5 to 30 minutes. The fractional distillation includes sequential distillation of ethanol and water, wherein the temperature of the ethanol distillation is 75 to 85°C and the temperature of the distilled water is 95 to 100°C.

[0041] The present invention also provides a precipitated fly ash adsorption and drying treatment system for citric acid chemical cleaning waste liquid, comprising a distillation and concentration device, a condenser, a liquid storage tank, a filtering device, a graded distillation device, and a drying device, wherein the outlet of the distillation and concentration device is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the liquid storage tank, an agitator and a liquid level gauge are arranged inside the liquid storage tank, the liquid storage tank contains ethanol solvent, the outlet of the liquid storage tank is connected to the inlet of the filtering device, the liquid outlet of the filtering device is connected to the inlet of the graded distillation device, the solid outlet of the filtering device is connected to the inlet of the drying device, and the graded distillation device is provided with a fly ash addition port, a distilled ethanol outlet, a distilled water outlet, and a distillation residue outlet.

[0042] Based on the above system, the liquid storage tanks specifically include a first liquid storage tank and a second liquid storage tank connected in sequence; the first liquid storage tank is provided with a liquid level gauge and a delivery pump, and the second liquid storage tank is provided with an agitator. The delivery pipe between the outlet of the first liquid storage tank and the inlet of the second liquid storage tank is adapted to the volume of the concentrated liquid in the first liquid storage tank.

[0043] The concentrated liquid in the condenser is transferred to the first liquid storage tank, and the volume of the concentrated liquid of this batch is obtained according to the liquid level gauge.

[0044] Specifically, when the volume of citric acid waste concentrate is 2 cubic meters or less, the delivery pipeline (small-diameter pipeline) refers to a pipeline with an outer diameter of 76 mm. When the volume of citric acid waste concentrate is 2 to 5 cubic meters, the delivery pipeline (small-diameter pipeline) refers to a pipeline with an outer diameter of 108 mm.

[0045] Based on the above treatment method, the specific treatment process corresponding to the system includes the following steps: (1) the concentrated liquid of the citric acid chemical cleaning waste liquid is pumped from the distillation concentration device to the condenser for cooling to reduce the solubility of the components; (2) the concentrated liquid in the condenser is transferred to the first liquid storage tank, and the volume of the concentrated liquid of the batch is obtained according to the liquid level gauge in the first liquid storage tank; (3) the agitator in the second liquid storage tank is turned on, and the waste liquid delivery pump is used in conjunction with the delivery pipeline (small-diameter pipeline) to quickly add the concentrated liquid in the first liquid storage tank to the second liquid storage tank containing ethanol solvent configured in a volume ratio. During this process, due to the precipitation effect, the ethanol-insoluble substances such as ferric citrate, ammonium ferric citrate, and ammonium citrate in the citric acid chemical cleaning waste liquid will be rapidly precipitated from the residual water; (4) After the ethanol-insoluble substances in the mixed solution are precipitated, the mixed solution in the second liquid storage tank is pumped to a filtration device (industrial rotary vacuum filter) for filtration, and the solid substances are scraped into a drying device with the help of a scraper of the industrial rotary vacuum filter to be dried to obtain easily peelable, non-sticky solid waste; (5) The mother liquor flows to the graded distillation device, and fly ash is added in proportion through the fly ash addition port. The ethanol in the solution is collected by graded distillation and returned to the second liquid storage tank (or ethanol collection tank) through the distilled ethanol outlet for cooling. The distilled water is pollution-free and can be discharged; the obtained distillation residue is the high-boiling point oily organic matter in the waste liquid adsorbed on the fly ash and a small amount of substances soluble in ethanol. The distillation residue-fly ash adsorbent is collected and combined with the dried solid waste (filter residue) to finally obtain the ash residue of the citric acid chemical cleaning solid waste. This process has high drying efficiency and good solid form for treating citric acid chemical cleaning waste liquid, avoiding the risk of citric acid chemical cleaning waste liquid sticking to the wall due to viscosity when directly drying, thereby damaging the scraper of the drying device; ethanol is reusable and more environmentally friendly; solid waste ash can be poured into the coal yard for co-combustion, thereby achieving rapid and harmless treatment of all citric acid chemical cleaning waste liquid.

[0046] Specifically, the process for treating the citric acid chemical cleaning waste liquid concentrate can be processed in batches according to the distillation rate of the distillation equipment or the size of the storage tank, and the volume of each batch of waste liquid concentrate is 1 to 5 cubic meters. The concentrate used in step (1) and the ethanol solvent used in (3) need to be cooled, and the temperature range is 0 to 50°C. The citric acid chemical cleaning waste liquid concentrate after distillation reduction in step (1) is required to have a water content between 30% and 50%. The volume ratio of ethanol to citric acid waste liquid concentrate in step (3) is 1:1 to 5:1. When the volume of the citric acid waste liquid concentrate is 2 cubic meters or less, the small-diameter pipe in step (3) refers to a pipe with an outer diameter of 76 mm. When the volume of the citric acid waste liquid concentrate is 2 to 5 cubic meters, the small-diameter pipe in (3) refers to a pipe with an outer diameter of 108 mm. The time for waiting for solid precipitation in step (4) is 5 to 30 minutes. The distillation temperature range for collecting ethanol in step (5) is 75-85° C., and the distillation temperature range for collecting water is 95-100° C. In step (5), the volume ratio of the added fly ash to each batch of citric acid waste liquid concentrate is 1:10-3:10.

[0047] After repeated reuse of the ethanol solvent, the final recovery rate is between 65% and 80%.

[0048] The use of the above-mentioned precipitated coal ash adsorption drying treatment system has the following advantages: 1) the process has high drying efficiency and good solid form for treating citric acid chemical cleaning waste liquid, avoiding the risk of citric acid chemical cleaning waste liquid being damaged by sticking to the wall due to viscosity when directly drying, thereby scraping the drying equipment; 2) ethanol can be reused, which is more environmentally friendly; 3) solid waste ash can be poured into the coal yard for co-combustion, thereby achieving rapid and harmless treatment of all citric acid chemical cleaning waste liquid.

[0049] Example 1:

[0050] A power plant used citric acid to chemically clean the boiler water-cooled walls and discharged the wastewater into a slag pool. The wastewater was first distilled using a distillation and concentration device to obtain approximately 30 cubic meters of wastewater concentrate with a water content of 30%. This concentrate was initially divided into 15 batches. Each batch of wastewater was treated as follows: (1) The citric acid chemical cleaning wastewater concentrate was pumped from the distillation and concentration device to a condenser and cooled to 20°C; (2) The concentrate in the condenser was transferred to a first liquid storage tank. The volume of the concentrate in the batch was 2 cubic meters according to the level gauge; (3) The agitator in the second liquid storage tank was turned on, and a wastewater transfer pump with a 76 mm outer diameter pipe was used to quickly transfer the concentrate in the first liquid storage tank to a second liquid storage tank containing 2 cubic meters of ethanol solvent in a volume ratio. During this process, a large amount of solids are precipitated due to precipitation; (4) After 20 minutes, the mixed solution in the second liquid storage tank is pumped to an industrial rotary vacuum filter for filtration, and the solid matter is scraped into the drying equipment with the help of the filter scraper to dry it to obtain easy-to-peel, non-sticky solid waste; (5) Fly ash is added to the storage tank of the graded distillation device through the fly ash addition port at a ratio of 1:10 between fly ash and citric acid chemical cleaning waste liquid concentrate, and the ethanol in the mother liquor is distilled and collected at 75°C, and returned to the ethanol collection tank for cooling. The water distilled at 100°C is discharged, and the distillation residue-fly ash adsorbent is collected and combined with the dried solid waste and poured into the coal yard for co-combustion.

[0051] The solid form of the citric acid chemical cleaning waste liquid after drying was good, the scraper of the drying equipment was not damaged, and the final recovery rate of ethanol was 80%.

[0052] Example 2:

[0053] A power plant used citric acid to chemically clean the boiler water-cooled walls and discharged the wastewater into a slag pool. The wastewater was first distilled using a distillation and concentration device to obtain approximately 10 cubic meters of wastewater concentrate with a water content of 30%. This concentrate was initially divided into 10 batches. Each batch of wastewater was treated as follows: (1) The citric acid chemical cleaning wastewater concentrate was pumped from the distillation and concentration device to a condenser and cooled to 20°C; (2) The concentrate in the condenser was transferred to a first liquid storage tank. The volume of the concentrate in the batch was 1 cubic meter as determined by the level gauge; (3) The agitator in the second liquid storage tank was turned on, and a wastewater transfer pump with a 76mm outer diameter pipe was used to quickly transfer the concentrate in the first liquid storage tank to a second liquid storage tank containing 5 cubic meters of ethanol solvent in a volume ratio. During this process, a large amount of solids are precipitated due to precipitation; (4) After 5 minutes, the mixed solution in the second liquid storage tank is pumped to an industrial rotary vacuum filter for filtration, and the solid matter is scraped into the drying equipment with the help of the filter scraper to be dried to obtain easy-to-peel, non-sticky solid waste; (5) Fly ash is added to the storage tank of the graded distillation device through the fly ash addition port at a ratio of 3:10 of fly ash and citric acid chemical cleaning waste liquid concentrate. The ethanol in the mother liquor is distilled and collected at 85°C, and returned to the ethanol collection tank for cooling. The water distilled at 100°C is discharged, and the distillation residue-fly ash adsorbent is collected and combined with the dried solid waste and poured into the coal yard for co-combustion.

[0054] The solid form of the citric acid chemical cleaning solid waste after drying was good and easy to transport. The scraper of the drying equipment was not damaged, and the final recovery rate of ethanol was 75%.

[0055] Example 3:

[0056] A power plant used citric acid to chemically clean the boiler water-cooled walls and discharged the wastewater into a slag pool. The wastewater was first distilled using a distillation and concentration device to obtain approximately 20 cubic meters of wastewater concentrate with a water content of 50%. This concentrate was initially divided into four batches. Each batch of wastewater was treated as follows: (1) The citric acid chemical cleaning wastewater concentrate was pumped from the distillation and concentration device to a condenser and cooled to 50°C; (2) The concentrate in the condenser was transferred to a first liquid storage tank. The volume of the concentrate in the batch was 5 cubic meters as determined by the level gauge; (3) The agitator in the second liquid storage tank was turned on, and a wastewater transfer pump with a 108 mm outer diameter pipe was used to quickly transfer the concentrate in the first liquid storage tank to a second liquid storage tank containing 5 cubic meters of ethanol solvent in a volumetric ratio. During this process, a large amount of solids precipitate due to precipitation; (4) After 30 minutes, the mixed solution in the second liquid storage tank is pumped to an industrial rotary vacuum filter for filtration, and the solid matter is scraped into the drying equipment with the help of the filter scraper to obtain easy-to-peel, non-sticky solid waste; (5) The ethanol in the filtered mother liquor is distilled and collected at 75°C through a graded distillation device, and returned to the ethanol collection tank for cooling. The water distilled at 95°C is discharged, and the distillation residue-fly ash adsorbent is collected and combined with the dried solid waste and poured into the coal yard for co-combustion.

[0057] The solid form of the citric acid chemical cleaning solid waste after drying was good and easy to transport. The scraper of the drying equipment was not damaged, and the final recovery rate of ethanol was 65%.

[0058] like Figure 2 As shown, two portions of citric acid chemical cleaning waste liquid concentrate with a water content of 30% were taken, A and B, each 100.0 g. The citric acid waste liquid concentrate A was directly dried in an oven to constant weight to obtain 70.0 g of solid waste A. The citric acid waste liquid concentrate B was subjected to a precipitation method-fly ash adsorption drying treatment, using 20.0 g of fly ash to obtain 90.0 g of solid waste B. The two portions of solid waste were placed in a glass dish and sealed with a woven bag. The glass dish was then placed in air with a humidity of 21% and weighed every 8 hours to obtain Figure 2 The weight gain curve is shown in Figure 2. Within 192 hours, solid waste B obtained through the precipitation-fly ash adsorption drying treatment only gained 5.02 g, while solid waste A obtained through direct drying gained 21.85 g. This indicates that the precipitation-fly ash adsorption drying treatment effectively extended the shelf life of the dried citric acid solid waste and provided better moisture resistance.

[0059] like Figure 3As shown, two portions of citric acid chemical cleaning waste liquid concentrate with a water content of 50% C and D were taken, each 100.0g. The citric acid waste liquid concentrate C was directly dried in an oven to constant weight to obtain a total of 50.0g of solid waste C. The citric acid waste liquid concentrate D was subjected to a precipitation method-fly ash adsorption drying treatment, using 10.0g of fly ash to obtain a total of 60.0g of solid waste D. The two portions of solid waste were placed in a glass dish and sealed with a woven bag. The two portions of solid waste were then placed in air with a humidity of 26% and weighed every 8 hours to obtain Figure 3 The weight gain curve is shown in the figure. Within 192 hours, solid waste D obtained through the precipitation-fly ash adsorption drying treatment only gained 3.77g, while solid waste C obtained through direct drying gained 14.24g. This indicates that the precipitation-fly ash adsorption drying treatment effectively extended the storage time of the dried citric acid solid waste and provided better moisture resistance.

[0060] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for treating precipitated coal ash from citric acid chemical cleaning wastewater by adsorption and drying, characterized in that: The following steps are involved: The citric acid chemical cleaning waste liquid is distilled, concentrated and cooled to obtain a concentrated liquid, which is then transferred to a liquid storage tank; The concentrated solution is stirred and mixed with the ethanol solvent in the liquid storage tank to obtain a mixed solution, and the ethanol-insoluble substances in the mixed solution are precipitated and then filtered to obtain a solid substance and a mother liquor; The solid matter is dried to obtain solid waste; the mother liquor is subjected to graded distillation while adding fly ash for adsorption to obtain distilled ethanol, distilled water and distillation residue; The distillation residue is combined with solid waste to complete the adsorption and drying treatment of the precipitated coal ash.

2. The method for adsorption and drying of precipitated coal ash from citric acid chemical cleaning wastewater according to claim 1, characterized in that: The volume of the concentrated liquid is 1 to 5 cubic meters; the water content of the concentrated liquid is 30% to 50%; and the cooling temperature is 0 to 50°C.

3. The method for treating precipitated coal ash by adsorption and drying of citric acid chemical cleaning waste liquid according to claim 1, characterized in that: The volume ratio of the ethanol solvent to the concentrated solution is (1-5):

1.

4. The method for treating precipitated coal ash by adsorption and drying of citric acid chemical cleaning waste liquid according to claim 1, characterized in that: The ethanol solvent in the liquid storage tank is cooled at a temperature of 0 to 50°C.

5. The method for treating precipitated coal ash by adsorption and drying of citric acid chemical cleaning waste liquid according to claim 1, characterized in that: The ethanol-insoluble substances in the mixed solution include but are not limited to ferric citrate, ammonium ferric citrate and ammonium citrate.

6. The method for treating precipitated coal ash by adsorption and drying of citric acid chemical cleaning waste liquid according to claim 1, characterized in that: The precipitation time is 5 to 30 minutes; the fractional distillation includes the distillation process of distilling ethanol and distilling water in sequence, wherein the temperature of distilling ethanol is 75 to 85° C., and the temperature of distilling water is 95 to 100° C.

7. The method for treating precipitated coal ash by adsorption and drying of citric acid chemical cleaning waste liquid according to claim 1, characterized in that: The volume ratio of the fly ash to the mother liquor is (1-3):

10.

8. The method for treating precipitated coal ash by adsorption and drying of citric acid chemical cleaning waste liquid according to claim 1, characterized in that: The distillation residue is high-boiling-point oily organic matter and a small amount of ethanol-soluble matter in the citric acid chemical cleaning waste liquid adsorbed on the fly ash.

9. A system for adsorption and drying of precipitated coal ash from citric acid chemical cleaning wastewater, characterized in that: The invention comprises a distillation and concentration device, wherein the outlet of the distillation and concentration device is connected to the inlet of a condenser, the outlet of the condenser is connected to the inlet of a liquid storage tank, an agitator and a liquid level gauge are provided inside the liquid storage tank, an ethanol solvent is contained in the liquid storage tank, the outlet of the liquid storage tank is connected to the inlet of a filtering device, the liquid outlet of the filtering device is connected to the inlet of a graded distillation device, the solid outlet of the filtering device is connected to the inlet of a drying device, and the graded distillation device is provided with a fly ash addition port, a distilled ethanol outlet, a distilled water outlet, and a distillation residue outlet.

10. The system for adsorption and drying of precipitated coal ash from citric acid chemical cleaning wastewater according to claim 9, characterized in that: The liquid storage tank comprises a first liquid storage tank and a second liquid storage tank connected in sequence; wherein the first liquid storage tank is provided with a liquid level gauge and a delivery pump, and the second liquid storage tank is provided with an agitator; The delivery pipe between the outlet of the first liquid storage tank and the inlet of the second liquid storage tank is adapted to the volume of the concentrated liquid in the first liquid storage tank.

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