Washing system for ammonium polyvanadate

Abstract

The utility model belongs to the technical field of ammonium salt purification treatment of vanadium, and particularly relates to an ammonium polyvanadate washing system which comprises a vacuum separation device, a re-pulping washing device and a pressurizing separation device, the vacuum separation device is used for carrying out solid-liquid separation on the ammonium polyvanadate slurry through a vacuum separator to obtain a filter cake; the re-pulping washing device is used for pulping and washing the filter cake through a re-pulping washing tank; the pressurized separation device is used for squeezing and blow-drying the washed slurry through a pressurized separator to obtain the low-impurity ammonium polyvanadate. And the filtrate is recycled to the vacuum separator through a pipeline to serve as washing water. Through multi-stage separation and filtrate circulation, the washing water consumption and the wastewater treatment cost are remarkably reduced, and meanwhile, the purity of ammonium polyvanadate is improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the ammonium salt purification treatment technical field of vanadium, specifically relates to a washing system of ammonium polyvanadate. BACKGROUND

[0002] Ammonium polyvanadate, as an important vanadium compound, is widely used in the production of vanadium oxides. It has a wide range of applications in the steel industry and energy storage materials. However, in the traditional production process, the use of acidic ammonium salt precipitation method to manufacture ammonium polyvanadate often leads to the presence of high concentrations of sodium, sulfur and other impurities in the product. The presence of these impurities seriously affects the quality and performance of vanadium products, especially in high-end application fields such as high-performance steel and advanced battery systems.

[0003] Traditionally, the method for removing sodium, sulfur and other impurities in ammonium polyvanadate mainly includes single solid-liquid separation operation using drum filter, plate and frame filter press and belt vacuum filter and other equipment. However, this method has obvious shortcomings: first, the consumption of fresh water is large, which greatly increases the production cost; second, the cost of treating vanadium-containing wastewater is high, which not only increases the economic burden of enterprises, but also causes potential harm to the environment.

[0004] In the prior art patent document 1 (CN106082335A), the washing of polyvanadate does not consider the reuse of the filtrate after pressure filtration, so there is a problem of relatively high water consumption. In addition, in patent document 2 (CN108439467A), the filtrate of three-stage countercurrent washing of ammonium polyvanadate is reused as washing water, which is not easy to balance the water consumption, resulting in an increase in the amount of washing water. They have not effectively solved the problem of low water resource utilization rate.

[0005] In summary, the washing method and process of ammonium polyvanadate in the prior art still need to be further optimized to further improve the utilization rate of water resources. UTILITY MODEL CONTENT

[0006] Therefore, the utility model aims to overcome the above technical problems and provides a washing system for ammonium polyvanadate. The system includes three main components: a vacuum separator, a re-pulping washing tank and a pressure separator. After the ammonium polyvanadate slurry is introduced into the vacuum separator for preliminary washing and solid-liquid separation, a filter cake is obtained, which is then washed and further purified in the re-pulping washing tank, and finally the pressure filtration and blow-drying process is realized by the pressure separator. The filtrate in this process is recycled and reused as washing water in the vacuum separator, thereby realizing the effective recycling of water resources, greatly reducing the demand for fresh water, reducing the cost of wastewater treatment, and improving the product quality.

[0007] The utility model discloses a technical scheme: the utility model provides a kind of ammonium polyvanadate washing system, comprising: vacuum separation device, re-pulping washing device and pressurized separation device;

[0008] Wherein, the vacuum separation device includes vacuum separator, the top of the body of vacuum separator is provided with filtrate inlet, the side of the body of vacuum separator is provided with first slurry inlet, waste liquid outlet, first water inlet and filter cake outlet from top to bottom;

[0009] The re-pulping washing device includes re-pulping washing tank, the re-pulping washing tank is arranged downstream of vacuum separator, the top of the tank body of the re-pulping washing tank is provided with filter cake inlet, the filter cake inlet is connected with the filter cake outlet by pipeline, the bottom of the tank body of the re-pulping washing tank is provided with re-pulping outlet;

[0010] And, the pressurized separation device includes pressurized separator, one end of the body of pressurized separator is provided with second slurry inlet, the opposite end of the second slurry inlet is provided with ammonium polyvanadate outlet, the second slurry inlet and the ammonium polyvanadate outlet are provided with filtrate outlet, the second slurry inlet is connected with the re-pulping outlet by pipeline, the filtrate outlet is connected with the filtrate inlet by pipeline.

[0011] In some embodiments, the vacuum separation device further includes high-level buffer tank, the high-level buffer tank is arranged upstream of the vacuum separator, and the horizontal position is higher than the vacuum separation device, the bottom of the high-level buffer tank is provided with ammonium polyvanadate slurry outlet, the ammonium polyvanadate slurry outlet is connected with the ammonium polyvanadate slurry inlet of the vacuum separator by pipeline.

[0012] In some embodiments, the re-pulping washing device further includes slurry storage tank, the slurry storage tank is located downstream of re-pulping washing tank, one end of the tank body of the slurry storage tank is provided with third slurry inlet, the third slurry inlet is connected with the re-pulping outlet by pipeline, the opposite end of the tank body of the slurry storage tank is provided with third slurry outlet with the third slurry inlet, the third slurry outlet is connected with the second slurry inlet by pipeline.

[0013] In some embodiments, the pressurized separation device further includes filtrate storage tank, the filtrate storage tank is arranged downstream of the pressurized separator, one end of the tank body of the filtrate storage tank is provided with tank inlet, the opposite end of the tank inlet is provided with tank outlet, the tank inlet is connected with the filtrate outlet by pipeline, and the tank outlet is connected with the filtrate inlet by pipeline.

[0014] In some embodiments, the high-level buffer tank is provided with a stirring mechanism, which includes stirring blades disposed on the bottom or top wall of the high-level buffer tank and extends along the tank axially.

[0015] In some embodiments, the vacuum separator includes a vacuum belt filter, and the filtrate inlet of the vacuum belt filter is provided with a flow regulating valve for controlling the filtrate reuse ratio.

[0016] In some embodiments, the pressure separator includes an automatic chamber filter press.

[0017] In some embodiments, a water purification module is provided between the first water inlet of the vacuum separator and the filtrate outlet of the pressurized separator. The water purification module includes a filter layer, which includes a filter screen and / or a filter element. The filter element includes an activated carbon or ion exchange resin layer.

[0018] In some embodiments, the ammonium polyvanadate outlet of the pressurized separator is provided with a drying module, the drying module including a dryer, the air outlet of the dryer being directly opposite the ammonium polyvanadate outlet.

[0019] In some embodiments, the system further includes a slurry conveying power module, which includes a screw pump and a pneumatic booster. The screw pump is installed on the pipeline between the re-slurry washing tank and the pressurized separator, and the pneumatic booster is integrated on the pipeline between the pressurized separator and the filtrate storage tank.

[0020] The beneficial effects of this invention include: the ammonium polyvanadate washing system integrates multiple advanced separation technologies, combining different physical separation methods—vacuum separation, resizing washing, and pressure separation—into a continuous process flow. This system is efficient, environmentally friendly, flexible, and easy to operate. The entire system design takes into account the maximization of resource utilization, which not only improves processing efficiency but also ensures high product purity, improves water resource utilization efficiency, reduces the amount of ammonium polyvanadate washing water used, and lowers wastewater treatment costs, providing strong technical support for the sustainable development of the vanadium chemical industry. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 only some embodiments of this utility model. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0022] Figure 1The diagram shown is a schematic process diagram of the washing process of the novel ammonium polyvanadate provided in one embodiment of the present invention.

[0023] Figure 2 The diagram shown is a schematic structural diagram of an ammonium polyvanadate washing system provided in one embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures

[0025] 11. High-level buffer tank; 1101. Ammonium polyvanadate slurry outlet; 12. Vacuum separator; 1201. Filtrate inlet; 1202. First slurry inlet; 1203. Waste liquid outlet; 1204. First water inlet; 1205. Filter cake outlet; 21. Re-pulping and washing tank; 2101. Filter cake inlet; 2102. Re-pulping outlet; 22. Slurry storage tank; 2201. Third slurry inlet; 2202. Third slurry outlet; 31. Pressure separator; 3101. Second slurry inlet; 3102. Ammonium polyvanadate outlet; 3103. Filtrate outlet; 32. Filtrate storage tank; 3201. Tank inlet; 3202. Tank outlet. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be further described in detail below with reference to specific examples and accompanying drawings.

[0027] It should be noted that all uses of "first" and "second" in the embodiments of this utility model are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of this utility model. Subsequent embodiments will not explain this in detail.

[0028] In this invention, the term "APV" is an abbreviation for ammonium polyvanadate.

[0029] In this invention, arrows indicate the direction of material flow.

[0030] This utility model provides a washing system for ammonium polyvanadate, comprising: a vacuum separation device, a re-pulping washing device, and a pressurized separation device;

[0031] The vacuum separation device includes a vacuum separator 12. The top of the vacuum separator 12 is provided with a filtrate inlet 1201, and the side of the vacuum separator 12 is provided with a first slurry inlet 1202, a waste liquid outlet 1203, a first water inlet 1204 and a filter cake outlet 1205 from top to bottom.

[0032] The re-pulp washing device includes a re-pulp washing tank 21, which is located downstream of the vacuum separator 12. The top of the re-pulp washing tank 21 is provided with a filter cake inlet 2101, which is connected to the filter cake outlet 1205 through a pipe. The bottom of the re-pulp washing tank 21 is provided with a re-pulp outlet 2102.

[0033] The pressurized separation device includes a pressurized separator 31. One end of the pressurized separator 31 is provided with a second slurry inlet 3101, and the opposite end of the second slurry inlet 3101 is provided with an ammonium polyvanadate outlet 3102. A filtrate outlet 3103 is provided between the second slurry inlet 3101 and the ammonium polyvanadate outlet 3102. The second slurry inlet 3101 is connected to the reprocessing slurry outlet 2102 through a pipe, and the filtrate outlet 3103 is connected to the filtrate inlet 1201 through a pipe.

[0034] By combining a vacuum separation unit, a re-pulping and washing unit, and a pressurized separation unit, impurities in ammonium polyvanadate can be effectively removed, improving the purity of the product. The vacuum separator 12 can efficiently separate the filtrate and the filter cake, while the re-pulping and washing tank 21 can further clean the filter cake. Finally, the pressurized separator 31 achieves solid-liquid separation. Through the synergistic effect of the three-stage separation and washing process (vacuum separation → re-pulping → pressurized separation), impurities such as sodium and sulfur are removed step by step, significantly improving the purity of ammonium polyvanadate. At the same time, the closed-loop circulation design of the filtrate reduces the consumption of fresh water and lowers wastewater treatment costs by more than 30%.

[0035] Maintaining a stable slurry flow rate in the system is a crucial aspect of ensuring smooth system operation. In some embodiments, the vacuum separation device further includes an elevated buffer tank 11, which is located upstream of the vacuum separator 12 and is positioned horizontally higher than the vacuum separation device. The bottom of the elevated buffer tank 11 is provided with an ammonium polyvanadate slurry outlet 1101, which is connected to the ammonium polyvanadate slurry inlet of the vacuum separator 12 via a pipeline.

[0036] The high-level buffer tank 11 uses gravity flow to stably supply material to the vacuum separator 12, avoiding slurry conveying pressure fluctuations, reducing pumping energy consumption, and preventing slurry stratification or pipe blockage. This ensures that the material has enough time to mix and settle before entering the vacuum separator 12, thereby improving the effect of subsequent filtration.

[0037] In some embodiments, the re-pulping and washing apparatus further includes a slurry storage tank 22, which is located downstream of the re-pulping and washing tank 21. One end of the slurry storage tank 22 is provided with a third slurry inlet 2201, which is connected to the re-pulping outlet 2102 via a pipe. The other end of the slurry storage tank 22 opposite to the third slurry inlet 2201 is provided with a third slurry outlet 2202, which is connected to the second slurry inlet 3101 via a pipe.

[0038] The slurry storage tank 22 temporarily stores the pre-treated slurry. The slurry storage tank 22 can serve as a buffer unit of the system to balance the slurry flow fluctuations between the reprocessing slurry washing tank 21 and the pressurized separator 31, ensuring continuous operation of the system and reducing losses caused by uneven system flow. This allows for flexible adjustment of the operating status of subsequent processes according to production needs, improving the flexibility and adaptability of the entire system.

[0039] To further reduce the system water consumption, in some embodiments the pressurized separation device also includes a filtrate storage tank 32. The filtrate storage tank 32 is located downstream of the pressurized separator 31. One end of the filtrate storage tank 32 is provided with an inlet 3201, and the opposite end is provided with an outlet 3202. The inlet 3201 is connected to the filtrate outlet 3103 through a pipe, and the outlet 3202 is connected to the filtrate inlet 1201 through a pipe.

[0040] The slurry may clump due to settling in the high-level buffer tank 11. In some embodiments, the high-level buffer tank 11 is equipped with a stirring mechanism, which includes stirring blades disposed on the bottom or top wall of the high-level buffer tank 11 and extending axially along the tank body. During use, the stirring mechanism continuously stirs the slurry to prevent ammonium polyvanadate from precipitating and clumping, ensuring slurry uniformity, improving the solid-liquid separation efficiency of the vacuum separator 12, and reducing the frequency of manual cleaning.

[0041] In some embodiments, the vacuum separator 12 includes a vacuum belt filter. The vacuum belt filter is provided with a flow regulating valve at the filtrate inlet 1201 for controlling the filtrate reuse ratio. The vacuum belt filter, in conjunction with the flow regulating valve, precisely controls the filtrate reuse ratio (e.g., 1.5-2.5 times the weight of APV), optimizes the distribution of washing water, and avoids excessive water use leading to secondary dissolution of impurities.

[0042] In some embodiments, the pressure separator 31 includes an automatic chamber filter press, which reduces the moisture content of ammonium polyvanadate to below 10% by high-pressure pressing (0.5-1.5MPa) and gas drying, while reducing the production cycle by 20%-30%.

[0043] In some embodiments, a water purification module is provided between the first water inlet 1204 of the vacuum separator 12 and the filtrate outlet 3103 of the pressurized separator 31. The water purification module includes a filter layer, which includes a filter screen and / or a filter element. The filter element includes an activated carbon or ion exchange resin layer. The water purification module (activated carbon + ion exchange resin) effectively removes sodium ions, sulfides, and suspended particles from the filtrate, ensuring the cleanliness of the recycled water and preventing impurities from circulating and contaminating the washing system.

[0044] In some embodiments, a drying module is provided at the ammonium polyvanadate outlet 3102 of the pressure separator 31. The drying module includes a dryer, the air outlet of which faces the ammonium polyvanadate outlet 3102. The drying module further reduces the moisture content of the ammonium polyvanadate to below 5% through hot air circulation (80-100℃), improving the quality of the finished product and meeting the vanadium oxide production standards.

[0045] In some embodiments, the system further includes a slurry conveying power module, which includes a screw pump and a pneumatic booster. The screw pump is installed on the pipeline between the reprocessing slurry washing tank 21 and the pressurized separator 31, and the pneumatic booster is integrated on the pipeline between the pressurized separator 31 and the filtrate storage tank 32. The slurry conveying power module can provide stable slurry conveying pressure, ensuring smooth slurry transmission throughout the system and enhancing the system's stability and reliability.

[0046] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not specified in the embodiments, they are based on conventional technical solutions in the art. Where manufacturers are not specified, they are all conventional products that can be obtained commercially.

[0047] To further explain the workflow of the ammonium polyvanadate washing system disclosed in this utility model, the process of using the ammonium polyvanadate washing system of this utility model is simplified as follows: Figure 1 The process shown includes three steps: a vacuum filtration step, which washes and separates the APV slurry from the APV to obtain an APV filter cake; a re-slurry washing step, in which the APV filter cake is washed with water to further reduce the content of impurities such as sodium and sulfur in the APV; and a pressure filtration step, in which the re-slurry washed APV slurry is pressed and dried to obtain APV with low impurity and moisture content, and the filtrate is returned to the vacuum filtration step as washing water.

[0048] In some embodiments, a schematic structural diagram of the ammonium polyvanadate washing system disclosed in this utility model is shown below. Figure 2As shown. The ammonium polyvanadate washing system includes, in sequence according to the slurry flow direction, a high-level buffer tank 11, a vacuum separator 12, a re-slurry washing tank 21, a slurry storage tank 22, a pressure separator 31, and a filtrate storage tank 32.

[0049] First, combined Figure 1 The vacuum filtration process is described below. The vacuum filtration process includes a high-level buffer tank 11 and a vacuum separator 12. The high-level buffer tank 11 stores the APV slurry. The high-level buffer tank 11 contains a mixture of APV and precipitated residue. The APV slurry is continuously fed from the high-level buffer tank 11 to the vacuum separator 12. The high-level buffer tank 11 is equipped with a stirring mechanism. Most of the sodium and sulfur impurities contained in the APV slurry are separated in the vacuum separator 12; the sodium and sulfur are treated separately after entering the waste liquid. The vacuum separator 12 consists of a vacuum belt filter, etc. The washing solution used in the vacuum separator 12 first uses the pressurized filtrate from the filtrate storage tank 32, and then water is added to wash the APV filter cake. The first stage filtrate addition amount in the vacuum separator 12 is set to be 1.5 to 2.5 times the weight ratio of ammonium polyvanadate, and the second stage water addition amount is set to be 1 to 1.5 times the weight ratio of ammonium polyvanadate.

[0050] Next, the re-slurry washing process will be described. The re-slurry washing process re-washes the APV filter cake after the vacuum filtration process. For this purpose, the re-slurry washing process consists of a re-slurry washing tank 21 and a slurry storage tank 22. In the re-slurry washing process, by adding water and slurrying, impurities such as sodium and sulfur are further precipitated from the APV into the aqueous solution, thus further purifying the APV. The amount of water added to the re-slurry washing tank 21 is set to a weight ratio of 1.5 to 2.5 times that of ammonium polyvanadate.

[0051] Next, the pressure filtration process will be described. The pressure filtration process separates the APV slurry from its solids and dries it after the re-pulping and washing process. For this purpose, the pressure filtration process consists of a pressure separator 31 and a filtrate storage tank 32. The pressure separator 31 may be, for example, an automatic chamber filter press. Through the pressure separator 31, solid-liquid separation is performed, removing the aqueous solution from the slurry. The pressed and dried APV then enters the subsequent vanadium processing process. The filtrate in the filtrate storage tank is returned to the vacuum separator 12 as the first-stage washing water.

[0052] As described above, according to this embodiment, the ammonium polyvanadate filter cake, after being washed and filtered in the vacuum separator 12, is then further slurried and washed in the re-slurry washing tank 21. This promotes the dissolution of impurities such as sodium and sulfur contained in the ammonium polyvanadate, reducing these impurities to levels that meet quality requirements. Simultaneously, the filtrate from the pressure filter is reused, reducing water consumption and lowering wastewater treatment costs.

[0053] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A washing system of ammonium polyvanadate, characterized by, The application relates to a vacuum separation device, a re-slurry washing device and a pressurized separation device. The vacuum separation device comprises a vacuum separator (12), the top of the body of the vacuum separator (12) is provided with a filtrate inlet (1201), and the side of the body of the vacuum separator (12) is provided with a first slurry inlet (1202), a waste liquid outlet (1203), a first water inlet (1204) and a filter cake outlet (1205) from top to bottom. The re-slurry washing device comprises a re-slurry washing tank (21), the re-slurry washing tank (21) is arranged downstream of the vacuum separator (12), the top of the tank body of the re-slurry washing tank (21) is provided with a filter cake inlet (2101), the filter cake inlet (2101) is connected with the filter cake outlet (1205) through a pipeline, and the bottom of the tank body of the re-slurry washing tank (21) is provided with a re-slurry outlet (2102). The pressurized separation device comprises a pressurized separator (31), one end of the body of the pressurized separator (31) is provided with a second slurry inlet (3101), the opposite end of the second slurry inlet (3101) is provided with an ammonium polyvanadate outlet (3102), a filtrate outlet (3103) is arranged between the second slurry inlet (3101) and the ammonium polyvanadate outlet (3102), the second slurry inlet (3101) is connected with the re-slurry outlet (2102) through a pipeline, and the filtrate outlet (3103) is connected with the filtrate inlet (1201) through a pipeline. The vacuum separation device further comprises a high-position buffer tank (11), the high-position buffer tank (11) is arranged upstream of the vacuum separator (12) and is arranged at a position higher than the vacuum separation device in the horizontal direction, and the bottom of the high-position buffer tank (11) is provided with an ammonium polyvanadate slurry outlet (1101), the ammonium polyvanadate slurry outlet (1101) is connected with the ammonium polyvanadate slurry inlet of the vacuum separator (12) through a pipeline.

2. The ammonium polyvanadate washing system according to claim 1, characterized in that, The re-slurry washing device further comprises a slurry storage tank (22), the slurry storage tank (22) is arranged downstream of the re-slurry washing tank (21), one end of the tank body of the slurry storage tank (22) is provided with a third slurry inlet (2201), the third slurry inlet (2201) is connected with the re-slurry outlet (2102) through a pipeline, and the opposite end of the tank body of the slurry storage tank (22) is provided with a third slurry outlet (2202), the third slurry outlet (2202) is connected with the second slurry inlet (3101) through a pipeline.

3. The ammonium polyvanadate washing system according to claim 1, characterized in that, ​ 4. The ammonium polyvanadate washing system of claim 1, wherein, The pressurized separation device further comprises a filtrate storage tank (32) arranged downstream of the pressurized separator (31), one end of the tank body of the filtrate storage tank (32) is provided with an inlet opening (3201), and the other end opposite to the inlet opening (3201) is provided with an outlet opening (3202), the inlet opening (3201) is connected with the filtrate outlet (3103) through a pipeline, and the outlet opening (3202) is connected with the filtrate inlet (1201) through a pipeline.

5. The ammonium polyvanadate washing system of claim 2, wherein, The high-position buffer tank (11) is internally provided with a stirring mechanism, which comprises stirring blades arranged on the internal bottom wall or top wall of the high-position buffer tank (11) and extending in the axial direction of the tank body.

6. The ammonium polyvanadate washing system of claim 1, wherein, The vacuum separator (12) comprises a vacuum belt filter, and a flow regulating valve for controlling the recycling proportion of filtrate is arranged at the filtrate inlet (1201) of the vacuum belt filter.

7. The ammonium polyvanadate washing system of claim 1, wherein The pressurized separator (31) comprises an automatic chamber filter press.

8. The ammonium polyvanadate washing system of claim 1, wherein, A water quality purification module is arranged between the first water inlet (1204) of the vacuum separator (12) and the filtrate outlet (3103) of the pressurized separator (31), the water quality purification module comprises a filter layer, the filter layer comprises a filter screen and / or a filter core, and the filter core comprises an activated carbon or ion exchange resin layer.

9. The ammonium polyvanadate washing system of claim 1, wherein, A drying module is arranged at the ammonium polyvanadate outlet (3102) of the pressurized separator (31), the drying module comprises a drying machine, and the air outlet of the drying machine is opposite to the ammonium polyvanadate outlet (3102).

10. The ammonium polyvanadate washing system of claim 1, wherein, The system further comprises a slurry conveying power module, the slurry conveying power module comprises a screw pump and a pneumatic booster, the screw pump is arranged on the pipeline between the reslurry washing tank (21) and the pressurized separator (31), and the pneumatic booster is integrated on the pipeline between the pressurized separator (31) and the filtrate storage tank (32).

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