CN112758938A - System for utilize tail gas preparation fluosilicic acid in hydrogen fluoride production process - Google Patents
System for utilize tail gas preparation fluosilicic acid in hydrogen fluoride production process Download PDFInfo
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Abstract
The invention relates to a system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process, which adopts a tail gas treatment process of four-stage water washing and one-stage alkali washing, and comprises a water washing tank, a No. 1 water washing tower, a No. 1 water washing pump, a circulating cooler, a No. 2 water washing tower, a No. 2 water washing pump, a No. 3 water washing tower, a No. 3 water washing pump, a No. 4 water washing tower, a No. 4 water washing pump, an alkali washing tower, an alkali washing tank, an alkali washing pump, a tail gas fan, an alkali supplementing pump, an alkali tank and a HF recovery No. 1 water washing pump.
Description
Technical Field
The invention belongs to the technical field of chemical processes, and particularly relates to a system for preparing fluosilicic acid by utilizing tail gas in a hydrogen fluoride production process.
Background
At present, the production of hydrogen fluoride is mainly based on a fluorite-sulfuric acid route in China, and the production technology has more than forty years of history in China. The fluorite powder contains a certain amount of silicon dioxide, and when the fluorite powder and concentrated sulfuric acid react in a rotary furnace with an external heating jacket, the silicon dioxide and the concentrated sulfuric acid react to generate silicon tetrafluoride. The boiling point of the silicon tetrafluoride is-86 ℃, part of the silicon tetrafluoride and water are hydrolyzed to generate fluosilicic acid, the fluosilicic acid enters crude hydrogen fluoride liquid, and most of the silicon tetrafluoride gas enters a tail gas recovery system. And the crude hydrogen fluoride liquid enters a rectifying tower and a degassing tower to remove high-boiling substances and low-boiling substances, fluosilicic acid is decomposed into silicon tetrafluoride, and the silicon tetrafluoride is discharged from the top of a condenser of the degassing tower and enters a tail gas recovery system. In the prior art, a tail gas recovery system adopts the traditional absorption method of a water washing tower and an alkali washing tower, but the absorption efficiency is not high, the equipment is various, each water washing tower corresponds to one water washing tank, the equipment occupies a large space, and fluorine-containing substances in exhaust gas exceed the standard, pollute the environment and waste resources. Along with the scarcity of fluorite powder resources, the quality of the fluorite powder cannot be guaranteed, and the content of silicon dioxide in some fluorite powder can exceed 2 percent. In order to fully recycle silicon tetrafluoride produced in the production process, save energy and solve the problem of environmental pollution, a tail gas treatment process is urgently needed to be researched to solve the problem.
Disclosure of Invention
The invention aims to provide a system for preparing fluosilicic acid by utilizing tail gas in a hydrogen fluoride production process, which adopts a tail gas treatment process of four-stage water washing and one-stage alkali washing, solves the problem of poor control of negative pressure of a hydrogen fluoride production system, simultaneously recycles silicon tetrafluoride generated in the hydrogen fluoride production process, achieves the recovery rate of the silicon tetrafluoride over 99 percent, and effectively solves the problem of environmental pollution.
In order to solve the technical problems, the invention is realized by the following technical scheme:
a system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process adopts a tail gas treatment process of four-stage water washing and one-stage alkali washing, and comprises a water washing tank, a 1# water washing tower, a 1# water washing pump, a circulating cooler, a 2# water washing tower, a 2# water washing pump, a 3# water washing tower, a 3# water washing pump, a 4# water washing tower, a 4# water washing pump, an alkali washing tower, an alkali washing tank, an alkali washing pump, a tail gas fan, an alkali supplementing pump, an alkali tank and a HF recovery 1# water washing pump, wherein the bottom of the 1# water washing tower is connected with the water washing tank, the bottom of the water washing tank is connected with the 1# water washing pump through an outlet pipeline, and the outlet material of the 1# water washing tower is respectively connected with the top of the 1# water washing tower and a fluosilicic acid; the method comprises the following steps that water washing liquid in a water washing tank is pumped to a feeding pipeline at the bottom of a circulating cooler through a No. 1 water washing pump, the circulating cooler is cooled by circulating water, the circulating water enters from the top of the circulating cooler and is in countercurrent contact with the water washing liquid rising from the bottom, the temperature of the water washing liquid is reduced, a thermometer is arranged in the water washing tank, the cooling water quantity of the circulating cooler is adjusted, and the temperature of the water washing liquid in the water washing tank is controlled within a certain process range; the washing tank is respectively connected with the bottom of the circulating cooler and the top of the No. 1 washing tower through a No. 1 washing pump; the water washing liquid in the No. 2 water washing tower overflows to a No. 1 water washing pump feeding pipeline through an overflow pipe; unabsorbed gas enters the bottom of a No. 2 water scrubber from the top of the No. 1 water scrubber, enters the bottom of a No. 3 water scrubber from the top of the No. 2 water scrubber, enters the bottom of a No. 4 water scrubber from the top of the No. 3 water scrubber, enters the bottom of an alkaline washing tower from the top of the No. 4 water scrubber, and is discharged from a tail gas fan connected with the top of the alkaline washing tower; the bottom of the No. 2 washing tower and the bottom of the No. 3 washing tower are connected with the upper part of the No. 2 washing tower through a No. 2 washing pump; the bottom of the 3# water washing tower and the bottom of the 4# water washing tower are connected with the upper part of the 3# water washing tower through a 3# water washing pump; the bottom of the No. 4 water washing tower is connected with the upper part of the No. 4 water washing tower through a No. 4 water washing pump; a tap water replenishing pipeline is arranged at the top of the No. 4 water washing tower and is connected with tap water, a flow meter is arranged on the tap water replenishing pipeline, a fluosilicic acid concentration meter is arranged in the washing tank, the tap water replenishing water quantity is adjusted according to the concentration displayed by the fluosilicic acid concentration meter, and the concentration of fluosilicic acid in the washing tank is controlled within a specified range; an alkali supplementing pipeline is arranged at the top of the alkali washing tower, liquid alkali in the alkali tank is pumped to the top of the alkali washing tank through an alkali supplementing pump, a flow meter is arranged on the alkali supplementing pipeline, the alkali supplementing amount is controlled within a specified range, and alkali washing liquid in the alkali washing tank is pumped to the top of the alkali washing tower through an alkali washing pump; part of the alkaline washing liquid in the alkaline washing tank is pumped to the top of the alkaline washing tower through an alkaline washing pump, part of the alkaline washing liquid is pumped to the sewage collecting tank, and the alkaline washing liquid in the alkaline washing tower automatically flows to the alkaline washing tank through the bottom; 2# washing tower, 3# washing tower and 4# washing tower top are equipped with the hydrofluoric acid pipeline, retrieve 1# washing pump outlet line respectively with HF and link to each other, when 2# washing tower, 3# washing tower and 4# washing tower negative pressure are unusual, open this hydrofluoric acid pipeline valve, wash 2# washing tower, 3# washing tower and 4# washing tower, after 2# washing tower, 3# washing tower and 4# washing tower negative pressure are normal, close this hydrofluoric acid pipeline valve.
Furthermore, hydrofluoric acid pipelines are respectively used at the tops of the four-stage water washing towers, and when the negative pressure of the water washing towers is abnormal, valves of the hydrofluoric acid pipelines at the tops of the corresponding water washing towers are opened to flush the water washing towers, so that the negative pressure of a production system is stable, and the negative pressure is ensured not to influence the production load; the water replenishing of the four-stage water washing tower is realized by adopting a 4# water washing tower, and a flow meter is arranged on a water replenishing pipeline, so that the concentration of the recovered fluosilicic acid is easy to control.
Furthermore, pall ring plastic packing is arranged in the No. 1 water washing tower, the No. 2 water washing tower, the No. 3 water washing tower and the No. 4 water washing tower, the packing layer is in full countercurrent contact with rising gas in the process that top spray liquid is sprayed from top to bottom, and partial silicon tetrafluoride gas is hydrolyzed with water or reacts with hydrofluoric acid to generate fluosilicic acid solution.
Furthermore, thermometers are arranged on gas inlet pipelines at the bottoms of the No. 1 water washing tower, the No. 2 water washing tower, the No. 3 water washing tower, the No. 4 water washing tower and the alkaline washing tower, so that whether the gas inlet pipelines are blocked by the crystallisates or not can be known in time.
Furthermore, the alkaline tower absorbs the gas in the alkaline tower by adopting a mode of spraying liquid caustic soda and spraying alkaline wash liquid on the top, the absorption effect is good, and the fluorine content of the gas out of the alkaline tower is reduced.
Furthermore, the rinsing bath is provided with an emptying pipeline which is connected with a gas inlet pipeline at the bottom of the No. 1 rinsing bath so as to prevent the pressure of the rinsing bath from being too high; the washing tank is provided with a liquid level meter, washing liquid in the washing tank is pumped to a fluosilicic acid removing storage tank through a No. 1 washing pump, a liquid level regulating valve is arranged on a pipeline of the fluosilicic acid removing storage tank, and the liquid level of the washing tank is controlled within a certain range; the washing tank is also provided with a fluosilicic acid remote transmission concentration meter, so that the concentration of fluosilicic acid can be known in time conveniently, and the pipeline is prevented from being blocked by the crystals with too high fluosilicic acid concentration; the water washing tank is also provided with a thermometer so as to conveniently know whether the air inlet pipeline of the No. 1 water washing tower is smooth or not and analyze the absorption efficiency.
Further, a PH meter is arranged in the alkaline washing tank, a flowmeter and a flow regulating valve are arranged on an alkaline supply pump and an alkaline supply pipeline of the alkaline washing tank, the flow regulating valve on the alkaline supply pipeline is matched with the PH meter in the alkaline washing tank, and the PH value of alkaline washing liquid in the alkaline washing tank is controlled within a specified range; the alkaline washing tank is provided with a liquid level meter, a liquid level regulating valve is arranged on a pipeline between the alkaline washing pump and the alkaline washing tank, the liquid level regulating valve is matched with the liquid level meter in the alkaline washing tank, and the liquid level of the alkaline washing tank is controlled within a specified range.
Furthermore, flowmeters are arranged on alkali supplementing and water supplementing pipelines of the alkali tank, liquid alkali and tap water are blended according to the proportion of 1:3, the concentration of the liquid alkali in the alkali tank is controlled, the phenomenon that the concentration of the liquid alkali is too high, the liquid alkali is sprayed from the top of the alkali washing tower, and the alkali washing liquid in the alkali washing tank is crystallized due to the too high concentration of sodium sulfite, so that the normal operation of an alkali washing system is influenced; the alkali tank is provided with a remote liquid level to prevent liquid overflow.
In the HF production, the non-condensable gas discharged in the crude product condensation and refining process contains a small amount of waste gas such as SO2, SiF4, HF and the like, and is sucked into the bottom of a sulfuric acid absorption tower under the action of a plastic fan in a negative pressure manner, the waste gas and the sulfuric acid which falls from the top are absorbed and cooled in a countercurrent manner in the tower, the gas such as SO2, SiF4 and HF which are not absorbed enters the bottom of a No. 1 water washing tower and is absorbed by top spray liquid, the absorption liquid of a washing tank is pumped to the top of the No. 1 water washing tower by a No. 1 water washing pump, the gas which is not recovered at the bottom of the No. 1 water washing tower rises from the bottom of the tower and is absorbed in a countercurrent manner with the absorption liquid at the top, the gas such as SO2, SiF4 and HF which are not absorbed enters the bottom of the No. 2 water washing tower from the top of the No. 1 water washing tower, the low-concentration absorption liquid in the No. 2 water washing tower enters the No. 1 water washing tower, forming a circulating absorption system, recovering the non-condensable gas entering the bottom of the No. 2 water washing tower by absorption liquid in the tower, pumping the absorption liquid in the tower to the top of the tower by a No. 2 water washing pump, enabling the gas which is not recovered at the bottom of the tower to rise through the bottom of the tower, enabling the gas such as SO2, SiF4, HF and the like which is not absorbed to enter the bottom of the No. 3 water washing tower from the top, and enabling the absorption liquid in the No. 2 water washing tower to be supplemented by the water overflow of the absorption liquid with the concentration at the bottom of the No. 3 water washing; by analogy, the non-condensable gas entering the 3# water scrubber rises from the bottom of the tower and is pumped to the bottom of the 4# water scrubber by the 3# water scrubber pump for countercurrent absorption, the non-absorbed gases such as SO2, SiF4 and HF enter the bottom of the 4# water scrubber from the top of the 3# water scrubber, the absorption liquid in the 3# water scrubber is supplemented by the overflow of the absorption liquid with the concentration of the bottom of the 4# water scrubber, the non-condensable gas entering the 4# water scrubber rises from the bottom of the tower and is pumped to the top of the tower by the 4# water scrubber pump for countercurrent absorption, the non-absorbed gases such as SO2, SiF4 and HF enter the bottom of the alkali scrubber from the top of the 4# water scrubber, the absorption liquid in the 4# water scrubber controls the addition of tap water according to the concentration of fluosilicic acid in the water scrubber, the tail gas entering the alkali scrubber rises from the bottom of the alkali scrubber tower, part of the tail gas is recovered at the bottom, 2 sets of the system share one alkali scrubber tank, and the alkali scrubber circulation liquid in the alkali scrubber, the tail gas which is not recovered and the alkaline washing circulating liquid at the top are subjected to countercurrent recovery, trace incondensable gas enters a chimney from the top of the tower and is discharged after reaching standards at high altitude, the alkaline washing circulating liquid in the alkaline washing tower is automatically supplemented by an alkaline washing tank through an alkaline washing pump according to the pH value of the alkaline washing liquid in the alkaline washing tank, hydrofluoric acid of a hydrofluoric acid system can be pumped into the tops of four washing towers through an HF recovery 1# washing pump, and when the negative pressure of the system is abnormal, a hydrofluoric acid valve at the top of the washing tower with abnormal negative pressure is opened to dredge a pipeline.
The invention has the following beneficial effects:
the invention adopts the tail gas treatment process of four-stage water washing and one-stage alkali washing to be applied to the fluosilicic acid recovery system, namely, the usage amount of tap water is reduced, the water washing and alkali washing systems are easier to operate, the fluosilicic acid concentration is controlled stably, the negative pressure of a hydrogen fluoride production system is easier to control, the production load is stable, the yield of hydrogen fluoride is improved, and the problem of environmental pollution is solved.
Drawings
FIG. 1 is a simplified diagram of the process of the present invention;
as shown in the figure: the system comprises a rinsing bath 1, a # 1 rinsing tower 2, a # 1 rinsing pump 3, a circulating cooler 4, a # 2 rinsing tower 5, a # 2 rinsing pump 6, a # 3 rinsing tower 7, a # 3 rinsing pump 8, a # 4 rinsing tower 9, a # 4 rinsing pump 10, an alkaline washing tower 11, an alkaline washing bath 12, an alkaline washing pump 13, a tail gas fan 14, an alkali supplementing pump 15, an alkaline tank 16 and an HF recovery # 1 rinsing pump 17.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
A system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process adopts a tail gas treatment process of four-stage water washing and first-stage alkali washing, and comprises a water washing tank 1, a # 1 water washing tower 2, a # 1 water washing pump 3, a circulating cooler 4, a # 2 water washing tower 5, a # 2 water washing pump 6, a # 3 water washing tower 7, a # 3 water washing pump 8, a # 4 water washing tower 9, a # 4 water washing pump 10, an alkali washing tower 11, an alkali washing tank 12, an alkali washing pump 13, a tail gas fan 14, an alkali supplementing pump 15, an alkali tank 16 and a HF recovery # 1 water washing pump 17, wherein the bottom 2 of the # 1 water washing tower is connected with the water washing tank 1, the bottom of the water washing tank 1 is connected with the # 1 water washing pump 3 through an outlet pipeline, and the outlet material of the # 1 water washing pump 3 is respectively connected with the top of the # 1 water washing tower 2 and a fluo; the washing liquid in the washing tank 1 is pumped to a feeding pipeline at the bottom of a circulating cooler 4 through a No. 1 washing pump 3, the circulating cooler 4 is cooled by circulating water, the circulating water enters from the top of the circulating cooler 4 and is in countercurrent contact with the washing liquid rising at the bottom, the temperature of the washing liquid is reduced, the washing tank 1 is provided with a thermometer, the cooling water quantity of the circulating cooler 4 is adjusted, and the temperature of the washing liquid in the washing tank 1 is controlled within a certain process range; the washing tank 1 is respectively connected with the bottom of the circulating cooler 4 and the top of the No. 1 washing tower 2 through a No. 1 washing pump 3; the water washing liquid in the No. 2 water washing tower 5 overflows to a feeding pipeline of a No. 1 water washing pump 3 through an overflow pipe; unabsorbed gas enters the bottom of a No. 2 water scrubber 5 from the top of a No. 1 water scrubber 2, enters the bottom of a No. 3 water scrubber 7 from the top of the No. 2 water scrubber 5, enters the bottom of a No. 4 water scrubber 9 from the top of the No. 3 water scrubber 7, enters the bottom of an alkaline tower 11 from the top of the No. 4 water scrubber 9, and is discharged from a tail gas fan 14 connected with the top of the alkaline tower 11; the bottom of the No. 2 water washing tower 5 and the bottom of the No. 3 water washing tower 7 are connected with the upper part of the No. 2 water washing tower 5 through a No. 2 water washing pump 6; the bottom of the No. 3 water washing tower 7 and the bottom of the No. 4 water washing tower 9 are connected with the upper part of the No. 3 water washing tower 7 through a No. 3 water washing pump 8; the bottom of the No. 4 water washing tower 9 is connected with the upper part of the No. 4 water washing tower 9 through a No. 4 water washing pump 10; a tap water replenishing pipeline is arranged at the top of the No. 4 water washing tower 9 and is connected with tap water, a flow meter is arranged on the tap water replenishing pipeline, a fluosilicic acid concentration meter is arranged in the washing tank 1, the tap water replenishing water quantity is adjusted according to the concentration displayed by the fluosilicic acid concentration meter, and the concentration of fluosilicic acid in the washing tank 1 is controlled within a specified range; an alkali supplementing pipeline is arranged at the top of the alkaline washing tower 11, liquid alkali in an alkali tank 16 is pumped to the top of the alkaline washing tank 12 through an alkali supplementing pump 15, a flow meter is arranged on the alkali supplementing pipeline, the alkali supplementing amount is controlled within a specified range, and alkaline washing liquid in the alkaline washing tank 12 is pumped to the top of the alkaline washing tower 11 through an alkaline washing pump 13; part of the alkaline washing liquid in the alkaline washing tank 12 is pumped to the top of the alkaline washing tower 11 through an alkaline washing pump 15, part of the alkaline washing liquid is pumped to a sewage collecting tank, and the alkaline washing liquid in the alkaline washing tower 11 automatically flows to the alkaline washing tank 12 through the bottom; 2# water scrubber 5, 3# water scrubber 7 and 4# water scrubber 9 top are equipped with the hydrofluoric acid pipeline, retrieve 1# rinsing pump 17 outlet line with HF respectively and link to each other, when 2# water scrubber 5, 3# water scrubber 7 and 4# water scrubber 9 negative pressure are not normal, open this hydrofluoric acid pipeline valve, wash 2# water scrubber 5, 3# water scrubber 7 and 4# water scrubber 9, after 2# water scrubber 5, 3# water scrubber 7 and 4# water scrubber 9 negative pressure is normal, close this hydrofluoric acid pipeline valve.
Hydrofluoric acid pipelines are respectively used at the tops of the four-stage water washing towers, and when the negative pressure of the water washing towers is abnormal, valves of the hydrofluoric acid pipelines at the tops of the corresponding water washing towers are opened to flush the water washing towers, so that the negative pressure of a production system is stable, and the negative pressure is ensured not to influence the production load; the water replenishing of the fourth-stage water washing tower is realized by adopting a 4# water washing tower 9, and a flow meter is arranged on a water replenishing pipeline, so that the concentration of the recovered fluosilicic acid is easy to control.
Pall ring plastic packing is arranged in the No. 1 water washing tower 2, the No. 2 water washing tower 5, the No. 3 water washing tower 7 and the No. 4 water washing tower 9, the top spraying liquid is fully contacted with the ascending gas in the counter-current manner in the packing layer in the top-down spraying process, and partial silicon tetrafluoride gas is hydrolyzed with water or reacts with hydrofluoric acid to generate fluosilicic acid solution.
The gas inlet pipelines at the bottoms of the No. 1 water scrubber 2, the No. 2 water scrubber 5, the No. 3 water scrubber 7, the No. 4 water scrubber 9 and the alkaline washing tower 11 are provided with thermometers, so that whether the gas inlet pipelines are blocked by crystallisates or not can be known in time.
The alkaline tower 11 absorbs the gas in the alkaline tower 11 by adopting a mode of spraying liquid caustic soda and spraying alkaline wash liquid on the top, the absorption effect is good, and the fluorine content of the gas out of the alkaline tower 11 is reduced.
The washing tank 1 is provided with an emptying pipeline, the emptying pipeline is connected with a gas inlet pipeline at the bottom of the No. 1 washing tower 2, and the washing tank 1 is prevented from being overhigh in pressure; the washing tank 1 is provided with a liquid level meter, washing liquid in the washing tank 1 is pumped to a fluosilicic acid removing storage tank through a No. 1 washing pump 3, a liquid level regulating valve is arranged on a pipeline of the fluosilicic acid removing storage tank, and the liquid level of the washing tank 1 is controlled within a certain range; the washing tank 1 is also provided with a fluosilicic acid remote transmission concentration meter, so that the concentration of fluosilicic acid can be known in time conveniently, and the pipeline is prevented from being blocked by the crystals with too high fluosilicic acid concentration; the washing tank 1 is also provided with a thermometer so as to conveniently know whether the air inlet pipeline of the No. 1 washing tower is smooth or not and analyze the absorption efficiency.
A PH meter is arranged in the alkaline washing tank 12, a flowmeter and a flow regulating valve are arranged in an alkaline supplementing pipeline of the alkaline supplementing pump 15 and the alkaline supplementing tank 12, the flow regulating valve on the alkaline supplementing pipeline is matched with the PH meter in the alkaline washing tank 12, and the PH value of the alkaline washing liquid in the alkaline washing tank 12 is controlled within a specified range; the alkaline washing tank 12 is provided with a liquid level meter, a liquid level regulating valve is arranged on a pipeline between the alkaline washing pump 13 and the alkaline washing tank 12, the liquid level regulating valve is matched with the liquid level meter in the alkaline washing tank 12, and the liquid level of the alkaline washing tank 12 is controlled within a specified range.
The alkali supplementing and water supplementing pipeline of the alkali tank 16 is provided with a flowmeter, liquid alkali and tap water are blended according to the proportion of 1:3, the concentration of the liquid alkali in the alkali tank 16 is controlled, the phenomenon that the concentration of the liquid alkali is too high, the liquid alkali is crystallized due to the fact that the concentration of sodium sulfite is too high in the process of spraying from the top of the alkali tower 11 and the alkali wash in the alkali wash tank 12, pipelines are blocked, and the normal operation of an alkali wash system is influenced is prevented; the caustic tank 16 is equipped with a remote liquid level to prevent liquid flooding.
In the HF production, the non-condensable gas discharged in the crude product condensation and refining process contains a small amount of waste gas such as SO2, SiF4, HF and the like, is sucked into the bottom of a sulfuric acid absorption tower under the action of a plastic fan in a negative pressure manner, and is absorbed and cooled in a countercurrent manner with sulfuric acid from the top in the tower, the unabsorbed SO2, SiF4 and HF gas enter the bottom of a No. 1 water scrubber 2 and are absorbed by top spray liquid, the absorption liquid in a water scrubber 1 is pumped to the top of the No. 1 water scrubber 2 by a No. 1 water scrubber pump 3, the gas which is not recovered at the bottom of the tower rises through the bottom of the tower and is absorbed in a countercurrent manner with the absorption liquid at the top, the unabsorbed SO2, SiF4, HF gas and the like enter the bottom of a No. 2 water scrubber 5 from the top of the No. 1 water scrubber 2, the low-concentration absorption liquid in the No. 2 enters the No. 1 water scrubber 2 through an overflow pipe, the circulating absorption liquid in the 1 water scrubber 2, the redundant absorption liquid is pumped into a fluosilicic acid storage tank through a No. 1 water washing pump 3 to form a circulating absorption system, the non-condensable gas entering the bottom of a No. 2 water washing tower 5 is recovered by the absorption liquid in the tower, the absorption liquid in the tower is pumped to the top of the tower through a No. 2 water washing pump 6, the gas which is not recovered at the bottom of the tower rises through the bottom of the tower, the gas such as SO2, SiF4 and HF which is not absorbed completely enters the bottom of a No. 3 water washing tower 7 from the top, and the absorption liquid in the No. 2 water washing tower 5 is supplemented by the water overflow of the absorption liquid with the concentration at the bottom of the No. 3 water washing tower 7; by analogy, the non-condensable gas entering the 3# water scrubber 7 rises from the bottom of the tower, the absorption liquid pumped to the top of the tower by the 3# water scrubber 8 is subjected to countercurrent absorption, the non-absorbed gases such as SO2, SiF4 and HF are fed from the top of the 3# water scrubber 7 to the bottom of the 4# water scrubber 9, the absorption liquid in the 3# water scrubber 7 is replenished by overflowing of the absorption liquid with the concentration at the bottom of the 4# water scrubber 9, the non-condensable gas entering the 4# water scrubber 9 rises from the bottom of the tower, the absorption liquid pumped to the top of the tower by the 4# water scrubber 10 is subjected to countercurrent absorption, the non-absorbed gases such as SO2, SiF4 and HF are fed from the top of the 4# water scrubber 9 to the bottom of the alkaline scrubber 11, the absorption liquid in the 4# water scrubber 9 controls the addition amount of tap water according to the concentration of fluosilicic acid in the water scrubber 1, the tail gas entering the alkaline scrubber 11 rises from the bottom of the alkaline scrubber 11, part of the tail gas is recovered at the bottom, and the 2-in-, the caustic wash circulating liquid of the caustic wash tank 12 is pumped to the top by the caustic wash pump 13, the unrecovered tail gas and the caustic wash circulating liquid at the top are subjected to countercurrent recovery, trace incondensable gas enters a chimney from the top of the tower and is discharged at high altitude, the caustic wash circulating liquid in the caustic wash tower 11 is automatically supplemented by the caustic wash tank 11 through the caustic wash pump 13 according to the PH value of the caustic wash liquid in the caustic wash tank 11, hydrofluoric acid of a hydrofluoric acid system can be pumped into the tops of the four water wash towers through the HF recovery 1# water wash pump 17, and when the negative pressure of the system is abnormal, a hydrofluoric acid valve at the top of the water wash tower with abnormal negative pressure is opened to dredge a pipeline.
When an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on or indirectly connected to the other element, or when an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.
The terms of orientation such as left, right, up, down, etc. in the present embodiment are only relative concepts or reference to the normal use state of the product, and should not be considered as limiting.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (9)
1. A system for preparing fluosilicic acid by utilizing tail gas in the production process of hydrogen fluoride is characterized in that: the tail gas treatment process adopting four-stage water washing and one-stage alkali washing comprises a water washing tank, a 1# water washing tower, a 1# water washing pump, a circulating cooler, a 2# water washing tower, a 2# water washing pump, a 3# water washing tower, a 3# water washing pump, a 4# water washing tower, a 4# water washing pump, an alkali washing tower, an alkali washing tank, an alkali washing pump, a tail gas fan, an alkali supplementing pump, an alkali tank and a HF recovery 1# water washing pump, wherein the bottom of the 1# water washing tower is connected with the water washing tank, the bottom of the water washing tank is connected with the 1# water washing pump through an outlet pipeline, and the outlet material of the 1# water washing pump is respectively connected with the top of the 1# water washing tower and a fluosilicic acid storage tank; the method comprises the following steps that water washing liquid in a water washing tank is pumped to a feeding pipeline at the bottom of a circulating cooler through a No. 1 water washing pump, the circulating cooler is cooled by circulating water, the circulating water enters from the top of the circulating cooler and is in countercurrent contact with the water washing liquid rising from the bottom, the temperature of the water washing liquid is reduced, a thermometer is arranged in the water washing tank, the cooling water quantity of the circulating cooler is adjusted, and the temperature of the water washing liquid in the water washing tank is controlled within a certain process range; the washing tank is respectively connected with the bottom of the circulating cooler and the top of the No. 1 washing tower through a No. 1 washing pump; the water washing liquid in the No. 2 water washing tower overflows to a No. 1 water washing pump feeding pipeline through an overflow pipe; unabsorbed gas enters the bottom of a No. 2 water scrubber from the top of the No. 1 water scrubber, enters the bottom of a No. 3 water scrubber from the top of the No. 2 water scrubber, enters the bottom of a No. 4 water scrubber from the top of the No. 3 water scrubber, enters the bottom of an alkaline washing tower from the top of the No. 4 water scrubber, and is discharged from a tail gas fan connected with the top of the alkaline washing tower; the bottom of the No. 2 washing tower and the bottom of the No. 3 washing tower are connected with the upper part of the No. 2 washing tower through a No. 2 washing pump; the bottom of the 3# water washing tower and the bottom of the 4# water washing tower are connected with the upper part of the 3# water washing tower through a 3# water washing pump; the bottom of the No. 4 water washing tower is connected with the upper part of the No. 4 water washing tower through a No. 4 water washing pump; a tap water replenishing pipeline is arranged at the top of the No. 4 water washing tower and is connected with tap water, a flow meter is arranged on the tap water replenishing pipeline, a fluosilicic acid concentration meter is arranged in the washing tank, the tap water replenishing water quantity is adjusted according to the concentration displayed by the fluosilicic acid concentration meter, and the concentration of fluosilicic acid in the washing tank is controlled within a specified range; an alkali supplementing pipeline is arranged at the top of the alkali washing tower, liquid alkali in the alkali tank is pumped to the top of the alkali washing tank through an alkali supplementing pump, a flow meter is arranged on the alkali supplementing pipeline, the alkali supplementing amount is controlled within a specified range, and alkali washing liquid in the alkali washing tank is pumped to the top of the alkali washing tower through an alkali washing pump; part of the alkaline washing liquid in the alkaline washing tank is pumped to the top of the alkaline washing tower through an alkaline washing pump, part of the alkaline washing liquid is pumped to the sewage collecting tank, and the alkaline washing liquid in the alkaline washing tower automatically flows to the alkaline washing tank through the bottom; 2# washing tower, 3# washing tower and 4# washing tower top are equipped with the hydrofluoric acid pipeline, retrieve 1# washing pump outlet line respectively with HF and link to each other, when 2# washing tower, 3# washing tower and 4# washing tower negative pressure are unusual, open this hydrofluoric acid pipeline valve, wash 2# washing tower, 3# washing tower and 4# washing tower, after 2# washing tower, 3# washing tower and 4# washing tower negative pressure are normal, close this hydrofluoric acid pipeline valve.
2. The system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process according to claim 1, characterized in that: hydrofluoric acid pipelines are respectively used at the tops of the four-stage water washing towers, and when the negative pressure of the water washing towers is abnormal, valves of the hydrofluoric acid pipelines at the tops of the corresponding water washing towers are opened to flush the water washing towers, so that the negative pressure of a production system is stable, and the negative pressure is ensured not to influence the production load; the water replenishing of the four-stage water washing tower is realized by adopting a 4# water washing tower, and a flow meter is arranged on a water replenishing pipeline, so that the concentration of the recovered fluosilicic acid is easy to control.
3. The system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process according to claim 1, characterized in that: pall ring plastic packing is arranged in the No. 1 water washing tower, the No. 2 water washing tower, the No. 3 water washing tower and the No. 4 water washing tower, the top spraying liquid is in full contact with the ascending gas in a countercurrent mode in the packing layer in the top-down spraying process, and part of silicon tetrafluoride gas is hydrolyzed with water or reacts with hydrofluoric acid to generate fluosilicic acid solution.
4. The system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process according to claim 1, characterized in that: the gas inlet pipeline at the bottom of the No. 1 water washing tower, the No. 2 water washing tower, the No. 3 water washing tower, the No. 4 water washing tower and the alkaline washing tower is provided with a thermometer, so that whether the gas inlet pipeline is blocked by the crystallisate or not can be known in time.
5. The system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process according to claim 1, characterized in that: the alkaline tower absorbs gas in the alkaline tower by adopting a mode of spraying liquid caustic soda and spraying alkaline wash liquid on the top, the absorption effect is good, and the fluorine-containing content of the gas out of the alkaline tower is reduced.
6. The system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process according to claim 1, characterized in that: the washing tank is provided with an emptying pipeline, the emptying pipeline is connected with a gas inlet pipeline at the bottom of the No. 1 washing tank, and the washing tank is prevented from being overhigh in pressure; the washing tank is provided with a liquid level meter, washing liquid in the washing tank is pumped to a fluosilicic acid removing storage tank through a No. 1 washing pump, a liquid level regulating valve is arranged on a pipeline of the fluosilicic acid removing storage tank, and the liquid level of the washing tank is controlled within a certain range; the washing tank is also provided with a fluosilicic acid remote transmission concentration meter, so that the concentration of fluosilicic acid can be known in time conveniently, and the pipeline is prevented from being blocked by the crystals with too high fluosilicic acid concentration; the water washing tank is also provided with a thermometer so as to conveniently know whether the air inlet pipeline of the No. 1 water washing tower is smooth or not and analyze the absorption efficiency.
7. The system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process according to claim 1, characterized in that: the alkaline washing tank is provided with a PH meter, the alkaline supply pump and an alkaline supply pipeline of the alkaline washing tank are provided with a flowmeter and a flow regulating valve, the flow regulating valve on the alkaline supply pipeline is matched with the PH meter in the alkaline washing tank, and the PH value of alkaline washing liquid in the alkaline washing tank is controlled within a specified range; the alkaline washing tank is provided with a liquid level meter, a liquid level regulating valve is arranged on a pipeline between the alkaline washing pump and the alkaline washing tank, the liquid level regulating valve is matched with the liquid level meter in the alkaline washing tank, and the liquid level of the alkaline washing tank is controlled within a specified range.
8. The system for preparing fluosilicic acid by utilizing tail gas in the hydrogen fluoride production process according to claim 1, characterized in that: flowmeters are arranged on alkali supplementing and water supplementing pipelines of the alkali tank, liquid alkali and tap water are blended according to the proportion of 1:3, the concentration of the liquid alkali in the alkali tank is controlled, the phenomenon that the concentration of the liquid alkali is too high, the liquid alkali is sprayed from the top of an alkali washing tower, and alkali washing liquid in an alkali washing tank is crystallized due to the too high concentration of sodium sulfite, so that the pipeline is blocked, and the normal operation of an alkali washing system is influenced; the alkali tank is provided with a remote liquid level to prevent liquid overflow.
9. The system for preparing fluosilicic acid by utilizing the tail gas in the hydrogen fluoride production process according to any one of claims 1 to 8, characterized in that: in the HF production, the non-condensable gas discharged in the crude product condensation and refining process contains a small amount of waste gas such as SO2, SiF4, HF and the like, and is sucked into the bottom of a sulfuric acid absorption tower under the action of a plastic fan in a negative pressure manner, the waste gas and the sulfuric acid which falls from the top are absorbed and cooled in a countercurrent manner in the tower, the gas such as SO2, SiF4 and HF which are not absorbed enters the bottom of a No. 1 water washing tower and is absorbed by top spray liquid, the absorption liquid of a washing tank is pumped to the top of the No. 1 water washing tower by a No. 1 water washing pump, the gas which is not recovered at the bottom of the No. 1 water washing tower rises from the bottom of the tower and is absorbed in a countercurrent manner with the absorption liquid at the top, the gas such as SO2, SiF4 and HF which are not absorbed enters the bottom of the No. 2 water washing tower from the top of the No. 1 water washing tower, the low-concentration absorption liquid in the No. 2 water washing tower enters the No. 1 water washing tower, forming a circulating absorption system, recovering the non-condensable gas entering the bottom of the No. 2 water washing tower by absorption liquid in the tower, pumping the absorption liquid in the tower to the top of the tower by a No. 2 water washing pump, enabling the gas which is not recovered at the bottom of the tower to rise through the bottom of the tower, enabling the gas such as SO2, SiF4, HF and the like which is not absorbed to enter the bottom of the No. 3 water washing tower from the top, and enabling the absorption liquid in the No. 2 water washing tower to be supplemented by the water overflow of the absorption liquid with the concentration at the bottom of the No. 3 water washing; by analogy, the non-condensable gas entering the 3# water scrubber rises from the bottom of the tower, the gas such as SO2, SiF4 and HF which is not absorbed enters the bottom of the 4# water scrubber from the top of the 3# water scrubber, the absorption liquid in the 3# water scrubber overflows from the absorption liquid water with the concentration of the bottom of the 4# water scrubber, the non-condensable gas entering the 4# water scrubber rises from the bottom of the tower, the absorption liquid which is pumped to the top of the tower by the 4# water scrubber is subjected to countercurrent absorption, the gas such as SO2, SiF4 and HF which is not absorbed enters the bottom of the alkali scrubber from the top of the 4# water scrubber, the addition amount of tap water is controlled by the absorption liquid in the 4# water scrubber according to the concentration of fluosilicic acid in the water scrubber, the tail gas entering the alkali scrubber rises from the bottom, part of the tail gas is recovered at the bottom, 2 sets of systems share one alkali scrubber, and the alkali washing circulating liquid in the alkali scrubber is pumped to the top by the alkali scrubber, the tail gas which is not recovered and the alkaline washing circulating liquid at the top are subjected to countercurrent recovery, trace incondensable gas enters a chimney from the top of the tower and is discharged after reaching standards at high altitude, the alkaline washing circulating liquid in the alkaline washing tower is automatically supplemented by an alkaline washing tank through an alkaline washing pump according to the pH value of the alkaline washing liquid in the alkaline washing tank, hydrofluoric acid of a hydrofluoric acid system can be pumped into the tops of four washing towers through an HF recovery 1# washing pump, and when the negative pressure of the system is abnormal, a hydrofluoric acid valve at the top of the washing tower with abnormal negative pressure is opened to dredge a pipeline.
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