Device and process for directly preparing sulfuric acid and hydrofluoric acid from rare earth concentrate roasting tail gas

Abstract

The invention discloses a device for directly preparing sulfuric acid and hydrofluoric acid from rare earth concentrate roasting tail gas, which is characterized by comprising an absorption tower, a spray tower, a heat exchanger and a delivery pump, the lower parts of the absorption tower and the spray tower are respectively provided with a tail gas inlet, a circulating water inlet and a circulating water outlet, and the top is provided with an exhaust port; the upper part of the absorption tower is provided with a concentrated sulfuric acid inlet and a concentrated sulfuric acid outlet, an exhaust port of the absorption tower is connected with a tail gas inlet of the spray tower through a gas pipeline, and respective feed liquid outlets of the absorption tower and the spray tower are respectively connected with a heat exchanger and a delivery pump through feed liquid pipelines; and a circulating water outlet and a circulating water inlet of the heat exchanger are respectively connected with a circulating drainage pipeline and a circulating water supply pipeline through circulating pipelines. The invention further discloses a process for directly preparing sulfuric acid and hydrofluoric acid from the rare earth concentrate roasting tail gas. The hydrofluoric acid of sulfuric acid in the rare earth concentrate roasting tail gas can be directly separated and recycled, and the whole technological process is shortened.

Description

Technical Field

[0001] The invention belongs to the field of rare earth concentrate roasting tail gas treatment, and specifically relates to a device and a process for directly preparing sulfuric acid and hydrofluoric acid from rare earth concentrate roasting tail gas. Background Art

[0002] Currently, rare earth concentrate is decomposed by roasting with concentrated sulfuric acid. Since rare earth concentrate contains a certain amount of fluorine, silicon and other elements, the tail gas after the reaction of rare earth concentrate and concentrated sulfuric acid at high temperature contains a large amount of mixed acidic gas of fluorine, silicon and sulfur.

[0003] like Figure 1 The figure shows a process flow chart of rare earth concentrate roasting tail gas treatment in the prior art.

[0004] The first-stage spray tower T201, the second-stage spray tower T202, the third-stage spray tower T203, the fourth-stage spray tower T204 and the purification tower T205 are connected in series. The circulating water pipeline of the first-stage spray tower T201 is provided with a first-stage heat exchanger E201, a first-stage spray tower delivery pump P201A and a first-stage spray tower standby pump P201B. The circulating water pipeline of the second-stage spray tower T202 is provided with a second-stage heat exchanger E202, a second-stage spray tower delivery pump P202A and a second-stage spray tower standby pump P202B. The circulating water pipeline of the three-stage spray tower T203 is equipped with a three-stage heat exchanger E203, a three-stage spray tower delivery pump P203A, and a three-stage spray tower standby pump P203B. The circulating water pipeline of the four-stage spray tower T204 is equipped with a four-stage heat exchanger E204, a four-stage spray tower delivery pump P204A, and a four-stage spray tower standby pump P204B. The circulating water pipeline of the purification tower T205 is equipped with a purification tower heat exchanger E205, a purification tower delivery pump P205A, and a purification tower standby pump P205B. The tail gas enters from the primary spray tower T201, is discharged from the purification tower T205 and enters the desulfurization and acid-making section. After the tail gas is sprayed with four-stage countercurrent circulating water, the spray liquid is enriched in the primary spray tower T201. At this time, the concentration of waste acid in the spray liquid is about 40%. The waste acid passes through the evaporation section again to separate the sulfuric acid and hydrofluoric acid in the waste acid, and the sulfuric acid with a mass percentage concentration of 65% is returned to the roasting section to continue roasting the rare earth concentrate.

[0005] Since the waste acid is a mixture of hydrofluoric acid and sulfuric acid, it is extremely corrosive, and the corrosion resistance of the evaporation separation equipment is required to be high, resulting in a high equipment failure rate, high processing costs, and low automation. In addition, when the sulfur dioxide and sulfur trioxide content in the tail gas fluctuates, the fluoride ion concentration in the primary spray tower and the secondary spray tower is unstable, which has a great impact on the stable operation of the evaporation separation section; at the same time, the on-site operating environment of the evaporation section is poor. Once the pipeline or equipment leaks, it poses a great threat to the safety of on-site operators. Summary of the invention

[0006] The object of the present invention is to provide a device and process for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting, which can directly separate and recover the sulfuric acid and hydrofluoric acid in the tail gas of rare earth concentrate roasting, remove the subsequent acid distillation section of the existing tail gas treatment process, and shorten the overall process flow.

[0007] To achieve the above objectives, the technical solutions used in the present invention are:

[0008] The device for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of roasting rare earth concentrate is characterized in that it comprises: an absorption tower, a spray tower, a heat exchanger, and a delivery pump. The lower parts of the absorption tower and the spray tower are respectively provided with a tail gas inlet, a circulating water inlet, and a circulating water outlet, and the top is provided with an exhaust port; the upper part of the absorption tower is provided with a concentrated sulfuric acid inlet and a concentrated sulfuric acid outlet, the exhaust port of the absorption tower is connected to the tail gas inlet of the spray tower through a gas pipeline, the respective liquid outlets of the absorption tower and the spray tower are respectively connected to the heat exchanger and the delivery pump through the liquid pipeline, and the circulating water outlet and the circulating water inlet of the heat exchanger are respectively connected to the circulating drainage pipeline and the circulating water supply pipeline through the circulating pipeline.

[0009] Furthermore, multiple absorption towers for collecting sulfur trioxide are connected in series to spray concentrated sulfuric acid in reverse direction; multiple spray towers for collecting hydrofluoric acid are connected in series to spray spray water in reverse direction.

[0010] Furthermore, the absorption tower includes: a primary absorption tower and a secondary absorption tower. The tail gas enters the primary absorption tower and enters the secondary absorption tower after coming out of the primary absorption tower; the concentrated sulfuric acid that absorbs sulfur trioxide enters the primary absorption tower after coming out of the secondary absorption tower. The feed liquid outlets of the primary absorption tower and the secondary absorption tower are respectively connected to heat exchangers and delivery pumps through feed liquid pipelines.

[0011] Furthermore, the spray tower includes: a first-level spray tower, a second-level spray tower, a third-level spray tower, and a fourth-level spray tower; the tail gas coming out of the second-level absorption tower enters the first-level spray tower, the second-level spray tower, the third-level spray tower, and the fourth-level spray tower in sequence, and the spray water flows through the fourth-level spray tower, the third-level spray tower, the second-level spray tower, and the first-level spray tower in sequence, and the feed liquid outlets of the first-level spray tower, the second-level spray tower, the third-level spray tower, and the fourth-level spray tower are respectively connected to heat exchangers and delivery pumps through feed liquid pipelines.

[0012] Furthermore, the absorption tower includes: a primary absorption tower and a secondary absorption tower; the spray tower includes: a primary spray tower, a secondary spray tower, a third spray tower and a fourth spray tower; the heat exchanger includes: a primary heat exchanger, a secondary heat exchanger, a third heat exchanger, a fourth heat exchanger and a fifth heat exchanger; the delivery pump includes: a primary sulfuric acid pump, a primary backup sulfuric acid pump, a secondary sulfuric acid pump, a secondary backup sulfuric acid pump, a primary spray pump, a primary backup spray pump, a secondary spray pump, a secondary backup spray pump, a third spray pump, a third backup spray pump, a fourth spray pump and a fourth backup spray pump; a concentrated sulfuric acid inlet and a concentrated sulfuric acid outlet are arranged at the top of the secondary absorption tower, and the exhaust port of the primary absorption tower is connected to the tail gas inlet of the secondary absorption tower through a gas pipeline. The feed liquid outlet of the secondary absorption tower is connected to the feed liquid inlet of the primary heat exchanger through a feed liquid pipeline, the secondary sulfuric acid pump and the secondary standby sulfuric acid pump connected in parallel are connected to the feed liquid inlet of the primary heat exchanger, the feed liquid outlet of the primary heat exchanger is connected to the feed liquid inlet of the primary absorption tower through a feed liquid pipeline, the feed liquid outlet of the primary absorption tower is connected to the feed liquid inlet of the secondary heat exchanger through a feed liquid pipeline, the feed liquid outlet of the secondary heat exchanger outputs concentrated sulfuric acid, the primary sulfuric acid pump and the primary standby sulfuric acid pump connected in parallel are arranged at the feed liquid inlet and outlet of the secondary heat exchanger; the exhaust port of the primary spray tower is connected to the tail gas inlet of the secondary spray tower through a gas pipeline, the exhaust port of the secondary spray tower is connected to the tail gas inlet of the tertiary spray tower through a gas pipeline, and the tertiary spray tower is connected to the tail gas inlet of the tertiary spray tower through a gas pipeline. The exhaust port of the spray tower is connected to the tail gas inlet of the four-stage spray tower through a gas pipeline; the liquid outlet of the four-stage spray tower is connected to the liquid inlet of the three-stage spray tower through a liquid pipeline, and the four-stage spray pump and the four-stage standby spray pump in parallel are connected to the liquid outlet of the four-stage spray tower. The tail gas discharged from the exhaust port of the four-stage spray tower is recycled to the desulfurization and acid production section, and the liquid inlet of the four-stage spray tower is used to add steam condensate; the liquid outlet of the three-stage spray tower is connected to the liquid inlet of the five-stage heat exchanger through a liquid pipeline, and the three-stage spray pump and the three-stage standby spray pump in parallel are connected to the liquid outlet of the three-stage spray tower. The liquid outlet of the five-stage heat exchanger is connected to the liquid inlet of the two-stage spray tower through a liquid pipeline; the liquid of the two-stage spray tower The outlet is connected to the liquid inlet of the four-stage heat exchanger through a liquid pipeline, the liquid outlet of the four-stage heat exchanger is connected to the liquid inlet of the first-stage spray tower through a liquid pipeline, and the parallel second-stage spray pump and the second-stage standby spray pump are connected to the liquid inlet of the four-stage heat exchanger; the liquid outlet of the first-stage spray tower is connected to the liquid inlet of the three-stage heat exchanger through a liquid pipeline, the liquid outlet of the three-stage heat exchanger is used to discharge the collected hydrofluoric acid, and the parallel first-stage spray pump and the first-stage standby spray pump are connected to the liquid inlet of the three-stage heat exchanger; the circulating water outlet and the circulating water inlet of the first-stage heat exchanger, the second-stage heat exchanger, the third-stage heat exchanger, the fourth-stage heat exchanger and the fifth-stage heat exchanger are respectively connected to the circulating drainage pipeline and the circulating water supply pipeline through the circulating pipeline.

[0013] The process for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting includes:

[0014] The tail gas from the roasting of rare earth concentrate enters the absorption tower, concentrated sulfuric acid is added to the absorption tower, and the concentrated sulfuric acid is used to absorb the sulfur trioxide in the tail gas. The tail gas without sulfur trioxide enters the spray tower;

[0015] The tail gas is sprayed with countercurrent water in the spray tower, and the spray water absorbs the hydrogen fluoride and silicon tetrafluoride in the tail gas and converts them into hydrofluoric acid.

[0016] Preferably, the absorption tower comprises: a primary absorption tower and a secondary absorption tower, the tail gas from the roasting of the rare earth concentrate enters from the tail gas inlet of the secondary absorption tower, and the tail gas from the secondary absorption tower enters the tail gas inlet of the primary absorption tower; the primary absorption tower and the secondary absorption tower both use concentrated sulfuric acid with a mass percentage concentration of 98% to spray the tail gas, and the sulfuric acid concentration after spraying is controlled by controlling the amount of 98% sulfuric acid added, the sulfuric acid concentration after spraying of the secondary absorption tower is controlled, the sulfuric acid after spraying is cooled by the primary heat exchanger and then transported to the primary absorption tower for spraying through the secondary sulfuric acid pump / secondary standby sulfuric acid pump, the sprayed sulfuric acid is cooled by the secondary heat exchanger and then discharged through the primary sulfuric acid pump / primary standby sulfuric acid pump and reused to the calcination section.

[0017] Preferably, the spray water is enriched with hydrofluoric acid by circulating spraying, and hydrofluoric acid is used as a by-product, and sulfur dioxide gas in the tail gas enters the desulfurization and acid-making process section.

[0018] Preferably, by controlling the amount of 98% sulfuric acid added, gases such as hydrogen fluoride and silicon tetrafluoride in the tail gas are converted into hydrofluoric acid, so that the sulfur element and the fluorine element in the tail gas are separated, thereby achieving the separation of sulfuric acid and hydrofluoric acid.

[0019] Preferably, the spray tower includes: a primary spray tower, a secondary spray tower, a tertiary spray tower, and a quaternary spray tower; the tail gas enters the primary spray tower T401 after being absorbed by sulfur trioxide, and this stage adopts waste acid spraying, the waste acid comes from the secondary spray tower, the hydrofluoric acid concentration is controlled at a mass percentage concentration of 12±5%, and the temperature is controlled at 90-95°C to obtain hydrofluoric acid; the tail gas enters the secondary spray tower through the primary spray tower, and performs secondary spraying, and this stage spraying adopts waste acid spraying, the waste acid comes from the tertiary spray tower, and the fluoride ion concentration is controlled at 105- 112g / L, the temperature is controlled at 80-85℃; the tail gas passes through the secondary spray tower and enters the tertiary spray tower for tertiary spraying. This stage of spraying adopts waste acid spraying, and the waste acid comes from the fourth spray tower. The fluoride ion concentration is controlled at 85-90g / L, and the temperature is controlled at 60-65℃; the tail gas passes through the third spray tower and enters the fourth spray tower for tertiary spraying. This stage of spraying adopts water spraying, and the water comes from the steam condensate in the desulfurization and acid production process. The fluoride ion concentration is controlled at 15-20g / L, and the temperature is controlled at 40-45℃.

[0020] The technical effects of the present invention include:

[0021] The process of the present invention treats the tail gas after high-temperature roasting of rare earth concentrate and concentrated sulfuric acid, which can remove the subsequent acid distillation stage of the existing tail gas treatment process, shorten the overall process flow, greatly reduce labor costs and production operation costs, and increase the stability of production process operation.

[0022] 1. The present invention can directly separate and recover sulfuric acid and hydrofluoric acid in the tail gas of rare earth concentrate roasting.

[0023] The sulfur trioxide component in the tail gas from the roasting of rare earth concentrate is directly absorbed by 98% sulfuric acid. By controlling the amount of 98% sulfuric acid added, the concentration of sulfuric acid after absorption is controlled at around 92%. The hydrogen fluoride, silicon tetrafluoride and other gases in the tail gas are converted into hydrofluoric acid. In this way, the sulfur element and the fluorine element in the tail gas are separated by spray absorption, thereby realizing the separation of sulfuric acid and hydrofluoric acid.

[0024] By adopting this process, even if the sulfur trioxide in the tail gas fluctuates greatly, it will be absorbed by 98% of the acid, and the unstable fluorine ion phenomenon in the spray towers at all levels will not occur, making the production operation more stable and the concentration of the output hydrofluoric acid and sulfuric acid more stable.

[0025] 2. Omit the waste acid evaporation section, simplify the process flow, improve the system operation stability, and greatly reduce the tail gas treatment operation cost.

[0026] By treating the tail gas after high-temperature roasting of rare earth concentrate and concentrated sulfuric acid, the subsequent acid distillation stage of the original tail gas treatment process is removed, the overall process flow is shortened, the labor cost and production operation cost are greatly reduced, and the stability of the production process operation is increased.

[0027] 3. Product quality is more stable.

[0028] By adopting this process, even if the sulfur trioxide in the tail gas fluctuates greatly, it will be absorbed by the 98% acid concentration, and the phenomenon of unstable fluorine ions in the spray towers at all levels will not occur. The content of fluorine ions and sulfate radicals in the absorption towers at all levels will be within a certain range, ensuring that the concentration of the produced sulfuric acid and hydrofluoric acid is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a process flow chart of rare earth concentrate roasting tail gas treatment in the prior art;

[0030] Figure 2 The present invention is a process flow chart for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting. DETAILED DESCRIPTION

[0031] The following description sufficiently illustrates specific embodiments of the invention to enable those skilled in the art to practice and reproduce the invention.

[0032] The device for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of roasting rare earth concentrate comprises: an absorption tower, a spray tower, a heat exchanger and a delivery pump; the lower parts of the absorption tower and the spray tower are respectively provided with a tail gas inlet, a circulating water inlet and a circulating water outlet, and the top is provided with an exhaust port, and the upper part of the absorption tower is provided with a concentrated sulfuric acid inlet and a concentrated sulfuric acid outlet; the exhaust port of the absorption tower is connected to the tail gas inlet of the spray tower through a gas pipeline, the respective liquid outlets of the absorption tower and the spray tower are connected to the liquid inlet of the heat exchanger through the liquid pipeline, and the circulating water outlet and the circulating water inlet of the heat exchanger are respectively connected to the circulating drainage pipeline and the circulating water supply pipeline through the circulating pipeline; the delivery pump is arranged on the liquid pipeline.

[0033] like Figure 2 The figure shows a process flow chart for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting in the present invention.

[0034] In the preferred embodiment, a two-stage absorption tower is used to spray and absorb sulfur trioxide in the tail gas, and the spray tower adopts a four-stage countercurrent water spray method to spray and absorb hydrogen fluoride and silicon tetrafluoride in the tail gas.

[0035] The absorption tower includes: the primary absorption tower T301, the secondary absorption tower T302; the spray tower includes: the primary spray tower T401, the secondary spray tower T402, the tertiary spray tower T403, the quaternary spray tower T404; the heat exchanger includes: the primary heat exchanger E301, the secondary heat exchanger E302, the tertiary heat exchanger E303, the quaternary heat exchanger E304, the quintuple heat exchanger E305; the delivery pump includes: the primary sulfuric acid pump P301A, first-level standby sulfuric acid pump P301B, second-level sulfuric acid pump P302A, second-level standby sulfuric acid pump P302B, first-level spray pump P401A, first-level standby spray pump P401B, second-level spray pump P402A, second-level standby spray pump P402B, third-level spray pump P403A, third-level standby spray pump P403B, fourth-level spray pump P404A, fourth-level standby spray pump P404B.

[0036] The two absorption towers for collecting sulfur trioxide are connected in series, and concentrated sulfuric acid is sprayed in reverse. The tail gas enters the primary absorption tower T301, and enters the secondary absorption tower T302 after coming out of the primary absorption tower T301; the concentrated sulfuric acid that absorbs sulfur trioxide enters the primary absorption tower T301 after coming out of the secondary absorption tower T302, and continues to absorb sulfur trioxide. The absorption tower includes: the primary absorption tower T301 and the secondary absorption tower T302. The upper part of the secondary absorption tower T302 is provided with a concentrated sulfuric acid inlet and a concentrated sulfuric acid outlet. The concentrated sulfuric acid inlet is used to inject concentrated sulfuric acid with a mass percentage concentration of 98%, and the concentrated sulfuric acid outlet is used to discharge concentrated sulfuric acid with a mass percentage concentration of 92.5%; the exhaust port of the primary absorption tower T301 is connected to the tail gas inlet of the secondary absorption tower T302 through a gas pipeline, and the liquid outlet of the secondary absorption tower T302 is connected to the liquid inlet of the primary heat exchanger E301 through a liquid pipeline. The parallel secondary sulfuric acid pump P302A and the secondary sulfuric acid pump P302A are connected to the secondary sulfuric acid pump P302A. The first-level standby sulfuric acid pump P302B is connected to the feed liquid inlet of the first-level heat exchanger E301, the feed liquid outlet of the first-level heat exchanger E301 is connected to the feed liquid inlet of the first-level absorption tower T301 through a feed liquid pipeline, the feed liquid outlet of the first-level absorption tower T301 is connected to the feed liquid inlet of the second-level heat exchanger E302 through a feed liquid pipeline, the feed liquid outlet of the second-level heat exchanger E302 outputs concentrated sulfuric acid with a mass percentage concentration of 92.5% for recycling to the roasting section, and the first-level sulfuric acid pump P301A and the first-level standby sulfuric acid pump P301B in parallel are arranged at the feed liquid inlet and outlet of the second-level heat exchanger E302.

[0037] The four spray towers for collecting hydrofluoric acid are connected in series to spray water in reverse direction; the first-stage spray tower T401, the second-stage spray tower T402, the third-stage spray tower T403, and the fourth-stage spray tower T404 are connected in series, and the exhaust port of the first-stage spray tower T401 is connected to the tail gas inlet of the second-stage spray tower T402 through a gas pipeline, the exhaust port of the second-stage spray tower T402 is connected to the tail gas inlet of the third-stage spray tower T403 through a gas pipeline, and the exhaust port of the third-stage spray tower T403 is connected to the tail gas inlet of the third-stage spray tower T404 through a gas pipeline. The tail gas inlet of the four-stage spray tower T404; the liquid outlet of the four-stage spray tower T404 is connected to the liquid inlet of the three-stage spray tower T403 through the liquid pipeline, the four-stage spray pump P404A and the four-stage standby spray pump P404B connected in parallel are connected to the liquid outlet of the four-stage spray tower T404, the tail gas discharged from the exhaust port of the four-stage spray tower T404 is recycled to the desulfurization and acid production section, and the liquid inlet of the four-stage spray tower T404 is used to add steam condensate; the liquid outlet of the three-stage spray tower T403 is connected to the liquid outlet of the three-stage spray tower T403. The liquid inlet of the five-stage heat exchanger E305 is connected to the liquid inlet of the two-stage spray tower T402 through the liquid pipeline; the liquid outlet of the two-stage spray tower T402 is connected to the liquid inlet of the four-stage heat exchanger E304 through the liquid pipeline; the liquid outlet of the four-stage heat exchanger E304 is connected to the liquid outlet of the one-stage heat exchanger E304 through the liquid pipeline. The liquid inlet of the first-stage spray tower T401, the second-stage spray pump P402A and the second-stage standby spray pump P402B in parallel are connected to the liquid inlet of the fourth-stage heat exchanger E304; the liquid outlet of the first-stage spray tower T401 is connected to the liquid inlet of the third-stage heat exchanger E303 through a liquid pipeline, the liquid outlet of the third-stage heat exchanger E303 discharges the collected hydrofluoric acid, and the first-stage spray pump P401A and the first-stage standby spray pump P401B in parallel are connected to the liquid inlet of the third-stage heat exchanger E303. The tail gas coming out of the secondary absorption tower T302 enters the primary spray tower T401, the secondary spray tower T402, the tertiary spray tower T403 and the quaternary spray tower T404 in turn, and the spray water flows through the quaternary spray tower T404, the tertiary spray tower T403, the secondary spray tower T402 and the primary spray tower T401 in turn, and the spray water absorbs hydrogen fluoride and silicon tetrafluoride in the tail gas to generate hydrofluoric acid.

[0038] The circulating water outlets and circulating water inlets of the primary heat exchanger E301, the secondary heat exchanger E302, the tertiary heat exchanger E303, the quaternary heat exchanger E304 and the fifth heat exchanger E305 are respectively connected to the circulating drainage pipeline and the circulating water supply pipeline through the circulating pipeline.

[0039] The process for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting includes:

[0040] Step 1: The tail gas from the roasting of rare earth concentrate enters the absorption tower, concentrated sulfuric acid is added to the absorption tower, the concentrated sulfuric acid is used to absorb the sulfur trioxide in the tail gas, and the tail gas without sulfur trioxide enters the spray tower;

[0041] The reaction equation of concentrated sulfuric acid and sulfur trioxide is: 2 SO 4 +SO 3 →H 2 S 2 O 7 (disulfuric acid).

[0042] The disulfuric acid that absorbs sulfur trioxide is added with an appropriate amount of water to obtain sulfuric acid, which is recycled to the calcination stage.

[0043] The tail gas from the roasting of rare earth concentrate enters from the tail gas inlet of the secondary absorption tower T302, and the tail gas from the secondary absorption tower T302 enters the tail gas inlet of the primary absorption tower T301. The sulfuric acid after spraying in the secondary absorption tower T302 is cooled by the primary heat exchanger E301 and then transported to the primary absorption tower T301 for spraying through the secondary sulfuric acid pump P302A / secondary standby sulfuric acid pump P302B. The sulfuric acid with a mass percentage concentration of about 92% after spraying is cooled by the secondary heat exchanger E302 and then discharged through the primary sulfuric acid pump P301A and the primary standby sulfuric acid pump P301B and reused to the calcination section.

[0044] Both the primary absorption tower T301 and the secondary absorption tower T302 use concentrated sulfuric acid with a mass percentage concentration of 98% to spray the tail gas, and a certain amount of concentrated sulfuric acid with a mass percentage concentration of 98% is added to the first absorption tower T301 and the secondary absorption tower T302 to absorb the sulfur trioxide in the tail gas. By controlling the amount of 98% sulfuric acid added, the concentration of sulfuric acid after spraying is controlled at a mass percentage concentration of about 92% ± 5. The recovered sulfuric acid with a mass percentage concentration of 92% is recycled to the roasting section after heat exchange and cooling.

[0045] Step 2: Spray the tail gas with countercurrent water in the spray tower. The spray water absorbs the hydrogen fluoride and silicon tetrafluoride in the tail gas and converts them into hydrofluoric acid.

[0046] The spray water is circulated and sprayed to enrich hydrofluoric acid, which is a byproduct. The sulfur dioxide gas in the tail gas enters the desulfurization and acid-making section.

[0047] By controlling the amount of 98% sulfuric acid added, the concentration of sulfuric acid after absorbing sulfur trioxide is controlled at about 92%; hydrogen fluoride, silicon tetrafluoride and other gases in the tail gas are converted into hydrofluoric acid, so that the sulfur element and fluorine element in the tail gas are separated by spray absorption, thereby realizing the separation of sulfuric acid and hydrofluoric acid.

[0048] First-stage spray tower T401: The tail gas enters the first-stage spray tower T401 after being absorbed by sulfur trioxide. This stage of spraying adopts waste acid spraying, and the waste acid comes from the second-stage spray tower T402. The concentration of hydrofluoric acid is controlled at a percentage concentration of about 12±5%, and the temperature is controlled at 90-95°C. The obtained hydrofluoric acid is sold after cooling.

[0049] Secondary spray tower T402: After the tail gas passes through the primary spray tower T401, it enters the secondary spray tower T402 for secondary spraying. This stage of spraying uses waste acid spraying, and the waste acid comes from the tertiary spray tower T403. The fluoride ion concentration is controlled at about 105-112g / L, and the temperature is controlled at 80-85℃.

[0050] Three-stage spray tower T403: After passing through the two-stage spray tower T402, the tail gas enters the three-stage spray tower T403 for three-stage spraying. This stage of spraying uses waste acid spraying, and the waste acid comes from the four-stage spray tower T404. The fluoride ion concentration is controlled at about 85-90g / L, and the temperature is controlled at 60-65℃.

[0051] Four-stage spray tower T404: After passing through the three-stage spray tower T403, the tail gas enters the four-stage spray tower T404 for four-stage spraying. This stage of spraying uses water spray. The water comes from the steam condensate in the desulfurization and acid production process. The fluoride ion concentration is controlled at about 15-20g / L and the temperature is controlled at 40-45℃.

[0052] After the tail gas enters the four-stage spraying in turn, the hydrogen fluoride, silicon tetrafluoride and other gases in the tail gas are recovered, and about 12% hydrofluoric acid is obtained in the first-stage spray absorption tower T401. The sulfur dioxide gas in the tail gas enters the desulfurization and acid-making section to convert sulfur dioxide into concentrated sulfuric acid.

[0053] The terms used in the present invention are illustrative and exemplary, rather than restrictive. Since the present invention can be implemented in various forms without departing from the spirit or essence of the technical solution, it should be understood that the above embodiments are not limited to any of the aforementioned details, but should be widely interpreted within the spirit and scope defined by the attached claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the attached claims.

Claims

1. A device for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting, characterized in that: include: Absorption tower, spray tower, heat exchanger, delivery pump, the lower part of the absorption tower and the spray tower is respectively provided with tail gas inlet, circulating water inlet, circulating water outlet, and the top is provided with an exhaust port; A concentrated sulfuric acid inlet and a concentrated sulfuric acid outlet are provided on the upper part of the absorption tower. The exhaust port of the absorption tower is connected to the tail gas inlet of the spray tower through a gas pipeline. The liquid outlets of the absorption tower and the spray tower are respectively connected to the heat exchanger and the delivery pump through the liquid pipeline. The circulating water outlet and the circulating water inlet of the heat exchanger are respectively connected to the circulating drainage pipeline and the circulating water supply pipeline through the circulating pipeline.

2. The device for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting as claimed in claim 1, characterized in that: Multiple absorption towers for collecting sulfur trioxide are connected in series and spray concentrated sulfuric acid in reverse; multiple spray towers for collecting hydrofluoric acid are connected in series and spray water in reverse.

3. The device for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting as claimed in claim 2, characterized in that: The absorption tower includes: a primary absorption tower and a secondary absorption tower. The tail gas enters the primary absorption tower and enters the secondary absorption tower after coming out of the primary absorption tower. The concentrated sulfuric acid that absorbs sulfur trioxide enters the primary absorption tower after coming out of the secondary absorption tower. The feed liquid outlets of the primary absorption tower and the secondary absorption tower are respectively connected to heat exchangers and delivery pumps through feed liquid pipelines.

4. The device for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting as claimed in claim 3, characterized in that: The spray tower includes: a primary spray tower, a secondary spray tower, a tertiary spray tower and a quaternary spray tower; the tail gas coming out of the secondary absorption tower enters the primary spray tower, the secondary spray tower, the tertiary spray tower and the quaternary spray tower in sequence, and the spray water flows through the quaternary spray tower, the tertiary spray tower, the secondary spray tower and the primary spray tower in sequence, and the liquid outlets of the primary spray tower, the secondary spray tower, the tertiary spray tower and the quaternary spray tower are respectively connected with heat exchangers and delivery pumps through liquid pipelines.

5. The device for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting as claimed in claim 2, characterized in that: The absorption tower includes: a primary absorption tower and a secondary absorption tower; the spray tower includes: a primary spray tower, a secondary spray tower, a tertiary spray tower and a quaternary spray tower; the heat exchanger includes: a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, a quaternary heat exchanger and a quintuple heat exchanger; the delivery pump includes: a primary sulfuric acid pump, a primary backup sulfuric acid pump, a secondary sulfuric acid pump, a secondary backup sulfuric acid pump, a primary spray pump, a primary backup spray pump, a secondary spray pump, a secondary backup spray pump, a tertiary spray pump, a tertiary backup spray pump, a quaternary spray pump and a quaternary backup spray pump; a concentrated sulfuric acid inlet and a concentrated sulfuric acid outlet are arranged on the upper part of the secondary absorption tower; the exhaust port of the primary absorption tower is connected to the tail gas inlet of the secondary absorption tower through a gas pipeline; the secondary absorption tower is provided with a concentrated sulfuric acid inlet and a concentrated sulfuric acid outlet ... The liquid outlet of the first-stage absorption tower is connected to the liquid inlet of the first-stage heat exchanger through a liquid pipeline, the second-stage sulfuric acid pump and the second-stage standby sulfuric acid pump in parallel are connected to the liquid inlet of the first-stage heat exchanger, the liquid outlet of the first-stage heat exchanger is connected to the liquid inlet of the first-stage absorption tower through a liquid pipeline, the liquid outlet of the first-stage absorption tower is connected to the liquid inlet of the second-stage heat exchanger through a liquid pipeline, the liquid outlet of the second-stage heat exchanger outputs concentrated sulfuric acid, the first-stage sulfuric acid pump and the first-stage standby sulfuric acid pump in parallel are arranged at the liquid inlet and outlet of the second-stage heat exchanger; the exhaust port of the first-stage spray tower is connected to the tail gas inlet of the second-stage spray tower through a gas pipeline, the exhaust port of the second-stage spray tower is connected to the tail gas inlet of the tertiary spray tower through a gas pipeline, and the tertiary spray tower The exhaust port is connected to the tail gas inlet of the four-stage spray tower through a gas pipeline; the liquid outlet of the four-stage spray tower is connected to the liquid inlet of the three-stage spray tower through a liquid pipeline, the four-stage spray pump and the four-stage standby spray pump in parallel are connected at the liquid outlet of the four-stage spray tower, the tail gas discharged from the exhaust port of the four-stage spray tower is recycled to the desulfurization and acid production section, and the liquid inlet of the four-stage spray tower is used to add steam condensate; the liquid outlet of the three-stage spray tower is connected to the liquid inlet of the five-stage heat exchanger through a liquid pipeline, the three-stage spray pump and the three-stage standby spray pump in parallel are connected at the liquid outlet of the three-stage spray tower, and the liquid outlet of the five-stage heat exchanger is connected to the liquid inlet of the two-stage spray tower through a liquid pipeline; the liquid outlet of the two-stage spray tower The feed liquid inlet of the four-stage heat exchanger is connected to the feed liquid inlet of the four-stage heat exchanger through a feed liquid pipeline, the feed liquid outlet of the four-stage heat exchanger is connected to the feed liquid inlet of the first-stage spray tower through a feed liquid pipeline, and the parallel second-stage spray pump and the second-stage standby spray pump are connected to the feed liquid inlet of the four-stage heat exchanger; the feed liquid outlet of the first-stage spray tower is connected to the feed liquid inlet of the three-stage heat exchanger through a feed liquid pipeline, the feed liquid outlet of the three-stage heat exchanger is used to discharge the collected hydrofluoric acid, and the parallel first-stage spray pump and the first-stage standby spray pump are connected to the feed liquid inlet of the three-stage heat exchanger; the circulating water outlet and circulating water inlet of the first-stage heat exchanger, the second-stage heat exchanger, the third-stage heat exchanger, the fourth-stage heat exchanger and the fifth-stage heat exchanger are respectively connected to the circulating drainage pipeline and the circulating water supply pipeline through the circulating pipeline.

6. The process for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting according to claim 1, characterized in that: include: The tail gas from the roasting of rare earth concentrate enters the absorption tower, concentrated sulfuric acid is added to the absorption tower, and the concentrated sulfuric acid is used to absorb the sulfur trioxide in the tail gas. The tail gas without sulfur trioxide enters the spray tower; The tail gas is sprayed with countercurrent water in the spray tower, and the spray water absorbs the hydrogen fluoride and silicon tetrafluoride in the tail gas and converts them into hydrofluoric acid.

7. The process for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting as claimed in claim 6, characterized in that: The absorption tower includes: a primary absorption tower and a secondary absorption tower. The tail gas from the roasting of rare earth concentrate enters from the tail gas inlet of the secondary absorption tower, and the tail gas from the secondary absorption tower enters the tail gas inlet of the primary absorption tower. The primary absorption tower and the secondary absorption tower both use concentrated sulfuric acid with a mass percentage concentration of 98% to spray the tail gas. By controlling the amount of 98% sulfuric acid added, the sulfuric acid concentration after spraying is controlled. The sulfuric acid sprayed from the secondary absorption tower is cooled by a primary heat exchanger and then transported to the primary absorption tower for spraying through a secondary sulfuric acid pump / a secondary standby sulfuric acid pump. The sprayed sulfuric acid is cooled by a secondary heat exchanger and then discharged through a primary sulfuric acid pump / a primary standby sulfuric acid pump and reused in the calcination section.

8. The process for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting as claimed in claim 6, characterized in that: The spray water is enriched with hydrofluoric acid through circulating spraying. Hydrofluoric acid is a by-product, and the sulfur dioxide gas in the tail gas enters the desulfurization and acid-making section.

9. The process for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting as claimed in claim 6, characterized in that: By controlling the amount of 98% sulfuric acid added, gases such as hydrogen fluoride and silicon tetrafluoride in the tail gas are converted into hydrofluoric acid, so that the sulfur element and the fluorine element in the tail gas are separated, thereby achieving the separation of sulfuric acid and hydrofluoric acid.

10. The process for directly preparing sulfuric acid and hydrofluoric acid from the tail gas of rare earth concentrate roasting as claimed in claim 6, characterized in that: The spray tower includes: a primary spray tower, a secondary spray tower, a tertiary spray tower, and a quaternary spray tower; the tail gas enters the primary spray tower T401 after being absorbed by sulfur trioxide. This stage uses waste acid spraying, and the waste acid comes from the secondary spray tower. The concentration of hydrofluoric acid is controlled at a mass percentage concentration of 12±5%, and the temperature is controlled at 90-95°C to obtain hydrofluoric acid; the tail gas passes through the primary spray tower and enters the secondary spray tower for secondary spraying. This stage uses waste acid spraying, and the waste acid comes from the tertiary spray tower. The fluoride ion concentration is controlled at 105-11 2g / L, the temperature is controlled at 80-85℃; the tail gas passes through the secondary spray tower and enters the tertiary spray tower for tertiary spraying. This stage of spraying uses waste acid spraying, and the waste acid comes from the fourth spray tower. The fluoride ion concentration is controlled at 85-90g / L, and the temperature is controlled at 60-65℃; the tail gas passes through the third spray tower and enters the fourth spray tower for tertiary spraying. This stage of spraying uses water spraying, and the water comes from the steam condensate in the desulfurization and acid production process. The fluoride ion concentration is controlled at 15-20g / L and the temperature is controlled at 40-45℃.

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