Harmless treatment method of arsenic-calcium slag

Abstract

The present invention provides a harmless treatment method for arsenic-calcium slag, which includes: obtaining arsenic-calcium slag and pyrite, inputting the two into a mixer for mixing, and outputting a mixed material; obtaining the mixed material, inputting it into a medium-temperature volatilization furnace through a volatilization furnace material inlet, heating the mixed material at a medium temperature, outputting a first tail gas containing arsenic oxide through the volatilization furnace gas outlet, and outputting a first tail gas containing calcium arsenate and pyrite through the volatilization furnace tail slag outlet; obtaining the first tail gas, inputting it into a high-temperature decomposition furnace through a decomposition furnace material inlet, heating the first tail gas at a high temperature, outputting a second tail gas containing arsenic oxide and sulfur dioxide through the decomposition furnace gas outlet, and outputting a second tail gas containing calcium oxide and ferrosoferric oxide through the decomposition furnace tail slag outlet; and obtaining the first tail gas and the second tail gas, and inputting them into a tail gas purification device. In the harmless treatment method for arsenic-calcium slag of the present invention, the second tail gas does not contain arsenic, thereby avoiding arsenic pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste treatment, in particular to a harmless treatment method for arsenic-calcium slag. Background Art

[0002] Arsenic calcium slag contains calcium arsenate and arsenic oxide. In order to avoid the risk of environmental arsenic pollution caused by the release of arsenic in the arsenic calcium slag, the arsenic calcium slag needs to undergo further stabilization treatment. At present, the stabilization treatment method of arsenic calcium slag is mainly cement solidification stabilization technology. Cement solidification stabilization technology mainly solidifies the arsenic calcium slag by mixing and solidifying it with cement, thereby improving the stabilization of the arsenic calcium slag. However, this technology not only produces a large amount of secondary arsenic-containing solid waste, but also has the problem of high cost. In addition, iron-arsenic co-precipitation technology can also be used for the stabilization treatment of arsenic calcium slag. This method uses a large amount of iron salts to solidify arsenic through co-precipitation and adsorption mechanisms, and finally forms arsenic into iron arsenate. However, this method uses a large amount of iron salts, and the molar ratio of iron to arsenic needs to reach more than 14, which not only increases the cost of solidifying arsenic, but also leads to an increase in the amount of slag, resulting in secondary pollution.

[0003] Therefore, it is necessary to provide a harmless treatment method for arsenic-calcium slag to solve the above technical problems. Summary of the Invention

[0004] The invention provides a harmless treatment method for arsenic-calcium slag, wherein the tailings finally obtained do not contain arsenic, thus avoiding arsenic pollution, and simultaneously improving the utilization rate of pyrite, saving cost and heat.

[0005] The technical solution of the present invention is:

[0006] A method for harmlessly treating arsenic-calcium slag, wherein the arsenic-calcium slag contains calcium arsenate and arsenic oxide, and an arsenic-calcium slag harmless treatment device is used to treat the arsenic-calcium slag, wherein the arsenic-calcium slag harmless treatment device comprises:

[0007] A mixer is provided with a mixing inlet and a mixing outlet;

[0008] A medium-temperature volatilization furnace is provided with a volatilization furnace material inlet, a volatilization furnace gas inlet, a volatilization furnace gas outlet and a volatilization furnace tail slag outlet; the volatilization furnace material inlet is connected to the mixing outlet;

[0009] A high-temperature decomposition furnace is provided with a decomposition furnace material inlet, a decomposition furnace gas inlet, a decomposition furnace gas outlet and a decomposition furnace tail slag outlet; the decomposition furnace material inlet is connected to the volatilization furnace tail slag outlet; and,

[0010] An exhaust gas purification device is provided with a purification inlet and a purification outlet, wherein the purification inlet is connected to both the volatilization furnace gas outlet and the decomposition furnace gas outlet;

[0011] The harmless treatment method for arsenic-calcium slag comprises:

[0012] S11, obtaining arsenic calcium slag and pyrite, inputting the two into the mixer through the mixing inlet, mixing the arsenic calcium slag and pyrite, and outputting the mixed material through the mixing outlet;

[0013] S12, obtaining a mixed material, feeding it into the medium-temperature volatilization furnace through the material inlet of the volatilization furnace, feeding nitrogen into the medium-temperature volatilization furnace through the gas inlet of the volatilization furnace, heating the mixed material at medium temperature, outputting a first tail gas containing arsenic oxide through the gas outlet of the volatilization furnace, and outputting a first tailing containing calcium arsenate and pyrite through the tailing outlet of the volatilization furnace;

[0014] S13, obtaining a first tailing, feeding it into the pyrolysis furnace through the decomposition furnace material inlet, feeding air into the pyrolysis furnace through the decomposition furnace gas inlet, heating the first tailing at high temperature, outputting a second tail gas containing arsenic oxide and sulfur dioxide through the decomposition furnace gas outlet, and outputting a second tailing containing calcium oxide and ferrosoferric oxide through the decomposition furnace tailing outlet; and,

[0015] S14 , obtaining the first tail gas and the second tail gas, inputting the first tail gas and the second tail gas into the tail gas purification device through the purification inlet, and discharging the purified tail gas through the purification outlet.

[0016] In the harmless treatment method for arsenic-calcium slag of the present invention, in step S12, the heating temperature is 550° C.-600° C., and the heating time is 60 min-90 min.

[0017] In the harmless treatment method for arsenic-calcium slag of the present invention, in step S13, the heating temperature is 800° C.-850° C., and the heating time is 60 min-90 min.

[0018] In the harmless treatment method for arsenic-calcium slag described in the present invention, calcium arsenate accounts for 70%-80% of the mass of the arsenic-calcium slag; in step S13, the air introduced into the pyrolysis furnace has oxygen content of 50%-60% of the mass of the arsenic-calcium slag; in step S11, the pyrite input into the mixer has ferrous disulfide content of 90%-100% of the mass of the arsenic-calcium slag.

[0019] In the harmless treatment method for arsenic-calcium slag of the present invention, the harmless treatment equipment for arsenic-calcium slag further comprises a paddle-type preheating feeder, the inner shell of which is provided with a feeder material inlet, a feeder gas outlet, and a feeder material outlet; the feeder material inlet is connected to the mixing outlet; the feeder material outlet is connected to the volatilization furnace material inlet;

[0020] The harmless treatment method of arsenic-calcium slag also includes step S15, obtaining a mixed material, inputting it into the paddle-type preheating feeder through the material inlet of the feeder, heating the mixed material, the heating temperature is 150°C-200°C, the heating time is 60min-120min, and water vapor is discharged through the gas outlet of the feeder, and the dehydrated mixed material is output through the material outlet of the feeder; step S15 is located after step S11 and before step S12.

[0021] In the harmless treatment method for arsenic-calcium slag of the present invention, the harmless treatment equipment for arsenic-calcium slag further comprises:

[0022] A high-temperature gas-solid separator is provided with a separator inlet, a separator solid outlet and a separator gas outlet; the separator inlet is connected to both the volatilization furnace gas outlet and the decomposition furnace gas outlet; and,

[0023] The condensation arsenic collection chamber is provided with an arsenic collection chamber inlet and an arsenic collection chamber gas outlet; the arsenic collection chamber inlet is connected to the separator gas outlet; the arsenic collection chamber gas outlet is connected to the purification inlet;

[0024] The harmless treatment method for arsenic-calcium slag further comprises the steps of:

[0025] S16, obtaining a first tail gas and a second tail gas, inputting the first tail gas and the second tail gas into the high-temperature gas-solid separator through the separator inlet, outputting impurities through the separator solid outlet, and outputting a third tail gas containing arsenic oxide and sulfur dioxide through the separator gas outlet; and

[0026] S17, obtaining the third tail gas, inputting it into the condensation arsenic collection chamber through the inlet of the arsenic collection chamber to collect the refined white arsenic, and outputting the fourth tail gas containing sulfur dioxide through the gas outlet of the arsenic collection chamber;

[0027] Step S16 and step S17 are located after step S13 and before step S14; step S14 is to obtain the fourth exhaust gas and input the fourth exhaust gas into the exhaust gas purification device for treatment.

[0028] In the harmless treatment method for arsenic-calcium slag of the present invention, the harmless treatment equipment for arsenic-calcium slag further comprises a condenser, which is provided with a condensation inlet and a condensation outlet, and the condensation inlet is connected to the gas outlet of the feeder;

[0029] The harmless treatment method for arsenic-calcium slag also includes step S18, obtaining water vapor, inputting it into the condenser through the condensation inlet, then outputting wastewater through the condensation outlet, and transporting the wastewater to a sewage treatment plant; step S18 is located after step S15.

[0030] In the harmless treatment method for arsenic-calcium slag of the present invention, the harmless treatment equipment for arsenic-calcium slag further comprises a discharge heat exchanger, the inner tank of the discharge heat exchanger is provided with a heat exchanger material inlet and a heat exchanger material outlet; the heat exchanger material inlet is connected to the decomposition furnace tail slag outlet;

[0031] The harmless treatment method for arsenic-calcium slag also includes step S19, obtaining second tailings, inputting them into the discharging heat exchanger through the material inlet of the heat exchanger, cooling the second tailings, and outputting the cooled second tailings through the material outlet of the heat exchanger; step S19 is located after step S13.

[0032] In the harmless treatment method for arsenic-calcium slag of the present invention, the outer shell of the paddle-type preheating feeder is further provided with a feeder hot oil inlet and a feeder cold oil outlet; the outer shell of the discharge heat exchanger is further provided with a heat exchanger cold oil inlet and a heat exchanger hot oil outlet; the heat exchanger hot oil outlet is connected to the feeder hot oil inlet;

[0033] In step S19, cold heat transfer oil is input into the outer tank of the discharging heat exchanger through the cold oil inlet of the heat exchanger to cool the second tailings, and hot heat transfer oil is output through the hot oil outlet of the heat exchanger; the arsenic-calcium slag harmless treatment method also includes step S20, obtaining the hot heat transfer oil output from the hot oil outlet of the heat exchanger, and inputting it into the outer tank of the paddle-type preheating feeder through the hot oil inlet of the feeder; step S20 is located after step S19; in step S15, cold heat transfer oil is output through the cold oil outlet of the feeder.

[0034] In the harmless treatment method for arsenic-calcium slag described in the present invention, the cold oil inlet of the heat exchanger is connected to the cold oil outlet of the feeder; the harmless treatment method for arsenic-calcium slag also includes step S21, obtaining the cold heat transfer oil output from the cold oil outlet of the feeder, and inputting it into the outer tank of the discharge heat exchanger through the cold oil inlet of the heat exchanger.

[0035] Compared with the prior art, the present invention has the following beneficial effects: the harmless treatment method of arsenic-calcium slag of the present invention comprises the following steps: first, the arsenic-calcium slag and pyrite are mixed in a mixer to ensure sufficient subsequent reaction; then, the mixture containing the arsenic-calcium slag and pyrite is input into a medium-temperature volatilization furnace to convert arsenic oxide in the mixture into a gaseous state and separate from a first tailing containing calcium arsenate and pyrite; the medium-temperature volatilization furnace is in a nitrogen atmosphere, which can prevent arsenic oxide from reacting with oxygen to generate solid arsenic pentoxide, thereby increasing the difficulty of subsequent treatment; and then, the first tailing is input into a high-temperature decomposition furnace; in an oxygen atmosphere, the calcium arsenate and pyrite in the first tailing chemically react to form arsenic in the form of gaseous arsenic oxide, which is separated from a second tailing containing calcium oxide and ferroferric oxide; the second tailing finally obtained does not contain arsenic; and the first tail gas and the second tail gas are treated by a tail gas purification device to avoid arsenic pollution. At the same time, the pyrite is first subjected to a medium-temperature treatment in a medium-temperature volatilization furnace and then to a high-temperature treatment in a high-temperature decomposition furnace, so that the pyrite in the medium-temperature volatilization furnace does not react with arsenic oxide, and all the pyrite reacts with calcium arsenate in the high-temperature decomposition furnace, thereby improving the utilization rate of the pyrite and saving costs; the arsenic oxide in the arsenic-calcium slag is first converted into a gaseous state and discharged in the medium-temperature volatilization furnace, so that the arsenic-calcium slag in the high-temperature decomposition furnace is only left with calcium arsenate, which can also shorten the treatment time in the high-temperature decomposition furnace and save heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. The drawings described below are only drawings corresponding to some embodiments of the present invention.

[0037] Figure 1 A schematic structural diagram of an arsenic-calcium slag harmless treatment device provided for a preferred embodiment of the invention.

[0038] Figure 2 A partial flow chart of the method for harmless treatment of arsenic-calcium slag provided for a preferred embodiment of the invention.

[0039] Figure 3 Another partial flow chart of the method for harmless treatment of arsenic-calcium slag provided for a preferred embodiment of the invention.

[0040] in,

[0041] 11. Mixer, 111. Mixing inlet, 112. Mixing outlet,

[0042] 12. Medium temperature volatilization furnace, 121. Volatilization furnace material inlet, 122. Volatilization furnace gas inlet, 123. Volatilization furnace gas outlet, 124. Volatilization furnace tail slag outlet,

[0043] 13. High-temperature decomposition furnace, 131. Decomposition furnace material inlet, 132. Decomposition furnace gas inlet, 133. Decomposition furnace gas outlet, 134. Decomposition furnace tailings outlet,

[0044] 14. Exhaust gas purification device, 141. Purification inlet, 142. Purification outlet,

[0045] 15. Paddle type preheating feeder, 151. Feeder material inlet, 152. Feeder gas outlet, 153. Feeder material outlet, 154. Feeder hot oil inlet, 155. Feeder cold oil outlet,

[0046] 16. High-temperature gas-solid separator, 161. Separator inlet, 162. Separator solid outlet, 163. Separator gas outlet,

[0047] 17. Condensation arsenic collection chamber, 171. Arsenic collection chamber entrance, 172. Arsenic collection chamber gas outlet,

[0048] 18. Discharging heat exchanger, 181. Heat exchanger material inlet, 182. Heat exchanger material outlet, 183. Heat exchanger cold oil inlet, 184. Heat exchanger hot oil outlet,

[0049] 19. Condenser, 191. Condensation inlet, 192. Condensation outlet.

[0050] In the figures, structurally similar elements are denoted by the same reference numerals. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0052] Directional terms mentioned in the present invention, such as "up", "down", "front", "back", "left", "right", "inside", "outside", "side", "top" and "bottom", are only used with reference to the directions of the drawings. The directional terms used are used to illustrate and understand the present invention, and are not used to limit the present invention.

[0053] The terms "first" and "second" in the present invention are used for descriptive purposes only and should not be understood as indicating or implying relative importance, and should not be used as a limitation on the order of precedence.

[0054] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0055] Arsenic calcium slag contains calcium arsenate and arsenic oxide. In order to avoid the risk of environmental arsenic pollution caused by the release of arsenic in the arsenic calcium slag, the arsenic calcium slag needs to undergo further stabilization treatment. At present, the stabilization treatment method of arsenic calcium slag is mainly cement solidification stabilization technology. Cement solidification stabilization technology mainly solidifies the arsenic calcium slag by mixing and solidifying it with cement, thereby improving the stabilization of the arsenic calcium slag. However, this technology not only produces a large amount of secondary arsenic-containing solid waste, but also has the problem of high cost. In addition, iron-arsenic co-precipitation technology can also be used for the stabilization treatment of arsenic calcium slag. This method uses a large amount of iron salts to solidify arsenic through co-precipitation and adsorption mechanisms, and finally forms arsenic into iron arsenate. However, this method uses a large amount of iron salts, and the molar ratio of iron to arsenic needs to reach more than 14, which not only increases the cost of solidifying arsenic, but also leads to an increase in the amount of slag, resulting in secondary pollution.

[0056] The following is a preferred embodiment of the harmless treatment method for arsenic-calcium slag provided by the present invention, which can solve the above technical problems.

[0057] Please refer to Figure 1 、 Figure 2 and Figure 3 The preferred embodiment of the present invention provides a method for harmlessly treating arsenic-calcium slag, wherein the arsenic-calcium slag contains calcium arsenate and arsenic oxide. The arsenic-calcium slag is treated using an arsenic-calcium slag harmless treatment device, which includes a mixer 11, a medium-temperature volatilization furnace 12, a high-temperature decomposition furnace 13, and an exhaust gas purification device 14. The mixer 11 is provided with a mixing inlet 111 and a mixing outlet 112. The medium-temperature volatilization furnace 12 is provided with a volatilization furnace material inlet 121, a volatilization furnace gas inlet 122, a volatilization furnace gas outlet 123, and a volatilization furnace tail slag outlet 124. The volatilization furnace material inlet 121 is connected to the mixing outlet 112. The high-temperature decomposition furnace 13 is provided with a decomposition furnace material inlet 131, a decomposition furnace gas inlet 132, a decomposition furnace gas outlet 133, and a decomposition furnace tail slag outlet 134. The decomposition furnace material inlet 131 is connected to the volatilization furnace tail slag outlet 124. The tail gas purification device 14 is provided with a purification inlet 141 and a purification outlet 142 . The purification inlet 141 is connected to both the volatilization furnace gas outlet 123 and the decomposition furnace gas outlet 133 .

[0058] The harmless treatment methods of arsenic-calcium slag include:

[0059] S11, obtaining arsenic calcium slag and pyrite, inputting the two into the mixer 11 through the mixing inlet 111, mixing the arsenic calcium slag and pyrite, and outputting the mixed material through the mixing outlet 112;

[0060] S12, obtaining a mixed material, inputting it into a medium-temperature volatilization furnace 12 through a volatilization furnace material inlet 121, inputting nitrogen into the medium-temperature volatilization furnace 12 through a volatilization furnace gas inlet 122, heating the mixed material at a medium temperature, outputting a first tail gas containing arsenic oxide through a volatilization furnace gas outlet 123, and outputting a first tailing containing calcium arsenate and pyrite through a volatilization furnace tailing outlet 124;

[0061] S13, obtaining a first tailing, inputting it into the high-temperature decomposition furnace 13 through the decomposition furnace material inlet 131, and inputting air into the high-temperature decomposition furnace 13 through the decomposition furnace gas inlet 132, heating the first tailing at high temperature, outputting a second tail gas containing arsenic oxide and sulfur dioxide through the decomposition furnace gas outlet 133, and outputting a second tailing containing calcium oxide and ferrosoferric oxide through the decomposition furnace tailing outlet 134; the reaction chemical formula of calcium arsenate and pyrite is:

[0062] Ca3(AsO4)2+3FeS2+7O2(g)=As2O3(g)+3CaO+6SO2(g)+Fe3O4;

[0063] S14 , obtaining the first tail gas and the second tail gas, inputting the two into the tail gas purification device 14 through the purification inlet 141 , and discharging the purified tail gas through the purification outlet 142 .

[0064] The harmless treatment method of arsenic-calcium slag of the present invention first mixes the arsenic-calcium slag and pyrite in a mixer 11 to ensure sufficient subsequent reaction; then, the mixture containing the arsenic-calcium slag and pyrite is input into a medium-temperature volatilization furnace 12, so that the arsenic oxide in the mixture becomes gaseous and is separated from the first tailings containing calcium arsenate and pyrite. The medium-temperature volatilization furnace 12 is in a nitrogen atmosphere, which can prevent the arsenic oxide from reacting with oxygen to generate solid arsenic pentoxide, which makes subsequent treatment more difficult; then, the first tailings is input into a high-temperature decomposition furnace 13, and in an oxygen atmosphere, the calcium arsenate and pyrite in the first tailings chemically react, so that the arsenic exists in the form of gaseous arsenic oxide, which is separated from the second tailings containing calcium oxide and ferroferric oxide. The final second tailings do not contain arsenic, and the first tail gas and the second tail gas are treated by a tail gas purification device 14 to avoid arsenic pollution. At the same time, the pyrite is first subjected to medium-temperature treatment in the medium-temperature volatilization furnace 12 and then to high-temperature treatment in the high-temperature decomposition furnace 13, so that the pyrite in the medium-temperature volatilization furnace 12 does not react with arsenic oxide, and all the pyrite reacts with calcium arsenate in the high-temperature decomposition furnace 13, thereby improving the utilization rate of the pyrite and saving costs; the arsenic oxide in the arsenic-calcium slag is first converted into gaseous form and discharged in the medium-temperature volatilization furnace 12, so that the arsenic-calcium slag in the high-temperature decomposition furnace 13 is left with only calcium arsenate, which can also shorten the treatment time in the high-temperature decomposition furnace 13 and save heat.

[0065] The heating temperature is 550°C-600°C and the heating time is 60min-90min, which can fully convert arsenic oxide into gas without causing arsenic oxide to react with pyrite.

[0066] The heating temperature is 800°C-850°C and the heating time is 60min-90min, which can make the calcium arsenate and pyrite react fully without causing heat waste.

[0067] The calcium arsenate content is 70%-80% of the mass of the arsenic calcium slag. In step S13, the air introduced into the pyrolysis furnace 13 contains oxygen at a level of 50%-60% of the mass of the arsenic calcium slag. This not only meets the requirements for the reaction between the calcium arsenate and pyrite, but also prevents excessive oxygen, which would cause arsenic oxide to react with oxygen to form solid arsenic pentoxide. In step S11, the pyrite introduced into the mixer 11 contains ferrous disulfide at a level of 90%-100% of the mass of the arsenic calcium slag. This ensures that the pyrite meets the requirements for the decomposition of the calcium arsenate, while also preventing waste of pyrite and increasing the amount of secondary tailings.

[0068] The arsenic-calcium slag harmless treatment equipment also includes a paddle-type preheating feeder 15, whose inner shell is provided with a feeder material inlet 151, a feeder gas outlet 152, and a feeder material outlet 153. The feeder material inlet 151 is connected to the mixing outlet 112; the feeder material outlet 153 is connected to the volatilization furnace material inlet 121.

[0069] The harmless treatment method for arsenic-calcium slag also includes step S15, obtaining a mixed material, feeding it into a paddle-type preheating feeder 15 through the feeder material inlet 151, heating the mixed material at a temperature of 150°C-200°C for a heating time of 60 minutes-120 minutes, discharging water vapor through the feeder gas outlet 152, and outputting the dehydrated mixed material through the feeder material outlet 153; step S15 is located after step S11 and before step S12. In the above steps, the paddle-type preheating feeder 15 can convert moisture in the mixed material into water vapor for discharge, thereby improving the processing efficiency of the subsequent medium-temperature volatilization furnace 12. The temperature of the paddle-type preheating feeder 15 is much lower than that of the medium-temperature volatilization furnace 12, thus saving heat.

[0070] The arsenic-calcium slag harmless treatment equipment also includes a high-temperature gas-solid separator 16 and a condensation arsenic collection chamber 17 .

[0071] The high-temperature gas-solid separator 16 is provided with a separator inlet 161 , a separator solid outlet 162 and a separator gas outlet 163 ; the separator inlet 161 is connected to both the volatilization furnace gas outlet 123 and the decomposition furnace gas outlet 133 .

[0072] The condensation arsenic collecting chamber 17 is provided with an arsenic collecting chamber inlet 171 and an arsenic collecting chamber gas outlet 172 ; the arsenic collecting chamber inlet 171 is connected to the separator gas outlet 163 ; and the arsenic collecting chamber gas outlet 172 is connected to the purification inlet 141 .

[0073] The harmless treatment method for arsenic-calcium slag also includes the following steps:

[0074] S16, obtaining the first tail gas and the second tail gas, inputting the two into the high-temperature gas-solid separator 16 through the separator inlet 161, outputting impurities through the separator solid outlet 162, and outputting the third tail gas containing arsenic oxide and sulfur dioxide through the separator gas outlet 163; and,

[0075] S17, obtaining the third tail gas, inputting it into the condensation arsenic collecting chamber 17 through the arsenic collecting chamber inlet 171 to collect the refined white arsenic, and outputting the fourth tail gas containing sulfur dioxide through the arsenic collecting chamber gas outlet 172;

[0076] Step S16 and step S17 are located after step S13 and before step S14; step S14 is to obtain the fourth exhaust gas and input the fourth exhaust gas into the exhaust gas purification device 14 for treatment.

[0077] In the above steps, high-temperature gas-solid separator 16 keeps arsenic oxide and sulfur dioxide in a gaseous state at high temperatures. Solid impurities are filtered out through the membrane tubes of high-temperature gas-solid separator 16, and a third tail gas containing arsenic oxide and sulfur dioxide but no impurities is output through separator gas outlet 163. The gas then enters condensation and arsenic collection chamber 17. Condensation and arsenic collection chamber 17 keeps sulfur dioxide in a gaseous state, while its low temperature environment converts arsenic trioxide into a solid powder, which can be collected to obtain refined white arsenic, thereby improving resource utilization.

[0078] The arsenic-calcium slag harmless treatment equipment further includes a condenser 19 , which is provided with a condensation inlet 191 and a condensation outlet 192 , and the condensation inlet 191 is connected to the feeder gas outlet 152 .

[0079] The harmless treatment method for arsenic-calcium slag also includes step S18, which captures water vapor, inputs it into condenser 19 through condensation inlet 191, and then outputs wastewater through condensation outlet 192, which is then transported to a sewage treatment plant. Step S18 follows step S15. In these steps, condenser 19 converts the water vapor into liquid water, which is then easily transported to the wastewater treatment plant for treatment, thus preventing environmental pollution.

[0080] The arsenic-calcium slag harmless treatment equipment also includes a discharge heat exchanger 18 , the inner tank of which is provided with a heat exchanger material inlet 181 and a heat exchanger material outlet 182 ; the heat exchanger material inlet 181 is connected to the decomposition furnace tail slag outlet 134 .

[0081] The harmless treatment method for arsenic-calcium slag further includes step S19, obtaining second tailings, feeding them into the discharge heat exchanger 18 through the heat exchanger material inlet 181, cooling the second tailings, and discharging the cooled second tailings through the heat exchanger material outlet 182. Step S19 is located after step S13. In these steps, cooling the second tailings by the discharge heat exchanger 18 facilitates their storage.

[0082] The outer shell of the paddle-type preheating feeder 15 is also provided with a feeder hot oil inlet 154 and a feeder cold oil outlet 155; the outer shell of the discharge heat exchanger 18 is also provided with a heat exchanger cold oil inlet 183 and a heat exchanger hot oil outlet 184; the heat exchanger hot oil outlet 184 is connected to the feeder hot oil inlet 154.

[0083] In step S19, cold heat transfer oil is input into the outer tank of the discharge heat exchanger 18 through the cold oil inlet 183 of the heat exchanger to cool the second tailings, and the hot heat transfer oil is output through the hot oil outlet 184 of the heat exchanger; the arsenic-calcium slag harmless treatment method also includes step S20, obtaining the hot heat transfer oil output from the hot oil outlet 184 of the heat exchanger, and inputting it into the outer tank of the paddle-type preheating feeder 15 through the hot oil inlet 154 of the feeder; step S20 is located after step S19; in step S15, the cold heat transfer oil is output through the cold oil outlet 155 of the feeder.

[0084] The high-temperature second tailings in the inner tank of the discharge heat exchanger 18 will transfer heat to the heat transfer oil in the outer tank of the discharge heat exchanger 18. In the above steps, the hot heat transfer oil output from the heat exchanger hot oil outlet 184 is transported to the outer tank of the paddle-type preheating feeder 15 through the feeder hot oil inlet 154, which can provide a heat source to heat the mixed material in the inner tank of the paddle-type preheating feeder 15, effectively saving and utilizing heat.

[0085] The heat exchanger cold oil inlet 183 is connected to the feeder cold oil outlet 155; the arsenic-calcium slag harmless treatment method also includes step S21, obtaining the cold heat transfer oil output from the feeder cold oil outlet 155, and inputting it into the outer tank of the discharge heat exchanger 18 through the heat exchanger cold oil inlet 183.

[0086] The heat of the heat transfer oil in the outer tank of the paddle-type preheating feeder 15 is transferred to the first mixture in the inner tank of the paddle-type preheating feeder 15. In the above steps, the cold heat transfer oil output from the feeder cold oil outlet 155 is input into the outer tank of the discharge heat exchanger 18 through the heat exchanger cold oil inlet 183, which can effectively cool the second tailings.

[0087] The harmless treatment method of arsenic-calcium slag according to the preferred embodiment of the present invention:

[0088] Obtain arsenic calcium slag and pyrite, input the two into the mixer 11 through the mixing inlet 111, mix the arsenic calcium slag and pyrite, and output the mixed material through the mixing outlet 112;

[0089] Obtain the mixed material and feed it into the paddle preheating feeder 15 through the feeder material inlet 151, heat the mixed material at a temperature of 150°C-200°C for 60min-120min, discharge water vapor through the feeder gas outlet 152, and output the dehydrated mixed material through the feeder material outlet 153;

[0090] The dehydrated mixed material is obtained and fed into the medium-temperature volatilization furnace 12 through the volatilization furnace material inlet 121. Nitrogen is fed into the medium-temperature volatilization furnace 12 through the volatilization furnace gas inlet 122 to heat the mixed material at a medium temperature. A first tail gas containing arsenic oxide is output through the volatilization furnace gas outlet 123, and a first tailing containing calcium arsenate and pyrite is output through the volatilization furnace tailing outlet 124.

[0091] Obtaining a first tailing, feeding it into the pyrolysis furnace 13 through the decomposition furnace material inlet 131, and feeding air into the pyrolysis furnace 13 through the decomposition furnace gas inlet 132, heating the first tailing at high temperature, outputting a second tail gas containing arsenic oxide and sulfur dioxide through the decomposition furnace gas outlet 133, and outputting a second tail gas containing calcium oxide and ferrosoferric oxide through the decomposition furnace tailing outlet 134;

[0092] Obtain the second tailings, input them into the discharging heat exchanger 18 through the heat exchanger material inlet 181, cool the second tailings, and output the cooled second tailings through the heat exchanger material outlet 182;

[0093] Obtain the hot heat transfer oil output from the heat exchanger hot oil outlet 184 and input it into the outer liner of the paddle type preheating feeder 15 through the feeder hot oil inlet 154;

[0094] Get the cold heat transfer oil output from the feeder cold oil outlet 155 and input it into the outer tank of the discharge heat exchanger 18 through the heat exchanger cold oil inlet 183;

[0095] Obtaining the first tail gas and the second tail gas, inputting the two into the high-temperature gas-solid separator 16 through the separator inlet 161, outputting impurities through the separator solid outlet 162, and outputting the third tail gas containing arsenic oxide and sulfur dioxide through the separator gas outlet 163;

[0096] The third tail gas is obtained and input into the condensation arsenic collecting chamber 17 through the arsenic collecting chamber inlet 171 to collect the refined white arsenic, and the fourth tail gas containing sulfur dioxide is output through the arsenic collecting chamber gas outlet 172;

[0097] Obtaining a fourth tail gas, inputting the fourth tail gas into the tail gas purification device 14 through the purification inlet 141, and discharging the purified tail gas through the purification outlet 142;

[0098] Water vapor is obtained and input into the condenser 19 through the condensation inlet 191 , and then waste water is output through the condensation outlet 192 and transported to a sewage treatment plant.

[0099] This is the process of the harmless treatment method of arsenic-calcium slag in this preferred embodiment.

[0100] The harmless treatment method for arsenic-calcium slag of the present invention comprises the following steps: firstly, mixing the arsenic-calcium slag and pyrite in a mixer to ensure sufficient subsequent reaction; then, inputting the mixture containing the arsenic-calcium slag and pyrite into a medium-temperature volatilization furnace to convert arsenic oxide in the mixture into a gaseous state and separate it from a first tailing containing calcium arsenate and pyrite; the medium-temperature volatilization furnace is provided with a nitrogen atmosphere, thereby preventing the arsenic oxide from reacting with oxygen to generate solid arsenic pentoxide, which would increase the difficulty of subsequent treatment; and finally, inputting the first tailing into a high-temperature decomposition furnace; in the presence of oxygen, the calcium arsenate and pyrite in the first tailing react chemically to form arsenic in the form of gaseous arsenic oxide, which is separated from a second tailing containing calcium oxide and ferroferric oxide; the second tailing finally obtained does not contain arsenic; and the first tail gas and the second tail gas are treated by a tail gas purification device to avoid arsenic pollution. At the same time, the pyrite is first subjected to a medium-temperature treatment in a medium-temperature volatilization furnace and then to a high-temperature treatment in a high-temperature decomposition furnace, so that the pyrite in the medium-temperature volatilization furnace does not react with arsenic oxide, and all the pyrite reacts with calcium arsenate in the high-temperature decomposition furnace, thereby improving the utilization rate of the pyrite and saving costs; the arsenic oxide in the arsenic-calcium slag is first converted into a gaseous state and discharged in the medium-temperature volatilization furnace, so that the arsenic-calcium slag in the high-temperature decomposition furnace is only left with calcium arsenate, which can also shorten the treatment time in the high-temperature decomposition furnace and save heat.

[0101] In summary, although the present invention has been disclosed as above in terms of preferred embodiments, the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the concept of the technical solution of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for harmlessly treating arsenic-calcium slag containing calcium arsenate and arsenic oxide, characterized in that: Arsenic-calcium slag harmless treatment equipment is used to treat the arsenic-calcium slag, and the arsenic-calcium slag harmless treatment equipment includes: A mixer is provided with a mixing inlet and a mixing outlet; A medium-temperature volatilization furnace is provided with a volatilization furnace material inlet, a volatilization furnace gas inlet, a volatilization furnace gas outlet and a volatilization furnace tail slag outlet; the volatilization furnace material inlet is connected to the mixing outlet; A high-temperature decomposition furnace is provided with a decomposition furnace material inlet, a decomposition furnace gas inlet, a decomposition furnace gas outlet and a decomposition furnace tail slag outlet; the decomposition furnace material inlet is connected to the volatilization furnace tail slag outlet; and, An exhaust gas purification device is provided with a purification inlet and a purification outlet, wherein the purification inlet is connected to both the volatilization furnace gas outlet and the decomposition furnace gas outlet; The harmless treatment method for arsenic-calcium slag comprises: S11, obtaining arsenic calcium slag and pyrite, inputting the two into the mixer through the mixing inlet, mixing the arsenic calcium slag and pyrite, and outputting the mixed material through the mixing outlet; S12, obtaining a mixed material, feeding it into the medium-temperature volatilization furnace through the material inlet of the volatilization furnace, feeding nitrogen into the medium-temperature volatilization furnace through the gas inlet of the volatilization furnace, heating the mixed material at medium temperature, outputting a first tail gas containing arsenic oxide through the gas outlet of the volatilization furnace, and outputting a first tailing containing calcium arsenate and pyrite through the tailing outlet of the volatilization furnace; S13, obtaining a first tailing, feeding it into the pyrolysis furnace through the decomposition furnace material inlet, feeding air into the pyrolysis furnace through the decomposition furnace gas inlet, heating the first tailing at high temperature, outputting a second tail gas containing arsenic oxide and sulfur dioxide through the decomposition furnace gas outlet, and outputting a second tailing containing calcium oxide and ferrosoferric oxide through the decomposition furnace tailing outlet; and, S14 , obtaining the first tail gas and the second tail gas, inputting the first tail gas and the second tail gas into the tail gas purification device through the purification inlet, and discharging the purified tail gas through the purification outlet.

2. The harmless treatment method for arsenic-calcium slag according to claim 1, characterized in that: In step S12, the heating temperature is 550°C-600°C, and the heating time is 60min-90min.

3. The harmless treatment method for arsenic-calcium slag according to claim 1, characterized in that: In step S13, the heating temperature is 800°C-850°C, and the heating time is 60min-90min.

4. The harmless treatment method for arsenic-calcium slag according to claim 1, characterized in that: The calcium arsenate is 70%-80% of the mass of the arsenic calcium slag; in step S13, the oxygen content of the air introduced into the pyrolysis furnace is 50%-60% of the mass of the arsenic calcium slag; in step S11, the pyrite input into the mixer has ferrous disulfide content of 90%-100% of the mass of the arsenic calcium slag.

5. The harmless treatment method for arsenic-calcium slag according to claim 1, characterized in that: The arsenic-calcium slag harmless treatment equipment also includes a paddle-type preheating feeder, the inner shell of which is provided with a feeder material inlet, a feeder gas outlet and a feeder material outlet; the feeder material inlet is connected to the mixing outlet; the feeder material outlet is connected to the volatilization furnace material inlet; The harmless treatment method of arsenic-calcium slag also includes step S15, obtaining a mixed material, inputting it into the paddle-type preheating feeder through the material inlet of the feeder, heating the mixed material, the heating temperature is 150°C-200°C, the heating time is 60min-120min, and water vapor is discharged through the gas outlet of the feeder, and the dehydrated mixed material is output through the material outlet of the feeder; step S15 is located after step S11 and before step S12.

6. The harmless treatment method for arsenic-calcium slag according to claim 5, characterized in that: The arsenic-calcium slag harmless treatment equipment also includes: A high-temperature gas-solid separator is provided with a separator inlet, a separator solid outlet and a separator gas outlet; the separator inlet is connected to both the volatilization furnace gas outlet and the decomposition furnace gas outlet; and, The condensation arsenic collection chamber is provided with an arsenic collection chamber inlet and an arsenic collection chamber gas outlet; the arsenic collection chamber inlet is connected to the separator gas outlet; the arsenic collection chamber gas outlet is connected to the purification inlet; The harmless treatment method for arsenic-calcium slag further comprises the steps of: S16, obtaining a first tail gas and a second tail gas, inputting the first tail gas and the second tail gas into the high-temperature gas-solid separator through the separator inlet, outputting impurities through the separator solid outlet, and outputting a third tail gas containing arsenic oxide and sulfur dioxide through the separator gas outlet; and S17, obtaining the third tail gas, inputting it into the condensation arsenic collection chamber through the inlet of the arsenic collection chamber to collect the refined white arsenic, and outputting the fourth tail gas containing sulfur dioxide through the gas outlet of the arsenic collection chamber; Step S16 and step S17 are located after step S13 and before step S14; step S14 is to obtain the fourth exhaust gas and input the fourth exhaust gas into the exhaust gas purification device for treatment.

7. The harmless treatment method for arsenic-calcium slag according to claim 5, characterized in that: The arsenic-calcium slag harmless treatment equipment further comprises a condenser, which is provided with a condensation inlet and a condensation outlet, wherein the condensation inlet is connected to the gas outlet of the feeder; The harmless treatment method for arsenic-calcium slag also includes step S18, obtaining water vapor, inputting it into the condenser through the condensation inlet, then outputting wastewater through the condensation outlet, and transporting the wastewater to a sewage treatment plant; step S18 is located after step S15.

8. The harmless treatment method for arsenic-calcium slag according to claim 5, characterized in that: The arsenic-calcium slag harmless treatment equipment further comprises a discharge heat exchanger, the inner tank of which is provided with a heat exchanger material inlet and a heat exchanger material outlet; the heat exchanger material inlet is connected to the decomposition furnace tail slag outlet; The harmless treatment method for arsenic-calcium slag also includes step S19, obtaining second tailings, inputting them into the discharging heat exchanger through the material inlet of the heat exchanger, cooling the second tailings, and outputting the cooled second tailings through the material outlet of the heat exchanger; step S19 is located after step S13.

9. The harmless treatment method for arsenic-calcium slag according to claim 8, characterized in that: The outer liner of the paddle-type preheating feeder is also provided with a feeder hot oil inlet and a feeder cold oil outlet; the outer liner of the discharge heat exchanger is also provided with a heat exchanger cold oil inlet and a heat exchanger hot oil outlet; the heat exchanger hot oil outlet is connected to the feeder hot oil inlet; In step S19, cold heat transfer oil is input into the outer tank of the discharge heat exchanger through the cold oil inlet of the heat exchanger to cool the second tailings, and hot heat transfer oil is output through the hot oil outlet of the heat exchanger. The arsenic-calcium slag harmless treatment method further includes step S20, obtaining the hot heat transfer oil output from the hot oil outlet of the heat exchanger, and inputting it into the outer tank of the paddle-type preheating feeder through the hot oil inlet of the feeder; Step S20 is located after step S19; in step S15, the cold heat transfer oil is output through the cold oil outlet of the feeder.

10. The harmless treatment method for arsenic-calcium slag according to claim 9, characterized in that: The cold oil inlet of the heat exchanger is connected to the cold oil outlet of the feeder; the arsenic-calcium slag harmless treatment method also includes step S21, obtaining the cold heat transfer oil output from the cold oil outlet of the feeder, and inputting it into the outer tank of the discharge heat exchanger through the cold oil inlet of the heat exchanger.

Images