A roasting method and system for simultaneously using multiple fuel gases for roasting aluminum hydroxide

Abstract

The present invention provides a roasting method in which multiple fuel gases are used for roasting aluminum hydroxide at the same time. In view of the fact that there are multiple industries in the park, a mixed gas obtained by mixing coal gas, surplus hydrogen on the chlor-alkali production line, and silicon-manganese smelting tail gas is preferably used for the joint gas supply for roasting aluminum hydroxide, so as to make full use of the originally exhausted hydrogen and silicon-manganese smelting tail gas resources, which can greatly reduce the use of low calorific value and polluted coal, and realize carbon emission reduction in the three industries of aluminum oxide, chlor-alkali, and silicon-manganese smelting on the basis of reducing the cost of aluminum oxide roasting. The present invention also provides a roasting system used in the roasting method in which multiple fuel gases are used for roasting aluminum hydroxide at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum hydroxide production, and in particular to a roasting method and system for simultaneously using multiple fuel gases for roasting aluminum hydroxide. Background Art

[0002] At present, the alumina industry basically uses coal gas as fuel to roast aluminum hydroxide to produce alumina. Due to the low calorific value of coal gas (calorific value of about 1550kcal), a large amount of coal gas is consumed when roasting aluminum hydroxide. Taking the alumina production line with a capacity of 1 million tons / a as an example, the coal gas for roasting aluminum hydroxide is provided by a pulverized coal furnace and eight two-stage coal gas generators (hereinafter referred to as "second-stage furnaces"), and the total coal gas capacity required is 51,000m 3 / h, and the production of coal gas consumes a lot of coal. Because pulverized coal furnaces and two-stage coal gasifiers produce a lot of hazardous waste during the gas production process, for example, they emit a lot of CO during the roasting process. 2 , and produces a large amount of difficult-to-handle coal slag, which does not meet the current national environmental protection requirements. In addition, according to the increasingly stringent national environmental protection requirements, restrictions on coal mining have been strengthened, which will inevitably affect the price of lump coal, thereby increasing the gasification cost of the two-stage gasifier. Summary of the invention

[0003] In response to the problems raised in the above background technology, the present invention provides a roasting method and system for roasting aluminum hydroxide using multiple fuel gases at the same time, which can reduce the amount of coal used in roasting aluminum hydroxide.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A roasting method for aluminum hydroxide using multiple fuel gases simultaneously, comprising:

[0006] Purify the silicon-manganese smelting tail gas generated by the silicon-manganese gas furnace, and detect the oxygen content of the purified silicon-manganese smelting tail gas. When the oxygen content of the silicon-manganese smelting tail gas is ≤3%, pressurize the silicon-manganese smelting tail gas to 23-27kpa and then transport it to the high-pressure buffer tank;

[0007] The oxygen content of the gas produced by the gasifier is tested. When the oxygen content of the gas is ≤0.6%, the gas is pressurized to 23-27kpa and then transported to the high-pressure buffer tank;

[0008] The oxygen content of hydrogen produced by the chlor-alkali production line is tested. When the oxygen content in the hydrogen is ≤1%, the hydrogen is pressurized to 29-33kpa and then transported to the high-pressure buffer tank;

[0009] The mixed gas consisting of coal gas, hydrogen and silicon-manganese smelting tail gas in the high-pressure buffer tank is introduced into the gas combustion station of the roaster for combustion, and the roasting temperature of the roaster is adjusted by controlling the delivery flow rate of the mixed gas to ensure that the roasting temperature is within the preset range. When the delivery amount of the mixed gas consisting of coal gas, hydrogen and silicon-manganese smelting tail gas cannot meet the preset roasting temperature range, natural gas is added to the natural gas combustion station of the roaster as a supplementary gas for the combustion of the roaster to ensure that the roasting temperature is within the preset range.

[0010] Furthermore, when the oxygen content of the silicon-manganese furnace smelting tail gas exceeds the standard, stop supplying the silicon-manganese furnace smelting tail gas to the high-pressure buffer tank; when the oxygen content of the coal gas exceeds the standard, stop supplying the coal gas to the high-pressure buffer tank; when the oxygen content of the hydrogen exceeds the standard, stop supplying the hydrogen to the high-pressure buffer tank.

[0011] Furthermore, the coal gas is mixed with the tail gas from silicon manganese smelting and then pressurized by the same compressor.

[0012] Furthermore, when it is detected that the pressure of the mixed gas of silicon manganese smelting tail gas and coal gas is too high or too low, the pressure of the mixed gas of silicon manganese smelting tail gas and coal gas is adjusted to be between 23-27 kPa by adjusting the flow rate of the mixed gas.

[0013] Furthermore, the purification method for silicon-manganese smelting tail gas is as follows: the silicon-manganese smelting tail gas from the silicon-manganese furnace is successively subjected to gravity dust removal, cooled in a steam-water separator, and then purified by bag dust removal, so that the dust content of the silicon-manganese smelting tail gas is ≤50mg / Nm 3 .

[0014] Furthermore, the dust content of silicon-manganese smelting tail gas is monitored by regularly discharging silicon-manganese smelting tail gas and igniting the purified tail gas, and judging whether the dust content of silicon-manganese smelting tail gas is ≤50mg / Nm by the color of the tail gas flame. 3 When the dust content of silicon-manganese smelting tail gas exceeds the standard, stop supplying silicon-manganese smelting tail gas to the high-pressure buffer tank.

[0015] The present invention also provides a roasting system for roasting aluminum hydroxide using multiple fuel gases at the same time, including a silicon manganese smelting tail gas supply part, a coal gas supply part, a compressor, a mixed gas delivery pipeline, a chlor-alkali production line hydrogen supply part, a natural gas supply part and a high-pressure buffer tank; wherein,

[0016] The tail gas supply part of silicon manganese smelting includes a tail gas delivery pipeline, a first control valve, a purification device, a tail gas pressure detection device, a tail gas flow detection device and an oxygen analyzer, and the first control valve, the purification device, the tail gas pressure detection device, the tail gas flow detection device and the oxygen analyzer are installed on the tail gas delivery pipeline at intervals;

[0017] The gas supply part includes a gas transmission pipeline, a second control valve and a gas flow detection device, and the second control valve and the gas flow detection device are installed on the gas transmission pipeline at intervals;

[0018] The output ends of the tail gas delivery pipeline and the gas delivery pipeline are both connected to the air inlet end of the compressor, the air outlet end of the compressor is connected to the input end of the mixed gas delivery pipeline, the output end of the mixed gas delivery pipeline is connected to the air inlet of the high-pressure buffer tank, and the mixed gas delivery pipeline is provided with a mixed gas pressure detection device and a third control valve at intervals;

[0019] The hydrogen supply part of the chlor-alkali production line includes a hydrogen gas pipeline, a fourth control valve, a hydrogen pressure detection device, a hydrogen flow detection device and a moisture separator. The third control valve, the hydrogen pressure detection device, the hydrogen flow detection device and the moisture separator are installed on the hydrogen gas pipeline at intervals, and the outlet end of the moisture separator is connected to the air inlet of the high-pressure buffer tank;

[0020] The gas outlet of the high-pressure buffer tank and the natural gas supply part are used to connect with the roasting furnace.

[0021] Furthermore, the mixed gas delivery pipeline is also connected to a relief pipe, and a relief flame arrester and a relief valve are installed on the relief pipe at intervals.

[0022] Furthermore, the hydrogen gas transmission pipeline and the tail gas transmission pipeline are both connected to a drain pipe, and a drain valve is installed on the drain pipe.

[0023] Furthermore, the purification device includes a gravity dust removal device, a steam-water separator device and a bag dust removal device which are sequentially arranged along the exhaust gas conveying direction.

[0024] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0025] 1. The roasting method and system for roasting aluminum hydroxide using the above-mentioned multiple fuel gases at the same time, in view of the characteristics of multiple industries in the park, preferably use the mixed gas of coal gas, surplus hydrogen on the chlor-alkali production line, and silicon-manganese smelting tail gas as the joint gas supply for roasting aluminum hydroxide, so as to make full use of the originally exhausted hydrogen and silicon-manganese smelting tail gas resources, which can greatly reduce the use of low calorific value and polluted coal, and achieve carbon emission reduction in the three industries of alumina, chlor-alkali, and silicon-manganese smelting on the basis of reducing the cost of alumina roasting. Considering that hydrogen and silicon-manganese smelting tail gas come from different production lines and their output has certain fluctuations, the present invention also uses natural gas as a supplementary gas for insufficient heat when the roasting temperature of the mixed gas combustion is insufficient to ensure the stability of the calorific value of the fuel gas.

[0026] Generally speaking, mixed combustion has a great risk of explosion. In the prior art, the explosion of mixed combustion is usually prevented by controlling the concentration of combustible gas. However, the silicon manganese smelting tail gas used in the present invention has a relatively complex composition, including CO, CO 2 , CH 4 、N 2 , H 2 , O 2 , and the proportion of gas components fluctuates to a certain extent. It is difficult to achieve the safety of mixed combustion by controlling the concentration of combustible gases. According to research, the three kinds of mixtures of coal gas, surplus hydrogen on the chlor-alkali production line, and silicon-manganese smelting tail gas can be stably burned by controlling the oxygen content of the three kinds of combustible gases. When the oxygen content of the tail gas from the silicon-manganese furnace is ≤3%, the oxygen content of coal gas is ≤0.6%, and the oxygen content of hydrogen is ≤1%, under normal operating conditions, the concentrations of the three kinds of combustible gases do not need to be controlled, and the three kinds of combustible gases can be mixed in any proportion. The mixture can be safely transported and stably burned, and the control method is relatively convenient.

[0027] 2. The roasting method and system for roasting aluminum hydroxide using the above-mentioned multiple fuel gases at the same time can ensure smooth ignition during roasting by controlling the pressure of silicon-manganese smelting tail gas, coal gas and hydrogen generated by the chlor-alkali production line. By purifying the silicon-manganese smelting tail gas, the calorific value of the silicon-manganese smelting tail gas can be further improved, the utilization rate can be improved, and the dust content of the silicon-manganese smelting tail gas can be reduced, thereby improving the quality of alumina prepared by roasting aluminum hydroxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a structural diagram of a roasting system in which multiple fuel gases are simultaneously used for roasting aluminum hydroxide according to a preferred embodiment of the present invention.

[0029] Figure 2 for Figure 1 The structure diagram of the silicon manganese smelting tail gas supply part, the coal gas supply part and the mixed gas transportation pipeline part in the roasting system in which multiple fuel gases are used simultaneously for the roasting of aluminum hydroxide.

[0030] Figure 3 for Figure 1 The diagram shows the structure of the hydrogen supply part and the natural gas supply part of the chlor-alkali production line in the roasting system in which multiple fuel gases are used simultaneously for the roasting of aluminum hydroxide.

[0031] Figure 4 for Figure 1 The diagram shows the structure of a purification device in a roasting system in which multiple fuel gases are used simultaneously for roasting aluminum hydroxide.

[0032] Figure 5 for Figure 4 Schematic diagram of the structure of the steam-water separation device shown.

[0033] Figure 6 for Figure 5 Schematic diagram of the structure of the heat exchanger in the steam-water separation device.

[0034] Main component symbols

[0035] 10. Silicon manganese smelting tail gas supply part; 11. Tail gas delivery pipeline; 112. First delivery pipe; 114. Second delivery pipe; 12. Positive pressure water seal tank; 121. Tank body; 122. Drain pipe; 123. Water inlet pipe; 124. Air supply pipe; 125. Pipeline valve; 126. First pipeline flame arrester; 127. Liquid level gauge; 13. First control valve; 131. First manual butterfly valve; 132. First glasses valve; 14. Purification device; 141. Gravity dust removal device; 142. Bag dust removal device; 15. Steam-water separation device; 150. Shell; 151. Air inlet; 152. Drain; 153. Exhaust; 154. Manhole door; 155. Heat exchanger; 1551. Heat exchange tube; 15 52. Water supply pipe; 1553. Water inlet pipe; 1554. Water inlet branch pipe; 1556. Water outlet pipe; 1557. Water outlet pipe; 1558. Water outlet branch pipe; 156. Droplet collector; 157. Water seal mechanism; 1570. Water seal assembly; 1571. Water seal box; 1572. First opening; 1573. Second opening; 1574. Overflow pipe; 158. Isolation mesh; 159. Connecting pipe; 16. Exhaust gas pressure detection device; 17. Exhaust gas flow detection device; 18. Oxygen analyzer; 20. Gas supply part; 21. Gas delivery pipeline; 22. Second control valve; 23. Gas flow detection device; 30. Pressurizer; 40. Mixed gas delivery pipeline; 41. Mixed gas pressure Pressure detection device; 42, third control valve; 421, mixed delivery glasses valve; 423, mixed gas delivery one-way valve; 424, mixed delivery pneumatic regulating valve; 425, mixed delivery pneumatic stop valve; 426, mixed gas manual butterfly valve; 50, hydrogen gas supply part of chlor-alkali production line; 51, hydrogen gas pipeline; 511, first pipeline; 512, second pipeline; 52, fourth control valve; 521, first butterfly valve; 523, first pneumatic valve; 524, second pneumatic valve; 525, second butterfly valve; 526, third pneumatic valve; 527, third butterfly valve; 528, fourth butterfly valve; 53, hydrogen pressure detection device; 531, first pressure transmitter; 532, second pressure transmitter; 54, hydrogen flow detection device Measuring device; 541, first flow meter; 543, second flow meter; 55, moisture separator; 56, maintenance water seal tank; 561, tank body; 562, discharge pipe; 563, water supply pipe; 564, air inlet pipe; 565, on-off valve; 567, second pipeline flame arrester; 568, liquid level gauge; 57, vent pipe; 581, stop valve; 573, fourth pipeline flame arrester; 60, natural gas supply part; 61, natural gas transmission pipeline; 62, natural gas on-off valve; 70, high-pressure buffer tank; 80, vent pipe; 81, vent flame arrester; 82, vent valve; 90, drain pipe; 91, drain valve; 92, nitrogen purge pipe; 93, purge valve; 94, temperature measuring device; 200, roasting furnace. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0039] See also Figure 1 A preferred embodiment of the present invention provides a roasting system in which multiple fuel gases are used simultaneously for roasting aluminum hydroxide, including a silicon manganese smelting tail gas supply part 10, a coal gas supply part 20, a compressor 30, a mixed gas transmission pipeline 40, a chlor-alkali production line hydrogen supply part 50, a natural gas supply part 60 and a high-pressure buffer tank 70.

[0040] Please also see Figure 2 The silicon-manganese smelting tail gas supply part 10 includes a tail gas conveying pipeline 11, a first control valve 13, a purification device 14, a tail gas pressure detection device 16, a tail gas flow detection device 17 and an oxygen analyzer 18. The first control valve 13, the purification device 14, the tail gas pressure detection device 16, the tail gas flow detection device 17 and the oxygen analyzer 18 are installed on the tail gas conveying pipeline 11 at intervals.

[0041] In this embodiment, the silicon-manganese smelting tail gas supply part 10 also includes a positive pressure water seal tank 12; the tail gas delivery pipeline 11 includes a first delivery pipe 112 and a second delivery pipe 114, the input end of the first delivery pipe 112 is connected to the silicon-manganese gas furnace, and the output end of the first delivery pipe 112 extends into the positive pressure water seal tank 12; one end of the second delivery pipe 114 is located in the positive pressure water seal tank 12, and the height position of the end of the second delivery pipe 114 located in the positive pressure water seal tank 12 is higher than the height position of the end of the first delivery pipe 112 located in the positive pressure water seal tank 12, and the other end of the second delivery pipe 114 is connected to the air inlet end of the compressor 30.

[0042] In this embodiment, the positive pressure water seal tank 12 includes a sealed tank body 121, a water discharge pipe 122 installed at the bottom of the tank body 121, and a water inlet pipe 123 and an air supply pipe 124 installed at intervals at the top of the tank body 121. The water discharge pipe 122, the water inlet pipe 123 and the air supply pipe 124 are all equipped with pipeline valves 125 for controlling the opening and closing of the corresponding pipelines. The air supply pipe 124 is also equipped with a first pipeline flame arrester 126, which is arranged at intervals from the pipeline valve 125 on the air supply pipe 124 and is located on the side of the pipeline valve 125 on the air supply pipe 124 facing away from the tank body 121. The first pipeline flame arrester 126 can prevent open flames, such as the open flame of a constantly lit lamp, from entering the fuel gas system and causing combustion and explosion accidents. In this embodiment, the positive pressure water seal tank 12 also includes a liquid level gauge 127, which is installed on the tank body 121 and is used to detect the liquid level in the tank body 121. The structure of the liquid level gauge 127 belongs to the prior art and is not described here for the sake of space. In this embodiment, the number of the first control valves 13 on the second delivery pipe 114 is three, which include two first manual butterfly valves 131 and a first glasses valve 132. The two first manual butterfly valves 131 and the first glasses valve 132 are arranged at intervals along the delivery direction of the exhaust gas. The first control valve 13 on the first delivery pipe 112 is a manual butterfly valve.

[0043] The purification device 14 is installed on the second delivery pipe 114 and is located between the first glasses valve 132 and the oxygen analyzer 18. Figure 4 In this embodiment, the purification device 14 includes a gravity dust removal device 141, a steam-water separation device 15 and a bag dust removal device 142 which are sequentially connected along the exhaust gas conveying direction, wherein the structures of the gravity dust removal device 141 and the bag dust removal device 142 belong to the prior art and will not be described here for the sake of space saving.

[0044] Please also see Figure 5 In this embodiment, the steam-water separation device 15 includes a shell 150, a heat exchanger 155, a droplet catcher 156 and a water seal mechanism 157, and the heat exchanger 155, the droplet catcher 156 and the water seal mechanism 157 are all connected to the shell 150.

[0045] The bottom of the housing 150 is provided with an air inlet 151 and a water outlet 152 at intervals, and the top of the housing 150 is provided with an air outlet 153. In this embodiment, the air inlet 151 is provided through the bottom of the peripheral wall of the housing 150, the water outlet 152 is provided through the bottom wall of the housing 150, and the air outlet 153 is provided through the top wall of the housing 150. The air inlet 151, the water outlet 152 and the air outlet 153 are all connected to the inner cavity of the housing 150.

[0046] Please also see Figure 6 The heat exchanger 155 includes a heat exchange tube 1551, a water supply tube 1552 and a water outlet tube 1556. The heat exchange tube 1551 is fixedly installed in the shell 150. One end of the water supply tube 1552 is connected to the water inlet of the heat exchange tube 1551 for introducing coolant into the heat exchange tube 1551. One end of the water outlet tube 1556 is connected to the water outlet of the heat exchange tube 1551 for discharging the coolant after heat exchange and temperature increase in the heat exchange tube 1551. In this embodiment, there are several heat exchange tubes 1551, which are all arranged vertically and connected to the outer shell 150 through a mounting frame (not shown in the figure), and two adjacent heat exchange tubes 1551 are arranged at intervals to form an air duct (not shown in the figure) for gas to pass through; the top of each heat exchange tube 1551 extends toward the top of the outer shell 150 and is provided with the water inlet, and the bottom of each heat exchange tube 1551 extends to below the air inlet 151 of the outer shell 150 and is provided with the water outlet. The water supply pipe 1552 is connected to the water inlets of the plurality of heat exchange tubes 1551, and the water outlet pipe 1556 is connected to the water outlets of the plurality of heat exchange tubes 1551. Specifically, the water supply pipe 1552 includes a water inlet main pipe 1553 and a plurality of water inlet branch pipes 1554, one ends of the plurality of water inlet branch pipes 1554 are connected to the water inlet main pipe 1553, and the other ends of the plurality of water inlet branch pipes 1554 are respectively connected to the water inlets of the plurality of heat exchange tubes 1551; the water outlet pipe 1556 includes a water outlet main pipe 1557 and a plurality of water outlet branch pipes 1558, one ends of the plurality of water outlet branch pipes 1558 are connected to the water outlet main pipe 1557, and the other ends of the plurality of water outlet branch pipes 1558 are respectively connected to the water outlets of the plurality of heat exchange tubes 1551. In this embodiment, the water outlet main pipe 1557 and the water inlet main pipe 1553 both pass through the outer shell 150 to the outside. The coolant discharged through the water outlet branch pipe 1558 flows along the water outlet main pipe 1557 to the outside for cooling and then enters the water inlet main pipe 1553 for recycling. The recycling of the coolant belongs to the existing technology and will not be described here to save space.

[0047] The droplet catcher 156 is installed in the housing 150 and is located between the heat exchange tube 1551 and the exhaust port 153. In this embodiment, an isolation mesh 158 is installed in the housing 150, and the isolation mesh 158 is located between the heat exchange tube 1551 and the exhaust port 153. The droplet catcher 156 is placed on the isolation mesh 158. The droplet catcher 156 preferably uses a plastic ball ring packing.

[0048] The water sealing mechanism 157 is connected to the drain port 152 of the housing 150 via a connecting pipe 159 . In this embodiment, the water seal mechanism 157 includes a plurality of water seal components 1570 connected in sequence, each water seal component 1570 includes a water seal box 1571 and an overflow pipe 1574, and a first opening 1572 and a second opening 1573 are respectively provided on opposite sides of each water seal box 1571, the height position of the second opening 1573 is lower than the height position of the first opening 1572, and the height positions of the second openings 1573 of the plurality of water seal boxes 1571 decrease in sequence along the drainage direction; one end of the overflow pipe 1574 is connected to the second opening 1573 of the corresponding water seal box 1571, and the other end of the overflow pipe 1574 extends into the water seal box 1571 of the next level through the first opening 1572 of the water seal box 1571 of the next level; the end of the connecting pipe 159 away from the housing 150 extends into the water seal box 1571 of the uppermost level through the first opening 1572 of the water seal box 1571 of the uppermost level. Specifically, in this embodiment, the water seal mechanism 157 includes four water seal assemblies 1570 connected in sequence, and an aqueous solution is placed in the water seal box 1571 of the water seal assembly 1570. The first opening 1572 of the water seal box 1571 of the uppermost water seal assembly 1570 is connected to the drain outlet 152 of the outer shell 150 through a connecting pipe 159, and the end of the connecting pipe 159 away from the outer shell 150 extends into the uppermost water seal box 1571 through the first opening 1572 of the uppermost water seal box 1571, and the end of the connecting pipe 159 away from the outer shell 150 is located below the liquid level in the water seal box 1571.

[0049] In this embodiment, the housing 150 is also provided with a manhole door 154. Specifically, there are two manhole doors 154, one of which is provided on the peripheral wall of the housing 150 to facilitate the inspection and repair of the heat exchanger 155; the other manhole door 154 is provided on the top wall of the housing 150 to facilitate the replacement of the droplet catcher 156. In this embodiment, the bottom of the inner cavity of the housing 150 is generally in an inverted cone shape, that is, the cross section of the bottom of the inner cavity of the housing 150 gradually decreases in the direction away from the heat exchanger 155. The end of the connecting pipe away from the water seal mechanism 157 is connected to the end of the inner cavity bottom of the housing 150 with a smaller cross section.

[0050] The above-mentioned steam-water separation device 15 has a heat exchange tube 1551 and a droplet collector 156 in its shell 150. When in use, the high-temperature silicon-manganese smelting tail gas produced by the silicon-manganese furnace enters the shell 150 through the air inlet 151 of the shell 150. In the process of the silicon-manganese smelting tail gas moving toward the exhaust port 153 of the shell 150, the silicon-manganese smelting tail gas exchanges heat with the coolant in the heat exchange tube 1551. After the heat exchange, the temperature of the silicon-manganese smelting tail gas is reduced, so that the water vapor contained in the silicon-manganese smelting tail gas is condensed into water droplets. The water droplets fall to the bottom of the shell 150 under the action of their own gravity and are discharged from the connecting pipe 159 to the water seal mechanism 157; when the water volume of the water seal mechanism 157 is too much, the excess water is discharged through the overflow pipe 1547 of the last-stage water seal assembly 1570; the silicon-manganese smelting tail gas after cooling continues to move upward, and the droplet collector 156 can further separate impurities such as moisture in the silicon-manganese smelting tail gas. The purified silicon-manganese smelting tail gas can eventually be discharged to the roasting furnace 200 through the exhaust port 153 of the shell 150 to be used as fuel gas for the roasting furnace 200 .

[0051] According to research, the low calorific value of silicon-manganese smelting tail gas is mainly caused by its excessively high water content. The steam-water separation device 15 of this embodiment can purify the silicon-manganese smelting tail gas: heat is exchanged with the silicon-manganese smelting tail gas entering the outer shell 150 through the heat exchange tube 1551 to cool the silicon-manganese smelting tail gas, thereby condensing the water vapor contained in the silicon-manganese smelting tail gas to remove the water contained in the silicon-manganese smelting tail gas; the droplet collector 156 can further separate the water impurities in the silicon-manganese smelting tail gas, thereby improving the calorific value of the silicon-manganese smelting tail gas to meet the combustion requirements of the roasting furnace 200, and then the combustible gas in the silicon-manganese smelting tail gas can be reused. It has been verified that after the steam-water separation device 15 of this embodiment is put into use, the temperature of the silicon-manganese smelting tail gas is effectively reduced. The temperature of the silicon-manganese smelting tail gas is reduced by about 26°C, and the water content of the silicon-manganese smelting tail gas is reduced by 27% to 30%, as shown in Table 1. The condensed water separated from the silicon-manganese smelting tail gas is discharged to the water seal mechanism 157 through the drain port 152. By setting the water seal mechanism 157, the silicon-manganese smelting tail gas can be prevented from overflowing from the drain port 152, which would cause leakage of the silicon-manganese smelting tail gas.

[0052] Table 1 Comparison of temperature and water content of silicon-manganese smelting tail gas before and after purification

[0053] Exhaust gas temperature (℃) Water content Before purification 72～73 35～40％ After purification 46～47 8～10％

[0054] The water seal mechanism 157 of the steam-water separation device 15 comprises a plurality of water seal assemblies 1570 connected in sequence, and a first opening 1572 and a second opening 1573 are respectively provided on opposite sides of each water seal box 1571, and the height position of the second opening 1573 is lower than the height position of the first opening 1572, and the height positions of the second openings 1573 of the plurality of water seal boxes 1571 decrease in sequence along the drainage direction. 4 The density of the water seal box 1571 is lower than that of the air, and it has a tendency to rise. Therefore, by gradually lowering the height of the second opening 1573 of the water seal box 1571 along the drainage direction, CO and CH 4 The overflow of silicomanganese smelting exhaust gas can be prevented, and the toxic gases CO and CH 4 leakage.

[0055] The droplet catcher 156 of the steam-water separation device 15 adopts a plastic ball ring filler, which can effectively remove impurities in the tail gas and also make the gas uniformly transported. The top of each heat exchange tube 1551 of the steam-water separation device 15 extends toward the droplet catcher 156 and is provided with the water inlet, and the bottom of each heat exchange tube 1551 extends to below the air inlet 151 of the shell 150 and is provided with the water outlet. When in use, the coolant in the heat exchange tube 1551 flows downward through the top of the heat exchange tube 1551, and the silicon-manganese smelting tail gas entering the shell 150 moves toward the exhaust port 153 at the top of the shell 150 through the feed port at the bottom of the shell 150, that is, the silicon-manganese smelting tail gas flows in the opposite direction to the coolant outside the heat exchange tube 1551, thereby further improving the cooling effect. The bottom of the inner cavity of the shell 150 of the steam-water separation device 15 is roughly inverted cone shape, which can more conveniently guide the condensed water to the connecting pipe for discharge.

[0056] In this embodiment, the tail gas pressure detection device 16, the tail gas flow detection device 17 and the oxygen analyzer 18 are installed on the second delivery pipe 114 of the tail gas delivery pipeline 11 at intervals, and are all located between the first glasses valve 132 and the pressurizer 30, wherein the tail gas pressure detection device 16 is used to detect the pressure of the silicon manganese smelting tail gas, the tail gas flow detection device 17 is used to detect the flow of the silicon manganese smelting tail gas, and the oxygen analyzer 18 is used to detect the oxygen content of the silicon manganese smelting tail gas. The structures of the tail gas pressure detection device 16, the tail gas flow detection device 17 and the oxygen analyzer 18 all belong to the prior art, and are not described here for the sake of space omission.

[0057] The above-mentioned silicon-manganese smelting tail gas supply part 10 uses the tail gas delivery pipeline 11 to transport the silicon-manganese smelting tail gas to the roasting furnace 200 for aluminum hydroxide production for combustion and reuse to save energy. The tail gas delivery pipeline 11 is equipped with a tail gas pressure detection device 16, a tail gas flow detection device 17 and a first control valve 13 for controlling the on-off of the tail gas delivery pipeline 11 at intervals, wherein the tail gas pressure detection device 16 is used to detect the air pressure in the tail gas delivery pipeline 11, and the tail gas flow detection device 17 is used to detect the gas flow in the tail gas delivery pipeline 11, so as to monitor the gas delivery situation in the tail gas delivery pipeline 11 and ensure safe delivery. A purification device 14 is arranged on the tail gas delivery pipeline 11, and the purification device 14 can further remove the moisture and impurities contained in the tail gas to improve the calorific value of the silicon-manganese smelting tail gas and prevent impurities from affecting the quality of the prepared alumina.

[0058] The above-mentioned silicon-manganese smelting tail gas supply part 10 also includes a positive pressure water seal tank 12. When the silicon-manganese smelting tail gas is used as the fuel gas of the roasting furnace 200, water is not introduced into the positive pressure water seal tank 12, so that the silicon-manganese smelting tail gas can be transmitted through the first conveying pipe 112 and the second conveying pipe 114 in sequence; when an emergency or failure occurs in the silicon-manganese smelting tail gas supply part 10, water can be introduced into the positive pressure water seal tank 12, and one end of the first conveying pipe 112 located in the tank body 121 is located below the liquid level, and one end of the second conveying pipe 114 located in the tank body 121 is located above the liquid level, so as to prevent air from entering the first conveying pipe 112 and mixing with the silicon-manganese smelting tail gas during maintenance to cause safety hazards. After water is introduced into the tank body 121 so that the water covers the free end of the first delivery pipe 112, the pressure in the tank body 121 will be increased as the water is introduced, making it difficult for water to enter the tank body 121. At this time, the pipeline valve 125 can be used to open the air supply pipe 124 to ensure that water can smoothly enter the tank body 121, thereby ensuring that the water pressure in the tank body 121 has sufficient pressure to improve the sealing effect.

[0059] The gas supply part 20 includes a gas delivery pipeline 21, a second control valve 22 and a gas flow detection device 23. The second control valve 22 and the gas flow detection device 23 are installed on the gas delivery pipeline 21 at intervals. In this embodiment, the second control valve 22 is a butterfly valve, and the gas flow detection device 23 is used to detect the flow of gas. The structures of the butterfly valve and the gas flow detection device 23 belong to the prior art and are not described here for the sake of space.

[0060] The output ends of the tail gas delivery pipeline 11 and the output ends of the gas delivery pipeline 21 are connected to the air inlet end of the compressor 30, the air outlet end of the compressor 30 is connected to the input end of the mixed gas delivery pipeline 40, the output end of the mixed gas delivery pipeline 40 is connected to the air inlet of the high-pressure buffer tank 70, and the mixed gas delivery pipeline 40 is provided with a mixed gas pressure detection device 41 and a third control valve 42 at intervals. The air outlet of the high-pressure buffer tank 70 is used to be connected to the gas combustion station of the roasting furnace 200.

[0061] The pressurizer 30 is used to pressurize the coal gas and silicon manganese smelting tail gas to 23-27kpa. The structure of the pressurizer 30 belongs to the prior art and will not be described here for the sake of space. The third control valve 42 includes a mixed delivery glasses valve 421, a mixed gas delivery check valve 423, a mixed delivery pneumatic regulating valve 424, a mixed delivery pneumatic stop valve 425 and a mixed gas manual butterfly valve 426. The mixed delivery glasses valve 421, the mixed gas delivery check valve 423, the mixed delivery pneumatic regulating valve 424, the mixed delivery pneumatic stop valve 425 and the mixed gas manual butterfly valve 426 are arranged in sequence along the gas delivery direction. Among them, the mixed gas manual butterfly valve 426 is the last set of valves set at the outlet of the mixed gas delivery pipeline 40. The main purpose is to manually close the mixed gas delivery pipeline 40 when it is temporarily disconnected for maintenance, so as to facilitate the safe operation of other pneumatic valves, or to temporarily close the mixed gas manual butterfly valve 426 for processing when a pneumatic valve fails; the mixed gas delivery pneumatic stop valve 425 has a short opening and closing time, and can achieve the purpose of rapid cutoff in the event of an emergency, thereby improving safety; the mixed gas delivery pneumatic regulating valve 424 can adjust the flow rate and air pressure of the mixed gas of silicon manganese smelting tail gas and coal gas as needed; the mixed gas delivery check valve 423 is used to prevent the mixed gas in the tank from backflowing when the pressure in the high-pressure buffer tank 70 changes; the mixed gas delivery glasses valve 421 has good sealing performance and can well cut off the mixed gas delivery pipeline 40 to eliminate hidden dangers. The valve group formed by the above valves can ensure that the mixed gas delivery pipeline 40 is reliably isolated and safe and reliable. The mixed gas pressure detection device 41 can detect the pressure of the gas in the mixed gas delivery pipeline 40 in real time. In this embodiment, the mixed gas pressure detection device 41 is arranged between the mixed delivery pneumatic stop valve 425 and the mixed gas manual butterfly valve 426. Its structure belongs to the prior art and will not be repeated here to omit space.

[0062] In this embodiment, a discharge pipe 80 is further connected to the mixed gas delivery pipeline 40, and a discharge flame arrester 81 and a discharge valve 82 are installed on the discharge pipe 80, wherein the discharge flame arrester 81 is closer to the free end of the discharge pipe 80 than the discharge valve 82. The discharge pipe 80 can discharge the remaining gas in the pipeline during maintenance, and when the pressure in the pipeline is too high, part of the gas can be discharged through the discharge pipe 80 to ensure that the gas pressure and flow in the pipeline are within a preset range to ensure safety.

[0063] Please also see Figure 3 The hydrogen supply part 50 of the chlor-alkali production line includes a hydrogen gas pipeline 51, a fourth control valve 52, a hydrogen pressure detection device 53, a hydrogen flow detection device 54 and a moisture separator 55. The fourth control valve 52, the hydrogen pressure detection device 53, the hydrogen flow detection device 54 and the moisture separator 55 are installed on the hydrogen gas pipeline 51 at intervals, and the output end of the hydrogen gas pipeline 51 is connected to the air inlet of the high-pressure buffer tank 70.

[0064] In this embodiment, the hydrogen supply part 50 of the chlor-alkali production line also includes a maintenance water seal tank 56, which is installed on the hydrogen gas transmission pipeline 51. Specifically, in this embodiment, the maintenance water seal tank 56 includes a sealed tank body 561, a discharge pipe 562 installed at the bottom of the tank body 561, and a water supply pipe 563 and an air intake pipe 564 installed at intervals on the top of the tank body 561. The discharge pipe 562, the water supply pipe 563 and the air intake pipe 564 are all equipped with an on-off valve 565 for controlling the on-off of the corresponding pipeline. The air intake pipe 564 is also equipped with a second pipeline flame arrester 567, which is spaced apart from the on-off valve 565 on the air intake pipe 564 and is located on the side of the on-off valve 565 on the air intake pipe 564 facing away from the tank body 561. The second pipeline flame arrester 567 can prevent open flames, such as the open flame of a constantly lit lamp, from entering the fuel gas system and causing combustion and explosion accidents. In this embodiment, the maintenance water seal tank 56 further includes a liquid level gauge 568, which is installed on the tank body 561 and is used to detect the liquid level in the tank body 561. The hydrogen gas transmission pipeline 51 includes a first pipeline 511 and a second pipeline 512. One end of the first pipeline 511 is used to connect with the surplus hydrogen on the chlor-alkali production line, and the other end of the first pipeline 511 is inserted into the tank body 561 of the maintenance water seal tank 56, and the outer peripheral wall of the first pipeline 511 is sealed and connected to the tank body 561; one end of the second pipeline 512 is inserted into the tank body 561 of the maintenance water seal tank 56, and the outer peripheral wall of the second pipeline 512 is sealed and connected to the tank body 561; the height position of one end of the second pipeline 512 located in the maintenance water seal tank 56 is higher than the height position of one end of the first pipeline 511 located in the maintenance water seal tank 56, and the other end of one end of the second pipeline 512 leads to the roasting furnace 200.

[0065] In this embodiment, the first pipeline 511 and the second pipeline 512 are both equipped with a fourth control valve 52, wherein the fourth control valve 52 on the first pipeline 511 includes a first butterfly valve 521, a first pneumatic valve 523, a second pneumatic valve 524 and a second butterfly valve 525 arranged in sequence along the gas transmission direction; the fourth control valve 52 on the second pipeline 512 includes a third pneumatic valve 526, a third butterfly valve 527 and a fourth butterfly valve 528 arranged in sequence along the gas transmission direction. The first pipeline 511 and the second pipeline 512 are both equipped with a hydrogen pressure detection device 53 for detecting the pressure of hydrogen. The structure of the hydrogen pressure detection device 53 belongs to the prior art and will not be described here for the sake of space saving. The hydrogen pressure detection device 53 on the first pipeline 511 includes a first pressure transmitter 531 and a second pressure transmitter 532 which are sequentially arranged at intervals along the gas transmission direction, wherein the first pressure transmitter 531 is located between the free end of the first pipeline 511 and the first butterfly valve 521, and the second pressure transmitter 532 is located between the second pneumatic valve 524 and the second butterfly valve 525; the hydrogen pressure detection device 53 on the second pipeline 512 is arranged between the third butterfly valve 527 and the fourth butterfly valve 528. A hydrogen flow detection device 54 is installed on both the first pipeline 511 and the second pipeline 512. In this embodiment, the hydrogen flow detection device 54 is a flow meter, wherein the hydrogen flow detection device 54 on the first pipeline 511 includes a first flow meter 541 and a second flow meter 543 which are sequentially arranged at intervals along the gas transmission direction, wherein the first flow meter 541 is arranged between the first pneumatic valve 523 and the second pneumatic valve 524, and the second flow meter 543 is arranged between the second pressure transmitter 532 and the second butterfly valve 525. The hydrogen flow detection device 54 on the second pipeline 512 is disposed between the third butterfly valve 527 and the fourth butterfly valve 528 .

[0066] The hydrogen supply part 50 of the chlor-alkali production line also includes two vent pipes 57, one of which is connected to the first pipeline 511, and the other is connected to the second pipeline 512. The vent pipe 57 is equipped with a stop valve 571 for controlling the opening and closing of the vent pipe 57; the vent pipe 57 is also equipped with a fourth pipeline flame arrester 573. The fourth pipeline flame arrester 573 is located at the free end of the corresponding vent pipe 57, which can prevent open flames, such as the open flame of a permanent lamp, from entering the fuel gas system and causing combustion and explosion accidents. In this embodiment, the moisture separator 55 and the high-pressure buffer tank 70 are installed on the second pipeline 512 at intervals along the hydrogen delivery direction; the structures of the moisture separator 55 and the high-pressure buffer tank 70 belong to the prior art, and are not repeated here to omit space.

[0067] In this embodiment, the hydrogen gas pipeline 51 and the tail gas pipeline 11 are both connected to a drain pipe 90, and a drain valve 91 is installed on the drain pipe 90. Among them, one end of the drain pipe 90 on the hydrogen gas pipeline 51 is connected to the first pipeline 511 and is located between the second flow meter 543 and the first flow meter 514; one end of the drain pipe 90 on the tail gas pipeline 11 is connected to the first delivery pipe 112 of the tail gas pipeline 11 and is located between the purification device 14 and the tail gas pressure detection device 16. The drain valve 91 preferably adopts a stop valve. The other end of the drain pipe 90 can be plugged under the liquid level of a liquid collecting container (not shown) to play a sealing role, and the liquid discharged from the drain pipe 90 can be collected by the liquid collecting container.

[0068] In this embodiment, a nitrogen purge pipe 92 is also installed on the hydrogen gas pipeline 51 and the tail gas pipeline 11, and a purge gas valve 93 is installed on the nitrogen purge pipe 92. Among them, one end of the nitrogen purge pipe 92 on the hydrogen gas pipeline 51 is connected to the first pipeline 511, and the nitrogen purge pipe 92 is located between the drain pipe 90 and the maintenance water seal groove 56. In this embodiment, the purge gas valve 93 adopts a stop valve, and the nitrogen purge pipe 92 is arranged between the second butterfly valve 525 and the maintenance water seal groove 56. One end of the nitrogen purge pipe 92 on the tail gas pipeline 11 is connected to the first delivery pipe 112 of the tail gas pipeline 11 and is located between the two first manual butterfly valves 131. In this embodiment, the second delivery pipe 114 of the tail gas pipeline 11 and the mixed gas delivery pipeline 40 are equipped with a temperature detection device 94, which is used to detect the temperature of the gas in the pipeline. The structure of the temperature detection device 94 belongs to the prior art, and it is not repeated here to omit space.

[0069] The chlor-alkali industry also refers to the method of using saturated salt water to produce chlorine, hydrogen, and caustic soda. In industry, the electrolysis of saturated NaCl solution is used to produce NaOH, Cl 2 and H 2 The chlor-alkali industry is one of the most basic chemical industries. Its products are widely used in light industry, textile industry, metallurgical industry, petrochemical industry and public utilities in addition to the chemical industry itself. In the actual production process, based on local demand and cost considerations, the chlorine produced by some chlor-alkali factories is used in the chlorine-consuming industries in the park, but no hydrogen-consuming industries such as hydrogen peroxide production lines are set up, resulting in excess hydrogen. At present, the excess hydrogen produced by chlor-alkali production is usually discharged, resulting in a waste of combustible gas.

[0070] The hydrogen supply part 50 of the above-mentioned chlor-alkali production line uses a hydrogen gas pipeline 51 to transport the surplus hydrogen produced by chlor-alkali production to the roasting furnace 200 for aluminum hydroxide production for combustion and reuse, so as to save energy. A hydrogen pressure detection device 53, a hydrogen flow detection device 54 and a fourth control valve 52 for controlling the on-off of the hydrogen gas pipeline 51 are installed at intervals on the hydrogen gas pipeline 51, wherein the hydrogen pressure detection device 53 is used to detect the gas pressure in the hydrogen gas pipeline 51, and the hydrogen flow detection device 54 is used to detect the gas flow in the hydrogen gas pipeline 51, so as to monitor the gas transportation situation in the hydrogen gas pipeline 51 and ensure safe transportation. A moisture separator 55 is arranged on the hydrogen gas pipeline 51, and the moisture separator 55 can further remove the moisture contained in the hydrogen to increase the calorific value of the hydrogen. Since the exhaust gas from silicon manganese smelting and the surplus hydrogen from chlor-alkali production have high temperatures, condensed water is easily generated when they are transported in the pipeline. The condensed water in the pipeline can be easily discharged through the drain pipe 90 to prevent water accumulation in the pipeline and ensure smooth transportation of gas.

[0071] The hydrogen gas supply part 50 of the chlor-alkali production line mentioned above also includes a maintenance water seal groove 56. When hydrogen is used as the fuel gas of the roasting furnace 200, water is not introduced into the maintenance water seal groove 56 so that the hydrogen can be transmitted through the first pipeline 511 and the second pipeline 512 in sequence; when an emergency or failure occurs in the hydrogen gas supply part 50 of the chlor-alkali production line, water can be introduced into the maintenance water seal groove 56, and one end of the first pipeline 511 located in the tank body 561 is located below the liquid surface, and one end of the second pipeline 512 located in the tank body 561 is located above the liquid surface, so as to prevent air from entering the first pipeline 511 and mixing with the hydrogen during maintenance to cause safety hazards. When water is introduced into the tank body 561 so that the water covers the free end of the first pipe 511, the pressure in the tank body 561 will increase as the water is introduced, making it difficult for water to enter the tank body 561. At this time, the on-off valve 565 can be used to open the air inlet pipe 564 to ensure that water can smoothly enter the tank body 561, thereby ensuring that the water pressure in the tank body 561 is sufficient to improve the sealing effect.

[0072] A nitrogen purge pipe 92 is also installed on the hydrogen gas pipeline 51 and the tail gas pipeline 11. Before the hydrogen gas supply part 50 of the chlor-alkali production line and the tail gas supply part 10 of the silicon-manganese smelting are used, nitrogen is introduced into the hydrogen gas pipeline 51 and the tail gas pipeline 11 for purging to remove residual impurities in the pipeline and discharge the air in the pipeline to ensure the safe transportation and combustion of the gas. The hydrogen gas supply part 50 of the chlor-alkali production line also includes two vent pipes 57, through which the remaining hydrogen in the first pipeline 511 and the second pipeline 512 can be discharged during maintenance, or when the pressure in the pipeline is too high, part of the hydrogen can be discharged through the vent pipe 57 to ensure that the hydrogen pressure and flow in the pipeline are within the preset range to ensure safety.

[0073] The hydrogen supply part 50 of the chlor-alkali production line is provided with a valve group consisting of a first butterfly valve 521, a first pneumatic valve 523, a second pneumatic valve 524 and a second butterfly valve 525 on the first pipeline 511, and a valve group consisting of a third pneumatic valve 526, a third butterfly valve 527 and a fourth butterfly valve 528 on the second pipeline 512, which can reliably isolate the first pipeline 511 and the second pipeline 512, which is safe and reliable, and can isolate the first pipeline 511 and the second pipeline 512 in sections, which is more convenient for the inspection and maintenance of instruments, etc. The high-pressure buffer tank 70 can temporarily store the surplus hydrogen, silicon manganese smelting tail gas and coal gas in the chlor-alkali production, and ensure that the gas pressure provided to the roasting furnace 200 is stable and reliable.

[0074] Please see again Figure 3 The natural gas supply part 60 includes a natural gas pipeline 61 and a natural gas on-off valve 62 arranged on the natural gas pipeline 61, etc. The natural gas pipeline 61 is connected to the natural gas combustion station of the roasting furnace 200 to provide natural gas for roasting in the roasting furnace 200. This part belongs to the prior art and will not be described here for the sake of space omission.

[0075] The embodiment of the present invention also provides a roasting method for roasting aluminum hydroxide using multiple fuel gases at the same time, which comprises the following steps:

[0076] The silicon-manganese smelting tail gas produced by the silicon-manganese gas furnace is purified, and the oxygen content of the purified silicon-manganese smelting tail gas is tested. When the oxygen content of the silicon-manganese smelting tail gas is ≤3% (volume ratio), the silicon-manganese smelting tail gas is pressurized to 23-27 kpa and then transported to the high-pressure buffer tank 70.

[0077] The oxygen content of the gas generated by the gasifier is detected. When the oxygen content of the gas is ≤ 0.6% (volume ratio), the gas is pressurized to 23-27 kPa and then transported to the high-pressure buffer tank 70;

[0078] The oxygen content of hydrogen produced by the chlor-alkali production line is detected. When the oxygen content of hydrogen is ≤1% (volume ratio), the hydrogen is pressurized to 29-33 kPa and then transported to the high-pressure buffer tank 70;

[0079] The mixed gas consisting of coal gas, hydrogen and silicon-manganese smelting tail gas in the high-pressure buffer tank 70 is introduced into the gas combustion station of the roasting furnace 200 for combustion. The roasting temperature of the roasting furnace is adjusted by controlling the delivery flow rate of the mixed gas to ensure that the roasting temperature is within the preset range. When the delivery amount of the mixed gas consisting of coal gas, hydrogen and silicon-manganese smelting tail gas cannot meet the preset roasting temperature range, clean natural gas is added to the natural gas combustion station of the roasting furnace as a supplementary gas for the combustion of the roasting furnace 200 to ensure that the roasting temperature is within the preset range.

[0080] The hydrogen produced by the coal gas and chlor-alkali production lines both contain a small amount of oxygen, and the oxygen content in the coal gas is usually ≤0.6%, and the oxygen content in the hydrogen produced by the chlor-alkali production line is usually ≤1%, which meets the safe mixed combustion conditions of this embodiment. Since the oxygen content of hydrogen and coal gas is usually relatively stable, it is necessary to focus on controlling the oxygen concentration in the silicon manganese smelting tail gas with large oxygen content fluctuations. Therefore, this embodiment is equipped with an oxygen analyzer 18 on the tail gas delivery pipeline 11 to perform real-time detection of the oxygen concentration in the silicon manganese smelting tail gas to ensure safety. When the oxygen content in the silicon manganese smelting tail gas is higher than 3%, it may cause the gas concentration in the roasting furnace 200 to reach between the upper and lower explosion limits, causing an explosion, resulting in equipment damage and casualties. Therefore, when the oxygen content in the silicon-manganese smelting tail gas is higher than 3%, it is necessary to cut off the supply of the silicon-manganese smelting tail gas through the first control valve 13, and stop supplying the silicon-manganese furnace smelting tail gas to the high-pressure buffer tank 70; similarly, when the oxygen content of the coal gas exceeds the standard, stop supplying the coal gas to the high-pressure buffer tank 70; when the oxygen content of the hydrogen exceeds the standard, stop supplying the hydrogen to the high-pressure buffer tank 70.

[0081] In addition, research has found that high dust concentration in silicon-manganese smelting tail gas may cause pipe blockage, severe wear of the compressor 30, and damage to the equipment; and excessive dust may also affect the appearance of the prepared alumina, increasing the apparent visible impurity content of the alumina. In this embodiment, first, a gravity dust removal device 141 is used to perform the first dust removal on the silicon-manganese smelting tail gas, and then a steam-water separation device 15 is used to cool the silicon-manganese smelting tail gas and remove moisture from the silicon-manganese smelting tail gas. Finally, a bag dust removal device 142 is used to remove dust and purify the cooled silicon-manganese smelting tail gas again. The triple purification can increase the calorific value of the silicon-manganese smelting tail gas, and make the dust content of the silicon-manganese smelting tail gas ≤50mg / Nm 3 The method for monitoring the dust content of silicon-manganese smelting tail gas is: regularly discharge the silicon-manganese smelting tail gas through the vent pipe 80 and ignite the purified tail gas, and judge whether the dust content of the silicon-manganese smelting tail gas is ≤50mg / Nm based on the color of the tail gas flame according to experience. 3 When the dust content of silicon-manganese smelting tail gas exceeds the standard, stop delivering silicon-manganese smelting tail gas to the high-pressure buffer tank, and check and repair the purification device 14. By controlling the dust content of silicon-manganese smelting tail gas to ≤50mg / Nm 3 , so that the impurity SiO in the prepared alumina 2 , Fe 2 O 3 The content is still within the required range of 0.02%, and the pipeline is prevented from being blocked and the press 30 is worn.

[0082] If the pressure of silicon-manganese smelting tail gas input to the roasting furnace 200 is too low, and the flow rate of silicon-manganese smelting tail gas is too small, it will lead to insufficient gas, causing the roasting furnace 200 to be abnormal, causing the roasting furnace 200 to be flamed out or stopped; if the pressure of silicon-manganese smelting tail gas input to the roasting furnace 200 is too high, and the flow rate of silicon-manganese smelting tail gas is too large, causing the roasting furnace 200 to be abnormal, causing the roasting furnace 200 to be flamed out or stopped, the roasting boiler is insufficiently supplied with oxygen, the combustion is incomplete or flamed out, and the operation is stopped, and the flow rate of silicon-manganese smelting tail gas is large, it may cause the gas concentration in the roasting furnace 200 to reach between the upper and lower explosion limits, causing an explosion, causing equipment damage and casualties. According to research, when the silicon-manganese smelting tail gas is pressurized to 23-27kpa (the pressure of the silicon-manganese smelting tail gas transmitted from the silicon-manganese smelting furnace is usually 16-18Kpa), the coal gas is pressurized to 23-27kpa, and the hydrogen is pressurized to 29-33kpa and then transported to the high-pressure buffer tank 70, the above problems can be avoided. At the same time, in this embodiment, it is found through research that the interval for pressurizing coal gas can be the same as the interval for pressurizing silicon manganese smelting tail gas. Therefore, when in use, coal gas and silicon manganese smelting tail gas can be mixed and then pressurized together using the pressurizer 30. As for the hydrogen generated by the chlor-alkali production line, since the pressure of the hydrogen transmitted from the chlor-alkali production line can reach 29-33kpa, there is no need to set up a pressurizer 30 to pressurize the hydrogen. When it is detected that the pressure of silicon manganese smelting tail gas or coal gas is too high or too low, the pressure and flow of the mixed gas composed of silicon manganese smelting tail gas and coal gas can be adjusted by the mixed delivery pneumatic regulating valve 424; when the hydrogen pressure is detected to be too high or too low, the fourth control valve 52 on the hydrogen gas transmission pipeline 51 is automatically closed.

[0083] For the roasting process, the main control is the outlet temperature of the roasting furnace 200, and the factor affecting the outlet temperature of the roasting furnace is the gas delivery flow rate, and the gas delivery flow rate depends on the opening of the flow valve of the roasting furnace combustion station. In this embodiment, the mixed gas composed of coal gas, hydrogen, and silicon manganese smelting tail gas is preferentially used for the combustion of the roasting furnace 200. By controlling the opening of the flow valve of the gas combustion station into which the mixed gas is introduced, it is ensured that the roasting temperature during its combustion meets the roasting temperature of about 1050°C required for the roasting of aluminum hydroxide. When the delivery amount of the mixed gas is too small to meet the preset roasting temperature range, the clean natural gas with a high calorific value is added to the natural gas combustion station of the roasting furnace 200 as a supplementary gas for the combustion of the roasting furnace 200 to ensure that the roasting temperature is within the preset range. The delivery flow rate of natural gas can be controlled by the opening of the flow valve of the natural gas combustion station, which belongs to the prior art and is omitted here for the sake of space.

[0084] In order to verify the safety of the combustion of the mixed gas, this example analyzes the explosion hazard of the combustion of the mixed gas composed of the tail gas of silicon manganese smelting and the hydrogen and coal gas generated in the chlor-alkali production line, as follows:

[0085] The composition of silicon manganese smelting tail gas (volume ratio) is: carbon monoxide 58.6%, carbon dioxide 15.8%, hydrogen 7.17%, oxygen 2.8%, methane 9.16%, and the rest are inert gases.

[0086] Composition of coal gas (volume ratio): 26.5% carbon monoxide, 17.5% hydrogen, 2.75% methane, 0.6% oxygen, and the rest are inert gases.

[0087] Hydrogen composition (volume ratio): hydrogen ≥ 99.0%, oxygen ≤ 1%.

[0088] The tail gas from silicon manganese smelting is first mixed with coal gas in any proportion, and then mixed with hydrogen in various proportions. The results of the explosion hazard analysis are shown in Table 2-10. The mixing ratio is calculated based on volume concentration.

[0089] (1) Calculation of explosion limits of mixed gases

[0090] The explosion limit of mixed gas is calculated using the Richard Chateli formula:

[0091] Lm=100 / (V 1 / L 1 +V 2 / L 2 +...+V i / L i ), where V i , L i Indicates the volume concentration and explosion limit of each gas.

[0092] There is currently no authoritative calculation method for the explosion limit of mixed gases containing inert gases. In order to ensure the safety and reliability of the calculation results for the process scheme, the gas components of this embodiment are considered to be combustible gas filled with inert gas, and only the explosion limit of the combustible gas part is calculated, excluding other components. The lowest concentration of the explosion limit is called the lower explosion limit, and the highest concentration of the explosion limit is called the upper explosion limit.

[0093] (2) Calculation of minimum oxygen concentration

[0094] In a certain combustible gas mixture, the combustible components can be regarded as a special mixture with the molecular formula C n H m O k F f , the concentration of combustible gas components when the reaction is complete can be calculated by the following chemical reaction formula:

[0095] C n H m O k F f +[n+(mf-2k) / 4]O 2-nCO 2 +[(mf) / 2]H 2 O+f

[0096] Where n, m, k, and f represent the atomic numbers of carbon, hydrogen, oxygen, and halogen elements, respectively.

[0097] According to the research materials such as "Discussion on the Safety Limit of Oxygen Content in Combustible Gases" (Wan Chenglue and Wang Li, Journal of China Safety Science, Vol. 9, No. 1, February 1999), and "Determination of the Maximum Allowable Oxygen Content of the Explosive Limit of Combustible Gases and Research on Influencing Factors" (Zhang Zengliang and Li Gemei, Journal of Hunan University of Science and Technology, Vol. 28, No. 3, September 2006):

[0098] When the concentration of combustible gas is at the lower explosion limit L, the theoretical oxygen concentration is the minimum oxygen concentration MOC:

[0099] MOC=L[n+(mf-2k) / 4]

[0100] (3) Calculation of minimum oxygen concentration when mixed with air

[0101] The oxygen content in the air is calculated as 21%, and the minimum oxygen concentration required to form an explosive mixed gas with air is MOC1

[0102] MOC1 = (100-L2) × 21%, where L2 is the upper limit of the explosion limit of the mixed gas

[0103] In the present embodiment, the calculation result of the minimum oxygen concentration mixed with air is used as a reference for comparison with the minimum oxygen concentration.

[0104] (4) Calculation of combustible gas concentration excess ratio

[0105] The combustible gas concentration excess ratio refers to the percentage by which the combustible gas concentration exceeds the explosion limit. The upper and lower limits of the explosion limit are calculated separately. The closer the minimum is to the explosion limit, the greater the degree of danger. This embodiment only calculates the minimum of the upper and lower limits of the explosion limit, that is, calculates the percentage X by which the combustible gas concentration exceeds the upper limit of the explosion limit:

[0106] X = (C1-L2) / L2, where L2 is the upper limit of the explosion limit of the mixed gas, and C1 is the concentration of the mixed gas.

[0107] (5) Calculation of oxygen ratio Y

[0108] Y = C2 / MOC, where MOC is the minimum oxygen concentration and C2 is the oxygen concentration in the mixed gas.

[0109] Table 2 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 9:1 mixture

[0110]

[0111] Table 3 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 8:2 mixture

[0112]

[0113]

[0114] Table 4 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 7:3 mixture

[0115]

[0116] Table 5 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 6:4 mixture

[0117]

[0118]

[0119] Table 6 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 5:5 mixture

[0120]

[0121] Table 7 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 4:6 mixture

[0122]

[0123]

[0124] Table 8 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 3:7 mixture

[0125]

[0126] Table 9 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 2:8 mixture

[0127]

[0128]

[0129] Table 10 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 1:9 mixture

[0130]

[0131] The above calculation results show that the three combustible gases of silicon-manganese smelting tail gas, coal gas and hydrogen can meet the following conditions when mixed in various proportions: the combustible gas concentration exceeds the explosion limit by more than 10% or the oxygen concentration is less than 50% of the minimum oxygen concentration. Therefore, the three combustible gases of silicon-manganese smelting tail gas, coal gas and hydrogen can be safely burned when mixed in various proportions within the safe range. In the case where the combustible gas concentration is difficult to control, the oxygen concentration should be strictly controlled, among which the oxygen content of hydrogen and coal gas is relatively stable, and the focus should be on controlling the oxygen concentration in the silicon-manganese smelting tail gas with large fluctuations and high oxygen content.

[0132] This embodiment also increases the oxygen content in the silicon-manganese smelting tail gas to verify the impact of the change in oxygen content. When the oxygen content in the silicon-manganese smelting tail gas is increased to 3%, the components of the silicon-manganese smelting tail gas are (volume ratio): carbon monoxide 58.6%, carbon dioxide 15.8%, hydrogen 7.17%, oxygen 3%, methane 9.16%, and the rest are inert gases; the parameters of coal gas and hydrogen remain unchanged, and the silicon-manganese smelting tail gas is first mixed with coal gas in any proportion, and then mixed with hydrogen in various proportions. The explosion hazard analysis results are shown in Tables 11-19, and the mixing ratio is measured by volume concentration.

[0133] Table 11 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 9:1 mixture

[0134]

[0135] Table 12 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 8:2 mixture

[0136]

[0137]

[0138] Table 13 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 7:3 mixture

[0139]

[0140] Table 14 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 6:4 mixture

[0141]

[0142]

[0143] Table 15 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 5:5 mixture

[0144]

[0145] Table 16 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 4:6 mixture

[0146]

[0147]

[0148] Table 17 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 3:7 mixture

[0149]

[0150] Table 18 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 2:8 mixture

[0151]

[0152] Table 19 Explosion hazard analysis calculation table of silicon manganese smelting tail gas, coal gas mixture: hydrogen = 1:9 mixture

[0153]

[0154] From the calculation results in Table 11-19, it can be seen that when the oxygen content of silicon-manganese smelting tail gas is 3%, the three combustible gases can meet the following conditions when mixed in various proportions: the combustible gas concentration exceeds the explosion limit by more than 10% or the oxygen concentration is less than 50% of the minimum oxygen concentration, and the three combustible gases can be safely burned when mixed in various proportions. However, in some states, the combustible gas concentration is closer to 10% at the explosion limit and the oxygen concentration is closer to 50% at the minimum oxygen concentration, which is close to the safety control requirement. Therefore, the upper limit of oxygen content control of silicon-manganese smelting tail gas is determined to be 3%.

[0155] After adopting the roasting method and system of the present embodiment for simultaneously using multiple fuel gases for roasting aluminum hydroxide, the total carbon emission can be reduced, and the environmental protection treatment of tail gas in the silicon manganese smelting industry and the safe utilization of surplus hydrogen in the chlor-alkali industry can be completed, which can reduce the carbon dioxide emission of tail gas from roasting aluminum hydroxide from 170 million m 3 / a reduced to 65 million m 3 / a or less, the roasting cost of aluminum hydroxide can be reduced by 24.3625 million yuan / a.

[0156] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A roasting method for roasting aluminum hydroxide using multiple fuel gases simultaneously, characterized in that: Purify the silicon-manganese smelting tail gas generated by the silicon-manganese gas furnace, and detect the oxygen content of the purified silicon-manganese smelting tail gas. When the oxygen content of the silicon-manganese smelting tail gas is ≤3%, pressurize the silicon-manganese smelting tail gas to 23-27kpa and then transport it to the high-pressure buffer tank; The oxygen content of the gas produced by the gasifier is tested. When the oxygen content of the gas is ≤0.6%, the gas is pressurized to 23-27kpa and then transported to the high-pressure buffer tank; The oxygen content of hydrogen produced by the chlor-alkali production line is tested. When the oxygen content in the hydrogen is ≤1%, the hydrogen is pressurized to 29-33kpa and then transported to the high-pressure buffer tank; The mixed gas consisting of coal gas, hydrogen and silicon-manganese smelting tail gas in the high-pressure buffer tank is introduced into the gas combustion station of the roaster for combustion, and the roasting temperature of the roaster is adjusted by controlling the delivery flow rate of the mixed gas to ensure that the roasting temperature is within the preset range. When the delivery amount of the mixed gas consisting of coal gas, hydrogen and silicon-manganese smelting tail gas cannot meet the preset roasting temperature range, natural gas is added to the natural gas combustion station of the roaster as a supplementary gas for the combustion of the roaster to ensure that the roasting temperature is within the preset range.

2. The roasting method of claim 1 wherein multiple fuel gases are simultaneously used for roasting aluminum hydroxide, characterized in that: When the oxygen content of the silicon-manganese furnace smelting tail gas exceeds the standard, stop supplying the silicon-manganese furnace smelting tail gas to the high-pressure buffer tank; when the oxygen content of the coal gas exceeds the standard, stop supplying the coal gas to the high-pressure buffer tank; when the oxygen content of the hydrogen exceeds the standard, stop supplying the hydrogen to the high-pressure buffer tank.

3. The roasting method of claim 1 wherein multiple fuel gases are simultaneously used for roasting aluminum hydroxide, characterized in that: The coal gas is mixed with the tail gas from silicon-manganese smelting and then pressurized by passing through the same compressor.

4. The roasting method of claim 3 in which multiple fuel gases are simultaneously used for roasting aluminum hydroxide, characterized in that: When it is detected that the pressure of the mixed gas of silicon manganese smelting tail gas and coal gas is too high or too low, the flow rate of the mixed gas is adjusted to make the pressure of the mixed gas composed of silicon manganese smelting tail gas and coal gas between 23-27kpa.

5. The roasting method for roasting aluminum hydroxide using multiple fuel gases simultaneously as claimed in claim 1, characterized in that: The purification method of silicon-manganese smelting tail gas is as follows: the silicon-manganese smelting tail gas from the silicon-manganese furnace is successively subjected to gravity dust removal, cooled in the steam-water separator, and then purified by bag dust removal, so that the dust content of the silicon-manganese smelting tail gas is ≤50mg / Nm 3 .

6. The roasting method for roasting aluminum hydroxide using multiple fuel gases simultaneously as claimed in claim 5, characterized in that: The monitoring method for the dust content of silicon-manganese smelting tail gas is: regularly discharge silicon-manganese smelting tail gas and ignite the purified tail gas, and judge whether the dust content of silicon-manganese smelting tail gas is ≤50mg / Nm by the color of the tail gas flame. 3 When the dust content of silicon-manganese smelting tail gas exceeds the standard, stop supplying silicon-manganese smelting tail gas to the high-pressure buffer tank.

7. A roasting system used in the roasting method of roasting aluminum hydroxide using multiple fuel gases simultaneously as claimed in claim 1, characterized in that: It comprises a silicon-manganese smelting tail gas supply part (10), a coal gas supply part (20), a compressor (30), a mixed gas transmission pipeline (40), a chlor-alkali production line hydrogen supply part (50), a natural gas supply part (60) and a high-pressure buffer tank (70); wherein: The silicon-manganese smelting tail gas supply part (10) comprises a tail gas delivery pipeline (11), a first control valve (13), a purification device (14), a tail gas pressure detection device (16), a tail gas flow detection device (17) and an oxygen analyzer (18). The first control valve (13), the purification device (14), the tail gas pressure detection device (16), the tail gas flow detection device (17) and the oxygen analyzer (18) are installed on the tail gas delivery pipeline (11) at intervals. The gas supply part (20) comprises a gas delivery pipeline (21), a second control valve (22) and a gas flow detection device (23), wherein the second control valve (22) and the gas flow detection device (23) are installed on the gas delivery pipeline (21) at intervals; The output ends of the tail gas delivery pipeline (11) and the output ends of the coal gas delivery pipeline (21) are both connected to the air inlet end of the compressor (30), the air outlet end of the compressor (30) is connected to the input end of the mixed gas delivery pipeline (40), the output end of the mixed gas delivery pipeline (40) is connected to the air inlet of the high-pressure buffer tank (70), and the mixed gas delivery pipeline (40) is provided with a mixed gas pressure detection device (41) and a third control valve (42) at intervals; The hydrogen supply part (50) of the chlor-alkali production line comprises a hydrogen gas pipeline (51), a fourth control valve (52), a hydrogen pressure detection device (53), a hydrogen flow detection device (54) and a moisture separator (55). The fourth control valve (52), the hydrogen pressure detection device (53), the hydrogen flow detection device (54) and the moisture separator (55) are installed on the hydrogen gas pipeline (51) at intervals, and the outlet end of the moisture separator (55) is connected to the air inlet of the high-pressure buffer tank (70); The gas outlet of the high-pressure buffer tank (70) and the natural gas supply part (60) are used to be connected to the roasting furnace (200).

8. The roasting system used in the roasting method for roasting aluminum hydroxide using multiple fuel gases simultaneously as claimed in claim 7, characterized in that: The mixed gas delivery pipeline (40) is also connected to a release pipe (80), and a release flame arrester (81) and a release valve (82) are installed on the release pipe (80) at intervals.

9. The roasting system used in the roasting method for roasting aluminum hydroxide using multiple fuel gases simultaneously as claimed in claim 7, characterized in that: The hydrogen gas transmission pipeline (51) and the tail gas transmission pipeline (11) are both connected to a drainage pipe (90), and a drainage valve (91) is installed on the drainage pipe (90).

10. The roasting system used in the roasting method for roasting aluminum hydroxide using multiple fuel gases simultaneously as claimed in claim 7, characterized in that: The purification device (14) comprises a gravity dust removal device (141), a steam-water separator device (15) and a bag dust removal device (142) which are sequentially arranged along the exhaust gas conveying direction.

Images