A method for reducing and decomposing gypsum with sulfur and a rotary kiln

Abstract

The application provides a method for reducing and decomposing gypsum by using sulfur and a rotary kiln, and relates to the technical field of reducing and decomposing gypsum. The rotary kiln for reducing and decomposing gypsum comprises a kiln head, a kiln tail and a rotary kiln body obliquely arranged between the kiln head and the kiln tail. A combustion pipe is arranged on the kiln head and extends into the rotary kiln body. A gas inlet pipe and an air inlet pipe are arranged on the combustion pipe. A combustion zone and a reaction zone are sequentially arranged on the front end of the combustion pipe from near to far. First and second gas pipes for supplying sulfur vapor into the rotary kiln body are arranged on the kiln head. The gas outlet of the first gas pipe is arranged in the combustion zone. The second gas pipe is a plurality of pipes, and the gas outlets are arranged in the reaction zone and are sequentially and spacedly arranged along the axial direction of the rotary kiln body. The application makes the industrial production of preparing calcium oxide by reducing and decomposing gypsum in the rotary kiln by using sulfur feasible, and saves energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reducing and decomposing gypsum, and particularly relates to a method for reducing and decomposing gypsum with sulfur and a rotary kiln. BACKGROUND

[0002] Phosphogypsum is a by-product of wet-process phosphoric acid production. Reducing and decomposing phosphogypsum to produce sulfuric acid is one of the effective ways for comprehensive utilization of gypsum industrial waste residue. Phosphogypsum for producing sulfuric acid and co-production of lime can effectively utilize by-product gypsum to produce sulfuric acid, and obtain lime product, which is a waste turned into treasure, and has good economic and environmental benefits.

[0003] Chinese patent CN103818884B discloses a gypsum spouted fluidized decomposition process, which discloses that solid materials are obtained by reacting sulfur-containing hot flue gas with a part of raw materials in a fluidized bed, and then the solid materials are reacted with a part of raw materials in a rotary kiln to finally obtain calcium oxide-containing solid residue. The method needs to be reacted in two devices to prepare calcium oxide, and the heat energy of the system is greatly lost, and the energy consumption is high. If the whole reaction process is directly arranged in the rotary kiln, although the energy loss of the whole reaction system can be reduced, the reducing atmosphere is difficult to control. Therefore, the method cannot be industrialized. SUMMARY

[0004] The present application solves the technical problem of providing a method for reducing and decomposing gypsum with sulfur and a rotary kiln which is convenient to control the reaction atmosphere in the rotary kiln.

[0005] The technical scheme adopted by the present application to solve its technical problem is: a rotary kiln for reducing and decomposing gypsum with sulfur, comprising a kiln head, a kiln tail and a rotary kiln body obliquely arranged between the kiln head and the kiln tail, a combustion pipe with an outlet end extending into the rotary kiln body is arranged on the kiln head, a gas inlet pipe and an air inlet pipe are arranged on the combustion pipe, a combustion zone and a reaction zone are sequentially arranged from near to far at the front end of the combustion pipe, a first gas pipe and a second gas pipe for passing sulfur vapor into the rotary kiln body are further arranged on the kiln head, the gas outlet of the first gas pipe is arranged in the combustion zone, the second gas pipe is a plurality of pipes, and the gas outlets are arranged in the reaction zone and are sequentially arranged along the axial direction of the rotary kiln body.

[0006] Further, the gas outlet of the second gas pipe is inclined downward and forms an angle of 30°-45° with the vertical direction.

[0007] Further, one end of the first gas pipe and the second gas pipe in the rotary kiln body is connected into a whole through a connecting piece.

[0008] Further, a support frame for supporting is arranged in the rotary kiln body and connected with the second gas pipe at the upper end, a lower end of the support frame is provided with a ball, and the support frame is in abutment with the inner wall of the rotary kiln body through the ball.

[0009] Further, the support frame is two, two support frame symmetrically arranged on both sides of the second air pipe, and triangularly arranged.

[0010] Further, the first air pipe and the second air pipe are both ceramic pipes.

[0011] Further, the first air pipe, the second air pipe, the gas inlet pipe and the air inlet pipe are all provided with flow control valves.

[0012] A method for reducing and decomposing gypsum by using sulfur, which uses the above-mentioned rotary kiln for reducing and decomposing gypsum by using sulfur, and includes the following steps:

[0013] After igniting the air and the gas by the air inlet pipe and the gas inlet pipe, respectively, the air and the gas are fully combusted in the combustion zone, and 500-800 DEG C sulfur vapor is introduced into the combustion zone through the first air pipe according to the excess amount of oxygen in the introduced air to digest the remaining oxygen in the hot flue gas generated in the combustion zone, wherein the amount of the gas and the air introduced into the gas inlet pipe and the air inlet pipe is controlled during the combustion process to make the temperature of the reaction zone be 600-800 DEG C.

[0014] The gypsum powder is sent into the kiln body from the feeding port at the kiln tail, 500-800 DEG C sulfur vapor is introduced into the reaction zone through the multiple second air pipes, respectively, so that the gypsum powder reacts with the sulfur vapor in the reaction zone, and the obtained solid material is finally discharged from the discharging port at the kiln head.

[0015] Further, the air introduced by the air inlet pipe and the gas introduced by the gas inlet pipe are in the range of 0-20% of the excess amount of air.

[0016] Further, the air is oxygen-enriched air, wherein the oxygen content is 21-30%.

[0017] The beneficial effects of the present application are: the method for reducing and decomposing gypsum with sulfur and the rotary kiln, the first gas pipe is arranged in the combustion zone of the rotary kiln, and the second gas pipe with a plurality of gas outlets is arranged in the reaction zone and is arranged along the axis direction of the rotary kiln body, sulfur vapor can be introduced through the first gas pipe to consume the residual oxygen in the hot flue gas generated by combustion, so that there is no or only a small amount of oxygen in the hot flue gas passing through the reaction zone, and the gypsum powder in the reaction zone is ensured to be in a reducing atmosphere; and the sulfur vapor can be introduced into the reaction zone from multiple points through the plurality of second gas pipes, that is, the sulfur vapor can be more uniformly introduced into the reaction zone through the plurality of second gas pipes, the gas phase conditions at different positions in the reaction zone can be controlled in zones, and the gypsum powder at different positions in the reaction zone can be fully contacted with the sulfur vapor, so that the decomposition rate of the gypsum can be more accurately controlled, the optimal product ratio relationship of 3:1 of calcium sulfate and calcium sulfide which can be directly used to prepare calcium oxide is formed, the industrialized production of calcium oxide raw materials in the rotary kiln by reducing and decomposing gypsum with sulfur becomes feasible, and energy consumption is saved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural schematic view of the rotary kiln of the present application;

[0019] Figure 2 is a setting schematic view of the support frame;

[0020] The kiln tail 1, the rotary kiln body 2, the kiln head 3, the combustion pipe 4, the first gas pipe 5, the second gas pipe 6, the support frame 7, the flow control valve 8, the combustion zone 21, the reaction zone 22, the air inlet pipe 41, the gas inlet pipe 42, the flame 43, and the ball 71 are shown in the figure. DETAILED DESCRIPTION

[0021] The present application will be further described below in combination with the drawings and examples.

[0022] As Figure 1 shown, the rotary kiln for reducing and decomposing gypsum with sulfur of the present application comprises a kiln head 3, a kiln tail 1, and a rotary kiln body 2 obliquely arranged between the kiln head 3 and the kiln tail 1, the kiln head 3 is provided with a combustion pipe 4 with a fire outlet end extending into the rotary kiln body 2, and the combustion pipe 4 is provided with a gas inlet pipe 42 and an air inlet pipe 41. The above structure is the same as the structure of the existing rotary kiln. In order to facilitate the control of the reaction atmosphere in the rotary kiln, the front end of the combustion pipe 4 of the rotary kiln of the present application is sequentially provided with a combustion zone 21 and a reaction zone 22 from near to far, and the kiln head 3 is further provided with a first gas pipe 5 and a second gas pipe 6 for introducing sulfur vapor into the rotary kiln body 2. The gas outlet of the first gas pipe 5 is arranged in the combustion zone 21, that is, the gas outlet end of the first gas pipe 5 extends into the combustion zone 21. The second gas pipe 6 is a plurality of pipes, and the gas outlets are arranged in the reaction zone 22 and are sequentially arranged along the axis direction of the rotary kiln body 2.

[0023] The specific method for decomposing gypsum by using the rotary kiln is as follows:

[0024] Step one, air and fuel gas are respectively introduced into the combustion pipe 4 through the air introduction pipe 41 and the fuel gas introduction pipe 42, ignited, and fully reacted and combusted in the combustion zone 21. According to the excess oxygen content in the introduced air, 500-800℃ sulfur vapor is introduced into the combustion zone 21 through the first gas pipe 5, and the residual oxygen in the hot flue gas generated in the combustion zone 21 is digested by the reaction of the sulfur vapor, so that there is no or only a small amount of oxygen in the hot flue gas passing through the reaction zone 22, ensuring that the material in the reaction zone 22 is in a reducing atmosphere. During the combustion process, the amount of fuel gas introduced into the fuel gas introduction pipe 42 and the amount of air introduced into the air introduction pipe 41 are controlled to ensure that the temperature of the reaction zone 22 is 600-800℃.

[0025] Step two, gypsum powder is fed into the rotary kiln body 2 from the feed inlet of the kiln tail 1. The raw material gradually enters the reaction zone 22 during the rotation of the rotary kiln, and 500-800℃ sulfur vapor is introduced into the reaction zone 22 through multiple second gas pipes 6, so that the gypsum powder is in a reducing atmosphere of sulfur vapor and fully reacts with the sulfur vapor. The solid material obtained by the reaction is finally discharged from the discharge port of the kiln head 3.

[0026] The fuel gas can be natural gas, coal gas, liquefied petroleum gas, etc. The gypsum can be various gypsums, such as phosphogypsum, salt gypsum, and natural gypsum.

[0027] In the above method, the air introduced through the air introduction pipe 41 and the fuel gas introduced through the fuel gas introduction pipe 42 can be arbitrarily set according to the air excess amount. Preferably, the air introduced through the air introduction pipe 41 and the fuel gas introduced through the fuel gas introduction pipe 42 are set according to the air excess amount of 0%-20%.

[0028] In the above method, the air can be conventional air with an oxygen content of 21%. In the embodiment of the present application, oxygen-enriched air is used. The use of oxygen-enriched air not only makes the fuel gas burn more completely, but also reduces the amount of nitrogen introduced into the rotary kiln, making it easier to control the temperature of the rotary kiln, and the dust carried out of the rotary kiln is also less. When oxygen-enriched air is used, the oxygen content is 21%-30%. When oxygen-enriched combustion is used, for every 1% increase in oxygen content, the total heat consumption of the system can be reduced by 2%, and the concentration of gas-phase sulfur dioxide can be increased by 0.3%, which will bring significant improvement in process indicators.

[0029] The first gas pipe is arranged in the combustion zone of the rotary kiln, and the second gas pipe with a plurality of gas outlets arranged along the axial direction of the rotary kiln body is arranged in the reaction zone. Sulfur vapor can be introduced into the first gas pipe during the reaction to consume the residual oxygen in the hot flue gas generated by combustion, so that there is no or only a small amount of oxygen in the hot flue gas passing through the reaction zone, and the gypsum powder in the reaction zone 22 is ensured to be in a reducing atmosphere. The second gas pipe can introduce sulfur vapor into the reaction zone at multiple points, that is, the second gas pipe can more uniformly introduce sulfur vapor into the reaction zone, and the gas phase strip in each part of the reaction zone can be controlled in a partitioned manner, so that the gypsum powder in each part of the reaction zone can fully contact with the sulfur vapor, and the required gas phase condition of the reaction zone is ensured, thereby the decomposition rate of the gypsum can be more accurately controlled, and the optimal product ratio relationship of 3:1 between calcium sulfate and calcium sulfide is formed.

[0030] The spacing between the gas outlets of the second gas pipe, that is, the density of the second gas pipe 6, will affect the control of the atmosphere of the reaction zone. It can be obtained by experiments according to the parameters such as the amount of material entering, the inner diameter of the rotary kiln, the flow of steam passing through the second gas pipe, and the diameter of the gas outlet of the second gas pipe.

[0031] In order to avoid the sulfur vapor reacting with the fuel gas and oxygen first, resulting in insufficient combustion of the fuel gas, it is understood that the gas outlet of the first gas pipe is preferably arranged at the flame tip or in front of the flame tip of the flame 43 in the combustion zone 21.

[0032] The gas outlet direction of the gas outlet of the second gas pipe 6 can be arbitrarily set, such as horizontal, inclined downward or upward, etc. In the rotary kiln, the gypsum powder is generally at the bottom of the rotary kiln. In order to make the sulfur vapor better contact with the gypsum powder, the gas outlet direction of the gas outlet of the second gas pipe 6 is preferably inclined downward and forms an angle of 30°-45° with the vertical direction.

[0033] Since the rotary kiln body rotates relative to the kiln head during operation, in order to avoid the first gas pipe 5 and the second gas pipe 6 rubbing against the kiln wall and damaging the kiln wall, the gas outlet end (the end extending into the rotary kiln body) of the first gas pipe 5 and the second gas pipe 6 is generally arranged in a suspended manner. In order to avoid the second gas pipe 6 from bending or deforming due to the length of the second gas pipe 6 extending into the rotary kiln being too long, the first gas pipe 5 and the second gas pipe 6 are connected into a whole through a connecting piece at one end in the rotary kiln body 2. The connecting piece can be a rope.

[0034] In order to avoid the second gas pipe 6 from bending or deforming due to the length of the second gas pipe 6 extending into the rotary kiln being too long, the first gas pipe 5 and the second gas pipe 6 are connected into a whole through a connecting piece at one end in the rotary kiln body 2. The connecting piece can be a rope. Figure 2As shown, in the embodiment of the present application, the rotary kiln body 2 is provided with a support frame 7 connected with the second gas pipe 6 at the upper end, the lower end of the support frame 7 is provided with a ball 71, and the support frame 7 is in abutment with the inner wall of the rotary kiln body 2 through the ball 71. In this way, the support frame 7 can support the gas outlet end of the second gas pipe 6, and since the support frame 7 is in abutment with the inner wall of the rotary kiln body 2 through the ball 71, the friction and wear of the support frame 7 to the rotary kiln wall is small. The ball 71 can be a ceramic ball or a high-temperature-resistant steel ball. The support frame 7 can be one or more, Figure 2 In some embodiments, the support frame 7 is two, and the two support frames 7 are symmetrically arranged on both sides of the second gas pipe 6 and arranged in a triangular shape. The above structure can better support and fix the second gas pipe 6, and a cavity is formed between the two support frames 7, which is convenient for the solid materials in the rotary kiln to pass through.

[0035] The first gas pipe 5 and the second gas pipe 6 are made of various materials that are resistant to high temperature and sulfur corrosion, such as high-temperature-resistant stainless steel pipes, ceramic pipes, etc. In the embodiment of the present application, the first gas pipe 5 and the second gas pipe 6 are both ceramic pipes. The surface of the first gas pipe 5 and the second gas pipe 6 can be cast with high-temperature-resistant castable.

[0036] In order to facilitate the control of the flow of gas in each pipe, the first gas pipe 5, the second gas pipe 6, the gas inlet pipe 42 and the air inlet pipe 41 are all provided with a flow control valve 8. Of course, in some embodiments, the flow of gas in each pipe can also be adjusted by the corresponding gas supply device.

Claims

1. A rotary kiln for reducing and decomposing gypsum with sulfur, comprising a kiln head (3), a kiln tail (1), and a rotary kiln body (2) inclined between the kiln head (3) and the kiln tail (1), wherein the kiln head (3) is provided with a combustion pipe (4) whose outlet end extends into the rotary kiln body (2), and the combustion pipe (4) is provided with a gas inlet pipe (42) and an air inlet pipe (41), characterized in that, The front end of the combustion pipe (4) is provided with a combustion zone (21) and a reaction zone (22) from near to far. The kiln head (3) is also provided with a first gas pipe (5) and a second gas pipe (6) for passing sulfur vapor into the rotary kiln body (2). The outlet of the first gas pipe (5) is located in the combustion zone (21). There are multiple second gas pipes (6), and the outlets are located in the reaction zone (22) and are arranged at intervals along the axis of the rotary kiln body (2). The rotary kiln body (2) is provided with a support frame (7) whose upper end is connected to the second air pipe (6). The lower end of the support frame (7) is provided with a ball bearing (71). The support frame (7) abuts against the inner wall of the rotary kiln body (2) through the ball bearing (71). The first gas pipe (5), the second gas pipe (6), the gas inlet pipe (42) and the air inlet pipe (41) are all equipped with flow control valves (8).

2. The rotary kiln for reducing and decomposing gypsum with sulfur as described in claim 1, characterized in that, The outlet of the second trachea (6) is inclined downward and forms an angle of 30° to 45° with the vertical direction.

3. The rotary kiln for reducing and decomposing gypsum with sulfur as described in claim 1, characterized in that, The first air pipe (5) and the second air pipe (6) are connected as a whole at one end inside the rotary kiln body (2) by a connector.

4. A rotary kiln for reducing and decomposing gypsum with sulfur as described in claim 1, characterized in that, There are two support frames (7), which are symmetrically arranged on both sides of the second air pipe (6) and form a triangular arrangement.

5. A rotary kiln for reducing and decomposing gypsum with sulfur as described in claim 1, characterized in that, Both the first trachea (5) and the second trachea (6) are ceramic tubes.

6. A method for reducing and decomposing gypsum with sulfur, employing a rotary kiln for reducing and decomposing gypsum with sulfur as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Air and fuel gas are introduced into the combustion tube (4) through the air inlet pipe (41) and the fuel gas inlet pipe (42) respectively and ignited, so that they are fully burned in the combustion zone (21). Sulfur vapor at 500-800°C is introduced into the combustion zone (21) through the first gas pipe (5) according to the excess oxygen in the introduced air to consume the remaining oxygen in the hot flue gas generated in the combustion zone (21). During the combustion process, the amount of fuel gas and air introduced into the fuel gas inlet pipe (42) and the air inlet pipe (41) is controlled so that the temperature of the reaction zone (22) is 600-800°C. The gypsum powder is fed into the rotary kiln body (2) from the feed port at the kiln tail (1). Sulfur vapor at 500-800℃ is introduced into the reaction zone (22) through multiple second gas pipes (6) so that the gypsum powder reacts with the sulfur vapor in the reaction zone (22). The solid material obtained from the reaction is finally discharged from the discharge port at the kiln head (3).

7. The method for reducing and decomposing gypsum with sulfur as described in claim 6, characterized in that, The air supplied through the air inlet pipe (41) and the gas supplied through the gas inlet pipe (42) are supplied with an air excess of 0% to 20%.

8. The method for reducing and decomposing gypsum with sulfur as described in claim 6, characterized in that, The air is oxygen-enriched, with an oxygen content of 21% to 30%.

Images