A phosphogypsum calcining system

Abstract

The invention discloses a phosphogypsum calcining system, comprising a phosphogypsum feeding hopper and a belt feeder connected to the phosphogypsum feeding hopper. A plurality of mutually connected aging devices are connected to one side of the belt feeder, each aging device comprises a feeding airflow pipe and a dust collector connected thereto, and a calcining device and a grinding device are respectively connected between the aging devices. The invention adopts a multi-stage airflow pipe to carry out gypsum powder aging in steps, and the gypsum powder is aged when it is fed into a feeding bin and can be used directly, thereby shortening the time. In addition, by adopting a process of over-burning before aging, that is, after the gypsum is calcined, the content of hemihydrate gypsum and anhydrous gypsum is high, and the content of dihydrate gypsum is extremely low, thereby ensuring that the gypsum is fully calcined and has high strength.

Description

Technical Field

[0001] The invention belongs to the technical field of gypsum powder production, and particularly relates to a phosphogypsum calcining system. Background Art

[0002] Nowadays, the application of phosphogypsum is becoming more and more common. After calcination, phosphogypsum becomes building gypsum, which is mainly composed of hemihydrate gypsum, and also contains some anhydrous gypsum and dihydrate gypsum. If the product is used directly in production, on the one hand, the dihydrate gypsum is inactive and the product hydration strength is low. On the other hand, due to the presence of anhydrous gypsum and the many surface defects and high activity of hemihydrate gypsum, there are also problems such as unstable setting time and cracking. Therefore, the building gypsum needs to be modified before use.

[0003] At present, construction gypsum is generally aged by methods such as calcination, pouring into warehouses, mixing, and long-term storage. The entire production cycle takes more than half a month, and the final effect fluctuates greatly.

[0004] That is, there is a need for a production device that can achieve efficient production and rapid aging of building gypsum from phosphogypsum, and can ensure product strength and non-cracking properties. Summary of the Invention

[0005] In view of this, an object of the present invention is to provide a phosphogypsum calcining system that can age quickly, produce efficiently and have high product strength.

[0006] The technical solution of the present invention is:

[0007] A phosphogypsum calcining system includes a phosphogypsum input hopper and a belt feeder connected to the phosphogypsum input hopper. Multiple stages of aging devices connected to each other are connected to one side of the belt feeder. Each stage of the aging device includes a feed airflow pipe and a dust collector connected thereto.

[0008] A calcining device is provided between the primary aging device and the secondary aging device.

[0009] The above-mentioned calcining device is a rotary kiln.

[0010] A grinding device is provided between the secondary aging device and the tertiary aging device.

[0011] The grinding device is a ball mill.

[0012] The above-mentioned aging device includes a primary air flow pipe for drying the water attached to phosphogypsum and a primary dust collector connected to it; a secondary air flow pipe for aging anhydrous gypsum and a secondary dust collector connected to it; a tertiary air flow pipe for aging hemihydrate gypsum and repairing cracks on the particle surface and a tertiary dust collector connected to it; the feed end of the primary air flow pipe is connected to the belt feeder, the discharge end is connected to the inlet of the secondary air flow pipe through a rotary kiln, and the outlet of the secondary air flow pipe is connected to the tertiary air flow pipe through a ball mill.

[0013] Mixed hot air is introduced into the bottom of the above-mentioned aging device.

[0014] The discharge port of the secondary air flow pipe is connected to the fan through the secondary dust collector, so that the tail gas in the secondary air flow pipe enters the primary air flow pipe for waste heat recovery.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention discloses a phosphogypsum calcining system comprising a multi-stage aging device. By replacing a conventional bucket elevator, an airflow tube is provided at the feed port of a dust collector, allowing mixed hot air to age the phosphogypsum in different states. A first-overburning-then-aging process is employed (i.e., the hemihydrate gypsum and anhydrous gypsum contents are high after calcining the gypsum), resulting in an extremely low dihydrate gypsum content. The first overburning process means that after burning, the anhydrous gypsum content is relatively high, with the dihydrate gypsum content being less than 1%. The second aging process means that the anhydrous gypsum is aged in the airflow tube to form hemihydrate gypsum. This system achieves efficient production and rapid aging of phosphogypsum for use in preparing building gypsum, while ensuring product strength and crack resistance. The system has the following advantages:

[0017] 1. Use multi-stage air flow pipes to introduce air with different temperatures and humidity, and age the gypsum powder in steps. The gypsum powder can be used directly after aging when it is fed into the silo, which shortens the time.

[0018] 2. The process of over-burning before aging is adopted (i.e. the anhydrous gypsum content is high after calcining the gypsum, exceeding 40%), and the dihydrate gypsum content is less than 1%, which ensures that the gypsum is fully calcined and has high strength (in the traditional process, appropriate under-burning is required, with the dihydrate gypsum content >4% and the anhydrous gypsum content <15%, otherwise the back-end aging time will be too long);

[0019] 3. Through the multi-stage air flow pipe, the calcination waste heat tail gas is rationally utilized, reducing the energy consumption of the system.

[0020] Other advantages, objectives and features of the present invention will be described in part in the following description, and to some extent, will be obvious to those skilled in the art based on an examination of the following, or can be taught from the practice of the present invention, and the objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a system structure diagram of the present invention.

[0022] In the figure: phosphogypsum feeding hopper 1; belt feeder 2; primary air flow pipe 3; primary dust collector 4; rotary kiln 5; secondary air flow pipe 6; secondary dust collector 7; ball mill 8; tertiary air flow pipe 9; tertiary dust collector 10; crusher 11; mixed hot air 12; fan 13; exhaust pipe 14; silo 15. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] like Figure 1 As shown, a phosphogypsum calcining system includes a phosphogypsum feeding hopper 1 and a belt feeder 2 connected to the phosphogypsum feeding hopper 1. A plurality of mutually connected aging devices are connected to one side of the belt feeder 2, and each aging device includes a feed air flow pipe and a dust collector connected thereto; a calcining device is provided between the first aging device and the second aging device, and the calcining device is a rotary kiln 5; a grinding device is provided between the second aging device and the third aging device, and the grinding device is a ball mill 8.

[0025] The aging device includes a primary air flow pipe 3 for drying the water attached to phosphogypsum and a primary dust collector 4 connected thereto; a secondary air flow pipe 6 for aging anhydrous gypsum and a secondary dust collector 7 connected thereto; a tertiary air flow pipe 9 for aging hemihydrate gypsum and repairing cracks on the particle surface and a tertiary dust collector 10 connected thereto; the feed end of the primary air flow pipe 3 is connected to the belt feeder 2, and the discharge end is connected to the inlet of the secondary air flow pipe 6 through the rotary kiln 5, and the outlet of the secondary air flow pipe 6 is connected to the tertiary air flow pipe 9 through the ball mill, and mixed hot air 12 is introduced into the bottom of the aging device.

[0026] The discharge port of the secondary air flow pipe 6 is connected to the fan through the secondary dust collector 7, so that the exhaust gas in the secondary air flow pipe 6 enters the primary air flow pipe 3 for waste heat recovery. After the primary air flow pipe 3 is dust-removed, the air flow contains a large amount of moisture. Part of this air flow is divided into the inlets of the secondary and tertiary air flow pipes, and part enters the exhaust pipe 14.

[0027] Specifically:

[0028] After the phosphogypsum is put into the hopper 1, it enters the crusher 11 and is then fed by the belt conveyor 2;

[0029] Entering the primary air flow pipe 3, the mixed hot air exchanges heat with the phosphogypsum, the attached water of the phosphogypsum evaporates, and after passing through the primary dust collector 4, the dried phosphogypsum enters the rotary kiln 5. The tail gas of the primary dust collector 4 contains a large amount of water. Part of the tail gas enters the air inlet of the secondary and tertiary air flow pipes through the fan 13, and part is discharged into the exhaust pipe 14;

[0030] The dried phosphogypsum enters a rotary kiln 5, where it is calcined to form building gypsum (primarily hemihydrate and anhydrous gypsum). The rotary kiln 5 uses steam or thermal oil as its heat source, and is internally distributed with multiple layers of heat exchange pipes. The gypsum powder discharged from the rotary kiln 5 has a temperature of approximately 160°C and enters a secondary airflow pipe 6. The air in this secondary airflow pipe 6 comes from the exhaust gas of the primary airflow pipe 3, contains a large amount of moisture, and has a temperature of approximately 90°C. This moisture and the gypsum powder come into contact with each other within the pipe. Under these high temperature and humidity conditions, the anhydrous gypsum in the gypsum powder absorbs the moisture and rapidly transforms into hemihydrate gypsum. The gypsum powder then enters a secondary dust collector 7. The exhaust gas, with a temperature exceeding 100°C, is directed back to the primary airflow pipe 3 for waste heat recovery. The gypsum powder then enters a ball mill 8.

[0031] In the ball mill 8, the gypsum particles are ground. Under the action of their own heat and the heat generated by grinding, the dihydrate gypsum inside the particles is further decomposed to form hemihydrate gypsum, and the discharge port of the ball mill enters the tertiary air flow pipe 9.

[0032] The inlet air of the tertiary air flow pipe 9 comes from the exhaust gas of the primary air flow pipe 3 and natural air in a ratio of 1:4. The temperature after mixing is about 40°C. The moisture in the air flow is in full contact with the gypsum powder, completing the aging of the semi-hydrated gypsum and the hydration repair of the surface defects of the particles. At the same time, after the air flow and the gypsum powder are heat exchanged, the temperature of the gypsum powder is rapidly reduced. The gypsum powder can be directly used after being sent to the silo 15, and the exhaust gas enters the exhaust pipe 14.

[0033] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. The preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the contents of this specification. The embodiments selected and described in detail in this specification are intended to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention.

Claims

1. A phosphogypsum calcining system, comprising a phosphogypsum feeding hopper (1) and a belt feeder (2) connected to the phosphogypsum feeding hopper (1), characterized in that: A plurality of mutually connected aging devices are connected to one side of the belt feeder (2), and each aging device includes a feeding airflow pipe and a dust collector connected thereto; a calcining device is provided between the first aging device and the second aging device; a grinding device is provided between the second aging device and the third aging device; the aging device includes a first airflow pipe (3) for drying attached water of phosphogypsum and a first dust collector (4) connected thereto; a second airflow pipe (6) for aging anhydrous gypsum and a second dust collector (7) connected thereto; a third airflow pipe (9) for aging hemihydrate gypsum and repairing cracks on the particle surface and a third dust collector (10) connected thereto; the feeding end of the first airflow pipe (3) is connected to the belt feeder (2), and the discharging end is connected to the inlet of the second airflow pipe (6) through the rotary kiln (5); the outlet of the second airflow pipe (6) is connected to the third airflow pipe (9) through the ball mill; mixed hot air is introduced into the bottom of the aging device.

2. The phosphogypsum calcining system according to claim 1, characterized in that: The calcining device is a rotary kiln (5).

3. The phosphogypsum calcining system according to claim 1, characterized in that: The grinding device is a ball mill (8).

4. The phosphogypsum calcining system according to claim 1, characterized in that: The discharge port of the secondary air flow pipe (6) is connected to the fan through the secondary dust collector (7), so that the tail gas in the secondary air flow pipe (6) enters the primary air flow pipe (3) for waste heat recovery.

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