Continuous magnesium oxide ammonia distillation process and continuous magnesium oxide ammonia distillation equipment for multistage stator-rotor series reaction device

Abstract

The invention provides a continuous magnesium oxide ammonia distillation process and equipment for a multistage stator-rotor reactor series device. According to the process, ammonium salt and magnesium oxide are used as raw materials for deamination, a stator-rotor reactor is used for strengthening mass transfer between gas and liquid in the reaction process, generated ammonia gas is efficiently recycled into ammonia water, generated magnesium chloride can be converted into magnesium oxide again to be used for ammonia distillation or applied to other aspects of the industry, and the process is simple and convenient. The deamination efficiency is improved while comprehensive recycling of resources is realized in the whole process; compared with a traditional deamination tower, a plurality of stator-rotor reactors are connected in series for continuous magnesium oxide ammonia distillation, so that the retention time of reaction liquid in equipment can be controlled while the blockage problem is solved, the contact time of magnesium oxide and ammonium salt is prolonged, and the deamination efficiency is improved. According to the method, the problems of low mass transfer efficiency and slow reaction when magnesium oxide is used for ammonia distillation are effectively solved, ammonium ions contained in ammonium salt can be efficiently removed at lower cost, and meanwhile, resources in the reaction process are recycled.

Description

Technical Field

[0001] The present invention relates to a process and equipment for continuously carrying out ammonia distillation of magnesium oxide through a multi-stage stator-rotor reaction device using magnesium oxide and ammonium salts as raw materials. It is characterized in that soluble ammonium salts are used as raw materials, and ammonia removal of magnesium oxide is carried out in a stator-rotor reactor to produce ammonia water and magnesium salts. It is a method with low cost, no pollution, high reaction efficiency and simple process, suitable for industrial production, and belongs to the fields of materials and chemical engineering. Background Art

[0002] Ammonium salts widely exist in nature, daily life and industry. The ammonia nitrogen in ammonium salts can cause eutrophication of water bodies, corrode metals, and even endanger human life safety. The traditional methods for removing ammonia nitrogen in ammonium salts mainly include: magnesium ammonium phosphate method, breakpoint chlorination method, biological method, stripping method, etc. Among them, the stripping method is the most widely used. The traditional alkali-added stripping ammonia uses calcium oxide for this process, which will produce calcium chloride wastewater, and the recycling value of calcium chloride is low, resulting in waste of resources. With the improvement of environmental protection requirements and the demand for efficient utilization of resources, it has become particularly important to recycle all resources in the ammonium salt ammonia removal process.

[0003] In the method for preparing magnesium chloride by the ammonium chloride method, magnesium oxide reacts with ammonium chloride to form magnesium salts and ammonia gas, and this method is applied to the ammonium salt ammonia nitrogen removal process. The addition of magnesium oxide can convert the ammonium ions in ammonium salts into ammonia water, while magnesium oxide is converted into magnesium salts. These two substances have great recycling value, and it is a process that maximally realizes resource recycling and reuse. However, the process of using magnesium oxide to remove ammonia nitrogen in ammonium salts belongs to a gas-liquid-solid reaction, and there are problems of low mass transfer efficiency and slow reaction rate in a common ammonia removal tower. Improving the reaction rate and mass transfer rate of magnesium oxide ammonia distillation is an important prerequisite for realizing the recycling and utilization of ammonium salt resources. Summary of the Invention

[0004] In view of the above, in the process of carrying out ammonium salt ammonia distillation using magnesium oxide, the present invention uses a stator-rotor reactor (patent number ZL200410042631.6) as the core equipment. Since the magnesium oxide ammonia distillation belongs to a chemical equilibrium reaction process, timely discharge of the generated ammonia gas can effectively promote the continuation of the reaction. The use of a stator-rotor reactor improves the mass transfer efficiency in the gas-liquid two-phase during the reaction process of magnesium oxide and ammonium solution, thereby improving the ammonia distillation efficiency. Using multiple stator-rotor reactor devices in series for continuous magnesium oxide ammonia distillation, compared with the traditional ammonia removal tower, the use of a stator-rotor reactor enables the control of the residence time of the raw material liquid in the reactor, increases the contact time between magnesium oxide and ammonium salts, and further improves the ammonia removal efficiency of this process. In addition, the entire process flow has material internal circulation, reduces wastewater discharge, and the generated ammonia gas can be recovered as ammonia water, realizing the comprehensive utilization of resources.

[0005] The process flow chart adopted by the present invention is as shown in the appendix Figure 2 as follows:

[0006] For the process flow adopted by the present invention, the key process steps are as follows:

[0007] a. Prepare the raw material liquid with a molar ratio of ammonium to magnesium of 1:1 to 5;

[0008] b. Feed the raw material liquid into the fixed-rotor reactors at all levels, start the equipment, adjust the rotor speed to 100 - 3000 rpm, and the circulation ratio to 10 - 100;

[0009] c. Input steam for heating and maintain the reaction temperature at 50 - 150 °C;

[0010] d. Maintain the system pressure at positive pressure or negative pressure and recover the generated ammonia gas;

[0011] e. Continuously input the raw material liquid, regularly take samples for detecting the magnesium chloride concentration and ammonia nitrogen concentration, and recover ammonia.

[0012] According to some embodiments of the present invention, step (A) includes: determining the content of magnesium oxide and identifying its main components. Steps (B), (C), and (D) include: diluting the samples taken at each time period, measuring the magnesium chloride concentration and ammonia nitrogen concentration, and calculating the ammonia nitrogen recovery rate.

[0013] Advantages of the present invention:

[0014] 1. The raw materials used are widely sourced and inexpensive.

[0015] 2. Magnesium oxide is used in the reaction. While converting ammonium salts into magnesium salts, ammonium ions are converted into ammonia gas and recovered as ammonia water, realizing the recycling and reuse of ammonium chloride resources during the reaction process.

[0016] 3. In the intermittent magnesium oxide ammonia distillation experiment using a single fixed-rotor reactor, the ammonia nitrogen recovery rate reached about 96% after 4 hours of reaction.

[0017] 4. In the continuous magnesium oxide ammonia distillation experiment using a single fixed-rotor reactor, the ammonia nitrogen recovery rate reached about 60%.

[0018] 5. In the continuous magnesium oxide ammonia distillation experiment using three fixed-rotor reactors, the ammonia nitrogen recovery rate reached about 90%.

[0019] 5. By using a fixed-rotor reactor, the mass transfer and micro-mixing in the reaction process are enhanced, the reaction time is shortened, the ammonia removal efficiency and ammonia recovery rate are improved, and the stable continuous preparation of ammonium chloride is realized. Description of the Drawings

[0020] Figure 1Process flow diagram of continuous magnesia ammonia distillation provided by the present invention.

[0021] Figure 2 Schematic diagram of the continuous magnesia ammonia distillation process in three stator-rotor reactors.

[0022] Figure 3 Graph of the change in ammonia nitrogen concentration during batch magnesia ammonia distillation in a single stator-rotor reactor in Example 1.

[0023] Figure 4 Graph of the ammonia nitrogen conversion rate during continuous magnesia ammonia distillation in a single stator-rotor reactor in Example 2.

[0024] Figure 5 Graph of the ammonia nitrogen conversion rate during continuous magnesia ammonia distillation in three stator-rotor reactors in Example 3.

[0025] The digital marks involved in the attached drawings are as follows:

[0026] 1 - Peristaltic pump; 2, 3, 4 - Circulation tanks; 5, 6, 7 - Stator-rotor reactors; 8, 9 - Heat exchangers; 10, 11, 12 - Circulation pumps; 13 - Feed liquid; 14 - Treated liquid; 15 - Low-pressure steam; 16 - Condensate; 17 - Condensate return water; 18 - Condensate feed water; 19 - Ammonia gas Specific implementation method

[0028] To more clearly illustrate the present invention, the present invention will be further described below in conjunction with examples and the attached drawings. Similar components in the attached drawings are represented by the same reference numerals. Those skilled in the art should understand that the specific content described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0029] Figure 2Schematic diagram of the continuous preparation of magnesium chloride in three stator-rotor reactors. The specific implementation is as follows: Add a certain amount of raw material liquid into three circulation tanks 2, 3, and 4. Start three stator-rotor reactors 5, 6, and 7, and adjust the rotation speed so that the rotation speed of the rotor in the stator-rotor reactor reaches the preset value. At the same time, start circulation pumps 10, 11, and 12, and close the connecting valves between each reactor, so that each reactor realizes self-circulation. After completion, start to introduce low-pressure steam into heat exchanger 8. After the liquid temperature reaches the preset temperature through heat exchange, measure the magnesium ions in the raw material liquid at regular intervals; after the concentration is stable, open peristaltic pump 1, continue to add raw material liquid into it, and at the same time open the connecting valves between each reactor, so that part of the liquid in circulation tanks 2 and 3 returns to circulation tanks 2 and 3 respectively by circulation pumps 10 and 11, and part of it flows into the next reactor for reaction. The liquid in circulation tank 4 returns to circulation tank 4 through heat exchanger 8 by circulation pump 12. The introduced raw material liquid continuously collides with the rotor and stator in the inner ring of the rotor of the stator-rotor reactor for multiple times. The raw material liquid is continuously dispersed, broken, and cut, so that the surface of the light-burned magnesium particles is quickly updated, and thus is further hydrated and reacts with ammonium chloride, strengthening the micro-mixing process. At the same time, the mass transfer between phases is also enhanced, significantly shortening the reaction time between magnesium hydroxide and ammonium ions. The raw material liquid after reaction in the stator-rotor reactor can return to the circulation tank and is pumped into the stator-rotor reactor again by the circulation pump, and circulates continuously for multiple times, enabling the slurry to fully react, realizing self-circulation, and reducing the waste of raw materials.

[0030] Example 1

[0031] Mix NH 4 Cl and MgO to prepare the raw material liquid according to a molar ratio of 1:1.2. After mixing, place it in the stator-rotor reactor, adjust the rotation speed to 2800 rpm, turn on the circulation pump, adjust the circulation volume to 400 L / h, turn on the steam generator to maintain a certain amount of steam to keep the reaction temperature at 110 °C, connect a vacuum pump at the gas outlet to maintain a certain vacuum degree, and the generated ammonia is absorbed by water and converted into ammonia water. During the process, samples are taken at regular intervals, titration and ammonia nitrogen concentration determination are carried out on the samples, and its conversion rate and ammonia recovery rate are calculated.

[0032] The change diagram of magnesium chloride concentration is shown in the appendix Figure 3 .

[0033] Example 2

[0034] Mix NH 4The raw material liquid is prepared with Cl and MgO at a molar ratio of 1:1.3. To prevent equipment blockage, magnesium oxide is subjected to a hydration treatment at 100 °C for 2 h and then mixed for standby. A certain amount of liquid is placed in advance in a stator-rotor reactor, the rotation speed is adjusted to 1960 rpm, the circulation pump is turned on, the circulation volume is adjusted to 400 L / h, the steam generator is turned on to maintain a certain amount of steam. When the reaction temperature reaches 110 °C, the gas outlet is connected to a vacuum pump to maintain a certain vacuum degree, and at the same time, feeding is started at a feeding rate of 19 ml / min. The generated ammonia is absorbed by water and converted into ammonia water. Samples are taken at regular intervals during the process, titration and ammonia nitrogen concentration determination are carried out on the samples, and their conversion rate and ammonia recovery rate are calculated.

[0035] The change diagram of ammonia nitrogen recovery rate is shown in the appendix Figure 4 。

[0036] Example 3

[0037] Mix (NH 4 ) 2 CO 3 and MgO to prepare the raw material liquid at a molar ratio of 1:1.3. To prevent equipment blockage, magnesium oxide is subjected to a hydration treatment at 100 °C for 2 h and then mixed for standby. Three stator-rotor reactors are connected in series. A certain amount of liquid is placed in advance in each stator-rotor reactor, the rotation speed is adjusted to 1960 rpm, the circulation pump is turned on, the circulation volume is adjusted to 400 L / h, the steam generator is turned on to maintain a certain amount of steam. When the reaction temperature reaches 110 °C, the gas outlet is connected to a vacuum pump to maintain a certain vacuum degree, and at the same time, feeding is started at a feeding rate of 38 ml / min. The generated ammonia is absorbed by water and converted into ammonia water. Samples are taken at regular intervals during the process, titration and ammonia nitrogen concentration determination are carried out on the samples, and their conversion rate and ammonia recovery rate are calculated.

[0038] The change diagram of ammonia nitrogen recovery rate is shown in the appendix Figure 5 。

Claims

1. A continuous magnesium oxide ammonia distillation system, characterized in that The following equipment and combinations are used: a. The main equipment includes: stator-rotor reactor, circulation pump, circulation tank, heat exchanger; b. At least three stator-rotor reactors are connected in series; c. The liquid phase outlet of each stator-rotor reactor is connected to the liquid phase inlet of the next stator-rotor reactor through a circulation tank and a circulation pump; the gas phase outlet of each stator-rotor reactor is connected to the gas phase inlet of the previous stator-rotor reactor; d. The exhaust gas from the gas phase outlet of the stator-rotor reactor is recovered under positive or negative pressure conditions; e. Steam heats the system through a heat exchanger.

2. A magnesium oxide ammonia distillation method based on the system of claim 1, characterized in that The following process steps and process parameters were used: a. Prepare the raw material solution, the molar ratio of ammonium to magnesium is 1:1 to 5; b. Put the raw material liquid into each level of stator-rotor reactor, start the equipment, adjust the rotor speed to 100-3000rpm, and the circulation ratio to 10-100; c. Input steam for heating to maintain the reaction temperature at 50-150°C; d. Maintain the system pressure at positive or negative pressure and recover the generated ammonia; e. Continuously input the raw liquid, take samples regularly to test the magnesium chloride concentration, and recover the ammonia.

3. A continuous magnesium oxide ammonia distillation process according to claim 2, characterized in that: a. The raw material ammonium salt is a soluble ammonium salt such as ammonium nitrate, ammonium chloride, ammonium sulfate, ammonium acetate, etc.

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