Heater for concentrating ammonium phosphate slurry

Abstract

The utility model provides a heater for concentrating ammonium phosphate slurry. The heater comprises a spiral baffle plate, a tube nest and a heater shell, a spiral baffle plate is arranged in the heater shell, holes are formed in the spiral baffle plate, and the tube nest penetrates through the holes and is connected with a slurry inlet and a slurry outlet which are formed in the two ends of the heater. According to the spiral baffle plate of the heater, the flowing dead zone of the spiral baffle plate is few, and the temperature distribution is uniform; the spiral plate is of an integral structure, induced vibration generated by back-and-forth collision of steam is reduced, and the failure rate of the heat exchanger is reduced; shell side flow velocity distribution is uniform, shell side scaling is not prone to occurring, and the service life of the heat exchanger is prolonged.

Description

Technical Field

[0001] The utility model belongs to the field of chemical equipment, and in particular relates to a heater for slurry concentration. Background Art

[0002] In order to solve some problems in the production of ammonium phosphate by the traditional "phosphoric acid concentration process", Sichuan University and Sichuan Yinshan Phosphate Fertilizer Plant jointly carried out laboratory experiments and intermediate test development research on the slurry ammonium phosphate project, successfully studied the theoretical basis of the core part of the slurry ammonium phosphate process, and preliminarily opened up the process in the intermediate test based on this theory. The process is: dihydrate wet phosphoric acid - dilute ammonium phosphoric acid neutralization - neutralization slurry closed-loop circulation double-effect concentration - concentrated slurry spraying (spray) drying - granular (powdered) monoammonium phosphate product. The process flow was verified and optimized in the pilot test using Kunyang medium-grade phosphate ore, and the slurry process was established as one of the basic process routes for the development of high-concentration phosphate compound fertilizer industry in my country. In the later stage, by solving a series of engineering amplification and equipment set-up and finalization problems, a model device was established, and a large number of engineering parameters and technical and economic data were obtained, so that the slurry process is fully equipped with the conditions for large-scale promotion in China in terms of technology and economy.

[0003] The slurry concentration heat exchanger is an important equipment for the closed-loop double-effect concentration of neutralized slurry. Its structure is a shell-and-tube heat exchanger, which is mainly composed of tube bundles, tube shells, tube sheets, and baffles. The slurry flows through the tube side, and the steam flows through the shell side. The first effect uses fresh steam, and the second effect uses the secondary steam evaporated from the slurry in the first effect. The industry has been using bow-shaped baffle heat exchangers so far. The use of bow-shaped heat exchangers in concentrated heating of ammonium phosphate slurry has the following main defects:

[0004] 1. The arcuate baffle has many blind areas (the arcuate plate corner is the blind area), uneven temperature distribution, and poor heat transfer efficiency;

[0005] 2. The shell resistance of steam returning back and forth is too high;

[0006] 3. The shell-side steam collides with the tubes back and forth to generate induced vibration, and the weld cracks are easy to occur at the joints between the heat exchange tubes and the tube sheets (the bow-shaped plate tail is set separately and is not connected as a whole to bear the force);

[0007] 4. The shell flow blind area is prone to scaling, the scaling rate is high, and the heat transfer performance of the heat exchanger decreases rapidly (especially the secondary steam with a small amount of ammonium phosphate slurry foam is more likely to scale in the blind area).

[0008] In order to solve the problem of using the phosphate ammonium slurry heat exchanger and address the current pain points, the utility model develops a spiral baffle type heater specially used for concentrating the phosphate ammonium slurry. Utility Model Content

[0009] The utility model adopts a spiral baffle heat exchanger to replace a traditional bow-shaped heat exchanger, thereby achieving the purpose of energy saving, consumption reduction and extended maintenance cycle.

[0010] A heater for concentrating ammonium phosphate slurry comprises a spiral baffle, a tube array and a heater shell; the heater shell is provided with a spiral baffle, the spiral baffle has holes, the tube array passes through the holes and is connected to a slurry inlet and a slurry outlet at both ends of the heater.

[0011] The heater housing is provided with a steam outlet at the upper left side and a steam inlet at the lower right side.

[0012] The spiral baffle is evenly provided with circular holes, the hole diameter is 32.35 mm, and the hole spacing is 8 mm.

[0013] The diameter of the tubes is 32 mm, and a margin for expansion is reserved between the tubes and the holes.

[0014] The outermost side of the tube array is also provided with a spiral baffle plate which plays a fixing role, and the spiral baffle plate and the spiral baffle plate are in a double spiral structure.

[0015] The beneficial effects of the utility model are as follows:

[0016] The patented heat exchanger has spiral baffles with fewer dead zones and uniform temperature distribution. Compared with traditional phosphate ammonium slurry heat exchangers, the heat transfer efficiency is increased by 10-30%, and the shell resistance of the steam spiral continuous flow is reduced by 20-50%. The spiral plate is an integral structure, which reduces the induced vibration caused by the back and forth collision of steam and reduces the failure rate of the heat exchanger. The shell velocity distribution is uniform, the shell is not easy to scale, and the service life of the heat exchanger is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the utility model.

[0018] Notes in the figure: 1. slurry inlet, 2. steam outlet, 3. spiral baffle, 4. heater shell, 5. tube array, 6. steam inlet, 7. slurry outlet, 8. spiral baffle. DETAILED DESCRIPTION

[0019] The implementation scheme of the utility model will be described in detail below in conjunction with examples. The following examples are only used to illustrate the utility model and should not be regarded as limiting the scope of the utility model.

[0020] Example 1

[0021] A heater for concentrating ammonium phosphate slurry comprises a spiral baffle 3, a tube array 5 and a heater shell 4; the spiral baffle 3 is arranged inside the heater shell 4, holes are evenly arranged on the spiral baffle 3, and the tube array 5 passes through the holes and is connected to a slurry inlet 1 and a slurry outlet 7 at both ends of the heater.

[0022] The heater housing 4 is provided with a steam outlet 2 at the upper left and a steam inlet 6 at the lower right.

[0023] The spiral baffle 3 is provided with circular holes with a hole diameter of 32.35 mm and a hole spacing of 8 mm.

[0024] The diameter of the tube array 5 is 32 mm, and a margin for expansion is reserved between the tube array 5 and the hole.

[0025] The outermost side of the tube array 5 is also provided with a spiral baffle 8 for fixing, and the spiral baffle 8 and the spiral baffle 3 are in a double spiral structure.

[0026] Example 2

[0027] The device of Example 1 is installed vertically, and this process uses indirect heat exchange in the countercurrent circulation. Under the action of the forced circulation pump, the ammonium phosphate slurry with a water content of about 65% enters the tube 5 (tube side) from the slurry inlet 1 and flows rapidly from bottom to top; the saturated steam with a pressure of 0.5MPa and a temperature of 160°C enters the heater shell 4 (shell side) from the steam inlet 6 at the upper part of the heat exchanger. Under the action of the spiral baffle 3, the saturated steam indirectly exchanges heat with the slurry in countercurrent. After the heat exchange, the boiling slurry enters the flash chamber from the slurry outlet 7 after exiting the heater tube 5, and evaporates water vapor to achieve the purpose of slurry concentration; the steam flows out from the steam outlet 2.

Claims

1. A heater for concentrating ammonium phosphate slurry, characterized in that: The heater shell (4) comprises a spiral baffle (3), a tube array (5), and a heater housing (4); the heater housing (4) is provided with a spiral baffle (3), the spiral baffle (3) has holes, the tube array (5) passes through the holes, and is connected to a slurry inlet (1) and a slurry outlet (7) at both ends of the heater; the outermost side of the tube array (5) is also provided with a spiral baffle (8) for fixing, and the spiral baffle (8) and the spiral baffle (3) are in a double helix structure.

2. A heater for concentrating ammonium phosphate slurry according to claim 1, characterized in that: The heater housing (4) is provided with a steam outlet (2) at the upper left and a steam inlet (6) at the lower right.

3. A heater for concentrating ammonium phosphate slurry according to claim 1, characterized in that: The spiral baffle (3) is provided with circular holes, the hole diameter is 32.35 mm, and the hole spacing is 8 mm.

4. A heater for concentrating ammonium phosphate slurry according to claim 1, characterized in that: The diameter of the tube array (5) is 32 mm, and a margin for expansion is reserved between the tube array (5) and the hole.

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