A nitrogen purification system for solid phase polycondensation

Abstract

The invention discloses a nitrogen purification system for solid phase polycondensation, which is characterized by comprising a mixed gas operation system, a nitrogen regeneration cooling system, a nitrogen regeneration medium and high temperature system, an air regeneration cooling system and an air regeneration medium and high temperature system. Compared with the prior art, the invention has the advantages of safety, energy saving, environmental protection, low cost and high efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of nitrogen purification for solid phase polycondensation, in particular to a nitrogen purification system for solid phase polycondensation. Background Art

[0002] Solid phase polycondensation refers to the polycondensation reaction of monomers or prepolymers under solid conditions. Reaction principle: The process of heating monomers or prepolymers with low molecular weight to above the glass transition temperature and below the melting point for polymerization reaction. There are crystalline and amorphous regions in the reaction particles of solid phase polycondensation. The repeating units of macromolecules and inactive reaction groups will be frozen in the crystalline region, while the chain end groups, small molecules, and catalyst components will be repelled to the amorphous region, which greatly increases the effective concentration of the reaction groups and strengthens the frequency of mutual collisions between the groups, thereby accelerating the rate of the polymerization reaction. The generated small molecule by-products flow out of the reaction system through vacuum or inert gas, prompting the reaction to continue in the direction of the product, so that the molecular weight of the product continues to increase and finally the desired high-viscosity polymer is obtained.

[0003] At present, large-scale production generally adopts continuous solid-phase polymerization process. In order to ensure that the polyester raw material does not undergo oxidative cracking under high temperature environment, oxidative cracking will reduce the intrinsic viscosity of polyester, darken the color, increase the carboxyl content, produce low molecular gas, and generate gel, which is not conducive to the spinnability and fiber strength of polyester. Nitrogen will be filled in the whole reaction process. Even if nitrogen is added, in solid-phase polymerization, many end groups in the polyester low molecular chain obtain a certain activation energy during heating, and chain growth reaction will occur between the polyester low molecular chains. At the same time, small molecular by-products such as ethylene glycol, acetaldehyde, and water will be precipitated, which need to be discharged in time, otherwise it will seriously affect the spinnability and product quality.

[0004] The conventional treatment method is to use a cooler to add chilled water to remove water at low temperature, and an adsorption tower to adsorb other low molecular weight substances. This treatment method has the following disadvantages:

[0005] 1. High energy consumption, requiring multiple sets of coolers to cool with chilled water;

[0006] 2. High cost, high requirements for nitrogen cleanliness, generally use high-purity nitrogen with an accuracy of more than 99.999%, which is relatively expensive;

[0007] 3. Low efficiency, because low molecular weight substances are basically removed by adsorption tower, and the adsorption capacity of adsorption tower is limited, so the efficiency will be affected to a certain extent;

[0008] 4. Not environmentally friendly, because when the adsorption tower is regenerated through air, the adsorbed low-molecular substances will be precipitated and discharged into the atmosphere, which may cause certain pollution to the space;

[0009] Some manufacturers now use catalytic combustion technology to deal with the problem, but they use flammable and explosive gases such as natural gas, which poses certain safety risks. Summary of the invention

[0010] The technical problem to be solved by the present invention is to overcome the above technical defects and provide a nitrogen purification system for solid phase polycondensation, which is safe, energy-saving, environmentally friendly, low-cost and high-efficiency.

[0011] In order to solve the above technical problems, the technical solution provided by the present invention is: a nitrogen purification system for solid phase polycondensation, comprising a mixed gas operation system, a nitrogen regeneration cooling system, a nitrogen regeneration medium and high temperature system, an air regeneration cooling system and an air regeneration medium and high temperature system;

[0012] The mixed gas operation system comprises a general nitrogen inlet and an air inlet, and the gas outlet ends of the general nitrogen inlet and the air inlet are sequentially connected with a heater 2, a catalytic reactor, a heat exchanger, a cooler 1 / cooler 2 / cooler 3, a cooler 4, a circulating Roots blower 1, a cooler 5, an adsorption tower 1, a nitrogen filter 1 / nitrogen filter 2 / nitrogen filter 3, a heater 1 and a solid phase polycondensation tower;

[0013] The nitrogen regeneration cooling system comprises a centrifugal fan, a cooler six, an adsorption tower one, a cooler seven and a water storage tank which are connected in sequence;

[0014] The nitrogen regeneration medium and high temperature system comprises a centrifugal fan, a heat exchanger, a heater three, an adsorption tower one and a water storage tank connected in sequence;

[0015] The air regeneration cooling system includes a refined nitrogen inlet N2-0.5bar, a cooler seven, a centrifugal fan, a cooler six, and an adsorption tower one connected in sequence;

[0016] The air regeneration medium and high temperature system includes a centrifugal fan, an air inlet 2ATMOS, a heat exchanger, a heater three and an adsorption tower one which are connected in sequence.

[0017] As an improvement, two adsorption towers are provided, which are adsorption tower 1 and adsorption tower 2 connected in parallel, and two circulating Roots blowers are provided, which are circulating Roots blowers 1 and circulating Roots blowers 2 connected in parallel. At the same time, providing spare adsorption tower 2 and circulating Roots blower 2 can effectively improve the stability of the device. When one breaks down, it can quickly switch to another to work, and the design is relatively reasonable.

[0018] The advantages of the present invention compared with the prior art are: 1. Safety. The electric heating used replaces the natural gas combustion heating, which is safer and more stable. The catalytic reactor can remove most of the oxygen, moisture and low molecular weight substances;

[0019] 2. Energy saving. Since most of the water is evaporated during high-temperature catalysis, the back-end cooler can use tap water as the refrigerant to filter out the remaining water. Compared with the use of condensed water, the energy consumption is much lower. In addition, multiple sets of heat exchangers are reasonably equipped to further improve the equipment efficiency.

[0020] 3. Environmental protection. The adsorption tower has two regeneration modes, air regeneration and nitrogen regeneration, which can be switched freely. Generally, the internal circulation mode of nitrogen regeneration is adopted. However, there is a problem with this mode. When the concentration of impurities adsorbed by the adsorption tower reaches a certain value, the regeneration function will fail because there is no place for the precipitated impurities to be discharged. It is necessary to switch to the air regeneration mode to discharge the impurities in the pipeline. The air regeneration outlet is connected to the exhaust gas treatment equipment pipeline, and no exhaust gas will be generated.

[0021] 4. Low cost, can use general nitrogen with purity of about 99.5%, saving costs;

[0022] 5. High efficiency. Since the components of this purification device are scientifically and reasonably configured, the purification efficiency is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a schematic diagram of the system structure of a nitrogen purification system for solid phase polycondensation.

[0024] A. General nitrogen inlet, B. Air inlet, 511A. Cooler 1, 511B. Cooler 2, 511C. Cooler 3, 514. Cooler 4, 513. Cooler 5, 602B. Cooler 6, 602A. Cooler 7, 512A. Circulating Roots blower 1, 512B. Circulating Roots blower 2, 515A. Nitrogen filter 1, 515B. Nitrogen filter 2, 515C. Nitrogen filter 3, 516. Heater 1, 522. Heater 2, 605. Heater 3, 601A. Adsorption tower 1, 601B. Adsorption tower 2, 523. Catalytic reactor, 521. Heat exchanger, 301. Solid phase polycondensation tower, 603. Centrifugal fan, 606. Water storage tank, 604. Heat exchanger. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0026] A nitrogen purification system for solid phase polycondensation comprises a mixed gas operation system, a nitrogen regeneration cooling system, a nitrogen regeneration medium and high temperature system, an air regeneration cooling system and an air regeneration medium and high temperature system.

[0027] Mixed gas operation system: General nitrogen with a purity of 99.5% enters the catalytic combustion device from the general nitrogen inlet A, and air enters from the air inlet B at a certain ratio, generally about 3%, for auxiliary combustion. After the mixed gas is heated to 300-400 degrees by the heater 2 522, it enters the catalytic reactor 523 for catalytic combustion to remove oxygen, water and other impurities in the general nitrogen. The nitrogen with some impurities removed is heat exchanged by the heat exchanger 521 for energy saving, and then enters the cooler 1 511) / cooler 2 511B / cooler 3 511C. 11C and cooler four 514 further separate the moisture in the nitrogen, and then pass through one of the circulating Roots blower one 512A / circulating Roots blower two 512B, and then enter the adsorption tower one 601A / adsorption tower two 601B, and then the other is kept in standby after being cooled again by cooler five 513. After adsorbing most of the impurities, it enters nitrogen filter one 515A / nitrogen filter two 515B / nitrogen filter three 515C to filter out the remaining impurities, and finally enters the solid phase polycondensation tower 301 after being heated by heater one 516;

[0028] Nitrogen regeneration cooling system: The centrifugal fan 603 is running, and the nitrogen in the pipeline is transported to the cooler six 602B for cooling and cleaning, and then enters the adsorption tower one 601A to slowly release the impurities in the adsorbent. The slowly released impurities enter the cooler seven 602A for cooling and cleaning, and then enter the centrifugal fan 603 for reciprocating circulation. The impurities such as water cooled and cleaned are discharged into the water storage barrel 606, and the heat exchanger 604 and heater three 605 passed through are not working;

[0029] Nitrogen regeneration medium and high temperature system: The centrifugal fan 603 is running, and the nitrogen in the pipeline is transported to the heat exchanger 604 for heat exchange, and then enters the heater three 605 for heating. The heated gas enters the adsorption tower one 601A to slowly release the impurities in the adsorbent, and the slowly released impurities enter the centrifugal fan 603 for reciprocating circulation. The cooler seven 602A / cooler six 602B passed by is not working;

[0030] Air regeneration cooling system: refined nitrogen is added from the refined nitrogen inlet N2-0.5bar, cooled and cleaned through cooler seven 602A, and then enters the centrifugal fan 603, and the nitrogen in the pipeline is transported to cooler six 602B for cooling and cleaning, and then enters the adsorption tower one 601A to slowly release the impurities in the adsorbent, and the slowly released impurities enter the waste treatment equipment for treatment. The impurities such as water cooled and cleaned are discharged into the water storage barrel 606, and the heat exchanger 604 and heater 605 passed through are not working;

[0031] Air regeneration medium and high temperature system: The centrifugal fan 603 is running, sucking air from the atmosphere through the air inlet 2ATMOS, and then sending it to the heat exchanger 604 for heat exchange, and then entering the heater 605 for heating. The heated air enters the adsorption tower 1 601A to slowly release the impurities in the adsorbent, and the slowly released impurities enter the waste treatment equipment for treatment after passing through the heat exchanger 604. The cooler 7 602A / cooler 6 602B passed through is not working.

[0032] The benefits of this application after the operation of the above systems are: 1. Safety. Electric heating is used instead of natural gas combustion heating, which is safer and more stable. The catalytic reactor can remove most of the oxygen, moisture and low molecular weight substances;

[0033] 2. Energy saving. Since most of the water is evaporated during high-temperature catalysis, the back-end cooler can use tap water as the refrigerant to filter out the remaining water. Compared with the use of condensed water, the energy consumption is much lower. In addition, multiple sets of heat exchangers are reasonably equipped to further improve the equipment efficiency.

[0034] 3. Environmental protection. The adsorption tower has two regeneration modes, air regeneration and nitrogen regeneration, which can be switched freely. Generally, the internal circulation mode of nitrogen regeneration is adopted. However, there is a problem with this mode. When the concentration of impurities adsorbed by the adsorption tower reaches a certain value, the regeneration function will fail because there is no place for the precipitated impurities to be discharged. It is necessary to switch to the air regeneration mode to discharge the impurities in the pipeline. The air regeneration outlet is connected to the exhaust gas treatment equipment pipeline, and no exhaust gas will be generated.

[0035] 4. Low cost, can use general nitrogen with purity of about 99.5%, saving costs;

[0036] 5. High efficiency. Since the components of this purification device are scientifically and reasonably configured, the purification efficiency is relatively high.

[0037] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A nitrogen purification system for solid phase polycondensation, characterized in that: It includes a mixed gas operation system, a nitrogen regeneration cooling system, a nitrogen regeneration medium and high temperature system, an air regeneration cooling system and an air regeneration medium and high temperature system; The mixed gas operation system comprises a general nitrogen inlet (A) and an air inlet (B), and the gas outlet ends of the general nitrogen inlet (A) and the air inlet (B) are sequentially connected to a heater 2 (522), a catalytic reactor (523), a heat exchanger (521), a cooler 1 (511A) / cooler 2 (511B) / cooler 3 (511C), a cooler 4 (514), a circulating Roots blower 1 (512A), a cooler 5 (513), an adsorption tower 1 (601A), a nitrogen filter 1 (515A) / nitrogen filter 2 (515B) / nitrogen filter 3 (515C), a heater 1 (516) and a solid phase polycondensation tower (301); The nitrogen regeneration cooling system comprises a centrifugal fan (603), a cooler six (602B), an adsorption tower one (601A), a cooler seven (602A) and a water storage tank (606) which are connected in sequence; The nitrogen regeneration medium and high temperature system comprises a centrifugal fan (603), a heat exchanger (604), a heater three (605), an adsorption tower one (601A) and a water storage tank (606) which are connected in sequence; The air regeneration cooling system includes a refined nitrogen inlet N2-0.5 bar, a cooler seven (602A), a centrifugal fan (603), a cooler six (602B), and an adsorption tower one (601A) connected in sequence; The air regeneration medium and high temperature system comprises a centrifugal fan (603), an air inlet 2ATMOS, a heat exchanger (604), a heater three (605) and an adsorption tower one (601A) which are connected in sequence.

2. A nitrogen purification system for solid phase polycondensation according to claim 1, characterized in that: Two adsorption towers are provided, which are adsorption tower 1 (601A) and adsorption tower 2 (601B) connected in parallel, and two circulating Roots blowers are provided, which are circulating Roots blowers 1 (512A) and circulating Roots blowers 2 (512B) connected in parallel.

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