WO2017101775A1 - 外冷式低纯氧空分系统及方法 - Google Patents

外冷式低纯氧空分系统及方法 Download PDF

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WO2017101775A1
WO2017101775A1 PCT/CN2016/109818 CN2016109818W WO2017101775A1 WO 2017101775 A1 WO2017101775 A1 WO 2017101775A1 CN 2016109818 W CN2016109818 W CN 2016109818W WO 2017101775 A1 WO2017101775 A1 WO 2017101775A1
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oxygen
lower tower
nitrogen
heat exchanger
liquid
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PCT/CN2016/109818
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English (en)
French (fr)
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张英辰
毛文军
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新疆天辰深冷技术有限公司
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04012—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling
    • F25J3/04018—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling of main feed air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04218—Parallel arrangement of the main heat exchange line in cores having different functions, e.g. in low pressure and high pressure cores
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • F25J3/0426—The cryogenic component does not participate in the fractionation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/044—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a single pressure main column system only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/72—Refluxing the column with at least a part of the totally condensed overhead gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/50—Oxygen

Definitions

  • the invention belongs to the field of air separation, and particularly relates to an externally cooled low purity oxygen air separation system and method.
  • Oxygen is widely used in industrial production and daily life.
  • the air contains 21% (by volume) oxygen, which is the cheapest oxygen-making material. Therefore, oxygen is generally produced by air separation.
  • the air separation device is a separation device for preparing oxygen and an inert gas such as nitrogen and argon from air.
  • the main raw material used in the preparation of oxygen, nitrogen, and inert gases (such as argon) by air separation units is the air that is filled in the atmosphere.
  • the air is liquefied by compressing, expanding and cooling the air, and is rectified and purified by a fractionation device to separate oxygen, nitrogen, and an inert gas (such as argon) from the air.
  • the raw material air used in the production does not require a special development process and can be obtained at will in the place of production.
  • the air separation industry is a branch of the chemical industry.
  • Chinese patent 201420741565.0 discloses a novel low-purity oxygen air separation device, which comprises an upper tower, a lower tower, a condensing evaporator, an air input pipeline, a liquid oxygen evaporator, a main heat exchanger, an oxygen output pipeline, and a condensing evaporator is arranged under Above the tower, the bottom of the upper tower is connected to the condensing evaporator by a liquid oxygen pump, and the bottom of the condensing evaporator is connected to the liquid oxygen evaporator through a liquid oxygen delivery pipe; the bottom of the lower tower passes through the oxygen-rich liquid-liquid pipeline and the middle of the upper tower Connected, the air input pipe is connected to the bottom of the lower tower through the main heat exchanger, the liquid oxygen evaporator is connected, the oxygen output pipe is connected to the liquid oxygen evaporator through the main heat exchanger; the liquid oxygen evaporator passes through the lean liquid output pipe and the upper The upper portion of the tower is connected; the upper tower is
  • the object of the present invention is to provide an externally cooled low-purity oxygen air separation system, which can combine a conventional air separation lower tower and an external cooling technology to form a self-contained system, operate independently, has a relatively simple structure, low energy consumption, and rapid startup. It is convenient to start and stop. When using liquid oxygen to replenish cold, ventilation can deliver oxygen.
  • Another object of the present invention is to provide an externally cooled low purity oxygen air separation method.
  • Externally cooled low purity oxygen air separation system including lower tower, condensing evaporator, oxygen input port, oxygen heat exchanger, nitrogen heat exchanger, throttle valve and conveying pipeline;
  • the condensing evaporator is disposed at a top of the lower tower, and the throttle valve is disposed at an outer side of the lower tower;
  • the liquid oxygen stagnated at the bottom of the lower tower is discharged to the lower tower, and is transported to the condensing evaporator at the top of the lower tower through a delivery pipe equipped with a throttle valve to participate in the above heat exchange as a cold source.
  • the invention also provides an externally cooled low purity oxygen air separation method comprising the following steps:
  • the raw material air at normal temperature is pre-cooled to a saturated temperature through an oxygen heat exchanger and a nitrogen heat exchanger, and then sent to the bottom of the lower tower;
  • the liquid oxygen is supplied from the liquid oxygen input port to the condensing evaporator, and the nitrogen gas rising from the bottom of the lower tower to the condensing evaporator is exchanged with the supplemental liquid oxygen, and the liquid oxygen is converted into oxygen and discharged from the condensing evaporator, and part of the nitrogen gas is discharged. Conversion to liquid nitrogen as reflux to reflux to the lower column;
  • the liquid oxygen remaining in the bottom of the lower tower is discharged to the lower tower, and is transported to the condensing evaporator at the top of the lower tower through the conveying pipe provided with the throttle valve outside the lower tower to participate in heat exchange;
  • the oxygen and nitrogen gas discharged from the condensing evaporator are reheated to a normal temperature by an oxygen heat exchanger and a nitrogen heat exchanger, respectively, and recovered.
  • the liquid oxygen retained in the bottom of the lower tower is directly passed through the peripheral conveying pipe with the throttle valve in the circulation process of the rectification air separation It is transported to the condensing evaporator at the top of the lower tower to participate in heat exchange, and finally converted into oxygen from the condensing evaporator, which not only improves the efficiency of rectification air separation, but also saves a lot of energy.
  • the externally cooled low-purity oxygen air separation device provided by the invention has the advantages of quick start-up, convenient opening and closing, no refrigeration speed, increased cooling in the startup phase, rapid cooling of the equipment to the working state, and shutdown within 8 hours, cold start At 0.5-1 hour.
  • ventilation can deliver oxygen.
  • the external cooling method can realize timely, rapid and accurate cold filling, and will not affect the rectification working condition. Therefore, the adjustment is flexible and the operation is stable.
  • the externally cooled low-purity oxygen air separation system and method provided by the invention can simultaneously produce low-purity oxygen and high-purity pressure nitrogen, and the oxygen purity is 40%-50%, which is most suitable for blast furnace gas supply, and the purity of nitrogen can reach 5 9, both products are available. And promote the "system energy saving" of blast furnace oxygen supply, the comprehensive energy saving effect exceeds 50%.
  • the pressure of the oxygen discharged can be adjusted by adjusting the pressure of the air supplied to the raw material to meet the individual needs of different users.
  • the supply pressure of the raw material air can be adjusted to be low, and when the higher pressure is required to satisfy the user's oxygen demand, the supply pressure of the raw material air can be adjusted.
  • This process can also meet industrial kiln, waste incineration, low calorific value fuel utilization oxygen demand, provide technical support for building materials, environmental protection industry energy saving and emission reduction.
  • FIG. 1 is a diagram of an externally cooled low purity oxygen air separation system provided by the present invention.
  • Fig. 1 is a view showing an externally cooled low-purity oxygen air separation system of the present embodiment.
  • the normal temperature air is precooled to the saturation temperature by the oxygen heat exchanger 3 and the nitrogen heat exchanger 4, respectively, and then enters the bottom of the lower tower 11. Since the boiling point of nitrogen is lower than the boiling point of oxygen at the same pressure, the liquid nitrogen in the lower column 1 is converted into nitrogen and the intrinsic nitrogen in the gas-liquid equilibrium phase rises along the inside of the lower column 11 to the condensing evaporator 2 at the top of the lower column 1. .
  • the liquid oxygen can be filled into the condensing evaporator 2 through the liquid oxygen input port 6 as a cold source, and the condensing portion and the evaporation portion in the condensing evaporator 2 are spaced apart, that is, into the condensing evaporator 2 Nitrogen and liquid oxygen are in separate spaces and are not in contact with each other.
  • the liquid oxygen and a part of the nitrogen are heat-exchanged in the condensing evaporator 2, and the liquid oxygen is converted into pure oxygen and discharged from the condensing evaporator 2, and is reheated by the oxygen heat exchanger 3 to a normal temperature and recovered.
  • Part of the nitrogen is converted into liquid nitrogen as reflux to the lower column 1.
  • the nitrogen which is not involved in the heat exchange is discharged from the condensing evaporator 2, and is recovered by the nitrogen heat exchanger 4 to recover to normal temperature.
  • the recovered nitrogen can be as pure as 5-9.
  • the nitrogen gas rising again to the condensing evaporator 2 is partially discharged from the condensing evaporator 2, and partially participates in heat exchange again in the condensing evaporator 2.
  • the liquid is usually taken out from the bottom of the column and heated to a normal temperature storage, and then cooled to a preset temperature, and sent to the condensing evaporator 2 for circulation.
  • This process not only wastes a lot of cold energy of the liquid at the bottom of the tower, but also requires a large amount of energy to be cooled again, and the equipment structure is relatively large.
  • the liquid oxygen remaining in the bottom of the lower column 1 is discharged to the lower column 1 and directly sent to the condensing evaporator 2 at the top of the lower column 1 through a transfer pipe provided with the throttle valve 5.
  • Liquid at the bottom of the lower tower 1 Although the body cannot automatically rise inside the lower tower 1, it is discharged from the bottom of the lower tower 1, and the pressure required to be transported through the conveying pipe to the condensing evaporator 2 at the top of the lower tower 1 is low, at the bottom of the lower tower 1 The pressure is large, and the pressure can be smoothly and automatically raised to the condensing evaporator 2 at the top of the upper tower by the pressure relief of the throttle valve 5 provided outside the lower tower 1, and the liquid oxygen is again involved in the heat exchange. In this process, not only a large amount of cold energy is saved, but also the air separation efficiency is greatly improved, and the entire process equipment is simple and easy to implement.
  • part of the nitrogen rising from the inside of the lower column 1 to the condensing evaporator 2 is again heat-exchanged with the liquid oxygen fed from the bottom of the lower column 1, and the liquid oxygen is evaporated into oxygen from the condensing evaporator 2
  • part of the nitrogen is again converted into liquid nitrogen and returned to the lower column 1, and the entire system is circulated.
  • the oxygen and nitrogen discharged from the system pass through the oxygen heat exchanger 3 and the nitrogen heat exchanger 4, respectively.
  • Both of the heat exchangers are preferably plate heat exchangers, which are non-contact type, and the two are respectively entered and entered in the heat exchanger.
  • the room temperature air is exchanged at room temperature, and the two are heated to normal temperature and then discharged and recovered. Because only the lower tower 1 has no upper tower in the device, the obtained oxygen purity is 40%-50%, which can meet the industrial furnace, garbage incineration, low calorific value fuel utilization oxygen demand, and meet the low purity of the preparation of the invention. Oxygen equipment requirements.
  • the externally cooled low-purity oxygen air separation system and method provided by the present invention can be manufactured and used industrially to meet the requirements of industrial applicability.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

提供一种外冷式低纯氧空分系统及方法，包括下塔（1）、冷凝蒸发器（2）、氧气入口、氧气换热器（3）、氮气换热器（4）、节流阀（5）和输送管道；冷凝蒸发器（2）设在下塔（1）的顶部，节流阀（5）设在下塔（1）的外侧；通过氧气输入口向冷凝蒸发器（2）内送入液氧；原料空气经过换热器预冷至饱和温度后进入下塔（1）的底部，其中的氮气上升至下塔（1）的顶部，并进入冷凝蒸发器（2）内，部分氮气与其内的液氧进行热交换，冷凝为液氮回流，部分氮气从冷凝蒸发器（2）内排出，并通过氮气换热器（4）复热至常温后回收；液氧转化为氧气从冷凝蒸发器（2）内排出，并通过氧气换热器（3）复热至常温后回收；停滞在下塔（1）底部的液氧排出下塔（1），并通过配设有节流阀（4）的输送管道输送至下塔（1）顶部的冷凝蒸发器（2）内，作为冷源参与热交换。

Description

外冷式低纯氧空分系统及方法 技术领域
本发明属于空分领域，具体涉及外冷式低纯氧空分系统及方法。
背景技术
氧气在工业生产和日常生活中有广泛地用途。空气中含有21％(体积浓度)的氧气，是最廉价的制氧原料，因此，氧气一般都通过空气分离制取。
工业上制取氧气的方法很多，常见的有电解水法(同时制取氢气和氧气)和分离空气制取氧气法两种。电解水制氧的方法由于耗电量大，只有在使用氢气的企业考虑综合利用。空分制氧有两种分离方法，一是全低压吸附工艺，二是深度冷冻法分离空气同时制取氧气和氮气。
空分装置是以空气为原料制备氧气和氮气及氩气等惰性气体的分离装置。空分机组制备氧气、氮气、惰性气体(如氩气)使用的主要原料就是充斥于大气层的空气。通过对空气进行压缩、膨胀制冷，进而使空气液化，利用分馏装置精馏提纯，在空气中分离出氧气、氮气和惰性气体(如氩气)等产品。生产中使用的原料空气不需要特殊开发过程，可以在生产地随意获得。目前空分行业是属于化工产业的一个分支行业。
中国专利201420741565.0，公开了一种新型低纯氧空分装置，包括上塔、下塔、冷凝蒸发器、空气输入管道、液氧蒸发器、主换热器、氧气输出管道，冷凝蒸发器设在下塔的上方，上塔的底部通过液氧泵与冷凝蒸发器连接，冷凝蒸发器的底部通过液氧输送管与液氧蒸发器连接；下塔的底部通过富氧液空管道与上塔的中部连接，空气输入管道通过主换热器分别于下塔的底部、液氧蒸发器连接，氧气输出管道通过主换热器与液氧蒸发器连接；液氧蒸发器通过贫液空输出管与上塔的上部连接；所述上塔为填料塔，下塔为筛板塔。
从上述方案可以看出，其装置设备设置依然相对复杂，能耗相当对较大。
发明内容
本发明的目的在于提供一种外冷式低纯氧空分系统，该装置将传统空分下塔与外冷技术结合即可自成系统，独立运行，结构相对简单，能耗低，启动迅速，开停方便，用液氧补冷时，通气即可送氧。
本发明的另一目的在于提供一种外冷式低纯氧空分方法。
为了实现上述目的，本发明的具体方案如下：
外冷式低纯氧空分系统，包括下塔、冷凝蒸发器、氧气输入口、氧气换热器、氮气换热器、节流阀和输送管道；
所述冷凝蒸发器设在所述下塔的顶部，所述节流阀设在所述下塔的外侧；
通过所述氧气输入口向所述冷凝蒸发器内送入液氧；原料空气经过所述氧气换热器、氮气换热器预冷至饱和温度后进入所述下塔的底部，其中的氮气上升至下塔的顶部，并进入所述冷凝蒸发器内，部分氮气与其内的液氧进行热交换，冷凝为液氮回流，部分氮气从所述冷凝蒸发器内排出，并通过氮气换热器复热至常温后回收；液氧转化为氧气从所述冷凝蒸发器内排出，并通过氧气换热器复热至常温后回收；
停滞在下塔底部的液氧排出下塔，并通过配设有节流阀的输送管道输送至下塔顶部的冷凝蒸发器内，作为冷源参与上述热交换。
本发明还提供了外冷式低纯氧空分方法，包括以下步骤：
a.将常温的原料空气分别经过氧气换热器和氮气换热器预冷至饱和温度后送入下塔的底部；
b.从液氧输入口向冷凝蒸发器内输送液氧，从下塔底部上升至冷凝蒸发器内的氮气与补充的液氧热交换，液氧转化为氧气从冷凝蒸发器内排出，部分氮气转化为液氮作为回流液回流至下塔；
c.精馏空分后滞留在下塔底部的液氧排出下塔，并通过下塔外部的配设有节流阀的输送管道，输送至下塔顶部的冷凝蒸发器内参与热交换；
d.从所述冷凝蒸发器内排出的氧气和氮气分别通过氧气换热器和氮气换热器复热至常温后回收。
通过本发明提供的外冷式低纯氧空分系统及方法，将滞留在下塔底部的液氧，在精馏空分的循环过程中直接通过外设的配设有节流阀的输送管道直接输送至下塔顶部的冷凝蒸发器内，使其参与热交换，最终转化为氧气从冷凝蒸发器内排出，不仅提高了精馏空分效率，同时节省了大量能量。
直接使用外部冷源液氧进行补冷，相比较传统工艺中使用的制冷压缩后的冷源进行补冷，本方案中补冷温度低，冷量大，增大了回流比，提高了精馏效率。
本发明提供的外冷式低纯氧空分装置，设备启动迅速，开停方便，不受制于制冷速度，启动阶段加大补冷，快速将设备冷却至工作状态，停机8小时内，冷启动在0.5-1小时。用液氧补冷时，通气即可送氧。外冷方式可实现及时、快速、精准补冷，不会对精馏工况产生影响，因此，调节灵活，运转平稳。
本发明提供的外冷式低纯氧空分系统及方法，可同时生产低纯氧和高纯压力氮气，氧气纯度为40％-50％，最适合高炉供气，氮气的纯度可达到5个9，两种产品均可利用。并促进高炉供氧“系统节能”，综合节能效果超过50％。
可以通过调节供给原料空气的压力，进而调节排出氧气的压力，满足不同用户的个性化需求。当排出较低压力的氧气即可满足用户需求时，可以调节原料空气的供给压力较低，当需要较高压力才可满足用户的用氧需求时，可调高原料空气的供给压力。
本流程也可满足工业窑炉，垃圾焚烧，低热值燃料利用供氧需求，为建材，环保行业节能减排提供技术支撑。
附图说明
图1为本发明提供的外冷式低纯氧空分系统图；
1.下塔，2.冷凝蒸发器，3.氧气换热器，4.氮气换热器，5.节流阀，6.液氧输入口。
本发明的较佳实施方式
参照附图对本发明的外冷式低纯氧空分系统及方法的实施方式进行说明。
图1为本实施方式的外冷式低纯氧空分系统图。
如图1所示，常温空气分别通过氧气换热器3和氮气换热器4预冷至饱和温度后进入下塔11的底部。因为在同等压力下氮气的沸点较氧气的沸点低，在下塔1内液氮转化为氮气与气液平衡相中的固有氮气一起沿下塔11内部上升至下塔1顶部的冷凝蒸发器2内。
开机前可以先通过液氧输入口6向冷凝蒸发器2内充入液氧作为冷源，该冷凝蒸发器2内的冷凝部分和蒸发部分为间隔设置，也就是，进入该冷凝蒸发器2内氮气和液氧分别在两个独立空间内，互不接触。液氧和部分氮气在该冷凝蒸发器2内进行热交换，液氧转化为纯的氧气从冷凝蒸发器2内排出，并通过氧气换热器3复热至常温后回收。部分氮气转化为液氮作为回流液流回至下塔1内，未参与热交换的氮气从冷凝蒸发器2内排出，并通过氮气换热器4复热至常温后回收。
此时，因为下塔1顶部的氮气浓度很高，其中的一部分氮气会直接从该冷凝蒸发器2排出被回收。回收的氮气其纯度可达到5个9。
因为氧气的沸点较低，液氧和氧气均无法上升至下塔1的顶部，回流的液氮与下塔1中部的氧气交汇，液氮再次转化为氮气蒸发上升，氧气转化为液氧回流至下塔1底部。
再次上升至冷凝蒸发器2内的氮气，部分从冷凝蒸发器2内排出，部分在冷凝蒸发器2内再次参与热交换。
此时，残留在下塔11底部的液氧，无法自动到达下塔1顶部参与循环。
在传统工艺中，通常将该部分液体从塔底导出并升温至常温存储，之后再将其降温至预设温度，输送入冷凝蒸发器2内参与循环。该过程不仅浪费了塔底液体本身的大量冷能，同时需要额外消耗大量能量进行再次降温，设备构架也比较庞大。
本实施方式中，将下塔1底部滞留的液氧排出下塔1，并通过配设有节流阀5的输送管道直接送入下塔1顶部的冷凝蒸发器2内。下塔1底部的液 体虽然不能在下塔1内部自动上升，但是，将其从下塔1底部排出，通过输送管道输送至下塔1顶部的冷凝蒸发器2内所需的压力值较低，此时下塔1底部的压力较大，通过下塔1外部设置的节流阀5泄压限流后，液体能够平稳自动上升至上塔顶端的冷凝蒸发器2内，液氧再次参与换热。在该过程中，不仅节省了大量的冷能，而且空分效率大幅提高，同时整个工艺设备简单，容易实施。
在接下来的循环中，从下塔1内部上升至冷凝蒸发器2内的部分氮气再次与从下塔1底部送入的液氧其进行热交换，液氧蒸发为氧气从冷凝蒸发器2内排出，部分氮气再次转化为液氮回流至下塔1内，整个系统以此循环。
从系统中排出的氧气和氮气分别通过氧气换热器3和氮气换热器4，这两个换热器均优选板式换热器，为不接触型，二者在换热器内分别与进入的常温原料空气进行热交换，二者升温至常温后被排出回收。因为该装置中只有下塔1无上塔，所以得到的氧气纯度为40％-50％，能够满足工业窑炉，垃圾焚烧，低热值燃料利用供氧需求，满足本发明所要达到的制备低纯氧设备的要求。
以上，虽然说明了本发明的几个实施方式，但是这些实施方式只是作为例子提出的，并非用于限定本发明的范围。对于这些新的实施方式，能够以其他各种方式进行实施，在不脱离本发明的要旨的范围内，能够进行各种省略、置换、及变更。这些实施方式和其变形，包含于本发明的范围和要旨中的同时，也包含于权利要求书中记载的发明及其均等范围内。
工业实用性
本发明提供的外冷式低纯氧空分系统及方法可以在工业上制造和使用，满足工业实用性的要求。

Claims (4)

  1. 外冷式低纯氧空分系统，其特征在于，包括下塔、冷凝蒸发器、氧气输入口、氧气换热器、氮气换热器、节流阀和输送管道；
    所述冷凝蒸发器设在所述下塔的顶部，所述节流阀设在所述下塔的外侧；
    通过所述氧气输入口向所述冷凝蒸发器内送入液氧；原料空气经过所述氧气换热器、氮气换热器预冷至饱和温度后进入所述下塔的底部，其中的氮气上升至下塔的顶部，并进入所述冷凝蒸发器内，部分氮气与其内的液氧进行热交换，冷凝为液氮回流，部分氮气从所述冷凝蒸发器内排出，并通过氮气换热器复热至常温后回收；液氧转化为氧气从所述冷凝蒸发器内排出，并通过氧气换热器复热至常温后回收；
    停滞在下塔底部的液氧排出下塔，并通过配设有节流阀的输送管道输送至下塔顶部的冷凝蒸发器内，作为冷源参与上述热交换。
  2. 根据权利要求1所述的外冷式低纯氧空分系统，其特征在于，所述氧气换热器和氮气换热器均为板式换热器。
  3. 外冷式低纯氧空分方法，其特征在于，包括以下步骤：
    a.将常温的原料空气分别经过氧气换热器和氮气换热器预冷至饱和温度后送入下塔的底部；
    b.从液氧输入口向冷凝蒸发器内输送液氧，从下塔底部上升至冷凝蒸发器内的氮气与补充的液氧热交换，液氧转化为氧气从冷凝蒸发器内排出，部分氮气转化为液氮作为回流液回流至下塔；
    c.精馏空分后滞留在下塔底部的液氧排出下塔，并通过下塔外部的配设有节流阀的输送管道，输送至下塔顶部的冷凝蒸发器内参与热交换；
    d.从所述冷凝蒸发器内排出的氧气和氮气分别通过氧气换热器和氮气换热器复热至常温后回收。
  4. 根据权利要求3所述的外冷式低纯氧空分方法，其特征在于，所述氧 气换热器和氮气换热器均为板式换热器。
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