1 condensation evaporator connected with upper and lower column
Multiple plate unit by monolayer, or in the tower plus assistant condensation evaporator. This kind of layout is the most conventional one, which is convenient to install, simple to arrange the pipeline, and also saves more space.
2 separately arranged condensing evaporator
Put several plate units in parallel in a cylindrical container, and connect them with the upper and lower towers by pipes, which is a single arrangement of condensing evaporator. Such structure form condensation evaporator and up and down tower separate, not section limit, but increases the equipment investment and pipe line configuration.
3-layer or double condensation evaporator
Multiple Plate-fin Heat Exchanger (main Cold Unit) by upper, lower two-layer configuration, layout in the upper and lower tower between, limited section layout with as large as possible heat transfer area, make condensation evaporator diameter and up and down tower diameter roughly the same, and variable load operation beneficial to obtain good operation stability and reliability, convenient transport, is a practical structure. Its drawback is the complex structure, manufacture installation is difficult.
4-high fever tube shell condensation evaporator
This condensation evaporator in the pipe inner surface boiling side have surface porous thin layer, pipe outer surface condensing side for longitudinal grooves. Because both sides phase-change heat transfer are enhanced, have improved overall heat transfer coefficient, reduce heat transfer temperature difference, reduce equipment energy consumption. Meanwhile, due to the high circulation rate of liquid through the porous surface, it can effectively prevent the explosion danger caused by partial concentration and accumulation of acetylene and hydrocarbon, which is beneficial to the safe operation of the equipment. But its cost expensive.
5 membrane condensing evaporator
Main cold put liquid oxygen face above, pass liquid oxygen pump liquid oxygen pressure into the cold, and qi dan as top-down through main cold adjacent channel, and heat transfer, make LOX evaporates qi dan condensation. Because the lox at main cold channel inner is form membranous to dirty and evaporation, so called diaphragm condensation evaporator. Because condensation evaporator no liquid oxygen column establish pressure difference, therefore oxygen boiling point unchanged, to enable the master cold on both sides of the oxygen, nitrogen temperature difference consistent.
Since the primary cold canceled within liquid oxygen column, can make Main cold temperature difference reduce, air compressor exit empty gas pressure also reduced accordingly. But security than Bath-main cold
Typical structure of condensing evaporator
With the iron and steel, oil, chemical, coal chemical industry, etc. large engineering construction, from reduce equipment investment, reduce energy consumption and convenient management eyes, corresponding requirements and engineering for the air separation equipment also tending to increase. According to China's industrial development of the actual demand, metallurgy, petrochemical, coal gasification, etc. engineering have been proposed and engineering for the air separation equipment needs, we through the experimental study and abroad large scale air separation unit of analysis, introduction and up and down tower integral join condensation evaporator, separate layout condensation evaporator, double-layer or multi-layer condensation evaporator, high fever tube shell condensation evaporator and diaphragm condensation evaporator five typical structure.
Large domestic and foreign air separation condensation evaporator can be summarized as five typical structure.
1, with the upper, lower ta lian extensions overall condensation evaporator
Multiple plate unit by monolayer, or in the tower plus assistant condensation evaporator. This arrangement style is the most conventional A, convenient installation, piping layout simple, also save space.
2, separate layout condensation evaporator
Put several plate units in parallel in a cylindrical container, and connect them with the upper and lower towers by pipes, which is a single arrangement of condensing evaporator.
Such structure form condensation evaporator and up and down tower separate, not section limit, but increases the equipment investment and pipe line configuration. (Figure 1)
Figure 1 Schematic diagram of condensing evaporator arranged separately.
3, multi-layer or double condensation evaporator
Multiple Plate-fin Heat Exchanger (main Cold Unit) by upper, lower two-layer configuration, layout in the upper and lower tower between, limited section layout with as large as possible heat transfer area, make condensation evaporator diameter and up and down tower diameter roughly the same, and variable load operation beneficial to obtain good operation stability and reliability, convenient transport, is a practical structure. Its drawback is the complex structure, manufacture installation is difficult. (Figure 2)
Figure 2 Schematic diagram of multilayer or double layer condensing evaporator
4, high fever tube shell condensation evaporator
US Union Carbide Company from 1970s, in large scale air separation unit on the high efficient heat transfer shell and tube condensation evaporator. This condensation evaporator in the pipe inner surface boiling side have surface porous thin layer, pipe outer surface condensing side for longitudinal grooves. Because the phase change heat transfer on both sides is enhanced, the total heat transfer coefficient is improved, the heat transfer temperature difference is reduced, and the energy consumption of the equipment is reduced. While for liquid through a porous surface circulation rate high, can effectively prevent acetylene and hydrocarbons local concentrated and accumulation of explosive hazard, conducive to the safe running of the equipment. But its cost expensive.
5, diaphragm condensation evaporator
Main cold put liquid oxygen face above, pass liquid oxygen pump liquid oxygen pressure into the cold, and qi dan as top-down through main cold adjacent channel, and heat transfer, make LOX evaporates qi dan condensation. Because the lox at main cold channel inner is form membranous to dirty and evaporation, so called diaphragm condensation evaporator. Because condensation evaporator no liquid oxygen column establish pressure difference, therefore oxygen boiling point unchanged, to enable the master cold on both sides of the oxygen, nitrogen temperature difference consistent.
Since the primary cold canceled within liquid oxygen column, can make Main cold temperature difference reduce, air compressor exit empty gas pressure also reduced accordingly. But security than Bath-main cold.
4 Conclusion and analysis
Large scale air separation unit condensation evaporator structure, through the above analysis can reach the following points:
(1) separate layout condensation evaporator, reduce boiling channel inner hydrostatic column on heat transfer temperature difference impact and reduce condensing channel inner condensing liquid film thermal resistance, improve the heat transfer surface heat transfer efficiency. Calculation shows that when boiling channel and condensing pass road use equivalent diameter de = 2. 75mm of fin, single $ height by 1800mm to 900mm when productivity mention high 8% ~ 10%. But such structure form because condenser and on lower tower separate, although not section limit, but increases the equipment investment and pipe line configuration, economy is poor.
(2) Linde company used double-layer condenser structure, limited section layout with as large as possible heat transfer area, make condensation evaporator diameter and up and down tower diameter roughly the same, and variable load operation beneficial to obtain good operation stability and reliability, convenient transport, is a practical the structure. Its drawback is the complex structure, manufacture installation is difficult.
(3) boiling side for porous surface, condensing side for longitudinal slot efficient shell and tube condensation evaporator, because it on both sides heat transfer coefficient have been enhanced, greatly improved oxygen, nitrogen between heat conduction, total heat transfer coefficient reach 9000 ~ 11000 W/m2 · K, than ordinary pipe improve 12 ~ 16 times, is one kind of advanced condensation evaporator, but its cost expensive.
(4) diaphragm condensation evaporator, because main cold canceled within liquid oxygen column, can make Main cold temperature difference per cent to about 0. 8 ℃, and Bath-main cold compared · reduce 0. 5 ~ 0. 7 ℃, lower tower pressure reduce about 0. 2 ~ 0. 3kPa, air compressor exit empty gas pressure and accordingly reduce the, the air compressor energy consumption can reduce about 2% ~ 2. 8%, the condensing evaporator of this kind of structure is a relatively advanced structure in the world at present.
(5) slit wei mo thermal siphon double-layer condensation evaporator boiling heat transfer has significant strengthening effect, its heat transfer coefficient to 900 W/m2 · K, than conventional Plate-fin condensing steam hair device is increased by 1. About 5 times, heat transfer temperature difference down 40% ~ 50%, and is simple in structure and convenient manufacture, is self-line development successful new condensation evaporator, it has been in a new generation large air separation equipment applied in, on our country air separation technology development of great significance.
