WO2016101593A1 - 一种具有高效气流分布的径向床设计方法及其径向床 - Google Patents

一种具有高效气流分布的径向床设计方法及其径向床 Download PDF

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WO2016101593A1
WO2016101593A1 PCT/CN2015/083647 CN2015083647W WO2016101593A1 WO 2016101593 A1 WO2016101593 A1 WO 2016101593A1 CN 2015083647 W CN2015083647 W CN 2015083647W WO 2016101593 A1 WO2016101593 A1 WO 2016101593A1
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gas
channel
product
flow rate
radial bed
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PCT/CN2015/083647
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English (en)
French (fr)
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李世刚
姜贺
王学通
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北京北大先锋科技有限公司
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds

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  • This invention relates to radial flow vessels, and more particularly to a method and apparatus for designing a radial bed having a high efficiency gas flow distribution for periodic operation to achieve efficient pressure equalization of the gas stream.
  • the gas distribution area of the inlet and outlet ports is not filled or filled with inert packing.
  • the gap of this part is called “dead space”.
  • dead space When it is used as a steady-state flow reactor, it does not affect the product. Yield.
  • the raw material at the feed end and the product stream at the product end are reversely released before the end of adsorption, and the amount of dead space directly affects the yield of the product.
  • the upper and lower heads of the axial bed will produce a large dead space.
  • the size of the dead space is proportional to the cube of the diameter.
  • the effective area of the reaction or separation is proportional to the square of the diameter, resulting in an increase in the dead space as the diameter increases. Larger and larger, so the product yield will be significantly affected when the production scale is increased.
  • Radial bed is a kind of energy-efficient reactor with excellent air distribution effect. It is often used in air purification, separation, purification, drying, reaction separation, particle exchange, etc. It is suitable for gas-solid and liquid-solid two-flow catalysis. And / or adsorption process. It has been widely used in chemical process industries such as petrochemical, carbon-chemical, chemical separation.
  • the radial bed container comprises: an inlet and an outlet, an annular flow passage through which the inlet gas flow (feedstream) is distributed, a flow passage through which the outlet gas flow (product stream) is collected, a flow passage and a fixed filler directly from the annular perforated plate and/or wire. The net is separated.
  • the perforated plate and/or the wire mesh can be composed of a plurality of concentric cylinders of different diameters depending on the process requirements.
  • the "dead space” of the radial bed includes: the inlet head and the annular inflow passage, and the collection passage of the outlet air flow.
  • the "dead space” of the annular channel can be controlled by controlling the width of the annulus. Because it is a radial bed, the height can be increased to reduce the diameter when the control volume is constant, which greatly reduces the "dead space” of the inlet head. ". Therefore, the radial bed can effectively reduce the dead space of the packing container.
  • Patent US5759242 uses an inner hollow tank to reduce the dead space at the intake end, and uses the inner hollow cylinder to reduce the dead space of the product end.
  • Patent CN102441350 states that the ratio of the cross-sectional area of the inner and outer channels can be determined by the ratio of the total mass flow rate into or out of the channel. It is desirable to maintain the same mass flux in these channels.
  • This design is suitable for steady-state operation; for unstable For the state or periodic operation, the mass flow rate of each phase in each channel is changed, and the variation range is very large, far exceeding the area ratio of the inner and outer channels given in the patent CN102441350 to 0.7-1.4 of the mass flow ratio. Scope, Because of the large variation in mass flow rate, the area ratio of the inner and outer channels of the design is uniquely determined by the ratio of the total mass flow rate that cannot enter or exit the channel.
  • the gas flow is much larger than the process gas of the product gas, resulting in an actual pressure drop of the gas production channel at this stage greater than the pressure drop calculated according to the process gas flow.
  • the present invention provides a radial bed design method with high efficiency gas flow distribution and a radial bed thereof, which utilizes cycle and yield to more accurately calculate the radial bed
  • the bed laminate is lowered and the area of each channel of the radial bed is determined to increase the uniformity of the airflow distribution of the radially operated radial bed.
  • a radial bed design method with a high efficiency gas flow distribution comprising a packing layer, an inner channel, an outer channel, an outer porous plate and an inner porous plate, by introducing a cycle and yield of radial bed operation
  • Calculating the bed lamination drop of the radial bed to determine the design area of the radially inner and outer channels, and increasing the uniformity of the airflow distribution of the radial bed including the following steps:
  • step 2) According to the value in step 1), the inner channel area and the outer channel area are calculated, the outer channel area is the cross-sectional area S Feed of the air inlet channel, and the inner channel area is the cross-sectional area S Product of the gas producing channel;
  • Equation 3 Calculate the area ratio S Feed /S Product and determine whether the area ratio satisfies Equation 3 or Equation 4:
  • the ratio of the cross-sectional area of the intake passage to the gas production passage S Feed /S Porduct calculated and judged by the volumetric flow rate of the raw material gas and the volumetric flow rate of the product process gas in Equation 3 during the period of unknown periodic operation;
  • the gas production time in the total cycle time and the total cycle time in Equation 4 is calculated and judged:
  • S Feed is the maximum cross-sectional area of the feed gas flow passage
  • S Product is the cross-sectional area at the outlet end of the gas feed passage
  • K v is the ratio of the ratio of the passage area in the periodic operation to the volumetric flow rate of the feed gas and the process product.
  • Proportional constant Q Product is the gas flow rate during gas production in the periodic operation, that is, the product process gas flow rate
  • Q feed is the raw material gas volume flow rate
  • the radial bed is a VPSA oxygen plant
  • the ratio of the area of the intake and gas passages is estimated by a ratio of process flow rates of intake and gas production, the ratio of the areas
  • the proportionality constant K v to the ratio of the raw gas and the product gas volume flow rate is 0.2 or more and less than 0.6. Preferably it is from 0.35 to 0.45;
  • Equation 4 can be used to calculate and determine the area ratio of the intake and gas passages:
  • Equation 4 a is the proportional relationship between the product gas flow rate and the raw material gas during gas production:
  • K ' is the ratio of gas and backflush flow process product stream;
  • T is the total time period;
  • T P is the total gas production period of time T;
  • Y is the product yield, the object product is an effective component in an amount of raw material The percentage of the amount of the gas active component;
  • x feed is the percentage of the useful component in the feed gas;
  • x product is the percentage of the useful component of the product gas in the gas stream;
  • K m is the proportionality constant of the ratio of the channel area in the periodic operation to the ratio of the product gas flow in the feed gas and the channel:
  • the principle of determining K m is: when designing the pressure drop in the channel, try to make the pressure drop of the inner and outer channels equal, and the up and down floating does not exceed 1 time.
  • the ratio of the resistance of the inner and outer channels is between 0.5 and 2. 0.66-1.5.
  • the flow resistance is related to the flow rate, and the flow resistance is proportional to the square of the flow velocity after the flow of the gas flow into the turbulent zone. Therefore, the value range of K m is between 0.5 0.5 and 2 0.5 , that is, between 0.707 and 1.414, preferably between 0.8 and 1.25.
  • step 5 If the area ratio S Feed /S Product does not satisfy Equation 3 or Equation 4, adjust the set shell radius or the inner cylinder radius, repeat steps 2) to 4); if the area ratio S Feed /S Product satisfies Equation 3 or 4, then proceeds to step 5);
  • ⁇ P is the internal channel pressure drop ⁇ P ichannel or the outer channel pressure drop ⁇ P ochannel ; correspondingly, ⁇ is the internal channel resistance coefficient or the external channel resistance coefficient, because one side of the opening can be considered according to the high roughness, The value is 0.02 to 0.15, and the optimum value is 0.06 to 0.1; L is the length of the inner channel or the length of the outer channel; d is the hydraulic diameter of the inner channel or the hydraulic diameter of the outer channel; K R is the inlet resistance coefficient or the outlet resistance coefficient According to the definition of local resistance, take -0.5 when inflow, 1 when flowing out; ⁇ is the density of airflow, the unit is kg/m3; ⁇ is the flow velocity of the inner or outer channel, the unit is m/s:
  • Equation 51 S Feed is the area value of the intake passage
  • S Product is the area value of the gas producing passage
  • Q Feed is the volume flow rate of the raw material gas
  • Q Pchannel is the volumetric flow rate of the product gas in the passage:
  • T is the total cycle time
  • T p is the gas production time in the total cycle time T
  • Q Pchannel is the product gas volume flow rate in the channel
  • Q Product is the gas flow rate during gas production in the periodic operation, that is, the product process gas Volume flow
  • Q Refulx is the amount of gas that is refilled or flushed by the product:
  • K' is the ratio of the backflow gas to the flow rate of the process product.
  • the process requires the product gas to be recharged or flushed.
  • the K' value ranges from 0.03 to 0.3, in the pressure swing adsorption system.
  • the oxygen process takes a value of 0.2 to 0.6;
  • ⁇ p bed pressure drop of the packing layer
  • ⁇ bed void ratio
  • ⁇ gas flow viscosity
  • dp particle diameter of the active filler
  • ⁇ air flow density in units of kg/m 3
  • Radius; ri radius of the inner porous plate
  • A, B and C are coefficients:
  • H is the height of the packing layer
  • Q feed is the volume flow rate of the raw material gas
  • a is the proportional relationship between the product gas flow rate and the raw material gas at the time of gas production, and is calculated by the formula 5
  • Radius of the plate ri: radius of the inner porous plate
  • step 7) judging whether the sum of the inner channel pressure drop ⁇ P ichannel and the outer channel pressure drop ⁇ P ochannel is less than 5% of the filler lamination drop ⁇ p bed ; if not, re-step 1) to step 7) to obtain an inner channel satisfying the above conditions
  • the area value S Product and the outer channel area value S Feed are used as the design area values of the inner channel and the outer channel, respectively, to obtain the radial bed design size.
  • the radial bed is a VPSA oxygen plant.
  • the proportionality constant of the gas volume flow rate Q Pchannel at the time of gas production in the radial bed periodic operation and the process gas volume flow rate Q Product is 1.5 to 3.5. It is preferably 2.0 to 2.5.
  • the present invention also provides a radial bed with a high efficiency airflow distribution for periodic operation using the radial bed design method described above, including an outer casing, a feed gas inlet, a product gas outlet, an outer passage pre-distribution head, an outer passage, and an inner a channel, an outer porous plate or mesh, an active filler layer and an inner porous plate or mesh, characterized in that, in the same operation cycle, the feed gas flow rate is equal to the process flow rate; and the feed gas inlet end is an outer passage cut
  • the area is the largest; the product gas outlet is the inner channel cross-sectional area; the sum of the inner channel pressure drop ⁇ P ichannel and the outer channel pressure drop ⁇ P ochannel is less than 5% of the filler lamination drop ⁇ p bed .
  • the outer casing is a centrally symmetrical cylindrical or truncated cone-shaped structure including an upper head and a lower head.
  • the feed gas inlet includes a tapered opening; the tapered opening is a combination of one or more of a tapered head, an elliptical head, and a butterfly head.
  • the perforated plate or screen has at least two pieces, and the plurality of perforated plates or wires are enclosed in concentric cylinders, and at least one end of the perforated plate or the screen is fixed.
  • the annular space enclosed by the perforated plate or the wire mesh is filled with one or more active adsorbents or catalysts.
  • the cross-sectional area of the inner passage along the flow direction may be fixed or gradually enlarged, and the cross-sectional area at the product gas outlet is the largest.
  • a cylinder for counteracting dead space such as a hollow cylinder, a hollow truncated cone or a hollow cone, may be placed inside the inner perforated plate.
  • the radial bed with a high efficiency gas flow distribution for periodic operation may be a VPSA or PSA process oxygen plant, a hydrogen plant, a purified carbon monoxide plant, a separate carbon dioxide or air drying unit.
  • the present invention provides a radial bed having a high-efficiency airflow distribution for periodic operation
  • the outermost porous plate or the passage between the wire mesh and the outer casing is an outer passage
  • the innermost porous plate or wire The passage inside the net is the inner passage;
  • the cross-sectional area of the outer passage along the flow direction may be constant or may be gradually reduced, that is, the cross-sectional area at the inlet of the raw material gas is the largest;
  • the cross-sectional area of the inner passage along the flow direction may be It is fixed or it can be gradually enlarged.
  • the cross-sectional area at the product gas outlet is the largest.
  • the radial bed provided by the present invention is concentric cylindrical, and the outermost and innermost sides of the concentric cylinder are used for the inflow or outflow of gas.
  • the pressure drop relative to the packing layer is much smaller.
  • the pressure drop inside the channel is proportional to the square of the maximum flow rate.
  • the flow resistance is related to the flow rate, and the flow resistance is proportional to the square of the flow velocity after the flow of the gas flow into the turbulent zone.
  • the present invention calculates the cross-sectional area of the inner and outer channels of the radial bed by correlating with the cycle and product yield.
  • the cross-sectional area of the inner and outer channels, the length of the channel, and the thickness of the filler layer, and improving the uniformity of the airflow distribution of the radially-operated radial bed it can be calculated that the pressure drop of the inner and outer channels is lower than that of the filler lamination under the working condition.
  • the cross-sectional area of the inner and outer channels, the length of the channel and the thickness of the packing layer in the case of 5%, and the irregularity of the flow rate calculated by the Ergun equation is less than 2.5%, so that the uniformity of the airflow distribution of the periodically operated radial bed is greatly improved. .
  • the present invention designs a radial bed for periodic operation to achieve a gas flow pressure distribution, and more accurately calculates the bed lamination drop of the radial bed by utilizing the cycle concept and the yield concept to determine the radial bed channels. area.
  • the technical scheme of the present invention can be used for the design of a cyclically operated active filler container such as adsorption separation, purification, drying, particle exchange, reaction and adsorption separation.
  • the invention designs the uniformity of the airflow distribution by using the resistance drop of the airflow flowing through the channel, and controls the sum of the pressure drops of the inlet and outlet channels to be 5% of the packing lamination drop, and calculates according to the relationship between the square of the flow velocity and the resistance.
  • the flow rate through the packing layer varies less than 2.5% over the entire channel, such that the flow rate distribution non-uniformity is controlled to within 2.5%, i.e., the velocity fluctuation of the gas stream flowing through any portion of the packing layer is controlled to within 2.5%.
  • Figure 1 is a block flow diagram of a radial bed design method of the present invention.
  • Figure 2 is a schematic structural view of a radial bed of the present invention
  • (a) is the radial bed at the bottom of the product gas outlet; (b) is the radial bed at the top of the product gas outlet; 1 - the feed gas inlet; 2 - the product gas outlet; 3 - the outer channel pre-distribution head 4 - outer channel; 5 - inner channel; 6 - outer porous plate or mesh; 7 - active filler layer; 8 - inner porous plate or wire mesh.
  • Figure 3 is a graph showing the change in flow rate for a periodic operation of a radial bed without a change in the flow cross section of the packing layer during the adsorption process.
  • Figure 4 is a graph showing the change in flow rate for a periodic operation of a radial bed without a change in the flow cross section of the packing layer during the desorption process.
  • Figure 5 is a diagram of the outer channel pre-distribution head
  • (a) is a tapered head;
  • (b) is an elliptical or dish-shaped head; and
  • (C) is an ellipse or a combination of a dish and a tapered head.
  • Figure 6 is a cross-sectional view of the inner passage
  • (a) is a hollow structure; (b) a hollow cylinder is placed in the inner orifice plate; (C) a hollow cone is placed in the inner orifice plate; and (D) a hollow cone is placed in the inner orifice plate.
  • Figure 7 is a cross-sectional view of the outer passage
  • the outer casing is a cylindrical body; and (b) the outer passage is a truncated cone.
  • the invention provides a radial bed adsorber design method for realizing periodic operation of gas flow pressure distribution, and can design an active filler for periodic operation such as adsorption separation, purification, drying, particle exchange, reaction and adsorption separation. container.
  • the flow block diagram of the radial bed design method of the present invention is as shown in FIG. 1.
  • the uniformity of the airflow distribution is designed by using the resistance drop of the airflow flowing through the channel, so that the unevenness of the flow velocity distribution is controlled within 2.5%, that is, the airflow.
  • the velocity fluctuations flowing anywhere through the packing layer are controlled within 2.5%.
  • the key to the design is to control the sum of the pressure drop of the inlet and outlet channels to 5% of the packing lamination drop. According to the relationship between the square of the flow velocity and the resistance, the flow rate through the packing layer is calculated to be less than the entire channel. 2.5%.
  • Figure 2 is a schematic view of the radial bed of the present invention, wherein: (a) is a radial bed at the bottom of the product gas outlet; and (b) is a radial bed at the top of the product gas outlet.
  • the radial bed provided by the design of the invention comprises a raw material gas inlet 1; a product gas outlet 2; an outer channel pre-distribution head 3; an outer channel 4; an inner channel 5; an outer porous plate or mesh 6; an active filler layer 7;
  • the layered perforated plate or screen 8 further includes a casing; wherein the raw material gas inlet 1 comprises a gradually wide opening; the tapered opening is a combination of a conical head or a conical head, an elliptical head and a butterfly head, The wide mouth uses an elliptical or butterfly-shaped head to gradually enlarge the flow area; as shown in the outer channel pre-distribution head in Fig.
  • the outer casing comprises upper and lower heads, which are centrally symmetrical cylindrical or truncated cone-shaped structures; as shown in the cross-sectional view of the outer passage of Fig. 7, wherein: (a) the outer casing is a cylindrical body; and (b) is an outer passage.
  • the outer casing is a truncated cone.
  • the inside of the container is a concentric cylinder made of a perforated plate or a wire mesh.
  • the perforated plate or the wire mesh is fixed at least at one end; at least two perforated plates or meshes; the outermost perforated plate or between the wire mesh and the outer casing
  • the passage is an outer passage, and the passage in the innermost perforated plate or the wire mesh is an inner passage; the annular space enclosed between the perforated plate or the wire mesh is filled with one or more active adsorbents or catalysts;
  • the cross-sectional area of the direction may be constant or may be gradually reduced, that is, the cross-sectional area at the inlet of the raw material gas is the largest; the cross-sectional area of the inner passage along the flow direction may be fixed or gradually enlarged, in other words. In other words, the cross-sectional area at the gas outlet of the product is the largest.
  • (a) is a hollow structure; (b) a hollow cylinder is placed in the inner hole plate; (C) a hollow truncated cone is placed in the inner hole plate; (D) is an inner hole Empty inside the board Heart cone.
  • the flow rate does not change significantly.
  • the porosity of the porous plate is selected to be no less than 50% of the void volume of the filler, otherwise the radial flow velocity will increase a lot, and the filler layer will flow into the filler layer.
  • the flow rate becomes smaller again, which causes a large resistance, and it is preferable that the opening ratio of the perforated plate is larger than 80% of the void ratio of the filler layer.
  • the void ratio refers to the particle volume of the filler divided by the packing volume of the filler.
  • the invention does not strictly limit the filling volume or filling mode of the filler, and may be a compact packing or a modular active filler.
  • the diameter of the granular packing should not be less than the fluidizing speed at the designed radial gas velocity.
  • the effective particle diameter of the modular packing should not affect the gas-solid mass transfer rate.
  • the pressure drop of the inner and outer passages it is necessary to estimate the pressure drop of the inner and outer passages, and also to estimate the pressure drop of the packing layer. It is generally required to control the sum of the pressure drop of the inner and outer passages not exceeding 10% of the bed lamination drop, further The pressure drop of each of the inner and outer channels is controlled to be less than 5% of the bed laminate drop.
  • the estimation of the bed lamination drop is the focus of the design of the present invention.
  • the flow volume is different at different cross sections due to adsorption or reaction. Therefore, it is not possible to directly and simply use one inlet volume divided by each. The area of the section.
  • the volume flow rate is basically fixed for purification, and the change is not large; for separation and purification, since the amount of adsorption is relatively large, the flow velocity toward the gas end of the product will become smaller and smaller, as shown in FIG.
  • the flow rate of the radial bed is changed when the flow cross section of the packing layer does not change during the adsorption process. When desorbing, the flow rate will increase with the direction of the gas volume. As shown in Fig. 4, the flow rate changes when the radial bed is not changed during the desorption process.
  • the negative sign indicates the opposite direction to the intake air.
  • the radial bed designed by the above method is a vacuum pressure swing adsorption (VPSA) oxygen generating device, wherein the radial velocity refers to the apparent velocity of the airflow through the filler layer, and the unit is m/s.
  • the channel velocity refers to the velocity of the airflow in the inner and outer channels, IC represents the velocity in the inner channel, and OC represents the velocity in the outer channel.
  • VPSA vacuum pressure swing adsorption
  • the dimensions of the VPSA oxygen generator are set as follows: the outer radius Ro: 1.6 m, the outer cylinder wall thickness 15 mm; the outer orifice radius r o : 1.485 m; the inner orifice radius ri: 0.375 m; according to Fig. 6 (b)
  • the structure is provided with a hollow column with a radius of 250 mm; the effective height of the filling is H: 2.632 m; the porosity of the molecular sieve is 0.39.
  • blower gas volume Q feed is 270 m 3 /min, ie 4.5 m 3 /s; period T is 50 s (including 4 s venting); periodic oxygen generation time T production It is 30 s; the ratio of oxygen return to product gas is 0.6; oxygen yield Y is 0.6; product oxygen concentration x product is 90%; air oxygen concentration x feed is 21%.
  • the product product Q product was 2088 m 3 /h; the product instantaneous gas production Q pchannel was 5806 m 3 /h.
  • the outer casing radius Ro is 1.6m, the outer cylinder wall thickness is 15mm; the outer orifice radius r o is 1.485m; the inner orifice radius ri is 0.375m; the hollow cylinder radius according to the structure of Fig. 6(b) is 250mm; The effective height H was 2.632 m; the molecular sieve void ratio was 0.39.

Abstract

一种具有高效气流分布的径向床及其设计方法，用于周期性操作实现气流的高效均压分布，该径向床包括外壳、原料气进口（1）、产品气出口（2）、外通道预分布封头（3）、外通道（4）、内通道（5）、外层多孔板或丝网（6）、活性填料层（7）和内层多孔板或丝网（8），在同一个操作周期内，原料气流速等于工艺流速；原料气进口（1）端为外通道（4）截面积最大处；产品气出口（2）端为内通道（5）截面积最大处；内通道（5）压降和外通道（4）压降之和小于填料层（7）压降的5％；通过引入径向床操作的周期和收率来计算径向床的床层压降，以确定径向床内通道（5）和外通道（4）的设计面积。

Description

一种具有高效气流分布的径向床设计方法及其径向床 技术领域
本发明涉及径向流容器，尤其涉及一种具有高效气流分布的径向床的设计方法和装置，用于周期性操作实现气流的高效均压分布。
背景技术
在化工过程中，经常使用到活性填料作为化工反应和/或分离的催化剂和/或吸附剂。盛装这些材料的容器很大一部分属于固定(填料)床。常用的固定床容器有轴向床和径向床。在生产规模较大时，气流分布成为制约产品收率和运行成本的关键问题。
填料床在用于化工催化和分离时，进出端口的气流分布区域不装或者装填惰性填料，这一部分的空隙叫做“死空间”，当作为稳态流的反应器时，它不会影响产品的收率。但作为周期性操作的分离或反应分离的容器时，吸附结束前在进料端的原料和产品端的产品物流都会被逆向放走，死空间的多少直接影响到产品的收率。轴向床的上下封头会产生很大的死空间，死空间的大小与直径的立方成正比，反应或分离的有效区域与直径的平方成正比，导致随直径的增大“死空间”增大幅度更大，所以在生产规模增大时会明显影响产品收率。
径向床是一种高效节能的反应器，具有优良的气流分布效果，常用于气流净化、分离、提纯、干燥、反应分离、粒子交换等领域，适用于气固、液固两项流的催化和/或吸附过程。已在石油化工、碳一化工、化工分离等化工过程工业中得到广泛应用。这种径向床容器包含：进口和出口，进口气流(原料流)分布的环形流通通道、出口气流(产品流)汇集的流通通道，流通通道与固定填料直接由环形的多孔板和/或丝网分隔开。多孔板和/或丝网根据工艺要求可以由多层不同直径的同心圆柱体构成。
径向床的“死空间”包括：入口的封头和环形流入通道，出口气流的汇集通道。环形通道的“死空间”可以通过控制环隙的宽度来控制，因为是径向床，控制容积不变的情况下可以增加高度来减小直径，大大减小了入口处封头的“死空间”。所以径向床能有效减小填料容器的死空间。专利US5759242使用内空的罐体来减少进气端死空间，使用内空的柱体减少产品气端死空间。专利CN102441350指出，内外通道的截面积之比可以通过进入或离开通道的总质量流率比来确定，希望保持这些通道内有相同的质量通量，这种设计适用于稳态操作；对于非稳态或者周期性操作来说，每个阶段在各通道的质量流率是变化的，而且变化幅度很大，远远超过专利CN102441350中给定的内外通道的面积比在质量流量比的0.7-1.4范围， 正因为质量流率变化幅度很大，导致设计内外通道的面积比不能通过进入或离开通道的总质量流率比来唯一确定。
上述专利CN102441350给出了一个利用计算填料床压降的Ergun方程来计算径向床压降的积分公式，做了一个在不同半径的截面上总的质量流率相等的假设，然后代入Ergun方程积分得到专利中的床层压降计算公式，按照该假设，不同半径上的流速等于总质量流率除以半径，半径越小流速就越大。这一假设偏离了变压吸附的实际情况，在吸附过程中，如图3所示，填料层流通截面不变化时，在流动方向上，质量流速变化是随吸附的进行越来越小的；而在解吸过程中，如图4所示，填料层流通截面不变化时流速变化随解吸的进行而越来越大，因此，该公式计算的填料层压降将会比实际压降大很多。
综上所述，现有技术对于非稳态或者周期性操作来说，存在的问题是：
1)在周期性或非稳态操作中，质量流率是变化的，无法解决内外通道的面积按照周期的哪个阶段来确定的问题。
2)在周期的某个阶段，产气气流远大于产品气的工艺气流，导致该阶段的产气通道实际压降大于按照工艺气流计算的压降。
3)填料层压降的计算值比实际压降偏差很大，导致设计出来的径向床容器的气流分布不均匀性比期望值偏大。
发明内容
为了满足周期性操作的径向床设计需要，本发明提供一种具有高效气流分布的径向床设计方法及其径向床，该设计方法利用周期和收率更为准确地计算径向床的床层压降并确定径向床各通道的面积，从而提高周期性操作的径向床的气流分布的均匀性。
本发明提供的技术方案是：
一种具有高效气流分布的径向床设计方法，所述径向床包括填料层、内通道、外通道、外层多孔板和内层多孔板，通过引入径向床操作的周期和收率来计算径向床的床层压降，以确定径向床内通道和外通道的设计面积，提高径向床的气流分布的均匀性，包括如下步骤：
1)设定径向床的外壳半径、内孔板半径、外孔板半径和高度的取值；若在内层多孔板的里面放置一个抵消死空间用的空心筒体作为内筒，还需设定内筒半径；
2)根据步骤1)中的取值，计算得到内通道面积和外通道面积，外通道面积为进气通道的截面积SFeed，内通道面积为产气通道的截面积SProduct；
3)计算得到面积比SFeed/SProduct，判断该面积比是否满足式3或式4：
进气通道与产气通道的截面积之比SFeed/SPorduct，在未知周期性操作中的周期时，通过式3中原料气体积流量和产品工艺气体积流量计算和判断；在已知周期性操作中的周期时，通过式4中周期总时间和周期总时间中的产气时间计算和判断：
Figure PCTCN2015083647-appb-000001
               (式3)
式中，SFeed为原料气流通通道的最大截面积；SProduct表示产气通道出口端的截面积；Kv为周期性操作中通道面积之比与原料气和工艺产品气体积流率之比的比例常数；QProduct是周期性操作中产气时的气体流量，即产品工艺气流量；QFeed是原料气体积流量；
在本发明的实施例中，所述径向床为VPSA制氧装置，所述进气和产气通道的面积之比通过进气和产气的工艺流速之比来估算，所述面积之比与原料气和产品气体积流率之比的比例常数Kv为大于等于0.2且小于0.6。优选为0.35至0.45；
设计者对工艺熟悉的情况下，可以使用式4计算和判断进气和产气通道的面积比：
Figure PCTCN2015083647-appb-000002
                    (式4)
式4中，a为产气时产品气流量与原料气之间的比例关系：
Figure PCTCN2015083647-appb-000003
               (式5)
K′为回冲气与工艺产品气流流量的比率；T为周期总时间；Tp为周期总时间T中的产气时间；Y为产品收率，是目的产品中有效组分的量占原料气有效组分的量的百分比；xfeed为原料气中有用组分的百分含量；xproduct为产品气中有用组分在气流中的百分含量；
式4中，Km为周期性操作中通道面积之比与原料气和通道内产品气流量之比的比例常数：
Figure PCTCN2015083647-appb-000004
                   (式6)
Km的确定原则是：在设计通道内的压降时，尽量让内外通道的压降相等，上下浮动不超过1倍，换句话说，内外通道阻力降之比在0.5-2之间，优选0.66-1.5。进一步地，流动阻力与流速具有相关性的，气流在通道中的流动进入湍流区后流动阻力与流速的平方成正比。所以Km的取值区间为0.50.5—20.5之间，即0.707—1.414之间，优选0.8—1.25之间。
4)若面积比SFeed/SProduct不满足式3或式4，则调整设定外壳半径或内筒半径，重复步骤2)～4)；若面积比SFeed/SProduct满足式3或式4，则进入步骤5)；
5)通过管道内压力计算公式计算得到内通道压降ΔPichannel和外通道压降ΔPochannel：
Figure PCTCN2015083647-appb-000005
                    (式50)
式50中，ΔP为内通道压降ΔPichannel或外通道压降ΔPochannel；相应地，λ为内通道阻力系 数或外通道阻力系数，因为一侧开孔，可按照粗糙度高来考虑，取值为0.02～0.15，优化取值为0.06～0.1；L为内通道长度或外通道长度；d为内通道的水力学直径或外通道的水力学直径；KR为进口阻力系数或出口阻力系数，根据局部阻力的定义，流入时取-0.5，流出时取1；ρ为气流密度，单位是kg/m3；υ为内通道或外通道的气流流速，单位是m/s：
Figure PCTCN2015083647-appb-000006
或
Figure PCTCN2015083647-appb-000007
                      (式51)式51中，SFeed为进气通道的面积值，SProduct为产气通道的面积值；QFeed是原料气体积流量；QPchannel为通道内产品气体积流量：
Figure PCTCN2015083647-appb-000008
          (式52)
式52中，T为周期总时间；Tp为周期总时间T中的产气时间；QPchannel为通道内产品气体积流量；QProduct是周期性操作中产气时的气体流量，即产品工艺气体积流量；QRefulx为产品气回充或冲洗的气量：
QRefulx＝K′×QProduct             (式53)
式53中，K′为回冲气与工艺产品气流流量的比率，因工艺要求需要使用产品气回充或冲洗，在空气干燥工艺中K＇取值范围是0.03～0.3，在变压吸附制氧工艺中取值为0.2～0.6；
6)设填料层各截面的流量为等比例减少，通过Ergun方程得到填料层的压降Δpbed：
Figure PCTCN2015083647-appb-000009
(式60)
式60中，Δpbed：填料层的压降；ε：床层空隙率；μ：气流粘度；dp：活性填料的颗粒直径；ρ：气流密度，单位为kg/m3；ro：外层多孔板的半径；ri：内层多孔板的半径；A、B和C为系数：
A＝(a×ro-ri)            (式61)
B＝(1-a)         (式62)
Figure PCTCN2015083647-appb-000010
           (式63)
式61～式63中，H为填料层高度；Qfeed为原料气的体积流量；a为产气时产品气流量与原料气之间的比例关系，通过式5计算得到；ro：外层多孔板的半径；ri：内层多孔板的半径；
7)判断内通道压降ΔPichannel和外通道压降ΔPochannel之和是否小于填料层压降Δpbed的5％；若不满足，重新步骤1)～步骤7)，得到满足上述条件的内通道的面积值SProduct和外通道的面积值SFeed，分别作为内通道和外通道的设计面积值，从而得到径向床设计尺寸。
在本发明实施例中，所述径向床为VPSA制氧装置。所述径向床周期性操作中产气时的气体体积流量QPchannel与工艺产气体积流量QProduct的比例常数为1.5～3.5。优选为2.0～2.5。
本发明还提供利用上述径向床设计方法实现的用于周期性操作的具有高效气流分布的径向床，包括外壳、原料气进口、产品气出口、外通道预分布封头、外通道、内通道、外层多孔板或丝网、活性填料层和内层多孔板或丝网，其特征是，在同一个操作周期内，原料气流速等于工艺流速；所述原料气进口端为外通道截面积最大；所述产品气出口处为内通道截面积最大；内通道压降ΔPichannel和外通道压降ΔPochannel之和小于填料层压降Δpbed的5％。
上述用于周期性操作的具有高效气流分布的径向床中，进一步地，所述外壳是中心对称的圆柱形或圆锥台形结构，包含上封头和下封头。
所述原料气进口包括渐阔口；渐阔口为锥形封头、椭圆封头和蝶形封头中的一种或几种的组合。
所述多孔板或丝网至少有两块，所述多块多孔板或丝网围成同心圆柱，所述多孔板或丝网至少有一端是固定的。
所述多孔板或丝网围成的同心圆柱的环形空间内装填一种或多种活性吸附剂或催化剂。
所述内通道沿流动方向截面积可以是固定的，也可以是逐渐扩大的，产品气出口处的截面积是最大的。在内层多孔板的里面可放置一个抵消死空间用的筒体，如空心圆柱、空心圆锥台或空心圆锥体。
所述用于周期性操作的具有高效气流分布的径向床可以为VPSA或PSA工艺的制氧装置、制氢装置、提纯一氧化碳装置、分离二氧化碳或空气干燥装置。
根据上述设计方法，本发明提供一种用于周期性操作的具有高效气流分布的径向床，最外层多孔板或丝网与外壳之间的通道为外通道，最里层多孔板或丝网之内的通道为内通道；外通道沿流动方向的截面积可以不变，也可以是逐渐缩小的，也就是说原料气进口处的截面积是最大的；内通道沿流动方向截面积可以是固定的，也可以是逐渐扩大的，换句话说，产品气出口处的截面积是最大的。本发明提供的径向床呈同心圆柱形，同心的圆柱的最外和最里侧用于气体的流入或流出。为了保证气流在通道内分布的均匀性，就要保证通道内的压降 相对于填料层的压降小得多。而通道里面的压降与最大流速的平方成正比。进一步地，流动阻力与流速具有相关性的，气流在通道中的流动进入湍流区后流动阻力与流速的平方成正比。但是，要确定通道内的流速相对比较困难，同时由于周期性操作，各个阶段的流速也是不一样的。所以可以通过使用工艺流速比较方便地来确定内外通道的截面积之比。由操作的周期性引入周期概念，在同一个周期内，原料气流速等于工艺流速，即可确定通道内产品气流速。本发明把径向床内外通道的截面积通过与周期及产品收率关联起来进行计算。通过确定内外通道的截面积、通道长度、填料层厚度，提高周期性操作的径向床的气流分布的均匀性，即可通过计算得到满足在工作状态下内外通道压降小于填料层压降的5％情况下的内外通道的截面积、通道长度和填料层厚度，进而利用Ergun方程计算得到其流速不均匀性小于2.5％，使得周期性操作的径向床的气流分布的均匀性大为提高。
与现有技术相比，本发明的有益效果是：
本发明设计一种实现气流均压分布的周期性操作使用的径向床，通过利用周期概念和收率概念更为准确地计算径向床的床层压降，从而确定径向床各通道的面积。本发明的技术方案能用于吸附分离、净化、干燥、粒子交换、反应和吸附分离一体等周期性操作的活性填料容器的设计。本发明通过使用气流流过通道的阻力降来设计气流分布的均匀性，把进出口通道的压降之和控制为填料层压降的5％，根据流速平方与阻力成正比的关系，从而计算到穿过填料层的流速在整个通道上的变化小于2.5％，使得流速分布的不均匀性控制在2.5％以内，也就是，气流流过填料层任何位置的速度波动控制在2.5％以内。
附图说明
图1是本发明径向床设计方法的流程框图。
图2是本发明径向床的结构示意图；
其中：(a)为产品气出口在底部的径向床；(b)为产品气出口在顶部的径向床；1—原料气进口；2—产品气出口；3—外通道预分布封头；4—外通道；5—内通道；6—外层多孔板或丝网；7—活性填料层；8—内层多孔板或丝网。
图3是周期性操作径向床在吸附过程填料层流通截面不变化时流速变化图。
图4是周期性操作径向床在解吸过程填料层流通截面不变化时流速变化图。
图5是外通道预分布封头图；
其中，(a)为锥形封头；(b)为椭圆或碟形封头；(C)为椭圆或碟形与锥形封头的组合。
图6是内通道截面图；
其中，(a)为中空结构；(b)内孔板内放置空心圆柱体；(C)为内孔板内放置空心圆锥台；(D)为内孔板内放置空心圆锥体。
图7是外通道的截面图；
其中：(a)为外通道的外壳为圆柱体；(b)为外通道的外壳为圆锥台。
具体实施方式
下面结合附图，通过实施例进一步描述本发明，但不以任何方式限制本发明的范围。
本发明提供一种实现气流均压分布的周期性操作使用的径向床吸附器设计方法，可设计用于吸附分离、净化、干燥、粒子交换、反应和吸附分离一体等周期性操作的活性填料容器。
本发明径向床设计方法的流程框图如图1所示，使用气流流过通道的阻力降来设计气流分布的均匀性，使得流速分布的不均匀性控制在2.5％以内，也就是说，气流流过填料层任何位置的速度波动控制在2.5％以内。设计的关键是要把进出口通道的压降之和控制为填料层压降的5％，根据流速平方与阻力成正比的关系，从而计算到穿过填料层的流速在整个通道上的变化小于2.5％。
图2是本发明径向床的结构示意图，其中：(a)为产品气出口在底部的径向床；(b)为产品气出口在顶部的径向床。本发明设计提供的径向床包括原料气进口1；产品气出口2；外通道预分布封头3；外通道4；内通道5；外层多孔板或丝网6；活性填料层7；内层多孔板或丝网8，还包括外壳；其中，原料气进口1包括渐阔口；渐阔口为锥形封头或锥形封头、椭圆封头和蝶形封头的任意组合，渐阔口利用椭圆或蝶形封头逐渐扩大流通面积；如图5中外通道预分布封头图所示，其中，(a)为锥形封头；(b)为椭圆或碟形封头；(C)为椭圆或碟形与锥形封头的组合。外壳包含上、下封头，是中心对称的圆柱形或圆锥台形结构；如图7外通道的截面图所示，其中：(a)为外通道的外壳为圆柱体；(b)为外通道的外壳为圆锥台。容器内部是以多孔板或丝网做成的同心圆柱，多孔板或丝网至少有一端是固定的；至少有两块多孔板或丝网；最外层多孔板或丝网与外壳之间的通道为外通道，最里层多孔板或丝网之内的通道为内通道；多孔板或丝网之间围成的环形空间内装填一种或多种活性吸附剂或催化剂；外通道沿流动方向的截面积可以不变，也可以是逐渐缩小的，也就是说原料气进口处的截面积是最大的；内通道沿流动方向截面积可以是固定的，也可以是逐渐扩大的，换句话说，产品气出口处的截面积是最大的。如图6内通道截面图所示，其中，(a)为中空结构；(b)内孔板内放置空心圆柱体；(C)为内孔板内放置空心圆锥台；(D)为内孔板内放置空 心圆锥体。
在本发明中，为了气流流过多孔板后流速不会明显变化，一般选择多孔板的开孔率不能小于填料装填空隙率的50％，否则会出现径向流速增大很多，而流入填料层流速又变小，这样会产生较大阻力，优选多孔板开孔率大于填料层的空隙率的80％。空隙率指的是填料的颗粒体积除以填料的装填体积。
本发明不对填料的装填体积或装填方式做严格限制，可以是紧密装填、也可以是模块化的活性填料。颗粒填料直径不应小于设计径向气速下的流化速度，模块化的填料有效颗粒直径应不影响气固传质速度为宜。
为了本发明的设计的目的，需要对内外通道的压降进行估算，也需要对填料层的压降进行估算，一般需要控制内外通道压降之和不超过床层压降的10％，更进一步，控制内外通道各自压降小于床层压降的5％。对于床层压降的估算是本发明设计的重点，实际中由于吸附、或者反应导致流通体积在不同截面处是不一样的，因此，不能直接简单地用一个固定地使用一个入口体积除以各个截面的面积。一般来说，对于净化来说体积流量基本固定，变化不大；对于分离提纯来说，由于吸附的量比较大，所以向产品气端的走向流速会越来越小，如图3所示周期性操作径向床在吸附过程填料层流通截面不变化时流速变化。在解吸时，流量会随气量的方向越来越大，如图4所示周期性操作径向床在解吸过程填料层流通截面不变化时流速变化情况，负号表示与进气方向相反。
本实施例中，利用本发明提供上述方法设计的径向床为一真空变压吸附(VPSA)制氧装置，该装置中，径向速度指的是气流通过填料层的表观速度，单位是m/s。通道速度指的是气流在内外通道内的速度，以IC表示内通道内的速度，以OC表示外通道内的速度。在计算填料层压降的时候，把填料层各截面的流量做简单处理，设定流量是等比例减少。根据Ergun方程积分得到填料层压降。
设定该VPSA制氧装置的尺寸为：外壳半径Ro:1.6m，外筒壁厚度15mm；外孔板半径ro：1.485m；内孔板半径ri：0.375m；按照图6(b)的结构设置半径为250mm的空心柱；装填有效高度H：2.632m；分子筛空隙率：0.39。
经过计算得到，外通道环缝宽度do＝1600-15-1485＝100mm；外通道截面积So＝0.964m2；内通道环缝宽度di＝375-250＝125mm；内通道通道截面积Si＝0.332m2；So/Si＝2.9。
上述真空变压吸附(VPSA)制氧装置的操作运行参数为：鼓风机气量Qfeed为270m3/min，即4.5m3/s；周期T为50s(包括4s放空)；周期产氧时间T产为30s；回氧气量占产品气量的比率为0.6；氧气收率Y为0.6；产品氧浓度xproduct为90％；空气中氧气浓度xfeed为21％。得 到产品气量Qproduct为2088m3/h；产品瞬时产气量Qpchannel为5806m3/h。Qfeed/Qproduct＝4.5/0.58＝7.76；
通过本发明提供的径向床设计方法，得到：
1)外通道最大流速uo＝4.67m/s；
2)外通道压降△Po＝22.6pa
3)内通道最大流速ui＝4.86m/s
4)内通道压降△Pi＝44.7pa
5)So/Si＝0.374Qfeed/Qproduct
6)床层压降△Pbed＝2.37kpa；
最后得到内外通道压降之和△Po+△Pi为67.3pa，占填料层压降的2.8％。因此，设定的径向床尺寸符合条件，各参数取值为：
外壳半径Ro为1.6m，外筒壁厚度为15mm；外孔板半径ro为1.485m；内孔板半径ri为0.375m；按照图6(b)的结构设置的空心柱半径为250mm；装填有效高度H为2.632m；分子筛空隙率为0.39。
需要注意的是，公布实施例的目的在于帮助进一步理解本发明，但是本领域的技术人员可以理解：在不脱离本发明及所附权利要求的精神和范围内，各种替换和修改都是可能的。因此，本发明不应局限于实施例所公开的内容，本发明要求保护的范围以权利要求书界定的范围为准。

Claims (15)

  1. 一种具有高效气流分布的径向床设计方法，所述径向床包括填料层、内通道、外通道、外层多孔板和内层多孔板，其特征是，所述径向床设计方法通过引入径向床操作的周期和收率来计算径向床的床层压降，以确定径向床内通道和外通道的设计面积，包括如下步骤：
    1)设定径向床的外壳半径、内孔板半径、外孔板半径和高度的取值；
    2)根据步骤1)中的取值，计算得到内通道面积和外通道面积，外通道面积为进气通道的截面积SFeed，内通道面积为产气通道的截面积SProduct；
    3)计算得到面积比SFeed/SProduct，判断该面积比是否满足式3或式4：
    Figure PCTCN2015083647-appb-100001
             (式3)
    式中，SFeed为原料气流通通道的最大截面积；SProduct表示产气通道出口端的截面积；Kv为周期性操作中通道面积之比与原料气和工艺产品气体积流率之比的比例常数；QProduct是周期性操作中产气时的气体流量，即产品工艺气流量；QFeed是原料气体积流量；
    Figure PCTCN2015083647-appb-100002
            (式4)
    式4中，a为产气时产品气流量与原料气之间的比例关系：
    Figure PCTCN2015083647-appb-100003
             (式5)
    K′为回冲气与工艺产品气流流量的比率；T为周期总时间；Tp为周期总时间T中的产气时间；Y为产品收率，是目的产品中有效组分的量占原料气有效组分的量的百分比；xfeed为原料气中有用组分的百分含量；xproduct为产品气中有用组分在气流中的百分含量；
    式4中，km为周期性操作中通道面积之比与原料气和通道内产品气流量之比的比例常数：
    Figure PCTCN2015083647-appb-100004
              (式6)
    4)若面积比SFeed/SProduct不满足式3或式4，则调整设定外壳半径，重复步骤2)～4)；若面积比SFeed/SProduct满足式3或式4，则进入步骤5)；
    5)通过管道内压力计算公式计算得到内通道压降ΔPichannel和外通道压降ΔPochannel：
    Figure PCTCN2015083647-appb-100005
            (式50)
    式50中，ΔP为内通道压降ΔPichannel或外通道压降ΔPochannel；相应地，λ为内通道阻力系数或外通道阻力系数，因为一侧开孔，可按照粗糙度高来考虑，取值为0.02～0.15，优化取值为0.06～0.1；L为内通道长度或外通道长度；d为内通道的水力学直径或外通道的水力学直径；KR为进口阻力系数或出口阻力系数，根据局部阻力的定义，流入时取-0.5，流出时取1；ρ为 气流密度，单位是kg/m3；υ为内通道或外通道的气流流速，单位是m/s：
    Figure PCTCN2015083647-appb-100006
    或
    Figure PCTCN2015083647-appb-100007
                 (式51)
    式51中，SFeed为进气通道的面积值，SProduct为产气通道的面积值；QFeed是原料气体积流量；QPchannel为通道内产品气体积流量：
    Figure PCTCN2015083647-appb-100008
            (式52)
    式52中，T为周期总时间；Tp为周期总时间T中的产气时间；QPchannel为通道内产品气体积流量；QProduct是周期性操作中产气时的气体流量，即产品工艺气体积流量；QRefulx为产品气回充或冲洗的气量：
    QRefulx＝K′×QProduct           (式53)
    式53中，K′为回冲气与工艺产品气流流量的比率；
    6)设填料层各截面的流量为等比例减少，通过Ergun方程得到填料层的压降Δpbed：
    Figure PCTCN2015083647-appb-100009
    Figure PCTCN2015083647-appb-100010
                (式60)
    式60中，Δpbed：填料层的压降；ε：床层空隙率；μ：气流粘度；dp：活性填料的颗粒直径；ρ：气流密度，单位为kg/m3；ro：外层多孔板的半径；ri：内层多孔板的半径；A、B和C为系数：
    A＝(a×ro-ri)              (式61)
    B＝(1-a)                   (式62)
    Figure PCTCN2015083647-appb-100011
                      (式63)
    式61～式63中，H为填料层高度；Qfeed为原料气的体积流量；a为产气时产品气流量与原料气之间的比例关系，通过式5计算得到；ro：外层多孔板的半径；ri：内层多孔板的半径；
    7)判断内通道压降ΔPichannel和外通道压降ΔPochannel之和是否小于填料层压降Δpbed的5％；若不满足，重新步骤1)～步骤7)，得到满足上述条件的内通道的面积值SProduct和外通道的面积值SFeed，分别作为内通道和外通道的设计面积值，从而得到径向床设计尺寸。
  2. 如权利要求1所述径向床设计方法，其特征是，若在所述内层多孔板的里面放置一个 抵消死空间用的空心筒体作为内筒，所述步骤1)还需设定内筒半径，步骤4)则调整设定所述外壳半径或内筒半径。
  3. 如权利要求1所述径向床设计方法，其特征是，步骤3)中，在未知周期性操作中的周期时，所述进气通道与产气通道的截面积之比SFeed/SProduct，通过式3中原料气体积流量和产品工艺气体积流量计算和判断；在已知周期性操作中的周期时，通过式4中周期总时间和周期总时间中的产气时间计算和判断。
  4. 如权利要求1所述径向床设计方法，其特征是，步骤3)中，所述径向床为VPSA制氧装置，所述式3中进气通道与产气通道的截面积之比与原料气和产品气体积流率之比的比例常数Kv为大于等于0.2且小于0.6。
  5. 如权利要求1所述径向床设计方法，其特征是，步骤3)中，所述径向床为VPSA制氧装置，所述式3中进气通道与产气通道的截面积之比与原料气和产品气体积流率之比的比例常数Kv为0.35至0.45。
  6. 如权利要求1所述径向床设计方法，其特征是，步骤3)中，所述周期性操作中通道面积之比与原料气和通道内产品气流量之比的比例常数Km为0.707～1.414。
  7. 如权利要求1所述径向床设计方法，其特征是，步骤3)中，所述周期性操作中通道面积之比与原料气和通道内产品气流量之比的比例常数Km为0.8～1.25。
  8. 如权利要求1所述径向床设计方法，其特征是，步骤5)中，所述式53回冲气与工艺产品气流流量的比率K′，在空气干燥工艺中K＇取值范围是0.03～0.3；在变压吸附制氧工艺中取值为0.2～0.6。
  9. 一种用于周期性操作的具有高效气流分布的径向床，包括外壳、原料气进口、产品气出口、外通道预分布封头、外通道、内通道、外层多孔板或丝网、活性填料层和内层多孔板或丝网，其特征是，在同一个操作周期内，原料气流速等于工艺流速；所述原料气进口端为外通道截面积最大；所述产品气出口处为内通道截面积最大；内通道压降和外通道压降之和小于填料层压降的5％。
  10. 如权利要求9所述用于周期性操作的具有高效气流分布的径向床，其特征是，所述外壳是中心对称的圆柱形或圆锥台形结构，包含上封头和下封头。
  11. 如权利要求9所述用于周期性操作的具有高效气流分布的径向床，其特征是，所述原料气进口1包括渐阔口；渐阔口为锥形封头、椭圆封头和蝶形封头中的一种或几种的组合。
  12. 如权利要求9所述用于周期性操作的具有高效气流分布的径向床，其特征是，所述多孔板或丝网至少有两块，所述多块多孔板或丝网围成同心圆柱，所述多孔板或丝网至少有一端是固定的。
  13. 如权利要求9所述用于周期性操作的具有高效气流分布的径向床，其特征是，所述多孔板或丝网围成的同心圆柱的环形空间内装填一种或多种活性吸附剂或催化剂。
  14. 如权利要求9所述用于周期性操作的具有高效气流分布的径向床，其特征是，所述内层多孔板的里面放置一个用于抵消死空间的筒体，所述空间的筒体为空心圆柱、空心圆锥台或空心圆锥体。
  15. 如权利要求9所述用于周期性操作的具有高效气流分布的径向床，其特征是，所述径向床为VPSA或PSA工艺的制氧装置、制氢装置、提纯一氧化碳装置、分离二氧化碳或空气干燥装置。
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