CN103011329A - Method of designing parameters of adsorption reactor of fixed bed based on equal ratio diffusion similarity principle - Google Patents

Abstract

The invention discloses a method of designing parameters of an adsorption reactor of a fixed bed based on an equal ratio diffusion similarity principle. According to the method, key parameters of reaction equipment in a laboratory room, which are designed based on the equal ratio diffusion similarity principle, enable the reactors in different sizes to have an equal ratio similar adsorbate diffusion characteristic; an adsorption breakthrough curve of the reactor in the laboratory room, which is obtained through short-time running determination, is similar to an adsorption breakthrough curve of the large adsorption reactor designed through size amplification according to amplification coefficients in equal ratio; the principle lies in that the mass transfer internal diffusion of the small reactor and the large reactor has equal ratio similar microcosmic characterization, and an internal mass transfer coefficient is in linear positive correlation with the particle size of an adsorbent; the performance of the engineering fixed bed can be rapidly quantitated; and therefore, the pre-production time is shortened, the design is reasonable, and the conditions that the design capability is insufficient, penetration occurs in short time, the adsorbent needs to be frequently replaced or unnecessary waste of materials and energy sources is caused by analysis and regeneration operation or oversize design are avoided.

Description

Based on the method for geometric ratio diffusion phase like principle design ADSORPTION IN A FIXED BED reactor parameter

Technical field

The present invention relates to environmental engineering purification of water quality field, particularly a kind of based on the method for geometric ratio diffusion phase like principle design ADSORPTION IN A FIXED BED reactor parameter.

Background technology

Absorption is one of significant element operation of separation and Purge gas and liquid mixture.Its principle is: selectivity is used some porosu solid, and one or several composition in porous medium surface enrichment flowing carrier makes it separate with flowing carrier targetedly.Adsorption results from the surface force of solid particulate, such as the chemical b ` between Van der Waals force or atom or the functional group.The absorption mass transfer is divided into external diffusion, internal diffusion and three steps of absorption.Adsorbate at first diffuses to the outside surface of solid particulate by the flow media main body by air film (or liquid film) convection current around the solid particulate, and this mass transfer step is called the external diffusion of component; Then, adsorbate diffuses to the internal surface of solid from the solid particulate outside surface along the solid interior micropore, is called the internal diffusion of component; At last, component is adsorbed by solid adsorbent.To most adsorption processes, the internal diffusion of component is the main resistance place of absorption mass transfer, so the speed of reaction of adsorption process is controlled by internal diffusion.

Adsorption operations is widely used in the industries such as chemical industry, medicine, environmental protection.In water technology, adsorption technology often is applied to remove the pollutent indexs such as organism in the sewage, ammonia nitrogen, total phosphorus, heavy metal ion by the form with fixed-bed adsorber.In engineering practice, because the raw water quality that each engineering project relates to has certain complicacy or uniqueness, for the design variable of definite adsorptive reactor and the operating parameter of adsorption operations, be necessary to build pilot plant and carry out pilot plant test.Yet in the Practical Project practice, because funds and time limitation, the technician often can't carry out the pilot plant test of several months consuming time, and only by reference estimation design variable numerical value, carries out the adsorptive reactor design.The problem that causes like this is: 1) reactor design scarce capacity, and the short period of time uses penetration phenomenon namely occurs, and needs the frequent sorbent material or carries out desorb and regenerative operation; 2) reactor design is excessive, brings unnecessary material and energy dissipation.

Summary of the invention

In order to overcome above-mentioned existing problem, the object of the invention is to develop a kind of based on the method for geometric ratio diffusion phase like principle design ADSORPTION IN A FIXED BED reactor parameter, with important parameters such as fast quantification and the ADSORPTION IN A FIXED BED reactor design reactor size relevant with operation, sorbent material consumption, empty bed flow velocitys, for moving, engineering design and equipment provides accurate information.

For achieving the above object, technical scheme proposed by the invention is: a kind of based on the method for geometric ratio diffusion phase like principle design ADSORPTION IN A FIXED BED reactor parameter, it is characterized in that: comprise the steps:

Step 1: at first determine engineering with sorbent material and use the empty bench grafting of the engineering time of touching of this sorbent treatment pollutent to be EBCT according to document and engineering experience _LC, described engineering is d with the sorbent material particle diameter _LC

Step 2: laboratory reaction apparatus is set, and the experiment of wherein said laboratory reaction apparatus is d with the sorbent material particle diameter _SC, described experiment sorbent material is that engineering grinds gained with sorbent material, the empty bench grafting of described experiment touches reaction times EBCT _SCDescribed experiment reaction unit adsorption column internal diameter is D _SCDescribed laboratory reaction apparatus adsorption column length is l _SCDescribed laboratory reaction apparatus satisfies following condition:

$\mathrm{SF}=\frac{d_{\mathrm{LC}}}{d_{\mathrm{SC}}},$ Described 0＜SF＜100;

${\mathrm{EBCT}}_{\mathrm{SC}}=\frac{{\mathrm{EBCT}}_{\mathrm{LC}}}{\mathrm{SF}};$

$\frac{D_{\mathrm{SC}}}{d_{\mathrm{SC}}}\≥25;$

$200\≤{\mathrm{Re}}_{\mathrm{SC}}\×{\mathrm{SC}}_{\mathrm{SC}}=\frac{D_{\mathrm{SC}}\×{\mathrm{EBCT}}_{\mathrm{SC}}\×{\mathrm{\ϵ}}_{\mathrm{SC}}}{v\×l_{\mathrm{SC}}}\×\frac{\mathrm{\μ}}{\mathrm{\ρD}}\≤200000;$

Wherein: Re: Reynolds number; ε _SC: the sorbent material voidage; μ is coefficient of viscosity, and ρ is density, and D is that spread coefficient, ν are empty bed flow velocity

Step 3: the break-through curve of determination experiment chamber reaction unit under each flow, and select optimum break-through curve, and described optimum break-through curve is that the break-through curve shape is steep, i.e. and within a short period of time, pollutent goes out water concentration and raises rapidly, and evening appears in breakthrough point; Can obtain total treatment capacity BV of laboratory reaction apparatus according to the breakthrough point of optimum break-through curve _SC, the total treatment capacity BV of corresponding engineering in the time of can determining that breakthrough point occurs according to scale-up factor again _LCAnd be that engineering reaction unit internal diameter is D according to the design variable that scale-up factor obtains the project scale adsorption unit _LC=D _SC* SF; Described engineering reactor length is l _LC=l _SC* SF.

Further, described reynolds number Re _SCWith Schmidt number SC _SCProduct is determined by the sorbent characteristics of selecting (factors such as chemical constitution and grain diameter) and the pollutent characteristics that are adsorbed; Purpose is to guarantee that the rate of mass transfer of adsorption process is leading by internal diffusion.

Further, the described experiment preferred 1-2mm of sorbent material particle diameter.

Adopt technique scheme, the present invention is based on the laboratory reaction apparatus key parameter that geometric ratio diffusion similarity principle arranges, make the reactor of different scales have the similar adsorbate diffusion characteristic of geometric ratio, the laboratory reaction apparatus adsorption breakthrough curve that obtains is measured in operation through the short period of time, similar with the adsorption breakthrough curve geometric ratio of the large-scale adsorptive reactor that is undertaken by scale-up factor designing after size is amplified, its principle is that the mass transfer internal diffusion of mini-reactor and large-scale reactor has the similar microcosmic of geometric ratio and characterizes, and inner transmission matter coefficient and the linear positive correlation of sorbent material particle diameter, and but fast quantification goes out the performance that engineering is used the ADSORPTION IN A FIXED BED reactor, shortened the pilot scale time, and reasonable in design, the designed capacity deficiency can not appear, penetration phenomenon namely occured in the short period of time, need the frequent sorbent material or resolve with regenerative operation or design excessively, bring the situations such as unnecessary material and energy dissipation.

Description of drawings

Fig. 1 is the laboratory reaction apparatus structural representation;

Fig. 2 is the break-through curve measured of laboratory reaction apparatus with scale-up factor is the break-through curve comparison that 10 pilot plant is measured;

Wherein: 1 water tank, 2 volume pumps, 3 valves, 4.PU connecting hose, 5. under meter, 6. adsorption column, 7. sorbent material.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention will be further described.

As shown in Figure 1, the purpose of adsorption operations is be to measure adsorption breakthrough curve, and adsorption breakthrough curve is the total relation curve between the water amount totally of residual contamination substrate concentration and adsorption column in the water outlet.Spending the water initial stage, pollutant load is lower than emission standard in the water outlet, and water quality is good.Along with the increase of processing the water yield, the concentration of pollutent increases gradually in the water outlet, and that Pollutant levels reach emission standard in water outlet is called breakthrough point, continues water flowing after crossing breakthrough point, the concentration of pollutent sharply increases in the water outlet, until close to influent concentration.Below be the operation steps of laboratory reaction apparatus:

Step 1: the sorbent material 7 usefulness deionized waters of certain mass are fully soaked (10-15 hour), then pack in the adsorption column 6, the purpose of fully soaking is to expand and cause that the bed space reduces for fear of sorbent material in operational process 7, filtration resistance increases, in addition, dress should be noted during post to make and particles filledly closely reduces porosity as far as possible, to avoid short stream;

Step 2: pending water is filled with water tank, with volume pump 2 with base runoff with pending water by in the adsorption column 6 of having filled certain mass sorbent material 7, after the absorption beginning, remove a certain amount of water sample from water outlet at regular intervals, measure the Pollutant levels of water outlet;

Step 3: flow is determined, measure before the break-through curve, select rational EBCT upper and lower bound scope according to document and engineering experience, in this scope, can choose several EBCT numerical value (being generally the 3-5 group), determine corresponding flow according to mathematical model, according to step 1,2 break-through curves of measuring under each flow condition, and choose optimum break-through curve.

Step 4: optimum break-through curve selection principle: shape is steep, i.e. within a short period of time, pollutent goes out water concentration and raises rapidly; Evening appears in breakthrough point; Corresponding adsorptive reactor size is suitable, and cost is reasonable.

Step 5: determine the time that breakthrough point occurs by the optimum break-through curve that step 3 records, this breakthrough point when occurring corresponding total treatment capacity (BV) be the empty bench grafting of the corresponding engineering of determining according to scale-up factor and touch under the time, corresponding BV when breakthrough point occurs can calculate design variable and the processing power of project scale adsorption unit thus.

Embodiment 1

Below illustrate and how to implement the method design adsorption tower, remove using on the water pollutant M in adsorbent A:

According to document, the EBCT scope that adsorbent A is removed water pollutant M is 10-30 minute, determines the adsorption column size according to EBCT=20min.The absorbent particles median size that the obtainable suitable engineering in market is used is 1 centimetre, and the particle median size is about 1 millimeter after grinding, and calculating scale-up factor is 10.Determine that the quick adsorption column internal diameter should be greater than 2.5 centimetres, therefore select 2.5 centimeter inner diameter Glass tubings.Similar, the pilot plant adsorption column internal diameter after 10 times of amplifications should greater than 25 centimetres, be selected 25 centimeter inner diameter pvc pipes.According to equation 2), pilot plant EBCT is 20min, then lab scale adsorption column EBCT is 2min.

Next determine adsorption column length with method of determining and calculating, to guarantee satisfying constraint condition according to Reynolds number and Schmidt's numerical value.In this concrete case, at first need avoid the space flow velocity in the lab scale adsorption column excessive, because can bring larger head loss like this.Simultaneously, this flow velocity is also unsuitable too small, because under the too small flow velocity, external diffusion will be more obvious for the restricted impact of absorption mass transfer process.Therefore, the product of Reynolds number and Schmidt number should be in 200-20000 scope interval, to guarantee mechanic diffusion.In this application-specific process, for the adsorption column of lab scale yardstick, the optimum scope of this product should satisfy 1000≤Re _SC* SC _SC≤ 3000.Satisfying under the constraint condition, can rationally reduce adsorption column length, with Reaction time shorten.The design variable of the pilot plant that experimental installation and amplification are 10 times is as shown in table 1, and the result is by shown in Figure 2.Two break-through curves have similarity as shown in Figure 2.Therefore, but use the break-through curve geometric ratio that above method fast method records to amplify.

Table 1 is based on lab scale and the pilot scale adsorptive reactor of the design of geometric ratio diffusion principle

(scale-up factor SF=10)

Parameter	The lab scale reactor	Pilot reactor
			Reactor inside diameter	2.5cm	25cm

The absorbent particles median size	1mm	1cm
			The sorbent material packing height	7.5cm	100cm
The sorbent material packing volume	36.8mL	49.1L
			EBCT	2min	20min
Re*Sc	2343	25000
			Apparent porosity	0.4	0.5

Although specifically show and introduced the present invention in conjunction with preferred embodiment; but the those skilled in the art should be understood that; within not breaking away from the spirit and scope of the present invention that appended claims limits; in the form and details the present invention is made a variety of changes, be protection scope of the present invention.

Claims (4)

1. based on the method for geometric ratio diffusion phase like principle design ADSORPTION IN A FIXED BED reactor parameter, it is characterized in that: comprise the steps:

Step 1: at first determine engineering with sorbent material and use the empty bench grafting of the engineering time of touching of this sorbent treatment pollutent to be EBCT according to document and engineering experience _LC, described engineering is d with the sorbent material particle diameter _LC

Step 2: laboratory reaction apparatus is set, and the experiment of wherein said laboratory reaction apparatus is d with the sorbent material particle diameter _SC, described experiment sorbent material is that engineering grinds gained with sorbent material, the empty bench grafting of described experiment touches reaction times EBCT _SCDescribed experiment reaction unit adsorption column internal diameter is D _SCDescribed laboratory reaction apparatus adsorption column length is lSC; Described laboratory reaction apparatus satisfies following condition:

Described 0＜SF＜100;

Wherein: Re: Reynolds number; ε _SC: the sorbent material voidage; μ is coefficient of viscosity, and ρ is density, and D is that spread coefficient, ν are empty bed flow velocity;

Step 3: the break-through curve of determination experiment chamber reaction unit under each flow, and select optimum break-through curve, and described optimum break-through curve is that the break-through curve shape is steep, i.e. and within a short period of time, pollutent goes out water concentration and raises rapidly, and evening appears in breakthrough point; Can obtain total treatment capacity BV of laboratory reaction apparatus according to the breakthrough point of optimum break-through curve _SC, the total treatment capacity BV of corresponding engineering in the time of can determining that breakthrough point occurs according to scale-up factor again _LCAnd be that engineering reaction unit internal diameter is D according to the design variable that scale-up factor obtains the project scale adsorption unit _LC=D _SC* SF.

2. according to claim 1 based on the method for geometric ratio diffusion phase like principle design ADSORPTION IN A FIXED BED reactor parameter, it is characterized in that: described reynolds number Re _SCWith Schmidt number SC _SCPreferred product determined by the sorbent characteristics of selecting and the pollutent characteristics that are adsorbed.

3. according to claim 2 based on the method for geometric ratio diffusion phase like principle design ADSORPTION IN A FIXED BED reactor parameter, it is characterized in that: described sorbent characteristics comprises sorbent material chemical constitution and grain diameter.

4. according to claim 1 based on the method for geometric ratio diffusion phase like principle design ADSORPTION IN A FIXED BED reactor parameter, it is characterized in that: described experiment is 1-2mm with the sorbent material particle diameter.