CN103182241A

CN103182241A - Technique for absorbing CO2 with high-viscosity hydramine solution

Info

Publication number: CN103182241A
Application number: CN2012102327220A
Authority: CN
Inventors: 于建国; 胡剑光; 刘佳特; 戴干策
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2012-07-06
Filing date: 2012-07-06
Publication date: 2013-07-03
Anticipated expiration: 2032-07-06
Also published as: CN103182241B

Abstract

The invention relates to a technique for absorbing CO2 with a high-viscosity hydramine solution. The technique comprises the following steps: moving a CO2/air mixed gas at a velocity of 0.1-3 m/s to go through a straight/flat passage vertical plate regular packing tower for counterflow or parallel-flow contact with a descending high-viscosity absorption solution (Mu larger than or equal to 3 mPa.s), so as to complete absorption. In the technique, the solution spray density is 10-100 m<3>/(m<2>h), the absorption temperature is 0-70 DEG C, and the volume fraction of CO2 in the mixed gas is 5-100%. As compared with low-viscidity absorbents, the mass transfer coefficient of the absorbent used in the invention is increased by at least 30-50% and the absorption efficiency is increased by more than 50%, as a result, the heat capacity of the absorption solution is reduced by at least 15%, and the energy consumption of desorption is reduced by 10-20%, and thus the energy consumption of the whole technique is significantly reduced as compared to the conventional absorption process.

Description

A kind of high viscosity alkanolamine solution absorbs CO 2Process

[technical field]

The present invention relates to the chemical process technical field, specifically, is that a kind of high viscosity alkanolamine solution absorbs CO ₂Process.

[background technology]

In recent years, CO ₂The reduction of discharging problem more and more is subjected to the extensive concern of international and domestic society, how effectively to reduce CO ₂Discharging is the common difficulty that human society needs to be resolved hurrily.In numerous discharge-reducing methods, be that the chemical absorption method of absorbent is one of the reduction of discharging means that realize heavy industrialization that are easy to most of generally acknowledging at present with alcamines solution.Yet existing absorption techniques ubiquity the energy consumption height, running cost this actuality difficult problem that remains high.Having report to think, is example with a tame power plant, even adopt state-of-the-art CO of present stage ₂Capture technology, needed energy consumption will make its generated energy loss 30%, and the unit electricity price goes up 80%.Therefore, explore new CO ₂Absorption technique is significant.

In existing absorption-desorb integral process, about 120 ℃, the desorb energy consumption accounts for more than 80% of total energy consumption to desorption temperature usually usually.Trace it to its cause, in the general alcamines absorbent content of water usually more than 50%, have in addition up to 80% because that specific heat of water holds is bigger, cause desorption process need consume lot of energy.Alkanolamine solution absorbs CO ₂Be a chemical reaction process in essence.Generally speaking, the important channel that absorbent is strengthened is improved its concentration exactly, can make reaction rate accelerates so on the one hand, and the unit volume absorption capacity of absorbent is strengthened, and consumption reduces, and table 1 is CO ₂Solubility and absorption rate are with N methyldiethanol amine (MDEA) concentration and viscosity change relation.In addition, because the thermal capacitance of organic solution only is 50% of water usually, if improve content of organics in the absorption liquid, its thermal capacitance will obviously descend, be example with MEA (MEA) and diethanol amine (DEA) aqueous solution, in the time of 38 ℃, when the hydramine mass fraction brings up to 50% by 15%, the solution specific heat capacity can descend 15%, thereby the energy consumption in its follow-up desorption process also will significantly descend.Yet, for CO ₂Absorption reaction has himself particularity again, at present the absorbent that uses, general viscosity is bigger, and table 2 is several alcamines absorbent viscosity numbers at normal temperatures commonly used, and as shown in Table 1, when the concentration of absorbent increases, will inevitably make the corresponding increase of its viscosity.

Yet it is generally acknowledged low sticking is basic demand to absorbent, is carrying out smoothly of guaranteeing to absorb, CO at present ₂The employed absorbent of absorption technique is commonly low sticking absorbent, and Chinese patent application numbers 200910235421.1 is disclosed, and " a kind of three-phase circulating fluidized bed ammonia process is caught the CO in the flue gas ₂Method and device " absorbent that adopts is 10%～30% ammoniacal liquor, reaction unit is three-phase circulating fluidized bed.The CO that Chinese patent application numbers 200920159721.1 disclosed " low-temp methanol purifies the crude synthesis gas systems " adopts ₂Absorbent is methyl alcohol.In addition, modification for the alcamines absorbent, generally adopt the method for adding activating agent or modifying agent to improve the absorbent properties of original solvent at present, be example with U.S. Patent number US2011/0168496 disclosed " a kind of renewable/non-regenerated acidic gas absorbent ", (Soluble Molasses Condensate, SMC) interworking becomes renewable or non-absorbent regeneration to improve absorbent properties by a certain percentage by alkanolamine solution and solubility syrup concentrate.For the preparation of Regeneratable absorbent, only add about 5% SMC on the basis of original alkanolamine solution, make that the water content in the solution is still higher, its follow-up energy of desorption consumption can't effectively descend.In order to improve CO ₂Absorption technique is to the adaptability of absorption liquid viscosity, and the present invention absorbs CO with diethanol amine (DEA) ₂Be example, propose the absorption technique that a kind of new raising absorption liquid sticking (dense) is spent, and improve its mass-transfer efficiency, and then realize the energy-saving and cost-reducing of whole desorb-absorption integrated technology.

Table 1 CO ₂Relation between solubility and absorption rate and the MDEA solubility

Viscosity under several alcamines absorbent normal temperature commonly used of table 2

[summary of the invention]

The objective of the invention is to overcome the deficiencies in the prior art, provide a kind of high viscosity alkanolamine solution to absorb CO ₂Process.

The objective of the invention is to be achieved through the following technical solutions:

Principle of the present invention is: concentration also increased thereupon when absorption liquid viscosity increased.For chemical absorbing, the increase of reactant concentration is conducive to improve chemical absorbing speed, namely improves enhancer β, on the other hand along with the increase k of viscosity _LCorrespondingly reduce, because liquid phase mass transfer coefficient K _L=β k _LIn certain solution viscosity scope, along with the increase of hydramine concentration, the amplitude that enhancer β increases is greater than k _LThe range of decrease, this moment show as mass tranfer coefficient K in macroscopic view _LIncrease with solution viscosity is amid a sharp increase on the contrary.Because content of organics obviously increases, corresponding desorb energy consumption significantly reduces.

A kind of high viscosity alkanolamine solution absorbs CO ₂Process, concrete steps are, with CO ₂With Air mixing gas be 0.1～3m/s by the whole packed tower (hereinafter to be referred as packed tower) of straight channel vertical plate gauge with gas speed, high sticking absorption liquid (μ 〉=3mPa.s) add from the packed tower top from tubular type or groove type distributor with certain flow, being membrane type along filler evenly flows down, the high viscosity absorption liquid that descends and the back flow of gas of rising or and flow and contact, gas is cross-flow along filler passage and moves upward, finish absorption, the adoptable liquid spraying density of this technology is 10～100m ³/ (m ²H), spendable absorption temperature is 0～70 ℃, CO ₂The volume fraction that accounts for mist is 5%～100%.For guaranteeing that the high viscosity absorption liquid does not have emulsification, foams or foamed phenomenon takes place and do not have extra energy consumption to increase in the falling film absorption process, the equipment that the present invention adopts be have wall and no wall liquid film alternately the straight channel vertical plate gauge of coexistence put in order packed tower.

Described absorption liquid is the solution of alcamines absorbent, and viscosity is greater than 3mPa.s;

Described alcamines absorbent is monoethanolamine, diethanol amine, triethanolamine, one or more in diisopropanolamine (DIPA) or the methyl diethanolamine.

Compared with prior art, good effect of the present invention is:

The invention enables the low sticking absorbent of mass tranfer coefficient of absorbent to improve 30%～50% at least, absorption efficiency improves more than 50%, corresponding absorption liquid thermal capacitance reduces by 15% at least, and the desorb energy consumption descends 10%～20%, thereby the more traditional absorption technique of the required energy consumption of whole technology reduces greatly.

[description of drawings]

Fig. 1 is high according to an exemplary embodiment of the present sticking (dense) degree absorption liquid CO ₂The absorption technique schematic diagram;

Liquid phase mass transfer coefficient K under the different sprinkle densities of Fig. 2 _LWith the variation diagram of DEA solution viscosity, 2a is 30m ³/ (m ²H); 2b is 60m ³/ (m ²H); 2c is 100m ³/ (m ²H);

Label in the accompanying drawing is respectively: 1, CO ₂Steel cylinder, 2, air, 3, gas flowmeter, 4, Water Tank with Temp.-controlled, 5, gas mixer chamber, 6, packed tower, 7, fluid flowmeter, 8, head tank, 9, drier, 10, CO ₂Infrared spectrum analyser, 11, centrifugal pump, 12, fluid reservoir.

[specific embodiment]

Below provide a kind of high viscosity alkanolamine solution of the present invention to absorb CO ₂The specific embodiment of process.

Embodiment 1

See also Fig. 1,2a, 2b, 2c, a kind of high viscosity alkanolamine solution absorbs CO ₂Process, concrete steps are, with CO ₂Mist is 0.1～3m/s by packed tower 6 with gas speed, with the high viscosity absorption liquid adverse current that descends or and stream contact, finish absorption.

The GAS ABSORPTION technology that this example uses as shown in Figure 1, CO ₂Steel cylinder 1 and air 2 by gas flowmeter 3 in Water Tank with Temp.-controlled 4 the insides after water vapour is saturated, 5 reach abundant mixing in gas mixer chamber, bottom by packed tower 6 enters again, flow out with the top from regular packed tower 6 behind diethanol amine (DEA) reactant aqueous solution, the effluent air drying enters CO ₂Infrared spectrum analyser 10.Absorption liquid is delivered to head tank 8 by fluid reservoir 12 through centrifugal pump 11 earlier, enters packed tower 6 through head tank 8 again, and the gas-liquid two-phase gross contact area is 2*100*600mm.

CO in this example ₂Volume fraction is 15～45%, and diethanolamine solution viscosity is 1～15mPa.s, and the corresponding mass mark is that 5～56% gas flow rates are 0.2～1m/s, and the absorption liquid sprinkle density is 30～100m ³/ (m ².h), experimental temperature is 30 ± 0.5 ℃.The result is 2a as shown in Figure 2,2b, 2c.

By the result as can be known, at different CO ₂Under volume fraction and the liquid spraying density, liquid phase mass transfer coefficient K _LVariation with the DEA solution viscosity presents identical rule, in the range of viscosities of 1-10mPa.s, and along with the increase of solution viscosity, liquid phase mass transfer coefficient K _LAlso increase thereupon, when absorption liquid viscosity during greater than 10mPa.s, liquid phase mass transfer coefficient K _LDescend slightly to some extent, but still under low viscosity (1～2mPa.s) K _LValue.Be the K of 1.8mPa.s DEA solution correspondence with viscosity _LValue is for benchmark, at identical liquid spraying density (30,60 and 100m ³/ (m ².h)) under, viscosity is the K of 10mPa.s DEA solution correspondence _LValue is respectively its 1.6,1.5,1.5 times, and viscosity is the K of 15mPa.s DEA solution correspondence _LValue is respectively its 1.5,1.4,1.3 times, shows that the sticking absorption technique of height that the present invention proposes can promote mass transfer effectively.

In addition, what deserves to be mentioned is, under experimental temperature, when the viscosity of diethanol amine (DEA) solution is brought up to 15mPa.s by 1mPa.s, it is about 17% that the specific heat capacity of solution descends, and follow-up desorb energy consumption descends 15%, shows that the sticking absorption technique of height that the present invention proposes is energy-saving and cost-reducing remarkable than traditional handicraft.

The above only is preferred embodiment of the present invention; should be pointed out that for those skilled in the art, without departing from the inventive concept of the premise; can also make some improvements and modifications, these improvements and modifications also should be considered within the scope of protection of the present invention.

Claims

1. a high viscosity alkanolamine solution absorbs CO ₂Process is characterized in that, concrete steps are, with CO ₂With Air mixing gas be 0.1～3m/s by the whole packed tower of straight channel vertical plate gauge with gas speed, with the high viscosity absorption liquid adverse current that descends or and stream contact, finish absorption; The liquid spraying density that adopts is 10～100m ³/ (m ²H), the absorption temperature of use is 0～70 ℃, CO ₂The volume fraction that accounts for mist is 5%～100%.

2. a kind of high viscosity alkanolamine solution as claimed in claim 1 absorbs CO ₂Process is characterized in that, described absorption liquid is the solution of hydramine absorbent, and viscosity is greater than 3mPa.s.

3. a kind of high viscosity alkanolamine solution as claimed in claim 1 absorbs CO ₂Process is characterized in that, described hydramine absorbent is monoethanolamine, diethanol amine, triethanolamine, one or more in diisopropanolamine (DIPA) or the methyl diethanolamine.