Utilize cement kiln tail gas to prepare the method for food-class liquid CO 2Technical field
The invention belongs to the technology of preparing of Chemicals, particularly a kind of method of utilizing cement kiln tail gas to prepare food-class liquid CO 2.
Background technology
Preparation CO purifies2Method have multiplely, roughly can divide physics method and chemical method two classes.Physical method comprises the physical solvent absorption process, adsorption method of separation, film permeation method and low-temperature distillation method.The physical solvent absorption process has the characteristics similar to chemical absorption method, utilizes liquid-absorbant to CO2Solubleness different with other gaseous fraction and separate. solvent commonly used has water, methyl alcohol, propylene carbonate etc.Membrane separation process is to realize isolating method with the rate of permeation difference of all gases in thin-film material, is used for CO2Isolating membrane separation apparatus has two kinds of tubular fibre tube bank and spiral wound, and this method must be used in combination with other separating technology at present.The fractionation by adsorption rule is that the equilibrium adsorption capacity that utilizes sorbent material changes with partial component pressure or system temperature and different characteristic row lock out operation, a simple absorption-desorb physical process sheerly, there are not problems such as desired solvent preparation of absorption process and solvent loss simultaneously in characteristics with technology simple, nontoxic, pollution-free (free from environmental pollution and source of the gas itself) yet.But this method is subjected to CO in the unstripped gas2The component restriction, CO2When content hanged down, energy consumption was very big.The low-temperature distillation method is utilized methane and CO2The difference of boiling point between component, with distillating method with CO2Separate, be mainly used in some and be rich in CO2The gas field reclaim CO2, use for secondary oil recovery.
The chemical process that the present invention relates to is then utilized CO2Be sour gas, can carry out absorption extraction with the principle of alkali substance reaction.Alkaline absorbent commonly used has: aqueous alkali carbonate solution, Monoethanolamine MEA BASF (MEA) aqueous solution etc.Wherein the sodium carbonate solution absorption process has the characteristics of the simple and less investment of Technology maturation, equipment, and domestic most of manufacturing enterprises are to be that the factory of source of the gas adopts this method to produce commodity CO with the lime-kiln gas2, but that the main drawback of this method is a productivity is low.
Cement kiln tail gas and common kiln tail gas have its similarity from the source of the gas composition, and its singularity is arranged again.Cement kiln tail gas is with its composition complexity and CO2Content is on the low side to be characteristics, in the cement kiln end waste gas, and CO2Be 10.0～15.0%, other component has N2, O2, SO2, H2S, COS, CS2, NOx, dust etc., wherein COS, CS2O in irreversible reaction, the while gas takes place with MEA2The content height, if adopt conventional alkali absorption method, it is serious that the MEA degraded can take place, the characteristics that solution active ingredient consumption is big.
Chinese patent " production method of a kind of food and Liquid carbon dioxide " (CN1147428C) and " food-grade carbon-dioxide production method " (CN1171783C) announced two patents, the technology contents that two patents relate to mainly is to utilize than clean gas source physical method removal of impurities, with the inventive method essential distinction is arranged.
Summary of the invention
The objective of the invention is to overcome the defective of prior art, a kind of method of utilizing cement kiln tail gas to prepare food-class liquid CO 2 is provided.
Purpose of the present invention realizes by following scheme: a kind of cement kiln tail gas that utilizes prepares the method for producing food-class liquid CO 2, is source of the gas with stove tail gas, and production process is: dedusting, boost, washing, once desulfurization, solution absorption CO2, intensification desorb, separation of C O2, secondary desulfurization, drying, liquefaction, above-mentioned solution absorption CO2Absorption liquid be potash multiplicity reactivation solution, absorb COc2To reaching vapor liquid equilibrium, above-mentioned stove tail gas is cement kiln tail gas;
It is the diethanolamine of 10-30% salt of wormwood, 0.5-5%, diamino-dimethyl of 0.5-5%-monopropylene glycol that described potash multiplicity reactivation solution contains weight percent, and all the other are water.
The present invention compared with prior art has following outstanding effect: first: the product purity height, and product purity can reach more than 99.9%, reaches the standard of international food level; Second: technology is simple: several impurity components of unstripped gas, can remove in a step; The the 3rd: easy and simple to handle, energy consumption is low; Generally all operate under normal temperature and normal pressure, equipment is simple; The 4th: the sorbent material life-span is long: after the sorbent material filling finishes, generally use more than 10 years; The the 5th: utilize cement furnace tail gas, turn waste into wealth, help the development of cement industry environmental pollution improvement and recycling economy.
Embodiment
The included following production craft step of the present invention: step 1: cement kiln end feed gas preprocessing operation: the cement kiln gas boosts to 3000Pa through bag collector dedusting, induced draft fan and enters wash tower bottoms, and the exhaust gas body goes gas blower to boost after water sepn is removed mechanical water; Go wash tower bottoms through cooled kiln exhaust gas, exhaust gas body SO2Decreasing ratio is greater than 95%, H2The S decreasing ratio reaches 40～50%, CO2Rate of loss control is below 5%; Kiln exhaust gas after water separator is removed mechanical water enters the once desulfurization jar of three parallel connections, goes out 30 ℃ of digester gas temperatures, pressure 10-15Kpa, SO in the gas2Content is less than 5mg/M3, H2S content is less than 20mg/M3, enter recoil T type filter again, go out the strainer kiln exhaust gas and enter CO2Carry bottom, dense operation absorption tower.Step 2: carbonic acid gas is put forward dense operation: enter CO2CO in the mixed gas of bottom, absorption tower2Component is absorbed by the potash composite solution in the absorption tower, and unabsorbed tail gas is cooled to through tail gas washing tower and is lower than 42 ℃, directly enters atmosphere again after the efficient scum dredger of cat head and separator are removed the washings of carrying secretly.Washings returns the washing liquid bath after cooling, boost, go into tail gas washing tower after cooling through the washing liquid pump again.Absorb CO2Reach equilibrated solution and be called rich solution.Rich solution is extracted out by the rich solution pump at the bottom of tower, is introduced into the resurgent gases condenser after the pressurization, enters poor rich liquid heat exchanger then, finally is heated to 85～90 ℃, after regeneration overhead portion shower nozzle spray into tower.In regenerator column, rich solution discharges CO2, CO2Flowed out by cat head in company with a large amount of water vapor and a small amount of active constituent steam, temperature is controlled at 90 ℃, and the about 0.020MPa of pressure enters resurgent gases condenser and the next solution heat exchange of rich solution pumping.The gas temperature that goes out the resurgent gases condenser is controlled at 70 ℃, and a large amount of water vapors are condensed, and lime set and gas together enter CO2Watercooler, with the water coolant heat exchange that supply mains on the recirculated water comes, logistics is further cooled to 30 ℃, removes CO then2Separator.In separator, the lime set of gas entrainment is separated, first product CO2Gas (purity is up to 99.8%) send next procedure by compressor pressurizes to 0.1MPa.Lean solution is drawn at the bottom of regenerator column, and being boosted by lean pump after poor-rich solution interchanger heat exchange absorbs Tata.Lime set flows into sloptank, sends into CO again through the backflow liquid pump again2Recovery system.Step 3: CO 2 refining liquefaction operation.Boost to 1.0Mpa from the carbon dioxide of product surge tank by compressor and remove two-stage secondary thionizer, one-level removes SO2And H2S, secondary remove COS and CS2(∑ S in the carbon dioxide after the desulfurization≤0.1ppm) by three grades of inlets of compressor, finally boost to 2.0Mpa goes into isobaric dehumidification system after the oil removing of oil removing tower to go out thionizer gas.Product carbon dioxide is after drying gone into vaporizer-condenser, product storage tank through three grades of compressions.Finally make purity and be higher than 99.9% the liquid CO of food grade2Finished product.