CN105385602B - A kind of integrated processes of both culturing microalgae and industrial waste gas denitration - Google Patents

Abstract

The present invention relates to the integrated processes of a kind of cultivating microalgae and industrial waste gas denitration, comprising: the step of Heterotrophic culture microalgae；The step of microalgae is to obtain microalgae and alkaline residue is isolated from the algae solution of harvest；The NOx in industrial waste gas is absorbed using the alkaline residue or neutralizes the acid solution after fixing NOx, and the step of then providing nitrogen source with it for cultivating microalgae.The present invention utilizes the NO in industrial waste gas_xNitrogen source is provided for cultivating microalgae, while pollutant emission reduction, obtains valuable microalgae biomass.

Description

A kind of integrated processes of both culturing microalgae and industrial waste gas denitration

Technical field

The present invention relates to the integrated processes of a kind of both culturing microalgae and exhaust gas denitration.

Background technique

Energy and environment are the major issues that human social is faced.On the one hand, the modern text of the support mankind Bright fossil energy is non-renewable, and exploitation alternative energy source is extremely urgent；It on the other hand, can not when processing and using fossil energy The emission problem of exhaust gas and sewage can be generated with avoiding, serious influence is caused on environment, these problems need system Raise the solution of coordination.

Microalgae is many kinds of and the extremely extensive aquatic rudimentary plant of distribution.They pass through efficient photosynthesis, will Luminous energy is converted into the chemical energy of the carbohydrate such as fat or starch, is known as " the activation factory of sunlight driving ".Utilize microalgae Production bioenergy and chemicals are expected to reach the dual purpose of " substitution fossil energy, purification exhaust gas and sewage " simultaneously.

Nitrogen oxides (NOx) in industrial waste gas is one of main atmosphere pollution, can not only generate photochemistry cigarette Mist and acid rain also result in serious greenhouse effects, are the main inducings of atmospheric haze, therefore the denitration problem day of industrial waste gas Benefit is valued by people.Catalytic reduction method (SCR) and noncatalytic reduction (SNCR) are currently used exhaust gas denitration methods, NOx is reduced into the nitrogen of low value by both methods, does not achieve the purpose that resource utilization NOx.Alkali absorption method Process flow and equipment are relatively easy, and can be by NOx conversion at useful nitrite and/or nitrate, but this method There are deficiencies below: concentration of lye cannot be too high, otherwise can crystallize during absorbing NOx, causes the stifled of absorption tower Plug, and under low alkaline concentration, it necessarily will increase the energy consumption for extracting salt made from earth containing a comparatively high percentage of sodium chloride.Nitric acid absorption process is the exhaust gas of another kind of industrial application Method of denitration, this method absorb NOx with aqueous solution of nitric acid, can obtain more nitric acid.Nitric acid absorption process is more suitable for nitric acid system Enterprise is made, for other enterprises, there are problems for the economy of the storage of nitric acid and absorption technique.

Nitrogen is consumption most one of fast, the nutrient most easily lacked during micro algae growth.The nitrogenous fertilizer largely consumed is to feeding It is expensive for growing for microalgae, if can combine cultivating microalgae with industrial waste gas denitration, on the one hand can use NOx is Micro algae growth provides nitrogenous fertilizer, to reduce the cost of cultivating microalgae；On the other hand the discharge that exhaust gas can be purified again, reduce NOx, Generate more overall situation benefit.It is existing that certain references disclose " industrial waste gas is passed directly into the side that both culturing microalgae device carries out denitration Method ", however there is following insoluble problem in these methods: 1. carrying out industrial waste gas denitration using microalgae must solve to limit Its commercialized some problem is made, for example cultivating microalgae needs illumination and warm weather conditions, and Changes in weather necessarily causes The variation of microalgae denitration efficiency, " being passed directly into industrial waste gas " will be difficult to match exhaust gas discharge operating condition and both culturing microalgae operating condition, make It interacts at two-stage process, is unable to satisfy the emission reduction requirement of actual production；2. nitric oxide (NO) is the main component of NOx, And the solubility of NO in water is extremely low, therefore " is passed directly into industrial waste gas " and can not solve a large amount of NO in NOx and is not soluble in water and difficult The problem of to absorb.

In general, photoautotrophic efficiency is less than 30g.m^-2.d^-1, the efficiency of outdoor large-scale culture is generally below 10g.m^{- 2}.d^-1, a large amount of soil can be occupied by carrying out industrial waste gas denitration with such efficiency, it is therefore necessary to further increase microalgae Breeding efficiency.In addition, will be unable to operate in illumination deficiency only with autotrophy culture, therefore there is a need to reduce overall process To the dependence of illumination.

Summary of the invention

In view of the deficiencies of the prior art, the present invention provides the integrated processes of a kind of both culturing microalgae and industrial waste gas denitration.

A kind of integrated processes of both culturing microalgae and industrial waste gas denitration, comprising the following steps:

(1) the step of Heterotrophic culture microalgae；The algae solution at the end of making this step is metabolized under light illumination by microalgae in alkalinity；

(2) the step of isolating microalgae from the algae solution that step (1) harvests to obtain microalgae and alkaline residue；

With

(3) combination of one or both of following step (A), step (B)；

(A) NOx in industrial waste gas is absorbed with the alkaline residue that step (2) obtains, is step with the solution after absorption NOx (1) cultivating microalgae process provides the step of nitrogen source；

It (B) is nitric acid and/or nitrous acid, the alkaline residue that step (2) is obtained and institute by the NOx conversion in industrial waste gas The step of stating nitric acid and/or nitrous acid mixing, providing nitrogen source with the mixed solution for the microalga cultivation process of step (1).

According to the present invention, as long as the microalgae is able to carry out Heterotrophic culture and photoautotrophy, without other aspects Limitation.The present invention preferably cultivates those microalgaes for being suitable for oil-producing, can not only obtain bioenergy in this way, but also can be with exhaust gas emission reduction Pollutant.

The necessary condition of micro algae growth needs, such as suitable temperature, sufficient illumination (photoautotrophy or luminous energy are simultaneous feeding), Enough water and CO₂The nutriments such as (photoautotrophy or luminous energy and support) and nitrogenous fertilizer, phosphate fertilizer, regulate and control dissolved oxygen in algae solution, PH value is in suitable range etc..Although these conditions are not quite similar for different microalgaes, these are all known in the art 's.

In general, cultivation temperature is 15~40 DEG C, preferable temperature is 25~35 DEG C；Algae solution pH value is 6~11, preferably Algae solution pH value be 7~9.

According to the Expenditure Levels of nutriment in the growth pattern of micro algae biomass and culture solution, need to be replenished in time not The nutriment of foot.According to the present invention, any mode for adding nutriment is all available, for example segmentation is added or continuously mended Add, as long as can control the amount of nutriment in suitable range.

Conventional Heterotrophic culture must carry out disinfecting action to culture environment, and do not provide illumination, do not provide inorganic carbon Source (for example contain CO₂Gas).According to the present invention, the difference of step (1) and above-mentioned usual manner is only that offer illumination, both Illumination can be provided in the whole of step (1), only can also provide illumination in the later period of step (1).According to the present invention, step (1) in, light intensity is 1000~200000 luxs, and preferable light intensity is 5000~150000 luxs.

According to the present invention, in step (1), available organic carbon source include but is not limited to sugar, organic acid, acylate, alcohol, At least one of cellulose hydrolysate and glucidtemns；Such as can be selected from glucose, fructose, acetic acid, sodium acetate, lactic acid, At least one of ethyl alcohol, methanol, cellulose hydrolysate and cellulose hydrolysate.For general microalgae, glucose, second Sour sodium or acetic acid are the organic carbon sources being very suitable for, wherein it is preferred that glucose.

The present inventor is had found by a large number of experiments, when the organic carbon source deficiency in Heterotrophic culture liquid, and is contained in culture solution Alkali nitrates, alkali metal nitrites salts, alkali carbonate, alkali metal hydrogencarbonate, alkali metal phosphate, alkali metal phosphorus When one of sour hydrogen salt or any combination thereof, provided that illumination, then microalgae is metabolized under light illumination can be such that the pH value of algae solution rises, special When containing alkali nitrates, alkali metal nitrites salts or combinations thereof in culture solution, (ratio is not as the aforementioned by fixed Industry Waste NOx in gas and the nitrogen source obtained) when, faster ascendant trend is presented in algae solution pH value.Utilize this phenomenon, so that it may in heterotrophism Late stage of culture (organic carbon source is depleted), being metabolized alkali metal nutritive salt above-mentioned under light illumination by microalgae terminates cultivation When algae solution in alkalinity, thus can use isolate microalgae alkaline residue absorb exhaust gas in NOx or neutralize fix Acid solution after NOx, and then required nitrogen source is provided for cultivating microalgae with it.

According to the present invention, in step (1), in the Heterotrophic culture later period, it is metabolized alkali metal nutritive salt under light illumination by microalgae Make the algae solution at the end of cultivating in alkalinity；The alkali metal nutritive salt is alkali nitrates, alkali metal nitrites salts, alkali gold Belong to one of carbonate, alkali metal hydrogencarbonate, alkali metal phosphate, alkali metal hydrogen phosphate or any combination thereof.It is above-mentioned each Kind alkali metal nutritive salt is preferably sodium salt and/or sylvite.

According to the present invention, in step (1), preferably relying upon microalgae metabolism makes pH value > 8 of algae solution at the end of cultivating, more preferably Make the pH value 9~11 of algae solution at the end of cultivating by microalgae metabolism.

Make us unexpected, compared with the lye of preparation, the alkaline residue after isolating microalgae is in industrial waste gas NOx have higher absorption efficiency.The NOx in industrial waste gas is absorbed using alkaline residue or neutralizes the acid after fixing NOx Liquid, it is available to contain NO₃ ^-And/or NO₂ ^-Solution, which directly can provide nitrogen source for next group both culturing microalgae, the nitrogen After source is metabolized by microalgae, algae solution can be made in alkalinity again, one mode can be in both culturing microalgae culture solution and industry in this way Closed circulation is realized between the absorbing liquid or neutralizer of exhaust gas denitration process, thus by " both culturing microalgae " and " Industry Waste qi exhaustion Nitre " organically connects, and not only can use microalgae and nitrogen pollutant is expeditiously converted to useful biomass, but also make " both culturing microalgae " and " exhaust gas denitration " becomes two relatively independent processes, avoids influencing each other for the two.

Alkali absorption method is a kind of exhaust gas denitration technique of maturation, absorbs grinding for exhaust gas NOx about using alkaline aqueous solution Study carefully also very much, the present invention can be using any one of these existing methods.It is known that in order to absorb NO completely, it can be Lye adds oxidizing tower before absorption tower, using in exhaust gas remaining oxygen or addition ozone NO is oxidized to NO₂, mentioned for alkali absorption method For optimum oxidizability (NO₂/ NO molar ratio).Catalyst for catalytic oxidation suitable for different situations be all it is known in the art, It for example with active carbon, activated carbon fiber, high silicon Na-ZSM-5 molecular sieve or total silicon beta-molecular sieve is catalyst at normal temperature by NO oxygen It is melted into NO₂。

According to the present invention, step (A) absorbs fixed NOx using alkali absorption method, for absorbing the absorption of fixed exhaust gas NOx Liquid is not provided with the extraction salt made from earth containing a comparatively high percentage of sodium chloride step of these existing soda liquor absorption techniques using the alkaline residue obtained in microalga cultivation process Suddenly, but by the solution obtained after NOx is absorbed nitrogen source directly is provided for cultivating microalgae.

According to the present invention, step (B) can be used any existing method by the NOx conversion in industrial waste gas be nitric acid and/ Or nitrous acid, such as nitric acid absorption process or the method for fixing NOx with nitrifier.

Some microalgaes can not be metabolized NO₂ ^-, when cultivating these microalgaes, the method for needing to select fixed NOx appropriate, with NOx is set largely or entirely to be converted into NO₃ ^-.According to the present invention, it is known that method be all available, such as with higher concentration nitric acid Oxidative absorption method for absorbent or the method for fixing NOx with nitrifier.

, according to the invention it is preferred to which NO can be metabolized simultaneously by cultivating those₃ ^-And NO₂ ^-Microalgae, such as the present invention filter out it is small Ball algae, single needle algae, scenedesmus or spirulina, there is no conversion NO at this time₂ ^-The problem of.

It according to the present invention, is preferably nitric acid and optional nitrous acid by the NOx conversion in industrial waste gas in step (B).

, according to the invention it is preferred to be resistant to the microalgae of high alkali environment, cultivating these microalgaes can be further improved alkalinity The pH value of raffinate, and then improve with nitric acid and/or nitrite reaction or absorb the efficiency of NOx.Inventor passes through a large number of experiments, Filter out the following microalgae that can be resistant to high alkali environment, such as chlorella, single needle algae, scenedesmus or spirulina, these microalgaes can be PH is healthy growth in the environment of 9~11.

, according to the invention it is preferred to which those can improve rapidly the microalgae of algae solution pH value by own metabolism under light illumination, support Growing these microalgaes can be further improved the efficiency of cultivating microalgae process.Inventor pass through a large number of experiments, filter out it is following can The microalgae of algae solution pH value is improved rapidly, and such as chlorella, single needle algae, scenedesmus or spirulina, above-mentioned microalgae can be at 1~24 hour It is interior that the pH value of algae solution is increased to 9~11, meet algae solution and efficiently fixes NOx with nitric acid and/or nitrite reaction or absorption Requirement.

It is that microalgae is provided in the solution of nitrogen source described in step (3) in preferred situation, in terms of nitrogen-atoms, nitrogen The amount for closing object is 90~30000 μ g/g, preferably 500~20000 μ g/g.

In industrial waste gas other than containing NOx, it may also contain other pollutants such as SOx, those skilled in the art are logical Cross simple test (such as variation degree by measurement NOx absorptivity or measurement micro algae growth rate), it will be able to confirm Whether contain in exhaust gas or excessively containing the pollutant made a significant impact on integrated processes of the invention.Invention human hair It is existing, when the SOx content in the flue gas of industrial discharge is higher, the feeding algae raffinate of alkalinity can be reduced to the absorption efficiency of NOx.According to need It wants, the SOx in exhaust gas can also be reduced to by conventionally known technological means and not significantly affect this by those skilled in the art The level that the integrated processes of invention are implemented.The flue gas of general industry discharge, contains a large amount of SOx, therefore especially in coal-fired flue-gas For these industrial waste gases, the SOx contained before exhaust gas denitration of the invention is needed to remove.

According to the present invention, the industrial waste gas does not contain SOx preferably or by desulfurization process (in removing exhaust gas SOx industrial waste gas).

The present invention achieves following technical effect.

According to the present invention, on the one hand, microalgae relies primarily on metabolism organic carbon source fast-growth, requires illumination condition wide Pine greatly reduces dependence of the breeding process to illumination while faster consuming inorganic nitrogen-sourced, reach improve denitration efficiency, The purpose for reducing occupied area, improving stable technical process；On the other hand, illumination is provided to be conducive to improve having for Heterotrophic culture Machine utilization of carbon source rate.

According to the present invention, it is higher to the NOx absorption efficiency in industrial waste gas to support the feeding algae raffinate of alkalinity caused by algae.

According to the present invention, both culturing microalgae and industrial waste gas denitration are two relatively independent processes, are avoided because exhaust gas is arranged Put it is different from both culturing microalgae operating condition and caused by influence each other, it is not soluble in water and be difficult to the problem of absorbing to avoid a large amount of NO, this Two processes are connected by the alkaline residue of microalgae, do not need additional alkaline absorption solution or alkaline neutralizer energy Nitrogen source is provided for microalgae using the NOx in industrial waste gas, this makes method aquaculture cost of the invention lower.

According to the present invention, specific microalgae, such as chlorella, scenedesmus, single needle algae or spirulina, they can be metabolized simultaneously NO₃ ^-And NO₂ ^-, the environment of high nitrogen concentration can be resistant to, moreover it is possible to which the metabolism by itself improves rapidly the pH of algae solution in the cultivation later period Value, cultivating these microalgaes can be further improved the efficiency of conversion NOx.

According to the present invention, the processing step for simplifying industrial waste gas denitration improves the economy of its technical process, than Such as, for alkali absorption method, additional alkaline absorption solution and salt made from earth containing a comparatively high percentage of sodium chloride extraction step are not needed；For NOx to be fixed as to the side of acid Method does not need large-scale storage sour container, at the same do not need additional alkaline neutralizer nitric acid/nitrous acid can be converted to it is higher The salt made from earth containing a comparatively high percentage of sodium chloride of value is used in cultivating microalgae.

The present invention has constructed the Mode of Circular of a kind of emission reduction industrial waste gas pollutant and production microalgae biomass.It utilizes NO in the exhaust gas of industrial discharge_xAs the nitrogen source in culture solution, while pollutant emission reduction, obtain valuable micro- Algal biomass.In the mode of such a circular economy, the departmental cost of industrial waste gas is administered for cultivating microalgae, factory subtracts Exhaust gas, discharge of wastewater and the pollution to environment are lacked, have formd closed circulation, outlet only has microalgae biomass.

Unless otherwise defined, all technical and scientific terms used herein all has those skilled in the art conventional The meaning of understanding.In case of conflict, it is subject to the definition of this specification.

In the context of the present specification, other than the content clearly stated, any matters or item that do not mention are equal It is directly applicable in those of known in the art without carrying out any change.

All features disclosed in this invention can in any combination, these combinations should be understood in disclosed in this invention Hold, unless those skilled in the art think that the combination is obviously unreasonable.Numerical point disclosed in this specification not only includes specific Disclosed numerical point further includes the endpoint of each numberical range, and the range of these numerical point institute any combination is regarded as this hair Bright published range, no matter whether separately disclosing these numerical value pair herein.

Detailed description of the invention

Fig. 1 is a kind of schematic diagram of preferred embodiment of the present invention.

Fig. 2 is the schematic diagram of denitrating technique.

Fig. 3 is the micro algae growth curve of embodiment 1.

Fig. 4 is the micro algae growth curve of embodiment 2.

Fig. 5 is the micro algae growth curve of embodiment 3.

Specific embodiment

With embodiment, the present invention will be described in detail below, but is not therefore construed as limiting the invention.

Algae solution OD value (OD₆₈₀Value) measurement:

OD value spectrophotometric determination, is compared with distilled water, measures extinction of the algae solution at wavelength 680nm Value, the index as microalgae concentration.

The culture medium of microalgae:

Media Components are shown in Table 1~table 2.

1 culture medium BG11 of table

Component	Composition, mg/L
		K2HPO4·3H2O	40
NaNO3	1500
		Na2CO3	20
MgSO4·7H2O	75
		CaCl2·2H2O	36
Citric acid	6
		Ferric citrate	6
EDETATE SODIUM	1
		Microelement A5	1

2 microelement A5 of table

Component	Composition, mg/L
		H3BO3	2860
MnCl2·4H2O	1810
		ZnSO4·7H2O	222
CuSO4·5H2O	79
		NaMoO4·5H2O	390
Co(NO3)2·6H2O	50

The measurement of solution nitrogen content

Using the NO in ICS3000 type ion chromatograph (Dionex company, the U.S.) measurement aqueous solution₃ ^?Content or NO₂ ^- Content, instrument are furnished with EG40 leacheate automatic generator, electric conductivity detector and chameleon chromatographic work station；IonPac AS11-HC Type splitter (250mm × 4mmi.d.)；IonPac AG11 type guard column (50mm × 4mmi.d.)；ASRS-ULTRA anion Itself suppressor.Leacheate: KOH solution；Flow velocity is 1mLmin^-1；Eluent concentration: 30mmolL^-1；Sample volume is 60 μ L；Column temperature is 30 DEG C；Inhibit electric current 100mA；External standard method peak area quantification.

Embodiment 1

Microalgae Heterotrophic culture: using automatic control glass light transmission fermentor carry out chlorella (come from Sinopec microalgae algae library, Number Chlorella sp.RIPP-1) Heterotrophic culture, culture medium be BG11 culture medium (table 1) in add glucose (glucose Concentration 30g/L), NaNO in algae solution₃Content is 17.6mmol/L, and controlled at 28 DEG C, algae initial concentration is OD₆₈₀= 1.1, it is passed through compressed air (0.08MPa) and is cultivated, the ventilatory capacity of every liter of culture medium is 1L/min, and speed of agitator is 200rpm makes pH 6.9~7.1 using 2M KOH solution and 70% acetic acid solution automatic adjustment medium pH value, is added 0.1% (v/v) defoaming agent (GPE) and 0.01g/L chloramphenicol prevent foam generation and living contaminants.The OD of daily sample detection algae solution₆₈₀ Value.Measure concentration of residual glucose and NO in culture solution₃ ^-Content, according to glucose and NaNO₃Expenditure Levels carry out feed supplement, make to train It is 30g/L that concentration of glucose is maintained in nutrient solution, maintains NO₃ ^-Content is 1000~1500 μ g/g.Continuous culture stops mending after 4 days Material, then continue under light illumination culture 4 days, detect that glucose is depleted in algae solution at this time, then again under light illumination after Continuous culture 4 days remains NO in algae solution at the end of detection culture₃ ^-Content is 20 μ g/g.Microalgae is centrifugated, detects and supports algae raffinate PH value be 8.7.The heterotrophic growth curve of the present embodiment is shown in Fig. 3.

It utilizes cultivation raffinate denitration: using NO₂Industrial waste gas is simulated with the gaseous mixture of NO, wherein NO content is 450ppm (v), NO₂Content is 30ppm (v), and using compressed air as carrier gas, " acid+alkali " two-step method process absorbs NOx, and flow chart is shown in Fig. 2, Wherein acid tower diameter 100mm, high 700mm, wherein the nitric acid 3L of 30m% is held, washing tower (for removing CO2) diameter 100mm, high 100mm, wherein containing Put the feeding algae raffinate of the pH=8.7 of the generation of 3L embodiment 1.Total gas flow rate is 150L/h when operation, as the pH of washing tower (for removing CO2) tower bottom liquid It is stopped operation when being 7.3, tower bottom liquid is taken out, measure NO therein₃ ^?With NO₂ ^?Total content be 6200 μ g/g.

Embodiment 2

The present embodiment is different from that of the embodiment 1 only in the following aspects: the washing tower (for removing CO2) tower bottom liquid (NO with embodiment 1₃ ^?With NO₂ ^?It is total Content is 6200 μ g/g) prepare micro algae culturing liquid.The heterotrophic growth curve of the present embodiment is shown in Fig. 4.

Embodiment 3

The present embodiment is different from that of the embodiment 1 only in the following aspects: culture single needle algae.The heterotrophic growth curve of the present embodiment is shown in Fig. 5.

Algae solution pH at the end of detection Heterotrophic culture is increased to 9.5 naturally.In the denitration stage, when tower bottom liquid pH is 7.3, inspection Survey NO in washing tower (for removing CO2) tower bottom liquid₃ ^?With NO₂ ^-Total content be 6700 μ g/g, which can be re-used for the cultivation of microalgae.

Embodiment 4

The present embodiment absorbs NOx with the feeding algae raffinate of alkalinity for illustrating.

The alkalinity of Example 1 supports algae raffinate 3L；Analyze the alkalinity support algae raffinate in Na ion concentration and potassium ion it is dense Degree, preparation are HCO with its aqueous solution 3L with identical Na ion concentration and potassium concentration, pairing anion₃ ^-And CO₃ ^2-, institute The pH value of water solution of preparation is 8.7, and it is identical to support the pH value of algae raffinate with the alkalinity of embodiment 1.Algae is supported with above-mentioned alkalinity respectively Raffinate and the aqueous solution of preparation are NOx absorbing liquid, as a result, it has been found that: the feeding algae raffinate of alkalinity compares obtained aqueous solution to the absorptivity of NOx It is about high by 15~25%.

Comparative example 1

The present embodiment, which is different from that of the embodiment 1 only in the following aspects:, uses ammonium nitrate as nitrogen source, concentration 16mmol/L.Knot Fruit discovery chlorella is unable to normal growth and dead, therefore can not carry out subsequent step.

Comparative example 2

The present embodiment is different from that of the embodiment 1 only in the following aspects: and does not provide illumination, and Heterotrophic culture stopped feed supplement after 4 days, after Continuous culture harvests after 2 days.Algae solution pH at the end of detection heterotrophism is 7.1, is absorbed in simulated exhaust with the feeding algae raffinate of acquisition NOx, as a result, it has been found that absorption efficiency is very low, NO in solution₃ ^?With NO₂ ^-Total content be only 70 μ g/g, it is difficult to it is normally fast to meet microalgae The long needs of fast-growing.

By Examples 1 to 4 as it can be seen that using method of the invention, the alkaline residue that both can use cultivating microalgae is effectively inhaled The NOx in industrial waste gas is received, and the absorbing liquid that can use after absorbing NOx quickly cultivates microalgae.

Claims (11)

1. the integrated processes of a kind of both culturing microalgae and industrial waste gas denitration, comprising the following steps: (1) step of Heterotrophic culture microalgae Suddenly；The algae solution at the end of making this step is metabolized under light illumination by microalgae in alkalinity；Inorganic carbon source is not provided in this step；(2) The step of isolating microalgae from the algae solution that step (1) harvests to obtain microalgae and alkaline residue；(3) following steps (B) Or the combination of step (A) and step (B)；(A) NOx in industrial waste gas is absorbed with the alkaline residue that step (2) obtains, with absorption The step of solution after NOx provides nitrogen source for the cultivating microalgae process of step (1)；It (B) is nitre by the NOx conversion in industrial waste gas Acid and/or nitrous acid, the alkaline residue that step (2) obtains is mixed with the nitric acid and/or nitrous acid, is with the mixed solution The microalga cultivation process of step (1) provides the step of nitrogen source.

2. the method according to claim 1, wherein cultivation temperature is 15~40 DEG C in step (1)；Algae solution pH Value is 6~11.

3. the method according to claim 1, wherein used organic carbon source is selected from sugar, has in step (1) At least one of machine acid, acylate, alcohol, cellulose hydrolysate and glucidtemns.

4. according to the method described in claim 3, it is characterized in that, used organic carbon source is selected from grape in step (1) At least one of sugar, fructose, acetic acid, sodium acetate, lactic acid, ethyl alcohol, methanol and cellulose hydrolysate.

5. the method according to claim 1, wherein in the Heterotrophic culture later period, existing by microalgae in step (1) Alkali metal nutritive salt is metabolized under illumination makes the algae solution at the end of cultivation in alkalinity；The alkali metal nutritive salt is alkali metal nitric acid One of salt, alkali metal nitrites salts, alkali metal phosphate, alkali metal hydrogen phosphate or any combination thereof.

6. the method according to claim 1, wherein making algae at the end of cultivating by microalgae metabolism in step (1) PH value > 8 of liquid.

7. according to the method described in claim 6, it is characterized in that, making algae at the end of cultivating by microalgae metabolism in step (1) The pH value of liquid is 9~11.

8. the method according to claim 1, wherein the microalgae is chlorella, single needle algae, scenedesmus or spiral Algae.

9. the method according to claim 1, wherein be that microalgae is provided in the solution of nitrogen source in step (3), with Nitrogen-atoms meter, the amount of nitrogenous compound are 90~30000 μ g/g.

10. according to the method described in claim 9, it is characterized in that, be that microalgae is provided in the solution of nitrogen source in step (3), In terms of nitrogen-atoms, the amount of nitrogenous compound is 500~20000 μ g/g.

11. the method according to claim 1, wherein the industrial waste gas is without containing SOx or to pass through desulfurization The industrial waste gas of processing.