JPH04502121A - Method for removing acid-forming gas from exhaust gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Gas 2, Law Lord Yu ■ Evening amount U.S. Government Saleta Contract Awarded by the U.S. Department of Energy to the University of California No. DE-ACO3-76SF 00098.

The present invention provides an improved method for the removal of acid gases, including NOx, from exhaust gases, especially smoke This invention relates to the combined removal of NOx and SO□ from road gas, etc. (Fue gas is usually No. These nitrogen oxides, including both NOx and No2, are collectively designated as NOx . ) Air pollution caused by acid rain is a growing concern around the world. Significant research effort has gone into removing acid-forming components from flue gases and other gases. Efforts are being made to provide effective treatment of these gases. However, currently The method suffers from drawbacks which are particularly serious with respect to NOx removal.

Early methods were primarily used to remove pollutants at very high concentrations. It was. As time progresses and as more volumes of gas are generated As a result, the permissible amount of emissions continues to decrease. At this point, the effluent should be cleaned using an aqueous solution. The scrubbing method used can be used to obtain an acceptable amount of SOz.

However, NOx removal presents problems, the most significant of which is the lack of effective removal and and economic requirements. In addition, the economics of using two methods are method to utilize wet scrubbing for the removal of both NOx and SO2. Efforts have been made and some successes have been achieved in this direction. Solubilize NO in aqueous solution These methods use expensive ingredients and often require disposal. gave other products.

Wet methods developed for NOx removal have been reported.

For example, issued on April 19, 1984 by the Federal Republic of Germany to Hoechst AG. Patent No. 3238424.6 discloses that N from flue gas.

and to remove NO8, red phosphorus in an inert medium is used.

However, the patent reports the treatment of very high concentrations of NO; Typical concentrations are as high as several thousand pp-, and 11,000 pp was processed in the patented In Example 7, only 40% of the two parts of Example 9 were removed. In , the patentee claims that 14.0OOpp- is treated in the first step and 13. Obtained 90% removal against 0OOppm, approximately 460pp+m in the second part. It is reported that approximately 65% removal was obtained. Such effluent concentrations are sufficiently low Rather, the present inventors have found that red phosphorus can be used to treat concentrations of 5OOppm or less. I found that it was not enough.

California recently enacted a law regarding emissions from natural gas-fired power plants. The standards set are 20 pp- or less for No. in Northern California, and In California, it is less than 10 pp-. At this point, the federal standard is 7Spp- It is as follows. Such criteria require selective catalytic reduction (SCR), which is very expensive. This can be achieved using the following methods: Its reduction to an amount of less than 100 pp- Another attempt has been made on “How to remove nitrogen oxides using a ferric ion-EDTA complex solution”. No. 4,079,118 (issued March 14, 1978) entitled It has been reported that various other wet methods have been opened to provide effective removal of NOx. It has been uttered.

However, these methods either require the use of expensive starting materials or or create disposal problems for the products of the process, or both. That's the way to go.

U.S. Patent No. 3.984.522, U.S. Patent No. 4.079.118, and U.S. Patent No. 4, 15 Numerous others, such as No. 8.044, disclose wet methods for the removal of NOx. patent was issued. In addition, a combination of both NO3 and NOx removal reservoirs is available. A number of patents have been issued disclosing methods that have been developed. Examples of such patents include Forgive me! 4.126.529 and 4.347.227. many of them Other systems are available and the list is too long to include them all. I can't. However, there are no practical findings regarding such pollutants, both singly and together. There is much room for improvement in providing a practical and effective removal method.

As mentioned above, sulfur oxides can be effectively removed by flue gas desulfurization scrubbers. . Most of these scrubbers currently used involve wet limestone methods; The method uses an aqueous slurry of limestone to remove flue gas NO, neutralizes sulfite and/or sulfuric acid produced by dissolution and subsequent oxidation.

Ca5O-! Contains /1llsO and gypsum (CaSOl・2IIsO) The resulting solid slurry can be taken away for disposal. Such a practice is It is common among power plants located in areas where there is no landfill space. On the other hand, dense A more practical solution for power plants located in populated areas is to install scrubbers. operating under forced oxidation conditions. Under these circumstances, the main scrubbing method A major by-product is gypsum, which has some commercial value as a building material.

Further flexibility during processing with flue gas desulfurization scrubbers is that limestone or It can be obtained by using other alkaline compounds. These are soda Ash (Na, CO-), nahcolite) (Na*H COs),) Rona (NatCOs/Na II CO-), Na, SO-, Naolf%KOH1Kz CO5/KTICO=,? Danesite (Mr; CO-), do 11 phyto ([a CO, / goods C (1!1), NH, OH 1 and (NH,)2 Coi/NH, HCO2.

These materials are more expensive than limestone and the volume of waste gas to be treated is If the amount of waste gas is small compared to the volume of waste gas, and if the plant is Frequently used in the chemical industry when adjacent to a manufacturing site.

The wet flue gas desulfurization scrubber described above is very effective in removing sOl from flue gas. However, they cannot remove sufficient No due to the low solubility of No in aqueous solutions. installation of a separate scrubber for flue gas denitrification requires additional capital investment in -S. Essential. Therefore, existing wet flues can be used for simultaneous removal of SOx and NOx emissions. Attempts to improve gas desulfurization processes have been considered throughout the world.

Several methods have been developed to enhance the absorption of NOx in scrubinda liquid. Ta. These are prepared using oxidizing agents such as No. 03, Ceoz, and KM04. oxidation of NO to more soluble NO2, as well as scrubbing to bind and activate NO. Including the addition of various iron (II> chelates) to binda liquid. None of these methods struggle with high removal efficiency for both SO and NOx; had not been demonstrated to be cost effective.

For Hatsu-Mameq The main object of the present invention is to have a residual fi of less than 75 ppm and optionally a NOx removed from exhaust gases such as flue gas to an extent that can be lower than 0-20ppm Our goal is to provide a hot scrubbing method that can The purpose is to contact the exhaust gases with an aqueous emulsion or suspension containing yellow phosphorus. This is achieved by a method for treating exhaust gas containing NOx, which includes the step of: exhaust gas The contacting may be by any suitable contacting method, such as in the case of a spray device, but It is best done in a wet scrubber. at least some oxygen or i A source of oxygen must be present in the exhaust gas, and most exhaust gases are However, if necessary or desired, air or Other oxygen sources may be added to the exhaust gas, the pressure is not critical and the method is generally required to move the ambient pressure or gas stream into the scrubber. This is done using positive pressure.

> The temperature of the method is valid within the liquid range for water, most desirable, about 0. ℃ to about 95℃, with a preferred range of about 45℃ to 75℃. necessary and The concentration of yellow phosphorus (also known as white phosphorus) 0.0 in an aqueous emulsion or suspension, although the It should be higher than 1%, and best higher than 0.1%. high level is , an amount that allows sufficient water to carry out the reaction and provide the desired safety conditions; It may be 20% or more at the front end of the contact device.

The preferred range for good results is about 0.1-10.0% by weight, with the most It is preferably 0.2 to 5% by weight. Also, pH varies over a large range. It appears that any pH is practical. However, the inventors is about 2.0 to about 11. It is considered best to operate with o, and the best Results are obtained in the range of about 3.0 to about 9.0 pl.

Another object of the present invention is to use equipment currently customary for Sol removal methods to and 302 are removed in a single method, yet valuable by-products are obtained. It is to provide.

As mentioned above, the yellow emulsidin or suspension has a pH of about 3.0 to about 9.0. It is particularly preferred when the adjustment is within a range, and such adjustment is optionally This may be done by using suitable alkaline substances. Emulsion is arca Sulfur oxides are also removed if the water is kept clean. coal stone or flue gas Using one of the alkaline compounds mentioned in the background section above for desulfurization The advantages of such a method are obtained with the elimination of No. Therefore, get By-products include calcium, magnesium, sodium, potassium and ammonia. Contains phosphates, nitrates, and sulfates of um. These products provide important nutrients to plants. It is a nutrient and constitutes the main component of fertilizers.

Yet another object of the invention is to remove substantially all of the NoX and No2 from the flue gas. No. and S. An object of the present invention is to provide a method for removing O□.

Still further objects and advantages are that the specification proceeds so far as to describe the preferred embodiments in detail. It will become clearer as it progresses.

Pounded Natsume F Setri Figure 1 shows a sample in which No is removed from a simulated flue gas using different amounts of yellow phosphorus. Data obtained from group experiments are presented in graphical form.

Figure 2 shows how NO is removed from a simulated flue gas using a yellow phosphorous emulsion at various temperatures. Data obtained from a group of experiments that are removed is shown in graphical form.

Figure 3 shows that No. 3 simulated smoke using an aqueous emulsion of yellow phosphorus at various pH conditions. Figure 3 presents in graphical form data from a series of experiments in which gas is removed from the air.

Figure 4 shows that No was removed from the simulated flue gas using yellow phosphorus and that No was removed from the flue gas. Figure 2 presents in graphical form data from a group of experiments in which the amount of oxygen in the air was varied.

Figure 5 shows that using a mixture of yellow phosphorous aqueous emulsion and limestone slurry, Data obtained from experiments where both No. and S07 were removed from simulated flue gas. is shown in graphical form.

Detailed description of the invention Some fuels are already low in sulfur, while others are low in sulfur to remove the sulfur before combustion. It had been processed accordingly. In such cases, sulfur oxide contamination is not a serious problem; Exhaust gases are generally released into the atmosphere without treatment.These fuels are Contains nitrogen compounds found in exhaust gas. In addition, No can be produced by high-temperature decomposition of N2 and 02 in the air during combustion, and currently, It is desirable to treat such exhaust gas.

For example, a power plant in California that uses natural gas has a No, it releases exhaust gas at 6 degrees, while California's current temperature is 2. It has been determined that less than 5 ppm of NO is required to be released.

The present inventors used an aqueous emulsion containing liquid yellow phosphorus to reduce No. It was discovered that it can be removed from affect the NO radiation removal effectiveness of our system. The factors are the amount of phosphorus used, the temperature of the aqueous emulsion, and the ρ of the aqueous emulsion. 11, and 02 concentration in the flue gas.

The NO ray removal mechanism is currently under investigation, and it is thought that the following chemistry will be applied to increase the amount by 1".

It appears that the reaction between yellow phosphorus and 02 can occur both in the aqueous and gas phase. . aqueous phase The reaction inside involves the oxidation of phosphorus by dissolved MO2, which occurs at the surface of the phosphorus droplet. It is. Therefore, by varying the liquid-to-gas ratio, reactor design, temperature, and dielectric constant of the aqueous phase, The parameters for adjusting molten phosphorus in water, such as additives that It affects oxidation and thus the NO removal rate 2) 4. In the gas phase, O! is at high temperature It appears to react with phosphorus vapor released from an aqueous emulsion of yellow phosphorus. Netpei Under equilibrium conditions, the partial pressure of P4 is approximately 365 pp- at 50°C and 60°C at 1 atm. It is about 775 ppm.

Therefore, if the partial pressure of NO in the flue gas is about 500 pp-, it is about 55 °C It can be balanced by using scrubinda liquid of P, where The partial pressure is approximately 550 pp-, assuming equilibrium conditions are obtained.

As used herein, the present inventors have used yellow emulsion for No removal. The effectiveness with respect to Required to remove 1 mole of N0, averaged over 2 hours) is defined as the number of moles of Therefore, the higher the stoichiometry, the more phosphorus required to remove each mole of NO, making it less effective for No removal, The reverse is also true.

The stoichiometric ratio P/No obtained so far is close to 4, which means that one 24 is removed. This suggests that each No should be oxidized. 0. and the reaction of P4 is , 0 and 0. (see Equations 1 and 2 below). one 0 ．． If only P4 is produced for each P4 that is oxidized, the P/No ratio 4 is N.

This indicates that most of the NO2 must be oxidized to generate NO2 before dissolution.

However, NO may react with NO2 to generate NzC)+ (see below) (see Equation 5 below), N, os is also readily soluble in water (see Equation 5 below). 7). Therefore, 2 moles of NO are associated with each No oxidized to NOx. The P/No ratio can be reduced to about 2 under ideal conditions.

The fact that P4 can react with 02 at a much faster rate than No, and the amount of at Pressure is 0 or 0. Considering the fact that the partial pressure of either Most of P4 is oxidized by 02, while oxidation of No to NOx (the following formula 3 and Equation 4) is likely to be performed by O or O5. instructor The NO7 generated in this reaction reacts with other molecules of No to generate N2O3. ) or may be duplicated to produce N,04 (see 26 below). Nokoki). Both N, O, and N2O4 are much more water soluble than No; dissolution in water results in the formation of nitrite and nitric acid (see Equations 7 and 8 below) ).

Therefore, the removal of No by P4 in the gas phase can be summarized by the equation below.

o) P4+oz...>P<O+0 <z) O+Ot+M...>03+M(3) N O+ O+M...> NOa+M(4) N O+ Om...> Now +0i(5) N O +N O2+M...)N, 03+M(fi>NOx +NOx +M ...> Nz 04 + M (7) Nt Os + IIi O ...> 2 11 NO.

(R)　N204　+l-L　O...＞　TlN0t　+IfNO-(in the formula, This proposed mechanism (M is any other molecule that remains unchanged after the reaction) is 0. is required for the No absorption reaction, and nitrite and IIi' Consistent with the finding that both 1iliI2 salts were found in the spent liquid material.

The mechanism of oxidation of phosphoric acid to phosphorus A-oxyacid (not shown in the formula) is more complex. This seems to be a rough idea and is currently being considered.

The reaction mechanism of No removal using yellow phosphorus is clearly different from the reaction mechanism using red phosphorus. It should be pointed out that the reaction between yellow phosphorus and NO is as follows: Low melting point of phosphorus <44. Due to the high vapor pressure of I t′>, r>7, the water phase and gas It appears to occur in both phases. On the other hand, red phosphorus has a temperature of about 417℃ at atmospheric pressure , it is solid until sublimation) and therefore the reaction temperature used in the present invention ( It has a very low vapor pressure between about 20°C and 95°C. In this case, the absorption of No is in the solid -Appears to be gaseous. Furthermore, N using yellow phosphorus.

= The induced products were found to include NO3- and No,- (both oxidation products of No). However, in the case of red phosphorus, the only reduction product that can be obtained is N3, that is, No. Is the nitrogen product of the above hekis? Asserted in AG's patent. Also, this N in the case of et al.

Differences in the derived products suggest that different reaction mechanisms are involved.

No removed from the simulated flue gas can be recovered as a mixture of nitrite and nitrate. On the other hand, the yellow phosphorus consumed by the No absorption reaction was Acid ion (H, PO, ~), phosphite ion (IIPO, -), and phosphoric acid ion on<III”O,°). We found that 1.5% by weight of Flue gas containing yellow phosphorus emulsion and 550 pp+a of No and 20% O3 The mass balance of N and P was studied at 113.60°C using the mixture.

Under these conditions, 300% of NO was removed during a 2 hour period. absorbed All of the NO added was converted to No, -, and N　O3- in a ratio of approximately 1 nia. Rin For the material balance of 90% of IIsPot-, llPO5-, and 1 in a ratio of about 1:10:40 We have found wood that can be collected by mixing lP04-. Less than phosphorus determination Recovery is due to the difficulty of recovering all of the phosphorus droplets remaining in the scrubber after the experiment. Caused by From these data, it appears that the removal of NO by phosphorus is mainly caused by nitrate. results in the formation of acid salts and phosphates (both of which are useful in the production of fertilizers) I know it's Zuko.

As mentioned above, the present invention also facilitates the removal of both NO and SO2 in a single method. do. The inventors have determined that yellow phosphorus is present at 1150.degree. − I found that there was no reaction.

However, simultaneous removal of aqueous emulsions of yellow phosphorus and alkaline materials such as limestone This can be done by mixing potash components. For example, at 55°C, p117.5, 3.3 fold % of yellow phosphorus and 5.0% by weight of Ca5O, an emulsion containing a slurry was used as Labinda liquid and 5.0% CaC0, slurry in the absorbent. When used, the simulated flue gas treated over a period of 3 hours was 560 p. Approximately 95% of pm NO and 2900 ppm SO in the removed flue gas. It had about 100%.

As mentioned above, the removal of NO by yellow phosphorus is shown in equations (7) and (8) above. It provides the acid forms of nitrite and nitric acid.

However, when alkaline compounds are added to the emulsion, these acids converted to salt. Additionally, when SOt is present, another chemical reaction occurs.

As shown in equation (9) below, SO7 converts NOw in -i to ammonia. Ru.

(0) NO+NO2+311tRO+611SOs-...>2NI+,.

+0S04” →-411°H3O,- arises from Sow as shown below .

G50z +61120...) 6 IIs 50s611, so,... ・>(ill, -1611SO, - These reactions together produce NO, and SO 3 may be written as shown in equation (10) below.

01m No+NO□ +6S ro, +911t o...>2N114' +6Sl+4−　10In　II’ Regarding formula (10), N　O+　N　Ot is Obtained from Xun Lin and NO as described below.

(10I', +11/20t+2NO+611.0...>NO+NO□+ 411. l’0. −+4111 alkaline compound is expressed by formula (10) or formula (11) 11' and induces the system to give by-products in the form of salts.

For example, when (:aCOs is used as an alkali compound, the formula (1 0) required to neutralize 1O1l' from 0) given to.

5CaCO, +5H, O---> 5Ca (0)I)z +5C0゜5Ca (OH)x・”>5CJ”+10011-Under these conditions, the formula (]2 ) replaces the expression (]O0.

(12>No 10NOt 4-GSDt 4-5 CaC0a + 4 1 12 0”・＞2NH4”+6SO4-+5Ca”+5CO*C generated O2 joins the flue gas in the scrubber, and Ca ions combine with sulfate ions to Produces soluble Ca5O. The product obtained in the scrubber is then It is of the ammonia family and is useful as a fertilizer. Similarly, CaC0, has the formula (I It absorbs 11゛ from generate. Thus, the overall reaction equation for yellow phosphorus and limestone is:

0:D l’4+ll/211t+2NIl+6Sflt+91j+COt+ 211hl]...>2(N11->2111"ll-46Ca5O--. 2112-Store-L3Cal'04-1120 1! 1cIl□Like this Therefore, all 41 products from the road gas treatment method of the present invention are wasteable materials. Most of the substances are t+li by-products.

As described in -1-, various alkali compounds can be used. However, different Lucari compounds yield somewhat different raw tr12 products. limestone and dolomite When used, the sulfate of insoluble generated. , To "1 → - J); When any of the thorium is used When a potassium-based alkaline compound is used, soluble sodium sulfate is produced. Potassium sulfate (and other fertilizers) is produced when These products and yellow All of the phosphates produced from phosphorus have commercial value. Therefore, it changes We offer different products that can be adapted to suit market conditions and Different starting materials are used to provide a solution to the acid rain problem while at the same time solving the acid rain problem. It is possible.

For example, if it is desired to provide a fertilizer containing nitrogen, ammonia Can be used as a caustic substance. A valid formula for the ammonia system is as follows: .

041 NO+NO! +6so, +9H2O...>’;njH4”+ 65O4°+IO)! 10 moles of NH are required to neutralize 10 H. The reaction is as shown below.

O5No + NOx + eso□ + 9) + 20 + l0NL...> 12 NRm　　　　　　　　65Oa“Yellow phosphorus is necessary to induce the oxidation of NO to NO2 The reaction is as follows.

Q[9Pa"ll/20z"2NO+61420...>No+N% +4HzPOa-”4H’Thus, the total reaction between yellow phosphorus and ammonia is as follows: That's right.

α7J　P, +11/20□+21JO+6SO□+14NN, 01(++ 420...>4 (NHa)Hz POa' +6 (NHallz SOa.

The reaction is such that the SOz to NO ratio of 3:1 reduces all of the No to ammonia. It is acceptable to show that you are giving. Excessive N.

produces significant amounts of nitrite and nitrate, and excess SO2 produces additional alkaline compounds, Preferably an alkaline solution that produces some insoluble g-salt to ensure removal of all SO□. Requires potassium compounds.

From a study of the chemistry of a given alkaline compound, how can other proposed alkaline compounds be developed? It can be inferred that potash compounds may act. Also shown in the background and used for wet desulfurization The list of alkaline compounds listed is not only effective, but also possible effective alkalis. It is recognized that this does not include all compounds.

The invention is further illustrated by the following examples, which do not exceed the scope of the invention. It should not be construed as limiting.

And~” Using a bench-scale scrubber to remove No. 1 from flue gases due to yellow phosphorus in water. I considered removing it. The scrubber has a glass filter plate bottom that can hold the aqueous liquid. Upright cylindrical Pyrex column (50n + inner diameter: <210 m). A thermometer and a thermometer to measure the temperature of the liquid in the scrubber. A pH electrode was attached to measure the pH of the liquid therein. Scrubber contents Provide a water jacket for heating or cooling objects and measure quantities for simulated flue gases Prepare appropriate supply piping to supply the gas.

With this equipment, precise amounts of No., N2.02 and SO2 are supplied to the scrubber. do. On the downstream side of the scrubber, a suitable cooler, absorber, cooling 1:f) knob and N Install ok and SO2 analyzer.

1 g of yellow phosphorus (melting point 44.1°C) was melted in water at 60°C in a scrubber. I understand. The pH of the aqueous phase was 3-4. Press the bottom of the column to -50 0 ppm N010~-20% 02, the balance N.

When blowing a gas mixture containing 60. Dispersed in water. ! In addition to these experiments in which the amount of phosphorus was varied, to change the temperature of the aqueous emulsion and the pi of the aqueous emulsion. and conducted other experiments.

The gas mixture leaving the reaction column was filtered through a condenser (length 390 mm), 0.2 M NaO H? A gas cleaning bottle containing 0.21 liquid, a second cooler (200 mm in length), and Passed through a cold trap (84°C). 4 degrees of NO and 4 degrees of NOx in exhaust gas, Thermoelectron Model (Ther＋＊oelectron Model) 14 A Chemiluminescence No. Measured using an analyzer. After 2 hours, stop the reaction. When the emulsion is cooled to room temperature, unused yellow phosphorus is collected and weighed to determine the phosphorus consumption. The cost amount was measured.

The amount of NO absorbed is determined by the NO concentration in the flue gas, the flue gas flow rate, the reaction time, and its period. It was measured from the ratio (%) of No removed during the test. Scrubbing liquid after experiment and NaOH absorbent? The pH of the 8 solutions were generally about 1.5 and 12.5, respectively.

f from No and phosphorus in the solution of the used agent in the scrubber and in the NaOH absorbent. The filtrated product was measured by ion chromatography.

Passage of a simulated flue gas mixture through a scrubbing column containing molten phosphorus Produces a fine yellow phosphorus dispersion. If 0□ is present in the flue gas, a thick white haze is generated, which if left unchecked will be can result in a significant response. This is caused by incomplete oxidation of phosphorus. This is thought to be due to Gakuluminescence. The partial pressure of 02 in the flue gas is increased and these conditions This interference is considerably reduced in the case of complete oxidation of the underlying phosphorus.

NaOH absorption and chemiluminescence spectrometers (which can be used for 65 minutes in half the time) NOy mode (with passage of gas mixture through a stainless steel field column at 0°C) Use of cold traps paired with scrubbed flue gas monitoring using seems to eliminate such interference. Industrial use where scrubbing liquid is circulated Along the way, capture of No, (produced by oxidation of No) and phosphorous oxide vapors appears to be even more effective than our laboratory scrubbing column, and the The use of fluid absorbents appears unnecessary. Further steps performed according to this example In the experiment, the present inventors determined that the stoichiometric ratio P/No was temperature of the emulsion, pH 1 of the aqueous emulsion and 0□ concentration and N in the flue gas. It has been found that this is influenced by the o concentration.

Using various amounts of phosphorus in emulsion (pH 3), 4% 0□ in simulated flue gas. The reaction was carried out at a concentration of These results are illustrated in FIG. Early No. The removal efficiency is even higher with higher concentrations of phosphorus, reaching approximately 90% with 2% by weight of phosphorus. It is clear that However, the stoichiometric ratio P/NO is This indicates a lower total No removal efficiency under these conditions. vinegar.

The effect of emulsion temperature was determined in several experiments and the results are shown in FIG. child In these experiments, the emulsion contained 0.5% yellow phosphorus at pH 3, and the flue gas The gas contained 550 PPM N0, 4.0% 0□, and the balance N2. initial Although the No removal efficiency was higher at higher temperature, the total efficiency of No removal was lower under these conditions. Lowered below! For example, if the temperature of the emulsion is increased from 50°C to 75°C, In this case, the initial removal rate of NO was increased from 78% to 99%. At the same time, P/No ratio increased from 7.1 to 24.5, indicating a significant decrease in removal efficiency.

We measured the effect of pH on the No removal efficiency of yellow phosphorus emulsions, and The experimental results are shown in Figure 3. In these experiments, the 0□ content was adjusted to 4% by volume. . As shown in FIG.

The efficiency of removal increases with increasing aqueous acidity over the pH range of 3.0 to 9.0. It increases over time. Specifically, when the pH is lowered from 9.0 to 3.0, the P/N The o ratio decreased from 10.5 to 7.1.

We also measured the influence of 02a degrees in the flue gas, and the data are shown in Figure 4. As shown, the presence of 0□ is essential for NO removal by yellow phosphorus emulsion. Ru. In addition, the efficiency of No removal of the phosphorus emulsion is significantly lower than 0.05% of the simulated flue gas mixture. increases as the content increases. In these experiments, 0.5% by weight of yellow The No absorption reaction was carried out at p) 13.60°C using a phosphorus emulsion. 0□ When the content was increased from 4% to 20%, the P/No ratio decreased from 7.1 to 5.0. It turns out that Therefore, the use of yellow phosphorus for the removal of flue gases requires forced oxidation. Works best under certain conditions.

A comparison of the No removal efficiency of yellow phosphorus and red phosphorus was carried out using the apparatus of Example 1, sooppm This study was carried out for use in treating simulated flue gas having a no. 0.5 weight 5% yellow phosphorus emulsion and 1.5% red phosphorus @ suspension were used together. 00pp-No and 4% 0. of simulated flue gas was treated at 60°C. Huang Ling'ae Mulsion removed up to 80% of No., but red phosphorus emulsion No. No detectable amounts were removed. At pH 9, yellow phosphorus emulsion is No. Up to 40% was removed, whereas red phosphorus was not removed in detectable amounts. pH 10.1, red phosphorus has some N.

was removed, but the efficiency was still very low. (P/No approx. 1.000) .

Type M-02/Niro atomizer (Nir) with centrifugal atomizer.

Spray drying experiments were conducted using a portaple spray dryer (Atomizer).

The capacity of the spray drying chamber was approximately 3,501 minutes, and the gas flow capacity was approximately 50,017 minutes.

Yellow phosphorus can be prepared in liquid form IILi (as an emulsion in water) or in solid granular form (as an emulsion in water). Fine particles in water prepared by rapid cooling of phosphorus in emulsion from about 80 °C to room temperature (as a granular suspension) into the spray dryer chamber. Simulated flue gas mixture (490 ppm No, 20% 02, and the balance N2), the inlet temperature was 170 °C. The exhaust gas temperature was 65°C. 0.25% by weight yellow phosphorus emulsion was used to remove up to 40% of the No. In another experiment, 3.2M A fine granular suspension of yellow phosphorus (5% by weight) containing urea of . The simulated flue gas contains about 5 soppa+ NO and removes up to about 70% of the NO. Ta. using a warmer phosphorus emulsion and/or under better operating conditions. It is expected that even higher removal rates will be obtained.

Yu-↓ In this example, the apparatus of Example 1 was used to treat various amounts of No in a simulated flue gas. did. In all cases except Example 4f, 150 cc of aqueous emulsion contains 1.0 g of C aC0, and in Example 4f an acetate buffer of po 4.3 was used. simulated flue The gas contained 11-12% 0□, and the total gas flow rate was 0.8-1.017 min. . The total experimental time ranged from 2-3 hours. Other operating conditions used and The results are shown in the table below.

−”C Example NO temperature Initial Added Maximum removal Average removal (IMp-) ('C) pH Phosphorus (g) Rate (%) Rate (%) 4a 60 50 6.5 1.5 10 0 1004b 65 50 6.3 0.8 100 1004c 400 50 6.2 0.8 80 434d 430 50 7.4 1.5 10 0 764e 1950 50 6.2 3.1 55 294f 2000 75 4.3 4.0 95 72 Let's remove low concentration No from these examples It can be seen that very effective removal is obtained at 50°C. In the example shown At 75° C., sufficient removal of higher concentrations of No was obtained.

■−】 N from simulated flue gas using yellow phosphorus emulsion mixed with limestone slurry Simultaneous removal of O and SO2 was performed. The equipment used in this experiment has a reactor of approximately 1 ．． Example 1 except that it had a capacity of 21<inner diameter 110m + sX 130akm) It is similar to the device. Contains 3.3% by weight of yellow phosphorus and 560% by weight of CaC0z. 0.9 f of the aqueous emulsion/slurry was dispersed with a magnetic stirring bar. school The temperature of the rubbing liquid was maintained at 55°C, and the pH was 7.5. 5.0 weight on absorbent A slurry of % CaC○ was added. 560ppm No, 2900ppm S A simulated flue gas mixture containing O2, 10% Oz, and the balance N2 was heated to about 1.3 A was blown into the slurry at a flow rate of /min. The reaction temperature was maintained at 55°C, and the slurry p H decreased from about 7.5 to about 4.2 after 3 hours. The removal rate of No. and S02 is As shown in Figure 5, from this figure, SO! The removal rate quickly reaches approximately 100%, and then It can be seen that the removal rate of No reached approximately 100% without any problems. From these data , the removal of No by the use of yellow phosphorus is enhanced in the presence of SO□ and limestone. It is clear that

The solid and liquid phases in the scrubber and absorbent were separated by suction filtration and analyzed. The solid recovered from the scrubber after the 0 reaction was subjected to laser Raman spectroscopy. It was analyzed using a thermometer, and in addition to unreacted CaC0 and yellow phosphorus, CaSO3.2H It was shown to contain 20. Only unreacted CaC0, downstream of the absorbent, is detected. Ta.

Ca　CO3・%HzO precipitate is not detected in either scrubber or absorbent It wasn't done.

Both the scrubbing liquid and the absorption liquid are Not-, NOx-1so3'', so, It was found to include ", Hz Pot -, HPOs" and HPO,".NO The recoveries of 2- and N0ff- account for only about 50% of the absorbed No. Since a significant amount of H5O,- was present in the scrubbing solution, the nitrogen-sulfur We investigated yellow compounds. In fact, we found that about 40% of the absorbed No. Nitrogen-sulfur compounds, i.e. hydrogen, in the slightly acidic (pH approximately 4) scrubbing solution Roxiamine disulfonate (HADS) and amine disulfonate (ADS) We found that this can be explained by the generation of . The inventors also found that the pH was approximately 2. When lowered, both HADS and ADS are subsequently treated with NH in the scrubbing solution. We found that NO, - and H3 in the scrubbing solution were hydrolyzed into Formation of nitrogen-sulfur compounds and their hydrolysis reactions via off-reactions Upon careful consideration, the formation of NH,'' is a result of these considerations.Therefore, , the use of yellowing emulsions for the removal of both NOx and SO□ is desirable. This results in the conversion of NO to NH,'', No, 1- and NO□-, which is These are all desirable chemicals for the production of fertilizers.

Although only illustrative embodiments have been described, it is recognized that various modifications may be made and The invention is to be limited only by the spirit and scope of the claims.

NO removal - $ (%) To → mouth Seal Too much No removal rate (%) Ko To → mouth circle No removal rate (%) l ω No removal rate (%) Ko tree Procedural amendment (formality) 2.9. -6 Heisei Year Month Day Director General of the Patent Office Toshi Ue Matsu 1. Indication of incident PCT/US8910460 i2, Name of invention Exhaust gas? Method 3 of removing acid-generated gas: Person performing the correction Relationship to the case: Applicant 5. Date of amendment order: Self-issued international search report

Claims (18)

[Claims] 1. A method for treating exhaust gas containing acid-forming pollutants such as nitrogen oxides, the method comprising: A step of contacting the above exhaust gas with an aqueous emulsion or suspension of yellow phosphorus. The above-mentioned method for treating exhaust gas, comprising: 2. Claims that the temperature of the aqueous emulsion or suspension is from about 20°C to about 95°C. The method for treating exhaust gas according to item 1. 3. Claim 1, wherein the temperature of the aqueous emulsion is from about 45°C to about 75°C. Exhaust gas treatment method. 4. The amount of yellow phosphorus in the emulsion is from about 0.01 to about 20.0% by weight. The method for treating exhaust gas according to item 1. 5. The claimed amount of yellow phosphorus in the emulsion is from about 0.1 to about 10.0% by weight. A method for treating exhaust gas according to Scope 1. 6. Claims that an alkaline substance is added to the emulsion to maintain a pH between about 2 and about 11. The method for treating exhaust gas according to item 1. 7. The method for treating exhaust gas according to claim 1, wherein the pH is adjusted to about 3 to about 9. . 8. Claims where the amount of oxygen in the flue gas being treated is from about 1% by volume to about 16% by volume The method for treating exhaust gas according to item 1. 9. Claim 8, wherein the oxygen content is adjusted by adding air to the exhaust gas. Exhaust gas treatment method described in section. 10. A method for treating exhaust gas containing NOx and SO2, the method comprising: aqueous emulsions or suspensions and aqueous emulsions or suspensions of yellow phosphorus. Contact with an alkaline compound in sufficient amount to maintain the pH in the suspension at about 3-9. The method for treating exhaust gas as described above, comprising the steps of: 11. The aqueous emulsion or suspension is maintained at a temperature of about 45°C to about 75°C. , An exhaust gas treatment method according to claim 10. 12. The exhaust gas according to claim 11, wherein the alkaline compound contains calcium carbonate. How to handle 13. The exhaust gas according to claim 11, wherein the alkaline compound contains ammonia. Processing method. 14. A method for treating exhaust gas containing about 25 to about 3000 ppm NOx, An aqueous emulsion of yellow phosphorus having an amount of phosphorus from about 0.1 to about 10.0% by weight. temperature of the solution is about 45°C to about 90°C), and the above gas is over a period of time sufficient to reduce the concentration of NO in the exhaust gas to less than about 25 ppm. the above-mentioned exhaust gas, characterized in that it includes a step of contacting the above-mentioned emulsion with the above-mentioned emulsion; How to process gas. 15. The exhaust gas also contains about 100 to about 3,000 ppm sulfur dioxide. The method according to item 14. 16. Claim 15, wherein the aqueous emulsion also contains an alkaline compound. Method. 17. Claim 14, wherein the aqueous emulsion also comprises calcium carbonate. Method. 18. A method for treating exhaust gas containing about 25 to about 1000 ppm NO, the method comprising: An aqueous emulsion of yellow phosphorus having an amount of phosphorus of about 0.1% to about 5.0% by weight tion temperature is about 45° C. to about 75° C.) and NO in the exhaust gas. the above gas for a contact time sufficient to reduce the concentration of x to less than about 20 ppm. The above-mentioned exhaust gas includes a step of passing the emulsion in direct contact with the emulsion. How to handle