CN108579368A - A kind of solid state chemistry absorption techniques purification nitrogen oxides - Google Patents

Abstract

The invention discloses a method for purifying nitrogen oxides by solid-phase chemical absorption technology. The method is as follows: the exhaust gas of nitrogen oxides to be treated is sequentially passed through a catalytic oxidation solid catalyst and a chemical absorption solid reagent to obtain purified exhaust gas; The catalytic oxidation solid catalyst is composed of two or more catalysts selected from carbon-based catalysts, molecular sieve catalysts or metal oxide catalysts; the chemical absorption solid reagent is to react with NO and NO to generate nitro _compounds solid absorbent. The method can realize high-efficiency purification of NO waste gas with medium and low concentrations at normal temperature, even zero emission, and has simple process, easy operation, high efficiency, wide practicability, and fully meets the current high requirements of environmental protection.

Description

Purification of Nitrogen Oxides by a Solid Phase Chemical Absorption Technology

(1) Technical field

The invention relates to the technical field of air pollution control, in particular to a treatment process for low-concentration NOx waste gas discharged at normal temperature and in a medium-concentration and semi-enclosed environment with high humidity.

(2) Background technology

Nitrogen oxides (NO _X ) emitted from power plants, chemical plants and automobile exhaust are one of the main sources of air pollution. The resulting environmental pollution, especially photochemical pollution, acid rain, and smog, has caused serious economic losses . At the same time, it threatens people's health all the time. Therefore, the treatment of nitrogen oxides cannot wait.

At present, among numerous denitrification technologies, Selective Catalytic Reduction (SCR) technology has high-efficiency denitrification characteristics and has been applied to most power plants for denitrification. However, for some flue gases with high NO content (accounting for more than 90% of NOx), low oxygen content, high humidity (close to saturated humidity), and normal temperature and pressure, it is difficult to use SCR technology for treatment. For the treatment of this kind of NOx exhaust gas, liquid phase absorption is often used in industry. But the strong oxidant (sodium chlorite, sodium hypochlorite Chinese patent: CN1986033, CN1883768, CN1843574) that liquid phase absorbs uses, H ₂ O ₂ (Chinese patent: CN102327735, CN106853328A), ozone (Chinese patent: CN19233410) and lye absorbent (Chinese patent: CN 101259368A) The cost is high, the requirements for equipment are high, and the implementation is difficult; at the same time, with the continuous improvement of environmental protection requirements, the country's emission limits for nitrogen oxides are becoming more and more strict, and the petrochemical industry pollutant discharge standards (GB 31571-2015) stipulates that the emission concentration of nitrogen oxides is 100mg/m ³ , and the emission concentration after liquid phase absorption is generally 150-300mg/m ³ . In addition, for some semi-enclosed environments (tunnels, parking lots, etc.) low-concentration (below 50mg/ ^m3 ) NOx treatment, the liquid phase absorption process is difficult to implement and difficult to operate. However, the existing technology cannot meet the requirements for the treatment of nitrogen oxides.

Aiming at the pollution of such low-concentration nitrogen oxides at room temperature, an economical and practical treatment process is urgently needed, which can not only meet the environmental protection emission requirements, but even zero emission, and contribute to my country's environmental protection.

(3) Contents of the invention

The purpose of the present invention is to provide a method for purifying nitrogen oxides by solid-phase chemical absorption technology, to realize high-efficiency removal of low-concentration NOx exhaust gas at room temperature, which is easy to operate and implement, and can meet current environmental protection requirements, even zero emission.

In order to realize the above-mentioned purpose of the invention, the specific technical scheme of the present invention is as follows:

A method for purifying nitrogen oxides by solid-phase chemical absorption technology, the method is as follows: the exhaust gas of nitrogen oxides to be treated is sequentially passed through a catalytic oxidation solid catalyst and a chemical absorption solid reagent to obtain purified exhaust gas; the catalytic oxidation The solid catalyst is composed of two or more catalysts selected from carbon-based catalysts, molecular sieve catalysts or metal _oxide catalysts; the chemical absorption solid reagent is a solid absorbent that reacts with NO and NO2 to generate nitro compounds .

The principle of exhaust gas treatment in this method is as follows: the catalytic oxidation solid catalyst catalyzes and oxidizes imported NO and O ₂ into NO ₂ to form a certain proportion of mixed gas of NO ₂ and NO. _The chemical absorption solid reagent reacts chemically with NO and NO2 flowing out from the catalytic oxidation solid catalyst to generate nitro compounds, thereby thoroughly purifying nitrogen oxide (NOx) pollutants.

Further, the catalytic oxidation solid catalyst and chemical absorption solid reagent can be granular, bar-shaped or other industrial catalysts and absorbent shapes required to ensure normal operation of NO purification.

Further, the carbon-based catalyst is activated carbon from various sources, such as polystyrene-based activated carbon, pitch-based activated carbon fiber, and coconut shell-based activated carbon.

Further, the molecular sieve catalysts are ZSM-5 molecular sieves or β molecular sieves with different silicon-aluminum ratios or all-silicon, exchanged with metal ions such as Li, Na, K, Rb, Mg, Ca, Fe, Co, Ni, Cu, Mn, etc. HZSM-5, Hβ molecular sieve or metal oxide supported HZSM-5, Hβ molecular sieve and some specific zeolite molecular sieves.

Further, the metal oxide catalysts include Mn, Cr, Co, Cu, Fe, Ni, Zn, Ti, Al and other metal oxide catalysts.

Further, the catalytic oxidation solid catalyst is preferably 1-50% Co ₂ O ₃ -HZSM-5 (the 1-50% Co ₂ O ₃ -HZSM-5 is a composite catalyst of Co ₂ O ₃ and HZSM-5, 1～50% is Co ₂ O ₃ accounting for the total mass percentage of the composite catalyst, the same below), 1～50% Co ₂ O ₃ -coconut shell activated carbon, 30～80% HZSM-5-coconut shell activated carbon or 1～20% Co ₂ O ₃ -30～55% HZSM-5- coconut shell activated carbon.

Furthermore, the catalytic oxidation solid catalyst is more preferably 10% Co ₂ O ₃ -HZSM-5, 10% Co ₂ O ₃ -coconut shell activated carbon, 50% HZSM-5-coconut shell activated carbon or 10% Co ₂ O ₃ -45% HZSM-5- Coconut Shell Activated Carbon.

Further, the solid absorbent is a composite absorbent composed of two or more absorbents: an inorganic solid absorbent and an organic polymer resin solid absorbent.

Further, the inorganic solid absorbent includes sodium hydroxide, sodium carbonate, sodium bicarbonate, calcium carbonate, calcium hydroxide, potassium carbonate or potassium hydroxide and the like.

Further, the organic polymer resin solid absorbent includes macromolecule resins such as styrene polymers, styrene-divinylbenzene polymers, and divinylbenzene polymers, as well as modified functional groups such as carboxyl groups, nitro groups, sulfonic acid groups, and amido groups. After the high polymer resin.

Further, the solid absorbent is preferably 10-50% Na ₂ CO ₃ -divinylbenzene resin (the 10-50% Na ₂ CO ₃ -divinylbenzene resin is Na ₂ CO ₃ and divinylbenzene Resin-like composite absorbent, 10% to 50% is Na ₂ CO ₃ as a percentage of the total mass of the composite absorbent, the same below), 10% to 80% phenolic resin-divinylbenzene resin, 10% to 80% CaO-Na ₂ CO ₃ or 10-50% CaO-divinylbenzene resin.

Furthermore, the solid absorbent is more preferably 30% Na ₂ CO ₃ -divinylbenzene resin, 30% CaO-divinylbenzene resin, 50% CaO-Na ₂ CO ₃ or 50% phenolic resin-di Vinyl benzene resin.

The invention can realize the purification of medium and low concentration NOx discharged at normal temperature through the method of gas-solid catalytic oxidation and solid-phase absorption, even zero discharge, and has simple process, convenient operation and low cost.

The features of the present invention are:

1. Reasonable use of catalytic oxidation technology makes full use of the oxygen in the exhaust gas, oxidizes NO to NO ₂ , increases the oxidation degree of NOx in the exhaust gas, and provides the basis for subsequent absorption; at the same time, the composite catalyst makes full use of the specificity of each single catalyst Function, realizing the multi-functionalization of the catalyst, better catalytic oxidation of NO in the exhaust gas to NO ₂ , and improving the NOx oxidation degree of the exhaust gas;

2. The use of composite solid-phase absorbents to remove nitrogen oxides from waste gas not only utilizes the unique adsorption properties of different absorbents, the NOx in the waste gas reacts chemically with the absorbent, and efficiently removes nitrogen oxides from the waste gas, but also easily Operation, low cost, wide practicability;

3. Exhaust gas treatment is carried out under normal temperature and pressure to reduce energy consumption.

The effective effect of the present invention is reflected in: it can realize high-efficiency purification of NO waste gas with medium and low concentration at normal temperature, even zero emission, and the process is simple, easy to operate, high in efficiency, wide in practicability, and fully adapts to the current high requirements of environmental protection.

(4) Description of drawings

Fig. 1 is the flowchart of the method of the embodiment of the present invention;

(5) Specific implementation methods

The present invention is further described below in conjunction with specific implementation, but protection scope of the present invention is not limited thereto:

Example 1:

The NOx exhaust gas passes through the solid catalyst bed, and the imported NO and O ₂ are catalyzed and partially oxidized into NO ₂ , thus forming a certain proportion of NO ₂ and NO mixed gas, and then pass through the solid absorbent bed, the nitrogen oxides in the exhaust gas and the solid adsorbent A chemical adsorption reaction occurs to generate nitro compounds, thoroughly purify NOx, and the purified gas is discharged into the air. The exhaust gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -HZSM-5 composite catalyst, in which Co ₂ O ₃ accounts for 10% of the mass of the composite catalyst, Co ₂ O ₃ and HZSM-5 are evenly mixed, the mass of the composite catalyst is 5.0g, and the catalyst is granular; The absorbent is 30% Na2CO3-divinylbenzene resin, of which Na ₂ CO3 accounts for 30% of the mass of the composite absorbent, Na ₂ CO ₃ and divinylbenzene resin are evenly mixed, the mass of the composite absorbent is 5.0g, and the absorbent is granules shape. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo 340).

Example 2:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -coconut shell activated carbon composite catalyst, wherein Co ₂ O ₃ accounts for 10% of the mass of the composite catalyst, Co ₂ O ₃ and coconut shell activated carbon are uniformly mixed, the mass of the composite catalyst is 5.0g, and the catalyst is granular; The absorbent is 30% Na ₂ CO ₃ -divinylbenzene resin, wherein Na ₂ CO ₃ accounts for 30% of the mass of the composite absorbent, and Na ₂ CO ₃ is uniformly mixed with the divinylbenzene resin, and the mass of the composite absorbent is 5.0g. The absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo340).

Example 3:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 50% HZSM-5-coconut shell activated carbon composite catalyst, wherein HZSM-5 accounts for 50% of the composite catalyst mass, HZSM-5 and coconut shell activated carbon are evenly mixed, the composite catalyst mass is 5.0g, and the catalyst is granular; the absorbent is 30% Na ₂ CO ₃ - divinylbenzene resin, wherein Na ₂ CO ₃ accounts for 30% of the composite absorbent mass, Na ₂ CO ₃ and divinylbenzene resin are evenly mixed, the composite absorbent mass is 5.0g, and the absorbent is grainy. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo 340).

Example 4:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -HZSM-5 composite catalyst, wherein Co2O3 accounts for 10% of the composite catalyst mass, Co ₂ O ₃ and HZSM-5 are evenly mixed, the composite catalyst mass is 5.0g, and the catalyst is granular; the absorbent is 30% CaO-divinylbenzene resin, in which CaO accounts for 30% of the mass of the composite absorbent, CaO and divinylbenzene resin are uniformly mixed, the composite absorbent mass is 5.0g, and the absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo340).

Example 5:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -HZSM-5 composite catalyst, in which Co ₂ O ₃ accounts for 10% of the mass of the composite catalyst, Co ₂ O ₃ and HZSM-5 are evenly mixed, the mass of the composite catalyst is 5.0g, and the catalyst is granular; The absorbent is 50% CaO-Na2CO3, of which CaO accounts for 50% of the mass of the composite absorbent, CaO and Na2CO3 are uniformly mixed, the composite absorbent has a mass of 5.0g, and the absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo 340).

Embodiment 6:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -45% HZSM-5-coconut shell activated carbon composite catalyst, in which Co ₂ O ₃ and HZSM-5 account for 10% and 45% of the composite catalyst mass, and Co ₂ O ₃ and HZSM-5 are uniform Mixed, the mass of the composite catalyst is 5.0g, the catalyst is granular; the absorbent is 30% Na ₂ CO ₃ -divinylbenzene resin, wherein Na ₂ CO ₃ accounts for 30% of the mass of the composite absorbent, Na ₂ CO ₃ and divinylbenzene The benzene resin is evenly mixed, the mass of the composite absorbent is 5.0g, and the absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo 340).

Embodiment 7:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -HZSM-5 composite catalyst, wherein Co2O3 accounts for 10% of the composite catalyst mass, Co ₂ O ₃ and HZSM-5 are evenly mixed, the composite catalyst mass is 5.0g, and the catalyst is granular; the absorbent is 50% phenolic resin-divinylbenzene resin, wherein the phenolic resin accounts for 50% of the mass of the composite absorbent, the phenolic resin and the divinylbenzene resin are uniformly mixed, the mass of the composite absorbent is 5.0 g, and the absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo 340).

Embodiment 8:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, saturated water vapor (RH=100%) at normal temperature, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -HZSM-5 composite catalyst, in which Co ₂ O ₃ accounts for 10% of the mass of the composite catalyst, Co ₂ O ₃ and HZSM-5 are evenly mixed, the mass of the composite catalyst is 5.0g, and the catalyst is granular; The absorbent is 30% Na ₂ CO ₃ -divinylbenzene resin, wherein Na ₂ CO ₃ accounts for 30% of the mass of the composite absorbent, and Na ₂ CO ₃ is uniformly mixed with the divinylbenzene resin, and the mass of the composite absorbent is 5.0g. The absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo 340).

Embodiment 9:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 10ppm NO, about 20% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -coconut shell activated carbon composite catalyst, wherein Co ₂ O ₃ accounts for 10% of the mass of the composite catalyst, Co ₂ O ₃ and coconut shell activated carbon are uniformly mixed, the mass of the composite catalyst is 5.0g, and the catalyst is granular; The absorbent is 30% Na ₂ CO ₃ -divinylbenzene resin, wherein Na ₂ CO ₃ accounts for 30% of the mass of the composite absorbent, and Na ₂ CO ₃ is uniformly mixed with the divinylbenzene resin, and the mass of the composite absorbent is 5.0g. The absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo340).

Example 10:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 10ppm NO, saturated water vapor (RH=100%) at normal temperature, about 20% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -HZSM-5 composite catalyst, wherein Co ₂ O ₃ accounts for 10% of the mass of the composite catalyst, HZSM-5 and coconut shell activated carbon are evenly mixed, the mass of the composite catalyst is 5.0g, and the catalyst is granular; The agent is 50% CaO-Na ₂ CO ₃ , in which CaO accounts for 50% of the mass of the composite absorbent, CaO and Na ₂ CO ₃ are uniformly mixed, the mass of the composite absorbent is 5.0g, and the absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo 340).

Example 11:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalyst is a 10% Co ₂ O ₃ -HZSM-5 composite catalyst, in which Co ₂ O ₃ accounts for 10% of the mass of the composite catalyst, Co ₂ O ₃ and HZSM-5 are evenly mixed, the mass of the composite catalyst is 5.0g, and the catalyst is granular; The absorption unit is an empty tube. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo 340).

Example 12:

The reactor and operating conditions are the same as in Example 1. The waste gas contains 500ppm NO, about 10% O ₂ , and the rest is N ₂ . The catalytic unit is an empty tube; the absorbent is 30% Na ₂ CO ₃ -divinylbenzene resin, of which Na ₂ CO ₃ accounts for 30% of the mass of the composite absorbent, Na ₂ CO ₃ and divinylbenzene resin are uniformly mixed, and the composite absorption The mass of the agent is 5.0g, and the absorbent is granular. The gas flow rate is 0.6L/min, the reaction is under normal temperature and pressure, and the NOx concentration at the inlet and outlet is detected and analyzed by a flue gas analyzer (testo340).

The purification efficiency of NOx under different conditions of each embodiment is shown in Table 1.

Table 1: NOx purification efficiency treatment effect under different conditions

Claims (7)

1. A method for purifying nitrogen oxides by solid-phase chemical absorption technology, characterized in that said method is: The nitrogen oxide exhaust gas to be treated is sequentially passed through a catalytic oxidation solid catalyst and a chemical absorption solid reagent to obtain purified exhaust gas; the catalytic oxidation solid catalyst is composed of two or more of carbon-based catalysts, molecular sieve catalysts or metal oxide catalysts Composition of _two or more catalysts; the chemical absorption solid reagent is a solid absorbent that reacts with NO and NO2 to generate nitro compounds. 2. The method according to claim 1, characterized in that: said solid absorbent is a composite absorbent composed of two or more absorbents of inorganic solid absorbent and organic polymer resin solid absorbent; The inorganic solid absorbent is sodium hydroxide, sodium carbonate, sodium bicarbonate, calcium carbonate, calcium hydroxide, potassium carbonate or potassium hydroxide; the organic polymer resin solid absorbent is styrene polymer, styrene-diethylene Benzene polymer, divinylbenzene polymer or polymer resin modified by carboxyl, nitro, sulfonic acid, amido functional groups. 3. The method according to claim 1 or 2, characterized in that: the carbon-based catalyst is activated carbon; the molecular sieve catalyst is ZSM-5 molecular sieve or beta molecular sieve with different silicon-aluminum ratios or all-silicon, with Li , Na, K, Rb, Mg, Ca, Fe, Co, Ni, Cu or Mn metal ion exchange HZSM-5, Hβ molecular sieve or metal oxide loaded HZSM-5, Hβ molecular sieve or zeolite molecular sieve; the metal oxide The catalyst is Mn, Cr, Co, Cu, Fe, Ni, Zn, Ti or Al metal oxide catalyst. 4. The method according to claim 1 or 2, characterized in that: the catalytic oxidation solid catalyst is 1 to 50% Co ₂ O ₃ -HZSM-5, 1 to 50% Co ₂ O ₃ -coconut shell activated carbon, 30-80% HZSM-5-coconut shell activated carbon or 1-20% Co ₂ O ₃ -30-55% HZSM-5-coconut shell activated carbon; the 1-50% Co ₂ O ₃ -HZSM-5 is Co ₂ For the composite catalyst of O ₃ and HZSM-5, 1-50% is Co ₂ O ₃ in the total mass percentage of the composite catalyst, and the rest of the catalytic oxidation solid catalyst is the same. 5. The method according to claim 2, characterized in that: the solid absorbent is 10-50% Na ₂ CO ₃ -divinylbenzene resin, 10%-80% phenolic resin-divinylbenzene resin , 10% to 80% CaO-Na ₂ CO ₃ or 10 to 50% CaO-divinylbenzene resin; the 10 to 50% Na ₂ CO ₃ -divinylbenzene resin is Na ₂ CO ₃ and divinylbenzene For the resin-like composite absorbent, 10-50% is Na ₂ CO ₃ in the total mass percentage of the composite absorbent, and the rest of the solid absorbent is the same. 6. The method according to claim 5, characterized in that: the solid absorbent is 30% Na ₂ CO ₃ -divinylbenzene resin, 30% CaO-divinylbenzene resin, 50% CaO-Na ₂ CO ₃ or 50% phenolic-divinylbenzene based resin. 7. The method according to claim 4, characterized in that: the catalytic oxidation solid catalyst is 10% Co ₂ O ₃ -HZSM-5, 10% Co ₂ O ₃ - coconut shell activated carbon, 50% HZSM-5- Coconut Shell Activated Carbon or 10% Co ₂ O ₃ -45% HZSM-5- Coconut Shell Activated Carbon.