138 results about "Urea decomposition" patented technology

A preferred process arrangement utilizes the enthalpy of the flue gas, which can be supplemented if need be, to convert urea (30) into ammonia for SCR. Urea (30), which decomposes at temperatures above 140 ° C., is injected (32) into a flue gas stream split off (28) after a heat exchanger (22), such as a primary superheater or an economizer. Ideally, the side stream would gasify the urea without need for further heating; but, when heat is required it is far less than would be needed to heat either the entire effluent (23) or the urea (30). This side stream, typically less than 3% of the flue gas, provides the required temperature and residence time for complete decomposition of urea (30). A cyclonic separator can be used to remove particulates and completely mix the reagent and flue gas. This stream can then be directed to an injection grid (37) ahead of SCR using a blower (36). The mixing with the flue gas is facilitated due to an order of magnitude higher mass of side stream compared to that injected through the AIG in a traditional ammonia-SCR process.

Disclosed are a process and apparatus for selective catalytic reduction of NO_x. The process is enabled by passing a heat exchanger section, such as an economizer, of the boiler in advance of an SCR unit at low load conditions to enable NO_x reduction even at low loads using urea instead of ammonia. In a preferred form, under high load conditions, the bypass can be almost fully closed and the economizer can be operated normally without excessively cooling the combustion gases, using only a portion of bypassed gases which are hot enough to decompose the urea into its active components including ammonia.

A preferred apparatus arrangement utilizes the enthalpy of the flue gas, which can be supplemented if need be, to convert urea (30) into ammonia for SCR. Urea (30), which decomposes at temperatures above 140.degree. C., is injected (32) into a flue gas stream split off (28) after a heat exchanger (22), such as a primary superheater or an economizer. Ideally, the side stream would gasify the urea without need for further heating; but, when heat is required it is far less than would be needed to heat either the entire effluent (23) or the urea (30). This side stream, typically less than 3% of the flue gas, provides the required temperature and residence time for complete decomposition of urea (30). A cyclonic separator can be used to remove particulates and completely mix the reagent and flue gas. This stream can then be directed to an injection grid (37) ahead of SCR using a blower (36). The mixing with the flue gas is facilitated due to an order of magnitude higher mass of side stream compared to that injected through the AIG in a traditional ammonia-SCR process.

This invention relates generally to the treatment of NOx in combustion flue gas. In certain embodiments, the invention relates to the use of a regenerative heat exchanger (RHE) to convert urea to ammonia in a side stream of flue gas. Ammonia and/or other urea decomposition products exit the heat exchanger, are mixed with the rest of the flue gas, and enter a selective catalytic reduction (SCR) unit for reduction of NOx in the flue gas. The use of an RHE significantly improves the thermal efficiency of the overall process. More particularly, in certain embodiments, the regenerative heat exchanger is a dual chamber RHE.

A method for reducing NOx emissions in the exhaust of a combined cycle gas turbine equipped with a heat recovery boiler and a catalyst effective for NOx reduction, wherein a slip stream of hot flowing exhaust gases is withdrawn from the primary gas flow after the catalyst at a temperature of 500° F. to 900° F. and directed through a fan to a continuous duct into which an aqueous based reagent is injected for decomposition to ammonia gas and the outlet of the continuous duct is connected to an injection grid positioned in the primary exhaust for injection of ammonia gas into the primary exhaust stream at a location upstream of the catalyst.

The invention discloses a technique to prepare ammonia from urea through thermolysis, comprising the steps that: step 1: a storage and dissolution system (1) for urea particles is set; step 2: a storage system (2) for urea solution is set; step 3: an urea thermolysis system is set; step 4: a waste liquid treatment system (4) is set; step 5: all systems of the whole technique are communicated; step 6: urea particles are stored and dissolved; step 7: urea is cleaved and ammonia is acquisited; and step 8: waste liquid is treated. The preparation method of ammonia of the invention has the advantages of low cost, simple operation, needing not high pressure, quick respond (the reaction can begin in 5 to 30 sec.), various heating means, and gas fuel or diesel and so on can be used.

The invention relates to a kind of Mg-Al hydrotalcite loaded bimetallic nano-catalyst and its preparation method, and relates to application of the catalyst system in oxidation of alcohol into corresponding carbonyl compounds. The catalyst preparation method consists of: 1) preparing an Mg-Al hydrotalcite carrier through a urea decomposition method; 2) loading the precursors of metal Pd and Au on the Mg-Al hydrotalcite surface; and 3) then reducing Pd (II) and Au (III) through NaBH4, thus obtaining the bimetallic nanometer particle catalyst. The catalyst provided in the invention has the advantages of high catalytic activity, good stability, separability, and easy recovery, thus being applicable to alcohol oxidation reactions in aqueous phases.

The invention relates to a two-way rotational flow cylinder type urea mixing device which comprises a nozzle base, a base supporting cover, a rotational flow pipe, a metal mesh ring, a supporting plate, a back rotational flow plate, a front rotational flow plate and a cylinder; the supporting plate is arranged inside the cylinder, a hole is formed in the front part of the supporting plate, the front rotational flow plate is installed inside the hole, the back rotational flow plate is installed at the rear part of the supporting plate, and the front rotational flow plate, the supporting plate and the back rotational flow plate form a mixing cavity inside the cylinder; the nozzle base, the base supporting cover, the rotational flow pipe and the metal mesh ring are sequentially fixedly connected from top to bottom, the base supporting cover penetrates through the hole in the cylinder and is fixedly connected with the cylinder, and the rotational flow pipe runs into the hole in the middle of the supporting plate to be fixedly connected with the supporting plate; the metal mesh ring stretches into the mixing cavity; the nozzle base, the base supporting cover, the rotational flow pipe and the metal mesh ring are inclined. On the condition of ensuring urea mixing uniformity, the crystallization problem that the urea decomposition efficiency is not high in an SCR system is solved.

An exhaust gas purification apparatus includes an oxidation catalyst provided in a passage through which exhaust gas flows, a urea decomposition accelerator, a selective catalytic reduction catalyst provided downstream of the urea decomposition accelerator and a urea water supplying device for supplying urea water to the urea decomposition accelerator. The urea decomposition accelerator is provided downstream end surface of the oxidation catalyst and has at least one of hydrophilic function and hydrolytic catalytic function.

The invention discloses a method and a device for spraying a reducing agent used for selective catalytic reduction (SCR) of NOx and belongs to the field of SCR of NOx. The method comprises the following steps of self-extracting out a small amount of flue gas in an area having a temperature of 500 to 900 DEG C in a boiler by a pressure difference, wherein the small amount of the extracted flue gas is used as urealysis flue gas, spraying a urea solution to the flue gas so that the urea solution is decomposed into ammonia and the ammonia is mixed with the flue gas, feeding back the mixed gas to a reactor for SCR of NOx, and carrying out denitration. The device comprises a denitration reducing agent channel of which one end is communicated with the area having a temperature of 500 to 900 DEG C in the boiler and the other end is communicated with an inlet flue gas channel of the reactor for SCR of NOx. The denitration reducing agent channel comprises a urealysis pipe, an ammonia/flue gas mixed gas pipe and an ammonia injection pipe, wherein the urealysis pipe, the ammonia/flue gas mixed gas pipe and the ammonia injection pipe are communicated orderly. The urealysis pipe is provided with a urea solution spray gun. The method and the device for spraying a reducing agent used for SCR of NOx have the advantages of low investment and operation costs, low energy consumption, high safety, high reliability and complete urealysis.

The application discloses a urea crystallization state monitoring method of a catalytic reduction reaction device and a storage medium. The method comprises the steps: obtaining exhaust effective energy and obtaining urea evaporation heat absorption energy; if the exhaust effective energy is greater than the urea evaporation heat absorption energy, obtaining a crystal elimination amount; otherwise, obtaining a crystal generation amount; obtaining the urea crystallization amount in the post-treatment according to the original crystallization amount, the crystal elimination amount and the crystal generation amount of the catalytic reduction reaction device; and if the urea crystallization amount in the post-treatment is greater than or equal to the urea crystallization amount limit value, triggering a de-crystallization treatment mode. According to the method provided by the invention, the crystallization state is judged on the basis of the difference between the real-time energy of thewaste gas and the energy required by urea decomposition, and when the crystallization amount of urea exceeds a threshold value, the de-crystallization treatment mode can be triggered in time, so thatcrystals are prevented from being further chemically reacted into stones, the conversion efficiency of the catalytic reduction reaction device is improved, and the risk of corrosion of an exhaust pipeis avoided.

The invention relates to a spinel-supported catalyst for dry reforming of coke oven gas and a preparation method of thereof and belongs to the technical fields of comprehensive utilization of metallurgical resources and preparation of catalysts. The spinel-supported catalyst is characterized in that large-specific surface area MgAl2O4 spinel with a mesoporous structure serves as a carrier, rare earth or a rare earth oxide solid solution serves as an aid, and one or two in Ni, Co, Ru, Pt and Pd are taken as active metal components, wherein the mass percent of the active metal components is 5-11 percent, and the mass percent of the aid is 0-5 percent. The large-specific surface area MgAl2O4 spinel with the mesoporous structure is prepared by adopting a uniform urea decomposition-template method, and the aid and the active metal components are impregnated step by step according to an impregnation method. By the catalyst prepared by the method, the carbon deposition tendency in the dry reforming reaction process of the coke oven gas can be effectively reduced; and the catalyst has the advantages of large specific surface area, high active metal dispersibility, high catalytic activity, high product selectivity and long service life.

The invention belongs to the field of purification of NOx in tail gas of diesel engines, and in particular relates to a selective urea decomposition catalyst taking a honeycomb metal alloy as a carrier and a preparation method for the catalyst. The catalyst consists of titanium dioxide, cerium dioxide and a phosphorus-containing compound; the mass/volume ratio of the catalyst to the carrier is 50-150g/L; and the catalyst comprises 5 to 25 mass percent of cerium dioxide, 70 to 90 mass percent of titanium dioxide and 1 to 10 mass percent of phosphorus-containing compound, namely CePO4. The catalyst can be firmly adhered to the metal alloy carrier; the titanium dioxide component in the catalyst has high ageing resistance, and when the temperature is lower than 600DEG C, the anatase crystalline phase cannot be converted to the rutile crystalline phase; and moreover, due to the metal alloy carrier, the active ingredients of the catalyst have low light-off temperature.

The invention discloses a method and device for evaluating the urea crystallization risk based on a steady-state working condition. According to the method for evaluating the urea crystallization risk based on the steady-state working condition, a urea crystallization risk coefficient eta is evaluated through three coefficients, including a quality coefficient eta m, a temperature coefficient eta t and an efficiency coefficient eta e. The urea crystallization risk coefficient is obtained through comprehensive calculation from the three aspects of quality, temperature and structure, the crystallization risk is quantified through a mathematical method, the urea crystallization threshold value can be obtained through calibration, the urea decomposition detailed mechanism is fused into the model, the chemical reaction path is expressed in the form of a mathematical equation, the influence of an SCR mixer on crystallization is quantified from the angle of SCR conversion efficiency, the urea crystallization risk coefficient is not a fixed formula and can be calibrated according to a bench steady-state test, and the method is deduced based on a urea crystallization basic principle and a mathematical formula and is high in reliability.

The invention belongs to the technical field of preparation of an inorganic non-metal magnetic nano-powder material and in particular relates to a preparation method of an alpha-Fe2O3 magnetic nano-powder material. The preparation method takes inorganic iron salt and urea as raw materials and comprises the following steps: dissolving Fe<3+> and the urea into water according to the mol ratio of no more than 5 to 1; controlling the concentration of the Fe<3+> to be 0.5mol/L to 3.0mol/L and stirring; raising the temperature to 85 DEG C to 98 DEG C and reacting; after reacting, centrifuging and separating; washing with distilled water and precipitating; drying sediment and grinding; putting the sediment into a program temprature controlling resistor furnace and calcining at 500 DEG C to 700 DEG C to obtain the alpha-Fe2O3 magnetic nano-powder material. The alpha-Fe2O3 magnetic nano-powder material is prepared by adopting the urea to uniformly disperse an iron source and carrying out urea decomposition reaction; the preparation method provided by the invention is simple in process, easy to operate, low in cost, low in equipment requirements and environmentally friendly; a product has uniform structure and shape and stable performances.

The invention discloses a method for preparing a visible-light-responsive nitrogen-doped TiO2 hollow nano material by adopting a TiOF2 nanocube as a template and urea as a nitrogen source. The TiOF2 nanocube with a cubic structure is obtained by using a solvothermal method. The method comprises the steps that the TiOF2 nanocube powder and different amount of urea are put together in a sealed tubular furnace for heating treatment, NH3 generated from urea decomposition participates in the process that the TiOF2 is heated for decomposition to cause reconstruction of crystal lattices and generate TiO2, so that the N doping is realized; and the products form a hollow cubic box structure, and the surface is formed by TiO2(001) crystal surfaces. According to the method, the doping amount of nitrogen in products can be simply controlled by controlling the use amount of the urea, so that the absorption range and the absorption intensity of the products in a visible-light area can be regulated. The method disclosed by the invention has the advantages that the operation is simple, the applicable reaction temperature is wider, and the use amount and the proportion of the materials can be regulated in a larger range, so that the controllability is good and the universality is very strong.

The present invention discloses one kind of non-protein nitrogen feed additive for ruminant and its production process. The non-protein nitrogen feed additive has reasonable recipe, easy production, low cost, high decomposition speed, urea decomposing speed matching the utilization speed of rumen to avoid ammonia accumulation in blood and good taste. The non-protein nitrogen feed additive consists of urea 35-50 wt%, corn starch 35-48 wt%, and coating material 2-20 wt%, and its production process includes the steps of dispersing urea and corn starch in coating material solution, grinding in a colloid mill to form emulsion, and spray drying at normal temperature to form microspherical feed additive. It may be also produced into powder, granule, tablet or capsule.

The invention discloses a preparation method of a lithium ion battery positive electrode material. According to the preparation method disclosed by the invention, the LiNi0.8Co0.1Mn0.1O2 nanoparticlesare synthesized by adopting a simple hydrothermal-calcining two-step method; when a precursor is prepared by using a hydrothermal synthesis method, a surfactant cetyltrimethylammonium bromide (CTAB)is added to achieve the effects of increasing the nucleation rate of crystals and refining crystal particles, and ammonia gas released by urea decomposition is used for providing an alkaline environment for a reaction solution; and in the lithium mixing and calcining stage, two-stage sintering is carried out, so that secondary recrystallization is facilitated. The method is simple to operate and low in cost; the condition that the technological factors such as the pH and the stirring speed of the solution needs to be controlled when the precursor is prepared by a coprecipitation method is avoided, good conditions are provided for further modification research of the high-nickel ternary cathode material, the diameter of spherical particles of the prepared lithium ion battery cathode material ranges from 100 nm to 300 nm, the structural stability is good, and the electrochemical performance is good.

The invention belongs to the technical field of diesel engine postprocessing, which particularly relates to a diesel engine SCR (selective catalytic reduction) system control method based on the urealysis efficiency. The diesel engine SCR system control method based on the urealysis efficiency comprises the following steps: firstly, proposing a concept of urealysis efficiency, and giving the expression eta=f(t,v,q) of the concept; on the basis, formulating one set of diesel engine SCR system control method; according to the revolving speed and the load percentage by weight of the diesel engine, obtaining the diesel engine exhaust gas flow and the concentration of NOx in exhaust gas by the static MAP picture of the diesel engine so as to solve the basic injection amount Q1 of urea aqueous solution; correcting Q1 by the urealysis efficiency to obtain Q2 which is the injection amount of the urea aqueous amount under the steady state; carrying out transient correction to Q2 by considering the transient condition of the diesel engine; and obtaining the injection amount Q3 of the urea aqueous solution, which is practically required by the diesel engine finally. According to the diesel engine SCR system control method based on the urealysis efficiency, which is disclosed by the invention, the parameter of the urealysis efficiency is introduced in, the injection amount of the urea aqueous solution can be precisely given according to different operation conditions of the diesel engine, and the NH3 leakage rage is effectively lowered while the high-efficiency conversion of NOx is realized.