A method of converting ammonia
(57) Abstract:The invention relates to processes of high-temperature catalytic conversion of ammonia to two-stage catalytic system, in the production of nitric and hydrocyanic acid, and has synthesis. The essence of the method consists in passing the reaction gas mixture containing ammonia and oxygen-containing gas through a two-stage catalytic system in which the first step in the direction of gas flow is a layer of platinum mesh, and the second stage catalytic systems use 2 - 5 spatially separated layers of catalyst a regular cell structures, each separate layer of the catalyst honeycomb structure have a distance of less than 60 mm from the adjacent layer, mainly at the distance of 0.5-1 wall thickness of the channel of the block between catalyst honeycomb structure include a gas-permeable inert material. The technical result is to increase the yield of the target product and increase the service life of the catalyst of the first stage. 9 C. p. F.-ly. The invention relates to processes of high-temperature catalytic conversion of ammonia to two-stage Catala what is a grid layer, made of alloys containing platinum, and the second stage catalysts containing noble metals. The scope of the invention extends to the use of nitrogen and hydrocyanic acid, and has synthesis.High-temperature catalytic conversion of ammonia is carried out usually at atmospheric and elevated pressures (0.1 - 1.8 MPa) is woven or knitted from the platinum filaments grids (an alloy of platinum with rhodium or platinum with rhodium, palladium and / or other platinum group metals). The reaction is accompanied by intense heat, comes with extremely high speed and is limited by mass transfer processes.The temperature of the gas in the production of hydrocyanic acid at a pressure of 0.2 MPa can reach 1300oC.In the production of nitric acid in the conversion of ammonia to nitric oxide at a pressure of from 0.7 to 1.8 MPa optimum temperature grids is 900-940oC and the output of oxides of nitrogen of about 95%. At atmospheric pressure the process occurs at 810 - 870oC with access 97 - 98%. The rest of the ammonia is consumed in the formation of nitrogen. The conversion of ammonia are characterized by small hydrodynamic Chem. and Ind. 4, 21(1981)114]. Depending on the process conditions, the service life of the platinum package nets ranges from 1.5 to 16 months.For all processes of high-temperature ammonia conversion performed on the platinum grids are characterized by significant loss of platinum during the industrial process.When carrying out catalytic reactions on platinum there is loosening of the corrosion resistance of the surface of the catalyst. Education during the oxidation of ammonia crystal structures is accompanied by an increase up to 20 times the catalyst surface (increasing the diameter of the platinum catalyst of the thread) and losses of platinum in the form volatile oxides of platinum (chemical loss) and mechanical entrainment of catalyst particles.By the end of the path, the first surface along the gas grid is reduced, mainly as a result of loss of platinum. Catalytic corrosion proceeds at different speeds depending on the location of the platinum mesh in the package. Correspondingly change as the surface of each grid, and loss of platinum for each grid. During the run the nets loss of platinum, accompanying the corrosion of the surface meshes can SOS the reagents is much higher what is characteristic to produce nitric acid, catalytic grid more fragile and tends to fusion grids. Loss of platinum also depend on the physico-chemical properties of the alloy.However, to a much greater extent than by the composition of the catalyst, loss of platinum depends on technological parameters and structural design process. In systems under pressure process is carried out at a higher temperature. Increase the tension of the catalyst, the linear velocity and the gas density. As a consequence, the direct loss of catalyst (for mileage) is significantly higher than at atmospheric pressure, which leads to a much shorter lifetime of service grids. Measurements of the velocity distribution in the contact devices shows that there is considerable heterogeneity of the flow cross section of the apparatus. Despite the use of different switchgear design for one-third area of the catalyst ammonia mixture can be almost three times greater rate than through the remaining two thirds of the area. Changing hydrodynamic conditions in the Converter has a significant influence on the magnitude of the losses of platinum.Layer regulationid nets allows not only to reduce the attachment of platinum by reducing the number of nets in the first stage, but also to reduce losses in the process of mileage grids while maintaining production of the product [RF Patent N 2100068, IPC 6 B 01 J 23/78, BI No. 36, 1997].Closest to the proposed technical solution is the method of catalytic oxidation of ammonia, which consists in passing the reaction gas mixture containing ammonia and oxygen, through a two-stage catalytic system in which the first step in the direction of gas flow is a layer of platinum mesh, and the second stage - one cell layer of the catalyst of the regular patterns, and the jets of the gas mixture moving in the cell channels of the catalyst supporting ratio of the average operating speed to the speed of sound in these conditions, in the range of 4.8 to 10-4- 0,024 [RF Application N 97118457/25, IPC 6 C 01 B 21/26, B N 21, 1998].The oxidation of ammonia as in the first stage (platinum mesh) and second stage (block catalyst), the process proceeds in vneshnediffuzionnoe mode. The efficiency of the oxidation process is determined by the rate of mass transfer between the surface of the catalyst (platinum grid block of the catalyst and the gas phase. Under any along the length of the channel everywhere except the input section of the unit. Due to the unsteady nature of the flow of gas at the entrance to block the catalyst mass transfer coefficients in these areas 3-5 times higher than the average for the length of the block. Thus, if instead of one block length of 100 mm will be installed 2 units of 50 mm, this will lead to an increase in the degree of conversion of ammonia. At the same time due to the unsteady nature of the flow of gas at the inlet sections of the channels in block catalyst increases the hydraulic resistance of the whole system. This leads to improved homogeneity of the hydrodynamic conditions in the catalyst bed. Thus, there will be a reduction of the initial discontinuity of the velocity field characteristic for a given reactor design. As a consequence, reduced local heterogeneity speed on individual sections of the platinum mesh and significantly reduces the loss of platinum.The problem to which the present invention is directed, is to increase the yield of the target product, for example, in the process of nitric acid, and it has synthesis nitric oxide, in the process of obtaining hydrogen cyanide is HCN.The problem is solved by passing the reaction gas mixture, sternly along the gas layer is a platinum mesh, and the second stage catalytic systems use 2 - 5 spatially separated layers of catalyst a regular cell structure. Each individual layer of the catalyst honeycomb structure have a distance of less than 60 mm from the adjacent layer, mainly at the distance of 0.5-1 wall thickness of the channel of the block between catalyst honeycomb structure include a gas-permeable inert material. The height of each layer of the catalyst honeycomb structure is not more than 0.5 Re dewhere Re is the Reynolds number, equal to 1 5 104de- hydraulic diameter of the channel of the catalyst is 1 to 20 mmThe ratio of the value of the hydraulic resistance of the second stage catalytic system to the value of the hydraulic resistance of the first is 0.2 - 4.In the process using the catalyst of honeycomb structure, porosity, characterizing the volume of voids or open surface of which is 0.1 to 0.6, the thickness of which (0,1 - 1,0) dewhere de- hydraulic diameter of the channel of the catalyst is 1 to 20 mmA catalyst honeycomb structure contains the oxides of the base metals and represents the mixed oxides total is - cations of Mn, Fe, Ni, Co, Cr, Cu, V or mixtures thereof, x = 0 - 2, y = 1 - 2, z = 0.8 - 1.7; MemOn- aluminium oxide and/or silicon oxide, zirconium, chromium, aluminum silicates, oxides of rare earth elements (REE), or mixtures thereof, m = 1-3, n = 1-2, k and f - wt.%, when the ratio k/f = 0.01 - 1, wt.%: iron oxide 70-94, aluminum oxide 1-29, silicon dioxide and/or oxides of rare-earth elements, zirconium oxide 1-29, specific surface area is greater than 5 m2/,The invention is illustrated by the following examples.Example 1. (Prototype). The process carried out at the industrial unit of production of weak nitric acid to the diameter of the reactor for the oxidation of ammonia 1500 mm oxidation of ammonia to nitric oxide is carried out on a two-stage catalytic system, where the first stage in the direction of gas flow have a catalytic package consisting of 9 woven platinum mesh wire diameter of 0.092 mm number of holes 1024 on 1 cm2with the composition of the platinum alloy: Pt - 81, Pd - 15, Rh - 3.5 and Ru - 0.5%. As the second stage in the direction of gas flow using a single layer cell block catalyst height 100 mm, with hydraulic diameter of the channel 7 mm and a wall thickness of 1 mm, a Porosity of the catalytic unit 0.77. Cell catalyst has a composition, by weight. %: Fe2O3- 70, Al
FIELD: chemical industry; production of nitric acid.
SUBSTANCE: the invention is dealt with production of nitric acid with the help of oxidation of ammonia by oxygen of the air and absorption of nitrogen oxides by water in installations with uniform pressure at the stages of oxidation of ammonia and absorption of nitrogen oxides. The method of production of nitric acid in the installations with uniform pressure at the stages of oxidation of ammonia and absorption of nitrogen oxides provides, that compression of the air up to a uniform terminal pressure is conducted continuously within one stage without intermediate cooling and after that the compressed and so heated air is divided into two streams, one of which intended for production of nitric acid is directed to be cooled with further mixing with ammonia, and another is fed directly into a fuel combustion chamber connected with a recuperation turbine. The design embodiment of the installation for production of nitric acid provides for usage in the gas-turbine plant as an air engine for compression of air of an axial-flow compressor mounted directly on a common shaft with the recuperation turbine, at which near the outlet of the air engine the line of a compressed air stream is divided into two parts, one of which intended for production of nitric acid is first connected with a compressed air cooler and then with a mixer of ammonia with air, and the second intended for incineration of fuel is directly connected with the recuperation turbine combustion chamber. Besides in the capacity of a the compressed air cooler they use a "boiling" economizer connected to a line of a feed water for a boiler-utilizer and with a vapor collector of the boiler-utilizer by a line of steam-and-water mixture. The line of the air intended for production of nitric acid is also connected through the reheater of ammonia with a nitric acid blowing column. The technical result is simplification of the method, decreased investments and specific consumption of fuel.
EFFECT: the invention ensures simplification of the method, decreased investments and specific consumption of fuel.
4 cl, 1 dwg
FIELD: chemical industry.
SUBSTANCE: the invention is pertinent to the field of chemical industry, in particular to production of a catalysts and processes of oxidation of ammonia in production of a weak nitric acid. The invention offers an ammonia conversion catalyst on the basis of the mixture of oxides of unitized structure and a method oxidation of ammonia in production of weak nitric acid. The catalyst represents a mixture of oxides of the over-all formula (AxByO3Z)k (MmOn)f, (NwPgvOv)r where: A - cation of Ca, Sr, Ba, Mg, Be, Ln or their mixtures; B - cations of Mn, Fe, Ni, Co, Cr, Cu, V, A1 or their mixtures; x=0-2, y=1-2, z=0.8-l.7; M - A1, Si, Zr, Cr, Ln, Mn, Fe, Co, Cu, V, Ca, Sr, Ba, Mg, Be or their mixtures; m=l-3, n=l-2; N - Ti, Al, Si, Zr, Ca, Mg, Ln, W, Mo or their mixtures, P - phosphorus, O - oxygen; w=0-2, g=0-2, v=l-3; k, f and r - mass %, at a ratio (k+f)/r=0-l, f/r=0-l, k/f = 0-100. The catalyst is intended for use in a composition of a two-stage catalytic system generated by different methods, also in a set with the trapping platinoid screens and-or inert nozzles. The technical result ensures activity, selectivity and stability of the catalyst to thermocycles at its use in two-stage catalytic system with a decreased loading of platinoid screens.
EFFECT: the invention ensures high activity, selectivity and stability of the catalyst to thermocycles at its use in two-stage catalytic system with a decreased loading of platinoid screens.
8 cl, 1 tbl, 5 ex
FIELD: initiating ammonia conversion reaction.
SUBSTANCE: proposed method is performed on reticular platinoid catalyst by passing the ammonia-containing gas mixture and oxygen-containing gas through it; local sections of catalyst surfaces are periodically heated to reaction initiating temperature by means of linear electric heating elements located directly on catalyst surface. Equivalent diameters of local sections of catalyst surface are selected between 1-5 of magnitude of external equivalent diameter of separate electric heating element; linear electric heating elements are connected to electric power source at duty factor from 20 to 1 s. Used as material for reticular platinoid catalyst are the following alloys: Pt-81, Pd-15, Rh-3.5 and Ru-0.5 mass-%; Pt-92,5, Pd -4.0 and Rh -3.5 mass-%; Pt-95 and Rh-5 mass-%; Pt-92.5 and Rh-7.5 mass-%. Initiating the ammonia conversion reaction by this method is performed in reactors for production of nitric and hydrocyanic acids and hydroxylamine sulfate.
EFFECT: reduction of time required for reaction over entire surface of catalyst; reduction of explosion danger.
2 cl, 10 ex
FIELD: inorganic compounds technologies.
SUBSTANCE: invention relates to ammonia conversion processes based on two-step catalytic system, which can be employed in production of nitric and hydrocyanic acids and in hydroxylamine sulfate production. Process according to invention comprises passing gaseous ammonia- and oxygen-containing mixture through two-step catalytic system, wherein first downstream step is embodied in a wire catalytic grate stack and second step in one or several layers of block honeycomb material, ratio of second-step hydraulic resistance value to the first-step one exceeding 4. Catalytic system steps are spaced from each other by distance equal to at most 10 and preferably 0.5 to 2 effective thickness of block channel σ calculated in terms of formula σ=2(S/(πn)1/2 (1-ε1/2), wherein S represents honeycomb block cross-section area, n number of channels in block, and ε open surface of block. Spacing between the steps is achieved by positioning between them spacing layer of gas-permeable chemically inactive material having hydraulic resistance coefficient below 100, hydraulic resistance of the second step being calculated as summary value of hydraulic resistances of honeycomb and spacing layers.
EFFECT: increased yield of desired products.
4 cl, 6 ex
FIELD: methods and devices for supporting of the catalytic meshes in the burners for oxygenation of ammonia.
SUBSTANCE: the invention is pertaining to the support system for catalytic meshes in the burners for oxygenation of ammonia and to the method of reduction of movement of the particulates of the ceramic substance caused by the thermal expansion. The support system consists of the catalytic meshes (1) and possibly, of the support sieves (2) which are supported by the ceramic filling agents placed in the burner box with metallic walls and the perforated bottom. The support structure (9) is attached to the metallic wall (4) and-or the outer part of the periphery of the bottom (5). The technical result of the invention is development of the support structure, which does not cause damage of the packet from the catalyzer during operation of the burner, and the development of the system preventing movement of the of the particulates of the ceramic substance.
EFFECT: the invention ensures development of the support structure, which does not cause damage of the packet from the catalyzer during operation of the burner, and the development of the system preventing movement of the of the particulates of the ceramic substance.
12 cl, 2 dwg, 2 tbl
FIELD: chemical industry; method of intensification of the installations for production of the non-concentrated nitric acid.
SUBSTANCE: the invention is pertaining to the method of intensification of the installations for production of the non-concentrated nitric acid and may be used for raising productivity of the installations for production of the non-concentrated nitric acid under pressure. The invention provides for creation of the excess pressure on the inlet of the air compressor by preliminary compression of the atmospheric air in the high-pressure fan. At that the heat of the compression process in the warm season of the year is withdrawn by the direct contact with the water at the inlet of the fan, and in the cold season the heat is used for heating, at that in full or partially excluding heating of the air in the preheater mounted to prevent the icing up of the guiding apparatuses of the air compressor. At the enterprises with the high degree of the air dusting or chemical pollution for the contact cooling of the air by water it is possible to use scrubbers-washers, which combine the functions of the air cooler and the purification device. The method is effective for the operating installations, in which as a result of the wear-out of the flow-through section of the air compressors and the gas turbines decreases not only productivity, but also the pressure in the system, and as the result of it the concentration of the nitric acid. The method allows to realize the intensification of the installations using already existed equipment due to the increased pressure in the system. Concentration of the nitric acid is not lowered, the degree of purification of the tailing gases is preserved, production cost and the specific consumption of the steam and the natural gas are reduced.
EFFECT: the invention allows to realize the intensification of the installations using already existed equipment, to reduce production cost and the specific consumption of the steam and the natural gas.
4 cl, 2 ex, 2 tbl, 2 dwg
FIELD: chemical industry; methods of manufacture of the building structures.
SUBSTANCE: the invention is pertaining to the field of the chemical industry, in particular, to production of the nitric acid, nitric fertilizers, the cyanhydric acid, the nitrites and nitrates and to other productions of chemical products, where the flow sheet of production provides for the catalytic conversion of ammonia up to the nitrogen oxides with usage of the platinoid mesh catalytic agents. The platinoid mesh catalytic agent formed in the form of the catalytic package produced out of the layer-by-layer stacked wire catalytic meshes and weaved out of the wires with the diameter of 0.06-0.1 mm consisting of the alloys of platinum with rhodium, palladium, ruthenium and other metals of the platinum group differs that the catalytic package consists of two different in the geometry of the braiding types of the meshes sequentially alternating in the height of the package. At that the geometry of the braiding of the first type of the catalytic meshes is characterized by the number of the wires interlacing per 1 cm2 in the interval of 1024-450, and the geometry of the braiding of the second type of the catalytic meshes is characterized by the number of the wires interlacing per 1 cm2 in the interval of 400-200. The technical result of the invention is the increased conversion of ammonia and the decreased share of the platinoids included in the mesh catalytic agent production processes providing for the catalytic conversion of ammonia in the flow sheet of the chemical goods production.
EFFECT: the invention ensures the increased conversion of ammonia and the decreased share of the platinoids included in the mesh catalytic agent production processes providing for the catalytic conversion of ammonia in the flow sheet of the chemical goods production.
FIELD: inorganic synthesis catalysts.
SUBSTANCE: decomposition if N2O under Ostwald process conditions at 750-1000°C and pressure 0.9-15 bar is conducted on catalyst, which comprises (A) support composed of α-Al2O3, ZrO2, SeO2, or mixture thereof and (B) supported coating composed of rhodium or rhodium oxide, or mixed Pd-Rh catalyst. Apparatus wherein N2O is decomposed under Ostwald process conditions on the above-defined catalyst is also described. Catalyst is disposed successively downstream of catalyst grids in direction of stream of NH3 to be oxidized.
EFFECT: increased catalyst activity.
8 cl, 2 tbl, 3 ex
FIELD: inorganic synthesis catalysts.
SUBSTANCE: invention relates to catalytic elements including ceramic contact of regular honeycomb structure for heterogeneous high-temperature reactions, e.g. ammonia conversion, and can be used in production of nitric acid, hydrocyanic acid, and hydroxylamine sulfate. Described is catalytic element for heterogeneous high-temperature reactions comprising two-step catalytic system consisting of ceramic contact of regular honeycomb structure made in the form of at least one bed constituted by (i) separate prisms with honeycomb canals connected by side faces with gap and (ii) platinoid grids, ratio of diameter of unit honeycomb canal to diameter of wire, from which platinoid grids are made, being below 20.
EFFECT: increased degree of conversion and degree of trapping of platinum, and prolonged lifetime of grids.
5 cl, 6 ex
SUBSTANCE: invention pertains to the method of obtaining porous substances on a substrate for catalytic applications, to the method of obtaining porous catalysts for decomposition of N2O and their use in decomposing N2O, oxidising ammonia and reforming methane with water vapour. Description is given of the method of obtaining porous substances on a substrate for catalytic applications, in which one or more soluble precursor(s) metal of the active phase is added to a suspension, consisting of an insoluble phase of a substrate in water or an organic solvent. The suspension undergoes wet grinding so as to reduce the size of the particles of the substrate phase to less than 50 mcm. The additive is added, which promotes treatment before or after grinding. A pore-forming substance is added and the suspension, viscosity of which is maintained at 100-5000 cP, undergoes spray drying, is pressed and undergoes thermal treatment so as to remove the pore-forming substance, and is then baked. Description is also given of the method of obtaining porous catalysts on a substrate for decomposing N2O, in which a soluble cobalt precursor is added to a suspension of cerium oxide and an additive, promoting treatment, in water. The suspension is ground to particle size of less than 10 mcm. A pore-forming substance, viscosity of which is regulated to approximately 1000 cP, is added before the suspension undergoes spray drying with subsequent pressing. The pore-forming substance is removed and the product is baked. Description is given of the use of the substances obtained above as catalysts for decomposition of N2O, oxidation of ammonia and reforming of methane with water vapour.
EFFECT: obtaining catalysts with homogenous distribution of active phases and uniform and regulated porosity for optimisation of characteristics in catalytic applications.