CN101870480B - Method for preparing ammonia gas from urea solid by dry pyrolysis - Google Patents

Method for preparing ammonia gas from urea solid by dry pyrolysis Download PDF

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CN101870480B
CN101870480B CN2010102109570A CN201010210957A CN101870480B CN 101870480 B CN101870480 B CN 101870480B CN 2010102109570 A CN2010102109570 A CN 2010102109570A CN 201010210957 A CN201010210957 A CN 201010210957A CN 101870480 B CN101870480 B CN 101870480B
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pyrolysis
gas
urea
pyrolysis oven
temperature
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CN101870480A (en
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黄丽娜
卢作基
徐晓亮
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CHINA CONSTRUCTION POWER AND ENVIRONMENT ENGINEERING Co.,Ltd.
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Nanjing No7425 Factory Of Zhongche Group
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

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Abstract

The invention discloses a method for preparing NH3 from a urea solid by dry pyrolysis. The method comprises the following steps of: delivering the urea solid into a pyrolysis oven by using a quantitative feeding device, wherein the feeding amount is adjusted corresponding according to actually-measured NOx amount in smoke gas; inputting high-temperature gas delivered by a high-temperature fan into the pyrolysis oven by using a flowmeter, wherein the high-temperature gas is fully contacted with urea; the urea is heated and decomposed into isocyanic acid and ammonia gas; and the isocyanic acid undergoes a further reaction with water vapor in the high-temperature gas so as to generate the ammonia gas and carbon dioxide; and replenishing heat supply when needed by using an electric heater in the pyrolysis oven, wherein pyrolysis gas is taken as a reducing agent used for removing NOx by selective catalyctic reduction and introduced into an ammonia spray grid after being exhausted from the pyrolysis oven. The method has the advantages of elimination of urea dissolving and solution storing steps, no water consumption, low energy consumption in a pyrolytic process, energy supply from a photovoltaic system, simple system technology, small floor area and low running cost.

Description

A kind of method of preparing ammonia gas from urea solid by dry pyrolysis
Technical field
The present invention relates to a kind of method of preparing ammonia gas from urea solid by dry pyrolysis, be specifically with urea solid directly in the pyrolysis oven pyrolysis, produce and to be used for SCR (SCR) and to remove flue gas NO XReductive agent NH 3, belong to oxynitride (NO in the coal-fired flue-gas X) process field.
Background technology
Existing coal-fired flue-gas is removed NO XTechnology in, selective catalytic reduction (SCR) is that denitration efficiency is the highest, develops the most sophisticated denitration technology.Reductive agent NH in the SCR technology 3The source mainly contain three kinds: liquefied ammonia, ammoniacal liquor and urea.Liquefied ammonia and ammoniacal liquor belong to hazardous substance, and strict provisions of laws and regulations is all arranged in storage and transportation.Comparatively speaking, urea is nontoxic, harmless chemical, is easy to transportation and preservation, does not need special security measures.
The method that urea is produced ammonia mainly adopts pyrogenic silica.Instability when urea is higher than 150 ℃ in temperature can resolve into NH 3And HNCO, and HNCO and water reaction generate NH 3And CO 2, reaction formula is following:
CO(NH 2) 2→NH 3+HNCO(1)
HNCO+H 2O→NH 3+CO 2(2)
Existing pyrolysis Ammonia Process mainly adopts 40%～60% urea soln, sprays into the pyrolysis chamber through after the special nozzle atomization, and the high temperature air mixed pyrolysis with coming via dilution blower fan and electric heater conveying generates NH 3, H 2O and CO 2, degradation production and diluent air mix and spray into denitrating system.The problem that existing technology exists is:
(1) dissolving of urea and solution store and all need be equipped with related device and utility appliance, and need additive decrementation steam, complex process, and floor space is big;
(2) urea soln easy and crystalline must be accompanied heat to all relevant container and pipelines, temperature is remained on the corresponding Tc, and there is certain corrodibility in urea soln, and the material of equipment and pipeline is had higher requirements;
(3) consume energy except urea decomposition in the pyrolytic process, evaporation of water also needs lot of energy in the solution, and for satisfying these energy consumption demands, the high temperature air temperature generally is controlled at more than 600 ℃, and the material of electric heater needs resistant to elevated temperatures steel alloy, and cost significantly improves;
(4) being used for the water of dissolved urea, strict requirement is arranged, must be pure water (water of condensation, water desalts); As without pure water, must use respective additive stable, because unpurified water can cause denitrating catalyst obstruction and sulphur/metal murder by poisoning etc., thereby shorten catalyst life, improve the reductive agent consumption, increase cost of investment; And the pyrolysis gas that generates contains unnecessary steam, and denitration efficiency is had certain restraining effect.
Summary of the invention
In order to overcome the deficiency of prior art, the object of the present invention is to provide a kind of energy-conservation, urea solid by dry pyrolysis system NH efficiently 3Method, a series of problems of avoiding existing process using urea soln pyrolysis to be produced.
In order to realize above-mentioned technical problem, the present invention is through urea solid by dry pyrolysis system NH 3Technical scheme realize, comprise the steps:
(1), the urea solid in the urea solid storage tank is transported to pyrolysis oven through measurement charging device, feeding quantity is discharged the NO that surveys in the flue gas according to boiler XMeasure corresponding adjusting;
(2), the high-temperature gas of high-temperature blower conveying is imported pyrolysis oven through under meter from the pyrolysis oven bottom; In the pyrolysis oven uphill process, fully contact with urea solid; Urea solid decomposes under the effect of high-temperature gas generates isocyanic acid and ammonia; Steam in isocyanic acid and the high-temperature gas further reacts and generates ammonia and carbonic acid gas, and the electric heater complementary heating is installed in the pyrolysis oven when needed;
(3), pyrolysis gas is imported into ammonia-spraying grid after pyrolysis oven is discharged, remove NO as SCR XReductive agent.
Described urea solid by dry pyrolysis system NH 3Method, said hot-gas temperature is 250～450 ℃, vapour content satisfies the demand that isocyanic acid changes ammonia and carbonic acid gas into, flow generates the ammonia amounts greater than 19 times of pyrolysis.
Described urea solid by dry pyrolysis system NH 3Method, said high-temperature gas is the flue gas of 0.3%～1% economizer exit, or wind at air preheater place 0.5%～1% or secondary air.
Described urea solid by dry pyrolysis system NH 3Method; Said pyrolysis oven Outlet Gas Temperature is in 300～400 ℃ of intervals; If the high-temperature gas shortage of heat, when pyrolysis gas is lower than 300 ℃, electric heater of installing in the pyrolysis oven and the heating system supplementary heating that is equipped with the photovoltaic generating system composition of accumulator system.
The invention has the beneficial effects as follows:
(1) saved urea dissolving and solution storing step, without heating for dissolving water, insulated tank, pipeline has been mixed heat, do not had the consumption of steam, and reduce related device, made technology simple, floor space is little;
(2) crystallization and the corrosive pipeline problem of avoiding urea soln to bring;
(3) direct pyrolysis urea solid, less energy consumption, and also the energy of heating is provided by the photovoltaic generating system that is equipped with accumulator system;
(4) moisture content is few in the pyrolysis gas, does not influence follow-up denitration effect.
Description of drawings
Fig. 1 is urea solid by dry pyrolysis system NH of the present invention 3The device synoptic diagram.
The explanation of main mark is following in the accompanying drawing 1: 1. urea solid storage tank, and 2. measurement charging device, 3. pyrolysis oven, 4. under meter, 5. high-temperature blower 6. is equipped with the photovoltaic generating system of accumulator system, 7. electric heater, 8. ammonia-spraying grid.
Embodiment
Below in conjunction with accompanying drawing the present invention is further specified.
Fig. 1 is urea solid by dry pyrolysis system NH of the present invention 3The device synoptic diagram, with reference to shown in Figure 1, a kind of urea solid by dry pyrolysis system NH 3Device, comprise urea solid storage tank 1, measurement charging device 2, pyrolysis oven 3, high-temperature blower 5, electric heater 7 and be equipped with the photovoltaic generating system 6 of accumulator system.Wherein, urea solid storage tank 1 is mounted to pyrolysis oven 3 through measurement charging device 2; The bottom of pyrolysis oven is connection traffic meter 4 and high-temperature blower 5 successively; Be provided with electric heater 7 in the pyrolysis oven, the photovoltaic generating system 6 that is equipped with accumulator system is connected with electric heater 7; The pyrolysis oven outlet links to each other with ammonia-spraying grid 8.
Said pyrolysis oven 3 adopts the alloy steel products preparation, and the middle part is provided with expansion joint, can reduce the steel stress influence of being heated.According to the high-temperature gas flow and the residence time, design pyrolysis oven volume.Urea solid pyrolysis institute energy requirement is mainly provided by high-temperature gas, and the pyrolysis oven Outlet Gas Temperature is in 300～400 ℃ of intervals; Be lower than 300 ℃ if detect pyrolysis gas; The heating system complementary heating that the photovoltaic generating system of electric heater and outfit accumulator system is formed; Make the abundant decomposes of urea become gas; Can effectively remove the urea solid of carrying secretly in the air-flow like this, prevent that urea solid is deposited on the SCR catalyzer, improves its purity.
Embodiment
Below in conjunction with certain 50MW engineering denitrating flue gas project the present invention is further described:
The original design data: this project exhaust gas volumn is 211600Nm 3/ h, 320 ℃ of cigarette temperature, moisture content are 9%, denitration efficiency 48%, the escaping of ammonia rate 3ppm, urea nitrogen content 46%.
(1) urea solid in the urea solid storage tank 1 is transported in the pyrolysis oven 3 by measurement charging device 2.The feeding quantity of urea is according to denitration unit load signal and from flue gas NO xThe feedback of analyser or CEM system is controlled in real time.Calculation formula is:
G = 0.625 K · Q · C NO × 10 - 4 η kg / h , - - - ( I )
Wherein K is NH 3/ NOx mol ratio; Q is an exhaust gas volumn, Nm 3/ h; C NOBe actual measurement NO volume content in the flue gas, μ L/L; η is a urea nitrogen content, %.The content that measures NO in real time is 200 μ L/L, and the urea amount that then adds pyrolysis oven 3 in real time is 29kg/h.
The flue gas of (2) drawing total exhaust gas volumn about 0.3% from economizer exit is carried by high-temperature blower 5 as high-temperature gas, and under meter 4 metering backs get into pyrolysis oven from pyrolysis oven 3 bottoms.High-temperature gas up flows at pyrolysis oven, and the urea solid that sprays into from the pyrolysis oven bottom is produced reactive force upwards, and urea is " boiling " state in air-flow, gas-solid two phase thorough mixing.At the pyrolysis oven lower region, urea solid stopped 2 seconds approximately, absorbed the high-temperature gas heat, decomposed to generate isocyanic acid and ammonia, and the steam in isocyanic acid and the gas further reacts and generates NH 3And CO 2
(3) electric heater 7 is installed in the pyrolysis oven 3, and power is 40kw, by the 60kw roof photovoltaic generating system power supply that is equipped with the 800kwh accumulator system.Behind high-temperature gas and the urea heat-shift, temperature descends, and in the pyrolysis oven uphill process, absorbs the heat that electric heater 7 provides, and gas temperature is raised to 350 ℃; Whole pyrolytic process is 5～25 seconds.
(4) discharge the pyrolysis gas that contains 3.4% ammonia concentration from the pyrolysis oven outlet and be imported into the ammonia-spraying grid the Benitration reactor, be used for the NO of SCR coal-fired flue-gas x
(5) technic index of embodiments of the invention and prior art is following:
Existing technology Embodiment one
The dilution water consumption, kg/hr 24 0
Steam consumption, T/d 16 0
The pyrolysis electrisity consumption, kw 130 40
Floor space, m 2 400 300
Equipment manufacturing cost, ten thousand yuan 400 200

Claims (4)

1. urea solid by dry pyrolysis system NH 3Method, it is characterized in that comprising the steps:
(1), the urea solid in the urea solid storage tank is transported to pyrolysis oven through measurement charging device, feeding quantity is discharged the NO that surveys in the flue gas according to boiler XMeasure corresponding adjusting;
(2), the high-temperature gas of high-temperature blower conveying is imported in the pyrolysis oven from the bottom of pyrolysis oven through under meter; In the pyrolysis oven uphill process, fully contact with urea; Urea decomposes under the effect of high-temperature gas generates isocyanic acid and ammonia; Steam in isocyanic acid and the high-temperature gas further reacts and generates ammonia and carbonic acid gas; The high-temperature gas shortage of heat, the heating system that the photovoltaic generating system of electric heater of installing in the pyrolysis oven when pyrolysis gas is lower than 300 ℃ and outfit accumulator system is formed is a pyrolysis gas complementary heating;
(3), pyrolysis gas is imported into ammonia-spraying grid after pyrolysis oven is discharged, remove NO as SCR XReductive agent.
2. urea solid by dry pyrolysis system NH according to claim 1 3Method, it is characterized in that said hot-gas temperature is 250～450 ℃, vapour content satisfies the demand that isocyanic acid changes ammonia and carbonic acid gas into, flow generates the ammonia amounts greater than 19 times of pyrolysis.
3. urea solid by dry pyrolysis system NH according to claim 1 3Method, it is characterized in that said high-temperature gas is the 0.3%-1% flue gas of economizer exit, or the wind of the 0.5%-1% of air preheater place or secondary air.
4. urea solid by dry pyrolysis system NH according to claim 1 3Method, it is characterized in that the said electric heater of in pyrolysis oven, installing, form heating system with the photovoltaic generating system that is equipped with accumulator system, guarantee that the pyrolysis oven Outlet Gas Temperature is in 300～400 ℃ of intervals.
CN2010102109570A 2010-06-25 2010-06-25 Method for preparing ammonia gas from urea solid by dry pyrolysis Active CN101870480B (en)

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CN102580529B (en) * 2012-02-27 2014-10-08 环境保护部华南环境科学研究所 Electro-pyrolytic urea solution ammonia production device used for selective catalytic denitration and application thereof
CN103950953B (en) * 2014-05-10 2015-12-09 南京宇行环保科技有限公司 A kind of device and method of denitrating flue gas urea pyrolysis ammonia
CN105498532A (en) * 2015-12-30 2016-04-20 安徽新力电业科技咨询有限责任公司 Automatic control SCR flue gas denitrification urea pyrolysis system
CN105883853B (en) * 2016-06-28 2019-01-04 盐城工学院 A kind of method that urea prepares ammonia
CN107739036A (en) * 2017-09-18 2018-02-27 华电电力科学研究院 A kind of dry type urea pyrolysis ammonia system and method
CN114177861A (en) * 2020-09-12 2022-03-15 陕西青朗万城环保科技有限公司 Method for preparing ammonia gas by urea solution microwave ultraviolet photolysis and control system thereof
CN112023695B (en) * 2020-09-16 2022-07-26 安徽工业大学 Urea pyrolysis denitration device and method for power flue gas
CN114247401A (en) * 2020-09-21 2022-03-29 陕西青朗万城环保科技有限公司 Microwave urea pyrolysis method and control system thereof
CN112340751B (en) * 2020-11-25 2024-06-07 山东利丰环保科技有限公司 Urea pyrolysis system
CN114856766B (en) * 2022-04-21 2023-04-25 国能龙源环保南京有限公司 Urea solution storage and transportation system and method for combined photovoltaic power generation
CN114733472B (en) * 2022-04-24 2024-05-03 中国科学院长春应用化学研究所 Reaction kettle suitable for multistage reaction

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DE10206028A1 (en) * 2002-02-14 2003-08-28 Man Nutzfahrzeuge Ag Process and apparatus for producing ammonia
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CN101439864A (en) * 2007-11-22 2009-05-27 宋爱军 Process for preparing low concentration ammonia gas mixture by using fluidized bed atomization decomposer

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Address after: 210008 No. 87 Dong Cun road, Jiangning Development Zone, Jiangsu, Nanjing

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