1. GENERAL

This chapter contains the basis of design, the material balance, steam balance and cooling water balance as used for the plant design.

2. DESIGN BASIS

2.1     Product Capacity

(1)   The Urea Synthesis Section shall produce sufficient quantity of the urea solution to be required for the production capacity of 3,250 MTPD of granulated urea in the Urea Granulation Section.

(2)   The Urea Plant is designed to operate satisfactorily at 60% turn down ratio.

(3)   Annual on stream day shall be 330 on-stream-days (7,920 hours) per year.

2.2     Urea Product from Urea Plant

Characteristics                         Standard Granule Size         Large Granule Size

Nitrogen Content (min.)                     46 wt%                              46 wt%

Moisture (max.)                                  0.3 wt%                             0.4 wt%

Biuret (max.)                                      0.8 wt%                             0.8 wt%

Formaldehyde (max.)                        0.55 wt%                           0.55 wt%

Crushing Strength (min.)         3.0 kg (Dia: 3.15 mm)        7.0 kg (Dia : 6.3 mm)

Average Diameter                                 3 mm                                6.3 mm

Size Distribution                            90 wt% (min)                     90 wt% (min)

                                                          2 to 4 mm                          4 to 8 mm

pH (10% Solution at 20 °C)      8.5 - 9.5 (expected)           8.5 - 9.5 (expected)

Angle of repose °D                     27 - 30 (expected)             27 - 30 (expected)

Bulk Density g/lit.                    750 / 760 (expected)          720 / 730 (expected)

(Loose / Tapped)

Dust (less than 0.55 mm)          0.2 wt% (expected)           0.2 wt% (expected)

Temperature (°C) (max.)                         48                                       48

2.3     Feedstock Characteristics

2.3.1    Ammonia Liquid Feed Condition from Ammonia Plant to Urea Plant

(1)   Composition

-    NH₃  :    min. 99.9 wt%

-    H₂O  :    max. 0.1 wt%

-    Oil    :    0

(2)   Supply press. / temp. at Urea Plant B. L.

-    Supply pressure          :    18 barA

-    Supply temperature    :    17 °C

(3)   Dissolved gas content in liquid ammonia feed to Urea Plant

-    H₂     :    max. 0.76 Nm³/ton NH₃

-    N₂      :    max. 0.47 Nm³/ton NH₃

-    Ar     :    max. 0.08 Nm³/ton NH₃

-    CH₄  :    max. 1.58 Nm³/ton NH₃

2.3.2    CO₂ Gas Feed Supply Conditions from Ammonia Plant to Urea Plant

(1)   Composition

-    CO₂  :    min. 99.0 dry mol%

-    H₂     :    max. 0.8 dry mol%      *1)

-    N₂     :    max. 0.2 dry mol%

-    H₂O  :    saturated at 1.8 barA and 43 °C

*1)  Design for H₂ Converter

(2)   Supply press. / temp. at Urea Plant B. L.

-    Supply pressure          :    1.8 barA

-    Supply temperature    :    43 °C

2.3.3    Formaldehyde Solution (UF85) Feed

The UF85 will be delivered by trucks or in ISO containers.

-    State                                  :    liquid

-    Temperature                      :    ambient

-    Pressure                             :    atm

-    Composition                      :

Urea                      :    25 wt%

Formaldehyde       :    60 wt%

Water                    :    balance

2.4     Utility Characteristics

Design Basis of The Ammonia and Urea Complex “00-ESS-PR-101-Rev. 0” shall be applied to the utilities characteristics.

2.5    Climatic Conditions

Design Basis of The Ammonia and Urea Complex “00-ESS-PR-101-Rev. 0” shall be applied to the Climatic Conditions.

2.6     Emission and Effluents

The expected quantity and quality of major waste streams from Urea Plant during normal operation at 3,250 MTPD standard size granule urea production are as follows:

2.6.1    Gaseous Effluent to atmosphere

2.6.1.1     Vent Gas from the MP Absorber (T-6501)

-     Flow rate                       :    2,424 Nm³/h

-     Temperature                   :    22.5 °C

-     M. W.                             :    27.6

-     Composition

CO₂                         :      14 vol. ppm

NH₃                        :      92 vol. ppm

H₂O                        :        0.3 vol%

N₂                           :      83.4 vol%

O₂                           :      12.7 vol%

H₂                           :        3.5 vol%

2.6.1.2     Vent Gas from the LP Absorber (T-7002)

-     Flow rate                       :    88.7 Nm³/h

-     Temperature                   :    19.7 °C

-     M. W.                             :    28.5

-     Composition

CO₂                         :      99 vol. ppm

NH₃                        :    446 vol. Ppm

H₂O                        :        2.3 vol%

N₂                           :      77.6 vol%

O₂                           :      19.9 vol%

H₂                           :        0.2 vol%

2.6.1.3     Exhaust Air from the Granulator Scrubber Exhaust Fan (C-8502) and the Cooler Scrubber Exhaust Fan (C-8506)

-     Flow rate                       :    1,191,700 kg/h

-     Temperature                   :    41 °C

-     Composition

Air                          :      92.4 vol%

H₂O                        :        7.59 vol%

Urea                        :        0.001 vol% (26 kg/h)

NH₃                        :      84 wtppm

-     Height of venting point :    approx. 42 meter from G. L.

2.6.2    Liquid Effluent

2.6.2.1     Condensate from Interstage Separators of the CO₂ Compressor (C-6001) (*1)

-     Flow rate                       :    Approx. 3 ton/h

-     Composition                  :    H₂O w/traces of dissolved CO gas

(*1)    Condensate from the Interstage Separators is sent to the Degasser (T-9001) and after degassing of CO₂ to be sent to the Polisher Unit in the Ammonia Plant.

2.6.2.2     Process Condensate from the Desorber (T-8001) bottom (export to the Polisher Unit of Ammonia Plant)

-     Flow rate                       :    40.5 t/h

-     Quality

Urea content                :    max. 1wtppm

Ammonia content        :    max. 1wtppm

Electric conductivity   :    10 - 20 micro s/cm at 25 °C

2.6.2.3     Steam Condensate from the Steam Condensate Tank (TK-8601) (export to the Polisher Unit of Ammonia Plant)

-     Flow Rate                      :    55.1 t/h

-     Quality

Conductivity          :    < 10 micro s/cm

pH                           :    7.0 - 9.5

Composition (ppm max.)

Fe                            :    0.2

Cu                           :    0.1

Chloride                  :    0.01

Silica                       :    0.3

TDS                        :    0.1

NH₄                        :    0.3

Oil                           :    none

Total hardness         :    6

2.6.2.4     Turbine Condensate from the Surface Condenser for CT-6001 (E-6004) (export to the Polisher Unit of Ammonia Plant)

-     Flow Rate                      :    52.7 t/h

-     Quality

Conductivity          :    < 10 micro s/cm

pH                           :    7.0 - 9.5

Composition (ppm max.)

Fe                            :    0.2

Cu                           :    0.1

Chloride                  :    0.01

Silica                       :    0.3

TDS                        :    0.1

NH₄                        :    0.3

Oil                           :    none

Total hardness         :    6

2.6.2.5     Condensate from Drop Separator of Air Chiller in the Granulation Plant (export to the O.S.B.L. through Waste Water Pit (Z-9501)

-     Flow Rate                      :    Approx. 3.7 t/h

-     Composition                  :    H₂O

2.6.2.6     Intermittent Liquid Effluent (export to the O.S.B.L. through Waste Water Pit (Z-9501) when flushing urea spilled from the Granulator shelter floor by water)

-     Flow Rate                      :    Max. 50 m³/h

-     Temperature                   :    Ambient

-     Composition                  :    Water dissolved with urea

-     pH                                  :    7

(*1)    Chemical tote tank are provided for pH adjustment on the Waste Water Pit (Z-9501).

3. MATERIAL BALANCE

Process flow diagrams and material balances are referred as:

-    Dwg. No. PFD-60-PR-0001-Rev. 3

-    Dwg. No. PFD-65-PR-0002-Rev. 3

-    Dwg. No. PFD-70-PR-0003-Rev. 2

-    Dwg. No. PFD-75-PR-0004-Rev. 3

-    Dwg. No. PFD-80-PR-0005-Rev. 2

-    Dwg. No. PFD-85-PR-0006-Rev. 2

-    Dwg. No. PFD-85-PR-0007-Rev. 1

-    Dwg. No. PFD-85-PR-0008-Rev. 2

-    Dwg. No. PFD-85-PR-0009-Rev. 2

-    Dwg. No. PFD-85-PR-0010-Rev. 1

-    Dwg. No. PFD-85-PR-0011-Rev. 2

-    Dwg. No. PFD-60-PR-0014-Rev. 2

-    Dwg. No. PFD-65-PR-0015-Rev. 1

-    Dwg. No. PFD-70-PR-0016-Rev. 1

-    Dwg. No. PFD-75-PR-0017-Rev. 1

-    Dwg. No. PFD-80-PR-0018-Rev. 1

-    Doc. No. 60-MHB-PR-001-Rev. 2

-    Doc. No. 60-MHB-PR-002-Rev. 2

4. STEAM AND CONDENSATE BALANCE

Steam and condensate balances are referred as:

-    Dwg. No. UFD-86-PR-0001-Rev. 3

-    Doc. No. 86-MHB-PR-003-Rev. 1

5. COOLING WATER BALANCE

Cooling water balance diagrams are referred as:

-    Dwg. No. UFD-90-PR-0002-Rev. 3

1. GENERAL

The following operating instructions have been prepared for the initial start-up and operation of the urea plant with a capacity of 3250 MTPD. Plant with pool condenser and evaporation section for integration with a Hydro Fertilizer Technology granulation section.

This manual has been compiled to assist those charged with the responsibility and supervision of the initial start-up and subsequent operation of the 3250 metric tons per day urea plant for Petrochemical Industries Development Management Company located at Bandar Assaluyeh, Iran.

Its primary objective is to provide flow descriptions and discussions of the processes involved and relating operating principles, together with suggested guideline procedures for the initial commissioning, start-up, normal shutdown and emergency shutdown of the plant.

It may also serve as a basis for the preparation of detailed operating instructions.

Such detailed instructions or plant operating manual depend on local conditions and should include instructions issued by equipment manufacturers (these are beyond Stamicarbon's scope). Under no circumstances should operations deviate from safety regulations and practices followed throughout the industry.

Operating conditions and techniques will evolve from actual operating experience and it is not possible to anticipate and present herein all potential circumstances, which may confront the operator during the commissioning, start-up, normal operation and shutdown of the unit. Consequently, this operating manual must be recognised as a guide and that conditions stipulated are not rigid standards, unless specifically noted as such.

Numerical values given in this manual are design figures indicating the ranges within which actual values may vary during normal operation and may need to be changed as a result of experience gained in the plant. Under no circumstances should these figures be regarded as guaranteed performance figures.

Special attention should be paid to housekeeping practices on the Urea Unit and the minimising of spillage/leakage of Urea from sample points etc. Regular clear-ups should be carried-out by picking-up any spillage/leakage and not by washing down.

Any and all information pertinent to the Stamicarbon proprietary process included in this Process Manual is disclosed in confidence for use in accordance with the agreement made between Chiyoda Corporation and STAMICARBON BV and should be treated accordingly.

Given the above, no claims for damages or losses in connection with this manual are accepted.

2. PRODUCT AND RAW MATERIALS

The raw materials for the preparation of urea are ammonia and carbon dioxide.

Carbon dioxide is obtained as a by-product from the ammonia plant.

Some applications of urea are: soil and leaf fertilisation, melamine production, urea-formaldehyde resins, nutrient for ruminant animals and miscellaneous other applications.

Urea product.

Urea solution at the exit of the Evaporation Section in the Urea Plant shall be about 96 wt. % urea (including biuret) solution which will be sent to the Granulation Plant for the production of Urea Granules.

The quality of the product urea solution from the plant shall be as follows:

Urea melt containing:

Urea plus Biuret                                                                    minimum    95.8 wt. %

Biuret                                                                                     maximum   0.70 wt. %

Free ammonia (indicator = methyl red)                                 maximum   650 ppm

Appearance and properties of urea (NH₂-CO-NH₂)

Urea is a white crystal, which is not inflammable, not conductive and has the following physical properties:

density (solid at 20 °C)                                                         : 1,335 kg/m³

melting point                                                                         : 132.6 °C

specific heat (melt)                                                                : 126 J/mol/°C

melting heat (melt point)                                                       : 13.6 kJ/mol

mol weight                                                                             :  60.056

                                                                                                        NH₂

structural formula                                                                  : C =  O

                                                                                                        NH₂

Appearance and properties of ammonia (NH₃)

Ammonia is under pressure, a liquified gas, which is recognizable at the smell.

Ammonia gas is lighter than air, and can be explosive and inflammable under certain circumstances.

Ammonia is soluble in water in an exothermic reaction.

Ammonia has the following physical properties:

density (liquid, 20 kg/cm², 25 °C)                                         : 603 kg/m³

melting point                                                                         : -78 °C

boiling point                                                                          : -33 °C

ignition temperature                                                              : 630 °C

lower explosion limit (in air)                                                  : 15 vol. % NH₃

upper explosion limit (in air)                                                  : 29 vol. % NH₃

mol. weight                                                                            : 17.03

                                                                                                               H

structural formula                                                                  : N            H

                                                                                                               H

Appearance and properties of carbon dioxide (CO₂).

Carbon dioxide is a colourless, odourless gas, which is not explosive and not inflamma­ble.

Carbon dioxide is heavier than air and has the following physical properties:

density (gas, 1 kg/cm², 25 °C)                                               : 1.8 kg/m³

triple point                                                                             : -57 °C and 5.1 atm.

critical point                                                                           : 31 °C and 72.8 atm.

mol. weight                                                                            : 44.01

                                                                                                               O

Structural formula                                                                   : C

                                                                                                               O

3. CONCISE PROCESS DESCRIPTION

Urea is produced by reacting liquid ammonia and gaseous carbon dioxide at about 170 ‑ 185 °C and 135 ‑ 145 barA according to the following reactions:

                        2 NH₃ + CO₂              <=====>        NH₂COONH₄                 (1)

                        NH₂COONH₄            <=====>        NH₂CONH₂ + H₂O        (2)

In the first reaction, carbon dioxide and ammonia are converted into ammonium carbamate. This reaction is fast and exothermic. In the second reaction, which is slow and endothermic, the ammonium carbamate dehydrates to produce urea and water.

3.1 Ammonia and Carbon dioxide compression

Liquid ammonia is supplied from the ammonia plant to the high pressure ammonia pump and compressed to about 171 barA. The pump discharges ammonia into the high pressure pool condenser via the high pressure ammonia ejector, where ammonia is the driving force for carbamate flowing over from the high pressure scrubber.

Carbon dioxide from the ammonia plant is supplied, together with a small amount of air, to the carbon dioxide compressor before it is compressed to about 150 barA.

A hydrogen converter is integrated in the carbon dioxide compressor. In this converter the hydrogen, present in the carbon dioxide, is removed by catalytic combustion. A portion of the supplied air is used for this catalytic combustion while the remainder is being used to passivate the equipment of the synthesis section and so prevent corrosion. The dehydrogenated carbon dioxide is introduced into the bottom part of the high pressure stripper.

The two feed stocks, ammonia and carbon dioxide, are fed to the synthesis section at a molar ratio of 2:1.

3.2 Synthesis

Ammonia with carbamate from the high pressure scrubber and carbon dioxide with off gas from the high pressure stripper is introduced into the high pressure pool condenser, which is a liquid submerged tube heat exchanger. The greater part of the gas will condense and convert with ammonia into carbamate.

The dehydration of ammonium carbamate into urea and water takes place in the pool condenser and subsequently in the urea reactor. The urea reactor effluent is distributed over the tubes of the high pressure stripper, which is a falling film type shell and tube heat exchanger. Here, the reactor effluent is contacted counter currently with carbon dioxide, causing the partial ammonia pressure to decrease and the carbamate to decompose. The heat, required for this purpose, is supplied by passing saturated middle pressure steam around the tubes of the high pressure stripper. This steam pressure is controlled by a pressure control valve so that the liquid, leaving the high pressure stripper, contains about 8.6 % by weight of ammonia.

The urea solution from the high pressure stripper, flows to the low pressure recirculation section whilst the high pressure stripper off gases are sent to the pool condenser which is a special design U-tube type heat exchanger. In the pool condenser condensation of strip gases takes place through the principle of pool condensation, i.e. the gases are dispersed into a pool of liquid, where the heat of condensation is being dissipated by submerged heat exchanger tubes. This heat of condensation is used to generate low pressure steam of 4.5 barA. This steam is used for heating and desorption as well as for the vacuum ejector.

The steam pressure at the tube side of the high pressure pool condenser is controlled by a pressure control valve in the steam discharge line of the LP steam drums. A change in this pressure will change the steam condensate temperature and hence the temperature difference between the shell side and the tube side. The steam drum pressure is set to such a value that the synthesis pressure is about 145 barA.

The pool of liquid in the pool condenser allows for a considerable amount of urea formation to take place here. The formed urea, non converted carbamate, excess ammonia and some non condensed ammonia and carbon dioxide are subsequently introduced into the bottom of the urea reactor where further conversion of carbamate into urea takes place. The urea reactor volume allows sufficient residence time for the reaction to approach equilibrium. The heat, required for the conversion and for heating the solution in the urea reactor, is supplied by additional condensation of ammonia and carbon dioxide.

The urea reactor contains five (5) high efficiency trays to ensure that the flow of liquid through the reactor approaches piston flow. Moreover the trays are designed such that negative effects (such as back-mixing, by-passing and stagnant zones in the reactor) are avoided.

The reactor effluent goes through the down comer to the high pressure stripper. The inert, introduced with the carbon dioxide and part of the unreacted ammonia and carbon dioxide, goes overhead to the high pressure scrubber which contains a shell and tube heat exchanger in the lower part and a packed bed in the upper part.

In the lower part of the high pressure scrubber the bulk of the ammonia and carbon dioxide are condensed, the heat of condensation being dissipated into tempered cooling water. In the upper part the gases, leaving the bottom section, are contacted counter currently with the carbamate solution which is formed in the low pressure recirculation section. The gases, substantially consisting of nitrogen and oxygen and containing only small amounts of ammonia and carbon dioxide, are vented to the granulation stack via an MP absorber operating at 7.8 barA.

The carbamate solution from the high pressure scrubber flows to the high pressure ammonia ejector. The ammonia feed pressure is such as to induce sufficient head in the high pressure ammonia ejector to convey the carbamate solution from the high pressure scrubber to the high pressure pool condenser.

3.3 Low pressure recirculation section

In this section essentially all of the small amounts of non converted ammonia and carbon dioxide are recovered from the urea / carbamate solution, leaving the bottom of the high pressure stripper. This solution is expanded to about 4 barA. As a result a portion of the carbamate, left in the solution, decomposes and evaporates. The remaining liquid is divided onto a bed of Pall rings in the rectifying column. The urea/ carbamate solution is sent from the bottom of the rectifying column to the recirculation heater where its temperature is raised to about 135 °C in order to decompose the remaining carbamate. The heat required is supplied by low pressure steam. In the separator (i.e. the bottom part of the rectifying column) the gas phase is separated from the liquid phase. The gases are sent to the rectifying column where they are cooled by the colder urea/ carbamate solution. This causes a portion of the water vapour contained in the gases to condense.

The gases leaving the rectifying column are introduced into the bottom part of the low pressure carbamate condenser where they are condensed almost completely. The heat of condensation is dissipated into tempered cooling water. Process condensate is also supplied to the low pressure carbamate condenser together with the condensed overhead vapours from the first desorber in order to control the water concentration in the carbamate solution.

The optimum ammonia / carbon dioxide ratio allows the water concentration to be as low as 31 % by weight. The pressure in the low pressure carbamate condenser is controlled at about 3.3 barA.

From the level tank of the low pressure carbamate condenser, the carbamate solution flows to the high pressure carbamate pump where its pressure is raised to about 154 barA and from where the carbamate solution is carried to the high pressure scrubber.

The urea solution, leaving the bottom of the rectifying column, flows to the flash separator via a level control valve. Due to the adiabatic flash to about atmospheric pressure, a portion of the water evaporates and some ammonia, carbon dioxide and inert are liberated. These vapours are partly condensed in the flash separator condenser and the remaining ammonia and carbon dioxide are scrubbed from the inert in the LP absorber by means of circulating process condensate and steam condensate. Condensate from the flash separator condenser is recycled to the reflux condenser.

3.4 Pre‑evaporation and evaporation

The solution from the flash separator is sent to the preevaporator.

A portion of the water in the solution is evaporated so as to increase the urea concentration from about 70 to 78 % by weight. The heat of evaporation is taken from the low pressure steam system. The recycled urea solution from the granulation section is introduced into the pre-evaporation feed line. Finally, the urea solution is sent to the urea solution tank.

The urea solution is pumped from the urea solution tank to the evaporator, where it is concentrated to about 96 % by weight. In the separator for the evaporator, the outlet from the evaporator is separated into a gas phase and a liquid phase. The vapour, leaving this separator, is condensed in the evaporator condenser together with the vapours from the vacuum flash separator. The urea solution from the separator for the evaporator flows to the suction side of the urea melt pump and is sent to the granulation section after mixing with urea formaldehyde solution. The condensate, leaving the evaporator condenser is sent to the ammonia water tank via a barometric leg.

3.5 Process condensate treatment

Process condensate from the evaporator condenser, containing ammonia, carbon dioxide and urea, is collected in the ammonia water tank and used as absorbent in the MP absorber and the LP absorber. Next the process condensate is pumped from the ammonia water tank to the first desorber via a desorber heat exchanger.

In the first desorber the bulk of the ammonia and carbon dioxide is stripped off by means of the overhead vapours of the second desorber and hydrolyser. The bottom effluent of this first desorber is pumped via a hydrolyser heat exchanger, where this condensate is heated from approximately 140 °C to 197 °C, to the top of the hydrolyser column. In the hydrolyser, the urea is decomposed into ammonia and carbon dioxide while being heated by means of live medium pressure steam, to about 195 °C. To obtain very small urea concentrations in the hydrolyser effluent (< 1 ppm wt), the process condensate is counter currently contacted with the live steam.

On leaving the hydrolyser the process condensate, containing traces of urea, goes via the hydrolyser heat exchanger to the second desorber. The overhead vapours of the hydrolyser being sent to the first desorber. After cooling the hydrolyser effluent in the hydrolyser heat exchanger to about 148 °C, this condensate is fed to the top of the second desorber. Here, the remaining ammonia and carbon dioxide is stripped off by means of live low pressure steam. The process condensate, leaving the second desorber, is cooled in the desorber heat exchanger and subsequently in the waste water cooler. It contains very small amounts of urea and ammonia (< 1 ppm wt ammonia and 1 ppm wt urea) and to be sent to the polisher unit in the ammonia plant for re-use. The overhead gases from the first desorber are condensed in the reflux condenser and are transferred as a carbamate solution to the low pressure carbamate condenser. The non condensed vapours are sent to the LP absorber.

4. BLOCK DIAGRAM UREA PROCESS

اصول کار گردگیری الکتروستاتیکی (الکتروفیلترها) نزدیک به یکصد سال است که شناخته و تاسیسات گردگیری از 60 سال پیش در صنعت بکار می رود، الکتروفیلترها را معمولا ته نشین کننده های الکتریکی یا ته نشین کننده های الکترواستاتیکی می نامند، مقایسه دقیق بین طرح های اولیه و حال الکتروفیلترها نشان می دهد که اصول اساسی بدون تغییر باقی مانده است، اما تغییرات بسیاری در اجزا آنها صورت گرفته است، این پیشرفت به نحوی است که گرد و غبار باقیمانده در گاز گردگیری شده خروجی از الکتروفیلترهای امروزی 10/1 مدل های اولیه است. در یک کارخانه سیمان از الکتروفیلترها برای گردگیری کوره آسیای مواد سیمان ، گردگیری از کلینکر استفاده می نمایند.

گاز همراه با گرد و غبار پس از خروج از سیستم (کوره ، پیش گرمکن ، آسیای مواد خام ، آسیای سیمان ، خنک کن کلینکر) بداخل الکتروفیلتر هدایت شده از یک میدان الکتریسیته با ولتاژ حدود 40 تا 80 کیلوولت عبور می نماید، در چنین ولتاژ بالائی که از تیغه های تخلیه کننده به صفحات جذب کننده جریان دارد گاز موجود یونیزه گردیده، ذرات گاز یونیزه شده گرد و غبار موجود را شارژ (باردار) گردانیده و آن را بسوی صفحات جذب کننده هدایت می نماید.
ويژگيها و عملكرد فيلترهاي الكترو استاتيك :

تصفيه به معناي جدا سازي ذرات الاينده از خروجي اگزوز كارخانجات ميباشد.اين آلودگيها شامل ذرات جامد انواع روغنها يا مواد اسيدي ناشي از فرايند كارخانجات هستند.

انواع فيلترهاي ابي كيسه اي شيميائي فيزيكي (شني) و سيكلونها در كنار فيلترهاي الكترواستاتيك رد صنايع مختلف كاربرد دارند.بسته به نوع آلودگي و نوع سيال مربوطه (گاز يا مايع) اسيدي بودن آتش گير بودن و خواص فيزيكي و شيميائي و كاربردهاي ان مواد نوع فيلتر تعيين ميشود.

اساس كار الكتروفيلترها بر ايجاد يك ميدان الكتروستاتيك و يونيزه كردن ذرات عبوري از اين ميدان و جذب ذرات باردار شده روي صفحات ميباشد.

 از آنجا كه نيروي وارده فقط به ذرات الاينده اعمال ميشود و از طرف ديگر مسير عبور گاز كاملا باز ميباشد انرژي مصرفي در اين نوع فيلترها به مراتب كمتراز انواع ديگر است.

بعلاوه بعلت عدم استفاده از قسمتهاي متحرك استهلاك الكتروفيلترها بسيار كم بوده وداراي طول عمر مفيد بسيار بيشتري نسبت به انواع ديگر مي باشند بهمين جهت علي رغم هزينه اوليه بيشتر هزينه هاي جاري و تعمير و نگهداري الكترو فيلترها در حداقل ممكن هستند.

مقايسه تقريبي هزينه الكتروفيلترها و فيلترهاي كيسه‌اي بعنوان پر مصرف ترين فيلترهاي مورد استفاده صنايع در شرايط يكسان در جدول زير آماده است: مثلا هر گاه هزينه يك فيلتر كيسه اي 100 واحد فرض شود و يك دستگاه الكترو فيلتر با همان ظرفيت 400 واحد در نظر گرفته شده است.

با احتساب هزينه هاي تعمير و نگهداري و انرژي مصرفي در سال هزينه كل انجام شده در طول عمر مفيد يك الكتروفيلتر مطابق جدول فوق خواهد بود.

همانطور كه در نمودار هزينه ها مشخص است پس از طي 4 سال (حتي با عدم احتساب تورم ساليانه) هزينه هاي يك فيلتر كيسه اي از الكترو فيلتر بالاتر رفته و در طول عمر مفيد يك الكتروفيلتر هزينه هاي انجام شده براي فيلتر كيسه اي نزديك به دو برابر هزينه هاي يك الكتروفيلتر خواهد بود.

لازم به ذكر است يك دستگاه الكتروفيلتر در شرايط كاملا آرام و بدون تنش و فشار و آلودگي صوتي به كار خود ادامه ميدهد كه اين امر باعث ايجاد حس آرامش و آسودگي خيال طي مدت زمان طولاني براي صاحبان صنايع خواهد بود.

مزایای شیشه فلوت رنگی آذر نسبت به سایر فلوت ها

آنیلینگ خوب که در هنگام سکوریت کردن کمترین ضایعات را دارد

توزیع رنگ یکنواخت نسبت به سایر تولیدات داخل و خارج

1.General Description

      Lubisol A-Seal is a monolithic high alumina kit used for hermetic sealing and hot repair of glass furnace fused-cast crowns. It is supplied as a dry mix packed in 26 kg paper bags and the LFS liquid bond, packed in 13 kg plastic canisters. They are mixed in a mortar mixer just before use in the following proportion (weight %): dry powder – 80 : liquid bond -20. Some small amount of water is added during the mixing to obtain the desired fluidity of the mix. For the convenience of the user 2 paper bags dry powder (52 kg) should be mixed with 1 canister (13 kg) LFS bond.

      The material is suitable for cold or hot application. The wet mix starts setting at room temperature after 2-3 hours.  

      The most important features of LUBISOL A-Seal are:

·         Strong and durable adhesive bond with alumina refractories up to 1650 °C, and a coefficient of thermal expansion - very similar to the one of alumina bricks.

·         Very high corrosion resistance against the action of alkali oxides and other fluxes.

·         High purity of the raw materials used, with very low Fe₂O₃ content.

·         Very long shelf life – more than 60 months.

2. Way of Application

      Lubisol A-Seal is applied as a protection hermetic sealing layer by patching over the fused-cast Al₂O₃ crown in a thickness of 20-30 mm. The application can be done before or after the heat-up of the glass furnace.

      Lubisol A-Seal is a heat setting composition, and it is converted into a hard body under the action of the heat of the glass furnace. A ceramic bond is developed later at higher temperatures. The material is suitable for hot application for hot repairs or hot sealing of expansion joints. An Application Technology is delivered by the supplier, together with the material.

3. Chemical Composition and Properties

            3.1. Chemical Composition of the dry mix (%)                                       

            3.2. Other Properties    

4. Safety Data Sheet

      The Liquid Bond Lubisol LFS contains a diluted mineral acid – H₃PO₄.

Safety measures should be taken to protect the eyes and hands of the workers from the action of the acid. They must be wearing protective goggles and gloves. The acid is easily soluble in water. If needed for any reasons, the skin and eyes should be washed with clean water.

1.General Description

     Lubisol –AZS-Seal is a monolithic refractory composition used for lining of various parts of industrial furnaces. It is very suitable for bottom lining applied under the AZS fused-cast bottom plates of glass furnaces. AZS-Seal is also suitable for hermetic sealing of AZS fused-cast crowns and port necks. AZS-Seal is suitable for many other applications: to be used as a refractory lining around the gas and oil burners of steam boilers and power generating plans, in the chemical industry, and in all other type of industrial furnaces and kilns. 

      LUBISOL AZS-Seal is supplied as a dry mix packed in 25 kg paper bags and it is mixed with Lubisol LFS liquid bond packed in 13 kg plastic canisters. The dry powder and liquid bond are mixed together in a mortar mixer before the application in a ratio of 88:12 weight %. For the convenience of the users they can mix 4 bags of dry powder with 1 canister of LFS liquid bond. Some small amount of water can be added at the end of the mixing to adjust the fluidity of the mix. The mixed concrete will start slowly setting at room temperature after about 1-2 hours and will become totally set after 8-10 hours. So, the material is suitable as castable or patching material for cold and hot application.

      Lubisol-AZS-Seal is a heat setting composition – a mixture of different refractory ingredients with high Al₂O₃ and ZrO₂ content. The wet mix is converted into a hard body by the heat of the industrial furnace.

     The shelf life of the material in a dry warehouse is more than 5 years.

3. Chemical Composition and Properties

3.1. Chemical Composition

3.2. Other Properties    

4. Safety Data Sheet

The material LUBISOL AZS–Seal is non flammable and non explosive. It is safe for any kind of transportation. No special requirements are needed. The liquid bond Lubisol LFS contains a diluted mineral acid. Safety measures should be taken to protect the hands and eyes of the workers with protective gloves and goggles. The acid is easily soluble in water.

         Lubisol Engineering Co.

Monolithic Silica Repair Kit

LUBISOL SI-Seal – Data Sheet   

8 www.lubisol.com

1.General Description

Lubisol Si-Seal is a monolithic silica repair kit used for hermetic sealing and hot repair of glass furnace silica crowns. It is supplied as a dry mix packed in 25 kg paper bags and a liquid chemical bond, packed in 13 kg plastic containers. They are mixed in a mortar mixer just before use in the following proportion (weight %): dry powder – 85: liquid bond -15.

Some water is added to obtain the desired fluidity of the mix.

The most important features of LUBISOL Si-Seal are:

·         Strong and durable adhesive bond with silica refractories up to 1620 °C, and a coefficient of thermal expansion - very similar to the one of silica bricks. The sealing process creating a very strong bond is described as Cold Chemical Welding.

·         Very high corrosion resistance against the action of alkalies and other fluxes.

2. Way of Application

            Lubisol Si-Seal is applied as a protection hermetic sealing layer by patching over the silica crown in a thickness of 15 mm. The application can be done during the heat-up of the furnace at 800 °C furnace temperature, or after the heat-up of the glass furnace.

            Lubisol Si-Seal is very suitable for hot application in the form of  plastic balls to fill up the Rat-holes during a hot repair or the expansion joints of a silica crown after heat-up.

            Lubisol Si-Seal is a heat setting composition, and it is converted into a hard body under the action of the heat of the silica crown.

An Application Technology is delivered by the supplier, together with the material.

3. Chemical Composition and Properties

3.1. Chemical Composition (%)                                      

3.2. Other Properties    

3.3. Safety Data Sheet

            The Liquid Bond Lubisol LFS contains a diluted mineral acid – H₃PO₄.

Safety measures should be taken to protect the eyes and hands of the workers from the action of the acid. They must be wearing protective goggles and gloves. The acid is easily soluble in water. If needed for any reasons, the skin and eyes should be washed with clean water.

Eu/Dy ions co-doped white light luminescence zinc-aluminoborosilicate glasses for white LED

Abstract

The luminescence properties of europium and dysprosium ions co-doped zinc-aluminoborosilicate glasses were analyzed.  A combination of blue, green, yellow and red emission bands was shown for these glasses, and white light emission could be observed under UV light excitation.  The color of luminescence could be adjusted by varying the proportions of europium and dysprosium.  The concentration quenching effect was also investigated in this paper.  Furthermore, the reduction of Eu³⁺→Eu²⁺ in air at high temperature was observed in the zinc-aluminoborosilicate glasses.

PACS: 78.20.-e; 78.40.-q; 78.55.-m; 78.55.Hx

Keywords: White light; Luminescence; Glass; Europium; Dysprosium

1. Introduction

Recently, white light emitting diodes (white LEDs) receive lots of attention in solid state lighting area, because of their advantages such as more efficient, less energy consumption, and longer lifetime compared with conventional lighting techniques (incandescent lamp and fluorescent lamp).  Thus, it seems that white LEDs show high potential for replacement of conventional lighting sources like incandescent and fluorescent lamps.  At present, commercial white LED is realized by using two or three kinds of phosphors or a kind of full color phosphor excited by the blue or UV LED chips [1, 2].

Compared with conventional phosphors used for white LED (e.g. Li-a-SiAlON:Eu²⁺ phosphors [2], Ca-a-SiAlON:Eu²⁺ phosphors [3], Ba₃MgSi₂O₈:Eu²⁺, Mn²⁺ phosphors [4], et al.), rare earth doped white color luminescence glass has some potential advantages.  For example, homogeneous light emitting, simpler manufacture procedure, lower production cost and better thermal stability and so on.  White light emitting glass was first developed by Zhang et al. in 1991 [5], and it receives increasing interest in recent years [6-12].  However, only a few studies were concerned on borosilicate glass matrix [5, 8, 12], which has good mechanical, thermal, and chemical stability compared with other glass matrices, and leads to more applications.  Moreover, among the glass components, Al₂O₃ has received significant consideration due to its high solubility of rare-earth ions [13].  In recent years, ZnO and the materials based on it are drawing more attention due to its non toxicity, non-hygroscopic nature, low cost, direct wide band gap, intrinsic emitting property and large exciton binding energy [14].  Thus, the zinc-aluminoborosilicate glass is taken into consideration as glass matrix in which rare earth ions doped in this study.

Present work prepared a kind of Eu₂O₃ and Dy₂O₃ co-doped zinc-aluminoborosilicate glass, which possess high glass transition temperature, good transmission at visible range, and emitting white light under UV excitation.  Besides, the dependence of luminescence properties on the proportions of europium and dysprosium, along with the total concentration of rare earth oxides are investigated in this study.

2. Experimental

The nominal general composition of the glass samples was (in mol%): xEu₂O₃-(0.25-x)Dy₂O₃-99.75ZABS and y(0.25Eu₂O₃-0.75Dy₂O₃)-(100-y)ZABS.  Here, x=0~0.25 mol%, y=0~2.0 mol% and ZABS represented the host glass SiO₂-Al₂O₃-B₂O₃-ZnO-Li₂O-BaO.  Analytical reagent SiO₂, Al₂O₃, H₃BO₃, ZnO, Li₂CO₃, BaCO₃, and high purity Eu₂O₃ (99.95%) and Dy₂O₃ (99.99%) were used for samples’ preparation.  The raw materials were mixed well and melted at 1500^oC for 2 hours.  Then, the melts were poured into a carbon mold, cooled in air and subsequently annealed for 2 hours.

Optical transmission spectra of the polished samples in the UV-VIS range were recorded at room temperature using Hitachi UV-4100 UV-VIS spectrophotometer.  Luminescence spectra were also obtained at room temperature using Hitachi F-4500 fluorescence spectrophotometer under excitation of Xe lamp.  The power of the Xe lamp was 150W.  The glass transition temperature (T_g) of the host glass was obtained using a DTA CRY-2, with heating rates at 10^oC/min.

3. Results and discussion

According to DTA result, the host glass ZABS possesses a high glass transition temperature (T_g) at 658^oC, which broadens the area of specific technological applications.  The vitreous host also exhibits high transmission, around 90.5% in visible range.  Fig. 1 presents the absorption spectra of single Eu₂O₃ and Dy₂O₃ doped ZABS.  Assignments of the bands for the excited states from the ground states of Eu³⁺ and Dy³⁺ are also performed in Fig. 1.  It should be noted that the Eu₂O₃:ZABS sample does not show typical absorption bands of Eu³⁺ ions, because some Eu³⁺ ions are reduced to Eu²⁺ ions, which results in an overlap of absorption bands near UV range.  The reduction of Eu³⁺ to Eu²⁺ ions could be confirmed by the photoluminescence spectra, which will be discussed below.

Fig. 2 exhibits the emission spectra of Eu₂O₃ and Dy₂O₃ doped ZABS glasses under 360nm excitation.  The six major emission bands are attributed to the transitions 5d→4f for Eu²⁺ at 421nm (blue), ⁴F_9/2→⁶H_15/2 for Dy³⁺ at 484nm (greenish blue), ⁴F_9/2→⁶H_13/2 for Dy³⁺ at 575nm (yellow), ⁵D₀→⁷F₁ for Eu³⁺ at 590nm (greenish yellow), ⁵D₀→⁷F₂ for Eu³⁺ at 616nm (yellowish red) and ⁵D₀→⁷F₄ for Eu³⁺ at 700nm (red).  Besides these, a small emission band at 720nm appears in the samples of x=0.0625, 0.1250, and 0.1875.  This band is probably due to part transparency of 360nm excitation light in the emission spectra measurements using 360nm UV cut filter.  These blue, green, yellow and red transitions can be excited by UV light simultaneously in the Eu₂O₃ and Dy₂O₃ co-doped case.  The intensity of these emission bands varies with variation of the proportions of europium and dysprosium.  Thus the white light emission can be achieved with appropriate combination of Eu₂O₃ and Dy₂O₃.  The luminescence colors of these xEu₂O₃-(0.25-x)Dy₂O₃-99.75ZABS samples are characterized by CIE chromaticity diagram and shown in Fig. 3.  It presents directly that the color of luminescence can be changed from yellowish white to bluish white and blue with different x values.  The typical white light emission is shown at x=0.0625 mol%, where the concentration proportion of europium and dysprosium is equal to 1:3.  This adjustability of luminescence color can also broaden application areas.

Moreover, it is interesting to note that the broad emission band from 370 to 570nm peaking at 421nm in the emission spectra, which is not belong to the host glass, Eu³⁺ ions or Dy³⁺ ions, is ascribed to the 5d-4f transition of Eu²⁺ ions [15, 16].  This result indicates that the doped Eu³⁺ ions could be partly reduced to Eu²⁺ ions in ZABS glasses prepared in air, and leads to coexistence of Eu³⁺ and Eu²⁺ ions in the glasses.  The reduction of Eu³⁺→Eu²⁺ occurred in air at high temperature has been reported in polycrystal powders like Eu:BaO-Al₂O₃ [17], Eu:Sr₄Al₁₄O₂₅ [18] and Eu:BaAl₂O₄ [19].  But few research concerned on this phenomenon in glass materials [15, 20, 21], especially in zinc-aluminoborosilicate glass.  According to previous study [20], the reduction behavior of Eu³⁺àEu²⁺ in air at high temperature in glass materials is probably associated with the optical basicity of glass matrix.  In the investigation of redox equilibria in silicate glass melts [22], it suggested that decrease the optical basicity of glass matrix led to decrease in the degree of negative charge on the constituent oxygen atoms and to a lower ‘electron donor power’.  As a result, the glass with lower optical basicity favored the lower positively charged cations, since they needed less negative charge for neutralizing their positive charge than the upper oxidation state ions.  It was also reported that the lower the optical basicity of the glass was, the more the lower valence state of Eu was preferred [20].  Thus, it is indicated that the reduction of Eu³⁺→Eu²⁺ occurring in this study is probably associated with the low optical basicity of the ZABS glass matrix.  The calculated optical basicity [23] of the ZABS glass matrix is equal to 0.6195.  The Ref. [20] provided a critical optical basicity for borate glass system, below which the Eu³⁺→Eu²⁺ process would be favored in any borate glasses synthesized in air atmosphere, and the critical value was 0.585.  However, the optical basicity of the ZABS glass is a little higher than the critical value.  This is probably due to the aluminoborosilicate glass system in this study is different from the borate glass system in Ref. [20].  The critical optical basicity in the aluminoborosilicate glass can not be achieved in present study, and is needed further investigation.

Fig. 4 presents the excitation spectra of 0.0625Eu₂O₃-0.1875Dy₂O₃-99.75ZABS (in mol%) glass monitored at 421nm emission of Eu²⁺, 484nm emission of Dy³⁺ and 616nm emission of Eu³⁺ at room temperature.  It shows that there is few overlap between excitation and emission spectra, which reduces self-absorption extensively.  Moreover, the excitation bands locate in different wavelength range.  It will allow adjusting the luminescence color by changing excitation wavelength.

Finally, the effect of rare earth oxides concentration on luminescence intensity is investigated in Fig. 5.  The total rare earth oxides concentration was varied form 0.1 to 2.0 mol%, and the proportions of europium and dysprosium was kept at 1:3.  It shows that intensity of the luminescence bands of Eu²⁺ and Eu³⁺ increases from y=0.1 mol% to y=1.0 mol%, and quenches above y=1.0 mol%.  While intensity of the luminescence bands of Dy³⁺ increases from y=0.1 mol% to y=0.5 mol%, and quenches above y=0.5 mol%.  Interestingly, it should be noted that the ratio between intensity of Eu²⁺ ion and that of Eu³⁺ ion,  does not keep constant,  but increases with the increasing RE₂O₃ concentration.  This is because when the RE₂O₃ contents increase, the rare earth ions require more negative charges in order to neutralize their positive charge.  However, the optical basicity of glass matrix has not been changed.  Thus, the relative ‘electron donor power’ of glass matrix for the rare earth ions is probably lower than that of before.  This leads to convert more Eu³⁺ ions to Eu²⁺ ions for neutralizing extra positive charges.

4. Conclusions

The europium and dysprosium ions co-doped SiO₂-Al₂O₃-B₂O₃-ZnO-Li₂O-BaO glasses were prepared in this study.  The host glass showed high glass transition temperature and high transmission in visible range.  A typical white luminescence was observed in the glass under 360nm excitation, and the color of luminescence could be adjusted by varying the concentration ratio between europium and dysprosium.  The concentration quenching effect was also investigated.  Moreover, the reduction of Eu³⁺→Eu²⁺ in air at high temperature was observed in the zinc-aluminoborosilicate glasses.  The behavior of this reduction was associated with the optical basicity of glass matrix.

Acknowledgement

This work is supported by the Ministry of Education, P. R. China, the cultivated financing project in the major project of scientific and technological innovation of higher learning institutions, No. 705026.

Reference

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Fig. 1. Absorption spectra of (a) 0.25mol%Eu₂O₃ and (b) 0.25mol%Dy₂O₃ doped ZABS glasses recorded at room temperat
ure.

Fig. 2. Emission spectra of xEu₂O₃-(0.25-x)Dy₂O₃-99.75ZABS (in mol%) glasses under 360nm excitation at room temperature.

Fig. 3. Chromaticity diagram of the emission of xEu₂O₃-(0.25-x)Dy₂O₃-99.75ZABS (in mol%) glasses under 360nm excitation at room temperature: (a) x=0, (b) x=0.0625, (c) x=0.125, (d) x=0.1875 and (e) x=0.25.

Fig. 4. Excitation spectra of 0.0625Eu₂O₃-0.1875Dy₂O₃-99.75ZABS (in mol%) sample monitored at 421nm emission of Eu²⁺, 484nm emission of Dy³⁺ and 616nm emission of Eu³⁺ at room temperature.

Fig 5. Emission spectra of y(0.25Eu₂O₃-0.75Dy₂O₃)-(100-y)ZABS (in mol%) glasses under 360nm excitation at room temperature.