CASALE COAL-BASED AMMONIA and METHANOL ... COAL-BASED AMMONIA and METHANOL SYNLOOPS By P. Moreo Ammonia Casale SA and Methanol Casale SA, Switzerland Abstract AMMONIA and METHANOL

6900 Lugano Switzerland, Via G. Pocobelli 6 Tel +41.91.641.72.00 Fax +41.91.641.72.91 www.casale.ch [email protected]

CASALE COAL-BASED AMMONIA

and METHANOL SYNLOOPS

by P. Moreo

CASALE GROUP Lugano, Switzerland

For presentation at the NITROGEN & SYNGAS CONFERENCE

February 21-24 2011 DUESSELDORF, Germany

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CASALE COAL-BASED AMMONIA and METHANOL SYNLOOPS

By P. Moreo

Ammonia Casale SA and Methanol Casale SA, Switzerland Abstract AMMONIA and METHANOL CASALE have a long tradition in supplying the technology for the synthesis loop in ammonia and methanol plants. In the period 1980-2000, with very few exceptions, this technology was always applied in plants fed with natural gas. Starting from early 2000, coal once again became a contender in the choice of feedstock: out of 44 synthesis loops, with capacities ranging from 300 t/d 2,050 t/d, that Ammonia Casale has supplied in the last ten out of which 30 were for coal-based plants. METHANOL CASALE has supplied in the last ten years, 30 were coal-based plants, while 12 of 16 synthesis loops, with capacities ranging from 1,350 t/d 7000 t/d, that Methanol Casale has supplied were for coal-based plants. These coal-based plants are all located in China, and the first 10 ammonia plants and the first four methanol plants are now in service. This paper is concerned with the influence of the synthesis gas composition and the location on these synthesis loops and converters. It describes the collaboration between Casale and the design institutes at the project execution level, the installation pre-commissioning and commissioning in collaboration with the Chinese companies, and the start-up and operating experience gained so far in these large-size plants. A case history is given of the Anhui 1,000-t/d ammonia plant which has recently been put on stream.



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1. INTRODUCTION Nowadays most of the world ammonia and methanol production is achieved with natural gas as feedstock. In the recent years a new scenario began to appear, in which the trend switched to the exploitation of different types of feedstock, like coal and petroleum coke, that are abundant and less expensive. China leaded this revolution, with the construction and commissioning of several ammonia and methanol plants based on coal gasification and reaching almost 33% of world ammonia production and 25% of world methanol production. Chinese ammonia and methanol production is mainly based on coal: the output of coal based ammonia and methanol account for 75% and 60% respectively of the total domestic production. The utilization of these solid feed-stocks requires different technological approaches, both in the preparation of the synthesis gas, and in its utilization to produce ammonia and methanol, mainly because of the composition of the synthesis gas obtained from gasification which is practically inert free for ammonia synthesis loop while, for methanol synloops, is rich in carbon oxides and low in hydrogen, and may contain catalyst poisons. Thanks to its advanced technologies in ammonia and methanol plants CASALE could successfully enter, as leading actor, in the Chinese market.



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2 CASALE TECHNICAL INVOLVEMENTS IN CHINESE PROJECTS CASALE is generally involved in the Chinese projects as licensor, technology provider, supplying its proprietary equipment for both ammonia and methanol projects either in the front end section either in the back end section. CASALE, world leader in the design of converters, has designed and supplied the perfect technologies for the sour CO-shift sections in seven coal based ammonia and methanol plants.

Fig. 1 – Coal Based Ammonia Plant Block Flow Diagram As a consequence of the success of its well-known three beds two interchangers ammonia synthesis converter, for thirty Chinese ammonia projects Casale could provide, License, Basic Design Engineering Package (BEDP) or Process Design Package (PDP) of the synthesis section, refrigeration section and, in some cases, ammonia cryogenic storage section, the proprietary internals of reactor and site services.

Fig. 2 – Coal Based Methanol Plant Block Flow Diagram Basing on the top performances of its Isothermal Methanol Converter, for twelve Chinese methanol projects Casale succeed in supplying, License, Basic Design Engineering Package (BEDP) or Process Design Package (PDP) of the synthesis section and, sometimes, of the distillation section, the proprietary internals of reactor and site services.

COAL GASIFIER CO SHIFT AGR

ASU

N2 WASH

O 2N 2

SYNLOOP

REFRIGERATIONSECTION

STORAGE

CO 2 & H 2 S

AMMONIA

AMMONIA

GASIFIER CO SHIFT AGR

ASUO 2

SYNLOOP

DISTILLATIONSECTION

STORAGE

CO 2 & H 2 S

METHANOL

COAL



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3 SOUR CO-SHIFT TECHNOLOGY: CASALE AXIAL-RADIAL CONVERTERS Depending on the desired product, methanol or ammonia, partial or full conversion of the CO is needed: hence the two processes have different needs for their shift section. The ammonia process requires maximum conversion of carbon monoxide to hydrogen, for maximum ammonia production at a given syngas capacity. This is generally achieved by carrying out the shift conversion reaction in multiple reactors, (two or three), with intermediate cooling. Staging is also required by the high CO content, which entails a large temperature rise across the converter, especially the first bed. Addition of nitrogen in the stoichiometric amount occurs in the downstream nitrogen wash unit. The methanol process, instead, requires that only a fraction of the CO feed is converted to hydrogen, to achieve a balance of hydrogen and carbon oxides at the inlet to the synthesis loop. One or two shift converters are usually installed. Removal of the excess carbon dioxide and H2S in coal gasification plants occurs in the downstream acid gas removal unit. It is apparent that the best design of the CO-shift section (and converters) holds a great importance for the efficiency and reliability of the ammonia and methanol plants, bearing in mind that it features more converters in series. Especially for large plants, the shift section should guarantee a low pressure drop during the entire life of the catalyst, to minimize the power consumption of the downstream syngas compressor. Moreover, the shift converters’ design must be mechanically robust and adequate to the challenging reaction environment. The CASALE design for shift converters successfully provides these and other advantageous features, through the application of the renowned axial-radial concept.

Fig. 3 - CASALE axial-radial catalyst bed In the axial-radial concept, the distribution of the gas is achieved by the perforated walls, which ensure a low pressure drop, stable with time as the catalyst ages or deteriorates, irrelevant also to caking of the



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catalyst top layer due to water droplets carry-over. Hence, by ensuring a higher suction pressure to the compressor through the catalyst life, it achieves a higher production rate. Moreover, since the pressure drop is unaffected by the catalyst, premature change of the catalyst batch is avoided: the life can easily reach and exceed 4 years, even in the case of the first sour shift converter, which is the one operating in the most severe conditions. The major feature of the CASALE axial-radial concept is the low pressure drop, which allows designing the converter with a much slimmer pressure vessel than the axial design would require, and a consequently thinner pressure vessel wall. This can result in significant capital cost saving, especially with regard to the first shift converter. Due to the high operating temperature, an axial bed must be designed either with a SS cartridge, and an annulus for flushing the pressure vessel, or with a refractory lined vessel. Instead, the axial-radial bed with inward flow, keeps the hot gas at the center of the converter, away from the vessel wall, so that only the outlet nozzle is exposed to high temperatures, allowing a much easier, cheaper and robust construction. The advanced design of Casale Sour Shift started to be successful in Chinese coal based plants with the Tianji project in 2005; these sour shift reactors were inspected during catalyst replacement in June 2009 and no repairing work were necessary. The Casale proven and reliable design jointly with the attractive cost saving and process performances has been persuading further Clients to select Casale Sour Shift technology.

CLIENT CASALE SCOPE OF WORK CAPACITY [MTD]

STATUS

RONGXIN CHEMICAL CO., LTD., Erdos City, Inner Mongolia, P. R. China

One sour shift converter for new methanol plant, CASALE axial-radial 3000 Start-up 2013

LUAN XINJIANG YILI COAL CHEMICAL

INDUSTRY CO., LTD. - P.R. of China

Two sour shift converters for new ammonia plant, CASALE axial-radial 1000 Start-up 2011

JIUTAI ENERGY CO. LTD. - P.R. of China

One sour shift converter for new methanol plant, CASALE axial-radial 3000 In operation since

2010

TIANJI COAL INDUSTRY GROUP CHEMICAL CO.,

Lucheng City, Shanxi Province, P.R. China

Two revamped sour shift converters and one new sour shift converter for ammonia plant, CASALE axial-radial 1500 In operation since

2005

Table 1 - CASALE Chinese Sour Shift converter reference list



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4 TECHNICAL ASPECTS FOR METHANOL PROJECTS

The gas composition obtainable from coal gasification can be adjusted to the necessity of the methanol synthesis, but, in general, its stoichiometric ratio is lower than two, and the inert content is low.

Table 2 -Typical Make-up gas composition Moreover, it has to be considered the possibility that the make-up gas could contain catalyst poisons, such as sulfur and arsenic. These compounds should be washed away in the gas treatment upstream the synthesis loop (Rectisol), but, there may also be problems due to upset, mal-operation or under performance of some treatment units that may leave more impurities than desired in the gas. As these poisons are irreversible, it is advisable to protect the catalyst by providing a guard on the make-up gas, which is able to absorb these dangerous substances. The type of guard bed that is most frequently installed protects the synthesis loop from sulfurous components. This guard bed can be installed either at the suction or at the discharge of the syngas compressor (before circulator) and can work in a temperature range from ambient up to 100°C. In the same vessel it is loaded a layer of hydrolization catalyst and a layer of zinc oxide catalyst. Methanol Synthesis loop design The synthesis loop then has to be designed to take into account and to take advantage of the available gas composition. This is normally done by providing some features that are not common in natural gas fed plants. One of these features is a hydrogen recovery unit on the loop purge gas. The recovered hydrogen needs to be added to the make-up gas to increase its stoichiometric number to a value around two, which is optimal for stoichiometric and kinetic reasons. The high carbon monoxide concentration raises also the problem of the formation of carbonyls, such as iron and nickel. Once formed, they will decompose on the catalyst reducing its activity and promoting undesired side reactions. The formation of carbonyls can be avoided by utilizing appropriate types of steel, that are higher grades than in gas based plants, in the areas where carbon monoxide concentration is high and the temperature is roughly in the range of 100 to 200°C. The fact that the make-up gas normally has a low inert content, and is rich in carbon, on the other hand, makes it possible to achieve high production rates with low recycle ratios and low catalyst volumes, provided that the converter design is appropriate. In fact, as the gas is very reactive it can easily create problems of catalyst overheating and hot spots in the converter. For this reason it is very important to provide the right reactor, as discussed in the following chapters.

Composition CO % mol 29.58 H2 66.90 CO2 3.00 CH4 0.06 Ar 0.14 N2 0.32



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Syngas quality - SR CG

Specific production MTD/m3cat ~ 15 ~ 30 Converter outlet pressure bar g 80-120 70-90

CH3OH at converter outlet % mol 4 - 6 12 - 17 MUG H2/COx mol/mol ~ 3.3 ~ 2

Circulation/MUG mol/mol 4.5-7.5 2.5-3.5

SR: Steam reforming, CG: Coal gasification Table 3 - TYPICAL PERFORMANCES– METHANOL LOOP

Overall the synthesis loop can be very simple. It consists in the synthesis converter, a gas-gas exchanger preheating the reacting gas entering the converter, a condenser (sometimes it can be split in air-cooled and water cooled condensers) to cool down the gas to the methanol condensation temperature, a separator to separate the liquid raw methanol from the unreacted gas, a purge recovery unit to recover hydrogen from the purge gas to correct the stoichiometric number, and the syngas and circulating compressor. There are six main items overall, to which a guard bed may be added on the make-up gas, for protection from possible spikes in poisons content. The steam rising converter is equipped with steam drum for steam disengagement and boiler feed water recycling pumps for assuring the boiler feed water forced circulation inside the plates. Sometimes the steam generated in the loop is superheated in an additional fired heater where the tail gas from Hydrogen Recovery Unit is burned. The low recycle ratio that can be used implies that these items are also quite small, enabling very large capacities in a single train, much larger then ever achieved so far in any plant of any type, provided, again, that the converter is of the right design.

Fig. 4 – Methanol Synthesis Loop Process Flow Diagram

There are four coal based Casale Methanol loops already in operation in China: Shanghai Coking Plant (1'350 MTD, in operation from June 2008), Xin'ao Plant (2'000 MTD, in operation from July 2009) and Huating Plant (2'000 MTD, in operation from November 2010) are based on Casale axial steam rising Isothermal Methanol Converter technology, while the Jiutai Plant, due its large capacity (3'000 MTD, in operation from October 2010), is based on Casale axial radial steam rising Isothermal Methanol Converter.



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Fig. 5 – Methanol Plant Distillation Section The methanol distillation section in Chinese projects is normally designed with a three or, alternatively, four columns scheme in order to manage high capacity distillation section and to assure minimum energy consumption (lower than 1.3 Low Pressure Steam MT/CH3OH MT) Casale typically specifies valve trays, as for the distillation sections downstream steam reforming plant, but in the recent projects also structured packing has been used to decrease columns dimensions



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Methanol Converter Design

Fig. 6 - Simplified layout of Axial and Axial Radial Steam Rising IMC converter

The type of converter that is proposed by METHANOL CASALE for this type of service is the "IMC” that stands for Isothermal Methanol Converter. This reactor design is characterized by the fact that the catalyst

bed is cooled by plates immersed in the catalyst, containing boiling water as cooling fluid. In the case of gasification plants, the amount of carbon monoxide and dioxide present in the synthesis gas is very significant. Normally the concentration of these gases is of about 15%v for CO and of 5%v for CO2 at reactor inlet. These high concentrations of carbon oxides imply that the converter must be provided with an heat sink, to control the reaction temperature. This heat sink is normally boiling water generating medium pressure steam that is around 25-30 bar. This pressure is selected because its corresponding temperature level matches the operating temperature in the catalyst bed well, and the steam produced can be usefully utilized in the plant in turbines. The steam production usually ranges from 1.1 to 1.3 MT/CH3OHMT depending on BFW feed temperature. As mentioned above, the plate-cooled converters make use of cooling plates immersed in the catalyst mass for heat removal. The boiling water enters the converter shell and is distributed at the bottom of the plates. It then flows inside the plates from the bottom to the top. The mixture water/steam is collected in a manifold and exits the converter. The construction of the converter internals is conceived so that there is no tube sheet, therefore there is no constraint in the converter size, and the construction is light, consisting of a normal pressure vessel containing the catalyst bed and the plates.

The plates are dimpled, obtained in an automatic production process consisting in their welding with a laser controlled by a computer. This results in a very high quality consistency, where the manual input is minimal.

Fig. 7 - Steam rising plate



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The plates are surrounded by the catalyst mass where the process gas is flowing. The process gas flow can be axial or axial-radial. In the latter case very large capacities in a single vessel with a low pressure drop, can be obtained. The main advantages of Casale IMC design are in terms of: ü better performances, resulting from the advanced design, ensuring the best catalyst temperature

profile with the highest uniformity; ü highest reliability thanks to the industrialized and automated production process of the reactor’s

internal components; easier catalyst replacement and maintenance of the internals. ü easier mechanical construction ü Casale experience in designing synthesis converters

Fig. 8/9 – Typical IMC Axial Radial Design / 2'000 MTD Xin'ao Axial Isothermal Methanol Converter



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5 TECHNICAL ASPECTS FOR AMMONIA PROJECTS The synthesis gas composition from coal gasification is characterized by the low inert content. Typically the Argon and Methane concentration in the make up gas to the synloop does not exceed 50 ppm by volume while the Hydrogen and Nitrogen concentration is about 75% / 25%. Ammonia Synthesis Loop Design The synthesis loop then has to be designed to take into account and to gain advantage of the available gas composition. Due the fact that the make-up gas normally has a minimum inert content, there is no loop purge and the flash gas from medium pressure separator is recycle back to the suction of syngas compressor in order to minimize the make up gas consumption. The overall low inert content at ammonia reactor inlet makes it possible to achieve high production rates with low recycle ratios and low catalyst volumes.

Fig. 10 – Ammonia Synthesis Loop Process Flow Diagram The synthesis loop is quite simple and not significantly different from the loop designed for natural gas feed stock. It consists in the ammonia synthesis converter, in the hot gas-gas exchanger preheating the reacting gas entering the converter, in the heat recovery section, in the water cooler, the cold gas gas heat exchanger, the two chillers, the high pressure separator necessary to separate the liquid ammonia from the unreacted gas, the medium pressure separator useful to recover the dissolved gas in the liquid ammonia, and in the syngas and circulating compressor.



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According to the overall plant steam system specific optimization, the heat recovery section can comprehend the steam super-heater, the waste heat boiler and boiler feed water pre-heater, or as alternative, only the waste heat boiler and the BFW pre-heater, or in unusual cases, only the BFW pre-heater. The recovered heat is generally higher than 0.6 Gcal / NH3 MT. Casale design normally provides the typical direct connection between ammonia converter and downstream exchanger (Casale has references for each of the above described alternatives) which is shown in the following figure. This feature of CASALE layout avoids the installation of pipe subjected to high temperature operating conditions: in fact the conditions of syngas leaving the converter (at more than 440°C) are favorable for a nitriding attack. Casale proposed layout has the following advantages: a high pressure high temperature stainless steel line is avoided, therefore the reliability and safety of the system are increased since a high pressure piping containing hydrogen and ammonia is avoided.

Fig. 11 - Direct connection between converter and waste heat boiler in a Chinese plant Casale usually supplies, as proprietary equipment, the heat exchanger directly connected to the converter which can be the steam super-heater or the waste heat boiler or boiler feed water pre-heater. However Casale is open to meet Client exigency to minimize the investment cost and can alternatively provide a reliable design which can be procured directly by the Client and manufactured by Chinese workshops. The steam super-heater is typically an horizontal exchanger (TEMA type DFU). Exchanger tubes are made, as minimum, by austenitic stainless steel as well as the syngas inlet chamber shall be overlaid by the same material to avoid nitriding due to the high metal temperature. Generally the Waste Heat Boiler is a NKU special type horizontally arranged with process gas flowing tube side. The exchanger can be coupled with the converter outlet (if no steam super-heater is present). Insulated ferrules in Nickel Alloy material protect inlet tubes keeping the hot end tube wall temperature inside the tube sheet below 380°C to avoid nitriding. All the parts in contact with process gas are in low ally steel to ensure a higher reliability and a longer lifetime. Parts in contact with MPS are in C.S. as minimum requirement.



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In case no super-heater and waste heat boiler are installed, the BFW Pre-heater is directly connected to the converter outlet. The exchanger is a NEU with hot gas shell side and BFW tubes side. The HP shell will be in low alloy steel being operated therefore at lower temperature. The tubes are “U” type in low ally steel too.

Fig. 12 – Refrigeration Section Process Flow Diagram Generally the ammonia plant refrigeration section is designed by Casale considering a "closed loop" scheme (as shown in the above picture) strictly dedicated to the ammonia chillers. Furthermore Casale is fully open to customize the Refrigeration Section in order to meet the specific Client requirement about cold duties export or inert specification in the liquid ammonia. Especially in case of stringent specification about inert content in ammonia product, the "open loop" scheme is adopted.



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Ammonia Converter Design The CASALE technology for this section of the plant relies on the ammonia synthesis converter with three adiabatic beds with two interchangers, as shown in following figure. The three catalytic beds have axial-radial flow, to minimize the pressure drop. The CASALE design for the ammonia synthesis converter has already proven its performance and reliability, on the grounds of the following key concepts:

ü the axial-radial flow in the catalyst beds ensures an optimal distribution of the gas in the catalyst, avoiding any hot spots, and full utilization of the catalyst;

ü the temperatures in each of the beds is controlled independently, to keep the converter optimized in any operating conditions;

ü the materials of construction used for the internals, i.e. SS 321 and Inconel 600, are chosen for their resistance to nitriding and hydrogen attack;

ü all the internal parts are connected with sliding joints, allowing unrestricted differential thermal expansions, and are free from leakages due to material aging;

ü the pressure vessel is flushed with cool gas, ensuring that it is not subject to embrittlement due to nitriding, which may lead, in the long run, to cracking;

ü the converter effluent is directly conveyed to the downstream exchanger, which is be lip-sealed to the converter, thus eliminating the hot converter outlet pipe, and allowing the use of safer horizontal exchangers.

Fig. 13 - Typical Casale 3-bed converter layout



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Altogether, the ammonia synthesis loop for coal based plants is not significantly different from the reforming plants, except for the better overall performances (lower recycle rate, no purge, higher specific heat recovery).

Syngas quality - SR CG Specific production MTD/m3cat ~ 15 ~ 20 Converter outlet pressure bar g 160 140 Converter ∆P bar < 3 < 3 Converter ∆NH3 % mol ~ 15 ~ 18 Converter Tout °C 430 430-450

SR: Steam reforming, CG: Coal gasification

Table 4. TYPICAL PERFORMANCES– 2’000 MTD AMMONIA LOOP There are ten coal based Casale Ammonia loops already in operation in China: their capacity ranges from 500 MTD to 1'000 MTD. The first of them is in operation from 1999, while the last has been put in operation during the November of 2009. The key equipment of all of them is the CASALE Converter with three adiabatic beds and two interchangers.

Fig. 14/15 – Chinese Ammonia Plant in operation



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6 PROJECTS AND INDUSTRIAL EXPERIENCE

In all Chinese projects Casale works in collaboration with local design institutes, typically playing the role of detail design contractors of the project. Usually the procurement activities, the construction, pre-commissioning, commissioning and start up are directly performed by the Client. Design institutes are involved in the project since the very preliminary phases, so that the design basis is agreed upon during contract negotiation. Casale typical scope of supply for the ammonia projects consists of basic or process design of the synthesis loop, refrigeration section and, sometimes, of the cryogenic storage section. For methanol projects it consists of basic or process design of the synthesis loop and, in some cases, of distillation section. For both methanol and ammonia projects the detail design and material supply is limited to the proprietary internals of synthesis converter, and, quite often, for ammonia projects, Casale supplies the heat exchanger directly connected to the converter like the steam super-heater, waste heat boiler or boiler feed water pre-heater and / or other critical heat exchangers of the loop. BEDP e PDP are provided by Casale in double language English/Chinese and according to relevant Sinopec standard. After BEDP or PDP delivery, a design review meeting is held with the participation of Client and Design Institute specialists, in which Casale gives detailed explanations and Client reviews and comments all the basic design documents, as necessary for the assessment of the documentation, allowing Design Institute to proceed with the detailed engineering development. Typically Client and Design Institute participate to this meeting with a delegation of about 10 people including project managers and specialists from all the major engineering disciplines, like process, mechanical, piping, instrumentation, electrical etc. Detail engineering design is then developed by Design Institute and Casale reviews this work to check compliance with the process design requirements. Also this phase is very important for a smooth development of the project and it ends with a Detail Design Review Meeting in the offices of the Design Institute. Typical project duration from contract signature to detail design review meeting is 12 months, with basic design review after 5 months from kick-off meeting. The collaboration between Casale and Client does not end with the design phase but it continues on field. In fact, one of the features of Casale converter internals is their modularity and their assembly on field with the same technique developed by Casale for in-situ retrofit. The installation is performed by the Client, under the supervision of Casale field engineers. Also the first catalyst loading is performed under Casale supervision. Casale assistance goes on with commissioning and start-up activities, including catalyst reduction. During this period Casale personnel also provides training to Client staff operators. Finally, last commitments for site activities concern parameters optimization and test-run. From the experience with the Chinese projects Casale has learnt once more how the assistance at site is important for a successful project. Therefore, Casale keep on maintaining close cooperation with the Client and full assistance in troubleshooting even after test-run period expiration.



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7 CASE HYSTORY: ANHUI HUAINAN CHEMICAL GROUP Co. Ltd PROJECT Design capacity of this ammonia plant is 1'000 MTD. Syngas is coming from coal gasification. Ammonia Casale is the licensor and the basic designer for the ammonia synthesis loop and for the refrigeration section. Casale performed the review of detailed engineering, developed by the Design Institute ECEC of Hefei, provided supervision for proprietary equipment installation and, finally, provided assistance at site during start up activities, catalyst reduction and test run. Since the successful test run, Casale has continued to be in close contact with the Client cooperating in troubleshooting and plant performances optimization.

Fig. 16 – Anhui Ammonia Synthesis Loop and Refrigeration Section Simplified Process Flow Diagram

Synthesis loop is characterized by a typical operating pressure for Chinese projects (140 bar g - SOR design) and the design composition of the syngas is quite typical too for coal-based process (total inert content in the make up gas is 20 ppm vol). The plant is equipped with Casale Ammonia Converter with three adiabatic beds with two interchangers. Casale designed and supplied also its proprietary steam super-heater, directly connected to the converter outlet, and the waste heat boiler.

Fig. 17/18 – Steam Super Heater and Waste Heat Boiler in operation in Anhui Plant

The performances of the plant are satisfying; Synthesis loop is working fine, with process parameters that



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are even better than design ones. The plant is able to reach easily the design capacity; the ammonia net concentration across the converter is more than 17.3%, about 1% higher than the guaranteed value, while the operating pressure of the loop is about 8 bars lower than the design value. The heat recovery train works properly, even better than design. The steam is generated and superheated at about 40 bar g, so it can be fed to steam turbine. The simulation of the steam super heater shows temperature approaches better than expected (10°C between the converter outlet and the super heated steam). The waste heat boiler is working fine too; the boiler feed water pre-heater has an optimum performances that closes the heat recovery of the synloop. As per Client request, the refrigeration section has been designed in order to supply the refrigeration duties not only to the chillers of the synthesis loop but also to some external users in the front end. The peculiarity of this refrigeration section, like in other several Chinese projects, is constituted by the particular operating conditions of ammonia compressor: the first stage of ammonia compressor operates under vacuum conditions (0.7 bar abs and -38°C) because it handles not only the vapor ammonia from atmospheric separator inside battery limits but also the ammonia stream coming back from Rectisol unit where it has exchanged frigories. The refrigeration compressor runs smoothly and the operating performances of the entire section are significantly better than the design.

Fig. 19/20 – Ammonia Synthesis Loop and Refrigeration Section DCS Printout The plant of ANHUI HUAINAN CHEMICAL GROUP Co. Ltd has been operated for more than one year since startup of 2009. A successful performance test has been signed at the beginning of June 2010.

Fig. 21/22 – ANHUI HUAINAN Ammonia Plant



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8 CONCLUSIONS Producing ammonia and methanol from gasification of coal requires tailor made solutions that can differ significantly from those so far utilized in the more common gas based plants, to take full advantage of the peculiarities of the synthesis gas generated with this process. Through the continuous development of its technologies, Casale has been able to develop successful and reliable processes for ammonia and methanol coal based plants. Casale has acquired valuable experience in coal gasification projects thanks principally to the Chinese experience and the fruitful and close collaboration with Chinese Clients and Design Institutes. With its advanced technology together with the proven experience and knowledge of the coal based plants, Casale is ready to respond to the future market demand in terms of challenging projects which require excellent know-how.



CASALE COAL-BASED AMMONIA and METHANOL ... COAL-BASED AMMONIA and METHANOL SYNLOOPS By P. Moreo Ammonia Casale SA and Methanol Casale SA, Switzerland Abstract AMMONIA and METHANOL

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