LURGI’S MPG GASIFICATION PLUS RECTISOL GAS PURIFICATION – ADVANCED PROCESS COMBINATION FOR RELIABLE SYNGAS PRODUCTION
Gasification Technologies 2005 San Francisco, October 9 – 12, 2005 Ulrich Koss, Holger Schlichting - Lurgi AG, Germany
ABSTRACT
Lurgi’s Multi Purpose Gasification Process (MPG) is the reliable partial oxidation process to convert hydrocarbon liquids, slurries and natural gas into valuable syngas. The MPG burner has once again proven its capabilities in an ammonia plant based on asphalt gasification. The advantages of a quick restart without inspection and the inherent safety increase the availability and flexibility of the plant. Lurgi is operating the HP-POX demonstration plant together with the University of Freiberg, Germany. Gasification tests have been conducted successfully at pressures of up to 100 bar. The results show that syngas for high pressure synthesis such as methanol and ammonia can be produced more economically. The Rectisol gas purification process yields ultra clean synthesis gas which is required to avoid problems in the downstream synthesis. Rectisol removes all trace components such as cyanide, ammonia, mercury, all sulfur types and metal carbonyls, and no additional process steps for gas purification are required. Pure carbon dioxide is produced as a separate stream and is readily available for sequestration, enhanced oil recovery or other uses. The reliability of the Rectisol process and the confidence of plant operators in this process are acknowledged by the fact that more than 75 % of the syngas produced world wide by coal, oil and waste gasification is purified in Rectisol units (reference GTC Gasification Data Base 2004). Virtually all coal gasification plants currently under construction rely on Rectisol.
The new, large GTL plants and hydrogen production facilities require effective CO2 removal. New developments make Rectisol attractive for this task.
LURGI’S HISTORY IN GASIFICATION
Lurgi’s process know-how in gasification started with the development of the fixed bed grate gasifier more than 70 years ago. This technology has been widely exploited and more than 120 gasifiers are in operation worldwide. The technology is especially advantageous for low-ranking coals and can handle very large ash and moisture contents. Today, more than 75 % of the syngas from coal produced
GTC2005-Lurgi Presentation 1 worldwide is generated with this type of gasifier (reference GTC Gasification Data Base 2004). The joint development by Lurgi and British Gas led to the slagging type BGL gasifier. The temperature at the bottom is raised above the ash melting point and the slag that forms is routed via the proprietary slag valve at the gasifier bottom to the slag hopper. This type of gasifier has been operated for more than five years now in the SVZ plant in Eastern Germany with a feedstock mixture of municipal waste, petcoke and coal.
The Multi Purpose Gasification (MPG) is Lurgi’s entrained flow gasification process for converting hydrocarbon liquid feedstock such as refinery residues, chemical waste streams and slurries to syngas. The MPG burner has been in commercial operation for more than 30 years with a wide variety of feedstock, which is shown in the following table.
GTC2005-Lurgi Presentation 2 Actual Operating Ranges Operating Limits Quench Configuration Boiler Configuration Component Oil Mode Waste/Slurry Mode C % wt 65 – 90 90 65 – 90 H % wt 9 – 14 14 9 – 14 S % wt 6 6 6 Cl % wt 2 8 50 ppm(wt) LHV MBTU/lb(MJ/kg) 15-18(35-42) 2-13(5-30) 15-18(35-42) Toluene insolubles % wt 6 45 Ash % wt 3 25 0,4 Water % wt 2 5 – 30 Viscosity cSt(at burner) 200 300 200 Particel size mm - 2 Trace components (selection only) Al ppmwt 600 70 000 30 Ag ppmwt 5 10 Ca ppmwt 3 000 170 000 20 Cu ppmwt 200 800 Fe ppmwt 2 000 40 000 Hg ppmwt 10 25 Na ppmwt 1 200 8 000 30 Ni ppmwt 50 500 approx. 1000 Pb ppmwt 200 10 000 0 V ppmwt 10 100 approx. 2000 Zn ppmwt 1 200 10 000 3
PCBs ppmwt 200 600 PAK ppmwt 20 000 40 000
FEATURES OF MULTI PURPOSE GASIFICATION
The special features of the MPG process are the very reliable burner and the quench. The burner uses a special diffuser nozzle system to atomize the feedstock into fine droplets which are required for good conversion. The burner allows the simultaneous feed of 2 or more different feedstock into the reactor via one burner. This is important for
applications where the
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Feed £¥¤¦¤¦§ feed are immiscible or,
¤¦
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¤ 2 each other. The second feature is the quench technology. It
allows the feed of ash ¡ ¡ containing feedstock. The
Quench ¡ Water ¡ Gas-offtake ash melts in the reactor,
forming a slag which flows ¢ ¢ along the refractory lined Soot Slurry wall. The hot gas and the slag are shock-cooled by water injection in the quench pipe. The slag is vitrified to a non-leachable solid and is routed with the water to the solids separation system, designated as the MARS unit (Metals Ash Recovery System).
GTC2005-Lurgi Presentation 3 ADVANTAGES OF THE MPG BURNER
The MPG burner affords a very high feedstock flexibility. No limitations exist regarding the flash point of the feedstock. This is often an issue in the case of high- viscous feedstock, which has to be heated to high temperatures before feeding it to the reactor in order to obtain a low viscosity at the burner tip. If the feedstock has a low flash point, vaporization of the low-boiling constituents of the feedstock starts in the burner nozzle, which disturbs the feedstock flow and results in damage to the burner tip. The MPG burner uses steam to atomize the oil into fine droplets in a proprietary diffuser nozzle system. Additional hydrocarbon vapors generated by heating the feedstock do not affect the feedstock flow at the burner tip. Due to the atomization of the feedstock with steam the burner can handle high- viscous feedstock and also particles in the mm range. MPG reactors afford a very good availability and reliability. This is the result of a combination of very long on-stream times and the option of restarting the reactor without burner inspection. This increases the operational flexibility and reduces the maintenance work. The burner is equipped with a pressurized cooling water system. This gives an inherent safety to the burner operation. A surveillance system detects and records any deterioration of the front plate and the burner nozzles. This information is analyzed and trips a safe shut down of the reactor, if necessary. The burner creates a low pressure drop across the feed system. This allows the use of inexpensive feedstock pumps. The burner is equipped with an integrated heat-up burner so that handling at the hot
reactor is not necessary during start up.
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Feed $ Feed Sat. HP-steam
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% % '©( )+*-,.) Oxidant '©( )+*-,.) Oxidant (O2 Air) (O2 Air)
Steam Steam %
% Syngas
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Quench 0-13254
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Soot Slurry Boiler Configuration Quench Configuration
COMPARISON OF QUENCH VS. BOILER CONFIGURATION
The MPG gasification reactor can be designed with either a quench or a waste heat boiler for gas cooling. In the quench configuration the hot raw gas leaves the reactor
GTC2005-Lurgi Presentation 4 at the bottom and is shock-cooled by the injection of water. If larger amounts of slag occur and have to be transported with the wash water, the soot slurry is routed to a slag lock system. In the boiler configuration the energy of the hot syngas is used in a specially designed boiler to produce valuable high-pressure steam. The quench solution has to be selected for feedstock with higher salt and ash content. It is also the process of choice for hydrogen production from gasification. The major portion of the steam required for the CO shift conversion is produced in the quench. This saves
Boiler Configuration Quench Configuration investment costs in the C C CO shift unit and Feedstock limitations due to Feedstock flexibility possible Boiler fouling reduces operating
costs by saving
C C HP-Steam available MP-steam available valuable high-pressure
highest thermal efficiency trade off efficiency versus costs steam.
C C 2 step gas cleaning Fastest route to hydrogen The highest thermal
strong Claus gas but weak Claus gas efficiency is achieved
C C Higher costs for boiler Lowest cost for hydrogen with the boiler solution. (normally payback < 2 years) production unit The energy of the hot raw gas from the reactor is used to produce valuable high- pressure steam. This route is open for the low ash containing feedstock typical for refinery residue streams such as vacuum residue and asphalt. The high-pressure steam is used in the plant as process steam, to drive large compressors and pumps or in an IGCC application to increase the overall plant efficiency.
THE HP-POX DEMONSTRATION PLANT
Lurgi built a demonstration plant for high-pressure gasification processes to further improve syngas production processes. The plant was built by Lurgi for a joint research project with Professor Meyer at the Technical University of Freiberg in Saxony, Germany. The project is supported by the German Ministry of Multi Process Test Facility: Economics and ATR, Gas-Pox, Technology and by MPG (liquid feedstock) the Saxony Ministry Feedstock: of State for Science and the Arts. Liquid Feedstock 500 kg/h The plant is Natural Gas 500 m3/h (0.5 MMSCFD) designed as a multi- process test facility Reactor: for catalytic auto- Operating Pressure 100 bar thermal reforming, so called ATR, and the non-catalytic
GTC2005-Lurgi Presentation 5 partial oxidation of natural gas, Gas-POX, as well as the gasification of liquid hydrocarbon streams, heavy oil and residues, designated as MPG operation. The maximum throughput is 500 m3/h for natural gas feedstock and 500 kg/h for liquid feedstock, respectively. Tests have already been successfully performed with pressures of up to 100 bar.
Fresh Water Steam Flue Gas water Treatment Generator Liquid Storage Feeds m e Natural t Compressor s Gas y S
e r a
Pump and l
Desulphurisation F Liquid O2 Vaporizier Reactor
Soot Water Soot Water Cooler
Nitrogen Instrument Air Measuring Power Supply Analytical Supply Supply Station Area
The plant is designed as a stand-alone unit including all utility systems. Natural gas is taken from the grid and compressed; liquid feedstock and oxygen are stored on site. High-pressure process steam is produced in a boiler. The reactor is a quench type reactor. The syngas produced is desulfurized and flared.
APPLICATION OF THE MPG BURNER IN AN AMMONIA PLANT BASED ON ASPHALT GASIFICATION
Fosfertils operates an ammonia plant based on asphalt gasification in Brazil. The syngas plant was originally built by Lurgi in the early 80s. The MPG burner was installed and commissioned in one of the existing reactors in 2001. Feedstock to the gasifiers is residue asphalt. The asphalt is solid at ambient condition and exhibits a high viscosity of 360 cSt at 180°C. It has to be heated to temperatures above 260°C to lower the feedstock viscosity for operation with the original burners. The low flashpoint of 170°C results from blending in the refinery and is frequently the reason for the short service life of the original burners. The feature of the MPG burner to operate with high-viscous feedstock has the advantage for plant operation that high-pressure steam for feedstock heating can be saved as the asphalt can be fed at lower temperatures. The higher viscosity and the low flash point do not affect the operation of the MPG burner.
GTC2005-Lurgi Presentation 6
970 tpd of asphalt are gasified in 3 reactors to yield 115,000 Nm3/h of hydrogen (100 MMSCFD) which are converted to 1,350 tpd of ammonia. The flow diagram below is applied in numerous ammonia plants worldwide operated on the basis of heavy residue gasification. The asphalt is converted with pure oxygen in the gasifier, the energy of the hot gas is used to generate high-pressure steam. The steam is utilized as process steam in the gasification and CO shift units and to
Air Air HP-Steam Refrigeration Separation Boiler Unit
O2 HP-Steam Liquid Ammonia
Feed Gasification Rectisol Rectisol Liquid NH CO-Shift 3 + WHB H2S Removal CO2 Removal N2 Wash Synthesis
Urea Carbon Pure CO2 Urea Claus Unit Recovery Synthesis
Soot and Ash Sulfur Pellets
drive the large compressors and pumps. The raw gas is desulfurized in a H2S Rectisol unit and then routed to the CO shift unit. The CO2 produced in the shift is completely removed from the raw hydrogen in the CO2 Rectisol unit. Inert gases such as argon, methane and unconverted CO are removed in a liquid nitrogen wash
GTC2005-Lurgi Presentation 7 unit where also the nitrogen for ammonia synthesis is added. The pure CO2 separated in the CO2 Rectisol plant is routed to the urea synthesis unit.
LURGI’S GAS PURIFICATION TECHNOLOGIES
The gas purification unit is the second most important process in a gasification plant, which defines plant reliability and operating costs such as maintenance and synthesis catalyst lifetime. Lurgi commands the full range of gas purification technologies, partly as proprietary technology, and specialist know how for the open- art technologies such as amine treating. The most suitable gas purification process is selected with respect to the specification of the final product syngas, fuel gas, pipeline gas and by-products required such as pure CO2. Rectisol is the process of choice for chemical synthesis and is also often beneficial for other applications.
Own Technology Specific Expertise
Ultra Pure Syngas Natural Gas Rectisol® Turbine Gas
Purisol® Pipeline Gas Raw Syngas
Pure Off-Gas aMDEA
Off-Gas MDEA / DEA Pure CO2 By-Product
Others Sulphur Tail Gas Sulphur Recovery Treating
Purisol is a selective physical absorption process and competes directly with UOP’s Selexol process. These processes achieve on-spec pipeline gas and fuel gas with regard to the total sulfur content remaining in the purified gas. Lurgi also commands vast experience in amine gas treating processes such as DEA, MDEA and aMDEA. The company performed the basic engineering for the world’s largest natural gas acid gas removal unit for the Qatagas LNG project. One major criterion for an appropriate process selection is the required gas purity. Rectisol removes all sulfur components so, typically, a total sulfur content below
0.1 ppm is achieved. In addition, a pure CO2 stream with very low sulfur content can be generated, which is suited for urea production, beverage industry sequestration or just venting.
GTC2005-Lurgi Presentation 8
Product Gas Purity
Process Purified Gas Quality Impurities
® Rectisol 0.1 – 1 ppm Total Sulfur (H2S + COS) 10 – 50 ppm CO2
5 ppm H2S in CO2 by-product ® Purisol 5 – 50 ppm H2S, no COS removal
MDEA 3 – 50 ppm H2S, no COS removal ® aMDEA 1- 50 ppm H2S 5 – 50 ppm CO2
The sulfur content in the purified gas is higher with Purisol, this normally being sufficient for fuel gas and pipeline gas qualities. The major portion of the sulfur remaining in the gas is COS, which is only partly removed by Purisol. Selexol, as the competing technology, exhibits a similar behavior in this respect. Generic MDEA can be designed for selective sulfur removal. The achievable sulfur concentration in the product gas is similar to that of the selective physical absorption process Purisol . COS is not removed either. Where bulk CO2 removal is required, activated MDEA (aMDEA) has to be selected. AMDEA also hydrolyses the major portion of the COS in the feed gas which results in low total sulfur concentrations in
the purified gas. Acid gas with high H2S concentration suitable for the Claus process can only be produced in a downstream concentration step as the CO2 is completely removed by the aMDEA process. Due to the chemical nature of the absorption process, amine regeneration consumes large amounts of LP and MP steam.
GAS PURIFICATION FOR GASIFICATION BASED HYDROGEN PLANT
Hydrogen can be economically produced from heavy residue feedstock. The selection of the appropriate gas purification technology depends on the required
hydrogen purity, the value of by-products fuel gas and CO2, and the plant emission regulations. High BTU Pure CO2 Feedstock Low Sulfur LP-Steam Fuel Gas The feedstock is gasified in a quench Steam
MPG Raw Gas Gas Hydrogen type MPG unit. D Rectisol D PSA Quench Shift Cooling Carbon monoxide is O2 H2S+CO2 converted to hydro-
Sulphur gen in a raw gas D OxyClaus D Carbon O2 Slurry shift, also referred to Process Water as sulfur tolerant ASU MARS Waste Water Treatment shift. After gas cooling the acid Air Metals/Ash gases have to be removed. This can be achieved with various processes.
GTC2005-Lurgi Presentation 9 In the first case, the Rectisol process produces an H2S-rich sour gas suitable for the Claus unit. In addition, CO2 bulk removal is economical and a pure CO2 stream is generated which can be used for sequestration, industry usage, and which can also be vented without further treatment. A PSA unit is used to free the raw hydrogen from trace components such as methane, nitrogen, CO and argon. The PSA off-gas is a high BTU, low-sulfur gas. In the second case Low BTU Impure Feedstock S > 100 ppm Rectisol is replaced CO LP-Steam 2 Fuel Gas by a selective acid
Steam gas removal process MPG Raw Gas Gas Selective Hydrogen PSA such as Purisol. The Quench Shift Cooling AGR
O2 selective acid gas H2S+CO2
Sulphur removal also
E OxyClaus E produces an H2S-rich Carbon O2 Slurry sour gas suitable for Process Water the Claus Unit. ASU MARS Waste Water Treatment Typically, 20 – 30 %
of the CO2 content of Air Metals/Ash the raw gas is removed in a selective gas purification process. This CO2 is produced as a separate, impure CO2 stream with a significant sulfur concentration. This sulfur impurity is normally no problem for sequestration purposes but simple venting is usually not permitted.
Since the AGR is selective, a considerable amount of CO2 passes to the PSA unit and is separated there. The PSA unit also separates the remaining sulfur impurities.
The PSA off-gas exhibits a low heating value due to the high CO2 content and also contains a significant amount of sulfur. In the third case, if the hydrogen is not required to have a high purity and the fuel gas is of low value, the Pure CO PSA unit can be Feedstock 2 LP-Steam replaced by a 97% methanation reactor, Steam Hydrogen
MPG Raw Gas Gas Metha- which converts CO F Rectisol F nation Quench Shift Cooling and CO2 to methane. O2 H2S+CO2 The gas purification
Sulphur unit has to remove all
F OxyClaus F Carbon O2 sulfur types to the Slurry Process Water ppb range and bulk ASU MARS Waste Water Treatment CO2 removal to the low ppm range is Air Metals/Ash required, since all impurities end up in the product hydrogen. Rectisol is the process of choice for this set up. A hydrogen purity of 97% can be achieved and no fuel gas is produced.
GTC2005-Lurgi Presentation 10 FEATURES OF RECTISOL
Rectisol is often described as an expensive process for gas purification. This has to be put into perspective considering the outstanding features of Rectisol which allow to perform 5 tasks in one process.
„Five in one“
1. Trace contaminants removal COS, CS2, NH3, HCN, Hg, … 2. Deep desulfurization Directly to synthesis feed quality total sulfur < 0.1 ppm (only with Rectisol)
3. Bulk CO2 removal 100 % CO2 can be recovered
4. CO2 purification Total S < 5 ppmV in CO2 Stream 5. Acid gas enrichment Claus-suited acid gas even at a CO2/H2S ratio of > 500
one Rectisol® unit compares with five tasks to be performed in five process steps
Rectisol removes all trace contaminants contained in the raw gas from the gasification unit such as organic sulfur compounds, ammonia and cyanide. Volatile metal components such as carbonyls are also completely removed by Rectisol. Mercury is equally trapped, which is important in coal gasification. Rectisol directly delivers syngas qualities with an extremely low total sulfur content. There is no need for any further gas purification.
Rectisol is suited for the economical removal of bulk CO2 and CO2 concentrations in the low ppm range are achieved in the purified gas. Due to the physical nature of the
absorption process, the energy required to remove large amounts of CO2 depends only on the total gas flow and gas pressure but not on the CO2 concentration in the feed gas. The CO2 product stream is of a very good quality with a very low sulfur content. It can be used for all purposes such as in the chemical industry (urea production), beverage industry and for sequestration.
Rectisol produces H2S-rich acid gases even from raw gases with very high CO2 to H2S ratios, which are typically found in gases downstream of CO shift units. For an evaluation of the process economics one Rectisol unit has to be compared against five process steps such as HCN and COS hydrolysis reactors and guard beds.
GTC2005-Lurgi Presentation 11 Capacity Installed & Operating
350
300 Pure IGCC s r
e Others i f i 250 s
a Rectisol G 200 x e
y
a 150 Today, Rectisol purifies d
/
G
3 75 % of the world´s synthetic m 100 gas produced from N
o oil residue, coal, & wastes
i
G M
50 90 % of synthesis gas produced by gasification 0 (non-IGCC use) 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Source: GTC Gasification Data Base
The advantages of the Rectisol gas purification process are reflected by its market share as can be seen from the above diagram. Today, 75% of the syngas produced from coal, heavy oil and wastes are purified in Rectisol units (source GTC Data Base). The share of syngas purified by Rectisol increases to 90% for the syngas produced for chemical synthesis such as ammonia and methanol (non-IGCC use). Over the last two years Lurgi has been awarded orders for six new Rectisol plants.
GTC2005-Lurgi Presentation 12