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COAL GASIFICATION - WASTE HEAT UTILIZATION [PHASE 2 STAGE 2]

Objectif

The aim of the project is the energetic optimization of the PRENLO-process for the gasification of solid fuels under pressure by development and testing of a new waste heat boiler system.
The engineering and construction of a PRENFLO-plant (Pressurized Entrained flow Coal Gasification) with a capacity of 48 t/d Coal throughput at design pressure (Contract LG/018/83/DE) and the execution of the subsequent test programme (Phase 2 of the project; LG/270/85/DE and the present contract, LG/354/87/DE) served to justify the technical and economic risks of commercializing the process on a large industrial scale and demonstrate the long-term availability of the system and of newly developed components.L%
Engineering and erection of the plant was completed early in 1986. The test operation of the plant amounts to date to 5700 hours of coal gasification with a total gas production of ca. 20 Mm3 NPT. Gasification results fulfilled all expectations.
The plant is designed for an operating pressure of 30 bar. for use in gas and steam turbine power plants (combined cycle), an operating pressure of 24 bar is required. The main test were performed at this pressure, corresponding. The main test were performed at this pressure, corresponding to a coal throughtput of 1. 8 t/h. In a short operating period, the design pressure of bar was adjusted with a coal throughtput of 2 t/h or 48 t/d.
Full loaded operation confirmed the design data
Test runs were conducted with high and medium oxygen purity with and without steam addition, using up to now 9 different coals.
The most characteristic data for the PRENFLO process are
- The high level of C-conversion (98. 0 - 99. 5 %)
- The high specific usefulgas yield ca. 20Mm3 NPT (CO+H2)/kg coal waf. )
- the correspondingly high cold gas efficiency of 80%
- the small levels of CO2 (0. 4 - 3. 5 %) in the raw gas.
A very pure gas with the main components CO and H2 is available following desulphurization.
The generation of steam in the gasifier and waste heat boiler increases the thermal net efficiency of PRENFLO gasification by around 13%.
In a campaign for the gasification of 1,000 t coal dust, together with the coal,870 t oxygen, 83 t steam and 4. 9 nitrogen were fed to the gasifier in 550 hours under constant operating conditions ( gasifier pressure 24 bar). 1,977,000 m NPT dry raw gas was produced with an average CO2 content of 3. 5%.
The average carbon conversion was 98. 5%, with 54% of the ash content in the coal being discharged in the form of granulated slag. The cleaned raw gas contained 0. 25mg/m3 NPT dust.
Coals with different chlorine and sulphur contents were gasified in the PRENFLO plant. Chlorine is absorbed mainly inthe pH-controlled waste water and forms sodium chloride. Sulphur remains in the raw gas as H2S and COS. Elemental sulphur of high purity can be recovered via sour gas scrub and Claus process. The newly installed waste heat boiler modules with mechanical cleaning systems were operated successfully. High chlorine containing coals (0. 35% C1) having a particular tendency to fouling of heat exchanger surfaces were gasified. The resulting fouling in the waste heat boiler system could be stabilized at different average degrees depending on the cleaning intervals.
A raw gas/pure gas heat exchanger was operated, utilizing a part of the low-temperature heat of the raw gas. Successful operation of this heat exchanger was achieved with the 3 types of coal used so far.
Leaching tests for slag, fly dust and filter cake ensured the low environmental impact by the coal ash by products of the process.
The PRENFLO process is based on the atmospheric Koppers-Totzek process. This new technology is characterized by high gasifier unit capacity, high thermal efficiency, independence of coal quality, high gas quality and low environmental impact.
To demonstrate the PRENFLO process and to test as well as optimize the components of the system a 48 t/d PRENFLO plant was erected on the site of the technology centre of the Saarbergwerke AG in Forstenhausen (Saarland, Germany), project LG/018/83/DE.
PRENFLO gasification operates according to the entrained flow principle. Coal dust with a grain size of <100 m is conveyed under pressure, using nitrogen, to a reactor with a water-cooled refractory lining. The gasification agents oxygen and steam are added at the gasifier burners. The gasification of the coal dust, i. e. reactor with a water-cooled refractory lining.
The gasification agents oxygen and steam are added at the gasifier burners. The gasification of the coal dust, i. e. the partialoxidation of the carbon to carbon monoxide, takes place in a flame reaction at temperatures of more than 2000 deg. C and a pressure of 24 to 30 bar, the coal substance being converted into CO, H2 and small amounts of CO2. The sulphur content in the coal is converted into H2S and to a limited extent COS, the chlorine into HCl.
Coal ash flows as liquid slag out of the gasifier into a water bath and is discharged from there as granulated inert high-temperature slag. Some of the coal ash is removed from the reactor as fly ash together with the raw gas. The raw gas leaves the reactor from the top and is normally quenched with cole and cleaned recycle gas in order to solidify discharged liquid ash particles.
The raw gas is further cooled in the waste heat boiler.
High pressure steam generation is coupled with the cooling system of the reactor. The steam produced in both systems is passed to superheaters. The downstream raw gas cleaning system comprises a dry dedusting unit, Venturi scrubber, a high-pressure separator and a scrubbing water circulation system with a pressure filter for separation of filter cake and a stripper for waste water purification.
In the present programme (LG/255/89/DE) the raw gas leaving the PRENFLO reactor is not quenched , as previously, prior to entering the radiation boiler, but enters the radiation boiler without quenching and at the reactor outlet temperature, whereby the passage from reactor to radiation boiler is effected without reducing the flow cross section. The design of the radiation boiler demands novel solutions for cleaning heat exchange surfaces and measures to improve heat transfer with the optically dense fluid ( raw gas). The advantages of the new system are higher thermal efficiency, lower CO2 emissions, lower overall height and reduced investment cost. The system will be tested in the 48 t/d PRENFLO plant in Furstenhausen.
In performance of the programme different coal qualities are gasified.

Appel à propositions

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Régime de financement

DEM - Demonstration contracts

Coordinateur

Krupp-Koppers GmbH
Contribution de l’UE
Aucune donnée
Adresse
Altendorfer Straße 120
45143 Essen
Allemagne

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