Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
  • C10J3/02—Fixed-bed gasification of lump fuel
  • C10J3/06—Continuous processes
  • C10J3/08—Continuous processes with ash-removal in liquid state
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
  • C10J3/02—Fixed-bed gasification of lump fuel
  • C10J3/20—Apparatus; Plants
  • C10J3/30—Fuel charging devices
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
  • C10J2300/0913—Carbonaceous raw material
  • C10J2300/093—Coal
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
  • C10J2300/0953—Gasifying agents
  • C10J2300/0959—Oxygen
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
  • C10J2300/0953—Gasifying agents
  • C10J2300/0973—Water
  • C10J2300/0976—Water as steam
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/18—Details of the gasification process, e.g. loops, autothermal operation
  • C10J2300/1807—Recycle loops, e.g. gas, solids, heating medium, water

Definitions

• This invention relates to coal gasification and in particular to recycling tar and other liquid by-products from the British Gas-Lurgi slagging gasifier such that they are gasified.
• the Lurgi dry-bottom gasifier and the British Gas-Lurgi slagging gasifier are well known in the art of coal gasification. They are described, for example in 'The Chemistry of Coal Utilization' 2nd Supplementary Volume, 1981, published by John Wiley & Son Inc.
• coal is intermittently supplied at the top through lock-hoppers to a distributor which spreads the coal continuously and uniformly on to a fixed bed'of coal and coal-derived solids in a vertical shaft. As it moves downwardly through the shaft, the coal is first heated, dried and partly de-volatilised in the presence of hot gases moving upwards from the base of the reactor. In the lower regions of the bed, the de-volatilised coal )i.e.
• char is gasified by reaction with steam and oxygen. Mineral matter contained in the coal passes through the gasifier and, in the conventional Lurgi process, is removed as a dry ash at a comparatively low temperature maintained by the use of excess steam. In contrast, mineral matter is fused to form a mobile slag in the British Gas development of the process. This slag drains from the fuel bed, is quenched with water and then discharged as a glassy frit.
• the top part of the fixed bed, where drying and de-volatilisation take place, is known as the 'de-volatilisation zone' and the lower part, where the coal char reacts with steam and where other reactions occur, is known as the 'gasification zone'.
• the steam and oxygen are injected through tuyeres and the fierce reaction zone in front of the tuyeres is known as the 'raceway'. This is where char oxidation predominates to give the temperatures high enough to fuse mineral matter and form mobile slag.
• the invention seeks to mitigate the disadvantages of increased oxygn consumption associated with the injection of tar, oils and phenols through the tuyeres of a slugging gasifier. Accordingly, the invention provides a process for the gasification of coal in a fixed bed-ash slagging gasifier wherein gasifying agents comprising steam and oxygen are fed into the bed through tuyeres leading to a raceway located below the bed and wherein condensible non-aqueous materials produced by the gasification of coal are recycled to the coal bed characterised in that said materials are recycled to the lower portion of the bed but above the raceway at a point where the bed temperature is sufficient to gasify said materials.
• the turbulence and vigour of combustion give way to gasification reactions in a more stable region (the gasification zone) composed of coal char particles moving down the bed in a reasonably uniform and steady pattern in countercurrent flow to hot gases. Much of the heat released in the combustion zone is carried into this region as sensible heat by the upflowing gases to support the endothermic reactions:
• the gases are cooled by these reactions and the bed temperature decreases from 1600-1800°C to about 1000°C as they move upwards, leading to lower reaction rates.
• the gas and char temperatures no longer suffice to support further endothermic reaction and the gasification processes effectively stop, setting the upper boundary of the gasification zone.
• Temperaturis at tie upper gasification zone boundary are significantly higher in the slagging gasifier than in a dry-bottoom gasifier.
• hydrocarbons such as methane from the recycled liquid by-products, particularly in the manufacture of substitute natural gas (SNG), because this is less endothermic than producing carbon monoxide and hydrogen. There is then an increase in the gasifier outlet temprature and little or no effect on oxygen consumption.
• SNG substitute natural gas
• the invention and the benefits which derive from it are exemplified by the gasification of a British coal (Rossington) in the slagging gasifier at a gauge pressure of 31 bars and a molar steam/oxygen ratio of 1.3 using oxygen of 98% purity.
• the relevant data are presented in Table 1. Comparable data are included for operation without recirculation of liquid by-products, column (1), and for operation with injection of these by-products into the raceway zone through the tuyeres, column (2).
• Production of the gas shown in column (1) yields as by-product a mixture of tar, oil and naphtha which, in total, amounts to 0.066 kg/kg when expressed in relation to the coal feed on a dry, ash-free (d.a.f.) basis.
• this mixture is injected through the tuyeres, to be gasified in the raceway to give the gas of column (2), it can be seen that the steam and oxygen comsumptions, in relation to the coal feed, are increased by rather more than 10%.
• This example shows, see column (3), that when liquid by-products are recycled and injected in accordance with the invention at a point about midway down the fixed bed, the increase in oxygen consumption required is less than half that necessary when injection is through the tuyeres.
• the product gas composition given is that obtained at about 0.1 kg/kg recycle when the rate of gasification of by-products is 0.066 kg/kg. That is to say when by-products are gasified at the same rate as they are produced even though some fraction escapes gasification when it is first recycled.
• the product gas calorific vsalue is raised, leading to greater efficiency in the manufacture of SNG because less methane has to be made in subsequent methanation stages.
• the benefit of making methane in the gasifier, as opposed to downstream, can be seen as a reduction in downstream equipment and heat losses and in utility demands associated with external methane formation.
• the ratio of methane made directly in the gasifier to the total quantity that it is theoretically possible to make from the product gas gives a first measure of this benefit. This ratio, for the product gas shown in column (3) of Table 1, amounts to 31%.
• the comparable values without recirculation and with injection through the tuyeres, columns (1) and (2), are 24% and 23%.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Gasification And Melting Of Waste (AREA)
• Processing Of Solid Wastes (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=10528960

Family Applications (1)

Country Status (4)

Cited By (6)

Family Cites Families (5)

• 1982
  • 1982-03-12 GB GB08207243A patent/GB2116580B/en not_active Expired
• 1983
  • 1983-01-21 EP EP83300310A patent/EP0089103A3/fr not_active Withdrawn
  • 1983-01-26 ZA ZA83506A patent/ZA83506B/xx unknown
  • 1983-03-01 JP JP58033666A patent/JPS58167685A/ja active Granted

Also Published As

Similar Documents

Legal Events