Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8637—Simultaneously removing sulfur oxides and nitrogen oxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8621—Removing nitrogen compounds
  • B01D53/8625—Nitrogen oxides
  • B01D53/8628—Processes characterised by a specific catalyst
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8621—Removing nitrogen compounds
  • B01D53/8625—Nitrogen oxides
  • B01D53/8631—Processes characterised by a specific device
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B45/00—Other details
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/202—Hydrogen
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/204—Carbon monoxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/208—Hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/102—Platinum group metals
  • B01D2255/1023—Palladium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20723—Vanadium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2258/00—Sources of waste gases
  • B01D2258/02—Other waste gases
  • B01D2258/0283—Flue gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/48—Sulfur compounds
  • B01D53/50—Sulfur oxides
  • B01D53/508—Sulfur oxides by treating the gases with solids

Definitions

• the present invention relates to a process for performing selective catalytic reduction (SCR) of a coke oven flue gas at low temperatures.
• SCR systems use catalysts to promote a reaction between flue gas NOx and a reducing agent, typically ammonia, that is injected into the flue gas stream.
• a reducing agent typically ammonia
• the catalysts for this purpose selectively convert NOx into nitrogen and wa ⁇ ter, thereby reducing NOx emissions by up to 97%.
• the SCR is a catalytic reaction of nitrogen oxides (NO and NO 2 ) with ammonia to form elemental nitrogen and water in accordance with the reaction schemes
• the first two reactions are the predominant ones, with one mole of ammonia consumed for each mole of NOx converted.
• the last two reactions occur in gases, in which large frac ⁇ tions of NOx are present as N0 2 .
• a catalyst is used.
• the most common SCR catalyst type is based on V 2 Os catalyst on a Ti0 2 carrier.
• Coke oven plants are facing increasingly stricter legislation with respect to NOx emissions, especially in China which is by far the largest market for coke production.
• coke is produced from coal in a coke oven.
• the volatile constituents in the coal are pyro- lyzed by heating to a temperature of 900 to 1400°C and then liberated and extracted.
• This forms the coke which con ⁇ sists essentially of carbon and an off-gas that contains the volatile constituents and is referred to as coking plant gas.
• the pyrolysis in the coke oven takes place in the absence of oxygen. This is in principle a batch pro ⁇ cess, and the composition of the liberated coking plant off-gas fluctuates.
• the average gas composition is subjected to only small fluctuations. So the coking plant gas formed contains H 2 (about 55%) , N 2 , CO, CO 2 , sulfur and higher hydrocarbons .
• Coke oven gas is a byproduct of the coke making pro ⁇ cess.
• COG consists of a complex mixture of various gases. Its composition typically consists of 55 % H 2 , 6 % CO, 25 % CH 4 (methane) , plus small percentages of CO 2 (carbon diox ⁇ ide) , H 2 O (moisture) , heavy tars, volatile hydrocarbons and sulfur impurities. It also contains some 2 (nitrogen) .
• the higher hydrocarbons, tars and aromatic compounds in the coke oven gas are often extracted from the gas stream through a series of cooling, condensation and separation steps. Such liquid by-products are marketed and known as coke oven tars which are traded on a worldwide basis.
• COG typically denotes the remaining gases from such a series of such tar extraction processing steps and is typically used as fuel gas for various heating applications within the steel plant, and surplus COG is used to produce either steam or electrical power, or it is flared.
• DRI direct reduced iron
• the heat for the coke oven furnace is provided through re ⁇ generative burners that combust the COG.
• Coke oven gas contains hydrocarbons such as BTX (mixtures of benzene, toluene and the three isomers (o, m and p) of xylene), methane, 3 ⁇ 4 and CO.
• Processing and utilization of COG not only boosts the energy efficiency of the steel in ⁇ dustry, but also prevents the emission of harmful green ⁇ house gases including CO 2 and methane.
• Coke oven gases with high hydrogen contents are of huge industrial and commer- cial value considering the future hydrogen economy. At present, many steel enterprises are aiming to minimize their COG surplus while utilizing the gas in various on-site pro ⁇ Des during steel manufacturing. Although extensive research and development has been carried out to utilize the COG surplus, substantial amounts of COG are still being wasted, resulting in poor production efficiencies and serious greenhouse gas emissions.
• US 2016/0083811 describes a method for the reduction of iron oxide to metallic iron using coke oven gas.
• the method comprises dividing coke oven gas into a plurality of coke oven gas streams, providing a first coke oven gas stream to a hydrogen enrichment unit to form a hydrogen-rich product stream that is delivered to a reduction shaft furnace as part of a reducing gas stream, and providing a tail gas stream from the hydrogen enrichment unit to a reforming re- actor to form a reformed gas stream that is delivered to a reduction shaft furnace as part of the reducing gas stream.
• a spent top gas stream from the reduction shaft furnace is cleansed of CO 2 and recycled back to the reduc ⁇ ing gas stream.
• a method for reducing nitrogen oxides from the exhaust gas of a coke oven comprises burning a combustible gas, consisting partly or entirely of coke oven gas, to produce a flue gas containing nitrogen oxides.
• a reducing agent preferably ammonia
• a reducing agent is fed into the flue gas at 700-1100°C to reduce the nitrogen oxide component of the flue gas by a homogene ⁇ ous gas reaction between the reducing agent and the nitro ⁇ gen oxides, while heat is recovered from the flue gas in a regenerator .
• CN 107014217 A discloses a system and a method for the uti ⁇ lization of coke oven gas from a coking plant and treatment of the flue gas.
• COG can be used for various other purposes, such as a feed- stock for hydrogen separation.
• PSA pressure swing ad ⁇ sorption
• the process is carried out in a cyclic adsorption-desorption operation us- ing different adsorbent materials such as alumina oxides or zeolites.
• COG reforming also provides an attractive alter ⁇ native to a less energy-intensive and more clean syngas production (Li et al . , Chem. Eng. Technol. 3_0, pages 91-98, 2007) .
• the flue gas from coke oven firing contains NOx (i.e. NO and NO 2 ) , SO 2 and particulate matter as the main pollu ⁇ tants.
• NOx i.e. NO and NO 2
• SO 2 sulfur dioxide
• the challenge in connection with gas control of flue gas emissions from coke oven plants is that the flue gas exits the regenerative heating/cooling block at a low tempera ⁇ ture.
• the heat depleted flue gas contains sulfur dioxide (SO 2 ) , and thus the formation of ammonia bisulfate and hence a rapid catalyst deactivation becomes a problem when ammonia is used as the reducing agent. Therefore, the idea of the present invention is to replace the normally used ammonia with coke oven gas as the reducing agent.
• the present invention relates to a process for perform- ing selective catalytic reduction (SCR) on a coke oven flue gas at low temperatures, wherein
• - coke oven gas is used as the reducing agent, which is mixed into the flue gas, and
• an SCR catalyst is used.
• the SCR catalyst used can be in the form of a catalytic filter bag or catalytic ceramic filter candles to simultaneously remove particulates and associated catalyst poisons along with NOx and residual hydrogen and hydrocarbons.
• methanol and/or DME can be used alone or in combination with the coke oven gas.
• the slip of 3 ⁇ 4, CO and BTX can be mitigated. This will provide a very efficient means to reduce NOx in coke oven plants.
• the low process temperature is preferably a temperature of 100-250°C, more preferably 150-230°C and most preferably 170-210°C.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)
• Industrial Gases (AREA)

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• 2018
  • 2018-08-27 CN CN201880059546.0A patent/CN111093808A/zh active Pending
  • 2018-08-27 KR KR1020207010294A patent/KR20200054245A/ko not_active Application Discontinuation
  • 2018-08-27 WO PCT/EP2018/073015 patent/WO2019052797A1/en active Application Filing

Patent Citations (7)

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