Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/36—Manufacture of hydraulic cements in general
  • C04B7/364—Avoiding environmental pollution during cement-manufacturing
• • 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
  • B01D53/64—Heavy metals or compounds thereof, e.g. mercury
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/36—Manufacture of hydraulic cements in general
  • C04B7/364—Avoiding environmental pollution during cement-manufacturing
  • C04B7/365—Avoiding environmental pollution during cement-manufacturing by extracting part of the material from the process flow and returning it into the process after a separate treatment, e.g. in a separate retention unit under specific conditions
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
  • F27D17/008—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases cleaning gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/102—Carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/60—Heavy metals or heavy metal compounds
  • B01D2257/602—Mercury or mercury compounds
• • 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
  • B01D2258/0233—Other waste gases from cement factories
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
  • F27B7/20—Details, accessories, or equipment peculiar to rotary-drum furnaces

Definitions

• the invention relates to a method and a plant for the production of cement clinker.
• a known method for reducing mercury emissions is described in US 5,505,766 AI and known under the name TOXECON.
• a highly porous, consisting of predominantly carbon, particulate adsorbent hereinafter called activated carbon
• activated carbon particulate adsorbent
• the mercury accumulates on the activated carbon particles and is then deposited in a filter.
• the flue gas flow and exhaust fume from the Brenng. Contains milling process, which mainly consists of calcium, iron, aluminum and silicon oxides or carbonates and has a several orders of magnitude larger mass flow than the adsorbent.
• the adsorbent is therefore injected after the process filter of a well-known cement production plant and requires an additional filter for deposition.
• this filter is very large, requires high investment costs, requires an additional induced draft fan with the associated energy consumption and rarely finds the space required for installation in existing plants.
• An improvement of this method is described in US Pat. No. 7,191,091 B2 and known under TOXECON II.
• the adsorbent is injected between an upstream and a downstream filter part.
• the dust deposited in the upstream filter part is not contaminated with the adsorbent, while in the downstream filter part the residual dust is mixed with adsorbent.
• no additional filter is necessary.
• the disadvantage is that there is still a large mismatch of the mass flows of adsorbent to process dust and this process also does not reach the efficiency of the TOXECON process.
• EP 0 461 305 B1 describes a method for purifying the exhaust gases of plants for the production of cement clinker, wherein the exhaust gases of a preheating zone are cleaned in a multi-stage filter zone, first by a separation of dust in a first filter stage and the exhaust gas thereafter at least one flows through another filter stage that is designed as adsorption stage and contains an adsorbent by the exhaust gas contained in the H x - integrated compounds, heavy metals, trace elements and / or S0 2 and NO x is at least partly reduced.
• the exhaust gases of the preheating zone are adjusted before the first filter stage to such a filter zone inlet temperature that in the first filter stage easily volatile pollutant elements and pollutant compounds are separated together with the dust from the exhaust gases.
• the invention is therefore based on the object of specifying a method and a plant for the production of cement clinker, which is characterized by a reduced mercury emission.
• the process according to the invention for producing cement clinker with a furnace system essentially has the following process steps:
• Raw material is preheated in a preheater by means of hot exhaust gases of the furnace system, the hot exhaust gas is after the preheater in a Vorentstaubungs adopted to a residual dust concentrations of max. 20 g / Nm 3 dedusted, the dedusted exhaust gas is purified in a selective catalytic flue gas cleaning system (SCR), at least a portion of the purified gas in the flue gas cleaning system is fed bypassing a raw material grinding plant a cooling device and there to temperatures of max. Cooled to 140 ° C, - Before the residual dust of the exhaust gas is deposited in a process filter and at least part of the deposited in the process filter residual dust is removed to remove mercury.
• SCR selective catalytic flue gas cleaning system
• the plant according to the invention for the production of cement clinker with the method described above consists essentially of a furnace system for burning raw material, a preheater operated by means of hot exhaust gases of the furnace system for preheating the raw material, a dedusting, the dedusting of the hot exhaust gas to a residual dust concentrations of max , 20 g / Nm 3 is formed, a selective catalytic flue gas cleaning system for purifying the dedusted exhaust gas, a process filter for separating the residual dust of the exhaust gas, arranged between selective catalytic flue gas cleaning plant and process filter raw material grinding plant for a combined operation, a arranged between selective catalytic flue gas cleaning system and process filter cooling device for a direct mode, which is for a cooling of the exhaust gas to a temperature of max. 140 ° C is formed and associated with the process filter mercury cleaning device for deposited in the process filter residual dust.
• cooling towers are predominantly dimensioned so that protection of the process filter against overheating is ensured. These temperatures are usually above 150 ° C, in many applications even up to 220 ° C and in some applications even higher, which is too high for effective adsorption of mercury.
• the adsorption is also improved by dedusting in the Vorentstaubungs adopted, since this not only leads to a decrease in the amount of dust, but the residual dust is also finer than before the Vorentstaubungs adopted. As a result, the surface-rich portions of the dust, which improve the adsorption, increased.
• an additional adsorbent for improved mercury adsorption after the cooling device is injected into the exhaust gas, which is deposited in the process filter together with the residual dust.
• Preferred sorbents are activated carbon, hearth furnace coke, lime, hydrated lime, limestone, filter dust or other substances which are suitable as sorbents because of their high mass-related surface area.
• the sorbent deposited in the process filter in front of the stack is preferably largely recirculated and the other, smaller portion is removed from the process to remove the mercury.
• sorbents for mercury adsorption such as activated carbon or hearth furnace coke
• they have the disadvantage in cement production that the filter dust is contaminated by carbon and therefore can only be added to a limited extent in the further cement production process, for example by metering in the grinding of the cement in the cement mill.
• a further disadvantage is that the chemical composition of the filter dust differs significantly from that of the ground raw meal. Discharge of the filter dust in these cases would reduce the chemical composition of the meal fed to the oven - which is a mixture of raw meal and filter dust - and consequently alter the chemical composition and mineralogy of the cement clinker.
• the filter dust quantities deposited in the process filter depend on the system circuit and the set operating mode.
• direct mode which is the operating state without using the exhaust gas for mill drying in the raw mill
• an oven emits dust concentrations of typically 30-150 g / Nm 3 (m 3 in the standard state). That is about 4-20% based on the amount of clinker produced.
• compound operation it is in advance divorce of the dust after the mill in cyclones about 25 g / Nm 3 , otherwise 300-500 g / Nm 3 . With the present large amounts of gas thus resulting in large amounts of dust.
• SCR catalyst has an oxidizing effect on elemental mercury when properly designed and sufficient halogen content in the flue gas.
• the advantage of mercury oxidation associated with the SCR catalyst is the significantly better separation of the oxidized mercury on the sorbent compared to unoxidized, ie elemental, mercury.
• halogens mainly occur in the form of chlorine, so that predominantly HgCl 2 forms.
• the mercury is largely adsorbed on the dust in the mill. This is on the one hand on the strong drop in the gas temperature in the mill and on the other
• the roll bowl mills commonly used here due to the very high loading of the gas with particles and the strong and highly turbulent recirculation of the particle-laden flow in the mill.
• the temperatures in the mill quickly reach a level usually less than or equal to 110 ° C, which greatly reduces the vapor pressure of the mercury species, thereby promoting adsorption.
• the adsorption does not take place uniformly over the grain size distribution but concentrates in the surface-rich finest area. This proportion is particularly poorly deposited in the frequently existing cyclone advance divorce between mill and process filter.
• the separation of the remaining ultrafine fractions with the already adsorbed mercury takes place.
• there is also an additional adsorption of mercury which is significantly lower than that in the raw mill.
• mercury emissions are therefore much lower than in direct operation without a mill due to the adsorption on the process dust, which is already predominantly carried out in the mill and partly in the filter.
• the mercury added between the kiln system and the mill or process filter in the process increases from the outside and is then emitted more intensively in direct operation.
• the time share of the combined operation in the total operating time is usually much higher than that of the direct operation and usually ranges in the range of 70-90%.
• the inventive method provides the sorbent injection preferably in direct operation, since in composite operation on the one hand the Mahltrocknung already reduces the emissions and the sorbent addition is not necessary and on the other hand, the sorbent would mix with the dust from the mill drying, with the already described adverse consequences.
• the proposed invention avoids the various disadvantages listed above. It avoids an additional filter for sorbent addition and solves the problem of high dilution of the sorbent due to mixing with the high dust load from the production process by a catalyst upstream filter (hot dedusting), which is preferably an electrostatic precipitator due to the prevailing temperatures.
• This filter reduces the dust content to values less than 20 g / Nm 3 , preferably to values less than 7 g / Nm 3 or even 2 g / Nm 3 . At the catalyst this dust reduction allows finer honeycomb structures and thus a smaller catalyst volume. Furthermore, the cleaning effort of the catalyst elements with the dust load decreases.
• the process and cement clinker plant described above not only reduces mercury emissions but also reduces PCDD / PCDF, VOC and NO x emissions. Most of the equipment already in the plant is used, so that the process and the plant are economically favorable.
• FIG. L schematic representation of a system according to the invention according to a first embodiment
• FIG. 2 shows a schematic representation of a system according to the invention according to a second embodiment.
• the plant for the production of cement clinker shown in Fig. 1 consists essentially of a furnace system 1 for burning raw material 2, a cooler 3 for cooling the fired in the furnace system raw material 2, a powered by hot exhaust gases of the furnace system 1 preheater 5 for preheating the raw material 2, a dedusting device 6, the dedusting of the hot exhaust gas 4 to a residual dust concentrations of max.
• a selective catalytic flue gas cleaning system 8 for the chemical cleaning of the dedusted exhaust gas 7 a process filter 12 for separating the residual dust of the exhaust gas, arranged between flue gas cleaning system 8 and process filter 12 Rohmahlmahlstrom 11 for a combined operation, arranged between flue gas cleaning system 8 and process filter 12 cooling device 10 for a Direct operation, for a cooling of the exhaust gas 9 to a temperature of max. 140 ° C is formed and a standing with the process filter 12 mercury cleaning device 13 for deposited in the process filter 12 residual dust 14th
• the predusting device 6 is preferably designed as an electrostatic precipitator and connects directly to the preheater 5.
• the hot exhaust gas 4 is in the Vorentstaubungs adopted 6 to a residual dust concentrations of max. 20 g / Nm 3 , preferably of max. 10 g / Nm 3 dedusted. Under certain circumstances, a dedusting to max. 5 g / Nm 3 makes sense.
• the dedusted exhaust gas 7 in the selective catalytic flue gas cleaning system is cleaned, the SCR catalyst in addition to a NO x reduction also has an oxidizing effect on elemental mercury, if a sufficient content of halogens in the flue gas is present , The mercury oxidation causes a much better deposition of the oxidized mercury on a sorbent compared to unoxidized, ie elemental mercury.
• cooling device 10 and raw material grinding plant 11 are connected in series, so that the exhaust gas 9 is guided in the composite operation by the cooling device 10, which is then not in operation.
• the cooling device 10 which is then not in operation.
• Usually 10 water is injected for cooling in the cooling device. This water injection is then switched off in the combined operation.
• the exhaust gas 9 is thus passed through the cooling device 10 without cooling and enters the raw material grinding plant 11.
• the temperatures reach there quickly a level of usually less than or equal to 110 ° C, which greatly reduces the vapor pressure of the mercury species and thereby promotes adsorption.
• the adsorption does not take place uniformly over the particle size distribution, but rather concentrates in the surface-rich microsphere. This proportion is particularly poorly deposited in the often existing cyclone advance divorce.
• the process filter 12 the deposition of the remaining ultrafine fractions with the already adsorbed mercury takes place.
• there is an additional adsorption of mercury which is significantly lower than that in the raw material grinding plant 11.
• the exhaust gas 9 is supplied to the process filter 12, bypassing the raw material grinding plant 11 via the line 15.
• the cooling device 10 is turned on to the exhaust gas 9 to temperatures of max. 140 ° C, preferably of max. 125 ° C or even max. To cool 110 ° C.
• the cooled exhaust gas is then passed via line 15 to the raw material grinding plant 11 to the process filter 12.
• an additional adsorbent 16 for improved mercury adsorption after the cooling device 10 is injected into the exhaust gas, which is deposited in the process filter 12 together with the residual dust 14.
• the additional adsorbent 16 may be, for example, activated carbon and / or recirculated residual dust 14 act.
• the exhaust gas purified in the process filter 12 is then released into the atmosphere via a chimney 17.
• Fig. 2 shows a second embodiment of the invention, which differs from the variant of FIG. 1 only by a parallel connection of the two equipment parts cooling device 10 and raw material grinding plant 11.
• the exhaust gases 9 do not have to be passed through the switched-off cooling device 10, but are led directly to the raw material grinding plant 11.
• this circuit also allows a mixed operation, in which a part of the exhaust gas 9 can be used in the raw material grinding plant 11, while the remaining part is passed through the cooling device 10.
• the hot dedusting in front of the catalytic flue gas purification unit 8 reduces the mixing of the sorbent (in the case of activated carbon or the like) with dust, thereby increasing the sorbent concentration in the process filter 12.
• the process filter 12 as a bag filter, adsorption on the filter cake additionally takes place.
• the exemplary embodiments described above are distinguished, above all, in direct mode by a reduced mercury emission.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Ceramic Engineering (AREA)
• Health & Medical Sciences (AREA)
• Materials Engineering (AREA)
• Environmental Sciences (AREA)
• Organic Chemistry (AREA)
• Structural Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Biodiversity & Conservation Biology (AREA)
• Ecology (AREA)
• Public Health (AREA)
• General Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biomedical Technology (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Treating Waste Gases (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=45722601

Family Applications (1)

Country Status (5)

Families Citing this family (11)

Family Cites Families (19)

• 2011
  • 2011-02-08 DE DE102011000564A patent/DE102011000564B4/de not_active Expired - Fee Related
• 2012
  • 2012-02-06 US US13/984,057 patent/US9028248B2/en not_active Expired - Fee Related
  • 2012-02-06 EP EP12705084.7A patent/EP2673583A1/fr not_active Withdrawn
  • 2012-02-06 CN CN201280007882.3A patent/CN103459963B/zh not_active Expired - Fee Related
  • 2012-02-06 WO PCT/EP2012/051968 patent/WO2012107404A1/fr active Application Filing

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events