Plant and process for the production of cement clinker with feed for power plant ash

Abstract

Plant (100, 200) for the production of cement clinker (Z), comprising, viewed in the direction of gas flow: - at least one clinker cooler (110, 210) for cooling the sintered cement clinker (Z), - at least one rotary kiln (120, 220) for sintering the cement clinker (Z), - at least one entrained flow reactor (130, 230) for deacidifying raw meal (R) as a feedstock, wherein the at least one entrained flow reactor (130, 230) for deacidifying raw meal (R) follows the at least one rotary kiln (120, 220), - at least one heat exchanger (140, 240) for preheating the raw meal (R), wherein a tertiary air line (150, 250) leads from the cooler inlet (111, 211) of the at least one clinker cooler (110, 210) into at least one entrained flow reactor (130, 230), wherein the tertiary air line (150, 250) is connected in flow connection with at least one further entrained flow reactor (160, 260), can be discharged into the power plant ash (KA), wherein at the end of the at least one further entrained flow reactor (160,260) a cyclone separator (170, 270) is arranged which separates the power plant ash (KA) treated in the at least one further entrained flow reactor (160, 260) from tertiary air (TL), characterized in that the further entrained flow reactor (160, 260) is a gooseneck reactor, the height (HS) of the upper reversal point (US) of which is preferably below the height (HC) of a reversal point (UC) of the entrained flow reactor (130, 230) for deacidifying raw meal (R).

Description

The invention relates to a plant for the production of cement clinker, comprising, viewed in the direction of gas flow, at least one clinker cooler for cooling the sintered cement clinker, at least one rotary kiln for sintering the cement clinker, at least one entrained flow reactor for deacidifying raw meal as a starting product, wherein the at least one entrained flow reactor for deacidifying raw meal follows the at least one rotary kiln, at least one heat exchanger for preheating the raw meal, wherein a tertiary air line leads from the cooler inlet of the at least one clinker cooler into the at least one entrained flow reactor, wherein the tertiary air line is connected in flow communication with at least one further entrained flow reactor, into which power plant ash can be fed, wherein a cyclone separator is arranged at the end of the at least one further entrained flow reactor, which separates the power plant ash treated in the at least one further entrained flow reactor from tertiary air.Power plant ash with low residual moisture and low oxidizable content has been used for cement production for many years, but its availability is dwindling due to the high demand and decreasing number of coal-fired power plants. However, very large quantities of low-grade power plant ash still exist, which, due to its high content of oxidizable components, is currently unsuitable for cement production. This power plant ash is typically stored in sludge reservoirs for long-term interim storage, resulting in a high water content that further complicates its use. The water content can reach up to 30 wt%, and the proportion of oxidizable components is so high that a loss on ignition of up to 20 wt% is achieved.Against the backdrop of the worsening CO2 emission problem and the price pressure in cement production, these power plant ashes are now also coming into focus for the production of cement. German patent application DE 32 37 343 A1 discloses a plant for the production of cement clinker in which an additional entrained-flow reactor is connected between the rotary kiln and the calciner for the rapid heating of the deacidified raw meal. The rapid heating under oxidizing conditions in the additional entrained-flow reactor leads to a higher alite yield. Low-grade fuels, such as coal with a high ash content, are used for the rapid heating process. Chinese utility model application CN 2 11 226 933 U discloses a system for the cooperative treatment of fly ash from municipal waste incineration in connection with a cement plant. The starting point is a conventional cement clinker plant with a rotary kiln, calciner, and heat exchanger stages, to which an additional treatment line for fly ash is connected. For this purpose, a partial stream of the cement plant's tertiary air is fed via a branch line to a suspension heater, into which fly ash from municipal waste incineration is introduced from a separate storage container. In this reactor, the fly ash is suspended in the hot gas stream and thermally treated. The treated fly ash-gas mixture is then fed to a high-temperature gas-solid separator, in which the solid components are separated from the gas phase.The separated fly ash is subsequently cooled and collected as a treated end product, while the gas stream undergoes a further condensation and cooling stage to remove chlorides. Only after this additional treatment is the remaining exhaust gas reintroduced into the calciner of the cement plant to utilize the waste heat. The system described in CN 2 11 226 933 U thus serves for the thermal detoxification and separation of pollutants from waste incineration fly ash using process heat from the cement plant. The invention is based on the objective of thermally treating low-grade power plant ashes, which are characterized by high proportions of water up to 30 wt.% and oxidizable components that lead to a loss on ignition of up to 20 wt.%, in a process integrated into clinker production, thus enabling their suitability for the production of cement. The problem according to the invention is solved by a plant for the production of cement clinker with the features of claim 1. A corresponding process for the production of cement clinker with the addition of power plant ash is claimed in claim 3. Further advantageous embodiments of the plant are specified in the dependent claim to claim 1. According to the invention, the tertiary air line of a generic cement clinker production plant is connected to at least one other entrained-flow reactor and can be fed with power plant ash. The tertiary air line thus splits into two gas streams. A first partial gas stream flows to the entrained-flow reactor where limestone is deacidified, and a second partial gas stream flows to the other entrained-flow reactor where the power plant ash is dried and combusted. Combustion occurs predominantly autothermally through the oxidizable components but can also be supported by the addition of fuel if necessary. The power plant ash must be burned under oxidizing conditions to prevent the oxidizable residual components from finding their way into the cement and reducing its quality. At the end of at least one additional entrained flow reactor is a cyclone separator that separates the treated power plant ash from the tertiary air. The treated and separated power plant ash is cooled and discharged from the cement clinker production plant, where it can then be used for cement production. The tertiary air, now containing less oxygen due to the residual combustion, is introduced into the rest of the cement clinker production plant. At the end of at least one additional entrained flow reactor is a cyclone separator that separates the treated power plant ash from the tertiary air. The treated and separated power plant ash is cooled and discharged from the cement clinker production plant, where it can then be used for cement production. The tertiary air, now containing less oxygen due to the residual combustion, is introduced into the rest of the cement clinker production plant. In a further embodiment of the inventive system, a gas outlet of the cyclone separator can be connected to the at least one entrained flow reactor for deacidifying raw meal, wherein the corresponding gas inlet on the at least one entrained flow reactor for deacidifying raw meal is preferably arranged above the tertiary air outlet. Alternatively or cumulatively, a solids outlet of the cyclone separator can be connected to the at least one heat exchanger for preheating the raw meal, with the corresponding solids inlet on the at least one heat exchanger for preheating the raw meal preferably corresponding to the solids inlet for raw meal. This ensures optimal mixing of the raw meal with the treated power plant ash, so that the cement clinker at the end of the plant has a uniform composition and does not exhibit domains of different clinker composition. To avoid the lifting work for suspending the power plant ash causing an excessive pressure loss in the plant, it is provided that the further entrained flow reactor is a gooseneck reactor, the height of which of the upper reversal point is preferably below the height of a reversal point of the entrained flow reactor for deacidifying raw meal. Corresponding to the plant, the process for producing cement clinker in the previously described plant consists of the following process steps: preheating raw meal in a heat exchanger, deacidification of the preheated raw meal in a fluidized bed reactor, sintering of the deacidified raw meal to cement clinker, and cooling of the sintered cement clinker. According to the invention, power plant ash, which is generated during the cooling of the cement clinker, is suspended in tertiary air. During suspension in the hot tertiary air, the suspended power plant ash is dried and burned off in a further fluidized bed reactor. After drying and burning off, the dried and burned-off power plant ash is separated from the tertiary air in a cyclone separator. The separated tertiary air is introduced into the fluidized bed reactor for deacidification of the preheated raw meal. The invention is explained in more detail with reference to the following figures. It shows: Fig. 1 a first embodiment of a plant according to the invention for the production of cement, Fig. 2 a second embodiment of a plant according to the invention for the production of cement. Figure 1 shows a first embodiment of a plant 100 according to the invention for the production of cement clinker Z. The plant 100 for the production of cement clinker Z comprises the following components in the direction of gas flow: first, at least one clinker cooler 110 for cooling the sintered cement clinker Z. It is possible for more than one clinker cooler 110 to operate in parallel or alternately. Following the direction of gas flow is at least one rotary kiln 120 for sintering the cement clinker Z. It is also possible for more than one rotary kiln 120 to operate in parallel. The capacity of the different rotary kilns 120 can be the same or different. Following the at least one rotary kiln 120 is at least one entrained-flow reactor 130 for deacidifying raw meal R as the starting material for the cement clinker Z.In the case of the flow reactors 130, more than one flow reactor can operate in parallel, and these different flow reactors 130 can have different capacities. The preheating of the raw meal R to near the deacidification temperature in the flow reactor 130 takes place in at least one heat exchanger 140. A tertiary air line 150 leads from the cooler inlet 111 of the at least one clinker cooler 110 into the at least one flow reactor 130 and terminates therein. The tertiary air TL has a high temperature and an atmospheric oxygen content. This hot ambient air is ideally suited for maintaining the deacidification temperature in the flow reactor 130 for deacidifying the raw meal R. The tertiary air line 150 is connected to at least one further flow reactor 160, into which power plant ash KA can be fed.The power plant ash KA is suspended in the entrained flow reactor 160, where it first dries in the hot tertiary air TL and then burns off. The oxygen content of the hot tertiary air TL is sufficient to burn off the remaining oxidizable components in the power plant ash KA. At the end of the at least one additional entrained flow reactor 160, a cyclone separator 170 is arranged, which separates the power plant ash KA treated in the at least one additional entrained flow reactor 160 from the tertiary air TL. The separated tertiary air TL flows into an upper part of the entrained flow reactor 130. Separated power plant ash KA, on the other hand, is discharged for cement production.The height HS of the reversal point US of the further entrained flow reactor 160 is below the height HC of the reversal point UC of the entrained flow reactor 130, in order to avoid the pressure drop in the further entrained flow reactor 160 becoming too high, so that the tertiary air TL does not preferentially flow into the entrained flow reactor 130 for the deacidification of the raw meal R. Figure 2 shows a second embodiment of a non-inventive plant 200 for the production of cement clinker Z. Like the previously described plant 100, the plant 200 for the production of cement clinker Z has the following components in the direction of gas flow: first, at least one clinker cooler 210 for cooling the sintered cement clinker Z. It is possible for more than one clinker cooler 210 to operate in parallel or alternately. Following this in the direction of gas flow is at least one rotary kiln 220 for sintering the cement clinker Z. It is also possible for more than one rotary kiln 220 to operate in parallel. The capacity of the different rotary kilns 220 can be the same or different. Following the at least one rotary kiln 220 is at least one entrained-flow reactor 230 for deacidifying raw meal R as the starting material for the cement clinker Z.In these flow-through reactors 230, more than one flow-through reactor 230 can operate in parallel, and the different flow-through reactors 230 can have different capacities. The preheating of the raw meal R to near the deacidification temperature in the flow-through reactor 230 takes place in at least one heat exchanger 240. A tertiary air line 250 leads from the cooler inlet 211 of the at least one clinker cooler 210 into the at least one flow-through reactor 230 and terminates therein. The tertiary air TL has a high temperature and an atmospheric oxygen content. This hot ambient air is ideally suited for maintaining the deacidification temperature in the entrained flow reactor 230 for deacidifying the raw meal R. The tertiary air line 250 is connected in flow connection with at least one further entrained flow reactor 260, into which power plant ash KA can be fed.The power plant ash KA is suspended in the entrained flow reactor 260, where it first dries in the hot tertiary air TL and then burns off. The oxygen content of the hot tertiary air TL is sufficient to burn off the remaining oxidizable components in the power plant ash KA. At the end of the at least one additional entrained flow reactor 260, a cyclone separator 270 is arranged, which separates the power plant ash KA treated in the at least one additional entrained flow reactor 260 from the tertiary air TL. The cyclone separator 270 shown here is arranged approximately at the level of the reversal point US of the entrained flow reactor 260 to avoid any loss of height for the extracted power plant ash KA. The separated tertiary air TL flows into an upper part of the entrained flow reactor 230. The separated power plant ash KA, on the other hand, is used for cement production. REFERENCE MARK LIST 100 Plant 110 Clinker cooler 111 Cooler inlet 120 Rotary kiln 130 Fluidized bed reactor 132 Gas inlet 140 Heat exchanger 141 Solids inlet 145 Heat exchanger cyclone 146 Heat exchanger cyclone 147 Heat exchanger cyclone 148 Heat exchanger cyclone 150 Tertiary air line 151 Tertiary air outlet 160 Fluidized bed reactor 170 Cyclone separator 171 Solids outlet 172 Gas outlet 200 Plant 210 Clinker cooler 211 Cooler inlet 220 Rotary kiln 230 Fluidized bed reactor 232 Gas inlet 231 Solids inlet 240 Heat exchanger 241 Solids inlet 245 Heat exchanger cyclone 246 Heat exchanger cyclone 247 Heat exchanger cyclone 248 Heat exchanger cyclone 250 Tertiary air duct 251 Tertiary air outlet 260 Fluidized bed reactor 270 Cyclone separator 271 Solids outlet 272 Gas outlet A Exhaust air B Fuel HCH height HSH height KA Power plant ash L Air R Raw meal TL Tertiary air UC Reversal point US Reversal point Z Cement clinker

Claims

Plant (100, 200) for the production of cement clinker (Z), comprising, viewed in the direction of gas flow: - at least one clinker cooler (110, 210) for cooling the sintered cement clinker (Z), - at least one rotary kiln (120, 220) for sintering the cement clinker (Z), - at least one entrained flow reactor (130, 230) for deacidifying raw meal (R) as a feedstock, wherein the at least one entrained flow reactor (130, 230) for deacidifying raw meal (R) follows the at least one rotary kiln (120, 220), - at least one heat exchanger (140, 240) for preheating the raw meal (R), wherein a tertiary air line (150, 250) leads from the cooler inlet (111, 211) of the at least one clinker cooler (110, 210) into at least one entrained flow reactor (130, 230), wherein the tertiary air line (150, 250) is connected in flow connection with at least one further entrained flow reactor (160, 260), can be discharged into the power plant ash (KA), wherein at the end of the at least one further entrained flow reactor (160,260) a cyclone separator (170, 270) is arranged which separates the power plant ash (KA) treated in the at least one further entrained flow reactor (160, 260) from tertiary air (TL), characterized in that the further entrained flow reactor (160, 260) is a gooseneck reactor, the height (HS) of the upper reversal point (US) of which is preferably below the height (HC) of a reversal point (UC) of the entrained flow reactor (130, 230) for deacidifying raw meal (R). Plant according to claim 1, characterized in that a gas outlet (172, 272) of the cyclone separator (170, 270) is connected to the at least one entrained flow reactor (130, 230) for deacidifying raw meal (R), wherein the corresponding gas inlet (132, 232) is arranged on at least one entrained flow reactor (130, 230) for deacidifying raw meal (R) preferably above the tertiary air outlet (151, 251). A process for producing cement clinker (Z) in a plant (100, 200) according to claims 1 or 2, comprising: - preheating raw meal (R) in a heat exchanger (140, 240), - deacidifying the preheated raw meal (R) in an entrained flow reactor (130, 230), - sintering the deacidified raw meal (R) to cement clinker (Z), - cooling the sintered cement clinker (Z), characterized by: - ​​suspending power plant ash (KA) in tertiary air (TL) generated during cooling of the cement clinker (Z), - drying and autothermally burning off the suspended power plant ash (KA) in a further entrained flow reactor (160, 260), - separating the dried and burned-off power plant ash (KA) from the tertiary air (TL), - supplying the separated tertiary air (TL) to the Flow reactor (130, 230) for deacidifying the preheated raw meal (R), - wherein the supply of the separated tertiary air (TL) into the flow reactor (130,230) for the deacidification of the preheated raw meal (R) above the feed of the separated power plant ash (KA) into the entrained flow reactor (130, 230).

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