Method for the production of cement clinker by processing accumulated carbon dioxide in order to form methanol
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- KHD HUMBOLDT WEDAG GMBH
- Filing Date
- 2024-07-29
- Publication Date
- 2026-06-17
Smart Images
Figure EP2024071457_13022025_PF_FP_ABST
Abstract
Description
[0001] Process for the production of cement clinker with processing of resulting carbon dioxide into methanol
[0002] The invention relates to a process for the production of cement clinker with processing of resulting carbon dioxide to methanol, comprising the steps of preheating raw meal from silicate-containing and calcareous rock in a preheater, calcining the raw meal in a calciner, sintering the calcined raw meal in a rotary kiln, wherein the exhaust gas from the rotary kiln enters the calciner and flows there into the preheater, cooling the sintered cement clinker in a clinker cooler, wherein a first part of the cooling air from the clinker cooler flows as primary air in a rotary kiln burner for heating the rotary kiln, and wherein a second part of the cooling air from the clinker cooler flows as tertiary air via a tertiary air line to the calciner, and wherein a third part of the cooling air from the clinker cooler is discarded as exhaust air or used for drying electrolysis sludge,wherein the exhaust gas from the preheater flows wholly or partly and directly or indirectly into a reactor for producing methanol (CH3OH) from the carbon dioxide (CO2) and carbon monoxide (CO) contained in the exhaust gas by reacting it with hydrogen (H2) in the reactor.
[0003] In recent decades, the harmful impact of anthropogenic emissions on the global climate has become apparent. The industrial sector, including cement clinker production facilities, remains one of the leading contributors to anthropogenic CO2 emissions. With the increasing demand for cement, there is an urgent need for solutions that mitigate the environmental impact of this important industry in terms of carbon dioxide (CO2) emissions.
[0004] In the production of cement clinker, a key step is the calcination of limestone, which leads to significant emissions of carbon dioxide (CO2) in addition to the release of carbon dioxide (CO2) from the combustion of fossil fuels because carbon dioxide (CO2) is formally thermally expelled from the limestone (calcium carbonate, CaCO3). The thermal expulsion of carbon dioxide (CO2)
[0005] CaCOs CaO + CO2 spontaneously decomposes in the heat from about 700°C to leave unslaked lime (CaO) for the further sintering of the unslaked lime with silicate rock, so since not only carbon dioxide (CO2) is produced from the combustion of fossil fuels, but also mineral-bound carbon dioxide (CO2) is released, the emission of carbon dioxide (CO2) is particularly high.
[0006] In order to avoid the unwanted emission of carbon dioxide (CO2) during the production of cement clinker, various processes are proposed for dealing with the inevitably produced carbon dioxide (CO2). For this purpose, processes are presented that produce cement clinker in a pure atmosphere of carbon dioxide (CO2). The pure carbon dioxide (CO2) is then injected into terrestrial aquifers. Processes are also proposed that wash out the carbon dioxide (CO2) present along with nitrogen (N2) and a residual amount of oxygen (O2) from the exhaust gases of a cement clinker production plant and then inject it. Other processes exist in which the resulting carbon dioxide (CO2) is further processed into methanol (CH3OH) with the addition of hydrogen (H2), regardless of the source.Binding hydrogen (H2) does have the disadvantage that part of the available combustion enthalpy is no longer available, thus reducing the calorific value of the hydrogen (H2). However, the advantage is that the energy contained in the hydrogen (H2) becomes easier to transport. Hydrogen (H2) must either be highly compressed, which requires very heavy tanks, or the hydrogen (H2) must be deep-frozen, which requires corresponding cryogenic facilities. Both types of storage, namely compression or deep-freezing, have proven too complex for widespread use as an energy source for transport and households. The German laid-open application DE 10 2016209 037 A1 discloses a process for coupling a process for producing cement clinker with a biotechnological process.Among other things, it is proposed to convert carbon dioxide (CO2) into methanol (CH3OH) with the addition of hydrogen (H2). However, the coupling efficiency of the systems taught there is still relatively low, so the energy balance for producing methanol (CH3OH) from carbon dioxide (CO2) for its de facto disposal is not economically very attractive.
[0007] The object of the invention is therefore to improve the energy balance for the production of methanol (CH3OH) from carbon dioxide (CO2) in such a way that less energy has to be used to produce methanol (CH3OH).
[0008] The object of the invention is thereby achieved by a method having the features of claim 1. Further advantageous embodiments are specified in the subclaims to claim 1.
[0009] According to the concept of the invention, it is proposed to generate synthesis gas for the production of methanol in a coupled process with a process for the production of cement clinker. The synthesis gas consists of carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2). Carbon dioxide (CO2) is inevitably produced during the production of cement clinker from calcareous and silicate-containing rock. Hydrogen (H2) is generated by high-temperature electrolysis of water (H2O). For this purpose, electrical power from renewable energies, in particular from wind power, is used directly for the high-temperature electrolysis of the water (H2O) to form hydrogen (H2) and oxygen (O2). The thermal energy required for the high-temperature electrolysis is taken from the process for the production of cement clinker.Carbon monoxide (CO) is ultimately produced during substoichiometric combustion of fossil fuels or low-calorie fuels with less oxygen (O2) than is necessary for complete combustion. Substoichiometric combustion can be achieved by using low-oxygen exhaust air. This low-oxygen exhaust air has a lower oxygen concentration than atmospheric air. To adjust the oxygen content of the low-oxygen air, exhaust air from a combustion process for the production of cement clinker, typically containing 4% oxygen (O2), can be mixed with atmospheric air. Low-calorie fuels can be industrial waste, household waste, but also a variety of other typical secondary fuels such as old tires, animal carcasses, wood waste, and various types of undried sludge. Finally, fermented biomass from gas generators can also be considered as a secondary fuel.
[0010] Overall, the coupling of a cement clinker production process with the methanol production process takes place at several points. Heat is extracted from the cement clinker production process. This heat is used to provide heat for high-temperature electrolysis. Electricity from renewable energies is used to carry out the electrolysis. In addition, secondary fuel is burned substoichiometrically. This produces a large excess of carbon monoxide (CO). The excess carbon monoxide (CO) reduces nitrogen oxide (NOx) produced during the combustion of the fuels in the upstream rotary kiln of the cement clinker production process. The slip of carbon monoxide (CO) resulting from the large excess of carbon monoxide (CO) is why the coupling with the methanol (CH3OH) production process is desirable for this purpose.Not only pure water, but also sludge and even manure from biogas production plants can be used as a source of hydrogen (H2). This, in turn, produces dry residual waste that can be used as a secondary fuel. Finally, the oxygen (O2) produced during high-temperature electrolysis can be used to generate a hotter flame in the rotary kiln with oxygen-enriched primary air.
[0011] The invention is explained in more detail with reference to the following figures. It shows:
[0012] Fig. 1 shows a plant for producing cement clinker for carrying out the process according to the invention.
[0013] Figure 1 outlines a plant 100 for producing cement clinker for carrying out the process according to the invention. Raw meal is fed into a cyclone heat exchanger 110, which has five heat exchanger cyclones 111, 112, 113, 114, and 115. In the cyclone heat exchanger 110, the fed raw meal flows toward hot exhaust air from the calciner 120. The raw meal heats up, and the exhaust air from the calciner 120 cools down. In the penultimate heat exchanger cyclone 114, the raw meal is separated and fed into the calciner 120. The calciner 120 operates as an entrained-flow reactor and entrains the raw meal originating from the heat exchanger cyclone 114 in the exhaust air of the exhaust gas flowing into it from the rotary kiln 130. During the flight in the exhaust gases from the rotary kiln 130, which are approximately 800°C to 850°C, the raw meal is deacidified, releasing carbon dioxide (CO2).After deacidification, the hot exhaust gas and the deacidified raw meal flow into the lowest heat exchanger cyclone 115, where the deacidified raw meal is separated from the exhaust gases of the calciner 120. From there, the raw meal is fed into the rotary kiln 130, where it is sintered at a temperature above 1,250°C with a flame at 1,450°C. After passing through the rotary kiln 130, the sintered cement clinker falls into a clinker cooler 140. At the head of the rotary kiln 140, which extends into the clinker cooler 140, cooling air obtained from atmospheric air heats up particularly strongly and reaches temperatures of up to 1,200°C. This portion of the cooler exhaust air is passed as tertiary air via a tertiary air line 150 into the calciner 120 in order to supply the calciner 120 with additional heat, because the pure exhaust air of the rotary kiln 130 alone is not sufficient to maintain the very heat-consuming deacidification process in the calciner 120.The tertiary air also has an oxygen content like atmospheric air and can therefore be used as preheated combustion air for the combustion of secondary fuels in the calciner 120. Typically, the secondary fuel in the calciner 120 is burned substoichiometrically, meaning it burns with too little oxygen compared to the available fuel quantity, producing carbon monoxide (CO). The carbon monoxide (CO) reacts with the nitrogen oxides (NOx) present in the hot exhaust air from the rotary kiln 120. Due to the very high sintering temperature in the rotary kiln 120, nitrogen oxides (NOx) form from atmospheric nitrogen and from organically bound nitrogen in the primary fuel for the rotary kiln burner 135. Cooling air flowing through the clinker cooler 140 at a greater distance from the rotary kiln head has a significantly lower temperature, ranging from 250°C to 300°C.This cooler cooler exhaust air is used here to dry secondary fuel, such as biomass, industrial waste or household waste in a fuel dryer 160.
[0014] In an initially parallel process, electrical power is generated using a wind turbine from individual wind power plants 200. The electrical energy is fed into a high-temperature electrolysis cell 210, where sludge, liquid manure, or even just water is electrolyzed as the electrolyte. This produces hydrogen (H2) and oxygen (O2). The oxygen (O2) can be fed into the primary air supply of the rotary kiln burner 135 to generate a higher temperature. The primary air can be extracted in the area of the clinker cooler 140, where the tertiary air is removed, or it is also possible to enrich atmospheric air with the extracted oxygen (O2). The oxygen-enriched atmospheric air is necessarily depleted of nitrogen, so that fewer nitrogen oxides (NOx) are produced from atmospheric nitrogen in the burner.The hydrogen (H2) produced in the high-temperature electrolysis cell 210 is finally fed into a reactor 220, where it reacts with carbon dioxide (CO2) and the excess carbon monoxide (CO) in the exhaust air flowing from the cyclone heat exchanger 110, producing methanol (CH3OH) according to the following reaction equations:.
[0015] CO + 2 H2CH3OH; AH = -90.8 kJ / mol at 300 K and -49.6 kJ / mol at 300 K
[0016] These two reactions are exothermic. According to Le Chatelier's principle, low temperatures and an increase in pressure shift the equilibrium to the right. The waste heat from methanol synthesis can be used to preheat the electrolyte in the high-temperature electrolysis cell 210. Copper-zinc oxide-aluminum oxide catalysts are used for methanol synthesis. These are produced by coprecipitation starting from copper, zinc, and aluminum hydroxycarbonates. Further steps include washing, aging, drying, calcination, and activation by reduction in a hydrogen / nitrogen stream, whereby the copper oxide formed during calcination is reduced to the metal. To purify the exhaust air, an exhaust air scrubber can be provided in a scrubber 105, which separates carbon dioxide (CO2) and carbon monoxide (CO). Nitrogen-enriched exhaust air remains, which can be discarded.
[0017] According to the concept of the invention, the high-temperature electrolysis cell 210 is heated with the heat extracted from the tertiary air in the tertiary air line 150 by a heat exchanger 155. Since the tertiary air in the tertiary air line 150 now has a lower temperature, the calciner 120 must be heated with more secondary fuel to maintain its heat-consuming deacidification process. The additional amount of secondary fuel can be replenished with sludge from the remaining electrolyte, dried by cooler exhaust air from the rear section of the clinker cooler 140, if the electrolyte consists of biomass, in particular liquid manure. If the electrolyte consists of water, then a larger amount of secondary fuel can simply be used, which is also dried by the cooler exhaust air from the clinker cooler 140.
[0018] The highly intensive integration of methanol production into the cement clinker production process presented here has several advantages: First, hydrogen from renewable energies is processed into methanol. This results in a significantly easier-to-handle fuel. Furthermore, it is possible to operate with a high excess of carbon monoxide in the cement clinker production process. This excess of carbon monoxide reduces nitrogen oxides (NOx). In conventional processes for producing cement clinker, it was previously necessary to control the amount of carbon monoxide very carefully in order to avoid creating a new problem of undesirable carbon monoxide slip during the chemical reduction of nitrogen oxides (NOx). A further advantage is that hydrogen (H2) can be produced with greater efficiency, meaning less energy is used with electricity to produce the same amount of hydrogen (H2).Finally, the process according to the invention can also be used to energetically recover fermented manure, which is a waste that is difficult to dispose of.
[0019] LIST OF REFERENCE SYMBOLS Plant 130 Rotary kiln scrubber 135 Rotary kiln burner cyclone heat exchanger 140 Clinker cooler heat exchanger cyclone 150 Tertiary air line heat exchanger cyclone 155 Heat exchanger heat exchanger cyclone 160 Fuel dryer heat exchanger cyclone 200 Wind power plant heat exchanger cyclone 210 High-temperature electrolysis cell calciner
[0020] 220 reactor
Claims
PATENT CLAIMS 1 . A process for producing cement clinker by processing carbon dioxide produced to methanol, comprising the steps Preheating of raw meal from silicate and calcareous rock in a preheater, Calcining the raw meal in a calciner (120), Sintering the calcined raw meal in a rotary kiln (130), whereby the exhaust gas from the rotary kiln (130) enters the calciner (120) and flows there into the preheater, Cooling the sintered cement clinker in a clinker cooler (140), wherein a first part of the cooling air from the clinker cooler (140) flows as primary air in a rotary kiln burner (135) for heating the rotary kiln (130), and wherein a second part of the cooling air from the clinker cooler (140) flows as tertiary air via a tertiary air line (150) to the calciner (120), and wherein a third part of the cooling air from the clinker cooler (140) is discarded as exhaust air or used for drying electrolysis sludge, wherein the exhaust gas from the preheater flows wholly or partly and directly or indirectly into a reactor (220) for producing methanol (CH3OH) from the carbon dioxide (CO2) and carbon monoxide (CO) contained in the exhaust gas by reacting it with hydrogen (H2) in the reactor (220), characterized by Heating a high-temperature electrolysis cell (210) with heat from the aforementioned method for generating hydrogen (H2) from a preheated electrolyte, so that the electrolyte is heated to a temperature between 100°C and 850°C.
2. Method according to claim 1, characterized by Heating a high-temperature electrolysis cell (210) with heat extracted via a heat exchanger (155) in the tertiary air line (150).
3. Method according to claim 1 or 2, characterized by Combustion of the electrolysis sludge remaining in the high-temperature electrolysis cell (210) in the calciner (120).
4. Method according to claim 1 to 3, characterized by Directing the oxygen (O2) produced during electrolysis into a primary air supply of a rotary kiln burner (135) for heating the rotary kiln (130).
5. Method according to one of claims 1 to 4, characterized by Feeding the hydrogen (H2) produced during electrolysis into the reactor to produce methanol (CH3OH).
6. Method according to claim 1, characterized by Scrub the exhaust gases from the preheater to separate carbon dioxide (CO2) and carbon monoxide (CO) and introduce the carbon dioxide (CO2) and carbon monoxide (CO) into the reactor to produce methanol (CH3OH).
7. Method according to claim 1, characterized by Using electrical power from renewable energy sources, particularly wind power or tidal power, to power electrolysis.
8. A process according to any one of claims 1 to 7, characterized by substoichiometric combustion of secondary fuel and / or electrolysis sludge in the calciner 8120) to produce carbon monoxide (CO).
9. Method according to one of claims 1 to 8, characterized by Using biomass as an electrolyte, especially using manure as an electrolyte.