Methanol Production via Solar Reforming of Methane

In der vorliegenden Arbeit wird ein solarer Reformierungsprozess zur Methanolherstellung untersucht. Der Prozess stellt eine Möglichkeit dar, die mit diesem Herstellungsprozess verbundenen Treibhausgasemissionen zeitnah bedeutend zu reduzieren. Hiermit wäre ein wesentlicher Schritt in der Entwicklung einer nachhaltigeren Chemieindustrie geleistet. Darüber hinaus lässt sich Methanol auch als Brennstoff einsetzen. So kann Methanol einen Beitrag zu einer klimaschonenderen Energieversorgung leisten, wenn er durch solare Reformierung produziert wird. Zunächst wurde in der Arbeit ein Gesamtprozess auf Basis der indirekt beheizten solaren Reformierung entwickelt. Hierbei war ein Ziel die anfallenden Abwärmeströme zu nutzen. Infolgedessen wird ein großer Teil der Abwärme in einem Wasser-Dampf-Kreislauf zur Stromproduktion genutzt, da es hierfür keine sinnvolle Verwendung im Prozess gibt. Darüber hinaus wird der Off-Gas-Strom der Methanolsynthese teilweise zur Stromproduktion eingesetzt. Der entwickelte Prozess nutzt Sonnenenergie und Erdgas und produziert hieraus Methanol und elektrischen Strom. Das Verhältnis der verschiedenen Ströme zueinander ist hierbei durch Parametervariation veränderbar. Eine Optimierung mit herkömmlichen Bewertungskriterien wie Energie- oder Exergiebilanzen ist daher nicht möglich. Folglich wurde ein Bewertungskriterium entwickelt, dass auf dem Ziel basiert den Verbrauch der Fossilen Rohstoffe und die damit verbundenen Treibhausgasemissionen zu reduzieren. Auf Basis dieses Bewertungskriteriums wurde der Prozess mithilfe von Parametervariationen optimiert. Die Ergebnisse zeigen, dass der Prozess das Potential hat Sonnenenergie effektiver zu nutzen, als dies bei der reinen Stromproduktion der Fall ist. Eine anschließende Wirtschaftlichkeitsbetrachtung zeigte, dass der Prozess zur konventionellen Sonnenenergienutzung theoretisch konkurrenzfähig ist. In der Praxis müssten hierfür jedoch entsprechende Fördermechanismen, wie sie für die Stromproduktion existieren, für die Herstellung von Chemierohstoffen eingeführt werden

On the economics of solar chemical processes - case study for solar co-production of methanol and power

In several studies, the efficiency of solarized industrial processes was assessed and showed promising results. However, the economic competitiveness of such processes is a mainly unanswered question. In this work, the economic performance of a solar aided methanol production process is determined. The assessment yields promising results for the considered co-production process. The presented results also show that for a penetration of renewable energies beyond electricity production, the common support model of fixed feed-in-tariffs is not suitable. A reasonable cost for CO2 emissions or reward for their reduction will allow finding the most economic application for renewable energies independent of the end product of the process. When reasonable rewards of 75 $/tCO2 for the reduction of CO2 emissions compared to fossil reference processes are considered, the process can produce methanol and electricity at competitive prices

Morgen Tanken wir Sonne

Morgen tanken wir Sonn

Methanol production via solar reforming of methane

In the present work, a solar reforming process for production of methanol was investigated. With this process, it is possible to reduce the greenhouse-gas emissions associated with the production of methanol significantly in the near-term future. This would be a significant step in the development of a more sustainable chemical industry. Furthermore, methanol can be applied as a fuel. Thus, methanol can contribute to a more climate friendly energy supply, if it is produced via solar reforming.First of all, the overall reforming process was developed based on the concept of indirectly heated solar reforming. One central aspect of this was to make use of the waste-heat streams. As a consequence a large fraction of the off heat is converted into electricity in a water steam cycle, because no other demand exists for this heat. Furthermore, the off-gas stream of the methanol synthesis is partly used for additional electricity production.The developed process uses solar energy and natural gas to produce methanol and electricity. The ratio between the different streams can be changed by parameter variation. An optimization of the process with conventional criteria such as energy- or exergy-balances is therefore not possible. Thus, a new evaluation criterion was developed. This criterion is based on the target to reduce fossil fuels reduction and the associated greenhouse-gas emissions.Based on this evaluation criterion, the process was optimized by parameter variation. The results show that the process has the potential to make more efficient use of solar energy than is the case for sole production of electricity. A subsequent economic investigation showed that the developed process can in theory be competitive with conventional solar energy utilization. However, in practice support mechanism, as they exist for solar electricity production, would have to be implemented for solar production of chemical feedstocks

(Solar) Mixed Reforming of Methane: Potential and Limits in Utilizing CO2 as Feedstock for Syngas Production—A Thermodynamic Analysis

The reforming of natural gas with steam and CO2 is commonly referred to as mixed reforming and considered a promising route to utilize CO2 in the production of synthetic fuels and base chemicals such as methanol. In the present study, the mixed reforming reaction is assessed regarding its potential to effectively utilize CO2 in such processes based on simple thermodynamic models. Requirements for the mixed reforming reactions based on process considerations are defined. These are the avoidance of carbon formation in the reactor, high conversion of the valuable inlet streams CH4 and CO2 as well as a suitable syngas composition for subsequent synthesis. The syngas composition is evaluated based on the module M = ( z H 2 − z CO 2 ) / ( z CO 2 + z CO ) ,   which should assume a value close to 2. A large number of different configurations regarding CO2/H2O/CH4 at the reactor inlet, operating pressure and outlet temperature are simulated and evaluated according to the defined requirements. The results show that the actual potential of the mixed reforming reaction to utilize CO2 as feedstock for fuels and methanol is limited to approximately 0.35 CO2/CH4, which is significantly lower than suggested in literature. At 900 °C and 7 bar at the reactor outlet, which is seen suitable for solar reforming, a ratio of H2O/CH4 of 1.4 can be set and the resulting value of M is 1.92 (CO2/CO/H2 = 0.07/0.4/1)

Moving Brick Receiver-Reactor (MBR2): A Solar Thermochemical Reactor and Process Design with a Solid-Solid Heat Exchanger and On-demand Production of Hydrogen and/or Carbon Monoxide

Two crucial aspects still to be overcome to achieve commercial competitiveness of the solar thermochemical splitting of water and carbon dioxide are recovering the heat and achieving continuous or on-demand production beyond the hours of sunshine. To tackle both aspects we propose a moving brick receiver-reactor (MBR2) design with a solid-solid heat exchanger. In short, the MBR2 consists of (i) bricks that are reversibly mounted on a high temperature transport mechanism, (ii) a receiver-reactor where the bricks are reduced by passing through the concentrated solar radiation, (iii) a solid-solid heat exchanger under partial vacuum in which the reduced bricks transfer heat to the oxidized bricks, (iv) a first storage for the reduced bricks, (v) an oxidation reactor, and (vi) a second storage for the oxidized bricks. Because of the high temperature of up to 1800 K in the receiver-reactor, the transport mechanism has to be made out of ceramic material, for example a ceramic chain. On such a ceramic chain grippers can be fixed in order to hold the bricks during transport. The velocity of the transport mechanism can be adjusted as desired depending on the actual incoming solar radiation and the reaction kinetics. The key benefits of the MBR2 include the possibility to efficiently recover the sensible heat in the reduced bricks, the precise residence time control of the bricks in the receiver-reactor, the steady-state operation of the receiver-reactor after startup, the adjustability of inclination of the receiver-reactor, the possibility to optimize the bricks for radiation absorption and reaction characteristics, the possibility to store the reduced bricks and feed the oxidation reactor continuously or on-demand, the reduction of dust production due to highly reduced abrasion, and the good scalability. To quantify the effects of these benefits on the overall efficiency we performed first theoretical calculations of the heat exchanger and receiver-reactor subsystems. We show that the heat exchanger may recover a large share of the sensible heat which typically is more than half of the total heat loss. On the basis of these calculations, we expect the MBR2 to increase the overall efficiency of solar syngas production substantially

Assessment of solid heat recovery strategies for solar thermochemical cycles – Proposal of a new particle based solid heat recovery concept

The most advanced solar thermochemical cycles in terms of demonstrated reactor efficiencies are based on temperature swing operated receiver-reactors with open porous ceria foams as redox material. The demonstrated efficiencies are encouraging but especially for cycles based on ceria as redox material studies have pointed out the importance for high solid heat recovery rates to reach competitive process efficiencies. Different concepts for solid heat recovery have been proposed mainly for other types of reactors and demonstration campaigns have shown first advances. Still, solid heat recovery remains an unsolved challenge. In this study chances and limitations for solid heat recovery using a thermal storage unit with gas as heat transfer fluid are assessed. A numerical model for the reactor is presented and used to analyze the performance of a storage unit coupled to the reactor. The results show that such a concept could decrease the solar energy demand by up to 40% and should be further investigated