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Process Simulations of High-Purity and Renewable Clean H2 Production by Sorption Enhanced Steam Reforming of Biogas
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2023-03-11 , DOI: 10.1021/acssuschemeng.2c07316
Alma Capa 1, 2 , Yongliang Yan 3 , Fernando Rubiera 1 , Covadonga Pevida 1 , María Victoria Gil 1 , Peter T. Clough 2
Affiliation  

Renewable clean H2 has a very promising potential for the decarbonization of energy systems. Sorption enhanced steam reforming (SESR) is a novel process that combines the steam reforming reaction and the simultaneous CO2 removal by a solid sorbent, such as CaO, which significantly enhances hydrogen generation, enabling high-purity H2 production. The CO2 sorption reaction (carbonation) is exothermic, but the sorbent regeneration by calcination is highly endothermic, which requires extra energy. Biogas is one of the available carbon-neutral renewable H2 production sources. It can be especially relevant for the energy integration of the SESR process since, due to the exothermic sorption reaction, the CO2 contained in the biogas provides extra heat to the system, which can help to balance the energy requirements of the process. This work studies different process configurations for the energy integration of the SESR process of biogas for high-purity renewable H2 production: (1) SESR with sorbent regeneration using a portion of the produced H2 (SESR+REG_H2), (2) SESR with sorbent regeneration using biogas (SESR+REG_BG), and (3) SESR with sorbent regeneration using biogas and adding a pressure swing adsorption (PSA) unit for hydrogen purification (SESR+REG_BG+PSA). When using biogas as fuel (Cases 2 and 3), these configurations were studied using air and oxy-fuel combustion atmospheres in the sorbent regeneration step, resulting in five case studies. A thermodynamic approach for process modeling can provide the optimal process operating conditions and configurations that maximize the energy efficiency of the process, which are the basis for subsequent optimization of the process at the practical level needed to scale up this technology. For this purpose, process simulations were performed using a steady-state plant model developed in Aspen Plus, incorporating a complex heat exchanger network (HEN) to optimize heat integration. A comprehensive parametric study assessed the effects of biogas composition, temperature, pressure, and steam to methane (S/CH4) ratio on the process performance represented by the selected key performance indicators, i.e., H2 purity, H2 yield, CH4 conversion, cold gas efficiency (CGE), net efficiency (NE), fuel consumption for the sorbent regeneration step, and CO2 capture efficiency. H2 with a purity of 98.5 vol % and a CGE of 75.7% with zero carbon emissions can be achieved. When adding a PSA unit, nearly 100% H2 purity and CO2 capture efficiency were achieved with a CGE of 77.3%. The use of oxy-fuel combustion during regeneration lowered the net efficiency of the process by 2.3% points (since it requires an air separation unit) but allowed the process to achieve negative carbon emissions.

中文翻译:

沼气吸附强化蒸汽重整生产高纯度可再生清洁氢气的过程模拟

可再生清洁 H 2在能源系统脱碳方面具有非常大的潜力。吸附强化蒸汽重整 (SESR) 是一种新工艺,它将蒸汽重整反应与通过固体吸附剂(例如 CaO)同时去除 CO 2相结合,从而显着提高氢气的产生,从而实现高纯度 H 2 的生产。CO 2吸附反应(碳酸化)是放热的,但通过煅烧的吸附剂再生是高度吸热的,这需要额外的能量。沼气是可用的碳中性可再生H 2生产来源之一。它与 SESR 过程的能量整合特别相关,因为由于放热吸附反应,CO沼气中所含的2为系统提供了额外的热量,这有助于平衡该过程的能量需求。这项工作研究了用于高纯度可再生 H 2生产的沼气 SESR 工艺的能量整合的不同工艺配置:(1) SESR 与吸附剂再生使用一部分产生的 H 2 (SESR+REG_H 2),(2)使用沼气进行吸附剂再生的 SESR(SESR+REG_BG),以及(3)使用沼气进行吸附剂再生并添加变压吸附(PSA)装置进行氢气纯化的 SESR(SESR+REG_BG+PSA)。当使用沼气作为燃料时(案例 2 和 3),这些配置在吸附剂再生步骤中使用空气和氧燃料燃烧气氛进行了研究,产生了五个案例研究。用于过程建模的热力学方法可以提供最佳过程操作条件和配置,最大限度地提高过程的能源效率,这是在扩大该技术所需的实际水平上进行后续过程优化的基础。为此,使用在 Aspen Plus 中开发的稳态工厂模型进行了过程模拟,结合复杂的热交换器网络 (HEN) 以优化热集成。一项全面的参数研究评估了沼气成分、温度、压力和蒸汽对甲烷 (S/CH4 )由所选关键性能指标表示的过程性能的比率,即H 2纯度、H 2产率、CH 4转化率、冷气效率(CGE)、净效率(NE)、吸附剂再生步骤的燃料消耗,和CO 2捕获效率。可以实现纯度为 98.5 vol% 和 CGE 为 75.7% 且碳排放为零的H 2 。添加 PSA 装置时,几乎 100% 的 H 2纯度和 CO 2捕获效率达到 77.3% 的 CGE。在再生过程中使用富氧燃烧将过程的净效率降低了 2.3 个百分点(因为它需要一个空气分离装置),但允许该过程实现负碳排放。
更新日期:2023-03-11
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