In this study, the process of carbon dioxide (CO₂) capture directly from ambient air in a conventional monoethanolamine (MEA) absorption process was simulated and optimized using a rate-based model in Aspen Plus. The process aimed to capture a specific amount (148.25 Nm³/h) of CO₂ from the air, which was determined by a potential application aiming to produce synthetic methane from the output of a 2.7 MW electrolyser (593 Nm³/h H₂). We investigated the technical performance of the process by conducting a sensitivity analysis around different parameters such as air humidity, capture rate defined as a ratio of moles of CO₂ captured during the process to the total mole of CO₂ in the feed stream, CO₂ loading of lean and rich absorption liquids and reboiler temperature, and evaluated the energy consumption and overall cost in this system. In order to meet the design requirement for standard packed columns, the rich absorption liquid was circulated to the top of the absorber. A capture rate of 50% was selected in this process as a baseline. At higher capture rates, the required energy per ton of captured CO₂ increases due to a higher steam stripping rate, required in the desorber, and at lower capture rates, the size of equipment, in particular, absorber and blowers increases due to the need for processing a significantly larger volume of air at the given CO₂ production volume. At the base case scenario, a reboiler duty of 10.7 GJ/tCO₂ and an electrical energy requirement of 1.4 MWh/tCO₂ were obtained. The absorber diameter and height obtained were 10.4 and 4.4 m, respectively. The desorber is found to be relatively small at 0.54 m in diameter and 3.0 m in height. A wash water section installed at top of the absorber decreased the MEA loss to 0.28 kg/ton CO₂. However, this increased capital cost by around 60% resulting in CO₂ capture costs of $1,691 per ton CO₂ for the MEA base scenario. Based on the techno-economic analysis, assuming a non-volatile absorbent rather than MEA thereby avoiding a wash water section, and using an absorption column built from cheaper materials, the estimated cost per ton of CO₂ produced was reduced to $676/tCO₂. The overall cost range was between $273 and $1,227 per ton of CO₂ depending on different economic parameters such as electricity ($20–$200/MWh) and heat price ($2–$20/GJ), plant life (15–25 years) and capital expenditure (±30%). In order to reduce the cost further, the use of innovative cheap gas-liquid contactors that operate at lower liquid to gas ratios is crucial.

在这项研究中，使用Aspen Plus中基于速率的模型模拟和优化了常规单乙醇胺（MEA）吸收过程中直接从环境空气中捕获二氧化碳（CO ₂）的过程。旨在过程以捕获特定的量（148.25牛顿米³ CO的/小时）₂从空气中，这是由一个潜在的应用，旨在从一个2.7 MW电解槽（593牛顿米的输出生产合成甲烷确定³ / h扬程H ₂）。我们通过围绕不同参数（例如空气湿度，捕获率定义为过程中捕获的CO ₂摩尔数与CO的总摩尔数之比）进行敏感性分析，研究了该过程的技术性能。₂进料流中，CO ₂的贫和富吸收液体和重沸器热负荷，并进行评价该系统中的能量消耗和总成本。为了满足标准填充塔的设计要求，将富吸收液循环到吸收塔的顶部。在此过程中，将捕获率选择为50％作为基准。在较高的捕集率下，由于解吸器需要较高的蒸汽汽提率，因此每吨捕集的CO ₂所需的能量会增加，而在较低的捕集率下，设备（尤其是吸收器和鼓风机）的尺寸会因需要而增加在给定的CO _2下用于处理大量空气生产量。在基本情况下，获得了10.7 GJ / tCO ₂的再沸器负荷和1.4 MWh / tCO _2的电能需求。得到的吸收体直径和高度分别为10.4和4.4m。发现解吸器相对较小，直径为0.54 m，高度为3.0 m。安装在吸收塔顶部的洗涤水段将MEA的损失降至0.28 kg /吨CO ₂。但是，这将使资本成本增加约60％，从而导致每吨CO _2的CO ₂捕集成本为1,691美元。适用于MEA基本方案。根据技术经济分析，假设使用非挥发性吸收剂而不是MEA，从而避免了洗涤水段，并使用由较便宜的材料制成的吸收塔，则每吨CO ₂的估计成本将降至$ 676 / tCO ₂。整个成本范围在每吨CO ₂ 273美元至1,227美元之间，具体取决于不同的经济参数，例如电费（$ 20– $ 200 / MWh）和热价（$ 2– $ 20 / GJ），工厂寿命（15–25年）和资本支出（±30％）。为了进一步降低成本，使用在较低的液气比下运行的新型廉价气液接触器至关重要。