EFRI DCheM: Making Cement Green by Low-Temperature Manufacturing of Calcium Hydroxide from Distributed Waste Sources

水泥可以说是世界上最重要的建筑材料，但它的生产占全球二氧化碳排放量的8%，这是满足降低全球变暖速度所需的碳预算的主要障碍。水泥行业的脱碳一直是一个长期存在的环境挑战，因为该行业的大部分二氧化碳排放来自石灰石煅烧过程中发生的化学反应，这是传统水泥生产的第一步。按照目前的做法，仅与水泥生产相关的排放量就将占2050年全球碳预算的40%，这一数字是基于2050年将变暖限制在1.5°C的50%机会所允许的排放量。为了应对这一挑战，将开发一种新型的无煅烧LoTeCH（低温氢氧化钙）工艺，以生产氢氧化钙，该工艺可以取代石灰石，作为来自再生混凝土，煤灰和金属冶炼渣等分布式废物流的关键水泥前体。由此产生的LoTeCH氢氧化钙可以无缝集成到现有的水泥制造基础设施中，以取代石灰石煅烧，减少二氧化碳排放量超过50%，并减少石灰石开采量。这项技术的扩展，以创建一个分布式和极低碳的水泥制造过程，将消耗来自发电厂烟道气的二氧化碳，也将寻求实现潜在的负碳水泥工业。除了开发新技术将水泥生产转变为可持续发展的行业外，该项目还将培养一批多样化的学生，共同努力解决这一全球关注的环境问题，采用多学科方法解决问题。该项目将直接聘请代表性不足的少数民族本科生和研究生研究人员从两个少数民族服务机构（英尺。刘易斯学院和伊利诺伊大学芝加哥分校）的研究任务，并将支持他们参与威斯康星大学麦迪逊分校的校园计划，为本科生提供获得研究经验的机会。项目小组将利用这些活动招募和教育代表性不足的少数民族学生。该项目还将致力于提高公众的科学素养和公众参与度，以了解建筑环境对碳排放的影响。拟议项目将开发一种节能、低碳排放的氢氧化钙生产工艺，用于可持续水泥生产。为了实现这一目标，该项目将产生基础工程知识，实现四步LoTeCH工艺循环，该工艺循环使用氨和离子交换工艺，在温和压力（2-3 bar）和亚沸点温度下从废料原料中生产Ca（OH）2。拟议的工作将产生溶解，运输和沉淀过程中使用原位表征方法的基本见解。将合成具有可调交换特性和增强的容量和稳定性的新型共价有机框架（COF）基离子交换剂，以支持关键的pH摆动工艺步骤。预测性多尺度和多物理场过程建模将利用高通量表征数据进行模型验证，并将使稳健的过程优化成为可能。使用这些建模方法和模拟技术，将开发新的过程强化方案，以创建一个有效的，分布式的生产过程，适用于预计在其组成高度可变的原料。工艺开发将以技术经济分析（TEA）、连续物质流分析（C-MFA）和生命周期评估（LCA）为指导，包括评估该技术对现有水泥行业的影响以及未来低碳水泥行业的潜在出现。通过整合矿物溶解和沉淀、材料合成、反应器设计和过程强化以及环境和可持续性工程方面的专业知识，该项目将拓宽对一个至关重要的工业过程的基本理解，并为如何生产水泥创造一个新的范例。该奖项反映了NSF的法定使命，并被认为值得通过利用基金会的智力价值和更广泛的影响审查标准。

Cement is arguably the world’s most important building material, but its production is responsible for up to 8% of global carbon dioxide emissions, representing a major impediment to meeting the carbon budget required to reduce the rate of global warming. Decarbonization of the cement industry has been a longstanding environmental challenge because the bulk of the industry’s carbon dioxide emissions result from the chemical reaction that takes place during limestone calcining, the first step in traditional cement production. Produced by current practices, emissions associated with cement production alone would account for as much as 40% of the world’s carbon budget in 2050, a figure based on emissions allowable for a 50% chance of limiting warming to 1.5°C in 2050. To address this challenge, a novel calcination-free LoTeCH (Low-Temperature Calcium Hydroxide) process will be developed to produce calcium hydroxide that can replace limestone as the key cement precursor from distributed waste streams such as recycled concrete, coal ash, and metal-smelting slag. The resulting LoTeCH calcium hydroxide can be seamlessly integrated into the existing cement-making infrastructure to replace limestone calcination, reducing CO2 emissions by more than 50% with the added benefit of reduced limestone mining. An extension of this technology to create a distributed and extremely low-carbon cement-making process that would consume carbon dioxide sourced from power-plant flue gas also will be pursued to enable a potentially carbon-negative cement industry. In addition to developing new technologies to transform cement production into a sustainable industry, the project will train a diverse cohort of students, working collaboratively to solve this environmental problem of global concern, taking a multidisciplinary approach to problem solving. The project will directly engage underrepresented minority undergraduate and graduate researchers from two minority serving institutions (Ft. Lewis College and University of Illinois at Chicago) within the research tasks and will support their participation in UW-Madison campus programs that offer undergraduate students opportunities to gain research experience. These activities will be used by the project team to recruit and educate underrepresented minority students. This project will also work to increase public scientific literacy and public engagement to understand the ways that the built environment is responsible for carbon emissions.The proposed project will develop an energy efficient, low carbon-emission calcium hydroxide production process for sustainable cement production. Towards this goal, the project will generate fundamental engineering knowledge enabling a four-step LoTeCH process cycle that uses ammonia and an ion-exchange process to produce Ca(OH)2 from waste material feedstocks under mild pressure (2-3 bar) and sub-boiling temperatures. The proposed work will generate fundamental insights into dissolution, transport, and precipitation processes using in-situ characterization methods. New covalent organic framework (COF)-based ion-exchangers with tunable exchange characteristics and enhanced capacity and stability will be synthesized to support the key pH-swing process step. Predictive multiscale and multiphysics process modeling will leverage high-throughput characterization data for model validation and will make possible robust process optimization. Using these modeling methods and simulation techniques, new process intensification schemes will be developed to create an efficient, distributed production process suitable for feedstocks that are expected to be highly variable in their composition. Process development will be guided by techno-economic analysis (TEA), continuous material flow analysis (C-MFA), and life cycle assessment (LCA), including an assessment of the impact of this technology on the existing cement industry and the potential emergence of a low-carbon cement industry in the future. By integrating expertise in mineral dissolution and precipitation, material synthesis, reactor design and process intensification, and environmental and sustainability engineering, this project will broaden fundamental understanding of a critically important industrial process and create a new paradigm for how cement is produced.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.