Cambridge Electric Cement: Zero-emissions cement from old concrete paste replacing flux in electric-arc furnaces

随着世界向零排放迈进，水泥脱碳通常被描述为最困难的挑战。用于制造混凝土和砂浆的波特兰水泥产量巨大（地球上每个人每年每人超过500公斤），价格便宜（每吨约60英镑），并且具有优异的建筑性能。然而，它造成了世界上四分之一的工业排放，这既是由于高温水泥窑的燃料燃烧，也是因为将石灰石转化为熟料（水泥的关键成分）的化学反应不可避免地会导致二氧化碳的释放。许多替代水泥成分正在开发中，但尽管有些可能会减少排放，但没有一种是零排放的。目前正在开发两种可能的捕获和储存排放物的方法——一种是捕获工厂的所有排放物并将其储存在地下，另一种是将排放物嵌入预制块中——但这两种方法都尚未大规模运行，而且都面临许多挑战。没有水泥，我们就没有混凝土，建筑将不得不发生根本性的变化，从新建到改造和改造。占世界GDP约70%的国家已经承诺到2050年或2060年实现零排放目标，因此水泥排放的问题既大又紧迫。该提案探索了世界上第一个可以生产无排放波特兰水泥的工艺。调查人员注意到，今天的电炉中使用的石灰熔剂与旧水泥浆的化学成分几乎相同——旧混凝土被粉碎后留下的物质，沙子和骨料被移除。在初步试验中，我们利用材料加工所的小型电弧炉，用废旧水泥代替了常规的助焊剂。在回收过程中，我们将漂浮在钢水表面的热液渣分离，并将其冷却成粉末，然后与石膏混合，浇注成小的水泥样品。对我们微小的试点研究水泥样本的分析表明，它们与传统的波特兰水泥非常相似。这表明了一种令人兴奋的可能性，即我们可以将水泥作为钢铁回收的副产品，而水泥可以由无排放的电力提供动力——因此我们可以同时实现零排放钢铁和零排放水泥。本提案旨在围绕这一发现探索科学。我们需要找出旧水泥的成分是如何变化的，以及这种变化是如何影响我们的新产品的。我们需要探索我们的新工艺对传统的钢铁回收有什么影响——它是否改变了钢铁的成分，是否破坏了炉衬，以及被回收的钢铁类型如何影响我们的新水泥？我们需要更多地了解我们的新水泥的特性：它有多耐用，它能多快达到完全强度，等等。如果这个新工艺像我们希望的那样好，我们将希望迅速将其发展到商业规模，而制造它的技术可能成为英国的主要出口产品。因此，我们建议的最后一个组成部分是制定一个“路线图”，将这个想法从实验室规模的试验带到全面部署。我们将与一个合作伙伴联盟、一个科学顾问小组以及能够帮助我们支持新方法的面向外部的合作伙伴一起探讨这个问题。

As the world moves towards zero emissions, decarbonising cement is often described as the most difficult challenge. Portland Cement, which is used to make concrete and mortar, is made in tremendous volumes (more than 500 kg per person per year for everyone on the planet), is cheap (~£60/tonne) and has excellent properties for construction. However, it causes a quarter of all the world's industrial emissions, both due to fuel combustion in high-temperature cement kilns, and because the chemistry of converting limestone into clinker, the key ingredient of cement, inevitably causes the release of carbon dioxide. Many alternative compositions of cement are under development, but although some may lead to reduced emissions, none have zero emissions. Two possible approaches to capturing and storing emissions are under development - one capturing all the emissions of a plant and storing them underground, and the other embedding emissions within pre-cast blocks - but neither is yet operating at scale, and both face many challenges.Without cement, we will have no concrete, and construction will have to change radically largely shifting from new-build to retrofit and adaption. Countries responsible for around 70% of the world's GDP have now committed to zero emissions targets by 2050 or 2060, so the problem of cement emissions is both large and urgent. This proposal explores the world's first process that could produce Portland cement with no emissions. The investigators noticed that the lime-flux used in today's electric steel-recycling furnaces has almost the same chemical composition as that of old cement paste - the material that is left when old concrete is crushed, and sand and aggregate is removed. In preliminary trials, using the small electric arc furnace of the Material Processing Institute, we replaced the conventional flux with used cement. We separated the hot liquid slag that floats on the surface of molten steel during recycling and cooled it to form a powder which we then mixed with gypsum and cast into small cement samples. Analysis of our tiny pilot study cement samples showed that they were very similar to conventional Portland cement. This points to the exciting possibility that we could make cement as a by-product of steel recycling, which could be powered by non-emitting electricity - therefore giving us both zero emissions steel and zero emissions cement.This proposal aims to explore the science around this discovery. We need to find out how the composition of old cement varies, and how this variation affects our new product. We need to explore what effect our new process has on conventional steel recycling - does it change the composition of the steel, does it damage the furnace lining, and how does the type of steel being recycled affect our new cement? And we need to find out more about the properties of our new cement: how durable is it, how quickly does it reach full strength, and so on.If this new process is as good as we hope, we will want to develop it rapidly to commercial scale, and the technique for making it could become a major UK export. The final component of our proposal is therefore to develop a "roadmap" for taking the idea from lab-scale trials to full deployment. We will explore this question with a consortium of partners, a science advisory panel, and with outward facing partners who could help us champion the new approach.