The LUREC~R process—key to economic smelter add plant operation

K.-H. Daum

摘要

Over many decades, numerous feasibility studies have demonstrated, that the production of sulphuric acid remains the most viable option of sulphur recovery from smelter off gas and abatement of SO_2 emissions to the atmosphere. This is particularly more pronounced as smaller but more concentrated off-gas flows are to be treated from smelters, and enhanced sulphuric acid processes become available. Off-gas handling systems represent a significant capital and operating cost burden to the metallurgical operation. Modern pyrometal-Iurgical smelter processes for sulphide ores based on the use of oxygen-enriched air, produce relatively small off-gas flows with high SO_2 concentrations in the smelter gas of 30-60 percent-vol. of SO_2. This is a prerequisite for substantial cost reductions in the smelter off-gas handling and treatment system. As an alternative to sulphuric acid production, numerous scrubbing concepts with alkali or dual-alkali combinations as well as organic absorbents have been proposed. Also the reduction of the SO_2 to elemental sulphur has frequently been studied. Very few of those alternative processes have been built in industrial scale, but all were generally characterized by none-sustainable operation due to cost reasons, problems with issues related to chemicals used and by-products or poor availability. Thus the traditional concept of converting the SO_2 to sulphuric acid is most common, although regarded as uneconomic, but is at least a proven, environmentally sustainable and reliable way of sulphur gas processing. With the high acid price levels these days, operating companies are even able to generate significant revenue with their otherwise 'fatal' acid. Even though smelter gas is available at high SO_2 concentrations, in a conventional acid plant one would add large amounts of air to dilute the gas down to a suitable concentration of 12-13 (14) percent-vol. SO_2. Dealing with higher SO_2 concentrations in smelter acid plants is not feasible, as the gas exit temperature of the catalytic oxidation step would exceed the allowable limit for the catalyst. Hence those conventional acid plants are characterized by the use of large equipment, i.e. high capital cost, high energy consumption and limited flexibility. The newly developed LUREC~R process can handle off-gas with significantly higher gas concentrations, even in excess of 25 percent-vol. SO_2. It is entirely based on well-proven equipment and unit operations. The first industrial application, operating with 16-18 percent-vol. SO_2 will be presented in this paper, along with the fundamentals of the process. It will be demonstrated that the process requires inherently lower capital cost, fewer operating costs, and offers better energy recovery and lower emis-sions as compared to conventional design. While most existing smelter acid plants would have some built-in spare capacity, any significant increase of smelter capacity, say of 30 percent, can basically not be accommodated without installing an additional parallel new acid plant unit. An add-on LUREC~R module can remove any such restriction, while simultaneously debottlenecking the existing acid plant. The paper also discusses the present status of the add-on technology for smelter acid plant expansions with respect to technical boundary conditions of different process alternatives as well as economic and environmental aspects. Application of the LUREC~R process to modern smelter acid plants operating with high SO_2 gas concentration, will lead to a substantial reduction of the specific size of the gas processing equipment and equivalent savings in capital and operating cost. The LUREC~R process is patented worldwide by OUTOTEC.

机译：数十年来，许多可行性研究表明，硫酸生产仍然是从冶炼厂废气中回收硫和减少向大气中排放SO_2的最可行选择。当要从冶炼厂处理更小但浓度更高的废气流时，这尤其显着，并且可以使用增强的硫酸工艺。废气处理系统代表了冶金运营的重大资金和运营成本负担。基于使用富氧空气的硫化物矿石的现代热金属-冶炼工艺，在体积比为30％至60％的冶炼气体中产生相对较小的废气流，其中SO_2浓度较高。的SO_2。这是大幅降低冶炼厂废气处理和处理系统成本的前提。作为硫酸生产的替代方案，已经提出了许多具有碱或双碱结合物以及有机吸收剂的洗涤方案。此外，还经常研究了将SO_2还原为元素硫的方法。这些替代方法中很少有以工业规模建造的，但由于成本原因，与所用化学品和副产品有关的问题或可获得性差，所有这些替代方法通常都具有无法持续运行的特点。因此，尽管被认为是不经济的，但是将SO 2转化为硫酸的传统概念是最普遍的，但至少是一种经过验证的，对环境可持续的，可靠的硫磺加工方式。如今，由于酸价居高不下，经营公司甚至可以用原本致命的酸来产生可观的收入。即使可以以高SO_2浓度获得冶炼厂气体，在传统的酸厂中，仍会添加大量空气以将气体稀释至12-13（14）％（体积）的合适浓度。 SO_2。在冶炼厂的酸工厂中处理更高的SO_2浓度是不可行的，因为催化氧化步骤的气体出口温度将超过催化剂的允许极限。因此，那些常规的酸工厂的特征在于使用大型设备，即高投资成本，高能耗和有限的灵活性。新开发的LUREC〜R工艺可以处理浓度显着更高（甚至超过25％vol）的废气。 SO_2。它完全基于久经考验的设备和单元操作。第一个工业应用，以16-18％的体积运行。本文将介绍SO_2，以及该过程的基本原理。可以证明，与传统设计相比，该工艺本质上需要较低的投资成本，较少的运营成本，并提供更好的能量回收和更低的排放。尽管大多数现有的冶炼厂制酸厂将具有一些内置的备用产能，但如果不安装额外的并行新制酸厂，基本上无法容纳任何冶炼厂产能的大幅增加（例如30％）。附加的LUREC_R模块可以消除任何此类限制，同时消除现有酸厂的瓶颈。本文还就不同工艺替代方案的技术边界条件以及经济和环境方面，讨论了冶炼酸工厂扩建附加技术的现状。 LUREC〜R工艺在SO_2气体浓度高的现代化冶炼厂中的应用，将导致气体处理设备特定尺寸的大幅减少，并节省资金和运营成本。 LUREC〜R工艺已获得OUTOTEC的全球专利。

The LUREC~R process—key to economic smelter add plant operation

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