Ammonia has been widely used in fertilizers and industrial applications. In recent years, with the increasing momentum toward carbon neutrality, expectations for low-carbon emission (decarbonization) are also becoming prevalent in conventional ammonia plants.
Mitsubishi Heavy Industries Compressor Corporation (MCO) has intensive experience manufacturing synthesis gas compressors (hereinafter referred to as syngas compressor) and associated steam turbine drivers (hereinafter referred to as syngas turbine) used in fertilizer plants with operating capacities up to 3,670 ton/day. We have utilized this experience in modernizing numerous syngas compressors & turbines which are in operation for the last 30 to 40 years. Based on this experience, this study introduces the case of a carbon footprint-based syngas compressor train modernization project.
In ammonia plants, some historic factories have low production capabilities due to the use of outdated low efficiency compressors. Replacing those with the latest best available, current compressor technology not only expands the plant capacity, but also can help customers to improve their OPEX via increased efficiency. When upgrading an existing plant, it is preferable to minimize the scope of modification in order to keep the overall investment costs low. Based on our vast experience in footprint replacement (i.e., having delivered more than 350 units and technologies), we are capable to propose optimization or minimalize the scope of modification according to the existing plant conditions or based on customer requests. For example, in case of plant capacity expansion project, applying conventional design may result in larger size of compressor, and thus modification of existing concrete foundation would be necessary. On the other hand, available period for the revamping or replacement work is usually limited since the work must be done during plant turnaround period and evaluation of soundness for existing old foundation is quite difficult. However, by applying MCO’s unique customized design, the new compressor can be arranged to fit within the existing foundation, minimizing the modification scope of the entire project and supporting customers in maximizing their return on investment.
Regarding steam turbine, in the past, two tandem turbines were used since there was no suitable blade especially for last stage (at low pressure section). However, as technology for turbines continued to advance, our experience has made it possible to replace the existing complex system with a simpler single turbine system. The benefit of this upgrade includes lower overall replacement costs (CAPEX) due to reduced piping, coupling, casing, and engineering costs, as well as lower maintenance costs (OPEX) due to reduced capital spare parts (such as rotors), 2-year spare parts, and overhaul costs, among other things. Less bearing loss, steam leakage, and pressure loss in the piping are some of the additional benefits to save steam, which contributes to the reduction of CO2 emissions and the achievement of sustainable development objectives.
The risks associated with this kind of revamp are also discussed in this study and the associated countermeasures are explained. Furthermore, the lessons learned during execution of a project of this sort are also elaborated.
In conclusion, there has been a recent trend toward increasing the productivity and carbon efficiency of current plants. And we believe that this study can serve as a reference for anyone associated with these plants. In addition, we hope this can educate new plant stakeholders regarding potential opportunities involved in design of a new plant.