Steam systems are a significant source of energy use globally (amounting to 30%), as well as a key part in most industrial processes today. Naturally, this widespread use points to high CO2 emissions, leading towards strategies and discussions on the potential for economic energy savings and for reducing greenhouse gas emissions. The energy-intensive industry sector shows potential, however limited, to reduce its contribution to GHG emissions.
One of the key aspects in the process of achieving energy efficiency targets is operating a healthy system that continuously supplies the end-users with a constant quality of product. It has been shown that a steam system has quite the impact on the operational regime of a power plant. This is mostly due to the widespread usage of steam systems in the industry and especially its role as a highly efficient heating source. Another advantage is that its flow through the system can be controlled and unaided by pumps, i.e. it can be easily transported, it has a high heat capacity and specific energy. The potential for improving energy efficiency of steam systems is high, however, energy efficiency as a concept still presents certain barriers, such as the lack of possibility for monitoring the cost-effectiveness of implemented measures. The low awareness of improvement possibilities of the systems’ technical aspects might lead to insufficient reliability of a given system altogether. A system might be in good condition, but that does not mean that it is functioning efficiently and effectively, and energy is neither cheap nor infinite for it to be wasted because of a sub-optimal mode of operation.
The typical steam system (heavy, medium or small) comprises generating, distributing, utilizing the steam as a product and then discharging the condensate formed through heat loss, however without any additional leakage. Based on the high specific energy, steam can be used for mechanical work, heat or in other processes. Because of the various ways of use, the equipment and system altogether greatly differ from site to site. Considering the diversity of systems currently in use in the Republic of Macedonia, all of them being adjusted to the specific needs of the power plants and enterprises, an individual system approach towards estimating the conditions the system operates in, is very much needed. This system approach requires extensive knowledge and understanding of the system and it does not base itself on simple replacement of equipment components.
The analysis is made by establishing the operating parameters, detecting possible areas for improvement and then succeeded by implementing certain optimization measures, such as minimizing excess air, introducing heat recovery equipment, cleaning boiler heat transfer surfaces, improving water treatment, repairing steam leaks, isolating steam from unused lines etc., to minimize operating costs. In order to achieve cost reduction through steam system optimization, a continuous monitoring of the process needs to be conducted before and after the implemented measures in order to detect the areas for improvement as well as to ensure that the system is running in the best possible configuration after any introduced changes.
There are many programmes and enterprises offering Energy Systems Optimization. Currently in Macedonia, similar to UNIDOs Compressed Air Systems Optimization programme, UNIDOs Steam Systems Optimization (SSO) programme consists of three elements – the EXPERT Training, USER Training & VENDOR Workshop. The USER Training targets facility engineers, operator and maintenance staff, equipment vendors and service providers. The EXPERT Training targets national energy efficiency experts, service providers, equipment vendors and industry engineers, providing them with in-depth technical knowledge for improving steam systems. The VENDOR Workshop targets local steam equipment vendors, suppliers and manufacturers. The workshop is designed to introduce these key market players to SSO techniques and service offerings.
Several best practices for optimizing Steam Systems are mentioned below. These best practices are an excerpt from the UNIDO Training Manual for the Industrial Steam System Optimization (SSO) Experts Training, courtesy of the authors Riyaz Papar, P.E., CEM, Greg Harrell, Ph.D., P.E. Ven Venkatesan, P.E., CEM, and several individuals, industrial plants, government agencies and programs that contributed significantly and shared valuable resources, time and effort to the development of the Training Manual.
Steam Generation Area Optimization Opportunities & Best Practices
- Minimize excess air
- Install heat recovery equipment
- Clean boiler heat transfer surfaces
- Improve water treatment
- Install an automatic boiler blowdown controller
- Recover energy from boiler blowdown
- Add/restore boiler refractory
- Minimize the number of operating boilers
- Investigate fuel switching
- Optimize deaerator operations
Steam Distribution Area Optimization Opportunities & Best Practices
- Repair steam leaks
- Minimize vented steam
- Ensure that steam system piping, valves, fittings and vessels are well insulated
- Isolate steam from unused lines
- Minimize flows through pressure reducing stations
- Reduce pressure drop in headers
- Drain condensate from steam headers
Steam End-Use Area Optimization Opportunities & BestPractices
It is extremely difficult to cover end-uses that are specific to industrial processes and plants. Process and utility integration leads to overall energy system optimization of the plant and the benefits are far-reaching. In the classic configuration, the main strategies to optimize steam in the end use area are:
- Eliminate or reduce the amount of steam used by a process
- Improve process efficiency and eliminate inappropriate steam usage
- Use steam at as low a pressure as possible which would possibly allow power generation
- Shift all or part of the steam demand to a waste heat source
- Upgrade low pressure (or waste) steam to supply process demands that would have otherwise used much higher pressure steam.
Condensate Recovery Area Optimization Opportunities & BestPractices
- Implement an effective steam-trap management and maintenance program
- Recover as much as possible of available condensate
- Recover condensate at the highest possible thermal energy
- Flash high pressure condensate to make low pressure steam
Combined Heat and Power Area Optimization Opportunities & BestPractices
The CHP optimization opportunity in industrial steam systems almost always relies on understanding the economic benefit of modifying operations of steam turbines. In industrial CHP applications, two major turbine configurations are encountered and they include: