The need for steam
With a large number of process heating applications requiring an efficient source of steam, Simon Tarr, Sales Manager for Industrial boilers at Bosch Commercial and Industrial Heating, provides an overview of the steam boiler industry; outlining some of the sector’s typical applications and explaining why there will always be a need for steam in key markets within the sector.
The requirement for steam in industrial applications ranges greatly. From power stations through to food and drink manufacturing, the demand for steam spans across both the private and public sectors. What was once associated with locomotives and the industrial revolution, is now an essential product of a number of sophisticated modern technologies.
In a modern context, steam provides industrial processes and applications with one of the most effective ways to transfer heat energy in a controlled manner. Whilst water is often used to transport heat, it has a much lower potential. By its very chemical nature, water can generally only be used up to a maximum temperature of 120°C, making it suitable for general space heating applications and low temperature industrial processes. However, when it comes to process heating, where much greater temperatures are required, steam is a much more appropriate option and can hold five or six times as much potential energy as an equivalent mass of water.
The accessibility and affordability of water means steam is often a viable option for a multitude of applications. Steam has the benefit of no environmental implications, which makes it a favourable option when compared to other heating sources, such as thermal oils.
Thermal fluids do have a part to play in today’s industrial process sector, but only where steam can’t be used for the transfer of high temperatures. For example, the heating of chemicals cannot be done by steam due to the potential for reactions to take place. The downside to the use of thermal fluids however, is that they are generally expensive and need replacing regularly, which places greater onus on a plant manager to maintain the supply.
The industries within which steam is used range from large oil and petrochemical plants to small local laundries. It is also common for steam to be used in production industries ranging from paper, textiles, brewing, food, and the heating and humidification of buildings.
One of the main strengths of steam is that it is extremely clean, and only requires minimal treatment of the water from the outset to maintain a pure supply. Consequently, it is a perfect fit for sterilisation in food, pharmaceutical and health processing environments.
Steam boiler versatility
Those requiring steam for industrial use generally have two possible options when it comes to selecting the most appropriate technology for steam generation – boilers and generators. Although steam is generated in both appliances, there are some significant differences in their construction, use and installation, so it is important not to confuse the two technologies.
In simple terms, a steam boiler consists of a pressure vessel with an integrated flame tube, reversing chambers and gas flues – all of which are surrounded by boiler water. The feed water is supplied through a water level controller which is fed by a duty/standby pump or external ring main system, independent of the heating. The steam escapes from the water level surface through a crown valve and is then transported to its relevant application.
A steam generator is a pressure system consisting of a water heating coil. The feed water is pumped through the pipe system using a piston pump, and the amount of water supplied corresponds with the steam output. Consequently, a generator is best suited to relatively small scale applications, where the requirement for steam is for local point of use and for predetermined periods of operation. The steam volume output is adapted to the amount of water supplied. This water is completely vaporised in one full run. Only a few minutes pass between a cold start and full steam output, which is why they are also referred to as ‘rapid steam generators’.
Whilst each of the technologies has their respective merits and strengths in terms of the types of application they are best suited to, steam boilers have the versatility of being able to cater for small to large industrial environments. Steam boilers can produce an almost unlimited amount of steam continually, which can be adjusted to meet the exact levels needed for each individual application. In an environment such as a power station, the provision of steam can be distributed to multiple end-users, thanks to a boiler’s ability to supply steam on demand.
When it comes to the physical delivery of steam to its point of use, the range of boilers available means different temperature and pressure requirements can be catered for. Using a steam boiler with three pass technology, it is possible to deliver saturated steam up to 235°C in temperature, at a pressure of up to 30 bar. This is ideal for the medium to high output requirements of applications such as hospitals, power stations and process facilities that require a high transfer of heat.
The introduction of steam boilers equipped with flame/smoke tubes, allow a greater recovery of heat contained in the flue gases. This increases the energy efficiency of the boiler by up to 7% in dry running operation, and up to 15% in condensing operations. By coupling this heat recovery capability with the latest burner technology, CO2 emissions can also be kept to a minimum. For those keen to establish favourable environmental credentials meanwhile, a completely neutral CO2 level is possible through the use of bio-oils or bio-gases for steam generation.
When it comes to industrial plant applications, heating provision should always be considered in its own right, as the requirements of the building, the application, and the end-user will always differ from case to case. That said, the steam boiler technology available to stakeholders in the industrial sector, is capable of providing a very efficient means of meeting process heating delivery requirements.
With energy costs at an all-time high, and industrial stakeholders having to face up to the challenge of fulfilling their need for steam without tarnishing their own environmental credentials, making the correct decision on the most suitable technology for process heating is essential.
It is now possible for a steam boiler to be partnered with a secondary technology, such as a Combined Heat and Power (CHP) module, to enhance efficiency levels. By implementing an innovative fourth smoke tube pass between the CHP unit and the steam boiler, the surplus heat generated can be driven back into the steam boiler, thus maximising the energy efficiency of steam production
The future of steam
While innovators within the industrial sector will always be looking to improve the ways heat can be transferred for process use, it seems extremely unlikely that steam will be replaced. Ultimately, the strengths of steam give industrial stakeholders exactly what they are looking for – efficiency, safety and affordability to meet a wide range of requirements.
With the steam boiler technology available to stakeholders in the industrial sector, there is a very efficient means of meeting process heating delivery requirements which is sure to be around for many years to come.