November 2019

One hard fact we have to face as a society is this: we are running out of fossil fuels. Oil, coal, and natural gas are still used to create 80-90 percent of energy worldwide. On one hand, it is good that we are running low on these fuels as they are commonly linked to global warming and climate change.

On the other hand, the great dependence on these materials means we will need to find new solutions as these sources start to dry up. Until renewable energy sources such as solar and wind power are more prevalent, one of the best solutions we can switch over to is a combined heat and power (CHP) factory. These factories use fuel more efficiently and have the potential to save up to 40 percent of energy in total. A win for our pocketbook and a win for the planet.

These types of plants create their own special industrial air filtration needs. Special types of filtration systems and filters must be implemented to protect workers as well as the environment surrounding these facilities. First, let’s take a deeper look into how combined heat and power systems work and what air filtration needs arise.

What is CHP?

To fully understand how a combined heat and power factory works, let’s compare it to a conventional power plant. Conventional power plants make electricity by burning a fossil fuel (such as oil, coal or natural gas) in a huge furnace to produce heat energy. The released heat energy is then used to boil large vats of water which then creates steam. The steam then powers a turbine which is connected to a generator which then produces electricity. This process is fairly inefficient overall as energy is wasted in every step of the process.

In contrast, the way a combined heat and power factory works is to actually utilize the byproducts of the conventional process in other ways. For example, instead of letting the released heat partially escape up the cooling towers, a combined heat and power system would reroute that water into people’s homes and offices as hot water. Electricity is often wasted in a conventional system, but in a CHP, electricity is used to its optimal efficiency. The term cogeneration essentially means that the electricity and heat are made at the same time.

Air Filtration for Combined Heat and Power Plants

Air filtration comes into the picture for combined heat and power plants in relation to the fossil fuel powered turbines. Proper air filtration is not only essential to the overall performance of these turbines, but it can also help in saving lots of money in the long run. The costs to operate these turbines is nearly 80 percent in comparison to the lifespan of the electricity, which means that small improvements to efficiency can really add up on the balance sheet.

Proper industrial air filters for these turbines can also immensely reduce the maintenance required to keep these machines running. The engine will run cleaner, there will be fewer functional shutdown require less frequent inspections which can save on labor costs. But what type of filter is right for this important job? Let’s dive deeper and see what filters are best suited to the task at hand.

Multi-Stage Filters for Combined Heat Power Plants

The primary filter system used is a multi-stage filtration system. An average filter system will include a guard filter, a sort of pre-filter that sits upstream of the chilling coils, while a panel-type filter sits downstream of the coils. The guard filter’s job is to keep the coils clean for maximum efficiency of heat transfer. This filter also helps keep the other finer filters in shape and serves to extend the life of those filters.

Next in the system if the fine filter element. This filter is mounted to the filter face of the inlet plenum and has a large surface area. This filter does the heavy lifting in terms of catching large particulate matter without causing any pressure drops to the air flow. As the air passes through these fine filters, the inlet filter assembly separates ventilation air from combustion air created by the turbines. These separated streams then flow through different ducts to the generator compartments. One of the added benefits of the phase of the multi-stage process is the noise reduction. An inlet silencer helps diffuse the noise and maintains a low noise level for the whole unit.

Next in the systems is the heating and cooling elements. There are evaporative coolers built in to maximize gas turbine performance on those hot summer days. These cooling systems use evaporation to reduce the air temperature in the inlet. In the winter, anti-icing coils will activate to prevent freezing and prevent a complete halting to the process.

Now we get to the optional and job specific filters that may be found in a multi-stage system. The two main types of filters here are pulse filters and static filters, and each serve a specific purpose depending on the job at hand. Environmental conditions such as the weather factor into which filter you need, as well as any specific contaminants you may be trying to filter out.

A pulse filter should be used when the dust it is trapping is .300 mg or higher. These are often used in areas with lots of dust or sand storms – deserts areas, steel mills, cement plants, etc. They are also used in snowy environments where snow or ice crystals threaten to interrupt the workflow. These filters are also unique in that they are self-cleaning.

Static filters are actually quite inexpensive and can serve as a semi-pre-filter for your system. The main purpose of a static filter is to extend the life of your barrier elements. The only downside to these filters is that they require quite a bit of regular maintenance and upkeep in order to keep your system running optimally. Most of these types of filters can’t be cleaned and thus must be replaced regularly, which can add to the cost of operating your plant.

Commercial air filtration is optimized to minimize foreign contaminants entering the gas turbine, and are largely based on the operating environment. Seasonal pollutants, rain, ice and snow, sand, dust, local industry exhausts, and other air contaminants must be taken into consideration when choosing the right system for your CHP.