Most desuperheater applications reduce the temperature of steam generated by high pressure/high temperature boilers to levels required in process operations. The primary function of a desuperheater is to lower the temperature of superheated steam or other vapors.
1. A desuper heater is for low and medium pressure and temperature application as required in process plants. Attemperator covers all the range depending on the steaming parameters of the boiler. The temperature regulation in attemperator is usually much more sophisticated than in a desuperheater.
This is because superheated steam has the same heat transfer coefficient of air, making it an insulator and poor conductor of heat. Saturated steam is preferred for heating applications, while superheated steam is used mostly in power generation and turbines.
PRDS Station Operation Principle
The high pressure high temperature steam enters the PRDS station as shown in the figure. The water flow control valve regulates the quantity of the spray water going into the spray nozzles depending on the steam load.Saturated steam is steam that is in equilibrium with heated water at the same pressure, i.e., it has not been heated above the boiling point for its pressure. This is in contrast to superheated steam, in which the steam (vapor) has been separated from the water droplets then additional heat has been added.
?Attemperation is the primary technique used for controlling the degree of superheat in a boiler or a Heat Recovery Steam Generator (HRSG). The temperature controller for this attemperator (called inter-stage) bases its temperature regulation on input from a temperature transmitter placed on the boiler/HRSG output.
Saturated steam is pure steam in direct contact with the liquid water from which it was generated and at a temperature of water at the existing pressure. For example, saturated steam at 50 PSIG has a temperature of 298°F. The same amount of heat is liberated when a pound of steam condenses back to a pound of water.
Saturated steam is the type of steam that occurs when the liquid and gaseous phases of water exist simultaneously at a given temperature and pressure. In simpler terms, the steam is in equilibrium with the heated water.
Disadvantages of Geothermal Energy
- 1 Environmental Issues. There is an abundance of greenhouse gases below the surface of the earth, some of which mitigates towards the surface and into the atmosphere.
- 2 Surface Instability (Earthquakes)
- 3 Expensive.
- 4 Location Specific.
- 5 Sustainability Issues.
If you have a correctly sized unit, you do not need a backup system. Geothermal unites are equipped with an auxiliary heating unit that runs on electric. By utilizing the constant temperature in the ground a geothermal heat pump does not need a backup radiator or furnace as supplemental heat on extremely cold days.
The homeowner said he was paying $150/month for propane, and if we deduce the average geothermal kWh use it would be around $138/month, a savings of $12/month. In today's dollars, the price of geo is 1/3 the cost of propane, so he would save $3,000 per year.
Geothermal heat pumps don't generate heat — they just transfer it from the ground into your home. For every 1 unit of energy used to power your geothermal system, on average 4 units of heat energy are supplied. Why geothermal heat pumps use more electricity than furnaces (but less than conventional air conditioners)
Geothermal Wells are typically anywhere from 150 feet deep to 400 feet deep. Some drilling companies have equipment that can drill wells deeper than 600 feet, but they are not typical.
How deep do you have to dig? For a horizontal loop you only need to dig between 6 - 8 feet deep. For a vertical loop you need to drill between 250 and 300 feet deep.
So, geothermal systems deliver warm air, not hot air. If the room temperature is 70°F the average delivered air temperature should be 90 – 95°F. The bottom line is it will heat your home for a lot less than any other automatic method. Of course free wood can do it for less, and wood is also renewable.
Trenches are normally four to six feet deep and up to 400 feet long, depending on how many pipes are in a trench. One of the advantages of a horizontal loop system is being able to lay the trenches according to the shape of the land. As a rule of thumb, 500-600 feet of pipe is required per ton of system capacity.
Geothermal Energy Pros and Cons
| Pros | Cons |
|---|
| Efficient (300- 500% compared to 90% of the best furnaces). | Electricity is still needed to operate heat pumps. |
| Geothermal energy is a renewable resource as long as the Earth exists. | Geothermal energy using wells requires an incredible usage of water. |
A geothermal heat pump uses electricity. In a lot of areas around the country, natural gas costs are very low. It is much cheaper to operate a natural gas furnace than to rely on an electric furnace. Basically, geothermal heating costs are going to be as good and often better than what a gas furnace can produce.
How deep do you have to dig? For a horizontal loop you only need to dig between 6 - 8 feet deep. For a vertical loop you need to drill between 250 and 300 feet deep.
Systems are generally sized in tons, an average home might be 3 tons, while a larger home might be 6 tons. Larger systems are more expensive because of the increased size of the loop field and larger geothermal unit. If an undersized system is installed it will strain to reach your desired heating and cooling needs.
Numbers from US Environmental Protection Agency (EPA) show that homeowners save 30-70% on heating and 20-50% on cooling costs by using geothermal heat pumps compared to other conventional systems. This translates to roughly $400 to $1,500 annual savings.
The initial cost for the field and power plant is around $2500 per installed kW in the U.S., probably $3000 to $5000/kWe for a small (<1Mwe) power plant. Operating and maintenance costs range from $0.01 to $0.03 per kWh.
Retrofits can be expected to take 6 to 8 weeks from start to finish. Installations in new construction typically take longer due to the coordination and scheduling with other contractors. Each stage of a geothermal installation can be expected to take the following lengths of time: Permitting and Design – 2 to 3 Weeks.
That means you'll only need (1,412.5kwh per person x 0.65) 918.125kwh of electricity per person. Compare the number above to $4,864 and you can see that you'll save 67.5% on your heating costs every year, for the lifespan of the heat pump.
The average national cost to install a geothermal heating and cooling system—also known as ground source heat pumps (GSHP)— ranges between $7,000-$30,000. Most homeowners pay around $15,000.
Answer: A ground source heat pump needs more space than an air source heat pump. A typical horizontal system requires around 700 square metres. A vertical system needs enough space for the drilling rig to access the site, but boreholes are only around 20 centimetres wide.
Ground Source Heat Pumps – Up To £31,500 Grant Available
This heat can then be used to heat radiators, underfloor, or warm air heating systems and hot water in your home. With the government grants that are available through the Renewable Heat Incentive the install costs can partially or fully recouped.Boreholes are drilled to a depth of 15 to 150 metres and may benefit from higher ground temperatures than trenches. There are a variety of types of pipe which can be used in a trench instead of a straight one, which increase the amount of heat absorbed from the ground and so enhance performance.
A ground source heat pump extracts heat from the ground – whose temperature will be warmer than the air in winter (and cooler than the air in summer). For this reason they are more efficient than air source heat pumps, especially in the coldest weather when they are most needed.
What do they look like? A Ground Source Heat Pump system comprises three basic elements – a ground heat exchange loop, the heat pump itself which concentrates available heat from the ground, and a heat distribution system. The ground loop is a pipe buried underground in a horizontal trench or a vertical borehole.
The ground source heat pump cost will differ from one project to another. The Energy Saving Trust estimates that the average ground source heat pump prices and installation costs are around £13,000–£35,000. The price would naturally vary depending on the system you select.
The main disadvantages of a ground source heat pump are:
- They are expensive to install.
- They are most effective if you have underfloor or air heating systems.
- The installation process will mean significant work and disruption to your garden.
How long does a Ground Source Heat Pump last? A well engineered commercial ground source heat pump can be expected to last 25 years – ten years longer than a combustion boiler – and the ground heat exchanger, the more expensive part of a GSHP installation, should have a life of over 100 years.
Ground source heat pumps (GSHPs) use pipes that are buried underground to extract heat from the ground, which is then used to heat radiators, underfloor or warm air heating systems and hot water in your home. Heat from the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump.
