Boilers and Steam

Question 1

Boilers are typically rated in terms of __ heat rate and MMBtu __ __
Boiler __ in horsepower
1 Boiler HP = 33,475 Btu per hour

Answer 1

input, per hour, output

Question 2

Excess air is required in the combustion process results in excess __ in the exhaust. This helps reduce __ __ in exhaust

Answer 2

oxygen, carbon monoxide

Question 3

Exact quantity of air required to convert all fuel Carbon to CO2 assuming perfect combustion is the ___ point.

typically CO2, N2, and H2O in the exhaust

Answer 3

stoichiometric

Question 4

Boiler efficiency can be increased by __% for each 3% reduction in excess oxygen or __ degree reduction in stack gas temperature

Answer 4

1%

40

Question 5

three key factors affecting combustion efficiency

Answer 5

fuel type (composition
Excess oxygen (sometimes CO2) 
Stack temperature rise (STR)

Question 6

We can __ efficiency by __ Stack Temperature rise

Answer 6

increase, reducing

Question 7

Common methods of increasing efficiency of stack temp rise

Answer 7

clean the heat transfer surfaces (tubes)
sensible heat recovery from exhaust to feedwater
Preheat incoming combustion air using an air preheat exchanger

Question 8

Boiler efficiency benefit is roughly __ % for every 100 degree increase in the combustion air temperature

Answer 8

2

Question 9

a sensible heat economizer __ heat from the exhaust to __ feed-water.

Answer 9

extracts, preheat

Question 10

Fuel Savings = Fuel Used initial - Fuel Used final

Fuel used = 10MMBtu/hour * 1/efficiency

Question 11

Some large boiler systems may utilize condensing economizers which extract the available __ heat of the water vapor in the exhaust stack
This is called a __ boiler or __ water heater

Answer 11

latent

condensing

Question 12

Condensing boilers reclaim latent energy of ___ Btu/lb of condensed water vapor
gain about __ % efficiency over non-condensing

Answer 12

~1,000

Question 13

a measure of thermal energy of a substance: h, Btu/lb

Answer 13

Enthalpy

Question 14

most boilers are ___ steam boilers, meaning no heat is added to the steam after the water vaporizes

Answer 14

saturated

Question 15

Adding heat to steam after fully vaporizing it into saturated steam is called __.

Answer 15

superheat

Question 16

superheat is added to produce __ steam for use in turbines such that no water droplets can exist, otherwise they will damage the turbine

Answer 16

dry

Question 17

In boiler blowdown, __ is removed

removes impurities, controls concentration of solids, continuous and low flow rate, possible source of heat for makewaup water or flash steam

Answer 17

water

Question 18

types of contaminants to control for boiler blowdown

Answer 18

suspended solids, dissolved solids, hardness, ions, dissolved gases

Question 19

Remove condensate
Remove non-condensable gases such as air and CO2
Block live steam
are all functions of __ trap

Answer 19

Steam Trap three functions

Question 20

If you can increase the % of condensate returned to the boiler then,

Answer 20

reduced makeup water
reduced fuel consumption
reduced risk of fines

Question 21

Consider the energized condensate in the diagram
pressure and temperature losses are unavoidable, such as dropping from high pressure to low pressure. results in the formation of vapor

Answer 21

Flash Steam