a16dbe075ce9cde3f202cec13a79e4ahhhff5.pptx

This is boiler types

1. Definition: a type of fired furnace used to boil water and produce steam ; also known as a steam generator. Steam is used to operate steam turbines, distillation systems, and reaction systems . Think and answer : Compare a boiler with a reboiler ? Boilers Heat transfer methods : Boilers use a combination of radiant, conductive, and convective heat transfer methods to change water to steam. A simple boiler consists of a heat source, water-containing drum, water inlet, and steam outlet. As heat is added to the drum, the temperature increases until the water boils . As the steam rises, it is captured in a line and sent on for further processing. Effective factors on boiler operation : density differences for internal circulation, pressure, temperature, and water level. Water to steam: Heat until start boiled : 23 C to 100C steam to super heating steam More than 100C Radiation Conduction Convection

2. Boiler Produce steam by converting water to steam To heat up the bottom product (liquid ) to separate the lighter components from heavier components Steam to tube wall to liquid Convection ….conduction….convection

3. 600C 100 C

4. Fire -Tube Boilers A more complicated boiler is the fire-tube boiler, which resembles a modified shell-and-tube heat exchanger. This type of boiler is composed of a shell and a series of tubes designed to transfer heat from the fire-tubes and into boiler feedwater . How it works? Combustion gases exit through a chamber similar to an exchanger head and pass safely out of the boiler. The water level in the boiler shell is maintained above the tubes to protect them from overheating. The term fire-tube denotes that the heat source is from within the tubes . A fire-tube boiler consists of a boiler shell with feed inlet and outlet connections , fire-tubes , a combustion tube , burner , feedwater inlet, steam outlet, combustion gas exhaust port , and tube sheets .

5. Fuel burning (radiation ) Flue gases

6. Water-Tube Boilers The most common type of large commercial boiler is a water-tube boiler. A water-tube boiler consists of an upper and lower drum connected by tubes. The lower drum and water-tubes are filled completely with water, whereas the upper drum is only partially full . This arrangement allows steam to pass through mechanical separators in the upper drum, flow to a superheater section, and then exit the boiler. As heat is applied to the boiler firebox, water flows from the upper drum through downcomers into the lower drum. Tubes, called risers, cause water and steam to flow into the upper drum because of density differences. Boiler water circulation operates under the principle of differential density . When a fluid is heated, it expands and becomes less dense. How it works? Refer to the video to understand better Cooler water flows from the upper—or steam—drum through the downcomers to the mud drum (the lower drum) and then rises as some steam is generated. Circulation continues, and makeup water is added to the upper drum to replace the steam that is generated. Water circulation continues in a water-tube boiler because steam bubbles in the lower drum move up the riser tubes and cause water density to decrease. The cooler water in the downcomer flows into the mud drum. The riser and steam-generating tubes are physically located near the burners. Steam moves up the riser and steam-generating tubes and into the upper steam-generating drum. Steam generation causes pressure to rise. When the target pressure is achieved, the boiler is “placed on the line.” Pressure is maintained by adding makeup water and continuously applying heat. NORMAL STEAM /CONDSATE STEAM DRY STEAM 600C

7. Question : What type of steam a water-tube boiler produces? SUPER HEATED STEAM (DRY STEAM )(600C) DESUPER HEATED STEAM (WET STEAM)(100 C) Basic boiler design removes the steam from the upper steam water drum and heats it up at essentially the same pressure. This process is referred to as superheating . Some plant processes cannot tolerate high temperatures. The process of cooling the superheated steam is referred to as de superheating . During the desuperheating process, part of the superheated steam is returned to the steam drum. The cooler liquid in the steam drum removes heat from the superheated stream and allows it to be used in specific plant processes. Steam in boilers

8. Steam is used in a variety of applications in industrial manufacturing environments. As steam flows from the boiler to the plant, it begins to cool. As it cools, condensate is formed . Condensate can cause many of serious problems as it flows with the steam. Slugs of water can damage equipment and lead to a condition known as water hammer . Devices known as steam traps are used to remove condensate . Steam traps are grouped into two categories: mechanical and thermostatic. Mechanical steam traps include inverted buckets and floats. Thermostatic traps include bellows-type traps. Steam traps Question : What is a steam strap?

9. Steam Generation System

10. A number of hazards are associated with the operation of a boiler system. Some of these hazards include: • Hazards associated with high-temperature steam, “burns” • Hazards associated with using natural gas • Hazards associated with leaks • Instrument failures • Hazards associated with confined space entry • Opening and blinding • Isolation of hazardous energy permit labeled “Lock-out, Tag-out” • Routine work on equipment and facilities • Hazards associated with lighting burners • Exceeding boiler temperatures or pressures • Hazards associated with using water treatment chemicals • Error with valve line-up resulting in explosion or fire