Course project - Boiler KE 25-14C

Contents

CONTENTS

Task

1 Characteristics of boiler unit

1.1 Technical characteristics of KE-25-14C boiler

2 Calculation of fuel by air and combustion products

2.1 Determination of combustion products quantity

2.2 Determination of enthalpy of combustion products

3 Calibration thermal calculation

3.1 Preliminary Heat Balance

3.2 Calculation of heat exchange in the furnace

3.3 Calculation of heat exchange in convective surface

3.4 Calculation of economizer

4 Final heat balance

Bibliographic list

Task

Perform the design of the stationary steam boiler in accordance with the following data:

- KE-25-14C boiler type

- full saturated steam capacity, D, kg/s 6.94

- operating pressure (overpressure), P, MPa 1.5

- feedwater temperature:

- up to economizer, tp1, Has 90

- for economizer, tp2, ° С 170

- temperature of air entering the furnace:

- to the airheater, tv1, ºС 25

- behind the airheater, tv2, ºС 180

- FP fuel - TO

- fuel composition: Sg = 76.9%

Ng = 5.4%

Sg = 0.6%

Og = 16.0%

Ng = 1.1%

- ash content of fuel As = 23%

- fuel humidity Wp = 7.5%

- excess air coefficient α = 1.28.

Boiler characteristics

Steam boiler KE2514C, with natural circulation with layered mechanical furnaces, is designed to generate saturated or superheated steam used for the technological needs of industrial enterprises, in heating, ventilation and hot water supply systems.

Combustion chamber of KE series boilers is formed by side screens, front and rear walls. The combustion chamber of KE boilers with a steam capacity of 2.5 to 25 t/h is divided by a brick wall into a furnace with a depth of 1605 2105 mm and a combustion chamber with a depth of 360 745 mm, which allows increasing the efficiency of the boiler by reducing mechanical underburn. Inlet of gases from furnace into combustion chamber and outlet of gases from boiler are asymmetric. Under the combustion chambers it is inclined so that the bulk of the fuel pieces falling into the chamber slides onto the grid.

The KE2514C boiler uses a single stage evaporation scheme. Water circulates as follows: feed water from the economizer is supplied to the upper drum under the water level through a perforated pipe. Water is drained into lower drum via rear heated pipes of boiling bundle. The front part of the bundle (from the front of the boiler) is lifting. Water is supplied from lower drum via bypass pipes to chambers of LH and RH screens. The screens are also fed from the upper drum along the downcomers located at the front of the boiler.

Boiler unit KE2514C rests with chambers of side screens on longitudinal channels. Chambers are welded to channels along the whole length. In the area of the convective bundle, the boiler unit rests on the rear and front transverse beams. Transverse beams are attached to longitudinal channels. Front beam is fixed, rear beam is movable.

The binding frame of the boiler KE2514C is installed at the corners welded along the chambers of the side screens along the entire length.

In order to be able to move the elements of the boiler units KE2514C in a given direction, part of the supports is made movable. They have oval holes for bolts, which are attached to the frame.

KE boilers with grille and economizer are supplied to the customer by one transportable unit. It is equipped with a takeaway return system and acute blow. The carryover settling in the four ash beds of the boiler is returned to the furnace by means of ejectors and introduced into the furnace chamber at a height of 400 mm from the grid. Mixing pipes of takeover return are made straight, without turns, which ensures reliable operation of the systems. Access to entrainment return ejectors for inspection and repair is possible through hatches located on the side walls. In the places where hatches are installed, the pipes of the extreme row of the bundle are introduced not into the collector, but into the lower drum.

Steam boiler KE2514C is equipped with a stationary device for cleaning heating surfaces according to the design of the plant.

Steam boiler KE2514C is equipped with a furnace of the ZPRPK type with pneumatic mechanical throwers and a grille with turning bars.

Water economizers shall be installed behind boiler units in case of burning of stone and brown coals with reduced humidity W < 8.

Boiler sites of KE type are located in the places necessary for maintenance of boiler valves. Main boiler sites: a side platform for servicing water display devices; side platform for servicing safety valves and shutoff valves on the boiler drum; a site on the rear wall of the boiler for servicing the purge line from the upper drum and for access to the upper drum during boiler repair.

Stairs lead to the side platforms, descent (short staircase) from the upper side platform to the rear platform.

Boiler KE2514 С is equipped with two safety valves, one of which is a control valve. For boilers with superheaters, a control safety valve is installed on the outlet header of the superheater. A pressure gauge is installed on the upper drum of each boiler; if there is a superheater, the pressure gauge is also installed on the outlet header of the superheater.

The following valves are installed on the upper drum: main steam valve or gate valve (boilers without superheater), valves for steam sampling, steam collection for their own needs. A shutoff valve with a conditional passage of 50 mm is installed on the knee for water lowering.

In the boiler KE2514C, periodic and continuous blowdown is carried out through the blowdown nozzle. Shut-off valves are installed on periodic blowdown lines from all lower chambers of screens. Drain valves for condensate discharge during line heating and shut-off valves for steam supply to the blowing device are installed on the blowing steam line. Instead of steam blowing, a gas pulse or shock wave generator (HLG) can be supplied.

Check valves and shut-off valves are installed on the feed pipelines in front of the economizer; Feed control valve is installed in front of check valve and is connected with boiler automatics actuator.

Steam boiler KE2514C provides stable operation in the range from 25 to 100% of nominal steam capacity. Testing and operating experience of a large number of KE type boilers confirmed their reliable operation at reduced, compared to nominal, pressure. With a decrease in the operating pressure, the efficiency of the boiler does not decrease, as confirmed by the comparative thermal calculations of the boilers at nominal and reduced pressure. In boilers intended for the production of saturated steam, boilers of the KE type under reduced pressure to 0.7 MPa provide the same productivity as at a pressure of 1.4 MPa.

For KE type boilers, the capacity of the relief valves corresponds to the rated steam capacity at an absolute pressure of 1.0 MPa.

When operating at reduced pressure, the boiler safety valves and the additional safety valves installed on the equipment shall be adjusted to the actual operating pressure.

With a decrease in pressure in boilers to 0.7 MPa, the configuration of boilers by economizers does not change, since in this case the underheating of water in feed economizers to the saturation temperature of steam in the boiler is 20 ° C, which meets the requirements of the rules of Gosgortekhnadzor.

1.1 Technical characteristics of KE-25-14C boiler

Steam capacity D = 25 t/h.

Pressure P = 24 kgf/cm2.

Temperature is couple of t = (194÷225) ºС.

Radiation (radiation-receiving) heating surface Nl = 92.1 m2.

Convective heating surface Nc = 418 m2.

Type of furnace device PMZ2700/5600.

The combustion mirror area is 13.4 m2.

Overall dimensions of the boiler (with platforms and stairs):

- length 13.6 m;

- width 6.0 m;

- height 6.0 m.

Boiler weight 39212 kg.