Course design Test design calculation of steam boiler BKZ-75-39 FB

Contents

Table of contents

Introduction

Chapter 1. Determination of steam boiler efficiency

1.1. Preparation of design and process diagram of steam boiler paths. Selection of excess air factors

1.2. Fuel and combustion products

1.3. Calculation of enthalpy by boiler flue

1.4. Thermal balance of the PC. Determination of design fuel consumption

1.4.1. Heat loss with chemical and mechanical failure

1.4.2. Heat loss with exhaust gases:

1.4.3. Heat loss from external cooling

1.4.4. Heat loss with slag

1.4.5. Gross Steam Boiler Efficiency

1.4.6. Fuel consumption supplied to the furnace

1.4.7. Estimated consumption of actually burned fuel

Chapter 2. Calibration thermal calculation of the furnace chamber and the feston

2.1. Selection of fuel firing circuit

2.2. Verification calculation of the furnace

2.2.1.The average value of the thermal efficiency coefficient

2.2.2. Active volume of the furnace chamber

2.2.3. Effective thickness of the radiating layer in the furnace

2.3. Calculation of heat exchange in the furnace

2.3.1. Useful heat generation in the furnace

2.3.2. Definition of M parameter

2.3.3. Determination of average total heat capacity of combustion products

2.3.4. Determination of furnace blackness degree

2.3.5. Design temperature of gases at the furnace outlet

2.3.6. Specific thermal stress of the furnace volume

2.3.7. Heat transferred by radiation in the furnace

2.3.8. Specific thermal stress of the furnace section in the burner area

2.4. Verification calculation of the feston

2.4.1. Live area for gas flow in each row

2.4.2. Heating Design Surface

2.4.3. Initial data for test thermal calculation of the feston

2.4.4. Enthalpy of gases behind the festone

2.4.5. Heat perception of the feston according to the equation of heat balance of heat carrier (combustion products)

2.4.6. Heat perception of the feston according to heat transfer conditions

2.4.7. Heat transfer coefficient for the feston

2.4.8. Heat Perception Imbalance

Chapter 3. Inspection and design calculation of superheater and tail surfaces of steam boiler heating

3.1. Determination of heat perceptions of economizer, air heater, superheater and reduction of heat balance of steam boiler

3.1.1. Thermal perception of superheater

3.1.2. Heat perception of air heater

3.1.3. Heat perception of air heater by combustion products

3.1.4. Thermal view of water economizer

3.1.5. Lack of heat balance of steam boiler

3.2. Calibration and design calculation of superheater

3.2.1. Heating surface of each stage

3.2.2. Area of living section for gas passage

3.2.3. Average gas velocity

3.2.4. Live section area for steam passage

3.2.5. Heat transfer coefficient

3.2.6. Determination of temperature head

3.2.7. Design surface of superheater by heat transfer equation

3.3. Calibration and design calculation of water economizer

3.3.1. Determination of enthalpy and feed water temperature after economizer

3.3.2. Defining the Economizer Type

3.3.3. Economizer design dimensions

3.3.4.Water and gas velocity at economizer inlet

3.3.5. Heat transfer coefficient

3.3.6. Determination of temperature head

3.3.7. Economizer Design Surface

3.3.8. Non-binding of heating surfaces

3.5. Calibration and design calculation of the air heater

3.5.1. Area of living section for gas passage

3.5.2. Area of living section for air passage

3.5.3. Heating surface of air heater

3.5.4. Average gas velocity

3.5.5. Average air speed

3.5.6. Heat transfer coefficient

3.5.7. Determination of temperature head

3.5.8. Design surface of air heater

3.5.9. Non-binding of heating surfaces

Chapter 4. Boiler start-up and shutdown

4.1. Boiler start-up

4.2. Boiler shutdown

List of literature

Introduction

In this project, check design calculation of steam boiler BKZ7539FB is performed. The purpose of the calculation is to determine the temperatures and velocities of gases throughout the path, as well as to determine possible changes in heating surfaces during the operation of the boiler at the IrshaBorodinsky coal (B2). Calculation includes verification calculation of furnace and feston and verification design calculation of superheater, water economizer and air heater. Preliminary calculation is performed by fuel, air, combustion products, heat balance.

Boilers of BKZ7539FB type.

Boiler unit of block structure of BKZ7539FB type is designed for operation on brown and stone coals, peat, anthracite pin and skinny coals. The boiler - single-drum, with natural circulation, is made according to a U-shaped scheme. The 460.2 m2 furnace chamber is completely shielded by pipes with a diameter of 60 mm and a wall thickness of 3 mm, and during the operation of the boiler on the ASh and peat - partially in the lower part by pipes with a diameter of 60 mm and a wall thickness of 4 mm, located with steps of 75 and 90 mm. Pipes of front, rear screens and lower part form cold funnel. In the upper part of the pipes of the rear screen are divided into a four-row feston. Screens are divided into 12 independent circulation circuits according to the number of staging units of the furnace.

To burn coal, the boiler furnace is equipped with three coal-dust burners located on the front of the boiler and four, but located two on each side wall.

The evaporation scheme is three-stage, designed for nutrient water with salt content of a dense residue up to 350 mg/l.

Boiler drum with internal diameter of 1500 mm. And the wall thickness of 36 mm is made of 16GS steel. The drum has a clean compartment of the first stage of evaporation and two salt compartments of the second stage (at the ends of the drum) equipped with intra-drum cyclones, the third stage is carried out into remote cyclones, steam from which enters the drum.

Superheater - convective, vertical design, coil with a corridor arrangement of pipes (the first four rows of the first stage are festonized), is made of two blocks located in a rotary gas duct between the furnace and the downhole gas duct. The overheating temperature is controlled by a surface cooler.

Economizer steel tubular with staggered arrangement of boiling type pipes, smooth tube.

Vertical type steel tubular air heater with staggered arrangement of pipes.

The boiler frame is metal, welded structure with skin. Three-layer coating in the form of slabs of lightweight type fixed on the frame.

3. Check design calculation of superheater and tail surfaces of steam boiler heating

3.1. Determination of heat perceptions of economizer, air heater, superheater and reduction of heat balance of boiler

Heat perception of superheater and air heater is determined by equation of thermal balance of working medium (steam, air); and heat perception of the economizer according to the equation of thermal balance of combustion products.

4. Boiler start-up and shutdown

4.1. Boiler start-up

The start-up of boilers is accompanied by significant changes in the stresses of all elements under the influence of thermal deformations and changing mechanical forces. The resulting additional voltages can reach dangerous limits, therefore the start-up and shutdown processes are the most responsible during the operation of boilers, require the maintenance personnel to accurately fulfill the conditions of reliability and safety in the conduct of these operations.

When starting the boiler from the cold state, a check and inspection is preliminary carried out, and during starting from repair - a special test. Only when the entire unit is serviceable, preparatory operations and melting of the boiler are started.

The boiler is started in the following sequence: external inspection, serviceability check of gate valves, burners, smoke pump, fan, opening of air vents, closing of the main steam valve and gate valve in front of the main line. Opening of gate valve upstream steam boiler, opening of blowdown line. Boiler is filled with warm water with temperature equal to 7080 0C after deaerator. In initial period filling of boiler is carried out with low flow rate of water. To avoid high internal stresses, it is recommended to fill the boiler with hot water for medium pressure boilers within 11.5 hour. The smoke is turned on and the gas ducts are ventilated for 1015 minutes. The dilution fuel oil nozzles and then the dust-coal burners are switched on. During the melting period, special attention is paid to monitoring the heating of the drum, screen surfaces, superheater, economizer.

The duration of the melt depends on the initial state of the boiler (cold or hot reserve), the size and design of the boiler are set individually on a case-by-case basis. For medium pressure boilers, the duration is 2 -4 hours. At Rb = 1-2 atm, the gate valve is opened in front of the main line, the valves on the blowdown lines are closed and the load on the boiler is raised in accordance with the needs of the station.

4.2. Boiler shutdown

When the boiler is shut down to the hot reserve, measures are taken to preserve the accumulated heat in the unit. During normal shutdowns in cold reserve, the boiler is cooled down, while observing the conditions of slow cooling, safe for the equipment.

Boiler shutdowns are performed with preliminary load removal, transferring it to parallel boilers or unloading turbines. Cooling of the boiler is mainly due to convective heat exchange between the heating surfaces and air, which penetrates into the boiler gas ducts due to gravity generated in them.

The evaporation surfaces of the boiler and the water in them are cooled quite quickly. The process of cooling the drum occurs due to the circulation of water.

The duration of the boiler cooldown depends on its size and design data and is usually 24 hours. During the first four hours, the boiler cools with fully closed dampers, hatches, with minimal blowing and makeup.

Sequence is cut off fuel supply, disconnected from steam line, blowdown line is opened for one hour. Slowly for 4-6 hours, the steam boiler is cooled down, smoke pumps and fans are stopped. Steam boiler is purged with feed water, normal level in drum is maintained. The cooling speed of the drum is determined by the pressure drop rate in German. This speed is adjusted so that the temperature difference between the top and bottom of the drum does not exceed 40 0C.

According to PTE, when any boilers are stopped for a period of more than three days, coal dust from the bunker must be operated to avoid tracking or spontaneous combustion.

чертеж1.dwg

чертеж2.dwg