Waste heat boiler, is a boiler that utilizes the waste heat in the exhaust gas, waste material or waste liquid of various industrial processes and the heat generated by the combustion of its combustible material to heat water to a certain working condition. Below, we will learn about the waste heat boiler classification, principle, characteristics and working characteristics.

    Waste heat boiler, is a boiler that utilizes the waste heat in the exhaust gas, waste material or waste liquid of various industrial processes and the heat generated by the combustion of its combustible material to heat water to a certain work quality. Waste heat boiler consists of boiler tube, movable smoke hood, furnace mouth section flue, inclined 1 section flue, inclined 2 section flue, the last 1 section flue, the last 2 section flue, charging pipe (downstream chute) tank, oxygen gun port, nitrogen sealing device and nitrogen sealing plug, manhole, differential pressure pressure pickup device, flue support and hanger and other components. Waste heat boiler is divided into six circulating circuits, each circulating circuit consists of descending pipe and ascending pipe, each section of the flue feed water from the drum through the descending pipe introduced into the lower collector box of each flue into the heating surface, the water passes through the heating surface and produces steam into the inlet collector box, and then introduced into the drum by the ascending pipe. Each flue is connected with flange.

Classification of waste heat boiler

Waste heat is not fully utilized in industrial production on the emission of heat, which belongs to the secondary energy, is a primary energy and combustible materials after the conversion of the product.

(A) according to the nature of waste heat can be divided into the following categories:

1. High-temperature flue gas waste heat: it is a common form, characterized by large production, production point concentration, continuity, easy to recover and use, the heat taken away accounted for 40 ~ 50% of the total heat, the waste heat boiler to recover heat, can be used for the production or living heat and power generation.

2. High-temperature slag waste heat: such as blast furnace slag, converter slag, electric furnace slag, etc., the slag temperature of more than 1,000 ℃, it takes away 20% of the total heat.

3. High-temperature product waste heat: such as coke oven coke, steel ingot billet, high-temperature forgings, etc., it is generally temperature . Very high, containing a large amount of waste heat.

4. Waste heat of combustible waste gas and waste liquid: such as blast furnace gas, catalytic cracking regeneration waste gas from refineries, black liquor from paper mills, etc., which can be utilized.

5. Waste heat of chemical reaction: such as metallurgy, sulfuric acid, phosphoric acid, fertilizers, chemical fibers, paints and other industrial sectors, all produce a large amount of waste heat of chemical reaction.

6. Waste heat of cooling medium: such as industrial furnaces and kilns, water jackets and other cooling devices discharged a large number of cooling water, various vaporization cooling device output steam contains a large amount of waste heat, they can be reasonably utilized.

7. Waste heat of condensate: the physical sensible heat of the steam used in the production process of various industrial sectors when it is condensed and reduced after the industrial process.

(ii) because of the waste heat is closely related to other production equipment and processes, so the use of waste heat and has the following characteristics:

1. The heat load is unstable, mainly determined by the production process.

2. The composition, concentration, particle size of the soot is relatively large differences. Thus, the boiler's heating surface arrangement is affected, and must consider anti-wear, plugging and dust removal.

3. The diversity of flue gas components, so that some flue gas corrosive. Such as SO2 in the flue gas, soot or slag in a variety of metal and non-metallic elements may produce low-temperature or high-temperature corrosion of waste heat equipment and ash accumulation.

4. By the installation of the inherent conditions of the limitations. If there are restrictions on the boiler inlet and outlet elevation; some of the boiler exhaust temperature limitations to meet the requirements of the production process.

(c) due to the different nature of the waste heat flue gas, so that the types of waste heat boilers, structural forms vary. According to the structural characteristics can be divided into two categories of shell and tube type waste heat boiler and flue type waste heat boiler. According to the waste heat boiler import flue gas dust content and flue gas characteristics can be divided into the following five categories:

1. Flue gas containing dust is not more than 20g/Nm3 of waste heat boilers for the first category of waste heat boilers;

2. Flue gas containing dust greater than 20g/Nm3 and not more than 70g/Nm3 of waste heat boilers for the second category of waste heat boilers;

3. Flue gas containing more than 70g / Nm3 of dust in the waste heat boiler for the third category of waste heat boilers;

4. The flue gas contains adhesive soot in the waste heat boiler for the fourth category of waste heat boilers;

5. The flue gas contains strong corrosive components or toxic fumes of the waste heat boiler for the fifth category of waste heat boilers.

Classification of waste heat boilers

According to the waste heat boiler steam generated by the pressure level classification

Waste heat boilers are currently used with single-pressure, double-pressure, double-pressure reheat, triple-pressure, triple-pressure reheat and other five major categories of vapor system.

1. Single-pressure class waste heat boiler: the waste heat boiler only produces a pressure of steam supplied to the turbine.

2. Double-pressure or multi-pressure level waste heat boiler: the waste heat boiler can produce two different pressures or a variety of different pressures of steam supplied to the turbine.

According to the arrangement of the heating surface classification

1. Horizontal arrangement of waste heat boilers

2. Vertical arrangement of waste heat boilers

According to the mass in the evaporation of the flow characteristics of the heating surface (principle of operation) classification

1. Natural circulation waste heat boiler: flue gas is horizontally flowing through the vertical direction of the installation of the tube cluster. Tube clusters in the water vapor mixture and the density difference between the cold water in the drop tube, is to maintain the evaporator in the vapor mixture of natural circulation of power.

2. Forced circulation waste heat boiler: the flue gas usually always flows vertically through the horizontally arranged tube cluster. Through the circulation pump to ensure that the evaporator circulation flow rate is constant.

3. DC waste heat boiler: DC waste heat boiler by the pressure head of the feed pump will feed water once through the heating surface into superheated steam. In the evaporation of the heated surface, the flow of the workpiece is realized by the feed pump pressure head.

Characteristics and differences of waste heat boilers

"Waste heat boilers are in general only a "pot" but not a "furnace".

"Waste heat boilers usually do not have a burner, but if high pressure and high temperature steam is required, an additional burner can be installed in the waste heat boiler. Through the combustion of fuel to raise the temperature of the entire flue gas, able to produce high parameters of steam.

For example, when a waste heat boiler is not equipped with a burner, the inlet flue gas temperature is 500°C. After installing an additional burner, the inlet flue gas temperature can reach 756°C. The steam pressure can be increased from 4MPa to 5MPa. The pressure of the steam can be increased from 4MPa to 10MPa, the temperature of the steam can be increased from 450℃ to 510℃, and the steam can be used for high temperature and high pressure turbine, thus increasing the electric power output.

Waste heat boilers mainly utilize exhaust gas as a heat source, so there is no need for a combustion system (unless there is a requirement for supplementary combustion).

The difference between a waste heat boiler and a conventional boiler:

Waste heat boilers utilize existing exhaust gas waste heat or solid sensible heat.

Waste heat boilers can produce steam under multiple pressures to improve heat recovery efficiency.

Waste heat boilers do not have fuel combustion devices.

Waste heat boiler as waste heat utilization should be adapted to the needs of the main process, can not affect the operation of the main process.

Waste heat boiler heating surface arrangement of diverse forms.

Waste heat boiler composition and working process

The gas discharged after doing work in the gas turbine still has a relatively high temperature, generally around 540 ℃, the use of this part of the gas heat energy, you can improve the thermal efficiency of the entire device.

This heat is usually utilized to heat water and turn it into steam. The steam can be used to power a steam turbine or generator, or it can be used for process heating or domestic heating.

The equipment that uses the heat from the exhaust of a gas turbine to produce steam is called a "heat recovery steam generator," indicating that the heat from the exhaust is recovered.

It is customarily called "waste heat boiler" in China, and the exhaust gas from the gas turbine is simply called "flue gas".

The high temperature flue gas from the gas turbine has two outlets, one way into the waste heat boiler, from the main chimney into the atmosphere, and the other way into the bypass chimney into the atmosphere. Each flue is equipped with a baffle, there are three baffles, the main flue baffle called "main baffle", the bypass flue baffle called "bypass baffle", the main chimney at the baffle called "chimney baffle "The baffles are used in conjunction with each other.

Usually, the waste heat boiler consists of economizer, evaporator, superheater, heat exchanger tubes and containers such as coupling box and steam bag, etc. In the steam cycle with reheater, reheater can be added.

In the economizer boiler feedwater to complete the task of preheating, so that the feedwater temperature rises to a level close to the saturation temperature; in the evaporator feedwater phase change into saturated steam; in the superheater in the saturated steam is heated to become superheated steam; in the reheater reheated steam is heated to the set reheat temperature.

When the gas turbine is working and the waste heat boiler is not working, the bypass baffle is opened and the main baffle is closed. If the gas turbine and the waste heat boiler are operating at the same time, the bypass flap is closed and the main flap is opened. On the other hand, in order to adjust the steam production of the waste heat boiler, the main baffle and bypass baffle can be partially opened or partially closed.

When the waste heat boiler is working, the chimney baffle should be opened. When the waste heat boiler is stopped for a short period of time, the chimney baffle can be closed to prevent heat loss in the waste heat boiler. Because the temperature inside the waste heat boiler is relatively high, the surrounding cold air can enter the waste heat boiler to form a natural convection to take away the heat, close the chimney baffle can prevent the outside airflow into the waste heat boiler to save heat, ready to start the waste heat boiler at any time. If the waste heat boiler is to be shut down for maintenance, and you want to cool it faster, you can open the chimney baffle.

Waste heat boiler application areas:

Cogeneration to provide process steam for plants; combined cycle power plants to provide steam for steam turbines.

Waste heat boiler design should have conditions

1, flue gas side parameters:

Flue gas volume (standard or working conditions), flue gas inlet temperature, flue gas composition, flue gas dust content, flue gas side pressure (positive or negative), boiler flue gas side system resistance

2. Boiler parameters:

Boiler rated evaporation, boiler rated steam pressure, boiler rated steam temperature, boiler exhaust temperature

3、Other parameters:

The industry to which the main flue gas system, the system process description, boiler installation form, boiler structure form, boiler installation of meteorological parameters or other special requirements.

Waste heat boiler in the production system

Due to the special characteristics of the production system and the thermal system of waste heat power generation, the boiler mainly plays the following roles in the whole system:

a) The boiler plays the role of lowering the temperature of the whole flue gas, which can guarantee the normal operation of the dust removal equipment in the system and achieve the low-temperature environmentally friendly emission of flue gas;

b) The boiler generates high-temperature and high-pressure steam by utilizing the waste heat to push the gas turbine and generator to generate electricity by matching with the supplementary combustion boiler as a whole, which provides power for the equipment of the whole cement production system;

c) The boiler has a certain self-dedusting function, and the separated dust can be recycled to achieve the function of "one machine with multiple uses".

d) It is conducive to reducing the energy consumption of the whole system and making full use of energy.

Types of waste heat boilers

The main types of waste heat boilers are: sinter waste heat boiler, three-waste mixing furnace and blowing gas waste heat boiler, cement kiln waste heat boiler, iron and steel waste heat boiler, hazardous waste waste heat boiler, waste incineration waste heat boiler, coking waste heat boiler, non-ferrous metal smelting waste heat boiler, sulphuric acid waste heat boiler, waste heat boiler of the mineral furnace industry, waste heat boiler, glass kiln waste heat boiler, dry quenching waste heat boiler, carbon kiln waste heat boiler, gas turbine waste heat boiler, steelmaking waste heat boiler and so on. boilers, steelmaking waste heat boilers, etc.

Cement kiln waste heat boiler

The pure low-temperature waste heat boiler is a high-efficiency boiler that mainly utilizes the low-temperature waste heat flue gas discharged from the clinker cooler at the kiln head and the kiln tail preheater at a temperature ranging from 250℃ to 400℃ to generate micro-superheated steam, and at the same time, utilizes the micro-superheated steam to push the turbine with low parameter to do work for power generation. The overall structure of this type of boiler adopts vertical arrangement form, with flexible arrangement, small footprint, low capital investment, small air leakage, low steel consumption and other significant features, favored by the majority of users. The low-temperature waste heat for power generation is an effective way to save energy, reduce consumption and realize the comprehensive utilization of resources, which can not only reduce the cost of cement production, improve the economic efficiency of enterprises, but also enhance the competitiveness of enterprises and partially alleviate the tension of electricity, at the same time, reduce the temperature of the exhaust smoke and the concentration of exhaust dust, as well as reduce the emission of C02, which greatly reduces the air pollution of the environment and the greenhouse effect, and makes the cement enterprise achieve resource recycling and realize clean production. Utilization of resources and realization of clean production.

Three-waste mixed combustion furnace and blowing gas waste heat boiler

The waste heat boiler of three-waste mixed combustion furnace and the waste heat boiler of blowing air are the ideal high-efficiency and energy-saving equipments applied in the fertilizer and chemical industry (especially methanol, ethanol, formaldehyde and synthetic ammonia). According to the characteristics of the industry's waste heat and flue gas, I developed the industry's waste heat boiler is mainly new vertical and traditional tunnel kiln horizontal two types of natural circulation waste heat boiler, the waste heat boiler is a typical energy-saving use of equipment for the chemical recycling economy, it is mixed with three wastes combustion furnace and blowing gas furnace as a whole package, so that the production enterprises to fully realize the "two coal into a coal ", "two furnaces into a furnace", for the enterprise to produce huge economic and environmental benefits, and truly achieve safety, environmental protection, increased production, efficiency and savings. Furnace type has vertical and horizontal and "L" type arrangement and other forms.

This type of waste heat boiler is mainly composed of water-cooled screen, superheater, convection tube bundle, economizer and air preheater and other heating surfaces, which has the following advantages:

The overall heating surface of the boiler adopts a suspended structure, which is conducive to absorbing the expansion of the boiler and has high operational safety;

The boiler adopts special sealing device to reduce the air leakage of the boiler and improve the efficiency of the boiler;

The boiler adopts reasonable smoke velocity design for each heating surface, which is conducive to preventing ash accumulation;

The boiler adopts a straight-through type arrangement, which can utilize the self-weight of dust for self-removal of ash, can maintain the cleanliness of the heating surface, and improve the efficiency of the boiler heat exchange;

The boiler reasonably organizes the flue gas power field, so that the flue gas flows smoothly and evenly, avoiding the generation of bias flow, and at the same time adopts the special anti-wear structure, which is conducive to preventing boiler wear and tear, and improving the life of the boiler;

The boiler convection tube bundle adopts assembly structure, short installation period and low cost.

Sinter cooler waste heat boiler

Sinter cooler waste heat boiler is mainly a waste heat boiler that utilizes the waste heat from the sintering process of iron and steel enterprises to generate electricity. There are two main parts of sintering waste heat recovery: one is the waste heat of exhaust gas at the end of the sintering machine, and the other is the waste heat of exhaust gas generated when the hot sintered ore is air-cooled in the front section of the cooling machine. Currently, there are four main forms of waste heat power generation projects in the industry: single-pressure waste heat power generation, double-pressure waste heat power generation, flash waste heat power generation and supplementary combustion waste heat power generation; and two types of power generation systems: saturated steam power generation system and superheated power generation system.

Carbon kiln waste heat boiler waste heat boiler

Mainly carbon rotary kiln waste heat boiler and tank-type waste heat boiler two series of natural circulation waste heat boiler. Vertical inverted π type arrangement, divided into two series of double-bottle transverse type and single-bottle transverse type.

Dust-containing flue gas net from the slag tube, superheater, convection tube bundle and steel pipe economizer and then discharged out of the furnace. Boiler slag condensate tube by the front wall water-cooled wall thinning and become. The superheater adopts suspended structure, divided into high and low temperature sections, with a temperature reduction device in the middle. The convective tube bundle is arranged in rows, and a folding plate is set in the middle to improve the heat exchange capacity of the tube bundle. Coal economizer adopts serpentine tube. The middle part of the water-cooled wall is a membrane wall partition, which not only increases the heating surface, but also improves the sealing and safety of the boiler. Membrane wall structure is adopted for both front and rear walls.

Glass kiln waste heat boiler

The glass industry is a major energy consumer, China's existing float glass process level has been in line with international standards, but the average energy consumption in the production of glass is about 20% higher than abroad. Float glass furnace flue gas waste heat power generation system can further improve the utilization rate of waste heat up to 70% or more, and fully recover the waste heat resources. By setting up a high-efficiency vertical water tube waste heat boiler to generate superheated steam, while the flue gas temperature is reduced to about 160 degrees for discharge. The superheated steam is passed into the turbine to generate electricity.

The inlet flue temperature of the waste heat boiler in this industry is generally 400~500 degrees, the melting point of ash is low (about 1g/Nm3), and the bonding is large, for the waste heat boiler in this industry is mainly to solve the problem of blowing and clearing the ash.

Dry quenching waste heat boiler

Dry coke quenching is the use of inert gas to cool coke, the heat-absorbed inert gas is transferred to the boiler, and then sent by the circulating fan into the dry quenching furnace for recycling. Dry coke quenching device has many advantages such as energy saving, cost reduction, environmental pollution reduction and coke quality improvement. Dry quenching waste heat boiler is the main energy-saving equipment applied in dry quenching device, whose function is to cool the circulating gas and produce steam.

Coking Waste Heat Boiler

Coking plants produce a large amount of coking waste gas at 550-950℃ in coking production. The supplementary-fired boiler adopts an automatic coke oven gas burner, and the coke oven gas is burned inside or outside the waste heat boiler before mixing with the coking exhaust gas to form high-temperature flue gas into the boiler for heat exchange to produce rated steam.

The exhaust gas is discharged out of the furnace through the slag condensate tube bundle, superheater, convection tube bundle and steel tube economizer, and then enters the tail desulfurization and dust removal device, and then discharged into the atmosphere through the induced draft fan and chimney.

Coking waste gas waste heat boiler, overcoming the shortcomings of the previous horizontal single-flue or multi-flue waste heat boiler, which can be the main components of the boiler in the function of the same case of organic combination, centralized arrangement of the heating surface, simplified the structure of the furnace, and to achieve the multi-functional combination of components.

Coking waste gas waste heat boiler, with high efficiency heat transfer, two-stage furnace soot separation, and with its compact and novel structure, low cost, small footprint and high efficiency, environmental protection, energy saving and other advantages.

Sulfuric acid waste heat boiler

According to the different processes of acid production, the waste heat boilers applied in sulfuric acid waste heat recovery and power generation projects mainly include sulfur acid waste heat boilers and sulfuric acid waste heat boilers, and the boiler structure is divided into two types of fire tube and water tube. The boiler water circulation is mainly based on natural circulation and forced circulation.

Hazardous waste, medical waste and other waste incineration waste heat boiler

Waste heat boiler in this industry refers to the waste heat boiler that is compatible with the waste incineration equipment for hazardous waste, medical waste and other wastes and utilizes the heat of the flue gas exported from the waste incineration equipment to produce steam with rated parameters.

According to the characteristics of the waste treatment process, the waste heat boiler has an extremely important role in preventing the generation of dioxin-like hazardous substances, and at the same time, the waste heat boiler has a very good adaptability to the waste incineration flue gas.

Mineral heat furnace industry waste heat boiler

Mineral heat furnace is mainly used to reduce smelting ores, carbonaceous reductants and solvents and other raw materials, the main production of ferrosilicon, ferromanganese, ferrochrome, ferrotungsten, silicomanganese alloys and other ferroalloys, is the metallurgical industry in the important industrial raw materials and calcium carbide and other chemical raw materials.

The waste heat boiler effectively solves the problems of ash cleaning and plugging that plague the waste heat boiler in this industry, and lays the foundation for the efficient operation of the boiler. The developed waste heat boiler is suitable for single-pressure waste heat power generation, double-pressure waste heat power generation, flash waste heat power generation, medium-temperature and medium-pressure waste heat power generation, combined-cycle waste heat power generation and other waste heat power generation thermal systems.

Non-ferrous metal smelting waste heat boiler

The energy-saving method of adopting waste heat boiler in non-ferrous metal smelting industry is now widely used. Waste heat boiler can not only recover the secondary energy in the high-temperature flue gas of the smelting plant, reduce the temperature of the flue gas, but more importantly, it is to puff up the soot in the high-temperature flue gas, recover the precious metals, reduce the dust content of the flue gas, ensure the smoothness of the process system, and create favorable conditions for the tail end of the process, but the modern metallurgical plant is very critical and essential equipment.

For the production process of metallurgical furnace and waste heat boiler work characteristics, mainly single-bottomed, horizontal (vertical), straight-through type, the whole membrane wall arrangement, for forced or natural circulation of the water tube boiler, which mainly has a water-cooled flue (flue jacket), radiant cooling chamber and convection zone of the three major parts of the heated surface components, the boiler ash pipe and the roof of the heated surface of the membrane-type water-cooled wall structure, boiler soot cleaning method using vibration soot cleaning, shockwave soot clearing The boiler ash cleaning method adopts vibration ash cleaning and shock wave ash cleaning, which is simple and effective and easy to control.

Gas steam turbine waste heat boiler

The gas-steam combined cycle power generation is a high-efficiency, low-pollution power generation technology that is developing extremely rapidly in the world today, and it has become the preferred system for new thermal power plants in various countries, with good social benefits and broad market prospects. The waste heat boilers developed according to the characteristics of gas turbine flue gas mainly have various structural forms, such as single-pressure, multi-pressure, vertical, horizontal, natural circulation and forced circulation, which can be adapted to the requirements of different processes. This series of waste heat boilers mainly have the following features:

1、Adopting modular structure design, reasonable arrangement and advanced performance;

2, the boiler can adapt to different fuel combustion engine, to meet the needs of different waste heat utilization;

3, the boiler can adapt to the requirements of the combustion engine frequent start and stop, strong peak shifting ability, start fast;

4、The boiler adopts multi-layer sheathing adiabatic heat preservation structure, strong airtightness and simple structure;

5, boiler components assembled from the factory, easy to install, short cycle.

Waste heat boiler for calcium carbide furnace

Calcium carbide furnace is mainly relying on the high temperature of the electric arc to lime and carbonaceous raw materials (coke, anthracite or petroleum coke) melted and reacted to generate calcium carbide a device.