What Is a Heating Plant?

Centralized heating refers to the way that steam, hot water generated by a centralized heat source, is supplied to a city (town) or part of the area through a pipe network, which is required for production, heating and living. Central heating is one of the infrastructures of modern cities and an important facility of urban utilities.

Central heating is an important infrastructure for building a modern city. Central heating can not only provide cities with stable and reliable high-grade heat sources and improve living environment conditions, but also save energy, reduce energy consumption, reduce urban pollution, and protect the ecological environment.

The central heating system consists of a heat source, a heating pipe network, and a heat user. Central heating heat sources include cogeneration power plants, centralized boiler rooms, industrial and other waste heat, geothermal,

1.Use the coefficient at the same time

Many heat users in the central heating area and many heating equipment in an enterprise cannot have the maximum heat load at the same time. Therefore, when calculating the maximum heat load in the heating area, it is necessary to consider the heat users (or each heat equipment) Use factor. It represents the ratio of the actual maximum thermal load to the total maximum thermal load of each thermal user (or each thermal device) when all the thermal devices are operating, that is:

K = the actual maximum thermal load when all the heating equipment is running / the sum of the maximum thermal loads of each heating equipment

Where K is the simultaneous use coefficient.

2.Maximum heat load utilization hours

Working hours in which the total heat consumption is calculated based on the design heat load within a certain period of time (heating period or year). Its value is equal to the ratio of total heat consumption to design heat load in a certain period of time, that is:

H ₁ = total heat consumption / design heat load within a certain period

Where H ₁ is the maximum number of hours of heat load utilization, h.

3.

In central heating design, heat load is the most important basic information. Regardless of determining the heating source, the heating system, or the selection of various heating equipment, it is inseparable from the heat load. Therefore, even operation managers should have some understanding of the calculation and determination of heat load.

In a central heating design, the heat load must first be determined. In order to accurately determine the heat load, it is necessary to collect and organize the heat load data. The heat load can be divided into heating heat load, ventilation heat load, production process heat load, domestic hot water supply heat load, and air conditioning cooling heat load.

There are two types of heat medium for central heating systems: steam and hot water.

The hot water medium has the following advantages:

High thermal energy efficiency. From an energy point of view, when hot water is used as the heat medium, the hot water is obtained by low-pressure extraction steam heating, so the cogeneration power generation can be increased.

Easy adjustment. The hot water temperature can be adjusted according to the outdoor air temperature to achieve the goals of energy saving and indoor heating temperature.

Strong hot water storage capacity and good thermal stability.

Long conveying distance. Generally it can reach 5 ~ 10km.

The heat loss is small.

The disadvantage of the hot water medium is that it consumes a large amount of power and cannot meet the needs of users of steam heat. The steam medium has the following advantages:

Can meet the needs of a variety of thermal users.

The conveying depends on its own pressure, and no circulation pump is needed.

There is no need to consider static pressure during use and transportation, even if it is transported to 15-20km, there will be no problem.

The use of steam media can reduce the area of heat dissipation equipment for thermal users.

However, the steam heat medium has the following disadvantages:

Low energy efficiency. The high pressure required to transport steam reduces the cogeneration capacity.

It is difficult to recover the condensed water after the steam is used. Not only the loss of brine (or demineralized water) is large, but the heat loss is also large.

The steam loss is large during use and transportation.

The transportation distance is shorter than the hot water medium, generally it can be transported to 3 ~ 5km, and the maximum can be transported to 5 ~ 7km.

The higher the hot water parameters, the greater the transmission capacity, and the more energy can be saved, but the high temperature is uneconomical. To increase hot water parameters requires high steam pressure, large energy consumption, and large investment in equipment. Therefore, when determining the hot water temperature, technical and economic comparisons are required. The steam parameters should be determined according to the needs of the heat user and the transportation distance.

Central heating boiler room

A boiler room that supplies heat to a single enterprise is called an enterprise-owned boiler room, and a boiler room that supplies heat to multiple enterprises (units) is called a regional boiler room.

1. Central heating system for steam boiler room

In industrial and mining enterprises, production processes require steam, heating requires hot water, and domestic hot water supply is also required. When the amount of process steam accounts for more than 30% of the total heat load of the boiler room, the boiler room should only be equipped with a steam boiler, and the required hot water is obtained through a steam-water heat exchanger. This system mainly uses process steam, and the boiler pressure should meet the steam pressure required by the process. The steam pressure required to heat the heating hot water is lower than the process steam pressure, which can be obtained through a pressure reducing valve.

2. Hot water heating system

This system is relatively simple. Regardless of the boiler capacity, the number of units, and the temperature of the water supply, the system principle is basically the same. The box drawn by the double-dotted line in the figure represents the water supply and pressure fixing device.

3.A system with hot water heating and domestic steam

This system is suitable for heating in hotels and restaurants. The steam generated by the steam boiler can be used for civil heating such as absorption refrigerators, kitchens, washing machine rooms, and domestic hot water heating. The steam pressure is generally 0.1 ~ 0.4MPa, the steam boiler operates at 0.4MPa pressure, and the low-pressure steam can be decompressed. The valve is decompressed. The hot water boiler is dedicated to heating in winter. If the heating user is a radiator system, the supply and return water temperature is 95/70 ° C or 80/60 ° C; if it is a fan coil system, the supply and return water temperature can also be reduced.

4.Steam and water boiler heating system

The system's hot water boiler can be converted by using a steam boiler. The system can be used for one furnace and two uses. It can also supply a small amount of steam while supplying hot water. When necessary, it can also operate as a steam boiler to completely supply steam. Have greater adaptability to the needs of thermal users.

District heating cogeneration plant

1. Steam heating system for production process

In the southern region, the heat users of industrial enterprises are mainly steam. Therefore, the central heating of thermal power plants is mainly provided by the extraction (exhaust) steam of condensing steam turbines and back pressure steam turbines, which are sent to the heat consumers through steam heating network pipes.

2.Heating heating system

In the northern region, heating is generally the main method. Therefore, the central heating of a thermal power plant is mainly based on the extraction of condensing turbines as the heat source, and the circulating water is heated by the heating network heater to provide users with heating hot water.

3.Multi-heat source centralized heating system

In central heating systems in large and medium-sized cities, there are often more than one heat source. Such systems are collectively referred to as multiple heat source central heating systems. This type of multi-heat source system has greater flexibility in operation and good standby. Therefore, it has been widely used in large and medium-sized urban central heating systems newly built in China in recent years. However, the multi-heat source system is more complicated in operation adjustment and design, for example, whether each heat source is started at the same time or successively, whether it is a common network operation or an off-grid operation, how to adjust management during operation, and so on.

4.Using the central heating system for central cooling

In summer districts with high temperature and high humidity, when the cooling load of public buildings such as hotels, restaurants, shopping malls, and theaters in the central heating area is large enough, and the heating system heating parameters can meet the cooling requirements, Try to use the existing centralized heating system to achieve centralized cooling (also known as thermal cooling). ^[3]