Suzhou Qiao Hui HVAC introduction: industrial ventilation pipe design common way

In the face of the basic status quo of poor ventilation efficiency in industrial ventilation duct design due to the impact of construction environment, this paper takes industrial environment construction and professional development of industrial design as the basic starting point, summarizes the basic status quo and existing problems of ventilation duct design, and puts forward suggestions to strengthen ventilation optimization design from the aspects of daily maintenance and control, ventilation skylight and safety. It provides basic guarantee for the sustainable development of industrial production and environmental engineering.

1 Purpose of industrial ventilation duct design

Because of the complexity of the industrial environment, it is necessary to combine various factors in the design of industrial ventilation pipes, consider them comprehensively, make preparations in advance, and ensure the rationality of the design of ventilation pipes. Ventilation ducts are designed for the following purposes: First, to remove pollutants. For the pollutants generated in the process manufacturing, the pollutants that meet the national health standards can be directly eliminated through the ventilation pipe, while the pollutants with harmful factors can be discharged to a special pollutant treatment place for purification, and then discharged after the treatment reaches the standard. Secondly, transport. Including a certain humidity or temperature, fresh air, etc., will be transported to the designated area, such as textile mills, paper mills and other industrial areas with temperature or humidity requirements, in order to meet the environmental needs of process manufacturing, but also to create a comfortable working environment. Finally, substitution. Supplement the shortage of internal air in the industrial environment from the ventilation pipe, maintain the balance of indoor air pressure, and avoid the adverse impact of external polluted air on the working environment or product quality. Or through the ventilation pipe to the indoor discharge, and into the outdoor fresh air, to achieve the effect of purifying the air or regulating the temperature.

2 Common ways of industrial ventilation duct design

With the in-depth development of social industrialization, there are also many categories of industrial ventilation pipe design, different production conditions, and different requirements for the operating environment. For example, chemical operations, due to the easy production of harmful factors in the process of such operations, ventilation pipes are often based on purifying air and other needs; The electronic work is mainly based on temperature control and humidity control. Finally, combined with the scope of its role, whether there is a dynamic system, etc., it can be divided into the following five ways. (1) Full ventilation. Comprehensive ventilation, subdivided into dilution, one-way flow, uniform flow, displacement of four ways. The purpose is to carry out air circulation or replacement of the overall area of the industrial area, dilute and exclude the harmful factors in the entire space area, the concentration is low, or the excess moisture, hot gas, etc. to the health standard limit value, and ensure the cleanliness of the air. (2) Local ventilation. Local ventilation is divided into two types: local supply air and local exhaust air. It is mainly the use of local air circulation to achieve the purpose of purifying the air and reducing the adverse effects of harmful factors. (3) Mechanical ventilation. Through the power system, the air pressure caused by the fan is used to promote air circulation and displacement. Common in the chemical industry, it can quickly discharge indoor toxic and harmful pollutants from the mechanical ventilation pipe to the designated treatment area for decomposition and purification. (4) Natural ventilation. Natural ventilation, as the name suggests, is a kind of wind pressure formed by outdoor wind, as well as the air circulation under hot pressure caused by the temperature difference between indoor and outdoor air, which is an unpowered ventilation mode relying on natural factors. Due to the instability of natural factors, it is rarely used by industry alone, and is often used in combination with other ways. (5) Emergency ventilation. Accident ventilation, is a very special type of ventilation in the industry, usually due to industrial accidents caused by a large number of toxic pollutants, or there is a potential explosion gas or steam to eliminate or dilute a ventilation mode, to ensure that when the accident occurs, there can be enough reliable ventilation duct to deal with the ventilation volume. In fact, in order to achieve a more comprehensive ventilation effect, it is common to combine at least two ventilation methods.

3 Common problems in industrial ventilation duct design

(1) Ventilation system division problem. For personal gain or convenience, some factories are often uniformly divided into a system, which not only cannot achieve good ventilation effects, but also buries security risks for factory operations. When the industrial area is wide and multiple exhaust air points are placed, a unified management system can be designed to form a whole with the main fan and a number of exhaust air points. The division of the system can be combined with the nature of industrial production, process, time, operating parameters, as well as the demand for air, humidity, temperature and other factors, the same or similar can be divided into a system for unified management, and two kinds of easy to mix and mix will produce more toxic gases, or easy to cause fire, explosion gas, it must not be divided into a system. Instead, independent ventilation systems should be designed [5].

(2) Material selection and section shape of ventilation pipes. The material and section shape of the pipeline is the root of achieving the good efficiency of industrial pipeline ventilation. Once the wrong material or shape is selected, it will not only damage the beauty of the industrial building structure, but also fail to achieve the effect and purpose of ventilation, and even bury security risks in the use stage of the ventilation pipeline due to the failure of the material. On the one hand, it is necessary to choose the right pipe material. For example, around the melting furnace, it is necessary to take into account the properties of high temperature resistance and choose alloy steel with high heat and wear resistance. On the other hand, the choice of suitable pipeline section shape is also particularly critical. In general, circular is more suitable for pipelines with high-speed flow requirements; When the pipeline section is large, the selection of rectangle is more appropriate, and it also has an auxiliary role in improving the utilization rate of space.

(3) Layout of ventilation pipes. The layout of the ventilation ducts needs to be as convenient as possible to keep the ducts straight, while the equipment used for regulation and detection can be installed in the ventilation ducts for real-time and systematic management of the operation of the ventilation ducts. In addition, it is also necessary to design according to the actual ventilation needs, such as when the conveyed gas contains liquid, the ventilation pipe can be arranged as a slope, so as to eliminate the purpose of liquid accumulation.

(4) The temperature balance of the ventilation duct. The temperature balance of the ventilation pipe is a very important part of the problem, once the design is unreasonable, it is very easy to cause the pipeline due to too high or too low temperature, or long-term in a humid environment caused by pipeline rupture and other problems. Especially because the ventilation pipe will bring a large amount of heat, cold and energy consumption in the operation process, the temperature control structure of the ventilation pipe has higher requirements, usually including insulation, moisture-proof and protective layer three layers of protection. The insulation layer is the core of the pipeline, and the moisture resistance is to avoid the contact between the pipeline material and water and water vapor, while the protective layer is to protect the insulation layer and the moisture resistance layer to avoid damage.