This chapter deals with the fundamentals of gas-cleaning technology. Gas-clean­ing technology deals with all types gases, from air to flue gases and process gases. In this section, due to the complex nature of the subject, only a simple approach to gas-cleaning technology is presented. The topics covered are of prime importance due to new international statutory requirements. The developing international market in this field is a very important one for designers and manufacturers.

Particle size distribution relating to gas cleaning is well understood in the industry. This section deals with general rules of thumb. Certain important is­sues not included in this section are flue gas desulfurization, flue gas denitrifi­cation, hazardous waste gas cleaning, waste incineration gas cleaning, and removal of C02 from flue gas. All these topics have special requirements, which must be considered separately in the design process.

Table 13.1 shows the physical and chemical nature of particles, from mo­lecular level to 10 mm size. Table 13.1 can be divided into three sections:

1. Chemical

2. Physical

3. Human behavior and methods

These sections are related to the same table but also can be used separately when connecting the particle size axis from the end of the table.

Table 13.1 can be used only as a provisional rule of thumb in order to ob­tain a general picture of what the end result will be. In the actual design pro­cess, the problem must be solved by a proven design approach.

Table 13.1 covers general information for different particulates, liquids in gas, typical particles and gas dispersoids, behavior of particles in the human body, charging mechanisms, principles of particle size analysis, methods for particle size analysis, and an estimation of the general collection efficiency of available commercial particle removal equipment.

TABLE 13.1 The Physical and Chemical Nature of Particles, From Molecular Level to 10 mm Size

0.0001 jim 0.001 nm 0.01 jim 0.1 Jim t Jim 10 pm 100|j. m 1mm


Note that the presented particle collection efficiencies cannot be as­sumed to be for the best available technology and are shown for equip meat existing in industry. Dimensioning of particle removal equipment makes it possible to achieve better removal efficiencies in most cases presented in Table 13.1. All particulate and gas-cleaning equipment must be separately designed to meet specified local conditions.

All definitions used in Table 13.1 are covered in the Appendix.