Calculation of heat engineering equipment - Floor chamber of PCD KISI

Contents

1. Introduction

2. Determining the main dimensions of the thermal plant

3. Calculation of the number of heat plants per specified program

4. Material Balance

5. Heat balance

6. Aerodynamic calculation

7. Occupational safety measures

8. List of used literature

Introduction

Hardening of reinforced concrete products can occur under natural conditions at normal temperature and under heat treatment conditions (artificial hardening conditions). Heat treatment, which allows to accelerate hardening of concrete mixture, is a necessary operation at Factory production of reinforced concrete products .

Currently, the following types of heat treatment are used: a) steaming products at normal pressure at a temperature of 60-100 ° C); b) steaming articles in autoclaves saturated with steam at a pressure of 0.9-1.3 MN/m2 (9-13 atm) and a temperature of 175-191 ° C; c) contact heating of articles; d) electric heating by passing electric current through the concrete thickness; e) heating concrete with infrared rays. In addition, hot molding is studied, in which the concrete mixture is heated by electric current or steam to a temperature of 75-85 ° C before being laid in a mold for 8-12 minutes and then held in the mold under thermos conditions of 4-6 hours.

For the formation of the concrete structure, as already noted, moisture hardening conditions are especially important, therefore, in many cases, thermal moisture treatment of reinforced concrete products (steaming and steaming) should be preferred. Thermal treatment of reinforced concrete products is carried out until concrete reaches a strength of about 70% of the design, which allows transporting the products to the construction site and mounting structures from them .

Steaming at normal pressure is carried out in periodic or continuous chambers, it is the most economical method of heat treatment. Of the intermittent steaming chambers, yam-type chambers are widely used. The most reasonable size of the chambers in the plan, obtained on the basis of technical and economic indicators, should correspond to the size of two steamed products. The walls of the chamber are usually made concrete, there is a massive cover on top of the chamber.

Molded articles in molds or on pallets are loaded into the chamber in several rows in height, after which the chamber is closed with a cover preventing heat and steam loss. Steam is supplied to the chamber from the boiler room constantly depending on the established steaming mode so that it provides a rate of temperature increase in the chamber from 20 to 35 ° C in 1 hour, to a maximum of 85-100 ° C. At the same time, the product is warmed up to the entire thickness and kept at this temperature for 6-8 hours, after which it is gradually cooled. The duration of steaming depends on the composition of the concrete and the property of the cement and is about 14-20 hours for plastic concrete mixtures and 4-8 hours for rigid ones.

The use of fast hardening cements makes it possible to reduce the duration of isothermal holding (at a lower heating temperature of 70-80 ° C) and reduce the total steaming time to 8-10 hours. Products from light concrete due to their lower thermal conductivity require a longer heat treatment time. The continuous steaming chamber is a tunnel that provides a set steaming mode for articles rolled on cars on one side of the tunnel and rolled out on the other. During the period of residence in the tunnel-type chamber of the product, the heating zone, the isothermal heating at the maximum temperature and the cooling zone pass. Tunnel chambers are mainly used in the conveyor production method. Heat treatment of concrete in steaming chambers accelerates its hardening time compared to hardening under natural conditions by about "7-8 times. Steaming of articles in autoclaves - special, hermetically closing devices, consists in the fact that at a saturated water vapor pressure of 0.9-1.3 MN/m2 (9-13 atm), water remains in the liquid phase even at a temperature of 175-191 ° C. This creates favorable conditions for accelerating hardening and formation of compounds having the properties of cementitious substances of high strength: Since concrete gains strength in the autoclave in the first 4-6 hours of heating, in autoclaves with a pressure of 1.1-1.3 MN/m2 (11-13 atm), it is possible to reduce the duration of isothermal heating to 3-5 hours.

Contact heating of articles is carried out by direct contact of the article with a heat source or with heating devices heated by mold walls or bench base (with bench technology), etc. Hot water steam, hot water, oils, etc. are used as a heat source. This heat treatment method is used in the manufacture of thin-walled articles in cassettes with sufficient sealing. In addition, with the help of these heat carriers, some types of products are treated in thermal tanks (hardening of products in hot water). After heat treatment, the technology of making reinforced concrete products, if no further surface finish is required, ends. The technical control department checks the products and sends the finished products to the warehouse.