tubular furnace for heat treatment of fuel oil

Contents

CONTENTS

INTRODUCTION

1 Production Area Flow Chart

1.1 Process diagram and its description

1.2 Design and operation of tubular furnace

1.3 Disadvantages of a tubular furnace

2 Literature Review and Patent Analysis

2.1 Literary Overview

2.2 Patent Analysis

2.3 Choice of method of intensification of heat transfer of fuel oil flow in product pipes

3 Process calculations

3.1 Furnace heat balance and calculation of fuel combustion process

3.2 Calculation of heat transfer in radiant chamber

3.3 Calculation of the metal band pitch required to reduce wall temperature

3.4 Calculation of heat transfer in the convection chamber

3.5 Hydraulic calculations

3.5.1 Hydraulic calculation of convection chamber

3.5.2 Hydraulic calculation of radiant chamber

3.6 Aerodynamic calculation

4 Instrumentation and Automation

5 Occupational safety and environmental issues

5.1 Occupational safety and safe operation conditions of the furnace

5.2 Environmental measures to reduce pollutant emissions

6 Economic rationale for modernization

CONCLUSIONS

LIST OF SOURCES USED

Introduction

An urgent problem in the operation of furnace equipment is the negative impact of operational factors for a long time, namely deposits on the heat exchange surfaces of contaminants, scale, products of chemical reactions, which can cause a decrease in the operating parameters of the apparatus and a gradual or sudden deterioration of the technical condition up to the failure. Also, the presence of deposits leads to an increase in the required surface due to an increase in thermal resistance. It is not always possible to assess the effects of contaminants because of the many factors and mechanisms that influence the process.

One of the solutions to the problem of improving reliability, reliability and increasing the life of TA is the use of various methods of intensifying heat exchange, which have a positive effect on reducing deposits on the heat exchange surface. In addition, this effect leads to an increase in the heat transfer coefficient and, accordingly, a decrease in the required surface area of the heat exchanger.

At the moment, a sufficient number of methods of intensifying heat exchange are known to increase the heat transfer coefficient from several percent to several times and even tens of times. In this case, as a rule, the hydraulic resistance in the heat exchanger increases depending on the selected method.

One method of intensification investigated in operation is swirling of the flow. A number of domestic authors, such as E.K. Kalinin, G.A. Dreytser, Blink V.K., V.K. Schukin, B.V. Dzyubenko, KuzmaKitcha Yu.A., I.A. Popov, O.V. Mitrofanova Yu.Ya. Pechenegov and others lit the researches to the twirled stream and, in particular, application of twisted tapes for its reproduction. Despite the long-standing fame of the method of twisting the stream with twisted ribbons, interest in this issue remains, which is confirmed by one of the last works of Mitrofanova O.V., Popov I.A., Laptev A.G., Tarasevich S. E., Kolyadin E.A., Eiamsaard S., Sami D. Salman.

The aim of the study: to propose technological measures to increase the time period between the cleaning of pipe coils of wisbreaking fuel oil furnaces.

The objectives of the study are to calculate the tubular furnace of fuel oil visbreaking using a passive means of intensifying heat exchange - twisted metal ribbons inserted into the tubes of the radiant section of the furnace, in order to obtain a lower temperature of the wall of the radiant pipes, and accordingly reduce the number of deposits on the walls, which in turn will increase the period of operation of the furnace between cleaning.

Literature Review and Patent Analysis

2.1 Literary Overview

For intensification of transfer phenomena various methods can be used, both active and passive [4]:

design of rough surfaces and surfaces of complex shape, which contribute to turbulence of flow in the wall layer (knurls, recesses, holes);

swirling the flow with screw devices, spiral ribs, swirlers installed at the inlet to the channel;

use of turbulising inserts in channels;

increasing the heat exchange surface area by finning;

exposure of coolant flow to electric, magnetic and ultrasonic fields;

turbulization of the wall layer by pulsation of the speed of the incoming flow and its swirling;

mechanical action on the heat exchange surface by means of its rotation and vibration;

application of granular nozzle in both stationary and pseudo-movable condition;

addition of solid particles or gas bubbles to heat carrier.

Recently, interest in studying the effect of flow fluctuations on heat exchange when resonant frequencies and amplitudes occur has increased. In a number of studies, for example in [5], [6], [7], it is shown that under resonant oscillations, the heat transfer coefficient can increase by 2-3 times compared to the stationary current in both laminar and turbulent modes.

With acoustic resonance in the channel, heat transfer significantly increases in the zone of the beam of the standing wave speed. At the same time, the average heat dissipation along the length of the channel [6] increases markedly. However, when analyzing the feasibility of using flow oscillations for intensification of heat exchange, it is necessary to take into account all the energy costs for excitation of oscillations. Pressure fluctuations, including sound, can be an effective means of intensifying heat exchange with free convection [8].

Since the 1980s, great interest among researchers involved in the intensification of heat exchange has received a highly energy-efficient method of turbulence of the wall flow - the use of discrete transverse protrusions performed on the inner surface of the tubes of heat exchangers. For the first time, E.K. Kalinin, G.A. Dreitzer and others demonstrated the possibility of an advanced increase in heat transfer compared to an increase in hydraulic resistance on round channels with transverse semicircular annular protrusions. With this method of intensifying heat exchange, the increase reached 2.9 times [9], [10]. However, the use of annular semicircular protrusions did not solve all the problems associated with intensification of heat exchange.

In some heat exchange devices, along with discrete annular projections, other methods of intimate intensification of heat exchange are widely used, for example, the use of spherical recesses. This method of intensification was noticed after a number of studies by G.I. Kiknadze et al., as a result of which results were obtained on the high energy efficiency of the system, applied to the surface of the channel of spherical excavations. The authors attribute this fact to self-organization in spherical recesses of deadly vortex structures. From the point of view of academician A.I. Leontiev, the intensification of heat exchange with spherical recesses has a perspective, and still requires new approaches to the description of turbulent heat exchange in the conditions of self-organizing deadly vortex structures [11], [12], [4], [13]

When using curvilinear channels under the influence of centrifugal forces, helical structures are developed that cover all sections of the channel. [14], [15] In addition, with fairly steep turns, tear zones with a system of two-dimensional and three-dimensional vortices in them can occur. A system of helical vortices with an opposite direction of rotation may appear on the concave wall, all of which causes additional turbulence of the flow, an increase in heat transfer and hydraulic resistance.

The use of combined intensification methods is often highly effective (combining turbulizers with finning of surfaces, the use of spiral ribs that simultaneously swirl the flow, the use of swirling devices, during the flow of suspensions, the combination of turbulizers with swirling of the flow)

2.3 Choice of method of intensification of heat transfer of fuel oil flow in product pipes

On the basis of the data obtained during the literary review and patent analysis for modernization of the tubular furnace, a method of intensifying heat exchange is chosen, which combines relative ease of use and high efficiency, namely introduction into the coil tubes of the radiant section of a means for passive turbulisation of the coolant flow in the form of a twisted flat metal tape

Conclusion

The paper proposes technological measures to increase the time period between cleaning of pipe coils of fuel oil visbreaking furnaces.

Calculation of the tubular furnace of fuel oil visbreaking was made using a passive means of intensifying heat exchange - twisted metal tapes inserted into the tubes of the radiant section of the furnace, in order to obtain a lower temperature of the wall of the radiant pipes, and accordingly reduce the number of deposits on the walls, which in turn will increase the period of operation of the furnace between the cleaning.

The tape twist pitch required to reduce wall temperature is calculated. The invention proposes a circuit of automatic control of operation of a tubular furnace providing a flow of heated fuel oil stable in flow rate and temperature. Labor safety standards and environmental requirements for repair and operation of furnace equipment are described. The economic justification of the proposed modernization measures is given .

To further improve the characteristics of the tubular furnace, various measures can be proposed to rationalize the use of fuel combustion heat, both in the furnace itself and the use of excess heat in other industries. In particular, it is possible to obtain superheated steam by using the heat of flue gases, as well as improving the thermal insulation properties of the furnace.

Conclusions

Calculation of tubular furnace of fuel oil visbreaking is carried out using passive means of intensification of heat exchange - twisted metal tapes inserted into tubes of radiant section of furnace, in order to obtain lower temperature of wall of radiant pipes, and accordingly decrease of amount of deposits on walls, which in turn will allow to increase period of furnace operation between cleaning .

The economic justification of the proposed measures to modernize the furnace is presented, as well as labor protection standards and environmental requirements for the repair and operation of furnace equipment .

The tape twist pitch required to reduce wall temperature is calculated. The invention proposes a circuit of automatic control of operation of a tubular furnace providing a flow of heated fuel oil stable in flow rate and temperature.

To further improve the characteristics of the tubular furnace, various measures can be proposed to rationalize the use of fuel combustion heat, both in the furnace itself and the use of excess heat in other industries. In particular, it is possible to obtain superheated steam by using the heat of flue gases, as well as improving the thermal insulation properties of the furnace.