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Abstract

Contents

Introduction

Kiln is designed to remove moisture from the iron ore concentrate with 9.5-10.5 % to 0.5 %. In the roasting process part of the intracrystalline moisture is removed, which leads to an increase in the percentage of iron in the concentrate. Oven – a long cylinder with a diameter of 4 meters and a length of 110 meters, the axis of which is inclined at an angle, sealed on both sides and rotating around its own axis. From the elevated portion of the cylinder it is loaded continuously moist concentrate which, when the cylinder is rotated slowly poured to the lower end, where there is a device for discharging the dehydrated concentrate.

Roasting of the concentrate is performed by a gas torch, and preheating by combustion products. Gas flows from the lower part of the furnace and hot gases rise toward the concentrate. Since the concentrate is exposed to gradually increasing temperature, which ensures its dehydration.

Feature of the firing process control is that the moisture content of the resulting product is determined indirectly via the temperature of the exhaust gases from the furnace. This is due to the lack of sensors that measure the moisture content of the intracrystalline.

The aim is to develop a system of automatic tracking and stabilization of temperature flue gases from the kiln at the optimal level, the value of which 230 0C [1].

Kiln consumes gas in an amount that uses the city with a population that exceeds a quarter of a million people. [2] The furnace is an power-consuming object, and optimize its energy consumption leads to great economic effect. Therefore, the development of ATS is an urgent task.

1. General formulation of of the problem

In constructing the ATS the control object considered from the point of view of the destination. ATS must stabilize the temperature of the exhaust gases from the furnace at 230 0C [1].

For maximum performance, we choose as the control action of the concentrate feed to the furnace, and the perturbation – the gas supply. Necessary to develop an automatic control system kiln which allows mutual cross-effects of the control channels of local temperature and performance against each other with the technological limitations on the capacity of the furnace (25-100 m/s) and gas (1500-6000 cub. m/hour).

As an actuator in the selected DPT with limit switches and gear, then in the steady state engine will "taxi up" the gas supply valve [6]. This management is continuous. An actuator of this kind is expensive but it can be applied because its cost is not commensurate with the cost of the furnace.

2. Methods of solving the problem

The projected ACS determines the quality of products, the amount of which reaches 11 million tons a year, you should choose a closed ATS management by exception, which is widely used in industry [3-5].

To control the system we select PD-control law to compensate for the harmful effects of the integrator, which describes the model of the angle valve.

Optimization held to the nominal capacity, which is 60% of the maximum value.

System simulation showed satisfactory results. Engine needs valve 500, while ensuring the gas flow 3600 m3/hr with increasing load on the furnace 80 tonnes/hour, which corresponds to its peak performance. The flap, opening at 710, misses 5120 m3 of gas, which does not exceed the limit on the gas flow rate 6000 m3. Warm-up time of the oven is 8 minutes. Feedforward compensation time is about 5 minutes. Even such a large increment on the oven as 80 t/h, with an acceptable technology not more than 3 tons/hour, barely noticeable effect on the transient characteristics of the flue gas temperature. Thus, the work of ACS compensate disturbance.

 

Conclusions

1. We consider the process as iron ore roasting facility management. This process is shown multiply, cross-channel effect control the flow rate of gas and furnace productivity at each other. As well as the presence of the perturbing effects of moisture in the form of a concentrate input to the furnace.

2. Investigated separately control channel flue gas temperature as a proxy for moisture concentrate on the output of the kiln. ATS flue gas temperature is built with the principle of management by exception. SAR study conducted with the restrictions on the productivity of the furnace 25-100 m/s and the gas flow 1500-6000 m3.

3. The simulation results shows that the ATS with DPT and tuned PD controller provides good control over the entire range of the furnace. 8 minutes of regulation time, overshoot is 0%, compensation for disturbance 5 minutes. Self-sustained oscillations in the modes of tracking and stabilization missing.

4. In a possible limitation of some gas levels that could lead to low productivity of the furnace, it is necessary to develop a SAR mode providing performance concentrate roasting furnace according to the current supply of gas at the required percentage of humidity ore concentrate output.

At the present day master's work is not yet complete. Terms of completing the work – December 2013.

References

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