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METALLURGY OF ZINC.

M.Sc. Degree.

1. Describe two types of mechanical roasters that are used successfully in the roasting of zinc blende. What are the chief items of cost in connection with this operation?

2. Discuss the losses of zinc experienced in the ordinary retort method of smelting zinc ores.

What controls the size of the retort employed in connection with this work?

Discuss the chemical reactions that take place in this smelting operation, and mention the effect of temperature on these changes.

3. Describe any method that has been tried of extracting zinc from its ores by means of converting it into the chloride, and discuss the advantages and disadvantages of the process.

4. Describe some method of smelting mixed lead-zinc ores in the electric furnace.

FACULTY OF PRACTICAL SCIENCE.

CHEMICAL ENGINEERING I.

Course D.

1. Give a detailed description of a modern sulphuric acid plant, explaining the functions of the various parts, and showing why and in what way improvements had been effected. The method of obtaining the sulphur dioxide and air mixture, i.e. the pyrites burners, need not be discussed.

2. What are the precise functions of a Glover and Gay Lussac tower in a sulphuric acid plant? Explain how they aid in the economy and steadiness of running, and whether they have any influence on the amount of acid produced.

3. What is the necessity for having a certain store of acid at the bottom of the chambers? How much acid is capable of being stored in this way? Discuss the advantages of atomised water sprays versus steam jets in a sulphuric acid plant, and show which type you would adopt in a plant working in a variable climate, such as Kingston.

4. Discuss the materials of construction available in the manufacture of nitric acid. How are the nitric oxides evolved recovered, and to what advantage?

5. Give a description of one type of furnace for fixing atmospheric nitrogen, and describe the rest of the manufacture in detail.

6. In manufacturing nitrobenzene a charge of 500 kilos is nitrated with a mixture of nitric and sulphuric acids. The

sulphuric is of 80% strength. The nitrating mixture is to contain 40% nitric acid, nitric acid of 96% being available, and 10% over the theoretical quantity is required. Calculate the amount of nitrobenzene formed, assuming a reasonable yield, and the composition of the waste acid. many litres of sulphuric acid of 95% strength and sp. gr. 1.840 are needed to make 1000 kilos of 80% acid?

FACULTY OF PRACTICAL SCIENCE.

CHEMICAL ENGINEERING II.
Course D.

1. A factory has a constant supply of dinitrotoluol, m.p. 70° aavilable. Likewise a nitric acid still and condensing plant, capable of giving 1,000 lbs. of 96% nitric acid per day of 24 hours, part of this acid being used in other departments. It is required to design a plant for the manufacture of trinitrotoluol. The following data are available: Dinitrotoluol when nitrated at about 80°C., with a mixture of the composition: 45% HNO3, 55% H2SO,, a 15% excess being used, gives a yield of trinitro- equal to 86% of the theoretical. The physical characteristics of the trinitro- and the phenomena occurring during nitration are known. The waste acids obtained by separation have the following composition: 10% HNO3, 74% H2SO, 16% H2O. There is also available fuming sulphuric acid, containing 20% SO3, for use in the nitrating mixture, and 98% sulphuric acid and 96% sodium nitrate.

(a) Design a suitable plant with all necessary accessories complete to produce 1,000 lbs. of trinitro- per 24 hours. Calculate the amount of nitrating acids required, the vessels, etc., to handle, store, and mix them, and show how to work the process.

Design the means required to purify the trinitro- by washing with water, and suggest and plan what should be done with the washings.

(b) Calculate the amount of waste acids obtained and show how they can be used in the nitric acid plant, in what amounts, and to what advantage. Work out the cost calcu

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