Plant Design Project for the Production of 72 MT of Sulfuric Acid per day.docx

Plant Design Project for the Production of 72 MT/day of 98 % Sulfuric Acid (Proposal). Submitted to: Prof.Dr.Mahmood Saleem Submitted by: Umar Draz CE-M10-24 Institute of Chemical Engineering and Technology University of the Punjab Lahore

Abstract Our objective is to design a 72 MT/day of Sulfuric Acid plant. This plant is comprised of a number of unit operations and process equipments including sulfur melter, sulfur furnace, waste heat boiler, 4 pass converter, hot and cold heat exchangers, Economizers # 1&2, inter pass absorption tower, final absorption tower, air drying tower, circulation tank, cooler and storage tank. These operations and processes are explained in detail and their material and energy balances data is (will be) provided.

Processes and Operations Following Process and operations are involved in production of sulfuric acid at LCFL.

1) Melting of Sulfur. Sulfur is fed to melting pits through belt conveyer. Here steam is used as heating medium. Pits are provided agitator and temperature in pits is 135-140 oC

2) Combustion of Sulfur. Furnace is made of mild steel lined with refractory bricks. In furnace molten sulfur is pumped at the top of furnace with the help of a gear pump. The rpm of this pump is 1500. At the top of furnace molten sulfur is mixed with air (Air comes from main blower after drying) and in the furnace combustion takes place and the following reaction took place; S (liq) + O2 (g)  SO2 (g)

ΔH = -296 kJ mol-1

The combustion of sulfur is an exothermic reaction. Temperature of combustion gases increases to 800- 850 oC. Temperature of combustion gases depends upon quantity of sulfur fed to the furnace.

3) Waste Heat Boiler. As the combustion gases are at above 800 oC. This heat is recovered in waste heat boiler. This waste heat boiler at Lyallpur Chemicals is water tube boiler. There are 6 headers and 198 tubes in the boiler. Boiler feed Water comes from water R.O (Reverse Osmosis) plant after passing through Economizer # 1 and 2 and is fed through multi stage pump. The level of water in boiler is controlled by a pneumatic operated level control globe valve. Steam is generated at 40 bar pressure and 270 oC temperature; this steam produced is saturated steam and is used to melt the sulfur in melting pits. This saturated steam is further passed through super heater to make super heated steam which is used for power generation in turbines.

4) Converter. This converter is a reactor and contains four beds of catalyst. Vanadium pent oxide is used as a catalyst. Gas comes at about 430 oC after passing through waste heat boiler

and mixing with bypass line. Sulfur dioxide and oxygen is fed at the top of the converter. At first bed the amount of catalyst is 2400 liters. Catalyst beds are supported at grids, quartz is placed at the top of catalyst which acts as a filter and removes any unwanted impurities. Quartz is there also to save the catalyst from any losses. Sulfur dioxide reacts with the oxygen in the presence of catalyst and sulfur trioxide is formed; 2SO2 + O2  2SO3

∆H= -196 kJmol-1

5) Super Heater. Gases after passing through 1st bed of converter are passed through super heater to decrease their temperature to an optimum value suitable for the conversion of SO2 to SO3. This is a shell and tube type heat exchanger.

6) Hot Heat Exchanger. Gaseous mixture after passing through 2nd bed of converter is passed through hot heat exchanger to reduce its temperature. The gases are entered to shell side of the heat exchanger. There is cold gaseous mixture on the tube side of heat exchanger coming from tube side of cold heat exchanger which is heated for further processing in 4 th bed of converter.

7) Economizer # 1&2. Gaseous mixture coming from the shell side of cold heat exchanger is passed through economizer no. 1 to regain the heat energy present in hot gases. Gases are introduced to the shell side and water is introduced to the tube side of this economizer. Water comes from the water treatment plant which after passing through the economizer no. 2 is introduced to the waste heat boiler for steam generation. No. of tubes in economizer # 1 is 60. Gaseous mixture coming from the 4th bed of converter is passed through economizer no. 2 to regain the heat energy present in hot gases. Gases are introduced to the shell side and water is introduced to the tube side of this economizer. Water comes from the tube side of economizer # 1 which is finally introduced to waste heat boiler. No. of tubes in economizer # 2 is 105.

8) Intermediate and final absorption tower. Gaseous mixture after passing through the economizer # 1 is introduced to the bottom of the intermediate absorption tower. Sulfuric acid is showered from the top of the tower. Sulfuric acid of 98.5% concentration in water is sprayed with the help of shower. The

shower is not exactly at the top of the tower; it is almost at the centre of tower and a mist eliminator is provided in the upper most portion of tower to remove any water or acid vapors from the un- absorbed gaseous stream coming out from the top of the tower. This is done as gaseous mixture has to pass through the 4th bed of converter, it will deactivate the catalyst if contains moisture. Gaseous mixture after passing through the economizer # 2 is introduced to the bottom of the final absorption tower. The entrance temperature of gaseous mixture in final absorption tower is 160 oC. Sulfuric acid is provided from the top of the tower. Sulfuric acid of 98.5% concentration in water is supplied with the help of dip pipes. The dip pipes are 56 in number and are of 5-6 feet height. The ends of these pipes are dipped in the packing. Dip pipes are provided with ceramic nozzles.

Fig 1: Sulfuric Acid Plant