Begg Cousland Envirotec Limited applications

Air or SO₂ is dried with H₂SO₄ before being fed to the sulphur burner or converter. The Drying Tower can be under pressure or under suction, with the main gas blower being, respectively, in front of or after the tower.  The physical limit of drying is 3 mg/SCF of gas as H₂O (= 16 mg/SCF as H₂SO₄) Large particles (>3 microns) are mechanically entrained from the acid distribution system or packing, typically as a load of 500 – 750 mg/m³. As the Drying Tower operates at relatively low temperature, mist is not thermodynamically formed.

Process Information: Case A Conventional H2SO4 Process: In a sulphur burning or metallurgical double absorption H2SO4 plant where no Oleum is produced upstream, SO3 gas exits the third catalyst pass, is cooled down and enters the first ( = intermediate ) absorption tower, where H2SO4 is distributed over ceramic packing to absorb the SO3. When the gas exits the I.A.T. it returns to the converter to go into the fourth catalyst pass after being reheated in a gas/gas heat exchanger. Due to the high inlet gas temperature and the relatively low inlet acid temperature, mist is formed thermodynamically and acid droplets are mechanically entrained from the acid distribution system or packing. In such processes the mist and droplets combine typically as a load of 2,000 – 2,500 mg/m3. The particle size spectrum will be sub-micron to medium sized ( 0.3 to 8 micron )

Tail Gas Scrubber Process Information: The SO2 conversion rate of single absorption plants is lower than double absorption, and many single absorption plants installed tail gas scrubbers to reduce this SO2 content rather than convert the plant to double absorption. Scrubbing the tail gas (tail gas scrubbing) to acceptable SO2 emission values can be done with seawater, caustic, lime slurry, hydrogen peroxide or ammonia. After exiting the absorber tower, the gas enters a tail gas scrubber tower where ammonia (NH3) is injected and contacts the SO2. Ammonium Sulphite and Bi-sulphite are formed and some of these salts are entrained in the exit air. These salts are soluble, but can be emitted in quite large volumes, e.g. 2,000 – 15,000 mg/m3 and are generally < 3 microns in size, with a large amount < 1 mircron.

Electrolysis of brines with chlorine production at the anode and hydrogen together with sodium or potassium hydroxide at the cathode.

Electrolysis of brines with chlorine production at the anode and hydrogen together with sodium or potassium hydroxide at the cathode.

Electrolysis of brines with chlorine production at the anode and hydrogen together with sodium or potassium hydroxide at the cathode.

Process Information: Electrolysis of brines with chlorine production at the anode and hydrogen together with sodium or potassium hydroxide at the cathode.

Process Information: SO3 gas is used in a sulphonation reaction process. Fibre filters which are installed before the sulphonation reactor remove very fine oleum mists. The SO3 gas (6-7%) can contain up to 7,000 mg/m³ of oleum mists, and due to the highly exothermic reaction, it is normal to trace heat and insulate the vessel to prevent oleum freezing.

Process Information: SO3 gas is used in a sulphonation reaction process. Fibre filters which are installed after the sulphonation reactor remove up to 4,000 mg/m³ sulphonated hydrocarbon mist. Due to the high viscosity liquid produced with over sulphonisation, it is recommended (a) to have a stand-by filter unit in parallel, or (b) to have an irrigated demister unit in front of the fibre filters; in any case a Δp metered wash spray system is normal on the candle filters, and the vessel may be trace heated and insulated.

Process Information: Candle Filters can be used in the dry process (electric furnace) described below; the phosphate rock is sintered or nodulized to facilitate escape of phosphorus vapours in the furnace and to prevent the blowing over of dust. After sintering, the material is sized and the fines returned to the sintering machine. Coke and sand are added and the materials charged to the electric furnace. The temperature of the furnace is approximately 2400 ºF.