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description of the process in the reactor unit sinesa DC-101



Synthesis section 
In this section urea is made from carbon dioxide gas, liquid ammonia, and the solution karbamat byrecycle. The main tool is the synthesis reactor (DC-101) of the vessel upright on the operating temperature of 195 0C and pressure of 200 kg/cm2. This reactor provides sufficient volume to conduct the reaction of urea synthesis, as close as close to the equilibrium reaction. According to the design capacity, residence time in the reactor is 25 minutes. Because the reactant and product substances are corrosive then the entire surface of contact with the solution given the protective layer of stainless steel. Usually stainless steel and stainless steel are also corrode the reactants, but with the addition of oxygen (air antikorosi), then the resistance higher will be obtained. Coating system stainless steel lining system. In this unit of urea produced by the reaction of eksotermis high NH3 and CO2 to form ammonium karbamat, followed by dehydration endotermis form urea ammonium karbamat. The reaction of urea ammonium karbamat be held only in the liquid phase so that the required high pressure. The increase in temperature and pressure will increase the conversion of urea formation to a certain extent. These reactors have feedback in the form of CO2 gas, liquid ammonia, and the solution of the recycle karbamat. CO2 gas from the ammonia plant, together with the air of 2500 ppm antikorosi fed to the Knock Out Drum (FA-161) to remove solid particles and liquid droplets that may be contained therein. Addition of air here is intended to prevent the occurrence of corrosion on Syntesis Urea Reactor (DC-101) due to oxygen in the air serves to oxidize the stainless steel because stainless steel corrosion is active as a drag when in the oxidized state. CO2 gas is compressed by the CO2 Booster Compressor (GB-102) until the pressure reaches 26 kg/cm2G. Type of compressor used was multistage Centrifugal driven by steam. Compression is then performed in the compressor GB-GB-101A and 101B are working in parallel so that the pressure to 200 kg/cm2G. This type of compressor is the Two Stage Reciprocating Compressor and driven by steam. CO2 gas into the reactor through the bottom at a temperature of 123 0C and 200 kg/cm2G pressure. Liquid ammonia as the feedback obtained from the ammonia plant is accommodated in Ammonia Reservoir (FA-401) before use. Ammonia Reservoir within this, ammonia mixed with ammonia from the process of recovery from Ammonia Condenser (EA-404 AD). Liquid ammonia Ammonia Ammonia Reservoir suppressed by Boost Up Pump (GA 404 A / B) type of centrifuge until the pressure reaches 21 kg/cm2. Then the liquid is pumped back by Liquid Ammonia Feed Pump (GA-101 A / D) to a reciprocating type reactor (DC-101). Some liquid ammonia from the GA-404 A / B is pumped into the High Pressure Absorber (DA-401) which is used as a solvent. Ammonia that flows into the first reactor is heated in two Preheater (EA-101 and EA-102). EA-101 Preheater using condensat steam as the heating medium, so that the temperature entering the reactor reached 81.40 C. Karbamat recycle solvents from High Pressure Absorber Cooler (EA-401) pumped by Recycle Solution Boost Up Pump (GA-401) type centrifuges. Then by Recycle Solution Feed Pump (GA-102) is inserted into the reactor (DC-101) through the bottom of reactor. Karbamat solution circulation flow through the suction recycle line from Recycle Feed Pump (GA-102) back to the High Pressure Absorber Cooler (EA-401) is required to prevent solidification karbamat solution in the pipe. The reaction in the reactor (DC-101) are as follows: 2 NH3 (g) + CO2 (g) becomes NH2COONH4 (l) + 38 kcal / mol (1) NH2COONH4 (l) becomes NH2CONH2 (l) + H2 O (l) - 7.7 kcal / mol (2) Products that come out of the reactor consisting of urea, water, ammonium karbamat, biuret and excess ammonia. At normal reactor conditions it will form a liquid. The first reaction conversion reaches 100%, while for the second reach 70%. There are several things that affect the above two reactions, namely:
1. Temperature 
The most optimal conditions in the reactor is about 200 0C the temperature at which the conversion approaches equilibrium with a residence time from 0.3 to 1 hour. When the temperature of the reactor down the conversion into urea ammonium karbamat be reduced, thus giving a heavier burden to the next sections. If the temperature drops to 150 0C, this situation will give rise to patch-patch in the reactor karbamat ammonium. Conversely, if the temperature exceeds 200 0C the rate of corrosion of stainless steel lining and the pressure will increase in the equilibrium mixture in the reactor from the reactor from the reaction mixture will exceed the required pressure, in addition side reactions are not desired may be enlarged in this condition . Such conditions will lead to the formation of urea conversion decrease. Temperature in the reactor can be controlled by: a) Set the amount of ammonia into a reactor. b) Adjust the karbamat ammonium solution into a reactor. c) setting the temperature of ammonia Ammonia bait Preheater. Temperature in the reactor is recorded in a recorder that the sensor takes place along the reactors.

2.Tekanan 
The first reaction takes place rapidly at high pressure. Optimum pressure is taken for this reaction is 200 kg/cm2G. The selection is based on the operating pressure of the consideration that the conversion of ammonium into urea karbamat occurs only in liquid phase. Liquid phase can be maintained by operating at high pressure due to high operating temperature (200 0C). Reactor pressure is set by the PRCA that his valve located on the pipe at the top expenditure reactor. When the pressure is too small then the valve in the pipe will be narrowed opening expenses. In addition reactor equipped with Interlock system will work to close the emergency valve, all contained in each tube bait.

3. Comparison of ammonia and carbon dioxide
 Comparison of NH3: CO2 ranged from 3.5 to 4. Besides affecting the reactor temperature, the amount of ammonia can affect the reaction directly. An excess of ammonia may accelerate the first reaction. In addition, the excess ammonia will also prevent the formation of biuret reaction, with the following reaction: 2 NH2 CONH2 (l) to NH2 CONHCONH2 (l) + NH3 (g) (Biuret) Biuret formation of excessive undesirable because it is toxic to plants so that the limited amount of 0.5% urea products.

4. The amount of water 
The amount of water especially influential in both the dissociation reaction becomes karbamat urea and water. Reaction as follows: NH2COONH4 (l) becomes NH2CONH2 (l) + H2O (l) The presence of water will affect the formation of urea from karbamat thus minimize the conversion.


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