CALCULATION OF AIR EMISSIONS FROM AN ACETYLENE PLANT

Transcription

1 CALCULATION OF AIR EMISSIONS FROM AN ACETYLENE PLANT IGC Doc 84/08/E Revision of IGC Doc 84/02/E EUROPEAN INDUSTRIAL GASES ASSOCIATION AISBL AVENUE DES ARTS 3-5 B 1210 BRUSSELS Tel : Fax : info@eiga.eu Internet :

2 IGC Doc 84/08/E CALCULATION OF AIR EMISSIONS FROM AN ACETYLENE PLANT PREPARED BY : S.C. Bradley Marco Arrighi AIR PRODUCTS PLC SAPIO S. Duboudin AIR LIQUIDE SA F. H. Finger EIGA F. Revuelta PRAXAIR Cristina Gomez Delgado PRAXAIR L. Simic MESSER Chris Szweda LINDE Disclaimer All technical publications of EIGA or under EIGA's name, including Codes of practice, Safety procedures and any other technical information contained in such publications were obtained from sources believed to be reliable and are based on technical information and experience currently available from members of EIGA and others at the date of their issuance. While EIGA recommends reference to or use of its publications by its members, such reference to or use of EIGA's publications by its members or third parties are purely voluntary and not binding. Therefore, EIGA or its members make no guarantee of the results and assume no liability or responsibility in connection with the reference to or use of information or suggestions contained in EIGA's publications. EIGA has no control whatsoever as regards, performance or non performance, misinterpretation, proper or improper use of any information or suggestions contained in EIGA's publications by any person or entity (including EIGA members) and EIGA expressly disclaims any liability in connection thereto. EIGA's publications are subject to periodic review and users are cautioned to obtain the latest edition. EIGA EIGA grants permission to reproduce this publication provided the Association is acknowledged as the source EUROPEAN INDUSTRIAL GASES ASSOCIATION AISBL Avenue des Arts 3-5 B 1210 Brussels Tel Fax info@eiga.eu Internet:

3 Table of Contents 1 Introduction Scope and purpose Scope Definitions Air of an Acetylene Plant Chemical Reaction Sources of Calculation of Air Excel Spreadsheet to calculate Air... 7

4 1 Introduction The basic philosophy is the minimization of emissions, nuisance and wastes of any kind and their safe and clean disposal as it is stated in ISO "Organizations of all kinds are increasingly concerned to achieve and demonstrate sound environmental performance by controlling the impacts of their activities, products or services on the environment, taking into account their environmental policy and objectives." (EN ISO 14001) This document describes a standard method of calculating air emissions from an acetylene plant. The user can input their own information specific to their plant and obtain an estimate of the air emissions. This document has an excel spreadsheet tool that can be used to calculate the emissions. 2 Scope and purpose 2.1 Scope This calculation considers the potential environmental impact of air emissions from acetylene plants. More details of best practices and other environmental impacts can be found in EIGA TN 515/95. 3 Definitions None. 4 Air of an Acetylene Plant 4.1 Chemical Reaction Acetylene is produced by reaction between calcium carbide and water: CaC H 2 O C 2 H 2 + Ca(OH) Sources of Acetylene could be considered a volatile organic compound (VOC) with a low ozone creation potental. Typical emission sources of an acetylene plant are: Generator (open or closed system) Lime Pits Gasholder Purification unit Compressors Filling station Cylinder maintenance The main sources for which a calculation is needed are the generator and the lime pits. The other main sources are estimate of the emissions from cylinder maintenance and compressor, which are fugitive emissions. The calculation for lime pits requires both theoretical background and various technical data for each single plant. For smaller quantities from other sources, it is recommended to determine the emissions by approximate calculation, as their share is < 5% of the total amount. The amount of gas which is emitted depends additionally on various parameters of the production process. The following paper will give an explanation of how to calculate and to estimate gaseous 1

5 emissions release during normal operation. This way ensures that all different figures of each plant will be considered. The emissions from the lime pit are estimated as follows. Figure 1 Figure 1 shows typical C 2 H 2 from a lime pit, based on a specific plant example Figure 2 Figure 2 shows the emission rate vs. temperature of lime resp. time NOTE It should be clearly stated that the following calculations are based on practical experience. 2

6 4.3 Calculation of Air 1. General Data Acetylene Production 1.1 Operating days/yr 1.2 Operating hours/day 1.3 Carbide consumption (t/yr) 1.4 Acetylene pressure in generator (mm water column) 1.5 Filling amount/charge (t) 1.6 Volume of water (m 3 ) / t of CaC 2 consumption 1.7 H 2 O - volume in the circle of acetylene generation (m 3 /yr / m 3 /hr) Closed generator system, low pressure Open generator system, low pressure Remarks in Bold printed data are fix and must be taken from the technical specification Figures given in this calculation are an example 1,7 1,7 Carbide consumption per filling amount 2520/1,7 ~ 1483 charges/yr / 4, / 4,20 in Italic printed data are predicted Formula calculations in brackets [Example: 1.3] refer to chapter in the 1st collumn [ ] = = 4, Impurities in Raw- Acetylene 2.1 PH 3 (ppm) / (mg/kg) 2.2 NH 3 (mg/m 3 ) / (mg/kg) 2.3 H 2 S (mg/m 3 ) / (mg/kg) 2.4 AsH 3 (mg/m 3 ) / (mg/kg) 300 / / 419 concentration in ppm is determined by analysis; concentrations should be analysed before a new calculation is made. 620 / / 436 dto. 10 / 14,05 10 / 14,05 dto. - - ignoring amount 1 ppm PH 3 = 1ml PH 3 /m 3 C 2 H 2 = 1,53mg PH 3 /m 3 C 2 H 2 = 1,53mg PH 3 /1,095 kg C 2 H ,53 300ppm PH 3 = = 1, mg PH 3 /kg C 2 H , ppm NH 3 = = 1, mg NH 3 /kg C 2 H ,539 10ppm H 2 S= = 1,095 14,05 mg H 2 S/kg C 2 H 2 3

7 3. Carbide dust emission (Cyclone) 3.1 Capacity, exhausting volume (m 3 /hr) 3.2 Concentration of carbide dust (mg/m 3 air) depends on the cyclone type and the exhausting time 3600 Estimation: operation time 1min 45 determination by measuring Carbide dust emission is not relevant for a closed generator 4. Acetylene Production 4.1 Acetylene (t/yr)/(kg/month) 4.2 Lime 25 % (t/yr) / (t/month) 895/ / / / 850 average production: 0,355 kg C 2 H 2 /kg CaC 2 26 Y = 0, (with Y= 0,875; 87.5% of the theoretical yield) Reaction: CaC 2 +2H 2 O C 2 H 2 +Ca(OH) 2 64kg CaC 2 form 74kg Ca(OH) 2, if there are no impurities in carbide; (theoretical yield). Lime may be used for different applications in different concentration. [ 1.3 0,355] = , t C 2 H 2 /yr; resp = kg C 2 H 2 /month Y t lime/yr; resp = 850t lime/month 12 This calculation predicts 25% Ca(OH) 2 in water suspension Charging the generator with carbide C 2 H 2 (kg/yr)/(kg/hr) E 1 : 1273 / 0,21 There are no direct emissions into the atmosphere during charging a closed generator system, because acetylene from the generator escapes into the closed carbide vessel, which will be subsequently released to the atmoshere. The amount of escaped acetylene in this vessel depends on both, the volume of the vessel and the acetylene pressure in the generator. Volume [m 3 ] (carbide vessel) x Number of charges x Pressure of the generator x density [kg/m 3 ] (C 2 H 2 ) ( ) 1, 095 2, = 1273 kg/yr resp. 0,21 kg/hr Remark: This calculation does not consider an inert atmosphere in the carbide vessel, which may not be replaced during charging carbide into the generator. If you want to do, multiply the results by 0,5-0,8 4

8 C 2 H 2 (kg/yr)/(kg/hr) PH NH H 2 S Carbide dust from cyclone (kg/yr) E 4 : 0,53 / 89 E 6 : 0,55 / 92 E 8 : 0,017 / 2,98 E 2 : 1184 / 0,20 E 3 : 1909 / 0,31 E 2 + E 3 : 3093 / 0,51 E 5 : 1,30 / 216 E 7 : 1,35 / 225 E 9 : 0,043 / 7,24 E 10 : 4,00 To calculate the acetylene emissions from an open generator system 2 amounts have to be considered: 1. Acetylene which is replaced by carbide in the generator during charging process = E Acetylene which escapes due to the overpressure in the generator = E 3. This acetylene amount depends on the gas pressure in the generator the time how long the charging process lasts the free area through which acetylene escapes. For generators of the Sirius type E 3 should be estimated by multiplication of E 2 with the factor of 1,5 and further multiplication (( )/10000) The calculation procedure relates on acetylene emissions calculated in and impurities from Carbide volume [m 3 ] x density [kg/m 3 ] (C 2 H 2 ) E 2 = 1, 095 = 1, 095 2,33 2,33 E 2 = 1184 kg/yr E resp. 2 = 0,2 kg/hr E 3 = [E 2 x 1,5 x (( )/10000)] = ,5 = E 3 = 1909kg/yr E resp. 3 = 0.3 kg/hr E 2 + E 3 = Emission from open generator charging closed generator system: E 4 = [E 1 x 2.1] = = 1273 kg/yr x 419 mg/kg x 10-6 = E 4 =0,53 kg/yr open generator system: E 5 = [(E 2 + E 3 ) x 2.1] = = 3093 kg/yr x 419 mg/kg x 10-6 = E 5 =1,30 kg/yr Calculation see E 4 and E 5 The calculation procedure relates on number of charging processes; cyclone operation time is estimated with 1 min. exhausting volume concentration of carbide dust (determination by measuring) Calculation see E 4 and E 5 There is no dust emission from a closed generator system E 10 = mg/yr E 10 = = 4,00 6 1,

9 5.2 from lime pit C 2 H 2 (kg/yr)/(kg/hr) PH 3 NH 3 H 2 S 5.3 from gasholder C 2 H 2 (kg/yr) PH 3 (kg/yr) NH 3 (kg/yr) H 2 S (kg/yr) 5.4 from overpressure relief system C 2 H 2 (kg/yr) PH 3 (kg/yr) NH 3 (kg/yr) H 2 S (kg/yr) 5.5 from compressors/ drying system/ filling station E 11 : 1764 / 0,30 E 13 : 0,73 / 122 E 15 : 0,76 / 128 E 17 : 0,03 / 4,1 17,64 0,0073 0,0076 0, ,64 0,0073 0,0076 0,0003 E 12 : 1764 / 0,30 E 14 : 0,73 / 122 E 16 : 0,76 / 128 E 18 : 0,03 / 4,1 C 2 H 2 (kg/yr) ,64 0,0073 0,0076 0, ,64 0,0073 0,0076 0,0003 see Figure 1 The calculation procedure relates on difference of concentrations of acetylene, phosphine, ammonia and hydrogen sulfide in fresh production lime water and residual water for the generator. The concentrations should be determined for each single plant to consider e.g. different sizes of the lime pits, specific water consumption for acetylene generation, lime temperature Estimation: 1% of Lime pit E 11 E 18 Estimation: 1% of Lime pit E 11 E 18 Estimation: ~ 0.5% of acetylene production; E 11 resp. E 12 = [1.7 x 1000 x 70 x 10-6 ]= x 1000 x 70 x 10-6 = E 11/12 =1764 kg/yr; resp. 0,30 kg/hr calculation E 13 E 18 : similar to E 11/12. Example for emissions: C 2 H 2 70 mg/l lime water PH 3 0,029 mg/l NH 3 0,030 mg/l H 2 S 0,0010 mg/l (impurities relates to the concentrations in raw acetylene) [1.3] x 1000 (kg) x Y (practical yield of acetylene from 1 kg CaC 2 ) ~ 1% in case of old or badly maintained compressors 6

10 5.6 from cylinder testing C 2 H 2 (kg/yr) Acetone (kg/yr) 118,1 118,1 Estimation: 1% of acetylene production If acetone is filled with a gas displacement device, these emissions can be neglected, if acetone vapour disperses into the atmosphere the amount of vapour can be calculated. Ae Ac A dv = = A dl Ac x 0,0033 = Ae = (40 x 895) x 0,0033 = Ae = 118,1 kg A typical figure of acetone consumption is about 40 kg acetone per ton C 2 H 2 Ae = acetone emission in kg Ac = acetone consumption per year (kg) A dv = density of acetone vapour (0,0026 kg/l) A dl = density of liquid acetone (0,79 kg/l) 6. Sum of emissions C 2 H 2 (kg/yr) PH 3 (kg/yr) NH 3 (kg/yr) H 2 S (kg/yr) Carbide dust (kg/yr) ,28 1,33 0, ,04 2,12 0,07 4, Excel Spreadsheet to calculate Air Accompanying this document is an Excel spreadsheet where the user can input the information described in section 4.3 above: Doc_84_08_E_Spreadsheet.xls. The spreadsheet will then perform the calculations according to the formulae described in