Factsheet & Process Description Regenerative Thermal Oxidizer (RTO) Vopak Terminal Amsterdam Westpoort

Transcription

1 Factsheet & Process Description Regenerative Thermal Oxidizer (RTO) Vopak Terminal Amsterdam Westpoort Authors Bart Muijtjens SHEQ Advisor Jeroen Broere Terminal Manager Martijn de Gier Project Manager Robin Jongen Document name: RTO-VTAW-FSH - v0 Project number: Document date: 10 June 2016 This document can be distributed to 3 rd parties involved in developing projects for Vopak. Use for projects or other activities outside Vopak is not permitted. Bijlage_7_Selectie_Technologie_

2 Contents 1 Introduction RTO Fact sheet Alternative processes... 8 Page 2 of 9

3 May 31 st For Permit Request Date: Version: Description: Page 3 of 9

4 1 Introduction Vopak Terminal Amsterdam Westpoort (VTAW) has installed a Vapour Recovery Unit (VRU) for the handling of vapours from loading of vessels and barges as well as (from mid-2015) vapours from filling up tanks after roof landings. The existing VRU is of the so-called Pressure Swing Adsorption (PSA) principle. The VTAW VRU consists of two units with a design capacity of 5,000 and 7,500 m 3 /h respectively, giving a combined design capacity of 12,500 m 3 /h. The environmental permit of VTAW stipulates a reduction of the non-methane VOC content of the treated vapours to 150 mgc/nm 3. Whenever the emission exceeds 150 mgc/nm3, the terminal is in a noncompliance situation. To ensure structural compliance to the environmental permitfurther process improvement is needed. In the Amsterdam Harbour more VRUs are operational, which show identical problems in continuously meeting the VOC emission limits. All these VRUs are of the same principle (PSA) and supplied by the same manufacturer (CarboVac). A team of specialists (Vopak Personnel, PSA suppliers and external consultants/psa/vapour treatment specialists) has been looking at the performance issues of the VRU. The joint conclusion was that the VRU, even with implementation of further improvements, will require a polishing technique to meet the VOC emission limits under all circumstances. Reference is made to Plan van aanpak verbeteringen VRU, Vopak Terminal Amsterdam Westpoort B.V. for more details. As polishing technique a Regenerative Thermal Oxidation (RTO) unit has been selected. Installation of an RTO will result in a sustainable solution to meet the VOC emission requirements. An additional advantage of an RTO is that the RTO will make the VTAW VRU future proof. This document describes the following items: 1. Functioning of the RTO and the combination with the VRU 2. Facts about the RTO (process data, etc.) 3. Alternative techniques investigated for achieving a compliance situation Page 4 of 9

5 2 RTO Fact sheet The table below sums up all key data for the RTO system: Item Description Remarks Capacity total VRU Nm 3 /h of vapour Capacity of existing VRU, to remain unchanged. Capacity RTO Nm3/h Nm3/h from VRU plus additional dilution and combustion air. Inlet concentration VRU 400 g/nm 3 As per design CarboVac. Inlet concentration RTO (= outlet VRU + dilution air) 0 x g/nm 3 Maximum depending on total flowrate. Max. 5 g/nm 3 possible at max flowrate from ships. During lower flowrates higher concentrations can be permitted to enter the system with dilution. Support fuel RTO Propane From local installed tank(s) Fuel requirements for RTO Propane is used as support fuel during start up and during operation when the inlet of the RTO is below 1.5 g/m3 of VOC. Operating modes: Minimum (5% of time): 4100 Nm3/h Flow rates from exhaust of RTO. Including feed from RTO Average (75% of time): Nm3/h Maximum (20% of time): Nm3/h Exhaust gas temperatures: Minimum 44 o C Average 98 o C Maximum 180 o C Temperatures at different operating conditions/flow rates. Uptime 98% uptime = 8580 h/a Including planned downtime for maintenance, etc. RTO weight kg RTO size 8,9 x 3,4 x 5,0 m (lxbxh) RTO height 5 m RTO box max. height. Stack height Stack diameter 15 m 600 mm Stack material: SS316 Page 5 of 9

6 Process description combination VRU + RTO + Chiller This process description briefly describes the process of vapour treatment in the combined VRU-RTO process including the additional chiller for the VRU. The VRU treats vapours from ship loading activities by adsorption of VOC on activated carbon beds. After passing through the bed the vapour stream is led to the stack from which it will be transferred to the RTO process. After a bed has been saturated (during a cycle of approx. 12 minutes) the bed is blocked from the vapour stream coming in from the ships and the installation switches to a new bed to continue the process of adsorption. The saturated bed is then regenerated by using a combination of deep vacuum and purging with ambient air. The contents of the bed together with air is led to the re-absorber where this stream is washed in counter-current with a flow of re-absorbent liquid (e.g. naphtha) from a dedicated tank. The VOC s are re-absorbed in the re-absorbent and led back to the storagetank. The remaining vapour stream is led back to the inlet of the VRU for further processing. The re-absorption process is sensitive to the vapour pressure and temperature of the liquid used. Also the vacuum process as well as the re-absorption generate heat that is transferred to this absorbent liquid (which is also used to cool de vacuumpumps). The optimum temperature for re-absorption has been defined to be 7 degrees C or lower. To achieve this temperature a chiller will be installed that cools the liquid flow before entering the re-absorbers. This chiller will work with ammonia as a coolant that is evaporated directly against the absorbent liquid in a dedicated heat exchanger. By eliminating any secondary coolant circuit the efficiency is increased and leakage risks are reduced, while also reducing the required plot space. In an RTO VOCs in the vapour coming from the VRU stack is oxidised to H 2 O and CO 2 on ceramic beds at temperatures of C. The RTO uses three reaction chambers, packed with ceramic material. The oxidation of the VOCs takes place in one of these reaction chambers. The heat generated by the oxidation is absorbed by the ceramic packing, the chamber in which the oxidation takes place is heated up. Upon entering the RTO, the vapour stream is routed through a hot chamber. From the hot chamber (pre-heating the vapour stream to be treated) the vapour stream is routed through a cold chamber. Between the chambers additional heat can be added, to reach the required Page 6 of 9

7 oxidation temperature. By frequent changing between chambers (entering through a hot chamber, exiting over a cold chamber) the heat of combustion will remain in the installation. RTOs can reach required VOC removal efficiencies. NO x formation in an RTO is very low. To operate an RTO properly a minimum of 6 vol% oxygen shall be present in the inlet. This is guaranteed by adding a variable amount of dilution air via the stack between VRU and RTO. LUCHT INLAAT GEREINIGDE DAMP STEUNBRANDSTOF ONGEREINIGDE DAMP ABSORBENT Picture 03 VRU/RTO connection PFD (general) Page 7 of 9

8 3 Alternative processes Several alternative options have been investigated for this project. These options include the following categories: 1. VRU upgrade 2. Addition of a polishing technique to the VRU Vopak is convinced that the present VRU is part of a reliable and sustainable vapour treatment system. Upgrade of the VRU is necessary and will be executed, in combination with a polishing technique. In general the following techniques are considered as polishing techniques: - Catalytic Oxidation - Non-thermal plasma - Combustors / Metal fibre oxidizers / gas engines - Regenerative Thermal Oxidation Catalytic Oxidation Catalytic Oxidation (CatOx) is deemed to be less suitable for this application. In a CatOx the VOCs present in the vapour streams to be treated are oxidized over a catalyst bed at a temperature of C. Energy efficient CatOx designs can run autothermally on a VOC inlet concentration of 3 5 g/m 3. The catalyst limits the maximum temperature in the oxidation chamber (in general maximum 600 C). To protect the catalyst (limit the temperature) the VOC concentration at the inlet must be kept below 10 g/m 3. The catalyst in a CatOx is susceptible to poisoning. Since seagoing vessels will be inerted with (cleaned) exhaust gasses, the chances of poisoning the catalyst are relatively high. Also the flow rate is too high to make a CatOx system financially viable (cost is exponentially higher at large flow rates). Page 8 of 9

9 Combustor / MFO / Gas engine Gas-engines and/or Metal Fibre Oxidisers are not considered as polishing techniques. These installations require an energy content of the vapour fed to these units of approximately 6 MJ/Nm 3 (corresponding to approximately 150 g/nm 3 VOC) which makes them less compatible with the existing VRU. Using a combustor for lower contents would result in very high support fuel consumption making this option financially unattractive and unsustainable from an environmental perspective. Non-thermal plasma Non-thermal plasma is generally used in odour reduction applications and is often applied at sewage treatment plants, pet food plants, etc. The NT plasma technology is relatively new and still under development. Application in (petro)chemical plants/terminals is not very common. Also an application at this scale has not been executed. Vopak prefers to use proven technology for this project, for this reason this option is not investigated further. Selection matrix Air Energy Reliability Overall CatOx /- + Combustor /- MFO Gas engine + +/- -- +/- NT plasma ++ - Not known +/- RTO Page 9 of 9