This 30,000 TPY DME Plant was newly built using modern technology and operated just for two years.
The unit was shutdown due to market constrain, put under Nitrogen and fenced-off.
It is rather small, well designed and compacted unit, ease for dismantling, packing and relocation as complete plant.
All process design package, detail engineering and vendors dossiers were well organized and complete in e-format and hard paper copy.
The equipment is almost new and of very good condition. Plant boundaries are clearly defined and selling package includes also three (3) bullets storages tanks (100 m3 each) for DME with pumping station for truck off-take, electrical switchgears and firefighting pump station. Spare charge of catalyst is in warehouse and good for service.
The Facility has further process units operating downstream of the main methanol plant. DME unit is a 30 mt/day Di-methylether nominal capacity.
This unit produces highest purity DME having a residual content of methanol of less than 1 ppm ( no color, no smell and zero Sulphur ).
The flowsheet of this plant has two single adiabatic stainless steel reactors in parallel (normally only one operating) with outlet temperature and pressure of 390 C and 15 bar (reactor design temperature and pressure of 425 C and 26 bar). After heat recovery and reactor product partial condensation the pure DME is recovered and separated from unconverted methanol and water as the overhead liquid in a multi tray distillation column, operating at about 12 bar. The unconverted methanol and water leaving the reboiler column bottom is separated in the methanol distillation unit, sec. 300 to permit complete recovery and recycle of this methanol.
The product DME is stored in several pressurized horizontal `bullet´ tanks having the same dimensions and design pressure, 17.5 kg/cm2g, / design temperature range, - 29 C to 65 C,D-101 A/B DME Reactors
Methanol is pumped by the Methanol Feed Pump (J405A/B) to the Cold Interchanger (E109) where i is heated by interchange against the crude reactor product. It is then fully vaporized by further interchange against the crude reactor product stream and also by MP steam in the Feed Heater (E101). The Feed Heater is a double bundle kettle vaporizer. A blow down pot is provided on the Feed Heater to purge non-volatiles. The methanol vapor is then superheated to 280°C by interchange against the reactor product stream in the Feed/Product Interchanger (E102) before being fed to the reactor. A line is provided at the bottom of the shell of the Feed/Product Interchange to drain any liquid carried over from the Feed Heater to the Lights Scrubber.In the reactor, the hot methanol vapor passes over the fixed bed of alumina pellets where it is dehydrated to dimethyl ether. The reaction is exothermic. The reactor operates adiabatically with a maximum bed temperature rise of 110°C. A bypass is provided around the tube-side of the Feed/Product Interchanger for controlling the temperature of the reactor feed. A globe valve is provided on the main process line to balance the pressure drop of the bypass control valve.
The primary reactor depressurization line to flare is provided at the tube-side exit of the Feed Heater. A secondary emergency depressurization line to atmosphere local to the reactors is also provided. Nitrogen is available to provide an emergency purge to the reactors should any of the bed temperature or exit bed temperature trips be activated.The crude product exiting the reactor is de-superheated by interchange in the Feed/Product Interchanger. The crude product is further de-superheated in the Feed Heater and then partially condensed by interchange in the Cold Interchanger before being let-down to the DME Column (D201).
D-203 Lights Scrubber
Non-condensable vapor from the Reflux Drum Vent Condenser (E103) is fed below the packed section of the Lights Scrubber (D203). Methanol from battery limit is fed into the top of the packed section. DME is recovered from the vent stream by scrubbing with this methanol. Liquid methanol from the shell of the Feed/Product Interchanger can be drained to the Lights Scrubber.
Methanol and recovered DME is pumped from the bottom of the Lights Scrubber by the Methanol Feed Pump (J405A/B) to the Cold Interchanger (E109).The uncondensed gases (mainly carbon monoxide, methane and hydrogen) are vented overhead to flare .
D-201 DME Column
Crude product from the Cold Interchanger (E109) is fed to the DME Column above tray 15. The DME Column (D201) removes dissolved gases, such as methane and carbon monoxide, and heavy components, such as water and methanol, from the crude DME product by distillation. The column contains 50 fixed valve trays to effect the required separation.
The vapors leaving the top of the column are partially condensed in the DME Column Condenser (E104). The top of the column operates at approximately 12 bara and 40°C. The condensate passes to the DME Column Reflux Drum (D301). Vapor from the DME Column Reflux Drum is partially condensed against glycol in the Reflux Drum Vent Condenser (E103). The non-condensable pass to the Lights Scrubber (D203). Liquid from the DME Column Reflux Drum is pumped back to the DME Column as reflux by the DME Column Reflux Pump (J401 A/B).
The refined DME product is removed as a partial liquid side draw from the upper section of the DME Column and pumped by the DME Product Pump (J404A/B) to the DME Product Cooler (E110) and on to battery limit. The DME Product Cooler cools the DME product to 38°C using cooling water.
Purges can be taken from above and below the main feed point. Purge location is selected from three different trays by means of block valves. The purges are directed to the flare KO drum. Purge flow and location are selected to remove minor reaction by-products and to maintain DME product specification. A line is also provided to feed DME to the DME Column Reflux Drum during start-up. Re-run DME from storage can be fed back into the DME Column .
Heat is supplied to the column base by the DME Column Reboiler (E105). This is a vertical thermosiphon reboiler heated by IP steam.
The bottoms stream from the DME Column, containing mainly methanol and water, is let-down to the Water Column (D202).
D-202 Water Column
The bottoms product from the DME Column (D201) is let-down to the Water Column (D202) above tray 25. The Water Column removes water effluent from the methanol by distillation. The column contains 50 fixed valve trays to effect the required separation.
The methanol overhead vapor leaving the column is condensed and subcooled against cooling water in the Water Column Condenser (E106). The condensed methanol collects in the Water Column Reflux Drum (D302). The column overhead pressure is controlled at approximately 1.5 bara.
The column reflux is returned by the Water Column Reflux Pump (J402A/B), A portion of the reflux is recycled to the Lights Scrubber. Purges can be taken from the reflux stream and from above the feed point of the Water Column. Purge location is selected by means of block valves. The purges are directed to the flare KO drum. Purge flow and location are selected to remove minor by-products and to maintain DME product specification.
Heat is supplied to the column base by the Water Column Reboiler (E107) This is a vertical thermosiphon reboiler heated by LP steam.
The bottoms stream from the Water Column is pumped by the Water Column Bottoms Pump (J403A/B) to the Water Effluent Cooler (E108) and then the water treatment The water effluent cooler uses cooling water to cool the effluent to around 40°C.
J-101 Nitrogen Circulation Loop
At start-up, the reactor is heated using nitrogen to prevent methanol condensing in the reactor. Loop circulation is provided by the Nitrogen Circulation Compressor (J 101). This is a rotary, oil-free machine with a differential pressure of 1 bar. A spill back is provided with pressure control at the exit Make-up nitrogen from battery limit is mixed with circulating gas at the compressor discharge.
The nitrogen passes first to the Reactor Startup Heater (E112) which heats it to 270°C using superheated MP steam. The hot nitrogen then passes through the DME Reactor (D101A/B) to heat the catalyst bed. The nitrogen from the reactor is then cooled by cooling water in the Nitrogen Cooler (E111) before passing to the Startup KO Pot (D303). The vapour from the Startup KO Pot is fed bad to the Nitrogen Circulation Compressor.
A line is provided at the inlet of the Reactor Start-Up Heater for superheating methanol vapour from the Feed/Product Interchanger. A separate line is also provided at the exit of the Reactor Start-Up Heater which feeds this superheated methanol to the DME Reactor.
Occasionally condensate may be produced from the Reactor Start-Up Heater. A line is provided to drain condensate from the shellside of this unit to a pot and then to drain.
Ball valves are provided to isolate each reactor. A continuous purge of nitrogen is passed through any offline reactor. This purge is vented to flare through FI-1027.
Methanol Grade A with the spec:Methanol : 99.85 wt%Acetone, maximum : 20 ppm wtAcidity (as acetic acid) : 0.003 wt%Appearance : Free of opalescence, suspended matter and sedimentCarbonizable impurities, colour, Platinum-Cobalt : No. 30Colour, Pt-Co, maximum : No 5Distillation Range at 760mm, maximum : 1.0°C (and shall include 64.6+/. 0.1 °C)Ethanol, maximum : 20 ppm wtNon-Volatile Matter, mg/100 ml, maximum :10 Odour : Characteristic, non-residualTotal Sulphur, maximum : 1 ppm wtAmines, maximum : 1 ppm wtPermanganate Time: No discharge of colour in 30 minutesSpecific Gravity at 20/20°C, maximum: 0.7928Water : 0.15 wt%
Dimethyl ether (DME), also known as methoxymethane, is the organic compound with the formula CH3OCH3, simplified to C2H6O. The simplest ether, a colorless gas and useful precursor to other organic compounds and an aerosol propellant that is currently being demonstrated for use in a variety of fuel applications. It is an isomer of ethanol.
Dimethyl ether is the main constituent of "freeze spray", a spot-coolant used in field-testing of electronic components. In this role it has supplanted halocarbon compounds (Freon), which have been suspected of contributing to ozone depletion in the Earth's atmosphere.
Dimethyl ether is also a component of certain high temperature "MAP-plus" blowtorch gas blends, supplanting the use of methyl acetylene and propadiene mixtures.
Dimethyl either is used as a propellant in aerosol products. Such products include hair spray, bug spray and some aerosol glue products. A potentially major use of dimethyl ether is as substitute for propane in LPG used as fuel in household and industry.
Dimethyl ether is a low-temperature solvent and extraction agent, applicable to specialized laboratory procedures.
Methanol Supplement Pump
Steam is provided from adjacent Methanol Plant: 27 bar at 300`C, and supplied saturated at 9 bar at a flowrate of 2.55 T/h.
Cooling water is provided from adjacent cooling tower: 3.5 bar / 2.0 bar ; 32`C / 43`C, Cooling Water Circulation is 155 m3/h.
Nitrogen is need only for start-up to purge the plant and to heat-up the DME reactor.
DME Dimethyl ether (Aerosol Grade)
Dimethyl ether plant produces aerosol grade DME (the highest purity DME) from feedstock methanol. Methanol is dehydrated in the vapor phase over an alumina catalyst. The crude product is then refined in two distillation columns where by-products and water are removed from the system. Unconverted methanol feedstock is recovered for recycle and product DME is obtained. The specification:Dimethyl Ether, minimum : 99.9 wt% C1-C4 alkanes, maximum : 50 ppmMethanol, maximum : 1 ppmWater, maximum : 100 ppmNon-volatiles, maximum : 25 ppm
This plant has two single adiabatic stainless steel reactors in parallel (normally only one operating) with outlet temperature and pressure of about 390 C and 15 bar ( reactor design temperature and pressure of 425 C and 26 bar ). After heat recovery and reactor product partial condensation the pure DME is recovered and separated from unconverted methanol and water as the overhead liquid in a multi tray distillation column, operating at about 12 bar. The unconverted methanol and water leaving the reboiler column bottom is separated in the methanol distillation unit, sec. 3000 to permit complete recovery and recycle of this methanol. The product DME is stored in 3 pressurized horizontal `bullet´ tanks having the same dimensions and design pressure, 17.5 kg/cm2g, / design temperature range, - 29 C to 65 C,
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