Compared with conventional drying techniques (including the burning of rice husks and waste fuels) Valueform's drying solutions saves between 10%-25% of energy costs in drying pulp moulded products. Read below to find out more. 

 

Valueform   drying solutions - Innovative fibre pulp moulded drying

 

1. Pulp moulding industry driers use, gas, electricity, biomass and in some cases liquid fossil fuel as a source for generating heat for hot air drying.
2. Heat generated is used in drying ovens to blow hot air for removal of moisture from fibre moulded items such as egg boxes and apple tryas or industrial mouldings for packaging.
3. This hot air is often recycled to raise temperature and save energy of inlet air ot the oven and /or raising temp. of water used in the moulding process.
4. In order to assess the potential for energy saving in such drying systems Valueform first observe and note the amount of moisture being removed from the moulded product all along the length of the drying oven and also note the energy input to achieve this.
5. Using a purpose built energy efficient heating station that can be coupled to the drying oven at a convenient and most effective position in the drying oven that Valueform can recommend a combined drying process for the moisture removal from fibre pulp moulded products that on the whole reduces the energy burden by 10 to 25% is achieved. This depends on the extent of moisture removed by in part by existing hot air drying method and the new combined drying method.
6. Efficiency and energy consumption varies with every design of oven. Hence the need for studying usage pattern, output levels, and moisture removal rates as well as any recovery aspects involved. In one case we have observed the following

 

Production rate- 2400 egg trays per hour at the end of pulp molding and drying oven.

 

Fuel used- Rice husks

 

For 100% , 90%, and 80% moisture removal( start wt. 183 gms- dry wt.58gms) total power used for drying including blowers was 1702kw, 1231kw and 995 kw . For removing 10% and 20% moisture by the new combined drying station in place the incremental power was only 30 kw and 60kw in addition to 1231kw and 995kw respectively giving an overall reduction from 1702kw of 25% and 38% in terms of energy used.

 

Although this company was not recycling the hot air it illustrates the possibilities using

 

Valueform proposed technology for drying.

 

The capital expenditure gave this company payback options on the extent of moisture removed and increase in throughput that were very attractive.

 

Valueform can:

 

1. for customers give an early indication of potential savings if moisture level data and energy usage data is provided for a given oven design.- no charge service
2. Undertake an onsite detailed study of molding plant and oven design and capture online data and provide an assessment for best position siting of the drying station we have developed at least cost including a demonstration of the drying station as a teach-in service in UK. Costs to implement the improvements project can be provided as part of the service. Includes capital costs as well as installation and service support.
3. The service in 2 above includes knowledge transfer, solution provision that works and implementation project costs.
4. Commercial terms will include consultancy charges for knowledge transfer, solution provision and implementation charge with a success fee.

 

Drying times and energy requirements for a commercial scale drying oven

 

Energy required to dry products

• Calculation based on 2,400 units being processed in one hour.
• Drying process removes 127g per unit
• Total water removed = 304.8 kg water
• Theoretical energy required (ignoring energy required to raise temperature of units) = 691,896kJ
• This is equivalent to 192kW continuous power supply

 

Energy delivery

• Energy source is rice husks 400 kg/hr

• Theoretical energy of rice husks: 18MJ/kg (International Energy Agency Data)

• Theoretical delivery of energy = 7,200 MJ/hr or 2,000 kW
• Therefore overall efficiency of this process is 9.6 % (i.e - 192/2,000)

 

Performance of dryer unit

The overall performance of the drying unit was measured by taking weights of the units at different points in the drying process.

 

A chart of drying rate against time was therefore obtained, along with the temperatures in the drying oven:

 

 

By analysing the drying rate it is possible to determine the efficiency of drying as a % of the water removed and also the kWhr performance.

 

% water removed	Overall Drying efficiency	kWhr required/kg water
10%	21%	3.02
20%	20%	3.11
30%	20%	3.21
40%	19%	3.32
50%	18%	3.45
60%	17%	3.61
70%	17%	3.81
80%	15%	4.08
90%	14%	4.49
100%	11%	5.59

 

The alternative process can be applied, and this has an overall performance that gives a drying efficiency of 0.98kWhr / kg of water evaporated. The efficiency does not decline as the product becomes drier. This was confirmed by trials at the original site by drying products removed towards the end of the drying process.

 

By using this new technology the following improvements on the overall drying performance could be achieved:

 

% water removed by Hot Air	100	90	80	70	60	50	40	30	20	10	0
Total power required kW	1702	1260	1054	903	780	675	584	502	428	360	298
kWhr/kg water	5.59	4.14	3.46	2.96	2.56	2.22	1.92	1.65	1.41	1.18	0.98
Efficiency (%)	11.29	15.24	18.22	21.28	24.63	28.45	32.91	38.26	44.85	53.24	64.32
Improvement over 100% HA (%)	0.00	25.94	38.05	46.95	54.16	60.32	65.69	70.49	74.83	78.80	82.45

 

The application of the new technology is independent of the product dryness, therefore improvements in efficiency can be achieved for all drying process that do not have an efficiency greater than requiring 0.98kWhr / kg water dried.

 

For the unit tested payback periods were calculated depending on various assumptions made. Payback periods varied from just over 1 year to longer periods, depending on the conditions used.

 

The new technology can be applied in a number of ways:

 

1. Supply sufficient energy to keep overall drying time the same as currently achieved and hence significantly reduce overall energy consumption.
2. Supply sufficient energy to reduce drying time significantly, and yet still use less energy than currently required
3. Supply much greater energy and significantly reduce drying time, but overall energy input is the same, but at a much greater cost.

 

The choice of which approach is best will depend on the value per unit and the cost of different forms of energy at the site. Advice will be given following the audit and in discussion with the client.